KR20210054957A - Method and apparatus for performing handover in a wireless communication system - Google Patents

Abstract

The present invention relates to a method for performing handover in a wireless communication system and a device thereof. An operating method in the wireless communication system comprises the following steps of: receiving a handover command from a source base station; generating a protocol layer device of a second bearer for a target base station based on information included in the handover command; performing random access to the target base station; and determining whether to maintain data transmission/reception with the source base station based on a predetermined condition.

Description

Method and apparatus for performing handover in a wireless communication system {METHOD AND APPARATUS FOR PERFORMING HANDOVER IN A WIRELESS COMMUNICATION SYSTEM}

The present disclosure relates to a method and apparatus for performing handover in a wireless communication system.

4G (4 ^th generation) to meet the traffic demand in the radio data communication system increases since the commercialization trend, efforts to develop improved 5G (5 ^th generation) communication system, or pre-5G communication system have been made. For this reason, the 5G communication system or the pre-5G communication system is called a communication system after a 4G network (Beyond 4G Network) or a system after an LTE system (Post LTE). In order to achieve a high data rate, the 5G communication system is being considered for implementation in the ultra-high frequency (mmWave) band (eg, 60 gigabyte (70 GHz) band). In order to mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves, 5G communication systems include beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO). ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed. In addition, in order to improve the network of the system, in 5G communication systems, advanced small cells, advanced small cells, cloud radio access networks (cloud RAN), and ultra-dense networks. , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, CoMP (Coordinated Multi-Points), and interference cancellation And other technologies are being developed. In addition, in 5G systems, advanced coding modulation (ACM) methods such as Hybrid FSK and QAM Modulation (FQAM) and SWSC (Sliding Window Superposition Coding), advanced access technologies such as Filter Bank Multi Carrier (FBMC), NOMA (non-orthogonal multiple access), and sparse code multiple access (SCMA) have been developed.

Meanwhile, the Internet is evolving from a human-centered connection network in which humans create and consume information, to an Internet of Things (IoT) network that exchanges and processes information between distributed components such as objects. IoE (Internet of Everything) technology, which combines IoT technology with big data processing technology through connection with cloud servers, etc., is also emerging. In order to implement IoT, technological elements such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required. , M2M), and MTC (Machine Type Communication) technologies are being studied. In the IoT environment, intelligent IT (Internet Technology) services that create new value in human life by collecting and analyzing data generated from connected objects can be provided. IoT is the field of smart home, smart building, smart city, smart car or connected car, smart grid, healthcare, smart home appliance, advanced medical service, etc. through the convergence and combination of existing IT (information technology) technology and various industries. Can be applied to.

Accordingly, various attempts have been made to apply a 5G communication system to an IoT network. For example, technologies such as sensor network, machine to machine (M2M), and machine type communication (MTC) are implemented by techniques such as beamforming, MIMO, and array antenna, which are 5G communication technologies. . The application of a cloud radio access network (cloud RAN) as the big data processing technology described above can be said as an example of the convergence of 3eG technology and IoT technology.

With the development of the wireless communication system as described above, it is possible to provide various services, and thus, there is a need for a method for smoothly providing these services.

Based on the above discussion, the present disclosure provides an apparatus and method capable of effectively providing a service in a mobile communication system.

A method of operating a terminal in a wireless communication system includes the steps of: receiving a handover command from a source base station; Generating a protocol layer apparatus of a second bearer for a target base station based on the information included in the handover command; Performing random access to the target base station; It may include determining whether to maintain data transmission/reception with the source base station based on a predetermined condition.

The disclosed embodiment provides an apparatus and method capable of effectively providing a service in a mobile communication system.

1A is a diagram illustrating a structure of an LTE system to which the present disclosure can be applied.
1B is a diagram showing a radio protocol structure in an LTE system to which the present disclosure can be applied.
1C is a diagram showing the structure of a next-generation mobile communication system to which the present disclosure can be applied.
1D is a diagram showing a radio protocol structure of a next-generation mobile communication system to which the present disclosure can be applied.
FIG. 1E is a diagram illustrating a procedure for establishing a connection with a network by switching from an RRC idle mode to an RRC connected mode by a terminal in the present disclosure.
1F is a diagram showing signaling procedures for performing handover proposed in the present disclosure in a next-generation mobile communication system.
1G shows specific steps of a first embodiment of an efficient handover method for minimizing data interruption time due to handover according to an embodiment of the present disclosure.
1H shows specific steps of a second embodiment of an efficient handover method for minimizing data interruption time due to handover according to an embodiment of the present disclosure.
FIG. 1I is a diagram illustrating structures of an efficient PDCP layer apparatus applied in a DAPS handover method, which is a second embodiment of an efficient handover method proposed in the present disclosure, and a method of applying the structures.
FIG. 1J is a diagram illustrating structures of an efficient SDAP layer device applied in a DAPS handover method, which is a second embodiment of an efficient handover method proposed in the present disclosure, and a method of applying the structures.
1K is a diagram illustrating a method of applying configuration information for each bearer when a DAPS handover method according to an embodiment of the present disclosure is configured.
1L is a diagram illustrating a terminal operation applicable to embodiments proposed in the present disclosure.
1M is a diagram illustrating an operation of a terminal performing a fallback procedure when a handover fails in the DAPS handover method proposed in the present disclosure.
1N is a diagram illustrating a structure of a terminal according to an embodiment of the present disclosure.
1O is a block diagram of a transmission and reception point (TRP) in a wireless communication system according to an embodiment of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in describing the present disclosure, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present disclosure, the detailed description will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present disclosure, which may vary according to the intention or custom of users or operators. Therefore, the definition should be made based on the contents throughout the present specification.

Advantages and features of the present disclosure, and a method of achieving them will be apparent with reference to embodiments described later in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below, but may be implemented in a variety of different forms, and only these embodiments make the disclosure of the present disclosure complete, and common knowledge in the technical field to which the present disclosure pertains. It is provided to fully inform the scope of the invention to those who have it, and the present disclosure is only defined by the scope of the claims. The same reference numerals refer to the same elements throughout the specification.

At this time, it will be appreciated that each block of the flowchart diagrams and combinations of the flowchart diagrams may be executed by computer program instructions. Since these computer program instructions can be mounted on the processor of a general purpose computer, special purpose computer or other programmable data processing equipment, the instructions executed by the processor of the computer or other programmable data processing equipment are described in the flowchart block(s). It creates a means to perform functions. These computer program instructions can also be stored in computer-usable or computer-readable memory that can be directed to a computer or other programmable data processing equipment to implement a function in a particular way, so that the computer-usable or computer-readable memory It is also possible for the instructions stored in the flow chart to produce an article of manufacture containing instruction means for performing the functions described in the flowchart block(s). Since computer program instructions can also be mounted on a computer or other programmable data processing equipment, a series of operating steps are performed on a computer or other programmable data processing equipment to create a computer-executable process to create a computer or other programmable data processing equipment. It is also possible for instructions to perform processing equipment to provide steps for executing the functions described in the flowchart block(s).

In addition, each block may represent a module, segment, or part of code that contains one or more executable instructions for executing the specified logical function(s). In addition, it should be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order depending on the corresponding function.

In this case, the term'~ unit' used in this embodiment refers to software or hardware components such as field programmable gate array (FPGA) or application specific integrated circuit (ASIC), and'~ unit' performs certain roles. do. However,'~ part' is not limited to software or hardware. The'~ unit' may be configured to be in an addressable storage medium, or may be configured to reproduce one or more processors. Thus, as an example,'~ unit' refers to components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, and procedures. , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, database, data structures, tables, arrays, and variables. Components and functions provided in the'~ units' may be combined into a smaller number of elements and'~ units', or may be further separated into additional elements and'~ units'. In addition, components and'~ units' may be implemented to play one or more CPUs in a device or a security multimedia card. Also, in an embodiment, the'~ unit' may include one or more processors.

In the following description of the present disclosure, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present disclosure, a detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings.

A term for identifying an access node used in the following description, a term for a network entity, a term for a message, a term for an interface between network objects, and various identification information. Terms and the like are exemplified for convenience of description. Accordingly, the present disclosure is not limited to terms to be described later, and other terms referring to objects having an equivalent technical meaning may be used.

For convenience of description below, the present disclosure uses terms and names defined in the 3GPP 3rd Generation Partnership Project Long Term Evolution (LTE) standard. However, the present disclosure is not limited by the terms and names, and may be equally applied to systems conforming to other standards. In particular, the present disclosure can be applied to 3GPP NR (New Radio: 5th Generation Mobile Communication Standard). In the present disclosure, the eNB may be used interchangeably with gNB for convenience of description. That is, a base station described as an eNB may represent a gNB. In addition, the term terminal may refer to mobile phones, NB-IoT devices, sensors as well as other wireless communication devices.

Hereinafter, the base station is a subject that performs resource allocation of the terminal, and may be at least one of a gNode B, an eNode B, a Node B, a base station (BS), a radio access unit, a base station controller, or a node on a network. The terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, or a multimedia system capable of performing a communication function. Of course, it is not limited to the above example.

The present disclosure proposes seamless handover methods that can minimize or make data interruption time due to handover to 0 ms in a next-generation mobile communication system.

Specifically, the efficient handover methods proposed in the present disclosure may have one or two or more of the following features.

In addition, in the efficient handover methods proposed in the present disclosure, different handover methods may be applied to different bearers.

- Data transmission or reception (uplink or downlink data transmission and reception) through each protocol layer device (PHY layer device or MAC layer device or RLC layer device or PDCP layer device) of the source base station and the first plurality of bearers. When the performing terminal receives a handover command message (for example, a handover command message or an RRC Reconfiguration message) from the source base station, the terminal corresponds to the protocol layer devices of the first plurality of bearers (for example, the same bearer identifier Setting up the protocol layer devices of the new second plurality of bearers, and without interrupting data transmission or reception (uplink or downlink data transmission and reception) through the first plurality of bearers with the source base station, It may be characterized in that it continuously maintains and performs data transmission/reception (uplink or downlink data transmission and reception).

- In the above, after the terminal receives the handover command message, the protocol layer devices (PHY layer device, MAC layer device, RLC layer device, or PDCP layer device) of the second plurality of bearers that are newly established are the handover command message. It characterized in that it is configured for data transmission and reception with the target base station based on the bearer configuration information or protocol layer device information included in the.

- In the above, the terminal performs data transmission or reception (uplink or downlink data transmission and reception) with the source base station by the protocol layer devices of the first plurality of bearers, while being used as the protocol layer device of the second plurality of bearers (e.g. For example, the MAC layer device) may be characterized in that it performs a random access procedure to the target base station. In the above, the random access procedure may include preamble transmission or random access response reception, message 3 transmission, or message 4 reception (for example, contention resolution MAC CE or uplink transmission resource reception).

- In the above, the UE performs data transmission or reception with the source base station to the protocol layer devices of the first plurality of bearers, and random access to the target base station to the protocol layer devices of the second plurality of bearers (for example, the MAC layer device). After completing the procedure, it may be characterized in that a handover completion message is transmitted to the target base station to the protocol layer devices of the second plurality of bearers.

- In the above, the terminal performs data transmission or reception with the source base station by the protocol layer devices of the first plurality of bearers, while the protocol layer device of the second plurality of bearers transmits or receives data randomly to the target base station (for example, the MAC layer device). After completing the access procedure, transmitting a handover completion message to the target base station to the protocol layer devices of the second plurality of bearers, and performing data transmission/reception (uplink or downlink).

- In the above, when the terminal successfully completes the random access procedure to the target base station and receives the uplink transmission resource from the target base station for the first time, the terminal stops transmitting data to the source base station to the protocol layer devices of the first plurality of bearers and uplinks. It may be characterized in that the link transmission is switched to transmit data to the target base station through a plurality of second bearers.

- In the above, when the terminal receives the handover command message, it continues to transmit and receive data (uplink or downlink data transmission and reception) with the source base station to the protocol layer devices of the first plurality of bearers, and the second plurality of bearers. When performing a random access procedure to the target base station with the protocol layer devices of the target base station, successfully completing the random access procedure, and receiving the uplink transmission resource from the target base station for the first time, the terminal is transferred to the protocol layer devices of the first plurality of bearers. It may be characterized in that the transmission of uplink data to the source base station is stopped and uplink data transmission is performed to the target base station only by protocol layer devices of a plurality of second bearers. In addition, the UE can continue to receive downlink data from the source base station to protocol layer devices of the first plurality of bearers, and continue to receive downlink data from the target base station to protocol layer devices of the second plurality of bearers. Characterized in that.

- In the above, the first bearer and the second bearer may be configured as a structure of a second PDCP layer device, and the second PDCP layer device structure is a first bearer for a source base station in one PDCP layer device ( For example, an RLC layer device or a MAC layer device or a PHY layer device) and a second bearer for the target base station (for example, an RLC layer device or a MAC layer device or a PHY layer device) are both connected, and the uplink data is Transmission may be performed through one of the first bearer or the second bearer through the PDCP layer device. That is, the UE performs a random access procedure to the target base station and transmits uplink data through the first bearer until the random access procedure is successfully completed and the uplink transmission resource is received from the target base station for the first time. If the base station performs the random access procedure, successfully completes the random access procedure, and receives the uplink transmission resource from the target base station for the first time, the terminal stops data transmission through the first bearer and switches to transmit the uplink data to the second. It can be transmitted to the target through a bearer. In this case, in the second PDCP layer device structure, the UE may receive downlink data from the source base station or the target base station through the first bearer or the second bearer.

Hereinafter, in the present disclosure, efficient handover procedures without data interruption time are proposed based on the above characteristics.

And when the terminal performs the efficient handover method without data interruption time proposed in the present disclosure, if the terminal fails to handover, the terminal quickly source using the features of the efficient handover method proposed in the present disclosure. The connection can be re-established by falling back to the base station. A characteristic of the efficient handover method proposed in the present disclosure may specifically mean that the terminal maintains a connection with the source base station even when performing a handover procedure. In addition, the present disclosure proposes a specific method of falling back by using a wireless connection connected to an existing source base station even if the terminal fails to handover.

The present disclosure provides a method and apparatus for efficiently performing different handover methods for each bearer in a next-generation mobile communication system.

The present disclosure relates to a method and apparatus for performing fallback when a handover fails when an efficient handover method without interruption of data transmission/reception is performed during handover in a next-generation mobile communication system.

According to an embodiment, in a next-generation mobile communication system, an efficient handover method may be required to support a service with low transmission delay and no data loss. In addition, in the case of a handover failure, a method of minimizing data downtime and falling back may be needed.

In the present disclosure, when a handover is performed in a next-generation mobile communication system, efficient and various handover methods can be proposed to prevent a data interruption time due to handover from occurring. Through this, a service without data loss can be supported. And, in the case of a handover failure, efficient methods for allowing the terminal to quickly fall back to the source base station are described.

1A is a diagram illustrating a structure of an LTE system to which the present disclosure can be applied.

Referring to Figure 1a, as shown, the radio access network of the LTE system is a next-generation base station (Evolved Node B, hereinafter ENB, Node B or base station) (1a-05, 1a-10, 1a-15, 1a-20) and It consists of MME (1a-25, Mobility Management Entity) and S-GW (1a-30, Serving-Gateway). User Equipment (hereinafter, UE or terminal) 1a-35 accesses an external network through ENBs 1a-05 to 1a-20 and S-GW 1a-30.

In FIG. 1A, ENBs 1a-05 to 1a-20 correspond to the existing node B of the UMTS system. The ENB is connected to the UEs 1a-35 through a radio channel and performs a more complex role than the existing Node B. In the LTE system, all user traffic including real-time services such as VoIP (Voice over IP) through Internet protocols are serviced through a shared channel, so status information such as buffer status, available transmission power status, and channel status of UEs A device that collects and performs scheduling is required, and ENB (1a-05 ~ 1a-20) is in charge of this. One ENB typically controls multiple cells. For example, in order to implement a transmission rate of 100 Mbps, the LTE system uses, for example, an orthogonal frequency division multiplexing (OFDM) in a 20 MHz bandwidth as a radio access technology. In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) that determines a modulation scheme and a channel coding rate according to a channel state of the terminal is applied. The S-GW 1a-30 is a device that provides a data bearer, and creates or removes a data bearer under the control of the MME 1a-25. The MME is a device responsible for various control functions as well as mobility management functions for a terminal, and is connected to a plurality of base stations.

1B is a diagram showing a radio protocol structure in an LTE system to which the present disclosure can be applied.

Referring to Figure 1b, the radio protocol of the LTE system is PDCP (Packet Data Convergence Protocol 1b-05, 1b-40), RLC (Radio Link Control 1b-10, 1b-35), MAC (Medium Access Control 1b-15, 1b-30). PDCP (Packet Data Convergence Protocol) (1b-05, 1b-40) is in charge of operations such as IP header compression/restore. The main functions of PDCP are summarized as follows.

-Header compression and decompression (ROHC only)

-Transfer of user data

-In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM

-Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

-Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM

-Retransmission of PDCP SDUs at handover and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM

-Encryption and decryption function (Ciphering and deciphering)

-Timer-based SDU discard in uplink.

Radio Link Control (hereinafter referred to as RLC) (1b-10, 1b-35) performs an ARQ operation by reconfiguring a PDCP packet data unit (PDU) to an appropriate size. The main functions of RLC are summarized as follows.

-Data transfer function (Transfer of upper layer PDUs)

-ARQ function (Error Correction through ARQ (only for AM data transfer))

-Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer)

-Re-segmentation of RLC data PDUs (only for AM data transfer)

-Reordering of RLC data PDUs (only for UM and AM data transfer)

-Duplicate detection (only for UM and AM data transfer)

-Error detection function (Protocol error detection (only for AM data transfer))

-RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer))

-RLC re-establishment

The MACs 1b-15 and 1b-30 are connected to several RLC layer devices configured in one UE, and perform an operation of multiplexing RLC PDUs to MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC are summarized as follows.

-Mapping between logical channels and transport channels

-Multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels

-Scheduling information reporting

-HARQ function (Error correction through HARQ)

-Priority handling between logical channels of one UE

-Priority handling between UEs by means of dynamic scheduling

-MBMS service identification

-Transport format selection

-Padding function

The physical layer (1b-20, 1b-25) channel-codes and modulates upper layer data, converts it into OFDM symbols, and transmits it to the radio channel, or demodulates OFDM symbols received through the radio channel and decodes the channel and transmits it to the upper layer. Do the action.

1C is a diagram showing the structure of a next-generation mobile communication system to which the present disclosure can be applied.

Referring to Figure 1c, as shown, the radio access network of the next-generation mobile communication system (hereinafter referred to as NR or 5G) is a next-generation base station (New Radio Node B, hereinafter referred to as NR gNB or NR base station) (1c-10) and NR CN (1c). -05, New Radio Core Network). The user terminal (New Radio User Equipment, hereinafter NR UE or terminal) 1c-15 accesses the external network through the NR gNB 1c-10 and NR CN 1c-05.

In FIG. 1c, the NR gNB 1c-10 corresponds to an Evolved Node B (eNB) of an existing LTE system. The NR gNB is connected to the NR UE 1c-15 through a radio channel and can provide a service superior to that of the existing Node B. In the next-generation mobile communication system, since all user traffic is serviced through a shared channel, a device that collects and schedules status information such as buffer status, available transmission power status, and channel status of UEs is required. (1c-10) is in charge. One NR gNB typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to the current LTE, it may have more than the existing maximum bandwidth, and an orthogonal frequency division multiplexing (hereinafter referred to as OFDM) may be used as a radio access technology, and additional beamforming technology may be applied. . In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) that determines a modulation scheme and a channel coding rate according to a channel state of the terminal is applied. The NR CN (1c-05) performs functions such as mobility support, bearer setup, and QoS setup. The NR CN is a device responsible for various control functions as well as a mobility management function for a terminal, and is connected to a plurality of base stations. In addition, the next-generation mobile communication system can be interlocked with the existing LTE system, and the NR CN is connected to the MME (1c-25) through a network interface. The MME is connected to an existing base station, the eNB (1c-30).

1D is a diagram showing a radio protocol structure of a next-generation mobile communication system to which the present disclosure can be applied. .

Referring to Figure 1d, the radio protocol of the next-generation mobile communication system is NR SDAP (1d-01, 1d-45), NR PDCP (1d-05, 1d-40), NR RLC (1d-10) in the terminal and the NR base station, respectively. , 1d-35), and NR MACs (1d-15, 1d-30).

The main functions of the NR SDAPs 1d-01 and 1d-45 may include some of the following functions.

- Transfer of user plane data

- QoS flow and data bearer mapping function for uplink and downlink (mapping between a QoS flow and a DRB for both DL and UL)

- Marking QoS flow ID for uplink and downlink (marking QoS flow ID in both DL and UL packets)

- A function of mapping a relective QoS flow to a data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

For the SDAP layer device, the UE may be configured with an RRC message to set whether to use the header of the SDAP layer device or the function of the SDAP layer device for each PDCP layer device, for each bearer, or for each logical channel, and the SDAP header When is set, the UE uses the NAS QoS reflection configuration 1-bit indicator (NAS reflective QoS) and the AS QoS reflection configuration 1-bit indicator (AS reflective QoS) in the SDAP header to map the QoS flow of the uplink and downlink and the data bearer. Can be instructed to update or reset. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used as data processing priority, scheduling information, etc. to support a smooth service.

The main functions of NR PDCP (1d-05, 1d-40) may include some of the following functions.

Header compression and decompression (ROHC only)

-Transfer of user data

-In-sequence delivery of upper layer PDUs

-Out-of-sequence delivery of upper layer PDUs

-Order reordering function (PDCP PDU reordering for reception)

-Duplicate detection of lower layer SDUs

-Retransmission of PDCP SDUs

-Encryption and decryption function (Ciphering and deciphering)

-Timer-based SDU discard in uplink.

In the above, the reordering function of the NR PDCP device refers to a function of rearranging the PDCP PDUs received from the lower layer in order based on the PDCP sequence number (SN), and the function of delivering data to the upper layer in the rearranged order. It may include, or may include a function of immediately delivering without considering the order, may include a function of recording lost PDCP PDUs by rearranging the order, and reporting the status of lost PDCP PDUs It may include a function of performing the transmission side, and may include a function of requesting retransmission of lost PDCP PDUs.

The main functions of the NR RLC (1d-10, 1d-35) may include some of the following functions.

-Data transfer function (Transfer of upper layer PDUs)

-In-sequence delivery of upper layer PDUs

-Out-of-sequence delivery of upper layer PDUs

-ARQ function (Error Correction through ARQ)

-Concatenation, segmentation and reassembly of RLC SDUs

-Re-segmentation of RLC data PDUs

-Reordering of RLC data PDUs

-Duplicate detection

-Protocol error detection

-RLC SDU discard function

-RLC re-establishment

In the above, the in-sequence delivery function of the NR RLC device refers to the function of delivering RLC SDUs received from the lower layer to the upper layer in order, and originally, one RLC SDU is divided into several RLC SDUs and received. If so, it may include a function of reassembling and delivering it, and may include a function of rearranging the received RLC PDUs based on an RLC sequence number (SN) or a PDCP sequence number (SN), and rearranging the order It may include a function of recording lost RLC PDUs, may include a function of reporting a status of lost RLC PDUs to a transmitting side, and a function of requesting retransmission of lost RLC PDUs. If there is a lost RLC SDU, it may include a function of transferring only RLC SDUs before the lost RLC SDU to a higher layer in order, or if a predetermined timer expires even if there is a lost RLC SDU, the timer It may include a function of delivering all RLC SDUs received before the start of the system in order to the upper layer, or if a predetermined timer expires even if there is a lost RLC SDU, all RLC SDUs received so far are sequentially transferred to the upper layer. It may include the ability to deliver. In addition, in the above, the NR RLC device may process RLC PDUs in the order of reception (regardless of the order of serial number and sequence number, in the order of arrival) and deliver them to the PDCP device regardless of the order (Out-of sequence delivery). In the case of a segment, the segments stored in the buffer or to be received in the future may be received, reconstructed into one complete RLC PDU, processed, and delivered to the PDCP device. The NR RLC layer may not include a concatenation function, and the function may be performed by the NR MAC layer or may be replaced with a multiplexing function of the NR MAC layer.

In the above, the out-of-sequence delivery function of the NR RLC device refers to the function of directly delivering RLC SDUs received from the lower layer to the upper layer regardless of the order. When received by being divided into SDUs, it may include a function of reassembling and transmitting them, and includes a function of storing the RLC SN or PDCP SN of the received RLC PDUs, sorting the order, and recording the lost RLC PDUs. I can.

The NR MACs 1d-15 and 1d-30 may be connected to several NR RLC layer devices configured in one terminal, and the main functions of the NR MAC may include some of the following functions.

-Mapping between logical channels and transport channels

-Multiplexing and demultiplexing function (Multiplexing/demultiplexing of MAC SDUs)

-Scheduling information reporting

-HARQ function (Error correction through HARQ)

-Priority handling between logical channels of one UE

-Priority handling between UEs by means of dynamic scheduling

-MBMS service identification

-Transport format selection

-Padding function

The NR PHY layer (1d-20, 1d-25) channel-codes and modulates upper layer data, makes it into OFDM symbols, and transmits it to the radio channel, or demodulates and channel-decodes OFDM symbols received through the radio channel to the upper layer. You can perform the transfer operation.

1E is a diagram illustrating a procedure for establishing a connection with a network by switching from an RRC idle mode to an RRC connected mode by a terminal in the present disclosure.

In FIG. 1e, the base station (gNB) may send an RRCConnectionRelease message to the terminal to switch the terminal to the RRC idle mode when the terminal transmitting and receiving data in the RRC connection mode does not transmit or receive data for a predetermined reason or for a predetermined period of time (1e- 01). In the future, the terminal for which the current connection is not established (hereinafter, the idle mode UE) performs an RRC connection establishment process with the base station when data to be transmitted occurs. The terminal establishes uplink transmission synchronization with the base station through a random access process and transmits an RRCConnectionRequest message to the base station (1e-05). In the RRCConnectionRequest message, the identifier of the terminal and the reason for establishing a connection (establishmentCause) are stored. The base station transmits an RRCConnectionSetup message so that the terminal establishes an RRC connection (1e-10).

The RRCConnectionSetup message includes configuration information for each service/bearer/each RLC device or logical channel or for each bearer, whether to use ROHC for each bearer/logical channel, and ROHC configuration information (e.g., ROHC version, initial information, etc. ), statusReportRequired information (information that the base station instructs the PDCP Status report to the terminal), drb-ContinueROHC information (configuration information to keep ROHC configuration information and use it as it is) are included in the PDCP layer device configuration information (pdcp-config) and transmitted Can be. In addition, RRC connection configuration information and the like are stored in the RRCConnectionSetup message. The bearer for RRC connection is also referred to as SRB (Signaling Radio Bearer), and is used for transmission and reception of an RRC message, which is a control message between the terminal and the base station.

The terminal that has established the RRC connection transmits an RRCConnetionSetupComplete message to the base station (1e-15). The RRCConnetionSetupComplete message includes a control message called SERVICE REQUEST that requests the MME to set up a bearer for a given service by the UE. The base station transmits the SERVICE REQUEST message contained in the RRCConnetionSetupComplete message to the MME or AMF (1e-20), and the MME or AMF determines whether to provide the service requested by the terminal. As a result of the determination, if the terminal decides to provide the requested service, the MME or AMF transmits an INITIAL CONTEXT SETUP REQUEST message to the base station (1e-25). The INITIAL CONTEXT SETUP REQUEST message includes QoS (Quality of Service) information to be applied when setting up the DRB (Data Radio Bearer), and security-related information (e.g., Security Key, Security Algorithm) to be applied to the DRB.

In addition, when the base station does not receive UE capability information from the MME or AMF, the base station may transmit a UE capability information request message to the UE to check capability information of the UE (1e-26). Upon receiving the UE capability information request message, the UE may construct and generate a UE capability information message and report it to the base station (1e-27). The terminal capability information message may include what kinds of handover methods the terminal supports. For example, information on whether the terminal supports or does not support the efficient handover method (dual activation protocol stack, dual active protocol stack, DAPS) proposed in the present disclosure can be reported to the base station through an indicator. have. When the base station checks the terminal capability information, the base station can instruct the terminal by defining an indicator for each handover method as to which handover to instruct in the handover command message when instructing the terminal to handover. For example, the base station may instruct the terminal of an efficient handover method (DAPS handover method) proposed in the present disclosure, and as another method, the DAPS handover method can be set for each bearer (DRB or SRB) of the terminal. I can. In the above, when the base station sets the DAPS handover method to the terminal, other handover methods (e.g., conditional handover method (setting of a plurality of target cells and setting of a plurality of conditions are set to the terminal), If the above conditions are satisfied in the selection procedure, the terminal is instructed to perform a handover procedure to one target cell) or a handover method without a random access procedure) to prevent data loss or transmission delay that may occur during handover. can do. The terminal may perform a handover procedure to the target base station according to the handover method indicated in the handover command message.

The base station exchanges a SecurityModeCommand message (1e-30) and a SecurityModeComplete message (1e-35) to configure security with the terminal. When the security configuration is completed, the base station transmits an RRCConnectionReconfiguration message to the terminal (1e-40).

The RRCConnectionReconfiguration message includes configuration information for each service/bearer/each RLC device or logical channel or for each bearer. ), statusReportRequired information (information that the base station instructs the PDCP Status report to the terminal), drb-ContinueROHC information (configuration information to maintain and use the ROHC configuration information as it is, included in the PDCP layer device configuration information (pdcp-config) to be transmitted. Can). In addition, the RRCConnectionReconfiguration message contains RRC connection configuration information. The bearer for RRC connection is also referred to as SRB (Signaling Radio Bearer), and is used for transmission and reception of an RRC message, which is a control message between the terminal and the base station.

In addition, the RRCConnectionReconfiguration message includes configuration information of the DRB in which user data is to be processed, and the terminal configures the DRB by applying the configuration information of the DRB and transmits an RRCConnectionReconfigurationComplete message to the base station (1e-45). The base station that has completed the DRB setup with the UE transmits an INITIAL CONTEXT SETUP COMPLETE message to the MME or AMF (1e-50), and the MME or AMF that receives it transmits the S1 BEARER SETUP message and S1 to set up the S-GW and S1 bearers. Exchange BEARER SETUP RESPONSE messages (1e-055, 1e-60). The S1 bearer is a connection for data transmission established between the S-GW and the base station, and corresponds to DRB and 1:1. When all of the above processes are completed, the terminal transmits and receives data through the base station and the S-GW (1e-65, 1e-70). This general data transmission process is largely composed of three steps: RRC connection setup, security setup, and DRB setup. In addition, the base station may transmit an RRC Connection Reconfiguration message to the terminal for a predetermined reason in order to newly, add, or change the configuration (1e-75).

In the present disclosure, the bearer may mean including SRB and DRB, SRB means Signaling Radio Bearer, and DRB means Data Radio Bearer. The SRB is mainly used to transmit and receive RRC messages of the RRC layer device, and the DRB is mainly used to transmit and receive user layer data. In addition, UM DRB refers to a DRB using an RLC layer device operating in an UM (Unacknowledged Mode) mode, and AM DRB refers to a DRB using an RLC layer device operating in an AM (Acknowledged Mode) mode.

In the present disclosure, the bearer for which the DAPS handover method is configured is a bearer whose identifier is included in the list of bearers for which the DAPS handover method is configured, or is not included in the list of bearers for which the DAPS handover method is not configured, or It may mean or indicate at least one bearer among a bearer having a DAPS handover method setting indicator in the configuration information for each bearer, or a bearer having a DAPS handover method configuration indicator in the PDCP layer device configuration information.

In the present disclosure, the bearer for which the DAPS handover method is not configured is a bearer whose identifier is not included in the list of bearers for which the DAPS handover method is configured, or is included in the list of bearers for which the DAPS handover method is not configured, Alternatively, it may mean or indicate at least one bearer among bearers without a DAPS handover method configuration indicator in the configuration information for each bearer, or a bearer in which the DAPS handover method configuration indicator is not configured in the PDCP layer device configuration information.

In the present disclosure, the source base station may be interpreted as a source cell (Pcell or Spcell or SCell) or a source cell group (cell group or master cell group), and the target base station is a target cell (Pcell or Spcell or SCell) or a target cell group ( cell group or master cell group).

1F is a diagram showing signaling procedures for performing handover proposed in the present disclosure in a next-generation mobile communication system.

The UE (1f-01) in the RRC connected mode state reports the cell measurement information (Measurement Report) to the current source base station (Source eNB, 1f-02) when a periodic or specific event is satisfied (1f-05). The source base station 1f-02 determines whether or not the terminal 1f-01 performs handover to an adjacent cell based on the measurement information. Handover is a technology for changing the source base station 1f-02, which provides a service to the terminal 1f-01 in the connected mode, to another base station (or a different cell of the same base station). If the source base station 1f-02 has determined the handover, the source base station 1f-02 is a new base station that will provide a service to the terminal 1f-01, that is, the target base station 1f-03 (Traget eNB, 1f-03). ) To request a handover by sending an HO (Handover) request message (for example, a Handover Preparation Information message) (1f-10). If the target base station 1f-03 accepts the handover request, it transmits a HO request Ack message (for example, a Handover Command message) to the source base station 1f-02 (1f-15). The source base station (1f-02) receiving the message transmits a handover command message (HO command message, an RRCReconfiguration message included in the DCCH (Dedicated Control Channel) of the HO request Ack message) to the terminal (1f-01) (1f -20). The handover command (HO command) message is extracted from the message received from the target base station 1f-03 by the source base station 1f-02 to the terminal 1f-01 and transmitted using an RRC Connection Reconfiguration message (1f- 20).

In the present disclosure, the source base station 1f-02 transmits a Handover Preparation information message (1f-10), and in response thereto, the target base station 1f-03 transmits a Handover Command message (1f-15) to the source base station 1f-02. ), we propose a method of determining an efficient DAPS handover method proposed in the present disclosure by using two messages (Handover Preparation information message (1f-10) and Handover Command message (1f-15)).

A first embodiment of determining an efficient DAPS handover method proposed in the present disclosure is as follows.

In the first embodiment, the subject determining the DAPS handover method may be the source base station 1f-02. In addition, in the first embodiment of the present disclosure, when the source base station 1f-02 requests the target base station 1f-03 for a DAPS handover method, the target base station 1f-03 always instructs or performs the DAPS handover method. can do.

- The source base station 1f-02 instructs the target base station 1f-03 that the source base station 1f-02 will perform the DAPS handover method proposed in the present disclosure by defining a new indicator in the Handover Preparation information message, and , DAPS handover method can be requested. The Handover Preparation information message may include current bearer configuration information or security key information or cell group configuration information or terminal 1f-01 capability information of the terminal 1f-01. The source base station 1f-02 can know in advance whether the target base station 1f-03 supports the DAPS handover method by implemenatively sharing the capabilities of the target base station 1f-03 in advance. The source base station 1f-02 instructs the target base station 1f-03 to perform the DAPS handover method, so that the source base station 1f-02 can perform early or early data forwarding. It is possible to inform the target base station 1f-03 of the presence and instruct the target base station 1f-03 to receive the data forwarding and prepare it so that it can be processed quickly. In the above, the source base station 1f-02 may request a request for a DAPS handover method for each bearer (DRB or SRB).

- When the target base station (1f-03) receives the Handover Preparation information message and confirms that the indicator requesting the DAPS handover method is included, the DAPS hand when configuring the RRCReconfiguration message to instruct the handover to the terminal 1f-01 RRCReconfiguration message including an indicator indicating the over method, and including bearer configuration information or bearer configuration information or security key information or cell group configuration information or system information required when the terminal 1f-01 performs the DAPS handover method Can be configured. The target base station 1f-03 may include the configured RRCReconfiguration message in the DL-DCCH message of the Handover command message and transmit it to the source base station 1f-02. The target base station 1f-03 may perform an indication of the DAPS handover method for each bearer (DRB or SRB).

- When receiving the Handover command message from the above, the source base station 1f-02 extracts the RRCReconfiguration message included in the Handover command message, and transmits the RRCReconfiguration message to the terminal 1f-01 to instruct handover. The source base station 1f-02 may check the indicated DAPS handover method for each bearer and perform the DAPS handover method for each bearer (DRB or SRB).

A second embodiment of determining an efficient DAPS handover method proposed in the present disclosure is as follows.

In the second embodiment of the present disclosure, the subject determining the DAPS handover method may be the target base station 1f-03. In addition, in the second embodiment of the present disclosure, when the source base station 1f-02 requests the target base station 1f-03 as an indicator of the DAPS handover method, the target base station 1f-03 rejects or accepts the request. Alternatively, another handover method may be indicated in the Handover command message to instruct the source base station 1f-02.

- The source base station 1f-02 instructs the target base station 1f-03 that the source base station 1f-02 will perform the DAPS handover method proposed in the present disclosure by defining a new indicator in the Handover Preparation information message, and , DAPS handover method can be requested. The Handover Preparation information message may include current bearer configuration information or security key information or cell group configuration information or terminal 1f-01 capability information of the terminal 1f-01. The source base station 1f-02 can know in advance whether the target base station 1f-03 supports the DAPS handover method by implemenatively sharing the capabilities of the target base station 1f-03 in advance. 1f-02) instructs the target base station 1f-03 to perform the DAPS handover method, indicating that the source base station 1f-02 can perform early data forwarding. 03) and instruct the target base station 1f-03 to prepare to receive the data forwarding and process it quickly. The source base station 1f-02 may request a request for a DAPS handover method for each bearer (DRB or SRB).

- When the target base station (1f-03) receives the Handover Preparation information message and confirms that the indicator requesting the DAPS handover method is included, whether or not the target base station (1f-03) can support the DAPS handover method or not Depending on the amount of transmission resources or scheduling, the request for DAPS handover of the source base station 1f-02 may be rejected or accepted, or another handover method may be instructed to the source base station 1f-02. The target base station 1f-03 may transmit a Handover command message including an indicator for rejecting a request for a DAPS handover request, an indicator for accepting, or an indicator indicating another type of handover method. When the target base station (1f-03) configures the RRCReconfiguration message to instruct the handover to the terminal (1f-01), when accepting the DAPS handover request, includes an indicator indicating the DAPS handover method, if DAPS When rejecting the handover request, includes an indicator indicating another handover method, and when the terminal 1f-01 performs a DAPS handover method or another handover method, necessary bearer configuration information or bearer configuration information or An RRCReconfiguration message including security key information, cell group setting information, or system information can be configured. In addition, the target base station 1f-03 may include the configured RRCReconfiguration message in the DL-DCCH message of the Handover command message and transmit it to the source base station 1f-02. In the above, the target base station 1f-03 may perform an indication of the DAPS handover method for each bearer (DRB or SRB).

- In the above, when the source base station 1f-02 receives the Handover command message, it can check whether the request for the DAPS handover method is accepted or rejected by checking the indicator included in the Handover command message. When the request for the DAPS handover method is accepted, the source base station 1f-02 performs the DAPS handover method, extracts the RRCReconfiguration message included in the Handover command message, and sends the RRCReconfiguration message to the terminal 1f-01 It can be transmitted to and instruct handover. When the source base station 1f-02 checks the indicator included in the Handover command message, if the request for the DAPS handover method is rejected, or if another handover method is instructed, the target base station 1f-03 indicates One other handover method can be performed. In addition, the source base station 1f-02 may extract the RRCReconfiguration message included in the Handover command message and transmit the RRCReconfiguration message to the terminal 1f-01 to instruct handover. As another method, the source base station (1f-02) reads the RRCReconfiguration message included in the handover command message, even if there is no separate indicator in the handover command message, and the handover method indicated by the target base station (1f-03) is It is possible to check whether it is the over method and whether the request for the DAPS handover method is accepted or rejected. The source base station 1f-02 may perform a handover method (eg, a DAPS handover method or another handover method) indicated in the RRCReconfiguration message. The source base station 1f-02 may check the indicated DAPS handover method for each bearer, and may perform the DAPS handover method for each bearer (DRB or SRB).

A third embodiment for determining an efficient DAPS handover method proposed in the present disclosure above is as follows.

In the third embodiment of the present disclosure, the subject determining the DAPS handover method may be a target base station. In addition, in the third embodiment of the present disclosure, the target base station 1f-03 checks the capabilities of the terminal 1f-01, and whether or not the target base station 1f-03 can support the DAPS handover method or not A handover method (for example, a DAPS handover method) may be determined according to the amount of transmission resources or scheduling.

- The source base station 1f-02 includes current bearer configuration information or security key information or cell group configuration information or terminal 1f-01 capability information of the terminal 1f-01 in the Handover Preparation information message. -03) can be sent a message to request a handover. The source base station 1f-02 can know in advance whether the target base station 1f-03 supports the DAPS handover method by implemenatively sharing the capabilities of the target base station 1f-03 in advance. If the target base station 1f-03 instructs to perform the DAPS handover method, the source base station 1f-02 may perform data forwarding early or early.

- In the above, the target base station 1f-03 receives the Handover Preparation information message, and the capability information of the terminal 1f-01 or whether the target base station 1f-03 can support the DAPS handover method or the current transmission resource The handover method (for example, DAPS handover) may be determined according to the amount of or scheduling. When determining the DAPS handover method, the target base station 1f-03 may transmit to the terminal 1f-01 including an indicator indicating the DAPS handover method in the Handover command message. When the target base station (1f-03) configures the RRCReconfiguration message to instruct the handover to the terminal (1f-01), when the DAPS handover is determined, includes an indicator indicating the DAPS handover method, if the DAPS handover When determining a handover method other than that, bearer configuration information or bearer configuration information required when the terminal 1f-01 performs a DAPS handover method or another handover method, including an indicator indicating another handover method. Alternatively, an RRCReconfiguration message including security key information, cell group setting information, or system information may be configured. The target base station 1f-03 may include the configured RRCReconfiguration message in the DL-DCCH message of the Handover command message and transmit it to the source base station 1f-02. The target base station 1f-03 may perform an indication of the DAPS handover method for each bearer (DRB or SRB).

- When receiving the Handover command message, the source base station 1f-02 may check whether the DAPS handover is determined by checking an indicator included in the Handover command message. When the DAPS handover method is instructed, the source base station 1f-02 also performs the DAPS handover method, extracts the RRCReconfiguration message included in the Handover command message, and transmits the RRCReconfiguration message to the terminal 1f-01 to hand Over can be ordered. When the source base station 1f-02 checks the indicator included in the Handover command message, if the DAPS handover method is not determined, or if another handover method is instructed, the target base station 1f-03 Handover method can be performed. In addition, the source base station 1f-02 may instruct handover by extracting the RRCReconfiguration message included in the Handover command message and transmitting the RRCReconfiguration message to the terminal 1f-01. As another method, the source base station 1f-02 reads the RRCReconfiguration message included in the Handover command message, even if there is no separate indicator in the Handover command message, and the handover method indicated by the target base station 1f-03 is It is possible to check whether it is the over method, and whether or not a decision on the DAPS handover method has been made, and if another handover method is indicated, the indicated handover method may be performed. The source base station 1f-02 may check the indicated DAPS handover method for each bearer and perform the DAPS handover method for each bearer (DRB or SRB).

The method of the first embodiment, the second embodiment, or the third embodiment for determining an efficient DAPS handover method proposed in the present disclosure may be combined to extend to a new embodiment.

According to an embodiment, in the RRCReconfiguration message, the base station may indicate to the terminal 1f-01 an efficient handover method (DAPS handover method) proposed in the present disclosure. A DAPS handover method can be set for each bearer (DRB or SRB) of ). For example, a new indicator indicating an efficient handover method (DAPS handover method) may be defined for bearer configuration information or PDCP configuration information or RLC configuration information for each bearer identifier or logical channel identifier in the RRC message, and the base station is the indicator It is possible to instruct the terminal 1f-01 to an efficient handover method for each bearer or for each logical channel identifier. When the base station sets the DAPS handover method to the terminal 1f-01, other handover methods (e.g., the conditional handover method (setting of multiple target cells and setting a plurality of conditions) to the terminal 1f-01 If the terminal (1f-01) satisfies the condition in the cell selection or reselection procedure, the terminal (1f-01) performs a handover procedure with one target cell) or a handover method without a random access procedure). By indicating together, data loss or transmission delay that may occur during handover can be prevented.

Upon receiving the RRCReconfiguration message, the terminal 1f-01 stops or continues data transmission/reception with the source base station 1f-02 according to the set handover method, and starts the T304 timer. T304 is the original setting of the terminal 1f-01 when the terminal 1f-01 does not succeed in handover to the target base station 1f-03 for a predetermined time (for example, when the T304 timer expires). Return and switch the terminal (1f-01) to the RRC Idle state. In addition, the terminal (1f-01) can trigger the RRC connection re-establishment procedure, an efficient handover method is set, and if the connection with the source base station (1f-02) is valid, it falls back to the source base station (1f). -02) can also be reported to the handover failure. The source base station (1f-02) transmits the sequence number (SN) status for uplink/downlink data to each bearer (for example, by RLC UM bearer or RLC AM bearer), and downlink or uplink If there is data, it is transmitted to the target base station 1f-03 (1f-30, 1f-35). The terminal 1f-01 attempts random access to the target cell indicated by the source base station 1f-02 (1f-40). The random access is for notifying the target cell that the terminal 1f-01 is moving through handover, and for synchronizing uplink synchronization. For random access, the terminal 1f-01 transmits a preamble ID provided from the source base station 1f-02 or a preamble corresponding to a randomly selected preamble ID to the target cell. After transmission of the preamble, after a specific number of subframes have passed, the terminal 1f-01 monitors whether a random access response message (RAR) is transmitted from the target cell. The time interval for monitoring RAR messages is referred to as a random access response window (RAR window). During the monitoring time period, if a random access response (RAR) is received (1f-45). The terminal 1f-01 transmits a handover complete (HO complete) message as an RRC Reconfiguration Complete message to the target base station 1f-03 (1f-55). When the random access response is successfully received from the target base station 1f-03 as described above, the terminal 1f-01 terminates the T304 timer (1f-50).

The target base station (1f-03) modifies the paths of bearers to the core network (1f-04) (i.e., MME/S-GW/AMF) in order to correct the paths of the bearers set as the source base station (1f-02). Requests (1f-60, 1f-65) and notifies the source base station 1f-02 to delete the UE context of the terminal 1f-01 (1f-70). The target base station 1f-03 may transmit an RRC message (e.g., RRCReconfiguration message, 1f-71) to the terminal 1f-01 and instruct to release the connection with the source base station 1f-02 as an indicator. . Alternatively, the target base station 1f-03 may instruct the terminal 1f-01 to release the connection with the source base station 1f-02 by transmitting MAC control information, RLC control information, or PDCP control information. have. The terminal 1f-01 attempts to receive data from the start of the RAR window to the target base station 1f-03, and after receiving the RAR, transmits an RRC Reconfiguration Complete message and receives a downlink transmission resource or an uplink transmission resource. Thus, data transmission/reception with the target base station 1f-03 is started.

According to an embodiment, the base station configures the second embodiment (DAPS handover method) proposed in the present disclosure using a handover command message or an RRC message (for example, an RRCReconfiguration message) to the terminal 1f-01 or Methods that can be applied when instructing are as follows. In the present disclosure, when the base station sets the DAPS handover method to the terminal 1f-01, or when the terminal 1f-01 receives a handover command message for setting the DAPS handover method from the base station, the following method One of the methods or several methods may be applied to perform the applied method.

-Method 1-1: When trying to instruct or set a handover to the terminal (1f-01), the base station (source base station (1f-02) or target base station (1f-03) or LTE base station or NR base station) is an RRCReconfiguration message Mobility Control Info or Reconfiguration With Sync setting information may be included. In the bearer configuration information (Radio Resource Config Dedicated or Radio Bearer Config) of the RRCReconfiguration message, the base station defines an indicator in SRB-ToAddMod or DRB-ToAddMod of SRB-ToAddModList, or DRB-ToAddModList, and each bearer through the defined indicator ( Each SRB or DRB) may indicate a DAPS handover method. In addition, the base station may indicate a DAPS handover method for each bearer by defining an indicator in pdcp-config in SRB-ToAddMod or DRB-ToAddMod. In addition, when the LTE base station instructs or sets the handover of the LTE RRCRecofiguration message to the terminal (1f-01), in the case of LTE, pdcp-config is not defined in the SRB-ToAddMod and the use of the default PDCP layer device setting is set. Therefore, the LTE base station defines an indicator in SRB-ToAddMod for SRB to set the DAPS handover method for each bearer, and for DRBs, the indicator is defined in pdcp-config in DRB-ToAddMod to define the DAPS handover method for each bearer. Can be set.

The terminal 1f-01 may perform a DAPS handover method for each bearer, for a bearer for which the DAPS handover method is set, according to the settings indicated in the received handover command message (RRCReconfiguration message), and the DAPS handover For bearers for which the method is not set, a general handover method can be performed. In addition, if the type of handover method for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message (e.g., MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) is included, and when a DAPS handover method is set for each bearer, the terminal 1f-01 uses the DAPS handover method of another handover method when performing a handover procedure for each bearer. It can be applied in preference to the type. For example, the terminal 1f-01 may perform a DAPS handover method for a bearer in which a DAPS handover method is set, and a handover for a bearer in which the DAPS handover method is not set according to the configuration. Instructs the type of handover method (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the command message, or The set handover method can be performed according to the set indicator. In addition, in order to reduce the complexity of implementing the terminal 1f-01, when the DAPS handover method is set to at least one bearer or a certain bearer, the terminal (1f) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message -01) for other handover methods (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) may not be indicated or set. In addition, when the terminal 1f-01 receives the handover command message (RRCReconfiguration message), when the DAPS handover method is set for at least one bearer for each bearer or a certain bearer in the handover command message (RRCReconfiguration message), the present The RRC layer device, SDAP layer device, MAC layer device, PHY layer device, or SRB processing method for performing the DAPS handover method proposed in the disclosure can be applied. A PDCP layer device or an RLC layer device processing method for performing the DAPS handover method proposed in the present disclosure may be applied.

- Method 1-2: When attempting to instruct or configure a handover to the terminal (1f-01), the base station (source base station (1f-02) or target base station (1f-03) or LTE base station or NR base station) indicates mobility in the RRCReconfiguration message. Control Info or Reconfiguration With Sync setting information may be included. The base station defines an indicator in the DRB-ToAddMod of the DRB-ToAddModList in bearer configuration information (Radio Resource Config Dedicated or Radio Bearer Config) of the RRCReconfiguration message, and instructs the DAPS handover method for each bearer (DRB) through the defined indicator. In addition, for SRBs, a separate indicator for setting the DAPS handover method may not be introduced. That is, when the DAPS handover method is set for at least one bearer (DRB) or a certain bearer (DRB) for each bearer in the received handover command message (RRCReconfiguration message), the terminal 1f-01 is proposed in the present disclosure. An SRB processing method for performing the DAPS handover method can be applied. In addition, the base station may indicate a DAPS handover method for each bearer by defining an indicator in pdcp-config in DRB-ToAddMod.

The terminal 1f-01 may perform a DAPS handover method for each bearer, for a bearer for which the DAPS handover method is set, according to the settings indicated in the received handover command message (RRCReconfiguration message), and the DAPS handover For bearers for which the method is not set, a general handover method can be performed. In addition, if the type of handover method for the terminal 1f-01 in mobility Control Info or Reconfiguration With Sync configuration information of the handover command message (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover) CHO) instructing or setting indicators are included, and when a DAPS handover method is set for each bearer, the terminal 1f-01 uses the DAPS handover method of another handover method when performing a handover procedure for each bearer. It can be applied in preference to the type. For example, the terminal 1f-01 may perform the DAPS handover method for a bearer in which the DAPS handover method is set for each bearer according to the configuration, and a handover command message for a bearer in which the DAPS handover method is not configured. Instructing or setting the type of handover method (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of The handover method set according to the indicator can be performed. In addition, in order to reduce the complexity of the implementation of the terminal 1f-01, when the DAPS handover method is set to at least one bearer or a certain bearer, the terminal (1f) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message -01) may be set so that other handover methods (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) cannot be indicated or set. In addition, when the terminal 1f-01 receives the handover command message (RRCReconfiguration message), when the DAPS handover method is set for at least one bearer for each bearer or a certain bearer in the handover command message (RRCReconfiguration message), the present The RRC layer device, SDAP layer device, MAC layer device, PHY layer device, or SRB processing method for performing the DAPS handover method proposed in the disclosure can be applied. A PDCP layer device or an RLC layer device processing method for performing the DAPS handover method proposed in the present disclosure may be applied.

- Method 2-1: When trying to instruct or set a handover to the terminal (1f-01), the base station (source base station (1f-02) or target base station (1f-03) or LTE base station or NR base station) in the RRCReconfiguration message Mobility Control Info or Reconfiguration With Sync configuration information may be included. The base station may define and include an indicator for indicating or setting the DAPS handover method in mobility Control Info or Reconfiguration With Sync, and may indicate that the DAPS handover method is configured for at least one bearer or a certain bearer through the indicator. . In addition, the base station defines an indicator in the bearer configuration information (Radio Resource Config Dedicated or Radio Bearer Config) of the RRCReconfiguration message, SRB-ToAddModList, or SRB-ToAddMod or DRB-ToAddMod of DRB-ToAddModList for each bearer (SRB or DRB). Separate) can indicate the DAPS handover method. In addition, the base station may indicate a DAPS handover method for each bearer by defining an indicator in pdcp-config in SRB-ToAddMod or DRB-ToAddMod. In addition, when the LTE base station instructs or sets the handover of the LTE RRCRecofiguration message to the terminal (1f-01), in the case of LTE, pdcp-config is not defined in the SRB-ToAddMod and the use of the default PDCP layer device setting is set. Therefore, the LTE base station defines an indicator in SRB-ToAddMod for SRB to set the DAPS handover method for each bearer, and for DRBs, the indicator is defined in pdcp-config in DRB-ToAddMod to define the DAPS handover method for each bearer. Can be set.

The terminal 1f-01 may perform a DAPS handover method for each bearer, for a bearer for which the DAPS handover method is set, according to the settings indicated in the received handover command message (RRCReconfiguration message), and the DAPS handover For bearers for which the method is not set, a general handover method can be performed. In addition, if the type of handover method for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message (e.g., MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) is included, and when a DAPS handover method is set for each bearer, the terminal 1f-01 uses the DAPS handover method of another handover method when performing a handover procedure for each bearer. Can be applied in preference to type For example, the terminal 1f-01 may perform a DAPS handover method for a bearer in which a DAPS handover method is set, and a handover for a bearer in which the DAPS handover method is not set according to the configuration. Instructs the type of handover method (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the command message, or The set handover method can be performed according to the set indicator. In addition, in order to reduce the complexity of implementing the terminal 1f-01, when the DAPS handover method is set to at least one bearer or a certain bearer, the terminal (1f) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message -01) for other handover methods (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) may not be indicated or set. In addition, when the terminal 1f-01 receives the handover command message (RRCReconfiguration message), the handover command message (RRCReconfiguration message) in Mobility Control Info or Reconfiguration With Sync instructs or sets the DAPS handover method. If included (or set), the RRC layer device or SDAP layer device or MAC layer device or PHY layer device or SRB processing method for performing the DAPS handover method proposed in the present disclosure may be applied, and the bearer For each bearer in which the DAPS handover method is configured, a PDCP layer device or a processing method of an RLC layer device for performing the DAPS handover method proposed in the present disclosure may be applied.

- Method 2-2: When trying to instruct or set a handover to the terminal (1f-01), the base station (source base station (1f-02) or target base station (1f-03) or LTE base station or NR base station) in the RRCReconfiguration message Mobility Control Info or Reconfiguration With Sync configuration information may be included. The base station may define and include an indicator for indicating or setting the DAPS handover method in mobility Control Info or Reconfiguration With Sync, and may indicate that the DAPS handover method is configured for at least one bearer or a certain bearer through the indicator. . In addition, the base station can instruct the DAPS handover method for each bearer (DRB) by defining an indicator in the DRB-ToAddMod of the DRB-ToAddModList in bearer configuration information (Radio Resource Config Dedicated or Radio Bearer Config) of the RRCReconfiguration message, For SRBs, a separate indicator for setting the DAPS handover method may not be introduced. That is, when the terminal 1f-01 receives the handover command message (RRCReconfiguration message), the handover command message (RRCReconfiguration message) receives the DAPS hand for at least one bearer (DRB) or a certain bearer (DRB) for each bearer. When the over method is set, the SRB processing method for performing the DAPS handover method proposed in the present disclosure may be applied. In addition, the base station 1f-03 may indicate a DAPS handover method for each bearer by defining an indicator in pdcp-config in DRB-ToAddMod.

The terminal 1f-01 may perform a DAPS handover method for each bearer, for a bearer for which the DAPS handover method is set, according to the settings indicated in the received handover command message (RRCReconfiguration message), and the DAPS handover For bearers for which the method is not set, a general handover method can be performed. In addition, if the type of handover method for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover) CHO) is included and the DAPS handover method is configured for each bearer, the terminal 1f-01 uses the DAPS handover method as a different type of handover method when performing a handover procedure for each bearer. It can be applied in priority over. For example, the terminal 1f-01 may perform a DAPS handover method for a bearer in which a DAPS handover method is set, and a handover for a bearer in which the DAPS handover method is not set according to the configuration. Instructs the type of handover method (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the command message, or The set handover method can be performed according to the set indicator. In addition, in order to reduce the complexity of implementing the terminal 1f-01, when the DAPS handover method is set to at least one bearer or a certain bearer, the terminal (1f) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message -01) for other handover methods (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) may not be indicated or set. In addition, when the terminal 1f-01 receives the handover command message (RRCReconfiguration message), the handover command message (RRCReconfiguration message) in Mobility Control Info or Reconfiguration With Sync instructs or sets the DAPS handover method. If included (or set), the RRC layer device or SDAP layer device or MAC layer device or PHY layer device or SRB processing method for performing the DAPS handover method proposed in the present disclosure may be applied, and the bearer For each bearer in which the DAPS handover method is configured, a PDCP layer device or a processing method of an RLC layer device for performing the DAPS handover method proposed in the present disclosure may be applied.

- Method 3-1: When instructing or setting a handover to the terminal (1f-01), the base station (source base station (1f-02) or target base station (1f-03) or LTE base station or NR base station) indicates mobility in the RRCReconfiguration message. Control Info or Reconfiguration With Sync setting information may be included. The base station defines and includes an indicator for indicating or setting the DAPS handover method in mobility Control Info or Reconfiguration With Sync, and can indicate that the DAPS handover method is configured for at least one bearer or a certain bearer through the indicator. have. In addition, the base station configures and includes a list of bearers for which the DAPS handover method is set in Mobility Control Info or Reconfiguration With Sync, and includes the identifiers (SRB or DRB) of the bearers for which the DAPS handover method is set in the list of bearers. , It can be indicated whether or not to set the DAPS handover method for each bearer. In addition, the base station configures and includes a list of bearers for which the DAPS handover method is not set in Mobility Control Info or Reconfiguration With Sync, and the identifiers of bearers for which the DAPS handover method is not set in the list of bearers (SRB or DRB ), it is possible to indicate whether to set the DAPS handover method for each bearer.

According to the configuration indicated in the received handover command message (RRCReconfiguration message), the terminal 1f-01 includes an identifier in the list of bearers for which the DAPS handover method is set or the bearer for which the DAPS handover method is set, for each bearer. For bearers that do not include an identifier in the list of bearers or bearers for which the DAPS handover method is not set, the DAPS handover method can be performed. A general handover method may be performed for a bearer not including an identifier in the list or a bearer including an identifier in a list of bearers for which the DAPS handover method is not configured. In addition, if the type of handover method for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover) CHO) instructing or setting indicators are included, and when the DAPS handover method is set for each bearer, the terminal 1f-01 uses the DAPS handover method of another handover method when performing a handover procedure for each bearer. It can be applied in preference to the type. For example, according to the configuration, the terminal 1f-01 is a bearer with an identifier in a list of bearers with a DAPS handover method set or a bearer with a DAPS handover method set for each bearer, or a DAPS handover method is not set. The DAPS handover method can be performed for a bearer that does not include an identifier in the bearer list, and a bearer or DAPS whose identifier is not included in the list of bearers for which the DAPS handover method is not set or the bearer for which the DAPS handover method is set. For bearers whose identifiers are included in the list of bearers for which the handover method is not configured, the type of handover method for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) may be indicated or a set handover method may be performed according to a set indicator. In addition, in order to reduce the complexity of implementing the terminal 1f-01, when the DAPS handover method is set to at least one bearer or a certain bearer, the terminal (1f) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message -01) for other handover methods (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) may not be indicated or set. In addition, the terminal 1f-01 includes an indicator indicating or setting the DAPS handover method in mobility Control Info or Reconfiguration With Sync of the handover command message (RRCReconfiguration message) when receiving the handover command message (RRCReconfiguration message). If (or set), the RRC layer device or SDAP layer device or MAC layer device or PHY layer device or SRB processing method for performing the DAPS handover method proposed in the present disclosure can be applied, and each bearer , DAPS proposed in this disclosure for a bearer with an identifier in which the DAPS handover method is set or a bearer with an identifier in the list of bearers in which the DAPS handover method is set, or a bearer in which the identifier is not included in the list of bearers with no DAPS handover method set A PDCP layer device or an RLC layer device processing method for performing the handover method may be applied.

- Method 3-2: When instructing or setting a handover to the terminal (1f-01), the base station (source base station (1f-02) or target base station (1f-03) or LTE base station or NR base station) is in the RRCReconfiguration message Control Info or Reconfiguration With Sync setting information may be included. The base station defines and includes an indicator for indicating or setting the DAPS handover method in mobility Control Info or Reconfiguration With Sync, and can indicate that the DAPS handover method is configured for at least one bearer or a certain bearer through the indicator. have. In addition, the base station configures and includes a list of bearers for which the DAPS handover method is set in Mobility Control Info or Reconfiguration With Sync, and includes the identifiers (SRB or DRB) of the bearers for which the DAPS handover method is set in the list of bearers. , It can be indicated whether or not to set the DAPS handover method for each bearer. In addition, the base station configures and includes a list of bearers for which the DAPS handover method is not set in Mobility Control Info or Reconfiguration With Sync, and the identifiers of bearers for which the DAPS handover method is not set in the list of bearers (SRB or DRB ), it is possible to indicate whether to set the DAPS handover method for each bearer. In addition, for SRBs, a separate indicator for setting the DAPS handover method may not be introduced. That is, when the terminal 1f-01 receives the handover command message (RRCReconfiguration message), the handover command message (RRCReconfiguration message) contains at least one bearer (DRB) or a DAPS hand to a certain bearer (DRB) for each bearer. When the over method is set, the SRB processing method for performing the DAPS handover method proposed in the present disclosure may be applied.

According to the configuration indicated in the received handover command message (RRCReconfiguration message), the terminal 1f-01 includes an identifier in the list of bearers for which the DAPS handover method is set or the bearer for which the DAPS handover method is set, for each bearer. For bearers that do not include an identifier in the list of bearers or bearers for which the DAPS handover method is not set, the DAPS handover method can be performed. A general handover method may be performed for a bearer not including an identifier in the list or a bearer including an identifier in a list of bearers for which the DAPS handover method is not configured. In addition, if the type of handover method for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover) CHO) is included and the DAPS handover method is configured for each bearer, the terminal 1f-01 uses the DAPS handover method as a different type of handover method when performing a handover procedure for each bearer. It can be applied in priority over. For example, terminal 1f-01) is a bearer with an identifier in a list of bearers with a DAPS handover method set or a bearer with a DAPS handover method set, or a bearer with no DAPS handover method set according to the configuration. The DAPS handover method can be performed for bearers that do not include an identifier in the list of, and bearers or DAPS hands that do not include an identifier in the list of bearers for which the DAPS handover method is not set or the bearers for which the DAPS handover method is set. For bearers whose identifiers are included in the list of bearers for which the over method is not configured, the type of handover method for the terminal (1f-01) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message (for example, MakeBeforeBreak A handover method set according to an indicator indicating or setting handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) may be performed. In addition, in order to reduce the complexity of implementing the terminal 1f-01, when the DAPS handover method is set to at least one bearer or a certain bearer, the terminal (1f) in the mobility Control Info or Reconfiguration With Sync configuration information of the handover command message -01) for other handover methods (for example, MakeBeforeBreak handover or Rach-skip handover or RACH-less handover or Conditional handover CHO) may not be indicated or set. In addition, the terminal 1f-01 includes (or, if configured) an indicator for indicating or setting the DAPS handover method in mobility Control Info or Reconfiguration With Sync in the received handover command message (RRCReconfiguration message). The RRC layer device, SDAP layer device, MAC layer device, PHY layer device, or SRB processing method for performing the DAPS handover method proposed in the disclosure can be applied, and the DAPS handover method is set for each bearer. PDCP layer device for performing the DAPS handover method proposed in the present disclosure for a bearer including an identifier in the list of bearers for which the handover method is configured, or for a bearer in which the identifier is not included in the list of bearers for which the DAPS handover method is not configured. Alternatively, a processing method of an RLC layer device may be applied.

Hereinafter, in the next-generation mobile communication system of the present disclosure, we propose a seamless handover method capable of minimizing a data interruption time due to handover or making it 0 ms.

The terminal 1f-01 sets the source base station 1f-02 and a plurality of first bearers, and configures each protocol layer device (PHY layer device or MAC layer device or RLC layer device or PDCP layer device) of each bearer. Although data transmission and reception (uplink or downlink data transmission and reception) can be performed, the following description of the present disclosure assumes that the terminal 1f-01 has one bearer in the drawings and description for convenience of explanation. do.

1G shows specific steps of a first embodiment of an efficient handover method for minimizing data interruption time due to handover according to an embodiment of the present disclosure.

According to an embodiment, in the first embodiment of the efficient handover method of FIG. 1G, the terminal 1g-20 transmits and receives data with the source base station 1g-05 in the first step (1g-01), Upon receiving the handover command message from the base station 1g-05, the connection with the source base station 1g-05 is released according to the handover method indicated in the handover command message (for example, RRCReconfiguration message), and the target base station It is possible to perform a random access procedure and a handover procedure as (1g-10). As another method, the terminal 1g-20 continuously transmits and receives data with the source base station 1g-05 in order to minimize the data interruption time that occurs during handover according to the indicated handover method. May be

According to an embodiment, the terminal 1g-20 is the target base station 1g-10 according to the handover method indicated in the handover command message received from the source base station 1g-05 in the second step (1g-02). ), when the terminal (1g-20) performs a random access procedure, or when transmitting a preamble to the μ base station (1g-10), or transmits data to an uplink transmission resource for the first time using a PUCCH or PUSCH transmission resource At this time, data transmission/reception (uplink data transmission and downlink data reception) with the source base station 1g-05 may be stopped.

According to an embodiment, the terminal 1g-20 (1g-20) completes the random access procedure to the target base station 1g-10 in the third step (1g-03), and the target base station 1g-10 The handover completion message may be transmitted, and data transmission/reception (uplink data transmission and downlink data reception) with the target base station 1g-10 may be started.

According to an embodiment, a first embodiment of an efficient handover method of the present disclosure is. In the present disclosure, a handover method performed when the DAPS handover method is not configured may be described.

1H shows specific steps of a second embodiment of an efficient handover method for minimizing data interruption time due to handover according to an embodiment of the present disclosure.

According to an embodiment, in the second embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 transmits and receives data with the source base station 1h-05 in the first step 1h-01, and then the source base station A handover command message can be received from (1h-05). In the handover command message, when the source base station 1h-05 indicates a handover method (for example, a DAPS handover method) according to the second embodiment of the efficient handover method proposed in the present disclosure, or handover for each bearer In the case of instructing, the terminal 1h-20 is the source base station 1h-05 and the first bearer in order to minimize the data interruption time that occurs during handover even when the handover command message is received. Data can be continuously transmitted and received through the protocol layer devices 1h-22.

In addition, the RRC layer device of the terminal 1h-20 indicates a handover method (for example, a DAPS handover method) according to the second embodiment of the efficient handover method proposed in the present disclosure in the handover command message. When confirming, or when confirming the indicator for the DAPS handover method for each bearer, the RRC layer device may deliver the indicator to each bearer or the PDCP layer device corresponding to the bearer in which the DAPS handover method is indicated. Upon receiving the indicator, the PDCP layer device may switch from the structure of the first PDCP layer device (1i-11 or 1i-12 in FIG. 1i) to the second PDCP layer device structure (1i-20 in FIG. 1i). .

The first step 1h-01 of FIG. 1H may describe a step in which the terminal 1h-20 receives a handover command message (RRCReconfiguration message) from the base station. In addition, when switching to the second PDCP layer device structure according to the settings included in the handover command message received by the terminal 1h-20, the terminal 1h-20 Protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device, 1h-21) of the bearer of the can be set or established in advance, and derive a security key for the target base station (1h-10) And update, and configure a header (or data) compression context for the target base station 1h-10. In addition, when the terminal 1h-20 receives a handover command message from the source base station 1h-05, and the source base station 1h-05 instructs the DAPS handover method proposed in the present disclosure in the handover command message , Or when a DAPS handover method is indicated for specific bearers, or when a PDCP reorder timer value is newly set, the terminal 1h-20 is the structure or function of the first PDCP layer device (1i-11 in FIG. 1I). Alternatively, in 1i-12), the structure or function of the second PDCP layer device proposed in the present disclosure (1i-20 in FIG. 1i) may be switched for each bearer or for a bearer in which the DAPS handover method is indicated. . When switching from the structure or function of the first PDCP layer device (1i-11 or 1i-12 in FIG. 1i) to the structure or function of the second PDCP layer device (1i-20 in FIG. 1i) proposed in the present disclosure, The terminal 1h-20 may update a variable for reordering to a PDCP serial number or a COUNT value expected to be received next, and stop and restart the reorder timer.

In addition, when receiving the handover command message (eg, RRC Reconfiguration message) in the above, the RRC layer device of the terminal 1h-20 may start a first timer (eg, T304). The first timer is when the terminal 1h-20 performs a random access procedure to the target base station 1h-10 in order to perform a handover and the random access procedure is successfully completed (for example, in the present disclosure When the proposed first condition is satisfied), it can be stopped. If the handover fails and the first timer expires, if the connection to the source base station 1h-05 is valid, the terminal 1h-20 performs a fallback and handovers the handover to the source base station 1h-05. The failure may be reported and connection recovery may be attempted, and if the connection to the source base station 1h-05 is not valid, an RRC connection re-establishment procedure may be performed.

The handover command message received by the terminal 1h-20 from the source base station 1h-05 is configured so that the data interruption time does not occur for each bearer, and the second bearer has the same bearer identifier as the first bearer, and It may contain information to establish. In addition, in the second embodiment of the present disclosure, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may logically operate as a single PDCP layer device, and a more detailed operation method thereof is shown in FIG. 1i. Explained in.

In addition, in the second embodiment of the present disclosure, when the terminal 1h-20 is capable of transmitting all of the uplink data to the source base station 1h-05 and the target base station 1h-10, the terminal 1h-20 In order to prevent a coverage reduction problem due to lack of transmission power or a problem (link selection) of determining which base station to request transmission resources to transmit uplink data to when transmitting uplink data, the terminal in the second embodiment (1h-20) can transmit uplink data to only one of the source base station 1h-05 and the target base station 1h-10. Specifically, in the second embodiment, if the UE 1h-20 does not have the ability to simultaneously transmit uplink data to different base stations at different frequencies or at the same frequency (dual uplink transmission), the UE 1h-20 In one time unit, uplink data can be transmitted to only one of the source base station 1h-05 and the target base station 1h-10. Accordingly, the terminal 1h-20 performs a scheduling request to only one of the source base station 1h-05 or the target base station 1h-10, and reports on the size of data to be transmitted from the PDCP layer device (e.g. For example, buffer status report transmission (Buffer status report) is transmitted to only one of the source base station (1h-05) or target base station (1h-10), and uplink only to one base station by receiving uplink transmission resources. Data can be transmitted. In addition, even if the terminal 1h-20 receives the handover command message from the source base station 1h-05, it initializes the MAC layer device of the first bearer to prevent data loss by continuing to transmit and receive data due to HARQ retransmission. I can't. In addition, in the case of an RLC layer device in the AM mode, RLC retransmission may also be continuously performed.

As another method, when the second embodiment (DAPS handover method) of the efficient handover method proposed in the present disclosure is indicated for each bearer in the handover command message, the terminal performs the second implementation in the handover command message. Yes (DAPS handover method) only for the PDCP layer device or RLC layer device or MAC layer device corresponding to the indicated bearer or logical channel identifier, or only for data corresponding to the bearer or logical channel identifier, the source base station (1h -05) and continue to transmit or receive data. In addition, even when the first condition proposed in the present disclosure is satisfied (for example, when the uplink data transmission is switched to the target base station 1h-10), the terminal performs the second execution in the handover command message. For only the PDCP layer device or RLC layer device or MAC layer device corresponding to the bearer or logical channel identifier for which YES (DAPS handover method) is indicated, RLC control data (RLC status report) or PDCP control data (ROHC feedback or PDCP status) Report) or HARQ retransmission may be continuously transmitted or received to the source base station 1h-05. In addition, when the second embodiment (DAPS handover method) of the efficient handover method proposed in the present disclosure is indicated or indicated for each bearer in the handover command message, the terminal may receive the second For a PDCP layer device, an RLC layer device, or a MAC layer device corresponding to a bearer or logical channel identifier for which an embodiment (DAPS handover method) is not indicated, data transmission or reception with the source base station (1h-05) may be stopped. have.

And, the terminal may receive a handover command message. In one embodiment, when the DAPS handover method proposed in this disclosure is indicated in the handover command message, or when the DAPS handover method is indicated for specific bearers, or the DAPS handover method for at least one bearer When this is set, or when a DAPS handover method is set for a certain bearer, or when QoS flow and bearer mapping information are newly set, the terminal is configured in the present disclosure in the structure or function (1j-10) of the first SDAP layer device. The structure or function (1j-20) of the proposed second SDAP layer device can be switched for each bearer or for a bearer in which the DAPS handover method is indicated.

And, in the structure of the second SDAP layer apparatus, it is necessary to process uplink data to be transmitted to the source base station and downlink data to be received from the source base station by maintaining the first QoS flow and bearer mapping information for the existing source base station. It can be a feature. The second QoS flow and bearer mapping information newly set in the handover command message can be set for the target base station, and are used to process uplink data to be transmitted to the target base station and downlink data to be received from the target base station. Can be That is, in the structure of the second SDAP layer device proposed in the present disclosure, the first QoS flow and bearer mapping information for the source base station or the second QoS flow and bearer mapping information are maintained, and the data and the target for the source base station are maintained. It may be characterized in that the data for the base station are classified and processed.

According to an embodiment, in the structure of the second SDAP layer device, the SDAP layer device transmits data received from a lower layer through a 1-bit indicator of the SDAP header or a 1-bit indicator of the PDCP header or information indicated by the PDCP layer device. It is possible to distinguish whether data is received from a source base station or data received from a target base station. And, if the base station instructs the DAPS handover method for each bearer to the terminal through a handover command message, the base station may always indicate the DAPS handover method for a default bearer (default DRB). Through this, when data is generated in a new QoS flow that does not correspond to the QoS flow and bearer mapping information during the DAPS handover procedure, the base station can enable the terminal to always transmit uplink data to the default bearer.

If the DAPS handover method is not configured for the default bearer, data interruption time may occur because uplink data transmission for a new QoS flow occurring during handover is impossible. In another method, the terminal receives a handover command message (e.g., RRCReconfiguration message), the second embodiment (DAPS handover method) is indicated, and SDAP layer device configuration information for the target base station in the RRC message or When the second QoS flow and bearer mapping information are configured, the UE may apply SDAP layer device configuration information or the second QoS flow and bearer mapping information when the first condition proposed in the present disclosure is satisfied. In addition, if the second embodiment (DAPS handover method) is indicated for each bearer in the handover command message above, when the UE maintains the first QoS flow and bearer mapping information for the source base station, the second embodiment indicates. Only the first QoS flow and bearer mapping information corresponding to the established bearer can be maintained and applied, and the first QoS flow and bearer mapping information corresponding to the bearer not indicated in the second embodiment above are released or applied. If the SDAP layer device configuration information for the target base station or the second QoS flow and bearer mapping information is configured in the RRC message, the terminal may be configured to the SDAP layer device configuration information or the second QoS flow and bearer mapping information. When the first condition proposed in the present disclosure is satisfied, it may be characterized in that it is applied for data transmission or reception with the target base station.

According to an embodiment, in the second embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 is the target base station 1h-10 indicated in the handover command message in the second step 1h-02. As a result, the terminal 1h-20 may perform a random access procedure through protocol layer devices of the second bearer. Even when performing a random access procedure through the protocol layer devices of the second bearer, the terminal 1h-20 transmits or receives (upward) data with the source base station 1h-05 through the protocol layer devices of the first bearer. Link data transmission or downlink data reception) can be continued. In the second step, the UE 1h-20 performs a cell selection or reselection procedure, and a random access procedure for the target cell indicated in the handover command message (RRCReconfiguration message) received from the source base station 1h-05 The steps to perform can be described.

According to an embodiment, in the second embodiment of the efficient handover method of FIG. 1H, if the terminal 1h-20 satisfies the first condition described above in the third step 1h-03, the DAPS handover method is performed. For the set bearer, transmission of uplink data to the source base station 1h-05 through the protocol layer devices 1h-22 of the first bearer is stopped, and the protocol layer devices 1h- 21), the uplink data may be transmitted to the target base station 1h-10. In this case, the terminal 1h-20 may continue to receive downlink data from the source base station 1h-05 and the target base station 1h-10 through protocol layer devices of the first bearer and the second bearer. The third step may be a step in which the terminal 1h-20 satisfies the first condition and switches uplink transmission from the source base station 1h-05 to the target base station 1h-10, and specifically, the terminal (1h-20) transmits uplink data to the source base station 1h-05 through the first bearer until the first condition is satisfied, and when the first condition is satisfied, the uplink data is transmitted through the first bearer. It may be a step of stopping transmitting the uplink data to the source base station 1h-05 and starting to transmit the uplink data to the target base station 1h-10 through the second bearer.

Specifically, in the second PDCP layer device structure proposed for a bearer in which the DAPS handover method is set in the present disclosure, the PDCP layer device satisfies the first condition while transmitting uplink data through the first bearer. Thus, when receiving an indicator from a lower layer device (when the random access procedure is successful from the MAC layer device to the target base station (1h-10)) or an upper layer device (when the first timer expires in the RRC layer device), the first Uplink data transmission through the second bearer may be stopped and switched to start uplink data transmission through the second bearer. In addition, like the PDCP layer device structure proposed in FIG. 1i, the receiving PDCP layer device 1h-21 of the second bearer may be driven as one device with the receiving PDCP layer device 1h-22 of the first bearer. , It is possible to continuously perform data reception from the source base station 1h-05 or the target base station 1h-10 using information such as stored transmission/reception data or serial number information or header compression and decompression context. The first condition may be one of the following conditions. The first condition proposed in the following is to propose an uplink data transmission switching time in which transmission resources are most efficiently used and data interruption time is minimized as much as possible.

- When the terminal 1h-20 successfully completes the random access procedure to the target base station 1h-10 through layer devices (for example, MAC layer devices) of the second bearer, or the terminal 1h-20 After successfully completing the random access procedure to the target base station 1h-10 through the layer devices of the second bearer (for example, the MAC layer device), the first uplink transmission resource from the target base station 1h-10 When is allocated, or when an uplink transmission resource is first indicated to the terminal 1h-20, it may be determined that the first condition is satisfied.

For example, if the terminal 1h-20 receives a handover command message from the source base station 1h-05 and is instructed to have random access to the target base station 1h-10, if the commanded random access If is a contention free random access procedure (CFRA, Contention Free Random Access) (for example, if a preamble or UE (1h-20) cell identifier (eg, C-RNTI) is assigned in advance),

◆When the terminal 1h-20 transmits a pre-designated preamble to the cell of the target base station 1h-10 and receives a Random Access Response (RAR) message, it can be considered that the random access procedure has been successfully completed. . Accordingly, when the terminal receives (or is allocated) the first uplink transmission resource allocated (or included or indicated) in the random access response message, it may be determined that the first condition is satisfied. . As another method, it may be determined that the first condition is satisfied when the UE receives the uplink transmission resource for the first time after RAR reception.

■If the terminal (1h-20) receives a handover command message from the source base station (1h-05) and is instructed to random access to the target base station (1h-10), if the instructed random access is contention-based random If the access procedure (CBRA, Contention-Based Random Access) (e.g., if a predetermined preamble or the terminal (1h-20) cell identifier (e.g., C-RNTI) is not assigned),

◆ The terminal (1h-20) transmits a preamble (for example, a random preamble) to the cell of the target base station (1h-10), receives a random access response (RAR) message, and the random access response message Sends message 3 (for example, a handover completion message) to the target base station using uplink transmission resources allocated (or included or indicated) in, and contention is resolved with message 4 from the target base station 1h-10 Upon receiving the MAC CE (Contention Resolution MAC CE) indicating that the terminal (1h-20) or receiving the uplink transmission resource through the PDCCH corresponding to the C-RNTI of the terminal (1h-20), the terminal (1h-20) -10), it can be seen that the random access procedure has been successfully completed. Therefore, when the UE (1h-20) monitors the PDCCH afterwards and receives the uplink transmission resource for the first time through the PDCCH corresponding to the C-RNTI of the UE (1h-20) (or when it is instructed for the first time). It can be judged that the condition of 1 is satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal 1h-20 can additionally transmit uplink data, the uplink transmission resource for the first time It may be determined that is received, and it may be determined that the first condition is satisfied. That is, when RAR is received, it may be determined that the UE has received the uplink transmission resource for the first time and that the first condition is satisfied.

- If the handover command message received by the terminal 1h-20 indicates a handover method that does not require a random access procedure (RACH-less handover),

■ If the handover command message contains uplink transmission resources for the target base station (1h-10),

◆ The terminal 1h-20 transmits a message 3 (for example, a handover complete message or an RRCReconfigurationComplete message) to the uplink transmission resource of the target base station 1h-10, and the terminal 1h-20 transmits a message 4 from the base station. Upon receiving the identifier confirmation MAC CE (UE Identity Confirmation MAC CE), or upon receiving the uplink transmission resource through the PDCCH corresponding to the C-RNTI of the terminal 1h-20, it is determined that the random access procedure has been successfully completed, and the It can be determined that the first condition is satisfied. As another method, after the random access procedure is successfully completed, when the UE monitors the PDCCH and receives the first uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE 1h-20, the first condition You may decide that you are satisfied with this.

■If the handover command message does not contain uplink transmission resources for the target base station (1h-10)

◆ When the terminal (1h-20) monitors the PDCCH for the target base station (1h-10) (or cell) and receives uplink transmission resources through the PDCCH corresponding to the C-RNTI of the terminal (1h-20), Or, when message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) is transmitted as the uplink transmission resource, and a UE (1h-20) identifier confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, or the terminal ( When the uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of 1h-20), it may be determined that the random access procedure has been successfully completed, and that the first condition is satisfied. As another method, after the random access procedure is successfully completed, when the UE monitors the PDCCH and receives the first uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE 1h-20, the first You can also judge that the conditions were satisfied.

Hereinafter, in the DAPS handover method proposed in the present disclosure, an efficient method of switching uplink data from the source base station 1h-05 to the target base station 1h-10 is proposed. Whether the above-described first condition is satisfied is determined by one of the following methods or a combination thereof in the MAC layer device or RRC layer device for the target base station 1h-10 corresponding to the second bearer Therefore, it can be identified.

- First method: For example, in the case of indicating DAPS handover in the RRCReconfiguration message received by the terminal 1h-20, the terminal 1h-20 is for the target base station 1h-10 corresponding to the second bearer. The MAC layer device may be configured, and the MAC layer device for the target base station may perform a random access procedure and check whether the above-described first condition is satisfied. In addition, if the first condition is satisfied, the MAC layer apparatus for the target base station performs uplink data transmission in the DAPS handover method proposed in the present disclosure from the source base station 1h-05 through the first bearer. The indicator to switch to the target base station 1h-10 through the bearer may be indicated as an indicator to an upper layer device (for example, a PDCP layer device) of a bearer in which the DAPS handover method is configured.

- Second method: As another method, for example, in the case of indicating DAPS handover in the RRCReconfiguration message received by the terminal 1h-20, the terminal 1h-20 is the target base station 1h corresponding to the second bearer. The MAC layer device for -10) is set, and the MAC layer device for the target base station performs a random access procedure, and can check whether the above-described first condition is satisfied. In addition, if the first condition is satisfied, the MAC layer apparatus for the target base station may indicate to a higher layer apparatus (for example, an RRC layer apparatus) that the first condition is satisfied. In addition, the higher layer device (for example, the RRC layer device) transmits uplink data in the DAPS handover method proposed in the present disclosure from the source base station 1h-05 through the first bearer to the target base station through the second bearer. The indicator to switch to (1h-10) may be indicated as an indicator to a lower layer device (for example, a PDCP layer device) of a bearer in which the DAPS handover method is configured. When the upper layer device (for example, the RRC layer device) satisfies the first condition proposed in the present disclosure, or when the random access procedure to the target base station 1h-10 is successfully performed, the first timer It can be stopped, and when the first timer is stopped, the RRC layer device may instruct the PDCP layer device of the bearer on which the DAPS handover method is configured to switch uplink data transmission as an indicator.

- Third method: When a DAPS handover is indicated in the RRCReconfiguration message received by the terminal 1h-20, the terminal 1h-20 is a MAC layer device for the target base station 1h-10 corresponding to the second bearer. And, if the RRC layer device of the terminal 1h-20 instructs a lower layer device (for example, a MAC layer device) to indicate that the RRC layer device performs a DAPS handover, the MAC layer device for the target base station performs a random access procedure. Then, it is possible to check whether the above-described first condition is satisfied. In addition, if the first condition is satisfied, the MAC layer device for the target base station performs uplink data transmission in the DAPS handover method proposed in the present disclosure from the source base station 1h-05 through the first bearer. The indicator to switch to the target base station 1h-10 through the bearer may be indicated as an indicator to an upper layer device (for example, a PDCP layer device) of a bearer in which the DAPS handover method is configured.

- Fourth method: In another method, when DAPS handover is indicated in the RRCReconfiguration message received by the terminal 1h-20, the terminal 1h-20 refers to the target base station 1h-10 corresponding to the second bearer. MAC layer device for the target base station can be set, and if the indicator that the RRC layer device of the terminal 1h-20 performs DAPS handover is indicated to the lower layer device (for example, the MAC layer device), the MAC layer device for the target base station May perform a random access procedure and check whether the above-described first condition is satisfied. In addition, if the first condition is satisfied, the MAC layer device may indicate to a higher layer device (for example, an RRC layer device) that the first condition is satisfied. When the indicator is checked, the higher layer device (for example, the RRC layer device) satisfies the first condition proposed in the present disclosure, or when the random access procedure to the target base station 1h-10 is successfully performed. , It is possible to stop the first timer. In addition, the higher layer device (for example, the RRC layer device) transmits uplink data in the DAPS handover method proposed in the present disclosure from the source base station 1h-05 through the first bearer to the target base station through the second bearer. The indicator to switch to (1h-10) may be indicated as an indicator to a lower layer device (for example, a PDCP layer device) of a bearer in which the DAPS handover method is configured.

According to the above-described first method, second method, third method, or fourth method, the second layer device (eg, RRC layer device) or a lower layer device (eg, MAC layer device) If the PDCP layer device receives an indicator indicating that the condition of 1 is satisfied or an indicator for switching uplink data transmission from the source base station 1h-05 to the target base station 1h-10 (for example, the DAPS handover method is If indicated), the PDCP layer device performs the protocol layer device operation proposed below in order to effectively switch uplink data transmission, and one of the following operations to prevent data loss due to uplink data transmission. Alternatively, a plurality of operations can be performed.

The following operations can be applied to a PDCP layer device connected to an AM DRB or UM DRB (RLC layer device operating in AM mode or RLC layer device operating in UM mode). If there is data to be transmitted in the buffer before the PDCP layer device satisfies the above-described first condition or receives an indicator that the first condition is satisfied, the size or amount of data to be transmitted (for example, PDCP data volume) Instructing the MAC layer apparatus of the first bearer for the source base station 1h-05 to notify that there is data to be transmitted, and perform uplink data transmission to the source base station 1h-05. Then, the MAC layer apparatus of the first bearer for the source base station 1h-05 may perform a scheduling request or a buffer status reporting procedure to receive uplink transmission resources allocated to the source base station 1h-05. When the above-described first condition is satisfied or when an indicator indicating that the first condition is satisfied, the uplink data transmission switching to the target base station 1h-10 for the bearer for which the DAPS handover method is set is performed next. It can be done like this:

- The UE uses the uplink or downlink ROHC context for the source base station (1h-05) without initializing it, and initializes the uplink or downlink ROHC context for the target base station (1h-10), and initializes the initial state (e.g. For example, you can start with the IR state in U mode).

- The PDCP layer apparatus switches the uplink data transmission from the first bearer for the source base station 1h-05 to the second bearer for the target base station 1h-10, for the source base station 1h-05. It may indicate to the MAC layer device of the first bearer that the size or amount of data to be transmitted is zero (or no). That is, the PDCP layer device may indicate to the MAC layer device of the first bearer that the data volume of the PDCP layer device is 0 to indicate that there is no more data to be transmitted (actually, the data to be transmitted is Even if there is, it may indicate that there is no data to be transmitted to the MAC layer device of the first bearer for the source base station 1h-05 in order to switch the uplink data transmission).

- However, as proposed in the present disclosure, when the handover method (DAPS handover method) of the second embodiment of the present disclosure is indicated or in the case of the bearer to which the handover method (DAPS handover method) of the second embodiment of the present disclosure is indicated. , Or if the first condition is satisfied, if RLC control data (RLC status report) or PDCP control data (PDCP status report or ROHC feedback) for the source base station 1h-05 is generated, the PDCP of the bearer The layer device instructs the MAC layer device for the source base station 1h-05 to a data volume corresponding to the RLC control data or PDCP control data, and provides the source base station 1h-05 or the source base station 1h-05. It is possible to perform data transmission to the RLC layer device for. However, as proposed in the present disclosure, when the handover method (DAPS handover method) of the second embodiment of the present disclosure is indicated or in the case of the bearer to which the handover method (DAPS handover method) of the second embodiment of the present disclosure is indicated. And, if the first condition is satisfied, if RLC control data (RLC status report) or PDCP control data (PDCP status report or ROHC feedback) for the target base station 1h-10 is generated, the PDCP of the bearer The layer device instructs a data volume corresponding to the RLC control data or PDCP control data to the MAC layer device for the target base station 1h-10 and for the target base station 1h-10 or the target base station 1h-10. Data can be transmitted to the RLC layer device. If the first condition is not satisfied in the above, the PDCP layer apparatus transfers the generated data (PDCP data PDU or PDCP control PDU) to the data volume corresponding to the data to the MAC layer for the source base station (1h-05). The device may be instructed, and data transmission may be performed to the source base station 1h-05 or the RLC layer device for the source base station 1h-05. Therefore, in the structure of the second PDCP layer device proposed for the bearer for which the DAPS handover method is set, when receiving an indicator indicating that the first condition is satisfied, the second PDCP layer device is PDCP control data or RLC control data or data to be transmitted to the bearer for the source base station 1h-05 or the MAC layer device for the source base station 1h-05 when instructing the data volume to the MAC layer device for -10) The data volume excluding the size of may be indicated to the MAC layer device for the target base station 1h-10.

- The PDCP layer device connected to the AM DRB (RLC layer device operating in the AM mode) (discard all previously stored PDCP PDUs (e.g., to prevent loss of original data, PDCP SDUs are not discarded). ) From the first data (for example, PDCP SDU) for which successful delivery is not confirmed from lower layers (for example, the RLC layer device corresponding to the first bearer for the source base station 1h-05) Before the condition is satisfied, or before receiving the indicator that the first condition is satisfied, the target base station for data (PDCP SDUs of the buffer) in ascending order of the allocated COUNT value (or PDCP serial number) ( A header compression procedure may be newly performed based on the header context for 1h-10). In addition, the PDCP layer apparatus performs the integrity procedure or encryption procedure again by applying the security keys for the target base station (1h-10), and configures the PDCP header to configure the lower layer device (second layer for the target base station (1h-10)). Retransmission or transmission may be performed by transferring it to the RLC layer device of the bearer of. That is, the PDCP layer device may perform cumulative retransmission from the first data for which successful delivery has not been confirmed. As another method, when performing retransmission in the above, the PDCP layer only for data for which successful delivery has not been confirmed from lower layers (e.g., RLC layer devices of the first bearer for the source base station 1h-05). The device may perform retransmission. More specifically, the PDCP layer device connected to the AM DRB (or the RLC layer device operating in the AM mode) is stored for transmission to the source base station 1h-05 through the first protocol layer device previously connected to the PDCP layer device. All of the PDCP PDUs being used are discarded (for example, PDCP SDUs may not be discarded to prevent the loss of original data), and lower layers, which are the first protocol layer devices for the source base station 1h-05 Receives an indicator that the first condition is satisfied or before the first condition is satisfied only for data for which successful delivery has not been confirmed (e.g., PDCP SDU) from (e.g., RLC layer devices) Based on the previously allocated COUNT value (or PDCP serial number), a header compression (or data compression) protocol context or security key corresponding to the target base station (1h-10) can be applied to perform a new header or data compression procedure. have. In addition, the PDCP layer device performs retransmission or transmission by performing the integrity procedure or the encryption procedure again, configuring the PDCP header, and transmitting it to the lower layer device, which is a second protocol layer device for transmission to the target base station (1h-10). I can. That is, the PDCP layer device may perform selective retransmission only on data for which successful delivery is not confirmed in order to prevent waste of transmission resources. In another method, the transmission or retransmission operation includes lower layers (e.g., a transmitting or receiving RLC layer device or a MAC layer device) as a first protocol layer device for transmitting data to the source base station 1h-05. It can also be released and executed. If the transmission or retransmission procedure is extended to UM DRB, the PDCP layer device connected to the RLC layer device operating in the UM mode, for data that has not yet been delivered to the lower layer device, or for data whose PDCP discard timer has not expired. , Or the data to which the PDCP serial number (or COUNT value) has already been allocated are regarded as data received from the upper layer device or newly received data, and the PDCP discard timer for each data is not restarted, and the target base station (1h-10) ) Header (or data) compression context or a security key for header (or data) compression on the data. Alternatively, the PDCP layer device may perform an encryption or integrity protection procedure, generate a PDCP header, splice and perform transmission or retransmission, process data in ascending order of the COUNT value allocated before the procedure was triggered, and transmit or retransmit You can do it. In addition, the window state variable of the PDCP layer device connected to the UM DRB or AM DRB is not initialized, but can be maintained and used as it is.

- In the above, if there is data to be transmitted in the buffer, the PDCP layer device instructs the MAC layer device of the second bearer for the target base station 1h-10 to indicate the size or amount of data to be transmitted (for example, PDCP data volume) to transmit the data. It is notified that there is a presence, and uplink data transmission switching may be performed to the target base station 1h-10. Then, the MAC layer apparatus of the second bearer for the target base station 1h-10 may perform a scheduling request or a buffer status reporting procedure to receive uplink transmission resources allocated to the target base station 1h-10.

- For the bearer indicated (or set) in the second embodiment (or DAPS handover method) above, when the first condition is satisfied, a data compression protocol (for the source base station) (e.g., Uplink data compression) protocol) may be released. Or, when the first condition is satisfied, the upper layer device (eg, RRC layer device) of the terminal sends configuration information or context for the data compression protocol (eg, Uplink data compression protocol) to the PDCP layer device. It can be instructed to turn off or reset it. However, the terminal releases the configuration information or context for the data compression protocol when the handover command message is received for the bearer for which the second embodiment (or DAPS handover method) is not indicated (or is not configured). Can (eg, Uplink data compression protocol). Or, when receiving the handover command message, the upper layer device (e.g., RRC layer device) of the terminal to the PDCP layer device (for the source base station) data compression protocol (e.g., Uplink data compression protocol) You can instruct or reset the setting information or context for it. This is because, for a bearer in which the DAPS handover method is configured, data must be compressed and transmitted to the source base station using the context or configuration information on the data compression protocol for the source base station until the first condition is satisfied. .

As described above, when a DAPS handover method is configured for at least one bearer among bearers configured for a terminal, or a DAPS handover method is configured for a certain bearer, if the first condition is satisfied, or When the terminal receives an indicator indicating that the first condition is satisfied, the terminal may perform one of the following methods for a bearer for which the DAPS handover method is not configured.

- Method 1: If the first condition is satisfied as described above, the upper layer device (e.g., RRC layer device) of the terminal is a PDCP re-establishment procedure for bearers or bearers for which the DAPS handover method is not configured. May trigger or request (even if the target base station configures the PDCP re-establishment procedure for the bearer in the handover command message, it may be performed when the first condition is satisfied). The PDCP layer device that has requested the PDCP re-establishment procedure may perform a different PDCP re-establishment procedure for each bearer. For example, the PDCP layer device initializes the window state variables for the UM DRB, and for data that has not yet been transmitted to the lower layer device or the PDCP discard timer has not expired, the header of the target base station is in ascending order of the COUNT value. (Or data) can be transmitted or retransmitted by compressing or encrypting based on the compression context or security key, or performing integrity protection. In addition, if the reordering timer is running, the PDCP layer device may stop, initialize, and sequentially process received data (PDCP SDU or PDCP PDU) and deliver them to the upper layer device. In addition, the PDCP layer device does not initialize the window state variables for AM DRB, and targets in ascending order of the PDCP serial number or COUNT value from the first data (PDCP SDU or PDCP PDU) for which successful delivery from the lower layer device is not confirmed. Transmission or retransmission may be performed by compressing, or encrypting, or performing integrity protection based on a header (or data) compression context or a security key of the base station. The reason for performing the PDCP re-establishment procedure when the handover command message is received for the bearer(s) for which the DAPS handover method is not set is not performed, and when the first condition is satisfied, , If the terminal fails the handover procedure to the target base station, it may perform fallback to the source base station.The bearers compress data in the header (or data) compression context of the target base station in the PDCP re-establishment procedure, and the target This is because data processed by performing encryption or integrity protection with the security key of the base station may become useless when the terminal needs to fall back, and thus must be discarded. In addition, when the terminal needs to fall back, by performing the PDCP re-establishment procedure again for the bearers, the data to be transmitted is compressed with the header (or data) compression context of the source base station, and the security key of the source base station is used. Because encryption or integrity protection must be performed again, unnecessary processing may occur. Accordingly, when the terminal performs the DAPS handover method, for a bearer for which the DAPS handover method is not configured, when the terminal receives a handover command message, the PDCP re-establishment procedure may be triggered or not performed. Alternatively, the target base station may not set the PDCP re-establishment procedure for the bearers in the handover command message, and when the first condition is satisfied, the PDCP re-establishment procedure may be triggered or performed. In addition, the PDCP re-establishment procedure is not performed for the bearer for which the DAPS handover method is configured.

- Second method: When a handover command message is received for a bearer(s) for which the DAPS handover method is not configured, the upper layer device (eg, RRC layer device) of the terminal triggers the PDCP re-establishment procedure or Can be requested. The PDCP layer device that has requested the PDCP re-establishment procedure may perform a different PDCP re-establishment procedure for each bearer. For example, the PDCP layer device that has received the request for the PDCP re-establishment procedure initializes window state variables for the UM DRB, and for data that has not yet been transmitted to the lower layer device or the PDCP discard timer has not expired. Transmission or retransmission may be performed by compressing, or encrypting, or performing integrity protection based on a header (or data) compression context or a security key of the target base station in ascending order of the COUNT value. Alternatively, the PDCP layer device that has requested the PDCP re-establishment procedure may stop, initialize, and sequentially process the received data (PDCP SDU or PDCP PDU) if the reordering timer is running, and transmit it to the upper layer device. . Alternatively, the PDCP layer device that has received the request for the PDCP re-establishment procedure does not initialize the window state variables for AM DRB, and the PDCP sequence from the first data (PDCP SDU or PDCP PDU) for which successful delivery is not confirmed from the lower layer device. Transmission or retransmission may be performed by compressing, encrypting, or performing integrity protection based on the header (or data) compression context or security key of the target base station in ascending order of number or COUNT value. When a handover command message is received for bearer(s) for which the DAPS handover method is not set, data is compressed in the header (or data) compression context of the target base station by the PDCP re-establishment procedure, and the security of the target base station Since data has been processed by performing encryption or integrity protection with a key, if the terminal fails the handover procedure to the target base station (e.g., if the first timer expires or the wireless connection to the target base station fails) And, if the UE performs fallback because it is possible to fall back to the source base station, the data generated or processed for transmission from the bearers to the target base station (for example, PDCP PDUs) are discarded and the header for the source base station ( Or data) In order to reprocess data (eg, PDCP SDUs) based on the compression context or security key, the terminal, the upper layer device (eg, RRC layer device) of the terminal, the DAPS handover method These bearers are not instructed to discard data (PDCP PDUs) processed based on configuration information (security key or header (or data) compression context) for the target base station, or PDCP re-establishment procedure or source base station. The configuration information (security key or header (or data) compression context) may be reset, and data may be requested or instructed to regenerate or process data based on the source base station configuration information.

Even after the terminal receives a handover command message (for example, RRCReconfiguration message) in the second embodiment of the efficient handover method proposed in the present disclosure (for example, the DAPS handover method), the terminal performs the source base station (1h- 05) through the protocol layer devices of the first bearer for the first bearer or the second bearer for the target base station 1h-10, the downlink data is continuously received from the source base station 1h-05 or the target base station 1h-10 can do. In one embodiment, so that the terminal can smoothly receive downlink data from the source base station 1h-05 (or target base station 1h-10), or the source base station 1h-05 (or target base station 1h- 10)) In order to smoothly transmit downlink data, for AM bearers, through protocol layer devices of the first bearer (or second bearer), the RLC status report, not data, is the source base station. It may be allowed to continuously perform uplink transmission to (1h-05) (or target base station 1h-10). That is, even if the UE has switched uplink data transmission to the target base station 1h-10 by satisfying the first condition above, the UE reports the RLC status or HARQ ACK or NACK or PDCP control data (PDCP) as described above. When it is necessary to transmit ROHC feedback or PDCP status report) to the source base station 1h-05, it may be allowed to transmit data through the first bearer for the source base station 1h-05. This is because, in the case of AM bearers, after transmitting data to the transmitting end, if successful delivery is not indicated by the RLC status report (ie, the RLC status report is not received), data cannot be continuously transmitted thereafter. Specifically, in the second embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 satisfies the first condition in the third step (1h-03), and the protocol layer apparatus of the first bearer Stop transmitting the uplink data to the source base station 1h-05 through the s1h-22, and switch the uplink data to the target base station through the protocol layer devices 1h-21 of the second bearer. Even if transmission to (1h-10) is started, the UE can smoothly receive downlink data from the source base station 1h-05 (or target base station 1h-10), or the source base station 1h- 05) Transmission of HARQ ACK or HARQ NACK information or RLC state through protocol layer devices of the first bearer (or second bearer) so that (or the target base station (1h-10)) can smoothly transmit downlink data Report (ACK or NACK information) or PDCP control data (eg, PDCP status report or ROHC feedback information) may be continuously transmitted.

In addition, in the second embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 satisfies the first condition in a third step (1h-03), and the protocol layer devices of the first bearer ( 1h-22) stops transmitting the uplink data to the source base station 1h-05, and switches the uplink data to the target base station 1h through the protocol layer devices 1h-21 of the second bearer. -10), in order to prevent data loss to the source base station (1h-05), the UE transmits data due to HARQ retransmission of the MAC layer device or data transmission due to retransmission of the AM mode RLC layer device. You can still do it. In the second embodiment of the efficient handover method of FIG. 1H above, the terminal 1h-20 satisfies the first condition in the third step (1h-03), and the protocol layer apparatus of the first bearer Stop transmitting the uplink data to the source base station 1h-05 through the s1h-22, and switch the uplink data to the target base station through the protocol layer devices 1h-21 of the second bearer. If transmission to (1h-10) is started, the source base station (1h-05) so that the uplink transmission resource to the target base station (1h-10) and the uplink transmission resource to the source base station (1h-05) do not collide. Alternatively, the target base station 1h-10 may allocate transmission resources to the terminal by dividing the time. If the uplink transmission resource to the target base station 1h-10 and the uplink transmission resource to the source base station 1h-05 collide and overlap, the terminal performs downlink data transmission from the source base station 1h-05. In order to continuously receive without maintenance or problem, the uplink transmission resource to the source base station 1h-05 may be prioritized and data transmission may be performed by the source base station 1h-05. As another method, if the uplink transmission resource to the target base station 1h-10 and the uplink transmission resource to the source base station 1h-05 collide and overlap, the terminal In order to maintain downlink data transmission, data transmission may be performed by the target base station 1h-10 by prioritizing uplink transmission resources to the target base station 1h-10.

Specifically, when the terminal receives a handover command message, when a handover (for example, a DAPS handover) corresponding to the second embodiment of the present disclosure is instructed or when instructed for each bearer, the terminal or the DAPS handover The bearer indicated by is, until the first condition is satisfied, performs a scheduling request through the first protocol layer device, and transmits a buffer status report to the source base station 1h-05 to receive uplink transmission resources. And uplink data can be transmitted. In addition, the terminal may receive downlink data from the source base station 1h-05. However, when the first condition is satisfied, the terminal no longer transmits data to the source base station 1h-05, but switches the uplink to perform a scheduling request through the second protocol layer device, and the buffer state The report may be transmitted to the target base station 1h-10 to receive uplink transmission resources and transmit uplink data to the target base station 1h-10. However, the UE may continue to receive downlink data from the source base station 1h-05, and even after switching uplink transmission, HARQ ACK or HARQ NACK or RLC status report or PDCP control data corresponding to the downlink data (e.g. PDCP status report or ROHC feedback information) may be continuously transmitted. In addition, even if the first condition is satisfied, the terminal may continue to receive downlink data from the source base station 1h-05 or the target base station 1h-10.

In the second embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20, if the second condition is satisfied in the fourth step (1h-04), the terminal is the protocol layer devices of the first bearer ( Through 1h-22), the reception of downlink data from the source base station 1h-05 (1h-05) may be stopped or the connection with the source base station 1h-05 may be released. In the above, the second condition may be one of the following conditions. In addition, the PDCP layer device 1h-21 of the second bearer stores transmission or reception data or serial number information stored in the PDCP layer device 1h-22 of the first bearer, or information such as header compression and decompression context. By using, it is possible to continuously perform data transmission or reception with the target base station 1h-10.

- When the terminal performs a random access procedure to the target base station 1h-10 through the layer devices 1h-21 of the second bearer and receives a random access response, the terminal may determine that the second condition has been satisfied. I can.

- When the terminal performs a random access procedure to the target base station 1h-10 through layer devices of the second bearer, receives a random access response, and constructs and transmits a handover completion message to the target base station 1h-10, The terminal may determine that the second condition is satisfied.

- When the terminal completes the random access procedure to the target base station (1h-10) through the layer devices of the second bearer and transmits data for the first time as a PUCCH or PUSCH uplink transmission resource, or a PUCCH or PUSCH uplink transmission resource When receiving for the first time, the terminal may determine that the second condition is satisfied.

- When the base station sets a separate timer to the terminal as an RRC message, and the timer expires, the terminal may determine that the second condition is satisfied.

■The timer is when the terminal receives a handover command message from the source base station 1h-05 or starts random access to the target base station 1h-10 (when a preamble is transmitted), or when the target base station 1h- It may be started when a random access response is received from 10), when a handover complete message is transmitted to the target base station 1h-10, or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

- After the terminal performs a random access procedure to the target base station (1h-10) through the layer devices of the second bearer, receives a random access response, configures and transmits a handover completion message to the target base station (1h-10) , When successful delivery of the handover completion message is confirmed by the MAC layer device (HARQ ACK) or the RLC layer device (RLC ACK), the UE may determine that the second condition is satisfied.

- After the terminal performs a random access procedure to the target base station 1h-10 through layer devices of the second bearer and receives a random access response or constructs and transmits a handover completion message to the target base station 1h-10, When an uplink transmission resource is first allocated from the target base station 1h-10, or when an uplink transmission resource is indicated for the first time, the terminal may determine that the second condition is satisfied.

- When the source base station 1h-05 performs the efficient handover proposed in the present disclosure, it may be determined when to stop transmitting downlink data to the terminal or when to release the connection with the terminal. For example, a predetermined method (e.g., when a predetermined timer expires (timer can be started after a handover instruction is possible) or the terminal from the target base station 1h-10 successfully performs handover to the target base station 1h-10 When the source base station (1h-05) receives an indication that it has been performed as, it may be determined by. In addition, if the downlink data is not received from the source base station 1h-05 for a predetermined time, the terminal may determine that the second condition has been satisfied, and determine that the connection with the source base station 1h-05 has been released. You can disconnect.

- The terminal receives an instruction to release the connection with the source base station 1h-05 from the target base station 1h-10 (for example, an RRC message (for example, an RRCReconfiguration message) or a MAC CE or RLC control PDU or a PDCP control PDU. If so, the terminal may determine that the second condition is satisfied.

- The terminal receives an instruction to release the connection with the source base station 1h-05 from the source base station 1h-05 (for example, an RRC message (for example, an RRCReconfiguration message) or a MAC CE or RLC control PDU or a PDCP control PDU. If so, the terminal may determine that the second condition is satisfied.

- If the terminal does not receive downlink data from the source base station 1h-05 for a predetermined period of time, the terminal may determine that the second condition has been satisfied.

- When the terminal successfully completes the random access procedure to the target base station 1h-10 through the layer devices of the second bearer (for example, the MAC layer device), or the terminal is targeted through the layer devices of the second bearer. When the random access procedure is successfully completed with the base station 1h-10 and the first uplink transmission resource is allocated from the target base station 1h-10, or when the uplink transmission resource is first indicated to the terminal, the terminal is It can be determined that the second condition has been satisfied.

For example, more specifically, if the UE receives a handover command message from the source base station (1h-05) and is instructed to random access to the target base station (1h-10), if the commanded random access is contention-free In the case of a random access procedure (CFRA, Contention Free Random Access) (for example, if a preamble or a terminal cell identifier (for example, C-RNTI) is assigned in advance)

◆When the terminal transmits a preamble designated in advance to the cell of the target base station (1h-10) and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed. When receiving the first uplink transmission resource allocated, included or indicated in the message, the terminal may determine that the second condition is satisfied. As another method, when the uplink transmission resource is received for the first time after RAR reception, the terminal may determine that the second condition is satisfied.

■If the terminal receives a handover command message from the source base station (1h-05) and is instructed to have random access to the target base station (1h-10), if the instructed random access is a contention-based random access procedure (CBRA) , Contention-Based Random Access) (for example, if a preamble or a terminal cell identifier (for example, C-RNTI) has not been assigned)

◆The terminal transmits a preamble (for example, a random preamble) to the cell of the target base station (1h-10), receives a random access response (RAR) message, and is allocated or included in the random access response message. MAC CE (Contention resolution MAC) indicating that message 3 (for example, a handover completion message) is transmitted using the designated or indicated uplink transmission resource, and contention resolution has been resolved with message 4 from the target base station 1h-10. CE), or when receiving uplink transmission resources through the PDCCH corresponding to the C-RNTI of the UE, the UE can be considered to have successfully completed the random access procedure to the target base station 1h-10. Therefore, after the UE monitors the PDCCH and receives the uplink transmission resource for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when it is instructed for the first time, the UE determines that the second condition is satisfied. I can. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, the terminal determines that the uplink transmission resource is received for the first time. It may be determined that the second condition is satisfied. That is, upon receiving the RAR, the UE may determine that the uplink transmission resource is received for the first time and that the second condition is satisfied.

- If, in the handover command message received by the terminal, a handover method that does not require a random access procedure (RACH-less handover) is also indicated,

■ If the handover command message contains uplink transmission resources for the target base station (1h-10),

◆ The terminal transmits a message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) to the uplink transmission resource of the target base station 1h-10, and confirms the terminal identifier in message 4 from the base station. CE), or when an uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the terminal, it may be determined that the random access procedure has been successfully completed. In addition, the terminal may determine that the second condition is satisfied. As another method, when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed, the UE determines that the second condition is satisfied. May be.

■If the handover command message does not contain uplink transmission resources for the target base station (1h-10)

- When the UE monitors the PDCCH for the target base station (1h-10) (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when receiving the uplink transmission resource as the uplink transmission resource, message 3 (e.g. For example, when transmitting a handover completion message or an RRCReconfigurationComplete message) and receiving a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, or when receiving an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE , The terminal may determine that the random access procedure has been successfully completed and determine that the second condition is satisfied. As another method, when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed, the UE determines that the second condition is satisfied. May be.

In the above, when the UE performs the second embodiment of the efficient handover method proposed in the present disclosure (for example, the DAPS handover method), if the RRC layer of the first bearer for the source base station 1h-05 of the UE That the device or the MAC layer device or the RLC layer device or the RRC layer device or the MAC layer device or the RLC layer device of the second bearer for the target base station (1h-10) satisfies the second condition proposed in the present disclosure. If confirmed, it may be indicated by an indicator that the second condition is satisfied to the PDCP layer device of the terminal or bearer performing the DAPS handover method. If the PDCP layer device of the terminal receives an indicator that the second condition is satisfied from a lower layer device or an upper layer device, or if the second condition is satisfied, the following for the bearer or the terminal for which the DAPS handover method is set. One or more of the procedures may be performed to successfully complete the second embodiment of the efficient handover method proposed in the present disclosure.

- The terminal may release the first bearer for the source base station 1h-05 and release the connection with the source base station 1h-05. In addition, before releasing the first bearer for the source base station 1h-05, an RLC re-establishment procedure may be performed on the RLC layer device corresponding to the first bearer for the source base station 1h-05 (for example, For example, if the rearrangement timer is running, the timer may be stopped or initialized, and if received data is stored in a buffer, the stored data may be processed and transferred to the upper layer device, and if the data to be transmitted is in the buffer, it may be discarded) or MAC layer devices can be initialized.

- When the terminal disconnects from the source base station 1h-05, the terminal triggers the PDCP status reporting procedure to report the reception status of downlink data received from the source base station 1h-05 to the target base station 1h-10, and By configuring the status report, the PDCP status report can be transmitted to the target base station 1h-10.

- When the second condition is satisfied, in the structure or function (1i-20) of the second PDCP layer device, the structure or function (1i-11 or 1i-12) of the first PDCP layer device proposed in the present disclosure ), you can switch for each bearer or for the bearer for which the DAPS handover method is indicated, initialize variables for realignment, stop and initialize the realignment timer, and for data stored in the buffer for realignment (e.g. For example, for data received from the source base station 1h-05), a decryption procedure or header (or data) decompression is performed by applying a security key or header decompression context for the source base station 1h-05, The terminal may discard the security key or header decompression context for the source base station 1h-05. In addition, the processed data can be delivered to the upper layer in ascending order. That is, in the above case, when the second condition is satisfied, the source base station 1h-05 for data stored in the buffer for rearrangement (for example, for data received from the source base station 1h-05). After performing a decryption procedure or header (or data) decompression by applying a security key or header decompression context for ), the security key or header decompression context for the source base station 1h-05 may be discarded. As another method, in the case where the UE satisfies the second condition, in the structure or function of the second PDCP layer device (1i-20), the structure or function of the third PDCP layer device proposed in the present disclosure (1i- 30), it is possible to switch for each bearer or for a bearer in which the DAPS handover method is indicated. In addition, the terminal can continue to use the variable for reordering and the reordering timer without stopping or initializing it. However, the data stored in the buffer for rearrangement (for example, data received from the source base station 1h-05) are decoded by applying a security key for the source base station (1h-05) or a header decompression context. After performing the procedure or header (or data) decompression, the security key or the header decompression context for the source base station 1h-05 may be discarded. In addition, the processed data can be delivered to the upper layer in ascending order. That is, in the above case, when the second condition is satisfied, the source base station 1h-05 for data stored in the buffer for rearrangement (for example, for data received from the source base station 1h-05). After performing a decryption procedure or header (or data) decompression by applying the security key or header decompression context for the source base station 1h-05, the security key or the header decompression context for the source base station 1h-05 may be discarded. In the above, the terminal is the QoS mapping information of the SDAP layer device for the source base station (1h-05) or the security key information for the source base station (1h-05) of the PDCP layer device or the header for the source base station (1h-05) (or Data) It is possible to release the compression context information or the RLC layer device or the MAC layer device for the source base station 1h-05. In the above structure or function of the second PDCP layer device (1i-20), it means that the structure or function of the first PDCP layer device proposed in the present disclosure is switched on a per bearer basis or for a bearer in which the DAPS handover method is indicated. May mean resetting the PDCP layer device. This reconfiguration may be performed when a reset indicator of the PDCP layer device is received from an upper layer device (eg, an RRC layer device). For example, the UE receives a handover command message, and a higher layer device (for example, an RRC layer device) sends a PDCP layer device reconfiguration indicator to the PDCP layer device of the bearer for a bearer for which the DAPS handover method is set. , The structure or function of the first PDCP layer device may be reset to the structure or function of the second PDCP layer device. If the second condition is satisfied, the higher layer device (for example, the RRC layer device) sends a PDCP layer device reconfiguration indicator to the PDCP layer device of the bearer, thereby indicating the structure or function of the second PDCP layer device. The structure or function of the PDCP layer device can be reset. For example, whenever a PDCP layer device reconfiguration indicator is received from an upper layer device (for example, an RRC layer device) in a toggle manner, the PDCP layer device of the bearer changes the structure or function of the first PDCP layer device to the second. The structure or function of the PDCP layer device may be reset, or the structure or function of the second PDCP layer device may be reset to the structure or function of the first PDCP layer device.

- When performing the DAPS handover method proposed in the present disclosure, and if the second condition proposed in this disclosure is satisfied, the UE is the second SDAP layer applied to each bearer or to the bearer in which the DAPS handover method is indicated. For the structure and function 1j-20 of the device, the first bearers for the source base station are released, and the structure and function 1j-10 of the first SDAP layer device can be switched back to be applied. And in the above, when the terminal satisfies the second condition, the terminal is the structure or function of the first SDAP layer device proposed in the present disclosure in the structure or function (1j-20) of the second SDAP layer device (1j-10). ), it is possible to switch for each bearer or for a bearer in which the DAPS handover method is indicated. In addition, the UE may maintain mapping information of the second bearer or the second QoS flow for the target base station and the bearer. And, before releasing the mapping information of the first bearer or the first QoS flow and the bearer for the source base station, the terminal is responsible for the data received from the source base station (for example, all data received from the source base station). After data processing is completed by applying the mapping information of the first QoS flow and the bearer, the mapping information of the first QoS flow and the bearer or the first bearer may be released. In addition, the terminal may deliver the processed data to a higher layer in ascending order. That is, in the above case, when the second condition is satisfied, the UE is the first QoS flow for the source base station and the bearer mapping information for data stored in the buffer (for example, data received from the source base station). Processes data by applying SDAP header information (e.g., reading SDAP header information and updating mapping information, configuring SDAP headers, or routing to an appropriate upper layer device or lower layer device based on the first QoS flow and bearer mapping information) Or a delivery procedure), then the mapping information of the first QoS flow and bearer for the source base station may be discarded. In the above, the SDAP layer device may define and apply a 1-bit indicator of a new SDAP header, a 1-bit indicator of a PDCP header, or SDAP control data (for example, a downlink end marker) or information indicated by a PDCP layer device. In addition, the SDAP layer device may check which data is the last data received from the source base station based on this. Therefore, after data processing is performed by applying the mapping information of the first QoS flow and bearer for the source base station to the last data received from the source base station, the mapping information of the first QoS flow and bearer for the source base station is discarded. I can. In the above, the SDAP layer apparatus may continue to maintain the mapping information of the second QoS flow and the bearer, and process uplink data or downlink data to the target base station based on this.

- The second PDCP layer device when initializing the MAC layer device for the source base station 1h-05 and converting the second PDCP layer device structure of the bearer to which the DAPS handover method is set to the first PDCP layer device structure In the structure, an RLC layer device re-establishment procedure or a release procedure may be performed for the RLC layer device for the source base station 1h-05.

■ In the present disclosure, when the second condition is satisfied or an indicator indicating that the second condition is satisfied is received from an upper layer device (eg, an RRC layer device) or a lower layer device (eg, a MAC layer device) If so, the procedure for re-establishing or releasing the RLC layer apparatus of the first bearer for the source base station in the above may specifically follow one of the following methods.

◆ First method: If the RLC layer device of the first bearer for the source base station is an LTE RLC layer device for a bearer in which the DAPS handover method is configured above, a higher layer device (for example, an RRC layer device ) May instruct to perform a re-establishment procedure for the LTE RLC layer device. Specifically, in the LTE RLC layer device, if the rearrangement timer is running, the rearrangement timer may be stopped or initialized. Alternatively, if there are stored data, the stored data is processed and transmitted to an upper layer device, thereby reducing a transmission delay due to a rearrangement timer. Also, variables can be initialized, and data for transmission can be discarded. Then, a higher layer device (eg, an RRC layer device) may instruct to release the LTE RLC layer device. However, if the RLC layer device of the first bearer for the source base station in the above is an NR RLC layer device, a higher layer device (for example, an RRC layer device) allows the NR RLC layer device to be released immediately without re-establishment. I can instruct. This is because, since the NR RLC layer device always performs out of order transmission, there may be no stored data, and even if there is stored data, it may be divided data, so there is no problem even if the stored data is simply discarded. Different procedures may be applied according to the RLC layer device configured for each bearer as described above.

◆ Second method: If the RLC layer device of the first bearer for the source base station is an LTE RLC layer device for a bearer for which the DAPS handover method is configured above, a higher layer device (for example, an RRC layer device) May instruct to perform a re-establishment procedure for the LTE RLC layer device. Specifically, if the reorder timer is running in the LTE RLC layer device, the reorder timer may be stopped or may be initialized. In addition, if there are stored data, the stored data is processed and transmitted to an upper layer device, thereby reducing a transmission delay due to a reorder timer. Also, variables can be initialized, and data for transmission can be discarded. Alternatively, an upper layer device (eg, an RRC layer device) may release the LTE RLC layer device. However, if the RLC layer device of the first bearer for the source base station in the above is an NR RLC layer device, a higher layer device (for example, an RRC layer device) allows the NR RLC layer device to be released immediately without re-establishment. I can instruct. This is because, since the NR RLC layer device always performs out of order transmission, there may be no stored data, and even if there is stored data, it may be divided data, so there is no problem even if the stored data is simply discarded. Different procedures may be applied according to the RLC layer device configured for each bearer as described above.

◆ Third method: If the RLC layer device of the first bearer for the source base station is an LTE RLC layer device for a bearer for which the DAPS handover method is configured above, the target base station connects the terminal to the source base station or When transmitting an RRC message (e.g., RRCReconfiguration) including an indicator to release the first bearer for the source base station to the terminal, configuration information of the LTE RLC layer device for the bearer in the RRC message (e.g., rlc- config) may include an indicator (eg, reestablishRLC) for re-establishing the LTE RLC layer device (or may include an indicator to release the LTE RLC layer device). Therefore, when an instruction to release the connection with the source base station is received or when the second condition is satisfied, a higher layer device (for example, an RRC layer device) can read the RRC message, and the LTE RLC According to an instruction for a re-establishment procedure (or release), the LTE RLC layer device may be instructed to perform a re-establishment procedure. Specifically, in the LTE RLC layer device, if the reorder timer is running, the reorder timer may be stopped or initialized. If there are stored data, the stored data is processed and transmitted to an upper layer device, so that transmission delay due to the reordering timer can be reduced. Also, variables can be initialized, and data for transmission can be discarded. Then, the higher layer device (for example, the RRC layer device) may release the LTE RLC layer device. If the RLC layer device of the first bearer for the source base station is an NR RLC layer device for a bearer in which the DAPS handover method is configured above, the target base station provides the terminal to the terminal for connection with the source base station or the source base station. When transmitting an RRC message (e.g., RRCReconfiguration) including an indicator to release the bearer of 1 to the terminal, in the RRC message, NR RLC in configuration information (e.g., rlc-config) of the NR RLC layer device for the bearer It may include an indicator to release the layer device and transmit. According to the RLC layer device configured for each bearer as described above, different procedures may be indicated by the target base station as an RRC message, and accordingly, the UE may apply each bearer.

◆ Fourth method: If the RLC layer device of the first bearer for the source base station is an LTE RLC layer device for a bearer for which the DAPS handover method is configured above, When transmitting an RRC message (e.g., RRCReconfiguration) including an indicator to release the first bearer for the source base station to the terminal, configuration information of the LTE RLC layer device for the bearer in the RRC message (e.g., rlc- config) may include an indicator (eg, reestablishRLC) for re-establishing the LTE RLC layer device (or may include an indicator to release the LTE RLC layer device). Therefore, when an instruction to release the connection with the source base station is received or when the second condition is satisfied, a higher layer device (for example, an RRC layer device) can read the RRC message, and the LTE RLC According to an instruction for a re-establishment procedure (or release), the LTE RLC layer device may be instructed to perform a re-establishment procedure. Specifically, in the LTE RLC layer device, if the reorder timer is running, the reorder timer may be stopped or initialized. If there are stored data, the stored data is processed and transmitted to an upper layer device, so that transmission delay due to the reordering timer can be reduced. Also, variables can be initialized, and data for transmission can be discarded. Alternatively, an upper layer device (eg, an RRC layer device) may release the LTE RLC layer device. If the RLC layer device of the first bearer for the source base station is an NR RLC layer device for a bearer in which the DAPS handover method is configured in the above, the target base station connects to the source base station or the first base station for the source base station. When transmitting an RRC message (e.g., RRCReconfiguration) including an indicator to release the bearer to the terminal, the RRC message includes an indicator to release the NR RLC layer device for the bearer or an indicator to re-establish the NR RLC layer device. I can. According to the RLC layer device configured for each bearer as described above, the target base station may indicate different procedures in an RRC message, and accordingly, the UE may apply each bearer.

- The receiving PDCP layer device can process or store the data received due to the re-establishment procedure of the lower layer device (for example, the RLC layer device), and for UM DRBs (from the source base station 1h-05). A header decompression procedure may be performed based on a header compression context (ROHC or Ethernet Header Compression (EHC)) (for the source base station 1h-05) on the received) stored data or all stored data.

- The receiving PDCP layer device can process or store the data received due to the re-establishment procedure of the lower layer device (e.g., RLC layer device), and for AM DRBs (from the source base station 1h-05). A header decompression procedure may be performed on the received) stored data or all stored data based on a header compression context (for the source base station 1h-05) (ROHC or Ethernet Header Compression (EHC)).

- Alternatively, the receiving PDCP layer device can process or store the received data due to the re-establishment procedure of the lower layer device (for example, the RLC layer device), and header compression for UM DRBs or AM DRBs. If the indicator to continue using the context (drb-Continue ROHC or drb-Continue EHC (Ethernet Header Compression)) is not set, the stored data (received from the source base station (1h-05)) or a header for all stored data A header decompression procedure may be performed based on a compression context (ROHC or Ethernet Header Compression (EHC)).

- After performing the above procedure, the transmitting or receiving PDCP layer apparatus may discard or release the security key or header compression contexts for the source base station 1h-05.

In FIG. 1f of the present disclosure, the base station defines indicators for the embodiments proposed in the present disclosure in the handover command message (e.g., RRCReconfiguration message) when transmitting a handover command message (1f-20) to the terminal. Whether to trigger the handover procedure corresponding to the embodiment may be instructed to the terminal. In addition, the terminal may perform a handover procedure according to the handover method indicated in the handover command message. For example, the terminal may perform handover to the target base station 1h-10 while minimizing data interruption time by performing the second embodiment (DAPS handover method) of the efficient handover method proposed in the present disclosure. As another method, in the handover command message, an indicator for the embodiments proposed in the present disclosure may be defined for each bearer, and a specific embodiment to which bearer to be applied during handover may be indicated in more detail. . For example, it may be instructed to apply the second embodiment of the present disclosure only to an AM bearer in which an RLC layer device driven in the AM mode is driven, or to a UM bearer in which an RLC layer device driven in the UM mode is driven. It can be extended and applied. In addition, it may be assumed that the embodiments proposed in the present disclosure are applied to DRB. However, if necessary (e.g., the UE maintains the SRB for the source base station 1h-05 and fails to handover to the target base station 1h-10, so that the handover fails to the SRB for the source base station 1h-05). If the message can be reported or recovered), it can also be extended and applied to the SRB.

In the embodiments of the present disclosure, the UE performs data transmission/reception with the source base station 1h-05 through the protocol layer devices of the first bearer, and the target base station 1h-10 through the protocol layer devices of the second bearer. When performing data transmission/reception, the MAC layer device of the first bearer and the MAC layer device of the second bearer operate separate DRX (Discontinuous Reception) cycles to reduce battery consumption of the terminal. That is, the UE may continue to apply the DRX cycle of the MAC layer device when transmitting and receiving data through the protocol layer devices of the first bearer even after receiving the handover command message. In addition, the terminal may stop DRX according to the first condition or the second condition of the present disclosure. In addition, the UE may separately apply the DRX cycle to the MAC layer device of the second bearer according to the instruction of the target base station 1h-10.

In addition, in the present disclosure, it means that the terminal stops uplink transmission to the source base station 1h-05 through the protocol layer devices of the first bearer and stops receiving downlink data from the source base station 1h-05. It means that the UE re-establishes, initializes, or releases protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device) of the bearer of 1.

In the embodiments of the present disclosure, for convenience of explanation, it has been described that the terminal sets the first bearer for the source base station 1h-05 or the second bearer for the target base station 1h-10. A case in which a plurality of first bearers for the base station 1h-05 or a plurality of second bearers for the target base station 1h-10 are configured can be easily extended and applied equally. As another method, a plurality of bearers for the plurality of target base stations 1h-10 can be easily extended and applied equally. For example, the terminal may perform a handover procedure to the first target base station (1h-10) to set the second bearers, and if the handover fails, the terminal is handed to the second target base station (1h-10). By performing the over procedure and setting the second bearers, the UE searches for and determines a cell that satisfies a predetermined condition (for example, a certain signal strength or more) among the plurality of target base stations 1h-10 and determines one It is also possible to perform a handover procedure by determining a cell.

FIG. 1I is a diagram illustrating structures of an efficient PDCP layer apparatus applied in a DAPS handover method, which is a second embodiment of an efficient handover method proposed in the present disclosure, and a method of applying the structures.

FIG. 1i is a detailed structure and functions of an efficient PDCP layer device applied in the DAPS handover method, which is a second embodiment of the efficient handover method proposed in the present disclosure, and the PDCP layer device proposed below while performing the DAPS handover procedure. It is characterized in that different PDCP hierarchical structures can be applied for each bearer at different points in time.

For example, before receiving the handover command message from the base station, the UE processes and transmits data by applying the first PDCP layer device structure and functions (1i-11 or 1i-12) proposed in this disclosure for each bearer. Can do it (1i-01).

However, if the terminal receives the handover command message from the base station in the above and indicates the DAPS handover method proposed in this disclosure in the handover command message or instructs the DAPS handover method for specific bearers, the terminal For each bearer or for bearers for which the DAPS handover method is indicated above, the second PDCP layer device structure and functions (1i-20) proposed in the present disclosure are applied to process and transmit or receive data. Can (1i-02). That is, when the terminal receives the handover command message and indicates the DAPS handover method proposed in the present disclosure in the handover command message, or when the DAPS handover method is indicated for specific bearers, In the structure or function (1i-11 or 1i-12) of the PDCP layer device of 1, the structure or function (1i-20) of the second PDCP layer device proposed in the present disclosure is a bearer in which the DAPS handover method is indicated or per bearer You can switch about.

In another method, when the first condition proposed in the present disclosure is satisfied, the terminal in the structure or function (1i-11 or 1i-12) of the first PDCP layer device used for each bearer in the present disclosure. The structure or function of the proposed second PDCP layer device (1i-20) can be switched for each bearer or for a bearer in which the DAPS handover method is indicated (1i-02). In addition, in the case where the UE receives the handover command message and indicates the DAPS handover method proposed in the present disclosure in the handover command message, or when the DAPS handover method is indicated for specific bearers, or the PDCP reorder timer value is When newly configured, the UE is configured for each bearer or DAPS in the structure or function (1i-20) of the second PDCP layer device proposed in the present disclosure in the structure or function (1i-11 or 1i-12) of the first PDCP layer device. When the handover method switches to the indicated bearer, the variable for reordering can be updated with the PDCP serial number or COUNT value that is expected to be received next, and the reordering timer can be stopped and restarted.

In addition, the UE performs the DAPS handover method proposed in the present disclosure, and if the second condition proposed in the present disclosure is satisfied, the second PDCP applied to each bearer or to the bearer in which the DAPS handover method is indicated. The structure and function (1i-20) of the layer device can be applied by releasing the first bearers for the source base station and switching back to the structure and function (1i-11 or 1i-12) of the first PDCP layer device. have. And in the above, when the terminal satisfies the second condition, the structure or function of the first PDCP layer device proposed in the present disclosure in the structure or function (1i-20) of the second PDCP layer device (1i-11 or 1i). -12), when switching for each bearer or for a bearer in which the DAPS handover method is indicated, a variable for reordering can be initialized, and the reorder timer can be stopped and initialized. In addition, the terminal applies a security key or header decompression context for the source base station to the data stored in the buffer for rearrangement (for example, data received from the source base station) to perform a decoding procedure or a header (or data). After decompression is performed, the security key or header decompression context for the source base station may be discarded. In addition, the terminal may deliver the processed data to a higher layer in ascending order. That is, in the above case, when the second condition is satisfied, the terminal sets a security key or header decompression context for the source base station for the data stored in the buffer for rearrangement (for example, for data received from the source base station). After applying the decryption procedure or header (or data) decompression, the security key for the source base station or the header decompression context may be discarded.

As another method, the UE performs the DAPS handover method proposed in the present disclosure, and if the second condition proposed in the present disclosure is satisfied, the first applied to each bearer or to the bearer in which the DAPS handover method is indicated. The structure and function 1i-20 of the PDCP layer apparatus 2 can be applied by releasing the bearers for the source base station and switching to the structure and function 1i-30 of the third PDCP layer apparatus. And, in the case where the UE satisfies the second condition, the structure or function of the second PDCP layer device (1i-20) to the structure or function of the third PDCP layer device (1i-30) proposed in the present disclosure. , When switching for each bearer or for a bearer in which the DAPS handover method is indicated, the variable for reordering and the reordering timer can be used continuously without stopping or initializing. However, the terminal compresses the decryption procedure or header (or data) by applying a security key or header decompression context for the source base station to the data stored in the buffer for rearrangement (for example, data received from the source base station). After performing the decompression, it is possible to discard the security key or header decompression context for the source base station. In addition, the terminal may deliver the processed data to the upper layer in ascending order. That is, in the above case, when the second condition is satisfied, the terminal sets a security key or header decompression context for the source base station for the data stored in the buffer for rearrangement (for example, for data received from the source base station). After applying the decryption procedure or header (or data) decompression, the security key for the source base station or the header decompression context may be discarded.

As suggested in FIG. 1i of the present disclosure above, the structure and function of the first PDCP layer device (1i-11 or 1i-12) or the structure of the second PDCP layer device, wherein the terminal is different for each bearer at different time points, and When performing handover by applying the function (1i-20) or the structure and function (1i-30) of the third PDCP layer device, the terminal can minimize data interruption time without data loss.

The structure of the first PDCP layer device (1i-11 or 1i-12) proposed in FIG. 1i is the following 1-1 PDCP layer device structure or the 1-2th PDCP layer device structure proposed in the present disclosure. Alternatively, it may have a 1-3th PDCP layer device structure or a 1-4th PDCP layer device structure, and an embodiment of the present disclosure may have the following features.

- 1> (if the structure of the PDCP layer device of 1-1) For example, if the PDCP layer device (eg E-UTRA PDCP layer device) connected to the AM RLC layer device (eg E-UTRA AM RLC layer device) If the UE applies the structure and function (1i-11) of the first PDCP layer device to the device or LTE PDCP layer device), it may have the following characteristics.

■2> The receiving PDCP layer device may first detect data outside the window or detect duplicate data with respect to received data. (The RLC AM has retransmission, and since the size of the LTE RLC SN and the PDCP SN may be different, duplicated data or data outside the window may be received. In the above, the window is a PDCP serial number or COUNT value area in which valid data is received. Represents.)

◆3> The terminal discards after performing a decoding procedure and a header decompression procedure before discarding the out-of-window data or redundant data. (Because it may contain useful information for the header decompression procedure (for example, IR packet or header compression information), it can be checked and discarded.)

■2> In the above, the terminal can decode the received data without being discarded in order and perform a header decompression procedure without ordering. This is because the E-UTRA AM RLC layer device arranges in order and delivers data to the PDCP layer device.

■2>And when passing to the upper layer, COUNT values are transferred in ascending order.

- 1> (if the structure of the 1-2th PDCP layer device) For example, if the UM RLC layer device (eg, E-UTRA UM RLC layer device) and the connected PDCP layer device (eg E-UTRA PDCP If the UE applies the structure and function (1i-11) of the first PDCP layer device to a layer device or an LTE PDCP layer device), an embodiment of the present disclosure may have the following features.

■2> It may be characterized by not performing a procedure for detecting data outside the window or detecting duplicate data. This is because the UM E-UTRA RLC layer device does not have a retransmission procedure.

■2> In addition, it may be characterized in that a decoding procedure is performed on the data received in the above and a header decompression procedure is performed.

■2> And the reordering procedure can be passed directly to the upper layer (for example, in ascending order). .

- 1> (If the structure of the 1-3th PDCP layer device) For example, if a split bearer (split bearer), a packet duplication bearer (packet duplication bearer) or a PDCP layer device configured as an LWA bearer (e.g., E- If the UE applies the structure and function (1i-11) of the first PDCP layer device to a UTRA PDCP layer device or an LTE PDCP layer device), an embodiment of the present disclosure always applies the sequence rearrangement procedure and the rearrangement timer. They can have the same characteristics.

■2> It may be characterized in that data detection outside the window or redundant data detection is first performed on the received data. (This is because data may be received at different times from retransmission of RLC AM or different RLC layer devices, and data outside the window or redundant data may be received because the sizes of the LTE RLC SN and the PDCP SN may be different.)

◆3> Execute the decryption procedure. However, the header compression decompression procedure is not performed. (Because E-UTRA PDCP cannot set header compression protocol for split bearer or LWQ bearer)

◆3> If integrity protection or verification procedures have been performed, discard them after performing them. If the integrity verification procedure fails, the data may be discarded and reported to an upper layer device.

◆3> Discard out-of-window or redundant data.

■2> If not discarded in the above, it may be characterized in that the decoding procedure is immediately performed without ordering the received data. In addition, when integrity protection or verification is set, integrity verification is performed. If an integrity protection or verification procedure has been performed, it is discarded after it has been performed. If the integrity verification procedure fails, the data may be discarded and reported to an upper layer device.

■2> Then, if the received data is sorted in order, and if the data is sequentially sorted in ascending order without gaps in the PDCP serial number or COUNT value, the header compression procedure is performed (the header compression procedure or the decompression procedure is set. Case) It may be characterized in that data is transferred to the upper layer in ascending order.

■2> If the reorder timer is running

◆3> If the data corresponding to the COUNT value that has the same value as subtracting 1 from the value held by the variable for reordering is transferred to the upper layer device, or there is no gap in the PDCP serial number (or COUNT value). If all the data has been delivered to the upper layer

●4> Stop and initialize the reorder timer.

■2> If the reorder timer is not running

◆3>If there is data stored in the buffer without being transferred to the upper layer device, or if there is a gap in the PDCP serial number (or COUNT value)

●4> Start the reorder timer.

●4> Then, the variable for reordering is updated with the PDCP serial number or COUNT value that is expected to be received next.

■2> If the reorder timer has expired

◆3>When the header decompression procedure is set in ascending order of the PDCP serial number or COUNT value for a value smaller than the reordering variable value for stored data, it performs the header decompression procedure and transfers it to the upper layer device.

◆3> If the header decompression procedure is set in ascending order of the PDCP serial number or COUNT value for values equal to or greater than the rearrangement variable value for stored data, the header decompression procedure is performed and transmitted to the upper layer device. .

◆3> Then, the variable value of the data finally transferred to the upper layer is updated with the PDCP serial number or COUNT value of the last transferred data.

◆3> If there is data stored in the buffer without being transferred to the upper layer device, or if there is a gap in the PDCP serial number (or COUNT value)

●4> Start the reorder timer.

●4>And update the variable for reordering with the PDCP serial number or COUNT value that is expected to be received next.

- 1> (If the structure of the PDCP layer device of the 1-4) For example, if the UE applies the structure and function (1i-12) of the PDCP layer device to the NR PDCP layer device, the sequence reorder procedure and the reorder timer Is always applied, and can have the following characteristics.

■2> It may be characterized by first performing a decoding procedure on the received data.

■2> When an integrity protection or verification procedure is set, an integrity protection or verification procedure may be performed on the received data, and if the integrity verification procedure fails, the data may be discarded and reported to a higher layer device.

■2> Detects data outside the window or detects duplicate data on the received data. (It may be characterized in that after the decryption procedure is performed, data outside the window or duplicate detection is performed. Another method is to detect data outside the window after performing the decryption procedure only when the integrity protection or verification procedure is set. If duplication detection is performed and integrity protection or verification procedures are not set, data detection outside the window or duplication detection can be performed, and then the decryption procedure can be performed only on the data that are not discarded.)

◆3> Discard out-of-window or redundant data.

■2> If not discarded in the above, ordering is performed on the received data, and if the data is sequentially arranged in ascending order without gaps in the PDCP serial number or COUNT value, the header compression procedure is performed (header compression procedure Alternatively, when a decompression procedure is set), data can be delivered to an upper layer in ascending order.

■2> And when transferring to the upper layer, it is transferred in ascending order of the COUNT value.

■2> If the reorder timer is running

◆3> If the data corresponding to the COUNT value that has the same value as subtracting 1 from the value held by the variable for reordering is transferred to the upper layer device, or there is no gap in the PDCP serial number (or COUNT value). If all data has been transferred to the upper layer, or the value of the variable storing the PDCP serial number or COUNT value of the data to be transferred to the upper layer is greater than or equal to the value of the variable for rearrangement.

●4> Stop and initialize the reorder timer.

■2> If the reorder timer is not running

◆3> If there is data stored in the buffer without being transferred to the upper layer device, or if there is a gap in the PDCP serial number (or COUNT value), or the value of the variable that stores the COUNT value of the first data that has not been transferred to the upper layer If it is less than the value of the variable for reordering

●4> Then, the variable for reordering is updated with the PDCP serial number or COUNT value that is expected to be received next.

●4> Start the reorder timer.

■2> If the reorder timer has expired

◆3> If the header decompression procedure is set in ascending order of the PDCP serial number or COUNT value for a value smaller than the reordering variable value for stored data, it performs the header decompression procedure and transfers it to the upper layer device.

◆3> If the header decompression procedure is set in ascending order of the PDCP serial number or COUNT value for values equal to or greater than the rearrangement variable value for stored data, the header decompression procedure is performed and transmitted to the upper layer device. .

◆3> Then, update the variable value for the first data that has not been transferred to the upper layer with the PDCP serial number or COUNT value of the first data that has not been transferred to the upper layer.

◆3> If there is data stored in the buffer without being transferred to the upper layer device, or if there is a gap in the PDCP serial number (or COUNT value), or the value of the variable that stores the COUNT value of the first data that has not been transferred to the upper layer If it is less than the value of the variable for reordering

●4> Then, the variable for reordering is updated with the PDCP serial number or COUNT value that is expected to be received next.

●4> Start the reorder timer.

The second PDCP layer device structure 1i-20 proposed in FIG. 1i may have the following PDCP layer device structure 2-1 or the PDCP layer device structure 2-2 proposed in the present disclosure, It can have the following characteristics.

In the present disclosure, a structure of a second PDCP layer device that is efficient in handover, such as 1i-20, is proposed. The structure of the second PDCP layer device may be applied to the second embodiment of an efficient handover method for minimizing data interruption time proposed in the present disclosure.

In the second PDCP layer device structure, the UE communicates with the source base station 1i-21 through protocol layer devices of the first bearer (for example, SDAP layer device or PDCP layer device or RLC layer device or MAC layer device). Data transmission or reception can be performed. In addition, the terminal can transmit or receive data with the target base station 1i-22 through the protocol layer devices of the second bearer (for example, SDAP layer device or PDCP layer device or RLC layer device or MAC layer device). have.

In the above, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may be configured in the terminal, respectively, but logically operate like one PDCP layer device, such as 1i-20. Specifically, the one PDCP layer device divides the functions of the PDCP layer device into the functions of the upper PDCP layer device (for example, a serial number assignment function or rearrangement function, an order transfer function, or a duplicate detection function), and each source base station and each Implementation of the functions of two lower PDCP layer devices for the target base station (e.g., decryption or encryption function or header (or data) compression or header (or data) decompression function or integrity protection or verification function or duplicate detection function) Can be. In addition, in the DAPS handover method as proposed above, the UE transmits uplink data transmission to the source base station and switches to the target base station when the first condition is satisfied, and downlink data is continuously received from the source base station and the target base station. I can. Therefore, the header (or data) compression protocol context maintains and applies only one context for the source base station or target base station for the uplink, and can maintain and apply two contexts for the source base station or target base station for the downlink. have.

Based on the second PDCP layer structure proposed above, the 2-1 PDCP layer structure (e.g., an E-UTRA PDCP layer device for a DAPS handover method) proposed in the present disclosure may have the following characteristics. have.

In the above, the upper transmission PDCP layer device function may perform a role of allocating a PDCP serial number to data received from the upper layer device. In addition, in the two lower transmission PDCP layer device functions (1i-21, 1i-22) for each source base station and each target base station, each source base station, each target base station, and the set separate security key are used to transmit to the source base station. The header (or data) compression context or security key set with the source base station is applied to the data, and the header (or data) compression context or security key set with the target base station is applied to the data to be transmitted to the target base station. If the compression procedure is set, the header (or data) compression procedure is applied, and if integrity protection is set, the integrity protection procedure is applied to the PDCP header and data (PDCP SDU), and the encryption procedure is applied and transmitted to the source base station. Data may be transmitted to the transmission RLC layer apparatus of the first bearer, and data to be transmitted to the target base station may be transmitted to the transmission RLC layer apparatus of the second bearer to perform transmission. In the above, the two lower transmission PDCP layer device functions (1i-21, 1i-22) perform parallel processing to perform header compression or integrity protection or encryption procedures in parallel in order to accelerate data processing speed. I can. In the two lower transmission PDCP layer device functions, the integrity protection or encryption procedure may be performed using different security keys. In addition, different data compression or integrity protection or encryption procedures may be performed logically by applying different compression contexts or security keys or security algorithms within one transmitting PDCP layer device.

In the above, the receiving PDCP layer device function is, in detail, for data received from each lower layer device, for data received from two RLC layer devices for each source base station and each target base station, the source base station or the target In the lower receiving PDCP layer device functions (1i-21, 1i-22) for the base station, out-of-window data detection or duplication detection procedure based on the PDCP serial number or COUNT value, data received from each RLC layer device Each can be performed independently. As another method, for convenience of implementation, a data detection or duplicate detection procedure outside the window based on the PDCP serial number or COUNT value may be performed on all received data without classifying each RLC layer device. As another method, for more accurate duplication detection, data outside the window is detected based on the PDCP serial number or COUNT value, and is performed on all received data without classifying each RLC layer device, and the duplicate detection procedure is performed on each RLC layer device. Each of the data received from may be independently performed. Alternatively, if data received from different base stations overlap each other, in order to prevent data loss for the header compression protocol, data detection outside the window based on the PDCP serial number or COUNT value does not distinguish each RLC layer device. It can be performed on all data received without. In addition, the duplication detection procedure may be performed on the entire data after receiving a decryption procedure, an integrity protection procedure, or a header (or data) decompression procedure for each data received from each RLC layer device. have.

In the above, the lower functions of the receiving PDCP layer device can directly apply a decryption procedure to received data using a separate header (or data) compression context or security key set with each source base station and each target base station. . In addition, when integrity protection is set for lower functions of the receiving PDCP layer device, an integrity verification procedure may be applied to the PDCP header and data (PDCP SDU).

In the PDCP layer device structure of the 2-1, a header (or data) decompression procedure may be immediately performed without ordering data received from RLC layer devices of the first bearer for each source base station, In addition, a header (or data) decompression procedure may be directly performed on data received from RLC layer devices of a second bearer for each target base station without ordering. In addition, in order to distinguish data received from RLC layer devices of the first bearer for each source base station and data received from RLC layer devices of the second bearer for each target base station, an indicator for each data It can be distinguished whether the data is received from the source base station or the data received from the target base station by defining. As another method, by defining a 1-bit indicator of the PDCP header, SDAP header, or RLC header, it is possible to distinguish whether data is received from the source base station or the target base station. In addition, the data received from the RLC layer devices of the first bearer for the source base station that has completed the header (or data) compression procedure above and the data received from the RLC layer devices of the second bearer for the target base station. For all, duplicate detection procedures based on the PDCP serial number or COUNT value (for each PDCP serial number or COUNT value, only one data (including previously received data or data transferred to a higher layer can be applied) The procedure of discarding all leftover) can be performed. And for all of the data received from the RLC layer devices of the first bearer for the source base station and the RLC layer devices of the second bearer for the target base station, the PDCP serial number or COUNT value. The rearrangement procedure may be performed in an ascending order based on, and data may be transmitted to the upper layer device in order. In the above, since one PDCP layer device can receive data from different base stations, that is, from the first bearer or the second bearer in any order, the reordering procedure may always be performed.

The two lower receiving PDCP layer device functions are parallel processing for performing header compression or integrity protection or encryption procedures in parallel to accelerate the data processing speed based on the PDCP serial number or COUNT value, respectively. I can do it. The integrity protection or encryption procedure or decompression procedure may be performed using different header (or data) compression contexts or security keys. In addition, by applying different header (or data) compression contexts or security keys or security algorithms in one transmitting PDCP layer device logically, integrity protection or encryption procedures or decompression procedures may be performed on different data. In addition, in the lower receiving PDCP layer device functions, out-of-sequence deciphering or an integrity verification procedure may be performed on each data received regardless of the order of the PDCP serial number or COUNT value.

When the one PDCP layer device distinguishes between the layer devices of the first bearer and the layer devices of the second bearer, considering that they are connected to different MAC layer devices, or to have different logical channel identifiers, Or, considering the fact that they are different RLC layer devices connected to different MAC layer devices, or considering that different encryption keys are used, layer devices of the first bearer (or first RLC layer devices) And second bearer layer devices (or second RLC layer devices) to perform encryption or decryption procedures with different security keys for uplink data and downlink data, and use different compression protocol contexts. It can be compressed or decompressed.

Based on the second PDCP layer structure proposed above, the 2-2 PDCP layer structure (for example, an NR PDCP layer device for a DAPS handover method) proposed in the present disclosure may have the following characteristics.

In the above, the upper transmission PDCP layer device function may perform a role of allocating a PDCP serial number to data received from the upper layer device. And in the two lower transmission PDCP layer device functions (1i-21, 1i-22) for each source base station and each target base station, each source base station, each target base station, and a separate security key set to the source base station are used. The header (or data) compression context or security key set with the source base station may be applied to the data to be transmitted, and the header (or data) compression context or security key set with the target base station is applied to the data to be transmitted to the target base station. Data) If the compression procedure is set, the header (or data) compression procedure is applied, and if integrity protection is set, the integrity protection procedure is applied to the PDCP header and data (PDCP SDU), the encryption procedure is applied, and the source base station Data to be transmitted may be transmitted to the transmission RLC layer apparatus of the first bearer, and the data to be transmitted to the target base station may be transmitted to the transmission RLC layer apparatus of the second bearer.

In the two lower transmission PDCP layer device functions (1i-21, 1i-22) above, parallel processing of header compression or integrity protection or encryption procedure is performed in parallel in order to accelerate data processing speed. can do. The integrity protection or encryption procedure may be performed by using different security keys in the two lower transmission PDCP layer device functions. In addition, it is possible to compress different data or perform an integrity protection or encryption procedure logically by applying different compression contexts or security keys or security algorithms in one transmitting PDCP layer device.

In the above, the receiving PDCP layer device function is a source base station or target base station for data received from each source base station and two RLC layer devices for each target base station in detail with respect to data received from each lower layer device. In the lower receiving PDCP layer device functions (1i-21, 1i-22) for each of the data received from each RLC layer device, a data detection or duplicate detection procedure outside the window is performed based on the PDCP serial number or COUNT value. Can be done independently. As another method, for convenience of implementation, a data detection or duplicate detection procedure outside the window based on the PDCP serial number or COUNT value may be performed on all received data without classifying each RLC layer device. As another method, the receiving PDCP layer device function performs detection of data outside the window based on the PDCP serial number or COUNT value for more accurate duplication detection on all received data without classifying each RLC layer device, and duplicate detection. The procedure may be independently performed on data received from each of the RLC layer devices. As another method, the receiving PDCP layer device function detects data outside the window based on the PDCP serial number or COUNT value in order to prevent data loss for the header compression protocol when data received from different base stations overlap each other. RLC layer devices are not classified and performed on all data received, and the duplicate detection procedure receives a decryption procedure, an integrity protection procedure, or a header (or data) decompression procedure for data received from each RLC layer device, respectively. After that, it is possible to perform a duplicate detection procedure on the entire data.

In the above, the sub-functions of the receiving PDCP layer device directly apply a decryption procedure to data received using a separate header (or data) compression context or security key set with each source base station and each target base station, and protect integrity. If set, the integrity verification procedure can be applied to the PDCP header and data (PDCP SDU).

In the 2-2 PDCP layer device structure, data received from RLC layer devices of a first bearer for each source base station and data received from RLC layer devices of a second bearer for each target base station After performing the reordering procedure for all of them, the header (or data) of each base station (source base station or target base station) is compressed for each data received from each base station (source base station or target base station) in ascending order of PDCP serial number or COUNT value. A header (or data) decompression procedure may be performed by applying the context. In addition, in order to distinguish data received from RLC layer devices of the first bearer for each source base station and data received from RLC layer devices of the second bearer for each target base station, an indicator for each data It can be distinguished whether the data is received from the source base station or the data received from the target base station by defining.

As another method, by defining a 1-bit indicator of the PDCP header, SDAP header, or RLC header, whether data is received from the source base station or the target base station may be distinguished. In addition, data received from RLC layer devices of the first bearer for the source base station for which the header (or data) compression procedure has been completed, and data received from RLC layer devices of the second bearer for the target base station For all of them, a duplicate detection procedure based on the PDCP serial number or COUNT value (one data for each PDCP serial number or COUNT value (including previously received data or data transmitted to a higher layer can be applied) The procedure of discarding all but leaving only) can be performed. And for all of the data received from the RLC layer devices of the first bearer for the source base station and the RLC layer devices of the second bearer for the target base station, the PDCP serial number or COUNT value. Based on, data may be delivered to the upper layer devices in ascending order in order. In the above, since one PDCP layer device can receive data from different base stations, that is, from the first bearer or the second bearer in any order, the reordering procedure may always be performed.

The two lower receiving PDCP layer device functions are, respectively, parallel processing for performing header compression or integrity protection or encryption procedures in parallel to accelerate the data processing speed based on the PDCP serial number or COUNT value, respectively. ) Can be done. In addition, the two lower receiving PDCP layer device functions may perform the integrity protection or encryption procedure or decompression procedure using different header (or data) compression contexts or security keys. In addition, by applying different header (or data) compression contexts or security keys or security algorithms in one transmitting PDCP layer device logically, integrity protection or encryption procedures or decompression procedures may be performed on different data. In addition, in the lower receiving PDCP layer device functions, out-of-sequence deciphering or an integrity verification procedure may be performed on each data received regardless of the order of the PDCP serial number or COUNT value.

When the one PDCP layer device distinguishes between the layer devices of the first bearer and the layer devices of the second bearer, consider that they are connected to different MAC layer devices, or have different logical channel identifiers. Or, considering the fact that they are different RLC layer devices connected to different MAC layer devices, or considering that different encryption keys are used, layer devices of the first bearer (or first RLC layer devices) And the layer devices of the second bearer (or the second RLC layer device) to perform an encryption or decryption procedure with different security keys for uplink data and downlink data, and different compression protocol contexts. It can be compressed or decompressed by using.

In the present disclosure, a structure of a third PDCP layer device that is efficient in handover, such as 1i-30, may be proposed. The structure of the third PDCP layer device may be applied to the second embodiment of an efficient handover method for minimizing data interruption time proposed in the present disclosure. In addition, in the structure of the third PDCP layer device proposed in the present disclosure, the function of the PDCP layer device may be the same as the structure of the second PDCP layer device proposed in the present disclosure. However, the third PDCP layer device structure may release the first bearer for the source base station in the second PDCP layer device structure. Specifically, the structure of the third PDCP layer device proposed in the present disclosure has the same function as the structure of the second PDCP layer device proposed above, but the first bearer for the source base station (e.g., SDAP layer device or PDCP layer device Device or RLC layer device or MAC layer device) may be released. Therefore, the structure of the third PDCP layer device is QoS mapping information of the SDAP layer device for the source base station, security key information for the source base station of the PDCP layer device, or header (or data) compression context information for the source base station or the source base station. It is possible to release the RLC layer device or the MAC layer device for.

1J is a diagram illustrating structures of an efficient SDAP layer apparatus applied in a DAPS handover method, which is a second embodiment of an efficient handover method proposed in the present disclosure, and a method of applying the structures.

1j is a detailed structure and functions of an efficient SDAP layer device applied in the DAPS handover method, which is a second embodiment of the efficient handover method proposed in the present disclosure, and the SDAP layer device proposed below while performing the DAPS handover procedure. It is characterized in that it is possible to apply different SDAP hierarchical structures for each bearer at different points in time.

For example, before receiving the handover command message from the base station, the terminal may process data and transmit or receive data by applying the first SDAP layer device structure and functions (1j-10) proposed in this disclosure for each bearer (1j). -01). In the structure and function of the first SDAP layer device, the SDAP layer device is used for transmitting uplink data or receiving downlink data (for example, for data received from a source base station), and one for the source base station. Process data by maintaining and applying mapping information of the first QoS flow and bearer (e.g., reading SDAP header information and updating mapping information, configuring an SDAP header, or mapping information of the first QoS flow and bearer) A routing or transfer procedure to a suitable upper layer device or a lower layer device) may be performed on the basis of.

However, if the terminal receives the handover command message from the base station in the above, and the DAPS handover method proposed in the present disclosure is indicated in the handover command message, or the DAPS handover method is indicated for specific bearers, The UE processes data by applying the second SDAP layer device structure and functions (1j-20) proposed in the present disclosure to each bearer or bearers for which the DAPS handover method is indicated above, and transmits or Can receive (1j-02). That is, the UE receives the handover command message, and when the DAPS handover method proposed in the present disclosure is indicated in the handover command message, or when the DAPS handover method is indicated for specific bearers, or at least one When a DAPS handover method is set for a bearer, or a DAPS handover method is set for a certain bearer, in the structure or function (1j-10) of the first SDAP layer device used for each bearer, proposed in the present disclosure. With the structure or function (1j-20) of the second SDAP layer device, the UE can switch for each bearer or for a bearer in which the DAPS handover method is indicated.

As another method, when the terminal satisfies the first condition proposed in the present disclosure (for example, when the random access procedure for the target base station is completed or when the first timer is stopped), the terminal is used for each bearer in the above. In the structure or function (1j-10) of the first SDAP layer device that was being performed, with the structure or function (1j-20) of the second SDAP layer device proposed in the present disclosure, the terminal may use the DAPS handover method for each bearer or a DAPS handover method. It is also possible to switch to the indicated bearer (1j-02). In the above, the UE receives the handover command message and the DAPS handover method proposed in the present disclosure is indicated in the handover command message, or when the DAPS handover method is indicated for specific bearers, or the QoS flow and When the bearer mapping information is newly set, the UE is the structure or function 1j-20 of the second SDAP layer device proposed in the present disclosure in the structure or function 1j-10 of the first SDAP layer device, or for each bearer. The DAPS handover method can be switched for the indicated bearer.

And, in the structure of the second SDAP layer apparatus, by maintaining the first QoS flow and bearer mapping information for the source base station, uplink data to be transmitted to the source base station and downlink data to be received from the source base station are processed. I can. The second QoS flow and bearer mapping information newly set in the handover command message may be set for the target base station, and the terminal processes uplink data to transmit the set information to the target base station and downlink data to be received from the target base station. Can be used to That is, in the second SDAP layer apparatus structure proposed in the present disclosure, the first QoS flow and bearer mapping information for the source base station or the second QoS flow and bearer mapping information are maintained, and the data for the source base station and the target base station are maintained. Data for each can be classified and processed.

In addition, when the first condition proposed in the present disclosure is satisfied, the DAPS handover method has to switch uplink data transmission to the target base station for the indicated bearers. A procedure of changing, switching, or resetting the QoS flow and bearer mapping information of 1 to the second QoS flow and bearer mapping information for the target base station may be performed. In addition, as the mapping information is changed from the first QoS flow and bearer mapping information to the second QoS flow and bearer mapping information as described above, the terminal is configured to use SDAP control data (e.g., changed QoS flow) generated for each changed QoS flow. End marker indicating that it is the last data for) is transmitted to the target base station, so that when the target base station receives uplink data from the terminal, the terminal reflects the change in QoS flow and bearer mapping information to perform data processing. I can. In the structure of the second SDAP layer device, the SDAP layer device receives data received from a lower layer from a source base station through a 1-bit indicator of the SDAP header, a 1-bit indicator of the PDCP header, or information indicated by the PDCP layer device. It is possible to distinguish whether data is received or data is received from a target base station. And in the above, if the base station instructs the DAPS handover method for each bearer by the handover command message, the default bearer (default DRB) always indicates the DAPS handover method. When data is generated in a new QoS flow that does not correspond to bearer mapping information, the UE can always transmit uplink data to the default bearer. If the DAPS handover method is not configured in the default bearer, data interruption time may occur because uplink data transmission for a new QoS flow occurring during handover is impossible.

In addition, the UE performs the DAPS handover method proposed in the present disclosure, and if the second condition proposed in the present disclosure is satisfied, the second SDAP applied to each bearer or to the bearer in which the DAPS handover method is indicated. The structure and function 1j-20 of the layer device can be applied by releasing the first bearers for the source base station and switching back to the structure and function 1j-10 of the first SDAP layer device. And, in the above, when the second condition is satisfied, in the structure or function of the second SDAP layer device (1j-20), the terminal is the structure or function of the first SDAP layer device proposed in the present disclosure (1j-10). As such, it is possible to switch for each bearer or for a bearer for which a DAPS handover method is indicated. In addition, the UE may maintain mapping information of the second bearer or the second QoS flow for the target base station and the bearer. And, the terminal for data received from the source base station (e.g., all data received from the source base station) before releasing the mapping information of the first bearer or the first QoS flow and bearer for the source base station, After data processing is completed by applying the mapping information of the first QoS flow and the bearer, the mapping information of the first QoS flow and the bearer or the first bearer may be released. In addition, the terminal may deliver the processed data to a higher layer in ascending order. That is, in the above, when the second condition is satisfied, the UE transmits the mapping information of the first QoS flow and bearer for the source base station with respect to the data stored in the buffer (for example, data received from the source base station). Apply and process data (e.g., read SDAP header information and update mapping information, configure SDAP header, or route to an appropriate upper layer device or lower layer device based on the first QoS flow and bearer mapping information, or Delivery procedure), the first QoS flow for the source base station and the bearer mapping information may be discarded.

In the above, the SDAP layer device may define and apply a 1-bit indicator of a new SDAP header, a 1-bit indicator of a PDCP header, or SDAP control data (for example, a downlink end marker) or information indicated by a PDCP layer device. In addition, the SDAP layer device may check which data is the last data received from the source base station based on this. Therefore, the SDAP layer apparatus applies the mapping information of the first QoS flow and bearer for the source base station to the last data received from the source base station and performs data processing, and then the first QoS flow for the source base station and the bearer. Mapping information can be discarded. In the above, the SDAP layer apparatus may continue to maintain the mapping information of the second QoS flow and the bearer, and may process uplink data or downlink data to the target base station based on this.

In the present disclosure below, when the UE receives the handover command message in FIG. 1F and applies the bearer configuration information included in the handover command message, different methods are used according to the handover type indicated in the handover command message. It is proposed to apply the bearer configuration information.

- When the terminal receives the handover command message, a first handover method (for example, the first embodiment of the present disclosure or a general handover method) is indicated in the handover command message, ReconfigWithSync information, or MobilityControlInfo information. In case, or if the second embodiment proposed in the present disclosure (DAPS handover method) is not set, or in the second embodiment proposed in the present disclosure (DAPS handover method), for any bearer in the bearer configuration information If not set

■ When a default bearer is configured in the SDAP layer device configuration information set in the handover command message, a default bearer for the source base station may be set as a default bearer for the target base station indicated in the configuration information.

■When the second QoS flow and bearer mapping information are set in the SDAP layer device configuration information set in the handover command message, the first QoS flow and bearer mapping information applied for the source base station are released, and the second QoS flow and bearer mapping information can be applied. As another method, the first QoS flow and bearer mapping information applied for the source base station may be replaced with the second QoS flow and bearer mapping information.

■ When a data discard timer value is set in the PDCP layer device configuration information set in the handover command message, the discard timer value may be directly applied to the PDCP layer device corresponding to the bearer identifier of the configuration information.

When the drb-ContinueROHC indicator is set to False in the PDCP layer device configuration information set in the handover command message, the PDCP layer device corresponding to the bearer identifier of the configuration information may initialize the context of the header compression or decompression protocol. . If the drb-ContinueROHC indicator is set to True, the PDCP layer device corresponding to the bearer identifier of the configuration information does not initialize the context of the header compression or decompression protocol.

■ When the reorder timer value is set in the PDCP layer device configuration information set in the handover command message, the reorder timer value may be directly applied to the PDCP layer device corresponding to the bearer identifier of the configuration information.

■ Upon receiving the handover command message, the PDCP layer device can be re-established. For example, for SRB, window state variables may be initialized, stored data (PDCP SDU or PDCP PDU) may be discarded, window state variables may be initialized for UM DRB, and data not yet transmitted to lower layer devices. Alternatively, data for which the PDCP revocation timer has not expired may be compressed or encrypted based on the header (or data) compression context or security key of the target base station in ascending order of the COUNT value, or integrity protection to perform transmission or retransmission. If the rearrangement timer is running, it can be stopped and initialized, and the received data (PDCP SDU or PDCP PDU) can be processed in order and delivered to the upper layer device.For AM DRB, window state variables are not initialized, but From the first data (PDCP SDU or PDCP PDU) for which successful delivery from the layer device is not confirmed, compresses or encrypts based on the header (or data) compression context or security key of the target base station in ascending order of the PDCP serial number or COUNT value. Alternatively, transmission or retransmission may be performed by performing integrity protection.

■When security key-related setting information or security algorithm is set in the security setting information set in the handover command message, the terminal uses the setting information to derive new security key or security setting information, and retrieves the existing security key or security setting information. It may be canceled or set by replacing the existing security key or security setting information with the new security key or security setting information.

When a new logical channel identifier is set in the RLC layer device configuration information set in the handover command message, the terminal releases the new logical channel identifier to the existing logical channel identifier corresponding to the bearer identifier indicated in the RLC layer device configuration information. Alternatively, the existing logical channel identifier may be replaced with the new logical channel identifier.

When the RLC re-establishment procedure is set in the RLC layer device configuration information set in the handover command message, the UE performs an RLC re-establishment procedure for the RLC layer device corresponding to the bearer identifier indicated in the RLC layer device configuration information. I can. That is, in detail, the UE may perform an RLC re-establishment procedure, and the transmitting RLC layer apparatus may perform a procedure of discarding all stored data. In addition, when the reordering timer is running, the receiving RLC layer device may stop and initialize the terminal, process all stored data, and transmit the processed data to the higher layer device. In addition, the terminal may initialize the MAC layer device. In addition, the terminal may initialize the MAC layer device for the source base station and use it for the target base station.

■ In the above, the MAC layer device is initialized, and data transmission or reception may be stopped for the source base station and each bearer. In addition, the MAC layer device may stop monitoring the PDCCH for the first terminal identifier (C-RNTI) allocated from the source base station. In addition, the MAC layer apparatus may stop a procedure for requesting scheduling from a source base station or may release transmission resources for scheduling. And the PHY or MAC layer device may perform a random access procedure to the target base station. The PHY or MAC layer device can resume data transmission or reception to the target base station if the handover procedure to the target base station is successfully completed, and for a second terminal identifier (C-RNTI) allocated from the target base station. You can start monitoring the PDCCH. In addition, the PHY or MAC layer device may receive a system frame number to a target base station and perform synchronization. In addition, the PHY or MAC layer device may initiate or perform a procedure for requesting scheduling to a target base station.

■ In the above, the PHY layer apparatus may perform channel measurement for the source base station, perform a channel measurement report, or stop a procedure for transmitting HARQ ACK or NACK. In addition, the PHY layer device performs a downlink synchronization procedure with respect to the target base station. In addition, configuration information for a target base station (or Spcell or Pcell) received in the handover command message may be set to a lower layer device or a PHY layer device. The PHY layer device may start or transmit HARQ ACK or NACK information to the target base station if the handover procedure is successfully completed to the target base station. In addition, the PHY or MAC layer device may receive a system frame number to a target base station and perform synchronization. In addition, the PHY or MAC layer device may initiate or perform a procedure for requesting scheduling to a target base station.

■ When the RLC layer device configuration information set in the handover command message is newly configured, the UE may perform an RLC re-establishment procedure for the RLC layer device corresponding to the bearer identifier indicated in the RLC layer device configuration information.

When the second priority for the logical channel is newly set in the MAC layer device configuration information set in the handover command message, the terminal releases the first priority corresponding to the logical channel identifier indicated in the configuration information. Alternatively, the first priority corresponding to the logical channel identifier may be set by replacing the newly set second priority.

■ When the second priority bit rate (prioritisedBitRate, PBR) for the logical channel is newly set in the MAC layer device configuration information set in the handover command message, the UE is The priority bit rate (prioritisedBitRate, PBR) of is released or the first priority bit rate (prioritisedBitRate, PBR) corresponding to the logical channel identifier is replaced with the newly set second priority bit rate (prioritisedBitRate, PBR). Can be set. In the above, the priority bit rate is a value that increases for each logical channel for a predetermined time (for example, every TTI), and when receiving an uplink transmission resource, the UE performs a logical channel prioritization (LCP) procedure, and the priority and the priority Data for the logical channel may be transmitted in consideration of the bit rate, and more data may be transmitted as the priority is higher or the priority bit rate is higher.

When the second bucket size (bucketSizeDuration) for a logical channel is newly set in the MAC layer device configuration information set in the handover command message, the UE is the first bucket size corresponding to the logical channel identifier indicated in the configuration information. It may be set by releasing (bucketSizeDuration) or replacing the first bucket size (bucketSizeDuration) corresponding to the logical channel identifier with the second bucket size (bucketSizeDuration) newly set above. In the above, the bucket size indicates a maximum value that a priority bit rate value can have when the priority bit rate is accumulated.

If the second allowed SCell information or allowed subcarrier spacing information or the maximum PUSCH period or logical channel group setting information is set in the MAC layer device setting information set in the handover command message, the UE Releases allowed SCell information or allowed subcarrier spacing information or maximum PUSCH period or logical channel group setting information, or previously set first allowed SCell information or allowed subcarrier spacing information or maximum PUSCH period or logical channel group The setting information may be set by replacing the newly set second allowed SCell information or allowed subcarrier spacing information, or the maximum PUSCH period or logical channel group setting information.

- When the terminal receives the handover command message, or in the handover command message, or in ReconfigWithSync information or mobilityControlInfo information, a second handover method (for example, in the second embodiment of the present disclosure or DAPS handover method) is indicated. If yes, if set, or if the DAPS handover method is indicated or set for each bearer identifier, or if the second embodiment (DAPS handover method) proposed in the present disclosure is configured for a certain bearer in the bearer configuration information, or as proposed in the present disclosure If the second embodiment (DAPS handover method) is configured for at least one bearer in the bearer configuration information

■ When the default bearer is set in the SDAP layer device configuration information set in the handover command message, the terminal performs the DAPS handover method proposed above of the present disclosure, and applies the second SDAP layer device structure to the existing source base station. The default bearer for the target base station may be maintained and default bearer information indicated in the configuration information may be set as a default bearer for the target base station. As another method, when the first condition proposed in the present disclosure is satisfied, the terminal may switch the default bearer for the existing source base station to the default bearer for the target base station indicated in the configuration information.

When the second QoS flow and bearer mapping information are set in the SDAP layer device configuration information set in the handover command message, the terminal performs the DAPS handover method proposed above of the present disclosure, and the second SDAP layer device structure By applying, the first QoS flow and bearer mapping information that have been applied for the source base station may be maintained, and the second QoS flow and bearer mapping information may be applied to data for the target base station. As another method, when the first condition proposed in the present disclosure is satisfied, the UE may apply the second QoS flow and bearer mapping information for the target base station.

When the data discard timer value is set in the PDCP layer device configuration information set in the handover command message, the terminal performs the DAPS handover method proposed in the above of the present disclosure, and the configuration is performed by applying the second PDCP layer device structure. The discard timer value can be directly applied to the PDCP layer device corresponding to the bearer identifier of the information.

■ In the handover command message, the PDCP layer device in which the DAPS handover method is indicated or set may perform the following procedures without re-establishing. For example, the terminal initializes the window state variables for the SRB (the variable initialization may be omitted for fallback in case of a DAPS handover failure) or the stored data (PDCP SDU or PDCP PDU) may be discarded, For UM DRB, window state variables are not initialized, and data transmission or reception with the source base station can be continuously performed on data that has not yet been transmitted to the lower layer device or data for which the PDCP discard timer has not expired. With respect to, the window state variables may not be initialized, and data transmission or reception with the source base station may be continuously performed.

■ In the handover command message, a PDCP layer device for which a DAPS handover method is not indicated or not configured may re-establish the PDCP layer device. For example, the UE may initialize window state variables for SRB and discard stored data (PDCP SDU or PDCP PDU), initialize window state variables for UM DRB, and have not yet been transmitted to lower layer devices. For data that has not expired or the PDCP discard timer has not expired, it is transmitted or retransmitted by compressing or encrypting based on the header (or data) compression context or security key of the target base station in ascending order of the COUNT value, or performing integrity protection. If the rearrangement timer is running, it can be stopped and initialized, and received data (PDCP SDU or PDCP PDU) can be processed in order and delivered to the upper layer device.For AM DRB, window state variables are not initialized. Without, from the first data (PDCP SDU or PDCP PDU) for which successful delivery from the lower layer device is not confirmed, compresses based on the header (or data) compression context or security key of the target base station in ascending order of the PDCP serial number or COUNT value. Alternatively, transmission or retransmission may be performed by encrypting or performing integrity protection. In addition, the RLC layer device may also perform a re-establishment procedure.

■If the DAPS handover method is indicated in the handover command message or the drb-ContinueROHC indicator is set to False in the set PDCP layer device configuration information, the UE performs the DAPS handover method proposed above of the present disclosure, and the second By applying the PDCP layer device structure of the PDCP layer device corresponding to the bearer identifier of the configuration information, the context of the header compression or decompression protocol for the source base station is used as it is, and the context of the header compression or decompression protocol for the target base station Is initialized and can be started from an initial state (eg IR state). If the drb-ContinueROHC indicator is set to True, the UE performs the DAPS handover method proposed in the above of the present disclosure, and applies the second PDCP layer device structure to the PDCP layer device corresponding to the bearer identifier of the configuration information. The context of the header compression or decompression protocol for the source base station may be used as it is, and the context of the header compression or decompression protocol for the target base station may be applied in the same manner as the context of the header compression or decompression protocol for the source base station. For example, the context of the header compression or decompression protocol for the source base station may be copied and applied as it is to the context of the header compression or decompression protocol for the target base station. Alternatively, the same header compression or decompression protocol context may be applied to the target base station or the source base station.

When the DAPS handover method is indicated in the handover command message or the reorder timer value is set in the set PDCP layer device configuration information, the UE performs the DAPS handover method proposed above of the present disclosure, and the second PDCP layer By applying the device structure, the reorder timer value can be applied directly to the PDCP layer device corresponding to the bearer identifier of the configuration information.

When the DAPS handover method is indicated in the handover command message or when security key-related setting information or security algorithm is set in the set security setting information, or when there is an indicator indicating a new procedure in the PDCP layer device setting information, the terminal Using the configuration information, a new security key or security configuration information is derived, and the DAPS handover method proposed in the present disclosure is performed, and an existing security key or security configuration for the source base station is applied by applying the second PDCP layer device structure. It is possible to maintain the information and set the security key or security setting information for the target base station with the new security key or security setting information.

When a DAPS handover method is indicated in the handover command message or a new logical channel identifier is set in RLC layer device configuration information of a set bearer, the DAPS handover method proposed in the present disclosure is performed, and the second PDCP By applying the layer device structure, for the RLC layer device or MAC layer device of the first bearer for the source base station corresponding to the bearer identifier indicated in the RLC layer device configuration information, the existing logical channel identifier is maintained, and for the target base station. The RLC layer device or the MAC layer device of the second bearer may be set as a new logical channel identifier indicated in the configuration information.

■ For the RLC layer device for the source base station in which the DAPS handover method configured in the handover command message is indicated or in the RLC layer device configuration information of the configured bearer, the UE may not perform an RLC re-establishment procedure. Specifically, without performing the RLC re-establishment procedure, the transmitting RLC layer device continues to transmit the stored data, and the receiving RLC layer device continues to process the stored data together with the received data, resulting in a data interruption time. You can avoid it. However, when the first condition proposed in the present disclosure is satisfied, the PDCP layer device in which the DAPS handover method is configured is data (PDCP) to the RLC layer device for the source base station for the AM bearer or the UM bearer according to the method proposed in this disclosure. In order to instruct data PDU) to be discarded, a data discard indicator may be transmitted for PDCP user data (PDCP Data PDU). Accordingly, the RLC layer apparatus for the source base station may perform transmission without discarding the PDCP data PDU but not discarding the PDCP control PDU.

For the RLC layer device of the bearer for which the DAPS handover method set in the handover command message is not indicated or not set, the RLC re-establishment procedure may be performed, or the RLC re-establishment if the RLC re-establishment procedure is set. The procedure can be carried out. That is, by performing the RLC re-establishment procedure in detail, the transmitting RLC layer apparatus may perform a procedure of discarding all stored data (PDCP Data PDU or PDCP control PDU). In addition, when the reordering timer is running, the receiving RLC layer device may stop and initialize, process all stored data, and transmit it to the upper layer device.

When a DAPS handover method is indicated in the handover command message or a new logical channel identifier is set in RLC layer device configuration information of a set bearer, the DAPS handover method proposed in the present disclosure is performed, and the second PDCP By applying the layer device structure, for the RLC layer device or MAC layer device of the first bearer for the source base station corresponding to the bearer identifier indicated in the RLC layer device configuration information, the existing logical channel identifier is maintained, and for the target base station. The RLC layer device or the MAC layer device of the second bearer may be set as a new logical channel identifier indicated in the configuration information.

If the DAPS handover method is indicated in the handover command message or the RLC layer device configuration information of the configured bearer is newly configured, the DAPS handover method proposed above of the present disclosure may be performed, and the second PDCP layer device For the RLC layer device of the first bearer for the source base station corresponding to the bearer identifier indicated in the RLC layer device configuration information by applying the structure, the existing RLC configuration information is maintained and the second bearer for the target base station is For the RLC layer device, it may be set with new RLC layer device configuration information indicated in the configuration information.

■ Method 1, Method 2, or Method 3 for configuring the MAC layer device proposed in FIG. 1K of the present disclosure may be performed.

Method 1 or Method 2 or Method 3 for configuring the MAC layer device proposed in FIG. 1K is performed, and data transmission or reception may be continuously performed on bearers for which the DAPS handover method is indicated or configured in the MAC layer device. have. In addition, data transmission or reception may be stopped for bearers for which the MAC layer device is not initialized and the DAPS handover method is not indicated or is not set.

■ In the above, without initializing the MAC layer device for the source base station, the PDCCH monitoring for the first terminal identifier (C-RNTI) allocated from the source base station may be continuously performed. In addition, the MAC layer apparatus for the source base station may continue to perform a procedure for requesting scheduling from the source base station. In addition, the PHY or MAC layer apparatus for the target base station may apply a setting as configuration information to be received in the handover command message, and perform a random access procedure to the target base station. The PHY or MAC layer device for the target base station can start data transmission or reception to the target base station if the handover procedure to the target base station is successfully completed, and a second terminal identifier (C-RNTI) allocated from the target base station. ) Can start monitoring the PDCCH. In addition, the PHY or MAC layer device may receive a system frame number to a target base station and perform synchronization. In addition, the PHY or MAC layer device for the target base station may initiate or perform a procedure for requesting scheduling to the target base station. Until the connection with the source base station is released above or until the second condition proposed in the present invention is satisfied, the UE is the PDCCH for the first UE identifier allocated from the source base station in the PHY or MAC layer device for the source base station. Monitoring may be performed, and PDCCH monitoring may be performed on the second terminal identifier allocated from the target base station in the PHY or MAC layer device for the target base station. In the above, if the connection with the source base station is released, or the second condition proposed in the present invention is satisfied, the UE monitors the PDCCH for the first UE identifier allocated from the source base station in the PHY or MAC layer device for the source base station. May be stopped, or a transmission resource for a scheduling request may be released.

In the above, the PHY layer device for the source base station may maintain configuration information or perform a channel measurement for the source base station, or perform a channel measurement report, or may continue to perform a procedure of transmitting HARQ ACK or NACK. . In addition, the PHY or MAC layer device for the target base station performs a downlink synchronization procedure with respect to the target base station. In addition, the PHY or MAC layer device for the target base station may set configuration information on the target base station (or Spcell or Pcell) received in the handover command message to a lower layer device or a PHY layer device for the target base station. The PHY or MAC layer device for the target base station may start or transmit HARQ ACK or NACK information to the target base station if the handover procedure to the target base station is successfully completed. In addition, the PHY or MAC layer device for the target base station may receive a system frame number from the target base station and perform synchronization. In addition, the PHY or MAC layer device for the target base station may initiate or perform a procedure for requesting scheduling to the target base station, a procedure for performing channel measurement, or a procedure for reporting a channel measurement result. Until the connection with the source base station is released above, or until the second condition proposed in the present invention is satisfied, the UE is the PDCCH for the first UE identifier allocated from the source base station in the PHY or MAC layer device for the source base station. Monitoring may be performed, and PDCCH monitoring may be performed on the second terminal identifier allocated from the target base station in the PHY or MAC layer device for the target base station. In the above, if the connection with the source base station is released or the second condition proposed in the present invention is satisfied, the terminal monitors the PDCCH for the first terminal identifier allocated from the source base station in the PHY or MAC layer device for the source base station. It is possible to stop or release a transmission resource for a scheduling request.

■ Method 1, Method 2, or Method 3 of setting or processing the SRB proposed in FIG. 1K of the present disclosure may be performed.

When the second priority for the logical channel is newly set in the MAC layer device configuration information set in the handover command message, the DAPS handover method proposed above of the present disclosure may be performed, and the second PDCP layer device Structure can be applied. In addition, existing configuration information may be maintained for the MAC layer device of the first bearer for the source base station corresponding to the bearer identifier indicated above, and the configuration information for the MAC layer device of the second bearer for the target base station. A new logical channel identifier indicated in the information may be set. In addition, a newly set second priority corresponding to the logical channel identifier indicated in the setting information may be set. As another method, when the first condition proposed in the present disclosure is satisfied, the priority may be applied to the MAC layer apparatus of the second bearer for the target base station for each logical channel identifier.

When the second priority bit rate (prioritisedBitRate, PBR) for the logical channel is newly set in the MAC layer device configuration information set in the handover command message, the UE can perform the DAPS handover method proposed above in the present disclosure. have. In addition, a second PDCP layer device structure may be applied, and existing configuration information is maintained for the MAC layer device of the first bearer for the source base station corresponding to the bearer identifier indicated above, and the second configuration information is maintained for the target base station. For the MAC layer device of the bearer of, a new logical channel identifier indicated in the configuration information may be configured. In addition, a newly set second priority bit rate corresponding to the logical channel identifier indicated in the setting information may be set. As another method, the second priority bit rate may start to be applied to the logical channel identifier in the MAC layer device of the second bearer for the target base station from when the first condition proposed in the present disclosure is satisfied. Thus, when different handover methods are indicated for each bearer, uplink transmission resources can be fairly allocated). In the above, when the priority bit rate starts to be applied to each logical channel identifier, a logical channel prioritization (LCP) procedure is performed when an uplink transmission resource is received at a value that increases for each logical channel at a predetermined time (e.g., every TTI). It may be performed, and data for the logical channel may be transmitted in consideration of a priority and the priority bit rate, and more data may be transmitted as the priority is higher or the priority bit rate is higher.

In addition, when applying the DAPS handover method above, when the terminal needs to transmit uplink data through the first bearer for the source base station because the first condition proposed in the present disclosure is not yet satisfied, the first When performing the LCP procedure, the MAC layer device of the bearer applies only to the bearer or logical channel identifiers for which the DAPS handover method (or the handover method that can continue to transmit data to the source base station after receiving the handover command message) is indicated. It can be selected as the target of the LCP procedure and the LCP procedure can be performed. This is because bearers or logical channel identifiers to which the DAPS handover method is not applied should not be selected as the target of the LCP procedure because uplink data cannot be transmitted to the source base station when a handover command message is received.

■ When a second bucket size (bucketSizeDuration) for a logical channel is newly set in the MAC layer device configuration information set in the handover command message, the UE may perform the DAPS handover method proposed above of the present disclosure. In addition, a second PDCP layer device structure may be applied, and existing configuration information is maintained for the MAC layer device of the first bearer for the source base station corresponding to the bearer identifier indicated above, and the second configuration information is maintained for the target base station. For the MAC layer device of the bearer of, a new logical channel identifier indicated in the configuration information may be set, and a newly set second bucket size corresponding to the logical channel identifier indicated in the configuration information may be set. As another method, the second bucket size may start to be applied to the logical channel identifier in the MAC layer device of the second bearer for the target base station from when the first condition proposed in the present disclosure is satisfied (by doing this When different handover methods are indicated for each bearer, uplink transmission resources can be fairly allocated). In the above, the bucket size indicates a maximum value that a priority bit rate value can have when the priority bit rate is accumulated.

■If the second allowed SCell information or allowed subcarrier spacing information, or the maximum PUSCH period or logical channel group setting information is set in the MAC layer device setting information set in the handover command message, the UE proposed in the above of the present disclosure. Performs the DAPS handover method, applies the second PDCP layer device structure, maintains existing configuration information for the MAC layer device of the first bearer for the source base station corresponding to the bearer identifier indicated above, and maintains the target base station. For the MAC layer device of the second bearer for, the second allowed SCell information or allowed subcarrier spacing information, or the maximum PUSCH period or logical channel group setting information indicated in the configuration information may be set.

1K is a diagram illustrating a method of applying configuration information for each bearer when a DAPS handover method according to an embodiment of the present disclosure is configured.

As suggested in the present disclosure in FIG. 1K, if the terminal receives the handover command message (1k-01), the second handover method in ReconfigWithSync information (for example, the second embodiment of the present disclosure or DAPS Handover method) is indicated, or DAPS handover method is indicated for each bearer identifier or logical channel identifier, or DAPS handover method is set for at least one bearer, or DAPS handover for a certain bearer When the method is set, the terminal may create or establish a MAC layer device for the target base station (or target cell) at the time of receiving the handover command message. In addition, the terminal bearers in which the DAPS handover method is indicated through the MAC layer device for the source base station (or source cell) from the time when the handover command message is received until the first condition proposed in the present disclosure is satisfied ( AM bearer or UM bearer) can continue to transmit or receive data with the source base station. In addition, when the first condition is satisfied, the terminal switches the uplink data to the target base station, and may receive downlink data from the source base station until the connection with the source base station is released. However, for bearers for which the DAPS handover method is not indicated in the above, the terminal may no longer communicate with the source base station from the time when the handover command message is received until the first condition proposed in the present disclosure is satisfied, or continuously. Transmission or reception cannot be performed. Therefore, in order for the terminal to perform the proposed operation of the present disclosure, one of the following methods or a plurality of methods may be applied and modeled as shown in FIGS. 1K-21 or 1K-22. In addition, if the source base station is released by satisfying the second condition proposed in the present disclosure, it may be modeled as 1k-31 or 1k-32.

- As proposed in the present disclosure, if the UE indicates a second handover method (for example, the second embodiment of the present disclosure or DAPS handover method) in ReconfigWithSync information when receiving the handover command message, or bearer If the DAPS handover method is indicated for each identifier or logical channel identifier, or if the DAPS handover method is set for at least one bearer, or if the DAPS handover method is set for a certain bearer, the SRB configured in the MAC layer device for the source base station Can be stopped, and the upper layer device of the terminal (for example, the RRC layer device) is configured except for the configuration information related to the bearer for which the DAPS handover method is not indicated in the handover command message in the configuration information of the current MAC layer device. Information may be instructed to perform reconfiguration (MAC reconfiguration) to the MAC layer device for the source base station. As another method, the upper layer device of the terminal (for example, the RRC layer device) is sourced from the configuration information of the current MAC layer device as configuration information including only configuration information related to the bearer for which the DAPS handover method is indicated in the handover command message. It is possible to instruct the MAC layer device for the base station to perform a reconfiguration (MAC reconfiguration). In the above, when the terminal resets the MAC layer device for the source base station, the MAC layer device for the source base station of the terminal has a priority corresponding to the logical channel identifiers or the logical channel identifiers in which the DAPS handover method is indicated in the above. Maintain only the priority bit rate or bucket size, and release or no longer use the logical channel identifiers corresponding to the bearer for which the DAPS handover method is not indicated, or the priority bit rate or bucket size corresponding to the logical channel identifiers. May or may no longer apply. In addition, in the above, the upper layer device (for example, the RRC layer device) of the terminal may perform a PDCP re-establishment procedure or an RLC re-establishment procedure for a bearer for which a DAPS handover method is not indicated in the above, and the handover message PDCP configuration information or RLC configuration information set in may be applied or the bearer may be stopped. Alternatively, the upper layer device of the terminal can stop the bearer in the MAC layer device for the source base station, or can be set in the MAC layer device for the target base station (when the first condition is satisfied, the MAC layer device for the target base station is In the handover command message, bearer configuration information, such as a logical channel identifier or priority bit rate or bucket size, set for the target base station for the bearer for which the DAPS handover method is not indicated, is transmitted to the MAC layer device for the target base station. It can instruct the MAC layer device for the target base station to set or apply to. Alternatively, the upper layer device of the terminal switches the connection of the PDCP layer device or RLC layer device corresponding to the bearer for which the DAPS handover method is not indicated, from the MAC layer device for the source base station to the MAC layer device for the target base station. I can. In this case, from that point in time, when the MAC layer device for the source base station of the terminal performs a logical channel prioritization (LCP) procedure for data transmission, only logical channel identifiers corresponding to the bearer in which the DAPS handover method is indicated above. It is selected as a candidate group, and the LCP procedure can be performed. In the above, the procedure for resetting the MAC layer device for the source base station by the upper layer device (for example, the RRC layer device) is to perform the same procedure by partially initializing the MAC layer device for the source base station (Partial MAC reset). You may. For example, configuration information of the MAC layer device for a bearer for which the DAPS handover method is not indicated above may be initialized or released, or application may be stopped. In addition, data transmission or reception with the source base station may be performed until the first condition proposed in the present disclosure is satisfied. For the logical channel identifier corresponding to the bearer for which the DAPS handover method is not indicated above, the MAC layer device for the source base station initializes the priority bit rate and no longer applies the priority bit rate accumulation calculation procedure, and the bearer is released or stopped. Can be. In addition, for the logical channel identifier corresponding to the bearer in which the DAPS handover method is indicated above, the MAC layer apparatus for the source base station continues to maintain a priority bit rate, and an accumulation calculation procedure may be performed. If the first condition is satisfied, data transmission is switched to the target base station, and the MAC layer device for the target base station includes newly set logical channel identifiers (a bearer in which the DAPS handover method is indicated, or the DAPS handover method is not indicated. The priority bit rate for the logical channel identifiers corresponding to the bearer) can be initialized, or cumulative calculation can be started (as another method, when a handover command message is received for the MAC layer device for the target base station, the priority bit rate is initialized. And start the cumulative calculation). If bearers for which the DAPS handover method is not indicated in the above are set or stopped, the MAC layer apparatus for the target base station may configure or resume to perform data transmission or reception with the target base station, and first initialize the bit rate or You can start the cumulative calculation. And data reception is performed from the source base station or the target base station until the second condition proposed in the present disclosure is satisfied, and when the second condition is satisfied (1k-03), the MAC layer device for the source base station is initialized, and the source RLC layer device or PDCP layer device or bearer configuration information corresponding to a bearer for which the DAPS handover method connected to the MAC layer device for the base station is not indicated may be released in the MAC layer device for the source base station, and the DAPS handover The RLC layer device or bearer configuration information corresponding to the bearer for which the method is indicated may be released in the structure of the second PDCP layer device or the MAC layer device for the source base station (1k-31 or 1k-32). If the handover procedure fails and the connection with the source base station is valid as proposed in the following of the present disclosure, the terminal performs a fallback procedure to the source base station (1k-02), and performs the SRB set in the MAC layer device of the source base station. Resume, report the handover failure, apply the existing bearer configuration information of the source base station before receiving the handover command message again, apply the configuration information of the original MAC layer device (for example, the RRC layer device It is possible to reset the configuration information of the MAC layer device used before the reception of the handover command message), and data transmission or reception with the source base station can be resumed for each bearer (1k-10). As another method, the upper layer device (for example, the RRC layer device) of the UE may instruct the RLC re-establishment procedure for a bearer in which the DAPS handover method is indicated or a bearer not indicated in the above. As another method, in the above, when the source base station performs the DAPS handover method, configuration information of the MAC layer device for the source base station to be applied may be set as an RRC message.

In the methods proposed in the present disclosure, if the second handover method (for example, the second embodiment of the present disclosure or the DAPS handover method) is indicated in the ReconfigWithSync information when the terminal receives the handover command message , Or when a DAPS handover method is indicated for each bearer identifier or logical channel identifier, or when a DAPS handover method is configured for at least one bearer, or when a DAPS handover method is configured for a certain bearer, the source base station The SRBs set in the MAC layer device for use may be applied by applying one method or a plurality of methods among the following methods.

- If the second handover method (for example, the second embodiment of the present disclosure or DAPS handover method) is indicated in the ReconfigWithSync information when the terminal receives the handover command message, or a bearer identifier or a logical channel identifier When a DAPS handover method is indicated for each, or a DAPS handover method is set for at least one bearer, or a DAPS handover method is set for a certain bearer.

■Method 1: SRB may be stopped in the MAC layer device for the source base station. Alternatively, window state variables are initialized by performing the re-establishment procedure of the RLC layer device of the SRBs or the re-establishment procedure of the PDCP layer device, and stored data (PDCP SDU or PDCP PDU or RLC SDU or RLC PDU) may be discarded. . Alternatively, SRBs may be configured in the MAC layer device for the target base station according to the configuration received in the handover message. Alternatively, the SRBs of the MAC layer device for the source base station may be set according to the settings received in the handover message, and may be connected by switching to the MAC layer device for the target base station. If the terminal fails the handover procedure and performs the fallback procedure, the terminal resumes SRBs stopped in the MAC layer device for the source base station or resets the SRBs set in the target base station to the existing configuration for the source base station, and It is also possible to switch to the MAC layer device for the base station to connect and resume.

■Method 2: SRB can be stopped in the MAC layer device for the source base station. Alternatively, the re-establishment procedure of the RLC layer device of the SRBs or the re-establishment procedure of the PDCP layer device may be stopped without being performed. Alternatively, SRBs may be configured in the MAC layer device for the target base station according to the configuration received in the handover message. Alternatively, the SRBs of the MAC layer device for the source base station may be set according to the settings received in the handover message, and may be switched to and connected to the MAC layer device for the target base station. If the terminal fails the handover procedure and performs the fallback procedure, the terminal resumes SRBs stopped in the MAC layer device for the source base station or resets the SRBs set in the target base station to the existing configuration for the source base station, and It is also possible to switch to the MAC layer device for the base station to connect and resume.

■Method 3: SRB may be stopped in the MAC layer device for the source base station. Alternatively, the re-establishment procedure of the RLC layer device of the SRBs or the re-establishment procedure of the PDCP layer device is not performed, and the window state variables are not initialized, but stored data (PDCP SDU or PDCP PDU or RLC SDU or RLC PDU) is discarded. Can (to prevent untransmitted RRC messages from being transmitted unnecessarily later). Alternatively, SRBs may be configured in the MAC layer device for the target base station according to the configuration received in the handover message. As another method, the UE may configure SRBs of the MAC layer device for the source base station according to the configuration received in the handover message, and switch to the MAC layer device for the target base station to connect. If the terminal fails the handover procedure and performs the fallback procedure, the terminal resumes SRBs stopped in the MAC layer device for the source base station or resets the SRBs set in the target base station to the existing configuration for the source base station, and It is also possible to switch to the MAC layer device for the base station to connect and resume.

In the present disclosure below, when the terminal performs the second embodiment (DAPS handover method) of the efficient handover method proposed in the present disclosure, if the terminal fails to handover, the features of the DAPS handover method proposed above are described. A method of re-establishing a connection by quickly falling back to a source base station is proposed. In the above, a characteristic of the DAPS handover method proposed in the present disclosure may specifically mean that data transmission or reception is performed by maintaining a connection with the source base station even when performing a handover procedure. In addition, even if the handover fails, fallback using a wireless connection connected to an existing source base station is specifically proposed in the present disclosure below.

As described in FIG. 1H of the present disclosure, in the second embodiment of the efficient handover method (DAPS handover method), even if the terminal receives a handover command message from the source base station, as proposed in 1h-02, the terminal is It is possible to perform a handover procedure to the target base station while maintaining data transmission or reception with the base station. In addition, in the present disclosure, when the handover procedure to the target base station fails in the above, a procedure for falling back to the source base station is proposed.

If the terminal fails the handover procedure to the target base station as suggested above, in order to fall back to the source base station, there must be a method to check whether the wireless connection between the terminal and the source base station is valid. This is because if the mobile station fails to handover and performs a fallback to the source base station when the wireless connection between the mobile station and the source base station is not valid, the fallback procedure to the source base station will also fail, resulting in a very long data interruption time, leading to significant data loss. Because it occurs. In addition, when the wireless connection between the terminal and the source base station is valid, it is also necessary to maintain the SRB set in the terminal and the source base station.

First, the present disclosure proposes new timers applicable to a handover method and specific operations of each timer. In addition, according to the present disclosure, specific operations of the timer may perform different operations according to the type of a handover method indicated by the base station in a handover command message. In addition, a method of releasing or maintaining connection with a source base station or SRB configuration according to a handover method is proposed.

In the present disclosure, in order to efficiently perform a handover procedure, a first timer (for example, T304) or a second timer (for example, T310), a third timer (for example, T312), or a fourth timer ( For example, a timer for fallback) may be introduced, and may be driven and applied in a handover procedure. A first timer (for example, T304) or a second timer (for example, T310) or a third timer (for example, T312) or a fourth timer (for example, a timer for fallback) proposed in the present disclosure ) May perform different operations as follows according to the type of handover method indicated in the handover command message. For example, in the above, the first timer (for example, T304) is a timer for determining whether handover has been successfully performed. In addition, the second timer (for example, T310) is a timer for determining whether the wireless connection is valid. In addition, the third timer (for example, T312) is an auxiliary timer for determining whether a wireless connection is valid, and a timer for triggering a frequency measurement procedure and reporting a frequency measurement result. And the fourth timer (for example, a timer for fallback) performs a fallback procedure to the source base station when handover fails while performing the second embodiment (DAPS handover method) of the efficient handover method proposed in the present disclosure. Thus, after transmitting a message indicating that the handover has failed to the source base station, this is a timer for determining whether the fallback procedure has been successfully performed or has failed.

The first timer (for example, T304) or the second timer (for example, T310) or the third timer (for example, T312) or the fourth timer proposed to support an efficient handover method in the present disclosure A specific operation for (for example, a timer for fallback) is proposed as follows according to the indicated handover method.

- 1> The terminal sets an out-of-sync indication from a lower layer device (for example, a MAC layer device or a PHY layer device) to a predetermined number of times (for example, the base station sets an out-of-sync indication). When it is detected that there is a problem in the physical layer device by receiving as much as possible), a second timer (for example, T310) may be started when the first timer is not running. And when the terminal receives an indicator (in-sync indication) that the synchronization of the radio connection signal is good for a predetermined number of times (for example, the base station can set it) from the lower layer device, or when the handover procedure is triggered. (When started) or when the RRC connection re-establishment procedure is started, the second timer is stopped. If the second timer expires, the UE triggers or starts an RRC connection re-establishment procedure. Alternatively, it transitions to the RRC idle mode and triggers or starts an RRC connection re-establishment procedure.

- 1> When the second timer is running, the terminal starts a third timer when a frequency measurement procedure is triggered for a frequency measurement identifier for which a third timer is set. And when the terminal receives an indicator (in-sync indication) that the synchronization of the radio connection signal is good for a predetermined number of times (for example, the base station can set it) from the lower layer device, or when the handover procedure is triggered. (When started) or when the RRC connection re-establishment procedure is started, the third timer is stopped. If the third timer expires, the UE triggers or starts an RRC connection re-establishment procedure. Alternatively, it transitions to the RRC idle mode and triggers or starts an RRC connection re-establishment procedure.

- 1> If the terminal receives a handover command message from the base station (for example, in the first embodiment or in the first embodiment or in the handover command message (a message including a mobility indication (MobilityControl info or ReconfigurationWithSync) or a handover indication in the RRCReocnfiguartion message) When a general handover method) is indicated, or if the terminal receives the handover command message, the first handover method (for example, the first handover method of the present disclosure) is in the handover command message, ReconfigWithSync information, or MobilityControlInfo information. An embodiment or general handover method) is indicated, or the second embodiment (DAPS handover method) proposed in the present disclosure is not set, or the second embodiment (DAPS handover method) proposed in the present disclosure is When no bearer is set in the bearer configuration information

■2> In the present disclosure, the UE triggers a handover procedure when receiving a handover command message (a message including a mobility control info or ReconfigurationWithSync or a handover instruction in the RRCReocnfiguartion message) from the above, and starts the first timer. do.

■2> When triggering the handover procedure in the above, the UE releases the SRB (e.g., SRB1) set for the source base station, and SRB (e.g., SRB) for the target base station based on the configuration information set in the handover command message. For example, set SRB1).

■2> When triggering the handover procedure in the above, the terminal may be characterized in that it stops if the second timer is running. And when the first timer is running, the second timer starts even when the condition for starting the second timer (when an asynchronous indicator of a wireless connection signal is received from a lower layer a predetermined number of times) is satisfied. It may not be. That is, when the first timer is running, the second timer may not be used.

■2> When triggering the handover procedure in the above, the terminal can stop if the third timer is running. And only when the second timer is running, when the terminal satisfies the condition of starting the third timer (when the frequency measurement procedure is triggered for the frequency measurement identifier in which the third timer is set), the third Can start the timer. That is, when the first timer is running, since the second timer is not used, the third timer may not be used.

■2> In the above, if the terminal successfully completes the handover procedure to the target base station or the random access procedure successfully, the first timer is stopped.

■2> If the first timer expires in the above (for example, if the handover procedure to the target base station fails), the terminal performs an RRC connection re-establishment procedure (releases the connection with the base station and performs the RRC connection procedure). It is performed again from the beginning, that is, a cell selection or reselection procedure may be performed, a random access procedure may be performed, and an RRC connection re-establishment request message may be transmitted).

- 1> If the UE receives a handover command message from the base station (a message including a mobility indication (MobilityControl info or ReconfigurationWithSync) or a handover indication in the RRCReconfiguartion message), the second handover method (for example, the second embodiment or DAPS handover method) is indicated (or can be extended and applied even when the conditional handover method is also indicated), or if the terminal receives the handover command message, the handover command message or ReconfigWithSync information or If the second embodiment (DAPS handover method) proposed in the present disclosure is configured in MobilityControlInfo information, or if the second embodiment (DAPS handover method) proposed in this disclosure is configured for a certain bearer in the bearer configuration information, or If the second embodiment (DAPS handover method) proposed in the present disclosure is configured for at least one bearer in the bearer configuration information

■2> In the present disclosure, the UE triggers a handover procedure when receiving a handover command message (a message including a mobility control info or ReconfigurationWithSync or a handover indication in the RRCReocnfiguartion message) in the above, and triggers a first timer. Start. If the conditional handover method is also indicated, the UE may start the first timer when selecting one cell from among a plurality of target cells and starting a handover procedure or performing a random access procedure.

■2> When triggering the handover procedure in the above, the UE, if starting the DAPS handover method, maintains or stops the SRB (for example, SRB1) set for the source base station, and setting information set in the handover command message SRB (for example, SRB1) for the target base station is set based on. As another method, when triggering the handover procedure in the above, the UE, if starting the DAPS handover method, maintains or stops the SRB (e.g., SRB1) set for the source base station, and for the SRB for the source base station. Re-establishing the PDCP layer device or re-establishing the RLC layer device to initialize the window state variable, or stop the timer and instruct to discard the stored data (PDCP SDU or PDCP PDU) (fallback procedure proposed in the present disclosure) It may be performed when is triggered) SRB (for example, SRB1) for the target base station may be set based on configuration information set in the handover command message. As another method, the UE may set the first bearer for the source base station and the second bearer for the target base station by applying the second PDCP layer device structure proposed in the present disclosure for the SRB. As another method, when applying the second PDCP layer device structure to the SRB, the UE reestablishes the PDCP layer device for the first bearer or reestablishes the RLC layer device to initialize the window state variable and stop the timer. And discard the stored data (PDCP SDU or PDCP PDU) (may be performed when the fallback procedure proposed in the present disclosure is triggered). That is, when the fallback procedure proposed in the present disclosure is triggered as another method, the terminal performs a procedure of discarding data (eg, old RRC messages) remaining in the SRB for the source base station or stored in the buffer. can do. Or, the terminal instructs a procedure for the upper layer device (eg, RRC layer device) of the terminal to discard data remaining in the PDCP layer device for the SRB or stored in the buffer (eg, old RRC messages) Or it can be triggered. This is because the old RRC message must be prevented from being transmitted to the source base station.

■2> If the terminal triggers the DAPS handover method when triggering the handover procedure in the above, it may not stop even if the second timer for the source base station is running. And when the condition of starting the second timer even when the first timer is running (or when not running) (when an asynchronous indicator of a wireless connection signal is received from a lower layer a predetermined number of times) is satisfied, , The second timer may be started. The second timer may be operated for wireless connection between the terminal and the source base station. In another way, two second timers are operated, one second timer is operated for the wireless connection between the terminal and the source base station, and another second timer is the radio between the terminal and the target base station. Can be operated on the connection. That is, even when the first timer is running, the second timer may be used for wireless connection with the source base station or the target base station. However, even if the second timer expires, if the first timer does not expire and is running, the terminal may not trigger an RRC connection re-establishment procedure. That is, specifically, even if the second timer for the source base station expires or a radio connection failure (RLF) occurs in the above, if the first timer is not expired and is running, or a random access procedure is performed to the target base station. If in progress, or if the handover procedure is being performed to the target base station, the terminal may release the radio connection with the source base station without triggering the RRC connection re-establishment procedure. In addition, the UE does not release RRC configuration information (eg, bearer configuration information, etc.) that has been set from the source base station, and may be reused if the RRC connection re-establishment procedure is triggered later. In addition, even if the second timer expires, if the first timer does not expire and is running, the terminal does not trigger the RRC connection re-establishment procedure, and the source base station may also report that the source connection has failed to the target base station, or The connection with the source base station may be released (eg, the first bearers for the source base station may be released) or the first bearers for the source base station may be stopped. However, when the second timer expires, if the first timer expires or is stopped, or if it is not driven because it has not started, the terminal may trigger an RRC connection re-establishment procedure. The reason for operating the second timer even when performing the handover procedure in the above is that when a handover failure occurs by monitoring the wireless connection between the terminal and the source base station or the target base station, the wireless connection with the source base station or the target base station If this is valid, this is to enable the terminal to perform a fallback procedure. In addition, when the second timer for the target base station in the above has expired, or when the wireless connection with the target base station has failed, the first timer has expired or has been stopped or is not running because it has not been started. If the random access procedure has been successfully performed, the RRC connection re-establishment procedure may be triggered.

■2> If the terminal triggers the DAPS handover method when triggering the handover procedure above, the terminal may not stop even if the third timer for the source base station is running. And when the condition of starting the third timer only when the second timer is running (when the frequency measurement procedure is triggered for the frequency measurement identifier for which the third timer is set) is satisfied, the terminal You can start the timer. That is, since the terminal uses the second timer even when the first timer is running, the third timer may also be used. The third timer may be operated for wireless connection between the terminal and the source base station. Alternatively, by operating two third timers, one third timer is operated for wireless connection between the terminal and the source base station, and another third timer operates for the wireless connection between the terminal and the target base station. Can be operated on the connection. That is, even when the first timer is running, the third timer may be used for wireless connection with the source base station or the target base station. However, even if the third timer expires, if the first timer does not expire and is running, the terminal may not trigger an RRC connection re-establishment procedure. In addition, even if the third timer expires, if the first timer does not expire and is running, the terminal does not trigger the RRC connection re-establishment procedure, and the source base station may report that the source connection has failed to the target base station, or The connection with the source base station may be released (eg, the first bearers for the source base station may be released) or the first bearers for the source base station may be stopped. However, when the third timer has expired, if the first timer has expired or has been stopped or is not driven because it has not started, an RRC connection re-establishment procedure may be triggered. The reason for operating the third timer even when performing the handover procedure in the above is that when a handover failure occurs by monitoring the wireless connection between the terminal and the source base station, when the wireless connection with the source base station is valid, fallback This is to enable the procedure to be performed, and to allow the frequency measurement result to be reported in the fallback procedure.

■2> In the above, if the terminal successfully completes the handover procedure to the target base station, the first timer is stopped.

■2> If the first timer expires in the above (for example, if the handover procedure to the target base station fails), or if the maximum number of retransmissions from the RLC layer device to the target base station is exceeded, or the handover command message is received in the above. However, if the terminal fails to handover because the configuration information of the handover command message exceeds the capability of the terminal, or an error occurs in the application of the configuration information, a random access problem has occurred to the target base station and continues to perform the random access procedure. If attempted, but the handover procedure fails due to the expiration of the first timer, or if the second timer or the third timer is driven for the target base station in the above, the second timer or the second timer before completing the handover procedure When the third timer expires, if it is determined that the T304 timer has been stopped or expired and the handover procedure has failed,

◆3> If the second timer or the third timer for the wireless connection between the terminal and the source base station in the above has not expired (or the second timer or the third timer for the wireless connection between the terminal and the source base station in the above) (If the timer is not started or is running) or if the wireless connection between the terminal and the source base station is valid

●4> The terminal may determine that the wireless connection between the terminal and the source base station is valid and perform the fallback procedure proposed in the present disclosure.

4> In the above, when the UE starts the fallback procedure, if the SRB set for the source base station (e.g., the MAC or RLC or PDCP layer device of SRB1 or SRB1) is stopped, it resumes or sets anew, and the SRB (e.g. For example, SRB1) can perform a fallback procedure. As another method, if the second PDCP layer device structure proposed in the present disclosure is applied to the SRB, the UE can perform a fallback procedure through the first bearer for the source base station, and the second bearer for the target base station. Can be turned off. For example, the terminal switches the uplink data transmission to the first bearer for the source base station, indicates that there is data to be transmitted to the RLC layer device or the MAC layer device of the first bearer, and reports a handover failure for a fallback procedure. The message can be transmitted through the first bearer. In addition, when the fallback procedure is triggered in the above, the terminal performs a procedure of discarding data (e.g., old RRC messages) remaining in the SRB for the source base station or stored in the buffer, or the upper layer of the terminal A device (eg, an RRC layer device) may instruct or trigger a procedure for discarding data (eg, old RRC messages) remaining in the PDCP layer device for the SRB or stored in a buffer. This is because it is necessary to prevent the old RRC message from being transmitted to the source base station.

●4> In the above, the fallback procedure is to report the handover failure to the source base station by constructing a report message indicating that the handover has failed through the SRB (for example, SRB1) configured with the source base station. In the above, when the terminal transmits the report message indicating that the handover has failed to the source base station, the frequency measurement result measured by the terminal is also reported to help to quickly restore the connection with the source base station. As another method, the UE may indicate that the handover has failed by indicating that there is data to be transmitted in the MAC control information (for example, new MAC control information or buffer status report, or by defining a special value) or RLC control. It is also possible to indicate to the source base station that the handover has failed by defining and transmitting information or PDCP control information. As another method, the UE may transmit an RRC connection re-establishment request message to the SRB (eg, SRB0 or SRB1) for the source base station in the above. As another method, in the fallback procedure in the above, when handover fails, the second bearer for the target base station is released for each bearer or in the second PDCP layer device structure of the bearer in which the DAPS handover method is configured, or the first It may be a procedure of switching to the PDCP layer device structure of the UE and resuming data transmission or reception through the first bearer for the source base station, indicating that there is data to be transmitted to the MAC layer device of the first bearer, The UE reports that there is a scheduling request or data to be transmitted to the source base station (e.g., buffer status report), or transmits new MAC CE or RLC control data or PDCP control data to fall back to the source base station to resume data transmission. Can instruct the base station. In addition, the SRB for the source base station may be newly configured or resumed. In addition, the fallback procedure in the above was previously set for each bearer when the handover fails, or bearers for which the DAPS handover method is not set, because they do not have a second PDCP layer device structure, and in the configuration information of the handover command message. The UE releases the reset PDCP layer device or RLC layer device or bearer configuration information or logical channel identifier information from the MAC layer device for the target base station or switches to the MAC layer device for the source base station, connects, and configures the source base station. The base station can resume data transmission or reception for each bearer. Because the UE can apply the bearer configuration information set in the handover command message to the MAC layer device for the target base station for the bearer for which the DAPS handover method is not indicated when receiving the handover command message, and the DAPS handover This is because the connection of the PDCP layer device or the RLC layer device corresponding to the bearer for which the over method is not indicated can be connected by switching from the MAC layer device for the source base station to the MAC layer device for the target base station. For example, when receiving the handover command message, the upper layer device (for example, the RRC layer device) of the terminal relates to a bearer for which the DAPS handover method is not indicated in the handover command message in the current MAC layer device configuration information. Configuration information other than the configuration information can be instructed to perform a reconfiguration (MAC reconfiguration) to the MAC layer device for the source base station, or the upper layer device (for example, RRC layer device) of the terminal is the current configuration information of the MAC layer device In the handover command message, it is possible to instruct the MAC layer device for the source base station to perform a reconfiguration (MAC reconfiguration) with configuration information including only configuration information related to the bearer in which the DAPS handover method is indicated. That is, when the handover command message is received, the configuration information of the PDCP layer device, RLC layer device, or MAC layer device of the bearer for which the DAPS handover method is not indicated is released from the MAC layer device for the source base station, and the target base station is released. Since it is possible to apply or perform connection to the MAC layer device for the target base station according to the bearer configuration for the target base station, when the terminal performs the fallback procedure, the bearer for which the DAPS handover method is not configured is transferred to the MAC layer device for the source base station. You need to perform a reset. For example, when the UE performs the fallback procedure, the upper layer device (for example, the RRC layer device) of the UE is related to the bearer for which the DAPS handover method is not indicated in the handover command message in the current MAC layer device configuration information. It can instruct the MAC layer device for the source base station to perform reconfiguration (MAC reconfiguration) with the configuration information along with the bearer configuration information in which the DAPS handover method is indicated, including configuration information, or when the fallback procedure is performed, the terminal Bearer settings (for example, PDCP layer device configuration information or RLC layer device configuration information or MAC layer device configuration information, or PHY layer device configuration information) before the over command message is received is reset or restored to provide a bearer for the source base station ( It can be applied to PDCP layer device configuration information or RLC layer device configuration information or MAC layer device configuration information or PHY layer device) of SRB or AM DRB or UM DRB.

4> In the fallback procedure, when the UE transmits a report message indicating that the handover has failed to the source base station (for example, the RRC message or MAC CE or RLC control data or PDCP control data proposed above), the fourth timer can be started. have. When receiving an instruction or message from the source base station in response to a report message indicating that the handover transmitted by the terminal has failed, the terminal may stop the fourth timer. However, if the fourth timer expires or if the response message is not received until the expiration, the terminal performs an RRC connection re-establishment procedure (releasing the connection with the base station and performing the RRC connection procedure again from the beginning, that is, A cell selection or reselection procedure may be performed, a random access procedure may be performed, and an RRC connection re-establishment request message may be transmitted). In addition, if the RRC connection re-establishment procedure is triggered due to the expiration of the fourth timer, the second timer or the third timer may be stopped if it is running.

◆3> If the second or third timer for the wireless connection between the terminal and the source base station or the target base station in the above has expired, or the wireless connection between the terminal and the source base station or the target base station is not valid.

●4> The terminal performs an RRC connection re-establishment procedure (releases the connection with the base station and performs the RRC connection procedure again from the beginning, that is, performs a cell selection or reselection procedure, performs a random access procedure, and re-establishes the RRC connection. Can transmit establishment request message).

■2> If the terminal satisfies the second condition proposed in the present disclosure when performing the DAPS handover procedure in the above, the connection with the source base station is released, or the SRB for the source base station is released, and the request for the source base station is released. If the second timer or the third timer is running, it can be stopped and initialized. In the above, it is possible to prevent unnecessary RRC connection re-establishment procedures due to expiration of the second timer or the third timer only by stopping the second timer or the third timer. Because when the second condition is satisfied, it may mean that the handover procedure has been successfully performed, so that the first timer is stopped and the expiration of the second timer or the third timer does not require an unnecessary RRC connection re-establishment procedure. Because it can be triggered. As another method, when the first condition proposed in the present disclosure is satisfied or the handover procedure is successfully completed, the UE releases the SRB for the source base station or the second timer or the third If the timer is running, it can be stopped and initialized. In the above, it is possible to prevent unnecessary RRC connection re-establishment procedures due to expiration of the second timer or the third timer only by stopping the second timer or the third timer. Because when the first condition is satisfied, it may mean that the handover procedure has been successfully performed, so that the first timer is stopped and the expiration of the second timer or the third timer triggers an unnecessary RRC connection re-establishment procedure. Because it can be done.

When the terminal determines that a handover failure has occurred according to the method proposed in the present disclosure and performs the fallback procedure by satisfying the condition proposed above, the terminal fails to handover to an RRC message (e.g., ULInformationTransferMRDC message or FailureInformation message). The source base station may check the handover failure of the terminal by transmitting the information indicating that the occurrence has occurred to SRB1 or SRB1 to which the second PDCP layer device structure is applied. In the above, when the source base station detects a handover failure of the terminal, it may configure an RRC message (for example, an RRCReconfiguration message or an RRCRelease message) to the terminal and transmit it to the terminal, in which the terminal responds to the handover failure report RRC When receiving the RRCReconfiguration message (SRB1 to which the second PDCP layer device structure is applied or the RRC message received through SRB1) as a message, the application of the configuration information is completed, and in response to the RRCReconfigurationComplete message, the second PDCP layer SRB1 or SRB1 to which the device structure is applied can be transmitted to the source base station, and if handover is instructed in the RRCReconfiguration or access to another cell is instructed, a random access procedure is completed to the cell and an RRCReconfigurationComplete message can be transmitted through SRB1. have. However, if the UE receives the RRCRelease message as a response RRC message to the handover failure report in the above, the UE may transition to the RRC idle mode or to the RRC deactivation mode according to the configuration information indicated in the RRCRelease message, An additional response RRC message to the RRC message may no longer be transmitted to the base station.

1L is a diagram illustrating a terminal operation applicable to embodiments proposed in the present disclosure.

In FIG. 1L, the terminal 1l-05 may transmit or receive data with the source base station through the first PDCP layer device structure for each bearer. However, when a handover command message is received and the DAPS handover method of the second embodiment proposed in the present disclosure is indicated in the handover command message, or when the DAPS handover method is indicated for each bearer, the target base station indicated in the message For each bearer or for bearers for which the DAPS handover method is indicated, the UE switches to the structure of the second PDCP layer device, sets and establishes the protocol layer devices of the second bearer, and configures the established protocol layer devices. Even when performing the random access procedure to the target base station through (1l-10, 1l-15), the terminal transmits or receives data with the source base station through the protocol layer devices of the first bearer (uplink data transmission and downlink data Receive) can continue (1l-20).

If the terminal satisfies the first condition (1l-25), the terminal stops transmitting the uplink data to the source base station through the protocol layer devices of the first bearer, and switches the uplink data transmission. Uplink data can be transmitted to the target base station through protocol layer devices. The UE may continue to receive downlink data from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer (1l-30). In addition, the PDCP layer device of the second bearer uses transmission or reception data or serial number information stored in the PDCP layer device of the first bearer or information such as header compression and decompression context to transmit data seamlessly with the target base station or You can continue to receive. In the above, if the first condition is not satisfied, the first condition can be checked while continuing the procedure previously performed (1l-35).

In addition, in the above, if the second condition is satisfied, the terminal may stop receiving downlink data from the source base station through the protocol layer devices of the first bearer (1l-45). In addition, the PDCP layer device of the second bearer uses transmission or reception data or serial number information stored in the PDCP layer device of the first bearer or information such as header compression and decompression context to transmit data seamlessly with the target base station or You can continue to receive.

If the second condition is not satisfied, the second condition can be checked while continuing the procedure previously performed (1l-50).

A specific embodiment of the PDCP layer apparatus proposed in the present disclosure may perform different procedures according to the type of handover indicated in the handover command message received by the terminal as follows.

- If the handover type indicated in the handover command message received from the source base station indicates the handover (for example, general handover procedure) of the first embodiment, or if the UE sends the handover command message When receiving, if the handover command message, ReconfigWithSync information, or MobilityControlInfo information indicates a first handover method (for example, the first embodiment of the present disclosure or a general handover method), or the second handover method proposed in the present disclosure If the embodiment (DAPS handover method) is not set, or if the second embodiment (DAPS handover method) proposed in the present disclosure is not configured for any bearer in the bearer configuration information, or the second embodiment proposed in the present disclosure For a bearer not set in the embodiment (DAPS handover method) in the bearer configuration information

■ The terminal may perform a PDCP layer device re-establishment procedure (PDCP re-establishment) to the PDCP layer device for each bearer. For example, the UE may initialize window state variables for SRB and discard stored data (PDCP SDU or PDCP PDU), initialize window state variables for UM DRB, and have not yet been transmitted to lower layer devices. Compressed based on the header (or data) compression context or security key of the target base station in ascending order of the COUNT value for data that has not expired or the PDCP discard timer has not expired, or is transmitted by encrypting or performing integrity protection. Retransmission can be performed. In addition, if the rearrangement timer is running, the UE can stop and initialize, process the received data (PDCP SDU or PDCP PDU) in order and deliver them to the upper layer device.For AM DRB, window state variables are not initialized, Compressed based on the header (or data) compression context or security key of the target base station in ascending order of the PDCP serial number or COUNT value from the first data (PDCP SDU or PDCP PDU) for which successful delivery from the lower layer device has not been confirmed, or Transmission or retransmission can be performed by encrypting or performing integrity protection. In addition, the receiving PDCP layer device can process or store data received due to the re-establishment procedure of a lower layer device (for example, an RLC layer device), and an indicator to continue using the header compression context for AM DRBs. In the absence of (drb-Continue ROHC), a header decompression procedure may be performed on the stored data based on a header compression context (ROHC). In addition, the receiving PDCP layer device can process or store the received data due to the re-establishment procedure of the lower layer device (for example, the RLC layer device), and header compression for data stored for AM DRBs A header compression decompression procedure may be performed based on the context (Ethernet Header Compression (EHC)). Alternatively, the receiving PDCP layer device can process or store the data received due to the re-establishment procedure of the lower layer device (for example, the RLC layer device), and continue the header compression context for AM DRBs. When there is no indication to use (drb-Continue Ethernet Header Compression (EHC)), a header compression decompression procedure may be performed on the stored data based on a header compression context (Ethernet header compression (EHC)).

- If the handover type indicated in the handover command message received from the source base station indicates the handover of the second embodiment (or is indicated for each bearer), or if the UE receives the handover command message When the second embodiment proposed in the present disclosure (DAPS handover method) is set in the handover command message, ReconfigWithSync information, or MobilityControlInfo information, or the second embodiment proposed in the present disclosure (DAPS handover method) Is configured for a certain bearer in the bearer configuration information, or if the second embodiment (DAPS handover method) proposed in the present disclosure is configured for at least one bearer in the bearer configuration information, or the second embodiment proposed in this disclosure For the bearer set in the embodiment (DAPS handover method) in the bearer configuration information

■ A PDCP layer device in which the terminal receives the handover command message and the DAPS handover method is indicated may perform the following procedures without performing a PDCP re-establishment procedure. For example, the terminal initializes the window state variables for the SRB (the variable initialization may be omitted for fallback in case of a DAPS handover failure) or the stored data (PDCP SDU or PDCP PDU) may be discarded, For UM DRB, window state variables are not initialized, and data transmission or reception with the source base station can be continuously performed on data that has not yet been transmitted to the lower layer device or data for which the PDCP discard timer has not expired. With respect to, the window state variables may not be initialized, and data transmission or reception with the source base station may be continuously performed. In addition, the uplink or downlink ROHC context for the source base station is not initialized and used as it is, the uplink or downlink ROHC context for the target base station is initialized, and can be started in an initial state (for example, an IR state in U mode). have. As another method, the uplink or downlink ROHC context for the source base station can be initialized and started in an initial state (for example, the U mode IR state), and the uplink or downlink ROHC context for the target base station is initialized. , It can start with the initial state (for example, the IR state in U mode).

■ The terminal may perform the proposed procedures for each bearer (or for the bearer indicated by the second embodiment) when the first condition is satisfied in the present disclosure.

■ The terminal may perform the proposed procedures for each bearer (or for the bearer indicated by the second embodiment) when the second condition in the present disclosure is satisfied.

The terminal uses a data compression protocol (for example, Uplink data compression protocol) when the handover command message is received for a bearer for which the second embodiment (or DAPS handover method) is not indicated (or not configured). You can release the setting information or context for. Or, when receiving the handover command message, the UE transmits the configuration information or context of the data compression protocol (eg, Uplink data compression protocol) to the PDCP layer device by the upper layer device (eg, RRC layer device) of the UE. You can tell it to turn off or reset it. However, for the bearer in which the second embodiment (or DAPS handover method) is indicated (or configured), the terminal configures the data compression protocol (for the source base station) when the first condition proposed in the present disclosure is satisfied. Information or context can be released (for example, Uplink data compression protocol). Or, when the first condition is satisfied, the upper layer device (e.g., RRC layer device) of the terminal to the PDCP layer device (for the source base station) data compression protocol (e.g., Uplink data compression protocol) configuration It can instruct or reset information or context to release. This is because, for a bearer in which the DAPS handover method is configured, data must be compressed and transmitted to the source base station using the context or configuration information on the data compression protocol for the source base station until the first condition is satisfied.

■ One of the following methods may be applied to a bearer or PDCP layer device for which a DAPS handover method is not indicated after receiving the handover command message.

◆ Method 1: For a bearer or PDCP layer device for which the DAPS handover method is not configured above, when a handover command message is received, the PDCP re-establishment procedure may not be triggered or performed. Alternatively, the target base station does not set the PDCP re-establishment procedure for the bearers in the handover command message), and when the first condition proposed in the present disclosure is satisfied, the PDCP re-establishment procedure may be triggered or performed (target base station Even if the PDCP re-establishment procedure is set for the bearer in this handover command message, it may be performed when the first condition is satisfied). Specifically, when the first condition is satisfied, the upper layer device (e.g., RRC layer device) of the terminal may trigger or request a PDCP re-establishment procedure for a bearer or bearers for which the DAPS handover method is not set. have. The PDCP layer device that has requested the PDCP re-establishment procedure may perform a different PDCP re-establishment procedure for each bearer. For example, the PDCP layer device initializes the window state variables for the UM DRB, and for data that has not yet been transmitted to the lower layer device or the PDCP discard timer has not expired, the header of the target base station is in ascending order of the COUNT value. (Or data) can be transmitted or retransmitted by compressing or encrypting based on the compression context or security key, or performing integrity protection. Alternatively, if the reordering timer is running, the PDCP layer device may stop, initialize, process received data (PDCP SDU or PDCP PDU) in order, and transmit the data to the upper layer device. Alternatively, the PDCP layer device does not initialize the window state variables for AM DRB, and the target base station in ascending order of the PDCP serial number or COUNT value from the first data (PDCP SDU or PDCP PDU) for which successful delivery from the lower layer device has not been confirmed. The header (or data) of the header (or data) may be compressed or encrypted based on a compression context or a security key, or integrity protection may be performed to perform transmission or retransmission. In the above, when a handover command message is received for bearer(s) for which the DAPS handover method is not configured, the PDCP re-establishment procedure is not performed, and the PDCP re-establishment procedure is performed when the first condition is satisfied. , If the terminal fails the handover procedure to the target base station, it may perform a fallback to the source base station.The bearers compress data in the header (or data) compression context of the target base station in the PDCP re-establishment procedure, and This is because data processed by performing encryption or integrity protection with a security key becomes useless when it needs to fall back and must be discarded. In addition, when the terminal needs to fall back, the bearers are re-established by performing a PDCP re-establishment procedure, compressing data with the header (or data) compression context of the source base station for the data to be transmitted, and encrypting the data with the security key of the source base station or This is because unnecessary processing occurs because integrity protection must be performed again. Therefore, when the terminal performs the DAPS handover method, for a bearer for which the DAPS handover method is not set, the PDCP re-establishment procedure is not triggered or performed when the handover command message is received, and the first condition must be satisfied. When the PDCP re-establishment procedure may be triggered or performed. In addition, a PDCP re-establishment procedure may not be performed for a bearer in which the DAPS handover method is configured.

◆Method 2: When a handover command message is received for a bearer(s) for which the DAPS handover method is not configured, the upper layer device (for example, RRC layer device) of the terminal may trigger or request a PDCP re-establishment procedure. . The PDCP layer device that has requested the PDCP re-establishment procedure may perform a different PDCP re-establishment procedure for each bearer. For example, for UM DRB, the window state variables are initialized, and the header (or data) of the target base station in ascending order of the COUNT value for data that has not yet been transmitted to the lower layer device or the PDCP discard timer has not expired. Transmission or retransmission may be performed by compressing or encrypting based on the compression context or security key, or performing integrity protection. In addition, if the reordering timer is running, the PDCP layer device may stop, initialize, process received data (PDCP SDU or PDCP PDU) in order, and transmit the data to the upper layer device. In addition, the PDCP layer device does not initialize the window state variables for AM DRB, and the target base station in ascending order of the PDCP serial number or COUNT value from the first data (PDCP SDU or PDCP PDU) that has not been successfully delivered from the lower layer device. The header (or data) of the header (or data) may be compressed or encrypted based on a compression context or a security key, or integrity protection may be performed to perform transmission or retransmission. When a handover command message is received for the bearer(s) for which the DAPS handover method is not set, data is compressed in the header (or data) compression context of the target base station by the PDCP re-establishment procedure, and the security of the target base station Since data has been processed by performing encryption or integrity protection with a key, if the terminal fails the handover procedure to the target base station (for example, if the first timer expires or if the wireless connection to the target base station fails), And if the UE performs fallback because it is possible to fall back to the source base station, data generated or processed for transmission from the bearers to the target base station (for example, PDCP PDUs) may be discarded. The higher layer device (eg, RRC layer device) of the terminal does not indicate the DAPS handover method so that data (eg, PDCP SDUs) can be processed again based on the header (or data) compression context or the security key. To bearers that are not instructed to discard data (PDCP PDUs) processed based on configuration information (security key or header (or data) compression context) for the target base station or PDCP re-establishment procedure or configuration information for the source base station ( Security key or header (or data) compression context) may be reset, and data may be requested or instructed to regenerate or process data based on source base station configuration information.

In addition, in the above of the present disclosure, when the source base station instructs the terminal to handover to apply the embodiments proposed in the present disclosure, the source base station may start data forwarding to the target base station when the following third condition is satisfied. The third condition may mean that one or more of the following conditions are satisfied.

- When receiving an indication that the terminal has successfully completed handover from the target base station

- When sending a handover command message to the terminal

- When transmitting a handover command message to the terminal and confirming successful delivery (HARQ ACK or NACK or RLC ACK or NACK) for the handover command message

- When the source base station receives an indication (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU) from the terminal to release the connection with the source base station

- When the timer expires by transmitting a handover command message to the terminal and driving a predetermined timer

- When information about successful delivery of downlink data (HARQ ACK or NACK or RLC ACK or NACK) from the terminal is not received for a predetermined time

In the following of the present disclosure, a terminal operation that specifically performs the techniques proposed above is proposed.

- 1> If the terminal receives a handover command message (e.g., RRCReconfiguration message) or ReconfigWithSync information (for NR base station) or MobilityControlInfo information (for LTE base station) in the RRCReconfiguration message, one of the following operations One or more operations may be performed.

■2> The first timer proposed in this disclosure is started.

2> If the second handover method (for example, the second embodiment of the present disclosure or the DAPS handover method) is not indicated above, or if the DAPS handover method is not indicated for each bearer identifier or logical channel identifier, or at least If the DAPS handover method is not set for one bearer, or if the DAPS handover method is not set for any bearer,

◆3> If the second timer for the source base station proposed in the present disclosure is running, it can be stopped.

2> If the second handover method (for example, the second embodiment of the present disclosure or the DAPS handover method) is indicated above, or if the DAPS handover method is indicated for each bearer identifier or logical channel identifier, or at least one When a DAPS handover method is configured for a bearer, a DAPS handover method is configured for a certain bearer, or a bearer for which the DAPS handover method is configured, one or more of the following operations may be performed.

◆3> Even if the second timer for the source base station proposed in this disclosure is running, it does not stop.

◆3> Stop SRBs for the source base station.

◆3> A MAC layer device for the target base station can be created or established.

◆3> A new terminal identifier (eg, C-RNTI) can be applied in the MAC or PHY layer device for the target base station or for the target base station.

◆3> Set configuration information for the target base station set in the handover message to lower layer devices (e.g., SDAP layer device, PDCP layer device, RLC layer device, MAC layer device or PHY layer device for target base station) I can.

◆3> SCells configured in the source base station can be regarded as inactive.

◆3> RLC layer devices may be created or established in the MAC layer device for the target base station or for the target base station based on the configuration information of the RLC layer device received in the handover command message.

◆3> Based on the configuration information of the MAC layer device received in the handover command message, the logical channel identifier or related configuration information (for example, priority or prioritizedBiteRate or BucketSizeDuration, etc.) in the MAC layer device for the target base station or for the target base station. ) Can be created or established.

◆3> Configuration of MAC layer devices related to bearers for which the DAPS handover method is not configured in the handover command message in the current or previous or existing configuration information (for example, MAC layer device configuration information) for the source base station Configuration information other than information (such as a logical channel identifier or priority or prioritizedBiteRate or BucketSizeDuration) may be reset to a lower layer device (eg, a MAC layer device). As another method, the DAPS handover method in the handover command message in the source base station or current or previous or existing configuration information (for example, MAC layer device configuration information (logical channel identifier or priority or prioritizedBiteRate or BucketSizeDuration, etc.)) Only configuration information of the MAC layer device related to the configured bearers may be reset to a lower layer device (for example, a MAC layer device). Specifically, the MAC layer device configuration information (logical channel identifier or priority or prioritizedBiteRate or BucketSizeDuration, etc.) for the bearer for which the DAPS handover method is set in the MAC layer device for the source base station is maintained or configured, and the DAPS handover method is not configured. MAC layer device configuration information for a bearer (such as a logical channel identifier or priority or prioritizedBiteRate or BucketSizeDuration) may be released. As another method, in the above, when the source base station performs the DAPS handover method, configuration information of the MAC layer device for the source base station to be applied may be set as an RRC message.

◆3> Create or establish a PDCP layer device corresponding to the SRB or SRB identifier for the target base station or the MAC layer device for the target base station, and encrypt or decrypt it together with security keys for the target base station received in the handover command message. An algorithm or integrity protection or integrity verification algorithm may be set in the PDCP layer device. The PDCP device may set the encryption function or the integrity protection function by applying the security key or algorithm if the encryption function or the integrity function is set or not released.

◆3> If there is PDCP layer device configuration information for the SRB or SRB identifier, apply, if not, apply default configuration.

◆3> For bearers (SRB or DRB) for which DAPS handover method is set, the PDCP re-establishment procedure indicator can always be set to False so that the PDCP re-establishment procedure cannot be triggered. This is because if the PDCP re-establishment procedure is performed, a data interruption time may occur in the DAPS handover method. As another method, the PDCP re-establishment procedure can be instructed for the SRB and the PDCP re-establishment procedure cannot be instructed for the DRB. This is because the SRB may be configured independently of the SRB for the source base station and the SRB for the target base station.

◆3> For a bearer (SRB or DRB) in which the DAPS handover method is set, the structure of the first PDCP layer device may be reset to the structure of the second PDCP layer device.

◆3> If the configuration information of the SDAP layer device (eg, QoS and bearer mapping information) is included, the configuration information of the SDAP layer device can be set for the target base station. The configuration information of the existing SDAP layer device for the source base station can be maintained, and can be released when the connection with the source base station is released.

◆3> If the entire configuration information is newly configured (Full configuration), the default value of the first timer or the second timer is applied to the target base station and operated, and the default setting is performed for the PHY layer device or the MAC layer device. Information is applied, and basic configuration information is also applied to SRBs. In addition, the current base station or source base station configuration information is maintained and applied as it is.

■2> If not (for example, if the second handover method (for example, the second embodiment of the present disclosure or the DAPS handover method) is not indicated above, or the DAPS handover method for each bearer identifier or logical channel identifier If this is not indicated, or if the DAPS handover method is not configured for at least one bearer, or if the DAPS handover method is not configured for any bearer, or for a bearer for which DAPS handover is not configured), one of the following operations: One or more operations may be performed.

◆3> The MAC layer device for the source base station or for the current base station can be initialized.

◆3> SCells configured in the source base station can be regarded as inactive.

◆3> A new terminal identifier (eg, C-RNTI) can be applied in the MAC or PHY layer device for the source base station or the current base station or for the current base station.

◆3> If the RLC re-establishment procedure is instructed, the RLC re-establishment procedure can be performed.

◆3> If the PDCP re-establishment procedure is instructed, the PDCP re-establishment procedure can be performed.

◆3> lower layer devices (e.g., SDAP layer device, PDCP layer device, RLC layer device, MAC layer device or PHY layer device for the current base station or cell group). ) Can be reset.

◆3> If the configuration information of the SDAP layer device (for example, QoS and bearer mapping information) is included, the configuration information of the current SDAP layer device can be reset to the configuration information of the SDAP layer device.

◆3> If all configuration information is newly configured (Full configuration), all the configuration information for the current base station or source base station (SDAP layer device or PDCP layer device or RLC layer device or MAC layer device or PHY layer device configuration information). Release. In addition, the default value of the first timer or the second timer is applied and operated for the current base station or the source base station, and the basic configuration information is applied to the PHY layer device or the MAC layer device, and the basic configuration information is also applied to the SRBs. Apply.

- 1> If the first timer proposed in this disclosure has expired (for example, if the handover procedure has failed)

■2> If the first timer for the source base station has expired

◆3> If it is set in the setting information related to random access, cancel the designated preamble information.

◆3> If the second handover method (for example, the second embodiment of the present disclosure or the DAPS handover method) is indicated above, or if the DAPS handover method is indicated for each bearer identifier or logical channel identifier, or at least one If the DAPS handover method is set for the bearer, or if the DAPS handover method is set for a bearer, and the radio connection between the source base station and the terminal has not failed or the radio connection has not failed (the second timer or the third 'S timer has not expired)

4> Resumes the suspended SRBs set in the MAC layer device for the source base station or for the source base station (or target base station).

●4> A handover failure message may be configured through the resumed SRBs and transmitted to the source base station. Alternatively, DRBs can be resumed and data transmission or reception can be resumed.

◆3> If not (for example, if the DAPS handover method is not set, or if the DAPS handover method is set but the wireless connection with the source base station fails)

●4> The configuration information of the terminal can be set by returning the configuration information previously used in the source base station.

●4> It is possible to trigger and perform an RRC connection re-establishment procedure.

- 1> If the terminal detects a wireless connection problem in the physical layer device

■2> If the second handover method (for example, the second embodiment of the present disclosure or the DAPS handover method) is set, or if the DAPS handover method is set for each bearer identifier or logical channel identifier, or at least one bearer If the DAPS handover method is set for, or if the DAPS handover method is set for a certain bearer, and the first timer is running, a radio connection signal from a lower layer device (for example, a MAC layer device or a PHY layer device) If it detects that there is a problem with the physical layer device by receiving the out-of-sync indication for a predetermined number of times (for example, the base station can set it)

◆3> A second timer (eg T310) can be started.

■2> An out-of-sync indication from a lower layer device (for example, a MAC layer device or a PHY layer device) indicating that the radio connection signal is out of synchronization is set a predetermined number of times (for example, the base station can set it). Yes) and detects that there is a problem in the physical layer device, and when the first timer or timer T300 or T301 or T304 or T311 or T319 is not running

◆3> A second timer (eg T310) can be started. However, if the first timer is running when the DAPS handover method is not set, the second timer is not started even when a physical layer problem is detected in the above.

- 1> When the RRC layer device of the terminal receives a handover command message (e.g., RRCReconfiguration message) or in the RRCReconfiguration message, ReconfigWithSync information (for NR base station) or MobilityControlInfo information (for LTE base station) or target If the random access procedure triggered by the base station or the MAC layer device of a cell group is successfully completed

■2> Stop the first timer for the source base station or target base station or cell group.

■2> If the second timer for the source base station is running (during handover), the second timer is stopped. This is because when the second timer expires, an unnecessary RRC connection re-establishment procedure may be triggered.

■2> If the second handover method (for example, the second embodiment of the present disclosure or the DAPS handover method) is set as another method, or if the DAPS handover method is set for each bearer identifier or logical channel identifier

◆3> If the second timer for the source base station is running, the second timer is stopped. This is because when the second timer expires, an unnecessary RRC connection re-establishment procedure may be triggered.

■2> Stop a third timer for the source base station or target base station or cell group.

1M is a diagram illustrating an operation of a terminal performing a fallback procedure when a handover fails in the DAPS handover method proposed in the present disclosure.

In FIG. 1M, the terminal 1m-01 may transmit or receive data with the source base station through the first PDCP layer device structure for each bearer. However, when the handover command message is received (1m-05) and the DAPS handover method of the second embodiment proposed in the present disclosure is indicated in the handover command message or the DAPS handover method is indicated for each bearer, in the message For the indicated target base station, the UE switches to the structure of the second PDCP layer device for each bearer or the bearers for which the DAPS handover method is indicated, sets and establishes the protocol layer devices of the second bearer, and establishes the established protocol. Even when performing the random access procedure to the target base station through layer devices (1m-10, 1m-15), the terminal transmits or receives data with the source base station through the protocol layer devices of the first bearer (uplink data transmission and Downlink data reception) can be continued (1m-20).

If the terminal successfully completes the handover procedure (1m-25), the terminal completes the handover procedure according to the second embodiment (DAPS handover method) of the handover method proposed in the present disclosure.

However, if the terminal fails the handover procedure (1m-25) (for example, if the first timer in the above has expired (for example, if the handover procedure fails to the target base station), or the maximum retransmission in the RLC layer device If the number of times is exceeded or the handover command message is received in the above, and the terminal fails to handover because the configuration information of the handover command message exceeds the capability of the terminal, or an error occurs in the application of the configuration information, or the target If the handover procedure fails due to a random access problem to the base station, or if the second timer or the third timer is driven for the target base station above, the second timer or the third timer is completed before the handover procedure is completed. If the timer of T304 stops or expires and it is determined that the handover procedure has failed), if the second timer or the third timer for the wireless connection between the terminal and the source base station in the above has not expired (or In the above, if the second timer or the third timer for wireless connection between the terminal and the source base station is not started or is running) (1m-40) or if the wireless connection between the terminal and the source base station is valid, the terminal It is determined that the wireless connection between the terminal and the source base station is valid, and the fallback procedure proposed in the present disclosure may be performed (1m-45). If the second timer or the third timer for the wireless connection between the UE and the source base station in the above has expired, or if the wireless connection between the UE and the source base station is not valid (1m-30), the UE performs an RRC connection re-establishment procedure. (It is possible to release the connection with the base station and perform the RRC connection procedure again from the beginning, that is, perform a cell selection or reselection procedure, perform a random access procedure, and transmit an RRC connection re-establishment request message) (1m -45).

1N is a diagram illustrating a structure of a terminal according to an embodiment of the present disclosure.

Referring to the drawing, the terminal includes a radio frequency (RF) processing unit 1n-10, a baseband, a processing unit 1n-20, a storage unit 1n-30, and a control unit 1n-40. do.

The RF processing unit 1n-10 performs functions for transmitting and receiving signals through a wireless channel, such as band conversion and amplification of signals. That is, the RF processing unit 1n-10 up-converts the baseband signal provided from the baseband processing unit 1n-20 to an RF band signal, and then transmits it through an antenna, and an RF band signal received through the antenna. Is down-converted to a baseband signal. For example, the RF processing unit 1n-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), and the like. I can. In the drawing, only one antenna is shown, but the terminal may include a plurality of antennas. In addition, the RF processing unit 1n-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1n-10 may perform beamforming. For the beamforming, the RF processing unit 1n-10 may adjust a phase and a magnitude of each of signals transmitted/received through a plurality of antennas or antenna elements. In addition, the RF processor may perform MIMO, and may receive multiple layers when performing the MIMO operation. The RF processing unit 1n-10 may perform reception beam sweeping by appropriately setting a plurality of antennas or antenna elements under the control of the controller, or adjust the direction and beam width of the reception beam so that the reception beam cooperates with the transmission beam. have.

The baseband processing unit 1n-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the system. For example, when transmitting data, the baseband processing unit 1n-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 1n-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 1n-10. For example, in the case of the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit 1n-20 generates complex symbols by encoding and modulating a transmission bit stream, and subcarriers the complex symbols. After mapping to, OFDM symbols are constructed through an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processing unit 1n-20 divides the baseband signal provided from the RF processing unit 1n-10 in units of OFDM symbols, and applies a fast Fourier transform (FFT) operation to subcarriers. After restoring the mapped signals, the received bit stream is restored through demodulation and decoding.

The baseband processing unit 1n-20 and the RF processing unit 1n-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1n-20 and the RF processing unit 1n-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, or a communication unit. Furthermore, at least one of the baseband processing unit 1n-20 and the RF processing unit 1n-10 may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit 1n-20 and the RF processing unit 1n-10 may include different communication modules to process signals of different frequency bands. For example, the different radio access technologies may include an LTE network, an NR network, and the like. In addition, the different frequency bands may include a super high frequency (SHF) (eg, 2.5GHz, 5Ghz) band, and a millimeter wave (eg, 60GHz) band.

The storage unit 1n-30 stores data such as a basic program, an application program, and setting information for the operation of the terminal. The storage unit 1n-30 provides stored data according to the request of the control unit 1n-40.

The controller 1n-40 controls overall operations of the terminal. For example, the controller 1n-40 may control components of the terminal to efficiently perform different handover methods for each bearer according to an embodiment of the present disclosure. Also, for example, the control unit 1n-40 transmits and receives signals through the baseband processing unit 1n-20 and the RF processing unit 1n-10. In addition, the control unit 1n-40 writes and reads data in the storage unit 1n-40. To this end, the control unit 1n-40 may include at least one processor. For example, the controller 1n-40 may include a communication processor (CP) that controls communication and an application processor (AP) that controls an upper layer such as an application program.

1O is a block diagram of a TRP (eg, a base station) in a wireless communication system according to an embodiment of the present disclosure.

As shown in the figure, the base station includes an RF processing unit (1o-10), a baseband processing unit (1o-20), a backhaul communication unit (1o-30), a storage unit (1o-40), and a control unit (1o-50). Consists of including.

The RF processing unit 1o-10 performs a function of transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processing unit 1o-10 up-converts the baseband signal provided from the baseband processing unit 1o-20 to an RF band signal, and then transmits it through an antenna, and an RF band signal received through the antenna. Downconvert to a baseband signal. For example, the RF processing unit 1o-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like. In the drawing, only one antenna is shown, but the first access node may include a plurality of antennas. In addition, the RF processing unit 1o-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1o-10 may perform beamforming. For the beamforming, the RF processing unit 1o-10 may adjust a phase and a magnitude of each of signals transmitted/received through a plurality of antennas or antenna elements. The RF processor may perform a downlink MIMO operation by transmitting one or more layers.

The baseband processing unit 1o-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the first wireless access technology. For example, when transmitting data, the baseband processing unit 1o-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 1o-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 1o-10. For example, in the case of the OFDM scheme, when transmitting data, the baseband processor 1o-20 generates complex symbols by encoding and modulating a transmission bit stream, mapping the complex symbols to subcarriers, and then IFFT OFDM symbols are configured through calculation and CP insertion. In addition, when receiving data, the baseband processing unit 1o-20 divides the baseband signal provided from the RF processing unit 1o-10 in units of OFDM symbols, and reconstructs signals mapped to subcarriers through FFT operation. After that, the received bit stream is restored through demodulation and decoding. The baseband processing unit 1o-20 and the RF processing unit 1o-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1o-20 and the RF processing unit 1o-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, a communication unit, or a wireless communication unit.

The communication unit 1o-30 provides an interface for performing communication with other nodes in the network.

The storage unit 1o-40 stores data such as a basic program, an application program, and setting information for the operation of the main station. In particular, the storage unit 1o-40 may store information on bearers allocated to the connected terminal, measurement results reported from the connected terminal, and the like. In addition, the storage unit 1o-40 may store information that is a criterion for determining whether to provide multiple connections to the terminal or to stop. In addition, the storage unit 1o-40 provides stored data according to the request of the control unit 1o-50.

The control unit 1o-50 controls overall operations of the main station. For example, the controller 1o-50 may control components of the terminal to efficiently perform different handover methods for each bearer according to an embodiment of the present disclosure. In addition, for example, the control unit 1o-50 transmits and receives signals through the baseband processing unit 1o-20 and the RF processing unit 1o-10 or through the backhaul communication unit 1o-30. In addition, the control unit 1o-50 writes and reads data in the storage unit 1o-40. To this end, the control unit 1o-50 may include at least one processor.

The methods according to the embodiments described in the claims of the present disclosure or the description of the invention may be implemented in the form of hardware, software, or a combination of hardware and software.

When implemented in software, a computer-readable storage medium or computer program product storing one or more programs (software modules) may be provided. One or more programs stored in a computer-readable storage medium or a computer program product are configured to be executable by one or more processors in an electronic device (device). The one or more programs include instructions for causing the electronic device to execute methods according to embodiments described in the claims or specification of the present disclosure.

These programs (software modules, software) include random access memory, non-volatile memory including flash memory, read only memory (ROM), and electrically erasable programmable ROM. (EEPROM: Electrically Erasable Programmable Read Only Memory), magnetic disc storage device, Compact Disc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or other types of It may be stored in an optical storage device or a magnetic cassette. Alternatively, it may be stored in a memory composed of a combination of some or all of them. In addition, a plurality of configuration memories may be included.

In addition, the program is accessed through a communication network such as Internet, Intranet, Local Area Network (LAN), Wide LAN (WLAN), or Storage Area Network (SAN), or a combination of these. It may be stored in an (access) attachable storage device. Such a storage device may access a device performing an embodiment of the present disclosure through an external port. In addition, a separate storage device on the communication network may access a device performing an embodiment of the present disclosure.

In the present disclosure, the term "computer program product" or "computer readable medium" refers to a medium such as a memory, a hard disk installed in a hard disk drive, and a signal as a whole. Is used for These "computer program products" or "computer-readable recording media" are means for providing a method for efficiently performing different handover methods for each bearer in the wireless communication system according to the present disclosure.

In the specific embodiments of the present disclosure described above, the constituent elements included in the present disclosure are expressed in the singular or plural according to the presented specific embodiments. However, the singular or plural expression is selected appropriately for the situation presented for convenience of description, and the present disclosure is not limited to the singular or plural constituent elements, and even constituent elements expressed in plural are composed of the singular or in the singular. Even the expressed constituent elements may be composed of pluralities.

Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, various modifications may be made without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure is limited to the described embodiments and should not be determined, and should be determined by the scope of the claims and equivalents as well as the scope of the claims to be described later.

Claims (1)

In the method of operating a terminal in a wireless communication system,
Receiving a handover command from a source base station;
Generating a protocol layer apparatus of a second bearer for a target base station based on the information included in the handover command;
Performing random access to the target base station;
And determining whether to maintain data transmission/reception with the source base station based on a predetermined condition.

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