WO2020256420A1 - Method and device for transmitting small data - Google Patents

Abstract

The present disclosure relates to a method and device for small data transmission by a terminal utilizing 5G NR wireless communication technology. According to one example, a terminal for transmitting small data performs the steps of: transmitting an RRC connection resume request to a lower stratum from a non-access stratum (NAS) of a terminal in an RRC inactive state; obtaining small data transmission instruction information by means of Message 3 (Msg 3) or Message A (Msg A) from a MAC entity on the basis of the RRC connection resume request; transmitting the Msg 3 or Msg A comprising small data to a base station; and receiving Msg 4 or Msg B comprising confirmation information with respect to the Msg 3 or Msg A from the base station.

Description

Small data transmission method and device

The present disclosure relates to a method and apparatus for transmitting a small amount of data by a terminal using 5G NR wireless communication technology.

There are demands for large-capacity data processing, high-speed data processing, and various service demands using wireless terminals in vehicles and industrial sites. As described above, there is a need for a technology for a high-speed and large-capacity communication system capable of processing various scenarios and large-capacity data, such as video, wireless data, and machine-type communication data, beyond a simple voice-oriented service. To this end, ITU-R discloses the requirements for adopting the IMT-2020 international standard, and research on next-generation wireless communication technology to meet the requirements of IMT-2020 is in progress.

In particular, 3GPP is conducting research on the LTE-Advanced Pro Rel-15/16 standard and the NR (New Radio Access Technology) standard in parallel to satisfy the IMT-2020 requirements referred to as 5G technology. It plans to receive approval as the next generation wireless communication technology.

Meanwhile, with the development of wireless communication technology, a number of application applications are installed in portable communication terminals and IoT terminals such as smart phones. Many application applications installed in smart phone terminals, MTC terminals, IoT terminals, etc. frequently transmit numerous small data packets. In these cases, the UE must transition to the RRC connected state in order to transmit a small amount of data, which causes signaling overhead as a whole. In addition, in terms of the terminal, it is inefficient because it causes power consumption due to frequent RRC state change procedures.

Accordingly, there is a need for a new method of data transmission and access control technology in order to reduce overall system overhead while minimizing power consumption of the terminal.

The present disclosure proposes a technique for transmitting a small amount of data while minimizing terminal system overhead.

In one aspect, a method of transmitting a small amount of data by the terminal is based on the step of transmitting an RRC connection resumption request to a lower layer in the non-access stratum (NAS) layer of the RRC inactive state terminal and the RRC connection resumption request. Thus, the steps of acquiring the instruction information for small data transmission through Msg 3 (Message 3) or Msg A (Message A) from the MAC entity and transmitting Msg 3 or Msg A including the small amount of data to the base station and Msg 3 or Msg And receiving Msg 4 or Msg B including confirmation information for A from the base station.

In another aspect, the method of receiving a small amount of data by the base station includes the steps of transmitting the small amount of data transmission configuration information necessary for the terminal to transmit small amount of data through Msg 3 (Message 3) or Msg A (Message A) to the terminal and from the terminal. Receiving Msg 3 or Msg A including a small amount of data, and transmitting Msg 4 or Msg B including confirmation information for Msg 3 or Msg A to the terminal.

In another aspect, the terminal transmitting a small amount of data transmits the RRC connection resumption request to the lower layer in the NAS (Non-Access Stratum) layer of the RRC inactive state terminal, and the MAC based on the RRC connection resumption request. A control unit that controls the entity to acquire small data transmission instruction information through Msg 3 (Message 3) or Msg A (Message A), a transmitter that transmits Msg 3 or Msg A containing small amount of data to the base station, and Msg 3 or Msg It provides a terminal device including a receiver for receiving Msg 4 or Msg B including confirmation information for A from a base station.

In another aspect, the base station receiving a small amount of data transmits a small amount of data transmission configuration information necessary for the terminal to transmit a small amount of data through Msg 3 (Message 3) or Msg A (Message A) to the terminal and a small amount from the terminal. It includes a receiving unit for receiving Msg 3 or Msg A including data, wherein the transmitting unit provides a base station apparatus further transmitting Msg 4 or Msg B including confirmation information for Msg 3 or Msg A to the terminal.

According to the present disclosure, it is possible to transmit a small amount of data while minimizing power consumption and system overhead of a terminal.

1 is a diagram schematically illustrating a structure of an NR wireless communication system to which the present embodiment can be applied.

2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.

3 is a diagram illustrating a resource grid supported by a radio access technology to which the present embodiment can be applied.

4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.

5 is a diagram illustrating a synchronization signal block in a wireless access technology to which the present embodiment can be applied.

6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.

7 is a diagram for explaining CORESET.

8 is a diagram illustrating an example in which different subcarrier spacings are arranged at a symbol level.

9 is a diagram illustrating an example of a terminal configuration including a 5GMM (or NAS MM) entity to which the present embodiment can be applied.

10 is a diagram for explaining a 2-step random accessor procedure (2-step RACH) to which the present embodiment can be applied.

11 is a flowchart illustrating an operation of a terminal according to the present embodiment.

12 is a flowchart illustrating an operation of a base station according to the present embodiment.

13 is a diagram illustrating an example of a mapping table for processing an access category to which the present embodiment can be applied.

14 is a diagram exemplarily showing setup cause information included in an RRC Setup Request message to which this embodiment can be applied.

15 is a diagram illustrating an Operator-defined access category definition format according to an embodiment.

16 is a diagram illustrating an Operator-defined access category definition format according to another embodiment.

17 is a diagram illustrating an operator-defined access category definition information element according to an embodiment.

18 is a diagram for describing a configuration of a terminal according to an embodiment.

19 is a diagram illustrating a configuration of a base station according to an embodiment.

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to exemplary drawings. In adding reference numerals to elements of each drawing, the same elements may have the same numerals as possible even if they are indicated on different drawings. In addition, in describing the embodiments, when it is determined that a detailed description of a related known configuration or function may obscure the gist of the present technical idea, the detailed description may be omitted. When "include", "have", "consists of" and the like mentioned in the present specification are used, other parts may be added unless "only" is used. In the case of expressing the constituent elements in the singular, the case including plural may be included unless there is a specific explicit description.

In addition, in describing the constituent elements of the present disclosure, terms such as first, second, A, B, (a) and (b) may be used. These terms are only for distinguishing the component from other components, and the nature, order, order, or number of the component is not limited by the term.

In the description of the positional relationship of the components, when two or more components are described as being "connected", "coupled" or "connected", the two or more components are directly "connected", "coupled" or "connected" ", but it will be understood that two or more components and other components may be further "interposed" to be "connected", "coupled" or "connected". Here, the other components may be included in one or more of two or more components "connected", "coupled" or "connected" to each other.

In the description of the temporal flow relationship related to the components, the operation method or the manufacturing method, for example, the temporal predecessor relationship such as "after", "after", "after", "before", etc. Alternatively, a case where a flow forward and backward relationship is described may also include a case that is not continuous unless "direct" or "direct" is used.

On the other hand, when a numerical value for a component or its corresponding information (e.g., level, etc.) is mentioned, the numerical value or its corresponding information is related to various factors (e.g., process factors, internal or external impacts, etc.) It can be interpreted as including an error range that may be caused by noise, etc.).

The wireless communication system in the present specification refers to a system for providing various communication services such as voice and data packets using radio resources, and may include a terminal, a base station, or a core network.

The embodiments disclosed below can be applied to a wireless communication system using various wireless access technologies. For example, the present embodiments include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA). Alternatively, it may be applied to various various wireless access technologies such as non-orthogonal multiple access (NOMA). In addition, the wireless access technology may mean not only a specific access technology, but also a communication technology for each generation established by various communication consultation organizations such as 3GPP, 3GPP2, WiFi, Bluetooth, IEEE, and ITU. For example, CDMA may be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with a radio technology such as global system for mobile communications (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented with a wireless technology such as IEEE (institute of electrical and electronics engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, E-UTRA (evolved UTRA), and the like. IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with a system based on IEEE 802.16e. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using evolved-UMTSterrestrial radio access (E-UTRA), and employs OFDMA in downlink and SC- in uplink. Adopt FDMA. As described above, the present embodiments may be applied to a wireless access technology currently disclosed or commercialized, and may be applied to a wireless access technology currently being developed or to be developed in the future.

Meanwhile, a terminal in the present specification is a generic concept that refers to a device including a wireless communication module that performs communication with a base station in a wireless communication system, and is used in WCDMA, LTE, NR, HSPA, and IMT-2020 (5G or New Radio). It should be interpreted as a concept that includes all of the UE (User Equipment) of, as well as the MS (Mobile Station), UT (User Terminal), SS (Subscriber Station), and wireless device in GSM. In addition, the terminal may be a user's portable device such as a smart phone according to the usage type, and in the V2X communication system, it may mean a vehicle, a device including a wireless communication module in the vehicle, and the like. In addition, in the case of a machine type communication system, it may mean an MTC terminal, an M2M terminal, a URLLC terminal, etc. equipped with a communication module so that machine type communication is performed.

The base station or cell of the present specification refers to the end of communication with the terminal in terms of the network, and Node-B (Node-B), eNB (evolved Node-B), gNB (gNode-B), LPN (Low Power Node), Sector, Site, various types of antennas, BTS (Base Transceiver System), Access Point, Point (e.g., Transmit Point, Receiving Point, Transmitting Point), Relay Node ), a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, a remote radio head (RRH), a radio unit (RU), and a small cell. Also, the cell may mean including a bandwidth part (BWP) in the frequency domain. For example, the serving cell may mean an activation BWP of the terminal.

In the various cells listed above, since there is a base station controlling one or more cells, the base station can be interpreted in two ways. 1) In relation to the radio area, the device itself may provide a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, and a small cell, or 2) the radio area itself may be indicated. In 1), all devices that are controlled by the same entity that provide a predetermined wireless area are controlled by the same entity, or all devices that interact to form a wireless area in collaboration are instructed to the base station. A point, a transmission/reception point, a transmission point, a reception point, etc. may be an embodiment of a base station according to the configuration method of the wireless area. In 2), it is also possible to instruct the base station to the radio region itself to receive or transmit a signal from the viewpoint of the user terminal or the viewpoint of a neighboring base station.

In the present specification, a cell refers to a component carrier having coverage of a signal transmitted from a transmission/reception point or a coverage of a signal transmitted from a transmission/reception point, and the transmission/reception point itself. I can.

Uplink (Uplink, UL, or uplink) refers to a method of transmitting and receiving data to a base station by a UE, and downlink (Downlink, DL, or downlink) refers to a method of transmitting and receiving data to a UE by a base station. do. Downlink may refer to a communication or communication path from multiple transmission/reception points to a terminal, and uplink may refer to a communication or communication path from a terminal to multiple transmission/reception points. In this case, in the downlink, the transmitter may be a part of the multiple transmission/reception points, and the receiver may be a part of the terminal. In addition, in the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of the multiple transmission/reception points.

Uplink and downlink transmit and receive control information through a control channel such as Physical Downlink Control CHannel (PDCCH), Physical Uplink Control CHannel (PUCCH), and the like, and The same data channel is configured to transmit and receive data. Hereinafter, a situation in which signals are transmitted and received through channels such as PUCCH, PUSCH, PDCCH, and PDSCH is expressed in the form of'transmitting and receiving PUCCH, PUSCH, PDCCH and PDSCH'. do.

In order to clarify the description, hereinafter, the present technical idea is mainly described with a 3GPP LTE/LTE-A/NR (New RAT) communication system, but the present technical feature is not limited to the corresponding communication system.

3GPP develops 5G (5th-Generation) communication technology to meet the requirements of ITU-R's next-generation wireless access technology after research on 4G (4th-Generation) communication technology. Specifically, 3GPP develops a new NR communication technology separate from 4G communication technology and LTE-A pro, which has improved LTE-Advanced technology as a 5G communication technology to meet the requirements of ITU-R. Both LTE-A pro and NR refer to 5G communication technology. Hereinafter, 5G communication technology will be described centering on NR when a specific communication technology is not specified.

The operation scenario in NR defined various operation scenarios by adding considerations to satellites, automobiles, and new verticals from the existing 4G LTE scenario.In terms of service, eMBB (Enhanced Mobile Broadband) scenario, high terminal density, but wide It is deployed in the range and supports the mMTC (Massive Machine Communication) scenario that requires a low data rate and asynchronous connection, and the URLLC (Ultra Reliability and Low Latency) scenario that requires high responsiveness and reliability and supports high-speed mobility. .

In order to satisfy this scenario, NR discloses a wireless communication system to which a new waveform and frame structure technology, a low latency technology, a mmWave support technology, and a forward compatible provision technology are applied. In particular, in the NR system, various technological changes are proposed in terms of flexibility to provide forward compatibility. The main technical features of the NR will be described below with reference to the drawings.

<NR system general>

1 is a diagram schematically showing a structure of an NR system to which this embodiment can be applied.

1, the NR system is divided into 5GC (5G Core Network) and NR-RAN parts, and NG-RAN controls user plane (SDAP/PDCP/RLC/MAC/PHY) and UE (User Equipment). It is composed of gNB and ng-eNB that provide plane (RRC) protocol termination. The gNB or gNB and ng-eNB are interconnected through an Xn interface. The gNB and ng-eNB are each connected to 5GC through the NG interface. The 5GC may include an Access and Mobility Management Function (AMF) in charge of a control plane such as a terminal access and mobility control function, and a User Plane Function (UPF) in charge of a control function for user data. NR includes support for both frequency bands below 6GHz (FR1, Frequency Range 1) and frequencies above 6GHz (FR2, Frequency Range 2).

gNB means a base station that provides NR user plane and control plane protocol termination to a terminal, and ng-eNB means a base station that provides E-UTRA user plane and control plane protocol termination to a terminal. The base station described in the present specification should be understood in a sense encompassing gNB and ng-eNB, and may be used as a means to distinguish between gNB or ng-eNB as necessary.

<NR wave form, numer roller and frame structure>

In NR, a CP-OFDM waveform using a cyclic prefix is used for downlink transmission, and CP-OFDM or DFT-s-OFDM is used for uplink transmission. OFDM technology is easy to combine with MIMO (Multiple Input Multiple Output), and has the advantage of being able to use a low complexity receiver with high frequency efficiency.

On the other hand, in NR, since the requirements for data rate, delay rate, and coverage are different for each of the three scenarios described above, it is necessary to efficiently satisfy the requirements for each scenario through a frequency band constituting an arbitrary NR system. . To this end, a technique for efficiently multiplexing a plurality of different numerology-based radio resources has been proposed.

Specifically, the NR transmission neuron is determined based on sub-carrier spacing and CP (cyclic prefix), and the value of μ is used as an exponential value of 2 based on 15khz as shown in Table 1 below. Is changed to.

μ	Subcarrier spacing	Cyclic prefix	Supported for data	Supported for synch
0	15	Normal	Yes	Yes
One	30	Normal	Yes	Yes
2	60	Normal, Extended	Yes	No
3	120	Normal	Yes		Yes
4	240	Normal	No	Yes

As shown in Table 1 above, the NR neuron can be classified into 5 types according to the subcarrier interval. This is different from the fixed subcarrier spacing of 15khz of LTE, one of the 4G communication technologies. Specifically, subcarrier intervals used for data transmission in NR are 15, 30, 60, and 120khz, and subcarrier intervals used for synchronization signal transmission are 15, 30, 12, and 240khz. In addition, the extended CP is applied only to the 60khz subcarrier interval. On the other hand, a frame structure in NR is defined as a frame having a length of 10 ms consisting of 10 subframes having the same length of 1 ms. One frame can be divided into 5 ms half frames, and each half frame includes 5 subframes. In the case of the 15khz subcarrier interval, one subframe consists of 1 slot, and each slot consists of 14 OFDM symbols.

2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.

Referring to FIG. 2, in the case of a normal CP, a slot is fixedly composed of 14 OFDM symbols, but the length in the time domain of the slot may vary according to the subcarrier interval. For example, in the case of a newer roller having a 15khz subcarrier interval, a slot is 1ms long and has the same length as the subframe. In contrast, in the case of a newer roller with a 30khz subcarrier spacing, a slot consists of 14 OFDM symbols, but two slots may be included in one subframe with a length of 0.5ms. That is, the subframe and the frame are defined with a fixed time length, and the slot is defined by the number of symbols, and the time length may vary according to the subcarrier interval.

Meanwhile, NR defines a basic unit of scheduling as a slot, and introduces a mini-slot (or sub-slot or non-slot based schedule) in order to reduce the transmission delay of the radio section. If a wide subcarrier spacing is used, the length of one slot is shortened in inverse proportion, so that transmission delay in the radio section can be reduced. The mini-slot (or sub-slot) is for efficient support for the URLLC scenario, and scheduling is possible in units of 2, 4, or 7 symbols.

In addition, unlike LTE, NR defines uplink and downlink resource allocation as a symbol level within one slot. In order to reduce HARQ delay, a slot structure capable of transmitting HARQ ACK/NACK directly within a transmission slot has been defined, and this slot structure is named and described as a self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slot formats are used in 3GPP Rel-15. In addition, a common frame structure constituting an FDD or TDD frame is supported through a combination of various slots. For example, a slot structure in which all symbols of a slot are set to downlink, a slot structure in which all symbols are set to uplink, and a slot structure in which a downlink symbol and an uplink symbol are combined are supported. In addition, NR supports that data transmission is distributed and scheduled in one or more slots. Accordingly, the base station may inform the UE of whether the slot is a downlink slot, an uplink slot, or a flexible slot using a slot format indicator (SFI). The base station can indicate the slot format by indicating the index of the table configured through UE-specific RRC signaling using SFI, and dynamically indicates through Downlink Control Information (DCI) or statically or through RRC. It can also be quasi-static.

<NR physical resource>

Regarding the physical resource in NR, the antenna port, resource grid, resource element, resource block, bandwidth part, etc. are considered. do.

The antenna port is defined so that a channel carrying a symbol on an antenna port can be inferred from a channel carrying another symbol on the same antenna port. When the large-scale property of a channel carrying a symbol on one antenna port can be inferred from a channel carrying a symbol on another antenna port, the two antenna ports are QC/QCL (quasi co-located or quasi co-location) relationship. Here, the wide-range characteristic includes at least one of delay spread, Doppler spread, frequency shift, average received power, and received timing.

3 is a diagram illustrating a resource grid supported by a radio access technology to which the present embodiment can be applied.

Referring to FIG. 3, since the NR supports a plurality of neurons in the same carrier, a resource grid may exist according to each neuron in the resource grid. In addition, the resource grid may exist according to an antenna port, a subcarrier spacing, and a transmission direction.

A resource block consists of 12 subcarriers, and is defined only in the frequency domain. In addition, a resource element consists of one OFDM symbol and one subcarrier. Accordingly, as shown in FIG. 3, the size of one resource block may vary according to the subcarrier interval. In addition, NR defines “Point A” that serves as a common reference point for the resource block grid, a common resource block, and a virtual resource block.

4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.

In NR, unlike LTE where the carrier bandwidth is fixed at 20Mhz, the maximum carrier bandwidth is set from 50Mhz to 400Mhz for each subcarrier interval. Therefore, it is not assumed that all terminals use all of these carrier bandwidths. Accordingly, in the NR, as shown in FIG. 4, a bandwidth part (BWP) can be designated within the carrier bandwidth and used by the terminal. In addition, the bandwidth part is associated with one neurology and is composed of a subset of consecutive common resource blocks, and can be dynamically activated over time. The UE is configured with up to four bandwidth parts, respectively, in uplink and downlink, and data is transmitted and received using the active bandwidth part at a given time.

In the case of a paired spectrum, uplink and downlink bandwidth parts are independently set, and in the case of an unpaired spectrum, unnecessary frequency re-tuning between downlink and uplink operations is prevented. For this purpose, the downlink and uplink bandwidth parts are set in pairs to share a center frequency.

<NR initial connection>

In NR, the terminal accesses the base station and performs cell search and random access procedures to perform communication.

Cell search is a procedure in which a terminal synchronizes with a cell of a corresponding base station, obtains a physical layer cell ID, and obtains system information by using a synchronization signal block (SSB) transmitted by a base station.

5 is a diagram illustrating a synchronization signal block in a wireless access technology to which the present embodiment can be applied.

Referring to FIG. 5, an SSB consists of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) occupying 1 symbol and 127 subcarriers, respectively, and a PBCH spanning 3 OFDM symbols and 240 subcarriers.

The terminal receives the SSB by monitoring the SSB in the time and frequency domain.

SSB can be transmitted up to 64 times in 5ms. A plurality of SSBs are transmitted in different transmission beams within 5 ms time, and the UE performs detection on the assumption that SSBs are transmitted every 20 ms period based on one specific beam used for transmission. The number of beams that can be used for SSB transmission within 5 ms time may increase as the frequency band increases. For example, up to 4 SSB beams can be transmitted under 3GHz, and up to 8 in a frequency band of 3 to 6GHz, and a maximum of 64 different beams in a frequency band of 6GHz or higher can be used to transmit SSBs.

Two SSBs are included in one slot, and the start symbol and the number of repetitions in the slot are determined according to the subcarrier interval as follows.

Meanwhile, the SSB is not transmitted at the center frequency of the carrier bandwidth, unlike the conventional LTE SS. That is, the SSB may be transmitted even in a place other than the center of the system band, and a plurality of SSBs may be transmitted in the frequency domain when broadband operation is supported. Accordingly, the UE monitors the SSB by using a synchronization raster, which is a candidate frequency location for monitoring the SSB. The carrier raster and synchronization raster, which are information on the center frequency of the channel for initial access, have been newly defined in NR, and the synchronization raster has a wider frequency interval than the carrier raster to support fast SSB search of the terminal. I can.

The UE can acquire the MIB through the PBCH of the SSB. The MIB (Master Information Block) includes minimum information for the terminal to receive remaining system information (RMSI, Remaining Minimum System Information) broadcast by the network. In addition, PBCH is information about the location of the first DM-RS symbol in the time domain, information for the UE to monitor SIB1 (e.g., SIB1 neurology information, information related to SIB1 CORESET, search space information, PDCCH Related parameter information, etc.), offset information between the common resource block and the SSB (the position of the absolute SSB in the carrier is transmitted through SIB1), and the like. Here, the SIB1 neurology information is equally applied to some messages used in the random access procedure for accessing the base station after the terminal completes the cell search procedure. For example, the neurology information of SIB1 may be applied to at least one of messages 1 to 4 for a random access procedure.

The aforementioned RMSI may mean System Information Block 1 (SIB1), and SIB1 is periodically broadcast (ex, 160ms) in a cell. SIB1 includes information necessary for the UE to perform an initial random access procedure, and is periodically transmitted through the PDSCH. In order for the UE to receive SIB1, it is necessary to receive newer roller information used for SIB1 transmission and CORESET (Control Resource Set) information used for SIB1 scheduling through the PBCH. The UE checks scheduling information for SIB1 using SI-RNTI in CORESET, and acquires SIB1 on the PDSCH according to the scheduling information. SIBs other than SIB1 may be periodically transmitted or may be transmitted according to the request of the terminal.

6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.

Referring to FIG. 6, when the cell search is completed, the UE transmits a random access preamble for random access to the base station. The random access preamble is transmitted through the PRACH. Specifically, the random access preamble is transmitted to the base station through a PRACH consisting of consecutive radio resources in a specific slot that is periodically repeated. In general, when a terminal initially accesses a cell, a contention-based random access procedure is performed, and when a random access is performed for beam failure recovery (BFR), a contention-free random access procedure is performed.

The terminal receives a random access response to the transmitted random access preamble. The random access response may include a random access preamble identifier (ID), a UL Grant (uplink radio resource), a temporary C-RNTI (Temporary Cell-Radio Network Temporary Identifier), and a TAC (Time Alignment Command). Since one random access response may include random access response information for one or more terminals, the random access preamble identifier may be included to inform which terminal the included UL Grant, temporary C-RNTI, and TAC are valid. The random access preamble identifier may be an identifier for the random access preamble received by the base station. TAC may be included as information for the UE to adjust uplink synchronization. The random access response may be indicated by a random access identifier on the PDCCH, that is, a Random Access-Radio Network Temporary Identifier (RA-RNTI).

Upon receiving a valid random access response, the terminal processes information included in the random access response and performs scheduled transmission to the base station. For example, the UE applies TAC and stores a temporary C-RNTI. Also, by using UL Grant, data stored in the buffer of the terminal or newly generated data is transmitted to the base station. In this case, information for identifying the terminal should be included.

Finally, the terminal receives a downlink message for resolving contention.

<NR CORESET>

The downlink control channel in NR is transmitted in CORESET (Control Resource Set) having a length of 1 to 3 symbols, and transmits uplink/downlink scheduling information, SFI (Slot Format Index), and TPC (Transmit Power Control) information. .

In this way, NR introduced the concept of CORESET to secure system flexibility. CORESET (Control Resource Set) means a time-frequency resource for a downlink control signal. The terminal may decode the control channel candidate using one or more search spaces in the CORESET time-frequency resource. A QCL (Quasi CoLocation) assumption for each CORESET is set, and this is used to inform the characteristics of the analog beam direction in addition to the delay spread, Doppler spread, Doppler shift, and average delay, which are characteristics assumed by conventional QCL.

7 is a diagram for explaining CORESET.

Referring to FIG. 7, CORESET may exist in various forms within a carrier bandwidth within one slot, and CORESET may consist of up to 3 OFDM symbols in the time domain. In addition, CORESET is defined as a multiple of 6 resource blocks up to the carrier bandwidth in the frequency domain.

The first CORESET is indicated through the MIB as part of the initial bandwidth part configuration so that additional configuration information and system information can be received from the network. After establishing the connection with the base station, the terminal may receive and configure one or more CORESET information through RRC signaling.

In this specification, frequencies, frames, subframes, resources, resource blocks, regions, bands, subbands, control channels, data channels, synchronization signals, various reference signals, various signals, or various messages related to NR (New Radio) Can be interpreted as a meaning used in the past or present, or in various meanings used in the future.

New Radio (NR)

As described above, NR, which has been recently conducted in 3GPP, has been designed to satisfy various QoS requirements required for each subdivided and specified usage scenario, as well as an improved data transmission rate compared to LTE. In particular, eMBB (enhancement mobile broadband), mMTC (massive MTC), and URLLC (Ultra Reliable and Low Latency Communications) were defined as representative usage scenarios for NR. flexible) frame structure design is required. Each usage scenario has different requirements for data rates, latency, reliability, and coverage. Accordingly, as a method for efficiently satisfying the requirements for each usage scenario through the frequency band constituting an arbitrary NR system, radio resource units (eg, subcarrier spacing, subframe, TTI, etc.) based on different numerology (eg subcarrier spacing, subframe, TTI, etc.) unit) is designed to be efficiently multiplexed.

For example, discussion has been made on a method of multiplexing and supporting numerology with different subcarrier spacing values based on TDM, FDM or TDM/FDM through one or more NR component carrier(s). lost. In addition, in configuring a scheduling unit in the time domain, a discussion has been made on a method of supporting more than one time unit. In this regard, in NR, a subframe is defined as a kind of time domain structure. As a reference numerology for defining the corresponding subframe duration, it was decided to define a single subframe duration consisting of 14 OFDM symbols of normal CP overhead based on 15kHz Sub-Carrier Spacing (SCS) same as LTE. Accordingly, in NR, the subframe has a time duration of 1 ms. However, unlike LTE, a subframe of NR is an absolute reference time duration, and slots and mini-slots may be defined as time units that are the basis of actual uplink/downlink data scheduling. In this case, the number of OFDM symbols constituting the slot and the y value were determined to have a value of y=14 regardless of the SCS value in the case of normal CP.

Accordingly, an arbitrary slot consists of 14 symbols. In addition, depending on the transmission direction of the corresponding slot, all symbols may be used for DL transmission, all symbols may be used for UL transmission, or DL portion + (gap) + UL portion. have.

In addition, in any numerology (or SCS), a mini-slot consisting of fewer symbols than the aforementioned slot is defined. A short time-domain scheduling interval for transmitting/receiving uplink/downlink data based on a mini-slot may be set, or a long time-domain scheduling interval for transmitting/receiving uplink/downlink data through slot aggregation. have. In particular, in the case of transmitting/receiving latency-sensitive data such as URLLC, it is difficult to satisfy the latency requirement when 1ms (14 symbols)-based slot unit scheduling defined in a numerology-based frame structure with a small SCS value such as 15 kHz is performed. I can. Accordingly, by defining a mini-slot composed of fewer OFDM symbols than a slot composed of 14 symbols, scheduling capable of satisfying the requirements of URLLC can be performed based on this.

8 is a diagram for exemplifying symbol level alignment between different SCSs in a radio access technology to which the present embodiment can be applied.

Referring to FIG. 8, R supports the following structure on the time axis. The difference from the existing LTE is that in NR, the basic scheduling unit is changed to the aforementioned slot. Also, as shown in FIG. 9, regardless of subcarrier spacing, a slot consists of 14 OFDM symbols. On the other hand, it supports a non-slot structure (mini-slot structure) composed of 2, 4, and 7 OFDM symbols, which are smaller scheduling units. The non-slot structure can be used as a scheduling unit for URLLC service.

■ Radio frame: Fixed 10ms regardless of numerology (SCS) (Fixed 10ms regardless of numerology).

■ Subframe: Fixed 1ms as a reference for time duration in the time domain. Unlike LTE, it is not used as a scheduling unit for data and control signals.

■ Slot: Mainly for eMBB scenario. Include 14 OFDM symbols.

■ Non-slot (i.e. mini-slot): Mainly for URLLC, but not limited to URLLC only. Include 2, 4, or 7 OFDM symbols (Include 2, 4, or 7 OFDM symbols).

■ One TTI duration: A time duration for data/control channel transmission. A number of OFDM symbols per a slot/non-slot in the time main

In addition, as described above, numerology having different SCS values in one NR carrier may be multiplexed in a TDM and/or FDM scheme to support. Therefore, a method of scheduling data according to latency requirements based on the slot (or mini-slot) length defined for each numerology is also considered. For example, when the SCS is 60 kHz, the symbol length is reduced by about 1/4 compared to the SCS 15 kHz, so when one slot is configured with the same 14 OFDM symbols, the 15 kHz-based slot length becomes 1 ms. On the other hand, the slot length based on 60 kHz is reduced to about 0.25 ms.

Small data transfer

Many application programs installed in smart phone terminals, MTC terminals, IoT terminals, etc. frequently or occasionally transmit small data packets. Whenever the terminal transmits a small amount of data, when performing an RRC connection state transition, signaling overhead and power consumption are caused, which is inefficient. For example, the RRC IDLE state UE must transition to the RRC connected state through the RRC setup procedure for small data transmission. Thereafter, the terminal must activate security to transmit user data and release the RRC connection. In order to solve this problem, various techniques have been proposed for efficiently transmitting small amounts of data.

However, in the case of the proposed prior art, a small amount of data was transmitted through an RRC message. Therefore, there is a problem that the overhead for RRC message generation and transmission/reception processing still exists. In addition, since RRC operates with various timers and detailed functions, there is an overhead for processing them. .

In order to solve this problem, the present disclosure proposes a procedure and apparatus capable of successfully transmitting and receiving a small amount of data without RRC signaling to an RRC inactive state terminal or an RRC idle state terminal based on NR. In addition, a method and apparatus for performing access control of a terminal on a procedure for transmitting a small amount of data without RRC signaling is proposed.

Hereinafter, a method of transmitting a small amount of data based on an NR radio access technology will be described. However, this is for better understanding, and the present embodiment may be applied to any radio access technology such as LTE technology or WiFi technology. In addition, embodiments described in the present disclosure include information elements and contents of operations specified in TS38.321, which is an NR MAC standard, and TS 38.331, which is an NR RRC standard. Even if the contents of the terminal operation related to the definition of the corresponding information element are not included in the present specification, the contents specified in the standard specification, which is a known technique, are included in the present embodiment to be understood.

Meanwhile, below, a small data transmission technique according to the present embodiment is described as SDT (small data transmission) as necessary. This is for convenience of description and is not limited to the corresponding name. In addition, the following description will focus on the SDT method and access control of the RRC inactive terminal, but the same or similar can be applied to the RRC idle terminal.

If the RRC inactive terminal can perform SDT without an RRC message, it is possible to reduce the overhead for processing the RRC message. However, if the RRC message is not provided, functions that could be provided through RRC procedure and signaling cannot be provided. For example, when the load on the base station is high, it becomes difficult to provide an access control function that prohibits the access of the terminal. In the prior art, in order for an NR-based RRC inactive terminal to process mobile outgoing data, an RRC connection resumption procedure had to be performed. When the upper layer of the terminal requests to resume the suspended RRC connection, the RRC initiated the RRC connection resumption procedure. Through the RRC connection resumption procedure, the UE and the base station resumed RRC connection by transmitting and receiving a corresponding RRC message.

In order to effectively perform SDT without an RRC message, it is necessary to modify/redesign an RRC connection resumption procedure or an RRC connection establishment procedure based on RRC signaling. Alternatively, an RRC connection resumption procedure based on RRC signaling or an RRC procedure different from the RRC connection establishment procedure must be defined. This may include an interworking function between an upper layer including NAS (NAS MM, NAS SM, application) and a lower layer including RRC (RRC, SDAP, PDCP, RLC, MAC, PHY). In addition, in the SDT technology, the RRC procedure may include an interworking function to trigger/instruct SDT without an RRC message in a lower layer. Hereinafter, a small amount of data transmission and an access control method therefor will be described. In addition, a procedure for providing the above-described additional functions for small data transmission without RRC signaling will also be described. The embodiments provided below may be applied individually or by arbitrarily combining/combining each of the embodiments. If there is no separate description below, the upper layer may represent one or more of NAS MM, NAS SM, and application. In addition, the lower layer may represent one or more of RRC, SDAP, PDCP, RLC, MAC, and PHY.

First, a NAS entity structure will be described for understanding of the present disclosure.

9 is a diagram illustrating an example of a terminal configuration including a 5GMM (or NAS MM) entity to which the present embodiment can be applied.

Referring to FIG. 9, the 5GMM (or NAS MM) entity 920 here represents an entity that processes a NAS signaling message between the UE 900 or the UE 900 and the Access and Mobility Management Function (AMF) within the AMF. In addition, the 5GSM (or NAS SM) entity 910 may interact/interact with upper layers such as an application and an operating system (OS). The upper layer may request the 5GSM entity 910 to establish a PDU session indicating at least one PDU session attribute. The 5GSM entity 910 in the terminal 900 may indicate an attribute of a newly established PDU session to a higher layer. The attribute of the PDU session includes, for example, one or more of PDU session identity, SSC mode, S-NSSAI, DNN, PDU session type, access type, and PDU address.

The AS layer 930 is configured under the NAS MM 920 and may include an RRC entity, an L2 entity, and an L1 entity.

Meanwhile, the present disclosure will be described based on an operation of transmitting a small amount of data through a random access procedure. Accordingly, the present disclosure may be applied to a 2-step random access procedure as well as an existing 4-step random access procedure.

10 is a diagram for explaining a 2-step random accessor procedure (2-step RACH) to which the present embodiment can be applied.

Referring to FIG. 10, the 2-step random access procedure is for simplifying the existing 4-step random access procedure, and refers to a procedure in which the terminal and the base station each perform one step.

For example, in the first step, the terminal 1000 transmits MsgA to the base station 1010, and in the second step, the base station 1010 transmits MsgB to the terminal 1000. MsgA includes a preamble on the PRACH and uplink data on the PUSCH. MsgB contains information for RA response and contention resolution.

In the 2-step RACH, the PUSCH okay is defined as a time-frequency resource for payload transmission. The PUSCH okays can be configured separately from the PRACH okays. Alternatively, the relative position of the PUSCH occasion may be configured with respect to the associated PRACH occasion. For example, a time/frequency relationship between PRACH preambles and PUSCH okays in the PRACH occasion(s) may have a single standard fixed value. For another example, the time/frequency relationship between each PRACH preamble in the PRACH occasion(s) for the PUSCH okay may have a single standard fixed value. For another example, a time/frequency relationship between PRACH preambles in the PRACH occasion(s) and the PUSCH okay may have a single semi-statically configured value. For another example, the time/frequency relationship between each PRACH preamble in the PRACH occasion(s) for the PUSCH okay may have a single semi-statically configured value.

Hereinafter, the operation of the terminal and the base station according to the present disclosure will be described.

11 is a flowchart illustrating an operation of a terminal according to the present embodiment.

Referring to FIG. 11, a method for a UE to transmit a small amount of data may include transmitting an RRC connection resumption request to a lower layer in a non-access stratum (NAS) layer of the RRC inactive state UE. (S1110). For example, a terminal in an RRC inactive state may trigger a small amount of data transmission in the NAS layer. In this case, the NAS layer may instruct the RRC connection resumption request to the lower layer.

In addition, the method of transmitting a small amount of data may include acquiring a small amount of data transmission instruction information through Msg 3 (Message 3) or Msg A (Message A) from the MAC entity based on the RRC connection resumption request (S1120). ). For example, when a request to resume an RRC connection in the NAS layer is indicated to a lower layer, the UE may instruct the MAC layer to transmit a small amount of data through Msg3 or MsgA. To this end, the MAC layer may receive indication information indicating Msg3 or MsgA transmission from a higher MAC layer.

On the other hand, the small amount of data transmission indication information through Msg3 or MsgA may further include at least one of RRC message type, RRC transaction identifier, terminal temporary identifier, authentication token for integrity protection, and reopening cause information. have.

The method of transmitting small amount of data may include transmitting Msg 3 or Msg A including small amount of data to the base station (S1130). For example, when Msg3 or MsgA transmission is determined based on the small amount of data transmission indication information through Msg3 or MsgA, the terminal may transmit Msg3 or MsgA to the base station.

For example, Msg 3 or Msg A for small data transmission may not include an RRC message. As another example, Msg 3 or Msg A for small amount of data transmission may further include information on at least one of a terminal temporary identifier, an authentication token for integrity protection, and a reason for reopening.

Meanwhile, the terminal temporary identifier may be composed of bits of a specific part of I-RNTI (Inactive-Radio Network Temporary Identity) or I-RNTI. For example, the specific part of the I-RNTI may mean only the bits of the part for identifying the UE context in the corresponding base station except for the base station part in the I-RNTI. Alternatively, the specific part of the I-RNTI may mean a bit of a part that is set in advance to identify the terminal or the terminal context between the terminal and the base station. Accordingly, the bits of the specific part of the I-RNTI may be determined as a few high or low bits of the I-RNTI.

The method of transmitting a small amount of data may include receiving Msg 4 or Msg B including confirmation information for Msg 3 or Msg A from the base station (S1140). After transmitting Msg3 or MsgA, the terminal receives Msg4 or MsgB from the base station.

For example, Msg 4 or Msg B may include information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle. That is, the base station may receive Msg 4 or MsgB and instruct the RRC state of the UE to not change unnecessary. For example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle may be included in the MAC CE. As another example, information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle may be included in the MAC RAR. As another example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle may be included in the MAC subheader. The above-described MAC CE or MAC RAR or MAC subheader may be included in Msg 4 or MsgB and received by the UE.

Thereafter, the terminal transmits the received information for indicating maintenance of the RRC inactive state or information for indicating the state transition to the RRC idle to the Non-Access Stratum (NAS) layer through the MAC entity. The NAS layer can recognize whether the state of the terminal has changed through the transmitted information.

12 is a flowchart illustrating an operation of a base station according to the present embodiment.

Referring to FIG. 12, a method of receiving a small amount of data by a base station includes the step of transmitting a small amount of data transmission configuration information necessary for the terminal to transmit small amount of data through Msg 3 (Message 3) or Msg A (Message A) to the terminal. Includes (S1210).

The small amount of data transmission configuration information means information necessary for the terminal to transmit small amount of data to the base station through a 4-step random access procedure or a 2-step random access procedure. For example, the so-called data transmission configuration information includes information on whether the base station supports small amount data transmission, condition information for a small amount data transmission trigger condition, TBS threshold information, and category information for access baring when transmitting so-called data. It may include. All information transmitted from the base station to the terminal for controlling the so-called data transmission described in this specification may be included in the so-called data transmission configuration information.

The method for the base station to receive the small amount of data includes receiving Msg 3 or Msg A including the small amount of data from the terminal (S1220).

When a small amount of data transmission is triggered by the terminal, the terminal transmits a small amount of data through Msg 3 or Msg A. For example, Msg 3 or Msg A does not include an RRC message, and may include at least one of a terminal temporary identifier, an authentication token for integrity protection, and a cause of reopening. Here, the terminal temporary identifier may be composed of bits of a specific part of I-RNTI (Inactive-Radio Network Temporary Identity) or I-RNTI. For example, the specific part of the I-RNTI may mean only the bits of the part for identifying the UE context in the corresponding base station except for the base station part in the I-RNTI. Alternatively, the specific part of the I-RNTI may mean a bit of a part that is set in advance to identify the terminal or the terminal context between the terminal and the base station. Accordingly, the bits of the specific part of the I-RNTI may be determined as a few high or low bits of the I-RNTI.

The method of receiving the small amount of data by the base station includes transmitting Msg 4 or Msg B including confirmation information for Msg 3 or Msg A to the terminal (S1230).

The base station checks Msg 3 or Msg A received from the terminal and receives a small amount of data. Thereafter, the base station transmits Msg 4 or Msg B to the terminal, through which the state of the terminal can be controlled.

For example, Msg 4 or Msg B may include information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle. That is, the base station may receive Msg 4 or MsgB and instruct the RRC state of the UE to not change unnecessary. For example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle may be included in the MAC CE. As another example, information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle may be included in the MAC RAR. As another example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle may be included in the MAC subheader. The aforementioned MAC CE or MAC RAR or MAC subheader may be included in Msg 4 or MsgB and transmitted to the terminal.

Through this operation, the terminal can deliver a small amount of data to the base station without an RRC message. Therefore, unnecessary state transition and system overhead of the terminal can be prevented, and power consumption of the terminal can be minimized. Detailed operations of each step and detailed embodiments of each step will be described in more detail below. In addition, the terminal may perform an access control operation when a small amount of data transmission is triggered, which will be described in more detail below.

The operation of the terminal and the base station described with reference to FIGS. 11 and 12 will be described in more detail below by dividing detailed embodiments. The detailed embodiments described below may be performed by the operations of the terminal and the base station described above, and may be performed as a separate operation in a specific operation step or before/after the aforementioned step.

Hereinafter, the overall operation of the terminal and the base station will be described based on individual operation embodiments. Each of the embodiments described below may be individually or all or partly combined with each other to be performed by a terminal or a base station.

First, a description will be given focusing on the terminal access barring operation when transmitting a small amount of data.

1. How to assign/divide standardized access categories for SDT on the NAS

In the conventional NR technology, access control was used when a terminal initiates a procedure for transmitting an RRC connection request message to a base station. To this end, the terminal receives a barring parameter (Unified Access Control information) broadcasted by the base station through system information. The terminal checks whether the terminal's access attempt is allowed or prohibited by performing an access baring check based on the received access control parameter. When the terminal needs access to the mobile communication network (e.g. 5G system) due to the following events, etc., the access baring check has been performed.

■ When an event (e.g. outgoing data, outgoing signaling, voice access attempt, paging reception (or outgoing signaling due to paging), etc.) occurs when the terminal is in the idle state and requires a transition to the connected state

■ When the terminal is in the connected state or RRC inactive state and the following events occur

-5GMM (or NAS MM) of the terminal receives a MO-MMTEL-voice-call-started indication, an MO-MMTEL-video-call-started indication or an MO-SMSoIP-attempt-started indication from an upper layer in the terminal time

-When the 5GMM of the terminal receives a request to send an SMS over NAS from an upper layer

-When 5GMM of the terminal receives a request to transmit a UL NAS TRANSPORT message for PDU session establishment/modification from an upper layer

-When the 5GMM of the terminal receives a user plane resource reconfiguration request for an existing PDU session,

-When 5GMM of the terminal is notified that there is an uplink user data packet to be sent for a PDU session with a suspended user plane resource (5GMM is notified that an uplink user data packet is to be sent for a PDU session with suspended user. -plane resources.)

When the terminal (the terminal's NAS) detects one of the above events, the terminal (the terminal's NAS) must map the type of request to one or more access identifiers and one access category. In addition, the NAS indicates the access identifier and the access category as a lower layer (for example, AS (RRC)). The lower layer of the terminal performs an access baring check on the triggered request based on the determined access identifier and access category.

Accordingly, even in the case of a small amount of data transmission, the terminal (the terminal's NAS) needs to perform an access control operation by classifying the SDT and mapping it to one access category. In order to perform an access control operation, an access category for SDT must be designated/divided, and an access baring check must be performed using this.

o Example of transferring SDT conditions received from RRC to NAS

When the terminal (NAS/higher layer of the terminal) detects the above-described event, the terminal may perform access control by distinguishing the SDT for the corresponding access attempt and mapping the SDT to one access category. When the terminal supports SDT in the serving cell camped on, the terminal (NAS/higher layer of the terminal) must be able to distinguish SDT. To this end, the RRC of the terminal may receive the SDT condition/instruction information broadcast from the serving cell and transmit it to the NAS/higher layer. The cell (base station) camped on by the corresponding terminal may broadcast information necessary for SDT (eg, small amount of data transmission configuration information). The RRC of the terminal may deliver the received information to the NAS/higher layer.

For example, information delivered from RRC to NAS/higher layers may include one or more of the following information.

-Information indicating SDT support/allowance in the cell received through system information

-Parameter for SDT received through system information or RRC-only message (e.g. RRC release)

-SDT fallback indication information received from a lower layer (e.g. a fallback instruction with a general RRC resumption procedure or an upper layer instructs a fallback with a request to resume an RRC connection for mobile originated data)

Here, the SDT parameter may further include one or more of preamble information, security information, and TBS information. TBS is the TBS size for the PUSCH of MsgA or the total TBS size of MsgA or the TBS size for the user data included in the PUSCH of MsgA or the TBS size for the PUSCH of Msg3 or the total TBS size of Msg3 for small data transmission without an RRC message. Alternatively, it may indicate the TBS size for user data included in Msg3. The SDT parameter described above and the information transmitted from the base station to the terminal may be included in the aforementioned configuration information for small data transmission.

o An embodiment in which the NAS identifies SDT access attempts and maps them to the corresponding access category

As described above, when the terminal (NAS/higher layer of the terminal) detects a specific event, access control may be performed by classifying the SDT for the corresponding access attempt and mapping the SDT to one access category. For this, as described above, the terminal may receive the SDT parameter from the base station. Alternatively, the terminal NAS can receive the SDT condition from the RRC.

For the corresponding access attempt, the NAS/higher layer of the terminal is calculated/expected that the size of the resulting user data (eg MAC PDU) including the total uplink data is less than or equal to the signaled TBS (ex, SDT parameter) size. At this time, the corresponding access attempt can be mapped to a specific access category and indicated to the RRC. Or, when the NAS/higher layer of the terminal calculates/expects that the payload size of the total uplink data detected according to the corresponding event is less than or equal to the signaled specific value size, the corresponding access attempt is assigned a specific access. It can be mapped to a category and indicated by RRC.

For example, the NAS/higher layer may perform access control by designating a corresponding SDT access attempt as one of a reserved standardized access category number. As another example, one of 9-31 values reserved as a standardized access category may be designated and assigned for access control.

o Duplicate access category processing rule configuration/definition example for classifying SDT

If, as in the above-described method, a standardized access category is designated for the SDT to perform access control, when the corresponding terminal attempts to access, it is necessary to unambiguously select an access category to be matched for a baring check. That is, when the terminal attempts SDT transmission, a clear access category selection rule is required. That is, when the terminal attempts access, one of the existing standardized access categories may be used. Accordingly, it is necessary for the terminal to set a rule in advance and configure the terminal to determine which access category the corresponding access attempt is mapped to among a plurality of access categories to perform a baring check.

The NAS must check the applicable rule to classify SDT. And the NAS must select and use one matching access category for baring check. If the access attempt matches more than one rule, an access category with a lower rule number (#) may be selected.

13 is a diagram illustrating an example of a mapping table for processing an access category to which the present embodiment can be applied.

Referring to FIG. 13, for example, even if an access attempt of a corresponding terminal satisfies the SDT condition, if the requirements/conditions of rules 1 to 8 are satisfied, an access category of a corresponding rule number may be selected. For example, even if the triggered access attempt satisfies the SDT condition, if it satisfies the requirements for MO MMTel voice call, MO MMTel video call, MO SMS over NAS or MO SMSoIP, the UE selects the corresponding access category from 1 to 8 times. You can choose. As another example, if the access attempt type corresponds to the UE NAS initiated 5GMM connection management procedure or 5GMM NAS transport procedure and satisfies the SDT condition as in rule 9, the UE may select this as an access category for SDT. As another example, as in rule 10, when the access attempt type corresponds to An uplink user data packet is to be sent for a PDU session with suspended user-plane resources and satisfies the SDT condition, this is the access category for SDT. You can choose For convenience of explanation, when some access attempts satisfy the SDT condition, a method of processing it has been described, but when a random access attempt satisfies the SDT condition, it is also included in the scope of the present embodiment.

o Example of transmitting the information to the NAS when changing cell/SDT condition/SDT related parameter

The UE in the RRC idle state or the RRC inactive state may perform cell reselection related measurement and evaluation according to movement. In addition, when the conditions for cell reselection are fulfilled, cell change may occur. When a cell change occurs, the changed cell may not support SDT. Alternatively, the configuration information/parameter for the SDT of the changed cell may have a different value from the previous serving cell. In this way, for cell change/SDT condition change reception/SDT related parameter change reception, etc., the RRC of the terminal may receive the changed information and transmit it to the NAS/higher layer.

o Example of adding the cause value for SDT to the cause value of RRC setting

The present disclosure describes an access control method for small data transmission without RRC signaling as a major embodiment. However, even when RRC signaling is used, the embodiment of the present disclosure may be partially or fully applied. For example, operations such as SDT condition change or access category setting may be equally applied regardless of whether RRC signaling is accompanied.

If RRC signaling is used, the setting cause value for SDT may be added to the RRC Setup Request message or the setting cause (EstablishmentCause or Resumecause) in the RRC resume request to control access to small data transmission. The base station was able to determine whether to accept or reject the RRC Setup/Resume Request based on the set cause value.

14 is a diagram exemplarily showing setup cause information included in an RRC Setup Request message to which this embodiment can be applied.

Referring to FIG. 14, the setting cause value may be assigned by designating one spare value of the setting cause information element. In addition, the setting cause information element may be included in the RRC Setup/Resume Request message.

2. How to assign/disaggregate operator-defined access categories for SDT

In the conventional NR technology, an operator-defined access category has been defined so that an operator can perform access control under one unified access control framework.

Operator-defined access category definitions may be delivered to the terminal through NAS signaling. Each operator-defined access category definition information includes the following parameters.

a) a precedence value which indicates in which order the UE shall evaluate the operator-defined category definition for a match;

b) an operator-defined access category number (i.e. access category number in the 32-63 range that uniquely identifies the access category in the PLMN in which the access categories are being sent to the UE);

c) criteria consisting of one or more access category criteria type and associated access category criteria type values.The access category criteria type can be set to one of the following:

1) DNN;

2) OS Id + OS App Id of application triggering the access attempt; or

3) S-NSSAI; and)

d) Optionally, a standardized access category.

Here, d) is a value used to determine the setting cause when using the operator-defined access category.

As described above, when the terminal (NAS/higher layer of the terminal) detects a specific event, the SDT is identified for the corresponding access attempt, and the terminal maps the SDT to one access category to perform access. For this, as described above, the SDT condition may be received from the RRC. Also, in this case, an operator-defined access category can be used. The following describes in more detail the use of operator-defined access categories.

o An embodiment of adding/linking SDT conditions to operator-defined access category criteria

The terminal may perform access control by dividing the SDT into an operator-defined access category. As an example, information for classifying SDT may be added to the operator-defined access category criterion so that the terminal (NAS of the terminal) can classify one access attempt into an operator-defined access category. Through this, access attempts corresponding to SDTs can be linked/divided into mapped operator-defined access categories.

15 is a diagram illustrating an Operator-defined access category definition format according to an embodiment. 16 is a diagram illustrating an Operator-defined access category definition format according to another embodiment. 17 is a diagram illustrating an operator-defined access category definition information element according to an embodiment.

15, 16, and 17 show an example of an Operator-defined access category definition information element format. The operator-defined access category information element is coded through FIGS. 15, 16, and 17, and may be included in NAS signaling and transmitted from the core network entity (e.g. AMF, UDM) to the terminal. Alternatively, the operator-defined access category information element may be transmitted to the terminal by OAM. The terminal stores valid operator-defined access category definition information received through NAS signaling.

As an example, an operator-defined access category number may be assigned to control access to SDT. The operator-defined access category definition information may additionally include an information element for classifying the SDT on the Criteria field.

As another example, the criteria value field for classifying the SDT on the Criteria field may be encoded as one sequence of the SDT condition identifier value count field. One SDT condition identifier value count field may indicate the number of included SDT condition value fields. The SDT condition identifier value count field may consist of one octet. The SDT condition identifier value count field may be coded as a length field of the included SDT condition value field. The SDT condition value length field indicates the length of the SDT condition value field in octets. The SDT condition value field may include the aforementioned SDT condition, a parameter for SDT (e.g. TBS, payload threshold), or an identifier mapping a parameter for SDT.

As another example, operator-defined access category definition information including criteria for classifying SDT is transmitted/instructed from a certain core network entity (eg AMF) to the terminal through NAS signaling (eg REGISTRATION ACCEPT message or CONFIGURATION UPDATE COMMAND message). Can be stored/configured in the terminal.

When the terminal needs access to the base station/5G system, the NAS (or NAS MM entity and/or NAS SM entity) of the terminal maps the corresponding access attempt to one or more access identifiers and one access category, and maps the corresponding access attempt to one or more access identifiers and one access category. RRC)). The lower layer of the terminal performs an access baring check on an access attempt based on the provided access identifier and access category. At this time, the NAS (or NAS MM entity and/or NAS SM entity) of the terminal maps the corresponding access attempt to one access category and directs it to the lower layer AS (RRC)). The NAS of the terminal can perform access control by dividing the corresponding access attempt into the SDT access category according to the SDT Criteria.

o OS Id + OS App Id of application triggering the access attempt information to identify SDT

As described above, when the terminal (NAS/higher layer of the terminal) detects a specific event, the SDT can be identified for the corresponding access attempt, and the SDT can be mapped to one access category to perform access control. For this, as described above, the terminal (NAS/higher layer of the terminal) may utilize the SDT condition received from the RRC. In addition, the terminal (NAS/higher layer of the terminal) may perform access control by identifying a specific OS or specific application that triggered the corresponding access attempt, and mapping the corresponding access attempt to an access category for SDT.

For example, in addition to the OS Id + OS App Id of application field on the Criteria field included in the operator-defined access category definition information, an operator-defined access category information field (or SDT access category information field) may be additionally included. can do. Through this, operator-defined access categories can be mapped and used for the corresponding OS or corresponding OS application.

As another example, when the terminal (the terminal's NAS/higher layer) maps the access category for the corresponding access attempt and transmits it to the RRC, it may additionally indicate the OS Id + OS App Id of application information that triggered the access attempt. I can. In initiating the SDT, the RRC may consider OS Id + OS App Id of application information that triggered a corresponding access attempt.

Through all or part of the operations described above, the terminal may perform an access control operation when transmitting a small amount of data. Hereinafter, a transmission embodiment in which the terminal transmits a small amount of data to the base station without RRC signaling will be described in detail. The following transmission procedure and the above-described access control procedure may be applied in combination with each other.

3. Basic operation of small data transmission procedure without RRC signaling

Hereinafter, a basic procedure operation for small amount data transmission without RRC signaling used to provide the above-described embodiments will be described.

As a method for a terminal to process SDT, there may be a method of transparently processing SDT in the NAS and a method of separately processing SDT in the NAS. That is, some transmission operations may vary depending on whether the NAS performs an operation to distinguish SDTs. Hereinafter, a method of transparently processing SDT in the NAS and a method of processing separately and separately will be briefly described, and an embodiment of the overall terminal operation may be applied in the same manner.

As an example, SDT may be triggered when an upper layer requests resumption of an RRC connection for mobile originated data. For example, the NAS (or 5GMM) of the terminal may be notified that an uplink user data packet is to be transmitted for a PDU session having a suspended user plane resource.

As another example, SDT may be triggered when an upper layer requests resumption of an RRC connection for mobile outgoing signaling or SMS. For example, the NAS of the terminal may want to perform mobile outgoing signaling. That is, the 5GMM of the terminal may receive a request to transmit a UL NAS TRANSPORT message for PDU session establishment/modification/reconfiguration, etc. from an upper layer. For another example, the NAS (or 5GMM) of the terminal may receive a request to send a mobile outgoing SMS over NAS from an upper layer. 5GMM initiates a NAS transport procedure to transmit SMS through UL NAS TRANSPORT message.

First, a case of transparently processing SDT in NAS will be described.

When the upper layer requests the resumption of the RRC connection, the RRC of the terminal checks the condition for SDT and may initiate the SDT when fulfilling this. This condition may be limited to the case where one or more of the following is satisfied.

-Receive information indicating SDT support/allowance in the cell through system information

-Receive parameters for SDT through system information or RRC-only message (e.g. RRC release)

-When the size of the resulting user data (e.g. MAC PDU) including the total uplink data is calculated/expected to be less than or equal to the signaled transport block size (TBS)/payload threshold size

-Does not receive SDT fallback indication information (e.g. fallback indication to the general RRC resume procedure) from the lower layer

-Receive OS Id + OS App Id of application information that triggered the access attempt from the upper layer

Next, an operation of distinguishing and processing SDTs in the NAS will be described.

In order for the upper layer to request the SDT separately, the upper layer may initiate the SDT if the condition for the SDT is checked and fulfilled. Related condition/instruction information may be transmitted to an upper layer through a lower layer (RRC). The indication information transmitted from the lower layer to the upper layer may include one or more of the following information.

-Information indicating SDT support/allowance in the cell received through system information

-Parameter for SDT received through system information or RRC-only message (e.g. RRC release)

-SDT fallback indication information received from a lower layer (e.g. a fallback instruction with a general RRC resumption procedure or an upper layer instructs a fallback with a request to resume an RRC connection for mobile originated data)

The upper layer may initiate SDT when the size of the resulting user data (e.g. MAC PDU) including the total uplink data is calculated/expected to be less than or equal to the signaled transport block size (TBS) size.

Meanwhile, the information indicating SDT support/allowance in the cell through system information includes information indicating SDT support/allowance through a 2-step random access procedure and information instructing SDT support/allowance through a 4-step random access procedure. Each can be indicated separately. The terminal may perform SDT by selecting one of SDT through a 2-step random access procedure and SDT through a 4-step random access procedure.

Here, the SDT parameter may include at least one of preamble information, security information, and TBS/payload threshold information. TBS is the TBS size for the PUSCH of MsgA for transmission without an RRC message or the total TBS size of MsgA or the TBS size for the user data included in the PUSCH of MsgA or the TBS size for the PUSCH of Msg3 or the total TBS size of Msg3 or Msg3 TBS size for user data included in may be indicated. In addition, the SDT parameter may include all the small amount of data transmission configuration information transmitted from the base station to the terminal.

If the upper layer provides an access category and an access identifier when requesting to resume the RRC connection, the terminal (RRC) performs the aforementioned unified access control procedure. If the access attempt is barred, the terminal (the RRC of the terminal) informs the upper layer that the access attempt for the access category has been barred. The terminal (the RRC of the terminal) ends the SDT procedure. If the access attempt is allowed, the terminal (the terminal's RRC) informs the upper layer that the access attempt for the access category is allowed.

The terminal (the RRC of the terminal) indicates the SDT to the lower layer. For example, for SDT without RRC signaling, the terminal (the terminal's RRC) instructs the parameters to be transmitted to the base station through the SDT through the MAC (e.g. terminal temporary identifier, authentication token for integrity protection, reopening cause). In addition, the information indicated by MAD to distinguish and process the signaling includes at least one of RRC message type and RRC transaction identifier, terminal temporary identifier, authentication token for integrity protection, and reopening cause information. can do. The RRC transaction identifier is for identifying the corresponding RRC signaling transaction, and all uplink RRC messages requesting a direct DL response message include the RRC transaction identifier. Thereafter, when the MAC of the UE receives a response from the base station and delivers it to the RRC, the RRC message type, RRC transaction identifier, information for instructing the UE to maintain the RRC inactive state, or state transition to RRC idle At least one piece of information for indicating

SDT can be provided through a random access procedure. It may be provided through a 4-step RACH or a 2-step RACH. When provided through a two-step RACH, information indicating whether to support/provide a two-step RACH may be broadcast through a corresponding cell.

Hereinafter, a detailed embodiment of the SDT procedure will be described for each RACH step, and can be applied regardless of whether the SDT transparent processing and classification in the above-described NAS.

First, a 4-step RACH procedure-based processing method will be described.

In the case of SDT through 4-step random access in the corresponding serving cell, an available set of PRACH resources for random access preamble transmission may be indicated to the terminal through RRC signaling (SIB or dedicated RRC message). The available set of PRACH resources may be provided in association with the coverage level. Alternatively, the available set of PRACH resources may be provided in connection with radio quality (eg (for SSB) rsrp threshold/measurement value/level). The base station may indicate a threshold value for selecting SDT through 4-step random access.

If the message size (uplink data for transmission + MAC header, MAC CE if necessary) is larger than the signaled TBS size, or in SDT through 4-step random access, a fallback is indicated by data transmission through a normal RRC resumption procedure. In the case where the radio quality is bad or the wireless quality is bad, SDT through 4-step random access may be canceled (cancel/abort). The terminal (the terminal's MAC) indicates this to the upper layer (RRC). Alternatively, RRC indicates this as an upper layer (NAS). The upper layer may fall back with a request to resume RRC connection for mobile originated data.

For example, when the PRACH resource linked to the SDT is not available, or when a random access preamble linked to the SDT is transmitted and the uplink grant provided in the random access response message is not for indicating the SDT, a fallback is indicated. Can be. For another example, when rsrp of the SSB is worse than a threshold signaled by the base station (eg, rsrp-ThresholdSSB), it may be indicated as a case of poor radio quality. In these cases, it may be difficult to transmit to the corresponding TBS, so it may be desirable to cancel. This makes it possible to provide a small amount of data transmission through SDT only when the radio quality or load is good.

If not canceled, the terminal selects the PRACH resource associated with the SDT for the terminal. The terminal transmits a random access preamble.

When a random access preamble through 4-step random access linked to the SDT is transmitted, an uplink grant may be provided in the random access response message. If the uplink grant received in the random access response is for indicating SDT and there is a MAC PDU in the Msg3 buffer, the UE transmits Msg3.

For example, if SDT is initiated through Msg3, the terminal recovers the security context from the stored terminal context. The UE recovers the PDCP state (eg PDCP sequence number) for a specific DRB for SDT (or for all SRBs or all DRBs). And the terminal resets the PDCP entity. The UE resumes a specific DRB (or all SRBs or all DRBs). A specific DRB for SDT may be indicated to the terminal through a dedicated RRC message (eg RRC release). The terminal may derive a K _UPenc key associated with a previously configured _ciphering algorithm. Alternatively, the terminal may derive a K _UPint key associated with a previously configured integrity protection algorithm.

For another example, the UE is an authentication token/message authentication code (MAC-I) used for data integrity protection on MAC CE or CCCH on Msg3 or on a DTCH multiplexed with 16 least significant bits of the calculated MAC-I. May include shortMAC-I. Alternatively, the UE may include an authentication token (MAC-I) on the MAC CE on the PUSCH included in Msg3 for integrity protection or shortMAC-I, which is 16 least significant bits of the calculated MAC-I. Alternatively, the terminal may include the establishment cause/resume cause information in the MAC CE. Alternatively, when the RRC receives a request to resume the RRC connection for mobile outgoing data from the upper layer, it transmits the terminal temporary identifier, authentication token for integrity protection, and setup cause/restart cause information to the MAC through 4-step random access. It can be instructed to perform SDT.

For another example, the terminal (the RRC of the terminal) may indicate that the RRC connection suspended in the upper layer is resumed. Alternatively, the terminal (the RRC of the terminal) may indicate that the SDT is initiated through the RRC connection suspended in the upper layer. This may be provided as information indicating that the suspended RRC connection has been resumed and other information. Through this, the UE can transmit user data to the lower layer by distinguishing that the upper layer is in a state in which data can be transmitted according to the RRC restart request. Through this, it can be seen that even if the terminal does not transmit an RRC message to the base station by using RRC signaling, the upper layer is in a state in which the lower layer can transmit data. If the MAC PDU data to be transmitted from the lower layer (MAC) is larger than the signaled TBS size, indication information for canceling the SDT may be transmitted to the upper layer (RRC). In addition, RRC can fall back to a normal RRC connection resumption procedure. Alternatively, the RRC may indicate the indication information for canceling the SDT to the upper layer, and the higher layer may fall back to the RRC connection resumption request for mobile origin data. For reference, in the prior art, only when the terminal transitions to the RRC connection state after receiving the RRC resume message from the base station, the RRC of the terminal indicated that the RRC connection suspended in the upper layer was resumed.

When the terminal (RRC of the terminal) indicates that the suspended RRC connection has been resumed to the upper layer, the DRB is resumed, Msg3 is transmitted, and the response is received for Msg3 transmission (eg, if HARQ is configured for user data transmission, HARQ ACK is received. , PDCCH reception and Msg4 reception).

The terminal (the RRC of the terminal) may indicate to the upper layer that data has been transmitted through the SDT. Through this, the terminal can distinguish that a small amount of data transmission has been completed in the upper layer, so that the user data can be processed later.

o An embodiment in which control information for small amount of data transmission without RRC signaling on Msg3 is divided and transmitted by CCCH

In order to transmit a small amount of data without RRC signaling, the UE may divide one or more control information (or all control information) included in Msg3 into a CCCH and transmit it. CCCH is a logical channel for transmitting control information between the UE and the network, and is used when the UE does not have an RRC connection with the network (Common Control Channel (CCCH): channel for transmitting control information between UEs and network.This channel is used for UEs having no RRC connection with the network.). If a small amount of data is transmitted without RRC signaling through Msg3, the RRC control parameter associated thereto may be defined as transmitting all on the CCCH assuming a control channel used without an RRC connection.

Msg3 does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled/used in RRC as one fixed-length MAC SDU. Alternatively, Msg3 does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled by RRC as one fixed-length MAC CE.

Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, 1 octet bit may be reduced by using a 1 octet MAC subheader format, compared to the conventional 2 octet or 4 octet MAC subheader for MAC SDU including UL CCCH. The corresponding MAC SDU can be distinguished from the conventional UL CCCH type, and the LCID value for the corresponding MAC SDU may be set to have a value different from the conventional UL CCCH LCID value.

Meanwhile, if Msg3 includes a small amount of data for transmission of small amount of data without RRC signaling, the small amount of data included in Msg3 may be included in a NAS container and separated by CCCH and transmitted. Alternatively, a small amount of data included in Msg3 may be included as an RRC information element and may be separated and transmitted by CCCH. If a small amount of data is transmitted without RRC signaling through Msg3, all user data that needs to be processed on the RRC associated thereto may be considered to be transmitted on the CCCH assuming that the control channel is used without an RRC connection.

Although the RRC message itself is not configured as a MAC SDU, information included as an information element in the conventional RRC message, parameters controlled by RRC, or user data processed by RRC are configured as one fixed-length MAC SDU or one fixed-length MAC CE. Can be used.

Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE may be set to have a value different from the conventional UL CCCH LCID value.

Meanwhile, Msg3 may include C-RNTI MAC CE on the CCCH. Alternatively, Msg3 may include a MAC PDU including a terminal temporary identifier on the CCCH or, Msg3 may include a MAC CE including a terminal temporary identifier on the CCCH. The corresponding MAC PDU or MAC CE may be located before the user data MAC PDU. Alternatively, Msg3 may include user data on the CCCH. The corresponding MAC PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. Alternatively, the corresponding MAC PDU may include a terminal temporary identifier in a part of the data field. Alternatively, the above-described control information including the terminal identifier included in Msg3 may be provided through one MAC PDU or one MAC CE. This can reduce the number of MAC subheader bits.

o An embodiment in which control information for small amount data transmission without RRC signaling on Msg3 is divided and transmitted by DCCH

In order to transmit a small amount of data without RRC signaling, one or more of the one or more control information (or all control information) included in Msg3 and the small amount of data included in Msg3 may be divided and transmitted by DCCH. DCCH represents a point-to-point control channel used to transmit dedicated control information between one UE and a network (Dedicated Control Channel (DCCH): 　a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network.Used by UEs having an RRC connection). When transmitting a small amount of data without RRC signaling through Msg3, if the RRC inactive UE recovers the stored UE context, SRB or DRB may be resumed. In this case, the above-described information included in Msg3 may be considered to be transmitted on the DCCH assuming a control channel used without an RRC connection. For example, the base station instructs/configures a pre-configured resource set for uplink data transmission using an SDT pre-configured resource in the RRC connection state to the terminal through an RRC-only message (eg RRC release message or RRC reconfiguration message). I can. The base station may identify the terminal through the pre-configured resource or through arbitrary information (e.g. identification information) included in the pre-configured resource.

In addition, transmission without RRC signaling means that there is no information element delivery for radio resource control through an arbitrary RRC message. However, since the information element for radio resource control may correspond to control information, it may be classified as a DCCH and transmitted. The UE does not configure the RRC message itself as a MAC SDU, but the information included as an information element in the conventional RRC message, parameters controlled/used in the RRC, or user data processed in the RRC is one fixed length MAC SDU or one fixed length. It can be configured and used as MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the LCID values currently reserved as spare can be used. Alternatively, a value different from the LCID (1-32) that can be allocated for SRB/DRB may be used. Alternatively, the LCID of the DRB/logical channel for a small amount of data for the corresponding MAC SDU may be included in the subheader.

The above-described control information including the terminal identifier included in Msg3 may be provided through one MAC PDU or one MAC CE. This can reduce the number of MAC subheader bits.

o An embodiment in which control information for small amount data transmission without RRC signaling on Msg3 is divided and transmitted by DTCH

In order to transmit a small amount of data without RRC signaling, at least one of one or more control information (or all control information) included in Msg3 and a small amount of data included in Msg3 may be divided and transmitted by DTCH. DTCH represents a point-to-point traffic channel used to transmit only user plane information between one terminal and a network (Dedicated Traffic Channel (DTCH): point-to-point channel, dedicated to one UE, for the transfer of user information. .A DTCH can exist in both uplink and downlink.).

When transmitting a small amount of data without RRC signaling through Msg3, if the RRC inactive terminal can restore the stored terminal context and resume SRB or DRB, and if Msg3 contains a small amount of data, the small amount of data included in Msg3 is user plane traffic. It can be considered a channel. In addition, for Msg3 transmission without RRC connection, the aforementioned one or more control information (or all control information) is also included in the DTCH and multiplexed to be transmitted, thereby further reducing overhead. For example, a corresponding MAC sub-PDU may be multiplexed to one MAC PDU and transmitted.

Msg3 may include information included as an information element in a conventional RRC message, or a parameter or user data controlled/used in RRC as one fixed-length MAC SDU or one fixed-length MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. Alternatively, the LCID may use one of the logical channel identifiers 1 to 32 for user data. Alternatively, the LCID for the DRB can be used.

o An embodiment in which control information for small amount data transmission without RRC signaling on Msg3 is classified and transmitted by MAC CE

In order to transmit a small amount of data without RRC signaling, one or more of the one or more control information (or all control information) included in Msg3 and the small amount of data included in Msg3 may be divided into MAC SDUs for MAC signaling and transmitted. For example, it may be defined and transmitted as a new MAC CE. If there is an information element to be transmitted with priority for user identification, content resolution, security processing, user data encryption, integrity protection, etc., it may be grouped and provided through a separate MAC CE.

When transmitting a small amount of data without RRC signaling through Msg3, if the RRC inactive terminal can resume SRB or DRB by recovering the stored terminal context, Msg3 is the information included as an information element in the conventional RRC message or in RRC. The control/used parameters or user data may include one or more fixed-length MAC SDUs and/or one or more fixed-length MAC CEs. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs.

The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the LCID (35~39) values currently reserved as spare status can be used. It is possible to use a value different from the LCID (1~32) that can be allocated for SRB/DRB. Alternatively, the LCID of the MAC CE including user data among the corresponding MAC CEs may use one of the logical channel identifiers (1-32) (for control data/user data). You can write the LCID for the DRB.

o An embodiment of multiplexing and transmitting CCCH, MAC CE, DTCH for small data transmission without RRC signaling on Msg3

Msg3 may consist of a CCCH and a DTCH multiplexed thereto. One or more control information (or all control information) included in Msg3 may be provided through a MAC SDU transmitted on the CCCH for RRC-free signaling. A small amount of data may be transmitted through the DTCH multiplexed thereto. Accordingly, a small amount of data may be provided through a MAC SDU having a separate subheader to distinguish it.

Alternatively, Msg3 may consist of a MAC CE and a DTCH multiplexed thereto. One or more of the above-described control information (or all control information) included in Msg3 may be provided through the MAC CE for signaling without RRC. A small amount of data may be transmitted through the DTCH multiplexed thereto. Accordingly, a small amount of data may be provided through a MAC SDU having a separate subheader to distinguish it.

Alternatively, Msg3 may include user data on the DTCH. The corresponding MAC SDU/subPDU/PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. Alternatively, the terminal may transmit, including control information, in addition to user data on the DTCH included in Msg3. Corresponding control information may be included with a fixed length field at a specific location.

o Another example for small data transmission without RRC signaling on Msg3

Msg3 may include user data on the DTCH. The MAC PDU may contain user data through the NAS information element (e.g. dedicatedInfoNAS). For another example, Msg3 may be addressed (or masked with C-RNTI) through C-RNTI, if the UE has a valid C-RNTI. Msg3 may include a terminal temporary identifier. For another example, Msg3 may be addressed (or masked with a terminal temporary identifier) through the terminal temporary identifier.

The terminal temporary identifier may be signaled by the base station. For example, the terminal temporary identifier may be a part for identifying the terminal context in the corresponding base station or a TC-RNTI except for a part of the I-RNTI or I-RNTI stored through the RRC release message, or a part of the base station in the I-RNTI. I can. For example, the terminal temporary identifier may be composed of 16 bits. In the case of an idle mode terminal, the terminal temporary identifier may be signaled by a core network entity. For example, the terminal temporary identifier corresponds to ng-5G-S-TMSI-Part1 or a part of ng-5G-S-TMSI-Part1 or ng-5G-S-TMSI-Part1 except for the core network entity/common part. It may be a part for the base station to identify the terminal/terminal context. The terminal temporary identifier may be composed of 16 bits. For another example, as the terminal temporary identifier, TC-RNTI included in the RAR may be used.

Msg3 may include user data on the CTCH. If user data is to be transmitted without an RRC message in the absence of an RRC connection, it is necessary to define a new type of logical channel for this. For example, a new type of logical channel may be defined as a CTCH (Common Traffic Channel) channel. The CTCH may perform a logical channel prioritization (LCP) procedure with a lower priority than the CCCH. Alternatively, the CTCH may perform a logical channel prioritization procedure with a lower priority than the MAC CE for C-RNTI. Alternatively, the CTCH may perform a logical channel prioritization procedure with the same or higher priority as the MAC CE for C-RNTI.

Msg3 may be an RRC request message in which user data is concatenated on the CCCH. In this case, user data may be included through the NAS information element (e.g. dedicatedInfoNAS) of the RRC message.

Msg3 may include the RRC message on the CCCH and user data on the multiplexed DTCH. Alternatively, Msg3 may include the RRC message on the CCCH and user data on the multiplexed DTCH. Alternatively, Msg3 may include user data on the multiplexed DTCH with the MAC CE on the CCCH. Alternatively, Msg3 may include user data on the multiplexed DTCH with the MAC PDU including the terminal identifier/terminal temporary identifier on the CCCH. The CCCH SDU may consist of 0 bits (or a fixed bit or a zero length octet string). Alternatively, the CCCH SDU may be configured virtually.

Through this, user data can be transmitted without an RRC message. In this case, it is possible to perform LCP similar to the CTCH described above. Alternatively, the CCCH SDU may include terminal temporary identifier information in fixed bits.

When Msg3 is transmitted, the MAC entity of the UE performs contention resolution based on the C-RNTI on the PDCCH or the UE contention resolution identity on the DL-SCH. The base station may want to instruct the terminal to maintain the RRC inactive state. If the base station has downlink data to be transmitted for the corresponding terminal (if received from the core network), it can transmit it to the terminal. When the confirmation message for Msg3 is Msg4, Msg4 transmitted from the base station to the terminal is information for contention resolution, information for instructing the terminal to maintain the RRC inactive state, information for instructing the terminal to transition to the RRC idle state And downlink data to be transmitted to the terminal.

For example, Msg4 may include user data on the DTCH. The corresponding MAC PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. For another example, Msg4 may include information for instructing the UE to maintain the RRC inactive state on the DCCH. For another example, Msg4 may include information for instructing the UE to maintain the RRC inactive state on the DTCH. The corresponding MAC PDU may be provided through MAC CE. Through this, indication information can be delivered without RRC signaling. For another example, Msg4 may provide information for instructing the UE to maintain the RRC inactive state through the MAC CE. For another example, Msg4 may include information for instructing the UE to maintain the RRC inactive state on the CCCH. As another example, Msg4 may be transmitted without an RRC message. For another example, Msg4 may include an RRC message on a CCCH and user data on a multiplexed DTCH. For another example, Msg4 may include an RRC message on a CCCH and user data on a multiplexed DTCH. As another example, Msg4 may include user data on a multiplexed DTCH with a MAC CE on a CCCH. As another example, the CCCH SDU may be composed of 0 bits (or a fixed bit or a zero length octet string). Alternatively, the CCCH SDU may be configured virtually. Through this, user data can be transmitted without an RRC message.

Meanwhile, upon receiving Msg4, the UE may indicate that the RRC connection has been suspended to the upper layer. For example, the MAC entity may indicate information for instructing the UE to maintain the RRC inactive state to the RRC, and the RRC may indicate that the RRC connection is suspended to an upper layer (e.g. NAS). Alternatively, the UE may indicate that SDT is performed and the RRC connection is suspended in response to the SDT initiation request to the upper layer.

Accordingly, the upper layer can distinguish that it is in the RRC inactive state, and can perform the operation in the RRC inactive state. This can be provided without RRC signaling.

Next, a two-step RACH procedure-based processing method will be described.

In the case of SDT through 2-step random access in the corresponding serving cell, an available set of PRACH resources for random access preamble transmission may be indicated to the terminal through RRC signaling (SIB or dedicated RRC message). The available set of PRACH resources may be provided in association with the coverage level. Alternatively, the available set of PRACH resources may be provided in connection with radio quality (eg (for SSB) rsrp threshold/measurement value/level). The base station may indicate a threshold value for selecting SDT through 2-step random access. The information element for the 2-step RACH procedure may be indicated with a different value distinguished from the information element for the 4-step RACH procedure.

If the message size (uplink data for transmission + MAC header, MAC CE if necessary) is larger than the signaled TBS size, or fall back from SDT through 2-step random access to SDT through 4-step random access or 2-step SDT may be canceled (cancel/abort) when a fallback is indicated by data transmission through a normal RRC resumption procedure in SDT through random access or when radio quality is poor.

The terminal (the terminal's MAC) indicates this to the upper layer (RRC). For example, if a fallback is instructed from SDT through 2-step random access to SDT through 4-step random access or from SDT through 2-step random access to data transmission through a normal RRC resumption procedure, the SDT is linked. This refers to a case where the 2-step random access PRACH resource is not available. Or, if a fallback is instructed from SDT through 2-step random access to SDT through 4-step random access or from SDT through 2-step random access to data transmission through a normal RRC resumption procedure, 2-step random linked to SDT This means a case where the access preamble is transmitted and the uplink grant provided in the 2-step random access response message is not for indicating SDT through 2-step random access. For example, the base station may indicate SDT through 4-step random access through a fallback random access response, or may indicate data transmission through a normal RRC resumption procedure.

If the 2-step random access response message is a success random access response for indicating success of the corresponding random access, the terminal can know that the SDT has been successfully completed. On the other hand, if the 2-step random access response message is a fallback random access response for indicating fallback of the corresponding random access, the UE falls back to 4-step random access by using an uplink grant included in the corresponding fallback random access response, and passes through Msg3. SDT can be performed. Alternatively, the terminal may transmit the RRC connection resumption request message through Msg3, and then transition to the RRC connection state and transmit uplink data according to the scheduling of the base station.

On the other hand, the case of poor radio quality may indicate a case where the rsrp of the SSB is worse than the threshold signaled by the base station (eg, MsgA-rsrp-ThresholdSSB through 2-step random access).

In the above-described cases, transmission to the corresponding TBS may be difficult, so it may be desirable to cancel. This makes it possible to provide a small amount of data transmission through SDT only when wireless quality or load is good.

The terminal selects a PRACH resource associated with the SDT for the terminal. The UE transmits a random access preamble and MsgA including user data.

For example, if SDT is initiated through MsgA, the terminal recovers the security context from the stored terminal context. The UE recovers the PDCP state (eg PDCP sequence number) for a specific DRB for SDT (or for all SRBs or all DRBs). And the terminal resets the PDCP entity. The UE resumes a specific DRB (or all SRBs or all DRBs). A specific DRB for SDT may be indicated to the terminal through a dedicated RRC message (eg RRC release or RRC release with suspendconfig). The terminal may derive a K _UPenc key associated with a previously configured _ciphering algorithm. Alternatively, the terminal may derive a K _UPint key associated with the previously configured integrity protection algorithm.

For another example, the UE may include an authentication token (MAC-I) on the MAC CE or CCCH on the MsgA or on the DTCH multiplexed with shortMAC-I, which is 16 least significant bits of the calculated MAC-I for integrity protection. . Alternatively, the UE may include an authentication token (MAC-I) on the MAC CE on the PUSCH included in the MsgA for integrity protection or shortMAC-I, which is 16 least significant bits of the calculated MAC-I.

On the other hand, the terminal (the RRC of the terminal) may indicate that the RRC connection suspended in the upper layer is resumed. Alternatively, the terminal (the RRC of the terminal) may indicate that the SDT is initiated through the RRC connection suspended in the upper layer. This may be provided as information indicating that the suspended RRC connection is resumed and other information. Through this, the upper layer of the terminal can transmit the user data to the lower layer by distinguishing that data can be transmitted according to the RRC resume request. In addition, even if the terminal does not transmit an RRC message to the base station through RRC signaling, the upper layer may be able to know that the lower layer is in a state in which data transmission is possible.

If the data to be transmitted in the lower layer is larger than the signaled TBS size, the terminal may control to transmit indication information for canceling the SDT to the upper layer (RRC). And RRC can fall back to the normal RRC connection resume procedure. Alternatively, the RRC may indicate this to a higher layer, and the higher layer may fall back to a request to resume an RRC connection for mobile origination data. For reference, in the prior art, after the terminal receives the RRC resume message from the base station, only when the terminal (the terminal's RRC) transitions to the RRC connection state, the terminal (the terminal's RRC) instructed that the RRC connection suspended in the upper layer was resumed.

When the terminal (RRC of the terminal) indicates that the suspended RRC connection has been resumed to the upper layer, the DRB is resumed, Msg3 is transmitted, and the response is received for Msg3 transmission (eg, if HARQ is configured for user data transmission, HARQ ACK is received. , PDCCH reception and Msg4 reception) at least one of.

The terminal (the RRC of the terminal) may indicate to the upper layer that data has been transmitted through the SDT. Through this, the terminal can distinguish that a small amount of data transmission has been completed in the upper layer, so that the user data can be processed later.

o An embodiment in which control information for small amount data transmission without RRC signaling on MsgA is divided and transmitted by CCCH

In order to transmit a small amount of data without RRC signaling, the UE may divide one or more control information (or all control information) included in the MsgA into a CCCH and transmit it. CCCH is a logical channel for transmitting control information between the terminal and the network, and is used when the terminal does not have an RRC connection with the network. If a small amount of data is transmitted without RRC signaling through MsgA, the RRC control parameter associated thereto may be defined as transmitting all on the CCCH assuming a control channel used without RRC connection. The MsgA does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled/used in RRC as one fixed-length MAC SDU. Alternatively, the MsgA does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled by RRC as one fixed-length MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header.

In addition, 1 octet bit may be reduced by using a 1 octet MAC subheader format, compared to the conventional 2 octet or 4 octet MAC subheader for MAC SDU including UL CCCH. The corresponding MAC SDU can be distinguished from the conventional UL CCCH type, and the LCID value for the corresponding MAC SDU may have a value different from the conventional UL CCCH LCID value.

On the other hand, for small data transmission without RRC signaling, if a small amount of data is included in MsgA, the small amount of data included in MsgA may be included in a NAS container and separated by CCCH and transmitted. Alternatively, a small amount of data included in the MsgA may be included as an RRC information element, separated by CCCH, and transmitted. If a small amount of data is transmitted without RRC signaling through MsgA, user data that needs to be processed on the RRC associated thereto may be considered to be transmitted on the CCCH assuming that the control channel is used without an RRC connection. MsgA does not configure the RRC message itself as a MAC SDU, but the information included as an information element in the conventional RRC message, parameters controlled by the RRC, or user data processed by the RRC, is one fixed-length MAC SDU or one fixed-length MAC CE. It can be composed of and included. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE may have a value different from the conventional UL CCCH LCID value.

MsgA may include C-RNTI MAC CE on the CCCH. Alternatively, MsgA may include a MAC PDU including a terminal temporary identifier on the CCCH, or, MsgA may include a MAC CE including a terminal temporary identifier on the CCCH. The corresponding MAC PDU or MAC CE may be located before the user data MAC PDU. Alternatively, MsgA may include user data on the CCCH. The corresponding MAC PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. Alternatively, the corresponding MAC PDU may include a terminal temporary identifier in a part of the data field. For another example, the above-described control information including the terminal identifier included in the MsgA may be provided through one MAC PDU or one MAC CE. This can reduce the number of MAC subheader bits.

o An embodiment in which control information for small amount data transmission without RRC signaling on MsgA is divided and transmitted by DCCH

In order to transmit a small amount of data without RRC signaling, at least one of one or more control information (or all control information) included in the MsgA and the small amount of data included in the MsgA may be separated and transmitted by a DCCH. DCCH represents a point-to-point control channel used to transmit dedicated control information between one terminal and a network. When transmitting a small amount of data without RRC signaling through MsgA, if the RRC inactive terminal can resume SRB or DRB by recovering the stored terminal context, the above information included in MsgA is assumed to be a control channel used without RRC connection. It can be considered to be transmitted on the DCCH. Although MsgA does not configure the RRC message itself as a MAC SDU, the information included as an information element in the conventional RRC message or the parameters controlled/used in the RRC or user data processed in the RRC are one fixed-length MAC SDU or one fixed-length. It can be configured and included as MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the LCID values currently reserved as spare can be used. As another example, the LCID of the DRB/logical channel for a small amount of data for the corresponding MAC SDU may be included in the subheader. For another example, the above-described control information including the terminal identifier included in the MsgA may be provided through one MAC PDU or one MAC CE. This can reduce the number of MAC subheader bits.

o An embodiment in which control information for small amount data transmission without RRC signaling on MsgA is divided and transmitted by DTCH

In order to transmit a small amount of data without RRC signaling, one or more pieces of control information (or all control information) included in the MsgA and the small amount of data included in the MsgA may be divided into DTCH and transmitted. DTCH represents a point-to-point traffic channel used to transmit only user plane information between one terminal and a network.

When transmitting a small amount of data without RRC signaling through MsgA, if the RRC inactive terminal recovers the stored terminal context and resumes SRB or DRB, and includes a small amount of data in MsgA, the small amount of data included in MsgA is user plane traffic. Can be considered as a channel. In addition, for MsgA transmission without RRC connection, the aforementioned one or more control information (or all control information) is also included in the DTCH and multiplexed to be transmitted, thereby further reducing overhead.

The MsgA may include information included as an information element in a conventional RRC message or a parameter or user data controlled/used in the RRC by configuring user data as one fixed-length MAC SDU or one fixed-length MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. Alternatively, the LCID may use one of the logical channel identifiers 1 to 32 for user data. Alternatively, you can write the LCID for the DRB.

o An embodiment in which control information for small amount data transmission without RRC signaling on MsgA is classified and transmitted by MAC CE

For transmission of a small amount of data without RRC signaling, one or more of the one or more control information (or all control information) included in the MsgA and the small amount of data included in the MsgA may be divided into MAC SDUs for MAC signaling and transmitted. For example, control information or small amount of data may be defined and transmitted as a new MAC CE. If there are information elements to be transmitted prior to user identification, content resolution, security processing, user data encryption, integrity protection, etc., they may be grouped and provided through a separate MAC CE. When transmitting a small amount of data without RRC signaling through MsgA, if the RRC inactive terminal can resume SRB or DRB by recovering the stored terminal context, information included as an information element in the above-described conventional RRC message included in MsgA or A parameter or user data controlled/used in RRC may be configured and included as one or a plurality of fixed-length MAC SDUs and/or one or a plurality of fixed-length MAC CEs. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the LCID values currently reserved as spare can be used. Alternatively, the LCID of the MAC CE including user data among the corresponding MAC CEs may use one of the logical channel identifiers 1 to 32 for user data. You can write the LCID for the DRB.

o An embodiment of multiplexing and transmitting CCCH, MAC CE, and DTCH for small data transmission without RRC signaling on MsgA

MsgA may consist of a CCCH and a DTCH multiplexed thereto. One or more control information (or all control information) included in MsgA may be provided through a MAC SDU transmitted on the CCCH for RRC-free signaling. A small amount of data may be transmitted through the DTCH multiplexed thereto. Accordingly, a small amount of data may be provided through a MAC SDU having a separate subheader to distinguish it.

Alternatively, MsgA may consist of MAC CE and DTCH multiplexed thereto. One or more of the above-described control information (or all control information) included in MsgA may be provided through MAC CE for signaling without RRC. A small amount of data may be transmitted through the DTCH multiplexed thereto. Accordingly, a small amount of data may be provided through a MAC SDU having a separate subheader to distinguish it.

Alternatively, MsgA may include user data on the DTCH. In MsgA, the corresponding MAC SDU/subPDU/PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. Alternatively, control information may be included and transmitted in addition to user data on the DTCH included in the MsgA. Corresponding control information may be included with a fixed length field at a specific location.

o Another example for small data transmission without RRC signaling on MsgA

MsgA may include user data on the DTCH. The MAC PDU may contain user data through the NAS information element (e.g. dedicatedInfoNAS). For another example, MsgA may be addressed (or masked with C-RNTI) through C-RNTI if the UE has a valid C-RNTI. For another example, MsgA may be addressed (or masked with a terminal temporary identifier) through the terminal temporary identifier.

The terminal temporary identifier may be signaled by the base station. For example, it may be a part of the I-RNTI or I-RNTI stored through the RRC release message, or a part for identifying the UE context in the corresponding base station or a TC-RNTI except for the base station part from the I-RNTI. The terminal temporary identifier may be composed of 16 bits. In the case of an idle mode terminal, the terminal temporary identifier may be signaled by a core network entity. For example, the terminal temporary identifier corresponds to ng-5G-S-TMSI-Part1 or a part of ng-5G-S-TMSI-Part1 or ng-5G-S-TMSI-Part1 except for the core network entity/common part. It may be a part for the base station to identify the terminal/terminal context. The terminal temporary identifier may be composed of 16 bits. For another example, as the terminal temporary identifier, TC-RNTI included in the RAR may be used.

MsgA may include user data on the CTCH. If user data is to be transmitted without an RRC message in the absence of an RRC connection, it is necessary to define a new type of logical channel for this. For example, a new type of logical channel for this can be defined as a CTCH (Common Traffic Channel) channel. The CTCH has a lower priority than the CCCH and a logical channel priority (LCP) procedure can be performed. Alternatively, a logical channel prioritization procedure may be performed for the CTCH with a lower priority than the MAC CE for C-RNTI. Alternatively, a logical channel prioritization procedure may be performed for the CTCH with the same or higher priority as the MAC CE for the C-RNTI.

MsgA may include an RRC request message in which user data is concatenated on the CCCH. In this case, user data may be included in the RRC message through the NAS information element (e.g. dedicatedInfoNAS). Alternatively, MsgA may include user data on a multiplexed DTCH with an RRC message on the CCCH. Alternatively, MsgA may include user data on a multiplexed DTCH with an RRC message on the CCCH. Alternatively, MsgA may include user data on the multiplexed DTCH with the MAC CE on the CCCH. Alternatively, MsgA may include user data on a multiplexed DTCH with a MAC PDU including a terminal identifier/terminal temporary identifier on the CCCH. Alternatively, the MsgA may include user data on the multiplexed DTCH with the MAC PDU including the terminal identifier/terminal temporary identifier on the MAC CE. The CCCH SDU may consist of 0 bits (or a fixed bit or a zero length octet string). Alternatively, the CCCH SDU may be configured virtually. Through this, user data can be transmitted without an RRC message. In this case, it is possible to perform LCP similar to the CTCH described above.

Alternatively, the CCCH SDU may include at least one of terminal temporary identifier information, authentication token (MAC-I), and shortMAC-I in a fixed bit. Alternatively, the MAC SDU/CE included in the MsgA may include at least one of terminal temporary identifier information, authentication token (MAC-I), and shortMAC-I in a fixed bit.

When MsgA is transmitted, the MAC entity of the UE may perform contention resolution based on the UE contention resolution identity on the C-RNTI on the PDCCH or on the DL-SCH. The base station may want to instruct the terminal to maintain the RRC inactive state. If the base station has downlink data to be transmitted for the corresponding terminal (if received from the core network), it can transmit it to the terminal. When the confirmation message for MsgA is referred to as MsgB, the MsgB transmitted by the base station to the terminal is information for contention resolution or information for instructing the terminal to maintain the RRC inactive state, or information indicating a state transition to RRC idle or the terminal It may contain downlink data to be transmitted for.

For example, MsgB may include user data on the DTCH. The corresponding MAC PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. For another example, the MsgB may include information for instructing the UE to maintain the RRC inactive state on the DCCH. For another example, the MsgB may include information for instructing the UE to maintain the RRC inactive state on the DTCH. The corresponding MAC PDU may be provided through MAC CE. For another example, the MsgB may provide information for instructing the UE to maintain the RRC inactive state through the MAC CE. Through this, it can be indicated without RRC signaling. For another example, the MsgB may include information for instructing the UE to maintain the RRC inactive state on the CCCH. For another example, MsgB may be transmitted without an RRC message. For another example, the MsgB may include the RRC message on the CCCH and user data on the multiplexed DTCH. For another example, the MsgB may include the RRC message on the CCCH and user data on the multiplexed DTCH. For another example, the MsgB may include user data on the multiplexed DTCH with the MAC CE on the CCCH.

In this case, the CCCH SDU may be composed of 0 bits (or a fixed bit or a zero length octet string). Alternatively, the CCCH SDU may be configured virtually. Alternatively, the CCCH SDU may include terminal temporary identifier information in fixed bits. Through this, user data can be transmitted without an RRC message.

Meanwhile, upon receiving the MsgB, the UE may indicate that the RRC connection has been suspended to the upper layer. For example, the MAC entity may indicate information for instructing the UE to maintain the RRC inactive state to the RRC, and the RRC may indicate that the RRC connection is suspended to an upper layer (e.g. NAS). Accordingly, the upper layer can distinguish that it is in the RRC inactive state, and can perform the operation in the RRC inactive state. This can be provided without RRC signaling.

For another example, the terminal may indicate that SDT is performed and the RRC connection is suspended in response to the SDT initiation request to the upper layer.

For another example, upon receiving the MsgB, the UE may indicate to the higher layer the indication information included in the MsgB to the higher layer. For example, when the UE is instructed to maintain the RRC inactive through the MsgB, it may indicate that the RRC connection is suspended. Alternatively, when the terminal is instructed to reject the SDT through the MsgB, it may indicate that the SDT is rejected. Alternatively, when the terminal is instructed to fail for SDT through MsgB, it may indicate that the SDT has failed. Alternatively, the terminal may indicate that the RRC connection is suspended when the transition to RRC idle is instructed through the MsgB. Alternatively, the terminal may indicate that the suspended RRC connection is resumed when the transition to the RRC connection state is instructed through the MsgB. Alternatively, in case of falling back to the RRC connection through MsgB, the UE may indicate fallback of the RRC connection. For the above-described embodiments, corresponding indication information may be included in the MsgB through the MAC CE.

In the above, for convenience of explanation, an embodiment of transmitting a small amount of data in a MAC PDU without RRC has been described, but the small amount of data may be included in an arbitrary Layer2 PDU and transmitted. For example, a small amount of data may be included in the RLC PDU and PDCP PDU, and in this case, the MAC CE may be replaced with the RLC control PDU and PDCP control PDU.

As described above, the present disclosure can provide an effect of efficiently controlling access to a small amount of data without or with an RRC connection. Hereinafter, configurations of a terminal and a base station in which the above-described embodiment according to the present disclosure can be performed will be described with reference to the drawings.

18 is a diagram for describing a configuration of a terminal according to an embodiment.

Referring to FIG. 18, a terminal 1800 transmitting a small amount of data transmits an RRC connection resumption request to a lower layer in a non-access stratum (NAS) layer of an RRC inactive state terminal, and requests to resume an RRC connection. Based on the MAC entity, the control unit 1810 controls to obtain information on a small amount of data transmission through Msg 3 (Message 3) or Msg A (Message A), and Msg 3 or Msg A including small amount of data is transmitted to the base station. And a receiving unit 1830 for receiving Msg 4 or Msg B including confirmation information for Msg 3 or Msg A from the base station.

For example, the terminal 1800 in the RRC inactive state may trigger a small amount of data transmission in the NAS layer. In this case, the controller 1810 may control the NAS layer to instruct the lower layer to request to resume RRC connection.

For example, the controller 1810 may control a small amount of data transmission through Msg3 or MsgA to be indicated to the MAC layer when a request to resume an RRC connection is indicated to a lower layer in the NAS layer. To this end, the MAC layer may receive indication information indicating Msg3 or MsgA transmission from a higher MAC layer.

On the other hand, the small amount of data transmission indication information through Msg3 or MsgA may further include at least one of RRC message type, RRC transaction identifier, terminal temporary identifier, authentication token for integrity protection, and reopening cause information. have.

For example, if the transmission unit 1820 is determined to transmit Msg3 or MsgA based on the small amount of data transmission instruction information through Msg3 or MsgA, the terminal may transmit Msg3 or MsgA to the base station. For example, Msg 3 or Msg A for small data transmission may not include an RRC message. As another example, Msg 3 or Msg A for small amount of data transmission may further include information on at least one of a terminal temporary identifier, an authentication token for integrity protection, and a reason for reopening.

Meanwhile, the terminal temporary identifier may be composed of bits of a specific part of I-RNTI (Inactive-Radio Network Temporary Identity) or I-RNTI. For example, the specific part of the I-RNTI may mean only the bits of the part for identifying the UE context in the corresponding base station except for the base station part in the I-RNTI. Alternatively, the specific part of the I-RNTI may mean a bit of a part that is set in advance to identify the terminal or the terminal context between the terminal and the base station. Accordingly, the bits of the specific part of the I-RNTI may be determined as a few high or low bits of the I-RNTI.

After Msg3 or MsgA is transmitted, the receiving unit 1830 receives Msg4 or MsgB from the base station.

For example, Msg 4 or Msg B may include information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle. That is, the base station may receive Msg 4 or MsgB and instruct the RRC state of the UE to not change unnecessary. For example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle may be included in the MAC CE. As another example, information for indicating maintenance of the RRC inactive state of the terminal 1800 or information for indicating a state transition to RRC idle may be included in the MAC RAR. As another example, information for indicating maintenance of the RRC inactive state of the terminal 1800 or information for indicating a state transition to RRC idle may be included in the MAC subheader. The above-described MAC CE or MAC RAR or MAC subheader may be included in Msg 4 or MsgB and received by the terminal 1800.

Thereafter, the controller 1810 transmits the received information for indicating maintenance of the RRC inactive state or information for indicating the state transition to the RRC idle to the Non-Access Stratum (NAS) layer through the MAC entity. The NAS layer can recognize whether the state of the terminal has changed through the transmitted information.

In addition, the control unit 1810 controls the overall operation of the terminal 1800 according to the small data access control operation and the small data transmission operation required to perform the above-described embodiments.

The transmitting unit 1820 and the receiving unit 1830 are used to transmit and receive signals, messages, and data necessary for carrying out the above-described embodiments with the base station.

19 is a diagram illustrating a configuration of a base station according to an embodiment.

Referring to FIG. 19, a base station 1900 receiving a small amount of data is a transmitter that transmits configuration information for transmitting small amount of data necessary for the terminal to transmit a small amount of data through Msg 3 (Message 3) or Msg A (Message A) to the terminal. (1920) and a receiving unit 1930 for receiving Msg 3 or Msg A including small amount of data from the terminal, wherein the transmitting unit 1920 includes Msg 4 or Msg B including confirmation information for Msg 3 or Msg A. It can be further transmitted to the terminal.

The small amount of data transmission configuration information means information necessary for the terminal to transmit small amount of data to the base station 1900 through a 4-step random access procedure or a 2-step random access procedure. For example, the so-called data transmission configuration information includes information on whether the base station 1900 supports small amount data transmission, condition information for a small amount data transmission trigger condition, TBS threshold information, and category information for access baring when transmitting so-called data. It may contain various information such as.

When a small amount of data transmission is triggered by the terminal, the terminal transmits a small amount of data through Msg 3 or Msg A. For example, Msg 3 or Msg A does not include an RRC message, and may include at least one of a terminal temporary identifier, an authentication token for integrity protection, and a cause of reopening. Here, the terminal temporary identifier may be composed of bits of a specific part of I-RNTI (Inactive-Radio Network Temporary Identity) or I-RNTI. For example, the specific part of the I-RNTI may mean only the bits of the part for identifying the UE context in the corresponding base station except for the base station part in the I-RNTI. Alternatively, the specific part of the I-RNTI may mean a bit of a part that is set in advance to identify the terminal or the terminal context between the terminal and the base station. Accordingly, the bits of the specific part of the I-RNTI may be determined as a few high or low bits of the I-RNTI.

The receiving unit 1930 checks Msg 3 or Msg A received from the terminal and receives a small amount of data. Thereafter, the transmitter 1920 transmits Msg 4 or Msg B to the terminal, through which the state of the terminal can be controlled.

For example, Msg 4 or Msg B may include information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle. That is, the control unit 1910 may receive Msg 4 or MsgB to control the RRC state change of the UE, which is not unnecessary, to occur. For example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle may be included in the MAC CE. As another example, information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle may be included in the MAC RAR. As another example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle may be included in the MAC subheader. The aforementioned MAC CE or MAC RAR or MAC subheader may be included in Msg 4 or MsgB and transmitted to the terminal.

In addition, the controller 1910 controls the overall operation of the base station 1900 according to controlling the small data access control operation and the small data transmission operation of the terminal required to perform the above-described present disclosure.

The transmission unit 1920 and the reception unit 1930 are used to transmit and receive signals, messages, and data necessary for carrying out the above-described present disclosure with the terminal.

The above-described embodiments may be supported by standard documents disclosed in at least one of IEEE 802, 3GPP and 3GPP2 wireless access systems. That is, steps, configurations, and parts not described in order to clearly reveal the present technical idea among the embodiments may be supported by the aforementioned standard documents. In addition, all terms disclosed in the present specification can be described by the standard documents disclosed above.

The above-described embodiments can be implemented through various means. For example, the present embodiments may be implemented by hardware, firmware, software, or a combination thereof.

In the case of implementation by hardware, the method according to the embodiments includes one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), and FPGAs. (Field Programmable Gate Arrays), a processor, a controller, a microcontroller, or a microprocessor.

In the case of implementation by firmware or software, the method according to the embodiments may be implemented in the form of an apparatus, procedure, or function that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor through various known means.

In addition, terms such as "system", "processor", "controller", "component", "module", "interface", "model", or "unit" described above generally refer to computer-related entity hardware, hardware and software. It may mean a combination of, software, or running software. For example, the above-described components may be, but are not limited to, a process driven by a processor, a processor, a controller, a control processor, an object, an execution thread, a program, and/or a computer. For example, both the controller or processor and the application running on the controller or processor can be components. One or more components may reside within a process and/or thread of execution, and the components may be located on one device (eg, a system, a computing device, etc.) or distributed across two or more devices.

The above description is merely illustrative of the technical idea of the present disclosure, and those of ordinary skill in the technical field to which the present disclosure pertains will be able to make various modifications and variations without departing from the essential characteristics of the technical idea. In addition, the present embodiments are not intended to limit the technical idea of the present disclosure, but to explain the technical idea, and thus the scope of the technical idea is not limited by these embodiments. The scope of protection of the present disclosure should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present disclosure.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is for patent application No. 10-2019-0074386 filed in Korea on June 21, 2019, and Patent Application No. 10-2019-0080348 filed in Korea on July 03, 2019, and June 2020. Priority is claimed in accordance with Article 119(a) of the U.S. Patent Law (35 USC § 119(a)) with respect to Patent Application No. 10-2020-0072018 filed in Korea on the 15th, all of which are incorporated herein by reference. Incorporated into the application. In addition, if this patent application claims priority for countries other than the United States for the same reason as above, all the contents are incorporated into this patent application as references.

Claims (16)

1. In the method for the terminal to transmit a small amount of data,

   Transmitting an RRC connection resumption request to a lower layer in a non-access stratum (NAS) layer of the RRC inactive state terminal;

   Obtaining a small amount of data transmission indication information through Msg 3 (Message 3) or Msg A (Message A) in the MAC entity based on the RRC connection resumption request;

   Transmitting Msg 3 or Msg A including the small amount of data to a base station; And

   And receiving, from the base station, Msg 4 or Msg B including confirmation information for Msg 3 or Msg A.
2. The method of claim 1,

   The small amount of data transmission instruction information through the Msg 3 or Msg A,

   A method including at least one of information on an RRC message type, an RRC transaction identifier, a terminal temporary identifier, an authentication token for integrity protection, and information on the cause of reopening.
3. The method of claim 1,

   The Msg 3 or Msg A,

   A method that does not include an RRC message, and further includes information of at least one of a terminal temporary identifier, an authentication token for integrity protection, and a cause of reopening.
4. The method of claim 3,

   The terminal temporary identifier,

   I-RNTI (Inactive-Radio Network Temporary Identity) or a method consisting of bits of a specific part of the I-RNTI.
5. The method of claim 1,

   The Msg 4 or Msg B,

   A method comprising information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle in the MAC CE or MAC RAR or MAC subheader.
6. The method of claim 5,

   Information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle,

   Method delivered to the NAS (Non-Access Stratum) layer through the MAC entity.
7. In the method for the base station to receive a small amount of data,

   Transmitting, by the terminal, a small amount of data transmission configuration information necessary for transmitting a small amount of data through Msg 3 (Message 3) or Msg A (Message A) to the terminal;

   Receiving the Msg 3 or Msg A including the small amount of data from the terminal; And

   A method comprising the step of transmitting Msg 4 or Msg B including confirmation information on the Msg 3 or Msg A to the terminal.
8. The method of claim 7,

   The Msg 3 or Msg A,

   A method that does not include an RRC message, and further includes information of at least one of a terminal temporary identifier, an authentication token for integrity protection, and a cause of reopening.
9. The method of claim 8,

   The terminal temporary identifier,

   I-RNTI (Inactive-Radio Network Temporary Identity) or a method consisting of bits of a specific part of the I-RNTI.
10. The method of claim 7,

    The Msg 4 or Msg B,

    A method comprising information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle in the MAC CE or MAC RAR or MAC subheader.
11. In a terminal transmitting a small amount of data,

    RRC inactive (RRC Inactive) state The non-access stratum (NAS) layer of the terminal transmits an RRC connection resumption request to a lower layer, and based on the RRC connection resumption request, Msg 3 (Message 3) or Msg A in the MAC entity A control unit for controlling to obtain small amount of data transmission instruction information through (Message A);

    A transmitter for transmitting Msg 3 or Msg A including the small amount of data to a base station; And

    Terminal comprising a receiving unit for receiving from the base station Msg 4 or Msg B including confirmation information for the Msg 3 or Msg A.
12. The method of claim 11,

    The small amount of data transmission instruction information through the Msg 3 or Msg A,

    A terminal including at least one of information on an RRC message type, an RRC transaction identifier, a terminal temporary identifier, an authentication token for integrity protection, and reopening cause information.
13. The method of claim 11,

    The Msg 3 or Msg A,

    A terminal that does not include an RRC message, and further includes information of at least one of a terminal temporary identifier, an authentication token for integrity protection, and a reason for reopening.
14. The method of claim 13,

    The terminal temporary identifier,

    A terminal configured with bits of an Inactive-Radio Network Temporary Identity (I-RNTI) or a specific part of the I-RNTI.
15. The method of claim 11,

    The Msg 4 or Msg B,

    A terminal comprising information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle in the MAC CE or MAC RAR or MAC subheader.
16. The method of claim 15,

    Information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle,

    Terminal delivered to the NAS (Non-Access Stratum) layer through the MAC entity.

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