WO2024148476A1

WO2024148476A1 - Devices and methods of communication

Info

Publication number: WO2024148476A1
Application number: PCT/CN2023/071417
Authority: WO
Inventors: Da Wang; Gang Wang
Original assignee: Nec Corporation
Priority date: 2023-01-09
Filing date: 2023-01-09
Publication date: 2024-07-18

Abstract

Embodiments of the present disclosure relate to devices and methods of communication. In one aspect, a MN determines that a SN is to be released while a set of candidate cells associated with the SN is maintained; and transmits, to the SN, a first indication for releasing a radio resource of a terminal device and maintaining the set of candidate cells. In this way, a solution of a subsequent conditional cell change may be enhanced.

Description

DEVICES AND METHODS OF COMMUNICATION

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication, and in particular, to devices and methods of communication for a conditional cell change.

BACKGROUND

For a conditional primary secondary cell (PSCell) change (CPC) /conditional PSCell addition (CPA) in third generation partnership project (3GPP) Release 17, a CPC/CPA-configured terminal device has to release a CPC/CPA configuration when completing random access towards a target PSCell. Hence the terminal device has no chance to perform subsequent CPC/CPA without prior CPC/CPA reconfiguration and re-initialization from the network side. This will increase a delay for a cell change and increase signaling overhead, especially in the case of frequent secondary cell group (SCG) changes when operating in frequency range 2 (FR2) . Therefore, multi-random access technology dual connectivity (MR-DC) with selective activation of cell groups aims at enabling subsequent CPC/CPA after SCG change, without reconfiguration and re-initialization on a CPC/CPA preparation from the network side. This results in a reduction of signaling overhead and an interrupting time for SCG change. However, a mechanism and a procedure of a subsequent CPC/CPA are still incomplete and need to be further developed.

SUMMARY

In general, embodiments of the present disclosure provide methods, devices and computer storage media of communication for a subsequent conditional cell change.

In a first aspect, there is provided a master node. The master node comprises a processor configured to cause the master node to: determine that a secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and transmit, to the secondary node, a first indication for releasing a radio resource of the terminal device and maintaining the set of candidate cells.

In a second aspect, there is provided a secondary node. The secondary node comprises a processor configured to cause the secondary node to: determine that the secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and receive, from a master node, a first indication for releasing a radio resource of the terminal device and maintaining the set of candidate cells.

In a third aspect, there is provided a terminal device. The terminal device comprises a processor configured to cause the terminal device to: receive a conditional reconfiguration associated with a secondary cell group supporting subsequent conditional cell change; and in accordance with a determination that a primary cell of the secondary cell group is changed from a first secondary node to a second secondary node, perform a first operation comprising at least one of the following: removing the conditional reconfiguration; deactivating the conditional reconfiguration; or deactivating a conditional reconfiguration evaluation for the conditional reconfiguration.

In a fourth aspect, there is provided a terminal device. The terminal device comprises a processor configured to cause the terminal device to: receive, from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value and a set of offset values for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determine, from the set of offset values, an offset value that has been unused; and determine, based on the counter value and the offset value, a security key for communication with the candidate cell.

In a fifth aspect, there is provided a terminal device. The terminal device comprises a processor configured to cause the terminal device to: receive, from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determine that the counter value has been used for determination of a first security key for the candidate cell; and determine a second security key for communication with the candidate cell based on at least one of the following: the first security key; a physical cell identity of the candidate cell; an absolute frequency of a synchronization signal block of the candidate cell; or a counter for the second security key.

In a sixth aspect, there is provided a method of communication. The method comprises: determining, at a master node, that a secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and transmitting, to the secondary node, a first indication for releasing a radio resource of the terminal device and maintaining the set of candidate cells.

In a seventh aspect, there is provided a method of communication. The method comprises: determining, at a secondary node, that the secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and receive, from a master node, a first indication for releasing a radio resource of the terminal device and maintaining the set of candidate cells.

In an eighth aspect, there is provided a method of communication. The method comprises: receiving, at a terminal device, a conditional reconfiguration associated with a secondary cell group supporting subsequent conditional cell change; and in accordance with a determination that a primary cell of the secondary cell group is changed from a first secondary node to a second secondary node, performing a first operation comprising at least one of the following: removing the conditional reconfiguration; deactivating the conditional reconfiguration; or deactivating a conditional reconfiguration evaluation for the conditional reconfiguration.

In a ninth aspect, there is provided a method of communication. The method comprises: receiving, at a terminal device and from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value and a set of offset values for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determining, from the set of offset values, an offset value that has been unused; and determining, based on the counter value and the offset value, a security key for communication with the candidate cell.

In a tenth aspect, there is provided a method of communication. The method comprises: receiving, at a terminal device and from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determining that the counter value has been used for determination of a first security key for the candidate cell; and determining a second security key for communication with the candidate cell based on at least one of the following: the first security key; a physical cell identity of the candidate cell; an absolute frequency of a synchronization signal block of the candidate cell; or a counter for the second security key.

In an eleventh aspect, there is provided a computer readable medium having instructions stored thereon. The instructions, when executed on at least one processor, cause the at least one processor to perform the method according to any of the sixth to tenth aspects of the present disclosure.

Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:

FIG. 1 illustrates an example communication network in which some embodiments of the present disclosure can be implemented;

FIG. 2 illustrates a schematic diagram illustrating an example process of secondary node (SN) release according to embodiments of the present disclosure;

FIG. 3A illustrates a schematic diagram illustrating an example process of master node (MN) initiated secondary node (SN) release according to embodiments of the present disclosure;

FIG. 3B illustrates a schematic diagram illustrating an example process of SN initiated SN release according to embodiments of the present disclosure;

FIG. 3C illustrates a schematic diagram illustrating an example process of SN release in a subsequent CPC according to embodiments of the present disclosure;

FIG. 4 illustrates a schematic diagram illustrating an example process in an inter-SN change according to embodiments of the present disclosure;

FIG. 5 illustrates a schematic diagram illustrating an example process of determining a security key for a subsequent conditional cell change according to embodiments of the present disclosure;

FIG. 6 illustrates a schematic diagram illustrating another example process of determining a security key for a subsequent conditional cell change according to embodiments of the present disclosure;

FIG. 7 illustrates an example method of communication implemented at a MN in accordance with some embodiments of the present disclosure;

FIG. 8 illustrates an example method of communication implemented at a SN in accordance with some embodiments of the present disclosure;

FIG. 9 illustrates an example method of communication implemented at a terminal device in accordance with some embodiments of the present disclosure;

FIG. 10 illustrates another example method of communication implemented at a terminal device in accordance with some embodiments of the present disclosure;

FIG. 11 illustrates still another example method of communication implemented at a terminal device in accordance with some embodiments of the present disclosure; and

FIG. 12 illustrates a simplified block diagram of a device that is suitable for implementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitations as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

As used herein, the term ‘terminal device’ refers to any device having wireless or wired communication capabilities. Examples of the terminal device include, but not limited to, user equipment (UE) , personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs) , portable computers, tablets, wearable devices, Internet of things (IoT) devices, Ultra-reliable and Low Latency Communications (URLLC) devices, Internet of Everything (IoE) devices, machine type communication (MTC) devices, device on vehicle for V2X communication where X means pedestrian, vehicle, or infrastructure/network, devices for Integrated Access and Backhaul (IAB) , Small Data Transmission (SDT) , mobility, Multicast and Broadcast Services (MBS) , positioning, dynamic/flexible duplex in commercial networks, reduced capability (RedCap) , Space borne vehicles or Air borne vehicles in Non-terrestrial networks (NTN) including Satellites and High Altitude Platforms (HAPs) encompassing Unmanned Aircraft Systems (UAS) , eXtended Reality (XR) devices including different types of realities such as Augmented Reality (AR) , Mixed Reality (MR) and Virtual Reality (VR) , the unmanned aerial vehicle (UAV) commonly known as a drone which is an aircraft without any human pilot, devices on high speed train (HST) , or image capture devices such as digital cameras, sensors, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing and the like. The ‘terminal device’ can further has ‘multicast/broadcast’ feature, to support public safety and mission critical, V2X applications, transparent IPv4/IPv6 multicast delivery, IPTV, smart TV, radio services, software delivery over wireless, group communications and IoT applications. It may also incorporated one or multiple Subscriber Identity Module (SIM) as known as Multi-SIM. The term “terminal device” can be used interchangeably with a UE, a mobile station, a subscriber station, a mobile terminal, a user terminal or a wireless device.

The term “network device” refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include, but not limited to, a Node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a next generation NodeB (gNB) , a transmission reception point (TRP) , a remote radio unit (RRU) , a radio head (RH) , a remote radio head (RRH) , an IAB node, a low power node such as a femto node, a pico node, a reconfigurable intelligent surface (RIS) , Network-controlled Repeaters, and the like.

The terminal device or the network device may have Artificial intelligence (AI) or Machine learning capability. It generally includes a model which has been trained from numerous collected data for a specific function, and can be used to predict some information.

The terminal or the network device may work on several frequency ranges, e.g. FR1 (410 MHz to 7125 MHz) , FR2 (24.25GHz to 71GHz) , frequency band larger than 100GHz as well as Tera Hertz (THz) . It can further work on licensed/unlicensed/shared spectrum. The terminal device may have more than one connections with the network devices under Multi-Radio Dual Connectivity (MR-DC) application scenario. The terminal device or the network device can work on full duplex, flexible duplex and cross division duplex modes.

The network device may have the function of network energy saving, Self-Organising Networks (SON) /Minimization of Drive Tests (MDT) . The terminal may have the function of power saving.

The embodiments of the present disclosure may be performed in test equipment, e.g. signal generator, signal analyzer, spectrum analyzer, network analyzer, test terminal device, test network device, channel emulator.

In one embodiment, the terminal device may be connected with a first network device and a second network device. One of the first network device and the second network device may be a master node and the other one may be a secondary node. The first network device and the second network device may use different radio access technologies (RATs) . In one embodiment, the first network device may be a first RAT device and the second network device may be a second RAT device. In one embodiment, the first RAT device is eNB and the second RAT device is gNB. Information related with different RATs may be transmitted to the terminal device from at least one of the first network device or the second network device. In one embodiment, first information may be transmitted to the terminal device from the first network device and second information may be transmitted to the terminal device from the second network device directly or via the first network device. In one embodiment, information related with configuration for the terminal device configured by the second network device may be transmitted from the second network device via the first network device. Information related with reconfiguration for the terminal device configured by the second network device may be transmitted to the terminal device from the second network device directly or via the first network device.

As used herein, the singular forms ‘a’ , ‘an’ and ‘the’ are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term ‘includes’ and its variants are to be read as open terms that mean ‘includes, but is not limited to. ’ The term ‘based on’ is to be read as ‘at least in part based on. ’ The term ‘one embodiment’ and ‘an embodiment’ are to be read as ‘at least one embodiment. ’ The term ‘another embodiment’ is to be read as ‘at least one other embodiment. ’ The terms ‘first, ’ ‘second, ’ and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.

In some examples, values, procedures, or apparatus are referred to as ‘best, ’ ‘lowest, ’ ‘highest, ’ ‘minimum, ’ ‘maximum, ’ or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.

In the context of the present application, the term “a cell change or addition” may be interchangeably used with “reconfigurationWithSync for SCG or master cell group (MCG) ” . In the context of the present application, the term “PSCell” refers to a SpCell of a SCG, the term “PCell” refers to a SpCell of a MCG, and the term “SpCell” refers to a primary cell of a SCG or MCG. The term “prepared PSCells” may be interchangeably used with “candidate PSCells” , “candidate cells” or “prepared candidate PSCells” .

As mentioned above, a mechanism and a procedure of a subsequent CPC are still incomplete and need to be further developed. In view of this, embodiments of the present disclosure provide a solution for enabling a subsequent conditional cell change. In the solution, a conditional reconfiguration is caused to comprise information indicating that a subsequent conditional cell change is enabled for at least one candidate cell in the set of candidate cells, and when a cell change or addition is performed, at least a portion of the conditional reconfiguration is maintained for the at least one candidate cell. In this way, an enabling of a subsequent conditional cell change can be achieved in an efficient and flexible way. Principles and implementations of the present disclosure will be described in detail below with reference to the figures.

It is to be understood that the present solution may be applied in a SCG change, and also may be applied in a MCG change. That is, the present solution may be applied for a subsequent CPC or a subsequent conditional handover. The subsequent CPC or subsequent conditional handover may also be referred to as a selective activation of cell groups, a selective activation of SCGs, a subsequent SCG change, a subsequent cell group change or a subsequent conditional cell change. For convenience, embodiments of the present disclosure will be described by taking a subsequent CPC as an example.

EXAMPLE OF COMMUNICATION NETWORK

FIG. 1 illustrates a schematic diagram of an example communication environment 100 in which embodiments of the present disclosure can be implemented. As shown in FIG. 1, the communication environment 100 may comprise a network device 110 and a terminal device 120. The network device 110 provides a cell 111 and the terminal device 120 is located in the cell 111 and served by the network device 110.

The communication environment 100 may also comprise one or more other network devices such as

network devices

130, 140 and 150. The network device 130 provides

cells

131, 132 and 133. The network device 140 provides

cells

141, 142 and 143, and the network device 150 provides

cells

151, 152 and 153. It should be noted that the number of the cells are not limited to three, and more or less cells may be provided by the

network devices

130, 140 and 150.

Assuming that the terminal device 120 may establish a dual connection (i.e., simultaneous connection) with two network devices. For example, the network device 110 may serve as a MN (for convenience, also referred to as MN 110 below) , and the network device 130 may serve as a SN (for convenience, also referred to as SN 130 below) . Although only the cell 111 is shown, the MN 110 may provide multiple cells, and these cells may form a MCG for the terminal device 120. Assuming that the cell 111 is a primary cell (i.e., PCell) in the MCG. Further, the

cells

131, 132 and 133 provided by the network device 130 may form a SCG for the terminal device 120. Assuming that the cell 131 is a primary cell (i.e., PSCell) in the SCG.

The communication environment 100 may also comprise a core network 160. The core network 160 may comprise a user port function (UPF) 161 and an access management function (AMF) 162. It is to be understood that the core network 160 may also comprise any other suitable elements.

The SN 130 may communicate with the terminal device 120 via a channel such as a wireless communication channel. Similarly, the MN 110 may also communicate with the terminal device 120 via a channel such as a wireless communication channel. The SN 130 may communicate with the MN 110 via a control-plane interface such as Xn-C. The MN 110 may communicate with the core network 160 such as the AMF 162 via a control-plane interface such as NG-C. The SN 130 may also communicate with the MN 110 via a user plane interface such as Xn-U, and communicate with the core network 160 such as the UPF 161 via a user plane interface such as NG-U.

It is to be understood that the number of devices or cells in FIG. 1 is given for the purpose of illustration without suggesting any limitations to the present disclosure. The communication environment 100 may involve any suitable number of network devices and/or terminal devices and/or cells adapted for implementing implementations of the present disclosure.

The communications in the communication environment 100 may conform to any suitable standards including, but not limited to, Global System for Mobile Communications (GSM) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , GSM EDGE Radio Access Network (GERAN) , Machine Type Communication (MTC) and the like. The embodiments of the present disclosure may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols, 5.5G, 5G-Advanced networks, or the sixth generation (6G) networks.

In some embodiments, the network device 110 may configure a conditional reconfiguration for the terminal device 120.

Assuming that the cells 131-133, 141-143 and 151-153 are configured to the terminal device 120 as candidate cells. In some scenarios, the terminal device 120 may initially communicate with only the network device 110. As the terminal device 120 moves, when a condition for a candidate cell (for example, the cell 131) is fulfilled, the terminal device 120 may be caused to establish the dual connection with the network device 110 and the network device 130. This process of SN addition may be called as a CPA.

In some scenarios, the terminal device 120 may establish a dual connection with the

network devices

110 and 130. The network device 110 serves as a MN and the network device 130 serves as a SN. As the terminal device 120 moves, a SN serving the terminal device 120 may be changed from the network device 130 (also referred to as a source SN or current SN 130) to the network device 140 (also referred to as a target SN 140) . This process of PSCell change may be called as a CPC. In some scenarios, after the terminal device is configured with conditional reconfiguration and with subsequent CPC being enabled, and before at least one execution condition is fulfilled for any candidate PSCell, the terminal device 120 may receive a RRC Reconfiguration message containing reconfigurationWithSync for SCG from the network device 110, and the terminal device 120 may perform a PSCell change or addition accordingly. This procedure is called as legacy PSCell change or addition. As an example, after the legacy PSCell change or addition procedure, the SN serving the terminal device 120 is the network device 140.

After the above CPA, CPC or legacy PSCell change/addition procedure, The UE does not release the conditional reconfiguration supporting subsequent CPA/CPC, and continues conditional reconfiguration evaluation. As the terminal device 120 further moves, when a condition for still another candidate cell (for example, the cell 151) is fulfilled, a SN serving the terminal device 120 may be changed from the network device 140 to the network device 150 (also referred to as a target SN 150) . This process of SN change may be called as a subsequent CPC.

In the subsequent CPC, the network device 110 (i.e., the MN) may indicate the terminal device 120 to release the source SN (i.e., the network device 140) . This is a process of SN release for a subsequent CPC.

As shown in FIG. 1, as the terminal device 120 further moves, the terminal device 120 may move out of coverage of a SN. The network device 110 (i.e., the MN) may indicate the terminal device 120 to release a previous SN (e.g., the network device 150) . In this case, the terminal device 120 may not release the conditional reconfiguration supporting subsequent CPA/CPC, and continue a conditional reconfiguration evaluation for subsequent CPA. This also is a process of SN release.

Continue to refer to FIG. 1, as the terminal device 120 further moves, when a condition for a candidate cell (for example, the cell 152) is fulfilled, the terminal device 120 may be caused to establish a dual connection with the network device 110 and the network device 150. This process may be called as a subsequent CPA.

Embodiments of the present disclosure provide a solution of communication for a subsequent CPA/CPC. In the context of the present disclosure, the term “subsequent CPA/CPC” may be interchangeably used with “selective activation of cell groups” , “selective activation of PSCell (SAP) ” , “subsequent CPAC” , “conditional selective cell group” , or “conditional subsequent cell change” .

EXAMPLE IMPLEMENTATION OF SN RELEASE

Conventionally, a SN release procedure is used to cancel all the prepared PSCells at a candidate SN and initiate a release of related UE context at the candidate SN. However, to support subsequent CPA/CPC, the SN release procedure needs to be enhanced.

In view of this, embodiments of the present disclosure provide a solution of communication for SN release. For illustration, the solution will be described in connection with FIG. 2. FIG. 2 illustrates a schematic diagram illustrating an example process 200 of SN release according to embodiments of the present disclosure. For the purpose of discussion, the process 200 will be described with reference to FIG. 1. The process 200 may involve a MN (e.g., the network device 110) and a SN to be released (e.g., the

network device

130 or 140 or 150) .

As shown in FIG. 2, the MN may determine 210 that a SN is to be released while a set of candidate cells associated with the SN is maintained.

With reference to the example of FIG. 1, during a subsequent CPC in which a SN serving the terminal device 120 is changed from the network device 140 to the network device 150, the network device 110 (i.e., the MN) may determine that the network device 140 (i.e., the source SN) is to be released while a set of candidate cells (i.e., the

cells

141, 142 and 143) associated with the SN is maintained.

Still with reference to the example of FIG. 1, when the terminal device 120 moves out of coverage of a SN, the network device 110 (i.e., the MN) may determine that the previous SN (e.g., the network device 150) is to be released while a set of candidate cells (i.e., the

cells

151, 152 and 153) associated with the SN is maintained.

With reference to FIG. 2, upon determination that a SN is to be released, the MN may transmit 220, to the SN, an indication (for convenience, also referred to as a first indication herein) for releasing a radio resource of the terminal device 120 and maintaining the set of candidate cells associated with the SN. In this way, SN release may be performed while maintaining candidate PSCells associated with the released SN.

For illustration, some example embodiments of SN release will be detailed in connection with Embodiments 1 to 3 below.

Embodiment 1

In this embodiment, a MN initiated SN release is performed while prepared PSCells for subsequent CPA/CPC at the SN is maintained.

FIG. 3A illustrates a schematic diagram illustrating an example process 300A of MN initiated SN release according to embodiments of the present disclosure. For the purpose of discussion, the process 300A will be described with reference to FIG. 1. The process 300A may involve the terminal device 120, the

network devices

110 and 150, the UPF 161 and the AMF 162 as illustrated in FIG. 1. In this example, the network device 110 is a MN serving the terminal device 120, and the network device 150 is a SN to be released.

As shown in FIG. 3A, a MN (e.g., the network device 110) may transmit 301, to a SN (e.g., the network device 150) , an indication (for convenience, also referred to as a second indication herein) for releasing the SN while maintaining a set of candidate cells associated with the SN. In some embodiments, the second indication may be carried by an Xn message. In some embodiments, the second indication may be an Xn message itself. In some embodiments, the Xn message may be a SN release request message that comprises an indication of maintaining prepared PSCells. It is to be understood that any other suitable messages existing or to be developed in future are also feasible.

As shown in FIG. 3A, upon reception of the second indication, the network device 150 may stop 302 providing user data to the terminal device 120. The network device 150 may transmit 303 an acknowledgement for the second indication. In some embodiments, the acknowledgement may be carried by an Xn message. In some embodiments, the acknowledgement may be an Xn message itself. In some embodiments, the Xn message may be a SN release request acknowledge message. It is to be understood that any other suitable messages existing or to be developed in future are also feasible.

The network device 110 may provide 304 forwarding address information to the network device 150. The network device 110 may transmit 305 a RRC reconfiguration message to the terminal device 120 to release SCG configuration but maintain the conditional reconfiguration which supports subsequent CPA/CPC. The terminal device 120 may reply 306 an RRC reconfiguration complete message to the network device 110.

The network device 150 may transmit 307 a SN status transfer message to the network device 110. Then data forwarding from the network device 150 to the network device 110 may start 308. The network device 150 may transmit 309 a secondary RAT data usage report message to the network device 110. If applicable, a PDU session path update procedure may be initiated 310.

Continue to refer to FIG. 3A, the network device 110 may transmit 311, to the network device 150, an indication (i.e., the first indication) for releasing a radio resource of the terminal device 120 and maintaining the set of candidate cells associated with the network device 150. In some embodiments, the first indication may be carried by an Xn message. In some embodiments, the first indication may be an Xn message itself. For example, the Xn message may be an UE context release message which comprises an indication of maintaining prepared PSCells. It is to be understood that any other suitable messages existing or to be developed in future are also feasible.

Upon reception of the first indication, the network device 150 may release 312 the radio resource of the terminal device 120 and maintain at least one of the prepared PSCells supporting CPA/CPC or control plane related resources of the terminal device 120.

In this way, a MN initiated SN release is enhanced for subsequent CPA/CPC.

Embodiment 2

In this embodiment, a SN initiated SN release is performed while prepared PSCells for subsequent CPA/CPC at the SN is maintained.

FIG. 3B illustrates a schematic diagram illustrating an example process 300B of SN initiated SN release according to embodiments of the present disclosure. For the purpose of discussion, the process 300B will be described with reference to FIG. 1. The process 300B may involve the terminal device 120, the

network devices

As shown in FIG. 3B, a SN (e.g., the network device 150) may transmit 320, to a MN (e.g., the network device 110) , an indication (for convenience, also referred to as a third indication herein) for releasing the SN while maintaining a set of candidate cells associated with the SN. Alternatively or additionally, the third indication may indicate stopping providing user data to the terminal device 120 while maintaining the set of candidate cells.

In some embodiments, the third indication may be carried by an Xn message. In some embodiments, the third indication may be an Xn message itself. For example, the Xn message may be a SN release required message that comprises an indication of maintaining prepared PSCells. It is to be understood that any other suitable messages existing or to be developed in future are also feasible.

As shown in FIG. 3B, upon reception of the third indication, the network device 110 may transmit 321 an acknowledgement for the third indication. In some embodiments, the acknowledgement may be carried by an Xn message. In some embodiments, the acknowledgement may be an Xn message itself. For example, the Xn message may be a SN release required acknowledge message. It is to be understood that any other suitable messages existing or to be developed in future are also feasible.

As shown in FIG. 3B, the network device 150 may stop 322 providing user data to the terminal device 120. In some embodiments, upon transmission of the third indication, the network device 150 may stop providing the user data to the terminal device 120. In some embodiments, upon reception of the acknowledgement for the third indication from the network device 110, the network device 150 may stop providing the user data to the terminal device 120.

The network device 110 may provide 323 forwarding address information to the network device 150. The network device 110 may transmit 324 a RRC reconfiguration message to the terminal device 120 to release SCG configuration but maintain the conditional reconfiguration which supports subsequent CPA/CPC. The terminal device 120 may reply 325 an RRC reconfiguration complete message to the network device 110.

The network device 150 may transmit 326 a SN status transfer message to the network device 110. Then data forwarding from the network device 150 to the network device 110 may start 327. The network device 150 may transmit 328 a secondary RAT data usage report message to the network device 110. If applicable, a PDU session path update procedure may be initiated 329.

Continue to refer to FIG. 3B, the network device 110 may transmit 330, to the network device 150, an indication (i.e., the first indication) for releasing a radio resource of the terminal device 120 and maintaining the set of candidate cells associated with the network device 150. In some embodiments, the first indication may be carried by an Xn message. In some embodiments, the first indication may be an Xn message itself. For example, the Xn message may be an UE context release message which comprises an indication of maintaining prepared PSCells. It is to be understood that any other suitable messages existing or to be developed in future are also feasible.

Upon reception of the first indication, the network device 150 may release 331 the radio resource of the terminal device 120 and maintain at least one of the prepared PSCells supporting CPA/CPC or control plane related resources of the terminal device 120.

In this way, a SN initiated SN release is enhanced for subsequent CPA/CPC.

Embodiment 3

In this embodiment, SN release in a subsequent CPC procedure is described.

FIG. 3C illustrates a schematic diagram illustrating an example process 300C of SN release in a subsequent CPC according to embodiments of the present disclosure. For the purpose of discussion, the process 300C will be described with reference to FIG. 1. The process 300C may involve the terminal device 120, the

network devices

110, 140 and 150, the UPF 161 and the AMF 162 as illustrated in FIG. 1. In this example, the network device 110 is a MN serving the terminal device 120, the network device 140 is a source SN, and the network device 150 is a target SN.

As shown in FIG. 3C, the terminal device 120 may determine 340 that an execution condition of a candidate PSCell (e.g., the cell 151) of the network device 150 is satisfied, and perform a subsequent CPC procedure. In this case, the terminal device 120 may apply an RRC reconfiguration corresponding to the cell 151. The terminal device 120 may transmit 341, to the network device 110, an RRC reconfiguration complete message (i.e., MN RRC reconfiguration complete message) comprising an RRC reconfiguration complete message (i.e., SN RRC reconfiguration complete message) for the cell 151 and the selected PSCell information.

The network device 110 may transmit 342, to the network device 140, an indication (i.e., the second indication) for releasing the network device 140 while maintaining a set of candidate cells associated with the network device 140. Other details of the second indication are similar to that described in Embodiment 1 and are not repeated here for concise.

As shown in FIG. 3C, the network device 140 may transmit 343 an acknowledgement for the second indication. The network device 140 may stop 344 providing user data to the terminal device 120. Other details of the acknowledgement for the second indication are similar to that described in Embodiment 1 and are not repeated here for concise.

The network device 110 may provide 345 address information of the network device 150 to the network device 140 to start late data forwarding. The network device 110 may transmit 346, to the network device 150, a SN reconfiguration complete message.

As shown in FIG. 3C, the network device 110 may transmit 347, to the network device 150, information of a set of forwarding addresses for a set of SNs other than the target node (i.e., the network device 150) , e.g., via an Xn-U address indication procedure. In this way, early data forwarding may be triggered. The terminal device 120 may perform 348 synchronization towards the network device 150.

The network device 140 may transmit 349 a SN status transfer message to the network device 110, and the network device 110 may transmit 350 a SN status transfer message to the network device 150. Then data forwarding among the network devices may be triggered 351. The network device 140 may transmit 352 a secondary RAT data usage report message to the network device 110. If applicable, a PDU session path update procedure may be initiated 353.

Continue to refer to FIG. 3C, the network device 110 may transmit 354, to the network device 140, an indication (i.e., the first indication) for releasing a radio resource of the terminal device 120 and maintaining the set of candidate cells associated with the network device 140. Other details of the first indication are similar to that described in Embodiment 1 and are not repeated here for concise.

Upon reception of the first indication, the network device 140 may release 355 the radio resource of the terminal device 120 and maintain at least one of the prepared PSCells supporting CPA/CPC or control plane related resources of the terminal device 120.

In this way, a SN release in a subsequent CPC procedure is enhanced.

EXAMPLE IMPLEMENTATION OF HANDLING IN INTER-SN CHANGE

Conventionally, a terminal device may receive an SN initiated conditional reconfiguration without MN involvement supporting subsequent CPC. In this case, if the terminal device changes to another SN (e.g., conditional or non-conditional change) , how does the terminal device handle the condition reconfiguration is still unclear.

In view of this, embodiments of the present disclosure provide a solution of communication in an inter-SN change. For illustration, the solution will be described in connection with FIG. 4. FIG. 4 illustrates a schematic diagram illustrating an example process 400 in an inter-SN change according to embodiments of the present disclosure. For the purpose of discussion, the process 400 will be described with reference to FIG. 1. The process 400 may involve the terminal device 120 and the

network devices

110 and 140 as illustrated in FIG. 1. In this example, the network device 110 is a MN serving the terminal device 120 and the network device 140 is a source SN.

As shown in FIG. 4, the terminal device 120 may receive 410 a conditional reconfiguration associated with a SCG supporting subsequent conditional cell change.

In some embodiments, the terminal device 120 may receive 411 the conditional reconfiguration from a MN (e.g., the network device 110) , e.g., via SRB1 of the MN. Via SRB1 of MN means that the conditional reconfiguration is included within a SN RRCReconfiguration message embedded in a RRCReconfiguration message received via SRB1.

In some embodiments, the terminal device 120 may receive 412 the conditional reconfiguration from a source SN (e.g., the network device 140) , e.g., via SRB3 of the source SN. Via SRB3 of S-SN means that the configuration reconfiguration is included in the RRCReconfiguration message received via SRB3.

In some embodiments, the PSCell of the terminal device 120 may be changed from the first SN to the second SN. In this case, the terminal device 120 may perform 430 an operation (for convenience, also referred to as a first operation herein) for the conditional reconfiguration associated with the SCG.

In some embodiments for the first operation, the terminal device 120 may remove the conditional reconfiguration associated with the SCG. For example, the terminal device 120 may remove all entries within an UE variable for the SCG (e.g., VarConditionalReconfig) . In some embodiments, the terminal device 120 may deactivate the conditional reconfiguration associated with the SCG. In other words, the terminal device 120 may suspend the conditional reconfiguration associated with the SCG. In some embodiments, the terminal device 120 may deactivate a conditional reconfiguration evaluation for the conditional reconfiguration associated with the SCG. In other words, the terminal device 120 may suspend the conditional reconfiguration evaluation. That is, the terminal device 120 may not perform the conditional reconfiguration evaluation. It is to be understood that any suitable combination of the above operations are also feasible.

With reference to FIG. 4, in some embodiments, the network device 140 (i.e. the source SN) may transmit 431, to the network device 110, an indication of the first operation. For example, the network device 140 may transmit an indication for removing or releasing or deactivating the conditional reconfiguration associated with the SCG supporting subsequent CPC. For example, after reception of an SN release message from the network device 100, the network device 140 may transmit the indication in an SN release request acknowledge message. Then the network device 110 may transmit 432, to the terminal device 120, an indication of the first operation. For example, the network device 110 may transmit an indication for removing or releasing or deactivating the conditional reconfiguration associated with the SCG supporting subsequent CPC. For example, the network device 110 may transmit the indication in an RRCReconfiguration message using SRB1.

Alternatively, the network device 140 (i.e. the source SN) may directly transmit 433, to the terminal device 120, an indication of the first operation. For example, the network device 140 may transmit the indication in an RRCReconfiguration message using SRB3. Then the terminal device 120 may perform the first operation based on reception of the indication.

In some embodiments, the PSCell may be changed back to the source SN (i.e., the network device 140) . In this case, continue to refer to FIG. 4, the terminal device 120 may perform 440 an operation (for convenience, also referred to as a second operation herein) for the conditional reconfiguration associated with the SCG again. In some embodiments, the terminal device 120 may activate the conditional reconfiguration associated with the SCG. In other words, the terminal device 120 may resume the conditional reconfiguration associated with the SCG. In some embodiments, the terminal device 120 may activate a conditional reconfiguration evaluation for the conditional reconfiguration associated with the SCG. In other words, the terminal device 120 may resume the conditional reconfiguration evaluation. That is, the terminal device 120 may perform the conditional reconfiguration evaluation. It is to be understood that any suitable combination of the above operations are also feasible.

Continue to refer to FIG. 4, in some embodiments, the network device 140 (i.e. the source SN) may transmit 441, to the network device 110, an indication of the second operation. For example, the network device 140 may transmit an indication for resuming or activating the conditional reconfiguration associated with the SCG supporting subsequent CPC. Then the network device 110 may transmit 442, to the terminal device 120, an indication of the second operation. For example, the network device 110 may transmit to the terminal device 120 an indication for resuming or deactivating the conditional reconfiguration associated with the SCG supporting subsequent CPC. For example, the network device 110 may transmit the indication in an RRCReconfiguration message using SRB1.

Alternatively, the network device 140 (i.e. the source SN) may directly transmit 443, to the terminal device 120, an indication of the second operation. For example, the network device 140 may transmit the indication in an RRCReconfiguration message using SRB3. Then the terminal device 120 may perform the second operation based on reception of the indication.

In this way, intra-SN subsequent CPC handling after inter-SN change is provided. If a terminal device changes from a SN to another SN, candidate PSCell (s) of the SN may not be considered for subsequent CPC.

EXAMPLE IMPLEMENTATION OF SECURITY KEY DETERMINATION

In legacy or conditional PSCell change/addition procedure, an RRCReconfiguration with reconfigurationWithSync for SN is applied only once, and thus a SN counter (e.g., sk-counter) configured is used only once. However, in case of subsequent CPC being enabled, a terminal device may perform CPC multiple times using the same RRCReconfiguration, but the SN counter configured for candidate PSCells in a conditional reconfiguration is configured only once. To support subsequent CPA/CPC, deriving of a security key needs to be further developed.

In view of this, embodiments of the present disclosure provide solutions of communication for security key determination. For illustration, the solutions will be described in connection with FIGs. 5 and 6.

FIG. 5 illustrates a schematic diagram illustrating an example process 500 of determining a security key for a subsequent conditional cell change according to embodiments of the present disclosure. For the purpose of discussion, the process 500 will be described with reference to FIG. 1. The process 500 may involve the terminal device 120 and the

network devices

110 and 140 as illustrated in FIG. 1. In this example, the network device 110 is a MN serving the terminal device 120, and the network device 140 is a SN serving the terminal device 120.

As shown in FIG. 5, the terminal device 120 may receive 510, from the network device 110, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change. The conditional reconfiguration comprises a counter value (e.g., sk-counter) and a set of offset values for a candidate cell (e.g., each candidate cell) in the set of candidate cells.

In some embodiments, the counter value and the set of offset values may be configured per UE. In this case, the conditional reconfiguration may comprise one counter value and one set of offset values. The one counter value and the one set of offset values are associated with all candidate cells in the set of candidate cells.

In some embodiments, the counter value and the set of offset values may be configured per candidate cell. In this case, the conditional reconfiguration may comprise a set of entries and each entry in the set of entries is configured for a candidate cell in the set of candidate cells. Each entry comprises a counter value and a set of offset values configured for the corresponding candidate cell. In other words, the counter value and the set of offset values in an entry are associated with the corresponding one of the set of candidate cells.

Continue to refer to FIG. 5, the terminal device 120 may determine 520 that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed. That is, a subsequent CPA or CPC to a candidate cell may occur. For example, if execution condition of the subsequent conditional cell change is satisfied for the candidate cell, the subsequent CPA or CPC may occur.

The terminal device 120 may determine 530, from the set of offset values, an offset value (e.g., Offset) that has been unused. Based on the configured counter value and the determined offset value, the terminal device 120 may determine 540 a security key (e.g., K _SN) for communication with the network device of the target candidate cell. For example, the terminal device 120 may use (sk-counter + Offset) as an input parameter to update or derive K _SN.

In some embodiments where a set of offset values is associated with all the candidate cell in the set of candidate cells, if the set of offset values is unavailable, the terminal device 120 may discard the conditional reconfiguration. For example, if no more spare offset value to use, the terminal device 120 may discard the conditional reconfiguration entries and measurement configuration for all the candidate cells.

In some embodiments where a set of offset values is associated with one of the set of candidate cells, if the set of offset values is unavailable for the one of the set of candidate cells, the terminal device 120 may discard an entry in the conditional reconfiguration corresponding to the one of the set of candidate cells. For example, if no more spare offset value to use for the one candidate cell, the terminal device 120 may discard the corresponding entry of conditional reconfiguration and measurement configuration from an UE variable.

Continue to refer to FIG. 5, if the subsequent conditional cell change is performed, the terminal device 120 may transmit 550 the determined offset value to the network device 110. In some embodiments, after triggering of subsequent CPA/CPC, the terminal device 120 may send, to a MN (i.e., the network device 110) , an RRCReconfigurationComplete message which comprises an identity of the conditional reconfiguration (CondReconfigId) . In the RRCreconfigurationComplete message, the offset value used to derive K _SN may also be comprised.

The network device 110 may determine 560 the security key of SN based on the sk-counter and received offset value. The operations of the step 560 may be similar to that of the step 540 and thus are not repeated here for concise.

The network device 110 may transmit 570 the determined security key of SN to the network device 140 (i.e., SN) for communication with the terminal device 120. For example, the network device 110 may transmit an SN Reconfiguration Complete message including the security key of SN. In another example, the network device 110 may transmit an SN modification Confirm message including the security key of SN.

In this way, a security key of subsequent CPA/CPC may be derived based on an offset to a counter value.

FIG. 6 illustrates a schematic diagram illustrating another example process 600 of determining a security key for a subsequent conditional cell change according to embodiments of the present disclosure. For the purpose of discussion, the process 600 will be described with reference to FIG. 1. The process 600 may involve the terminal device 120 and the

network devices

As shown in FIG. 6, the terminal device 120 may receive 610, from the network device 110, a conditional reconfiguration for a set of candidate cells supporting subsequent CPA/CPC. The conditional reconfiguration comprises a counter value (e.g., sk-counter) for a candidate cell (e.g., each candidate cell) in the set of candidate cells.

In some embodiments, the counter value may be configured per UE. In this case, the conditional reconfiguration may comprise a single counter value. The single counter value may be associated with all the candidate cells in the set of candidate cells.

In some embodiments, the counter value may be configured per candidate cell. In this case, the conditional reconfiguration may comprise a set of counter values. Each counter value in the set of counter values may be associated with a corresponding one of the set of candidate cells.

In some embodiments, the terminal device 120 may determine 620 that the subsequent conditional cell change to a candidate cell in the set of candidate cells is to be performed after a cell change or addition is performed. That is, a subsequent CPA or CPC to a candidate cell may occur. For example, if execution condition of the subsequent conditional cell change is satisfied for the candidate cell (i.e., a target candidate cell) , the subsequent CPA or CPC may occur. Then the terminal device 120 may determine 630 a security key for communication with a network device of the target candidate cell.

With reference to FIG. 6, the terminal device 120 may determine 631 whether the counter value has been used for determination of a security key (for convenience, also referred to as a first security key herein) for the candidate cell.

In some embodiments, if the counter value has not been used, or if this is the first time UE connects to the target candidate cell or secondary node, the terminal device 120 may derive 632, based on the counter value, a security key (i.e., the first security key) for communication with the candidate cell. In some embodiments, the terminal device 120 may store 633 the first security key for the candidate cell. In some embodiments, the terminal device 120 may initialize 634 a counter (referred also as a second counter herein) for determination of another security key.

In some embodiments, if the counter value has been used, or if this is not the first time UE connects to the target candidate cell or secondary node, the terminal device 120 may determine 632’ another security key (for convenience, also referred to as a second security key herein) for communication with the network device of the candidate cell based on at least one of the following: the first security key; a physical cell identity (PCI) of the candidate cell; an absolute frequency of an SSB of the candidate cell (i.e., frequency absolute radio frequency channel number-downlink (ARFCN-DL) of the PCI) ; or the second counter.

In some embodiments, the terminal device 110 may replace 633’ the first security key with the second security key for storage. In other words, the terminal device 110 may replace the stored K _SN for the corresponding PSCell or target SN with the new derived K _SN. In some embodiments, the terminal device 110 may increase 634’ the second counter by a predetermined number (e.g., 1 or any other integer values) . This will facilitate a determination of a further security key for subsequent CPA/CPC.

Continue to refer to FIG. 6, the network device 110 may determine 640 a security key of SN by similar operations in the step 630. The network device 110 may transmit 650 the determined security key of SN to the network device 140 (i.e., SN) for communication with the terminal device 120.

In this way, a security key of subsequent CPA/CPC may be derived based on a previous security key.

It is to be understood that the steps and the order of the steps in FIGs. 2 to 6 are merely for illustration, and not for limitation.

EXAMPLE IMPLEMENTATION OF METHODS

Accordingly, embodiments of the present disclosure provide methods of communication implemented at a terminal device and a network device. These methods will be described below with reference to FIGs. 7 to 11.

FIG. 7 illustrates an example method 700 of communication implemented at a MN in accordance with some embodiments of the present disclosure. For example, the method 700 may be performed at the network device 110 as shown in FIG. 1. It is to be understood that the method 700 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At block 710, a MN (e.g., the network device 110) determines that a SN (e.g., the network device 140) is to be released while a set of candidate cells associated with the SN is maintained.

In some embodiments, the MN may transmit, to the SN, a second indication for releasing the SN while maintaining the set of candidate cells, and receive, from the SN, an acknowledgement for the second indication. In some embodiments, the MN may receive, from the SN, a third indication for releasing the SN while maintaining the set of candidate cells, and transmit, to the SN, an acknowledgement for the third indication.

At block 720, the MN transmits, to the SN, a first indication for releasing a radio resource of a terminal device (e.g., the terminal device 120) and maintaining the set of candidate cells.

In some embodiments where the terminal device is to be switched from the SN to a further SN, the MN may transmit, to the further SN, information of a set of forwarding addresses for a set of SNs other than the further SN.

In this way, a procedure of SN release may be enhanced for subsequent CPA/CPC.

FIG. 8 illustrates an example method 800 of communication implemented at a SN in accordance with some embodiments of the present disclosure. For example, the method 800 may be performed at the

network device

130, 140 or 150 as shown in FIG. 1. It is to be understood that the method 800 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

As shown in FIG. 8, at block 810, a SN (e.g., the

network device

130, 140 or 150) determines that the SN is to be released while a set of candidate cells associated with the SN is maintained.

In some embodiments, the SN may receive, from a MN (e.g., the network device 110) , a second indication for releasing the SN while maintaining the set of candidate cells, and transmit, to the MN, an acknowledgement for the second indication.

In some embodiments, the SN may transmit, to the MN, a third indication for releasing the SN while maintaining the set of candidate cells, and receive, from the MN, an acknowledgement for the third indication.

At block 820, the SN receives, from the MN, a first indication for releasing a radio resource of a terminal device (e.g., the terminal device 120) and maintaining the set of candidate cells.

In this way, a procedure of SN release may also be enhanced for subsequent CPA/CPC.

FIG. 9 illustrates an example method 900 of communication implemented at a terminal device in accordance with some embodiments of the present disclosure. For example, the method 900 may be performed at the terminal device 120 as shown in FIG. 1. It is to be understood that the method 900 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

As shown in FIG. 9, at block 910, the terminal device 120 may receive a conditional reconfiguration associated with a SCG supporting subsequent conditional cell change. In some embodiments, the terminal device 120 may receive the conditional reconfiguration from a MN. In some embodiments, the terminal device 120 may receive the conditional reconfiguration from a source SN.

At block 920, the terminal device may determine that a PSCell is changed from a first SN to a second SN.

At block 930, the terminal device 120 may perform a first operation comprising at least one of the following: removing the conditional reconfiguration; deactivating the conditional reconfiguration; or deactivating a conditional reconfiguration evaluation for the conditional reconfiguration.

In some embodiments, the terminal device 120 may receive an indication of the first operation, and perform the first operation based on reception of the indication. In some embodiments, the terminal device 120 may receive, from the MN, the indication of the first operation. In some embodiments, the terminal device 120 may receive, from the source SN, the indication of the first operation.

In some embodiments, if the PSCell is changed back to the first SN, the terminal device 120 may perform a second operation comprising at least one of the following: activating the conditional reconfiguration; or activating a conditional reconfiguration evaluation for the conditional reconfiguration.

In some embodiments, the terminal device 120 may receive an indication of the second operation, and perform the second operation based on reception of the indication. In some embodiments, the terminal device 120 may receive, from the MN, the indication of the second operation. In some embodiments, the terminal device 120 may receive, from the source SN, the indication of the second operation.

In this way, intra-SN subsequent CPC handling may be achieved after inter-SN change.

FIG. 10 illustrates another example method 1000 of communication implemented at a terminal device in accordance with some embodiments of the present disclosure. For example, the method 1000 may be performed at the terminal device 120 as shown in FIG. 1. It is to be understood that the method 1000 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

As shown in FIG. 10, at block 1010, the terminal device 120 may receive, from a MN (e.g., the network device 110) , a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value and a set of offset values for a candidate cell in the set of candidate cells.

At block 1020, the terminal device 120 may determine that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed.

At block 1030, the terminal device 120 may determine, from the set of offset values, an offset value that has been unused.

At block 1040, the terminal device 120 may determine, based on the counter value and the offset value, a security key for communication with the candidate cell. In some embodiments, the terminal device 120 may use a sum of the counter value and the offset value as an input parameter to derive the security key. The deriving may be carried out in any suitable ways existing or to be developed in future.

In some embodiments, the set of offset values may be associated with each of the set of candidate cells. In these embodiments, if the set of offset values is unavailable, the terminal device 120 may discard the conditional reconfiguration.

In some embodiments, the set of offset values may be associated with one (i.e., the candidate cell) of the set of candidate cells. In these embodiments, if the set of offset values is unavailable for the one of the set of candidate cells, the terminal device 120 may discard an entry in the conditional reconfiguration corresponding to the one of the set of candidate cells.

In some embodiments, if the subsequent conditional cell change is performed, the terminal device 120 may transmit the offset value to the MN.

In this way, a security key for SN may be determined based on an offset to a SN counter.

FIG. 11 illustrates still another example method 1100 of communication implemented at a terminal device in accordance with some embodiments of the present disclosure. For example, the method 1100 may be performed at the terminal device 120 as shown in FIG. 1. It is to be understood that the method 1100 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

As shown in FIG. 11, at block 1110, the terminal device 120 receives, from a MN (e.g., the network device 110) , a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value for a candidate cell in the set of candidate cells.

At block 1120, the terminal device 120 determines that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed.

At block 1130, the terminal device 120 determines whether the counter value has been used for determination of a first security key for the candidate cell. If the counter value has been used, the method 1100 may proceed to block 1140.

At block 1140, the terminal device 120 determines a second security key for communication with the candidate cell based on at least one of the following: the first security key; a physical cell identity of the candidate cell; an absolute frequency of a synchronization signal block of the candidate cell; or a counter for the second security key.

In some embodiments, if the counter value has been not used for determination of the first security key for the candidate cell, the terminal device 120 may perform at least one of the following: determining, based on the counter value, the first security key for communication with the candidate cell; storing the first security key for the candidate cell; or initializing the counter.

In some embodiments, the terminal device 120 may replace the first security key with the second security key for storage. In some embodiments, the terminal device 120 may increase the counter by a predetermined number.

In this way, a security key for SN may be determined based on a previous security key.

EXAMPLE IMPLEMENTATION OF DEVICE

FIG. 12 is a simplified block diagram of a device 1200 that is suitable for implementing embodiments of the present disclosure. The device 1200 can be considered as a further example implementation of the terminal device 120 or the

network device

110, 130, 140 or 150 as shown in FIG. 1. Accordingly, the device 1200 can be implemented at or as at least a part of the terminal device 120 or the

network device

110, 130, 140 or 150.

As shown, the device 1200 includes a processor 1210, a memory 1220 coupled to the processor 1210, a suitable transmitter (TX) and receiver (RX) 1240 coupled to the processor 1210, and a communication interface coupled to the TX/RX 1240. The memory 1210 stores at least a part of a program 1230. The TX/RX 1240 is for bidirectional communications. The TX/RX 1240 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2/Xn interface for bidirectional communications between eNBs/gNBs, S1/NG interface for communication between a Mobility Management Entity (MME) /Access and Mobility Management Function (AMF) /SGW/UPF and the eNB/gNB, Un interface for communication between the eNB/gNB and a relay node (RN) , or Uu interface for communication between the eNB/gNB and a terminal device.

The program 1230 is assumed to include program instructions that, when executed by the associated processor 1210, enable the device 1200 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to FIGs. 1 to 11. The embodiments herein may be implemented by computer software executable by the processor 1210 of the device 1200, or by hardware, or by a combination of software and hardware. The processor 1210 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 1210 and memory 1220 may form processing means 1250 adapted to implement various embodiments of the present disclosure.

The memory 1220 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 1220 is shown in the device 1200, there may be several physically distinct memory modules in the device 1200. The processor 1210 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1200 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

In some embodiments, a master node comprises circuitry configured to: determine that a secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and transmit, to the secondary node, a first indication for releasing a radio resource of a terminal device and maintaining the set of candidate cells.

In some embodiments, a secondary node comprises circuitry configured to: determine that the secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and receive, from a master node, a first indication for releasing a radio resource of a terminal device and maintaining the set of candidate cells.

In some embodiments, a terminal device comprises a circuitry configured to: receive a conditional reconfiguration associated with a secondary cell group supporting subsequent conditional cell change; and in accordance with a determination that a primary cell of the secondary cell group is changed from a first secondary node to a second secondary node, perform a first operation comprising at least one of the following: removing the conditional reconfiguration; deactivating the conditional reconfiguration; or deactivating a conditional reconfiguration evaluation for the conditional reconfiguration.

In some embodiments, a terminal device comprises a circuitry configured to: receive, from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value and a set of offset values for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determine, from the set of offset values, an offset value that has been unused; and determine, based on the counter value and the offset value, a security key for communication with the candidate cell.

In some embodiments, a terminal device comprises a circuitry configured to: receive, from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determine that the counter value has been used for determination of a first security key for the candidate cell; and determine a second security key for communication with the candidate cell based on at least one of the following: the first security key; a physical cell identity of the candidate cell; an absolute frequency of a synchronization signal block of the candidate cell; or a counter for the second security key.

The term “circuitry” used herein may refer to hardware circuits and/or combinations of hardware circuits and software. For example, the circuitry may be a combination of analog and/or digital hardware circuits with software/firmware. As a further example, the circuitry may be any portions of hardware processors with software including digital signal processor (s) , software, and memory (ies) that work together to cause an apparatus, such as a terminal device or a network device, to perform various functions. In a still further example, the circuitry may be hardware circuits and or processors, such as a microprocessor or a portion of a microprocessor, that requires software/firmware for operation, but the software may not be present when it is not needed for operation. As used herein, the term circuitry also covers an implementation of merely a hardware circuit or processor (s) or a portion of a hardware circuit or processor (s) and its (or their) accompanying software and/or firmware.

In summary, embodiments of the present disclosure may provide the following solutions.

In one solution, a master node comprises a processor configured to cause the master node to: determine that a secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and transmit, to the secondary node, a first indication for releasing a radio resource of a terminal device and maintaining the set of candidate cells.

In some embodiments, the master node is further caused to: transmit, to the secondary node, a second indication for releasing the secondary node while maintaining the set of candidate cells; and receive, from the secondary node, an acknowledgement for the second indication.

In some embodiments, the terminal device is to be switched from the secondary node to a further secondary node, and the master node is further caused to: transmitting, to the further secondary node, information of a set of forwarding addresses for a set of secondary nodes other than the further secondary node.

In some embodiments, the master node is caused to determine that the secondary node is to be released while the set of candidate cells is maintained by: receiving, from the secondary node, a third indication for releasing the secondary node while maintaining the set of candidate cells; and transmitting, to the secondary node, an acknowledgement for the third indication.

In another solution, a secondary node comprises a processor configured to cause the secondary node to: determine that the secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and receive, from a master node, a first indication for releasing a radio resource of a terminal device and maintaining the set of candidate cells.

In some embodiments, the secondary node is caused to determine that the secondary node is to be released while the set of candidate cells is maintained by: receiving, from the master node, a second indication for releasing the secondary node while maintaining the set of candidate cells; and transmitting, to the master node, an acknowledgement for the second indication.

In some embodiments, the secondary node is caused to determine that the secondary node is to be released while the set of candidate cells is maintained by: transmitting, to the master node, a third indication for releasing the secondary node while maintaining the set of candidate cells; and receiving, from the master node, an acknowledgement for the third indication.

In another solution, a terminal device comprises a processor configured to cause the terminal device to: receive a conditional reconfiguration associated with a secondary cell group supporting subsequent conditional cell change; and in accordance with a determination that a primary cell of the secondary cell group is changed from a first secondary node to a second secondary node, perform a first operation comprising at least one of the following: removing the conditional reconfiguration; deactivating the conditional reconfiguration; or deactivating a conditional reconfiguration evaluation for the conditional reconfiguration.

In some embodiments, the terminal device is caused to perform the first operation by:receiving an indication of the first operation; and performing the first operation based on reception of the indication.

In some embodiments, the terminal device is further caused to: in accordance with a determination that the primary cell of the secondary cell group is changed back to the first secondary node, perform at least one of the following: activating the conditional reconfiguration; or activating a conditional reconfiguration evaluation for the conditional reconfiguration.

In some embodiments, the terminal device is caused to perform the second operation by: receiving an indication of the second operation; and performing the second operation based on reception of the indication.

In another solution, a terminal device comprises a processor configured to cause the terminal device to: receive, from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value and a set of offset values for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determine, from the set of offset values, an offset value that has been unused; and determine, based on the counter value and the offset value, a security key for communication with the candidate cell.

In some embodiments, the set of offset values is associated with each of the set of candidate cells, and wherein the terminal device is further caused to: in accordance with a determination that the set of offset values is unavailable, discard the conditional reconfiguration.

In some embodiments, the set of offset values is associated with the candidate cell, and wherein the terminal device is further caused to: in accordance with a determination that the set of offset values is unavailable for the candidate cell, discard an entry in the conditional reconfiguration corresponding to the candidate cell.

In some embodiments, the terminal device is further caused to: in accordance with a determination that the subsequent conditional cell change is performed, transmit the offset value to the master node.

In another solution, a terminal device comprises a processor configured to cause the terminal device to: receive, from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determine that the counter value has been used for determination of a first security key for the candidate cell; and determine a second security key for communication with the candidate cell based on at least one of the following: the first security key; a physical cell identity of the candidate cell; an absolute frequency of a synchronization signal block of the candidate cell; or a counter for the second security key.

In some embodiments, the terminal device is further caused to: in accordance with a determination that the counter value has been not used for determination of the first security key for the candidate cell, perform at least one of the following: determining, based on the counter value, the first security key for communication with the candidate cell; storing the first security key for the candidate cell; or initializing the counter.

In some embodiments, the terminal device is further caused to perform at least one of the following: replacing the first security key with the second security key for storage; or increasing the counter by a predetermined number.

In another solution, a method of communication comprises: determining, at a master node, that a secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and transmitting, to the secondary node, a first indication for releasing a radio resource of a terminal device and maintaining the set of candidate cells.

In another solution, a method of communication comprises: determining, at a secondary node, that the secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and receive, from a master node, a first indication for releasing a radio resource of a terminal device and maintaining the set of candidate cells.

In another solution, a method of communication comprises: receiving, at a terminal device, a conditional reconfiguration associated with a secondary cell group supporting subsequent conditional cell change; and in accordance with a determination that a primary cell of the secondary cell group is changed from a first secondary node to a second secondary node, performing a first operation comprising at least one of the following: removing the conditional reconfiguration; deactivating the conditional reconfiguration; or deactivating a conditional reconfiguration evaluation for the conditional reconfiguration.

In another solution, a method of communication comprises: receiving, at a terminal device and from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value and a set of offset values for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determining, from the set of offset values, an offset value that has been unused; and determining, based on the counter value and the offset value, a security key for communication with the candidate cell.

In another solution, a method of communication comprises: receiving, at a terminal device and from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value for a candidate cell in the set of candidate cells; in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determining that the counter value has been used for determination of a first security key for the candidate cell; and determining a second security key for communication with the candidate cell based on at least one of the following: the first security key; a physical cell identity of the candidate cell; an absolute frequency of a synchronization signal block of the candidate cell; or a counter for the second security key.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it will be appreciated that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the process or method as described above with reference to FIGs. 1 to 11. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium, which may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A master node comprising:

a processor configured to cause the master node to:

determine that a secondary node is to be released while a set of candidate cells associated with the secondary node is maintained; and

transmit, to the secondary node, a first indication for releasing a radio resource of a terminal device and maintaining the set of candidate cells.
The master node of claim 1, wherein the master node is further caused to:

transmit, to the secondary node, a second indication for releasing the secondary node while maintaining the set of candidate cells; and

receive, from the secondary node, an acknowledgement for the second indication.
The master node of claim 2, wherein the terminal device is to be switched from the secondary node to a further secondary node, and the master node is further caused to:

transmitting, to the further secondary node, information of a set of forwarding addresses for a set of secondary nodes other than the further secondary node.
The master node of claim 1, wherein the master node is caused to determine that the secondary node is to be released while the set of candidate cells is maintained by:

receiving, from the secondary node, a third indication for releasing the secondary node while maintaining the set of candidate cells; and

transmitting, to the secondary node, an acknowledgement for the third indication.
A terminal device comprising:

a processor configured to cause the terminal device to:

receive, from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value and a set of offset values for a candidate cell in the set of candidate cells;

in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determine, from the set of offset values, an offset value that has been unused; and

determine, based on the counter value and the offset value, a security key for communication with the candidate cell.
The terminal device of claim 5, wherein the set of offset values is associated with each of the set of candidate cells, and wherein the terminal device is further caused to:

in accordance with a determination that the set of offset values is unavailable, discard the conditional reconfiguration.
The terminal device of claim 5, wherein the set of offset values is associated with the candidate cell, and wherein the terminal device is further caused to:

in accordance with a determination that the set of offset values is unavailable for the candidate cell, discard an entry in the conditional reconfiguration corresponding to the candidate cell.
The terminal device of claim 5, wherein the terminal device is further caused to:

in accordance with a determination that the subsequent conditional cell change is performed, transmit the offset value to the master node.
A terminal device comprising:

a processor configured to cause the terminal device to:

receive, from a master node, a conditional reconfiguration for a set of candidate cells supporting subsequent conditional cell change, the conditional reconfiguration comprising a counter value for a candidate cell in the set of candidate cells;

in accordance with a determination that the subsequent conditional cell change to the candidate cell is to be performed after a cell change or addition is performed, determine that the counter value has been used for determination of a first security key for the candidate cell; and

determine a second security key for communication with the candidate cell based on at least one of the following:

the first security key;

a physical cell identity of the candidate cell;

an absolute frequency of a synchronization signal block of the candidate cell; or

a counter for the second security key.
The terminal device of claim 9, wherein the terminal device is further caused to:

in accordance with a determination that the counter value has been not used for determination of the first security key for the candidate cell, perform at least one of the following:

determining, based on the counter value, the first security key for communication with the candidate cell;

storing the first security key for the candidate cell; or

initializing the counter.
The terminal device of claim 9, wherein the terminal device is further caused to perform at least one of the following:

replacing the first security key with the second security key for storage; or

increasing the counter by a predetermined number.