Method performed by User Equipment

Abstract

A piece of user equipment UE (3) executes a first conditional mobility, if an execution condition for one candidate target cell among a plurality of candidate target cells for the first conditional mobility is satisfied, by applying a setting corresponding to said one candidate target cell. The UE (3) reuses, for a subsequent second conditional mobility, one or more execution conditions related to one or more candidate target cells other than said one candidate target cell, and switches a reference cell for each execution condition from a source cell of the first conditional mobility to the one candidate target cell. The foregoing contributes to, for example, the realization of a function or an operation mode which enables a subsequent second conditional mobility, after a first conditional mobility, without reconfiguration or re-initialization from a network.

Description

[Technical Field]

[0001] TECHNICAL FIELD The present disclosure relates to wireless communication systems, and more particularly to conditional mobility for wireless terminals. [Background technology]

[0002] The 3rd Generation Partnership Project (3GPP (registered trademark)) Release 16 supports conditional handover (CHO) and conditional primary secondary cell group (SCG) cell (PSCell) change (CPC) (see, for example, Non-Patent Documents 1 and 2). Note that CPC in 3GPP Release 16 is an inter-Secondary Node (SN) CPC without Master Node (MN) involvement, and supports conditional PSCell change from a source PSCell to one of one or more candidate cells (i.e., candidate PSCells) within a single SN. This CPC is also called SN-initiated Conditional SN Modification without MN involvement.

[0003] The 3GPP Radio Access Network (RAN) Working Group is currently considering enhancements to conditional mobility, which will be introduced in 3GPP Release 17 (see, for example, Non-Patent Document 3). The new conditional mobility features to be introduced in 3GPP Release 17 include Conditional PSCell Addition (CPA) and inter-SN (inter-SN) CPC. CPA is also called conditional SN addition, and inter-SN CPC is also called conditional SN change. Inter-SN CPC or conditional SN change can be initiated by the MN or the source SN.

[0004] Furthermore, for 3GPP Release 18, discussions have begun on further mobility enhancements, including "Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups" (see, for example, Non-Patent Documents 4 and 5). In Release 17 CPA and CPC, a UE must select one of the candidate target PSCells and perform random access to the selected target PSCell, thereby releasing unused (unselected) CPC / CPA configurations. Therefore, the UE has no opportunity to perform subsequent CPC without CPC reconfiguration and reinitialization from the network. "Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups" aims to address this issue. Specifically, according to Non-Patent Document 5, MR-DC with selective activation of cell groups aims to enable subsequent CPC / CPA after changing the SCG without reconfiguration and reinitialization of CPC / CPA preparation from the network, thereby reducing CPC / CPA signaling overhead and interruption time. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] 3GPP TS 38.300 V16.7.0 (2021-09), "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; NR and NG-RAN Overall Description; Stage 2, (Release 16)", September 2021 [Non-patent document 2] 3GPP TS 37.340 V16.7.0 (2021-09), "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-connectivity; Stage 2 (Release 16)", September 2021 [Non-patent document 3] CATT, "Introduction of CPA and inter-SN CPC", R2-2111640, 3GPP TSG-RAN WG2 Meeting #116-e, November 1-12, 2021 [Non-patent document 4] MediaTek, "Moderator's summary of discussion for [94e-14-R18-MobEnh]", RP-213541, 3GPP TSG RAN Meeting #94e, December 6-17, 2021 [Non-patent document 5] MediaTek, "New WID on Further NR mobility enhancements", RP-213565, 3GPP TSG RAN Meeting #94e, December 6-17, 2021 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors have studied mechanisms and procedures for realizing a function or operation mode called "Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups" and have found various problems.

[0007] One of these issues relates to the reuse of the CPC execution condition in subsequent CPCs. According to the current discussions on 3GPP Release 17 (see, for example, Non-Patent Document 3), in SN-initiated inter-SN CPC initiated by the source SN, the source SN generates the CPC execution condition. Therefore, this CPC execution condition is set based on the source SN or the source SCG (e.g., the source PSCell). Specifically, the CPC execution condition may be composed of one or more trigger conditions. The condition or criterion for triggering a CPC event may be similar to that for a measurement report event, and may be, for example, CondEvent A3 or CondEvent A5. CondEvent A3 is "Conditional reconfiguration candidate becomes amount of offset better than PCell / PSCell." CondEvent A5 is "PCell / PSCell becomes worse than absolute threshold1 AND Conditional reconfiguration candidate becomes better than another absolute threshold2." In this condition, "PCell / PSCell" is the PSCell in the case of SN-initiated inter-SN CPC, i.e., the source PSCell provided by the source SN or the current serving PSCell. Therefore, if the serving PSCell of the UE changes due to the execution of CPC, the CPC execution condition cannot be reused as it is for the subsequent CPC.

[0008] Another of these challenges relates to using a source PSCell (i.e., a previous serving PSCell) before intra-SN or inter-SN CPC execution as one of the candidate PSCells for a subsequent CPC. According to the current specifications of 3GPP Release 16 and the current discussions on Release 17, the UE releases the configuration of the source PSCell (or the previous serving PSCell) in response to CPC execution on the selected PSCell. Therefore, in order to use the source PSCell as one of the candidate PSCells for a subsequent CPC, reconfiguration or reinitialization of the CPC is required.

[0009] Yet another of these challenges relates to the use of delta configuration. The configuration of a candidate PSCell for a conditional CPC may be a delta configuration based on the configuration of the source PSCell. However, the configuration of a candidate PSCell for which the delta configuration is used cannot be easily reused in a subsequent CPC because the delta configuration is based on the configuration of the source PSCell before the first CPC is executed, and is not based on the configuration of the new source PSCell after the first CPC is executed. Therefore, the target SN after the subsequent CPC is executed (i.e., the new source SN after the subsequent CPC is executed) needs to perform RRC reconfiguration before resuming data communication.

[0010] In addition to these, another issue concerns how to deal with the case where there is an SN that does not support "Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups." This function or operation mode may not work properly if at least some of multiple candidate SNs support CPC but do not support the function or operation mode.

[0011] Yet another issue concerns realizing a function or operation mode in CHO similar to "Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups." For example, after a UE performs a first CHO from a source cell to one of the candidate target cells, enabling the UE to perform a subsequent second CHO without reconfiguration or reinitialization of CHO preparation from the network may contribute to mobility enhancement. However, at present, the mechanism and procedure for realizing this function or operation mode for CHO is unclear.

[0012] One of the objectives to be achieved by the embodiments disclosed in this specification is to provide an apparatus, a method, and a program that contribute to solving at least one of multiple problems, including the above-mentioned problem, related to realizing a function or an operation mode that enables a subsequent second conditional mobility after a first conditional mobility without resetting or reinitialization from the network. It should be noted that this objective is only one of multiple objectives to be achieved by the multiple embodiments disclosed in this specification. Other objectives or objectives and novel features will become apparent from the description of this specification or the accompanying drawings. [Means for solving the problem]

[0013] A first aspect is directed to a UE. The UE includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to evaluate a plurality of execution conditions for a plurality of candidate target cells for a first conditional mobility. The at least one processor is configured to execute the first conditional mobility by applying a configuration corresponding to the one candidate target cell if an execution condition for one of the plurality of candidate target cells is satisfied. Additionally, the at least one processor is configured to reuse one or more execution conditions for one or more candidate target cells other than the one candidate target cell for a subsequent second conditional mobility, and to switch a reference cell for the one or more execution conditions from a source cell of the first conditional mobility to the one candidate target cell.

[0014] A second aspect is directed to a method performed by a UE, the method including the steps of: (a) evaluating a plurality of execution conditions for a plurality of candidate target cells for a first conditional mobility; (b) if an execution condition for one of the plurality of candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; and (c) Reusing one or more execution conditions relating to one or more candidate target cells other than the one candidate target cell for a subsequent second conditional mobility, and switching the reference cell in the one or more execution conditions from the source cell of the first conditional mobility to the one candidate target cell.

[0015] A third aspect is directed to a UE. The UE includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to evaluate a plurality of execution conditions for a plurality of candidate target cells for a first conditional mobility. The at least one processor is configured to execute the first conditional mobility by applying a configuration corresponding to the one candidate target cell if an execution condition for one of the plurality of candidate target cells is satisfied. The at least one processor is configured to reuse one or more configurations of one or more candidate target cells other than the one candidate target cell for a subsequent second conditional mobility. Furthermore, the at least one processor is configured to receive updated one or more execution conditions for the subsequent second conditional mobility for the one or more candidate target cells from a radio access network (RAN) node of the one candidate target cell.

[0016] A fourth aspect is directed to a method performed by a UE, the method including the steps of: (a) evaluating a plurality of execution conditions for a plurality of candidate target cells for a first conditional mobility; (b) if an execution condition for one of the plurality of candidate target cells is satisfied, executing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; (c) reusing one or more configurations of one or more candidate target cells other than the one candidate target cell for a subsequent second conditional mobility; and (d) receiving, from a radio access network (RAN) node of the one candidate target cell, one or more updated execution conditions for the subsequent second conditional mobility for the one or more candidate target cells;

[0017] A fifth aspect is directed to a Radio Access Network (RAN) node, the RAN node including at least one memory and at least one processor coupled to the at least one memory, configured to provide to the UE a plurality of configurations for a plurality of candidate target cells for a first conditional mobility of the UE, and further configured to, once one of the plurality of candidate target cells is selected by the UE, provide to the UE one or more updated execution conditions for the one or more candidate target cells to enable a subsequent second conditional mobility in which one or more configurations of one or more candidate target cells other than the selected candidate target cell are reused by the UE.

[0018] A sixth aspect is directed to a method performed by a RAN node, the method comprising the steps of: (a) providing a plurality of configurations for a plurality of candidate target cells for a first conditional mobility of the UE; and (b) if one of the plurality of candidate target cells is selected by the UE, providing the UE with updated one or more execution conditions for the one or more candidate target cells to enable a subsequent second conditional mobility in which one or more settings of one or more candidate target cells other than the selected candidate target cell are reused by the UE.

[0019] A seventh aspect is directed to a UE. The UE includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to evaluate a plurality of execution conditions for one or more candidate target cells for a first conditional mobility from a source cell. The at least one processor is configured to perform the first conditional mobility by applying a configuration corresponding to the one candidate target cell if an execution condition for one of the one or more candidate target cells is satisfied. Further, the at least one processor is configured to maintain the source cell configuration after the first conditional mobility for reuse in a subsequent second conditional mobility in which the source cell is a new candidate target cell.

[0020] An eighth aspect is directed to a method performed by a UE, the method including the steps of: (a) evaluating a plurality of execution conditions for one or more candidate target cells for a first conditional mobility from a source cell; (b) if an execution condition for one of the one or more candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; and (c) after the first conditional mobility, maintaining the configuration of the source cell for reuse in a subsequent second conditional mobility in which the source cell is a new candidate target cell;

[0021] A ninth aspect is directed to a RAN node, the RAN node including at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a control message from a source node or a Master Node (MN) requesting preparation of a candidate target cell for a first conditional mobility of a UE. Additionally, the at least one processor is configured to apply a full configuration to the configuration of the candidate target cell without applying a delta configuration based on a configuration of a current source cell to the configuration of the candidate target cell if a configuration of the candidate target cell provided to the UE for the first conditional mobility needs to be reused by the UE for a subsequent second conditional mobility after the first conditional mobility.

[0022] A tenth aspect is directed to a method performed by a RAN node, the method comprising the steps of: (a) receiving a control message from a source node or an MN requesting preparation of a candidate target cell for a first conditional mobility of the UE; and (b) if the configuration of the candidate target cell provided to the UE for the first conditional mobility needs to be reused by the UE for a subsequent second conditional mobility after the first conditional mobility, applying a full configuration to the configuration of the candidate target cell without applying a delta configuration based on the configuration of the current source cell to the configuration of the candidate target cell.

[0023] An eleventh aspect is directed to a RAN node, the RAN node including at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a control message from a source node or an MN requesting preparation of a candidate target cell for a first conditional mobility of a UE. The control message indicates a recommended operation mode in which the candidate target cell configuration provided to the UE for the first conditional mobility is reused by the UE for a subsequent second conditional mobility after the first conditional mobility. The at least one processor is configured to send a second control message to the source node or the MN indicating rejection of the preparation of the candidate target cell if the RAN node does not support the operation mode.

[0024] A twelfth aspect is directed to a method performed by a RAN node, the method comprising the steps of: (a) receiving a control message from a source node or an MN requesting preparation of a candidate target cell for a first conditional mobility of a UE, wherein the control message indicates a recommended operation mode in which the candidate target cell configuration provided to the UE for the first conditional mobility is reused by the UE for a subsequent second conditional mobility after the first conditional mobility; and (b) if the RAN node does not support the operation mode, sending a second control message to the source node or the MN indicating a rejection of the preparation of the candidate target cell.

[0025] A thirteenth aspect is directed to a RAN node, the RAN node including at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a control message from a source node or an MN requesting preparation of a candidate target cell for a first conditional mobility of a UE. The control message indicates a recommended operation mode in which the candidate target cell configuration provided to the UE for the first conditional mobility is reused by the UE for a subsequent second conditional mobility after the first conditional mobility. If the RAN node does not support the operation mode but can prepare the candidate target cell for the first conditional mobility, the at least one processor is configured to send a second control message to the source node or the MN indicating acceptance of the candidate target cell configuration.

[0026] A fourteenth aspect is directed to a method performed by a RAN node, the method including the steps of: (a) receiving a control message from a source node or an MN requesting preparation of a candidate target cell for a first conditional mobility of a UE, wherein the control message indicates a recommended operation mode in which the candidate target cell configuration provided to the UE for the first conditional mobility is reused by the UE for a subsequent second conditional mobility after the first conditional mobility; and (b) if the RAN node does not support the operation mode but can prepare the candidate target cell for the first conditional mobility, sending a second control message to the source node or the MN indicating acceptance of the configuration of the candidate target cell.

[0027] A fifteenth aspect is directed to a program, the program including a set of instructions (software code) that, when loaded into a computer, causes the computer to perform the method according to any of the above aspects. [Effects of the Invention]

[0028] According to the above-described aspects, an apparatus, a method, and a program can be provided that contribute to solving at least one of several problems related to realizing a function or operating mode that enables a subsequent second conditional mobility after a first conditional mobility without reconfiguration or reinitialization from the network. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a diagram illustrating an example of the configuration of a wireless communication system according to an embodiment. [Figure 2] 1 is a diagram illustrating an example of the configuration of a wireless communication system according to an embodiment. [Figure 3] 1 is a diagram illustrating an example of the configuration of a wireless communication system according to an embodiment. [Figure 4] FIG. 1 is a diagram illustrating a configuration example of a RAN node according to an embodiment. [Figure 5] 10 is a flowchart illustrating an example of an operation of a UE according to the embodiment. [Figure 6] FIG. 10 is a conceptual diagram for explaining switching of a reference cell for a conditional mobility execution condition. [Figure 7] 10 is a flowchart illustrating an example of an operation of a UE according to the embodiment. [Figure 8] FIG. 10 is a sequence diagram showing an example of signaling related to Inter-SN CPC (or conditional SN change) according to an embodiment. [Figure 9] 10 is a flowchart illustrating an example of an operation of a UE according to the embodiment. [Figure 10] FIG. 10 is a sequence diagram showing an example of signaling related to Inter-SN CPC (or conditional SN change) according to an embodiment. [Figure 11] FIG. 10 is a sequence diagram showing an example of signaling related to Inter-SN CPC (or conditional SN change) according to an embodiment. [Figure 12] FIG. 10 is a diagram for explaining the operation of a UE according to the embodiment. [Figure 13] 10 is a flowchart illustrating an example of an operation of a RAN node according to an embodiment. [Figure 14] 10 is a flowchart illustrating an example of an operation of a RAN node according to an embodiment. [Figure 15] 10 is a flowchart illustrating an example of an operation of a RAN node according to an embodiment. [Figure 16] FIG. 2 is a block diagram illustrating a configuration example of a RAN node according to the embodiment. [Figure 17] FIG. 2 is a block diagram illustrating an example of the configuration of a UE according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary.

[0031] The multiple embodiments described below can be implemented independently or in appropriate combination. These multiple embodiments have different novel features. Therefore, these multiple embodiments contribute to solving different purposes or problems and to achieving different effects.

[0032] The following embodiments will be described primarily with respect to the 3GPP Long Term Evolution (LTE) system and the fifth generation mobile communication system (5G system). However, these embodiments may be applied to other wireless communication systems that support technologies similar to 3GPP multi-connectivity (e.g., dual connectivity). The term LTE used in this specification includes improvements and developments of LTE and LTE-Advanced that enable interworking with the 5G system, unless otherwise specified.

[0033] As used herein, depending on the context, "if" may be construed to mean "when," "at or around the time," "after," "upon," "in response to determining," "in accordance with a determination," or "in response to detecting." These expressions may be construed to have the same meaning, depending on the context.

[0034] First, the configurations and operations of multiple network elements common to multiple embodiments will be described. Figure 1 illustrates an example configuration of a wireless communication system according to multiple embodiments. In the example of Figure 1, the wireless communication system includes RAN node 1, RAN node 2, RAN node 4, and UE 3. Each element (network function) illustrated in Figure 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an application platform.

[0035] RAN node 1 may be a Central Unit (e.g., eNB-CU or gNB-CU) in a cloud RAN (C-RAN) deployment, or may be a combination of a CU and one or more Distributed Units (e.g., eNB-DUs or gNB-DUs). C-RAN is also referred to as a CU / DU split. Furthermore, a CU may include a Control Plane (CP) Unit (e.g., gNB-CU-CP) and one or more User Plane (UP) Units (e.g., gNB-CU-UP). Thus, RAN node 1 may be a CU-CP or a combination of a CU-CP and a CU-UP. Similarly, each of RAN nodes 2 and 4 may be a CU or a combination of a CU and one or more DUs. Each of RAN nodes 2 and 4 may be a CU-CP or a combination of a CU-CP and a CU-UP.

[0036] Each of RAN nodes 1, 2, and 4 may be an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (EUTRAN) node or a Next Generation Radio Access Network (NG-RAN) node. The EUTRAN node may be an eNB or an en-gNB. The NG-RAN node may be a gNB or an ng-eNB. The en-gNB provides NR user plane and control plane protocol terminations to the UE and operates as a secondary node (SN) for E-UTRA-NR Dual Connectivity (EN-DC). The ng-eNB provides E-UTRA user plane and control plane protocol terminations to the UE and is connected to the 5GC via the NG interface. The Radio Access Technology (RAT) of RAN node 1 may be different from that of RAN nodes 2 and 4.

[0037] RAN node 1 and RAN node 2 communicate with each other via a node-to-node interface (i.e., X2 interface or Xn interface) 103. RAN node 1 and RAN node 2 act as a master node (MN) and a secondary node (SN) of dual connectivity, respectively. Furthermore, RAN node 1 and RAN node 4 communicate with each other via a node-to-node interface (i.e., X2 interface or Xn interface) 105. RAN node 1 and RAN node 4 can act as an MN and an SN of a DC, respectively.

[0038] RAN nodes 1, 2, and 4 and UE 3 support inter-SN CPC from the SCG provided by RAN node 2 to the SCG provided by RAN node 4. Therefore, hereinafter, RAN node 1 may be referred to as MN 1, RAN node 2 may be referred to as source SN (S-SN) 2, and RAN node 4 may be referred to as target SN (T-SN) 4 or candidate SN 4. Inter-SN CPC may also be referred to as conditional SN change. Inter-SN CPC (or conditional SN change) is an inter-SN PSCell change procedure (or SN change procedure) that is performed only if a CPC execution condition is met.

[0039] Although not shown in FIG. 1, multiple candidate cells (i.e., candidate PSCells) provided by multiple candidate SNs 4 may be prepared for inter-SN CPC. In the inter-SN CPC procedure, the UE 3 receives from the MN 1 the configuration of one or more candidate PSCells prepared by one or more candidate SNs and one or more CPC execution conditions associated therewith. More specifically, the configuration of each candidate PSCell is an information element (IE) (e.g., condRRCReconfig) of the RRC message from the MN 1, and the configuration of one or more candidate PSCells and the associated CPC execution conditions are included in conditional mobility configuration information (e.g., conditionalReconfiguration IE) generated by the MN 1.

[0040] The configuration of each candidate PSCell is generated by the candidate SN (e.g., candidate SN4) that provides (or prepares) this candidate PSCell. The configuration of each candidate PSCell includes at least configuration information for the candidate PSCell. The configuration of each candidate PSCell may further include configuration information for one or more SCells associated with the candidate PSCell (i.e., configured together with or in association with the candidate PSCell). The configuration of each candidate PSCell may be a radio bearer (RB) configuration, a cell group (CG) configuration, an SCG configuration, an SCG radio resource configuration, or any combination thereof. More specifically, the configuration of each candidate PSCell may be an SN RRC Reconfiguration message generated by the candidate SN (e.g., candidate SN4) that provides (or prepares) this candidate PSCell. Some or all of the configurations of one or more candidate PSCells are included in the CPC configuration sent from MN1 to UE3. The CPC configuration of the Inter-SN CPC is a list of one or more MN RRC Reconfiguration messages. Each MN RRC Reconfiguration message includes the configuration of the candidate PSCell received from the candidate SN (eg, one or any combination of the RB configuration, CG configuration, SCG configuration, SCG radio resource configuration, and SN RRC Reconfiguration message).

[0041] On the other hand, the CPC execution condition is generated by the MN1 in the case of MN-initiated inter-SN CPC, and is generated by the source SN2 in the case of SN-initiated inter-SN CPC. The CPC execution condition may consist of one or more trigger conditions. The conditions or criteria for triggering a CPC event may be similar to those for a measurement report event, and may be, for example, CondEvent B1, CondEvent A3, CondEvent A4, or CondEvent A5. CondEvent B1 is "Conditional reconfiguration candidate becomes better than absolute threshold". CondEvent A3 is "Conditional reconfiguration candidate becomes amount of offset better than PCell / PSCell". CondEvent A4 is "Conditional reconfiguration candidate becomes better than absolute threshold". CondEvent A5 is "PCell / PSCell becomes worse than absolute threshold1 AND Conditional reconfiguration candidate becomes better than another absolute threshold2". The UE3 evaluates the CPC execution conditions. If the execution condition of one candidate PSCell is satisfied, the UE 3 applies the PSCell configuration (e.g., one or any combination of RB configuration, CG configuration, SCG configuration, SCG radio resource configuration, and SN RRC Reconfiguration message) corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution condition is satisfied). If a bearer requiring SCG radio resources is configured, the UE 3 synchronizes to the selected PSCell.If the execution conditions of two or more candidate PSCells are met, the UE 3 may select one of the candidate PSCells and perform the above-mentioned operations.

[0042] UE3 communicates with MN1 and S-SN2 via air interfaces 101 and 102, and provides dual connectivity between the MCG provided by MN1 and the SCG provided by S-SN2. Also, by performing inter-SN CPC, UE3 communicates with MN1 and T-SN4 via air interfaces 101 and 104, and provides dual connectivity between the MCG provided by MN1 and the SCG provided by T-SN4.

[0043] This dual connectivity may be Multi-Radio Dual Connectivity (MR-DC). MR-DC includes E-UTRA-NR Dual Connectivity (EN-DC), NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), NR-E-UTRA Dual Connectivity (NE-DC), and NR-NR Dual Connectivity (NR-DC). Accordingly, the MN1 may be a master eNB (in EN-DC), a master ng-eNB (in NGEN-DC), or a master gNB (in NR-DC and NE-DC). Similarly, the S-SN2 and T-SN4 may be an en-gNB (in EN-DC), a secondary ng-eNB (in NE-DC), or a secondary gNB (in NR-DC and NGEN-DC). In EN-DC, the UE3 is connected to an eNB operating as the MN1 and an en-gNB operating as the S-SN2 or T-SN4. In NGEN-DC, UE3 is connected to an ng-eNB operating as MN1 and a gNB operating as S-SN2 or T-SN4. In NE-DC, UE3 is connected to a gNB operating as MN1 and a ng-eNB operating as S-SN2 or T-SN4. In NR-DC, UE3 is connected to one gNB (or gNB-DU) operating as MN1 and another gNB (or gNB-DU) operating as S-SN2 or T-SN4.

[0044] The MCG is a group of serving cells associated with (or provided by) the MN1, and includes an SpCell (i.e., a Primary Cell (PCell)) and optionally one or more Secondary Cells (SCells). On the other hand, the SCG is a group of serving cells associated with (or provided by) the S-SN2 or T-SN4, and includes a Primary SCG Cell (PSCell) and optionally one or more Secondary Cells (SCells). The PSCell is a Special Cell (SpCell) of the SCG, and supports Physical Uplink Control Channel (PUCCH) transmission and contention-based Random Access. Note that in LTE (e.g., LTE-DC and NE-DC), PSCell may be an abbreviation for Primary SCell.

[0045] As used herein, the term "primary SCG cell" and its abbreviation "PSCell" refer to a cell included in a cell group provided by a dual connectivity SN, having an uplink component carrier, and configured with uplink control channel (e.g., PUCCH) resources. Specifically, the term "primary SCG cell" and its abbreviation "PSCell" may refer to the Primary SCG Cell of a cell group provided by an SN supporting 5G NR (e.g., en-gNB in ​​EN-DC, gNB in ​​NGEN-DC, or gNB in ​​NR-DC), or the Primary SC Cell of a cell group provided by an SN supporting E-UTRA (e.g., eNB in ​​LTE DC, or ng-eNB in ​​NE-DC).

[0046] Figure 2 illustrates another exemplary configuration of a wireless communication system according to various embodiments. In the example of Figure 2, the wireless communication system includes RAN node 1, RAN node 2, and UE 3. Each element (network function) illustrated in Figure 2 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on the dedicated hardware, or as a virtualized function instantiated on an application platform.

[0047] 2 may have the same configurations and functions as those in the example of FIG. 1. Specifically, RAN node 1 and RAN node 2 communicate with each other via an inter-node interface (i.e., X2 interface or Xn interface) 103. RAN node 1 and RAN node 2 operate as MN and SN, respectively, for dual connectivity. UE 3 communicates with MN 1 and SN 2 via air interfaces 101 and 102, and performs dual connectivity for MCG and SCG. This dual connectivity may be Multi-Radio Dual Connectivity (MR-DC).

[0048] RAN nodes 1 and 2 and UE 3 support conditional PSCell addition (CPA), which adds an SCG provided by RAN node 2 for UE 3. Therefore, hereinafter, RAN node 1 may be referred to as MN 1, and RAN node 2 may be referred to as candidate SN 2. CPA may also be referred to as conditional SN addition. CPA (or conditional SN addition) is a PSCell addition procedure (or SN addition procedure) that is executed only when a CPA execution condition is met.

[0049] Although not shown in Fig. 2, multiple candidate PSCells provided by multiple candidate SNs 2 may be prepared for CPA. In the CPA procedure, the UE 3 receives from the MN 1 the configuration of one or more candidate PSCells prepared by one or more candidate SNs and one or more CPA execution conditions associated therewith. More specifically, the configuration of each candidate PSCell is an information element (IE) (e.g., condRRCReconfig) in the RRC message of the MN 1, and the configuration of one or more candidate PSCells and the associated CPA execution conditions are included in conditional mobility configuration information (e.g., conditionalReconfiguration IE) generated by the MN 1.

[0050] The configuration of each candidate PSCell is generated by a candidate SN (e.g., candidate SN2) that provides (or prepares) this candidate PSCell. The configuration of each candidate PSCell includes at least configuration information for the candidate PSCell. The configuration of each candidate PSCell may further include configuration information for one or more SCells associated with the candidate PSCell (i.e., configured together with or in association with the candidate PSCell). The configuration of each candidate PSCell may be one or any combination of RB configuration, CG configuration, SCG configuration, and SCG radio resource configuration. More specifically, the configuration of each candidate PSCell may be an SN RRC Reconfiguration message generated by a candidate SN (e.g., candidate SN2) that provides (or prepares) this candidate PSCell. Some or all of the configurations of one or more candidate PSCells are included in a CPA configuration sent from MN1 to UE3. The CPA configuration is a list of one or more MN RRC Reconfiguration messages. Each MN RRC Reconfiguration message includes the configuration of the candidate PSCell received from the candidate SN (eg, one or any combination of the RB configuration, CG configuration, SCG configuration, SCG radio resource configuration, and SN RRC Reconfiguration message).

[0051] Meanwhile, the CPA execution condition is generated by the MN 1. The CPA execution condition may consist of one or more trigger conditions. The conditions or criteria for triggering a CPA event may be similar to those for a measurement report event, such as CondEvent A3, CondEvent A4, or CondEvent A5. The UE 3 evaluates the CPA execution conditions. If the execution condition for one candidate PSCell is met, the UE 3 applies the PSCell configuration (i.e., one or any combination of RB configuration, CG configuration, SCG configuration, SCG radio resource configuration, and SN RRC Reconfiguration message) corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution condition is met). If a bearer requiring SCG radio resources is configured, the UE 3 synchronizes to the selected PSCell. If the execution conditions for two or more candidate PSCells are met, the UE 3 may select one of the candidate PSCells and perform the above-mentioned operations.

[0052] In addition, the RAN node 2 and the UE 3 support intra-SN CPC, which may also be called SN-initiated Conditional SN Modification without MN involvement. Intra-SN CPC is an intra-SN PSCell change procedure that is executed only when the CPC execution conditions are met.

[0053] In the Intra-SN CPC procedure, UE3 receives from SN2 the configuration of one or more candidate PSCells prepared by SN2 and one or more CPC execution conditions associated with the configuration. The configuration of each candidate PSCell and the associated CPC execution conditions are included in the CPC configuration for intra-SN CPC. SN2 may send these to UE3 via MN1 or may send them to UE3 via a direct signaling radio bearer (i.e., Signaling Radio Bearer 3 (SRB3)) between SN2 and UE3. More specifically, the configuration of each candidate PSCell is an information element (IE) (e.g., condRRCReconfig) of an RRC message from SN2, and the configuration of one or more candidate PSCells and the associated CPC execution conditions are included in conditional mobility configuration information (e.g., conditionalReconfiguration IE) generated by SN2.

[0054] The configuration of each candidate PSCell includes at least configuration information for the candidate PSCell. The configuration of each candidate PSCell may further include configuration information for one or more SCells associated with the candidate PSCell (i.e., configured together with or in association with the candidate PSCell). The configuration of each candidate PSCell may be a radio bearer (RB) configuration, a cell group (CG) configuration, an SCG configuration, an SCG radio resource configuration, or any combination thereof. Specifically, the configuration of each candidate PSCell may be an SN RRC Reconfiguration message generated by the SN2.

[0055] The CPC execution condition for Intra-SN CPC may consist of one or more trigger conditions. The conditions or criteria for triggering a CPC event may be similar to those for a measurement report event, such as CondEvent A3, CondEvent A4, or CondEvent A5. The UE 3 evaluates the CPC execution conditions. If the execution condition for one candidate PSCell is met, the UE 3 detaches from the source PSCell, applies the configuration corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution condition is met), and synchronizes with the selected candidate PSCell. If the execution conditions for two or more candidate PSCells are met, the UE 3 may select one of the candidate PSCells and perform the above-mentioned operations.

[0056] FIG. 3 illustrates yet another exemplary configuration of a wireless communication system according to several embodiments. In the example of FIG. 3, the wireless communication system includes a RAN node 6, a RAN node 7, and a UE 3. Each element (network function) illustrated in FIG. 3 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on the dedicated hardware, or as a virtualized function instantiated on an application platform. Each of the RAN nodes 6 and 7 may be an EUTRAN node or an NG-RAN node. The EUTRAN node may be an eNB or an en-gNB. The NG-RAN node may be a gNB or an ng-eNB. The RAT of the RAN node 6 may be different from that of the RAN node 7.

[0057] The RAN node 6 provides at least one cell 61. The RAN node 7 provides one or more cells (e.g., four cells 71 to 74). In the example of FIG. 3, the cell 61 provided by the RAN node 6 is the current serving cell of the UE 3, and the UE 3 is handed over from the cell 61 to one of the cells provided by the RAN node 7. Therefore, hereinafter, the RAN node 6 may be referred to as a source node or a source RAN node, and the RAN node 7 may be referred to as a target node or a target RAN node. The cell 61 is referred to as a source cell. The source node 6, the target node 7, and the UE 3 support conditional handover (CHO). CHO is a handover procedure that is executed only when the CHO execution conditions are met.

[0058] Although not shown in FIG. 3 , multiple candidate target cells provided by multiple candidate target nodes 7 may be prepared for CHO. In the CHO procedure, the UE 3 receives from the source node 6 configurations of one or more candidate target cells prepared by one or more candidate target nodes and one or more associated CHO execution conditions (e.g., condExecutionCond). The configurations of one or more candidate target cells and the associated CHO execution conditions are included in the CHO configuration. More specifically, the configuration of each candidate target cell is an information element (IE) (e.g., condRRCReconfig) in an RRC message from the source node 6, and the configurations of one or more candidate target cells and the associated CHO execution conditions are included in conditional mobility configuration information (e.g., conditionalReconfiguration IE) generated by the source node 6.

[0059] The configuration of each candidate target cell is generated by a candidate target node (e.g., target node 7) that serves (or prepares) this candidate target cell. The configuration of each candidate target cell may be a radio bearer (RB) configuration, a radio resource configuration, or an RRC Reconfiguration message, or any combination thereof, generated by the candidate target node (e.g., target node 7) that serves (or prepares) this candidate target cell.

[0060] Meanwhile, the CHO execution condition is generated by the source node 6. The CHO execution condition may consist of one or more trigger conditions. The conditions or criteria for triggering a CHO event may be similar to those for a measurement report event, e.g., CondEvent A3, CondEvent A4, or CondEvent A5. The UE 3 evaluates the CHO execution conditions. If the execution condition for one candidate target cell is met, the UE 3 detaches from the source node 6, applies the configuration corresponding to the selected candidate target cell (i.e., the candidate target cell whose execution condition is met), and synchronizes with the selected candidate target cell. If the execution conditions for two or more candidate target cells are met, the UE 3 may select one of the candidate target cells and perform the above-mentioned operations.

[0061] One or more of the RAN nodes 1, 2, 4, 6, and 7 may have the configuration shown in Figure 4. Each element (network function) shown in Figure 4 may be implemented, for example, as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an application platform. One or more of the RAN nodes 1, 2, 4, 6, and 7 may include, but are not limited to, a CU 41 and one or more DUs 42 as shown in Figure 4. The CU 41 and each DU 42 are connected by an interface 401. A UE 3 is connected to at least one DU 42 via at least one air interface 402.

[0062] The CU41 may be a logical node that hosts the Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP) protocols (or the RRC and PDCP protocols) of the gNB. The DU42 may be a logical node that hosts the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of the gNB. If the CU41 is a gNB-CU and the DUs42 are gNB-DUs, the interface 401 may be an F1 interface. The CU41 may include a CU-CP and a CU-UP.

[0063] The term conditional mobility is used herein as a general term to refer to one or more of CHO, CPA, intra-SN CPC (or conditional SN modification), and inter-SN CPC (or conditional SN modification).

[0064] The embodiments described below provide an improvement to conditional mobility. Specifically, the following embodiments provide an improvement to conditional mobility to support a function or operation mode called "Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups." Note that, in this specification, this function or operation mode may also be applied to conditional mobility that does not necessarily involve MR-DC, i.e., CHO. Furthermore, this function or operation mode may also be applied to an improved CHO in which an SCG (at least a PSCell) is added together with the execution of CHO. As defined in this specification, this function or operation mode enables, for example, a subsequent second conditional mobility after changing or adding a serving cell, a serving cell group, a PSCell, or an SCG in a first conditional mobility without at least re-initializing the conditional mobility preparation. In other words, as defined herein, the function or operation mode enables the UE 3 to reuse or maintain at least a portion of the candidate target cell configuration or candidate PSCell configuration (e.g., one or any combination of RB configuration, CG configuration, SCG configuration, radio resource configuration, and SCG radio resource configuration) received from the network in the first conditional mobility for the subsequent second conditional mobility. At least a portion of the execution conditions for the first conditional mobility may be reset, updated, or modified for the second conditional mobility. Similarly, at least a portion of information related to the security key configuration for the first conditional mobility (e.g., sk-Counter, Next Hop (NH), NH Chaining Count (NCC)) or security key information (e.g., SN Security Key) may be reset, updated, or modified for the second conditional mobility. The type of the second conditional mobility may be different from the type of the first conditional mobility.For example, the first conditional mobility may be a CPA, while the second conditional mobility may be an Inter-SN CPC or an Intra-SN CPC. Alternatively, the first conditional mobility may be an Inter-SN CPC, while the second conditional mobility may be an Intra-SN CPC.

[0065] This function or operation mode may be referred to as, for example, but not limited to, selective cell activation, selective cell group (CG) activation, selective SCG activation, adaptive cell switch, adaptive CG switch, adaptive SCG switch, subsequent cell change, subsequent CG change, subsequent CG selection, CPC kept, or CHO kept. For convenience of explanation, in the following embodiments, this function or operation mode is referred to as selective CG activation or selective cell activation. The term selective CG activation may be used for conditional mobility with MR-DC (e.g., CPA, inter-SN CPC, intra-SN CPC). On the other hand, the term selective cell activation may be used for conditional mobility that does not necessarily involve MR-DC (e.g., CHO).

[0066] In this specification, a combination of candidate Special Cells (SpCells) and SCell(s) may be referred to as a candidate Cell Group (CG) set for conditional mobility or selective CG activation. Selective CG activation may also be considered as a change or switch of the serving SCG among multiple candidate CG sets. A candidate CG set includes at least a candidate SpCell and optionally includes one or more SCells. A candidate cell (candidate SpCell) may be the current SCell (i.e., an SCell included in the current SCG) or a non-serving cell not provided to the UE 3. The UE 3 may be configured with multiple candidate CG sets, each of which has different candidate SpCells. For conditional mobility (e.g., CHO) for MCG, the candidate SpCells are candidate PCells, and the multiple candidate CG sets are candidate MCG sets. On the other hand, if the mobility is conditional on SCG (eg, CPA, intra-SN CPC, inter-SN CPC), the candidate SpCells are candidate PSCells, and the multiple candidate CG sets are multiple candidate SCG sets.

[0067] In this specification, the terms MN RRC message, MN RRC Reconfiguration message, SN RRC message, and SN RRC Reconfiguration message are used. These terms are used for convenience to distinguish RRC messages generated by the MN from RRC messages generated by the SN. Therefore, the MN RRC message and the MN RRC Reconfiguration message may be simply referred to as the RRC message and the RRC Reconfiguration message. Similarly, the SN RRC message and the SN RRC Reconfiguration message may be simply referred to as the RRC message and the RRC Reconfiguration message.

[0068] First Embodiment This embodiment provides improvements to CHO, intra-SN CPC, and inter-SN CPC for selective CG / cell activation. Specifically, this embodiment relates to reuse in subsequent conditional mobility after a conditional mobility execution condition. A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in FIG. 1, FIG. 2, or FIG. 3.

[0069] In a first implementation, the UE 3 reuses the execution condition for the candidate target cell of the first conditional mobility for the subsequent second conditional mobility, and switches the reference cell in the execution condition from the source cell of the first conditional mobility to the candidate target cell selected in the first conditional mobility. The first conditional mobility may be any of CHO, intra-SN CPC, and inter-SN CPC. The inter-SN CPC may be an SN-initiated inter-SN CPC initiated by the source SN 2. When the first conditional mobility is a CPC, the candidate target cell refers to the candidate (target) PSCell. For example, both the first and second conditional mobility may be CHO. Both the first and second conditional mobility may be intra-SN CPC. Alternatively, the first conditional mobility may be an SN-initiated inter-SN CPC, and the second conditional mobility may be an intra-SN CPC or an inter-SN CPC.

[0070] FIG. 5 shows an example of the operation of the UE 3 for the first implementation described above. In step 501, the UE 3 evaluates multiple execution conditions for multiple candidate target cells for the first conditional mobility. In step 502, if the execution condition for one of the multiple candidate target cells is satisfied, the UE 3 performs the first conditional mobility by applying a configuration corresponding to the selected candidate target cell (i.e., the candidate target cell for which the execution condition is satisfied). In step 503, the UE 3 reuses one or more execution conditions for one or more candidate target cells other than the selected candidate target cell for the subsequent second conditional mobility. In step 504, the UE 3 switches the reference cell in the reused execution condition from the source cell of the first conditional mobility to the selected candidate target cell.

[0071] The execution condition of the first conditional mobility, i.e., the condition or criterion that triggers the conditional mobility event, may be similar to that for the measurement report event, and may be, for example, CondEvent A3 or CondEvent A5. The reference cell of CondEvent A3 or CondEvent A5 is the source cell when the first conditional mobility is CHO, and is the source PSCell when it is intra-SN CPC and SN-initiated inter-SN CPC. When the reference cell is the source cell when the first conditional mobility is CHO, the UE 3 switches the reference cell in the reused execution condition (e.g., CondEvent A3 or CondEvent A5) from the source cell of CHO to the selected candidate target cell. When the reference cell is the source cell when the first conditional mobility is intra-SN CPC and SN-initiated inter-SN CPC, the UE 3 switches the reference cell in the reused execution condition (e.g., CondEvent A3 or CondEvent A5) from the source PSCell of CPC to the selected candidate PSCell. That is, the UE 3 autonomously updates or modifies the reference cell of the execution condition of the first conditional mobility, so that the UE 3 can start evaluating the execution condition for the subsequent second conditional mobility without receiving signaling for updating the execution condition.

[0072] FIG. 6 shows an example of autonomous execution condition update or modification by UE 3 in intra-SN CPC and SN-initiated inter-SN CPC. In step 601, UE 3 uses the source PSCell (i.e., cell #10) of the CPC as a reference cell and compares the quality of the source PSCell with the quality of each of four candidate PSCells (i.e., cells #11, #12, #21, and #22) (e.g., CondEvent A3). In step 602, in response to the execution condition of Cell #11 being satisfied, UE 3 performs a PSCell change to Cell #11. In step 603, UE 3 switches the reference cell of the execution conditions of the three unselected candidate PSCells (i.e., cells #12, #21, and #22) to the new source PSCell (cell #11). Then, UE 3 starts evaluating the execution conditions for the second conditional mobility.

[0073] In the second implementation, the RAN node serving the candidate target cell selected by the UE 3 in the first conditional mobility updates the execution conditions of the non-selected candidate target cells for the subsequent second conditional mobility. Similar to the first implementation, the first conditional mobility may be any of CHO, intra-SN CPC, and inter-SN CPC. The inter-SN CPC may be an SN-initiated inter-SN CPC initiated by the source SN 2. When the first conditional mobility is a CPC, the candidate target cell refers to a candidate (target) PSCell. For example, both the first and second conditional mobility may be CHO. Both the first and second conditional mobility may be intra-SN CPC. Alternatively, the first conditional mobility may be an SN-initiated inter-SN CPC, and the second conditional mobility may be an intra-SN CPC or an inter-SN CPC. If the first conditional mobility is CHO, the RAN node serving the candidate target cell is the candidate target node (e.g., target node 7). If the first conditional mobility is intra-SN CPC within SN2, the RAN node serving the candidate target cell is SN2. If the first conditional mobility is inter-SN CPC, the RAN node serving the candidate target cell is the candidate target SN (e.g., candidate SN4). That is, UE3 receives updated or modified execution conditions from the RAN node serving the selected candidate target cell. This allows UE3 to start evaluating the execution conditions for the subsequent second conditional mobility.

[0074] FIG. 7 shows an example of the operation of the UE 3 for the second implementation described above. Steps 701 and 702 are the same as steps 501 and 502 in FIG. 5. In step 703, the UE 3 reuses one or more configurations (e.g., one or any combination of RB configuration, radio resource configuration, SCG configuration, and SCG radio resource configuration) of one or more candidate target cells other than the selected candidate target cell for the subsequent second conditional mobility. In step 704, the UE 3 receives one or more updated execution conditions for the subsequent second conditional mobility for these one or more candidate target cells from the RAN node of the selected candidate target cell. Specifically, when the second conditional mobility is CHO, the UE 3 may receive the updated execution conditions via a direct signaling radio bearer (e.g., SRB1) with the candidate target node 7. When the second conditional mobility is an intra-SN CPC, the UE 3 may receive the updated execution condition through a direct signaling radio bearer (e.g., SRB3) with the SN 2 or the candidate SN 4, or via the MN 1. When the second conditional mobility is an inter-SN CPC, the UE 3 may receive the updated execution condition through a direct signaling radio bearer (e.g., SRB3) with the candidate SN 4, or via the MN 1.

[0075] FIG. 8 shows an example of signaling in an inter-SN CPC (or conditional SN change) procedure for the second implementation described above. In step 801, inter-SN CPC is prepared for multiple candidate PSCells provided by two candidate (target) SNs 4A and 4B. In step 802, UE3 selects one candidate PSCell provided by candidate SN 4A and performs a PSCell change to the selected candidate PSCell. Thus, candidate SN 4A becomes the new serving SN for UE3. In steps 803 and 804, candidate SN 4A provides updated or modified CPC execution conditions to UE3 via MN1. In step 805, UE3 updates or modifies the CPC execution conditions of the non-selected PSCell(s), i.e., the CPC execution conditions prepared in step 801, with the CPC execution conditions received in step 804. An SN-initiated SN Modification with MN involvement procedure may be used to transmit the updated or modified CPC execution conditions to the UE 3 in steps 803 and 804. Specifically, in step 803, the candidate SN 4 may send the updated or modified CPC execution conditions (e.g., an SN RRC configuration message including the CPC execution conditions) to the MN 1 via an SN Modification Required message. In step 804, the MN 1 may transmit the CPC execution conditions received from the candidate SN 4A (e.g., an SN RRC configuration message including the CPC execution conditions) to the UE 3 via an MN RRC Reconfiguration message.

[0076] The operations of the MN1, candidate SN4, and UE3 shown in Fig. 8 may be modified as follows: The MN1 may reset, update, or modify security key information (e.g., SN Security Key) for selective CG activation and transmit it to the candidate SN4 (e.g., 4A) selected by the UE3 in the first conditional mobility (inter-SN CPC). For example, the MN1 may transmit the security key information to the selected candidate SN4 (e.g., 4A) in step 802 or after step 802. Furthermore, the MN1 may reset, update, or modify at least a portion of information related to security key configuration (e.g., sk-Counter, Next Hop (NH), NH Chaining Count (NCC)) for selective CG activation and transmit it to the UE3.

[0077] The MN1 may reset, update, or modify security key information (e.g., SN Security Key) for selective CG activation and transmit it to the candidate SN4 (e.g., 4B) that was not selected by the UE3 in the first conditional mobility (inter-SN CPC). For example, the MN1 may transmit security key information to the candidate SN4 (e.g., 4B) that was not selected by the UE3 in the first conditional mobility (inter-SN CPC) after step 802. Furthermore, the MN1 may reset, update, or modify at least a portion of information related to security key configuration (e.g., sk-Counter, Next Hop (NH), NH Chaining Count (NCC)) for selective CG activation and transmit it to the UE3.

[0078] <Second embodiment> This embodiment provides improvements to CHO, intra-SN CPC, and inter-SN CPC for selective CG / cell activation. Specifically, this embodiment provides improvements to enable a source cell of conditional mobility to be used as one of candidate target cells for subsequent conditional mobility. A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in FIG. 1, FIG. 2, or FIG. 3.

[0079] After the first conditional mobility, the UE 3 maintains or keeps the source cell configuration for reuse in a subsequent second conditional mobility in which the source cell of the first conditional mobility is a new candidate target cell. The first conditional mobility may be any of CHO, intra-SN CPC, and inter-SN CPC. When the first conditional mobility is a CPC, the source cell refers to the source PSCell. For example, both the first and second conditional mobility may be CHO. Both the first and second conditional mobility may be intra-SN CPC. Alternatively, both the first and second conditional mobility may be inter-SN CPC.

[0080] The UE 3 may receive, from the RAN node of the selected candidate target cell, an execution condition for the second conditional mobility for a new candidate target cell corresponding to the source cell of the first conditional mobility. Specifically, when the first and second conditional mobility are CHO, the UE 3 may receive the execution condition via a direct signaling radio bearer (e.g., SRB1) with the candidate target node 7. When the first and second conditional mobility are intra-SN CPC, the UE 3 may receive the execution condition via a direct signaling radio bearer (e.g., SRB3) with the SN 2 or via the MN 1. When the first and second conditional mobility are inter-SN CPC, the UE 3 may receive the execution condition via a direct signaling radio bearer (e.g., SRB3) with the candidate SN 4 or via the MN 1. In this case, the second conditional mobility is, or can be considered to be, an SN-initiated inter-SN CPC. Alternatively, when the first and second conditional mobility are inter-SN CPCs, the UE3 may receive from the MN1 an execution condition for the second conditional mobility with respect to a new candidate target cell corresponding to the source cell in the first conditional mobility, in which case the second conditional mobility is, or can be considered to be, an MN-initiated inter-SN CPC.

[0081] 9 shows an example of the operation of UE 3. In step 901, UE 3 evaluates multiple execution conditions for one or more candidate target cells for a first conditional mobility from a source cell. In step 902, if the execution condition for one of the one or more candidate target cells is met, UE 3 performs the first conditional mobility by applying a configuration corresponding to the selected candidate target cell (i.e., the candidate target cell for which the execution condition is met). In step 903, after the first conditional mobility, UE 3 maintains the configuration of the previous source cell for reuse in a subsequent second conditional mobility in which the previous source cell is the new candidate target cell.

[0082] Figure 10 shows an example of signaling in the preparation phase of an inter-SN CPC (or conditional SN change) procedure. In step 1001, when source SN2 initiates inter-SN CPC, source SN2 sends an SN Change Required message to MN1. The SN Change Required message includes a list of proposed PSCell candidates recommended by source SN2 and associated CPC execution conditions. In the case of MN-initiated inter-SN CPC, step 1001 is omitted.

[0083] In step 1002, MN1 sends an SN Addition Request message to each of one or more candidate target SNs 4 (e.g., SNs 4A and 4B). The SN Addition Request message includes a list of PSCell candidates, which indicate one or more candidate PSCells proposed by MN1 in the case of an MN-initiated inter-SN CPC, or one or more candidate PSCells proposed by source SN2 in the case of an SN-initiated inter-SN CPC.

[0084] In step 1003, each candidate target SN 4 sends an SN Addition Request Acknowledge message to MN 1. The SN Addition Request Acknowledge message includes the configuration of each of one or more candidate PSCells prepared by the candidate target SN 4. As already described, the configuration of each candidate PSCell may be one or any combination of RB configuration, CG configuration, SCG configuration, SCG radio resource configuration, and SN RRC Reconfiguration message.

[0085] In the case of an SN-initiated inter-SN CPC, step 1004, or steps 1004 and 1005, may be performed. In step 1004, MN1 may indicate to source SN2 one or more candidate PSCells accepted by candidate target SN4, if necessary, for example, if candidate target SN4 has not accepted all candidate PSCells proposed by source SN2. In step 1005, source SN2 may provide MN1 with updated or modified configurations for CPC (e.g., measurement configurations or CPC execution conditions).

[0086] In step 1006, the MN1 sends an MN RRC Reconfiguration message (RRC Reconfiguration*) including a CPC configuration (e.g., condRRCReconfig) and associated CPC execution conditions (conditions) to the UE3. The CPC configuration of the Inter-SN CPC is a list of one or more MN RRC Reconfiguration messages (RRC Reconfiguration**). Each MN RRC Reconfiguration message (RRC Reconfiguration**) includes the configuration of a candidate PSCell received from a candidate SN (i.e., SN RRC Reconfiguration message (RRC Reconfiguration***)). The CPC configuration (i.e., list of MN RRC Reconfiguration messages (RRC Reconfiguration**)) and associated CPC execution conditions are included in conditional mobility configuration information (e.g., conditionalReconfiguration IE) in the MN RRC Reconfiguration message (RRC Reconfiguration*).

[0087] In one example, as shown in Figure 10 as Option 1, MN1 informs each candidate SN4 that the source SN2 or source PSCell is subject to selective CG activation. MN1 may include an indication of this (e.g., "S-SN kept" or "Source PSCell kept") in the SN Addition Request message (step 1002).

[0088] In one example, as shown in Figure 10 as Option 2, SN2 informs MN1 that selective CG activation to source SN2 or source PSCell is requested, recommended, or available. SN2 may include an indication of this (e.g., "S-SN kept" or "Source PSCell kept") in the SN Change Required message (step 1001).

[0089] In one example, as shown in Figure 10 as Option 3, the MN1 informs the UE3 that the source SN2 or the source PSCell is subject to selective CG activation. The MN1 may include an indication of this (e.g., "S-SN kept" or "Source PSCell kept") in the MN RRC Reconfiguration message (step 1006). Options 1, 2, and 3 described above may be used or implemented in any suitable combination.

[0090] Figure 11 shows an example of signaling in the execution phase of an inter-SN CPC (or conditional SN change) procedure. Step 1101 in Figure 11 corresponds to steps 1001 to 1006 in Figure 10. In step 1102, UE3 evaluates CPC execution conditions. If the execution condition for one candidate PSCell is met, UE3 sends a corresponding MN RRC Reconfiguration Complete message to MN1 (step 1103). This MN RRC Reconfiguration Complete message contains an SN RRC Reconfiguration Complete message for the candidate PSCell whose execution condition is met (i.e., the selected candidate PSCell) and further contains information about the selected candidate PSCell. The information about the selected candidate PSCell may be implicitly (or indirectly) indicated by an identifier (e.g., CondReconfigId) associated with the candidate PSCell's configuration and CPC execution condition (e.g., condExecutionCond or condExecutionCondSN). In step 1104, the MN1 sends an SN Reconfiguration Complete message to the candidate SN4 (selected candidate SN4) (e.g., 4A) that provides the selected candidate PSCell. The SN Reconfiguration Complete message includes the SN RRC Reconfiguration Complete message received from the UE3.

[0091] The MN1 informs the source SN2 that the source SN2 or the source PSCell is to be subject to selective CG activation. This notification may be made when the initiation of inter-SN CPC is decided by the MN1. In one example, as shown in step 1105 of FIG. 11 as option 4, the MN1 may send a new Xn / X2 message (e.g., UE Context Kept) to the source SN2 indicating that the UE context needs to be maintained, instead of the UE Context Release message. Alternatively, the MN1 may send an indication of this (e.g., "S-SN kept" or "Source PSCell kept") to the source SN2 during the CPC preparation phase (step 1101 or FIG. 10). The source SN2 now becomes a new candidate SN4 (e.g., 4C).

[0092] The operations of the MN1, candidate SN4, and UE3 shown in Fig. 11 may be modified as follows: The MN1 may reset, update, or modify security key information (e.g., SN Security Key) for selective CG activation and transmit it to the candidate SN4 (e.g., 4A) selected by the UE3 in the first conditional mobility (inter-SN CPC). For example, the MN1 may transmit the security key information to the selected candidate SN4 (e.g., 4A) in step 1104 or after step 1104. Furthermore, the MN1 may reset, update, or modify at least a portion of information related to security key configuration (e.g., sk-Counter, Next Hop (NH), NH Chaining Count (NCC)) for selective CG activation and transmit it to the UE3.

[0093] The MN1 may reset, update, or modify security key information (e.g., SN Security Key) for selective CG activation and transmit it to the candidate SN4 (e.g., 4B) that was not selected by the UE3 in the first conditional mobility (inter-SN CPC). For example, the MN1 may transmit security key information to the candidate SN4 (e.g., 4B) that was not selected by the UE3 in the first conditional mobility (inter-SN CPC) after step 1104. Furthermore, the MN1 may reset, update, or modify at least a portion of information related to security key configuration (e.g., sk-Counter, Next Hop (NH), NH Chaining Count (NCC)) for selective CG activation and transmit it to the UE3.

[0094] FIG. 12 shows an example in which UE3 performs an inter-SN CPC (or conditional SN change) procedure as a first conditional mobility, and then performs another inter-SN CPC (or conditional SN change) procedure as a second conditional mobility. Before the first inter-SN CPC, SN#1 (e.g., SN2) is the source SN, and SN#2 (e.g., SN4A) and SN#3 (e.g., SN4B) are candidate SNs. SN#1 provides (S)CG set# to UE3. SN#2 (e.g., SN4A) and SN#3 (e.g., SN4B) prepare (S)CG set#2 and (S)CG set#3 for UE3, respectively. When the execution conditions for the candidate PSCell provided by SN#2 are met, UE3 applies the configuration of the selected candidate PSCell. In other words, UE3 applies the information (or configuration or configuration information) of the selected (S)CG set#2. At this time, the UE 3 stores the configuration of the source PSCell. In other words, the UE 3 stores information (or configuration or configuration information) of the source (S)CG set #1 including the source PSCell. Similarly, the UE 3 stores information of the (S)CG set #3 including the non-selected candidate PSCells. Subsequently, when the execution conditions for the candidate PSCell (i.e., the previous source PSCell) prepared by the source SN #1 of the first CPC are met, the UE 3 restores the information of the (S)CG set #1 it stored and executes the CPC there. According to the current specifications of 3GPP Release 16 and the current discussions regarding Release 17, the UE 3 releases the information of the source PSCell when executing the first inter-SN CPC, so it cannot execute the second CPC for the (S)CG set #1 including the previous source PSCell. In contrast, this is possible in this embodiment. After the second CPC, the UE 3 continues to store information of the (S)CG set #3 including the non-selected candidate PSCells. After the second CPC, the UE3 may retain information of the (S)CG set #2 that includes the source PSCell of the second CPC.

[0095] According to the operation and procedure of the UE 3 described in this embodiment, it is possible to enable the source cell of the conditional mobility to be used as one of the candidate target cells for subsequent conditional mobility.

[0096] <Third embodiment> This embodiment provides an improvement of CHO and inter-SN CPC for selective CG / cell activation. Specifically, this embodiment contributes to solving problems caused by the use of a delta configuration. A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in FIG. 1 or FIG. 3.

[0097] An example of the operation of a RAN node serving a candidate target cell for a first conditional mobility will be described below with reference to Figure 13. If the first conditional mobility is CHO, the RAN node serving the candidate target cell is candidate target node 7. If the first conditional mobility is inter-SN CPC, the RAN node serving the candidate target cell is candidate target SN 4.

[0098] In step 1301, the RAN node receives a control message from a source node (eg, source node 6 or source SN2) or MN1 requesting the preparation of a candidate target cell for a first conditional mobility of UE3.

[0099] In step 1302, the RAN node determines whether the configuration of the candidate target cell provided to the UE 3 for the first conditional mobility needs to be reused by the UE 3 for the subsequent second conditional mobility. If the configuration of the candidate target cell needs to be reused for the subsequent second conditional mobility, the RAN node applies full configuration to the configuration of the candidate target cell without applying delta configuration based on the configuration of the current source cell. The delta configuration may also be called delta config or delta signaling, and the full configuration may also be called full config or full signaling. Note that in this embodiment, the delta configuration based on the RB configuration of the source cell may be applied to the RB configuration of the candidate target cell.

[0100] In one example, the RAN node may determine that the configuration of the candidate target cell needs to be reused for a subsequent second conditional mobility if it receives an indication for selective CG / cell activation from a source node (e.g., source node 6 or source SN2) or MN1. In another example, the RAN node may autonomously decide whether to perform, utilize, prepare for, or recommend selective CG / cell activation. In other words, the RAN node may autonomously determine whether the configuration of the candidate target cell needs to be reused for a subsequent second conditional mobility.

[0101] According to the operation of the RAN node described in this embodiment, when selective CG / cell activation is performed, used, prepared, or recommended, full configuration is applied to the configuration of the candidate target cell of the first conditional mobility. This allows the configuration of the candidate target cell of the first conditional mobility to be easily reused after the subsequent second conditional mobility is performed. In other words, after the subsequent second conditional mobility is performed, the new serving RAN node does not necessarily need to perform RRC reconfiguration before the UE 3 resumes data communication. Therefore, this embodiment can contribute to solving problems caused by the use of delta configuration.

[0102] <Fourth embodiment> This embodiment provides improvements to CHO, CPA, and inter-SN CPC for selective CG / cell activation. Specifically, this embodiment relates to dealing with a case where there is a target node or target SN that does not support selective CG / cell activation. A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in FIG. 1, FIG. 2, or FIG. 3.

[0103] An example of the operation of a RAN node serving a candidate target cell for a first conditional mobility will be described below with reference to Figure 14. If the first conditional mobility is CHO, the RAN node serving the candidate target cell is candidate target node 7. If the first conditional mobility is CPA, the RAN node serving the candidate target cell is candidate SN2. If the first conditional mobility is inter-SN CPC, the RAN node serving the candidate target cell is candidate target SN4.

[0104] In step 1401, the RAN node receives a message indicating a request for conditional mobility and a request for selective CG / cell activation from the source node 6 or MN1. In step 1402, if the RAN node does not support selective CG / cell activation, it replies to the source node 6 or MN1 with a response message indicating rejection of the conditional mobility. In other words, if the RAN node does not support selective CG / cell activation, it rejects the preparation of the conditional mobility regardless of whether it can prepare a candidate target cell for the conditional mobility.

[0105] For example, the MN 1 may associate an indication of a request for selective CG activation with a CPA request or a CPC request and transmit it to the candidate SN 2. Specifically, the MN 1 may add the indication of a request for selective CG activation as a sub-information element (IE) of a CPA request or a CPC request in an SN Addition Request message. The CPA request may be indicated by a Conditional PSCell Addition Information Request IE. Meanwhile, the CPC request may be indicated by a Conditional PSCell Addition Information Request IE or a Conditional PSCell Change Information Request IE. Similarly, the source node 6 may associate an indication of a request for selective cell activation with a CHO request sent to the candidate target node 7, and may add it as a sub-IE of the CHO request in a Handover Request message for CHO. The CHO request may be indicated by a Conditional Handover Information Request IE. A RAN node that does not support Selective CG / cell activation may respond to the MN 1 or source node 6 with a CPA request reject, a CPC request reject, or a CHO request reject message.

[0106] 15 shows another example of the operation of a RAN node providing a candidate target cell for first conditional mobility. In step 1501, the RAN node receives a message indicating a request for conditional mobility and a request for selective CG / cell activation from the source node 6 or MN1. In step 1502, if the RAN node does not support selective CG / cell activation but can prepare the candidate target cell for conditional mobility, it replies to the source node 6 or MN1 with a response message indicating acceptance of conditional mobility. In other words, if the RAN node does not support selective CG / cell activation but can prepare the candidate target cell for conditional mobility, it accepts the preparation.

[0107] For example, the MN1 may include an IE indicating a request for selective CG activation, independent of the IE for the CPA request or the CPC request, in the SN Addition Request message. Similarly, the source node 6 may include an IE indicating a request for selective CG activation, independent of the IE for the CHO request, in the Handover Request message. A RAN node that does not support selective CG / cell activation may ignore the IE indicating the request for selective CG / cell activation and respond with an SN Addition Request Acknowledge message. On the other hand, a RAN node that supports selective CG / cell activation may take into account the IE indicating the request for selective CG / cell activation and respond with an SN Addition Request Acknowledge message. A RAN node that supports selective CG / cell activation transmits information indicating whether or not selective CG / cell activation is acceptable to the MN1 or the source node 6. This information may be for each candidate target cell. If a RAN node supports Selective CG / cell activation but does not permit the execution or application of Selective CG / cell activation, the RAN node may send an SN Addition Request Acknowledge message containing information indicating the non-acceptance of selective CG / cell activation.

[0108] Next, exemplary configurations of RAN nodes 1, 2, 4, 6, and 7 and UE 3 according to the above-described embodiments will be described below. FIG. 16 is a block diagram illustrating an exemplary configuration of RAN node 1 according to the above-described embodiments. The configurations of the other RAN nodes 2, 4, 6, and 7 may be similar to the configuration illustrated in FIG. 16. Referring to FIG. 16, RAN node 1 includes a radio frequency transceiver 1601, a network interface 1603, a processor 1604, and a memory 1605. The RF transceiver 1601 performs analog RF signal processing for communication with UEs, including UE 3. The RF transceiver 1601 may include multiple transceivers. The RF transceiver 1601 is coupled to an antenna array 1602 and a processor 1604. The RF transceiver 1601 receives modulation symbol data from the processor 1604, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1602. The RF transceiver 1601 also generates a baseband receive signal based on the received RF signal received by the antenna array 1602 and supplies the baseband receive signal to the processor 1604. The RF transceiver 1601 may include an analog beamformer circuit for beamforming. The analog beamformer circuit may include, for example, multiple phase shifters and multiple power amplifiers.

[0109] The network interface 1603 is used to communicate with network nodes (e.g., RAN nodes 2 and 4, and control and forwarding nodes of the core network). The network interface 1603 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0110] The processor 1604 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 1604 may include multiple processors. For example, the processor 1604 may include a modem processor (e.g., a Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a Central Processing Unit (CPU) or a Micro Processing Unit (MPU)) that performs control plane processing.

[0111] For example, digital baseband signal processing by the processor 1604 may include signal processing of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a Medium Access Control (MAC) layer, and a Physical (PHY) layer. Also, control plane processing by the processor 1604 may include processing of Non-Access Stratum (NAS) messages, RRC messages, MAC Control Elements (CE), and Downlink Control Information (DCI).

[0112] The processor 1604 may include a digital beamformer module for beamforming, which may include a multiple input multiple output (MIMO) encoder and precoder.

[0113] The memory 1605 is configured by a combination of volatile memory and nonvolatile memory. The volatile memory is, for example, Static Random Access Memory (SRAM), Dynamic RAM (DRAM), or a combination thereof. The nonvolatile memory is, for example, Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or a hard disk drive, or any combination thereof. The memory 1605 may include storage located remotely from the processor 1604. In this case, the processor 1604 may access the memory 1605 via the network interface 1603 or an I / O interface (not shown).

[0114] The memory 1605 may store one or more software modules (computer programs) 1606 including instructions and data for performing the processing by the RAN node 1 described in the above embodiments. In some implementations, the processor 1604 may be configured to read and execute the software modules 1606 from the memory 1605 to perform the processing by the RAN node 1 described in the above embodiments.

[0115] Note that if the RAN node 1 is a CU (eg, eNB-CU or gNB-CU) or a CU-CP, the RAN node 1 may not include the RF transceiver 1601 (and the antenna array 1602).

[0116] FIG. 17 is a block diagram showing an example configuration of UE 3. Radio Frequency (RF) transceiver 1701 performs analog RF signal processing for communication with RAN nodes 1, 2, 4, 6, and 7. RF transceiver 1701 may include multiple transceivers. The analog RF signal processing performed by RF transceiver 1701 includes frequency up-conversion, frequency down-conversion, and amplification. RF transceiver 1701 is coupled to antenna array 1702 and baseband processor 1703. RF transceiver 1701 receives modulation symbol data (or OFDM symbol data) from baseband processor 1703, generates a transmit RF signal, and provides the transmit RF signal to antenna array 1702. RF transceiver 1701 also generates a baseband receive signal based on the receive RF signal received by antenna array 1702 and provides the baseband receive signal to baseband processor 1703. RF transceiver 1701 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0117] The baseband processor 1703 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) transmission format (transmission frame) generation / decomposition, (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) using Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management for Layer 1 (e.g., transmit power control), Layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and Layer 3 (e.g., signaling related to attachment, mobility, and call management).

[0118] For example, digital baseband signal processing by the baseband processor 1703 may include signal processing of an SDAP layer, a PDCP layer, an RLC layer, a MAC layer, and a PHY layer. Also, control plane processing by the baseband processor 1703 may include processing of a Non-Access Stratum (NAS) protocol, an RRC protocol, MAC CEs, and DCIs.

[0119] The baseband processor 1703 may perform MIMO encoding and precoding for beamforming.

[0120] The baseband processor 1703 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 1704, which will be described later.

[0121] The application processor 1704 is also referred to as a CPU, MPU, microprocessor, or processor core. The application processor 1704 may include multiple processors (multiple processor cores). The application processor 1704 executes a system software program (operating system (OS)) and various application programs (e.g., a calling application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 1706 or a memory not shown, thereby realizing various functions of the UE3.

[0122] In some implementations, the baseband processor 1703 and the application processor 1704 may be integrated on a single chip, as indicated by the dashed line (1705) in Figure 17. In other words, the baseband processor 1703 and the application processor 1704 may be implemented as a single System on Chip (SoC) device 1705. An SoC device may also be called a system Large Scale Integration (LSI) or a chipset.

[0123] The memory 1706 is volatile memory, nonvolatile memory, or a combination thereof. The memory 1706 may include multiple physically independent memory devices. The volatile memory is, for example, SRAM, DRAM, or a combination thereof. The nonvolatile memory is, for example, MROM, EEPROM, flash memory, or a hard disk drive, or any combination thereof. For example, the memory 1706 may include an external memory device accessible from the baseband processor 1703, the application processor 1704, and the SoC 1705. The memory 1706 may also include an internal memory device integrated within the baseband processor 1703, the application processor 1704, or the SoC 1705. Furthermore, the memory 1706 may include memory within a Universal Integrated Circuit Card (UICC).

[0124] The memory 1706 may store one or more software modules (computer programs) 1707 including instructions and data for performing the processing by the UE 3 described in the above-described embodiments. In some implementations, the baseband processor 1703 or the application processor 1704 may be configured to read and execute the software modules 1707 from the memory 1706, thereby performing the processing by the UE 3 described in the above-described embodiments using the drawings.

[0125] It should be noted that the control plane processing and operations performed by UE3 described in the above embodiment can be realized by elements other than the RF transceiver 1701 and the antenna array 1702, namely, at least one of the baseband processor 1703 and the application processor 1704, and the memory 1706 storing the software module 1707.

[0126] As described with reference to Figures 16 and 17, each of the processors included in the RAN nodes 1, 2, 4, 6, and 7 and the UE 3 according to the above-described embodiments can execute one or more programs including instructions for causing a computer to perform the algorithms described with reference to the drawings. The programs include instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The programs may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disk (DVD), Blu-ray® disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage device. The programs may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0127] The above-described embodiments are merely examples of application of the technical ideas obtained by the inventors of the present invention. In other words, the technical ideas are not limited to the above-described embodiments, and various modifications are possible.

[0128] For example, some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0129] (Appendix 1) User Equipment (UE), At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: Evaluating a plurality of execution conditions for a plurality of candidate target cells for the first conditional mobility; If an execution condition of one of the plurality of candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; reusing one or more execution conditions related to one or more candidate target cells other than the one candidate target cell for a subsequent second conditional mobility, and switching a reference cell in the one or more execution conditions from the source cell of the first conditional mobility to the one candidate target cell; It is configured as follows: UE. (Appendix 2) The first conditional mobility is a conditional handover, a conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or a conditional Secondary Node (SN) change; UE as described in Appendix 1. (Appendix 3) A method performed by User Equipment (UE), comprising: evaluating a plurality of execution conditions for a plurality of candidate target cells for the first conditional mobility; If an execution condition of one of the plurality of candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; and reusing one or more execution conditions related to one or more candidate target cells other than the one candidate target cell for a subsequent second conditional mobility, and switching a reference cell in the one or more execution conditions from the source cell of the first conditional mobility to the one candidate target cell; A method for providing the above. (Appendix 4) A program for causing a computer to perform a method for User Equipment (UE), The method comprises: evaluating a plurality of execution conditions for a plurality of candidate target cells for the first conditional mobility; If an execution condition of one of the plurality of candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; and reusing one or more execution conditions related to one or more candidate target cells other than the one candidate target cell for a subsequent second conditional mobility, and switching a reference cell in the one or more execution conditions from the source cell of the first conditional mobility to the one candidate target cell; A program that includes: (Appendix 5) User Equipment (UE), At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: Evaluating a plurality of execution conditions for a plurality of candidate target cells for the first conditional mobility; If an execution condition of one of the plurality of candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; Reusing one or more configurations of one or more candidate target cells other than the one candidate target cell for a subsequent second conditional mobility; receiving, from a Radio Access Network (RAN) node of the one candidate target cell, one or more updated execution conditions for the subsequent second conditional mobility for the one or more candidate target cells; It is configured as follows: UE. (Appendix 6) The first conditional mobility is a conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change or a conditional Secondary Node (SN) change; the Radio Access Network (RAN) node is a Secondary Node (SN) in dual connectivity; The at least one processor is configured to receive the updated one or more execution conditions from the SN via a Master Node (MN). UE as described in Appendix 5. (Appendix 7) A method performed by User Equipment (UE), comprising: evaluating a plurality of execution conditions for a plurality of candidate target cells for the first conditional mobility; If an execution condition for one of the plurality of candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; reusing one or more configurations of one or more candidate target cells other than the one candidate target cell for a subsequent second conditional mobility; and receiving, from a Radio Access Network (RAN) node of the one candidate target cell, one or more updated execution conditions for the subsequent second conditional mobility for the one or more candidate target cells; A method for providing the above. (Appendix 8) A Radio Access Network (RAN) node, comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: providing a plurality of configurations for a plurality of candidate target cells for a first conditional mobility of a User Equipment (UE); If one of the plurality of candidate target cells is selected by the UE, providing the UE with updated one or more execution conditions for the one or more candidate target cells to enable a subsequent second conditional mobility in which one or more settings of one or more candidate target cells other than the selected candidate target cell are reused by the UE; It is configured as follows: RAN node. (Appendix 9) The first conditional mobility is a conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change or a conditional Secondary Node (SN) change; the Radio Access Network (RAN) node is a Secondary Node (SN) in dual connectivity; The at least one processor is configured to provide the updated one or more execution conditions to the UE via a Master Node (MN). RAN node as described in Appendix 8. (Appendix 10) 1. A method performed by a Radio Access Network (RAN) node, comprising: providing a plurality of configurations for a plurality of candidate target cells for a first conditional mobility of a User Equipment (UE); and If one of the plurality of candidate target cells is selected by the UE, providing the UE with updated one or more execution conditions for the one or more candidate target cells to enable a subsequent second conditional mobility in which one or more settings of one or more candidate target cells other than the selected candidate target cell are reused by the UE; A method for providing the above. (Appendix 11) User Equipment (UE), At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: evaluating a plurality of execution conditions for one or more candidate target cells for the first conditional mobility from the source cell; If an execution condition for one of the one or more candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; maintaining the source cell configuration for reuse in a subsequent second conditional mobility after the first conditional mobility in which the source cell is a new candidate target cell; It is configured as follows: UE. (Appendix 12) the at least one processor is configured to receive an execution condition for the second conditional mobility for the new candidate target cell corresponding to the source cell in the first conditional mobility from a Radio Access Network (RAN) node of the one candidate target cell or from a Master Node (MN) when the RAN node is a Secondary Node (SN); UE as described in Appendix 11. (Appendix 13) A method performed by User Equipment (UE), comprising: evaluating a plurality of execution conditions for one or more candidate target cells for the first conditional mobility from the source cell; If an execution condition for one of the one or more candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; and maintaining a configuration of the source cell after the first conditional mobility for reuse in a subsequent second conditional mobility in which the source cell is a new candidate target cell; A method for providing the above. (Appendix 14) A Radio Access Network (RAN) node, comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: Receive a control message from a source node or a Master Node (MN) requesting preparation of a candidate target cell for a first conditional mobility of a User Equipment (UE); If the configuration of the candidate target cell provided to the UE for the first conditional mobility needs to be reused by the UE for a subsequent second conditional mobility after the first conditional mobility, apply a full configuration to the configuration of the candidate target cell without applying a delta configuration based on the configuration of the current source cell to the configuration of the candidate target cell. RAN node. (Appendix 15) The first conditional mobility is a conditional handover, a conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or a conditional Secondary Node (SN) change; The second conditional mobility is a conditional handover, an intra-SN conditional PSCell change, an inter-SN conditional PSCell change, or a conditional SN change. RAN node as described in Supplementary Note 14. (Appendix 16) 1. A method performed by a Radio Access Network (RAN) node, comprising: Receiving a control message from a source node or a Master Node (MN) requesting preparation of a candidate target cell for a first conditional mobility of a User Equipment (UE); and if the configuration of the candidate target cell provided to the UE for the first conditional mobility needs to be reused by the UE for a subsequent second conditional mobility after the first conditional mobility, applying a full configuration to the configuration of the candidate target cell without applying a delta configuration based on a configuration of a current source cell to the configuration of the candidate target cell; A method for providing the above. (Appendix 17) A Radio Access Network (RAN) node, comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor is configured to receive a control message from a source node or a Master Node (MN) requesting preparation of a candidate target cell for a first conditional mobility of a User Equipment (UE); The control message indicates a recommended operation mode in which the candidate target cell configuration provided to the UE for the first conditional mobility is reused by the UE for a subsequent second conditional mobility after the first conditional mobility; and the at least one processor is configured to send a second control message to the source node or the MN indicating a rejection of the preparation of the candidate target cell if the RAN node does not support the operation mode. RAN node. (Appendix 18) 1. A method performed by a Radio Access Network (RAN) node, comprising: receiving a control message from a source node or a Master Node (MN) requesting preparation of a candidate target cell for a first conditional mobility of a User Equipment (UE); wherein the control message indicates a recommended operation mode in which the candidate target cell configuration provided to the UE for the first conditional mobility is reused by the UE for a subsequent second conditional mobility after the first conditional mobility; and If the RAN node does not support the operation mode, sending a second control message to the source node or the MN indicating a rejection of the preparation of the candidate target cell; A method for providing the above. (Appendix 19) A Radio Access Network (RAN) node, comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor is configured to receive a control message from a source node or a Master Node (MN) requesting preparation of a candidate target cell for a first conditional mobility of a User Equipment (UE); The control message indicates a recommended operation mode in which the candidate target cell configuration provided to the UE for the first conditional mobility is reused by the UE for a subsequent second conditional mobility after the first conditional mobility; and the at least one processor is configured to, if the RAN node does not support the operation mode but can prepare the candidate target cell for the first conditional mobility, send a second control message to the source node or the MN indicating acceptance of configuration of the candidate target cell. RAN node. (Appendix 20) 1. A method performed by a Radio Access Network (RAN) node, comprising: receiving a control message from a source node or a Master Node (MN) requesting preparation of a candidate target cell for a first conditional mobility of a User Equipment (UE); wherein the control message indicates a recommended operation mode in which the candidate target cell configuration provided to the UE for the first conditional mobility is reused by the UE for a subsequent second conditional mobility after the first conditional mobility; and If the RAN node does not support the operation mode but is able to prepare the candidate target cell for the first conditional mobility, sending a second control message to the source node or the MN indicating acceptance of the configuration of the candidate target cell; A method for providing the above.

[0130] This application claims priority based on Japanese Patent Application No. 2021-215150, filed on December 28, 2021, the entire disclosure of which is incorporated herein by reference. [Explanation of symbols]

[0131] 1 Master Node (MN) 2. Source Secondary Node (S-SN) 3. User Equipment (UE) 4. Target Secondary Node (T-SN) 6 Source Node 7 Target Node 1504 processor 1505 memory 1506 modules 1603 Baseband Processor 1604 Application Processor 1606 memory 1607 Modules

Claims

1. A User Equipment (UE), at least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor evaluating a plurality of execution conditions for one or more candidate target cells for the first conditional mobility from the source cell; If an execution condition for one of the one or more candidate target cells is satisfied, performing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; maintaining the source cell configuration after the first conditional mobility for reuse in a subsequent second conditional mobility in which the source cell is a new candidate target cell; It is configured as follows: UE.

2. the at least one processor is configured to receive an execution condition for the second conditional mobility for the new candidate target cell corresponding to the source cell in the first conditional mobility from a Radio Access Network (RAN) node of the one candidate target cell or from a Master Node (MN) if the RAN node is a Secondary Node (SN). The UE of claim 1.

3. 1. A method performed by a User Equipment (UE), comprising: evaluating a plurality of execution conditions for one or more candidate target cells for the first conditional mobility from the source cell; If an execution condition for one of the one or more candidate target cells is satisfied, executing the first conditional mobility by applying a configuration corresponding to the one candidate target cell; and maintaining the source cell configuration for reuse in a subsequent second conditional mobility after the first conditional mobility in which the source cell is a new candidate target cell; A method for providing

4. The method further comprises receiving an execution condition for the second conditional mobility for the new candidate target cell corresponding to the source cell in the first conditional mobility from a Radio Access Network (RAN) node of the one candidate target cell, or from a Master Node (MN) if the RAN node is a Secondary Node (SN). The method of claim 3.

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