Method performed by user equipment

Abstract

To provide selective activation of cells within a single Radio Access Network (RAN) node through Layer 1 / Layer 2 (L1 / L2)-based mobility.SOLUTION: User Equipment (UE) receives configuration information from a RAN node, including information about candidate cells for L1 / L2-based mobility, performs L1 measurements for L1 / L2-based mobility, and when the execution of L1 / L2-based mobility is triggered, performs random access to switch the serving cell. At the time of completion of the random access execution, the UE's Medium Access Control (MAC) layer notifies the UE's Radio Resource Control (RRC) layer of the completion of the execution of L1 / L2-based mobility.SELECTED DRAWING: Figure 15

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 investigated mechanisms and procedures for realizing a function or operation mode called "MR-DC with selective activation of cell groups" and have found various problems.

[0007] One of these issues concerns the clarification of various procedures related to a feature or mode of operation called "MR-DC with selective activation of cell groups." For example, at present, the procedures for utilizing this feature or mode of operation when applied to intra-SN CPC are unclear. In addition, when a Radio Access Network (RAN) node (e.g., gNB) includes a Central Unit (CU) and one or more Distributed Units (DUs), the signaling required between the CU and one or more Distributed Units (DUs) to support this feature or mode of operation is unclear.

[0008] Another of these challenges relates to Layer 1 / layer 2 (L1 / L2)-based inter-cell mobility. According to Non-Patent Document 5, one of the objectives for 3GPP Release 18 is to specify the mechanisms and procedures for MR-DC with selective activation of cell groups through Layer 3 (L3) enhancements. However, certain scenarios, such as selective activation of cell groups within one RAN node (e.g., MN or SN), may be feasible with Layer 1 / layer 2 (L1 / L2)-based inter-cell mobility instead of L3-based inter-cell mobility.

[0009] 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]

[0010] A first aspect is directed to a RAN node configured to operate as an SN associated with a Secondary Cell Group (SCG) in dual connectivity for a UE, 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 transmit, to the UE via an MN or via a direct signaling radio bearer between the SN and the UE, a first SN Radio Resource Control (RRC) message including configurations of multiple candidate PSCells for a first conditional PSCell change. The first SN RRC message indicates that an operation mode is applicable, required, recommended, or available in which configurations of at least one candidate PSCell not selected in the first conditional PSCell change are reused by the UE for a subsequent second conditional PSCell change.

[0011] A second aspect is directed to a method performed by a RAN node configured to operate as an SN associated with an SCG in dual connectivity for a UE, the method including transmitting to the UE via an MN or via a direct signaling radio bearer between the SN and the UE a first SN RRC message including configuration of multiple candidate PSCells for a first conditional PSCell change, the first SN RRC message indicating that an operation mode is applicable, required, recommended, or available in which the configuration of at least one candidate PSCell not selected in the first conditional PSCell change is reused by the UE for a subsequent second conditional PSCell change.

[0012] A third aspect is directed to a UE, 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 first SN RRC message, via an MN or via a direct signaling radio bearer between the UE and an SN, including configurations of multiple candidate PSCells for a first conditional PSCell change. The at least one processor is configured to, if an execution condition for one of the multiple candidate PSCells is satisfied, apply a configuration corresponding to the one candidate PSCell for which the execution condition is satisfied. The at least one processor is further configured to, if the first SN RRC message indicates that an operation mode for the configuration of at least one candidate PSCell not selected in the first conditional PSCell change is applicable, required, recommended, or available to be reused by the UE for a subsequent second conditional PSCell change, maintain the configuration of the at least one candidate PSCell for use in the second conditional PSCell change.

[0013] A fourth aspect is directed to a method performed by a UE, the method including the steps of: (a) receiving, via an MN or via a direct signaling radio bearer between the UE and an SN, a first SN RRC message including configuration of multiple candidate PSCells for a first conditional PSCell change; (b) if an execution condition of one of the plurality of candidate PSCells is satisfied, applying a configuration corresponding to the one candidate PSCell whose execution condition is satisfied; and (c) if the first SN RRC message indicates that the configuration of at least one candidate PSCell not selected in the first conditional PSCell change is applicable, required, recommended, or available for reuse by the UE for a subsequent second conditional PSCell change, maintaining the configuration of the at least one candidate PSCell for use in the second conditional PSCell change.

[0014] A fifth aspect is directed to a Central Unit (CU) of a RAN node. The CU 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 send a first message to a Distributed Unit (DU) and receive a second message from the DU in response to the first message. The first message indicates a request for a first conditional mobility for a UE. Additionally, the first message indicates that an operation mode is applicable, required, recommended, or available, in which configurations of at least one candidate target cell not selected in the first conditional mobility are reused by the UE for a subsequent second conditional mobility.

[0015] A sixth aspect is directed to a method performed by a CU of a RAN node, the method including sending a first message to a DU and receiving a second message from the DU in response to the first message, the first message indicating a request for a first conditional mobility for a UE, and indicating that an operation mode is applicable, required, recommended, or available in which configurations of at least one candidate target cell not selected in the first conditional mobility are reused by the UE for a subsequent second conditional mobility.

[0016] A seventh aspect is directed to a DU of a RAN node. The DU 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 receive a first message from a CU and send a second message to the CU in response to the first message. The first message indicates a request for a first conditional mobility for a UE. Additionally, the first message indicates that an operation mode is applicable, required, recommended, or available in which configurations of at least one candidate target cell not selected in the first conditional mobility are reused by the UE for a subsequent second conditional mobility.

[0017] An eighth aspect is directed to a method performed by a DU of a RAN node, the method including receiving a first message from a CU and sending a second message to the CU in response to the first message, the first message indicating a request for a first conditional mobility for a UE, and indicating that an operation mode is applicable, required, recommended, or available in which configurations of at least one candidate target cell not selected in the first conditional mobility are reused by the UE for a subsequent second conditional mobility.

[0018] A ninth aspect is directed to a CU of a RAN node, the CU including at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to receive a first message from a first DU indicating candidate target cells that a UE has successfully accessed during a first conditional mobility, the first message indicating that the readiness of other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility.

[0019] A tenth aspect is directed to a method performed by a CU of a RAN node, the method including receiving a first message from a first DU indicating candidate target cells that a UE successfully accessed during a first conditional mobility, the first message indicating that provisions of other candidate target cells accepted for the first conditional mobility are maintained for a subsequent second conditional mobility.

[0020] An eleventh aspect is directed to a DU of a RAN node, the DU including at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to send a first message to a CU indicating candidate target cells that a UE has successfully accessed during a first conditional mobility, the first message indicating that the readiness of other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility.

[0021] A twelfth aspect is directed to a method performed by a DU of a RAN node, the method including sending a first message to a CU indicating candidate target cells that a UE successfully accessed during a first conditional mobility, the first message indicating that the readiness of other candidate target cells accepted for the first conditional mobility are maintained for a subsequent second conditional mobility.

[0022] A thirteenth aspect is directed to a CU of a RAN node, the CU including at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to receive a first message from a first DU indicating candidate target cells that a UE successfully accessed during a first conditional mobility, and the at least one processor configured, after receiving the first message, to send a second message to a second DU indicating that the readiness of one or more candidate target cells for the first conditional mobility should be maintained for a subsequent second conditional mobility.

[0023] A fourteenth aspect is directed to a method performed by a CU of a RAN node, the method including the steps of: (a) receiving a first message from a first DU indicating candidate target cells that the UE successfully accessed during a first conditional mobility; and (b) after receiving the first message, sending a second message to a second DU indicating that the readiness of one or more candidate target cells for the first conditional mobility needs to be maintained for a subsequent second conditional mobility;

[0024] A fifteenth aspect is directed to a CU of a RAN node, the CU including at least one memory and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to receive, from a first DU, a first message indicating candidate target cells that a UE has successfully accessed during a first conditional mobility. Additionally, the at least one processor is configured, after receiving the first message, to send a second message to a source DU serving the source cell indicating that a configuration of the source cell for the first conditional mobility should be maintained for a subsequent second conditional mobility.

[0025] A sixteenth aspect is directed to a method performed by a CU of a RAN node, the method including the steps of: (a) receiving a first message from a first DU indicating candidate target cells that the UE successfully accessed during a first conditional mobility; and (b) after receiving the first message, sending a second message to a source DU that serves the source cell, informing the source DU that the source cell configuration of the first conditional mobility needs to be maintained for a subsequent second conditional mobility;

[0026] A seventeenth aspect is directed to a UE 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, from a RAN node, configurations of multiple candidate cell group (CG) sets, each of which includes a different candidate special cell (SpCell). The at least one processor is further configured to select one candidate SpCell through Layer 1 / layer 2-based inter-cell mobility and apply the configuration of the candidate CG set corresponding to the selected candidate SpCell.

[0027] An eighteenth aspect is directed to a method performed by a UE, the method including the following steps: (a) a candidate SpCell receives configurations of multiple different candidate CG sets from a RAN node; and (b) Selecting one candidate SpCell by Layer 1 / layer 2-based inter-cell mobility and applying the configuration of the candidate CG set corresponding to the selected candidate SpCell.

[0028] A nineteenth 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 a method according to any of the above aspects. [Effects of the Invention]

[0029] 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]

[0030] [Figure 1] 1 is a diagram illustrating an example of the configuration of a wireless communication system according to an embodiment. [Figure 2] FIG. 1 is a diagram illustrating a configuration example of a RAN node according to an embodiment. [Figure 3] 10 is a flowchart showing an example of the operation of a RAN node (ie, SN) according to an embodiment. [Figure 4] 10 is a flowchart illustrating an example of an operation of a UE according to the embodiment. [Figure 5A] FIG. 10 is a sequence diagram illustrating an example of signaling related to Intra-SN CPC (or conditional SN modification) according to an embodiment. [Figure 5B] FIG. 10 is a sequence diagram illustrating an example of signaling related to Intra-SN CPC (or conditional SN modification) according to an embodiment. [Figure 6A] FIG. 10 is a sequence diagram illustrating an example of signaling related to Intra-SN CPC (or conditional SN modification) according to an embodiment. [Figure 6B] FIG. 10 is a sequence diagram illustrating an example of signaling related to Intra-SN CPC (or conditional SN modification) according to an embodiment. [Figure 7] FIG. 10 is a sequence diagram showing an example of signaling between a CU and a DU according to the embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of the format of a UE CONTEXT MODIFICATION REQUEST message according to the embodiment. [Figure 9]FIG. 10 is a diagram illustrating an example of a format of a UE CONTEXT MODIFICATION RESPONSE message according to the embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of the format of a UE CONTEXT SETUP REQUEST message according to the embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of a format of a UE CONTEXT SETUP RESPONSE message according to the embodiment. [Figure 12] FIG. 10 is a sequence diagram showing an example of signaling between a CU and a DU according to the embodiment. [Figure 13] FIG. 10 is a sequence diagram showing an example of signaling between a CU and a DU according to the embodiment. [Figure 14] FIG. 10 is a sequence diagram showing an example of signaling between a CU and a DU according to the embodiment. [Figure 15] 10 is a flowchart illustrating an example of an operation of a UE according to the embodiment. [Figure 16] FIG. 2 is a sequence diagram illustrating an example of signaling related to L1 / L2-based inter-cell mobility according to an embodiment. [Figure 17] FIG. 2 is a block diagram illustrating a configuration example of a RAN node according to the embodiment. [Figure 18] FIG. 2 is a block diagram illustrating an example of the configuration of a UE according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 a RAN node 1, a RAN node 2, and a 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 the dedicated hardware, or as a virtualized function instantiated on an application platform.

[0036] The 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, the RAN node 1 may be a CU-CP or a combination of a CU-CP and a CU-UP. Similarly, the RAN node 2 may be a CU or a combination of a CU and one or more DUs. The RAN node 2 may be a CU-CP or a combination of a CU-CP and a CU-UP.

[0037] Each of RAN nodes 1 and 2 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 node 2.

[0038] 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 act as a master node (MN) and a secondary node (SN) of dual connectivity, respectively. Therefore, hereinafter, RAN node 1 may be referred to as MN1, and RAN node 2 may be referred to as candidate SN2.

[0039] 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 SN2 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 SN2. In NGEN-DC, UE3 is connected to an ng-eNB operating as MN1 and a gNB operating as SN2. In NE-DC, UE3 is connected to a gNB operating as MN1 and a ng-eNB operating as SN2. In NR-DC, UE3 is connected to one gNB (or gNB-DU) operating as MN1 and another gNB (or gNB-DU) operating as SN2.

[0040] The MCG is a group of serving cells associated with (or provided by) 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) SN2, and includes a Primary SCG Cell (PSCell) and optionally one or more Secondary Cells (SCells). A 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.

[0041] 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).

[0042] 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. 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 CPA execution conditions are met.

[0043] Although not shown in FIG. 1, multiple candidate cells (i.e., 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) of 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.

[0044] The configuration of each candidate PSCell is generated by the 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 a radio bearer (RB) configuration, a 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 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).

[0045] Meanwhile, a CPA execution condition is generated by the MN1. 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, and may be, for example, CondEvent A3, CondEvent A4, or CondEvent A5. 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 CPA execution conditions. If the execution conditions for one candidate PSCell are met, 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 conditions are 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] One or both of RAN nodes 1 and 2 may have the configuration shown in Figure 2. Each element (network function) shown in Figure 2 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. One or both of RAN nodes 1 and 2 may include, but are not limited to, a CU 21 and one or more DUs 22 as shown in Figure 2. The CU 21 and each DU 22 are connected by an interface 201. A UE 3 is connected to at least one DU 22 via at least one air interface 202.

[0051] CU21 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). DU22 may be a logical node that hosts the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of the gNB. If CU21 is a gNB-CU and DUs22 are gNB-DUs, interface 201 may be an F1 interface. CU21 may include a CU-CP and a CU-UP.

[0052] 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).

[0053] 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.

[0054] 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).

[0055] 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.

[0056] 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.

[0057] First Embodiment This embodiment provides an improvement of intra-SN CPC for selective CG activation. Specifically, this embodiment relates to clarifying various procedures related to selective CG / cell activation. An example of the configuration of a wireless communication system according to this embodiment may be the same as the example shown in FIGS. 1 and 2.

[0058] In some implementations, when starting intra-SN CPC, the SN2 determines whether to perform, use, prepare, or recommend selective CG activation. In other words, when providing the CPC configuration for the first CPC to the UE3, the SN2 determines whether the configuration of at least one candidate PSCell that was not selected in the first CPC needs to be maintained by the UE3 for the subsequent second CPC. If it is determined to perform, use, prepare, or recommend selective CG activation, the SN2 operates as shown in FIG. 3.

[0059] In step 301, an SN RRC message is generated that includes a configuration of multiple candidate PSCells for a first CPC and an indication of selective CG activation. The indication of selective CG activation indicates to the UE 3 that selective CG activation is applied, required, recommended, or available. In other words, the indication of selective CG activation indicates that an operating mode in which the configuration of at least one candidate PSCell not selected in the first CPC is reused by the UE 3 for a subsequent second CPC is applied, required, recommended, or available. The indication of selective CG activation may also be referred to as selective CG activation configuration, for example. In step 302, the SN 2 transmits the generated SN RRC message to the UE 3. The SN 2 may send the SN RRC message to the UE 3 via the MN 1 or via a direct signaling radio bearer (i.e., Signaling Radio Bearer 3 (SRB3)) between the SN 2 and the UE 3.

[0060] Figure 4 shows the operation of UE3 corresponding to the operation of SN2 in Figure 3. In step 401, UE3 receives from SN2 an SN RRC message including configuration of multiple candidate PSCells for a first CPC and an indication of selective CG activation. In step 402, if an execution condition of one of the multiple candidate PSCells is satisfied, UE3 applies the configuration corresponding to the selected one candidate PSCell (i.e., the candidate PSCell whose execution condition is satisfied). In step 403, if the SN RRC message of step 401 includes an indication of selective CG activation, UE3 maintains the configuration of at least one candidate PSCell not selected in the first CPC for use in a subsequent second CPC.

[0061] The operations of the SN2 and the UE3 described with reference to Figures 3 and 4 may be modified as appropriate. For example, after the completion of the first CPC, the SN2 may update or modify the CPC execution condition for at least one candidate PSCell that was not selected in the first CPC for the second CPC. For example, the SN2 may switch the reference cell in one or more CPC execution conditions (e.g., CondEvent A3 or CondEvent A5) from the source PSCell of the initial CPC to the PSCell selected in the first CPC. In this case, after the completion of the first CPC, the SN2 may send an SN RRC message to the UE3 including the updated or modified CPC execution condition for the second CPC. The UE3 may receive the SN RRC message and update the CPC execution condition for at least one candidate PSCell that was not selected in the first CPC.

[0062] For example, the UE 3 may reuse an execution condition for a candidate PSCell not selected in a first CPC for a subsequent second CPC and autonomously switch a reference cell in the execution condition from the source PSCell of the first CPC to the candidate PSCell selected in the first CPC. That is, the UE 3 may autonomously update or modify the reference cell of the execution condition of the first CPC. This allows the UE 3 to start evaluating the execution condition for the subsequent second CPC without receiving signaling from the SN 2 to update the execution condition.

[0063] For example, the UE 3 may maintain the configuration of the source PSCell of the first CPC without releasing it after the completion of the first CPC in order to use the source PSCell as one of the candidate PSCells in the second CPC. This may enable the source cell of the CPC to be used as one of the candidate PSCells in the subsequent CPC. The SN 2 may inform the UE 3 whether the source PSCell of the first CPC is to be a candidate PSCell in the subsequent second CPC. Specifically, the SN 2 may use the SN RRC message (step 302 in FIG. 3 , step 401 in FIG. 4 ) sent to the UE 3 to configure the first CPC to indicate to the UE 3 that the source PSCell of the first CPC is to be one of the candidate PSCells in the subsequent second CPC. If the SN RRC message (step 302 in FIG. 3 , step 401 in FIG. 4 ) indicates so, the UE 3 may maintain the configuration of the source PSCell without releasing it after the completion of the first CPC.

[0064] After the completion of the first CPC, the SN2 may send to the UE3 an execution condition for a subsequent second conditional mobility for a new candidate PSCell corresponding to the source PSCell of the first CPC. The SN2 may send the execution condition to the UE3 using an SN RRC message. The UE3 may receive from the SN2 the CPC execution condition for the new candidate PSCell corresponding to the source PSCell of the first CPC and use it for the second CPC.

[0065] 5A and 5B show an example of signaling of an intra-SN CPC procedure in which a direct SRB (i.e., SRB3) between SN2 and UE3 is used. In step 501, SN2 sends an SN RRC Reconfiguration message to UE3 via SRB3 to configure CPC. The SN RRC Reconfiguration message includes a CPC configuration and a selective CG activation indication (or setting). As described above, the CPC configuration for intra-SN CPC includes the configuration of one or more candidate PSCells and associated CPC execution conditions. There is no particular limitation on how the CPC configuration and the selective CG activation configuration are included in the SN RRC Reconfiguration message. Specifically, an information element (IE) or field indicating the CPC configuration may be independent of an IE or field indicating the selective CG activation configuration. In this case, an IE or field indicating the selective CG activation configuration may mean that the associated CPC configuration applies to selective CG activation (or is subject to selective CG activation). Alternatively, an information element (IE) or field indicating a CPC configuration may include an IE or field indicating a selective CG activation configuration, or vice versa. For example, an IE or field indicating a CPC configuration may be condRRCReconfig, and the SN RRC Reconfiguration message it contains may further include an IE or field indicating a selective CG activation configuration. In this case, it may mean that the configuration specified by the SN RRC Reconfiguration applies to (or is subject to) selective CG activation.The IE or field indicating the selective CG activation setting may be, for example, selectiveCG-Activation, adaptiveCG-Switch, subsequentCell-Change, subsequentCG-Change, or cpc-Kept.

[0066] In step 502, the UE 3 applies the new configuration and starts evaluating the CPC execution conditions for multiple candidate PSCells. The UE 3 maintains the connection with the source PSCell and responds via the SRB 3 to the SN 2 with an SN RRC Reconfiguration Complete message.

[0067] In step 503, if the execution conditions for one candidate PSCell (here, candidate cell #1) are met, the UE 3 starts CPC execution while keeping the selective CG activation configuration (and CPC configuration). Specifically, the UE 3 detaches from the source PSCell, applies the stored configuration corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution conditions are met), and synchronizes with the candidate PSCell. In step 504, the UE 3 completes the CPC execution procedure by sending an SN RRC Reconfiguration Complete message to the selected candidate PSCell (i.e., Cell #1).

[0068] After the CPC execution is completed, the UE 3 maintains the configuration of one or more non-selected candidate PSCells for reuse in a subsequent CPC. The UE 3 may maintain the CPC execution conditions associated with the non-selected candidate PSCells. As described above, the UE 3 may autonomously change the reference cell of these CPC execution conditions from the source PSCell to the selected candidate PSCell (i.e., Cell #1). The UE 3 may determine whether to autonomously change the reference cell of the CPC execution condition based on the selective CG activation configuration received in step 501. Alternatively, the UE 3 may receive updated or modified CPC execution conditions from the SN 2.

[0069] Furthermore, the UE 3 may use the source PSCell of the first CPC as one of the candidate PSCells of the subsequent CPC. The UE 3 may determine whether to use the source PSCell of the first CPC as a new candidate PSCell based on the selective CG activation configuration received in step 501.

[0070] In step 505, the UE 3 may receive an SN RRC Reconfiguration message from the SN 2 via the SRB 3, indicating updated or modified CPC execution conditions. This SN RRC Reconfiguration message may include the CPC execution conditions for the source PSCell of the initial CPC, which is to become the new candidate PSCell. In step 506, the UE 3 applies the received CPC execution conditions and responds to the SN 2 via the SRB 3 with an SN RRC Reconfiguration Complete message. If no update, modification, or addition of CPC execution conditions is required, steps 505 and 506 may be omitted.

[0071] After the initial CPC is completed, the UE 3 continues to evaluate the execution conditions of the non-selected candidate PSCell(s). The UE 3 may start evaluating the CPC execution conditions for the source PSCell of the initial CPC, which is now the new candidate PSCell. In step 507, if the execution conditions of one candidate PSCell (here, candidate cell #2) are met, the UE 3 starts CPC execution while keeping the selective CG activation configuration (and CPC configuration). Specifically, the UE 3 detaches from the current source PSCell (i.e., Cell #1), applies the stored configuration corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution conditions are met), and synchronizes with the selected candidate PSCell. In step 508, the UE 3 completes the CPC execution procedure by sending an SN RRC Reconfiguration Complete message to the selected candidate PSCell (i.e., Cell #2).

[0072] After step 508, the UE 3 may continue to evaluate the CPC execution conditions of the remaining non-selected candidate PSCell(s). The UE 3 may autonomously change the reference cell of these CPC execution conditions from the source PSCell (i.e., Cell #1) to the selected candidate PSCell (i.e., Cell #2). The UE 3 may determine whether to autonomously change the reference cell of the CPC execution condition based on the selective CG activation configuration received in step 501. Alternatively, the UE 3 may receive updated or modified CPC execution conditions from the SN 2. Furthermore, the UE 3 may use the source PSCell (i.e., Cell #1) as one of the candidate PSCells. The UE 3 may determine whether to set the source PSCell (i.e., Cell #1) as a new candidate PSCell based on the selective CG activation configuration received in step 501.

[0073] 6A and 6B show an example of signaling of an intra-SN CPC procedure in which a direct SRB (i.e., SRB3) between SN2 and UE3 is not used. The procedures of FIGS. 6A and 6B are the same as those of FIGS. 5A and 5B, except that the transfer of SN RRC messages between SN2 and UE3 is performed via MN1. Specifically, steps 601 and 602 correspond to step 501. In step 601, SN2 sends an SN Modification Required message to MN1, which includes an SN RRC Reconfiguration message including CPC settings. In step 602, MN1 includes the SN RRC Reconfiguration message in an MN RRC Reconfiguration message and forwards it to UE3.

[0074] Steps 603 and 604 correspond to step 502. In step 603, UE3 responds to MN1 with an MN RRC Reconfiguration message that includes an SN RRC Reconfiguration Complete message. UE3 maintains the connection with the source PSCell and starts evaluating CPC execution conditions for multiple candidate PSCells. In step 604, MN1 forwards the SN RRC Reconfiguration Complete message to SN2, including it in an SN Modification Confirm message.

[0075] Step 605 corresponds to step 503. Steps 606 and 607 correspond to step 504. In step 606, UE3 completes the CPC execution procedure by sending a UL Information Transfer MRDC message to MN1. The UL Information Transfer MRDC message includes an (embedded) SN RRC Reconfiguration Complete message to the selected candidate PSCell (i.e., Cell #1). In step 607, MN1 forwards the SN RRC Reconfiguration Complete message to SN2, including it in an RRC Transfer message.

[0076] Steps 608 and 609 correspond to step 505. In step 608, the SN2 may send an SN Modification Required message to the MN1, which message contains an SN RRC Reconfiguration message indicating the updated or modified CPC execution conditions. In step 609, the MN1 forwards the SN RRC Reconfiguration message to the UE3, including it in an MN RRC Reconfiguration message.

[0077] Steps 610 and 611 correspond to step 506. In step 610, UE3 responds to MN1 with an MN RRC Reconfiguration message that includes an SN RRC Reconfiguration Complete message. In step 611, MN1 forwards the SN RRC Reconfiguration Complete message to SN2, including it in an SN Modification Confirm message.

[0078] Step 612 corresponds to step 507. Steps 613 and 614 correspond to step 508. In step 613, UE3 completes the CPC execution procedure by sending a UL Information Transfer MRDC message to MN1. The UL Information Transfer MRDC message includes an (embedded) SN RRC Reconfiguration Complete message to the selected candidate PSCell (i.e., Cell #2). In step 607, MN1 forwards the SN RRC Reconfiguration Complete message to SN2, including it in an RRC Transfer message.

[0079] <Second embodiment> This embodiment provides details of signaling between a CU and a DU to support selective cell / CG activation. A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in FIGS. 1 and 2.

[0080] The SN2 of this embodiment may have the CU-DU configuration shown in Fig. 2. The SN2 may include a CU 21 and one or more DUs 22. In this case, the SN2 supports intra-DU conditional mobility of a UE 3 within one DU. Similarly, the SN2 supports inter-DU conditional mobility of a UE 3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CPC or CPA. Inter-DU conditional mobility may be inter-SN CPC.

[0081] Additionally or alternatively, the MN 1 of this embodiment may have the CU-DU configuration shown in Fig. 2. The MN 21 may include a CU 21 and one or more DUs 22. In this case, the MN 1 supports intra-DU conditional mobility of the UE 3 within one DU. Similarly, the MN 1 supports inter-DU conditional mobility of the UE 3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CHO, i.e., conditional intra-MN handover (or conditional PCell change).

[0082] 7 shows an example of signaling between CU21 and DU22. As mentioned above, CU21 and DU22 may belong to SN2 or MN1. In step 701, CU21 sends a CU-DU control message (e.g., F1AP message) to DU22 indicating a request for first conditional mobility for UE3. The control message requests DU22 to prepare one or more candidate target cells for the first conditional mobility for UE3. The first conditional mobility may be any of CHO, CPA, and CPC. When the first conditional mobility is CPA or CPC, the candidate target cell means a candidate (target) PSCell.

[0083] In addition, the control message of step 701 includes an indication of selective cell / CG activation. The indication of selective cell / CG activation indicates to the DU 22 that selective cell / CG activation is applied, requested, recommended, or available. In other words, the indication of selective cell / CG activation indicates that an operation mode in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE 3 for the subsequent second conditional mobility is applied, requested, recommended, or available. The indication of selective cell / CG activation may also be rephrased as a request for selective cell / CG activation, for example. The first and second conditional mobility may both be CHO. The first and second conditional mobility may both be CPC. Alternatively, the first conditional mobility may be CPA and the second conditional mobility may be CPC. This allows the DU 22 to recognize whether the preparation of candidate target cells for the first conditional mobility needs to be maintained even after the first conditional mobility to any of the candidate target cells is completed.

[0084] In step 702, the DU 22 sends a response message to the CU 21. The response message may indicate whether the DU 22 has determined that selective cell / CG activation does not apply to one or more candidate target cells prepared by the DU 22. Alternatively, the response message may indicate whether the DU 22 has prepared selective cell / CG activation for one or more candidate target cells prepared by the DU 22. If the DU 22 can accept the preparation of one or more candidate target cells for the first conditional mobility but cannot accept the request for selective cell / CG activation, the DU 22 may inform the CU 21 of the acceptance of the preparation for the first conditional mobility and the rejection of selective cell / CG activation in the response message.

[0085] The request message in step 701 may be a UE CONTEXT MODIFICATION REQUEST message or a UE CONTEXT SETUP REQUEST message. The response message in step 702 may be a UE CONTEXT MODIFICATION RESPONSE message or a UE CONTEXT SETUP RESPONSE message. More specifically, if the first conditional mobility is intra-DU mobility, the request message in step 701 may be a UE CONTEXT MODIFICATION REQUEST message, and the response message in step 702 may be a UE CONTEXT MODIFICATION RESPONSE message. If the first conditional mobility is inter-DU mobility, the request message in step 701 may be a UE CONTEXT SETUP REQUEST message, and the response message in step 702 may be a UE CONTEXT SETUP RESPONSE message.

[0086] 8 shows an example of the format of the UE CONTEXT MODIFICATION REQUEST message. In the example of FIG. 8, if the Selective CG Activation IE is included in the Conditional Intra-DU Mobility Information IE in the UE CONTEXT MODIFICATION REQUEST message, the DU 22 recognizes that selective cell / CG activation is applied, required, recommended, or available for the first conditional mobility indicated by the Conditional Intra-DU Mobility Information IE. In other words, the DU 22 recognizes that it is requested to maintain the preparation for the first conditional mobility indicated by the Conditional Intra-DU Mobility Information IE for subsequent conditional mobility after the first conditional mobility.

[0087] The format of Fig. 8 may be modified as appropriate. For example, one of the possible values ​​of the CHO Trigger IE, which is an enumerated IE, may be a value indicating a selective cell / CG activation request (e.g., Selective CG Activation-initiation).

[0088] 9 shows an example of the format of the UE CONTEXT MODIFICATION RESPONSE message. In the example of FIG. 9, if the Selective CG Activation IE is included in the UE CONTEXT MODIFICATION RESPONSE message, the IE indicates whether selective cell / CG activation has been accepted (or prepared) by the DU 22.

[0089] 10 shows a specific example of the format of a UE CONTEXT SETUP REQUEST message. In the example of FIG. 10, if the Selective CG Activation IE is included in the Conditional Inter-DU Mobility Information IE in the UE CONTEXT SETUP REQUEST message, the DU 22 recognizes that selective cell / CG activation is applied, required, recommended, or available for the first conditional mobility indicated by the Conditional Inter-DU Mobility Information IE. In other words, the DU 22 recognizes that it is requested to maintain the preparation for the first conditional mobility indicated by the Conditional Inter-DU Mobility Information IE for subsequent conditional mobility after the first conditional mobility.

[0090] The format of Fig. 10 may be modified as appropriate. For example, one of the possible values ​​of the CHO Trigger IE, which is an enumerated IE, may be a value indicating a selective cell / CG activation request (e.g., Selective CG Activation-initiation).

[0091] Figure 11 shows an example of the format of a UE CONTEXT SETUP RESPONSE message. In the example of Figure 11, if a Selective CG Activation IE is included in the UE CONTEXT SETUP RESPONSE message, the IE indicates whether selective cell / CG activation has been accepted (or prepared) by the DU 22.

[0092] The signaling between the CU and DU described in this embodiment can contribute to supporting selective cell / CG activation in a CU-DU configuration.

[0093] <Third embodiment> This embodiment provides details of signaling between a CU and a DU to support selective cell / CG activation. A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in FIGS. 1 and 2.

[0094] The SN2 of this embodiment may have the CU-DU configuration shown in Fig. 2. The SN2 may include a CU 21 and one or more DUs 22. In this case, the SN2 supports intra-DU conditional mobility of a UE 3 within one DU. Similarly, the SN2 supports inter-DU conditional mobility of a UE 3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CPC or CPA. Inter-DU conditional mobility may be inter-SN CPC.

[0095] Additionally or alternatively, the MN 1 of this embodiment may have the CU-DU configuration shown in Fig. 2. The MN 21 may include a CU 21 and one or more DUs 22. In this case, the MN 1 supports intra-DU conditional mobility of the UE 3 within one DU. Similarly, the MN 1 supports inter-DU conditional mobility of the UE 3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CHO, i.e., conditional intra-MN handover (or conditional PCell change).

[0096] 12 shows an example of signaling between the CU21 and the target DU22A. In step 1201, the target DU22A sends a CU-DU control message (e.g., F1AP message) to the CU21, indicating candidate target cells that the UE3 has successfully accessed during the first conditional mobility. The control message may be an ACCESS SUCCESS message. The first conditional mobility may be any of CHO, CPA, and CPC. When the first conditional mobility is CPA or CPC, the candidate target cells refer to candidate (target) PSCells.

[0097] In addition, the control message indicates that the preparation of other candidate target cells accepted by the target DU 22A for the first conditional mobility is maintained for the subsequent second conditional mobility. Both the first and second conditional mobility may be CHO. Both the first and second conditional mobility may be CPC. Alternatively, the first conditional mobility may be CPA and the second conditional mobility may be CPC. This allows the CU 21 to recognize that the preparation of candidate target cells by the target DU 22A for the first conditional mobility is maintained even after the first conditional mobility to the selected candidate target cell is completed.

[0098] In response to receiving the message of step 1201, CU21 may operate as follows: After receiving the message of step 1201, CU21 may inform a target DU of the first conditional mobility, different from target DU 22A, that the readiness of one or more candidate target cells for the first conditional mobility needs to be maintained for the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message, so that the other target DUs can know that the readiness of candidate target cells for the first conditional mobility needs to be maintained even after the first conditional mobility is completed.

[0099] Additionally or alternatively, after receiving the message of step 1201, CU21 may inform the source DU that provides the source cell of the first conditional mobility that the configuration of the source cell needs to be maintained for the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. This allows the source DU to know that the configuration of the source cell of the first conditional mobility needs to be maintained for the subsequent second conditional mobility. In other words, the source DU can know that the source cell of the first conditional mobility is one of the candidate target cells for the subsequent second conditional mobility.

[0100] <Fourth embodiment> This embodiment provides details of signaling between a CU and a DU to support selective cell / CG activation. A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in FIGS. 1 and 2.

[0101] The SN2 of this embodiment may have the CU-DU configuration shown in Fig. 2. The SN2 may include a CU 21 and one or more DUs 22. In this case, the SN2 supports intra-DU conditional mobility of a UE 3 within one DU. Similarly, the SN2 supports inter-DU conditional mobility of a UE 3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CPC or CPA. Inter-DU conditional mobility may be inter-SN CPC.

[0102] Additionally or alternatively, the MN 1 of this embodiment may have the CU-DU configuration shown in Fig. 2. The MN 21 may include a CU 21 and one or more DUs 22. In this case, the MN 1 supports intra-DU conditional mobility of the UE 3 within one DU. Similarly, the MN 1 supports inter-DU conditional mobility of the UE 3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CHO, i.e., conditional intra-MN handover (or conditional PCell change).

[0103] 13 shows an example of signaling between CU 21 and two target DUs 22A and 22B. In step 1301, target DU 22A sends a CU-DU control message (e.g., F1AP message) to CU 21 indicating candidate target cells that UE 3 has successfully accessed during the first conditional mobility. The control message may be identical to the existing ACCESS SUCCESS message.

[0104] In step 1302, after receiving the message in step 1301, CU21 informs the target DU 22B of the first conditional mobility, which is different from the target DU 22A, that the readiness of one or more candidate target cells for the first conditional mobility needs to be maintained for the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message, so that the target DU 22B knows that the readiness of the candidate target cells for the first conditional mobility needs to be maintained even after the first conditional mobility is completed.

[0105] Furthermore, after receiving the message of step 1301, CU21 may inform the source DU that provides the source cell of the first conditional mobility that the configuration of the source cell needs to be maintained for the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. This allows the source DU to know that the configuration of the source cell of the first conditional mobility needs to be maintained for the subsequent second conditional mobility. In other words, the source DU can know that the source cell of the first conditional mobility is one of the candidate target cells for the subsequent second conditional mobility.

[0106] The operations of CU11, MN1, candidate SN4, and UE3 shown in FIG. 13 may be modified as follows.

[0107] <Fifth embodiment> This embodiment provides details of signaling between a CU and a DU to support selective cell / CG activation. A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in FIGS. 1 and 2.

[0108] The SN2 of this embodiment may have the CU-DU configuration shown in Fig. 2. The SN2 may include a CU 21 and one or more DUs 22. In this case, the SN2 supports intra-DU conditional mobility of a UE 3 within one DU. Similarly, the SN2 supports inter-DU conditional mobility of a UE 3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CPC or CPA. Inter-DU conditional mobility may be inter-SN CPC.

[0109] Additionally or alternatively, the MN 1 of this embodiment may have the CU-DU configuration shown in Fig. 2. The MN 21 may include a CU 21 and one or more DUs 22. In this case, the MN 1 supports intra-DU conditional mobility of the UE 3 within one DU. Similarly, the MN 1 supports inter-DU conditional mobility of the UE 3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CHO, i.e., conditional intra-MN handover (or conditional PCell change).

[0110] 14 shows an example of signaling between CU 21 and two target DUs 22A and 22B. In step 1401, target DU 22A sends a CU-DU control message (e.g., F1AP message) to CU 21 indicating candidate target cells that UE 3 has successfully accessed during the first conditional mobility. The control message may be identical to the existing ACCESS SUCCESS message.

[0111] In step 1402, after receiving the message in step 1401, the CU21 notifies the source DU22S, which provides the source cell of the first conditional mobility, that the configuration of the source cell needs to be maintained for the second conditional mobility. The CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. This allows the source DU22S to know that the configuration of the source cell of the first conditional mobility needs to be maintained for the subsequent second conditional mobility. In other words, the source DU22S can know that the source cell of the first conditional mobility is one of the candidate target cells for the subsequent second conditional mobility.

[0112] Sixth Embodiment This embodiment provides selective activation of cell groups within one RAN node (e.g., MN1 or SN2) through L1 / L2-based inter-cell mobility. A configuration example of the wireless communication system according to this embodiment may be similar to the examples shown in Figs. 1 and 2.

[0113] L1 / L2-based inter-cell mobility may be inter-cell mobility based on Layer 1 (L1) measurements. The L1 measurements may be L1 Synchronization Signal (SS)-RSRP measurements, L1 Channel State Information (CSI)-RSRP measurements, or both. Alternatively, L1 / L2-based inter-cell mobility may be inter-cell mobility using L1 signaling or L2 signaling. The L1 signaling may be, for example, Uplink Control Information (UCI) on the Physical Uplink Control Channel (PUCCH). The L2 signaling may be, for example, Medium Access Control (MAC) Control Element (CE). Alternatively, L1 / L2-based inter-cell mobility may be inter-cell mobility based on L1 measurements and using L1 or L2 signaling.

[0114] When the execution of L1 / L2-based inter-cell mobility is triggered, when the execution starts, or when the execution is completed (from the L1 / L2 perspective), the L1 (Physical (PHY) layer) or L2 (e.g., MAC layer) of the UE 3 may notify the RRC layer of the execution of L1 / L2-based inter-cell mobility. At this time, the L1 or L2 of the UE 3 may notify the RRC layer to which candidate cell (e.g., PCell, PSCell) the serving cell should be changed (or switched) to. Alternatively, the L1 or L2 of the UE 3 may notify the RRC layer to which CG set the serving cell should be changed (or switched) to. In response to this, the RRC layer of the UE 3 may change (or switch) the CG set to be used. Similarly, when L1 or L2 of the RAN node detects that UE3 is performing (or has completed) L1 / L2-based inter-cell mobility, L1 or L2 of the RAN node may notify the RRC layer of the RAN node. At this time, L1 or L2 of the RAN node may notify the RRC layer of which candidate cell (e.g., PCell, PSCell) the serving cell should be changed to (or switched to). Alternatively, L1 or L2 of the RAN node may notify the RRC layer of which CG set the serving cell should be changed to (or switched to).

[0115] The RAN node (i.e., MN1 or SN2) may transmit configurations for candidate cells and information for executing L1 / L2-based inter-cell mobility to the UE3 in advance. These may be collectively referred to as L1 / L2-based inter-cell mobility configuration information (e.g., L1 / L2 mobility configuration). The configurations for candidate target cells may include, for example, a cell group configuration (CellGroupConfig) (generated by the DU) and a radio bearer configuration (RadioBearerConfig) (generated by the CU). The information for executing L1 / L2-based inter-cell mobility may include execution / triggering conditions (generated by the DU or CU).

[0116] The RAN node and UE 3 consider a combination of a candidate Special Cell (SpCell) and SCell(s) when a candidate cell is a candidate SpCell as a candidate Cell Group (CG) set. 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 is configured with multiple candidate CG sets, each of which contains different candidate SpCells. If the RAN node is MN 1, the candidate SpCells are candidate PCells, and the multiple candidate CG sets are multiple candidate MCG sets. On the other hand, if the RAN node is SN 2, the candidate SpCells are candidate PSCells, and the multiple candidate CG sets are multiple candidate SCG sets. The UE 3 switches the serving CG among multiple candidate CG sets through Layer 1 / layer 2-based inter-cell mobility.

[0117] Figure 15 shows an example of the operation of UE3. In step 1501, UE3 receives configurations of multiple candidate CG sets, each of which has a different candidate SpCell, from a serving RAN node (i.e., MN1 or SN2). In step 1502, UE3 selects one candidate SpCell using Layer 1 / Layer 2-based inter-cell mobility and applies the configuration of the candidate CG set corresponding to the selected candidate SpCell. In other words, UE3 switches from the current CG set to the candidate CG set corresponding to the selected candidate SpCell.

[0118] In one example, the UE 3 initiates a PSCell change if it determines based on L1 measurements that the execution / triggering condition of one candidate cell is met. A lower layer (e.g., MAC layer or Physical (PHY) layer) of the UE 3 notifies the RRC layer of the UE 3 of the PSCell change, and the RRC layer may change or switch the RRC configuration to a configuration corresponding to the selected candidate cell.

[0119] The UE3 (e.g., PHY, MAC, RRC) may report to the serving RAN node that it has performed L1 / L2-based inter-cell mobility. Alternatively, the serving RAN node may detect that the UE3 has performed L1 / L2-based inter-cell mobility from the UE3's random access to the selected candidate cell. The DU of the serving RAN node may report that the UE3 has performed L1 / L2-based inter-cell mobility to the CU. The DU may report this to the CU using an ACCESS SUCCESS message. Based on the report from the UE3 or the detection by the serving RAN node, the serving RAN node switches from the current CG set to the candidate CG set corresponding to the candidate SpCell selected by the UE3.

[0120] An example of signaling for preparing and executing L1 / L2-based inter-cell mobility is shown in Figure 16. In the example of Figure 16, the serving RAN node is SN2, and UE3 switches its serving SCG among a set of candidate SCGs provided by SN2.

[0121] In step 1601, the SN2 configures multiple candidate SCG sets in the UE3. Specifically, the SN2 provides the UE3 with the configuration of the multiple candidate SCG sets and information (e.g., execution / triggering condition) for the execution of L1 / L2-based inter-cell mobility. The SN2 sends these configurations to the UE3 using an SN RRC Reconfiguration message. The SN RRC Reconfiguration message is sent to the UE3 via a direct SRB between the SN2 and the UE3 or via the MN1. In step 1602, the UE3 responds to the SN2 with an SN RRC Reconfiguration Complete message.

[0122] In step 1603, if the UE 3 determines based on L1 measurements that the execution / triggering condition of one candidate cell (here, candidate cell #1) is satisfied, the UE 3 initiates a PSCell change to the selected candidate PSCell (i.e., Cell #1). Specifically, the UE 3 detaches from the source PSCell, applies the stored SCG configuration corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution condition is satisfied), and synchronizes with the candidate PSCell (i.e., Cell #1). In step 1604, the UE 3 may perform random access to the candidate PSCell (i.e., Cell #1).

[0123] After the SCG switch, the UE 3 continues to evaluate the execution / triggering conditions for the candidate SCG set. In step 1605, if the UE 3 determines based on L1 measurements that the execution / triggering conditions of another candidate cell (here, candidate cell #2) are satisfied, the UE 3 initiates a PSCell change to the selected candidate PSCell (i.e., Cell #2). In step 1606, the UE 3 may perform random access to the candidate PSCell (i.e., Cell #1).

[0124] According to the operation of the UE 3 and the RAN node described in this embodiment, selective activation of cell groups within one RAN node (e.g., MN or SN) can be realized by L1 / L2-based inter-cell mobility.

[0125] Next, exemplary configurations of RAN nodes 1 and 2 and UE 3 according to the above-described embodiments will be described below. FIG. 15 is a block diagram illustrating an exemplary configuration of RAN node 1 according to the above-described embodiments. The configuration of RAN node 2 may also be similar to the configuration illustrated in FIG. 17. Referring to FIG. 17, RAN node 1 includes a radio frequency transceiver 1701, a network interface 1703, a processor 1704, and a memory 1705. The RF transceiver 1701 performs analog RF signal processing for communication with UEs, including UE 3. The RF transceiver 1701 may include multiple transceivers. The RF transceiver 1701 is coupled to an antenna array 1702 and a processor 1704. The RF transceiver 1701 receives modulation symbol data from the processor 1704, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1702. The RF transceiver 1701 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1702 and provides the baseband receive signal to the processor 1704. The RF transceiver 1701 may include analog beamformer circuitry for beamforming, which may include, for example, multiple phase shifters and multiple power amplifiers.

[0126] The network interface 1703 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 1703 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0127] The processor 1704 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 1704 may include multiple processors. For example, the processor 1704 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.

[0128] For example, digital baseband signal processing by the processor 1704 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 1704 may include processing of Non-Access Stratum (NAS) messages, RRC messages, MAC Control Elements (CE), and Downlink Control Information (DCI).

[0129] The processor 1704 may include a digital beamformer module for beamforming, which may include a Multiple Input Multiple Output (MIMO) encoder and precoder.

[0130] The memory 1705 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 1705 may include storage located remotely from the processor 1704. In this case, the processor 1704 may access the memory 1705 via the network interface 1703 or an I / O interface (not shown).

[0131] The memory 1705 may store one or more software modules (computer programs) 1706 including instructions and data for performing the processing by the RAN node 1 described in the above embodiments. In some implementations, the processor 1704 may be configured to read and execute the software modules 1706 from the memory 1705 to perform the processing by the RAN node 1 described in the above embodiments.

[0132] 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 1701 (and the antenna array 1702).

[0133] FIG. 18 is a block diagram showing an example configuration of UE3. Radio Frequency (RF) transceiver 1801 performs analog RF signal processing for communication with RAN nodes 1, 2, 4, 6, and 7. RF transceiver 1801 may include multiple transceivers. The analog RF signal processing performed by RF transceiver 1801 includes frequency up-conversion, frequency down-conversion, and amplification. RF transceiver 1801 is coupled to antenna array 1802 and baseband processor 1803. RF transceiver 1801 receives modulation symbol data (or OFDM symbol data) from baseband processor 1803, generates a transmit RF signal, and provides the transmit RF signal to antenna array 1802. RF transceiver 1801 also generates a baseband receive signal based on the receive RF signal received by antenna array 1802 and provides the baseband receive signal to baseband processor 1803. RF transceiver 1801 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0134] The baseband processor 1803 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).

[0135] For example, digital baseband signal processing by the baseband processor 1803 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 1803 may include processing of a Non-Access Stratum (NAS) protocol, an RRC protocol, MAC CEs, and DCIs.

[0136] The baseband processor 1803 may perform MIMO encoding and precoding for beamforming.

[0137] The baseband processor 1803 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 1804, which will be described later.

[0138] The application processor 1804 is also referred to as a CPU, MPU, microprocessor, or processor core. The application processor 1804 may include multiple processors (multiple processor cores). The application processor 1804 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 1806 or a memory not shown, thereby realizing various functions of the UE3.

[0139] In some implementations, the baseband processor 1803 and the application processor 1804 may be integrated on a single chip, as indicated by the dashed line (1805) in Figure 18. In other words, the baseband processor 1803 and the application processor 1804 may be implemented as a single System on Chip (SoC) device 1805. An SoC device may also be called a system Large Scale Integration (LSI) or a chipset.

[0140] The memory 1806 is volatile memory, nonvolatile memory, or a combination thereof. The memory 1806 may include multiple physically independent memory devices. The volatile memory is, for example, SRAM, DRAM, or a combination thereof. The nonvolatile memory is MROM, EEPROM, flash memory, a hard disk drive, or any combination thereof. For example, the memory 1806 may include an external memory device accessible from the baseband processor 1803, the application processor 1804, and the SoC 1805. The memory 1806 may also include an internal memory device integrated within the baseband processor 1803, the application processor 1804, or the SoC 1805. Furthermore, the memory 1806 may include memory within a Universal Integrated Circuit Card (UICC).

[0141] The memory 1806 may store one or more software modules (computer programs) 1807 including instructions and data for performing the processing by the UE 3 described in the above-described embodiments. In some implementations, the baseband processor 1803 or the application processor 1804 may be configured to read and execute the software modules 1807 from the memory 1806, thereby performing the processing by the UE 3 described using the drawings in the above-described embodiments.

[0142] 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 1801 and the antenna array 1802, namely, at least one of the baseband processor 1803 and the application processor 1804, and the memory 1806 storing the software module 1807.

[0143] As described with reference to Figures 17 and 18, each of the processors included in the RAN nodes 1 and 2 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 (registered trademark) disc 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.

[0144] 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.

[0145] For example, some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0146] (Appendix 1) 1. A Radio Access Network (RAN) node configured to operate as a Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for User Equipment (UE), 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 send a first SN Radio Resource Control (RRC) message to the UE via a Master Node (MN) or via a direct signaling radio bearer between the SN and the UE, the RRC message including a configuration of a plurality of candidate PSCells for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change; The first SN RRC message indicates that an operation mode is applied, requested, recommended, or available in which the configuration of at least one candidate PSCell not selected in the first conditional PSCell change is reused by the UE for a subsequent second conditional PSCell change. RAN node. (Appendix 2) the at least one processor is configured to determine whether a configuration of at least one candidate PSCell that was not selected in the first conditional PSCell change needs to be maintained by the UE for the subsequent second conditional PSCell change. RAN node as described in Appendix 1. (Appendix 3) the at least one processor is configured to, after completion of the first conditional PSCell change, send to the UE a second SN RRC message including at least one updated execution condition for the subsequent second conditional mobility regarding the at least one candidate PSCell. RAN node as defined in Supplementary Note 1 or 2. (Appendix 4) the first SN RRC message indicates to the UE that the source PSCell of the first conditional PSCell change is to be one of the candidate PSCells in the subsequent second conditional PSCell change; 4. The RAN node according to any one of Supplementary Note 1 to 3. (Appendix 5) the at least one processor is configured to, after completion of the first conditional PSCell change, send to the UE a third SN RRC message including an execution condition for the subsequent second conditional mobility regarding a new candidate PSCell corresponding to the source PSCell. RAN node as described in Appendix 4. (Appendix 6) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for User Equipment (UE), comprising: sending a first SN Radio Resource Control (RRC) message to the UE via a Master Node (MN) or via a direct signaling radio bearer between the SN and the UE, the RRC message including configuration of a plurality of candidate Primary Secondary Cell Group (SCG) Cells (PSCells) for a first conditional PSCell change; The first SN RRC message indicates that an operation mode is applied, requested, recommended, or available in which the configuration of at least one candidate PSCell not selected in the first conditional PSCell change is reused by the UE for a subsequent second conditional PSCell change. method. (Appendix 7) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for User Equipment (UE), the method comprising: The method comprises sending a first SN Radio Resource Control (RRC) message to the UE via a Master Node (MN) or via a direct signaling radio bearer between the SN and the UE, the first SN Radio Resource Control (RRC) message comprising configuration of a plurality of candidate PSCells for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change; The first SN RRC message indicates that an operation mode is applied, requested, recommended, or available in which the configuration of at least one candidate PSCell not selected in the first conditional PSCell change is reused by the UE for a subsequent second conditional PSCell change. program. (Appendix 8) 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: receiving a first Secondary Node (SN) Radio Resource Control (RRC) message via a Master Node (MN) or via a direct signaling radio bearer between the UE and an SN, the RRC message including configuration of multiple candidate Primary Secondary Cell Group (SCG) Cells (PSCells) for a first conditional PSCell change; If an execution condition of one of the plurality of candidate PSCells is satisfied, applying a configuration corresponding to the one candidate PSCell whose execution condition is satisfied; If the first SN RRC message indicates that a configuration of at least one candidate PSCell not selected in the first conditional PSCell change is applicable, required, recommended, or available for reuse by the UE for a subsequent second conditional PSCell change, maintaining the configuration of the at least one candidate PSCell for use in the second conditional PSCell change. UE. (Appendix 9) the at least one processor is configured to receive, after completion of the first conditional PSCell change, a second SN RRC message from the SN, the second SN RRC message including at least one updated execution condition for the subsequent second conditional PSCell change for the at least one candidate PSCell. UE as described in Appendix 8. (Appendix 10) the at least one processor is configured to maintain a configuration of the source PSCell of the first conditional PSCell change after completion of the first conditional PSCell change in order to use the source PSCell as one of the candidate PSCells in the subsequent second conditional PSCell change. 10. The UE according to claim 8 or 9. (Appendix 11) the at least one processor is configured to, if the first SN RRC message indicates that the source PSCell of the first conditional PSCell change is to be one of the candidate PSCells in the subsequent second conditional PSCell change, maintain a configuration of the source PSCell for use in the second conditional PSCell change. 10. The UE according to claim 8 or 9. (Appendix 12) the at least one processor is configured to receive, after completion of the first conditional PSCell change, a third SN RRC message from the SN, the third SN RRC message including an execution condition for the subsequent second conditional PSCell change regarding a new candidate PSCell corresponding to the source PSCell. 12. The UE of claim 10 or 11. (Appendix 13) A method performed by User Equipment (UE), comprising: receiving a first Secondary Node (SN) Radio Resource Control (RRC) message via a Master Node (MN) or via a direct signaling radio bearer between the UE and an SN, the RRC message including configuration of multiple candidate Primary Secondary Cell Group (SCG) Cells (PSCells) for a first conditional PSCell change; If an execution condition of one of the plurality of candidate PSCells is satisfied, applying a configuration corresponding to the one candidate PSCell whose execution condition is satisfied; and maintaining the configuration of at least one candidate PSCell not selected in the first conditional PSCell change for use in the second conditional PSCell change if the first SN RRC message indicates that an operation mode to be reused by the UE for a subsequent second conditional PSCell change applies, is requested, is recommended, or is available; A method for providing the above. (Appendix 14) A program for causing a computer to perform a method for User Equipment (UE), The method comprises: receiving a first Secondary Node (SN) Radio Resource Control (RRC) message via a Master Node (MN) or via a direct signaling radio bearer between the UE and an SN, the RRC message including configuration of multiple candidate Primary Secondary Cell Group (SCG) Cells (PSCells) for a first conditional PSCell change; If an execution condition of one of the plurality of candidate PSCells is satisfied, applying a configuration corresponding to the one candidate PSCell whose execution condition is satisfied; and maintaining the configuration of at least one candidate PSCell not selected in the first conditional PSCell change for use in the second conditional PSCell change if the first SN RRC message indicates that an operation mode to be reused by the UE for a subsequent second conditional PSCell change applies, is requested, is recommended, or is available; A program that includes: (Appendix 15) A Central Unit (CU) of 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 send a first message to a Distributed Unit (DU) and receive a second message from the DU that is a response to the first message; The first message indicates a request for a first conditional mobility for User Equipment (UE) and indicates that an operation mode is applied, required, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE for a subsequent second conditional mobility. CU. (Appendix 16) The second message indicates whether the DU has determined that the operation mode does not apply to one or more candidate target cells prepared by the DU. CU as described in Appendix 15. (Appendix 17) The second message indicates whether the DU has prepared the operation mode for one or more candidate target cells prepared by the DU. CU as described in Appendix 15. (Appendix 18) the first message is a UE CONTEXT MODIFICATION REQUEST message or a UE CONTEXT SETUP REQUEST message; the second message is a UE CONTEXT MODIFICATION RESPONSE message or a UE CONTEXT SETUP RESPONSE message; A CU according to any one of appendices 15 to 17. (Appendix 19) The first conditional mobility is a conditional handover, a conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or a conditional PSCell addition; the subsequent second conditional mobility is a conditional handover or a conditional PSCell change. A CU according to any one of appendices 15 to 18. (Appendix 20) 1. A method performed by a Central Unit (CU) of a Radio Access Network (RAN) node, comprising: sending a first message to a Distributed Unit (DU); and receiving a second message from the DU that is a response to the first message; Equipped with The first message indicates a first conditional mobility request for User Equipment (UE) and indicates that an operation mode is applied, requested, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility change is reused by the UE for a subsequent second conditional mobility change. method. (Appendix 21) A Distributed Unit (DU) of 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 first message from a Central Unit (CU) and send a second message to the CU in response to the first message; The first message indicates a request for a first conditional mobility for User Equipment (UE) and indicates that an operation mode is applied, required, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE for a subsequent second conditional mobility. DU. (Appendix 22) The second message indicates whether the DU has determined that the operation mode does not apply to one or more candidate target cells prepared by the DU. DU as described in Appendix 21. (Appendix 23) The second message indicates whether the DU has prepared the operation mode for one or more candidate target cells prepared by the DU. DU as described in Appendix 21. (Appendix 24) the first message is a UE CONTEXT MODIFICATION REQUEST message or a UE CONTEXT SETUP REQUEST message; the second message is a UE CONTEXT MODIFICATION RESPONSE message or a UE CONTEXT SETUP RESPONSE message; DU according to any one of appendices 21 to 23. (Appendix 25) The first conditional mobility is a conditional handover, a conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or a conditional PSCell addition; the subsequent second conditional mobility is a conditional handover or a conditional PSCell change. A DU according to any one of appendices 21 to 24. (Appendix 26) 1. A method performed by a Distributed Unit (DU) of a Radio Access Network (RAN) node, comprising: receiving a first message from a Central Unit (CU); and sending a second message to the CU in response to the first message; Equipped with The first message indicates a request for a first conditional mobility for User Equipment (UE) and indicates that an operation mode is applied, required, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE for a subsequent second conditional mobility. method. (Appendix 27) A Central Unit (CU) of 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 first message from a first Distributed Unit (DU) indicating candidate target cells that a User Equipment (UE) has successfully accessed during a first conditional mobility; The first message indicates that the readiness of the other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility. CU. (Appendix 28) the at least one processor is configured to, after receiving the first message, inform a second DU that the readiness of one or more candidate target cells for the first conditional mobility needs to be maintained for the subsequent second conditional mobility. CU as described in Appendix 27. (Appendix 29) the at least one processor is configured to, after receiving the first message, inform a source DU serving a source cell of the first conditional mobility that a configuration of the source cell needs to be maintained for the subsequent second conditional mobility. A CU as described in Appendix 27 or 28. (Appendix 30) the first message is an ACCESS SUCCESS message; A CU according to any one of appendices 27 to 29. (Appendix 31) 1. A method performed by a Central Unit (CU) of a Radio Access Network (RAN) node, comprising: receiving a first message from a first Distributed Unit (DU) indicating candidate target cells that a User Equipment (UE) has successfully accessed during a first conditional mobility; The first message indicates that the readiness of the other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility. method. (Appendix 32) A Distributed Unit (DU) of 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 send a first message to a Central Unit (CU) indicating candidate target cells that a User Equipment (UE) has successfully accessed during a first conditional mobility; The first message indicates that the readiness of the other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility. DU. (Appendix 33) the first message is an ACCESS SUCCESS message; DU as described in Appendix 32. (Appendix 34) 1. A method performed by a Distributed Unit (DU) of a Radio Access Network (RAN) node, comprising: sending a first message to a Central Unit (CU) indicating candidate target cells that a User Equipment (UE) has successfully accessed during a first conditional mobility; The first message indicates that the readiness of the other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility. method. (Appendix 35) A Central Unit (CU) of 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: receiving a first message from a first Distributed Unit (DU) indicating candidate target cells that a User Equipment (UE) has successfully accessed during a first conditional mobility; After receiving the first message, sending a second message to a second DU indicating that the readiness of one or more candidate target cells for the first conditional mobility should be maintained for a subsequent second conditional mobility. It is configured as follows: CU. (Appendix 36) the at least one processor is configured to, after receiving the first message, send a third message to a source DU serving the source cell, indicating that a configuration of the source cell of the first conditional mobility needs to be maintained for the subsequent second conditional mobility. CU as described in Appendix 35. (Appendix 37) 1. A method performed by a Central Unit (CU) of a Radio Access Network (RAN) node, comprising: receiving a first message from a first Distributed Unit (DU) indicating candidate target cells that a User Equipment (UE) has successfully accessed during a first conditional mobility; and sending, after receiving the first message, a second message to a second DU indicating that the readiness of one or more candidate target cells for the first conditional mobility should be maintained for a subsequent second conditional mobility; A method for providing the above. (Appendix 38) A Central Unit (CU) of 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: receiving a first message from a first Distributed Unit (DU) indicating candidate target cells that a User Equipment (UE) has successfully accessed during a first conditional mobility; configured to, after receiving the first message, send a second message to a source DU serving the source cell, indicating that the configuration of the source cell of the first conditional mobility needs to be maintained for a subsequent second conditional mobility; CU. (Appendix 39) 1. A method performed by a Central Unit (CU) of a Radio Access Network (RAN) node, comprising: receiving a first message from a first Distributed Unit (DU) indicating candidate target cells that a User Equipment (UE) has successfully accessed during a first conditional mobility; and After receiving the first message, sending a second message to a source DU serving the source cell, indicating that the source cell configuration of the first conditional mobility should be maintained for a subsequent second conditional mobility; A method for providing the above. (Appendix 40) 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: A candidate Special Cell (SpCell) receives a configuration of a plurality of different candidate Cell Group (CG) sets from a Radio Access Network (RAN) node; Selecting one candidate SpCell by Layer 1 / layer 2-based inter-cell mobility and applying the configuration set of the candidate CG corresponding to the selected candidate SpCell; UE. (Appendix 41) A method performed by User Equipment (UE), comprising: A candidate Special Cell (SpCell) receives a configuration of a plurality of different candidate Cell Group (CG) sets from a Radio Access Network (RAN) node; and selecting one candidate SpCell by Layer 1 / layer 2 based inter-cell mobility and applying a configuration set of the candidate CG corresponding to the selected candidate SpCell; A method for providing the above.

[0147] This application claims priority based on Japanese Patent Application No. 2021-215151, filed on December 28, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0148] 1 Master Node (MN) 2. Source Secondary Node (S-SN) 3. User Equipment (UE) 1704 processor 1705 memory 1706 Modules 1803 Baseband Processor 1804 Application Processor 1806 memory 1807 modules

Claims

1. A method for Layer 1 / Layer 2 (L1 / L2) based mobility performed by a User Equipment (UE), comprising: receiving configuration information from a Radio Access Network (RAN) node, the configuration information including information regarding candidate cells for L1 / L2 based mobility; performing L1 measurements for L1 / L2 based mobility; When the execution of L1 / L2 based mobility is triggered, performing random access to switch the serving cell; Upon completion of the random access, a Medium Access Control (MAC) layer of the UE notifies a Radio Resource Control (RRC) layer of the UE of completion of the L1 / L2-based mobility; A method for providing the above.

2. receiving, from the RAN node, a condition for performing L1 / L2 based mobility associated with the L1 measurements; and starting execution of the L1 / L2-based mobility when a condition for executing the L1 / L2-based mobility is satisfied. The method of claim 1.

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