Methods performed by a radio access network node and methods performed by a User Equipment

Abstract

According to the present invention, a secondary node (SN) (2) transmits, to a UE (3), an SN RRC message that contains settings of a plurality of candidate PS Cells for first condition-attached PS Cell modification, via a master node (MN) or via a direct signaling wireless bearer between the SN (2) and the UE (3). The SN RRC message indicates that an operational mode is applied, requested, recommended, or is usable, the operational mode being reused by the UE (3) for second condition-attached PS Cell modification in which the settings of at least one candidate PS Cell which has not been selected in the first condition-attached PS Cell modification, are continued. This feature can contribute, for example, to the realization of a functional or operational mode that enables a continued second condition-attached mobility without resetting or reinitialization by the network after a first condition-attached mobility.

Description

Technical Field

[0001] The present disclosure relates to a wireless communication system, and more particularly to conditional mobility of a wireless terminal.

Background Art

[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 the CPC in 3GPP Release 16 is an inter-SN CPC without Master Node (MN) involvement, and supports conditional PSCell change from a source PSCell to one or more candidate cells (i.e., candidate PSCs) within a single SN. This CPC is also referred to as an 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 conditional mobility newly planned to be introduced in 3GPP Release 17 includes Conditional PSCell Addition (CPA) and 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 is initiated by the MN or the source SN.

[0004] Furthermore, for 3GPP Release 18, discussions on further enhancing mobility functions, including "Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups", have been initiated (see, for example, Non-Patent Documents 4 and 5). In the Release 17 CPA and CPC, the UE needs to release the unused (unselected) CPC / CPA settings in response to selecting any candidate target PSCell and performing random access to the selected target PSCell. Therefore, the UE has no opportunity to execute subsequent CPCs without reconfiguring and re-initializing the CPC 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 without reconfiguring and re-initializing the CPC / CPA preparation from the network after changing the SCG, thereby reducing the signaling overhead and interruption time of CPC / CPA.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0006] The inventors examined the mechanism and procedure for realizing a function or operation mode called "MR-DC with selective activation of cell groups" and found various problems.

[0007] One of these problems relates to the clarification of various procedures regarding a function or operation mode called "MR-DC with selective activation of cell groups". For example, at present, when applying this function or operation mode to intra-SN CPC, the procedures for utilizing the function are not clear. 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 DUs to support this function or operation mode is not clear.

[0008] Another one of these problems relates to Layer 1 / layer 2 (L1 / L2)-based inter-cell mobility. According to Non-Patent Document 5, for 3GPP Release 18, one of the purposes is to clarify the mechanism and procedures of MR-DC with selective activation of cell groups through Layer 3 (L3) enhancement. However, selective activation of cell groups within a specific scenario, for example, within one RAN node (e.g., MN or SN), may be achievable by Layer 1 / layer 2 (L1 / L2)-based inter-cell mobility instead of L3-based inter-cell mobility.

[0009] One of the purposes to be achieved by the embodiments disclosed in this specification is to contribute to providing an apparatus, method, and program that solve at least one of a plurality of problems related to the realization of a function or operation mode that enables a subsequent second conditional mobility without reconfiguration or re-initialization from the network after the first conditional mobility, including the problems described above. It should be noted that this purpose is only one of the plurality of purposes to be achieved by the plurality of embodiments disclosed in this specification. Other purposes or problems and novel features will be clarified from the description of this specification or the attached drawings.

Means for Solving the Problem

[0010] The first aspect is directed to a RAN node configured to operate as a SN associated with a Secondary Cell Group (SCG) in dual connectivity for a UE. The RAN node 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 transmit a first SN Radio Resource Control (RRC) message including a setting of a plurality of candidate PSCs for a first conditional PSCell change to the UE, either via the MN or via a direct signaling radio bearer between the SN and the UE. The first SN RRC message indicates that an operation mode in which settings 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 is applicable, required, recommended, or available.

[0011] The second aspect is directed to a method performed by a RAN node configured to operate as a SN associated with a SCG in dual connectivity for a UE. The method includes transmitting a first SN RRC message including a setting of a plurality of candidate PSCs for a first conditional PSCell change to the UE, either via the MN or via a direct signaling radio bearer between the SN and the UE. The first SN RRC message indicates that an operation mode in which settings 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 is applicable, required, recommended, or available.

[0012] The third aspect is directed to a UE. The UE includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive, via the MN or via a direct signaling radio bearer between the UE and the SN, a first SN RRC message that includes settings of a plurality of candidate PSCs for a first conditional PSCell change. The at least one processor is configured to apply a setting corresponding to one candidate PSCell for which an execution condition is satisfied if the execution condition of one of the plurality of candidate PSCs is satisfied. Further, the at least one processor is configured to maintain the setting of at least one candidate PSCell that was not selected in the first conditional PSCell change for use in a second conditional PSCell change if the first SN RRC message indicates that an operation mode in which the setting of at least one candidate PSCell that was not selected in the first conditional PSCell change is reused by the UE for a subsequent second conditional PSCell change is applicable, required, recommended, or available.

[0013] The fourth aspect is directed to a method performed by a UE. The method includes the following steps: (a) Receiving, via the MN or via a direct signaling radio bearer between the UE and the SN, a first SN RRC message that includes settings of a plurality of candidate PSCs for a first conditional PSCell change; (b) Applying a setting corresponding to one candidate PSCell for which an execution condition is satisfied if the execution condition of one of the plurality of candidate PSCs is satisfied; and (c) Maintaining the setting of at least one candidate PSCell that was not selected in the first conditional PSCell change for use in a second conditional PSCell change if the first SN RRC message indicates that an operation mode in which the setting of at least one candidate PSCell that was not selected in the first conditional PSCell change is reused by the UE for a subsequent second conditional PSCell change is applicable, required, recommended, or available.

[0014] The 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, which is a response to the first message, from the DU. The first message indicates a request for a first conditional mobility for a UE. Additionally, the first message indicates that an operation mode in which settings of at least one candidate target cell not selected by the first conditional mobility are reused by the UE for a subsequent second conditional mobility is applicable, requested, recommended, or available.

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

[0016] The seventh aspect is directed to the 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, which is a response to the first message, to the CU. The first message indicates a request for a first conditional mobility for a UE. In addition, the first message indicates that an operation mode in which settings of at least one candidate target cell not selected by the first conditional mobility are reused by the UE for a subsequent second conditional mobility is applicable, required, recommended, or available.

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

[0018] The ninth aspect is directed to the 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 receive from a first DU a first message indicating a candidate target cell that the UE has successfully accessed during a first conditional mobility. The first message indicates that preparations for other candidate target cells accepted for the first conditional mobility are maintained for a subsequent second conditional mobility.

[0019] Aspect 10 is directed to a method performed by a CU of a RAN node. The method includes receiving, from a first DU, a first message indicating a candidate target cell to which the UE has successfully accessed during a first conditional mobility. The first message indicates that the preparation of other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility.

[0020] Aspect 11 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 send, to a CU, a first message indicating a candidate target cell to which the UE has successfully accessed during a first conditional mobility. The first message indicates that the preparation of other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility.

[0021] Aspect 12 is directed to a method performed by a DU of a RAN node. The method includes sending, to a CU, a first message indicating a candidate target cell to which the UE has successfully accessed during a first conditional mobility. The first message indicates that the preparation of other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility.

[0022] The 13th aspect is directed to the 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 receive, from a first DU, a first message indicating a candidate target cell to which a UE has successfully accessed during a first conditional mobility. In addition, after receiving the first message, the at least one processor is configured to send, to a second DU, a second message indicating that the preparation of one or more candidate target cells for the first conditional mobility needs to be maintained for a subsequent second conditional mobility.

[0023] The 14th aspect is directed to a method performed by the CU of a RAN node. The method includes the following steps: (a) Receiving, from a first DU, a first message indicating a candidate target cell to which a UE has successfully accessed during a first conditional mobility; and (b) After receiving the first message, sending, to a second DU, a second message indicating that the preparation of one or more candidate target cells for the first conditional mobility needs to be maintained for a subsequent second conditional mobility.

[0024] The 15th aspect is directed to the 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 receive, from a first DU, a first message indicating a candidate target cell to which a UE has successfully accessed during a first conditional mobility. In addition, after receiving the first message, the at least one processor is configured to send, to a source DU providing the source cell, a second message informing that the setting of the source cell for the first conditional mobility needs to be maintained for a subsequent second conditional mobility.

[0025] The 16th aspect is directed to a method performed by the CU of a RAN node. The method includes the following steps: (a) receiving, from a first DU, a first message indicating a candidate target cell to which a UE has successfully accessed during a first conditional mobility; and (b) after receiving the first message, sending, to a source DU providing the source cell, a second message notifying that the setting of the source cell of the first conditional mobility needs to be maintained for a subsequent second conditional mobility.

[0026] The 17th aspect is directed to a UE. The UE includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive, from a RAN node, settings of a plurality of candidate Cell Group (CG) sets in which candidate Special Cells (SpCells) are different from each other. Further, the at least one processor is configured to select one candidate SpCell by layer 1 / layer 2 based inter-cell mobility and apply the setting of the candidate CG set corresponding to the selected candidate SpCell.

[0027] The 18th aspect is directed to a method performed by a UE. The method includes the following steps: (a) receiving, from a RAN node, settings of a plurality of candidate CG sets in which candidate SpCells are different from each other, and (b) selecting one candidate SpCell by layer 1 / layer 2 based inter-cell mobility and applying the setting of the candidate CG set corresponding to the selected candidate SpCell.

[0028] The 19th aspect is directed to a program. The program includes a set of instructions (software code) for causing a computer to perform the method according to any of the above aspects when loaded into the computer.

Advantages of the Invention

[0029] According to the above aspect, it is possible to provide an apparatus, a method, and a program that contribute to solving at least one of a plurality of problems related to the realization of a function or an operation mode that enables a subsequent second conditional mobility without reconfiguration or re-initialization from a network after the first conditional mobility.

Brief Description of the Drawings

[0030]

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BEST MODE FOR CARRYING OUT 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 denoted by the same reference numerals, and redundant descriptions are omitted as necessary for clarity of explanation.

[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 objectives or problems and to achieving different effects.

[0033] The multiple embodiments shown below are mainly described with respect to the 3GPP Long Term Evolution (LTE) system and the 5th generation mobile communication system (5G system). However, these embodiments may be applied to other wireless communication systems that support technologies similar to 3GPP's multi-connectivity (e.g., Dual Connectivity). Note that the term LTE as used in this specification includes, unless otherwise specified, the improvements and developments of LTE and LTE-Advanced for enabling interworking with the 5G System.

[0034] As used in this specification, depending on the context, "(if)~then" may be interpreted 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 interpreted to have the same meaning depending on the context.

[0035] First, the configuration and operation of a plurality of network elements common to a plurality of embodiments are described. FIG. 1 shows a configuration example of a wireless communication system according to a plurality of embodiments. In the example of FIG. 1, the wireless communication system includes RAN Node 1, RAN Node 2, and UE 3. Each element (network function) shown in FIG. 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an application platform.

[0036] 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 CU / DU split. Further, the CU may include a Control Plane (CP) Unit (e.g., gNB-CU-CP) and one or more User Plane (UP) Units (e.g., gNB-CU-UP). Thus, RAN Node 1 may be a CU-CP, or may be a combination of a CU-CP and a CU-UP. Similarly, RAN Node 2 may be a CU, or may be a combination of a CU and one or more DUs. RAN Node 2 may be a CU-CP, or may be a combination of a CU-CP and a CU-UP.

[0037] Each of RAN Node 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 is a node that provides NR user plane and control plane protocol termination to the UE and operates as a secondary node (SN) for E-UTRA-NR Dual Connectivity (EN-DC). The ng-eNB is a node that provides E-UTRA user plane and control plane protocol termination 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 operate as the master node (MN) and the 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, MN1 may be any of a master eNB (in EN-DC), a master ng-eNB (in NGEN-DC), and a master gNB (in NR-DC and NE-DC). Similarly, SN2 may be any of an en-gNB (in EN-DC), a secondary ng-eNB (in NE-DC), and a secondary gNB (in NR-DC and NGEN-DC). In EN-DC, UE3 is connected to an eNB operating as MN1 and is also connected to an en-gNB operating as SN2. In NGEN-DC, UE3 is connected to a ng-eNB operating as MN1 and is also connected to a gNB operating as SN2. In NE-DC, UE3 is connected to a gNB operating as MN1 and is also connected to a ng-eNB operating as SN2. In NR-DC, UE3 is connected to one gNB (or gNB-DU) operating as MN1 and is also connected to another gNB (or gNB-DU) operating as SN2.

[0040] MCG is a group of serving cells associated with (or provided to) MN1, including a SpCell (i.e., Primary Cell (PCell)) and optionally one or more Secondary Cells (SCells). On the other hand, SCG is a group of serving cells associated with (or provided to) SN2, including a Primary SCG Cell (PSCell) and optionally one or more Secondary Cells (SCells). The PSCell is the 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), the PSCell may also be an abbreviation for Primary SCell.

[0041] As used herein, the terms "Primary SCG Cell" and its abbreviation "PSCell" refer to a cell that is included in the cell group provided by the SN for dual connectivity, has an uplink component carrier, and has an uplink control channel (e.g., PUCCH) resource configured. Specifically, the terms "Primary SCG Cell" and its abbreviation "PSCell" may refer to the Primary SCG Cell of the cell group provided by an SN that supports 5G NR (e.g., en-gNB in EN-DC, gNB in NGEN-DC, or gNB in NR-DC), or may refer to the Primary SCell of the cell group provided by an SN that supports 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) to add the 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 the CPA execution conditions are met.

[0043] Although not shown in FIG. 1, a plurality of candidate cells (i.e., candidate PSCs) provided by a plurality of candidate SN2s may be prepared for CPA. In the CPA procedure, UE 3 receives from MN1 the configuration of one or more candidate PSCs prepared by one or more candidate SNs and one or more CPA execution conditions associated therewith. More specifically, the configuration of each candidate PSC is an information element (IE) (e.g., condRRCReconfig) of the RRC message of MN1, and the configuration of one or more candidate PSCs and the associated CPA execution conditions are included in the conditional mobility configuration information (e.g., conditionalReconfiguration IE) generated by MN1.

[0044] The configuration of each candidate PSCell is generated by a candidate SN (e.g., candidate SN2) that provides (or prepares) this candidate PSCell. The configuration of each candidate PSCell includes at least configuration information for the candidate PSCell. The configuration of each candidate PSCell may further include configuration information for one or more SCells that are associated with (i.e., configured together with or associated with) the candidate PSCell. The configuration of each candidate PSCell may be a radio bearer (RB) configuration, a CG configuration, an SCG configuration, or 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 a candidate SN (e.g., candidate SN2) that provides (or prepares) this candidate PSCell. Some or all of the configurations of one or more candidate PSCs are included in the 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 (e.g., RB configuration, CG configuration, SCG configuration, SCG radio resource configuration, and one or any combination of the SN RRC Reconfiguration messages).

[0045] On one hand, the CPA execution conditions are generated by MN1. The CPA execution conditions may be composed 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, 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". UE3 evaluates the CPA execution conditions. If the execution conditions of one candidate PSCell are met, UE3 applies the settings of the PSCell corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution conditions are met), such as one or any combination of RB settings, CG settings, SCG settings, SCG radio resource settings, and SN RRC Reconfiguration messages. If there is a bearer configured to require SCG radio resources, UE3 synchronizes to the selected PSCell. If the execution conditions of two or more candidate PSCs are met, UE3 may select one from those candidate PSCs and perform the above operations.

[0046] In addition, RAN node 2 and UE 3 support intra-SN CPC. Intra-SN CPC may be referred to as 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, UE 3 receives from SN2 the configuration of one or more candidate PSCs prepared by SN2 and one or more CPC execution conditions associated therewith. The configuration of each candidate PSC and the associated CPC execution conditions are included in the CPC configuration for intra-SN CPC. SN2 may send these to UE 3 via MN1, or may send them to UE 3 via a direct signalling radio bearer (i.e., Signalling Radio Bearer 3 (SRB3)) between SN2 and UE 3. More specifically, the configuration of each candidate PSC is an information element (IE) (e.g., condRRCReconfig) of an RRC message of SN2, and the configuration of one or more candidate PSCs 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 (i.e., configured together with or associated 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, or 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 SN2.

[0049] The CPC execution conditions of Intra-SN CPC may be configured by one or more trigger conditions. The conditions or criteria for triggering a CPC event may be similar to those for a measurement report event, for example, CondEvent A3, CondEvent A4, or CondEvent A5. UE3 evaluates the CPC execution conditions. If the execution conditions for one candidate PSCell are met, UE3 detaches from the source PSCell, applies the configuration corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution conditions are met), and synchronizes to the selected candidate PSCell. If the execution conditions for two or more candidate PSCs are met, UE3 may select one of those candidate PSCs and perform the above operations.

[0050] One or both of RAN nodes 1 and 2 may have the configuration shown in FIG. 2. Each element (network function) shown in FIG. 2 can be implemented, for example, as a network element on dedicated hardware, as a software instance operating 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, CU21 and one or more DUs22 as shown in FIG. 2. The CU21 and each DU22 are connected by an interface 201. The UE3 is connected to at least one DU22 via at least one air interface 202.

[0051] The CU21 may be a logical node that hosts the gNB's Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP) protocols (or the gNB's RRC and PDCP protocols). The DU22 may be a logical node that hosts the gNB's Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers. If the CU21 is the gNB-CU and the DUs22 are the gNB-DUs, the interface 201 may be the F1 interface. The CU21 may include CU-CP and CU-UP.

[0052] In this specification, the term conditional mobility is used. Conditional mobility is a general term that refers to one or more of CHO, CPA, intra-SN CPC (or conditional SN modification), and inter-SN CPC (or conditional SN change).

[0053] The embodiments described below provide an improvement in conditional mobility. Specifically, the following embodiments provide an improvement in conditional mobility for supporting a function or operating mode called "Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups". Note that in this specification, the function or operating mode may be applied to conditional mobility that does not necessarily involve MR-DC, i.e., CHO. Further, the function or operating mode may be applied to an improved CHO in which an SCG (at least the PSCell) is added along with the execution of CHO. In the definition in this specification, the function or operating mode enables, for example, a subsequent second conditional mobility without at least re-initialization of conditional mobility preparation after changing or adding a serving cell, a serving cell group, a PSCell, or an SCG in a first conditional mobility. In other words, in the definition in this specification, the function or operating mode enables, for example, UE3 to reuse or maintain at least a part of the candidate target cell setting or the candidate PSCell setting (e.g., one or any combination of RB setting, CG setting, SCG setting, radio resource setting, and SCG radio resource setting) received from the network in a first conditional mobility for a subsequent second conditional mobility. At least a part of the execution conditions for the first conditional mobility may be reset, updated, or modified for the second conditional mobility. Similarly, at least a part of the information regarding the setting of the security key for the first conditional mobility (e.g., sk-Counter, Next Hop (NH), NH Chaining Count (NCC)), or the 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, while the first conditional mobility is CPA, the second conditional mobility may be Inter-SN CPC or Intra-SN CPC. Alternatively, while the first conditional mobility is Inter-SN CPC, the second conditional mobility may be Intra-SN CPC.

[0054] The function or operation mode may be called, but is not limited to, for example, 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 the sake of convenience of explanation, in the following embodiments, the function or operation mode is called selective CG activation or selective cell activation. The term selective CG activation may be used for conditional mobility (e.g., CPA, inter-SN CPC, intra-SN CPC) involving MR-DC. On the other hand, the term selective cell activation may be used for conditional mobility (e.g., CHO) not necessarily involving MR-DC.

[0055] In this specification, a combination of a candidate Special Cell (SpCell) and SCell(s) may be referred to as a candidate Cell Group (CG) set for conditional mobility or selective CG activation. Selective CG activation can also be regarded as a change or switch of the serving SCG among a plurality of candidate CG sets. One candidate CG set includes at least a candidate SpCell and optionally one or more SCells. A candidate cell (candidate SpCell) may be the current SCell (i.e., the SCell included in the current SCG) or a non-serving cell not provided to UE3. UE3 may be configured with a plurality of candidate CG sets in which those candidate SpCells are different from each other. If it is conditional mobility (e.g., CHO) regarding MCG, the candidate SpCells are candidate PCells, and the plurality of candidate CG sets are a plurality of candidate MCG sets. On the other hand, if it is conditional mobility (e.g., CPA, intra-SN CPC, inter-SN CPC) regarding SCG, the candidate SpCells are candidate PSCs, and the plurality of candidate CG sets are a plurality of 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 simply be referred to as the RRC message and the RRC Reconfiguration message. Similarly, the SN RRC message and the SN RRC Reconfiguration message may simply be referred to as the RRC message and the RRC Reconfiguration message.

[0057] <The first embodiment> This embodiment provides an improvement to the intra-SN CPC for selective CG activation. Specifically, this embodiment relates to the clarification of various procedures related to selective CG / cell activation. A configuration example of the wireless communication system according to this embodiment may be the same as the examples shown in FIGS. 1 and 2.

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

[0059] In step 301, an SN RRC message is generated that includes the configuration of a plurality of candidate PSCs for the first CPC and the indication of selective CG activation. The indication of selective CG activation indicates to UE3 that selective CG activation is applied, requested, recommended, or available. In other words, the indication of selective CG activation indicates that an operation mode in which the configuration of at least one candidate PSC not selected in the first CPC is reused by UE3 for a subsequent second CPC is applied, requested, recommended, or available. The indication of selective CG activation may be referred to as, for example, a selective CG activation configuration. In step 302, SN2 transmits the generated SN RRC message to UE3. SN2 may send the SN RRC message to UE3 via MN1, or may send the SN RRC message to UE3 via a direct signaling radio bearer between SN2 and UE3 (i.e., Signaling Radio Bearer 3 (SRB3)).

[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 that includes the configuration of a plurality of candidate PSCs for the first CPC and the indication of selective CG activation. In step 402, if the execution condition of one of the plurality of candidate PSCs is satisfied, UE3 applies the configuration corresponding to the selected one candidate PSC (i.e., the candidate PSC whose execution condition is satisfied). In step 403, if the SN RRC message in step 401 includes the indication of selective CG activation, UE3 maintains the configuration of at least one candidate PSC not selected in the first CPC for use in a subsequent second CPC.

[0061] The operations of SN2 and UE3 described with reference to FIGS. 3 and 4 can be appropriately changed. For example, after the completion of the first CPC, SN2 may update or modify the CPC execution conditions for at least one candidate PSCell not selected by the first CPC for the second CPC. For example, 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 first CPC to the PSCell selected by the first CPC. In this case, after the completion of the first CPC, SN2 may send an SN RRC message including the updated or modified CPC execution conditions for the second CPC to UE3. UE3 may receive the SN RRC message and update the CPC execution conditions for at least one candidate PSCell not selected by the first CPC.

[0062] For example, UE3 may reuse the execution conditions for candidate PSCells not selected by the first CPC for the subsequent second CPC and autonomously switch the reference cell in the execution conditions from the source PSCell of the first CPC to the candidate PSCell selected by the first CPC. That is, UE3 may autonomously update or modify the reference cell of the execution conditions of the first CPC. Thereby, UE3 can start the evaluation of the execution conditions for the subsequent second CPC without receiving signaling from SN2 to update the execution conditions.

[0063] For example, in order for the UE3 to use the source PSCell of the first CPC as one of the candidate PSCells in the second CPC, the UE3 may maintain the configuration of the source PSCell without releasing it after the completion of the first CPC. This can enable the use of the source cell of the CPC as one of the candidate PSCells for a subsequent CPC. The SN2 may notify the UE3 whether the source PSCell of the first CPC will be used as a candidate PSCell in the subsequent second CPC. Specifically, the SN2 may use the SN RRC message (step 302 in FIG. 3, step 401 in FIG. 4) sent to the UE3 for configuring the first CPC to indicate to the UE3 that the source PSCell of the first CPC will be used as 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 UE3 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 the UE3 the execution conditions for subsequent second conditional mobility regarding a new candidate PSCell corresponding to the source PSCell of the first CPC. The SN2 may send the UE3 the execution conditions using the SN RRC message. The UE3 may receive the CPC execution conditions regarding the new candidate PSCell corresponding to the source PSCell of the first CPC from the SN2 and use them for the second CPC.

[0065] Figures 5A and 5B show an example of the signaling of the intra-SN CPC procedure in which the 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 the 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 PSCs and the associated CPC execution conditions. There is no particular limitation on how the CPC configuration and the selective CG activation setting are included in the SN RRC Reconfiguration message. Specifically, the information element (IE) or field indicating the CPC configuration may be independent of the IE or field indicating the selective CG activation setting. In this case, the IE or field indicating the selective CG activation setting may mean that the associated CPC configuration is applied to the selective CG activation (or is the target of the selective CG activation). Alternatively, the information element (IE) or field indicating the CPC configuration may include the IE or field indicating the selective CG activation setting, or vice versa. For example, the IE or field indicating the CPC configuration is condRRCReconfig, and the SN RRC Reconfiguration message it includes may further include an IE or field indicating the selective CG activation setting. In this case, it may mean that the setting specified by the SN RRC Reconfiguration is applied to the selective CG activation (or is the target of the selective CG activation).Note that 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 UE3 applies the new settings and starts evaluating the CPC execution conditions for a plurality of candidate PSCs. The UE3 maintains the connection with the source PSCell and responds to the SN2 via SRB3 with an SN RRC Reconfiguration Complete message.

[0067] In step 503, if the execution conditions of one candidate PSCell (here, candidate cell #1) are satisfied, the UE3 starts CPC execution while keeping the selective CG activation setting (and the CPC setting). Specifically, the UE3 detaches from the source PSCell, applies the stored settings corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution conditions are satisfied), and synchronizes with the candidate PSCell. In step 504, the UE3 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 completion of the CPC execution, the UE3 maintains the configuration of one or more candidate PSCs that were not selected for reuse in subsequent CPCs. The UE3 may maintain the CPC execution conditions associated with one or more candidate PSCs that were not selected. As described above, the UE3 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 UE3 may determine whether to autonomously change the reference cell of the CPC execution conditions based on the selective CG activation setting received in step 501. Alternatively, the UE3 may receive updated or modified CPC execution conditions from the SN2.

[0069] Furthermore, the UE3 may use the source PSCell of the first CPC as one of the candidate PSCs for subsequent CPCs. The UE3 may determine whether to use the source PSCell of the first CPC as a new candidate PSCell based on the selective CG activation setting received in step 501.

[0070] In step 505, the UE3 may receive an SN RRC Reconfiguration message indicating updated or modified CPC execution conditions from the SN2 via the SRB3. This SN RRC Reconfiguration message may include the CPC execution conditions for the source PSCell of the first CPC that is to be a new candidate PSCell. In step 506, the UE3 applies the received CPC execution conditions and responds to the SN2 via the SRB3 with an SN RRC Reconfiguration Complete message. If updating, modifying, or adding CPC execution conditions is not necessary, steps 505 and 506 may be omitted.

[0071] After the completion of the initial CPC, UE3 continues to evaluate the execution conditions of the candidate PSCell(s) that were not selected. UE3 may start evaluating the CPC execution conditions for the source PSCell of the first CPC that becomes a new candidate PSCell. In step 507, if the execution conditions of one candidate PSCell (here, assume it is candidate cell #2) are met, UE3 starts CPC execution while keeping the selective CG activation setting (and CPC setting). Specifically, UE3 detaches from the current source PSCell (i.e., Cell #1), applies the stored setting corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution conditions are met), and synchronizes to the candidate PSCell. In step 508, UE3 completes the CPC execution procedure by sending an SN RRC Reconfiguration Complete message to the selected candidate PSCell (i.e., Cell #2).

[0072] Even after step 508, UE3 may continue to evaluate the CPC execution conditions of the remaining unselected candidate PSCell(s). UE3 may autonomously change the reference cell for these CPC execution conditions from the source PSCell (i.e., Cell #1) to the selected candidate PSCell (i.e., Cell #2). UE3 may determine whether to autonomously change the reference cell for the CPC execution conditions based on the selective CG activation setting received in step 501. Alternatively, UE3 may receive updated or modified CPC execution conditions from SN2. Furthermore, UE3 may use the source PSCell (i.e., Cell #1) as one of the candidate PSCells. UE3 may determine whether to make the source PSCell (i.e., Cell #1) a new candidate PSCell based on the selective CG activation setting received in step 501.

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

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

[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, including it in an RRC Transfer message, to SN2.

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

[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, including it in an SN Modification Confirm message, to SN2.

[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, including it in an RRC Transfer message, to SN2.

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

[0080] SN2 of this embodiment may have the CU-DU configuration shown in FIG. 2. SN2 may include CU21 and one or more DUs22. In this case, SN2 supports intra-DU conditional mobility of UE3 within one DU. Similarly, SN2 supports inter-DU conditional mobility of UE3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CPC or CPA. The inter-DU conditional mobility may be inter-SN CPC.

[0081] Furthermore or alternatively, the MN1 of the present embodiment may have the CU-DU configuration shown in FIG. 2. MN21 may include CU21 and one or more DUs22. In this case, MN1 supports the intra-DU conditional mobility of UE3 within one DU. Similarly, MN1 supports the inter-DU conditional mobility of UE3 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] FIG. 7 shows an example of signaling between CU21 and DU22. As described above, CU21 and DU22 may belong to SN2 or MN1. In step 701, CU21 sends a CU-DU control message (e.g., F1AP message) indicating a request for the first conditional mobility for UE3 to DU22. 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 in step 701 includes an indication of selective cell / CG activation. The indication of selective cell / CG activation indicates to the DU22 that selective cell / CG activation is applicable, required, recommended, or available. In other words, the indication of selective cell / CG activation indicates that an operation mode in which the settings of at least one candidate target cell not selected in the first conditional mobility are reused by the UE3 for a subsequent second conditional mobility is applicable, required, recommended, or available. The indication of selective cell / CG activation may be referred to as, for example, a request for selective cell / CG activation. Both the first and second conditional mobilities may be CHO. Both the first and second conditional mobilities may be CPC. Alternatively, the first conditional mobility may be CPA and the second conditional mobility may be CPC. Thereby, the DU22 can recognize whether the preparation of the 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, DU22 sends a response message to CU21. The response message may indicate whether DU22 determines that selective cell / CG activation is not applicable to one or more candidate target cells prepared by DU22. Alternatively, the response message may indicate whether DU22 has prepared selective cell / CG activation for one or more candidate target cells prepared by DU22. If DU22 can accept the preparation of one or more candidate target cells for the first conditional mobility but cannot accept the requirement of selective cell / CG activation, DU22 may inform CU21 in the response message of accepting the preparation for the first conditional mobility and rejecting the selective cell / CG activation.

[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] Figure 8 shows a specific example of the format of the UE CONTEXT MODIFICATION REQUEST message. In the example of Figure 8, if the Selective CG Activation IE is included in the Conditional Intra-DU Mobility Information IE within the UE CONTEXT MODIFICATION REQUEST message, DU22 recognizes that selective cell / CG activation is applicable, requested, recommended, or available for the first conditional mobility indicated by the Conditional Intra-DU Mobility Information IE. In other words, DU22 recognizes that it is required 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 Figure 8 may be changed as appropriate. For example, one of the possible values of the CHO Trigger IE, which is an enumerated type IE, may be a value indicating a selective cell / CG activation request (e.g., Selective CG Activation-initiation).

[0088] Figure 9 shows a specific example of the format of the UE CONTEXT MODIFICATION RESPONSE message. In the example of Figure 9, if the Selective CG Activation IE is included in the UE CONTEXT MODIFICATION RESPONSE message, the IE indicates whether the selective cell / CG activation has been accepted (or prepared) by DU22.

[0089] Figure 10 shows a specific example of the format of the UE CONTEXT SETUP REQUEST message. In the example of Figure 10, if the Selective CG Activation IE is included in the Conditional Inter-DU Mobility Information IE within the UE CONTEXT SETUP REQUEST message, DU22 recognizes that selective cell / CG activation is applicable, requested, recommended, or available for the first conditional mobility indicated by the Conditional Inter-DU Mobility Information IE. In other words, DU22 recognizes that it is required 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 Figure 10 may be changed as appropriate. For example, one of the possible values of the CHO Trigger IE, which is an enumerated type IE, may be a value indicating a selective cell / CG activation request (e.g., Selective CG Activation-initiation).

[0091] Figure 11 shows a specific example of the format of the UE CONTEXT SETUP RESPONSE message. In the example of Figure 11, if the 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 DU22.

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

[0093] <Embodiment 3> This embodiment provides details of the signaling between the CU and the DU to support selective cell / CG activation. The configuration example of the wireless communication system according to this embodiment may be the same as the examples shown in FIGS. 1 and 2.

[0094] SN2 of this embodiment may have the CU-DU configuration shown in FIG. 2. SN2 may include CU21 and one or more DUs22. In this case, SN2 supports the intra-DU conditional mobility of UE3 within one DU. Similarly, SN2 supports the inter-DU conditional mobility of UE3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CPC or CPA. The inter-DU conditional mobility may be inter-SN CPC.

[0095] Furthermore or alternatively, MN1 of this embodiment may have the CU-DU configuration shown in FIG. 2. MN21 may include CU21 and one or more DUs22. In this case, MN1 supports the intra-DU conditional mobility of UE3 within one DU. Similarly, MN1 supports the inter-DU conditional mobility of UE3 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] FIG. 12 shows an example of signaling between CU21 and target DU22A. In step 1201, target DU22A sends a CU-DU control message (e.g., F1AP message) indicating a candidate target cell to which UE3 has successfully accessed during the first conditional mobility to CU21. 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 cell means a candidate (target) PSCell.

[0097] In addition, the control message indicates that the preparation of other candidate target cells accepted by target DU22A for the first conditional mobility is maintained for a subsequent second conditional mobility. Both the first and second conditional mobilities may be CHO. Both the first and second conditional mobilities may be CPC. Alternatively, the first conditional mobility may be CPA and the second conditional mobility may be CPC. Thereby, CU21 can recognize that the preparation of candidate target cells by target DU22A 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 in step 1201, CU21 may operate as follows. After receiving the message in step 1201, CU21 may inform a target DU of the first conditional mobility, different from target DU22A, that the preparation of one or more candidate target cells for the first conditional mobility needs to be maintained for a second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. Thereby, other target DUs can recognize that the preparation of candidate target cells for the first conditional mobility needs to be maintained even after the first conditional mobility is completed.

[0099] Further or alternatively, after receiving the message in step 1201, CU21 may inform the source DU that provides the source cell for the first conditional mobility that the settings of the source cell need to be maintained for the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. Thereby, the source DU can recognize that the settings of the source cell for the first conditional mobility need to be maintained for the subsequent second conditional mobility. In other words, the source DU can recognize that the source cell for 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 the signaling between the CU and the DU to support selective cell / CG activation. The configuration example of the wireless communication system according to this embodiment may be the same as the examples shown in FIGS. 1 and 2.

[0101] SN2 of this embodiment may have the CU-DU configuration shown in FIG. 2. SN2 may include CU21 and one or more DUs22. In this case, SN2 supports the intra-DU conditional mobility of UE3 within one DU. Similarly, SN2 supports the inter-DU conditional mobility of UE3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CPC or CPA. The inter-DU conditional mobility may be inter-SN CPC.

[0102] Further or alternatively, the MN1 of the present embodiment may have the CU-DU configuration shown in FIG. 2. MN21 may include a CU21 and one or more DUs22. In this case, MN1 supports intra-DU conditional mobility of the UE3 within one DU. Similarly, MN1 supports inter-DU conditional mobility of the UE3 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] FIG. 13 shows an example of signaling between the CU21 and two target DUs22A and 22B. In step 1301, the target DU22A sends a CU-DU control message (e.g., an F1AP message) indicating a candidate target cell to which the UE3 has successfully accessed during the first conditional mobility to the CU21. The control message may be the same as the existing ACCESS SUCCESS message.

[0104] In step 1302, after receiving the message of step 1301, the CU21 notifies the target DU22B, which is different from the target DU22A for the first conditional mobility, that the preparation of one or more candidate target cells for the first conditional mobility needs to be maintained for the second conditional mobility. The CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. Thereby, the target DU22B can recognize that the preparation of the candidate target cell for the first conditional mobility needs to be maintained even after the first conditional mobility is completed.

[0105] Furthermore, after receiving the message in step 1301, CU21 may inform the source DU that provides the source cell for the first conditional mobility that the settings of the source cell need to be maintained for the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. Thereby, the source DU can recognize that the settings of the source cell for the first conditional mobility need to be maintained for the subsequent second conditional mobility. In other words, the source DU can recognize that the source cell for 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] <The Fifth Embodiment> This embodiment provides details of the signaling between the CU and the DU to support selective cell / CG activation. A configuration example of the wireless communication system according to this embodiment may be the same as the examples shown in FIGS. 1 and 2.

[0108] SN2 of this embodiment may have the CU-DU configuration shown in FIG. 2. SN2 may include CU21 and one or more DUs22. In this case, SN2 supports the intra-DU conditional mobility of UE3 within one DU. Similarly, SN2 supports the inter-DU conditional mobility of UE3 between DUs. These intra-DU conditional mobility and inter-DU conditional mobility may be CPC or CPA. The inter-DU conditional mobility may be inter-SN CPC.

[0109] Furthermore or alternatively, the MN1 of the present embodiment may have the CU-DU configuration shown in FIG. 2. MN21 may include CU21 and one or more DUs22. In this case, MN1 supports the intra-DU conditional mobility of UE3 within one DU. Similarly, MN1 supports the inter-DU conditional mobility of UE3 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] FIG. 14 shows an example of signaling between CU21 and two target DUs22A and 22B. In step 1401, the target DU22A sends a CU-DU control message (e.g., F1AP message) indicating the candidate target cell to which UE3 has successfully accessed during the first conditional mobility to CU21. The control message may be the same as the existing ACCESS SUCCESS message.

[0111] In step 1402, after receiving the message in step 1401, CU21 notifies the source DU22S that provides the source cell of the first conditional mobility that the setting 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. Thereby, the source DU22S can recognize that the setting 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 recognize 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) by L1 / L2-based inter-cell mobility. A configuration example of the wireless communication system according to this embodiment may be the same as 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, or 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, a 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 L1 (Physical (PHY) layer) or L2 (e.g., MAC layer) of UE3 is triggered to execute L1 / L2-based inter-cell mobility, starts the execution, or (from the L1 / L2 perspective) completes the execution, it may notify the RRC layer of UE3 of the execution of L1 / L2-based inter-cell mobility. At this time, the L1 or L2 of UE3 may notify the RRC layer which candidate cell (e.g., PCell, PSCell) to change (or switch) the serving cell to. Alternatively, the L1 or L2 of UE3 may notify the RRC layer which CG set to change (or switch) to. In response, the RRC layer of UE3 may change (or switch) the CG set to be used. Similarly, when the L1 or L2 of the RAN node detects that UE3 is executing (or has completed the execution of) L1 / L2-based inter-cell mobility, the L1 or L2 of the RAN node may notify its RRC layer of this. At this time, the L1 or L2 of the RAN node may notify the RRC layer which candidate cell (e.g., PCell, PSCell) to change (or switch) the serving cell to. Alternatively, the L1 or L2 of the RAN node may notify the RRC layer which CG set to change (or switch) to.

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

[0116] When the RAN node and the UE3 consider a candidate cell as a candidate Special Cell (SpCell), the combination of the SpCell and the SCell(s) is regarded as a candidate Cell Group (CG) set. One candidate CG set includes at least the candidate SpCell and optionally includes one or more SCells. The candidate cell (candidate SpCell) may be the current SCell (i.e., the SCell included in the current SCG) or a non-serving cell not provided to the UE3. The UE3 sets a plurality of candidate CG sets in which those candidate SpCells are different from each other. If the RAN node is MN1, the candidate SpCells are candidate PCells, and the plurality of candidate CG sets are a plurality of candidate MCG sets. On the other hand, if the RAN node is SN2, the candidate SpCells are candidate PSCs, and the plurality of candidate CG sets are a plurality of candidate SCG sets. The UE3 switches the serving CG among the plurality of candidate CG sets by layer 1 / layer 2 based inter-cell mobility.

[0117] Figure 15 shows an example of the operation of the UE3. In step 1501, the UE3 receives from the serving RAN node (i.e., MN1 or SN2) the setting of a plurality of candidate CG sets in which the candidate SpCells are different from each other. In step 1502, one candidate SpCell is selected by layer 1 / layer 2 based inter-cell mobility, and the setting of the candidate CG set corresponding to the selected candidate SpCell is applied. In other words, the UE3 switches from the current CG set to the candidate CG set corresponding to the selected candidate SpCell.

[0118] In one example, if UE3 determines based on L1 measurements that the execution / triggering condition of one candidate cell is satisfied, UE3 starts a PSCell change. The lower layer (e.g., MAC layer or Physical (PHY) layer) of UE3 notifies the RRC layer of UE3 of the PSCell change, and the RRC layer may change or switch the RRC configuration to the configuration corresponding to the selected candidate cell.

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

[0120] FIG. 16 shows an example of the signaling for the preparation and execution of L1 / L2-based inter-cell mobility. In the example of FIG. 16, the serving RAN node is SN2, and UE3 switches the serving SCG among a plurality of candidate SCG sets provided by SN2.

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

[0122] In step 1603, if UE3 determines based on L1 measurement that the execution / triggering condition of one candidate cell (here candidate cell #1) is satisfied, it starts the PSCell change to the selected candidate PSCell (i.e., Cell #1). Specifically, UE3 detaches from the source PSCell, applies the stored SCG settings corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution condition is satisfied), and synchronizes to the candidate PSCell (i.e., Cell #1). In step 1604, UE3 may perform a random access to the candidate PSCell (i.e., Cell #1).

[0123] Even after the SCG switch, UE3 continues to evaluate the execution / triggering conditions for the candidate SCG sets. In step 1605, if UE3 determines based on L1 measurement that the execution / triggering condition of another candidate cell (here candidate cell #2) is satisfied, it starts the PSCell change to the selected candidate PSCell (i.e., Cell #2). In step 1606, UE3 may perform a random access to the candidate PSCell (i.e., Cell #1).

[0124] According to the operations of the UE3 and the RAN node described in this embodiment, selective activation of a cell group within one RAN node (e.g., MN or SN) can be realized by L1 / L2-based inter-cell mobility.

[0125] Subsequently, hereinafter, configuration examples of the RAN nodes 1 and 2 and the UE3 according to the above-described multiple embodiments will be described. FIG. 15 is a block diagram showing a configuration example of the RAN node 1 according to the above-described embodiment. The configuration of the RAN node 2 may also be the same as the configuration shown in FIG. 17. Referring to FIG. 17, the 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 to communicate with UEs including the UE3. The RF transceiver 1701 may include a plurality of transceivers. The RF transceiver 1701 is coupled to the antenna array 1702 and the processor 1704. The RF transceiver 1701 receives modulation symbol data from the processor 1704, generates a transmission RF signal, and supplies the transmission RF signal to the antenna array 1702. Also, the RF transceiver 1701 generates a baseband reception signal based on the reception RF signal received by the antenna array 1702 and supplies this to the processor 1704. The RF transceiver 1701 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, a plurality of phase shifters and a plurality of power amplifiers.

[0126] The network interface 1703 is used to communicate with network nodes (e.g., RAN nodes 2 and 4, and control nodes and transfer 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] Processor 1704 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Processor 1704 may include a plurality of processors. For example, Processor 1704 may include a modem processor (e.g., Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) that performs control plane processing.

[0128] For example, the digital baseband signal processing by Processor 1704 may include signal processing of the Service Data Adaptation Protocol (SDAP) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control (MAC) layer, and Physical (PHY) layer. Also, the control plane processing by Processor 1704 may include processing of Non-Access Stratum (NAS) messages, RRC messages, MAC Control Elements (CE), and Downlink Control Information (DCI).

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

[0130] Memory 1705 is composed of a combination of volatile memory and non-volatile memory. The volatile memory is, for example, Static Random Access Memory (SRAM) or Dynamic RAM (DRAM) or a combination thereof. The non-volatile memory is Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or a hard disk drive, or any combination thereof. Memory 1705 may include storage located away from processor 1704. In this case, processor 1704 may access memory 1705 via network interface 1703 or an I / O interface (not shown).

[0131] Memory 1705 may store one or more software modules (computer programs) 1706 containing instruction groups and data for performing the processing by RAN node 1 described in the above-described multiple embodiments. In some implementations, processor 1704 may be configured to perform the processing of RAN node 1 described in the above embodiments by reading and executing the software module 1706 from memory 1705.

[0132] Note that when RAN node 1 is a CU (e.g., eNB-CU or gNB-CU) or CU-CP, RAN node 1 may not include RF transceiver 1701 (and antenna array 1702).

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

[0134] The baseband processor 1803 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) generation / decomposition of a transmission format (transmission frame), (d) channel coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT), etc. On the other hand, the control plane processing includes communication management of layer 1 (e.g., transmission 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, the digital baseband signal processing by the baseband processor 1803 may include signal processing of the SDAP layer, PDCP layer, RLC layer, MAC layer, and PHY layer. Also, the control plane processing by the baseband processor 1803 may include processing of the Non-Access Stratum (NAS) protocol, 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 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 a plurality of processors (a plurality of processor cores). The application processor 1804 realizes various functions of the UE3 by executing a system software program (Operating System (OS)) and various application programs (e.g., call application, WEB browser, mailer, camera operation application, music playback application) read from the memory 1806 or a memory not shown.

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

[0140] The memory 1806 is volatile memory, non-volatile memory, or a combination thereof. The memory 1806 may physically include multiple independent memory devices. Volatile memory is, for example, SRAM, DRAM, or a combination thereof. Non-volatile memory is MROM, EEPROM, flash memory, or 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 include an embedded memory device integrated within the baseband processor 1803, the application processor 1804, or the SoC 1805. Further, the memory 1806 may include the memory within a Universal Integrated Circuit Card (UICC).

[0141] The memory 1806 may store one or more software modules (computer programs) 1807 including instruction groups and data for performing the processing by the UE3 described in the above-described embodiments. In some implementations, the baseband processor 1803 or the application processor 1804 may be configured to perform the processing of the UE3 described with reference to the drawings in the above-described embodiments by reading and executing the software module 1807 from the memory 1806.

[0142] Note that the control plane processing and operations performed by the UE3 described in the above embodiments can be realized by other elements excluding the RF transceiver 1801 and the antenna array 1802, that is, 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 FIGS. 17 and 18, each of the processors included in the RAN nodes 1 and 2 and the UE3 according to the above embodiments can execute one or more programs including a set of instructions for causing a computer to perform the algorithms described with reference to the drawings. The program includes a set of instructions (or software code) for causing a computer to perform one or more functions described in the embodiments when loaded into the computer. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, the computer-readable medium or tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD), or other memory technologies, CD-ROM, digital versatile disk (DVD), Blu-ray (registered trademark) disk, or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage devices. The program may be transmitted on a transient computer-readable medium or a communication medium. By way of example and not limitation, the transient computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0144] The above-described embodiments are merely examples regarding the application of the technical idea obtained by the present inventor. That is, the technical idea is not limited to the above-described embodiments only, and various modifications are of course possible.

[0145] For example, some or all of the above embodiments may be described as follows in the appended claims, but are not limited thereto.

[0146] (Appendix 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 a user equipment (UE), at least one memory, at least one processor coupled to the at least one memory, comprising, the at least one processor is configured to transmit a first SN radio resource control (RRC) message including a set of a plurality of candidate PSCs for a first conditional primary secondary cell group (SCG) cell (PSCell) change to the UE, either via a master node (MN) or via a direct signaling radio bearer between the SN and the UE, the first SN RRC message indicates that an operation mode in which a set of at least one candidate PSC not selected in the first conditional PSC change is reused by the UE for a subsequent second conditional PSC change is applicable, required, recommended, or available, RAN node. (Appendix 2) the at least one processor is configured to determine whether a set of at least one candidate PSC not selected in the first conditional PSC change needs to be maintained by the UE for the subsequent second conditional PSC change, The RAN node according to Appendix 1. (Appendix 3) The at least one processor is configured to transmit, to the UE, a second SN RRC message that includes at least one execution condition updated for the subsequent second conditional mobility regarding the at least one candidate PSCell after completion of the first conditional PSCell change. The RAN node according to Appendix 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 PSCs in the subsequent second conditional PSCell change. The RAN node according to any one of Appendices 1 to 3. (Appendix 5) The at least one processor is configured to transmit, to the UE, a third SN RRC message that includes an execution condition for the subsequent second conditional mobility regarding a new candidate PSCell corresponding to the source PSCell after completion of the first conditional PSCell change. The RAN node according to Appendix 4. (Appendix 6) 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 a user equipment (UE), including transmitting, to the UE, a first SN radio resource control (RRC) message that includes setting of a plurality of candidate PSCs for a first conditional primary secondary cell group (SCG) cell (PSCell) change, via a master node (MN) or via a direct signaling radio bearer between the SN and the UE. The first SN RRC message indicates that an operation mode in which the settings 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 is applicable, required, recommended, or available. Method. (Appendix 7) 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 a user equipment (UE), The method includes transmitting, to the UE, a first SN Radio Resource Control (RRC) message including settings of a plurality of candidate PSCs for a first conditional primary secondary cell group (SCG) cell (PSCell) change, via a master node (MN) or via a direct signaling radio bearer between the SN and the UE. The first SN RRC message indicates that an operation mode in which the settings 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 is applicable, required, recommended, or available. Program. (Appendix 8) User Equipment (UE), At least one memory, At least one processor coupled to the at least one memory, Comprising, The at least one processor, Receive a first Secondary Node (SN) Radio Resource Control (RRC) message including settings of a plurality of candidate Primary Secondary Cell Group (SCG) Cells (PSCells) for a first conditional PSCell change, either via a Master Node (MN) or via a direct signaling radio bearer between the UE and the SN, If an execution condition for one of the plurality of candidate PSCs is satisfied, apply the settings corresponding to the one candidate PSC for which the execution condition is satisfied, If the first SN RRC message indicates that an operation mode in which settings of at least one candidate PSC not selected in the first conditional PSC change are reused by the UE for a subsequent second conditional PSC change is required, recommended, or available, maintain the settings of the at least one candidate PSC for use in the second conditional PSC change, UE. (Appendix 9) The at least one processor is configured to receive, from the SN, a second SN RRC message including at least one updated execution condition for a subsequent second conditional PSC change regarding the at least one candidate PSC after completion of the first conditional PSC change, The UE according to Appendix 8. (Appendix 10) The at least one processor is configured to maintain the settings of the source PSC after completion of the first conditional PSC change for use as one of the candidate PSCs in the subsequent second conditional PSC change, The UE according to Appendix 8 or 9. (Appendix 11) If the first SN RRC message indicates that the source PSCell of the first conditional PSCell change is to be one of the candidate PSCs in the subsequent second conditional PSCell change, the at least one processor is configured to maintain the configuration of the source PSCell for use in the second conditional PSCell change. The UE according to Appendix 8 or 9. (Appendix 12) After completion of the first conditional PSCell change, the at least one processor is configured to receive from the SN a third SN RRC message including execution conditions for a subsequent second conditional PSCell change for a new candidate PSC corresponding to the source PSCell. The UE according to Appendix 10 or 11. (Appendix 13) A method performed by a User Equipment (UE), Receiving, via a Master Node (MN) or via a direct signaling radio bearer between the UE and the SN, a first Secondary Node (SN) Radio Resource Control (RRC) message including a configuration of a plurality of candidate PSCs for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change; If an execution condition of one of the plurality of candidate PSCs is satisfied, applying the configuration corresponding to the one candidate PSC for which the execution condition is satisfied, and If the first SN RRC message indicates that an operation mode in which the configuration of at least one candidate PSC not selected in the first conditional PSCell change is reused by the UE for a subsequent second conditional PSCell change is required, recommended, or available, maintaining the configuration of the at least one candidate PSC for use in the second conditional PSCell change. A method comprising. (Appendix 14) A program for causing a computer to perform a method for a User Equipment (UE), comprising: The method includes: Receiving, via a Master Node (MN) or via a direct signaling radio bearer between the UE and a Secondary Node (SN), a first Secondary Node (SN) Radio Resource Control (RRC) message including setting of a plurality of candidate Primary Secondary Cell Group (SCG) Cells (PSCells) for a first conditional PSCell change; If an execution condition for one of the plurality of candidate PSCs is satisfied, applying a setting corresponding to the one candidate PSC for which the execution condition is satisfied; and If the first SN RRC message indicates that an operation mode in which settings of at least one candidate PSC not selected in the first conditional PSC change are reused by the UE for a subsequent second conditional PSC change is applicable, required, recommended, or available, maintaining the settings of the at least one candidate PSC for use in the second conditional PSC change. A program comprising the above. (Appendix 15) A Central Unit (CU) of a Radio Access Network (RAN) node, comprising: 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, which is a response to the first message, from the DU. ​The first message indicates a request for first conditional mobility for a User Equipment (UE), and an operation mode is applied, required, recommended, or available, in which settings of at least one candidate target cell not selected by the first conditional mobility are reused by the UE for subsequent second conditional mobility. CU. (Appendix 16) The second message indicates whether the DU determines that the operation mode is not applicable to one or more candidate target cells prepared by the DU. The CU 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. The CU 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. The CU described in any one of Appendices 15 to 17. (Appendix 19) The first conditional mobility is conditional handover, conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or conditional PSCell addition. The subsequent second conditional mobility is conditional handover or conditional PSCell change. The CU described in any one of Appendices 15 to 18. (Appendix 20) A method performed by a Central Unit (CU) of a Radio Access Network (RAN) node, Sending the first message to a Distributed Unit (DU), and Receiving, from the DU, a second message that is a response to the first message, comprising wherein the first message indicates a request for first conditional mobility for a User Equipment (UE), and an operation mode is applied, required, recommended, or available, in which settings of at least one candidate target cell not selected by the first conditional mobility are 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, and at least one processor coupled to the at least one memory, comprising wherein the at least one processor is configured to receive a first message from a Central Unit (CU) and send a second message, which is a response to the first message, to the CU, wherein the first message indicates a request for first conditional mobility for a User Equipment (UE), and an operation mode is applied, required, recommended, or available, in which settings of at least one candidate target cell not selected by the first conditional mobility are reused by the UE for a subsequent second conditional mobility change. DU. (Appendix 22) wherein the second message indicates whether the DU has determined that the operation mode is not applied to one or more candidate target cells prepared by the DU. The DU according to 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. The DU according to Supplementary Note 21. (Supplementary Note 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. The DU according to any one of Supplementary Notes 21 to 23. (Supplementary Note 25) The first conditional mobility is conditional handover, conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or conditional PSCell addition, The subsequent second conditional mobility is conditional handover or conditional PSCell change. The DU according to any one of Supplementary Notes 21 to 24. (Supplementary Note 26) A method performed by a Distributed Unit (DU) of a Radio Access Network (RAN) node, Receiving a first message from a Central Unit (CU), and Sending a second message, which is a response to the first message, to the CU, Comprising, The first message indicates a request for a first conditional mobility for a User Equipment (UE), and an operation mode in which the settings of at least one candidate target cell not selected by the first conditional mobility are reused by the UE for a subsequent second conditional mobility is applicable, requested, recommended, or available. Method. (Supplementary Note 27) A Central Unit (CU) of a Radio Access Network (RAN) node, at least one memory, and at least one processor coupled to the at least one memory, comprising, the at least one processor is configured to receive, from a first Distributed Unit (DU), a first message indicating a candidate target cell that a User Equipment (UE) has successfully accessed during a first conditional mobility, the first message indicates that the preparation of other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility, CU. (Appendix 28) after receiving the first message, the at least one processor is configured to notify a second DU that the preparation of one or more candidate target cells for the first conditional mobility needs to be maintained for the subsequent second conditional mobility, The CU according to Appendix 27. (Appendix 29) after receiving the first message, the at least one processor is configured to notify a source DU that provides a source cell for the first conditional mobility that the setting of the source cell needs to be maintained for the subsequent second conditional mobility, The CU according to Appendix 27 or 28. (Appendix 30) the first message is an ACCESS SUCCESS message, The CU according to any one of Appendices 27 to 29. (Appendix 31) A method performed by a Central Unit (CU) of a Radio Access Network (RAN) node, Receiving, from a first Distributed Unit (DU), a first message indicating a candidate target cell to which a User Equipment (UE) has successfully accessed during a first conditional mobility, wherein the first message indicates that the preparation of 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, and wherein the at least one processor is configured to send, to a Central Unit (CU), a first message indicating a candidate target cell to which a User Equipment (UE) has successfully accessed during a first conditional mobility, wherein the first message indicates that the preparation of other candidate target cells accepted for the first conditional mobility is maintained for a subsequent second conditional mobility, DU. (Appendix 33) wherein the first message is an ACCESS SUCCESS message, The DU according to Appendix 32. (Appendix 34) A method performed by a Distributed Unit (DU) of a Radio Access Network (RAN) node, comprising sending, to a Central Unit (CU), a first message indicating a candidate target cell to which a User Equipment (UE) has successfully accessed during a first conditional mobility, wherein the first message indicates that the preparation of 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, At least one memory, and At least one processor coupled to the at least one memory, Comprising The at least one processor Receives a first message from a first Distributed Unit (DU) indicating a candidate target cell successfully accessed by a User Equipment (UE) during a first conditional mobility, After receiving the first message, transmits a second message to a second DU indicating that the preparation of one or more candidate target cells for the first conditional mobility needs to be maintained for a subsequent second conditional mobility, Is configured to CU (Appendix 36) After receiving the first message, the at least one processor is configured to transmit a third message to a source DU providing the source cell, informing that the setting of the source cell of the first conditional mobility needs to be maintained for the subsequent second conditional mobility, The CU according to Appendix 35 (Appendix 37) A method performed by a Central Unit (CU) of a Radio Access Network (RAN) node, Receiving a first message from a first Distributed Unit (DU) indicating a candidate target cell successfully accessed by a User Equipment (UE) during a first conditional mobility, and After receiving the first message, transmitting a second message to a second DU indicating that the preparation of one or more candidate target cells for the first conditional mobility needs to be maintained for a subsequent second conditional mobility, A method comprising (Appendix 38) A Central Unit (CU) of a Radio Access Network (RAN) node, at least one memory, and at least one processor coupled to the at least one memory, comprising wherein the at least one processor is configured to: receive, from a first Distributed Unit (DU), a first message indicating a candidate target cell to which a User Equipment (UE) has successfully accessed during a first conditional mobility; after receiving the first message, send a second message to a source DU providing the source cell, the second message informing that the setting of the source cell of the first conditional mobility needs to be maintained for a subsequent second conditional mobility. The CU. (Appendix 39) A method performed by a Central Unit (CU) of a Radio Access Network (RAN) node, the method comprising: receiving, from a first Distributed Unit (DU), a first message indicating a candidate target cell to which 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 providing the source cell, the second message informing that the setting of the source cell of the first conditional mobility needs to be maintained for a subsequent second conditional mobility. The method. (Appendix 40) A User Equipment (UE) comprising: at least one memory, and at least one processor coupled to the at least one memory, comprising wherein the at least one processor is configured to: A User Equipment (UE) receives, from a Radio Access Network (RAN) node, settings of a plurality of candidate Cell Group (CG) sets in which candidate Special Cells (SpCells) are different from each other, selects one candidate SpCell by layer 1 / layer 2 based inter-cell mobility, and applies a set of settings of a candidate CG corresponding to the selected candidate SpCell. UE. (Appendix 41) A method performed by a User Equipment (UE), wherein the method includes receiving, from a Radio Access Network (RAN) node, settings of a plurality of candidate Cell Group (CG) sets in which candidate Special Cells (SpCells) are different from each other, and selecting one candidate SpCell by layer 1 / layer 2 based inter-cell mobility, and applying a set of settings of a candidate CG corresponding to the selected candidate SpCell. The method comprising the steps.

[0147] This application claims priority based on Japanese Patent Application No. 2021-215151 filed on Dec. 28, 2021, and incorporates the entire disclosure thereof herein.

Description of Reference Numerals

[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 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 a User Equipment (UE), comprising: sending, to the UE, a first SN Radio Resource Control (RRC) message including a setting of a plurality of candidate Primary Secondary Cell Group (SCG) Cells (PSCells) for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, via a Master Node (MN) or via a direct signaling radio bearer between the SN and the UE; wherein the first SN RRC message indicates that an operation mode in which a setting 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 is applicable, required, recommended, or available; a method.

2. The method according to claim 1, further comprising determining whether a setting of at least one candidate PSCell not selected in the first conditional PSCell change needs to be maintained by the UE for the subsequent second conditional PSCell change. The method according to claim 1.

3. The method according to claim 1 or 2, further comprising, after completion of the first conditional PSCell change, sending, to the UE, a second SN RRC message including at least one execution condition updated for subsequent second conditional mobility regarding the at least one candidate PSCell. The method according to claim 1 or 2.

4. The method according to claim 1 or 2, wherein the first SN RRC message indicates to the UE that a source PSCell of the first conditional PSCell change is one of candidate PSCs in the subsequent second conditional PSCell change. The method according to claim 1 or 2.

5. The method according to claim 4, further comprising, after completion of the first conditional PSCell change, sending, to the UE, a third SN RRC message including an execution condition for subsequent second conditional mobility regarding a new candidate PSCell corresponding to the source PSCell. The method according to claim 4.

6. A method performed by a User Equipment (UE), comprising: Receiving, via a Master Node (MN) or via a direct signaling radio bearer between the UE and a Secondary Node (SN), a first Secondary Node (SN) Radio Resource Control (RRC) message including a setting of a plurality of candidate Primary Secondary Cell Group (SCG) Cells (PSCells) for a first conditional PSCell change; Applying a setting corresponding to one candidate PSCell for which an execution condition is satisfied if the execution condition for one of the plurality of candidate PSCs is satisfied; and Maintaining the setting of at least one candidate PSCell not selected in the first conditional PSCell change for use in a subsequent second conditional PSCell change if the first SN RRC message indicates that an operation mode in which the setting 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 is required, recommended, or available; A method comprising the above. **Claim 7**: The method according to claim 6, further comprising receiving, from the SN, a second SN RRC message including at least one updated execution condition for a subsequent second conditional PSCell change related to the at least one candidate PSCell after completion of the first conditional PSCell change. The method according to claim 6. **Claim 8**: The method according to claim 6, further comprising maintaining the setting of the source PSCell of the first conditional PSCell change for use as one of the candidate PSCs in the subsequent second conditional PSCell change after completion of the first conditional PSCell change. The method according to claim 6. **Claim 9**: The method according to claim 6, further comprising maintaining the setting of the source PSCell for use in the second conditional PSCell change if the first SN RRC message indicates that the source PSCell of the first conditional PSCell change is to be one of the candidate PSCs in the subsequent second conditional PSCell change. The method according to claim 6.

10. Further comprising receiving, from the SN, a third SN RRC message including execution conditions for a subsequent second conditional PSCell change for a new candidate PSCell corresponding to the source PSCell after completion of the first conditional PSCell change. The method according to claim 8 or 9.

11. 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, from the DU, a second message that is a response to the first message. The method is characterized in that: The first message indicates a request for a first conditional mobility for a User Equipment (UE), and an operation mode is applied in which settings of at least one candidate target cell not selected by the first conditional mobility are reused by the UE for a subsequent second conditional mobility change, which is required, recommended, or available. Method.

12. The second message indicates whether the DU has determined that the operation mode is not applicable to one or more candidate target cells prepared by the DU. The method according to claim 11.

13. The second message indicates whether the DU has prepared the operation mode for one or more candidate target cells prepared by the DU. The method according to claim 11.

14. 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. The method according to any one of claims 11 to 13.

15. The first conditional mobility is conditional handover, conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or conditional PSCell addition. The subsequent second conditional mobility is conditional handover or conditional PSCell change. The method according to any one of claims 11 to 13.

16. 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, which is a response to the first message, to the CU, wherein the first message indicates a request for a first conditional mobility for a User Equipment (UE), and an operation mode is applied, required, recommended, or available, in which settings of at least one candidate target cell not selected by the first conditional mobility are reused by the UE for a subsequent second conditional mobility; Method.

17. The second message indicates whether the DU determines that the operation mode is not applied to one or more candidate target cells prepared by the DU. The method according to claim 16.

18. The second message indicates whether the DU has prepared the operation mode for one or more candidate target cells prepared by the DU. The method according to claim 16.

19. The first message is a UE CONTEXT MODIFICATION REQUEST message or a UE CONTEXT SETUP REQUEST message, and the second message is a UE CONTEXT MODIFICATION RESPONSE message or a UE CONTEXT SETUP RESPONSE message. The method according to any one of claims 16 to 18.

20. The first conditional mobility is conditional handover, conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or conditional PSCell addition, and the subsequent second conditional mobility is conditional handover or conditional PSCell change. The method according to any one of claims 16 to 18.

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