Method performed by user equipment

Abstract

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

Description

Technical Field

[0001] This disclosure relates to a wireless communication system, and more particularly to conditional mobility of wireless terminals.

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-Secondary Node (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 one SN. This CPC is also called SN-initiated Conditional SN Modification without MN involvement.

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

[0004] Furthermore, discussions have been initiated for 3GPP Release 18 regarding further mobility enhancements, including “Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups” (see, for example, Non-Patent Documents 4 and 5). In Release 17's CPA and CPC, the UE must release unused (unselected) CPC / CPA settings depending on which candidate target PSCell is selected and random access is made to the selected target PSCell. Therefore, the UE does not have the opportunity to perform subsequent CPCs without reconfiguring and reinitializing 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 CPCs / CPAs without reconfiguration and reinitialization of CPC / CPA preparations from the network after changing the SCG, thereby reducing CPC / CPA signaling overhead and downtime. [Prior art documents] [Non-patent literature]

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

[0006] The inventors investigated mechanisms and procedures for realizing a function or operating mode called "MR-DC with selective activation of cell groups," and identified various challenges.

[0007] One of these challenges concerns clarifying various procedures related to a function or operating mode called “MR-DC with selective activation of cell groups.” For example, currently, the procedures for utilizing this function or operating mode when applying it to an intra-SN CPC are unclear. In addition, when a Radio Access Network (RAN) node (e.g., gNB) includes a Central Unit (CU) and one or more Distributed Units (DUs), the signaling required between the CU and one or more DUs to support this function or operating mode is unclear.

[0008] Another of these challenges relates to Layer 1 / layer 2 (L1 / L2) based inter-cell mobility. According to Non-Patent Literature 5, one of the objectives for 3GPP Release 18 is to specify the mechanism and procedure of MR-DC with selective activation of cell groups via Layer 3 (L3) enhancement. However, in certain scenarios, such as selective activation of cell groups within a single RAN node (e.g., MN or SN), it may be possible to achieve this by Layer 1 / layer 2 (L1 / L2) based inter-cell mobility instead of L3 based inter-cell mobility.

[0009] One of the objectives that the embodiments disclosed herein seek to achieve is to provide an apparatus, method, and program that contribute to solving at least one of several problems relating to realizing a function or operating mode that enables a subsequent second conditional mobility without reconfiguration or reinitialization from the network after a first conditional mobility, including the problems described above. It should be noted that this objective is only one of several objectives that the embodiments disclosed herein seek to achieve. Other objectives or problems and novel features will be evident from the description herein or from the accompanying drawings. [Means for solving the problem]

[0010] The first aspect is directed to a RAN node configured to act as an 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 to the UE, either via an MN or via a direct signaling radio bearer between the SN and the UE, containing the configuration of several candidate PSCells for a first conditional PSCell change. The first SN RRC message indicates that an operating mode is applied, requested, recommended, or available in which the configuration of at least one candidate PSCell not selected in the first conditional PSCell change is reused by the UE for a subsequent second conditional PSCell change.

[0011] A second aspect relates to a method performed by a RAN node configured to act as an SN associated with an SCG in dual connectivity for a UE. This method includes transmitting a first SN RRC message to the UE, via an MN or via a direct signaling radio bearer between the SN and the UE, which contains the settings of a plurality of candidate PSCells for a first conditional PSCell change. The first SN RRC message indicates that an operating mode is applied, requested, recommended, or available 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.

[0012] A third aspect is directed to a UE, which 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 SN RRC message via an MN or via a direct signaling radio bearer between the UE and the SN, which contains settings for a plurality of candidate PSCells for a first conditional PSCell change. The at least one processor is configured to apply the settings corresponding to the candidate PSCell for which the execution condition is met if one of the plurality of candidate PSCells is met. Furthermore, the at least one processor is configured to maintain the settings of at least one candidate PSCell for use in a second conditional PSCell change if the first SN RRC message indicates that an operating mode is applied, requested, recommended, or available 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.

[0013] The fourth aspect is directed to a method performed by the UE, which includes the following steps: (a) Receiving a first SN RRC message, via the MN or via a direct signaling radio bearer between the UE and the SN, which includes the setting of multiple candidate PSCells for a first conditional PSCell modification; (b) If one of the execution conditions among the multiple candidate PSCells is met, apply the settings corresponding to the candidate PSCell whose execution condition is met; and (c) If the first SN RRC message indicates that an operating mode is applied, requested, recommended, or available in which the settings of at least one candidate PSCell that were not selected in the first conditional PSCell change are reused by the UE for a subsequent second conditional PSCell change, then the settings of at least one candidate PSCell that were not selected in the first conditional PSCell change are maintained for use in the second conditional PSCell change.

[0014] A fifth aspect is directed to a Central Unit (CU) of a RAN node, which 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 to receive a second message from the DU, which is a response to the first message. The first message indicates a request for a first conditional mobility for a UE. In addition, the first message indicates that an operating mode is applied, requested, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE for a subsequent second conditional mobility.

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

[0016] A seventh aspect is directed to a DU of a RAN node, which includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a first message from a CU and send a second message to the CU, which is a response to the first message. The first message indicates a request for a first conditional mobility for a UE. In addition, the first message indicates that an operating mode is applied, requested, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE for a subsequent second conditional mobility.

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

[0018] A ninth aspect is directed to a CU of a RAN node, which 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 first DU indicating a candidate target cell that the UE 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.

[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 a 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.

[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 a 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.

[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 a 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.

[0022] The 13th aspect is directed to the CU of the 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 the UE has successfully accessed during a first conditional mobility. In addition, after receiving the first message, the at least one processor is configured to transmit, 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 the RAN node. The method includes the following steps: (a) 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; and (b) After receiving the first message, transmitting, 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 the 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 the UE has successfully accessed during a first conditional mobility. In addition, after receiving the first message, the at least one processor is configured to transmit, to the 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 sixteenth aspect relates to a method performed by a CU of a RAN node. This method includes the following steps: (a) The UE receives a first message from the first DU indicating a candidate target cell that was successfully accessed during the first conditional mobility; and (b) After receiving the first message, send a second message to the source DU providing the source cell indicating that the source cell configuration for the first conditional mobility needs to be maintained for a subsequent second conditional mobility.

[0026] A 17th aspect is directed to a UE, which 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 for a plurality of different candidate Cell Group (CG) sets for candidate Special Cells (SpCells). Furthermore, the at least one processor is configured to select a candidate SpCell by Layer 1 / layer 2 based inter-cell mobility and to apply the settings for the candidate CG set corresponding to the selected candidate SpCell.

[0027] The 18th aspect is directed to a method performed by the UE, which includes the following steps: (a) Candidate SpCells receive configurations for multiple different candidate CG sets from the RAN node, and (b) Select a candidate SpCell based on Layer 1 / layer 2 inter-cell mobility and apply the settings of the candidate CG set corresponding to the selected candidate SpCell.

[0028] The 19th aspect is directed to a program, which, when loaded into a computer, includes a set of instructions (software code) for causing the computer to perform any of the methods described in the above aspects. [Effects of the Invention]

[0029] According to the above-described embodiment, it is possible to provide an apparatus, method, and program that contribute to solving at least one of several problems related to realizing a function or operating mode that enables a subsequent second conditional mobility without requiring reconfiguration or reinitialization from the network after the first conditional mobility. [Brief explanation of the drawing]

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

[0031] The following describes specific embodiments in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and redundant explanations are omitted where necessary for clarity.

[0032] The multiple embodiments described below can be implemented independently or in combination as appropriate. These multiple embodiments have novel features that differ from each other. Therefore, these multiple embodiments contribute to solving different objectives or problems and contribute to producing different effects.

[0033] The embodiments described below primarily focus on 3GPP Long Term Evolution (LTE) systems and fifth-generation mobile communication systems (5G systems). However, these embodiments may also be applied to other wireless communication systems that support 3GPP's multi-connectivity (e.g., Dual Connectivity) and similar technologies. The term LTE as used herein includes improvements and developments of LTE and LTE-Advanced to enable interworking with 5G systems, unless otherwise specified.

[0034] As used herein, depending on the context, “(if)” may be interpreted as meaning “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 as having the same meaning depending on the context.

[0035] First, the configuration and operation of several network elements common to multiple embodiments will be described. Figure 1 shows an example configuration of a wireless communication system according to one of the multiple embodiments. In the example in Figure 1, the wireless communication system includes RAN node 1, RAN node 2, and UE3. Each element (network function) shown in Figure 1 can be implemented, for example, as a network element on dedicated hardware, as a running software instance on dedicated hardware, or as an instantiated virtualization function 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 a combination of a CU and one or more Distributed Units (e.g., eNB-DUs or gNB-DUs). C-RAN is also called a CU / DU split. Furthermore, a CU may include a Control Plane (CP) Unit (e.g., gNB-CU-CP) and one or more User Plane (UP) Units (e.g., gNB-CU-UP). Therefore, RAN node 1 may be a CU-CP, or a combination of a CU-CP and a CU-UP. Similarly, RAN node 2 may be a CU, or a combination of a CU and one or more DUs. RAN node 2 may be a CU-CP, or a combination of a CU-CP and a CU-UP.

[0037] Each of RAN nodes 1 and 2 may be an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (EUTRAN) node or a Next-generation Radio Access Network (NG-RAN) node. An EUTRAN node may be an eNB or an en-gNB. An NG-RAN node may be a gNB or an ng-eNB. An 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) of E-UTRA-NR Dual Connectivity (EN-DC). An ng-eNB is a node that provides E-UTRA user plane and control plane protocol termination to the UE and is connected to 5GC via an NG interface. The Radio Access Technology (RAT) of RAN node 1 may differ 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 secondary node (SN) of a dual connectivity system, respectively. Therefore, RAN Node 1 may be referred to as MN1 and RAN Node 2 as candidate SN2 in the following discussion.

[0039] This dual connectivity may also 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 a master eNB (in EN-DC), a master ng-eNB (in NGEN-DC), or a master gNB (in NR-DC and NE-DC). Similarly, SN2 may be an en-gNB (in EN-DC), a secondary ng-eNB (in NE-DC), or a secondary gNB (in NR-DC and NGEN-DC). In EN-DC, UE3 is connected to an eNB operating as MN1 and to an en-gNB operating as SN2. In NGEN-DC, UE3 is connected to an ng-eNB operating as MN1 and to a gNB operating as SN2. In NE-DC, UE3 is connected to a gNB operating as MN1 and to an ng-eNB operating as SN2. In NR-DC, UE3 is connected to one gNB (or gNB-DU) operating as MN1 and to another gNB (or gNB-DU) operating as SN2.

[0040] MCG is a group of serving cells associated with (or provided by) MN1, and includes 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 by) SN2, and includes a Primary SCG Cell (PSCell) and optionally one or more Secondary Cells (SCells). PSCell is a Special Cell (SpCell) of SCG and supports Physical Uplink Control Channel (PUCCH) transmission and contention-based Random Access. Note that in LTE (e.g., LTE-DC and NE-DC), PSCell may be an abbreviation for Primary SCell.

[0041] As used herein, the terms “Primary SCG Cell” and its abbreviation “PSCell” mean a cell that is part of a cell group provided by a dual connectivity SN, has an uplink component carrier, and is configured with uplink control channel (e.g., PUCCH) resources. Specifically, the terms “Primary SCG Cell” and its abbreviation “PSCell” may mean a Primary SCG Cell of a cell group provided by a 5G NR-supporting SN (e.g., en-gNB in ​​EN-DC, gNB in ​​NGEN-DC, or gNB in ​​NR-DC), or a Primary SCell of a cell group provided by an E-UTRA-supporting SN (e.g., eNB in ​​LTE DC, or ng-eNB in ​​NE-DC).

[0042] RAN nodes 1 and 2, as well as UE3, support conditional PSCell addition (CPA), which adds the SCG provided by RAN node 2 for UE3. CPA may also be called 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 Figure 1, multiple candidate cells (i.e., candidate PSCells) provided by multiple candidate SN2 may be prepared for CPA. In the CPA procedure, UE3 receives from MN1 the configurations of one or more candidate PSCells prepared by one or more candidate SNs, and one or more CPA execution conditions associated with them. More specifically, the configuration of each candidate PSCell is an Information Element (IE) (e.g., condRRCReconfig) in MN1's RRC message, and the configurations of one or more candidate PSCells and their associated CPA execution conditions are contained in conditional mobility configuration information (e.g., conditionalReconfiguration IE) generated by MN1.

[0044] The configuration for each candidate PSCell is generated by the candidate SN (e.g., candidate SN2) that provides (or prepares) this candidate PSCell. The configuration for each candidate PSCell includes at least configuration information for the candidate PSCell. The configuration for 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 for 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 for each candidate PSCell may be an SN RRC Reconfiguration message generated by the candidate SN (e.g., candidate SN2) that provides (or prepares) this candidate PSCell. Some or all of the configuration for one or more candidate PSCells is 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 contains the candidate PSCell settings received from the candidate SN (e.g., RB settings, CG settings, SCG settings, SCG radio resource settings, and SN RRC Reconfiguration messages, or any combination thereof).

[0045] On the other hand, the CPA execution conditions are generated by MN1. The CPA execution conditions may consist of one or more trigger conditions. The conditions or criteria that trigger a CPA event may be similar to those for measurement reporting events, and may be, for example, CondEvent A3, CondEvent A4, or CondEvent A5. CondEvent A3 is "Conditional reconfiguration candidate becomes amount of offset better than PCell / PSCell". CondEvent A4 is "Conditional reconfiguration candidate becomes better than absolute threshold". CondEvent A5 is "PCell / PSCell becomes worse than absolute threshold 1 AND Conditional reconfiguration candidate becomes better than another absolute threshold 2". UE3 evaluates the CPA execution conditions. If the execution conditions for 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 were met) (e.g., one or any combination of RB settings, CG settings, SCG settings, SCG wireless resource settings, and SN RRC Reconfiguration messages). If a bearer requiring SCG wireless resources is configured, UE3 synchronizes to the selected PSCell. If the execution conditions for two or more candidate PSCells are met, UE3 may select one of those candidate PSCells and perform the actions described above.

[0046] In addition, RAN node 2 and UE3 support intra-SN CPC. Intra-SN CPC may also be called SN-initiated Conditional SN Modification without MN involvement. Intra-SN CPC is an intra-SN PSCell modification procedure that is executed only when the CPC execution conditions are met.

[0047] In the Intra-SN CPC procedure, UE3 receives from SN2 one or more candidate PSCell configurations and one or more CPC execution conditions associated with them. Each candidate PSCell configuration and associated CPC execution condition are included in the CPC configuration for intra-SN CPC. SN2 may send these to UE3 via MN1 or directly to UE3 via a Signaling Radio Bearer 3 (SRB3) between SN2 and UE3. More specifically, each candidate PSCell configuration is an information element (IE) (e.g., condRRCReconfig) in SN2's RRC message, and the one or more candidate PSCell configurations and associated CPC execution conditions are included in conditional mobility configuration information (e.g., conditionalReconfiguration IE) generated by SN2.

[0048] Each candidate PSCell configuration includes at least configuration information for the candidate PSCell. Each candidate PSCell configuration may further include configuration information for one or more SCells associated with the candidate PSCell (i.e., configured together with or in association with the candidate PSCell). Each candidate PSCell configuration 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, each candidate PSCell configuration may be an SN RRC Reconfiguration message generated by SN2.

[0049] The CPC execution conditions for Intra-SN CPC may consist of one or more trigger conditions. The conditions or criteria that trigger a CPC event may be similar to those for measurement reporting events, 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 settings corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution conditions are met), and synchronizes with the selected candidate PSCell. If the execution conditions for two or more candidate PSCells are met, UE3 may select one of those candidate PSCells and perform the actions described above.

[0050] One or both of RAN nodes 1 and 2 may have the configuration shown in Figure 2. Each element (network function) shown in Figure 2 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualization function instantiated on an application platform. One or both of RAN nodes 1 and 2 may include, but are not limited to, a CU21 and one or more DUs22 as shown in Figure 2. The CU21 and each DU22 are connected by interface 201. UE3 is connected to at least one DU22 via at least one air interface 202.

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

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

[0053] The embodiments described below provide improvements to conditional mobility. Specifically, the embodiments below provide improvements to conditional mobility to support a function or operating mode called “Multi-Radio Dual Connectivity (MR-DC) with selective activation of cell groups.” In this specification, this function or operating mode may also apply to conditional mobility that does not necessarily involve MR-DC, i.e., CHO. Furthermore, this function or operating mode may also apply to an improved CHO in which an SCG (at least PSCell) is added along with the execution of the CHO. In this specification, this function or operating mode enables a subsequent second conditional mobility without at least re-initialization of the conditional mobility preparation after modifying or adding a serving cell, serving cell group, PSCell, or SCG in a first conditional mobility. In other words, as defined herein, the function or mode of operation enables UE3 to reuse or maintain at least a portion of the candidate target cell settings or candidate PSCell settings (e.g., RB settings, CG settings, SCG settings, radio resource settings, and SCG radio resource settings, one or any combination thereof) received from the network in a first conditional mobility for a subsequent second conditional mobility. At least a portion of the execution conditions for the first conditional mobility may be reconfigured, updated, or modified for the second conditional mobility. Similarly, at least a portion of the security key settings information (e.g., sk-Counter, Next Hop (NH), NH Chaining Count (NCC)) or security key information (e.g., SN Security Key) for the first conditional mobility may be reconfigured, updated, or modified for the second conditional mobility. The type of the second conditional mobility may differ from the type of the first conditional mobility.For example, the first conditional mobility may be CPA, while the second conditional mobility may be Inter-SN CPC or Intra-SN CPC. Alternatively, the first conditional mobility may be Inter-SN CPC, while the second conditional mobility may be Intra-SN CPC.

[0054] The function or operating mode may be called, 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, but is not limited to these. For convenience of explanation, in the following embodiments, the function or operating mode will be referred to as selective CG activation or selective cell activation. The term selective CG activation may be used for conditional mobility with MR-DC (e.g., CPA, inter-SN CPC, intra-SN CPC). On the other hand, the term selective cell activation may be used for conditional mobility that does not necessarily involve MR-DC (e.g., CHO).

[0055] In this specification, a combination of candidate Special Cells (SpCells) and SCell(s) may be referred to as a candidate Cell Group (CG) set of conditional mobility or selective CG activation. Selective CG activation can also be considered as a change or switch of the serving SCG between multiple candidate CG sets. A single candidate CG set contains at least a candidate SpCell and optionally one or more SCells. A candidate cell (candidate SpCell) may be the current SCell (i.e., a SCell included in the current SCG) or a non-serving cell not provided to UE3. UE3 may configure multiple candidate CG sets in which those candidate SpCells are different from each other. If it is conditional mobility (e.g., CHO) with respect to an MCG, then candidate SpCells are candidate PCells, and multiple candidate CG sets are multiple candidate MCG sets. On the other hand, if we are dealing with conditional mobility related to SCG (e.g., CPA, intra-SN CPC, inter-SN CPC), then candidate SpCells are candidate PSCells, and multiple candidate CG sets are multiple candidate SCG sets.

[0056] In this specification, the terms MN RRC message, MN RRC Reconfiguration message, SN RRC message, and SN RRC Reconfiguration message are used. These terms are used for convenience to distinguish RRC messages generated by MN from RRC messages generated by SN. Therefore, MN RRC messages and MN RRC Reconfiguration messages may also be simply referred to as RRC messages and RRC Reconfiguration messages. Similarly, SN RRC messages and SN RRC Reconfiguration messages may also be simply referred to as RRC messages and RRC Reconfiguration messages.

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

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

[0059] In step 301, SN2 generates an SN RRC message that includes the configuration of multiple candidate PSCells for the first CPC and an indication of selective CG activation. The indication of selective CG activation indicates to UE3 that selective CG activation is applied, required, recommended, or available. In other words, the indication of selective CG activation indicates that an operating mode is applied, required, recommended, or available in which the configuration of at least one candidate PSCell that was not selected in the first CPC is reused by UE3 for the subsequent second CPC. The indication of selective CG activation may be rephrased as, for example, a selective CG activation configuration. In step 302, SN2 sends the generated SN RRC message to UE3. SN2 may send the SN RRC message to UE3 via MN1 or directly to UE3 via a Signaling Radio Bearer 3 (SRB3) between SN2 and UE3.

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

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

[0062] For example, UE3 may reuse the execution conditions for candidate PSCells that were not selected in the first CPC for a subsequent second CPC, and autonomously switch the reference cell in those execution conditions from the source PSCell of the first CPC to the candidate PSCell selected in the first CPC. In other words, UE3 may autonomously update or modify the reference cell of the execution conditions for the first CPC. This allows UE3 to start evaluating the execution conditions for the subsequent second CPC without receiving a signal from SN2 to update the execution conditions.

[0063] For example, UE3 may retain the source PSCell setting after the completion of the first CPC in order to use the source PSCell of the first CPC as one of the candidate PSCells in the second CPC. This makes it possible to use the source cell of a CPC as one of the candidate PSCells in a subsequent CPC. SN2 may inform UE3 whether the source PSCell of the first CPC will be a candidate PSCell in the subsequent second CPC. Specifically, SN2 may use the SN RRC message sent to UE3 to set up the first CPC (step 302 in Figure 3, step 401 in Figure 4) to indicate to UE3 that the source PSCell of the first CPC will be one of the candidate PSCells in the subsequent second CPC. If the SN RRC message (step 302 in Figure 3, step 401 in Figure 4) indicates this, UE3 may retain the source PSCell setting after the completion of the first CPC.

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

[0065] Figures 5A and 5B show an example of signaling for an intra-SN CPC procedure in which direct SRB (i.e., SRB3) is used between SN2 and UE3. In step 501, SN2 sends an SN RRC Reconfiguration message to UE3 via SRB3 to configure the CPC. The SN RRC Reconfiguration message includes the CPC configuration and the selective CG activation indication (or configuration). As described above, the CPC configuration for intra-SN CPC includes the configuration of one or more candidate PSCells and the associated CPC execution conditions. How the CPC configuration and selective CG activation configuration are included in the SN RRC Reconfiguration message is not particularly limited. Specifically, an information element (IE) or field indicating the CPC configuration may be independent of the IE or field indicating the selective CG activation configuration. In this case, the IE or field indicating the selective CG activation configuration may mean that the associated CPC configuration is applied to (or subject to) selective CG activation. Alternatively, an information element (IE) or field indicating a CPC setting may contain an IE or field indicating a selective CG activation setting, or vice versa. For example, an IE or field indicating a CPC setting may be condRRCReconfig, and the SN RRC Reconfiguration message it contains may further contain an IE or field indicating a selective CG activation setting. In this case, it may mean that the setting specified by the SN RRC Reconfiguration is applied to (or is subject to) selective CG activation.The IE or field indicating the selective CG activation setting may also be, for example, selectiveCG-Activation, adaptiveCG-Switch, subsequentCell-Change, subsequentCG-Change, or cpc-Kept).

[0066] In step 502, the new configuration is applied, and the evaluation of CPC execution conditions for multiple candidate PSCells begins. UE3 maintains a connection with the source PSCell and responds to SN2 via SRB3 with an SN RRC Reconfiguration Complete message.

[0067] In step 503, if the execution conditions for one candidate PSCell (in this case, candidate cell #1) are met, UE3 starts CPC execution while retaining the selective CG activation settings (and CPC settings). Specifically, 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 met), and synchronizes with that candidate PSCell. In step 504, 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, UE3 retains the settings of one or more unselected candidate PSCells for reuse in subsequent CPCs. UE3 may retain the CPC execution conditions associated with one or more unselected candidate PSCells. As described above, UE3 may autonomously change the reference cell for these CPC execution conditions from the source PSCell to the selected candidate PSCell (i.e., Cell #1). 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.

[0069] Furthermore, UE3 may use the source PSCell of the first CPC as one of the candidate PSCells for subsequent CPCs. UE3 may decide whether or not to make the source PSCell of the first CPC a new candidate PSCell based on the selective CG activation setting received in step 501.

[0070] In step 505, UE3 may receive an SN RRC Reconfiguration message from SN2 via SRB3 indicating updated or modified CPC execution conditions. This SN RRC Reconfiguration message may include CPC execution conditions for the source PSCell of the first CPC which is a new candidate PSCell. In step 506, UE3 applies the received CPC execution conditions and responds to SN2 via SRB3 with an SN RRC Reconfiguration Complete message. If no updates, modifications, or additions to the CPC execution conditions are required, steps 505 and 506 may be omitted.

[0071] After the initial CPC is complete, UE3 continues to evaluate the execution conditions of the unselected candidate PSCell(s). UE3 may also begin evaluating the CPC execution conditions for the source PSCell of the initial CPC, which has been designated as a new candidate PSCell. In step 507, if the execution conditions for one candidate PSCell (let's call it candidate cell #2) are met, UE3 starts the CPC execution while retaining the selective CG activation settings (and CPC settings). Specifically, UE3 detaches from the current source PSCell (i.e., Cell #1), applies the stored settings corresponding to the selected candidate PSCell (i.e., the candidate PSCell whose execution conditions are met), and synchronizes with that 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] Beyond step 508, UE3 may continue evaluating the CPC execution conditions for 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 decide whether or not 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 decide whether or not 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 signaling for an intra-SN CPC procedure in which direct SRB (i.e., SRB3) is not used between SN2 and UE3. The procedure in Figures 6A and 6B is identical to the procedure in Figures 5A and 5B, except that the forwarding of SN RRC messages between SN2 and UE3 is done via MN1. Specifically, steps 601 and 602 correspond to step 501. In step 601, SN2 sends an SN Modification Required message to MN1, which contains an SN RRC Reconfiguration message containing the CPC settings. 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 containing an SN RRC Reconfiguration Complete message. UE3 maintains a connection with the source PSCell and begins evaluating the CPC execution conditions for multiple candidate PSCells. In step 604, MN1 forwards the SN RRC Reconfiguration Complete message to SN2, including it in an SN Modification Confirm message.

[0075] Step 605 corresponds to step 503. Steps 606 and 607 correspond to step 504. In step 606, UE3 completes the CPC execution procedure by sending a UL Information Transfer MRDC message to MN1. The UL Information Transfer MRDC message contains 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 the 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 contains an SN RRC Reconfiguration message indicating the 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 to SN2, including it in an SN Modification Confirm message.

[0078] Step 612 corresponds to step 507. Steps 613 and 614 correspond to step 508. In step 613, UE3 completes the CPC execution procedure by sending a UL Information Transfer MRDC message to MN1. The UL Information Transfer MRDC message contains 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 the RRC Transfer message, to SN2.

[0079] <Second Embodiment> This embodiment provides details of signaling between CU and 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 example shown in Figures 1 and 2.

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

[0081] Furthermore, or alternatively, the MN1 of this embodiment may have the CU-DU configuration shown in Figure 2. The MN21 may include the CU21 and one or more DUs22. In this case, the MN1 supports intra-DU conditional mobility of the UE3 within one DU. Similarly, the MN1 supports inter-DU conditional mobility of the UE3 between DUs. These intra-DU and inter-DU conditional mobilitys may be CHOs, i.e., conditional intra-MN handovers (or conditional PCell changes).

[0082] Figure 7 shows an example of signaling between CU21 and DU22. As mentioned above, CU21 and DU22 may belong to SN2 or MN1. In step 701, CU21 sends a CU-DU control message (e.g., an F1AP message) to DU22 indicating a request for a first conditional mobility for UE3. This 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 CHO, CPA, or 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 tells DU22 that selective cell / CG activation is applied, requested, recommended, or available. In other words, the indication of selective cell / CG activation indicates that an operating mode is applied, requested, recommended, or available in which the configuration of at least one candidate target cell that was not selected in the first conditional mobility is reused by UE3 for the subsequent second conditional mobility. The indication of selective cell / CG activation may also be rephrased as, for example, a request for selective cell / CG activation. Both the first and second conditional mobilitys may be CHO. Both the first and second conditional mobilitys may be CPC. Alternatively, the first conditional mobility may be CPA and the second conditional mobility may be CPC. This allows DU22 to recognize whether the preparation of candidate target cells for the first conditional mobility needs to be maintained 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 has determined that selective cell / CG activation is not applied 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 is willing to accept the preparation of one or more candidate target cells for the first conditional mobility but is not willing to accept the request for selective cell / CG activation, DU22 may inform CU21 in a response message that it accepts the preparation for the first conditional mobility and rejects the request for 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 a UE CONTEXT MODIFICATION REQUEST message. In the example in Figure 8, if a Selective CG Activation IE is included in a Conditional Intra-DU Mobility Information IE within a 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 requested to maintain the preparation of 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 modified as appropriate. For example, one of the possible values ​​for the enumerated type IE, CHO Trigger 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 a UE CONTEXT MODIFICATION RESPONSE message. In the example in Figure 9, if a 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 a UE CONTEXT SETUP REQUEST message. In the example in Figure 10, if a Selective CG Activation IE is included in a 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 requested to maintain the preparation of 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 modified as appropriate. For example, one of the possible values ​​for the enumerated type IE, CHO Trigger 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 in Figure 11, if a Selective CG Activation IE is included in the UE CONTEXT SETUP RESPONSE message, the IE indicates whether the selective cell / CG activation has been accepted (or prepared) by DU22.

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

[0093] <Third Embodiment> This embodiment provides details of signaling between CU and 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 example shown in Figures 1 and 2.

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

[0095] Furthermore, or alternatively, the MN1 of this embodiment may have the CU-DU configuration shown in Figure 2. The MN21 may include the CU21 and one or more DUs22. In this case, the MN1 supports intra-DU conditional mobility of the UE3 within one DU. Similarly, the MN1 supports inter-DU conditional mobility of the UE3 between DUs. These intra-DU and inter-DU conditional mobilitys may be CHOs, i.e., conditional intra-MN handovers (or conditional PCell changes).

[0096] Figure 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) to CU21 indicating a candidate target cell that UE3 successfully accessed during the first conditional mobility. This control message may also be an ACCESS SUCCESS message. The first conditional mobility may be CHO, CPA, or 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 the subsequent second conditional mobility. Both the first and second conditional mobilitys may be CHO. Both the first and second conditional mobilitys may be CPC. Alternatively, the first conditional mobility may be CPA and the second conditional mobility may be CPC. This allows CU21 to 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 act 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 the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. This allows other target DUs to 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] Furthermore, or alternatively, after receiving the message in step 1201, CU21 may inform the source DU providing the source cell for the first conditional mobility that the source cell configuration needs to be maintained for the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. This allows the source DU to recognize that the source cell configuration for the first conditional mobility needs 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 signaling between CU and 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 example shown in Figures 1 and 2.

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

[0102] Furthermore, or alternatively, the MN1 of this embodiment may have the CU-DU configuration shown in Figure 2. The MN21 may include the CU21 and one or more DUs22. In this case, the MN1 supports intra-DU conditional mobility of the UE3 within one DU. Similarly, the MN1 supports inter-DU conditional mobility of the UE3 between DUs. These intra-DU and inter-DU conditional mobilitys may be CHOs, i.e., conditional intra-MN handovers (or conditional PCell changes).

[0103] Figure 13 shows an example of signaling between CU21 and two targets DUs22A and 22B. In step 1301, target DU22A sends a CU-DU control message (e.g., F1AP message) to CU21 indicating a candidate target cell that UE3 successfully accessed during the first conditional mobility. This control message may be identical to an existing ACCESS SUCCESS message.

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

[0105] Furthermore, after receiving the message in step 1301, CU21 may inform the source DU providing the source cell for the first conditional mobility that the source cell configuration needs to be maintained for the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. This allows the source DU to recognize that the source cell configuration for the first conditional mobility needs 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 Figure 13 may be modified as follows.

[0107] <Fifth Embodiment> This embodiment provides details of signaling between CU and 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 example shown in Figures 1 and 2.

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

[0109] Furthermore, or alternatively, the MN1 of this embodiment may have the CU-DU configuration shown in Figure 2. The MN21 may include the CU21 and one or more DUs22. In this case, the MN1 supports intra-DU conditional mobility of the UE3 within one DU. Similarly, the MN1 supports inter-DU conditional mobility of the UE3 between DUs. These intra-DU and inter-DU conditional mobilitys may be CHOs, i.e., conditional intra-MN handovers (or conditional PCell changes).

[0110] Figure 14 shows an example of signaling between CU21 and two targets DUs22A and 22B. In step 1401, target DU22A sends a CU-DU control message (e.g., F1AP message) to CU21 indicating a candidate target cell that UE3 successfully accessed during the first conditional mobility. This control message may be identical to an existing ACCESS SUCCESS message.

[0111] In step 1402, after receiving the message in step 1401, CU21 informs the source DU22S providing the source cell for the first conditional mobility that the source cell configuration needs to be maintained for the second conditional mobility. CU21 may send this notification via a UE CONTEXT MODIFICATION REQUEST message. This allows the source DU22S to recognize that the source cell configuration for 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 for 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 a single RAN node (e.g., MN1 or SN2) using L1 / L2-based inter-cell mobility. The configuration example of the wireless communication system according to this embodiment may be the same as the example shown in Figures 1 and 2.

[0113] L1 / L2-based inter-cell mobility may also be inter-cell mobility based on Layer 1 (L1) measurements. The L1 measurement may be L1 Synchronization Signal (SS)-RSRP measurement, L1 Channel State Information (CSI)-RSRP measurement, 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, the 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 UE3's L1 (Physical (PHY) layer) or L2 (e.g., MAC layer) is triggered to perform L1 / L2-based inter-cell mobility, when it starts, or when it completes (from an L1 / L2 perspective), it may notify UE3's RRC layer of the L1 / L2-based inter-cell mobility performance. At this time, UE3's L1 or L2 may notify the RRC layer which candidate cell (e.g., PCell, PSCell) to change (or switch) the serving cell to. Alternatively, UE3's L1 or L2 may notify the RRC layer which CG set to change (or switch) to. In response, UE3's RRC layer may change (or switch) the CG set to use. Similarly, when L1 or L2 of a RAN node detects that UE3 is performing (or has completed) L1 / L2-based inter-cell mobility, L1 or L2 of the RAN node may notify the RRC layer of the RAN node. At this time, L1 or L2 of the RAN node may notify the RRC layer which candidate cell (e.g., PCell, PSCell) to change (or switch) the serving cell to. Alternatively, L1 or L2 of the RAN node may notify which CG set to change (or switch) to.

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

[0116] The RAN node and UE3 consider a combination of a candidate Special Cell (SpCell) and SCell(s) as a candidate Cell Group (CG) set. A candidate CG set contains at least a candidate SpCell and optionally one or more SCells. A candidate cell (candidate SpCell) may be the current SCell (i.e., a SCell included in the current SCG) or a non-serving cell not provided to UE3. UE3 configures multiple candidate CG sets, each containing different candidate SpCells. If the RAN node is MN1, candidate SpCells are candidate PCells, and multiple candidate CG sets are multiple candidate MCG sets. On the other hand, if the RAN node is SN2, candidate SpCells are candidate PSCells, and multiple candidate CG sets are multiple candidate SCG sets. UE3 switches the serving CG between multiple candidate CG sets using Layer 1 / layer 2 based inter-cell mobility.

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

[0118] In one example, UE3 initiates a PSCell change if it determines, based on L1 measurements, that the execution / triggering condition for one candidate cell has been met. The lower layer of UE3 (e.g., the MAC layer or the Physical (PHY) layer) notifies the RRC layer of the PSCell change, and the RRC layer may change or switch its RRC settings to those 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 UE3's random access to selected candidate cells. 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 an ACCESS SUCCESS message. Based on the report from UE3 or detection by the serving RAN node, the serving RAN node switches from the current CG set to the candidate CG set corresponding to the candidate SpCell selected by UE3.

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

[0121] In step 1601, SN2 configures multiple candidate SCG sets in UE3. Specifically, SN2 provides UE3 with the configuration of multiple candidate SCG sets and information for the execution of L1 / L2-based inter-cell mobility (e.g., execution / triggering conditions). SN2 sends these configurations to UE3 using the SN RRC Reconfiguration message. The SN RRC Reconfiguration message is sent to UE3 either directly via 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 the L1 measurement, that the execution / triggering condition of one candidate cell (in this case, candidate cell #1) has been met, it begins modifying the PSCell 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 has been met), and synchronizes with that candidate PSCell (i.e., Cell #1). In step 1604, UE3 may perform random access to that candidate PSCell (i.e., Cell #1).

[0123] Even after the SCG switch, UE3 continues to evaluate the execution / triggering conditions for the candidate SCG set. In step 1605, if UE3 determines, based on the L1 measurement, that the execution / triggering conditions for the other candidate cell (in this case, candidate cell #2) have been met, it begins changing the PSCell to the selected candidate PSCell (i.e., Cell #2). In step 1606, UE3 may perform random access to the candidate PSCell (i.e., Cell #1).

[0124] According to the operation of the UE3 and RAN node described in this embodiment, selective activation of cell groups within a single RAN node (e.g., MN or SN) can be achieved through L1 / L2-based inter-cell mobility.

[0125] Next, configuration examples of RAN nodes 1 and 2 and UE3 according to the above-described embodiments will be explained. Figure 15 is a block diagram showing a configuration example of RAN node 1 according to the above-described embodiment. The configuration of RAN node 2 may be the same as the configuration shown in Figure 17. Referring to Figure 17, RAN node 1 includes a radio frequency transceiver 1701, a network interface 1703, a processor 1704, and a memory 1705. The RF transceiver 1701 performs analog RF signal processing to communicate with UEs, including UE3. The RF transceiver 1701 may include multiple transceivers. The RF transceiver 1701 is coupled with an antenna array 1702 and a processor 1704. The RF transceiver 1701 receives modulation symbol data from the processor 1704, generates a transmit RF signal, and supplies the transmit RF signal to the antenna array 1702. The RF transceiver 1701 also generates a baseband receive signal based on the received 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 may include, for example, multiple phase shifters and multiple power amplifiers.

[0126] The network interface 1703 is used to communicate with network nodes (e.g., RAN nodes 2 and 4, as well as the control and forwarding nodes of the core network). The network interface 1703 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0127] Processor 1704 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Processor 1704 may include multiple 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 for 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. Furthermore, 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] The processor 1704 may include a digital beamformer module for beamforming. The digital beamformer module may include a Multiple Input Multiple Output (MIMO) encoder and precoder.

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

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

[0132] Furthermore, if RAN node 1 is a CU (e.g., eNB-CU or gNB-CU) or CU-CP, RAN node 1 does not need to include RF transceiver 1701 (and antenna array 1702).

[0133] Figure 18 is a block diagram showing an example configuration of UE3. The 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 multiple transceivers. The analog RF signal processing performed by the RF transceiver 1801 includes frequency upconversion, frequency downconversion, and amplification. The RF transceiver 1801 is coupled with the antenna array 1802 and the baseband processor 1803. The RF transceiver 1801 receives modulation symbol data (or OFDM symbol data) from the baseband processor 1803, generates a transmit RF signal, and supplies the transmit RF signal to the antenna array 1802. The RF transceiver 1801 also generates a baseband receive signal based on the received RF signal received by the antenna array 1802 and supplies it to the baseband processor 1803. The RF transceiver 1801 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, multiple phase shifters and multiple power amplifiers.

[0134] The baseband processor 1803 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) generation / decomposition of transmission format (transmission frame), (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT). Control plane processing, on the other hand, includes communication management at Layer 1 (e.g., transmit power control), Layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and Layer 3 (e.g., signaling related to attach, mobility, and call management).

[0135] For example, the digital baseband signal processing by the baseband processor 1803 may include signal processing for the SDAP layer, PDCP layer, RLC layer, MAC layer, and PHY layer. Furthermore, the control plane processing by the baseband processor 1803 may include processing for 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) for performing digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) for performing control plane processing. In this case, the protocol stack processor for performing control plane processing may be shared with the application processor 1804 described later.

[0138] The application processor 1804 is also called a CPU, MPU, microprocessor, or processor core. The application processor 1804 may include multiple processors (multiple processor cores). The application processor 1804 implements various functions of UE3 by executing system software programs (Operating System (OS)) and various application programs (e.g., calling applications, web browsers, mail clients, camera operation applications, music playback applications) read from memory 1806 or memory not shown.

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

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

[0141] Memory 1806 may store one or more software modules (computer programs) 1807 containing instruction sets and data for performing the processing by UE3 as described in the above embodiments. In some implementations, the baseband processor 1803 or application processor 1804 may be configured to read and execute the software modules 1807 from memory 1806 to perform the processing of UE3 as described with reference to the drawings in the above embodiments.

[0142] Furthermore, the control plane processing and operation performed by the UE3 described in the above embodiment can be realized by other elements other than the RF transceiver 1801 and antenna array 1802, namely at least one of the baseband processor 1803 and application processor 1804 and the memory 1806 storing the software module 1807.

[0143] As illustrated with reference to Figures 17 and 18, each of the processors in RAN nodes 1 and 2 and UE3 according to the above embodiment can execute one or more programs containing a set of instructions for causing a computer to perform the algorithms described with reference to the drawings. The program, when loaded into a computer, contains a set of instructions (or software code) for causing the computer to perform one or more functions described in the embodiment. The program may be stored on a non-temporary computer-readable medium or a physical storage medium. Examples, but not limited, of the computer-readable medium or physical storage medium include 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® disc or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage devices. The program may be transmitted over a temporary computer-readable medium or a communication medium. Examples, but not limited, of the temporary computer-readable medium or communication medium include electrical, optical, acoustic or other forms of propagating signals.

[0144] The embodiments described above are merely examples of how the technical concept obtained by the present inventor can be applied. In other words, the technical concept is not limited to the embodiments described above, and various modifications are certainly possible.

[0145] For example, some or all of the above embodiments may also be described as follows, but are not limited to the following.

[0146] (Note 1) A radio access network (RAN) node configured to operate as a Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for User Equipment (UE), At least one memory, The at least one processor coupled to the at least one memory, Equipped with, The at least one processor is configured to transmit a first SN Radio Resource Control (RRC) message to the UE via the Master Node (MN) or via a direct signaling radio bearer between the SN and the UE, which includes the setting of a plurality of candidate PSCells for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) modification. The first SN RRC message indicates that an operating mode is applied, requested, recommended, or available in which the settings of at least one candidate PSCell that were not selected in the first conditional PSCell change are reused by the UE for a subsequent second conditional PSCell change. RAN node. (Note 2) The at least one processor is configured to determine whether the settings of at least one candidate PSCell that were not selected in the first conditional PSCell change need to be maintained by the UE for the subsequent second conditional PSCell change. The RAN node described in Appendix 1. (Note 3) The at least one processor is configured to send the UE a second SN RRC message after the completion of the first conditional PSCell modification, which includes at least one updated execution condition for the subsequent second conditional mobility relating to the at least one candidate PSCell. The RAN node described in Appendix 1 or 2. (Note 4) The first SN RRC message indicates to the UE that the source PSCell of the first conditional PSCell modification is one of the candidate PSCells in the subsequent second conditional PSCell modification. A RAN node as described in any one of the following appendices 1 to 3. (Note 5) The at least one processor is configured to send the UE a third SN RRC message after the completion of the first conditional PSCell modification, which includes the execution conditions for the subsequent second conditional mobility relating to a new candidate PSCell corresponding to the source PSCell. The RAN node described in Appendix 4. (Note 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 User Equipment (UE), The system includes transmitting a first SN Radio Resource Control (RRC) message to the UE via the Master Node (MN) or via a direct signaling radio bearer between the SN and the UE, which includes the configuration of multiple candidate PSCells for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) modification. The first SN RRC message indicates that an operating mode is applied, requested, recommended, or available in which the settings of at least one candidate PSCell that were not selected in the first conditional PSCell change are reused by the UE for a subsequent second conditional PSCell change. method. (Note 7) A program for causing a computer to perform a method for a radio access network (RAN) node configured to act as a Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for User Equipment (UE), The method comprises transmitting a first SN Radio Resource Control (RRC) message to the UE via the Master Node (MN) or via a direct signaling radio bearer between the SN and the UE, which includes the configuration of a plurality of candidate PSCells for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) modification. The first SN RRC message indicates that an operating mode is applied, requested, recommended, or available in which the settings of at least one candidate PSCell that were not selected in the first conditional PSCell change are reused by the UE for a subsequent second conditional PSCell change. program. (Note 8) User Equipment (UE), At least one memory, The at least one processor coupled to the at least one memory, Equipped with, The aforementioned at least one processor is A first Secondary Node (SN) Radio Resource Control (RRC) message, which includes the setting of multiple candidate PSCells for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) modification, is received via the Master Node (MN) or via a direct signaling radio bearer between the UE and the SN. If one of the above multiple candidate PSCells is found to be executed, the settings corresponding to the candidate PSCell whose execution condition is found are applied. If the first SN RRC message indicates that an operating mode is applied, requested, recommended, or available in which the settings of at least one candidate PSCell that were not selected in the first conditional PSCell change are reused by the UE for a subsequent second conditional PSCell change, then the settings of at least one candidate PSCell are maintained for use in the second conditional PSCell change. UE. (Note 9) The at least one processor is configured to receive from the SN a second SN RRC message after the completion of the first conditional PSCell modification, which includes at least one updated execution condition for the subsequent second conditional PSCell modification relating to the at least one candidate PSCell. UE as described in Appendix 8. (Note 10) The at least one processor is configured to maintain the settings of the source PSCell after the completion of the first conditional PSCell change in order to use the source PSCell of the first conditional PSCell change as one of the candidate PSCells in the subsequent second conditional PSCell change. UE as described in Appendix 8 or 9. (Note 11) The at least one processor is configured to maintain the settings of the source PSCell for use in the second conditional PSCell change if the first SN RRC message indicates that the source PSCell for the first conditional PSCell change is one of the candidate PSCells in the subsequent second conditional PSCell change. UE as described in Appendix 8 or 9. (Note 12) The at least one processor is configured to receive from the SN, after the completion of the first conditional PSCell modification, a third SN RRC message containing the execution conditions for the subsequent second conditional PSCell modification relating to a new candidate PSCell corresponding to the source PSCell. UE as described in Appendix 10 or 11. (Note 13) A method performed by User Equipment (UE), Receiving a first Secondary Node (SN) Radio Resource Control (RRC) message, which includes the setting of multiple candidate PSCells for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) modification, via the Master Node (MN) or via a direct signaling radio bearer between the UE and the SN, If one of the execution conditions among the multiple candidate PSCells is met, the settings corresponding to the candidate PSCell whose execution condition is met will be applied, and If the first SN RRC message indicates that an operating mode is applied, requested, recommended, or available in which the settings of at least one candidate PSCell that were not selected in the first conditional PSCell change are reused by the UE for a subsequent second conditional PSCell change, then maintain the settings of at least one candidate PSCell for use in the second conditional PSCell change. A method for providing this. (Note 14) A program for causing a computer to perform methods for User Equipment (UE), The aforementioned method, Receiving a first Secondary Node (SN) Radio Resource Control (RRC) message, which includes the setting of multiple candidate PSCells for a first conditional Primary Secondary Cell Group (SCG) Cell (PSCell) modification, via the Master Node (MN) or via a direct signaling radio bearer between the UE and the SN, If one of the execution conditions among the multiple candidate PSCells is met, the settings corresponding to the candidate PSCell whose execution condition is met will be applied, and If the first SN RRC message indicates that an operating mode is applied, requested, recommended, or available in which the settings of at least one candidate PSCell that were not selected in the first conditional PSCell change are reused by the UE for a subsequent second conditional PSCell change, then maintain the settings of at least one candidate PSCell for use in the second conditional PSCell change. A program that includes the following features. (Note 15) A Central Unit (CU) of a Wireless Access Network (RAN) node, At least one memory, The at least one processor coupled to the at least one memory, Equipped with, The at least one processor is configured to send a first message to a Distributed Unit (DU) and to receive a second message from the DU which is a response to the first message. The first message indicates a request for a first conditional mobility for User Equipment (UE), and indicates that an operating mode is applied, requested, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE for a subsequent second conditional mobility. CU. (Note 16) The second message indicates whether the DU has determined that the operating mode is not applicable to one or more candidate target cells prepared by the DU. CU as described in Appendix 15. (Note 17) The second message indicates whether the DU has prepared the operating mode for one or more candidate target cells prepared by the DU. CU as described in Appendix 15. (Note 18) The first message is either a UE CONTEXT MODIFICATION REQUEST message or a UE CONTEXT SETUP REQUEST message. The second message is either a UE CONTEXT MODIFICATION RESPONSE message or a UE CONTEXT SETUP RESPONSE message. CU as described in any one of the items 15-17 in the appendix. (Note 19) The first conditional mobility is a conditional handover, a conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or a conditional PSCell addition. The subsequent second conditional mobility is a conditional handover or a conditional PSCell change. CU as described in any one of the items 15-18 in the appendix. (Note 20) A method performed by the Central Unit (CU) of a Wireless Access Network (RAN) node, Sending the first message to the Distributed Unit (DU), and Receiving a second message from the DU, which is a response to the first message, Equipped with, The first message indicates a request for a first conditional mobility for User Equipment (UE), and indicates that an operating mode is applied, requested, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE for a subsequent second conditional mobility change. method. (Note 21) A Distributed Unit (DU) of a Wireless Access Network (RAN) node, At least one memory, The at least one processor coupled to the at least one memory, Equipped with, The at least one processor is configured to receive a first message from the Central Unit (CU) and send a second message to the CU, which is a response to the first message. The first message indicates a request for a first conditional mobility for User Equipment (UE), and indicates that an operating mode is applied, requested, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE for a subsequent second conditional mobility. DU. (Note 22) The second message indicates whether the DU has determined that the operating mode is not applicable to one or more candidate target cells prepared by the DU. DU as described in Appendix 21. (Note 23) The second message indicates whether the DU has prepared the operating mode for one or more candidate target cells prepared by the DU. DU as described in Appendix 21. (Note 24) The first message is either a UE CONTEXT MODIFICATION REQUEST message or a UE CONTEXT SETUP REQUEST message. The second message is either a UE CONTEXT MODIFICATION RESPONSE message or a UE CONTEXT SETUP RESPONSE message. The DU specified in any one of the appendices 21 to 23. (Note 25) The first conditional mobility is a conditional handover, a conditional Primary Secondary Cell Group (SCG) Cell (PSCell) change, or a conditional PSCell addition. The subsequent second conditional mobility is a conditional handover or a conditional PSCell change. The DU specified in any one of the appendices 21-24. (Note 26) A method performed by a Distributed Unit (DU) of a Wireless Access Network (RAN) node, The first message is received from the Central Unit (CU), and Sending a second message to the CU, which is a response to the first message, Equipped with, The first message indicates a request for a first conditional mobility for User Equipment (UE), and indicates that an operating mode is applied, requested, recommended, or available in which the configuration of at least one candidate target cell not selected in the first conditional mobility is reused by the UE for a subsequent second conditional mobility. method. (Note 27) A Central Unit (CU) of a Wireless Access Network (RAN) node, At least one memory, The at least one processor coupled to the at least one memory, Equipped with, The at least one processor is configured to receive a first message from a first Distributed Unit (DU) indicating a candidate target cell that the User Equipment (UE) 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 will be maintained for the subsequent second conditional mobility. CU. (Note 28) The at least one processor is configured to inform the second DU, after receiving the first message, 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. CU as described in Appendix 27. (Note 29) The at least one processor is configured, after receiving the first message, to inform the source DU providing the source cell for the first conditional mobility that the settings of the source cell need to be maintained for the subsequent second conditional mobility. CU as described in Appendix 27 or 28. (Note 30) The first message mentioned above is an ACCESS SUCCESS message. CU as described in any one of the items 27-29 in the appendix. (Note 31) A method performed by the Central Unit (CU) of a Wireless Access Network (RAN) node, The User Equipment (UE) receives a first message from a first Distributed Unit (DU) indicating a candidate target cell that was 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 will be maintained for the subsequent second conditional mobility. method. (Note 32) A Distributed Unit (DU) of a Wireless Access Network (RAN) node, At least one memory, The at least one processor coupled to the at least one memory, Equipped with, The at least one processor is configured to send a first message to the Central Unit (CU) indicating a candidate target cell that the User Equipment (UE) 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 will be maintained for the subsequent second conditional mobility. DU. (Note 33) The first message mentioned above is an ACCESS SUCCESS message. DU as described in Appendix 32. (Note 34) A method performed by a Distributed Unit (DU) of a Wireless Access Network (RAN) node, The User Equipment (UE) sends a first message to the Central Unit (CU) indicating a candidate target cell that was 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 will be maintained for the subsequent second conditional mobility. method. (Note 35) A Central Unit (CU) of a Wireless Access Network (RAN) node, At least one memory, The at least one processor coupled to the at least one memory, Equipped with, The aforementioned at least one processor is The User Equipment (UE) receives a first message from the first Distributed Unit (DU) indicating a candidate target cell that it successfully accessed during the first conditional mobility. After receiving the first message, a second message is sent to the second DU indicating 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. Structured in such a way CU. (Note 36) The at least one processor is configured to, after receiving the first message, send a third message to the source DU providing the source cell indicating that the source cell configuration for the first conditional mobility needs to be maintained for the subsequent second conditional mobility. CU as described in Appendix 35. (Note 37) A method performed by the Central Unit (CU) of a Wireless Access Network (RAN) node, The User Equipment (UE) receives a first message from the first Distributed Unit (DU) indicating a candidate target cell that was successfully accessed during the first conditional mobility, and After receiving the first message, a second message is sent to the second DU indicating 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. A method for providing this. (Note 38) A Central Unit (CU) of a Wireless Access Network (RAN) node, At least one memory, The at least one processor coupled to the at least one memory, Equipped with, The aforementioned at least one processor is The User Equipment (UE) receives a first message from the first Distributed Unit (DU) indicating a candidate target cell that it successfully accessed during the first conditional mobility. After receiving the first message, the system is configured to send a second message to the source DU providing the source cell, indicating that the source cell configuration for the first conditional mobility needs to be maintained for a subsequent second conditional mobility. CU. (Note 39) A method performed by the Central Unit (CU) of a Wireless Access Network (RAN) node, The User Equipment (UE) receives a first message from the first Distributed Unit (DU) indicating a candidate target cell that was successfully accessed during the first conditional mobility, and After receiving the first message, a second message is sent to the source DU providing the source cell, indicating that the source cell configuration for the first conditional mobility needs to be maintained for a subsequent second conditional mobility. A method for providing this. (Note 40) User Equipment (UE), At least one memory, The at least one processor coupled to the at least one memory, Equipped with, The aforementioned at least one processor is Candidate Special Cells (SpCells) receive configurations for multiple different candidate Cell Group (CG) sets from a Wireless Access Network (RAN) node. A single candidate SpCell is selected based on Layer 1 / layer 2 inter-cell mobility, and the corresponding candidate CG settings set is applied to the selected candidate SpCell. UE. (Note 41) A method performed by User Equipment (UE), Candidate Special Cells (SpCells) receive configurations for multiple different candidate Cell Group (CG) sets from a Radio Access Network (RAN) node, and Select a candidate SpCell based on Layer 1 / layer 2 inter-cell mobility, and apply the candidate CG settings set corresponding to the selected candidate SpCell. A method for providing this.

[0147] This application claims priority based on Japanese Patent Application No. 2021-215151, filed on 28 December 2021, and incorporates all of its disclosures herein. [Explanation of Symbols]

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

Claims

1. A method for Layer 1 / layer 2 (L1 / L2) based mobility performed by User Equipment (UE), Receiving configuration information from a Radio Access Network (RAN) node, including information about candidate cells for L1 / L2-based mobility. Performing L1 measurements for L1 / L2-based mobility, When L1 / L2-based mobility is triggered, random access is performed to switch serving cells. Upon completion of the aforementioned random access, the Medium Access Control (MAC) layer of the UE notifies the Radio Resource Control (RRC) layer of the UE that the execution of L1 / L2-based mobility has been completed. A method for providing this.

2. Receiving execution conditions for L1 / L2-based mobility linked to L1 measurements from the RAN node. Furthermore, it includes the ability to initiate L1 / L2-based mobility execution when the execution conditions for L1 / L2-based mobility are met. The method according to claim 1.

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