Wireless access network node and method thereof

Abstract

In the present invention, a target secondary node (T-SN) (4) indicates, to a master node (MN) (1) in a response message for an inter-SN Condtional PSCell Change (CPC) request, whether or not all of a plurality of candidate PSCells proposed by the MN (1) or by a source SN (S-SN) (2) have been accepted. When all of the plurality of candidate PSCells have been accepted, the MN (1) transmits an MN RRC reconfiguration message to a UE (3) to instruct an inter-SN CPC while skipping additional signaling with the S-SN (2) or without waiting for the completion of the additional signaling. Otherwise, the MN (1) transmits an MN RRC reconfiguration message to the UE (3) after additional signaling with the S-SN (2). This, for example, prevents a delay in preparation of a SN-initiated inter-SN CPC from increasing.

Description

[Technical field]

[0001] The present disclosure relates to wireless communication systems, and more particularly to mobility of wireless terminals in multi-connectivity (eg, dual connectivity). [Background technology]

[0002] The 3rd Generation Partnership Project (3GPP (registered trademark)) is currently studying Release 17. 3GPP is discussing the application of conditional mobility to cell changes (i.e., inter-SN PSCell change) between secondary nodes (SNs) of a primary cell (PSCell) of a secondary cell group (SCG) of a dual connectivity (DC) (see, for example, non-patent documents 1-7). This is called inter-SN conditional PSCell change (CPC). The PSCell is a special cell (SpCell) of the SCG of the DC. When performing a handover procedure (or a reconfiguration with sync procedure), the UE randomly accesses the PSCell. An SCG is a group of serving cells associated with an SN, including an SpCell (ie, a PSCell) and optionally one or more Secondary Cells (SCells).

[0003] CPC is a PSCell change procedure that is executed only when one or more execution conditions are met or satisfied. After receiving a PSCell change instruction from a Master Node (MN), a wireless terminal (i.e., User Equipment (UE)) maintains a connection with a Source SN (S-SN) and an SCG, and starts evaluation of execution condition(s) configured by the instruction. Then, the UE starts accessing a Target SN (T-SN) in response to the execution condition being satisfied. That is, CPC differs from a normal PSCell change in that the UE starts accessing a target PSCell (or a new PSCell) in response to the execution condition being satisfied by the instruction, not in response to a PSCell change instruction.

[0004] An inter-SN CPC can be initiated by the MN or a source SN. An inter-SN CPC initiated by the MN is called an MN initiated inter-SN CPC. On the other hand, an inter-SN CPC initiated by an S-SN is called an SN initiated inter-SN CPC. In an MN initiated inter-SN CPC, the MN generates a CPC execution condition, and the T-SN generates a PSCell configuration (or SCG configuration). In contrast, in an SN initiated inter-SN CPC, the S-SN generates a CPC execution condition and sends it to the MN. In both the MN-initiated CPC and SN-initiated CPC, the T-SN generates an SCG configuration and sends it to the MN. Then, the MN transmits a CPC configuration (e.g., a Conditional Reconfiguration Information Element (IE)) including the CPC execution condition and the SCG configuration to the UE via a Radio Resource Control (RRC) (Connection) Reconfiguration message. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Vice Chairman (Nokia), "Report on LTE legacy, Mobility, DCCA, Multi-SIM and RAN slicing", R2-2106471, 3GPP TSG-RAN WG2 Meeting #114-e, May 19-27, 2021 [Non-Patent Document 2] CATT, "TS 37.340 CR for CPA and inter-SN CPC", R2-2105062, 3GPP TSG-RAN WG2 Meeting #114-e, May 19-27, 2021 [Non-Patent Document 3] Huawei, "(TP to CPAC TS 37.340 BL CR) Consideration on conditional PSCell change / addition", R3-212833, 3GPP TSG-RAN WG3 Meeting #112-e, May 17-28, 2021 [Non-Patent Document 4] Samsung, "(TP to TS 38.423, LTE_NR_DC_enh2-Core) Adding CPAC Procedure", R3-212968, 3GPP TSG-RAN WG3 Meeting #112-e, May 17-27, 2021 [Non-Patent Document 5] Samsung, "(TP to TS 36.423, LTE_NR_DC_enh2-Core) Adding CPAC Procedure", R3-212969, 3GPP TSG-RAN WG3 Meeting #112-e, May 17-27, 2021 [Non-Patent Document 6] Huawei, "Support of Conditional PSCell Change and Addition", R3-212995, 3GPP TSG-RAN WG3 Meeting #112-e, May 17-27, 2021 [Non-Patent Document 7] Nokia, Nokia Shanghai Bell, "CPAC BL CR to TS 36.423", R3-212994, 3GPP TSG-RAN WG3 Meeting #112-e, May 17-28, 2021 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors have considered inter-SN CPC and found various problems. One of these problems relates to the details of the procedure of SN-initiated inter-SN CPC. As described above, in SN-initiated inter-SN CPC, the MN generates a CPC configuration (e.g., Conditional Reconfiguration IE) including the CPC execution condition received from the S-SN and the PSCell configuration (or SCG configuration) received from the T-SN, and transmits this to the UE via an RRC (Connection) Reconfiguration message. In one example, the MN can receive the CPC execution condition for each of a plurality of candidate PSCells from the S-SN in an SN Change Required message, and can then receive the PSCell configuration for each of all or a subset of the plurality of candidate PSCells from the T-SN in an SN Addition Request Acknowledge message. However, if the T-SN rejects some of the candidate PSCells indicated by the S-SN, the MN may need to perform additional signaling with the S-SN to receive updated CPC execution conditions for only the subset of candidate PSCells accepted by the T-SN. In addition, in some implementations, the MN may not know whether the PSCell configuration(s) received from the T-SN correspond to all candidate PSCells specified by the S-SN. In this case, the MN may need to perform additional signaling with the S-SN to receive updated CPC execution conditions, regardless of whether the T-SN rejected some of the candidate PSCells indicated by the S-SN. Such additional signaling may increase the delay of CPC preparation.

[0007] Another problem that the inventors have obtained relates to the details of the SN-initiated inter-SN CPC procedure and the details of the MN-initiated inter-SN CPC procedure. It is proposed that the MN transmits a Conditional PSCell Change Notification message to the S-SN. However, in the current discussion of 3GPP, it is not clear when the MN transmits the Conditional PSCell Change Notification message to the S-SN.

[0008] One of the objectives that the embodiments disclosed in this specification aim to achieve is to provide an apparatus, a method, and a program that contribute to solving at least one of the problems including the problems described above. It should be noted that this objective is only one of the objectives that the embodiments disclosed in this specification aim to achieve. Other objectives or objectives and novel features will be apparent from the description of this specification or the accompanying drawings. [Means for solving the problem]

[0009] A first aspect is directed to a RAN node configured to operate as a MN associated with a Master Cell Group (MCG) in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a first inter-node message from an S-SN indicating a request for SN-initiated inter-SN CPC. The first inter-node message includes one or more CPC execution condition information items indicating a plurality of CPC execution conditions each associated with a respective one of a plurality of candidate PSCells. The at least one processor is configured to send a second inter-node message to a T-SN indicating the request for inter-SN CPC and including information of the plurality of candidate PSCells, and to receive a third inter-node message from the T-SN. The third inter-node message includes one or more PSCell configuration information items each indicating a PSCell configuration for a respective one of one or more accepted candidate PSCells. The third inter-node message indicates to the MN whether all of the plurality of candidate PSCells have been accepted. If the third inter-node message indicates that all of the plurality of candidate PSCells have been accepted, the at least one processor sends a first MN RRC reconfiguration message to the UE, including the one or more CPC execution condition information items and the one or more PSCell configuration information items, while skipping additional signaling with the S-SN or without waiting for completion of the additional signaling.On the other hand, if the third inter-node message indicates that only a subset of the plurality of candidate PSCells has been accepted, the at least one processor is configured to perform the additional signaling with the S-SN to receive one or more updated CPC execution condition information items, and to send a first MN RRC reconfiguration message to the UE including the one or more updated CPC execution condition information items and the one or more PSCell configuration information items.

[0010] A second aspect is directed to a method performed by a RAN node configured to act as a MN associated with an MCG in dual connectivity for a UE, the method comprising the steps of: (a) receiving a first inter-node message from an S-SN indicating a request for an SN-initiated inter-SN CPC, where the first inter-node message includes one or more CPC execution condition information items indicating a plurality of CPC execution conditions each associated with a respective one of a plurality of candidate PSCells; (b) sending a second inter-node message to the T-SN indicating a request for an inter-SN CPC and including information of the plurality of candidate PSCells; (c) receiving a third inter-node message from the T-SN, where the third inter-node message includes one or more PSCell configuration information items each indicating a PSCell configuration of a respective one of one or more accepted candidate PSCells, and the third inter-node message indicates to the MN whether all of the plurality of candidate PSCells have been accepted; (d) if the third inter-node message indicates that all of the plurality of candidate PSCells have been accepted, sending a first MN RRC reconfiguration message to the UE, the first MN RRC reconfiguration message including the one or more CPC execution condition information items and the one or more PSCell configuration information items, while skipping additional signaling with the S-SN or without waiting for completion of the additional signaling; and (e) if the third inter-node message indicates that only a subset of the plurality of candidate PSCells has been accepted, performing the additional signaling with the S-SN to receive one or more updated CPC execution condition information items, and sending a first MN RRC reconfiguration message to the UE containing the one or more updated CPC execution condition information items and the one or more PSCell configuration information items.

[0011] A third aspect is directed to a RAN node configured to operate as a T-SN associated with an SCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to receive a second inter-node message from an MN indicating a request for an inter-SN CPC and including information of a plurality of candidate PSCells, and to transmit a third inter-node message to the MN, the third inter-node message including one or more PSCell configuration information items each indicating a PSCell configuration for a respective one of one or more accepted candidate PSCells, the third inter-node message indicating to the MN whether all of the plurality of candidate PSCells have been accepted.

[0012] A fourth aspect is directed to a method performed by a RAN node configured to act as a T-SN associated with an SCG in dual connectivity for a UE, the method including receiving a second inter-node message from an MN indicating a request for an inter-SN CPC and including information of a plurality of candidate PSCells, and transmitting a third inter-node message to the MN, the third inter-node message including one or more PSCell configuration information items each indicating a PSCell configuration for a respective one of one or more accepted candidate PSCells, the third inter-node message indicating to the MN whether all of the plurality of candidate PSCells have been accepted.

[0013] A fifth aspect is directed to a RAN node configured to operate as a MN associated with an MCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to receive a first inter-node message from an S-SN indicating a request for SN-initiated inter-SN CPC, the first inter-node message including a plurality of cell identity information items, each indicating a respective one of a plurality of candidate PSCells, and a plurality of CPC execution condition information items, each associated with a respective one of the plurality of cell identity information items, the at least one processor configured to send a second inter-node message to a T-SN indicating a request for inter-SN CPC and including information of the plurality of candidate PSCells, and to receive a third inter-node message from the T-SN including one or more PSCell configuration information items, each indicating a PSCell configuration for a respective one of one or more accepted candidate PSCells. The at least one processor is configured to select one or more CPC execution information items from the plurality of CPC execution condition information items corresponding to the one or more accepted candidate PSCells. The at least one processor is configured to send a first MN RRC reconfiguration message to the UE, the message including the one or more selected CPC execution information items and the one or more PSCell configuration information items.

[0014] A sixth aspect is directed to a method performed by a RAN node configured to act as a MN associated with an MCG in dual connectivity for a UE, the method comprising the steps of: (a) receiving a first inter-node message from an S-SN indicating a request for SN-initiated inter-SN CPC, where the first inter-node message includes a plurality of cell identity information items, each indicating a respective one of a plurality of candidate PSCells, and a plurality of CPC execution condition information items, each associated with a respective one of the plurality of cell identity information items; sending a second inter-node message to the target SN indicating a request for an inter-SN CPC and including information of the plurality of candidate PSCells; receiving a third inter-node message from the target SN including one or more PSCell configuration information items each indicating a PSCell configuration of a respective one of the one or more accepted candidate PSCells; selecting, from the plurality of CPC execution condition information items, one or more CPC execution information items corresponding to the one or more accepted candidate PSCells; and Sending a first MN RRC reconfiguration message to the UE, the message including the one or more selected CPC execution information items and the one or more PSCell configuration information items.

[0015] A seventh aspect is directed to a RAN node configured to operate as an S-SN associated with an SCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to transmit a first inter-node message to an MN indicating a request for SN-initiated inter-SN CPC, the first inter-node message including a plurality of cell identity information items each indicating a respective one of a plurality of candidate PSCells and a plurality of CPC execution condition information items each associated with a respective one of the plurality of cell identity information items.

[0016] An eighth aspect is directed to a method performed by a RAN node configured to operate as a MN associated with an MCG in dual connectivity for a UE, the method including transmitting a first inter-node message to the MN indicating a request for SN-initiated inter-SN CPC, the first inter-node message including a plurality of cell identity information items each indicating a respective one of a plurality of candidate PSCells and a plurality of CPC execution condition information items each associated with a respective one of the plurality of cell identity information items.

[0017] A ninth aspect is directed to a RAN node configured to operate as an MN associated with an MCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to send an MN RRC reconfiguration message to the UE including an execution condition of an inter-SN CPC and a candidate PSCell configuration, and to receive a first MN RRC reconfiguration complete message from the UE in response to the MN RRC reconfiguration message. The at least one processor is configured to receive a second MN RRC reconfiguration complete message sent from the UE in response to the execution of the CPC or the establishment of the execution condition. The at least one processor is configured to send a Conditional PSCell Change Notification message to an S-SN in response to receiving the second MN RRC reconfiguration complete message.

[0018] A tenth aspect is directed to a method performed by a RAN node configured to act as a MN associated with an MCG in dual connectivity for a UE, the method comprising the steps of: (a) sending an MN RRC reconfiguration message to the UE, the message including an inter-SN CPC execution condition and a candidate PSCell configuration; (b) receiving a first MN RRC reconfiguration complete message from the UE in response to the MN RRC reconfiguration message; (c) receiving a second MN RRC reconfiguration complete message transmitted from the UE in response to execution of the CPC or establishment of the execution condition; and (d) in response to receiving the second MN RRC reconfiguration complete message, sending a Conditional PSCell Change Notification message to the S-SN.

[0019] An eleventh aspect is directed to a program comprising a set of instructions (software code) for causing a computer to carry out a method according to the second, fourth, sixth, eighth or tenth aspect when the program is loaded into the computer. Effect of the Invention

[0020] According to the above-mentioned aspects, it is possible to provide an apparatus, a method, and a program that contribute to solving at least one of a number of problems related to inter-SN CPC, including the problems described above. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram illustrating an example of the configuration of a wireless communication network according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a configuration example of a RAN node according to an embodiment. [Diagram 3] 11 is a flowchart showing an example of a process performed by an MN according to the embodiment. [Figure 4] 1 is a flowchart illustrating an example of a process performed by a T-SN according to an embodiment. [Diagram 5] A sequence diagram showing an example of processing performed by an MN, an S-SN, a T-SN, and a UE according to an embodiment. [Figure 6] A sequence diagram showing an example of processing performed by an MN, an S-SN, a T-SN, and a UE according to an embodiment. [Figure 7] 11 is a flowchart showing an example of a process performed by an MN according to the embodiment. [Figure 8] 13 is a flowchart showing an example of processing performed by an S-SN according to the embodiment. [Figure 9] A sequence diagram showing an example of processing performed by an MN, an S-SN, a T-SN, and a UE according to an embodiment. [Figure 10] FIG. 13 is a diagram illustrating an example of the format of a cell identification information item and an execution condition information item according to an embodiment. [Figure 11] FIG. 13 is a diagram illustrating an example of the format of a cell identification information item and an execution condition information item according to an embodiment. [Figure 12] 11 is a flowchart showing an example of a process performed by an MN according to the embodiment. [Figure 13] A sequence diagram showing an example of processing performed by an MN, an S-SN, a T-SN, and a UE according to an embodiment. [Figure 14] A sequence diagram showing an example of processing performed by an MN, an S-SN, a T-SN, and a UE according to an embodiment. [Figure 15] FIG. 2 is a block diagram showing a configuration example of a RAN node according to the embodiment. [Figure 16] FIG. 2 is a block diagram showing an example of the configuration of a UE according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In the following, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and duplicated descriptions will be omitted as necessary for clarity of explanation.

[0023] The multiple embodiments described below can be implemented independently or in appropriate combination. These multiple embodiments have different novel features. Therefore, these multiple embodiments contribute to solving different objects or problems and provide different effects.

[0024] The following embodiments are described with a focus on the 3GPP Long Term Evolution (LTE) system and the fifth generation mobile communication system (5G system). However, these embodiments may be applied to other wireless communication systems that support technologies similar to 3GPP multi-connectivity (e.g. Dual Connectivity). In addition, the term LTE used in this specification includes improvements and developments of LTE and LTE-Advanced to enable interworking with the 5G system, unless otherwise specified.

[0025] As used herein, depending on the context, "if" may be interpreted to mean "when," "at or around the time," "after," "upon," "in response to determining," "in accordance with a determination," or "in response to detecting." These expressions may be interpreted to have the same meaning, depending on the context.

[0026] <First embodiment> Fig. 1 illustrates an example of a configuration of a wireless communication network according to a number of embodiments including the present embodiment. In the example of Fig. 1, the wireless communication network includes a RAN node 1, a RAN node 2, a RAN node 4, and a UE 3. Each element (network function) illustrated in Fig. 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on the dedicated hardware, or as a virtualized function instantiated on an application platform.

[0027] The RAN node 1 may be a Central Unit (e.g., eNB-CU or gNB-CU) in a cloud RAN (C-RAN) deployment, or may be a combination of a CU and one or more Distributed Units (e.g., eNB-DUs or gNB-DUs). C-RAN is also referred to as a CU / DU split. Furthermore, a CU may include a Control Plane (CP) Unit (e.g., gNB-CU-CP) and one or more User Plane (UP) Units (e.g., gNB-CU-UP). Thus, the RAN node 1 may be a CU-CP or a combination of a CU-CP and a CU-UP. Similarly, each of the RAN nodes 2 and 4 may be a CU or a combination of a CU and one or more DUs. Each of the RAN nodes 2 and 4 may be a CU-CP or a combination of a CU-CP and a CU-UP.

[0028] Each of the RAN nodes 1, 2, and 4 may be an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (EUTRAN) node or a Next generation Radio Access Network (NG-RAN) node. The EUTRAN node may be an eNB or an en-gNB. The NG-RAN node may be a gNB or an ng-eNB. The en-gNB is a node that provides NR user plane and control plane protocol terminations towards the UE and acts as a secondary node (SN) in E-UTRA-NR Dual Connectivity (EN-DC). The ng-eNB is a node that provides E-UTRA user plane and control plane protocol terminations towards the UE and is connected to the 5GC via the NG interface. The Radio Access Technology (RAT) of the RAN node 1 may be different from that of the RAN nodes 2 and 4.

[0029] RAN node 1 and RAN node 2 communicate with each other via an inter-node interface (i.e., X2 interface or Xn interface) 103. RAN node 1 and RAN node 2 act as a master node (MN) and a secondary node (SN) of dual connectivity, respectively. Furthermore, RAN node 1 and RAN node 4 communicate with each other via an inter-node interface (i.e., X2 interface or Xn interface) 105. RAN node 1 and RAN node 4 can act as a MN and a SN of a DC, respectively. RAN nodes 1, 2, and 4 support inter-SN CPC from an SCG provided by RAN node 2 to an SCG provided by RAN node 4. In the following, RAN node 1 may be referred to as MN 1, RAN node 2 may be referred to as source SN (S-SN) 2, and RAN node 4 may be referred to as target SN (T-SN) 4. UE 3 communicates with MN 1 and S-SN 2 via air interfaces 101 and 102 to perform dual connectivity of MCG provided by MN 1 and SCG provided by S-SN 2. Also, by performing inter-SN CPC, the UE 3 communicates with the MN 1 and the T-SN 4 via the air interfaces 101 and 104, and performs dual connectivity of the MCG provided by the MN 1 and the SCG provided by the T-SN 4.

[0030] This dual connectivity may be Multi-Radio Dual Connectivity (MR-DC). MR-DC includes E-UTRA-NR Dual Connectivity (EN-DC), NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), NR-E-UTRA Dual Connectivity (NE-DC), and NR-NR Dual Connectivity (NR-DC). Accordingly, the MN1 may be any of a master eNB (in EN-DC), a master ng-eNB (in NGEN-DC), and a master gNB (in NR-DC and NE-DC). Similarly, each of the S-SN2 and the T-SN4 may be any of an en-gNB (in EN-DC), a secondary ng-eNB (in NE-DC), and a secondary gNB (in NR-DC and NGEN-DC). In the EN-DC, the UE3 is connected to an eNB operating as the MN1 and is connected to an en-gNB operating as the S-SN2 or the T-SN4. In NGEN-DC, UE3 is connected to an ng-eNB operating as MN1 and to a gNB operating as S-SN2 or T-SN4. In NE-DC, UE3 is connected to a gNB operating as MN1 and to an ng-eNB operating as S-SN2 or T-SN4. In NR-DC, UE3 is connected to one gNB (or gNB-DU) operating as MN1 and to another gNB (or gNB-DU) operating as S-SN2 or T-SN4.

[0031] The MCG is a group of serving cells associated with (or provided to) the MN1, and includes an SpCell (i.e., a Primary Cell (PCell)) and, optionally, one or more Secondary Cells (SCells). On the other hand, the SCG is a group of serving cells associated with (or provided to) the S-SN2 or T-SN4, and includes a Primary SCG Cell (PSCell) and, optionally, one or more Secondary Cells (SCells). The PSCell is a Special Cell (SpCell) of the SCG, and supports Physical Uplink Control Channel (PUCCH) transmission and contention-based Random Access. Note that in LTE (e.g., LTE-DC and NE-DC), PSCell may be an abbreviation for Primary SCell.

[0032] As used herein, the term "primary SCG cell" and its abbreviation "PSCell" refer to a cell included in a cell group provided by a dual connectivity SN, having an uplink component carrier, and having uplink control channel (e.g. PUCCH) resources configured. Specifically, the term "primary SCG cell" and its abbreviation "PSCell" may refer to a Primary SCG Cell of a cell group provided by an SN supporting 5G NR (e.g. en-gNB in ​​EN-DC, gNB in ​​NGEN-DC, or gNB in ​​NR-DC), or may refer to a Primary SCell of a cell group provided by an SN supporting E-UTRA (e.g. eNB in ​​LTE DC, or ng-eNB in ​​NE-DC).

[0033] One or more of the MN1, S-SN2, and T-SN4 may have the configuration shown in FIG. 2. Each element (network function) shown in FIG. 2 may be implemented, for example, as a network element on dedicated hardware, as a software instance running on the dedicated hardware, or as a virtualized function instantiated on an application platform. One or more of the MN1, S-SN2, and T-SN4 may include, but are not limited to, a CU21 and one or more DUs 22 as shown in FIG. 2. The CU21 and each DU 22 are connected by an interface 201. The UE3 is connected to at least one DU 22 via at least one air interface 202.

[0034] The CU21 may be a logical node that hosts the Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP) protocols (or the RRC and PDCP protocols) of the gNB. The DU22 may be a logical node that hosts the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of the gNB. If the CU21 is a gNB-CU and the DUs22 are gNB-DUs, the interface 201 may be an F1 interface. The CU21 may include a CU-CP and a CU-UP.

[0035] In the following, the operations of MN1, S-SN2, and T-SN4 regarding inter-SN CPC will be described. FIG. 3 shows an example of the operations of MN1 regarding SN-initiated inter-SN CPC. In step 301, MN1 receives a first inter-node message from S-SN2 indicating a request for SN-initiated inter-SN CPC. The first inter-node message may be a SN Change Required message (e.g. SgNB Change Required, or S-NODE Change Required). The first inter-node message includes one or more CPC execution condition information items indicating a plurality of CPC execution conditions each associated with a respective one of a plurality of candidate PSCells. In one example, the plurality of CPC execution conditions may be included in one CPC execution condition information item. In this case, the one CPC execution condition information item indicating the plurality of CPC execution conditions may be sent by the first inter-node message using a container transparent to MN1. In other words, one CPC execution condition information item indicating multiple CPC execution conditions may be an information item whose contents are not recognized or cannot be recognized by the MN 1. The container transparent to the MN 1 may be an RRC container sent from the S-SN 2 to the UE 3 via the MN 1.

[0036] The first inter-node message of step 301 may include an information item indicating candidate PSCells suggested by the S-SN2. In one example, the one or more information items may be RRC level information items. Specifically, the one or more information items may be included in a candidateCellInfoListSN field in an inter-node RRC message (e.g., CG-Config). The candidateCellInfoListSN field indicates information indicating candidate PSCells. The candidateCellInfoListSN field may further indicate measurement results of one or more neighbor cells (candidate PSCells) measured by the UE3. Additionally or alternatively, the one or more information items may be X2 / Xn level information items. Specifically, the first inter-node message (e.g., SN Change Required) may include an information element (IE) indicating a list of candidate PSCells suggested by the S-SN2.

[0037] In step 302, the MN1 transmits a second inter-node message indicating a request for an inter-SN CPC and including information of multiple candidate PSCells to the T-SN4. The second inter-node message may be a SN Addition Request message (e.g., SgNB Addition Request, or S-NODE Addition Request).

[0038] In step 303, the MN1 receives a third inter-node message from the T-SN4. The third inter-node message may be a SN Addition Request Acknowledge message (e.g., SgNB Addition Request Acknowledge, or S-NODE Addition Request Acknowledge). The third inter-node message includes one or more PSCell configuration information items, each indicating a PSCell configuration for one or more accepted candidate PSCells. Each PSCell configuration may be an SCG configuration. Each PSCell configuration information item may be an SN RRC Reconfiguration message including a PSCell configuration. In other words, each PSCell configuration information item may be an RRC container including a corresponding one PSCell configuration. The third inter-node message may include a list of inter-node RRC messages (e.g., a list of CG-Config) for each of the candidate PSCells accepted by the T-SN4. The third inter-node message may include inter-node RRC messages (eg, CG-Config) in the same number as the number (N) of candidate PSCells accepted by the T-SN4 as one or more (<=N) RRC containers.

[0039] Furthermore, the third inter-node message of step 303 explicitly or implicitly indicates to MN1 whether all of the candidate PSCells indicated in the second inter-node message have been accepted. In other words, the third inter-node message explicitly or implicitly indicates to MN1 whether all of the candidate PSCells indicated (or proposed) by MN1 or S-SN2 have been accepted. The third inter-node message may further include information at the X2 / Xn level indicating the candidate PSCells accepted by T-SN4.

[0040] In one example, this may be indicated at the RRC level. Specifically, the T-SN4 may indicate whether all of the candidate PSCells have been accepted, either explicitly or implicitly, in an inter-node RRC message (e.g., CG-Config). For example, the T-SN4 may include information in the inter-node RRC message (e.g., CG-Config) that explicitly indicates that all of the candidate PSCells have been accepted (or that some have not been accepted). Alternatively, the inter-node RRC message (e.g., CG-Config) may indicate a list of identifiers (PSCell IDs) of one or more candidate PSCells that have been rejected (i.e., not accepted) by the T-SN4. The MN1 may recognize that the T-SN4 has accepted all the candidate PSCells (i.e., may understand that all the candidate PSCells have been accepted) by the absence of such a list. Additionally or alternatively, the inter-node RRC message (e.g., CG-Config) may indicate a list of one or more candidate PSCell identifiers (PSCell IDs) accepted by the T-SN4. In this case, the S-SN2 transmits a list of candidate PSCells proposed by the S-SN2 in advance in the first inter-node message in a form that the MN1 can understand (recognize). The MN1 may then compare the list received from the S-SN2 with the list received from the T-SN4 to determine whether all the candidate PSCells have been accepted. The candidate PSCell identifiers (PSCell IDs) may be NR Cell Global Identifiers (NR-CGI) or Evolved Universal Terrestrial Radio Access Network (E-UTRAN) CGI (ECGI). In this case, the list may indicate to the MN1 whether all of the candidate PSCells indicated by the MN1 or the S-SN2 have been accepted.

[0041] In another example, this may be indicated at the X2 / Xn level. Specifically, the T-SN4 may indicate whether all of the candidate PSCells indicated by the MN1 or S-SN2 have been accepted, either explicitly or implicitly, in an information element (IE) included in the third inter-node message. More specifically, for example, the third inter-node message (e.g., SN Addition Request Acknowledge) may include an information element that explicitly indicates that all of the candidate PSCells have been accepted by the T-SN4 (or that some have not been accepted). Alternatively, the third inter-node message may include a list of identifiers (PSCell IDs) of one or more candidate PSCells that have been rejected (i.e., not accepted) by the T-SN4. The MN1 may recognize that the T-SN4 has accepted all the candidate PSCells (i.e., may understand that all the candidate PSCells have been accepted) by the absence of such a list. Additionally or alternatively, the third inter-node message may include a list (e.g., Candidate PSCell ID List IE) of one or more candidate PSCells accepted by the T-SN4. The list may associate an identifier (PSCell ID) of each accepted candidate PSCell with a corresponding one PSCell configuration (e.g., RRC container, SN RRC Reconfiguration message). In this case, the S-SN2 may transmit the list of candidate PSCells proposed by the S-SN2 at the X2 / Xn level in advance in the first inter-node message. Then, the MN1 may determine whether all candidate PSCells have been accepted by comparing the list received from the S-SN2 with the list received from the T-SN4. The identifier (PSCell ID) of the candidate PSCell may be NR-CGI or ECGI. In this case, the list may indicate to the MN1 whether all of the candidate PSCells indicated by the MN1 or the S-SN2 have been accepted.Specifically, MN1 can find out whether all of the multiple candidate PSCells indicated (or proposed) by MN1 or S-SN2 have been accepted by checking one or more PSCell IDs included in the list.

[0042] In step 304, the MN1 detects that all of the multiple candidate PSCells have been accepted by the T-SN4 by checking the third inter-node message. In this case, the MN1 skips the additional signaling with the S-SN2 or does not wait for the completion of the additional signaling, and transmits to the UE3 an MN RRC (connection) reconfiguration message including one or more CPC execution condition information items received from the S-SN2 (step 301) and one or more PSCell setting information items received from the T-SN4 (step 303). The MN RRC reconfiguration message instructs the UE3 to perform a conditional reconfiguration for CPC. In response to receiving the MN RRC reconfiguration message, the UE3 starts evaluation of the CPC execution condition. Then, in response to the establishment of the CPC execution condition for any of the candidate PSCells, the UE3 starts access to the T-SN4.

[0043] The MN RRC reconfiguration message of step 304 may include a ConditionalReconfiguration IE. The ConditionalReconfiguration IE may include a condReconfigToAddModList IE. The condReconfigToAddModList IE may map each candidate PSCell's PSCell configuration (i.e. SN RRC Reconfiguration message) to a corresponding CPC execution condition. The CPC execution condition may be specified by a measurement identity (measId). The measurement identity associates a measurement object (MeasObject) with a report configuration (ReportConfig). The MeasObject indicates information that applies to intra / inter-frequency measurements and indicates the identities of one or more candidate PSCells. The ReportConfig specifies the criteria for triggering of a CPC event.

[0044] On the other hand, if only a subset of the candidate PSCells is accepted by T-SN4, MN1 performs step 305 instead of step 304. In step 305, MN1 performs additional signaling with S-SN to receive one or more updated CPC execution condition information items. For example, MN1 transmits an inter-node message to S-SN2 indicating identifiers of candidate PSCells accepted by T-SN4, and S-SN2 responds by transmitting an inter-node message to MN1 indicating an updated CPC execution condition information item (if necessary). Here, the updated CPC execution condition information item may be a CPC execution condition information item already transmitted by S-SN2 to MN1, from which the CPC execution conditions for candidate PSCells not accepted by T-SN4 have been deleted. Furthermore, at this stage, S-SN2 may modify the CPC execution conditions for the candidate PSCells accepted by T-SN4 and transmit the modified CPC execution condition information item to MN1. Thereafter, MN1 sends an MN RRC reconfiguration message to UE3, which includes one or more CPC execution condition information items updated by S-SN2 and one or more PSCell setting information items received from T-SN4.

[0045] FIG. 4 shows an example of the operation of the T-SN4. Step 401 corresponds to step 302 in FIG. 3. Specifically, the T-SN4 receives a second inter-node message from the MN1, indicating a request for inter-SN CPC and including information of multiple candidate PSCells. Meanwhile, step 402 corresponds to step 303 in FIG. 3. Specifically, the T-SN4 transmits a third inter-node message to the MN1. The third inter-node message may be a SN Addition Request Acknowledge message (e.g. SgNB Addition Request Acknowledge, or S-NODE Addition Request Acknowledge). The third inter-node message includes one or more PSCell configuration information items, each indicating a PSCell configuration of a respective one of the one or more accepted candidate PSCells. Furthermore, the third inter-node message explicitly or implicitly indicates to the MN1 whether all of the multiple candidate PSCells indicated in the second inter-node message have been accepted. An example of the third inter-node message is similar to that described with respect to step 303 of FIG.

[0046] According to the operations described with reference to Figures 3 and 4, if all of the candidate PSCells proposed by MN1 or S-SN2 are accepted by T-SN4, MN1 sends an MN RRC reconfiguration message to UE3 to indicate CPC while skipping additional signaling with S-SN2 or without waiting for the completion of the additional signaling, thus preventing an increase in the delay of CPC preparation due to additional signaling.

[0047] FIG. 5 shows an example of the operations of MN1, S-SN2, T-SN4 and UE3. The procedure shown in FIG. 5 is based on the operations of MN1 shown in steps 301-304 in FIG. 3 and the operations of T-SN4 shown in FIG. 4. In step 501, S-SN2 initiates an inter-SN CPC procedure by sending an SN Change Required message (e.g. SgNB Change Required or S-NODE Change Required) to MN1. In the message, S-SN2 indicates CPC initiation to MN1. The message includes an identifier of T-SN4. The message further includes one or more CPC execution condition information items indicating a plurality of CPC execution conditions each associated with a respective one of a plurality of candidate PSCells. MN1 may or may not be able to comprehend the CPC execution condition (i.e. one or more CPC execution condition information items) set by S-SN2. The CPC execution condition may be included in an RRC container that is transparent to MN1. In other words, one or more CPC execution condition information items may be an RRC container that is transparent to the MN1.

[0048] In step 502, the MN1 requests the T-SN4 to allocate resources for the UE3 using the SN Addition procedure. Specifically, the MN1 sends an SN Addition Request message (e.g., SgNB Addition Request, or S-NODE Addition Request) to the T-SN4. This message indicates CPC initiation to the T-SN4 and indicates multiple candidate PSCells to the T-SN4. In this message, the MN1 may provide the T-SN4 with an upper limit (or maximum number) of the candidate PSCells.

[0049] In step 503, the T-SN4 responds to the MN1 with a SN Addition Request Acknowledge message (e.g. SgNB Addition Request Acknowledge, or S-NODE Addition Request Acknowledge). The message indicates that all of the candidate PSCells proposed by the MN1 or S-SN2 have been accepted (or prepared). The message contains one or more PSCell configuration information items, each indicating a PSCell configuration for a respective one of the accepted candidate PSCells. Each PSCell configuration may be an SCG configuration. Each PSCell configuration information item may be an SN RRC Reconfiguration message containing the PSCell configuration. In other words, each PSCell configuration information item may be an RRC container containing a corresponding one PSCell configuration.

[0050] By checking the SN Addition Request Acknowledge message, the MN1 detects that all of the candidate PSCells proposed by the MN1 or the S-SN2 have been accepted by the T-SN4. In response, in step 504, the MN1 transmits an MN RRC (connection) reconfiguration message to the UE3 to instruct the UE3 to perform a conditional reconfiguration for CPC. The MN RRC reconfiguration message includes one or more CPC execution condition information items (step 501) received from the S-SN2 and one or more PSCell setting information items (step 503) received from the T-SN4. In response to receiving the MN RRC reconfiguration message, the UE3 starts evaluation of the CPC execution condition. Then, in response to the establishment of the CPC execution condition for any of the candidate PSCells, the UE3 starts access to the T-SN4.

[0051] In step 505, MN1 sends a SN Change Confirm message (e.g. SgNB Change Confirm, S-NODE Change Confirm) to S-SN2. The message informs S-SN2 that the allocation of resources of T-SN4 for inter-SN CPC has been successful. Note that the SN Change Confirm message in step 505 causes S-SN2 to continue providing user data to UE3 until future CPC execution. In other words, S-SN2 receives the SN Change Confirm message but does not stop providing user data to UE3. The SN Change Confirm message may include information indicating that this message is for inter-SN CPC.

[0052] The message transmission order shown in Fig. 5 is merely an example. For example, the SN Change Confirm message in step 505 may be sent to the S-SN2 before sending the MN RRC Reconfiguration message in step 504. In other words, in response to receiving the SN Addition Request Acknowledge message, the MN1 may send a MN RRC Reconfiguration message to the UE3 while sending a SN Change Confirm message to the S-SN2.

[0053] Fig. 6 shows an example of operations of MN1, S-SN2, T-SN4, and UE3. The procedure shown in Fig. 6 is based on the operations of MN1 shown in steps 301 to 303 and 305 in Fig. 3 and the operations of T-SN4 shown in Fig. 4. Steps 601 and 602 are similar to steps 501 and 502 in Fig. 5.

[0054] In step 603, T-SN4 responds to MN1 with an SN Addition Request Acknowledge message (e.g. SgNB Addition Request Acknowledge, or S-NODE Addition Request Acknowledge), indicating that only a subset of the candidate PSCells proposed by MN1 or S-SN2 has been accepted (or prepared). Based on this fact, MN1 performs additional signaling with S-SN2 to receive one or more updated CPC execution condition information items. This additional signaling includes steps 604 and 605.

[0055] Specifically, in step 604, MN1 sends an inter-node message to S-SN2. The inter-node message may be an SN Change Confirm message (e.g., SgNB Change Confirm, S-NODE Change Confirm) or an SN Modification Request message (e.g., SgNB Modification Request, S-NODE Modification Request). The inter-node message indicates which candidate PSCell(s) have been accepted or rejected by T-SN4. In step 605, S-SN2 responds to MN1 with another inter-node message. The inter-node message in step 605 may be a newly defined Xn / X2 message (e.g., SN Change Confirm Ack). Alternatively, the inter-node message in step 605 may be an SN Modification Request Acknowledge message (e.g., SgNB Modification Request Acknowledge, S-NODE Modification Request Acknowledge). The inter-node message in step 605 includes one or more updated CPC execution condition information items. These one or more updated CPC execution condition information items indicate one or more CPC execution conditions only for one or more candidate PSCells accepted by T-SN 4. These one or more updated CPC execution condition information items may be sent by an inter-node message (step 605) using one or more containers (e.g., RRC containers) transparent to MN 1. In other words, one CPC execution condition information item indicating multiple CPC execution conditions may be an information item whose contents are not recognized or cannot be recognized by MN 1.

[0056] After completing the additional signaling (i.e., steps 604 and 605), in step 606, the MN1 sends an MN RRC (connection) reconfiguration message to the UE3 to instruct the UE3 to perform a conditional reconfiguration for the CPC. The MN RRC reconfiguration message includes one or more CPC execution condition information items updated by the S-SN2 (step 605) and one or more PSCell setting information items received from the T-SN4 (step 603).

[0057] <Second embodiment> A configuration example of a wireless communication network according to this embodiment is similar to the example shown in Figures 1 and 2. In the following, the operations of MN1, S-SN2, and T-SN4 regarding the inter-SN CPC will be described.

[0058] FIG. 7 shows an example of an operation of MN1 regarding SN-initiated inter-SN CPC. In step 701, MN1 receives a first inter-node message from S-SN2 indicating a request for SN-initiated inter-SN CPC. The first inter-node message may be a SN Change Required message (e.g. SgNB Change Required or S-NODE Change Required). The first inter-node message includes a plurality of cell identity information items each indicating a respective one of a plurality of candidate cells (candidate PSCells) and a plurality of CPC execution condition information items each associated with a respective one of the plurality of cell identity information items. Each CPC execution condition information item indicates a CPC execution condition for a corresponding one candidate PSCell. Each CPC execution condition information item may be sent by the first inter-node message using a container transparent to MN1. In other words, each CPC execution condition information item may be an information item whose contents are not recognized or cannot be recognized by MN1. Each CPC execution condition information item may be an RRC container sent from the S-SN 2 to the UE 3 via the MN 1 .

[0059] Each cell identity information item is an information item that is opaque to MN1 (i.e., recognizable by MN1). Each cell identity information item may indicate an identifier of a corresponding one of multiple candidate PSCells. Each cell identity information item may be, for example, a Physical Cell ID (PCI) and a carrier frequency (e.g., Absolute Radio Frequency Channel Number (ARFCN)), or CGI-info. On the other hand, each CPC execution condition information item may be an information item that is transparent to MN1. Each CPC execution condition information item may include one or more measurement identities (measId).

[0060] FIG. 8 shows a specific example of a cell identification information item and an execution condition information item. In the example of FIG. 8, a first inter-node message transmitted from S-SN2 to MN1 includes a CG-Config message 801, which is an inter-node RRC message. The CG-Config message 801 includes a CondExecutionCondList IE (or field) 802, which is an information element including a cell identification information item and an execution condition information item. Each entry of the CondExecutionCondList IE 802 indicates information of one candidate PSCell (CPC-CandidateCellInfo (803)). Specifically, each entry of the CondExecutionCondList IE 802 includes a cgi-Info field 804 and a CPC-ExecutionCond field 805. The cgi-Info field 804 may be a CGI-InfoNR IE, and indicates information of a candidate PSCell including an identifier of the candidate PCell. The CPC-ExecutionCond field 805 indicates a CPC execution condition. The cgi-Info field 804 is opaque to the MN 1 and can be recognized by the MN 1. On the other hand, the CPC-ExecutionCond field 805 may be transparent to the MN 1. For example, the MN 1 may associate the CPC execution condition received in the CPC-ExecutionCond field 805 with an identifier of a candidate PSCell and transfer it directly to the UE 3 in an MN RRC (connection) reconfiguration message. The association between the cgi-Info field 804 and the CPC-ExecutionCond field 805 allows the MN 1 to identify a CPC execution condition information item for a certain candidate PSCell (cell identifier).

[0061] FIG. 9 shows another specific example of a cell identity information item and an execution condition information item. In the example of FIG. 9, the first inter-node message is an SgNB Change Required message. This SgNB Change Required message includes a list of candidate PSCells proposed by S-SN2 (e.g., Candidate Cells to be Prepared List IE). The Candidate Cells to be Prepared List IE includes one or more Candidate Cells to be Prepared Item IEs. Each Candidate Cells to be Prepared Item IE includes a Candidate cell ID IE and an RRC Container IE. The Candidate cell ID IE indicates an identifier (e.g., NR-CGI, ECGI) of one candidate PSCell. The RRC Container IE includes a CPC execution condition. That is, one pair of the Candidate cell ID IE and the RRC Container IE included in each Candidate Cells to be Prepared Item IE indicates an association between one candidate PSCell and a CPC execution condition for the candidate PSCell. For example, the MN 1 may associate the CPC execution condition received in the RRC Container IE with the identifier of the candidate PSCell and transfer it to the UE 3 as it is in an MN RRC (connection) reconfiguration message. Therefore, the information included in the RRC Container IE may be transparent to the MN 1. The MN 1 can identify a CPC execution condition information item for a certain candidate PSCell (cell identifier) ​​by the pair of the Candidate cell ID IE and the RRC Container IE.

[0062] Returning to Fig. 7, in step 702, MN1 transmits a second inter-node message indicating a request for an inter-SN CPC and including information of multiple candidate PSCells to T-SN4. The second inter-node message may be a SN Addition Request message (e.g., SgNB Addition Request, or S-NODE Addition Request).

[0063] In step 703, the MN1 receives a third inter-node message from the T-SN4. The third inter-node message may be a SN Addition Request Acknowledge message (e.g., SgNB Addition Request Acknowledge, or S-NODE Addition Request Acknowledge). The third inter-node message includes one or more PSCell configuration information items, each indicating a PSCell configuration for one or more accepted candidate PSCells. Each PSCell configuration may be an SCG configuration. Each PSCell configuration information item may be an SN RRC Reconfiguration message including a PSCell configuration. In other words, each PSCell configuration information item may be an RRC container including a corresponding one PSCell configuration. The third inter-node message may include a list of inter-node RRC messages (e.g., a list of CG-Config) for each of the candidate PSCells accepted by the T-SN4. The third inter-node message may include inter-node RRC messages (eg, CG-Config) in the same number as the number (N) of candidate PSCells accepted by the T-SN4 as one or more (<=N) RRC containers.

[0064] In step 704, MN1 selects one or more CPC execution information items corresponding to one or more accepted candidate PSCells from the multiple CPC execution condition information items received by S-SN2 (step 701). In step 705, MN1 transmits an MN RRC (connection) reconfiguration message to UE3 to instruct UE3 to perform a conditional reconfiguration for CPC. The MN RRC reconfiguration message includes one or more CPC execution information items selected in step 704 and one or more PSCell setting information items received from T-SN4 (step 703).

[0065] FIG. 10 shows an example of the operation of S-SN2. In step 1001, S-SN1 decides to initiate inter-SN CPC for a PSCell of the SCG of UE1. Step 1002 corresponds to step 701 of FIG. 7. Specifically, S-SN2 sends a first inter-node message indicating a request for SN-initiated inter-SN CPC to MN1. The first inter-node message may be a SN Change Required message (e.g. SgNB Change Required, or S-NODE Change Required). The first inter-node message includes a plurality of cell identity information items, each indicating a respective one of a plurality of candidate PSCells, and a plurality of CPC execution condition information items, each associated with a respective one of the plurality of cell identity information items. Specific examples of the plurality of cell identity information items and the plurality of CPC execution condition information items are similar to those described with respect to step 701 of FIG. 7.

[0066] According to the operations described with reference to Figures 7 to 10, the MN 1 sends an MN RRC reconfiguration message to the UE 3 to indicate CPC while skipping additional signaling with the S-SN 2 or without waiting for the completion of the additional signaling, regardless of whether all of the candidate PSCells proposed by the MN 1 or the S-SN 2 have been accepted by the T-SN 4. This can therefore prevent an increase in the delay of CPC preparation due to the additional signaling.

[0067] FIG. 11 shows an example of the operations of MN1, S-SN2, T-SN4, and UE3. The procedure shown in FIG. 11 is based on the operation of MN1 shown in FIG. 7 and the operation of S-SN2 shown in FIG. 10. In step 1101, S-SN2 initiates an inter-SN CPC procedure by sending an SN Change Required message (e.g. SgNB Change Required, or S-NODE Change Required) to MN1. In the message, S-SN2 indicates CPC initiation to MN1. The message includes an identifier of T-SN4. The message further includes a number of cell identity information items, each indicating a respective one of a number of candidate PSCells, and a number of CPC execution condition information items, each associated with a respective one of the number of cell identity information items. Additionally or instead of the identifier of T-SN4, S-SN2 may include identifiers of candidate PSCells in the message.

[0068] In step 1102, the MN1 requests the T-SN4 to allocate resources for the UE3 using the SN Addition procedure. Specifically, the MN1 sends an SN Addition Request message (e.g., SgNB Addition Request, or S-NODE Addition Request) to the T-SN4. This message indicates CPC initiation to the T-SN4 and indicates multiple candidate PSCells to the T-SN4. In this message, the MN1 may provide the T-SN4 with an upper limit (or maximum number) of the candidate PSCells.

[0069] In step 1103, the T-SN4 responds to the MN1 with a SN Addition Request Acknowledge message (e.g. SgNB Addition Request Acknowledge, or S-NODE Addition Request Acknowledge). The message includes information indicating one or more candidate PSCells accepted by the T-SN4. Additionally or alternatively, the message includes one or more PSCell configuration information items, each indicating a PSCell configuration of a respective one of the one or more accepted candidate PSCells. Each PSCell configuration may be an SCG configuration. Each PSCell configuration information item may be an SN RRC Reconfiguration message including the PSCell configuration. In other words, each PSCell configuration information item may be an RRC container including a corresponding one PSCell configuration.

[0070] By checking the SN Addition Request Acknowledge message, MN1 can learn of one or more candidate PSCells accepted by T-SN4. In step 1104, MN1 selects one or more CPC execution information items corresponding to one or more accepted candidate PSCells from the multiple CPC execution condition information items already received by S-SN2 (step 1101).

[0071] In step 1105, the MN RRC (connection) reconfiguration message is sent to the UE3 to instruct the UE3 to perform a conditional reconfiguration for CPC. The MN RRC reconfiguration message includes one or more CPC execution information items selected in step 1104 and one or more PSCell setting information items received from the T-SN4 (step 1103). In response to receiving the MN RRC reconfiguration message, the UE3 starts evaluation of the CPC execution condition. Then, in response to the establishment of the CPC execution condition of any of the candidate PSCells, the UE3 starts access to the T-SN4.

[0072] In step 1106, MN1 sends an SN Change Confirm message (e.g. SgNB Change Confirm, S-NODE Change Confirm) to S-SN2. The message informs S-SN2 that the allocation of resources of T-SN4 for inter-SN CPC has been successful. Note that the SN Change Confirm message in step 1106 causes S-SN2 to continue providing user data to UE3 until future CPC execution. In other words, S-SN2 receives the SN Change Confirm message but does not stop providing user data to UE3. The SN Change Confirm message may include information indicating that this message is for inter-SN CPC.

[0073] The message transmission order shown in Figure 11 is merely an example. For example, the SN Change Confirm message in step 1106 may be sent to S-SN2 before sending the MN RRC Reconfiguration message in step 1105. In other words, in response to receiving the SN Addition Request Acknowledge message, MN1 may send a MN RRC Reconfiguration message to UE3 while sending a SN Change Confirm message to S-SN2.

[0074] The SN Change Confirm message of step 1106 may indicate to the S-SN2 which candidate PSCell(s) have been accepted or rejected (i.e., not accepted) by the T-SN4. After receiving the SN Change Confirm message, the S-SN2 may perform additional signaling with the MN1 to modify or update one or more CPC execution conditions already sent to the UE1. Specifically, the S-SN2 may send an additional inter-node message to the MN1. The inter-node message may be an SN Modification Required message (e.g., SgNB Modification Required, S-NODE Modification Required). Alternatively, the inter-node message may be a newly defined Xn / X2 message (e.g., SN Change Confirm Ack). The inter-node message may include at least one updated CPC execution condition information item for at least one of the one or more candidate PSCells accepted by the T-SN4. The MN 1 may send a second MN RRC reconfiguration message containing the at least one updated CPC execution condition information item to the UE 3. The second MN RRC reconfiguration message causes the UE 3 to replace its current CPC execution information with the corresponding CPC execution information included in the newly received CPC execution information item.

[0075] <Third embodiment> A configuration example of a wireless communication network according to this embodiment is similar to the example shown in Figures 1 and 2. In the following, the operations of MN1, S-SN2, and T-SN4 regarding inter-SN CPC will be described.

[0076] 12 shows an example of an operation of the MN1 for inter-SN CPC. This inter-SN CPC may be initiated by the MN1 or may be initiated by the S-SN2. In step 1201, the MN1 transmits an MN RRC (connection) reconfiguration message to the UE3 to instruct the UE3 of a conditional reconfiguration for CPC. The MN RRC reconfiguration message includes a CPC execution condition and a PSCell configuration (or an SCG configuration) of a candidate PSCell.

[0077] In step 1202, the MN1 receives from the UE3 a first MN RRC reconfiguration complete message which is a response to the MN RRC reconfiguration message of step 1201. The first MN RRC reconfiguration complete message does not include an SN RRC response message (SN RRC reconfiguration complete message) addressed to the T-SN4.

[0078] In step 1203, the MN 1 receives a second MN RRC reconfiguration complete message transmitted from the UE 3 in response to CPC execution or the establishment of a CPC execution condition for any of the candidate PSCells. The second MN RRC reconfiguration complete message includes an SN RRC response message (SN RRC reconfiguration complete message) addressed to the T-SN 4.

[0079] In step 1204, in response to receiving the second MN RRC reconfiguration complete message (step 1203), the MN1 sends a Conditional PSCell Change Notification message to the S-SN2. The Conditional PSCell Change Notification message may cause the S-SN2 to stop providing user data to the UE3.

[0080] Although not shown, in response to receiving the second MN RRC reconfiguration complete message (step 1203), MN1 may forward the SN RRC reconfiguration complete message included in the second MN RRC reconfiguration complete message to T-SN4 via a SN Reconfiguration Complete message.

[0081] According to the operation described with reference to Fig. 12, the MN1 transmits a Conditional PSCell Change Notification message to the S-SN2 in response to CPC (execution) being triggered or in response to a CPC execution condition being satisfied, which can optimize the transmission timing of the Conditional PSCell Change Notification message.

[0082] Figure 13 shows an example of the operations of MN1, S-SN2, T-SN4 and UE3 regarding SN-initiated inter-SN CPC. In step 1301, S-SN2 initiates inter-SN CPC procedure by sending a SN Change Required message (e.g. SgNB Change Required or S-NODE Change Required) to MN1. In the message, S-SN2 indicates CPC initiation to MN1. The message includes an identifier of T-SN4. The message further includes CPC execution conditions. MN1 may or may not be able to comprehend the CPC execution conditions set by S-SN2.

[0083] In step 1302, the MN1 requests the T-SN4 to allocate resources for the UE3 using the SN Addition procedure. Specifically, the MN1 sends an SN Addition Request message (e.g., SgNB Addition Request, or S-NODE Addition Request) to the T-SN4. In this message, the MN1 may indicate CPC initiation to the T-SN4 and provide an upper limit of candidate PSCells to the T-SN4.

[0084] In step 1303, the T-SN4 sends the PSCell ID(s) of one or more accepted (or prepared) candidate PSCells to the MN1 via an SN Addition Request Acknowledge message. In addition, the T-SN4 sends the PSCell configuration (or SCG configuration) of each accepted candidate PSCell to the MN1 via an SN Addition Request Acknowledge message.

[0085] In step 1304, the MN1 transmits an MN RRC (connection) reconfiguration message to the UE3 to instruct the UE3 to perform a conditional reconfiguration for the CPC. The MN RRC reconfiguration message includes a CPC configuration (e.g., ConditionalReconfiguration IE), and the CPC configuration includes the CPC execution condition set by the S-SN2 and the PSCell configuration (or SCG configuration) set by the T-SN4.

[0086] In step 1305, the UE3 sends to the MN1 a first MN RRC reconfiguration complete message which is a response to the MN RRC reconfiguration message of step 1304. The first MN RRC reconfiguration complete message does not include an SN RRC response message (SN RRC reconfiguration complete message) addressed to the T-SN4.

[0087] In step 1306, MN1 sends an SN Change Confirm message (e.g. SgNB Change Confirm, S-NODE Change Confirm) to S-SN2. MN1 may send the SN Change Confirm message (step 1306) to S-SN2 before receiving the MN RRC Reconfiguration Complete message (step 1305) or before sending the MN RRC Reconfiguration message (step 1304). The SN Change Confirm message informs S-SN2 that the allocation of T-SN4 resources for inter-SN CPC has been successful. The SN Change Confirm message causes S-SN2 to continue providing user data to UE3 until a future CPC execution. In other words, S-SN2 receives the SN Change Confirm message but does not stop providing user data to UE3. The SN Change Confirm message may include information indicating that this message is for inter-SN CPC.

[0088] After receiving the MN RRC reconfiguration message (step 1304), the UE3 maintains the connection with the S-SN2 and starts evaluating the CPC execution condition set by the MN RRC reconfiguration message. Then, in step 1307, the UE3 detects that the CPC execution condition for any of the candidate PSCells is satisfied. In step 1308, in response to the establishment of the CPC execution condition, the UE3 transmits a second MN RRC reconfiguration complete message to the MN1. The second MN RRC reconfiguration complete message includes an SN RRC response message (SN RRC reconfiguration complete message) addressed to the T-SN4.

[0089] In step 1309, the MN1 informs the T-SN4 of the success of the SN RRC Reconfiguration procedure via an SN Reconfiguration Complete message, which forwards the SN RRC reconfiguration complete message that was included in the second MN RRC reconfiguration complete message to the T-SN4.

[0090] In step 1310, the MN1 transmits a Conditional PSCell Change Notification message to the S-SN2 in response to receiving the second MN RRC reconfiguration complete message (step 1308). The Conditional PSCell Change Notification message may cause the S-SN2 to stop providing user data to the UE3. The order of steps 1309 and 1310 is not limited to that shown in Fig. 13. The MN1 may transmit the Conditional PSCell Change Notification message to the S-SN2 prior to transmitting the SN RRC reconfiguration complete message (step 1309).

[0091] Figure 14 shows an example of the operation of MN1, S-SN2, T-SN4, and UE3 for MN-initiated inter-SN CPC. In step 1401, MN1 initiates the inter-SN CPC procedure by requesting T-SN4 to allocate resources for UE3 using the SN Addition procedure. Specifically, MN1 sends an SN Addition Request message (e.g. SgNB Addition Request, or S-NODE Addition Request) to T-SN4. In this message, MN1 indicates CPC initiation to T-SN4 and may provide an upper limit (or maximum number) of candidate PSCells to T-SN4.

[0092] In step 1402, the T-SN4 sends the PSCell ID(s) of one or more prepared candidate PSCells to the MN1 via an SN Addition Request Acknowledge message. In addition, the T-SN4 sends the PSCell configuration (or SCG configuration) to the MN1 via an SN Addition Request Acknowledge message.

[0093] In step 1403, MN1 sends an SN Release Request message (e.g. SgNB Release Request, S-NODE Release Request) to S-SN2. The SN Release Request message informs S-SN2 that the allocation of T-SN4 resources for inter-SN CPC has been successful. The SN Release Request message causes S-SN2 to continue providing user data to UE3 until a future CPC execution. In other words, S-SN2 receives the SN Release Request but does not stop providing user data to UE3. The SN Release Request may include information indicating that this message is for an inter-SN CPC. In step 1404, S-SN2 responds to MN1 with an SN Release Request Acknowledge message.

[0094] The MN1 generates a CPC execution condition. The MN1 generates a CPC configuration (e.g., ConditionalReconfiguration IE) including the CPC execution condition generated by the MN1 and the PSCell configuration (or SCG configuration) received from the T-SN4. Then, in step 1405, the MN1 transmits the CPC configuration to the UE3 via an MN RRC (Connection) Reconfiguration message. The MN RRC reconfiguration message instructs the UE3 to perform a conditional reconfiguration for the CPC.

[0095] In step 1406, UE3 sends a first MN RRC reconfiguration complete message, which is a response to the MN RRC reconfiguration message in step 1405, to MN1. The first MN RRC reconfiguration complete message does not include an SN RRC response message (SN RRC reconfiguration complete message) addressed to T-SN4.

[0096] After receiving the MN RRC reconfiguration message (step 1405), UE3 maintains the connection with S-SN2 and starts evaluating the CPC execution conditions set by the MN RRC reconfiguration message. Then, in step 1407, UE3 detects that the CPC execution conditions for any of the candidate PSCs are met. In step 1408, in response to the establishment of the CPC execution conditions, UE3 sends a second MN RRC reconfiguration complete message to MN1. The second MN RRC reconfiguration complete message includes an SN RRC response message (SN RRC reconfiguration complete message) addressed to T-SN4.

[0097] In step 1409, MN1 notifies T-SN4 of the success of the SN RRC Reconfiguration procedure via an SN Reconfiguration Complete message. The SN Reconfiguration Complete message forwards the SN RRC reconfiguration complete message, which was included in the second MN RRC reconfiguration complete message, to T-SN4.

[0098] In step 1410, the MN1 transmits a Conditional PSCell Change Notification message to the S-SN2 in response to receiving the second MN RRC reconfiguration complete message (step 1408). The Conditional PSCell Change Notification message may cause the S-SN2 to stop providing user data to the UE3. The order of steps 1409 and 1410 is not limited to that shown in Fig. 14. The MN1 may transmit the Conditional PSCell Change Notification message to the S-SN2 prior to transmitting the SN RRC reconfiguration complete message (step 1409).

[0099] Next, configuration examples of MN1, S-SN2, T-SN4, and UE3 according to the above-mentioned embodiments will be described below. FIG. 15 is a block diagram showing a configuration example of MN1 according to the above-mentioned embodiments. The configurations of S-SN2 and T-SN4 may also be similar to the configuration shown in FIG. 15. Referring to FIG. 15, MN1 includes a Radio Frequency transceiver 1501, a network interface 1503, a processor 1504, and a memory 1505. The RF transceiver 1501 performs analog RF signal processing to communicate with UEs including UE3. The RF transceiver 1501 may include multiple transceivers. The RF transceiver 1501 is coupled to an antenna array 1502 and a processor 1504. The RF transceiver 1501 receives modulation symbol data from the processor 1504, generates a transmission RF signal, and provides the transmission RF signal to the antenna array 1502. The RF transceiver 1501 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1502 and supplies the baseband receive signal to the processor 1504. The RF transceiver 1501 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, multiple phase shifters and multiple power amplifiers.

[0100] The network interface 1503 is used to communicate with network nodes (e.g., S-SN2, T-SN4, and control and forwarding nodes of the core network). The network interface 1503 may include, for example, a network interface card (NIC) that complies with the IEEE 802.3 series.

[0101] The processor 1504 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 1504 may include multiple processors. For example, the processor 1504 may include a modem processor (e.g., Digital Signal Processor (DSP)) performing digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) performing control plane processing. The processor 1504 may include a digital beamformer module for beamforming. The digital beamformer module may include a Multiple Input Multiple Output (MIMO) encoder and a precoder.

[0102] The memory 1505 is configured by a combination of volatile memory and non-volatile memory. The volatile memory is, for example, Static Random Access Memory (SRAM) or Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or a hard disk drive, or any combination thereof. The memory 1505 may include storage located remotely from the processor 1504. In this case, the processor 1504 may access the memory 1505 via the network interface 1503 or an I / O interface not shown.

[0103] The memory 1505 may store one or more software modules (computer programs) 1506 including instructions and data for performing the processing by the MN1 described in the above-mentioned embodiments. In some implementations, the processor 1504 may be configured to read the software modules 1506 from the memory 1505 and execute them to perform the processing by the MN1 described in the above-mentioned embodiments.

[0104] In addition, when the MN1 is a CU (eg, eNB-CU or gNB-CU) or a CU-CP, the MN1 does not need to include the RF transceiver 1501 (and the antenna array 1502).

[0105] FIG. 16 is a block diagram showing a configuration example of the UE3. The Radio Frequency (RF) transceiver 1601 performs analog RF signal processing to communicate with the MN1, the S-SN2, and the T-SN4. The RF transceiver 1601 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 1601 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 1601 is coupled to the antenna array 1602 and the baseband processor 1603. The RF transceiver 1601 receives modulation symbol data (or OFDM symbol data) from the baseband processor 1603, generates a transmission RF signal, and provides the transmission RF signal to the antenna array 1602. The RF transceiver 1601 also generates a baseband reception signal based on the reception RF signal received by the antenna array 1602, and provides the baseband reception signal to the baseband processor 1603. The RF transceiver 1601 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0106] The baseband processor 1603 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 line coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management of layer 1 (e.g., transmission power control), layer 2 (e.g., radio resource management, and hybrid automatic repeat request (HARQ) processing), and layer 3 (e.g., signaling related to attachment, mobility, and call management).

[0107] For example, the digital baseband signal processing by the baseband processor 1603 may include signal processing of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a MAC layer, and a PHY layer. Also, the control plane processing by the baseband processor 1603 may include processing of a Non-Access Stratum (NAS) protocol, an RRC protocol, and a MAC Control Element (CE).

[0108] The baseband processor 1603 may perform MIMO encoding and precoding for beamforming.

[0109] The baseband processor 1603 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 1604 described later.

[0110] The application processor 1604 is also called a CPU, an MPU, a microprocessor, or a processor core. The application processor 1604 may include multiple processors (multiple processor cores). The application processor 1604 executes a system software program (operating system (OS)) and various application programs (e.g., a calling application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 1606 or a memory not shown, thereby implementing various functions of the UE3.

[0111] In some implementations, the baseband processor 1603 and the application processor 1604 may be integrated on a single chip, as shown by the dashed line (1605) in Figure 16. In other words, the baseband processor 1603 and the application processor 1604 may be implemented as a single System on Chip (SoC) device 1605. An SoC device may also be called a system Large Scale Integration (LSI) or a chipset.

[0112] The memory 1606 is a volatile memory or a non-volatile memory, or a combination thereof. The memory 1606 may include a plurality of physically independent memory devices. The volatile memory is, for example, an SRAM or a DRAM, or a combination thereof. The non-volatile memory is an MROM, an EEPROM, a flash memory, or a hard disk drive, or any combination thereof. For example, the memory 1606 may include an external memory device accessible from the baseband processor 1603, the application processor 1604, and the SoC 1605. The memory 1606 may include an internal memory device integrated in the baseband processor 1603, the application processor 1604, or the SoC 1605. Furthermore, the memory 1606 may include a memory in a Universal Integrated Circuit Card (UICC).

[0113] The memory 1606 may store one or more software modules (computer programs) 1607 including instructions and data for performing processing by the UE 3 described in the above-mentioned embodiments. In some implementations, the baseband processor 1603 or the application processor 1604 may be configured to read the software modules 1607 from the memory 1606 and execute them to perform processing by the UE 3 described in the above-mentioned embodiments using the drawings.

[0114] In addition, the control plane processing and operations performed by UE3 described in the above embodiment can be realized by elements other than the RF transceiver 1601 and the antenna array 1602, i.e., at least one of the baseband processor 1603 and the application processor 1604, and the memory 1606 storing the software module 1607.

[0115] As described with reference to FIG. 15 and FIG. 16, each of the processors included in MN1, S-SN2, T-SN4, and UE3 according to the above-mentioned embodiments can execute one or more programs including instructions for making a computer perform the algorithms described with reference to the drawings. The programs include instructions (or software codes) for making a computer perform one or more functions described in the embodiments when the programs are loaded into a computer. The programs may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disk (DVD), Blu-ray (registered trademark) disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The programs may be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, the transitory computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0116] <Other embodiments> In one or more of the above-described embodiments, the T-SN4 selects a candidate PSCell to be a target of the CPC from one or more candidate PSCells proposed by the S-SN2. Alternatively, the T-SN4 may select one or more other cells different from (i.e., not included in) the proposed candidate PSCells as a PSCell candidate by itself. In this case, the T-SN4 may transmit information indicating one or more candidate PSCells proposed by the S-SN2 and accepted by the T-SN4 and the candidate PSCells selected by the T-SN4 to the MN1 in a third inter-node message. The T-SN4 further transmits a PSCell configuration (or an SCG configuration) for each of the candidate PSCells selected by itself to the MN1. Even if all of one or more candidate PSCells proposed by S-SN2 are accepted, if MN1 is notified of one or more other candidate PSCells from T-SN4 (i.e., candidate cells for the PSCell selected by T-SN4 itself), MN1 transmits information about this to S-SN2. In response to this, S-SN2 transmits an updated CPC execution condition information item to MN1. Note that the updated CPC execution condition information item includes at least the CPC execution condition for the candidate cell for the PSCell selected by T-SN4. This makes it possible to apply the above-mentioned embodiment even when T-SN4 can flexibly select candidate cells for the PSCell of the CPC.

[0117] In one or more of the above-described embodiments, the T-SN4 transmits information of one or more accepted candidate PSCells to the M-SN1 in a third inter-node message. At this time, the T-SN4 may generate an inter-node RRC message (e.g., CG-Config) for each of the one or more candidate PSCells and include it in the third inter-node message. The third inter-node message may include a list (e.g., a list of CG-Config) of inter-node RRC messages for each of the candidate PSCells accepted by the T-SN4. More specifically, the third inter-node message may include as many inter-node RRC messages (e.g., CG-Config) as the number (N) of candidate PSCells accepted by the T-SN4 as one or more (<=N) RRC containers. The T-SN4 may link each of the inter-node RRC messages (e.g., CG-Config) to each of the X2 / Xn level information items indicating the accepted candidate PSCells (e.g., in list format) and transmit these to the MN1.

[0118] Furthermore, the above-described embodiment is merely an example of application of the technical idea obtained by the inventor of the present invention. In other words, the technical idea is not limited to the above-described embodiment, and various modifications are possible.

[0119] For example, some or all of the above embodiments may be described as, but are not limited to, the following supplementary notes.

[0120] (Appendix 1) A Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: receiving a first inter-node message from a source Secondary Node (SN) indicating a request for an SN-initiated inter-SN Conditional PSCell Change (CPC), where the first inter-node message includes one or more CPC execution condition information items indicating a plurality of CPC execution conditions each associated with a respective one of a plurality of candidate Primary SCG Cells (PSCells); sending a second inter-node message to the target SN indicating a request for an inter-SN CPC and including information of the plurality of candidate PSCells; receiving a third inter-node message from the target SN, where the third inter-node message includes one or more PSCell configuration information items each indicating a PSCell configuration for a respective one of one or more accepted candidate PSCells, the third inter-node message indicating to the MN whether all of the plurality of candidate PSCells have been accepted; if the third inter-node message indicates that all of the plurality of candidate PSCells have been accepted, sending a first MN Radio Resource Control (RRC) reconfiguration message to the UE, the first MN Radio Resource Control (RRC) reconfiguration message including the one or more CPC execution condition information items and the one or more PSCell configuration information items, while skipping additional signaling with the source SN or without waiting for completion of the additional signaling; if the third inter-node message indicates that only a subset of the plurality of candidate PSCells is accepted, performing the additional signaling with the source SN to receive one or more updated CPC execution condition information items, and transmitting a first MN RRC reconfiguration message to the UE containing the one or more updated CPC execution condition information items and the one or more PSCell configuration information items; RAN node. (Appendix 2) the one or more updated CPC execution condition information items indicate one or more CPC execution conditions for only the one or more accepted candidate PSCells; RAN node as described in Appendix 1. (Appendix 3) The additional signaling includes: sending a fourth inter-node message to the source SN indicating the one or more accepted candidate PSCells or one or more candidate PSCells rejected by the target SN; and receiving by the MN from the source SN a fifth inter-node message including the one or more updated CPC execution condition information items; Including, 3. The RAN node according to claim 1 or 2. (Appendix 4) The one or more CPC execution condition information items are sent by the first inter-node message using one or more containers transparent to the MN. 4. The RAN node according to claim 1 , (Appendix 5) The one or more updated CPC execution condition information items are sent by the fifth inter-node message using one or more containers transparent to the MN. RAN node as described in Appendix 3. (Appendix 6) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: receiving a first inter-node message from a source Secondary Node (SN) indicating a request for an SN-initiated inter-SN Conditional PSCell Change (CPC), where the first inter-node message includes one or more CPC execution condition information items indicating a plurality of CPC execution conditions each associated with a respective one of a plurality of candidate Primary SCG Cells (PSCells); sending a second inter-node message to the target SN indicating a request for an inter-SN CPC and including information of the plurality of candidate PSCells; receiving a third inter-node message from the target SN, where the third inter-node message includes one or more PSCell configuration information items each indicating a PSCell configuration for a respective one of one or more accepted candidate PSCells, the third inter-node message indicating to the MN whether all of the plurality of candidate PSCells have been accepted; If the third inter-node message indicates that all of the plurality of candidate PSCells have been accepted, sending a first MN Radio Resource Control (RRC) reconfiguration message to the UE, the first MN Radio Resource Control (RRC) reconfiguration message including the one or more CPC execution condition information items and the one or more PSCell configuration information items, while skipping additional signaling with the source SN or without waiting for completion of the additional signaling; and if the third inter-node message indicates that only a subset of the plurality of candidate PSCells is accepted, performing the additional signaling with the source SN to receive one or more updated CPC execution condition information items, and sending a first MN RRC reconfiguration message to the UE containing the one or more updated CPC execution condition information items and the one or more PSCell configuration information items; A method for providing the above. (Appendix 7) A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for User Equipment (UE), the method comprising: receiving a first inter-node message from a source Secondary Node (SN) indicating a request for an SN-initiated inter-SN Conditional PSCell Change (CPC), where the first inter-node message includes one or more CPC execution condition information items indicating a plurality of CPC execution conditions each associated with a respective one of a plurality of candidate Primary SCG Cells (PSCells); sending a second inter-node message to the target SN indicating a request for an inter-SN CPC and including information of the plurality of candidate PSCells; receiving a third inter-node message from the target SN, where the third inter-node message includes one or more PSCell configuration information items each indicating a PSCell configuration for a respective one of one or more accepted candidate PSCells, the third inter-node message indicating to the MN whether all of the plurality of candidate PSCells have been accepted; If the third inter-node message indicates that all of the plurality of candidate PSCells have been accepted, sending a first MN Radio Resource Control (RRC) reconfiguration message to the UE, the first MN Radio Resource Control (RRC) reconfiguration message including the one or more CPC execution condition information items and the one or more PSCell configuration information items, while skipping additional signaling with the source SN or without waiting for completion of the additional signaling; and if the third inter-node message indicates that only a subset of the plurality of candidate PSCells is accepted, performing the additional signaling with the source SN to receive one or more updated CPC execution condition information items, and sending a first MN RRC reconfiguration message to the UE containing the one or more updated CPC execution condition information items and the one or more PSCell configuration information items; A program that includes: (Appendix 8) A Radio Access Network (RAN) node configured to operate as a target Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: Receive a second inter-node message indicating a request for an inter-SN Conditional PSCell Change (CPC) and including information of a plurality of candidate Primary SCG Cells (PSCells) from a Master Node (MN); configured to transmit a third inter-node message to the MN; The third inter-node message includes one or more PSCell configuration information items, each indicating a PSCell configuration of a respective one of the one or more accepted candidate PSCells, and the third inter-node message indicates to the MN whether all of the plurality of candidate PSCells have been accepted. RAN node. (Appendix 9) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a target Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: receiving a second inter-node message from a Master Node (MN) indicating a request for an inter-SN CPC and including information of a plurality of candidate Primary SCG Cells (PSCells); and transmitting a third inter-node message to the MN; The third inter-node message includes one or more PSCell configuration information items, each indicating a PSCell configuration of a respective one of the one or more accepted candidate PSCells, and the third inter-node message indicates to the MN whether all of the plurality of candidate PSCells have been accepted. method. (Appendix 10) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a target Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for User Equipment (UE), the method comprising: receiving a second inter-node message from a Master Node (MN) indicating a request for an inter-SN CPC and including information of a plurality of candidate Primary SCG Cells (PSCells); and transmitting a third inter-node message to the MN; The third inter-node message includes one or more PSCell configuration information items, each indicating a PSCell configuration of a respective one of the one or more accepted candidate PSCells, and the third inter-node message indicates to the MN whether all of the plurality of candidate PSCells have been accepted. program. (Appendix 11) A Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: receiving a first inter-node message from a source Secondary Node (SN) indicating a request for an SN-initiated inter-SN Conditional PSCell Change (CPC), where the first inter-node message includes a plurality of cell identity information items, each indicating a respective one of a plurality of candidate Primary SCG Cells (PSCells), and a plurality of CPC execution condition information items, each associated with a respective one of the plurality of cell identity information items; sending a second inter-node message to the target SN indicating a request for an inter-SN CPC and including information of the plurality of candidate PSCells; receiving a third inter-node message from the target SN including one or more PSCell configuration information items each indicating a PSCell configuration of a respective one of the one or more accepted candidate PSCells; selecting one or more CPC execution information items from the plurality of CPC execution condition information items corresponding to the one or more accepted candidate PSCells; and transmitting a first MN Radio Resource Control (RRC) reconfiguration message to the UE, the first MN RRC reconfiguration message including the one or more selected CPC execution information items and the one or more PSCell configuration information items. RAN node. (Appendix 12) The at least one processor: sending a fourth inter-node message to the source SN indicating the one or more accepted candidate PSCells or one or more candidate PSCells rejected by the target SN; configured to receive a fifth inter-node message from the source SN after transmitting the fourth inter-node message; The first MN RRC reconfiguration message is transmitted to the UE before the MN receives the fifth inter-node message. 13. The RAN node according to claim 11. (Appendix 13) the fifth inter-node message includes at least one updated CPC execution condition information item for at least one of the one or more accepted candidate PSCells; The at least one processor is configured to send a second MN RRC reconfiguration message to the UE, the second MN RRC reconfiguration message including the at least one updated CPC execution condition information item. 13. The RAN node according to claim 12. (Appendix 14) the plurality of cell identity information items are sent in a non-transparent manner to the MN in the first inter-node message; Each of the plurality of CPC execution condition information items is sent by the first inter-node message using a container transparent to the MN. 14. The RAN node according to any one of Supplementary Notes 11 to 13. (Appendix 15) the first inter-node message is a SN Change Required message; the second inter-node message is an SN Addition Request message; The third inter-node message is an SN Addition Request Acknowledge message. 15. The RAN node according to any one of Supplementary Notes 11 to 14. (Appendix 16) The fourth inter-node message is a SN Change Confirm message. 13. The RAN node according to claim 12. (Appendix 17) The fifth inter-node message is a SN Modification Required message. 16. The RAN node according to claim 16. (Appendix 18) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: receiving a first inter-node message from a source Secondary Node (SN) indicating a request for an SN-initiated inter-SN Conditional PSCell Change (CPC), where the first inter-node message includes a plurality of cell identity information items, each indicating a respective one of a plurality of candidate Primary SCG Cells (PSCells), and a plurality of CPC execution condition information items, each associated with a respective one of the plurality of cell identity information items; sending a second inter-node message to the target SN indicating a request for an inter-SN CPC and including information of the plurality of candidate PSCells; receiving a third inter-node message from the target SN including one or more PSCell configuration information items each indicating a PSCell configuration of a respective one of the one or more accepted candidate PSCells; selecting, from the plurality of CPC execution condition information items, one or more CPC execution information items corresponding to the one or more accepted candidate PSCells; and sending a first MN Radio Resource Control (RRC) reconfiguration message to the UE, the first MN RRC reconfiguration message including the one or more selected CPC execution information items and the one or more PSCell configuration information items; A method for providing the above. (Appendix 19) A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for User Equipment (UE), the method comprising: receiving a first inter-node message from a source Secondary Node (SN) indicating a request for an SN-initiated inter-SN Conditional PSCell Change (CPC), where the first inter-node message includes a plurality of cell identity information items, each indicating a respective one of a plurality of candidate Primary SCG Cells (PSCells), and a plurality of CPC execution condition information items, each associated with a respective one of the plurality of cell identity information items; sending a second inter-node message to the target SN indicating a request for an inter-SN CPC and including information of the plurality of candidate PSCells; receiving a third inter-node message from the target SN including one or more PSCell configuration information items each indicating a PSCell configuration of a respective one of the one or more accepted candidate PSCells; selecting, from the plurality of CPC execution condition information items, one or more CPC execution information items corresponding to the one or more accepted candidate PSCells; and sending a first MN Radio Resource Control (RRC) reconfiguration message to the UE, the first MN RRC reconfiguration message including the one or more selected CPC execution information items and the one or more PSCell configuration information items; A program that includes: (Appendix 20) 1. A Radio Access Network (RAN) node configured to operate as a source Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor is configured to transmit a first inter-node message indicating a request for an SN-initiated inter-SN Conditional PSCell Change (CPC) to a Master Node (MN), where the first inter-node message includes a plurality of cell identity information items, each indicating a respective one of a plurality of candidate Primary SCG Cells (PSCells), and a plurality of CPC execution condition information items, each associated with a respective one of the plurality of cell identity information items. RAN node. (Appendix 21) The first inter-node message enables the MN to select from among the plurality of CPC execution condition information items one or more CPC execution information items corresponding to one or more accepted candidate PSCells accepted by the target SN. 20. The RAN node according to claim 20. (Appendix 22) the plurality of cell identity information items are sent in a non-transparent manner to the MN in the first inter-node message; Each of the plurality of CPC execution condition information items is sent by the first inter-node message using a container transparent to the MN. 22. The RAN node of claim 20 or 21. (Appendix 23) The first inter-node message is a SN Change Required message. 23. The RAN node according to any one of Supplementary Notes 20 to 22. (Appendix 24) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a source Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: The method comprises transmitting a first inter-node message indicating a request for an SN-initiated inter-SN Conditional PSCell Change (CPC) to a Master Node (MN), where the first inter-node message includes a plurality of cell identity information items, each indicating a respective one of a plurality of candidate Primary SCG Cells (PSCells), and a plurality of CPC execution condition information items, each associated with a respective one of the plurality of cell identity information items. method. (Appendix 25) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a source Secondary Node (SN) associated with a Secondary Cell Group (SCG) in dual connectivity for User Equipment (UE), the method comprising: The method comprises transmitting a first inter-node message indicating a request for an SN-initiated inter-SN Conditional PSCell Change (CPC) to a Master Node (MN), where the first inter-node message includes a plurality of cell identity information items, each indicating a respective one of a plurality of candidate Primary SCG Cells (PSCells), and a plurality of CPC execution condition information items, each associated with a respective one of the plurality of cell identity information items. program. (Appendix 26) A Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: Sending an MN Radio Resource Control (RRC) reconfiguration message to the UE, the message including an execution condition of an inter-SN Conditional PSCell Change (CPC) and a configuration of a candidate Primary SCG Cell (PSCell); receiving a first MN RRC reconfiguration complete message from the UE in response to the MN RRC reconfiguration message; receiving a second MN RRC reconfiguration complete message transmitted from the UE in response to execution of the CPC or establishment of the execution condition; In response to receiving the second MN RRC reconfiguration complete message, the second MN is configured to send a Conditional PSCell Change Notification message to a source Secondary Node (SN). RAN node. (Appendix 27) The Conditional PSCell Change Notification message causes the source SN to stop providing user data to the UE. 26. The RAN node according to claim 26. (Appendix 28) The second MN RRC reconfiguration complete message includes an SN RRC reconfiguration complete message; The at least one processor is configured to, in response to receiving the second MN RRC reconfiguration complete message, forward the SN RRC reconfiguration complete message to a target SN via a SN Reconfiguration Complete message. 28. The RAN node of claim 26 or 27. (Appendix 29) The at least one processor: configured to send an SN Release Request message or an SN Change Confirm message to the source SN during a procedure of preparing the inter-SN CPC performed prior to receiving the second MN RRC reconfiguration complete message; 29. The RAN node according to any one of Supplementary Notes 26 to 28. (Appendix 30) The SN Release Request message or the SN Change Confirm message causes the source SN to continue providing user data to the UE until the execution of the CPC. 29. The RAN node of claim 29. (Appendix 31) The SN Release Request message or the SN Change Confirm message includes information indicating that the message is for an inter-SN CPC; 31. The RAN node of claim 29 or 30. (Appendix 32) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: sending an MN Radio Resource Control (RRC) reconfiguration message to the UE, the message including an execution condition of an inter-SN Conditional PSCell Change (CPC) and a configuration of a candidate Primary SCG Cell (PSCell); receiving a first MN RRC reconfiguration complete message from the UE in response to the MN RRC reconfiguration message; receiving a second MN RRC reconfiguration complete message transmitted from the UE in response to execution of the CPC or establishment of the execution condition; and In response to receiving the second MN RRC reconfiguration complete message, sending a Conditional PSCell Change Notification message to a source Secondary Node (SN); A method for providing the above. (Appendix 33) A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for User Equipment (UE), the method comprising: sending an MN Radio Resource Control (RRC) reconfiguration message to the UE, the message including an execution condition of an inter-SN Conditional PSCell Change (CPC) and a configuration of a candidate Primary SCG Cell (PSCell); receiving a first MN RRC reconfiguration complete message from the UE in response to the MN RRC reconfiguration message; receiving a second MN RRC reconfiguration complete message transmitted from the UE in response to execution of the CPC or establishment of the execution condition; and In response to receiving the second MN RRC reconfiguration complete message, sending a Conditional PSCell Change Notification message to a source Secondary Node (SN); A program that includes:

[0121] This application claims priority based on Japanese Patent Application No. 2021-116603, filed on July 14, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0122] 1 Master Node (MN) 2. Source Secondary Node (S-SN) 3. User Equipment (UE) 4. Target Secondary Node (T-SN) 1504 Processor 1505 Memory 1506 Modules 1603 Baseband Processor 1604 Application Processor 1606 Memory 1607 Modules

Claims

1. 1. A method performed by a Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving an SgNB Change Required message sent from a source Secondary Node (SN) to initiate an inter-SN Conditional PSCell Change (CPC) procedure, where the SgNB Change Required message indicates CPC initiation and the SgNB Change Required message includes one or more CPC Execution Condition information items indicating a plurality of CPC execution conditions each associated with a respective one of a plurality of candidate Primary SCG Cells (PSCells); sending an SgNB Addition Request message to the target SN, indicating a request for CPC and including information of the plurality of candidate PSCells; If not all of the plurality of candidate PSCells are accepted but some of the plurality of candidate PSCells are accepted, sending an SgNB Modification Request message to the source SN indicating the accepted candidate PSCells, receiving an SgNB Modification Request Acknowledge message including one or more updated CPC execution condition information items from the source SN, and sending an RRC Connection reconfiguration message including one or more configuration information items and the updated CPC execution condition information items to the UE; and If all of the plurality of candidate PSCells are accepted, skipping the transmission of the SgNB Modification Request message to the source SN, and transmitting an RRC Connection reconfiguration message to the UE, the RRC Connection reconfiguration message including the one or more CPC execution condition information items and the one or more configuration information items; A method for providing the above.

2. the one or more updated CPC execution condition information items indicate one or more CPC execution conditions for only the accepted candidate PSCells; The method of claim 1.

3. The one or more CPC execution condition information items are sent by the SgNB Change Required message using one or more containers transparent to the MN. The method of claim 1.

4. The one or more updated CPC execution condition information items are sent by the SgNB Modification Request Acknowledge message using one or more containers transparent to the MN. The method of claim 1.

5. The SgNB Change Required message further includes cell identification information for identifying each of the plurality of candidate PSCells; the cell identity is received from the source SN in a format recognizable by the MN; The CPC execution condition information item is received from the source SN in a transparent format that is not recognizable by the MN. The method of claim 1.

6. 1. A Radio Access Network (RAN) node configured to operate as a Master Node (MN) associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: means for receiving from a source Secondary Node (SN) an SgNB Change Required message sent to initiate an Inter-SN Conditional PSCell Change (CPC) procedure, where the SgNB Change Required message indicates CPC initiation, and the SgNB Change Required message includes one or more CPC execution condition information items indicating a plurality of CPC execution conditions each associated with a respective one of a plurality of candidate Primary SCG Cells (PSCells); A means for sending an SgNB Addition Request message to a target SN, the SgNB Addition Request message indicating a request for a CPC and including information of the plurality of candidate PSCells; If not all of the plurality of candidate PSCells are accepted but some of the plurality of candidate PSCells are accepted, a means for sending an SgNB Modification Request message indicating the accepted candidate PSCells to the source SN, receiving an SgNB Modification Request Acknowledge message including one or more updated CPC execution condition information items from the source SN, and sending an RRC Connection reconfiguration message including one or more configuration information items and the updated CPC execution condition information items to the UE; If all of the plurality of candidate PSCells are accepted, skipping the transmission of the SgNB Modification Request message to the source SN and transmitting an RRC Connection reconfiguration message to the UE, the RRC Connection reconfiguration message including the one or more CPC execution condition information items and the one or more configuration information items; RAN node comprising:

7. the one or more updated CPC execution condition information items indicate one or more CPC execution conditions for only the accepted candidate PSCells; 7. The RAN node of claim 6.

8. The one or more CPC execution condition information items are sent by the SgNB Change Required message using one or more containers transparent to the MN.

7. The RAN node of claim 6.

9. The one or more updated CPC execution condition information items are sent by the SgNB Modification Request Acknowledge message using one or more containers transparent to the MN.

7. The RAN node of claim 6.

10. The SgNB Change Required message further includes cell identification information for identifying each of the plurality of candidate PSCells; the cell identity is received from the source SN in a format recognizable by the MN; The CPC execution condition information item is received from the source SN in a transparent format that is not recognizable by the MN.

7. The RAN node of claim 6.

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