Master node and communication method

Abstract

A master node according to an embodiment is a master node (200, 200M) connected to a communication device (100). The master node comprises: a control unit (230) that controls a procedure for the communication device to execute conditional PS cell changes on the basis of primary secondary (PS) cell settings; a reception unit (212) that receives, from the communication device, a radio resource control (RRC) resetting completion message based on the conditional PS cell change, and a transmission unit (221). The transmission unit transmits a change request message to the source secondary node when, in the procedure, the reception unit receives the RRC resetting completion message and the source secondary node is a candidate secondary node, and transmits a release request message to the source secondary node when the reception unit receives the RRC resetting completion message and the source secondary node is not a candidate secondary node.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from patent application serial number 2023-062951, filed April 7, 2023, the entire contents of which are incorporated herein by reference. [Technical Field]

[0002] The present disclosure relates to a master node and a communication method. [Background technology]

[0003] Dual Connectivity (DC) has been introduced in mobile communication systems that comply with the technical specifications of 3GPP (Third Generation Partnership Project), a standardization project for mobile communication systems. In DC, a communication device communicates with a master node (also referred to as a "master base station") and a secondary node (also referred to as a "secondary base station").

[0004] The 3GPP technical specifications prescribe primary / secondary cell (PS cell) change (see Non-Patent Document 1). One procedure for changing a PS cell is the conditional PS cell change (CPC) procedure. In the CPC procedure, a communication device can change the candidate secondary node to one that controls a cell for which an execution condition is satisfied among multiple candidate secondary nodes, based on settings for multiple candidate secondary nodes (hereinafter referred to as CPC settings as appropriate). This allows the communication device to switch the secondary node from a source secondary node to a target secondary node without an instruction from the master node.

[0005] Here, in the current 3GPP technical specifications, when a communication device changes a secondary node (source secondary node) to another secondary node (target secondary node) based on a CPC setting, the master node transmits a release request message (specifically, an SN Release Request message) requesting the release of resources associated with the communication device to associated nodes other than the target secondary node (e.g., the source secondary node and a potential secondary node that could become the target secondary node based on the CPC setting).

[0006] In recent years, selective activation of cell groups has been discussed, for example, to enable continuous cell changes when a communication device is moving at high speed. With selective SCG activation, even after the secondary node has been changed to another secondary node as a result of a successful CPC procedure, the secondary node can be further changed without instructions from the master node based on the CPC settings held by the communication device. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] 3GPP TS 37.340 V17.3.0 “NR; Multi-connectivity; Overall description; Stage-2” Summary of the Invention

[0008] A master node according to a first aspect is a master node connected to a communication device. The master node includes: a control unit that controls a procedure for the communication device to perform a conditional PS cell change based on a primary secondary (PS) cell configuration; a receiving unit that receives a radio resource control (RRC) reconfiguration complete message based on the conditional PS cell change from the communication device; and a transmitting unit. In the procedure, the transmitting unit transmits a change request message to the source secondary node if the receiving unit receives the RRC reconfiguration complete message and the source secondary node is a candidate secondary node, and transmits a release request message to the source secondary node if the receiving unit receives the RRC reconfiguration complete message and the source secondary node is not a candidate secondary node.

[0009] A communication method according to a second aspect is a communication method executed by a master node connected to a communication device, the communication method comprising the steps of: receiving, from the communication device, a radio resource control (RRC) reconfiguration complete message based on a conditional PS cell change based on a primary secondary (PS) cell configuration, by the communication device; receiving the RRC reconfiguration complete message and, if a source secondary node is a candidate secondary node, transmitting a change request message to the source secondary node; and receiving the RRC reconfiguration complete message and, if the source secondary node is not a candidate secondary node, transmitting a release request message to the source secondary node. [Brief explanation of the drawings]

[0010] The objects, features, advantages, and other features of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Figure 1] FIG. 1 is a diagram showing a configuration of a mobile communication system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a protocol stack in the mobile communication system according to the embodiment. [Figure 3]FIG. 3 is a diagram illustrating an overview of dual connectivity (DC) according to the embodiment. [Figure 4] FIG. 4 is a diagram illustrating a configuration of a user equipment (UE) according to the embodiment. [Figure 5] FIG. 5 is a diagram illustrating a configuration of a base station according to the embodiment. [Figure 6] FIG. 6 is a sequence diagram (part 1) showing a first example of operation of the mobile communication system according to the embodiment. [Figure 7] FIG. 7 is a sequence diagram (part 2) showing a first operation example of the mobile communication system according to the embodiment. [Figure 8] FIG. 8 is a sequence diagram showing a second operation example of the mobile communication system according to the embodiment. [Figure 9] FIG. 9 is a sequence diagram showing a third operation example of the mobile communication system according to the embodiment. [Figure 10] FIG. 10 is a flowchart showing a fourth operation example of the mobile communication system according to the embodiment. [Figure 11] FIG. 11 is a sequence diagram showing a fifth operation example of the mobile communication system according to the embodiment. [Figure 12] FIG. 12 is a sequence diagram showing a sixth operation example of the mobile communication system according to the embodiment. [Figure 13] FIG. 13 is a sequence diagram showing a seventh operation example of the mobile communication system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0012] In the current 3GPP technical specifications, when a communication device changes a secondary node to a target secondary node based on CPC settings during selective activation, the master node is assumed to send a release request message to an associated node other than the target secondary node. Upon receiving the release request message, the associated node releases resources associated with the communication device. However, if the communication device subsequently accesses the associated node, the released resources based on the release request message may prevent the node from accepting the access, potentially resulting in improper execution of selective activation. Therefore, one objective of the present invention is to provide a base station and a communication method that enable proper execution of selective activation.

[0013] (Configuration of a mobile communication system) The configuration of a mobile communication system 1 according to an embodiment will be described with reference to Fig. 1. The mobile communication system 1 is, for example, a system that complies with the 3GPP Technical Specification (TS). In the following, the mobile communication system 1 will be described using as an example a 5th Generation System (5GS) of the 3GPP standard, that is, a mobile communication system based on NR (New Radio).

[0014] The mobile communication system 1 includes a network 10 and user equipment (UE) 100 that communicates with the network 10. The network 10 includes a next generation radio access network (NG-RAN) 20 that is a 5G radio access network, and a 5G core network (5GC) 30 that is a 5G core network.

[0015] The UE 100 is an example of a communication device. The UE 100 may be a device used by a user. The UE 100 may be user equipment defined in the 3GPP technical specifications. The UE 100 may be a mobile device, such as a mobile phone terminal such as a smartphone, a tablet terminal, a laptop PC, a communication module, or a communication card. The UE 100 may be a vehicle (e.g., a car, a train, etc.) or a device provided therein. The UE 100 may be a transport vehicle other than a vehicle (e.g., a ship, an airplane, etc.) or a device provided therein. The UE 100 may be a sensor or a device provided therein. The UE 100 may be called by other names such as a mobile station, a mobile terminal, a mobile device, a mobile unit, a subscriber station, a subscriber terminal, a subscriber device, a subscriber unit, a wireless station, a wireless terminal, a wireless device, a wireless unit, a remote station, a remote terminal, a remote device, or a remote unit. The UE 100 is an example of a terminal, and the terminal may include factory equipment, etc.

[0016] The NG-RAN 20 includes multiple base stations 200. Each base station 200 manages at least one cell. A cell constitutes the smallest unit of a communication area. For example, one cell belongs to one frequency (carrier frequency) and is composed of one component carrier. The term "cell" may refer to wireless communication resources or to a communication target of the UE 100. Each base station 200 can perform wireless communication with the UE 100 located in its own cell. The base station 200 communicates with the UE 100 using a RAN protocol stack. The base station 200 is connected to other base stations 200 (which may be referred to as neighbor base stations) via an Xn interface. The base station 200 communicates with the neighbor base stations via the Xn interface. The base station 200 also provides NR user plane and control plane protocol termination for the UE 100 and is connected to the 5GC 30 via an NG interface. Such an NR base station 200 may be referred to as a gNodeB (gNB).

[0017] The 5GC 30 includes a core network device 300. The core network device 300 includes, for example, an Access and Mobility Management Function (AMF) and / or a User Plane Function (UPF). The AMF performs mobility management for the UE 100. The UPF provides functions specialized for user plane processing. The AMF and the UPF are connected to the base station 200 via an NG interface.

[0018] An example of the configuration of a protocol stack in the mobile communication system 1 according to the embodiment will be described with reference to FIG.

[0019] The protocol for the wireless section between UE 100 and base station 200 includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a radio resource control (RRC) layer.

[0020] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the base station 200 via a physical channel.

[0021] A physical channel consists of multiple OFDM symbols in the time domain and multiple subcarriers in the frequency domain. One subframe consists of multiple OFDM symbols in the time domain. A resource block is a resource allocation unit and consists of multiple OFDM symbols and multiple subcarriers. A frame can be configured to be 10 ms long and can include 10 subframes, each 1 ms long. A subframe can contain a number of slots depending on the subcarrier spacing.

[0022] Among physical channels, the physical downlink control channel (PDCCH) plays a central role for purposes such as downlink scheduling assignment, uplink scheduling grant, and transmit power control. For example, the UE 100 performs blind decoding of the PDCCH using a Cell-Radio Network Temporary Identifier (C-RNTI) and a Modulation and Coding Scheme-C-RNTI (MCS-C-RNTI) or a Configured Scheduling-RNTI (CS-RNTI) assigned to the UE 100 by the base station 200, and acquires successfully decoded DCI as DCI addressed to the UE. Here, CRC parity bits scrambled by the C-RNTI and the MCS-C-RNTI or the CS-RNTI are added to the DCI transmitted from the base station 200.

[0023] In NR, the UE 100 can use a bandwidth narrower than the system bandwidth (i.e., the cell bandwidth). The base station 200 configures the UE 100 with a bandwidth portion (BWP) consisting of consecutive PRBs. The UE 100 transmits and receives data and control signals in the active BWP. For example, up to four BWPs can be configured for the UE 100. Each BWP may have a different subcarrier spacing or may overlap in frequency. When multiple BWPs are configured for the UE 100, the base station 200 can specify which BWP to activate by controlling the downlink. This allows the base station 200 to dynamically adjust the UE bandwidth according to the amount of data traffic of the UE 100, etc., and can reduce UE power consumption.

[0024] For example, base station 200 can configure up to three control resource sets (CORESETs) for each of up to four BWPs on the serving cell. A CORESET is a radio resource for control information to be received by UE 100. Up to 12 CORESETs can be configured for UE 100 on the serving cell. Each CORESET has an index of 0 to 11. For example, a CORESET consists of six resource blocks (PRBs) and one, two, or three consecutive OFDM symbols in the time domain.

[0025] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of base station 200 via a transport channel. The MAC layer of base station 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to UE 100.

[0026] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the base station 200 via logical channels.

[0027] The PDCP layer performs header compression / decompression and encryption / decryption.

[0028] An SDAP (Service Data Adaptation Protocol) layer may be provided above the PDCP layer, which maps IP flows, which are units for Quality of Service (QoS) control by the core network, to radio bearers, which are units for QoS control by the AS (Access Stratum).

[0029] The RRC layer controls logical channels, transport channels, and physical channels in response to the establishment, re-establishment, and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the UE 100 and the RRC layer of the base station 200. layer and the RRC of the base station 200 layer When there is an RRC connection between the UE 100 and the RRC layer and the RRC of the base station 200 layer When there is no RRC connection between the UE 100 and the RRC layer and the RRC of the base station 200 layer The UE 100 is in an RRC inactive state when the RRC connection between the UE 100 and the

[0030] The NAS layer located above the RRC layer performs session management and mobility management for the UE 100. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the core network device 300 (AMF). Note that the UE 100 has an application layer and the like in addition to a radio interface protocol.

[0031] (DC Overview) An overview of dual connectivity (DC) according to the embodiment will be described with reference to FIG.

[0032] In DC, the UE 100 simultaneously communicates with a master cell group (MCG) 201M managed by a master node (MN) 200M and a secondary cell group (SCG) 201S managed by a secondary node (SN) 200S. The MN 200M may be an NR base station (gNB) or an LTE base station (eNB). The MN 200M is also referred to as a master base station. The master node may be referred to as an M-NG-RAN node. The SN 200S may be an NR base station (gNB) or an LTE base station (eNB). The SN 200S is also referred to as a secondary base station. The secondary node may be referred to as an S-NG-RAN node.

[0033] For example, the MN 200M transmits a predetermined message (for example, an SN Addition Request message) to the SN 200S, and the MN 200M transmits an RRC Reconfiguration message to the UE 100, thereby starting the DC.

[0034] The UE 100 in the RRC connected state is assigned radio resources by the respective schedulers of the MN 200M and the SN 200S, which are connected to each other via a backhaul network communication unit, and performs radio communication using the radio resources of the MN 200M and the radio resources of the SN 200S. The network communication unit between the MN 200M and the SN 200 may be an Xn interface or an X2 interface. The MN 200M and the SN 200 communicate with each other via this network communication unit.

[0035] The MN 200M may have a control plane connection with the core network. The MN 200M provides primary radio resources for the UE 100. The MN 200M manages the MCG 201M. The MCG 201M is a group of serving cells associated with the MN 200M. The MCG 201M has a primary cell (PCell) and optionally has one or more secondary cells (SCells).

[0036] The SN 200S may not have a control plane connection with the core network. The SN 200S provides additional radio resources to the UE 100. The SN 200S manages the SCG 201S. The SCG is associated with the SN 200S. The SCG 201S has a primary and secondary cell (PS cell) and optionally one or more SCells. The PCell of the MCG 201M and the PS cell of the SCG 201S are also called special cells (SpCells).

[0037] The 3GPP technical specifications prescribe primary / secondary cell (PS cell) change. One procedure for changing the PS cell is the conditional PS cell change (CPC) procedure. Based on the configuration of multiple candidate secondary nodes (hereinafter referred to as CPC configuration), UE 100 can change the candidate secondary node to one that controls a cell for which an execution condition is satisfied, among multiple candidate secondary nodes. This allows UE 100 to switch the secondary node from a source secondary node to a target secondary node without an instruction from the master node.

[0038] Here, in the current 3GPP technical specifications, when UE100 changes the secondary node (source secondary node) to another secondary node (target secondary node) based on the CPC setting, the master node sends a release request message (specifically, an SN Release Request message) requesting the release of resources associated with UE100 to related nodes other than the target secondary node (e.g., the source secondary node and a potential secondary node that could become the target secondary node based on the CPC setting).

[0039] In recent years, selective activation of cell groups has been discussed so that cells can be changed continuously when, for example, UE 100 moves at high speed. With selective SCG activation, even after the secondary node has been changed to another secondary node as a result of a successful CPC procedure, the secondary node can be further changed based on the settings (e.g., CPC settings) held by UE 100 without instructions from the master node.

[0040] In the current 3GPP technical specifications, in selective activation, when UE100 changes the secondary node to the target secondary node based on the CPC setting, it is assumed that the master node sends a release request message to associated nodes other than the target secondary node.

[0041] Here, when the related node receives the release request message, it releases the resources associated with the UE 100. However, when the UE 100 subsequently accesses the node, the access may not be accepted due to the release of the resources based on the release request message, and selective activation may not be performed appropriately. Therefore, an operation for enabling selective activation to be performed appropriately will be described.

[0042] (Configuration of user device) The configuration of the UE 100 according to the embodiment will be described with reference to Fig. 4. The UE 100 includes a communication unit 110 and a control unit 120.

[0043] The communication unit 110 performs wireless communication with the base station 200 by transmitting and receiving radio signals to and from the base station 200. The communication unit 110 has at least one transmission unit 111 and at least one reception unit 112. The transmission unit 111 and the reception unit 112 may be configured to include multiple antennas and RF circuits. The antenna converts a signal into radio waves and radiates the radio waves into space. The antenna also receives radio waves in space and converts the radio waves into a signal. The RF circuit performs analog processing of the signal transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, etc.

[0044] The control unit 120 performs various controls in the UE 100. The control unit 120 controls communication with the base station 200 via the communication unit 110. The operations of the UE 100 described above and below may be controlled by the control unit 120. The control unit 120 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute the program to perform the operations of the control unit 120. The control unit 120 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a RAN protocol stack. The memory stores programs executed by the processor, parameters related to the programs, and data related to the programs. The memory may include at least one of a read-only memory (ROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a random access memory (RAM), and a flash memory. All or a part of the memory may be included in the processor.

[0045] In the UE 100 configured as described above, the receiver 112 receives a radio resource control (RRC) message including a conditional PS cell change (CPC) configuration, which is a configuration for changing a primary-secondary cell (PS cell) that is a primary cell of a secondary cell group when an execution condition is satisfied, and determination information for the UE 100 to determine whether to release the CPC configuration. The controller 120 determines whether to release the CPC configuration based on the determination information. This enables the UE 100 to appropriately discard the CPC configuration based on the determination information.

[0046] (Base station configuration) The configuration of the base station 200 according to the embodiment will be described with reference to Fig. 5. The base station 200 includes a radio communication unit 210, a network communication unit 220, and a control unit 230.

[0047] The wireless communication unit 210 receives a wireless signal from the UE 100 and transmits the wireless signal to the UE 100, for example. The wireless communication unit 210 has at least one transmitting unit 211 and at least one receiving unit 212. The transmitting unit 211 and the receiving unit 212 may be configured to include an RF circuit. The RF circuit performs analog processing of a signal transmitted and received via an antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, etc.

[0048] The network communication unit 220 transmits and receives signals to the network. For example, the network communication unit 220 receives signals from adjacent base stations connected via an Xn interface, which is an interface between base stations, and transmits the signals to the adjacent base stations. The network communication unit 220 also receives signals from the core network device 300 connected via an NG interface, and transmits the signals to the core network device 300. The network communication unit 220 may include a transmitter 221 that transmits information such as messages to other nodes, and a receiver 222 that receives information such as messages from other nodes.

[0049] The control unit 230 performs various controls in the base station 200. The control unit 230 controls, for example, communication with the UE 100 via the radio communication unit 210. The control unit 230 also controls, for example, communication with a node (e.g., a neighboring base station, the core network device 300) via the network communication unit 220. The operations of the base station 200 described above and below may be operations controlled by the control unit 230. The control unit 230 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute the program to perform the operations of the control unit 230. The control unit 230 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a protocol stack of the RAN. The memory stores the program executed by the processor, parameters related to the program, and data related to the program. All or a part of the memory may be included in the processor.

[0050] When base station 200 configured as described above operates as a master node in network 10 including UE 100 communicating with the master node and secondary nodes, when UE 100, which has settings for multiple candidate secondary nodes in selective activation, changes the secondary node from a source secondary node to a target secondary node, transmitter 221 transmits a release request message requesting the release of resources to a released secondary node, among the source secondary node and the multiple candidate secondary nodes, that does not hold resources associated with UE 100. When UE 100 changes the secondary node, controller 230 performs non-release control, using the release request message, to a non-released secondary node, among the source secondary node and the multiple candidate secondary nodes, that holds resources. As a result, when UE 100 accesses a non-released secondary node, the non-released secondary node has not released resources based on the release request message, making it possible to properly execute selective activation.

[0051] Furthermore, when base station 200 is a base station 200 capable of operating as a secondary node in a network including communication devices that communicate with a master node and a secondary node, receiver 222 receives a release request message from the master node requesting the release of resources associated with UE 100 when UE 100, which has configurations related to multiple candidate secondary nodes in selective activation, changes its secondary node from a source secondary node to a target secondary node. Controller 230 halts the release of resources based on the release request message if the base station is a candidate secondary node after UE 100, which has configurations, changes its secondary node. This allows selective activation to be properly performed when UE 100 accesses base station 200 through selective activation, because the base station 200 has not released resources based on the release request message.

[0052] (Example of operation of a mobile communication system) An example of the operation of the mobile communication system will be described below. Note that the description of the same content as that already explained may be omitted.

[0053] (Example 1) An example of operation of the mobile communication system 1 according to the embodiment will be described with reference to Fig. 6 and Fig. 7. As shown in Fig. 6, it is assumed that DC is set by the UE 100, the MN 200M, and the source SN 200S1. At the initial stage of Fig. 6, the UE 100 communicates with the MCG of the MN 200M and the SCG of the SN 200S1. In the following, communication between the UE 100 and the MCG (P cell) will be described as communication between the UE 100 and the MN 200M, as appropriate. Similarly, communication between the UE 100 and each SCG (PS cell) will be described as communication between the UE 100 and each SN 200S, as appropriate.

[0054] 6, in step S101, the transmitter 221 of the MN 200M transmits an SN addition request message to each candidate target SN. In this operation example, the candidate target SNs are SN 200S2 and SN 200S3. The receivers 222 of the SN 200S2 and SN 200S3 receive the SN addition request message.

[0055] The control unit 230 of the MN 200M may determine one or more candidate secondary nodes for selective activation based on the measurement results from the UE 100. In this operation example, the control unit 230 of the MN 200M determines SN 200S1, SN 200S2, and SN 200S3 as the candidate secondary nodes. When the control unit 230 of the MN 200M has determined the candidate secondary nodes for selective activation, the control unit 230 may control so that the operation of step S101 is executed.

[0056] Note that the control unit 230 may determine a candidate secondary node that is not subject to selective activation. For example, the control unit 230 may determine a normal candidate secondary node (e.g., a candidate secondary node that is subject to CPA (Conditional PSCell Addition) and / or CPC (Conditional PSCell Change)).

[0057] Furthermore, the control unit 230 of the MN 200M may determine whether to perform selective activation. If selective activation is to be performed, the control unit 230 may determine that all candidate secondary nodes are targets of selective activation. If selective activation is not to be performed, the control unit 230 may determine that all candidate secondary nodes are not targets of selective activation.

[0058] The control unit 230 of each of SN 200S2 and SN 200S3 may determine, for example, whether or not to operate as a candidate secondary node in selective activation. In this operation example, each control unit 230 determines to operate as a candidate secondary node and executes the process of step S102.

[0059] Furthermore, the control unit 230 of each of the SN 200S2 and the SN 200S3 holds resources of the UE 100. The resources may include context information of the UE 100. The resources may be settings for the UE 100 in each candidate secondary node (for example, RRC settings, settings used to provide radio resources, etc.).

[0060] The control unit 230 of the MN 200M may include information indicating that the MN 200M is a target of selective activation in the SN addition request message.

[0061] In step S102, the transmitting unit 221 of each candidate target SN transmits an SN addition request acceptance message to the MN 200M. The receiving unit 222 of the MN 200M receives the SN addition request acceptance message from each candidate target SN.

[0062] The control unit 230 of each candidate target SN may include an RRC reconfiguration message including the new SCG radio resource configuration in the SN addition request accept message.

[0063] In step S103, the transmitting unit 211 of the MN 200M transmits an RRC reconfiguration message to the UE 100. The receiving unit 112 of the UE 100 receives the RRC reconfiguration message from the MN 200M.

[0064] The RRC reconfiguration message may include configuration information for multiple candidate secondary nodes in selective activation. The configuration information may be configuration information used to configure multiple conditional reconfigurations for the UE 100. The multiple conditional reconfigurations are for configuring multiple candidate target PS cells. Here, when there are multiple candidate secondary nodes that control the candidate target PS cells, the configuration information indicates configurations for the multiple candidate secondary nodes.

[0065] The configuration information may be CPC configuration information. The configuration information includes one or more conditional reconfiguration information. Each conditional reconfiguration information includes an RRC reconfiguration message to be applied when an execution condition is met. The configuration information may be a list of RRC reconfiguration messages associated with the execution conditions. The RRC reconfiguration message included in the conditional reconfiguration information includes configuration information for configuring a candidate target PS cell.

[0066] The configuration information may include information that sets execution conditions that must be met to trigger execution of the conditional reconfiguration (eg, "condExecutionCond," "condExecutionCondSCG," etc.).

[0067] Furthermore, the configuration information may include, for example, information (e.g., an indicator) indicating whether or not to discard the configuration related to selective activation. The indicator may indicate that the configuration is to be discarded or that the configuration is to be maintained. The information (indicator) may be an instruction common to all SCGs. Alternatively, the control unit 230 may associate the indicator with a candidate target PS cell (or a candidate secondary node). Note that the configuration may be, for example, a CPA configuration and / or a CPC configuration.

[0068] The control unit 120 of the UE 100 applies the RRC reconfiguration complete message and stores the configuration information.

[0069] In step S104, the transmitting unit 111 of the UE 100 transmits an RRC reconfiguration completion message to the MN 200M. The receiving unit 212 of the MN 200M receives the RRC reconfiguration completion message from the UE 100.

[0070] Thereafter, the control unit 120 of the UE 100 measures radio signals from each cell. The control unit 120 of the UE 100 evaluates an execution condition based on, for example, the measurement result. Specifically, the control unit 120 determines whether an execution condition (event) of a candidate target PS cell is satisfied based on the measurement result. If the execution condition is satisfied, the control unit 120 of the UE 100 regards the target candidate cell associated with the satisfied execution condition as a triggered cell. If there are multiple triggered cells, the control unit 120 selects one cell from the multiple triggered cells for executing conditional reconfiguration. If there is only one triggered cell, the control unit 120 regards the cell as a cell selected for executing conditional reconfiguration. The control unit 120 starts executing conditional reconfiguration for the selected cell and performs the following operations. In this operation example, the control unit 120 selects a cell controlled by the SN 200S2 and starts executing conditional reconfiguration. Since the SN 200S2 is a node different from the source secondary node, it triggers a change of the secondary node.

[0071] Control unit 120 of UE 100 applies the conditional reconfiguration information of the selected cell. As a result, control unit 120 of UE 100 applies the RRC reconfiguration included in the conditional reconfiguration information of the selected cell.

[0072] In step S105, the transmitting unit 111 of the UE 100 transmits an RRC reconfiguration completion message to the MN 200M. The receiving unit 212 of the MN 200M receives the RRC reconfiguration completion message from the UE 100. Note that the RRC reconfiguration completion message here is an RRC reconfiguration completion message based on a trigger for changing the secondary node. On the other hand, the RRC reconfiguration completion message in step S104 is not an RRC reconfiguration completion message based on a trigger for changing the secondary node.

[0073] The control unit 120 of the UE 100 may include, in the RRC reconfiguration completion message, predetermined information instructing execution (or non-execution) of non-release control, which will be described later. As a result, the transmission unit 111 transmits the predetermined information to the network 10.

[0074] The control unit 120 may include predetermined information in a message terminated at the MN 200M. The control unit 120 may include predetermined information in a field other than the field of the message that is included in the RRC reconfiguration completion message and is sent to the target SN through the MN 200M. of This allows the transmitting unit 111 to transmit the predetermined information to the MN 200M by a message terminated at the MN 200M.

[0075] The control unit 120 may determine whether to perform selective activation based on information indicating whether to discard settings related to selective activation. The control unit 120 may decide to release settings based on whether or not it has received information (e.g., an indicator) indicating whether or not it has discarded settings. For example, the control unit 120 may decide to release settings when it has received at least one of a message including an indicator to discard settings or a message not including an indicator to retain settings from the MN 200M. For example, the control unit 120 may decide not to release settings when it has received at least one of a message including an indicator to retain settings or a message not including an indicator to discard settings from the MN 200M. The indicator may be a common setting for all SCGs.

[0076] The message may be an RRC reconfiguration message. The message may be, for example, any of (a) an RRC reconfiguration message initially transmitted from a master node, (b) an RRC reconfiguration message including configuration information for base station 200 operating as a master node (or target master node) to initially configure settings related to selective activation in UE 100, or (c) an RRC reconfiguration message including settings for initiating DC. The message may be referred to as an initial RRC reconfiguration message.

[0077] Furthermore, an indicator may be associated with a candidate target PS cell (or a candidate secondary node). In this case, the control unit 120 may decide to release the configuration of the candidate secondary node (and / or source secondary node) associated with an indicator that discards the configuration (or does not retain the configuration). Furthermore, the control unit 120 may decide not to release the configuration of the candidate secondary node (and / or source secondary node) associated with an indicator that does not discard the configuration (or retain the configuration).

[0078] When the control unit 120 determines to release all settings or the target settings based on the information indicating whether to discard the settings, the control unit 120 releases (discards) the settings. When the control unit 120 determines to hold all settings or the target settings based on the information indicating whether to discard the settings, the control unit 120 holds the settings without releasing them.

[0079] In step S106, the transmitting unit 221 of the MN 200M transmits an SN reconfiguration completion message to the SN 200S2. The receiving unit 222 of the SN 200S2 receives the SN reconfiguration completion message from the MN 200M. As a result, the MN 200M notifies the SN 200S2 of the PS cell selected by the UE 100.

[0080] The transmitting unit 221 of the MN 200M may perform this operation after, for example, any of steps S110 to S114 described later.

[0081] 7, in step S110, the control unit 230 of the MN 200M determines non-release control using a release request message to not release resources for the source secondary node and a non-release secondary node among the multiple candidate secondary nodes that holds the resources associated with the UE 100. The control unit 230 may, for example, perform the non-release control determination for the source secondary node and each candidate secondary node. The control unit 230 may perform the non-release control determination based on reception of the RRC reconfiguration completion message in step S105.

[0082] The control unit 230 may determine whether or not UE100 changes the secondary node from the source secondary node to the target secondary node. For example, when changing the PS cell from a cell controlled by SN200S1 to a cell controlled by a candidate secondary node, the control unit 230 may determine to change the secondary node. When UE100 changes the secondary node, the control unit 230 may determine whether or not to perform non-release control for each associated node. The associated node may be a node associated with the DC other than the target secondary node.

[0083] The control unit 230 may, for example, determine whether the source secondary node (SN200S1 in this operation example), which is an associated node, is a candidate secondary node in selective activation. If, for example, SN200S3 is a candidate secondary node in selective activation, the control unit 230 may determine to perform non-release control.

[0084] The control unit 230 may determine whether to perform non-release control based on the RRC reconfiguration complete message. For example, if the RRC reconfiguration complete message includes predetermined information, the control unit 230 may determine to perform non-release control based on the predetermined information. For example, if the RRC reconfiguration complete message includes predetermined information instructing the execution of non-release control, the control unit 230 may determine to perform non-release control. Alternatively, the control unit 230 may determine to perform non-release control if the RRC reconfiguration complete message does not include predetermined information instructing not to execute non-release control. Furthermore, for example, if the RRC reconfiguration complete message does not include predetermined information instructing the execution of non-release control, the control unit 230 may determine not to perform non-release control. Alternatively, the control unit 230 may determine not to perform non-release control if the RRC reconfiguration complete message includes predetermined information instructing not to execute non-release control.

[0085] For example, the control unit 230 may determine to perform non-release control when it receives information from the SN 200S1 indicating that the source secondary node (specifically, the SN 200S1) is a candidate secondary node in selective activation. The control unit 230 may determine not to perform non-release control when it receives information from the SN 200S1 indicating that the SN 200S1 is not a candidate secondary node in selective activation. This information may be included in, for example, an SN Change Required message.

[0086] Furthermore, the control unit 230 may, for example, determine whether or not a candidate secondary node (SN200S3 in this operation example) is a candidate secondary node in selective activation. For example, if SN200S3 is a candidate secondary node in selective activation, the control unit 230 may perform the operation of step S113. The control unit 230 may determine that a candidate secondary node that has transmitted an SN addition request message including information indicating that it is a target of selective activation is a candidate secondary node in selective activation. Note that the SN addition request message may be a message requesting the preparation of resources for DC operation for a specific UE.

[0087] Furthermore, the control unit 230 may determine whether to perform non-release control based on whether information (for example, an indicator) indicating whether to discard the configuration has been transmitted to the UE 100. The control unit 230 may determine to perform non-release control when the configuration is to be released in the UE 100, as will be described below. On the other hand, the control unit 230 may determine not to perform non-release control when the configuration is to be retained in the UE 100.

[0088] For example, the control unit 230 may decide to release the configuration when at least one of a message including an indicator to discard the configuration and a message not including an indicator to retain the configuration has been transmitted to the UE 100. For example, the control unit 230 may decide not to release the configuration when at least one of a message including an indicator to retain the configuration and a message not including an indicator to discard the configuration has been transmitted to the UE 100.

[0089] The indicator may be a common setting for all SCGs. In this case, if the control unit 230 determines to release the setting based on whether or not the indicator has been transmitted, the control unit 230 may execute the processes of steps S111 and S113. On the other hand, if the control unit 230 determines not to release the setting based on whether or not the indicator has been transmitted, the control unit 230 may skip (omit) the processes of steps S111 and S113.

[0090] Furthermore, when an indicator is associated with a candidate target PS cell (SCG) or a candidate secondary node, the control unit 230 may determine whether or not to perform non-release control for each candidate secondary node. The control unit 230 may decide to release the configuration of a candidate secondary node (and / or source secondary node) associated with an indicator that discards the configuration (or does not retain the configuration). The control unit 230 may also decide not to release the configuration of a candidate secondary node (and / or source secondary node) associated with an indicator that does not discard the configuration (or retain the configuration).

[0091] The control unit 230 may execute the process of step S111 for a source secondary node for which it has determined that the configuration should be released. On the other hand, the control unit 230 may skip the process of step S111 for a source secondary node for which it has determined that the configuration should not be released. Similarly, the control unit 230 may execute the process of step S113 for a candidate secondary node for which it has determined that the configuration should be released. On the other hand, the control unit 230 may skip the process of step S113 for a candidate secondary node for which it has determined that the configuration should not be released.

[0092] In step S111, the control unit 230 performs non-release control on a candidate secondary node (appropriately referred to as a non-release secondary node) that is the target of the non-release control. As the non-release control, the control unit 230 determines not to transmit a release request message to the non-release secondary node. For example, when not transmitting a release request message, the control unit 230 may skip (omit) the generation or transmission of the release message, or may cancel the generation or transmission of the release message. For example, when the SN200S1 that is the source secondary node is a non-release secondary node, the control unit 230 cancels the transmission of the release request message to the SN200S1. In this case, the control unit 230 of the SN200S1 does not release the resources of the UE100 because it has not received the release request message.

[0093] The release request message may be an SN Release Request message requesting the release of resources.

[0094] On the other hand, if SN200S1 is not a non-release secondary node (i.e., a release secondary node), the control unit 230 controls the transmission of a release request message to SN200S1. As a result, the transmission unit 221 transmits the release request message to SN200S1. The reception unit 222 of SN200S1 receives the release request message.

[0095] In step S112, if the release request message is accepted, the transmitter 221 of the SN 200S1 transmits a release request accept message to the MN 200M. The receiver 222 of the MN 200M receives the release request accept message from the SN 200S1. The SN 200S1 releases the resources of the UE 100 based on the release request message. Note that the release request accept message may be an SN release request accept message for confirming a request to change the resources of the SN 200S for a specific UE (UE 100).

[0096] In step S113, similarly to step S111, the control unit 230 performs non-release control on the non-released secondary node. If the SN200S3 is a non-released secondary node, the control unit 230 stops sending a release request message to the SN200S3, which is a candidate secondary node. In this case, the control unit 230 of the SN200S3 does not release the resources of the UE100 because it has not received the release request message.

[0097] On the other hand, if SN200S3 is not a non-release secondary node (it is a release secondary node), the control unit 230 controls the transmission of a release request message to SN200S1. As a result, the transmission unit 221 transmits the release request message to SN200S1. The reception unit 222 of SN200S1 receives the release request message.

[0098] In step S114, similarly to step S112, if the release request message is accepted, the transmitting unit 221 of the SN 200S3 transmits a release request accept message to the MN 200M. The receiving unit 222 of the MN 200M receives the release request accept message from the SN 200S3. The SN 200S3 releases the resources of the UE 100 based on the release request message.

[0099] In step S115, the UE 100 and the SN 200S2 execute a random access procedure. After that, the UE 100 communicates with the MN 200M (MCG) and the SN 200S2 (SCG) in the DC.

[0100] As described above, in this operation example, when UE 100, which has settings for multiple candidate secondary nodes in selective activation, changes the secondary node from a source secondary node to a target secondary node, the transmitter 221 of the MN 200M transmits a release request message requesting the release of resources to a release secondary node, among the source secondary node and the multiple candidate secondary nodes, that does not hold resources associated with UE 100. When UE 100 changes the secondary node, the controller 230 of the MN 200M performs non-release control, using the release request message, not to release resources to a non-release secondary node, among the source secondary node and the multiple candidate secondary nodes, that holds resources. As a result, when UE 100 accesses a non-released secondary node, the non-released secondary node has not released resources, making it possible to properly execute selective activation.

[0101] Furthermore, the control unit 230 of the MN 200M may determine not to transmit a release request message to the non-release secondary node as non-release control. The control unit 230 may, for example, perform control to stop transmission of the release request message. As a result, the non-release secondary node does not receive the release request message, and therefore, release of resources based on the release request message is not performed, and selective activation can be executed appropriately.

[0102] Furthermore, the control unit 230 of the MN 200M may determine whether to perform non-release control when receiving an RRC reconfiguration complete message based on a trigger for changing the secondary node from the UE 100. As a result, the control unit 230 determines whether to perform non-release control when receiving an RRC reconfiguration complete message from the UE 100, whereas the existing 3GPP technical specifications require the control unit 230 to transmit a release request message. When non-release control is performed, resources are not released based on the release request message, and selective activation can be appropriately executed.

[0103] Furthermore, the RRC reconfiguration completion message may include predetermined information instructing execution of non-release control. The control unit 230 of the MN 200M may determine whether to perform non-release control based on the predetermined information. This allows the control unit 230 to determine whether to perform non-release control after taking into consideration the instruction from the UE 100.

[0104] In addition, the control unit 230 may control the SCG (the source secondary node and / or candidate secondary node that manages it) corresponding to the UE 100 that has been instructed to be retained (or not instructed to be discarded (released)) based on information contained in the RRC reconfiguration message (for example, the above-mentioned indicator) so as not to send a release request message.

[0105] (Example 2) An operation example 2 of the mobile communication system 1 according to the embodiment will be described with reference to Fig. 8. Descriptions of parts similar to the above operation examples will be omitted. In this operation example, the MN 200M performs non-release control to transmit a predetermined message to the non-release secondary node to hold at least the context information of the UE 100 as a resource. Note that in this operation example, the predetermined information is a change request message requesting preparation for a resource change.

[0106] Step S210 is similar to step S110.

[0107] In step S211, the control unit 230 performs non-release control by controlling the transmission of a predetermined message to the non-released secondary node. In this operation example, when the SN200S1, which is the source secondary node, is a non-released secondary node, the control unit 230 controls the transmission of a change request message, which requests preparation for a resource change, as the predetermined message. As a result, the transmitting unit 221 transmits the change request message to the SN200S1. The receiving unit 222 of the SN200S1 receives the change request message.

[0108] The modification request message may be, for example, an SN Modification Request message. The SN modification request message may be a message requesting preparation to modify resources of a secondary node for a specific UE. The SN modification request message may be a message inquiring about the current SCG configuration. The SN modification request message may be a message for providing related information (e.g., S-RLF-related information) to the secondary node.

[0109] On the other hand, if SN200S1 is not a non-release secondary node (i.e., a release secondary node), the control unit 230 controls to transmit a release request message that is not a predetermined message to SN200S1. As a result, the transmitting unit 221 transmits the release request message to SN200S1. The receiving unit 222 of SN200S1 receives the release request message.

[0110] When the control unit 230 of the SN 200S1 receives the change request message, the control unit 230 may determine not to release the resources of the UE 100. On the other hand, when the control unit 230 receives the release request message, the control unit 230 may determine to release the resources of the UE 100.

[0111] In step S212, if the transmission unit 221 of the SN 200S1 accepts the change request message, it transmits a change request accept message to the MN 200M. The reception unit 222 of the MN 200M receives the change request accept message from the SN 200S1. On the other hand, if the transmission unit 221 of the SN 200S1 accepts the release request message, it transmits a release request accept message to the MN 200M. The reception unit 222 of the MN 200M receives the release request accept message from the SN 200S1.

[0112] In step S213, similarly to step S211, if SN200S3, which is a candidate secondary node, is a non-released secondary node, the control unit 230 controls the transmission of a change request message as a predetermined message. As a result, the transmission unit 221 transmits the change request message to SN200S3. The reception unit 222 of SN200S3 receives the change request message.

[0113] On the other hand, if the SN 200S3 is not a non-release secondary node, the control unit 230 performs control to transmit a release request message that is not a predetermined message to the SN 200S3. As a result, the transmission unit 221 transmits the release request message to the SN 200S3. The reception unit 222 of the SN 200S3 receives the release request message.

[0114] When the control unit 230 of the SN200S3 receives a change request message, it may determine not to release the resources of the UE100. When the control unit 230 does not release the resources of the UE100, it retains at least the context information of the UE100. The control unit 230 may retain the settings for the UE100 in its own station (for example, RRC settings, settings used for providing radio resources, etc.) as resources. On the other hand, when the control unit 230 receives a release request message, it may determine to release the resources of the UE100.

[0115] In step S214, if the transmission unit 221 of the SN 200S3 accepts the change request message, it transmits a change request accept message to the MN 200M. The reception unit 222 of the MN 200M receives the change request accept message from the SN 200S3. On the other hand, if the transmission unit 221 of the SN 200S3 accepts the release request message, it transmits a release request accept message to the MN 200M. The reception unit 222 of the MN 200M receives the release request accept message from the SN 200S3.

[0116] Step S215 is similar to step S115.

[0117] As described above, in this operation example, the control unit 230 of the MN 200M performs non-release control by controlling the non-released secondary node to transmit a predetermined message for causing the non-released secondary node to hold at least the context information of the UE 100 as a resource. This allows the non-released secondary node to hold at least the context information of the UE 100 as a resource. As a result, selective activation can be performed more appropriately compared to the case where resources are released.

[0118] Furthermore, the control unit 230 of the MN 200M controls to transmit the change request message as a predetermined message. As a result, when the change request message is an existing message, it is possible to reduce the influence on the mobile communication system compared to when a predetermined message is newly defined.

[0119] Furthermore, similar to operation example 1, the control unit 230 may control the transmission of a predetermined message to the SCG (the source secondary node and / or candidate secondary node that manages it) corresponding to the UE 100 that has been instructed to be retained (or not instructed to be discarded (released)) based on information contained in the RRC reconfiguration message (for example, the above-mentioned indicator).

[0120] (Example 3) An operation example 3 of the mobile communication system 1 according to the embodiment will be described with reference to Fig. 9. Descriptions of parts that are the same as those in the above operation examples will be omitted. In this operation example, as non-release control, the MN 200M controls to transmit, as a predetermined message, a release message including an indicator indicating whether or not context information is held in the non-released secondary node, to the non-released secondary node.

[0121] Step S310 is similar to step S110.

[0122] In step S311, if SN200S1, which is the source secondary node, is a non-released secondary node, the control unit 230 controls to transmit a release request message including an indicator indicating whether the context information is held in the non-released secondary node as a predetermined message. As a result, the transmission unit 221 transmits the release request message to SN200S1. The reception unit 222 of SN200S1 receives the release request message.

[0123] The indicator may be, for example, a UE Context Kept Indicator. The UE context kept indicator may indicate whether the UE context is kept in the secondary node. If the UE context kept indicator indicates keeping (e.g., is "True"), the UE-associated signaling connection between the master node and the secondary node is kept. li The UE context retention indicator may be information that causes the secondary node to initiate only the release of resources related to the UE context retention indicator (e.g., other than “True”). The UE context retention indicator may be information that causes the secondary node not to initiate the release of the resources if the UE context retention indicator does not indicate retention (e.g., is other than “True”).

[0124] The control unit 230 of the MN 200M may include, in the release request message, an indicator indicating that the UE context is held in the secondary node. The control unit 230 of the MN 200M may include, in the release request message, an indicator indicating something other than that the UE context is held in the secondary node (for example, other than "True").

[0125] Furthermore, when transmitting a release request message including an indicator as a predetermined message, the control unit 230 of the MN 200M may control to transmit information instructing the non-released secondary node to resume providing resources based on context information. The control unit 230 may include this information in the release request message including the indicator. The control unit 230 may include this information in a message different from the release request message including the indicator, and the transmission unit 221 may transmit this message to the SN 200S1 separately from the release request message.

[0126] On the other hand, if the SN 200S1 is not a non-release secondary node, the control unit 230 controls to transmit a release request message that does not include an indicator to the SN 200S1. As a result, the transmission unit 221 transmits the release request message to the SN 200S1. The reception unit 222 of the SN 200S1 receives the release request message.

[0127] When the control unit 230 of the SN 200S1 receives a release request message including an indicator, the control unit 230 may determine not to release the resources of the UE 100. On the other hand, when the control unit 230 receives a release request message not including an indicator, the control unit 230 may determine to release the resources of the UE 100.

[0128] Furthermore, the control unit 230 of the SN 200S1 may resume providing the resource when it receives information instructing it to resume providing the resource based on the context information.

[0129] In step S312, if the transmission unit 221 of the SN 200S1 accepts the release request message, it transmits a release request acceptance message to the MN 200M. The reception unit 222 of the MN 200M receives the release request acceptance message from the SN 200S1.

[0130] In step S313, similarly to step S211, if the SN200S3 that is a candidate secondary node is a non-released secondary node, the control unit 230 controls the sending unit 221 to send a release request message including an indicator as a predetermined message. release The SN 200S3 transmits the release request message to the SN 200S3. The receiving unit 222 of the SN 200S3 receives the release request message including the indicator.

[0131] On the other hand, if the SN 200S3 is not a non-released secondary node, the control unit 230 controls to transmit a release request message to the SN 200S3. As a result, the transmission unit 221 transmits the release request message to the SN 200S3. The reception unit 222 of the SN 200S3 receives the release request message.

[0132] When the control unit 230 of the SN 200S3 receives a release request message including an indicator, the control unit 230 may determine not to release the resources of the UE 100. On the other hand, when the control unit 230 receives a release request message not including an indicator, the control unit 230 may determine to release the resources of the UE 100.

[0133] Similarly to step S311, when transmitting a release request message including an indicator as a predetermined message, the control unit 230 of the MN200M may perform control to transmit information instructing the SN200S3 to resume providing resources based on the context information. When receiving information instructing the SN200S3 to resume providing resources based on the context information, the control unit 230 of the SN200S3 may resume providing resources.

[0134] In step S314, if the release request message is accepted, the transmitting unit 221 of the SN 200S3 transmits a release request acceptance message to the MN 200M. The receiving unit 222 of the MN 200M receives the release request acceptance message from the SN 200S3.

[0135] Step S315 is similar to step S115.

[0136] As described above, in this operation example, the control unit 230 of the MN 200M may perform control to transmit, as a predetermined message, a release request message including an indicator indicating whether context information is held in the non-released secondary node. This allows the non-released secondary node to hold at least the context information of the UE 100 as a resource. As a result, selective activation can be performed appropriately compared to the case where resources are released.

[0137] Furthermore, when transmitting a release request message including an indicator as a predetermined message, the control unit 230 of the MN 200M may perform control so as to transmit information instructing the non-released secondary node to resume providing resources based on context information. As a result, by the non-released secondary node resuming providing resources based on context information, selective activation can be performed more appropriately than in the case of releasing resources.

[0138] (Example 4) An operation example 4 of the mobile communication system 1 according to the embodiment will be described with reference to Fig. 10. Descriptions of parts similar to the above operation examples will be omitted. In this operation example, the MN 200M determines a predetermined message to be transmitted to a non-released secondary node from among a plurality of types of predetermined messages based on a change in context information of the UE 100.

[0139] In step S411, the control unit 230 of the MN 200M determines whether or not to perform non-release control for each associated node (specifically, the source secondary node, the candidate secondary node, etc.). The control unit 230 may make the determination in the same way as in step S110.

[0140] If the control unit 230 determines that non-release control is to be performed, the control unit 230 may execute the process of step S412. On the other hand, if the control unit 230 determines that non-release control is not to be performed, the control unit 230 may execute the process of step S415.

[0141] In step S412, the control unit 230 determines whether or not there is a change in the UE context information in the associated node. If there is a change in the UE context information, the control unit 230 executes the process of step S413. On the other hand, if there is no change in the UE context information, the control unit 230 executes the process of step S414.

[0142] In step S413, the control unit 230 determines to transmit an SN change request message as the predetermined message. In this case, the same operation as in the second operation example may be executed.

[0143] In step S414, the control unit 230 determines to transmit an SN release request message including the above-mentioned indicator (for example, a UE Context Kept Indicator) as the predetermined message. In this case, the same operation as in Operation Example 3 may be executed.

[0144] In step S415, the control unit 230 determines to transmit an SN release request message that does not include the above-mentioned indicator (for example, UE Context Kept Indicator) as the predetermined message. In this case, the same operation as in Operation Example 3 may be executed.

[0145] As described above, in this operation example, the control unit 230 may determine a predetermined message to be transmitted to a non-released secondary node from among a plurality of types of predetermined messages based on a change in the context information of the UE 100. This allows the control unit 230 to use different predetermined messages based on a change in the context information. This allows the MN 200M to flexibly control the SN 200SN.

[0146] Furthermore, the control unit 230 may perform control to transmit a change request message as a predetermined message when there is a change in the context information of the UE 100. In this way, the control unit 230 can explicitly notify the non-released secondary node that there is a change in the context information of the UE 100 by using the change request message.

[0147] Furthermore, the control unit 230 may perform control so that, when there is no change in the context information, a release request message including an indicator is transmitted as a predetermined message. This allows the control unit 230 to explicitly notify the non-released secondary node that there is no change in the context information of the UE 100 by using the release request message including the indicator.

[0148] (Example 5) 11, a fifth operation example of the mobile communication system 1 according to the embodiment will be described. Descriptions of parts that are the same as those in the above-described operation examples will be omitted. In this operation example, an operation will be described in which at least part of the information of the settings held by the UE 100 is released.

[0149] In step S501, the control unit 230 of the MN 200M determines to release the setting. The control unit 230 may determine to release at least part of the information of the setting by, for example, updating the setting. The control unit 230 may determine to update the setting when, for example, notifying the UE 100 of a new setting. Furthermore, the control unit 230 may determine to update the setting when a handover to another master node is executed. Furthermore, the control unit 230 may determine to update the setting when an SCG failure occurs. Note that the setting here is at least a setting related to selective activation. The setting may be, for example, a CPA setting or a CPC setting.

[0150] In addition, the control unit 230 may decide to release all of the settings held by the UE 100 (specifically, the settings related to multiple candidate secondary nodes in selective activation), or may decide to release some of the settings (for example, the settings related to some of the candidate secondary nodes among multiple candidate secondary nodes in selective activation).

[0151] The control unit 230 may execute the process of step S502 when releasing at least a part of the settings held by the UE 100. In this case, the control unit 230 may perform new settings (settings related to multiple candidate secondary nodes in selective activation) for the UE 100.

[0152] The control unit 230 may execute the process of step S504 and / or step S506 before step S502 and step S503.

[0153] In step S502, the transmitting unit 211 of the MN 200M transmits an RRC reconfiguration message to the UE 100 to release at least a part of the information of the configuration. The receiving unit 112 of the UE 100 receives the RRC reconfiguration message from the MN 200M.

[0154] The control unit 120 of the UE 100 releases the corresponding configuration based on the configuration information (updated configuration information) included in the RRC reconfiguration message. The control unit 120 may apply a new configuration based on the updated configuration information.

[0155] In step S503, the transmitting unit 111 of the UE 100 transmits an RRC reconfiguration completion message to the MN 200M. The receiving unit 212 of the MN 200M receives the RRC reconfiguration completion message from the UE 100.

[0156] In step S504, when at least a part of the information of the setting held by UE 100 is released, the control unit 230 controls to transmit a release request message to a corresponding secondary node, among the source secondary node and multiple candidate secondary nodes, that is associated with the information to be released. In this step, the control unit 230 controls to transmit the release request message to the source secondary node as the corresponding secondary node. As a result, the transmitting unit 221 of the MN 200M transmits the release request message to the SN 200S1. The receiving unit 222 of the SN 200S1 receives the release request message from the MN 200M.

[0157] The control unit 230 may execute the process of step S504 and / or S506 when an RRC reconfiguration complete message is received in response to the RRC reconfiguration message of step S502.

[0158] In step S505, if the release request message is accepted, the transmitting unit 221 of the SN 200S1 transmits a release request accept message to the MN 200M. The receiving unit 222 of the MN 200M receives the release request accept message from the SN 200S1. In response to receiving the release request message, the SN 200S1 releases the resources of the UE 100.

[0159] In step S506, similarly to step S504, the control unit 230 controls to transmit a release request message to the candidate secondary node as the corresponding secondary node. As a result, the transmitting unit 221 of the MN 200M transmits the release request message to the SN 200S3. The receiving unit 222 of the SN 200S3 receives the release request message from the MN 200M.

[0160] In step S507, if the release request message is accepted, the transmitting unit 221 of the SN 200S3 transmits a release request accept message to the MN 200M. The receiving unit 222 of the MN 200M receives the release request accept message from the SN 200S3. In response to receiving the release request message, the SN 200S3 releases the resources of the UE 100.

[0161] As described above, the control unit 230 of the MN 200M may perform control to transmit a release request message to a corresponding secondary node associated with the information to be released, among the source secondary node and multiple candidate secondary nodes, when at least a part of the information of the settings held by the UE 100 is released. This makes it possible to prevent the corresponding secondary node from continuing to hold the resources of the UE 100 when selective activation is executed and when at least a part of the information of the settings held by the UE 100 is released, and makes it possible to appropriately execute selective activation.

[0162] (Example 6) An operation example 6 of the mobile communication system 1 according to the embodiment will be described with reference to Fig. 12. Descriptions of parts similar to the above operation examples will be omitted. In this operation example, an operation will be described in which at least part of information of settings held by the UE 100 is released at a timing related to a PS cell change.

[0163] In step S601, similarly to step S103, the transmitting unit 211 of the MN 200M transmits an RRC reconfiguration message to the UE 100. The receiving unit 112 of the UE 100 receives the RRC reconfiguration message from the MN 200M.

[0164] Here, the control unit 230 of the MN 200M may generate an RRC reconfiguration message including release information regarding the release (ie, discard) of the configuration.

[0165] The release information may include, for example, information instructing to release the configuration when changing the PS cell regardless of whether an execution condition (event) based on the configuration is satisfied. The release information may also include information instructing to release the configuration when an execution condition (event) based on the configuration is satisfied. The release information may also include information instructing to release the configuration when an execution condition (event) is satisfied.

[0166] Furthermore, the release information may include, for example, count information indicating the number of times the UE 100 holds the configuration related to selective activation. The release information may include timer information indicating a period during which the UE 100 holds the configuration related to selective activation. The release information may include event information indicating a condition under which the UE 100 releases the configuration related to selective activation. The release information may be associated with a candidate target PS cell (or a candidate secondary node).

[0167] Step S602 is similar to step S104.

[0168] In step S603, the control unit 120 of the UE 100 determines to release at least a portion of the information of the configuration related to selective activation. The control unit 120 may determine whether to release at least a portion of the information of the configuration based on, for example, the release information.

[0169] For example, when the release information includes information instructing that the configuration be released when the PS cell is changed regardless of whether an execution condition (event) based on the configuration is satisfied, the control unit 120 may determine to release at least part of the information of the configuration at the timing of changing the PS cell.Furthermore, when the release information includes information instructing that the configuration for which the execution condition (event) is satisfied be released, the control unit 120 may determine to release the configuration at the timing of changing the PS cell to a cell for which the execution condition (event) is satisfied.

[0170] The control unit 120 may decide to release at least a portion of the information of the settings based on, for example, the number of times the UE 100 holds the settings related to selective activation. Ma Furthermore, the control unit 120 may determine to release at least part of the information of the setting based on whether or not a period for which the UE 100 retains the setting has expired. Furthermore, the control unit 120 may determine to release at least part of the information of the setting based on whether or not a condition for releasing the setting has been satisfied.

[0171] When the control unit 120 decides to release the configuration based on the release information, if the release information is associated with a candidate target PS cell (or a candidate secondary node), the control unit 120 may decide to release the configuration of the associated candidate target PS cell (or candidate secondary node).

[0172] When it is determined that at least a portion of the information in the configuration related to selective activation is to be released, the control unit 120 may perform control to transmit an RRC reconfiguration complete message. The RRC reconfiguration complete message may be an RRC reconfiguration complete message based on a trigger of a change in the secondary node. Note that the control unit 120 may transmit a message other than the RRC reconfiguration complete message. Note that when it is determined that at least a portion of the information in the configuration is to be released, the control unit 120 may release at least a portion of the information in the configuration before transmitting the RRC reconfiguration complete message.

[0173] In step S604, the transmitting unit 111 of the UE 100 transmits an RRC reconfiguration completion message to the MN 200M. The receiving unit 212 of the MN 200M receives the RRC reconfiguration completion message from the UE 100.

[0174] The RRC reconfiguration message may include information indicating that the UE 100 has decided to release at least part of the configuration information. The information may include information indicating a corresponding secondary node (or a cell of the corresponding secondary node).

[0175] In step S605, the MN 200M may determine whether to release the configuration based on the reception of the RRC reconfiguration message.

[0176] The control unit 230 of MN200M may, for example, perform control to send a release request message to the corresponding secondary node when it receives an RRC reconfiguration completion message from UE100 including information indicating that UE100 has decided to release at least some of the configuration information.

[0177] The control unit 230 of the MN 200M may identify a corresponding secondary node based on the information, and may execute the processing of the subsequent steps for the identified corresponding secondary node.

[0178] Furthermore, the control unit 230 of the MN 200M may determine, based on the release information transmitted to the UE 100, whether to execute the processing of the subsequent steps.

[0179] For example, if the control unit 230 has transmitted information instructing that the configuration be released when the PS cell is changed, regardless of whether the execution condition (event) based on the configuration is satisfied, the control unit 230 may execute the processing of the subsequent steps based on the reception of an RRC reconfiguration completion message based on the trigger of the PS cell change or secondary node change (i.e., based on the execution condition of the PS cell change being satisfied).

[0180] For example, if the control unit 230 has transmitted to the UE 100 information instructing the UE 100 to release the configuration when changing the PS cell regardless of whether or not the execution condition (event) based on the configuration is satisfied, the control unit 230 may execute the processing of the subsequent steps based on the reception of an RRC reconfiguration completion message based on the trigger of the PS cell change or secondary node change (i.e., based on the execution condition of the PS cell change being satisfied).

[0181] Furthermore, when the control unit 230 has transmitted to the UE 100 information instructing the release of a configuration for which the execution condition (event) is satisfied, the control unit 230 may determine not to execute the processing of subsequent steps for a candidate secondary node (i.e., a target secondary node) associated with the configuration for which the execution condition is satisfied, i.e., to perform non-release control. Thereafter, when the SN 200S operating as the target secondary node becomes a source secondary node due to a subsequent PS cell change, the control unit 230 may execute the processing of subsequent steps for the SN 200S. Furthermore, the control unit 230 may determine not to execute the processing of subsequent steps for a candidate secondary node associated with a configuration other than the configuration for which the execution condition is satisfied, i.e., to perform non-release control.

[0182] The control unit 230 may execute the subsequent steps for a candidate target PS cell (or a candidate secondary node) associated with the release information instructing release, and may determine not to execute the subsequent steps for a candidate target PS cell (or a candidate secondary node) not associated with the release information instructing release, i.e., to perform non-release control.

[0183] Steps S606 to S609 correspond to steps S504 to S507.

[0184] As described above, the control unit 230 of the MN 200M may perform control to transmit a release request message to the corresponding secondary node when receiving a message (for example, an RRC reconfiguration completion message) including information indicating that the UE 100 has decided to release at least a part of the information of the configuration from the UE 100. In this way, even when the UE 100 has autonomously decided to release at least a part of the information of the configuration, the release request message is transmitted to the corresponding secondary node, so that it is possible to prevent the corresponding secondary node from continuing to hold the resources of the UE 100, and it becomes possible to appropriately perform selective activation.

[0185] (Example 7) An operation example 7 of the mobile communication system 1 according to the embodiment will be described with reference to Fig. 13. Explanation of the same parts as those in the above operation examples will be omitted. In Fig. 13, the operation before step S701 is the operation before step S110, and therefore explanation thereof will be omitted. Note that in this operation example, the SN200 autonomously stops the release of resources based on the release request message.

[0186] Note that, similar to the above-described operation example, the UE 100 has settings related to a plurality of candidate secondary nodes in selective activation.

[0187] In step S701, when UE 100 having the above setting changes the secondary node from a source secondary node to a target secondary node, the transmitter 221 of MN 200M transmits an SN release request message to SN 200S1. The receiver 222 of SN 200S1 receives the SN release request message from MN 200M. Note that in this operation example, the controller 230 of MN 200M does not need to determine whether or not to perform non-release control.

[0188] In step S702, the control unit 230 of the SN200S1 determines whether to perform non-release control to stop the release of resources based on the release request message. If the SN200S1 is a candidate secondary node after the UE100 changes its secondary node, the control unit 230 of the SN200S1 may determine to perform non-release control. For example, if the previously received SN addition request message contains information indicating that the SN200S1 is a target of selective activation, the control unit 230 may determine to perform non-release control, assuming that the SN200S1 is a candidate secondary node. Alternatively, if the SN change request message transmitted to the MN200M contains information indicating that the SN200S1 is a candidate secondary node in selective activation, the control unit 230 may determine to perform non-release control, assuming that the SN200S1 is a candidate secondary node.

[0189] On the other hand, the control unit 230 of the SN200S1 may determine to perform non-release control if the SN200S1 is not a candidate secondary node after the UE100 changes the secondary node. For example, if the previously received SN addition request message contains information indicating that the SN200S1 is not a target for selective activation, the control unit 230 may determine that the SN200S1 is not a candidate secondary node and not perform non-release control. Alternatively, if the SN change request message transmitted to the MN200M does not contain information indicating that the SN200S1 is a candidate secondary node in selective activation, the control unit 230 may determine that the SN200S1 is not a candidate secondary node and not perform non-release control.

[0190] When the control unit 230 of the SN200S1 determines that non-release control is to be performed, it may cancel the release of resources based on the release request message (i.e., it may not release the resources). Therefore, the control unit 230 may ignore the instruction based on the release request message. The control unit 230 may skip (omit) the release of resources. On the other hand, when the control unit 230 determines that non-release control is not to be performed, it releases the resources based on the release request message.

[0191] Step S703 is the same as step S312. Step S704 is the same as step S113. In this operation example, the control unit 230 of the MN 200M may execute the operation of step S704 without determining whether or not to perform non-release control.

[0192] In step S705, similarly to step S702, the control unit 230 of the SN 200S3 determines whether or not to perform non-release control.

[0193] Step S706 is the same as step S314. Step S707 is the same as step S115.

[0194] As described above, when UE 100, which has configuration for multiple candidate secondary nodes in selective activation, changes its secondary node from a source secondary node to a target secondary node, receiving unit 222 of SN 200S1 and SN 200S3 receives from the master node a release request message requesting the release of resources associated with UE 100. If UE 100, which has configuration for multiple candidate secondary nodes, changes its secondary node from a source secondary node to a target secondary node, control unit 230 of SN 200S1 and SN 200S3 cancels the release of resources based on the release request message if the UE itself is a candidate secondary node after the UE 100 changes its secondary node. This prevents the release of resources based on the release request message when UE 100 accesses SN 200S1 and SN 200S3 through selective activation, enabling proper execution of selective activation.

[0195] [Other embodiments] In the above-described embodiment, the predetermined message has been described as an example of a change request message (SN change request message) and / or a release request message (SN release request message), but is not limited to this. The predetermined message may be another message, such as a new message. In this case, the predetermined message may include at least a portion of the information included in the release request message or at least a portion of the information included in the change request message. This makes it possible to reduce the impact on the mobile communication system when the change request message (SN change request message) and the release request message (SN release request message) are existing messages, compared to when a new predetermined message is defined.

[0196] The operational sequences (and operational flows) in the above-described embodiments do not necessarily have to be executed in chronological order according to the order depicted in the flow diagrams or sequence diagrams. For example, the steps in the operations may be executed in an order different from that depicted in the flow diagrams or sequence diagrams, or may be executed in parallel. Some of the steps in the operations may be deleted, or additional steps may be added to the processing. The operational sequences (and operational flows) in the above-described embodiments may be executed independently, or two or more operational sequences (and operational flows) may be executed in combination. For example, some steps in one operational flow may be added to another operational flow, or some steps in one operational flow may be replaced with some steps in another operational flow.

[0197] In the above-described embodiment, an NR-based mobile communication system has been described as an example of the mobile communication system 1. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system compliant with a TS of any of LTE (Long Term Evolution) or other generation systems (e.g., 6th generation) of the 3GPP standard. The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol termination for the UE 100 in LTE. The mobile communication system 1 may be a system compliant with a TS of a standard other than the 3GPP standard. The base station 200 may be an IAB (Integrated Access and Backhaul) donor or an IAB node.

[0198] A program may be provided that causes a computer to execute each process performed by UE 100 or base station 200. The program may be recorded in a computer-readable medium. Using the computer-readable medium, the program can be installed in a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM (Compact Disk Read Only Memory) or a DVD-ROM (Digital Versatile Disk Read Only Memory). Furthermore, circuits that execute each process performed by UE 100 or base station 200 may be integrated, and at least a part of UE 100 or base station 200 may be configured as a semiconductor integrated circuit (chip set, SoC (System On Chip)).

[0199] In the above embodiments, "transmit" may mean processing at least one layer in a protocol stack used for transmission, or may mean physically transmitting a signal wirelessly or via a wired connection. Alternatively, "transmit" may mean a combination of processing at least one layer and physically transmitting a signal wirelessly or via a wired connection. Similarly, "receive" may mean processing at least one layer in a protocol stack used for reception, or may mean physically receiving a signal wirelessly or via a wired connection. Alternatively, "receive" may mean a combination of processing at least one layer and physically receiving a signal wirelessly or via a wired connection. Similarly, "obtain / acquire" may mean obtaining information from stored information, obtaining information from information received from another node, or obtaining information by generating information. Similarly, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless otherwise specified. The phrase "based on" means both "based only on" and "based at least in part on." Similarly, the phrase "depending on" means both "depending only on" and "depending at least in part on." Similarly, "include" and "comprise" do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Similarly, in this disclosure, "or" does not mean an exclusive or, but does mean a logical or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements.Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0200] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0201] (Addendum) The following additional notes are about the features of the above-described embodiment.

[0202] (Appendix 1) A base station (200) operating as a master node in a network including a communication device (100) that communicates with a master node and a secondary node, a transmitter (221) capable of transmitting a release request message to a release secondary node that does not hold resources associated with the communication device, among the source secondary node and the plurality of candidate secondary nodes, when the communication device having settings related to a plurality of candidate secondary nodes in selective activation changes the secondary node from a source secondary node to a target secondary node, to request the release of the resources; a control unit (230) that, when the communication device changes the secondary node, performs non-release control to prevent a non-release secondary node that holds the resource from releasing the resource using the release request message, among the source secondary node and the plurality of candidate secondary nodes. Base station.

[0203] (Appendix 2) The control unit determines, as the non-release control, not to transmit the release request message to the non-release secondary node. 1. A base station as defined in claim 1.

[0204] (Appendix 3) The control unit controls, as the non-release control, to transmit a predetermined message to the non-release secondary node for holding at least context information of the communication device as the resource. 1. A base station as defined in claim 1.

[0205] (Appendix 4) The control unit controls to transmit a change request message requesting preparation for the change of the resource as the predetermined message. 10. A base station as defined in claim 3.

[0206] (Appendix 5) The control unit controls the communication device to transmit the change request message as the predetermined message when there is a change in the context information of the communication device. 5. A base station as defined in claim 4.

[0207] (Appendix 6) The control unit controls to transmit the release request message including an indicator indicating whether the context information is held in the non-released secondary node as the predetermined message. 6. The base station of any one of Supplementary Notes 3 to 5.

[0208] (Appendix 7) The control unit controls the release request message including the indicator to be transmitted as the predetermined message when there is no change in the context information. 7. A base station as defined in claim 6.

[0209] (Appendix 8) When the control unit transmits the release request message including the indicator as the predetermined message, the control unit controls to transmit, to the non-released secondary node, information instructing the node to resume providing the resource based on the context information. 8. A base station according to claim 6 or 7.

[0210] (Appendix 9) The predetermined message includes at least a part of the information included in the release request message or at least a part of the information included in a change request message requesting preparation for change of the resource. 9. The base station of any one of Supplementary Notes 3 to 8.

[0211] (Appendix 10) The control unit determines a predetermined message to be transmitted to the non-released secondary node from among a plurality of types of predetermined messages based on a change in context information of the communication device. 10. The base station of any one of Supplementary Notes 3 to 9.

[0212] (Appendix 11) The control unit determines whether to perform the non-release control when receiving a radio resource control (RRC) reconfiguration completion message based on the trigger of the change of the secondary node from the communication device. 11. The base station of claim 1.

[0213] (Appendix 12) The RRC reconfiguration complete message includes predetermined information instructing execution of the non-release control, The control unit determines whether or not to perform the non-release control based on the predetermined information. 12. The base station of claim 11.

[0214] (Appendix 13) When at least a part of the information of the setting held by the communication device is released, the control unit controls to transmit the release request message to a corresponding secondary node associated with the information to be released, among the source secondary node and the plurality of candidate secondary nodes. 14. The base station of any one of Supplementary Notes 1 to 13.

[0215] (Appendix 14) The control unit controls transmission of the release request message to the corresponding secondary node when at least part of the information of the setting is released by updating the setting. 14. The base station of claim 13.

[0216] (Appendix 15) The control unit controls transmission of the release request message to the corresponding secondary node when receiving, from the communication device, a message including information indicating that the communication device has decided to release at least a part of the information of the setting. 15. The base station according to claim 13 or 14.

[0217] (Appendix 16) A base station (200) capable of operating as a secondary node in a network including a communication device (100) that communicates with a master node and a secondary node, a receiving unit (2) for receiving, from the master node, a release request message requesting the release of resources associated with the communication device when the communication device having settings related to a plurality of candidate secondary nodes in selective activation changes the secondary node from a source secondary node to a target secondary node; 12 )and, a control unit (230) that stops the release of the resources based on the release request message when the base station is the candidate secondary node after the communication device having the setting changes the secondary node. Base station.

[0218] (Appendix 17) A communication method executed by a base station operating as a master node in a network including a communication device that communicates with a master node and a secondary node, comprising: When the communication device, which has settings related to multiple candidate secondary nodes in selective activation, changes the secondary node from a source secondary node to a target secondary node, transmitting a release request message to a release secondary node, among the source secondary node and the multiple candidate secondary nodes, that does not hold the resources associated with the communication device, to request the release of the resources; and when the communication device changes the secondary node, performing non-release control of not releasing the resources using the release request message on a non-release secondary node that holds the resources, among the source secondary node and the plurality of candidate secondary nodes. Communication method.

[0219] (Appendix 18) 1. A communication method performed in a base station capable of operating as a secondary node in a network including a communication device that communicates with a master node and a secondary node, comprising: receiving a release request message from the master node requesting release of resources associated with the communication device when the communication device, having configuration for multiple candidate secondary nodes in selective activation, changes its secondary node from a source secondary node to a target secondary node; and after the communication device having the configuration changes the secondary node, if the base station is the candidate secondary node, canceling the release of the resources based on the release request message. Communication method. (Appendix 19) A master node (200, 200M) connected to a communication device (100), Pa control unit (230) for controlling a procedure for performing a conditional PS cell change based on a primary secondary (PS) cell configuration; a receiving unit (212) that receives a radio resource control (RRC) reconfiguration completion message based on the conditional PS cell change from the communication device; a transmitting unit (221), In the procedure, the transmitting unit The receiver receives the RRC reconfiguration complete message, and if the source secondary node is a candidate secondary node, sends a change request message to the source secondary node; The receiver receives the RRC reconfiguration complete message, and if the source secondary node is not a candidate secondary node, sends a release request message to the source secondary node. Master node. (Appendix 20) The release request message includes information for determining whether the source secondary node should release only resources associated with the connection of the communication device between the master node and the source secondary node. 19. The master node described in Appendix 19. (Appendix 21) the control unit determines whether to retain resources of the communication device in the source secondary node; The transmission unit If the resource is held, sending the modification request message to the source secondary node; If the resource is to be released, sending the release request message to the source secondary node. 21. The master node of claim 19 or 20. (Appendix 22) the modification request message is used to request modification of context information of the communication device at the source secondary node; 22. The master node of any one of Appendix 19 to 21. (Appendix 23) the release request message is used to request the release of context information of the communication device in the source secondary node; 23. The master node of any one of Appendix 19 to 22. (Appendix 24) The conditional PS cell change is performed continuously without reconfiguration of the PS cell configuration from the master node. 24. The master node of any one of Appendix 19 to 23. (Appendix 25) A communication method executed by a master node connected to a communication device (100), comprising: receiving a conditional PS cell change based radio resource control (RRC) reconfiguration complete message from the communication device based on a primary secondary (PS) cell configuration; receiving the RRC reconfiguration complete message, and if the source secondary node is a candidate secondary node, sending a modification request message to the source secondary node; receiving the RRC reconfiguration complete message and, if the source secondary node is not a candidate secondary node, sending a release request message to the source secondary node; Communication method. (Appendix 26) The release request message includes information for determining whether the source secondary node should release only resources associated with the connection of the communication device between the master node and the source secondary node. 25. A communication method as described in Appendix 25. (Appendix 27) determining whether to retain resources of the communication device in the source secondary node; If the resource is held, sending the modification request message to the source secondary node; If the resource is to be released, sending the release request message to the source secondary node. 27. A communication method as described in Appendix 25 or 26. (Appendix 28) the modification request message is used to request modification of context information of the communication device at the source secondary node; 28. The communication method of any one of appendices 25 to 27. (Appendix 29) the release request message is used to request the release of context information of the communication device in the source secondary node; 29. The communication method of any one of appendices 25 to 28. (Appendix 30) The conditional PS cell change is performed continuously without reconfiguration of the PS cell configuration from the master node. 30. The communication method of any one of appendixes 25 to 29.

Claims

1. A master node (200, 200M) connected to a communication device (100), a wireless communication unit and a network communication unit, The wireless communication unit transmitting information for configuring a conditional PS cell change to the communication device using a Radio Resource Control (RRC) reconfiguration message, the information including information indicating one or more execution conditions; receiving, from the communication device, an RRC reconfiguration complete message based on which an execution condition for one PS cell is satisfied according to the evaluation of the one or more execution conditions and an RRC reconfiguration corresponding to the one PS cell is applied; The network communication unit (220) receiving the RRC reconfiguration complete message and, if a source secondary node is configured as a candidate secondary node for the conditional PS cell change, sending a change request message to the source secondary node; receiving the RRC reconfiguration complete message and, if the source secondary node is not configured as a candidate secondary node in the conditional PS cell change, sending a release request message to the source secondary node; Master node.

2. The release request message includes an identifier indicating whether a context of the communication device is maintained in the source secondary node. The master node of claim 1 .

3. the modification request message is used to request modification of context information of the communication device at the source secondary node; The master node according to claim 1 or 2.

4. the release request message is used to request the release of context information of the communication device in the source secondary node; The master node according to claim 1 or 2.

5. The conditional PS cell change is performed continuously without reconfiguration of the conditional PS cell change from the master node. The master node according to claim 1 or 2.

6. A communication method executed by a master node (200, 200M) connected to a communication device (100), comprising: transmitting information for configuring a conditional PS cell change to the communication device using a Radio Resource Control (RRC) reconfiguration message, the information including information indicating one or more execution conditions; receiving an RRC reconfiguration complete message from the communication device, based on which an execution condition for one PS cell is satisfied according to the evaluation of the one or more execution conditions and an RRC reconfiguration corresponding to the one PS cell is applied; receiving the RRC reconfiguration complete message and, if a source secondary node is configured as a candidate secondary node in the conditional PS cell change, sending a change request message to the source secondary node; receiving the RRC reconfiguration complete message and, if the source secondary node is not configured as a candidate secondary node in the conditional PS cell change, sending a release request message to the source secondary node. Communication method.

7. The release request message includes an identifier indicating whether a context of the communication device is maintained in the source secondary node. The communication method according to claim 6.

8. the modification request message is used to request modification of context information of the communication device at the source secondary node; The communication method according to claim 6 or 7.

9. the release request message is used to request the release of context information of the communication device in the source secondary node; The communication method according to claim 6 or 7.

10. The conditional PS cell change is performed continuously without reconfiguration of the conditional PS cell change from the master node. The communication method according to claim 6 or 7.

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