Communication device, base station, and communication method

Abstract

A communication device (100) according to one embodiment of the present invention comprises: a reception unit (112) that receives, from a base station (200), a radio resource control (RRC) message including LTM configuration information used to provide one or more items of layer 1 / layer 2 triggered mobility (LTM) candidate information, and receives, from the base station, a medium access control (MAC) control element (CE) including a cell switch command that triggers an LTM cell switch; and a control unit (130) that executes the LTM cell switch in accordance with the LTM candidate information on the basis of the cell switch command. The control unit determines whether or not to execute a subsequent LTM cell switch on the basis of information configured by the LTM configuration information.

Description

Communication device, base station, and communication method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from Patent Application No. 2023-168918, filed September 28, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a communication device, a base station, and a communication method.

[0003] In a mobile communication system that complies with the technical specifications of 3GPP (registered trademark; the same applies hereinafter) (Third Generation Partnership Project), a standardization project for mobile communication systems, the introduction of L1 (Layer 1) / L2 (Layer 2) triggered mobility (LTM) is planned (see, for example, Non-Patent Document 1). In LTM, a base station changes the serving cell of a communication device by transmitting a cell switch command to the communication device via a media access control (MAC) control element (CE) based on an L1 measurement report received from the communication device. Compared to a cell change based on a radio resource control (RRC) message, the communication device can dynamically perform a cell change and reduce mobility delay.

[0004] Currently, UE 100 performs a cell change (hereinafter, a first cell change) from a source cell to a target cell according to the setting information for LTM, and then performs a cell change (hereinafter, a second cell change) without RRC reconfiguration (i.e., without receiving an RRC reconfiguration message). The introduction of LTM (hereinafter, subsequent LTM) is being considered (see, for example, Non-Patent Document 1).

[0005] "R2-2211101" (Report of 3GPP TSG RAN WG2 meeting #119bis-e, Online)

[0006] A communication device according to a first aspect includes: a receiver that receives, from a base station, a radio resource control (RRC) message including one or more Layer 1 / Layer 2 triggered mobility (LTM) configuration information used to provide one or more LTM candidate information; and a medium access control (MAC) control element (CE) that includes a cell change command that triggers an LTM cell change from the base station. The controller determines whether to perform a subsequent LTM cell change based on the cell change command and in accordance with the LTM candidate information.

[0007] A base station according to a second aspect includes a transmitter that transmits, to a communication device, a radio resource control (RRC) message including one or more Layer 1 / Layer 2 triggered mobility (LTM) configuration information used to provide LTM candidate information, and a medium access control (MAC) control element (CE) that includes a cell change command to trigger an LTM cell change, and a controller that controls, based on the cell change command, execution of an LTM cell change in accordance with the LTM candidate information. The controller controls whether to execute a subsequent LTM cell change based on information configured in the LTM configuration information.

[0008] A communication method according to a third aspect is a communication method executed by a communication device, the communication method comprising: receiving, from a base station, a radio resource control (RRC) message including one or more Layer 1 / Layer 2 triggered mobility (LTM) configuration information used to provide LTM candidate information; receiving, from the base station using a medium access control (MAC) control element (CE), a cell change command for triggering an LTM cell change; and performing an LTM cell change based on the received cell change command and in accordance with the LTM candidate information. In the performing LTM cell change, determining whether to perform a subsequent LTM cell change based on information configured in the LTM configuration information.

[0009] Objects, features, advantages, etc. of the present disclosure will become clearer from the following detailed description with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram illustrating an example configuration of a protocol stack according to an embodiment. FIG. 3 is a diagram illustrating an overview of LTM. FIG. 4 is a diagram illustrating a configuration of a UE according to an embodiment. FIG. 5 is a diagram illustrating a configuration of a base station according to an embodiment. FIG. 6 is a sequence diagram (part 1) illustrating a first operation example according to an embodiment. FIG. 7 is a sequence diagram (part 2) illustrating the first operation example according to an embodiment. FIG. 8 is a diagram illustrating a hierarchical structure of an RRC reconfiguration message according to an embodiment. FIG. 9 is a flowchart (part 1) illustrating an example determination operation according to an embodiment. FIG. 10 is a flowchart (part 1) illustrating an example determination operation according to an embodiment. FIG. 11 is a sequence diagram illustrating a second operation example according to an embodiment.

[0010] 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.

[0011] However, in the subsequent LTM, the RRC reconfiguration message is not received in the cell after the first cell change is performed. Therefore, the UE 100 may attempt to perform the subsequent LTM even though the second cell change by the subsequent LTM cannot be performed in the cell after the first cell change is performed. As a result, the subsequent LTM may not be properly performed, and the cell change may fail.

[0012] Therefore, one object of the present disclosure is to provide a communication device, a base station, and a communication method that enable subsequent LTM to be performed appropriately.

[0013] (System Configuration) First, the configuration of a mobile communication system 1 according to this 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 (5G system) of the 3GPP standard, i.e., a mobile communication system based on NR (NR (New Radio) radio access).

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

[0015] The UE 100 is a communication device that communicates via the base station 200. The UE 100 may be a device used by a user. 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 (e.g., a Vehicle UE). The UE 100 may be a transport vehicle other than a vehicle (e.g., a ship, an airplane, etc.) or a device provided therein (e.g., an Aerial UE). The UE 100 may be a sensor or a device provided therein. Note that the UE 100 may be referred to by other names such as a terminal, a terminal device, 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. Furthermore, the UE 100 is an example of a terminal, and the terminal may include factory equipment or the like.

[0016] The NG-RAN 20 includes multiple base stations 200. Each base station 200 manages at least one cell. One or more base stations 200 may correspond to one or more cells. In this embodiment, the base station 200 may be replaced with a cell. A cell constitutes the smallest unit of a communication area. One cell belongs to one frequency (carrier frequency). 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. Details of the protocol stack will be described later. Furthermore, 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. In addition, the base station 200 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 is sometimes 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 AMF (Access and Mobility Management Function) and / or a UPF (User Plane Function). The AMF performs mobility management for the UE 100. The UPF provides functions specialized for U-plane processing. The AMF and the UPF are connected to the base station 200 via an NG interface.

[0018] (Configuration Example of Protocol Stack) Next, a configuration example of a protocol stack according to this embodiment will be described with reference to FIG.

[0019] The protocol of 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] 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.

[0022] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and the 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.

[0023] The PDCP layer performs header compression / decompression and encryption / decryption.

[0024] A Service Data Adaptation Protocol (SDAP) layer may be provided as an upper layer above the PDCP layer. The SDAP layer 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 an Access Stratum (AS).

[0025] The RRC layer controls logical channels, transport channels, and physical channels according 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. When an RRC connection exists between the RRC of the UE 100 and the RRC of the base station 200, the UE 100 is in an RRC connected state. When there is no RRC connection between the RRC of the UE 100 and the RRC of the base station 200, the UE 100 is in an RRC idle state. When the RRC connection between the RRC of the UE 100 and the RRC of the base station 200 is suspended, the UE 100 is in an RRC inactive state.

[0026] The NAS layer, which is located above the RRC layer in the UE 100, 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.

[0027] The UE 100 has an application layer and the like in addition to the radio interface protocol.

[0028] (Radio Frame Configuration) In a 5G system, downlink transmission and uplink transmission are configured within a radio frame having a duration of 10 ms. For example, a radio frame is represented by a system frame number (SFN) ranging from 0 to 1023. For example, a radio frame is configured with 10 subframes. For example, one subframe may be 1 ms. Furthermore, one subframe may be configured with one or more slots. For example, the number of symbols that make up one slot is 14 for a normal CP (Cyclic Prefix) and 12 for an extended CP. Furthermore, the number of slots that make up one subframe varies depending on the set subcarrier spacing. For example, for a normal CP, if the subcarrier spacing is set to 15 kHz, the number of slots per subframe is 1 (i.e., 14 symbols); if the subcarrier spacing is set to 30 kHz, the number of slots per subframe is 2 (i.e., 28 symbols); if the subcarrier spacing is set to 60 kHz, the number of slots per subframe is 4 (i.e., 56 symbols); and if the subcarrier spacing is set to 120 kHz, the number of slots per subframe is 8 (i.e., 128 symbols). Furthermore, if the subcarrier spacing is set to 60 kHz for an extended CP, the number of slots per subframe is 4 (i.e., 48 symbols). That is, the number of slots constituting one subframe is determined based on the subcarrier spacing set by the base station 200. Furthermore, the number of symbols constituting one subframe is determined based on the subcarrier spacing set by the base station 200. That is, the number of symbols constituting a 1 ms subframe is determined based on the subcarrier spacing set by the base station 200, and the length of each symbol (length in the time direction) changes.

[0029] (LTM) In a mobile communication system 1 conforming to the technical specifications of 3GPP, introduction of L1 (Layer 1) / L2 (Layer 2) triggered mobility (LTM) is planned. As shown in Fig. 3, in LTM, the following operations can be performed.

[0030] Step S10: LTM Preparation The UE 100 in the RRC connected state may perform the following operation as an operation for LTM preparation.

[0031] Step S11: The UE 100 transmits a measurement report message to the base station 200. The base station 200 determines to use the LTM and starts candidate cell preparation.

[0032] Step S12: The base station 200 transmits an RRC reconfiguration message including LTM candidate cell configuration of one or more candidate cells.

[0033] Step S13: The UE 100 stores the LTM candidate cell configuration. The UE 100 transmits an RRC reconfiguration complete (RRCReconfigurationComplete) message to the base station 200.

[0034] Step S20: Early synchronization The UE 100 may perform the following operation as the early synchronization operation.

[0035] Step S21: Before receiving the cell switching command, the UE 100 performs downlink (DL) synchronization with the candidate cell. The UE 100 may perform DL synchronization based on a synchronization signal (SS) and a physical broadcast channel (PBCH) block (SSB).

[0036] Step S22: Before receiving the cell switch command, the UE 100 performs timing advance (TA) acquisition. The UE 100 may perform TA acquisition based on a PDCCH order (specifically, a PDCCH ordered RACH). The PDCCH order may be triggered only by the source cell.

[0037] Step S30: LTM execution The UE 100 may execute the following operation as the LTM execution operation.

[0038] Step S31: The UE 100 performs L1 measurement on the candidate cell configured by the LTM candidate cell configuration. The UL 100 transmits a lower-layer measurement report (hereinafter, L1 measurement report) based on the L1 measurement to the base station 200.

[0039] Step S32: The base station 200 determines to perform a cell change to the target cell. The base station 200 transmits a MAC CE that triggers the cell change by including a candidate configuration index of the target cell. The UE 100 switches the configuration of the target cell.

[0040] Step S33: If the cell change needs to include the execution of a random access (RA) procedure, the UE 100 executes the RA procedure toward the target cell.

[0041] Step S40: LTM Completion The UE 100 may perform the following operation as an operation for completing LTM.

[0042] Step S41: The UE 100 indicates that the cell change to the target cell has been successfully completed.

[0043] It should be noted that UE 100 may execute steps S20 to S40 multiple times for subsequent LTM cell switching based on the configuration provided in step S12 without releasing the configuration.

[0044] As described above, in LTM, the base station 200 changes the serving cell of the UE 100 by transmitting a cell change command that triggers a cell change to the UE 100 by MAC CE based on the L1 measurement report received from the UE 100. Compared to a cell change based on an RRC message, the UE 100 can dynamically perform a cell change, and mobility delay can be reduced.

[0045] Currently, UE 100 performs a cell change (hereinafter, referred to as a first cell change) from a source cell to a target cell according to the setting information for LTM, and then performs a cell change (hereinafter, referred to as a second cell change) without RRC reconfiguration (i.e., without receiving an RRC reconfiguration message). The introduction of LTM (hereinafter, referred to as a subsequent LTM) is being considered.

[0046] However, in the subsequent LTM, the RRC reconfiguration message is not received in the cell after the first cell change is performed. Therefore, there is a concern that the UE 100 will attempt to perform the subsequent LTM even though the second cell change by the subsequent LTM cannot be performed in the cell after the first cell change is performed. As a result, there is a concern that the subsequent LTM cannot be properly performed and the cell change will fail. Therefore, later, an operation for properly performing the subsequent LTM will be described.

[0047] (Configuration of User Equipment) 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.

[0048] 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 (Radio Frequency) 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.

[0049] 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 operations 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 the program executed by the processor, parameters related to the program, and data related to the program. The memory may include at least one of read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), and flash memory. All or a portion of the memory may be contained within the processor.

[0050] The control unit 120 may include a MAC processing unit that performs processing in the MAC layer and an upper layer processing unit that performs processing in a layer higher than the MAC layer. The MAC processing unit may be referred to as a MAC entity. The upper layer processing unit performs processing in a layer higher than the MAC layer. The upper layer processing unit may include a PDCP processing unit that performs processing in the PDCP layer and an RRC processing unit that performs processing in the RRCP layer. The PDCP processing unit may be referred to as a PDCP entity. The RRC processing unit may be referred to as an RRC entity. Note that, for the upper layer processing unit, information from the MAC processing unit may be information from a lower layer.

[0051] Each of the MAC processing unit and the upper layer processing unit (PDCP processing unit and / or RRC processing unit) may be configured by one processor or multiple processors. The operations of the MAC processing unit and the upper layer processing unit may be operations of the control unit 120. Of the operations of each layer processing unit, the transmission and / or reception operations may be operations of the communication unit 110 (transmission unit 111 and / or reception unit 112).

[0052] In the UE 100 configured as described above, the receiver 112 receives from the base station 200 an RRC message including LTM configuration information used to provide one or more LTM candidate cell configurations. When the controller 130 receives from the base station 200 a cell change command via MAC CE that triggers a first cell change from the source cell of the base station 200 to a target cell, the controller 130 executes the first cell change in accordance with the LTM configuration information. Based on the RRC message, the controller 130 determines whether a second cell change, which is executed without receiving an RRC reconfiguration message after executing the first cell change, is permitted. This allows the UE 100 to determine whether the second cell change is permitted or not. For example, if the second cell change is not permitted, the UE 100 does not execute the second cell change, thereby preventing cell change failures due to execution of subsequent LTM. As a result, the UE 100 is able to properly execute subsequent LTM.

[0053] (Configuration of Base Station) The configuration of the base station 200 according to this embodiment will be described with reference to Fig. 5. The base station 200 includes a communication unit 210, a network communication unit 220, and a control unit 230.

[0054] The communication unit 210 receives, for example, a radio signal from the UE 100 and transmits the radio signal to the UE 100. The communication unit 210 has at least one transmission unit 211 and at least one reception unit 212. The transmission unit 211 and the reception unit 212 may be configured to include an RF circuit. The RF circuit performs analog processing of signals transmitted and received via an antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, etc.

[0055] The network communication unit 220 transmits and receives signals to and from 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.

[0056] 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 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 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 RAN protocol stack. The memory stores programs executed by the processor, parameters related to the programs, and data related to the programs. All or a part of the memory may be included in the processor.

[0057] In the base station 200 configured as described above, the control unit 230 generates an RRC message including one or more pieces of LTM setting information. The transmission unit 211 transmits the RRC message to the UE 100. The transmission unit 211 transmits a cell change command to the UE 100 by MAC CE to trigger a first cell change so that the UE 100 performs the first cell change in accordance with the LTM setting information. The control unit 230 generates an RRC message based on the RRC message so that the UE 100 determines whether a second cell change, which is performed without receiving an RRC reconfiguration message after performing the first cell change, is permitted. This allows the UE 100 to determine whether the second cell change is permitted by determining based on the RRC message. For example, if the second cell change is not permitted, the UE 100 does not perform the second cell change, thereby preventing cell change failures due to the execution of subsequent LTM. As a result, the UE 100 can properly perform subsequent LTM.

[0058] (First Operation Example) A first operation example will be described with reference to Figs. 6 to 8. Previous descriptions may be omitted. In the mobile communication system 1 of this operation example, the base station 200 includes a base station 201 and a base station 202. The base station 201 and the base station 202 manage different cells. The base station 202 may be, for example, a neighboring base station for the base station 201.

[0059] The UE 100 is in an RRC connected state with a cell (source cell) managed by the base station 201. Thereafter, the UE 100 performs communication with the base station 201 in the source cell until a cell change to a target cell is performed.

[0060] Note that, for UE 100, communication with base station 200 may be communication with a cell. Therefore, for UE 100, receiving information / messages, etc. from base station 200 may be receiving information / messages, etc. from a cell, and transmitting information / messages, etc. to base station 200 may be transmitting information / messages, etc. to a cell.

[0061] Step S101: The transmitter 111 of the UE 100 transmits capability information to the base station 201. The base station 200 receives the capability information from the UE 100. The capability information may be at least one of information indicating whether the UE 100 supports a cell change (hereinafter, sometimes referred to as a second cell change) that is performed without receiving an RRC reconfiguration message after performing a first cell change (described later), and information indicating whether the UE 100 supports subsequent LTM.

[0062] Here, the subsequent LTM may be any of the following operations: (i) an operation of performing a cell change (hereinafter sometimes referred to as a first cell change) in accordance with LTM configuration information received from the base station 200 (i.e., the source cell) and then performing a cell change without RRC reconfiguration; (ii) an operation of performing a cell change without receiving an RRC reconfiguration message in accordance with a first cell change; (iii) an operation of performing a cell change in accordance with the LTM configuration information in accordance with the first cell change without discarding the LTM configuration information (i.e., the LTM configuration information received from a previous source cell, not the current source cell); (iv) an operation of performing a cell change between L1 / L2 mobility candidates without RRC reconfiguration; (v) an operation of performing successive cell changes between L1 / L2 mobility candidates without RRC reconfiguration.

[0063] Note that the cell change in this operation example (i.e., the cell change due to the LTM) may be referred to as an LTM cell change. The LTM cell change may include a first cell change and a second cell change.

[0064] The first cell change may be a cell change according to LTM configuration information received directly from the source cell, and may also be referred to as a first LTM (or a first LTM cell change).

[0065] The second cell change may be a cell change according to LTM configuration information not directly received from the source cell. Therefore, the second cell change may be a cell change performed without RRC reconfiguration (without directly receiving an RRC reconfiguration message from the source cell). The second cell change may also be referred to as a subsequent LTM (or second LTM cell change).

[0066] Step S102: The transmitter 111 of the UE 100 transmits a measurement report (message) to the base station 201. The receiver 212 of the base station 201 receives the measurement report from the UE 100.

[0067] The control unit 230 of the base station 201 determines whether to use LTM. The control unit 230 may determine whether to use LTM based on, for example, a measurement report. If the control unit 230 determines to use LTM, it starts candidate cell preparation.

[0068] As a candidate cell preparation, the control unit 230 may select a candidate cell for the target cell in LTM based on the measurement report. The control unit 230 may select the candidate cell from among the cells managed by the base station 201, for example. The candidate cell may also be referred to as an LTM candidate cell.

[0069] Furthermore, the control unit 230 may generate setting information related to LTM (hereinafter, LTM setting information). The control unit 230 may include the generated LTM setting information (for example, LTM-Config) in an RRC reconfiguration message, for example (see E1 and E12 in FIG. 8). The control unit 230 may instruct the UE 100 to execute LTM (an operation related to LTM) by including the LTM setting information in the RRC reconfiguration message. The UE 100 may execute LTM (an operation related to LTM) when the LTM setting information is included in the RRC reconfiguration message.

[0070] The LTM configuration information (e.g., LTM-Config) may be information used to provide (one or more) LTM candidate cell configurations. The control unit 230 may include, in the LTM configuration information (e.g., LTM-Config), at least one of information on a list for releasing a candidate cell (hereinafter, sometimes referred to as an LTM candidate release list (e.g., ltm-CandidateToReleaseList)) and information on a list for adding or changing a candidate cell (hereinafter, sometimes referred to as an LTM addition / modification list (e.g., ltm-CandidateToAddModList)).

[0071] The LTM candidate release list may be a list of LTM candidate cell configurations to be removed. The LTM candidate release list may be configured by the identifiers of the candidate cells (e.g., ltm-CandidateId).

[0072] The LTM addition change list may be a list configured by LTM candidate information (e.g., LTM-Candidate). The LTM addition change list may be a list of LTM candidate cell settings to be added and / or changed. The LTM candidate information may include, for example, at least one of the following information. - Identifier of the candidate cell (e.g., ltm-CandidateId) - LTM candidate configuration information (e.g., ltm-CandidateConfig) - LTM configuration completion information (e.g., ltm-ConfigComplete) indicating whether the LTM candidate cell configuration is a complete configuration (Complete Configuration) or a differential configuration (Delta-Configuration) - Configuration information for setting information to be used for early synchronization (e.g., ltm-EarlyUL-SyncConfig) - Identifier indicating whether an L2 reset for the LTM candidate cell is not performed in the LTM cell change procedure (e.g., ltm-NoResetID) A list for adding / changing information used for early synchronization (e.g., ltm-Candidate-Tci-States-ToAddModList) An identifier for canceling (deleting) information used for early synchronization (e.g., ltm-Candidate-Tci-States-ToReleaseList)

[0073] The identifier of the candidate cell may be an identifier of the LTM candidate cell configuration. The LTM candidate cell configuration may be information indicating (or including) the LTM candidate cell configuration (which may be referred to as LTM candidate cell configuration information). The LTM candidate cell configuration may include an RRC reconfiguration message used to configure one LTM candidate cell. Thus, the LTM candidate cell configuration may include an RRC (re)configuration (RRC reconfiguration message) configured in the UE 100. The LTM candidate cell configuration may include cell group configuration information (e.g., CellGroupConfig) including serving cell configuration information (e.g., ServingCellConfig) and the like. The LTM configuration completion information may indicate whether the LTM candidate cell configuration in the LTM candidate cell configuration information is a complete configuration.

[0074] The LTM candidate cell configuration may be a configuration based on LTM candidate information (e.g., LTM-Candidate) or a configuration indicated by the LTM candidate information. The LTM candidate cell configuration may also be referred to as LTM candidate cell configuration information. As described above, the LTM configuration information may include RRC reconfiguration information to be applied to the cell after cell change. The RRC reconfiguration information may be information indicating RRC reconfiguration or may be an RRC reconfiguration message.

[0075] In this specification, when simply referred to as an RRC reconfiguration message, the RRC reconfiguration message may be an RRC reconfiguration message including LTM configuration information, or may be an RRC reconfiguration message included in an LTM candidate cell configuration. For example, when simply referred to as an RRC reconfiguration message, the RRC reconfiguration message may be an RRC reconfiguration message transmitted from base station 200 (base station 201 in this operation example) (received by UE 100), or may be an RRC reconfiguration message included in an LTM candidate cell configuration corresponding to a target configuration identifier indicated by the MAC layer when LTM is executed.

[0076] The control unit 120 may include a MAC processing unit that performs processing in the MAC layer and an upper layer processing unit that performs processing in a layer higher than the MAC layer. The MAC processing unit may be referred to as a MAC entity. The upper layer processing unit performs processing in a layer higher than the MAC layer. The upper layer processing unit may include a PDCP processing unit that performs processing in the PDCP layer and an RRC processing unit that performs processing in the RRCP layer. The PDCP processing unit may be referred to as a PDCP entity. The RRC processing unit may be referred to as an RRC entity. For the upper layer processing unit, information from the MAC processing unit may be information from a lower layer.

[0077] The control unit 230 of the base station 201 may determine whether to use the subsequent LTM. The control unit 230 may determine whether to use the subsequent LTM based on capability information from the UE 100, for example.

[0078] The control unit 230 may determine to use subsequent LTM when the capability information indicates that the UE 100 supports subsequent LTM (or second cell change). On the other hand, the control unit 230 may determine not to use subsequent LTM when the capability information indicates that the UE 100 does not support subsequent LTM (or second cell change). When the control unit 230 determines to use subsequent LTM, it may start candidate cell preparation. The control unit 230 may start candidate cell preparation in the same way as LTM.

[0079] When causing the UE 100 to perform an LTM cell change to a cell of another base station 200 (for example, the base station 201) based on the measurement report, the control unit 230 may perform the following processing.

[0080] Step S103: The network communication unit 220 of the base station 201 transmits, for example, a handover request message requesting preparation of resources for handover to the base station 202. The network communication unit 220 of the base station 202 receives the handover request message from the base station 201. Note that the message may be a message other than the handover request message. The message may be a message used to request preparation for a cell change by LTM and / or subsequent LTM.

[0081] The handover request message may include information requesting a cell change (LTM cell change) to the cell of the base station 202 by LTM and / or subsequent LTM. The handover request message may include information identifying candidate cells among the cells managed by the base station 202.

[0082] The control unit 230 of the base station 202 may determine whether to approve the LTM cell change based on, for example, the handover request message. If the control unit 230 approves the LTM cell change, the control unit 230 may execute the following process.

[0083] Step S104: The network communication unit 220 of the base station 202 transmits a Handover Request Acknowledge message to the base station 201 to inform the source base station (i.e., the base station 201) of the prepared resources at the target. The network communication unit 220 of the base station 201 receives the Handover Request Acknowledge message from the base station 202. The message may be a message used to notify approval of preparation for cell change by LTM and / or subsequent LTM.

[0084] The handover request acknowledgement message may include information about a cell managed by the base station 202 that should be included in the LTM configuration information. For example, the control unit 230 of the base station 202 may include at least a part or all of the LTM candidate cell configuration (LTM candidate cell configuration information) about the candidate cell of the base station 202 in the message.

[0085] If the control unit 230 does not approve the LTM cell change, it may, for example, send a handover preparation failure message to the base station 201 to inform the source base station (i.e., the base station 201) that the handover preparation has failed.

[0086] The control unit 230 of the base station 201 may include an LTM candidate cell setting (LTM candidate cell setting information) related to a candidate cell of the base station 202 in the LTM setting information. Alternatively, the control unit 230 of the base station 201 may generate not only the LTM candidate cell setting of the base station 201 itself but also the LTM candidate cell setting of the base station 202. The control unit 230 may include the generated LTM candidate cell setting in the LTM setting information. The control unit 230 generates an RRC message including the LTM setting information.

[0087] Step S105: The transmitting unit 211 of the base station 201 transmits an RRC reconfiguration message including the LTM setting information to the UE 100. The receiving unit 112 of the UE 100 receives the RRC reconfiguration message as an RRC message from the base station 201. The control unit 120 of the UE 100 stores the LTM setting information.

[0088] Step S106: The transmitter 111 of the UE 100 transmits an RRC reconfiguration completion message to the base station 201. The receiver 212 of the base station 201 receives the RRC reconfiguration completion message from the UE 100.

[0089] Step S107: As an early synchronization operation, downlink synchronization with each candidate cell may be performed. The control unit 120 of the UE 100 performs downlink synchronization based on, for example, an SSB transmitted from each candidate cell.

[0090] Furthermore, as an operation of early synchronization, uplink synchronization with each candidate cell may be executed. The transmitter 211 of the base station 201 may, for example, transmit to the UE 100, a physical downlink control channel (PDCCH) order (i.e., downlink control information (DCI)) for starting an RA procedure for early synchronization in each candidate cell set for the UE 100 by the LTM candidate cell setting. The receiver 112 of the UE 100 may receive the PDCCH order from the base station 201. Note that the PDCCH order in early synchronization may be a PDCCH order (PDCCH ordered-RACH for TA Acquisition without RAR) used to acquire a TA value without an RA response. The control unit 120 of the UE 100 may start the RA procedure based on the PDCCH order.

[0091] In each candidate cell, the transmitter 111 of the UE 100 transmits an RA preamble (message 1) to the base station 201 on a physical random access channel (PRACH). In each candidate cell, the receiver 212 of the base station 201 receives the RA preamble from the UE 100. The controller 230 of the base station 201 calculates a timing advance (TA) value based on the RA preamble from the UE 100. The controller 230 may execute control to omit transmission of an RA response (i.e., message 2), which is a response to the RA preamble.

[0092] Note that the control unit 230 may include information instructing the UE 100 to execute RACH-less LTM in the RA response (i.e., message 2). The information may include information instructing the UE 100 to skip the RA procedure for LTM cell change. The information may be information instructing the UE 100 to execute RACH-less LTM when the UE 100 should apply the same TA as the source cell (base station 200 that manages the source cell).

[0093] Step S108: After performing L1 measurement in each candidate cell configured by the LTM configuration information, the transmitter 111 of UE 100 transmits an L1 measurement report to the base station 201. The receiver 212 of the base station 201 receives the L1 measurement report from UE 100. The L1 measurement report is a measurement report of a lower layer based on the L1 measurement. The L1 measurement report is transmitted in a layer lower than the RRC layer. Note that the measurement report in step S110 is transmitted in the RRC layer.

[0094] The control unit 230 of the base station 201 determines a target cell in LTM (i.e., an LTM target cell) based on the L1 measurement report. In addition, the control unit 230 may determine whether to cause the UE 100 to execute RACH-less LTM (RACH-less LTM) in which the UE 100 performs uplink transmission without executing an RA procedure between the UE 100 and the base station 201, or whether to cause the UE 100 to execute RACH-based LTM (RACH-base LTM) in which the RA procedure between the UE 100 and the base station 201, in the LTM execution.

[0095] The control unit 230 generates a MAC CE for transmitting the cell change command. This MAC CE may be referred to as an LTM cell change command MAC CE, for example. This MAC CE may also be referred to as a cell change command (i.e., may be a cell change command). Hereinafter, the LTM cell change command MAC CE may be referred to as a cell change command as appropriate. The cell change command may include, for example, at least one of the following information (i.e., fields): a target configuration identifier (Target Configuration ID) indicating the index of the candidate target configuration to apply to the LTM cell change; a timing advance command (Timing Advance Command) indicating whether the TA for the LTM target cell is valid; a transmission configuration indication (TCI state ID) state identifier indicating and activating the TCI state for the LTM target cell; an uplink TCI state identifier indicating and activating the uplink TCI state for the LTM target cell (UL TCI state ID); an identifier of the downlink bandwidth portion to be activated in the LTM target cell (DL BWP ID); an identifier of the uplink bandwidth portion to be activated in the LTM target cell (UL BWP ID). - Information related to contention-free random access (CFRA) resources

[0096] The target setting identifier may be an identifier of a candidate cell that will become a target cell, which is a cell after the change, among the identifiers of the candidate cells described above.

[0097] The Timing Advance Command (field) may indicate whether a TA (TA value) is valid for a target cell (e.g., SpCell) corresponding to the target configuration (i.e., LTM candidate cell configuration) indicated by the Target Configuration Identifier (field). When a predetermined value (e.g., FFF) is set as the value of this field, this field may indicate that valid timing adjustment is not available for the primary timing advance group (PTAG) of the LTM target cell. In this case, the UE 100 needs to perform an RA procedure to the LTM target cell. That is, the UE 100 performs RACH-based LTM. On the other hand, when a value other than the predetermined value (e.g., FFF) is set as the value of this field, this field indicates an index value (i.e., TA value) used to control the amount of timing adjustment to be applied by the MAC entity of the UE 100. That is, the timing advance command (field) indicates that the RA procedure for the LTM cell change can be skipped. In this case, the UE 100 performs RACH-less LTM. Here, the predetermined value may be defined in advance by a specification or the like and may be a value known between the base station 201 and the UE 100.

[0098] The control unit 120 of the UE 100 may execute the RACH-less LTM when the same TA as that of the source cell (the base station that manages the source cell) should be applied (or will be applied). The control unit 120 may execute the RACH-less LTM when the timing advance command (field) is the same as the TA applied in the current source cell. Alternatively, the cell change command may include, apart from the timing advance command (field), information (field) indicating (instructing) that the same TA as that of the source cell (the base station that manages the source cell) should be applied (or will be applied).

[0099] The information (fields) related to the CFRA resource may indicate the resource (e.g., radio resource, preamble index of which RA preamble to use, etc.) to be used when the UE 100 executes the CFRA.

[0100] Step S109: The transmitting unit 211 of the base station 201 transmits the cell change command by MAC CE to the UE 100. The receiving unit 112 of the UE 100 receives the cell change command from the base station 201 by MAC CE.

[0101] The control unit 120 of the UE 100 switches the setting of the target cell based on the identifier of the candidate cell (i.e., the target setting identifier) ​​included in the cell change command (MAC CE). For example, the control unit 120 applies the LTM candidate cell setting associated with the identifier of the candidate cell that is the same as the target setting identifier included in the cell change command (MAC CE). For example, the MAC layer in the UE 100 may notify the RRC layer of information (and the target setting identifier) ​​notifying that the cell change command (MAC CE) has been received. Furthermore, when the RRC layer in the UE 100 is provided with information (and the target setting identifier) ​​notifying that the cell change command has been received from the MAC layer, the RRC layer may apply the candidate cell setting information associated with the identifier of the candidate cell that is the same as the target setting identifier. That is, the UE 100 (the RRC layer) may apply the LTM candidate cell setting based on receiving information indicating that the cell change procedure has been triggered by the MAC layer (information indicating that the cell change procedure has been triggered from the MAC layer). Here, the LTM candidate cell configuration may be an LTM candidate cell configuration corresponding to a target configuration identifier indicated from the MAC layer.

[0102] The control unit 120 determines whether to execute the RACH-based LTM or the RACH-less LTM based on the value included in the timing advance command. When a predetermined value (e.g., FFF) is set in the timing advance command, the control unit 120 determines to execute the RACH-based LTM. On the other hand, when a value other than the predetermined value (e.g., FFF) is set in the timing advance command, the control unit 120 determines to execute the RACH-less LTM. The control unit 120 may determine to execute the RACH-less LTM when the same TA as that of the current source cell is (should be) applied. The control unit 120 may determine whether the same TA as that of the current source cell is (should be) applied based on information received from the base station 201 (e.g., information included in the RA response and / or information included in the cell change command).

[0103] When the control unit 120 of the UE 100 receives a cell change command by MAC CE from the base station 200, the control unit 120 executes a first cell change in accordance with the LTM setting information. In this operation example, the explanation will proceed assuming that the cell change is to a cell managed by the base station 201.

[0104] Step S110: When the control unit 120 of the UE 100 determines to perform the RACH-based LTM, the control unit 120 performs a random access (RA) procedure.

[0105] Step S111: When the UE 100 executes the RACH-based LTM, the control unit 120 of the UE 100 may consider that the LTM execution procedure has been successfully executed (i.e., LTM completion has been executed) when the random access (RA procedure) has been successfully completed. The control unit 230 of the base station 201 may determine that the LTM execution procedure has been successfully executed (i.e., LTM completion has been executed) based on reception of a preamble in the RA procedure (contention-free RA (CFRA)) or reception of message 3 or message A in the RA procedure (contention-based RA (CBRA)).

[0106] On the other hand, when UE 100 executes RACH-less LTM, transmission unit 111 of UE 100 transmits uplink transmission (for example, initial uplink data) to base station 201. When control unit 130 of UE 100 determines that the network has successfully received the uplink transmission, it may consider that the LTM execution procedure has been successfully executed (i.e., LTM completion has been executed).

[0107] The receiver 112 of the base station 201 receives an uplink transmission from the UE 100. The controller 230 of the base station 201 may recognize that the UE 100 has changed the serving cell to the target cell based on the reception of the uplink transmission (e.g., initial uplink data) in the target cell. As a result, the controller 230 may determine that the LTM execution procedure has been successfully executed (i.e., LTM completion has been executed).

[0108] Step S112: The control unit 130 of the UE 100 determines whether the second cell change is permitted. The control unit 130 may determine whether the execution of the subsequent LTM is permitted (or whether the subsequent LTM can be (executed)). Details of this determination will be described later.

[0109] If the second cell change is permitted, the control unit 130 may execute the process of step S121. On the other hand, if the second cell change is not permitted, the control unit 130 may end the process in this operation example. In this case, the control unit 130 may release the LTM setting information received from the source cell before the cell change.

[0110] In addition, the control unit 130 may perform communication with the target cell by applying RRC reconfiguration information (RRC reconfiguration message) included in the LTM candidate cell configuration of the candidate cell corresponding to the target cell based on the execution of the cell change. The control unit 120 of the UE 100 may disable the LTM candidate cell configuration of the candidate cell corresponding to the target cell based on the execution of the cell change to the target cell.

[0111] Steps S121 to S125: Steps S121 to S125 correspond to steps S107 to S110.

[0112] Note that, when the control unit 120 disables the LTM candidate cell configuration of a candidate cell corresponding to the target cell, the candidate cell associated with the LTM candidate cell configuration (i.e., the current serving cell) is not included in the target cell. Therefore, the control unit 120 does not include the current serving cell in the target of the L1 measurement report. The control unit 120 may perform control so that the L1 measurement report for the cell associated with the disabled LTM candidate cell configuration is not triggered.

[0113] Furthermore, the control unit 120 may, for example, omit transmitting an L1 measurement report for the source cell to the source cell. The control unit 120 may also perform control so that an L1 measurement report for a cell associated with an LTM candidate cell configuration including an identifier (e.g., a cell ID) of the source cell is not triggered.

[0114] Note that the UE 100 has not directly received an RRC reconfiguration message from the current serving cell (i.e., the target cell before the cell change) after the first cell change. Therefore, the cell change based on the cell change command in step S123 is a second cell change.

[0115] The control unit 120 may enable the disabled LTM candidate cell setting based on the execution of a cell change after the target cell is set as the source cell.

[0116] Step S126: As in step S112, the control unit 120 of the UE 100 may determine whether the second cell change is permitted in the current serving cell (i.e., the cell after the second cell change is performed).

[0117] As described above, the control unit 230 of the base station 201 generates an RRC message including one or more pieces of LTM configuration information. The transmission unit 211 of the base station 201 transmits the RRC message to the UE 100. The transmission unit 211 transmits a cell change command to the UE 100 by MAC CE to trigger a first cell change so that the UE 100 performs the first cell change in accordance with the LTM configuration information. The control unit 230 generates an RRC message based on the RRC message so that the UE 100 determines whether a second cell change, which is performed without receiving an RRC reconfiguration message after performing the first cell change, is permitted. Furthermore, the reception unit 112 of the UE 100 receives from the base station 200 an RRC message including LTM configuration information used to provide one or more LTM candidate cell configurations. When the control unit 130 receives a cell change command from the base station 200 via the MAC CE, which triggers a first cell change from the source cell of the base station 200 to a target cell, the control unit 130 executes the first cell change in accordance with the LTM configuration information. The control unit 130 determines, based on the RRC message, whether a second cell change, which is executed without receiving an RRC reconfiguration message after executing the first cell change, is permitted. This allows the UE 100 to determine whether the second cell change is permitted or not. For example, if the second cell change is not permitted, the UE 100 does not execute the second cell change, thereby preventing a cell change failure due to execution of the subsequent LTM. As a result, the UE 100 can appropriately execute the subsequent LTM.

[0118] Furthermore, when the UE 100 can execute the first LTM and the second LTM (i.e., subsequent LTM) based on the same LTM setting information, the UE 100 can distinguish whether the first LTM and the second LTM can be executed based on the RRC message. As a result, the network 10 can control the execution of the subsequent LTM.

[0119] (Determination Operation) Next, details of an example of the determination operation of UE 100 will be described with reference to Figures 8 to 10. The control unit 130 of UE 100 may determine whether or not the second cell change is permitted by at least one of the following methods. Note that the determination that the second cell change is permitted may be, for example, a determination that execution of the second cell change is instructed, that subsequent LTM is permitted, that subsequent LTM is executable, or that subsequent LTM is supported. On the other hand, the determination that the second cell change is not permitted may be, for example, a determination that non-execution of the second cell change is instructed, that subsequent LTM is not permitted, that subsequent LTM is not executable, or that subsequent LTM is not supported.

[0120] In the first method, the control unit 130 makes the determination based on whether or not the RRC reconfiguration information in the LTM candidate cell configuration includes predetermined LTM configuration information (see FIG. 9).

[0121] Step S211: The control unit 130 determines whether or not predetermined LTM configuration information used to provide an LTM candidate cell configuration in the cell after the change (i.e., the target cell before the cell change) is included in the RRC reconfiguration information.

[0122] If the predetermined LTM setting information is included in the RRC reconfiguration information, the control unit 130 executes the process of step S212. On the other hand, if the predetermined LTM setting information is not included in the RRC reconfiguration information, the control unit 130 executes the process of step S213.

[0123] For example, as shown in Fig. 8, the RRC reconfiguration message received by the UE 100 from the serving cell (source cell) includes RRC reconfiguration information (e.g., RRCReconfiguration) (see field E1 in Fig. 8). The RRC reconfiguration information includes LTM setting information (e.g., LTM-Config) applied in the serving cell (source cell) (see field E12 in Fig. 8). The LTM setting information corresponds to the LTM setting information described in step S102.

[0124] The LTM setting information includes an LTM addition modification list (e.g., ltm-CandidateToAddModList) (see field E22 in FIG. 8). The LTM addition modification list is a list of multiple LTM candidate information (e.g., first LTM candidate information (e.g., LTM-Candidate #1), second LTM candidate information (e.g., LTM-Candidate #2), ...) (see fields E31 and E32 in FIG. 8).

[0125] The first LTM candidate information (see field E31 in FIG. 8 ) includes an identifier of a first candidate cell (e.g., ltm-CandidateId#1) and a first LTM candidate configuration (e.g., ltm-candidateconfig). The first LTM candidate configuration (see field E312 in FIG. 8 ) includes RRC reconfiguration information (e.g., RRCReconfiguration) (see field E41 in FIG. 8 ). The RRC reconfiguration information may be an RRC reconfiguration message. Similarly, the second LTM candidate information E32 includes an identifier of a second candidate cell (e.g., ltm-CandidateId#2) and a second LTM candidate configuration. Each of the second LTM candidate configurations (see field E322 in FIG. 8) includes RRC reconfiguration information (e.g., RRCReconfiguration) (see field E42 in FIG. 8).

[0126] Here, it is assumed that UE 100 performs a cell change to a target cell corresponding to a candidate cell identified by the identifier of the first candidate cell. UE 100 performs a cell change according to the first LTM candidate information. In this case, the control unit 130 of UE 100 determines whether or not the RRC reconfiguration information (field E41) included in the first LTM candidate configuration (field E312) includes LTM configuration information (corresponding to predetermined LTM configuration information). For example, the control unit 130 determines whether or not the LTM configuration information is included in field E51 in the first LTM candidate configuration (field E312). Therefore, the LTM configuration information here is different from the LTM configuration information (field E12).

[0127] In addition, when the control unit 130 is performing a cell change in accordance with the second LTM candidate information, it determines whether or not the RRC reconfiguration information (field E52) included in the second LTM candidate setting (field E322) includes LTM setting information.

[0128] Step S212: The control unit 130 determines whether the content of the predetermined LTM setting information is null or whether it is specific information (the value of the specific information).

[0129] If the content of the predetermined LTM setting information is null, the control unit 130 executes the process of step S214.

[0130] If the content of the predetermined LTM setting information is specific information (i.e., the predetermined LTM setting information includes specific information), the control unit 130 executes the process of step S214. If the content of the predetermined LTM setting information is not specific information (i.e., the predetermined LTM setting information does not include specific information), the control unit 130 executes the process of step S213. The specific information may be, for example, information for releasing the LTM candidate cell setting. The specific information may be, for example, a value indicating that the content of the predetermined LTM setting information is null. The specific information may be, for example, a value indicating that subsequent LTM is not permitted. Therefore, the specific information is different from, for example, the LTM addition change list included in field E22. The specific information is information that does not provide (effective) LTM candidate cell setting, such as an LTM addition change list. Therefore, the predetermined LTM setting information including specific information may be set with only the value of the specific information. The effective LTM candidate cell setting may be, for example, a setting in which the UE 100 can perform LTM operation. The UE 100 may not be able to perform the LTM cell change based on specific information alone.

[0131] The control unit 120 may execute the process of step S214 when the content of the predetermined LTM setting information is only specific information, that is, when the content of the predetermined LTM setting information is specific information and does not include an LTM addition change list, etc. The control unit 120 may execute the process of step S213 when the predetermined LTM setting information provides a (substantial) LTM candidate cell setting such as an LTM addition change list.

[0132] Furthermore, the control unit 130 may execute the process of step S213 when the predetermined LTM setting information includes information for providing a (substantial) LTM candidate cell setting.

[0133] If the content of the predetermined LTM setting information is null, the control unit 130 may release the predetermined LTM setting information. If the content of the predetermined LTM setting information is specific information, the control unit 130 may release the predetermined LTM setting information.

[0134] Step S213: The control unit 130 determines that the subsequent LTM is permitted, that is, the control unit 130 determines that the second cell change is permitted.

[0135] If the second cell change is permitted, the control unit 130 may perform LTM and / or subsequent LTM according to the LTM setting information (see field E12).

[0136] Here, when the control unit 130 receives the RRC reconfiguration message (field E1), it may store the LTM setting information (field E12) in a predetermined location (for example, a variable (LTM setting information variable) (for example, LTM-configuration)) in the UE 100. The control unit 130 may control (execute) the LTM by referring to the stored content. Note that the variable (for example, LTM-configuration) may represent an LTM setting variable (for example, VarLTM-Config) and / or an LTM UE setting variable (for example, VarLTM-UE-Config) and / or an LTM serving cell initialization determination variable (for example, VarLTM-ServingCellNoResetIF). Here, LTM-configuration may include variables for LTM configuration (e.g., VarLTM-Config) and / or UE configuration variables for LTM (e.g., VarLTM-UE-Config) and / or variables for LTM serving cell initialization determination (e.g., VarLTM-ServingCellNoResetIF).

[0137] If the RRC reconfiguration (field E41) in the LTM candidate cell configuration does not include LTM configuration information, the control unit 130 may continue to store the LTM configuration information variable without updating or deleting it. The control unit 130 may control (execute) the LTM by referring to the stored content.

[0138] Furthermore, when the RRC reconfiguration (field E41) in the LTM candidate cell configuration includes LTM configuration information and the LTM configuration information includes information for providing the LTM candidate cell configuration, the control unit 120 updates and stores the LTM configuration information variable based on the information (for example, an LTM addition / change list). The control unit 120 of the UE 100 may control (execute) the LTM by referring to the updated stored content.

[0139] The UE 100 may be able to perform the LTM only in a state where there is an LTM setting information variable, for example. A state in which the UE 100 holds the LTM setting information variable may represent a "state in which the second cell change is permitted."

[0140] Step S214: The control unit 130 determines that the subsequent LTM is not permitted, that is, the control unit 130 determines that the second cell change is not permitted.

[0141] The control unit 130 may delete the LTM setting information variable if the RRC reconfiguration (field E41) in the LTM candidate cell configuration includes LTM setting information and the content of the LTM setting information is null (NULL) or specific information. In this case, the UE 100 does not have the LTM setting information variable, and therefore may not be able to perform the second cell change. A state in which the UE 100 does not hold the LTM setting information variable may represent a "state in which the second cell change is not permitted." In the second method, the control unit 130 makes a determination based on the determination information (see FIG. 10 ).

[0142] Step S221: The control unit 130 may determine, for example, whether the determination information indicates that the subsequent LTM is permitted. The control unit 130 may determine, for example, whether the determination information indicates that the second cell change is permitted.

[0143] When the determination information indicates that the subsequent LTM is permitted (e.g., the second cell change is permitted), the control unit 130 executes the process of step S222. On the other hand, when the determination information does not indicate that the subsequent LTM is permitted (e.g., the second cell change is permitted), the control unit 130 executes the process of step S223.

[0144] The SLTM decision information may be included in an RRC message, for example, the RRC reconfiguration message in step S105 may include the SLTM decision information.

[0145] The SLTM decision information may indicate, for example, whether a second cell change (or subsequent LTM) is permitted in all cells after the first cell change is performed. In this case, the SLTM decision information may be included in, for example, a field (e.g., field E11 in FIG. 8 ) separate from the LTM setting information (field E12). Furthermore, the SLTM decision information may be included in a field (e.g., field E21 in FIG. 8 ) separate from the field in the LTM addition / change list, which is a field in the LTM setting information (field E12).

[0146] The SLTM decision information may indicate, for example, whether a second cell change is permitted only in a cell changed according to the LTM candidate cell configuration including the SLTM decision information. Therefore, the SLTM decision information may indicate whether a second cell change is permitted only in one cell. In this case, the SLTM decision information may be included in each of one or more LTM candidate cell configurations. Furthermore, the SLTM decision information may be included in, for example, a field (e.g., field E311) in the LTM candidate cell configuration (e.g., field E311) that is different from a field in the LTM candidate configuration information (e.g., field E312). Furthermore, the SLTM decision information may be included in, for example, a field (e.g., field E51) in an RRC reconfiguration (e.g., field E41) applied when a cell change is performed.

[0147] If the SLTM determination information is included in both a field outside the LTM candidate cell setting (e.g., field E11 or E21) and a field within the LTM candidate cell setting (e.g., field E311 or E51), the control unit 130 may prioritize the SLTM determination information of the field within the LTM candidate cell setting over the SLTM determination information of the field outside the LTM candidate cell setting.

[0148] Steps S222 and S223: Steps S222 and S223 are similar to steps S213 and S214.

[0149] In this way, the control unit 130 may determine whether the second cell change is permitted based on the SLTM determination information, regardless of whether the predetermined LTM setting information is included in the RRC reconfiguration information. Therefore, the control unit 130 may determine that the second cell change is permitted even if the predetermined LTM setting information is included in the RRC reconfiguration information. In this case, the control unit 130 may execute the second cell change regardless of whether the predetermined LTM setting information is included in the RRC reconfiguration information. Furthermore, the control unit 130 may determine that the second cell change is not permitted even if the predetermined LTM setting information is not included in the RRC reconfiguration information. In this case, the control unit 130 may not execute the second cell change regardless of whether the predetermined LTM setting information is included in the RRC reconfiguration information.

[0150] As described above, the LTM configuration information may include RRC reconfiguration information to be applied in the post-change cell after the first cell change is executed. The control unit 130 of the UE 100 may determine whether the second cell change is permitted based on whether predetermined LTM configuration information used to provide an LTM candidate cell configuration in the post-change cell is included in the RRC reconfiguration information. This allows the UE 100 to make the determination based on the predetermined LTM configuration information.

[0151] Furthermore, the LTM configuration information may include RRC reconfiguration information to be applied in a post-change cell after the first cell change is executed. When predetermined LTM configuration information used to provide an LTM candidate cell configuration in a post-change cell is included in the RRC reconfiguration information, and when the predetermined LTM configuration information includes information for providing the LTM candidate cell configuration, the control unit 130 of the UE 100 may determine that the second cell change is permitted. This allows the UE 100 to determine that the second cell change is permitted without specifying a new information element. This reduces the impact on the mobile communication system 1 (or the technical specifications).

[0152] In addition, even if predetermined LTM setting information is included in the RRC reconfiguration information, if the content of the predetermined LTM setting information is null or information for releasing the LTM candidate cell setting, the control unit 130 may determine that the second cell change is not permitted. This allows the UE 100 to determine the predetermined LTM setting information.

[0153] Furthermore, the RRC message may include determination information indicating whether or not the second cell change is permitted. The control unit 130 may determine whether or not the second cell change is permitted based on the determination information. This allows the network 10 to explicitly indicate whether or not the second cell change is permitted by the determination information. For example, compared to a case in which the determination is made based on whether or not predetermined LTM setting information is included in the RRC reconfiguration information, the UE 100 may be able to determine whether or not the second cell change is permitted even when the RRC reconfiguration information is not applied (e.g., before applying the RRC reconfiguration information (e.g., at the time of the first LTM), during a flow other than the flow in which the RRC reconfiguration information applied in the post-change cell after executing the first cell change is applied, etc.). The UE 100 may be able to determine whether or not the second cell change is permitted earlier.

[0154] Furthermore, the LTM configuration information may include RRC reconfiguration information to be applied in a post-change cell after the first cell change is executed. The control unit 130 may determine whether or not the second cell change is permitted based on the determination information, regardless of whether predetermined LTM configuration information used to provide an LTM candidate cell configuration in the post-change cell is included in the RRC reconfiguration information. This makes it possible to determine whether or not to permit the second cell change, for example, even when the base station 200 that generates the determination information does not generate the predetermined LTM configuration information (i.e., when another base station 200 generates the predetermined LTM configuration information).

[0155] Furthermore, the determination information may indicate whether the second cell change is permitted in all cells after the first cell change is performed, thereby making it possible to reduce the amount of information in the entire determination information compared to when the determination information indicates whether the second cell change is permitted in each cell.

[0156] The determination information may be included in each of one or more LTM candidate cell configurations. The determination information may indicate whether or not a second cell change is permitted only in a cell changed according to the LTM candidate cell configuration including the determination information. This allows for determining whether or not a second cell change is permitted for each LTM candidate cell configuration, thereby enabling flexible control of subsequent LTM.

[0157] (Second Operation Example) A second operation example will be described with reference to Fig. 6 and Fig. 11. Previous descriptions may be omitted. In this operation example, the operation when the UE 100 does not support the second cell change (i.e., subsequent LTM) will be mainly described.

[0158] S301: Step S301 is the same as step S101. The transmitter 111 may transmit, to the base station 200, capability information indicating whether the UE 100 supports the second cell change.

[0159] Step S302: Step S302 may be the same as the operations from steps S102 to S111.

[0160] The control unit 230 of the base station 201 may generate an RRC message based on the capability information when receiving the capability information from the UE 100. The control unit 230 may generate an RRC reconfiguration message (the RRC reconfiguration message transmitted in step S105) based on the capability information.

[0161] For example, when the capability information indicates that the UE 100 does not support the second cell change, the control unit 230 may generate an RRC message so that the UE 100 determines that the second cell change is not permitted. Furthermore, even when the capability information indicates that the UE 100 supports the second cell change, the control unit 230 may generate an RRC message so that the UE 100 determines that the second cell change is not permitted for a cell for which the second cell change is not permitted.

[0162] The control unit 230 may generate an RRC reconfiguration message to be transmitted to the UE 100, for example, so that the RRC reconfiguration information included in each LTM candidate configuration (e.g., ltm-candidateconfig) includes LTM configuration information and the content of the LTM configuration information is null. The control unit 230 may generate an RRC reconfiguration message to be transmitted to the UE 100, for example, so that the RRC reconfiguration information included in each LTM candidate configuration (e.g., ltm-candidateconfig) includes LTM configuration information and the content of the LTM configuration information is specific information and the predetermined LTM configuration information does not include an LTM addition change list or the like. Therefore, the control unit 230 may generate an RRC reconfiguration message to be transmitted to the UE 100 so that the predetermined LTM configuration information does not provide a (substantial) LTM candidate cell configuration. Furthermore, the control unit 230 may include SLTM decision information indicating that the second cell change is not permitted in the RRC message.

[0163] In addition, if the capability information indicates that UE100 does not support the second cell change, the control unit 230 may generate LTM setting information so that UE100 does not perform the second cell change (i.e., subsequent LTM).

[0164] On the other hand, if the capability information indicates that UE 100 supports the second cell change, the control unit 230 may generate an RRC message so that UE 100 determines that the second cell change is permitted.

[0165] The control unit 230 may generate an RRC reconfiguration message to be transmitted to the UE 100, for example, so that the RRC reconfiguration information included in each LTM candidate configuration (e.g., ltm-candidateconfig) does not include LTM configuration information. Alternatively, the control unit 230 may generate an RRC reconfiguration message to be transmitted to the UE 100, for example, so that the RRC reconfiguration information included in each LTM candidate configuration (e.g., ltm-candidateconfig) includes LTM configuration information and the content of the LTM configuration information is not null. The control unit 230 may generate an RRC reconfiguration message to be transmitted to the UE 100, for example, so that the RRC reconfiguration information included in each LTM candidate configuration (e.g., ltm-candidateconfig) includes the LTM configuration information (e.g., predetermined LTM configuration information). Here, the content of the predetermined LTM setting information may not be null and may not be specific information. Therefore, the predetermined LTM setting information may provide a (substantial) LTM candidate cell setting by including an LTM addition change list, etc. The control unit 230 may include SLTM decision information indicating that the second cell change is permitted in the RRC message.

[0166] Step S303: Step S303 is the same as step S112 and the above-described determination operation. If the UE 100 does not support the second cell change, the control unit 130 may omit this step S303.

[0167] Step S304: When the UE 100 does not support the second cell change, the control unit 130 of the UE 100 may release the LTM setting information based on the execution of the first cell change. The control unit 130 may release the LTM setting information regardless of the determination based on the RRC message. Therefore, the control unit 130 may release the LTM setting information even when it is possible to determine that the second cell change is permitted based on the RRC message.

[0168] The control unit 130 may generate an RRC message indicating that the LTM setting information has been released, based on the release of the LTM setting information. For example, the control unit 130 may generate an RRC message including release information indicating that the LTM setting information has been released.

[0169] Step S305: The transmitter 111 of the UE 100 may transmit an RRC message indicating that the LTM setting information has been released in the post-change cell after the first cell change has been performed. The receiver 212 of the base station 201 that manages the post-change cell may receive the RRC message indicating that the LTM setting information has been released.

[0170] Step S306: When the control unit 230 of the base station 201 receives an RRC message indicating that the LTM setting information has been released, the control unit 230 may release the LTM setting information set in the UE 100. When the control unit 230 receives release information, for example, the control unit 230 may release the LTM setting information set in the UE 100.

[0171] If the control unit 130 has set a cell managed by the base station 202 as a candidate cell, i.e., if the LTM setting information includes an LTM candidate cell setting for the cell managed by the base station 202, the control unit 130 may perform the following processing.

[0172] Step S307: The transmitting unit 211 of the base station 201 transmits release information indicating that the UE 100 has released the LTM setting information to the base station 202. The receiving unit 212 of the base station 201 receives the release information from the base station 201.

[0173] The release information may be the same as or different from the release information received from the UE 100. The release information may be, for example, information indicating that the UE 100 has released the LTM candidate cell setting of the cell managed by the base station 202.

[0174] Step S308: When the control unit 230 of the base station 202 receives the release information, the control unit 230 may release the LTM candidate cell setting of the base station set in the UE 100.

[0175] As described above, when UE 100 does not support the second cell change, control unit 130 of UE 100 may release the LTM setting information based on the execution of the first cell change. When the LTM setting information is released, transmission unit 111 may transmit an RRC message indicating that the LTM setting information has been released in the post-change cell after the first cell change is executed. This allows base station 200 managing the post-change cell to know that UE 100 has released the LTM setting information. UE 100 and network 10 can share information that UE 100 has released the LTM setting information, thereby suppressing the occurrence of malfunctions due to misunderstandings regarding the LTM setting information.

[0176] Furthermore, the transmitting unit 111 may transmit capability information indicating whether or not the UE 100 supports the second cell change to the base station 200. This allows the base station 200 to know whether or not the UE 100 supports the second cell change. The base station 200 can generate LTM setting information based on the capability information.

[0177] (Other Embodiments) In the above-described embodiment, if the UE 100 does not support the second cell change based on the reception of the RRC reconfiguration message in step S105, the UE 100 may transmit, as release information, information indicating that the LTM configuration information will be released after the first cell change to the base station 201 in the source cell before the first cell change. In step S106, the UE 100 may transmit an RRC reconfiguration complete message including the information to the base station 201 in the source cell. Therefore, the release information may be sent from the UE 100 to the base station 201, and may be notified from the base station 201 to the base station 202.

[0178] Alternatively, if the UE 100 does not support the second cell change based on the reception of the RRC reconfiguration message in step S105, the UE 100 may have transmitted release information to the base station 202 in the new source cell (i.e., the old target cell) after the first cell change to the target cell. The UE 100 may transmit an RRC reconfiguration complete message including the release information to the base station 202 in the new source cell based on, for example, application of the RRC reconfiguration included in the LTM candidate cell configuration. Thus, the release information may be transmitted (notified) directly from the UE 100 to the base station 202.

[0179] Furthermore, when the UE 100 does not support the second cell change, the UE 100 may release the configuration related to only the subsequent LTM among the LTM configuration information based on the reception of the RRC reconfiguration message in step S105. The UE 100 may have transmitted, as release information, information indicating that the configuration related to only the subsequent LTM will be released after the first cell change to the base station 201 in the source cell before the first cell change. In step S106, the UE 100 may transmit an RRC reconfiguration complete message including the information to the base station 201 in the source cell.

[0180] In the above-described embodiment, the explanation has been focused on the permission of the second cell change, but the operation related to the permission (execution) of the second cell change may be replaced with the operation related to the permission (execution) of the subsequent LTM. Furthermore, the release (of information) performed by the UE 100 and the base station 200 may be replaced with, for example, discard, ignore, clear, deactivate, etc.

[0181] 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 the TS of either LTE or another generation system (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 toward the UE 100 in LTE. The mobile communication system 1 may be a system compliant with the 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.

[0182] 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 that complies with the TS of either LTE (Long Term Evolution) or another generation system (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 that complies with the TS of a standard other than the 3GPP standard.

[0183] The steps in the operations of 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 process. Furthermore, the above-described operational flows are not limited to being executed independently, but may be executed by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow.

[0184] A program may be provided that causes a computer to execute each process performed by the UE 100 or the base station 200. The program may be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on 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 Disc Read Only Memory). Furthermore, circuits that execute each process performed by the UE 100 or the base station 200 may be integrated, and at least a part of the UE 100 or the base station 200 may be configured as a semiconductor integrated circuit (chip set, SoC (System On Chip)).

[0185] In the above-described embodiments, "transmit" may mean performing 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 performing processing at least one layer and physically transmitting a signal wirelessly or via a wired connection. Similarly, "receive" may mean performing 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 the information. Similarly, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "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 rather 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.

[0186] 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.

[0187] (Additional Notes) Additional notes will be given regarding the features of the above-described embodiment.

[0188] (Supplementary Note 1) A communications device comprising: a receiver that receives, from a base station, a radio resource control (RRC) message including one or more Layer 1 / Layer 2 triggered mobility (LTM) configuration information used to provide LTM candidate cell configuration; and a controller that, when a cell change command that triggers a first cell change from a source cell of the base station to a target cell is received from the base station by a medium access control (MAC) control element (CE), performs the first cell change in accordance with the LTM configuration information, wherein the controller determines, based on the RRC message, whether a second cell change that is performed without receiving an RRC reconfiguration message after performing the first cell change is permitted.

[0189] (Supplementary Note 2) The communication device according to Supplementary Note 1, wherein the LTM configuration information includes RRC reconfiguration information to be applied in a post-change cell after executing the first cell change, and the control unit determines whether the second cell change is permitted based on whether predetermined LTM configuration information used to provide the LTM candidate cell configuration in the post-change cell is included in the RRC reconfiguration information.

[0190] (Supplementary Note 3) The communication device according to Supplementary Note 1 or 2, wherein the LTM setting information includes RRC reconfiguration information to be applied in a post-change cell after executing the first cell change, and the control unit determines that the second cell change is permitted when predetermined LTM setting information used to provide the LTM candidate cell setting in the post-change cell is included in the RRC reconfiguration information and the predetermined LTM setting information includes information for providing the LTM candidate cell setting.

[0191] (Supplementary Note 4) The communication device according to any one of Supplementary Notes 1 to 3, wherein the control unit determines that the second cell change is not permitted when the content of the predetermined LTM setting information is null or information for releasing the LTM candidate cell setting, even if the predetermined LTM setting information is included in the RRC reconfiguration information.

[0192] (Supplementary Note 5) The communication device according to any one of Supplementary Notes 1 to 4, wherein the RRC message includes determination information indicating whether or not the second cell change is permitted, and the control unit determines whether or not the second cell change is permitted based on the determination information.

[0193] (Supplementary Note 6) The communication device according to Supplementary Note 5, wherein the LTM configuration information includes RRC reconfiguration information to be applied in a post-change cell after executing the first cell change, and the controller determines whether the second cell change is permitted based on the determination information, regardless of whether predetermined LTM configuration information used to provide the LTM candidate cell configuration in the post-change cell is included in the RRC reconfiguration information.

[0194] (Supplementary Note 7) The communication device according to Supplementary Note 5 or 6, wherein the determination information indicates whether the second cell change is permitted in all cells after the first cell change is executed.

[0195] (Supplementary Note 8) The communication device according to any one of Supplementary Notes 5 to 7, wherein the determination information is included in each of the one or more LTM candidate cell configurations, and the determination information indicates whether the second cell change is permitted only in a cell changed in accordance with the LTM candidate cell configuration including the determination information.

[0196] (Supplementary Note 9) The communication device according to any one of Supplementary Notes 1 to 8, wherein the control unit releases the LTM configuration information based on execution of the first cell change when the communication device does not support the second cell change.

[0197] (Supplementary Note 10) The communication device according to Supplementary Note 9, further comprising: a transmitter configured to transmit, in a post-change cell after performing the first cell change, an RRC message indicating that the LTM setting information has been released, when the LTM setting information has been released.

[0198] (Supplementary Note 11) The communication device according to any one of Supplementary Notes 1 to 10, further comprising: a transmitter configured to transmit capability information indicating whether the communication device supports the second cell change to the base station.

[0199] (Supplementary Note 12) A base station comprising: a controller configured to generate a Radio Resource Control (RRC) message including one or more Layer 1 / Layer 2 Triggered Mobility (LTM) configuration information used to provide one or more LTM candidate cell configurations; and a transmitter configured to transmit the RRC message to a communication device, wherein the transmitter transmits a cell change command to the communication device by a Medium Access Control (MAC) control element (CE) to trigger a first cell change from a source cell of the base station to a target cell according to the LTM configuration information, and the controller generates the RRC message based on the RRC message so that the communication device determines whether a second cell change, which is performed without receiving an RRC reconfiguration message after performing the first cell change, is permitted.

[0200] (Supplementary Note 13) A communication method executed by a communication device, comprising: receiving from a base station a Radio Resource Control (RRC) message including one or more Layer 1 / Layer 2 Triggered Mobility (LTM) configuration information used to provide LTM candidate cell configuration; when a Medium Access Control (MAC) control element (CE) receives from the base station a cell change command triggering a first cell change from a source cell of the base station to a target cell, performing the first cell change according to the LTM configuration information; and determining, based on the RRC message, whether a second cell change is permitted after performing the first cell change without receiving an RRC reconfiguration message.

[0201] (Supplementary Note 14) A communication device (100) comprising: a receiver (112) that receives, from a base station (200), a radio resource control (RRC) message including one or more Layer 1 / Layer 2 triggered mobility (LTM) configuration information used to provide LTM candidate information, and receives, from the base station, a medium access control (MAC) control element (CE) including a cell change command that triggers an LTM cell change; and a controller (130) that executes the LTM cell change based on the cell change command and in accordance with the LTM candidate information, wherein the controller determines whether to execute a subsequent LTM cell change based on information set in the LTM configuration information.

[0202] (Supplementary Note 15) The communication device according to Supplementary Note 14, wherein the subsequent LTM cell change is performed without releasing the LTM candidate information after the LTM cell change is completed.

[0203] (Supplementary Note 16) The communication device according to Supplementary Note 14 or 15, wherein the control unit, when the LTM setting information includes an addition / change list of the LTM candidate information, adds and / or changes the LTM candidate information included in the addition / change list, when the LTM setting information includes a release list of the LTM candidate information, deletes the LTM candidate information included in the release list, and when specific information is set in the LTM setting information, releases the LTM setting information.

[0204] (Supplementary Note 17) A base station (200) comprising: a transmitter (211) that transmits to a communication device (100) a Radio Resource Control (RRC) message including one or more Layer 1 / Layer 2 Triggered Mobility (LTM) candidate information, and transmits to the communication device a Medium Access Control (MAC) control element (CE) including a cell change command that triggers an LTM cell change; and a controller (230) that controls, based on the cell change command, execution of an LTM cell change in accordance with the LTM candidate information, wherein the controller controls whether to execute a subsequent LTM cell change based on information set in the LTM setting information.

[0205] (Supplementary Note 18) The base station according to Supplementary Note 17, wherein the subsequent LTM cell change is performed without releasing the LTM candidate information after the LTM cell change is completed.

[0206] (Supplementary Note 19) The base station according to Supplementary Note 17 or 18, wherein the control unit, when the LTM setting information includes an addition / alteration list of the LTM candidate information, sets addition and / or alteration of the LTM candidate information based on the addition / alteration list, when the LTM setting information includes a release list of the LTM candidate information, sets deletion of the LTM candidate information based on the release list, and when the LTM setting information includes specific information, sets release of the LTM setting information based on the specific information.

[0207] (Supplementary Note 20) A communication method for a communication device (100), comprising: a step of receiving, from a base station (200), a radio resource control (RRC) message including one or more Layer 1 / Layer 2 triggered mobility (LTM) configuration information used to provide LTM candidate information; a step of receiving, from the base station using a medium access control (MAC) control element (CE), a cell change command for triggering an LTM cell change; and a step of performing an LTM cell change in accordance with the LTM candidate information based on the reception of the cell change command, wherein in the step of performing the LTM cell change, the communication method determines whether to perform a subsequent LTM cell change based on information set in the LTM configuration information.

[0208] (Supplementary Note 21) The communication method according to Supplementary Note 20, wherein the subsequent LTM cell change is performed without releasing the LTM candidate information after the LTM cell change is completed.

[0209] (Supplementary Note 22) The communication method according to Supplementary Note 20 or 21, wherein in the step of executing the LTM cell change, if the LTM setting information includes an addition / change list of the LTM candidate information, adding and / or changing the LTM candidate information included in the addition / change list, if the LTM setting information includes a release list of the LTM candidate information, deleting the LTM candidate information included in the release list, and if specific information is set in the LTM setting information, releasing the LTM setting information.

Claims

1. A communications device (100), comprising: a receiver (112) that receives from a base station (200) a radio resource control (RRC) message including one or more Layer 1 / Layer 2 triggered mobility (LTM) candidate information, and receives from the base station a medium access control (MAC) control element (CE) including a cell change command that triggers an LTM cell change; and a controller (130) that performs the LTM cell change in accordance with the LTM candidate information based on the cell change command, wherein the controller determines whether to perform a subsequent LTM cell change based on information set in the LTM setting information.

2. The communication device according to claim 1, wherein the subsequent LTM cell change is performed without releasing the LTM candidate information after the LTM cell change is completed.

3. The communication device according to claim 1 or 2, wherein the control unit adds and / or changes the LTM candidate information included in the addition / change list when the LTM setting information includes an addition / change list of the LTM candidate information, deletes the LTM candidate information included in the release list when the LTM setting information includes a release list of the LTM candidate information, and releases the LTM setting information when specific information is set in the LTM setting information.

4. A base station (200), comprising: a transmission unit (211) that transmits a radio resource control (RRC) message including one or more Layer 1 / Layer 2 triggered mobility (LTM) candidate information to a communication device (100), and transmits a medium access control (MAC) control element (CE) including a cell change command that triggers an LTM cell change to the communication device; and a control unit (230) that controls execution of an LTM cell change in accordance with the LTM candidate information based on the cell change command, wherein the control unit controls whether or not to execute a subsequent LTM cell change based on information set in the LTM setting information.

5. The base station according to claim 4, wherein the subsequent LTM cell change is performed without releasing the LTM candidate information after the LTM cell change is completed.

6. The base station according to claim 4 or 5, wherein the control unit, when the LTM setting information includes an addition / alteration list of the LTM candidate information, sets the addition and / or alteration of the LTM candidate information based on the addition / alteration list; when the LTM setting information includes a release list of the LTM candidate information, sets the deletion of the LTM candidate information based on the release list; and when the LTM setting information includes specific information, sets the release of the LTM setting information based on the specific information.

7. A communication method of a communication device (100), comprising: a step of receiving a radio resource control (RRC) message from a base station (200) including one or more Layer 1 / Layer 2 triggered mobility (LTM) setting information used to provide LTM candidate information; a step of receiving a cell change command from the base station using a medium access control (MAC) control element (CE) to trigger an LTM cell change; and a step of performing an LTM cell change in accordance with the LTM candidate information based on the reception of the cell change command, wherein in the step of performing the LTM cell change, the communication method determines whether to perform a subsequent LTM cell change based on information set in the LTM setting information.

8. The communication method according to claim 7, wherein the subsequent LTM cell change is performed without releasing the LTM candidate information after the LTM cell change is completed.

9. The communication method according to claim 7 or 8, wherein in the step of executing the LTM cell change, if the LTM setting information includes an addition / change list of the LTM candidate information, adding and / or changing the LTM candidate information included in the addition / change list; if the LTM setting information includes a release list of the LTM candidate information, deleting the LTM candidate information included in the release list; and if specific information is set in the LTM setting information, releasing the LTM setting information.

Images