Wireless terminal, radio access network node, and methods therefor

Abstract

This wireless terminal receives, from a radio access network (RAN) node, a configuration of each of one or more candidate cells for conditional L1 / L2-triggered mobility (LTM), and after receiving said configuration, evaluates an execution condition of the conditional LTM with respect to each of the one or more candidate cells. When an execution condition with respect to one candidate cell has been established, the wireless terminal transmits, to the RAN node, layer 1 signaling or layer 2 signaling indicating a transmission configuration indicator (TCI) state selected for said one candidate cell. In the conditional LTM, for example, this contributes to enabling the wireless terminal and a network to agree on recognition of the TCI state applied to a target cell.

Description

Wireless terminal, radio access network node, and methods thereof

[0001] TECHNICAL FIELD The present disclosure relates to wireless communication systems, and more particularly to mobility of wireless terminals.

[0002] The 3rd Generation Partnership Project (3GPP®) Release 18 specifies mechanisms and procedures for Layer-1 (L1) / Layer-2 (L2) Triggered Mobility (LTM) (see, for example, Non-Patent Documents 1-6). When a wireless terminal (i.e., User Equipment (UE)) in the Radio Resource Control (RRC)_CONNECTED state moves from the coverage area of ​​one cell to another, a serving cell change must be performed at some point. The serving cell change, as specified in 3GPP Release 17 and earlier, is triggered by Layer-3 (L3) measurements and involves reconfiguration with synchronization triggered by RRC signaling for the change of Primary Cell (PCell) and Primary Secondary Cell Group (SCG) Cell (PSCell), and the release and addition of Secondary Cells (SCells), if applicable.

[0003] In contrast, LTM is a procedure in which a base station (i.e., gNB) receives L1 measurement reports from a UE and, based on these, the gNB changes one or more serving cells of the UE through L2 signaling, specifically, Medium Access Control (MAC) Control Element (MAC CE). The gNB prepares one or more candidate cells and provides the candidate cell configurations to the UE through an RRC message. Then, the gNB selects one of the candidate cell configurations as the target configuration for LTM, triggering an LTM cell switch. The gNB sends a Cell Switch Command MAC CE to the UE. The Cell Switch Command MAC CE indicates the target configuration selected by the gNB (which corresponds to one target cell). In response to receiving the Cell Switch Command MAC CE, the UE initiates a cell switch to the target cell. The UE performs a Random Access Channel (RACH)-less LTM cell switch or a RACH-based LTM cell switch. Subsequent LTM between candidate cells (i.e., after LTM is triggered, the UE does not release other candidate cell configurations) can be performed without RRC reconfiguration. Candidate cell configurations can be added, modified, or released only by the network (i.e., gNB) via RRC signaling.

[0004] LTM supports both intra-gNB Distributed Unit (gNB-DU) mobility and intra-gNB-CU inter-gNB-DU mobility. LTM supports not only intra-frequency mobility but also inter-frequency mobility. LTM supports the following scenarios: PCell change in non-Carrier Aggregation (CA) scenario; PCell change without SCell change in CA scenario; PCell change with SCell change in CA scenario; and Dual Connectivity scenario. PCell change with SCell change in CA scenario includes a) the case where the target PCell or target SCell(s) is not the current serving cell (i.e., CA-to-CA scenario with PCell change), b) the case where the target PCell is the current SCell, and c) the case where the target SCell is the current PCell. The Dual Connectivity scenario includes at least a PSCell change without MN involvement.

[0005] Non-Patent Document 5 discloses details of the Cell Switch Command MAC CE. As mentioned above, the Cell Switch Command MAC CE is sent by the gNB to the UE to trigger an LTM cell switch by the UE to a target cell selected by the gNB. The Cell Switch Command MAC CE includes, among other fields, a Target Configuration ID field, a Timing Advance Command field, a Transmission Configuration Indicator (TCI) state ID field, an Uplink (UL) TCI state ID field, and a Random Access Preamble index field.

[0006] The Target Configuration ID field indicates the index of the candidate target configuration to be applied to the LTM cell switch. The candidate target configuration is the candidate cell configuration of the target cell selected by the gNB.

[0007] The Timing Advance Command field indicates whether Timing Advance (TA) is valid for the LTM target cell (i.e., the Special Cell (SpCell) corresponding to the target configuration indicated in the Target Configuration ID field). If the value of the Timing Advance Command field is set to FFF, this field indicates that valid timing adjustment is not available for the TA Group (TAG) of the LTM target cell. Otherwise, this field indicates the TA value used to control the amount of timing adjustment that the UE's MAC entity must apply, and indicates that the UE can skip the random access procedure for this LTM cell switch.

[0008] The TCI state ID field indicates and activates the TCI state of the LTM target cell (i.e., the SpCell of the target configuration indicated in the Target Configuration ID field). The TCI state indicated by the TCI state ID field is for a joint TCI state or a downlink TCI state. The UL TCI state ID field indicates and activates the uplink TCI state of the LTM target cell.

[0009] The Random Access Preamble index field indicates the random access preamble index of the contention-free random access resources.

[0010] 3GPP plans to consider extensions to LTM for 3GPP Release 19 (see, for example, Non-Patent Document 7). LTM extensions under consideration include conditional LTM (CLTM), which may also be called by other names such as UE triggered LTM. 3GPP aims to support CLTM, which includes defining the conditions to be evaluated by the UE to trigger CLTM (CLTM execution).

[0011] Non-Patent Documents 8-11 disclose findings and proposals regarding CLTM. Non-Patent Document 8 states that when CLTM is introduced, the LTM mechanisms of 3GPP Release 18, such as UE-based TA (not early TA) and RACH-less operation, can be reused to perform handover with low latency.

[0012] Non-Patent Document 9 describes the features and advantages of conditional reconfiguration, i.e., L3 conditional mobility, and states that CLTM can be considered to improve robustness. Non-Patent Document 9 discloses that potential enhancements for CLTM include L1 measurement-based execution conditions and enhanced procedures such as early TA acquisition.

[0013] Non-Patent Document 10 states that CLTM, i.e., UE-initiated LTM execution based on configured conditions, can be effective in improving the robustness of LTM. Non-Patent Document 10 includes the following description regarding CLTM: The UE autonomously executes LTM when configured conditions are met. The configured conditions relate to, for example, L1 / L2-based triggers and Beam Failure Detection (BFD). For CLTM execution, resources to be used in the target cell may be specified regardless of whether source cell notification is received. The resources to be used in the target cell include, for example, configured Scheduling Request (SR), Sunding Reference Signal (SRS), or Configured Grant (CG), and Dynamic Grant (DG) for the intra-DU case. For target cell synchronization, early synchronization (before conditional LTM is performed) may be required, which can be UE-based synchronization or an early LTM RACH with a Random Access Response (RAR) or MAC CE providing TA.

[0014] Non-Patent Document 11 includes the following description regarding CLTM: Applicable CLTM scenarios include Contention-Based Random Access (CBRA)-based CLTM, Contention-Free RA (CFRA)-based CLTM, and RACH-less CLTM. For CFRA-based CLTM, provisioning and validity management of CFRA resources need to be considered. For RACH-less CLTM, both RA-based and UE-based TA acquisition are supported for early TA acquisition. For RA-based early TA acquisition, RA including RAR is used as the baseline. For beam indication, pre-beam indication from the network is considered. In CLTM, it is important to reduce candidate cell management operations. For example, it is possible to reduce Channel State Information (CSI)-related operations and TA acquisition operations based on L3 measurements of candidate cells. Regarding the coexistence of 3GPP Release 18 LTM and CLTM, dynamic activation of CLTM evaluation for configured candidate cells is considered.

[0015] MediaTek Inc., vivo, "Introduction of NR further mobility enhancements in TS 38.300", R2-2313832, 3GPP TSG-RAN WG2 Meeting #124, Chicago, USA, November 13-17, 2023Huawei, Ericsson, Nokia, Nokia Shanghai Bell, ZTE, NEC, LG Electronics, Lenovo, Samsung, CATT, Google, "Introduction of L1L2Mob and S-CPAC", R3-238088, 3GPP TSG-RAN WG3 Meeting #122, Chicago, USA, November 13-17, 2023ZTE Corporation, Sanechips, CATT, "Introduction of NR further mobility enhancements in TS 37.340", R2-2313647, 3GPP TSG-RAN WG2 Meeting #124, Chicago, USA, November 13-17, 2023Ericsson, "Introduction of further NR mobility enhancements", R2-2314056, 3GPP TSG-RAN WG2 Meeting #124, Chicago, USA, November 13-17, 2023Huawei, HiSilicon, "Introduction of NR further mobility enhancements in TS 38.321", R2-2314040, 3GPP TSG-RAN WG2 Meeting #124, Chicago, USA, November 13-17, 2023Ericsson, Huawei, Nokia, Nokia Shanghai Bell, ZTE, NEC, LG Electronics Inc., Lenovo, CATT, Samsung, Qualcomm Incorporated, "Additions for L1 / L2 triggered mobility", R3-238152, 3GPP TSG-RAN WG3 Meeting #122, Chicago, USA, November 13-17, 2023Intel, "New WID: NR mobility enhancements Phase 4", RP-234036, 3GPP TSG RAN Meeting #102, Edinburgh, Scotland, December 11-15, 2023Samsung, "Scope of Mobility Enhancements in Rel-19", RP-232916, 3GPP TSG RAN Meeting #102, Edinburgh, Scotland, December 11-15, 2023vivo, "Views on Rel-19 Mobility enhancements (RAN2-led)", RP-233056, 3GPP TSG RAN Meeting #102, Edinburgh, Scotland, December 11-15, 2023Qualcomm Incorporated, "Views on scope for NR Mobility enhancements in Rel-19", RP-233214, 3GPP TSG RAN Meeting #102, Edinburgh, Scotland, December 11-15, 2023LG Electronics, " Work scope of mobility enhancements in Rel-19", RP-233466, 3GPP TSG RAN Meeting #102, Edinburgh, Scotland, December 11-15, 2023.

[0016] The inventors have investigated support for CLTM in cellular networks and found various challenges. One of these challenges relates to the recognition by the UE and the network (e.g., gNB or target or candidate DU) of the TCI state applied to the target cell. This TCI state may include joint TCI state or downlink TCI state, and may also include uplink TCI state. Specifically, in CLTM, it is unclear how the UE and the network agree on the recognition of the TCI state applied to the target cell. As mentioned above, in normal LTM specified in 3GPP Release 18, the gNB (e.g., source gNB-DU) decides to perform an LTM cell switch and sends a Cell Switch Command MAC CE to the UE in the serving cell. The Cell Switch Command MAC CE may include a TCI state ID field to indicate and activate the TCI state of the LTM target cell. However, in CLTM, the UE is expected to evaluate the execution conditions and, if the conditions are met, perform LTM autonomously. In other words, in CLTM, the UE may not receive a Cell Switch Command MAC CE from the gNB based on the cell switch decision made by the gNB.

[0017] One of the objectives of the embodiments disclosed herein is to provide an apparatus, a method, and a program that contribute to solving at least one of the problems related to CLTM, including the problems described above. It should be noted that this objective is only one of the objectives of the embodiments disclosed herein. Other objectives or objectives and novel features will become apparent from the description of this specification or the accompanying drawings.

[0018] A first aspect is directed to a wireless terminal configured to receive from a Radio Access Network (RAN) node a configuration for each of one or more candidate cells for conditional LTM, the wireless terminal configured, after receiving the configuration, to evaluate an execution condition for the conditional LTM for each of the one or more candidate cells, and the wireless terminal configured, if the execution condition is met for one of the one or more candidate cells, to transmit Layer 1 or Layer 2 signaling to the RAN node indicating a selected TCI state for the one candidate cell.

[0019] A second aspect is directed to a method performed by a wireless terminal, the method comprising the steps of: (a) receiving from a Radio Access Network (RAN) node a configuration for each of one or more candidate cells for conditional LTM; (b) after receiving the configuration, the wireless terminal evaluates an execution condition for the conditional LTM for each of the one or more candidate cells; and (c) if the execution condition is met for one of the one or more candidate cells, sending Layer 1 or Layer 2 signaling to the RAN node indicating a selected TCI state for the one candidate cell.

[0020] A third aspect is directed to a RAN node, configured to transmit a configuration for each of one or more candidate cells for conditional LTM to a wireless terminal, and after transmitting the configuration, receive Layer 1 or Layer 2 signaling transmitted by the wireless terminal in response to the wireless terminal determining that a condition for executing the conditional LTM is met for one of the one or more candidate cells, the Layer 1 or Layer 2 signaling indicating a TCI state selected for the one candidate cell.

[0021] A fourth aspect is directed to a method performed by a RAN node, the method including: (a) transmitting a configuration for each of one or more candidate cells for conditional LTM to a wireless terminal; and (b) receiving, after transmitting the configuration, Layer 1 or Layer 2 signaling transmitted by the wireless terminal in response to the wireless terminal determining that a condition for performing the conditional LTM is met for one of the one or more candidate cells, the Layer 1 or Layer 2 signaling indicating a selected TCI state for the one candidate cell.

[0022] A fifth aspect is directed to a wireless terminal configured to evaluate an execution condition for conditional LTM for each of one or more candidate cells. The wireless terminal is configured to perform a cell switch to one of the one or more candidate cells if the execution condition is met for the one candidate cell. For the cell switch, the wireless terminal is configured to determine whether to use a first cell switch procedure that skips a random access procedure based at least on whether the wireless terminal has a valid Timing Advance value and whether a reference signal beam for the one candidate cell, for which the execution condition is determined to be met, was used to acquire the valid Timing Advance value in an early Timing Advance acquisition procedure performed for the one candidate cell.

[0023] A sixth aspect is directed to a method performed by a wireless terminal, the method including: (a) evaluating an execution condition for conditional LTM for each of one or more candidate cells; and (b) performing a cell switch to one of the one or more candidate cells if the execution condition is met for the one candidate cell, wherein performing the cell switch includes determining whether to use a first cell switch procedure that skips a random access procedure based at least on whether the wireless terminal has a valid Timing Advance value and whether a reference signal beam for the one candidate cell for which the execution condition is determined to be met was used to acquire the valid Timing Advance value in an early Timing Advance acquisition procedure performed for the one candidate cell.

[0024] A seventh aspect is directed to a program, which includes a set of instructions (software code) that, when loaded into a computer, causes the computer to perform the method according to the second, fourth, or sixth aspect.

[0025] According to the above-described aspects, it is possible to provide an apparatus, a method, and a program that contribute to solving at least one of a plurality of problems related to CLTM, including the above-described problems.

[0026] 1 illustrates an example configuration of a wireless communication system according to one or more embodiments. 2 illustrates an example configuration of a wireless communication system according to one or more embodiments. 3 illustrates an example signaling procedure for LTM according to one or more embodiments. 4 illustrates an example signaling procedure for conditional LTM according to one or more embodiments. 5 illustrates a flowchart of an example UE operation according to one or more embodiments. 6 illustrates a flowchart of an example RAN node operation according to one or more embodiments. 7 illustrates an example CLTM-related operation performed by a RAN node and a UE according to one or more embodiments. 8 illustrates an example signaling between a UE, a CU, a source DU, and a candidate DU for intra-CU inter-DU CLTM according to one or more embodiments. 9 illustrates an example UE operation according to one or more embodiments. 10 illustrates an example RAN node operation according to one or more embodiments. 11 illustrates an example CLTM-related operation performed by a RAN node and a UE according to one or more embodiments. 12 illustrates an example signaling between a UE, a CU, a source DU, and a candidate DU for intra-CU inter-DU CLTM according to one or more embodiments. 13 illustrates an example UE operation according to one or more embodiments. 14 illustrates an example RAN node operation according to one or more embodiments. 15 illustrates an example CLTM-related operation performed by a RAN node and a UE according to one or more embodiments. 16 illustrates an example signaling between a UE, a CU, a source DU, and a candidate DU for intra-CU inter-DU CLTM according to one or more embodiments. 17 illustrates an example UE operation according to one or more embodiments. 1 is a block diagram illustrating an example configuration of a CU, a CU-CP, a CU-UP, and a DU, in accordance with one or more embodiments; 2 is a block diagram illustrating an example configuration of a UE, in accordance with one or more embodiments;

[0027] Hereinafter, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary.

[0028] The multiple embodiments described below may be used independently, or two or more embodiments may be combined as appropriate. These multiple embodiments may have different novel features. Therefore, these multiple embodiments may contribute to achieving different objectives or solving different problems, and may contribute to achieving different effects.

[0029] Each drawing is merely an example for describing one or more embodiments. Each drawing may not relate to only one particular embodiment, but may also relate to one or more other embodiments. As will be understood by those skilled in the art, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings to create, for example, an embodiment not explicitly shown or described. Not all features or steps shown in any one drawing are necessary to describe an exemplary embodiment, and some features or steps may be omitted. The order of steps described in any drawing may be changed as appropriate.

[0030] The following embodiments are described primarily for the 3GPP 5th generation mobile communication system (5G system), but may also be applied to other wireless communication systems that support technologies similar to 3GPP LTM.

[0031] As used herein, depending on the context, "if" may be interpreted to mean "when," "while," "at or around the time," "after," "upon," "in response to determining," "in accordance with a determination," or "in response to detecting." These expressions may be interpreted to have the same meaning, depending on the context.

[0032] First, the configurations and operations of several network elements common to several embodiments will be described. Figure 1 shows an example configuration of a wireless communication system related to several embodiments. In the example of Figure 1, the wireless communication system includes a gNB-CU 10, gNB-DUs 21 and 22, TRPs 31 to 34, and a UE 40. The UE 40 may also be referred to by other terms such as a radio terminal, a mobile terminal, a mobile station, or a wireless transmit receive unit (WTRU). Each element (network function) shown in Figure 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an application platform.

[0033] The gNB-CU10 and gNB-DUs 21 and 22 correspond to one gNB1. In other words, the gNB1 includes the gNB-CU10 and the gNB-DUs 21 and 22. Alternatively, the gNB1 includes the TRPs 31 to 34 in addition to the gNB-CU10 and the gNB-DUs 21 and 22. The gNB1 is an NG-RAN node. The gNB1 may also be referred to as a RAN node, a base station, a radio station, or an access point. The gNB-CU10, the gNB-DUs 21 and 22, and the TRPs 31 to 34 may also be referred to as a RAN node.

[0034] The gNB1 may be an en-gNB, which provides NR user plane and control plane protocol termination to the UE and operates as a secondary node for Evolved Universal Terrestrial Radio Access (E-UTRA)-NR Dual Connectivity (EN-DC).

[0035] The gNB-CU10 is a logical node that controls the operation of one or more gNB-DUs (e.g., gNB-DUs 21 and 22). The gNB-CU10 hosts the RRC, Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP) protocols of the gNB1 (or the RRC and PDCP protocols of the gNB). If the gNB1 is an en-gNB, the gNB-CU10 hosts the RRC and PDCP protocols of the en-gNB. The gNB-CU10 may include a Control Plane (CP) Unit (i.e., gNB-CU-CP) and one or more User Plane (UP) Units (i.e., gNB-CU-UPs).

[0036] Each of the gNB-DUs 21 and 22 is a logical node that hosts the Radio Link Control (RLC) layer and MAC layer of the gNB1 and hosts part of the gNB1's Physical (PHY) layer, i.e., the upper PHY layer. The remaining PHY layer signal processing, i.e., the lower PHY layer, is located in the TRPs 31 to 34. One gNB-DU supports one or more cells. One cell is supported by only one gNB-DU. In the example of FIG. 1, the gNB-DU 21 is connected to the TRPs 31 and 32, while the gNB-DU 22 is connected to the TRPs 33 and 34. The TRPs 31 to 34 provide separate cells 51 to 54, respectively. In other words, the gNB-DU 21 provides multiple cells 51 and 52, and the TRPs 31 and 32 correspond to the cells 51 and 52, respectively. Similarly, gNB-DU 22 provides multiple cells 53 and 54, and TRPs 33 and 34 correspond to cells 53 and 54, respectively.

[0037] Each of the TRPs 31-34 can communicate with the UE 40 using a beam. The TRPs 31-34 may also be referred to as Radio Units (RUs) or Remote Radio Heads (RRHs). Each of the TRPs 31-34 provides lower PHY layer signal processing and analog Radio Frequency (RF) signal processing. Each TRP includes or is connected to one or more antenna arrays. Each TRP has multiple RF chains equal to or less than the total number of antenna elements included in the one or more antenna arrays. Each TRP also includes a Digital Front End (DFE). The DFE provides lower PHY layer signal processing and digital radio signal processing. The lower PHY layer signal processing includes, for example, fast Fourier transform (FFT) and inverse FFT (IFFT). The lower PHY layer signal processing may further include cyclic prefix (CP) addition and removal, and physical RACH (PRACH) extraction or filtering. Digital radio signal processing may include, for example, digital pre-distortion (DPD), crest factor reduction (CFR), digital up-conversion (DUC), digital down-conversion (DDC), and transmit and receive baseband channel filters. The DFE may perform digital baseband precoding for beamforming. If a hybrid beamforming scheme is employed, an analog beamformer circuit or analog precoder (e.g., a phase shifter matrix) may be located between one or more antenna arrays and multiple RF chains.

[0038] The interface between the gNB-CU 10 and each of the gNB-DUs 21 and 22 is an F1 interface. A direct interface, connection, or backhaul may be provided to communicatively connect the gNB-DU 21 and the gNB-DU 22. Similarly, a direct interface, connection, or backhaul may be provided to communicatively connect two TRPs serving adjacent cells, for example, between TRPs 31 and 32, between TRPs 32 and 33, and between TRPs 33 and 34.

[0039] Figure 2 shows an example configuration of a gNB1. In the example of Figure 2, the gNB-CU10 includes a gNB-CU-CP11 and one or more gNB-CU UPs 12. The gNB-CU-CP11 is a logical node that hosts the control plane portion of the gNB-CU10's RRC and PDCP protocols. The gNB-CU-CP11 terminates an E1 interface connected to each gNB-CU-UP and an F1-C interface connected to each gNB-DU. The E1 interface uses the E1 Application Protocol (E1AP). The F1-C interface uses the F1 Application Protocol (F1AP). The gNB-CU-CP11 also terminates an NG-C interface connected to a control plane node (i.e., Access and Mobility management Function (AMF)) in the core network.

[0040] The gNB-CU-UP 12 is a logical node that hosts the user plane portion of the PDCP protocol of the gNB-CU 10 for the en-gNB, or the user plane portion of the PDCP protocol and the SDAP protocol of the gNB-CU 10 for the gNB. The gNB-CU-UP 12 terminates the E1 interface connected to the gNB-CU-CP 11 and the F1-U interface connected to each gNB-DU. The F1-U interface uses a General Packet Radio Service Tunneling Protocol User Plane (GTP-U) tunnel. The gNB-CU-UP 12 also terminates the NG-U interface connected to a user plane node (i.e., User Plane Function (UPF)) in the core network.

[0041] The gNB1 and the UE 40 support LTM (normal LTM and CLTM). In this specification, the term "LTM" refers to a broad concept that includes both normal LTM (normal LTM) and conditional LTM. The term "normal LTM (or normal LTM)" refers to non-conditional LTM as defined in 3GPP Release 18. Specifically, normal LTM is an LTM in which the UE 40 performs an LTM cell switch in response to the UE 40 receiving a layer 1 or layer 2 cell switch command from a source DU. In contrast, in CLTM, the UE 40 evaluates an execution condition set by the network, and performs an LTM cell switch in response to the UE 40 determining that the execution condition is met.

[0042] Regular LTM is a procedure in which the gNB1 receives L1 measurement reports from the UE 40 and, based on the reports, changes one or more serving cells (e.g., cell groups) of the UE 40 through L1 or L2 signaling (e.g., MAC CE). The gNB1 prepares one or more candidate cells and provides candidate cell configurations to the UE 40 through an RRC message. Then, the gNB1 selects one of the candidate cell configurations as a target configuration for regular LTM, triggering an LTM cell switch. Candidate cell configurations can only be added, changed, or released by the network (i.e., the gNB1) via RRC signaling. However, as an exception, the UE 40 may autonomously release or remove at least some of the candidate cell configurations only in certain circumstances or when certain conditions are met.

[0043] In both regular LTM and CLTM, the LTM candidate cell configuration may be provided on top of the reference configuration or as a delta configuration to the reference configuration. The reference configuration is managed separately from the delta configuration of each candidate cell, and the UE 40 stores the reference configuration as a configuration separate from the delta configuration of each candidate cell. In both regular LTM and CLTM, security is not updated during LTM (or LTM execution or LTM cell switch execution). In both regular LTM and CLTM, subsequent LTM between candidate cells (i.e., after LTM is triggered, the UE 40 does not release other candidate cell configurations) can be performed without RRC reconfiguration.

[0044] In both normal LTM and CLTM, the LTM candidate cell configuration includes multiple candidate Transmission Configuration Indicator (TCI) state configurations. Each candidate TCI state configuration indicates a reference signal that serves as a path loss reference for at least one of the Physical Downlink Control Channel (PDCCH), Physical Downlink Shared Channel (PDSCH), Physical Uplink Control Channel (PUCCH), and Physical Uplink Sheared Channel (PUSCH) in the corresponding candidate TCI state.

[0045] The TCI state (or TCI state ID or TCI state setting) indicates the Quasi Co-Location (QCL) relationship between the antenna port used for downlink or uplink transmission and the antenna port used for transmitting a specific reference signal. Two antenna ports are said to be QCLed (Quasi Co-located) if the characteristics of the channel through which symbols on one antenna port are transmitted can be inferred from the channel through which symbols on the other antenna port are transmitted. QCL is an index that indicates the statistical properties of a signal or channel. If two antenna ports or two signals transmitted on these two antenna ports are QCLed, it means that these two signals have passed through similar wireless channels that share similar characteristics in at least one of Doppler shift, Doppler spread, average delay, delay spread, and spatial reception (Rx) parameters. If two antenna ports are QCLed, the two signals transmitted on these two antenna ports can be considered to arrive at the receiver through similar channels. Therefore, if the receiver can detect one signal and know the channel characteristics of that signal, the channel characteristics can help it detect the other signal.

[0046] The specific downlink transmission may be, for example, a PDCCH transmission or a PDSCH transmission. The specific uplink transmission may be, for example, a PUCCH transmission or a PUSCH transmission. The specific reference signal may be, for example, a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) or a Channel State Information (CSI) Reference Signal (CSI-RS).

[0047] The TCI state indicates, for example, the QCL relationship between the antenna port used for PDSCH transmission and the antenna port used for transmitting a specific SSB or a specific CSI-RS. Additionally or alternatively, the TCI state indicates the QCL relationship between the antenna port used for PDCCH transmission and the antenna port used for transmitting a specific SSB or a specific CSI-RS. In other words, the TCI state indicates, for example, the QCL relationship between the Demodulation Reference Signal (DMRS) port used for demodulating the PDSCH or PDCCH and a specific downlink SSB or CSI-RS port.

[0048] LTM (regular LTM and CLTM) supports both intra-gNB-DU mobility and intra-gNB-CU inter-gNB-DU mobility. LTM supports not only intra-frequency mobility but also inter-frequency mobility. LTM supports the following scenarios: PCell change in a non-CA scenario; PCell change without SCell change in a CA scenario; PCell change with SCell change in a CA scenario; and Dual Connectivity scenario. PCell change with SCell change in a CA scenario includes a) the case where the target PCell or target SCell(s) is not the current serving cell (i.e., CA-to-CA scenario with PCell change), b) the case where the target PCell is the current SCell, and c) the case where the target SCell is the current PCell. Dual Connectivity scenarios include at least a PSCell change without MN involvement.

[0049] The mobility 120 shown in Fig. 1 is intra-DU (intra-DU) LTM. Specifically, the UE 40 moves from the beam of the cell 52 of the TRP32 associated with the same gNB-DU21 to the beam of the cell 51 of the TRP31. In contrast, the mobility 140 shown in Fig. 1 is inter-DU (inter-DU) LTM. Specifically, the UE 40 moves from the beam of the cell 52 of the TRP32 associated with the gNB-DU21 to the beam of the cell 53 of the TRP33 associated with another gNB-DU22.

[0050] Before and after the LTM cell switch, the termination points of radio bearers (e.g., Signaling Radio Bearers (SRBs), Data Radio Bearers (DRBs)) for the UE 40 are fixed at the gNB-CU10 and remain unchanged. One or more QoS flows belonging to the PDU session of the UE 40 pass through the same gNB-CU10 (e.g., gNB-CU-UP) after the LTM cell switch as before the switch. Therefore, radio bearer configurations may be inherited or maintained in the UE 40 and the gNB1 (i.e., gNB-CU10, or gNB-CU10 and the (target) gNB-DU 21 or 22) before and after the LTM. Alternatively, the target gNB-DU (e.g., gNB-DU 22) or gNB-CU10 may have transmitted radio bearer configurations for the target cell to the UE 40 via the source gNB-DU (e.g., gNB-DU 21) during LTM preparation. If UE 40 does not receive explicit radio bearer configuration for after the LTM cell switch from gNB1 (e.g., gNB-CU10 or target gNB-DU), UE 40 may carry over the radio bearer configuration in the serving cell to the target cell after the LTM cell switch. In other words, UE 40 may continue to use the radio bearer configuration in the serving cell in the target cell after the LTM cell switch.

[0051] The control plane handling for normal LTM will be described in more detail below. A cell switch command (or cell switch trigger information) sent by the gNB1 to the UE 40 may be conveyed in a MAC CE (i.e., LTM Cell Switch Command MAC CE). This MAC CE includes at least an index (i.e., Target Configuration ID) of a candidate target configuration associated with a target cell selected by the gNB1 from one or more prepared LTM candidate cells. Simultaneously with the LTM triggered by the MAC CE, activation of one or more SCells associated with the candidate target configuration may be performed. The UE 40 may perform CBRA or CFRA during a cell switch.

[0052] The Cell Switch Command MAC CE is sent by gNB1 to UE 40 to trigger an LTM cell switch by UE 40 to a target cell selected by gNB1. The Cell Switch Command MAC CE includes, among other fields, a Target Configuration ID field, and may further include a Timing Advance Command field, a TCI state ID field, an Uplink (UL) TCI state ID field, and a Random Access Preamble index field.

[0053] The Target Configuration ID field indicates the index of the candidate target configuration to be applied to the LTM cell switch. The candidate target configuration is the candidate cell configuration of the target cell selected by gNB1.

[0054] The Timing Advance Command field indicates whether Timing Advance (TA) is valid for the LTM target cell (i.e., the Special Cell (SpCell) corresponding to the target configuration indicated in the Target Configuration ID field). If the value of the Timing Advance Command field is set to FFF, this field indicates that valid timing adjustment is not available for the TA Group (TAG) of the LTM target cell. Otherwise, this field indicates a TA value used to control the amount of timing adjustment that the MAC entity of UE 40 must apply, and indicates that UE 40 can skip the random access procedure for this LTM cell switch.

[0055] The TCI state ID field indicates and activates the TCI state of the LTM target cell (i.e., the SpCell of the target configuration indicated in the Target Configuration ID field). The TCI state indicated by the TCI state ID field is for a joint TCI state or a downlink TCI state. The UL TCI state ID field indicates and activates the uplink TCI state of the LTM target cell.

[0056] The Random Access Preamble index field indicates the random access preamble index of the contention-free random access resources.

[0057] If the UE 40 has a valid Timing Advance (TA) of the target cell and does not need to acquire the TA of the target cell during an LTM cell switch, the UE 40 can skip the random access procedure. An LTM cell switch procedure in which the UE skips the random access procedure is called RACH-less LTM. The UE 40 can acquire the TA through early TA acquisition. Early TA acquisition is triggered by a Physical Downlink Control Channel (PDCCH) order or achieved by UE-based TA measurement.

[0058] In early TA acquisition via a PDCCH order, the gNB1 (e.g., source DU) triggers the UE 40 to perform CFRA to a candidate cell via a PDCCH order via the serving cell. The UE 40 transmits a first random access message (e.g., a random access preamble) to the candidate cell. To minimize data interruption in the serving cell due to the CFRA to the candidate cell, the UE 40 does not monitor or receive a random access response from the candidate cell. The serving cell may also be referred to as a source cell from a mobility (e.g., LTM) perspective. The candidate cell does not transmit a random access response to the CFRA. The TA value of the candidate cell is indicated to the UE 40 by the LTM Cell Switch Command MAC CE. Note that the TA value of the candidate cell is indicated in the LTM Cell Switch Command MAC CE only when the candidate cell is selected as a target cell for cell switch. Alternatively, the TA value of the candidate cell may be refined as indicated in the LTM Cell Switch Command MAC CE regardless of whether the candidate cell is selected as a target cell for cell switch.

[0059] UE-based TA measurement is configured by RRC in the UE 40. In UE-based TA measurement, the UE 40 derives the TA of the candidate cell based on the reception timing difference between the current serving cell and the candidate cell and the TA value of the current serving cell.

[0060] 3 shows an example of the overall procedure of normal LTM. Subsequent LTMs are performed by repeating the procedures of early synchronization, LTM execution, and LTM completion without releasing other candidate cell settings after each LTM completion. Note that early synchronization is intended to allow UE 40 to synchronize with a candidate cell before the LTM execution phase and skip the random access procedure in the LTM execution phase. However, early synchronization is optional and does not necessarily have to be performed.

[0061] Steps 301 to 304 are the LTM preparation phase. In step 301, UE 40 in an RRC_CONNECTED state sends an L3 measurement report to gNB1. Specifically, UE 40 transmits a MeasurementReport message to gNB1. The MeasurementReport message indicates L3 measurement results. The MeasurementReport message may indicate measurement results of the serving cell and neighboring cells. The measurement results for each cell include Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), or Signal-to-Interference and Noise Ratio (SINR), or any combination thereof.

[0062] In step 302, based on the L3 measurement report, gNB1 decides to use LTM and starts preparing one or more LTM candidate cells. An LTM candidate cell may also be referred to as an LTM candidate target cell. In step 303, gNB1 sends an RRCReconfiguration message to UE 40, including the configuration of one or more LTM candidate cells. In step 304, UE 40 stores the configuration of one or more LTM candidate cells and sends an RRCReconfigurationComplete message to gNB1.

[0063] Step 305 is the early synchronization phase, in which UE 40 may perform downlink (DL) synchronization and uplink (UL) TA acquisition with one or more candidate cells before receiving the LTM cell switch command.

[0064] Steps 306 to 310 are the LTM execution phase. In step 306, the UE 40 performs L1 measurements on the configured LTM candidate cells and sends L1 measurement reports to the gNB1. The L1 measurement reports may be carried by L1 signaling (e.g., Uplink Control Information (UCI)) or MAC CE. In step 307, the gNB1 decides to perform an LTM cell switch to one of the prepared candidate cells and sends an LTM cell switch command (i.e., LTM Cell Switch Command MAC CE) including an identifier of the target cell (e.g., LTM candidate ID) to the UE 40 (step 308). The LTM switch command includes a Target Configuration ID associated with the target cell, triggering the UE 40 to perform an LTM cell switch. In step 309, the UE 40 switches to the target cell configuration specified by the gNB1. In other words, the UE 40 detaches from the source cell and applies the target cell configuration. In step 310, if a TA is not available, the UE 40 performs a random access procedure towards the target cell.

[0065] Step 311 is the LTM completion phase. The UE 40 completes the LTM cell switch procedure by sending an RRCReconfigurationComplete message to the target cell. Alternatively, if the UE 40 performs a random access procedure in the LTM execution phase, the UE 40 determines that the execution of the LTM cell switch has been successfully completed when the random access procedure has been successfully completed. In the case of RACH-less LTM, the UE 40 determines that the execution of the LTM cell switch has been successfully completed when the UE 40 determines that the network has successfully received the first uplink data.

[0066] 4 shows an example of the overall procedure of CLTM. Subsequent CLTMs are performed by repeating the procedure of early synchronization, CLTM execution, and CLTM completion without releasing other candidate cell settings after each CLTM completion. Note that early synchronization is intended to allow UE 40 to synchronize with a candidate cell before the CLTM execution phase and skip the random access procedure during the CLTM execution phase. However, early synchronization is optional and does not necessarily have to be performed.

[0067] Steps 401 to 404 are the CLTM preparation phase. In step 401, UE 40 in RRC_CONNECTED state sends an L3 measurement report to gNB 1. Step 401 may be the same as step 301 in FIG. 3 .

[0068] In step 402, based on the L3 measurement report, gNB1 decides to use CLTM and starts preparing one or more CLTM candidate cells. A CLTM candidate cell may also be called a CLTM candidate target cell. In step 403, gNB1 sends an RRCReconfiguration message to UE 40, which includes the configuration of one or more CLTM candidate cells and the CLTM execution condition for each candidate cell. In step 404, UE 40 stores the CLTM candidate cell configuration and the CLTM execution condition, and sends an RRCReconfigurationComplete message to gNB1.

[0069] Note that gNB1 may decide to use both regular LTM and CLTM. CLTM cell switch may be used for some of the multiple candidate cells prepared in steps 402 and 403, and regular LTM cell switch may be used for the remaining cells. For example, a CLTM cell switch triggered by UE 40 determining that an execution condition is met may be applied to a cell switch from a source cell (serving cell) or a first candidate cell to another candidate cell, while a regular LTM cell switch triggered by an LTM cell switch command by gNB1 may be applied to a cell switch from a second candidate cell to another candidate cell. In another example, a CLTM cell switch may be applied to a cell switch from a source cell to a first candidate cell, while a regular LTM cell switch may be applied to a cell switch from a source cell to a second candidate cell.

[0070] Additionally or alternatively, CLTM cell switch and normal LTM may be used for the purpose of cell switch from a source cell to the same candidate cell or cell switch between the same candidate cell pair. In this case, UE 40 may perform cell switch triggered by either the satisfaction of a CLTM execution condition or the receipt of an LTM cell switch command from gNB1, whichever occurs first. Note that even when UE 40 performs LTM cell switch triggered by the LTM cell switch command received from gNB1, it also retains CLTM-specific settings (e.g., CLTM execution conditions) for subsequent CLTM.

[0071] Step 405 is an early synchronization phase in which UE 40 may perform DL synchronization and UL TA acquisition with one or more candidate cells. Step 405 may be performed in parallel with step 406, which will be described below.

[0072] Step 406 is a CLTM evaluation phase in which the UE 40 evaluates the CLTM execution conditions of each candidate cell.

[0073] Steps 407 and 408 are CLTM execution phases. In step 407, UE 40 determines that the execution conditions are met for any of the candidate cells and decides to execute a cell switch to the candidate cell. UE 40 detaches from the source cell and applies the target cell configuration. In step 408, if TA is not available, UE 40 executes a random access procedure toward the target cell.

[0074] In some implementations, in step 4071, after determining that an execution condition is met for any candidate cell (i.e., target cell) (and before detaching from the source cell), the UE 40 may transmit L1 or L2 (L1 / L2) signaling to the gNB1 (e.g., source DU) in the source cell. The L1 / L2 signaling includes an identifier or index (e.g., Target Configuration ID) indicating the target cell or a candidate target configuration associated with the target cell. The L1 / L2 signaling in step 4071 may further indicate that the cell switch by the UE 40 using CLTM is performed in a RACH-less or CFRA-based manner. The L1 / L2 signaling may be a MAC CE. The name of the MAC CE may be, for example, CLTM Indication MAC CE or CLTM Triggering Indication MAC CE. Alternatively, the L1 / L2 signaling may be UCI on the PUCCH.

[0075] The L1 / L2 signaling in step 4071 enables UE 40 to inform gNB1 that the CLTM execution condition has been met for the target cell or that a CLTM cell switch to the target cell will be initiated, although step 4071 may be omitted.

[0076] After or in response to receiving the L1 / L2 signaling in step 4071, the source DU may notify the CU of the initiation of a CLTM cell switch. This notification may include the target cell ID. This notification may be performed using an F1AP message, such as a DU-CU CELL SWITCH NOTIFICATION message. Furthermore, the CU may notify a candidate DU (i.e., target DU) serving the target cell of the initiation of a CLTM cell switch to the target cell. The notification from the CU to the target DU may include the target cell ID. This notification may be performed using an F1AP message, such as a CU-DU CELL SWITCH NOTIFICATION message. In other words, the source DU may notify the target DU via the CU of the initiation of a CLTM cell switch to the target cell. These signalings allow the target DU to know that the UE 40 has initiated a CLTM cell switch to the target cell. In other words, these signalings allow the target DU to know that the cell switch to the target cell initiated by the UE 40 is based on CLTM rather than normal LTM.

[0077] Step 409 is the CLTM completion phase, which may be similar to step 311 in FIG.

[0078] <First Embodiment> A configuration example of a wireless communication system according to this embodiment is similar to the configuration example described with reference to Fig. 1 and Fig. 2. This embodiment relates to details for the UE 40 and the network (e.g., gNB1 or target or candidate DU) to agree on recognition of the TCI state applied to the target cell when the UE 40 performs a CLTM cell switch.

[0079] 5 shows an example of the operation of UE 40. In step 501, UE 40 receives configurations of each of one or more candidate cells for CLTM from gNB1 (e.g., CU10 or source DU). As already described, UE 40 may receive the candidate cell configurations from gNB1 via an RRC message (e.g., RRCReconfiguration message). Step 501 may correspond to step 403 in FIG. 4.

[0080] In step 502, UE 40 evaluates the CLTM execution condition for each of one or more candidate cells. As already described, UE 40 may receive the CLTM execution condition for CLTM to each of one or more candidate cells from gNB1. The CLTM execution condition may be generated by the source DU, candidate DU, or CU and provided to UE 40 via the source DU and source cell. Step 502 may correspond to step 406 of FIG. 4.

[0081] In step 503, UE 40 determines that an execution condition is met for one of the one or more candidate cells. Then, UE 40 transmits L1 or L2 (L1 / L2) signaling to gNB1 (e.g., CU10 or source DU) indicating the TCI state selected for the candidate cell. Specifically, UE 40 may transmit the L1 / L2 signaling toward the source DU in the CLTM source cell. After transmitting the L1 / L2 signaling, UE 40 may initiate a cell switch to the target cell (i.e., the candidate cell for which the CLTM execution condition is met).

[0082] The L1 / L2 signaling may include an identifier (e.g., TCI state ID) for identifying a TCI state selected by the UE 40 or a TCI state configuration corresponding to the selected TCI state. As described above, each candidate cell configuration provided in step 501 may include multiple candidate TCI state configurations. Each candidate TCI state configuration indicates a reference signal (e.g., SSB or CSI-RS) that serves as a path loss reference for at least one of the PDCCH, PDSCH, PUCCH, and PUSCH in the corresponding candidate TCI state. The UE 40 may select one TCI state (one TCI state configuration) from the multiple candidate TCI state configurations of the candidate cell for which the CLTM execution condition is satisfied and notify the gNB 1 of the selected TCI state. The selected TCI state is used by the UE 40, for example, when performing a RACH-less cell switch or a CFRA-based cell switch in CLTM to the target cell.

[0083] The L1 / L2 signaling in step 503 may be a MAC CE. The name of the MAC CE may be, for example, CLTM Indication MAC CE or CLTM Triggering Indication MAC CE. Alternatively, the L1 / L2 signaling in step 503 may be a UCI transmitted on a PUCCH. The L1 / L2 signaling in step 503 may further include an identifier or index (e.g., Target Configuration ID) indicating the target cell or indicating a candidate target configuration associated with the target cell. The L1 / L2 signaling may further indicate a TA value obtained by measurement by the UE 40 and applied to the target cell. The L1 / L2 signaling may further indicate that the cell switch via CLTM by the UE 40 is performed in a RACH-less or CFRA-based manner.

[0084] 6 shows an example of the operation of the gNB1. In step 601, the gNB1 transmits configurations of one or more candidate cells for CLTM to the UE 40. The gNB-CU 10 may transmit an RRC message (e.g., an RRCReconfiguration message) including the candidate cell configurations to the UE 40 via the source DU (e.g., the gNB-DU 21) and the source cell. Step 601 may correspond to step 403 in FIG. 4.

[0085] In step 602, the gNB1 (e.g., gNB-CU10 or source DU) receives L1 / L2 signaling transmitted by the UE 40 in response to the UE 40 determining that the CLTM execution condition is met for one of one or more candidate cells. The L1 / L2 signaling indicates the TCI state selected by the UE 40 for the candidate cell (i.e., the target cell for which the CLTM execution condition is met). Details of the L1 / L2 signaling are similar to those described with respect to step 503.

[0086] According to the operations of the gNB1 and the UE 40 described with reference to Figures 5 and 6, the UE 40 can inform the gNB1 of the selected TCI state (or TCI state setting) for the target cell. This enables the UE 40 and the gNB1 to agree on the recognition of the TCI state to be applied to the target cell when the UE 40 performs a CLTM cell switch.

[0087] Figure 7 shows an example of the operation of UE 701 and gNB 702. UE 701 shown in Figure 7 may be UE 40 of Figures 1 and 2, and gNB 702 shown in Figure 7 may be gNB 1 of Figures 1 and 2. In step 721, gNB 702 transmits an RRC message (e.g., an RRC Reconfiguration message) to UE 701 including CLTM configuration for each of one or more candidate cells. The RRC message further includes a CLTM execution condition. Step 721 may correspond to step 403 of Figure 4, step 501 of Figure 5, and step 601 of Figure 6.

[0088] In step 722, the UE 701 stores the CLTM candidate cell configuration and the CLTM execution condition, and sends an RRCReconfigurationComplete message to the gNB 702. Step 722 may correspond to step 404 in FIG.

[0089] In step 723, the UE 701 performs early TA acquisition for one or more candidate cells. As already explained, early TA acquisition can be triggered by a PDCCH order in the source cell or achieved by UE-based TA measurement. However, early TA acquisition is not necessarily required. In this case, step 723 can be omitted.

[0090] In step 724, the gNB 702 (source DU) sends the TA values ​​of each of one or more candidate cells to the UE 701. The transmission in step 724 may be performed using MAC CE. Step 724 is performed in relation to early TA acquisition based on a PDCCH order. Therefore, if the UE 701 performs early TA acquisition based on UE-based TA measurements, step 724 may be omitted. Also, if early TA acquisition (step 723) is not performed, step 724 may be omitted.

[0091] In step 725, the UE 701 determines that an execution condition is met for one of the one or more candidate cells. In step 726, the UE 701 transmits L1 / L2 signaling to the gNB 702, indicating the selected TCI state for the candidate cell (i.e., the target cell) for which the execution condition is met. The L1 / L2 signaling may be a MAC CE, which may be called a CLTM Indication MAC CE. Additionally or alternatively, the L1 / L2 signaling may be a PUCCH. The MAC CE or PUCCH may be a MAC CE or PUCCH used for event-triggered L1 measurement reporting, which transmits an L1 measurement report in response to the detection of a predetermined event. In this case, the event may be configured as at least part of the execution condition.

[0092] The L1 / L2 signaling or MAC CE in step 726 may include information about the target cell (e.g., Target Configuration ID) and information about the selected TCI state (e.g., TCI state ID). The L1 / L2 signaling or MAC CE may further include a TA value obtained by measurement by the UE 40 and applied to the target cell. Additionally or alternatively, the L1 / L2 signaling or MAC CE may include information that the cell switch by the UE 40 via CLTM is performed in a RACH-less or CFRA-based manner. Step 726 may correspond to step 503 in FIG. 5 and step 602 in FIG. 6.

[0093] In step 727, the UE 701 initiates a cell switch to the target cell. Specifically, the UE 701 detaches from the source cell and applies the target cell configuration. If the UE 701 has a valid TA for the target cell, the UE 701 performs a RACH-less cell switch. If a TA is not available, the UE 701 performs a random access procedure toward the target cell. At this time, if the UE 701 has a configuration for a CFRA-based cell switch, it may perform a CFRA-based cell switch. Step 727 may correspond to steps 407 and 408 of FIG. 4.

[0094] According to the operation of UE 701 and gNB 702 described with reference to Figure 7, UE 701 can inform gNB 702 of the selected TCI state (or TCI state setting) for the target cell. This allows UE 701 and gNB 702 to agree on the understanding of the TCI state that will be applied to the target cell when UE 701 performs a CLTM cell switch.

[0095] Figure 8 shows an example of the operations of a UE 801, a CU 802, a source DU 803, and a candidate DU 804 regarding intra-CU inter-DU CLTM. The UE 801 may be the UE 40 of Figures 1 and 2. The CU 802 may be the gNB-CU 10 of Figures 1 and 2. The source DU 803 may be the gNB-DU 21 of Figures 1 and 2. The candidate DU 804 may be the gNB-DU 22 of Figures 1 and 2.

[0096] Step 821 is similar to step 726 in Figure 7. Specifically, the UE 801 sends L1 / L2 signaling (e.g., MAC CE or UCI) to the source DU 803 indicating the selected TCI state for the candidate cell (i.e., target cell) for which the execution condition is met.

[0097] In step 822, after or in response to receiving the L1 / L2 signaling of step 821, the source DU 803 notifies the CU 802 of the initiation of a CLTM cell switch to the target cell. This notification indicates whether the cell switch to the target cell initiated by the UE 40 is related to (or based on) regular LTM or CLTM. In the case of Figure 8, this notification indicates that the cell switch to the target cell is based on CLTM rather than regular LTM.

[0098] As shown in Figure 8, the notification in step 822 may be performed using an F1AP message, such as a DU-CU CELL SWITCH NOTIFICATION message. In this case, the DU-CU CELL SWITCH NOTIFICATION message is extended to include the CLTM indication. The CLTM indication may be a new IE (or sub-IE) included in the LTM Cell Switch Information information element (IE) in the DU-CU CELL SWITCH NOTIFICATION message. Alternatively, the CLTM indication may be a new IE included in the DU-CU CELL SWITCH NOTIFICATION message separately from the LTM Cell Switch Information IE.

[0099] In one example, the name of the new IE (or sub-IE) for CLTM indication may be CLTM indication IE. The CLTM indication IE may be enumerated and indicate "true". In this case, if the CLTM indication IE set to "true" is included in the DU-CU CELL SWITCH NOTIFICATION message (or the LTM Cell Switch Information IE therein), the CU 802 assumes that the cell switch initiated by the UE 801 is related to (or based on) CLTM rather than normal LTM.

[0100] In another example, the name of the new IE (or sub-IE) for CLTM indication may be LTM indication IE. The LTM indication IE may be enumerated and indicate "ltm" or "cltm". In this case, if the LTM indication IE set to "cltm" is included in the DU-CU CELL SWITCH NOTIFICATION message (or the LTM Cell Switch Information IE therein), the CU 802 assumes that the cell switch initiated by the UE 801 is related to (or based on) CLTM rather than normal LTM. In contrast, if the LTM indication IE set to "ltm" is included in the DU-CU CELL SWITCH NOTIFICATION message (or the LTM Cell Switch Information IE therein), the CU 802 assumes that the cell switch initiated by the UE 801 is related to (or based on) normal LTM.

[0101] In step 823, after or in response to receiving the notification in step 822, the CU 802 notifies the candidate DU 804 (i.e., target DU) of the initiation of a CLTM cell switch to the target cell. The CU 802 may forward the notification (e.g., CLTM indication) received from the source DU 803 in step 822 to the candidate DU 804. The notification in step 823 indicates whether the cell switch to the target cell initiated by the UE 40 is related to (or based on) normal LTM or CLTM. In the case of Figure 8, this notification indicates that the cell switch to the target cell is based on CLTM rather than normal LTM. This notification may include a CLTM indication.

[0102] As shown in Figure 8, the notification in step 823 may be performed using an F1AP message, such as a CU-DU CELL SWITCH NOTIFICATION message. In this case, the CU-DU CELL SWITCH NOTIFICATION message is extended to include the CLTM indication. The CLTM indication may be a new IE (or sub-IE) included in the LTM Cell Switch Information IE in the CU-DU CELL SWITCH NOTIFICATION message. Alternatively, the CLTM indication may be a new IE included in the CU-DU CELL SWITCH NOTIFICATION message separately from the LTM Cell Switch Information IE. Details of the new IE (or sub-IE) for the CLTM indication in step 823 are similar to those described for the new IE (or sub-IE) for the CLTM indication in step 822.

[0103] The operations of the CU 802, source DU 803, and candidate (or target) DU 804 described with reference to Figure 8 enable the target DU 804 to know of the initiation of a CLTM cell switch to the target cell by the UE 40. In other words, this enables the target DU 804 to know that the cell switch to the target cell initiated by the UE 40 is based on CLTM rather than normal LTM.

[0104] <Second Embodiment> A configuration example of a wireless communication system according to this embodiment is similar to the configuration example described with reference to Fig. 1 and Fig. 2. This embodiment relates to details for the UE 40 and the network (e.g., gNB1 or target or candidate DU) to agree on recognition of the TCI state applied to the target cell when the UE 40 performs a CLTM cell switch.

[0105] FIG. 9 shows an example of the operation of UE 40. Steps 901 and 902 are similar to steps 501 and 502 in FIG. 5. In step 903, UE 40 transmits one or more L1 measurement reports to gNB1 (i.e., source DU) while UE 40 is evaluating the CLTM execution conditions. In other words, while UE 40 is configured for CLTM and is evaluating the CLTM execution conditions, UE 40 may transmit L1 measurement reports similar to the operation in normal LTM (e.g., step 306 in FIG. 3). UE 40 may transmit the L1 measurement report periodically. Alternatively, UE 40 may transmit the L1 measurement report only once. Additionally or alternatively, UE 40 may transmit the L1 measurement report in response to the detection of a predetermined event.

[0106] The L1 measurement report of step 903 may indicate a best reference signal beam measured in any candidate cell included in one or more candidate cells. Alternatively, the L1 measurement report may indicate a best TCI state (or TCI state setting, or TCI state setting identifier) ​​corresponding to the best reference signal beam. The reference signal beam may be an SSB beam or a CSI-RS beam.

[0107] If a CLTM execution condition is met for one of the one or more candidate cells after transmitting one or more Layer 1 measurement reports, the UE 40 initiates a cell switch to the one candidate cell (i.e., target cell). The UE 40 may determine a TCI state (or TCI state setting) to be selected for the target cell based on at least one of the one or more reported Layer 1 measurement reports. Specifically, the UE 40 may select a TCI state to be applied to the target cell according to one of the following two methods.

[0108] In the first method, the UE 40 selects the best TCI state corresponding to the best reference signal beam of the target cell reported in a predetermined number of recent L1 measurement reports. The predetermined number is one or more. The best TCI state may be, for example, the best TCI state among the predetermined number of L1 measurement reports, or one or more TCI states reported as best in each of the predetermined number of L1 measurement reports. In the latter case, the UE 40 may determine and use one of the one or more TCI states when actually performing a cell switch. The first method can be called number-based determination.

[0109] In the second method, the UE 40 selects the best TCI state corresponding to the best reference signal beam of the target cell reported by at least one L1 measurement report within a recent predetermined time period. The predetermined time period may be specified in milliseconds. The recent predetermined time period may be a predetermined time period before the time when the CLTM execution condition is met for the target cell. The best TCI state may be, for example, the best TCI state among the L1 measurement reports within the predetermined time period, or one or more TCI states reported as best in each of the L1 measurement reports within the predetermined time period. In the latter case, the UE 40 may determine and use one of the one or more TCI states at the time of actually performing the cell switch. The second method may be called a time-based determination.

[0110] Figure 10 shows an example of the operation of gNB1. Step 1001 is similar to step 601 of Figure 6. In step 1002, gNB1 (source DU) receives one or more L1 measurement reports from UE 40 while UE 40 is evaluating the CLTM execution conditions for each of one or more candidate cells. Details of these one or more L1 measurement reports are similar to those described with respect to step 803.

[0111] The gNB1 knows how the UE 40 selects the TCI state for the target cell. Specifically, the gNB1 assumes that the UE 40 selects the TCI state to apply to the target cell from the best beam or best TCI state indicated by the UE 40 in one or more L1 measurement reports reported for the target cell. The gNB1 may assume that the UE 40 follows either the first or second method described above with reference to FIG. 9.

[0112] According to the operations of gNB1 and UE 40 described with reference to Figures 9 and 10, gNB1 can implicitly know the TCI state that will be selected for the target cell by UE 40 based on one or more L1 measurement reports already reported by UE 40. This allows UE 40 and gNB1 to agree on the understanding of the TCI state that will be applied to the target cell when UE 40 performs a CLTM cell switch.

[0113] In addition, UE 40 may further operate as follows when performing a cell switch to a target cell. If the CLTM execution condition of the target cell is met for the best reference signal beam reported in one or more L1 measurement reports, UE 40 performs a RACH-less cell switch or a CFRA-based cell switch. A RACH-less cell switch is a cell switch procedure that skips the random access procedure. A CFRA-based cell switch is a cell switch procedure that uses CFRA. If UE 40 has a valid TA value of the target cell, UE 40 may perform a RACH-less cell switch. Otherwise, UE 40 may perform a CFRA-based cell switch. On the other hand, if the CLTM execution condition of the target cell is met for a reference signal beam other than the best reference signal beam reported, UE 40 performs a CBRA-based cell switch. A CBRA-based cell switch is a cell switch procedure that uses CBRA. According to this operation, in a situation where an implicit agreement regarding the TCI state of the target cell is not valid between UE 40 and gNB 1, UE 40 can perform CBRA using a preamble corresponding to a selected reference signal beam, thereby enabling agreement to be formed between UE 40 and gNB 1 regarding the TCI state of the target cell during execution of a cell switch.

[0114] Figure 11 shows an example of the operation of a UE 1101 and a gNB 1102. The UE 1101 shown in Figure 11 may be the UE 40 in Figures 1 and 2, and the gNB 1102 shown in Figure 11 may be the gNB 1 in Figures 1 and 2. Steps 1121 to 1124 are similar to steps 721 to 724 in Figure 7.

[0115] In step 1125, the UE 1101 transmits one or more L1 measurement reports to the gNB 1102 (i.e., source DU) while the UE 1101 is evaluating the CLTM execution conditions. Each L1 measurement report may indicate a best reference signal beam measured in any candidate cell included in one or more candidate cells. Alternatively, each L1 measurement report may indicate a best TCI state (or TCI state setting, or a TCI state setting identifier) ​​corresponding to the best reference signal beam. The reference signal beam may be an SSB beam or a CSI-RS beam. Step 1125 may correspond to step 803 of FIG. 8 and step 902 of FIG. 9.

[0116] In step 1126, the UE 1101 determines that an execution condition is met for one of the one or more candidate cells. In step 1127, the UE 1101 initiates a cell switch to the candidate cell (i.e., the target cell) for which the execution condition is met. Specifically, the UE 1101 detaches from the source cell and applies the target cell configuration. If the UE 1101 has a valid TA for the target cell, the UE 1101 performs a RACH-less cell switch. If a TA is not available, the UE 1101 performs a random access procedure toward the target cell. Step 1127 may correspond to steps 407 and 408 of FIG. 4.

[0117] According to the operation of UE 1101 and gNB 1102 described with reference to Figure 11, gNB 1102 can implicitly know the TCI state that will be selected for the target cell by UE 1101 based on one or more L1 measurement reports already reported by UE 1101. This allows UE 1101 and gNB 1102 to agree on the recognition of the TCI state that will be applied to the target cell when UE 1101 performs a CLTM cell switch.

[0118] Figure 12 shows an example of the operations of a UE 1201, a CU 1202, a source DU 1203, and a candidate DU 1204 regarding intra-CU inter-DU CLTM. The UE 1201 may be the UE 40 of Figures 1 and 2. The CU 1202 may be the gNB-CU 10 of Figures 1 and 2. The source DU 1203 may be the gNB-DU 21 of Figures 1 and 2. The candidate DU 1204 may be the gNB-DU 22 of Figures 1 and 2.

[0119] Step 1221 is similar to step 1125 in Figure 11. Specifically, while UE 1201 is evaluating the CLTM execution condition, UE 1201 transmits one or more L1 measurement reports to source DU 1203. Each L1 measurement report may indicate a best reference signal beam measured in any candidate cell included in one or more candidate cells. Alternatively, each L1 measurement report may indicate a best TCI state (or TCI state setting, or TCI state setting identifier) ​​corresponding to the best reference signal beam. The reference signal beam may be an SSB beam or a CSI-RS beam.

[0120] In step 1222, the source DU 1203 sends information about the top N best beams of each of one or more candidate cells (e.g., one or more TCI state IDs), where N is an integer greater than or equal to 1, to the CU 1202. The source DU 1203 may determine the top N best beams of each candidate cell based on one or more L1 measurement reports received from the UE 1201. Furthermore, the source DU 1203 may determine the top N best beams of each candidate cell based on the same method as the TCI state selection by the UE 1201, for example, either the first method (number-based determination) or the second method (time-based determination) described above.

[0121] The transmission of the best beam-related information in step 1222 may be performed using an F1AP message. This F1AP message may be newly defined, and its name may be, for example, a DU-CU Beam Information Transfer message. The source DU 1203 may generate an F1AP message in step 1222 for each candidate cell and transmit the F1AP message generated for each candidate cell that includes the best beam-related information of the corresponding candidate cell. Alternatively, the source DU 1203 may generate an F1AP message in step 1222 for each candidate DU and transmit the F1AP message generated for each candidate DU that includes the best beam-related information of one or more candidate cells provided by the corresponding candidate DU. Alternatively, the source DU 1203 may generate and transmit an F1AP message that collectively includes best beam-related information for multiple candidate cells provided by multiple candidate DUs.

[0122] In step 1223, after receiving or in response to the notification in step 1222, the CU 1202 forwards the best beam-related information of each candidate cell received from the source DU 1203 to the corresponding candidate D 1204 that provides the candidate cell. As described above, the CU 1202 may receive an F1AP message in step 1222 that collectively includes best beam-related information for multiple candidate cells provided by multiple candidate DUs. In this case, the CU 1202 separates the best beam-related information for each candidate DU from the message received in step 1222 and transmits the separated information to the corresponding candidate DU. The transmission of the best beam-related information in step 1223 may be performed using an F1AP message. This F1AP message may be newly defined, and its name may be, for example, a CU-DU Beam Information Transfer message.

[0123] According to the operations of CU 1202, source DU 1203, and candidate DU 1204 described with reference to Figure 12, best beam related information for each candidate cell based on the L1 measurement report sent from UE 1201 that is evaluating the CLTM execution conditions is sent to the candidate DU that serves the candidate cell. This enables candidate DU 1204 to implicitly know the TCI state that will be selected for the candidate cell by UE 1201 if UE 1201 decides to cell switch to the candidate cell.

[0124] <Third Embodiment> A configuration example of a wireless communication system according to this embodiment is the same as the configuration example described with reference to Figures 1 and 2. This embodiment provides details of the use of a RACH-less LTM cell switch when UE 40 determines that the CLTM execution condition is met.

[0125] 13 shows an example of the operation of UE 40. In step 1301, UE 40 evaluates the CLTM execution condition for each of one or more candidate cells. In step 1302, UE 40 determines whether the CLTM execution condition is met for one of the one or more candidate cells.

[0126] In step 1303, UE 40 determines whether to use a RACH-less cell switch procedure for a cell switch to the selected candidate cell. Specifically, UE 40 determines whether to use the RACH-less cell switch procedure based at least on whether UE 40 has a valid TA value and whether the reference signal beam for which the execution condition for the candidate cell is determined to be met was used to acquire a valid TA value in the early TA acquisition procedure performed for the candidate cell. The reference signal beam used to determine whether the execution condition for the candidate cell is met may be an SSB beam or a CSI-RS beam. UE 40 performs the RACH-less cell switch procedure if UE 40 has a valid TA value and if the reference signal beam was used to acquire the valid TA value in the early TA acquisition procedure. That is, UE 40 skips the random access procedure and accesses the selected candidate cell (i.e., target cell). Otherwise, UE 40 performs a RACH-based cell switch using the random access procedure.

[0127] The operation of UE 40 described with reference to FIG. 13 can provide details of the use of a RACH-less LTM cell switch when UE 40 determines that the CLTM execution condition is met. Specifically, the operation of UE 40 in FIG. 13 provides, for example, the following advantages: A candidate cell selected as a target cell (or a candidate DU managing the cell) can know in advance which uplink beam associated with which reference signal beam it should use to prepare to receive the (first) uplink signal in the cell switch procedure. In other words, the candidate cell (or the candidate DU managing the cell) can know the beam that UE 40 will use to transmit the (first) uplink signal in the cell switch procedure from information about the reference signal associated with the random access preamble used by UE 40 in the order of early TA acquisition. These advantages are realized based on the fact that the correspondence between the reference signal beam, the beam of the random access preamble, and the beam of the uplink signal can be known in advance from their settings (or information thereon).

[0128] <Other Embodiments> CLTM may be valid only within a predetermined or specific group of multiple cells. UE 40 may evaluate the CLTM execution conditions only for one or more candidate cells that belong to the same group as the current serving cell. For example, CLTM may be valid only within a group of cells served by the same DU (intra-DU cell group).

[0129] Next, the following describes example configurations of the gNB-CU10, gNB-CU-CP11, gNB-CU-UP12, gNB-DUs 21 and 22, and UE 40. Fig. 14 is a block diagram showing an example configuration of the gNB-CU10. The configurations of the gNB-CU-CP11, gNB-CU-UP12, and gNB-DUs 21 and 22 may also be similar to the configurations shown in Fig. 14.

[0130] 14, the gNB-CU10 includes a network interface 1401, a processor 1402, and a memory 1403. The network interface 1401 is used to communicate with network nodes (e.g., gNB-DUs, and control plane (CP) nodes and / or user plane (UP) nodes in the core network). The network interface 1401 may include multiple interfaces. The network interface 1401 may include, for example, an optical fiber interface for communication between the CU and DU and a network interface compliant with the IEEE 802.3 series.

[0131] The processor 1402 may include multiple processors. If the gNB-CU10 is a gNB-CU-CP, the processor 1402 performs, for example, control plane processing, such as processing related to NGAP, RRC, E1AP, and F1AP signaling. If the gNB-CU10 includes a gNB-CU-UP, the processor 1402 performs, for example, termination of the NG-U interface, termination of the F1-U interface, and data processing for the SDAP and PDCP layers.

[0132] In the case of the gNB-DUs 21 and 22, the processor 1402 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. For example, the processor 1402 may include a modem processor (e.g., a Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a Central Processing Unit (CPU) or a Micro Processing Unit (MPU)) that performs control plane processing. The digital baseband signal processing may include signal processing for the RLC, MAC, and PHY layers. The control plane processing may include processing of MAC CEs and DCIs. The processor 1402 may include a digital beamformer module for beamforming. The digital beamformer module may include a multiple-input multiple-output (MIMO) encoder and precoder.

[0133] The memory 1403 is configured by a combination of volatile memory and non-volatile memory. The volatile memory is, for example, Static Random Access Memory (SRAM), Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or a hard disk drive, or any combination thereof. The memory 1403 may include storage located remotely from the processor 1402. In this case, the processor 1402 may access the memory 1403 via the network interface 1401 or another I / O interface.

[0134] The memory 1403 may store one or more software modules (computer programs) 1404 including instructions and data for performing the processing by the gNB-CU 10 described in the above-described embodiments. In some implementations, the processor 1402 may be configured to read and execute the one or more software modules 1404 from the memory 1403, thereby performing the processing by the gNB-CU 10 described in the above-described embodiments.

[0135] Fig. 15 is a block diagram showing an example configuration of the UE 40. The configurations of the UEs (e.g., UE 701, UE 801, UE 1101, UE 1201) described in the above embodiments may also be similar to the configuration shown in Fig. 15.

[0136] The RF transceiver 1501 performs analog RF signal processing for communication with the TRPs. The RF transceiver 1501 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 1501 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 1501 is coupled to the antenna array 1502 and the baseband processor 1503. The RF transceiver 1501 receives modulation symbol data (or OFDM symbol data) from the baseband processor 1503, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1502. The RF transceiver 1501 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1502 and provides the baseband receive signal to the baseband processor 1503. The RF transceiver 1501 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, multiple phase shifters and multiple power amplifiers.

[0137] The baseband processor 1503 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communications. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) transmission format (transmission frame) generation / decomposition, (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) using Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management for Layer 1 (e.g., transmit power control), Layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and Layer 3 (e.g., signaling related to attachment, mobility, and call management).

[0138] For example, the digital baseband signal processing by the baseband processor 1503 may include signal processing of the SDAP layer, PDCP layer, RLC layer, MAC layer, and PHY layer. Also, the control plane processing by the baseband processor 1503 may include processing of the Non-Access Stratum (NAS) protocol, the RRC protocol, MAC CEs, and DCIs.

[0139] The baseband processor 1503 may perform MIMO encoding and precoding for beamforming.

[0140] The baseband processor 1503 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 1504, which will be described later.

[0141] The application processor 1504 is also referred to as a CPU, MPU, microprocessor, or processor core. The application processor 1504 may include multiple processors (multiple processor cores). The application processor 1504 executes a system software program (operating system (OS)) and various application programs (e.g., a call application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 1506 or a memory not shown, thereby realizing various functions of the UE 40.

[0142] In some implementations, the baseband processor 1503 and the application processor 1504 may be integrated on a single chip, as indicated by the dashed line (1505) in Figure 15. In other words, the baseband processor 1503 and the application processor 1504 may be implemented as a single System on Chip (SoC) device 1505. An SoC device is sometimes called a system Large Scale Integration (LSI) or chipset.

[0143] The memory 1506 is volatile memory, nonvolatile memory, or a combination thereof. The memory 1506 may include multiple physically independent memory devices. The volatile memory may be, for example, SRAM, DRAM, or a combination thereof. The nonvolatile memory may be MROM, EEPROM, flash memory, a hard disk drive, or any combination thereof. For example, the memory 1506 may include an external memory device accessible from the baseband processor 1503, the application processor 1504, and the SoC 1505. The memory 1506 may also include an internal memory device integrated within the baseband processor 1503, the application processor 1504, or the SoC 1505. Furthermore, the memory 1506 may include memory within a Universal Integrated Circuit Card (UICC).

[0144] The memory 1506 may store one or more software modules (computer programs) 1507 including instructions and data for performing the processing by the UE 40 described in the above-described embodiments. In some implementations, the baseband processor 1503 or the application processor 1504 may be configured to read and execute the software modules 1507 from the memory 1506, thereby performing the processing by the UE 40 described in the above-described embodiments using the drawings.

[0145] It should be noted that the control plane processing and operations performed by UE 40 described in the above embodiment can be realized by elements other than RF transceiver 1501 and antenna array 1502, namely, at least one of baseband processor 1503 and application processor 1504, and memory 1506 storing software module 1507.

[0146] As described with reference to Figures 14 and 15, each of the processors included in the gNB-CUs, gNB-CU-CPs, gNB-CU-UPs, gNB-DUs, and UEs according to the above-described embodiments can execute one or more programs including instructions for causing a computer to perform the algorithms described with reference to the drawings. The programs include instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The programs may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disk (DVD), Blu-ray (registered trademark) disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage device. The programs may also be transmitted on a transitory computer-readable medium or a communication medium. By way of example, and not limitation, transitory computer-readable or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0147] The above-described embodiments are merely examples of application of the technical ideas obtained by the inventors of the present invention. In other words, the technical ideas are not limited to the above-described embodiments, and various modifications are possible.

[0148] For example, some or all of the above embodiments may also be described as, but are not limited to, the following appendices. Some or all of the elements (e.g., configurations and functions) described in appendices directed to devices (e.g., RAN nodes, wireless terminals) may naturally also be described as appendices directed to methods and programs. For example, some or all of the elements described in appendices 2-16, which are dependent on appendices 1, may also be described as appendices dependent on appendices 17 and 18, due to the same dependency relationship as appendices 2-16. Similarly, some or all of the elements described in appendices 20-34, which are dependent on appendices 19, may also be described as appendices dependent on appendices 35 and 36, due to the same dependency relationship as appendices 20-34. Some or all of the elements described in any appendice may be applicable to various hardware, software, recording means for recording software, systems, and methods.

[0149] The above-described embodiments are merely examples of application of the technical ideas obtained by the inventors of the present invention. In other words, the technical ideas are not limited to the above-described embodiments, and various modifications are possible.

[0150] For example, some or all of the above embodiments may also be described as, but are not limited to, the following appendices. Some or all of the elements (e.g., configurations and functions) described in appendices directed to devices (e.g., wireless terminals, RAN nodes) may naturally also be described as appendices directed to methods and programs. For example, some or all of the elements described in appendices 2-11, which are dependent on appendices 1-11, may also be described as appendices dependent on appendices 12 and 13, due to the same dependency relationship as appendices 2-11. Similarly, some or all of the elements described in appendices 15-24, which are dependent on appendices 14, may also be described as appendices dependent on appendices 24 and 25, due to the same dependency relationship as appendices 15-24. Some or all of the elements described in any appendice may be applicable to various hardware, software, recording means for recording software, systems, and methods.

[0151] (Supplementary Note 1) A wireless terminal comprising: means for receiving from a Radio Access Network (RAN) node a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); means for evaluating an execution condition for the conditional LTM for each of the one or more candidate cells after receiving the configuration; and means for transmitting Layer 1 or Layer 2 signaling to the RAN node, if the execution condition for one of the one or more candidate cells is met, indicating a selected Transmission Configuration Indicator (TCI) state for the one candidate cell. (Supplementary Note 2) The wireless terminal of Supplementary Note 1, wherein the transmitting means is configured to transmit the Layer 1 or Layer 2 signaling in a source cell of the conditional LTM. (Supplementary Note 3) The wireless terminal of Supplementary Note 1 or 2, further comprising means for initiating a cell switch to the one candidate cell after transmitting the Layer 1 or Layer 2 signaling. (Supplementary Note 4) The radio terminal according to any one of Supplements 1 to 3, wherein the Layer 1 or Layer 2 signaling includes an identifier for identifying the selected TCI state or a TCI state setting corresponding to the selected TCI state. (Supplementary Note 5) The radio terminal according to any one of Supplements 1 to 4, wherein the Layer 1 or Layer 2 signaling further includes an identifier or index indicating the one candidate cell or a candidate target setting associated with the one candidate cell. (Supplementary Note 6) The radio terminal according to any one of Supplements 1 to 5, wherein the Layer 1 or Layer 2 signaling is obtained by measurement by the radio terminal and further indicates a Timing Advance value to be applied to the one candidate cell.(Supplementary Note 7) The radio terminal according to any one of Supplementary Notes 1 to 6, wherein the configuration of each of the candidate cells includes a plurality of candidate TCI state configurations, each candidate TCI state configuration indicating a reference signal used as a reference for path loss of at least one of a Physical Downlink Control Channel (PDCCH), a Physical Downlink Shared Channel (PDSCH), a Physical Uplink Control Channel (PUCCH), and a Physical Uplink Sheared Channel (PUSCH) in a corresponding candidate TCI state, and the transmitting means is configured to select the selected TCI state from the plurality of candidate TCI state configurations of the one candidate cell. (Supplementary Note 8) The radio terminal according to any one of Supplementary Notes 1 to 7, wherein the Layer 1 or Layer 2 signaling is a Medium Access Control (MAC) Control Element (CE). (Supplementary Note 9) The radio terminal according to any one of Supplements 1 to 8, wherein the receiving means is configured to further receive from the RAN node a configuration of the execution conditions for each of the one or more candidate cells. (Supplementary Note 10) The radio terminal according to any one of Supplements 1 to 9, wherein the receiving means is configured to receive from the RAN node a Radio Resource Control (RRC) message including the configuration of the one or more candidate cells. (Supplementary Note 11) The radio terminal according to any one of Supplements 1 to 10, wherein the RAN node includes a Central Unit (CU) and one or more Distributed Units (DUs).(Supplementary Note 12) A method performed by a wireless terminal, comprising: receiving from a radio access network (RAN) node a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); after receiving the configuration, evaluating an execution condition for the conditional LTM for each of the one or more candidate cells; and, if the execution condition is met for one of the one or more candidate cells, transmitting Layer 1 or Layer 2 signaling to the RAN node indicating a selected Transmission Configuration Indicator (TCI) state for the one candidate cell. (Supplementary Note 13) A program for causing a computer to perform a method for a wireless terminal, comprising: receiving, from a radio access network (RAN) node, configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); after receiving the configuration, evaluating an execution condition of the conditional LTM for each of the one or more candidate cells; and, if the execution condition is met for one of the one or more candidate cells, transmitting Layer 1 or Layer 2 signaling to the RAN node indicating a selected Transmission Configuration Indicator (TCI) state for the one candidate cell. (Supplementary Note 14) A Radio Access Network (RAN) node comprising: means for transmitting, to a wireless terminal, a configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); and means for receiving, after the transmission of the configuration, Layer 1 or Layer 2 signaling transmitted by the wireless terminal in response to the wireless terminal determining that an execution condition for the conditional LTM is met for one of the one or more candidate cells, wherein the Layer 1 or Layer 2 signaling indicates a Transmission Configuration Indicator (TCI) state selected for the one candidate cell.(Supplementary Note 15) The RAN node according to Supplementary Note 14, wherein the receiving means is configured to receive the Layer 1 or Layer 2 signaling in a source cell of the conditional LTM. (Supplementary Note 16) The RAN node according to Supplementary Note 14 or 15, wherein the Layer 1 or Layer 2 signaling is transmitted after the radio terminal determines that an execution condition for the conditional LTM is met for the one candidate cell and before the radio terminal initiates a cell switch to the one candidate cell. (Supplementary Note 17) The RAN node according to any one of Supplements 14 to 16, wherein the Layer 1 or Layer 2 signaling includes an identifier for identifying the selected TCI state or a TCI state setting corresponding to the selected TCI state. (Supplementary Note 18) The RAN node according to any one of Supplements 14 to 17, wherein the Layer 1 or Layer 2 signaling further includes an identifier or index indicating the one candidate cell or a candidate target setting associated with the one candidate cell. (Supplementary Note 19) The RAN node according to any one of Supplementary Notes 14 to 18, wherein the Layer 1 or Layer 2 signaling is obtained by measurement by the radio terminal and further indicates a Timing Advance value to be applied to the one candidate cell. (Supplementary Note 20) The RAN node according to any one of Supplementary Notes 14 to 19, wherein the configuration of each candidate cell includes a plurality of candidate TCI state configurations, each candidate TCI state configuration indicating a reference signal used as a path loss reference for at least one of a Physical Downlink Control Channel (PDCCH), a Physical Downlink Shared Channel (PDSCH), a Physical Uplink Control Channel (PUCCH), and a Physical Uplink Sheared Channel (PUSCH) in a corresponding candidate TCI state, and the selected TCI state is selected by the radio terminal from the plurality of candidate TCI state configurations of the one candidate cell.(Supplementary Note 21) The RAN node according to any one of Supplements 14 to 20, wherein the Layer 1 or Layer 2 signaling is a Medium Access Control (MAC) Control Element (CE). (Supplementary Note 22) The RAN node according to any one of Supplements 14 to 21, wherein the transmitting means is configured to further transmit to the radio terminal a configuration of the execution conditions for each of the one or more candidate cells. (Supplementary Note 23) The RAN node according to any one of Supplements 14 to 22, wherein the transmitting means is configured to transmit to the radio terminal a Radio Resource Control (RRC) message including the configuration of the one or more candidate cells. (Supplementary Note 24) The RAN node according to any one of Supplements 14 to 23, wherein the RAN node includes a central unit (CU) and one or more distributed units (DUs). (Supplementary Note 25) A method performed by a Radio Access Network (RAN) node, comprising: transmitting to a radio terminal a configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); and receiving, after the transmission of the configuration, Layer 1 or Layer 2 signaling transmitted by the radio terminal in response to the radio terminal determining that a condition for executing the conditional LTM is met for one of the one or more candidate cells, wherein the Layer 1 or Layer 2 signaling indicates a Transmission Configuration Indicator (TCI) state selected for the one candidate cell.(Supplementary Note 26) A program for causing a computer to perform a method for a Radio Access Network (RAN) node, comprising: transmitting to a wireless terminal a configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); and receiving, after transmitting the configuration, Layer 1 or Layer 2 signaling transmitted by the wireless terminal in response to the wireless terminal determining that an execution condition for the conditional LTM is met for one of the one or more candidate cells, wherein the Layer 1 or Layer 2 signaling indicates a Transmission Configuration Indicator (TCI) state selected for the one candidate cell. (Supplementary Note 27) A radio terminal comprising: means for receiving from a Radio Access Network (RAN) node a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM), means for evaluating an execution condition for the conditional LTM for each of the one or more candidate cells after receiving the configuration, and means for transmitting one or more Layer 1 measurement reports to the RAN node while the execution condition is being evaluated. (Supplementary Note 28) The radio terminal of Supplementary Note 27 further comprises: means for performing a cell switch for the conditional LTM to the one candidate cell if the execution condition is met for one of the one or more candidate cells after transmitting the one or more Layer 1 measurement reports, and means for determining a TCI state to be selected for the one candidate cell based on at least one of the one or more Layer 1 measurement reports. (Supplementary Note 29) The wireless terminal according to Supplementary Note 28, wherein the determining means is configured to select a best Transmission Configuration Indicator (TCI) state corresponding to a best reference signal beam of the one candidate cell reported by a predetermined number of most recent Layer 1 measurement reports.(Supplementary Note 30) The radio terminal according to Supplementary Note 28, wherein the determining means is configured to select a best Transmission Configuration Indicator (TCI) state corresponding to a best reference signal beam of the one candidate cell reported by at least one Layer 1 measurement report within a most recent predetermined time period. (Supplementary Note 31) The radio terminal according to Supplementary Note 27, further comprising: means for performing a cell switch to the one candidate cell if the execution condition is met for one of the one or more candidate cells after reporting the one or more Layer 1 measurement reports, wherein the cell switching means is configured to: perform a cell switch procedure skipping a random access procedure or a cell switch procedure using contention-free random access if the execution condition for the one candidate cell is met for a best reference signal beam reported in the one or more Layer 1 measurement reports, and perform a cell switch procedure using contention-based random access if the execution condition for the one candidate cell is met for a reference signal beam other than the reported best reference signal beam. (Supplementary Note 32) The radio terminal according to any one of Supplementary Notes 27 to 31, wherein the Layer 1 measurement report indicates a best reference signal beam measured in any candidate cell included in the one or more candidate cells, or a best Transmission Configuration Indicator (TCI) state corresponding to the best reference signal beam. (Supplementary Note 33) The radio terminal according to Supplementary Note 32, wherein the reference signal beam is a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) beam or a Channel State Information (CSI) Reference Signal (CSI-RS) beam.(Supplementary Note 34) A method performed by a wireless terminal, comprising: receiving from a radio access network (RAN) node a configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered mobility (LTM), after receiving the configuration, evaluating an execution condition for the conditional LTM for each of the one or more candidate cells, and transmitting one or more Layer 1 measurement reports to the RAN node while the execution condition is being evaluated. (Supplementary Note 35) A program for causing a computer to perform a method for a wireless terminal, comprising: receiving from a radio access network (RAN) node a configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered mobility (LTM), after receiving the configuration, evaluating an execution condition for the conditional LTM for each of the one or more candidate cells, and transmitting one or more Layer 1 measurement reports to the RAN node while the execution condition is being evaluated. (Supplementary Note 36) A Radio Access Network (RAN) node comprising: means for transmitting to a radio terminal a configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM), and means for receiving from the radio terminal one or more Layer 1 measurement reports after transmitting the configuration while the radio terminal is evaluating an execution condition for the conditional LTM for each of the one or more candidate cells. (Supplementary Note 37) The RAN node of Supplementary Note 36 further comprises means for, if a cell switch for the conditional LTM is performed by the radio terminal to one of the one or more candidate cells after receiving the one or more Layer 1 measurement reports, determining a TCI state expected to be selected by the radio terminal for the one candidate cell based on at least one of the one or more Layer 1 measurement reports.(Supplementary Note 38) The RAN node of Supplementary Note 37, wherein the determining means is configured to select a best Transmission Configuration Indicator (TCI) state corresponding to a best reference signal beam of the one candidate cell reported by a predetermined number of most recent Layer 1 measurement reports. (Supplementary Note 39) The RAN node of Supplementary Note 37, wherein the determining means is configured to select a best Transmission Configuration Indicator (TCI) state corresponding to a best reference signal beam of the one candidate cell reported by at least one Layer 1 measurement report within a predetermined most recent time period. (Supplementary Note 40) The RAN node of any one of Supplements 36 to 39, wherein the Layer 1 measurement report indicates a best reference signal beam measured in any candidate cell included in the one or more candidate cells, or a best Transmission Configuration Indicator (TCI) state corresponding to the best reference signal beam. (Supplementary Note 41) The RAN node according to Supplementary Note 40, wherein the reference signal beam is a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) beam or a Channel State Information (CSI) Reference Signal (CSI-RS) beam. (Supplementary Note 42) The RAN node according to any one of Supplements 36 to 41, wherein the RAN node includes a central unit (CU) and one or more distributed units (DUs). (Supplementary Note 43) A method performed by a Radio Access Network (RAN) node, comprising: transmitting a configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered mobility (LTM) to a radio terminal; and receiving one or more Layer 1 measurement reports from the radio terminal after transmitting the configuration while the radio terminal is evaluating a condition for executing the conditional LTM for each of the one or more candidate cells.(Supplementary Note 44) A program for causing a computer to perform a method for a Radio Access Network (RAN) node, comprising: transmitting to a wireless terminal a configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); and receiving, after transmitting the configuration, one or more Layer-1 measurement reports from the wireless terminal while the wireless terminal is evaluating execution conditions for the conditional LTM for each of the one or more candidate cells. (Supplementary Note 45) A wireless terminal comprising: means for evaluating an execution condition for conditional Layer-1 / Layer-2 triggered Mobility (LTM) for each of one or more candidate cells; and means for performing a cell switch to one of the one or more candidate cells if the execution condition is met for the one candidate cell, wherein the means for performing the cell switch is configured to determine whether to use a first cell switch procedure that skips a random access procedure based at least on whether the wireless terminal has a valid Timing Advance value and whether a reference signal beam for the one candidate cell for which the execution condition is determined to be met was used to acquire the valid Timing Advance value in an early Timing Advance acquisition procedure performed for the one candidate cell. (Supplementary Note 46) The wireless terminal described in Supplementary Note 45, wherein the means for performing the cell switch is configured to: perform a first cell switch procedure that skips a random access procedure if the wireless terminal has the valid Timing Advance value and if the reference signal beam was used to acquire the valid Timing Advance value in the early Timing Advance acquisition procedure; and otherwise perform a second cell switch procedure that uses a random access procedure.(Supplementary Note 47) The radio terminal according to Supplementary Note 45 or 46, wherein the reference signal beam is a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) beam or a Channel State Information (CSI) Reference Signal (CSI-RS) beam. (Supplementary Note 48) A method performed by a radio terminal, comprising: evaluating an execution condition for conditional Layer-1 / Layer-2 triggered Mobility (LTM) for each of one or more candidate cells; and performing a cell switch to the one candidate cell if the execution condition is met for one of the one or more candidate cells, wherein performing the cell switch includes determining whether to use a first cell switch procedure that skips a random access procedure based at least on whether the radio terminal has a valid Timing Advance value and whether the reference signal beam for the one candidate cell for which the execution condition is determined to be met was used to acquire the valid Timing Advance value in an early Timing Advance acquisition procedure performed for the one candidate cell.(Supplementary Note 49) A program for causing a computer to perform a method for a wireless terminal, the method comprising: evaluating an execution condition for conditional Layer-1 / Layer-2 triggered Mobility (LTM) for each of one or more candidate cells; and performing a cell switch to one of the one or more candidate cells if the execution condition is met for the one candidate cell; wherein performing the cell switch includes determining whether to use a first cell switch procedure that skips a random access procedure based at least on whether the wireless terminal has a valid Timing Advance value and whether a reference signal beam for the one candidate cell for which the execution condition is determined to be met was used to acquire the valid Timing Advance value in an early Timing Advance acquisition procedure performed for the one candidate cell.

[0152] This application claims priority based on Japanese Patent Application No. 2024-020585, filed February 14, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0153] 1 gNB 10 gNB-CU 11 gNB-CU-CP 12 gNB-CU-UP 21, 22 gNB-DU 31, 32, 33, 34 TRP 40 UE 51, 52, 53, 54 Cell 120 Intra-DU LTM 140 Inter-DU LTM 1402 Processor 1403 Memory 1503 Baseband processor 1504 Application processor 1506 Memory

Claims

1. A wireless terminal comprising: means for receiving, from a Radio Access Network (RAN) node, a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); means for evaluating an execution condition for the conditional LTM for each of the one or more candidate cells after receiving the configuration; and means for transmitting Layer 1 or Layer 2 signaling to the RAN node indicating a selected Transmission Configuration Indicator (TCI) state for the one candidate cell if the execution condition for the one candidate cell is met.

2. The wireless terminal of claim 1, wherein the means for transmitting is configured to transmit the Layer 1 or Layer 2 signaling in a source cell of the conditional LTM.

3. The wireless terminal according to claim 1 or 2, further comprising: means for initiating a cell switch to the one candidate cell after transmitting the layer 1 or layer 2 signaling.

4. A wireless terminal according to any one of claims 1 to 3, wherein the layer 1 or layer 2 signaling includes an identifier for identifying the selected TCI state or for identifying a TCI state setting corresponding to the selected TCI state.

5. The wireless terminal according to any one of claims 1 to 4, wherein the layer 1 or layer 2 signaling further includes an identifier or index indicating the one candidate cell or indicating a candidate target configuration associated with the one candidate cell.

6. The radio terminal according to any one of claims 1 to 5, wherein the layer 1 or layer 2 signaling is obtained by measurements by the radio terminal and further indicates a Timing Advance value to be applied to the one candidate cell.

7. The radio terminal according to any one of claims 1 to 6, wherein the configuration of each of the candidate cells includes a plurality of candidate TCI state configurations, each candidate TCI state configuration indicating a reference signal that is used as a reference for path loss of at least one of a Physical Downlink Control Channel (PDCCH), a Physical Downlink Shared Channel (PDSCH), a Physical Uplink Control Channel (PUCCH), and a Physical Uplink Sheared Channel (PUSCH) in a corresponding candidate TCI state, and wherein the transmitting means is configured to select the selected TCI state from the plurality of candidate TCI state configurations of the one candidate cell.

8. The wireless terminal according to any one of claims 1 to 7, wherein the layer 1 or layer 2 signaling is Medium Access Control (MAC) Control Element (CE).

9. A radio terminal according to any one of claims 1 to 8, wherein the receiving means is further configured to receive from the RAN node the configuration of the execution conditions for each of the one or more candidate cells.

10. A radio terminal according to any one of claims 1 to 9, wherein said receiving means is configured to receive a Radio Resource Control (RRC) message from said RAN node containing said configuration of said one or more candidate cells.

11. A wireless terminal according to any one of claims 1 to 10, wherein the RAN node comprises a central unit (CU) and one or more distributed units (DU).

12. A method performed by a wireless terminal, comprising: receiving from a radio access network (RAN) node a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); after receiving the configuration, evaluating an execution condition for the conditional LTM for each of the one or more candidate cells; and, if the execution condition is met for one of the one or more candidate cells, transmitting Layer 1 or Layer 2 signaling to the RAN node indicating a selected Transmission Configuration Indicator (TCI) state for the one candidate cell.

13. A program for causing a computer to perform a method for a wireless terminal, the method comprising: receiving, from a radio access network (RAN) node, a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); after receiving the configuration, evaluating an execution condition for the conditional LTM for each of the one or more candidate cells; and, if the execution condition for one of the one or more candidate cells is met, transmitting Layer 1 or Layer 2 signaling to the RAN node indicating a selected Transmission Configuration Indicator (TCI) state for the one candidate cell.

14. A Radio Access Network (RAN) node comprising: means for transmitting a configuration of each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM) to a wireless terminal; and means for receiving, after transmitting the configuration, Layer 1 or Layer 2 signaling transmitted by the wireless terminal in response to the wireless terminal determining that an execution condition for the conditional LTM is met for one of the one or more candidate cells, wherein the Layer 1 or Layer 2 signaling indicates a Transmission Configuration Indicator (TCI) state selected for the one candidate cell.

15. The RAN node of claim 14, wherein the means for receiving is configured to receive the Layer 1 or Layer 2 signaling at a source cell of the conditional LTM.

16. The RAN node according to claim 14 or 15, wherein the Layer 1 or Layer 2 signaling is transmitted after the radio terminal determines that a condition for executing the conditional LTM is met for the one candidate cell and before the radio terminal initiates a cell switch to the one candidate cell.

17. A RAN node according to any one of claims 14 to 16, wherein the Layer 1 or Layer 2 signaling includes an identifier for identifying the selected TCI state or for identifying a TCI state setting corresponding to the selected TCI state.

18. A RAN node according to any one of claims 14 to 17, wherein the Layer 1 or Layer 2 signaling further comprises an identifier or index indicating the one candidate cell or indicating a candidate target configuration associated with the one candidate cell.

19. A RAN node according to any one of claims 14 to 18, wherein the Layer 1 or Layer 2 signaling further indicates a Timing Advance value to be applied to the one candidate cell, obtained by measurements by the radio terminal.

20. The RAN node according to any one of claims 14 to 19, wherein the configuration of each of the candidate cells includes a plurality of candidate TCI state configurations, each candidate TCI state configuration indicating a reference signal used as a reference for path loss of at least one of a Physical Downlink Control Channel (PDCCH), a Physical Downlink Shared Channel (PDSCH), a Physical Uplink Control Channel (PUCCH), and a Physical Uplink Sheared Channel (PUSCH) in a corresponding candidate TCI state, and the selected TCI state is selected by the radio terminal from the plurality of candidate TCI state configurations of the one candidate cell.

21. The RAN node of any one of claims 14 to 20, wherein the Layer 1 or Layer 2 signaling is Medium Access Control (MAC) Control Element (CE).

22. A RAN node according to any one of claims 14 to 21, wherein the transmitting means is further configured to transmit to the radio terminal the configuration of the execution conditions for each of the one or more candidate cells.

23. A RAN node according to any one of claims 14 to 22, wherein the transmitting means is configured to transmit a Radio Resource Control (RRC) message to the radio terminal containing the configuration of the one or more candidate cells.

24. The RAN node according to any one of claims 14 to 23, wherein the RAN node comprises a central unit (CU) and one or more distributed units (DU).

25. A method performed by a Radio Access Network (RAN) node, comprising: transmitting to a wireless terminal a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); and, after transmitting the configuration, receiving Layer 1 or Layer 2 signaling transmitted by the wireless terminal in response to the wireless terminal determining that a condition for executing the conditional LTM is met for one of the one or more candidate cells, wherein the Layer 1 or Layer 2 signaling indicates a selected Transmission Configuration Indicator (TCI) state for the one candidate cell.

26. A program for causing a computer to perform a method for a Radio Access Network (RAN) node, comprising: transmitting to a wireless terminal a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); and, after transmitting the configuration, receiving Layer 1 or Layer 2 signaling transmitted by the wireless terminal in response to the wireless terminal determining that an execution condition for the conditional LTM is met for one of the one or more candidate cells, wherein the Layer 1 or Layer 2 signaling indicates a Transmission Configuration Indicator (TCI) state selected for the one candidate cell.

27. A wireless terminal comprising: means for receiving, from a Radio Access Network (RAN) node, a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); means for evaluating, after receiving the configuration, an execution condition for the conditional LTM for each of the one or more candidate cells; and means for transmitting one or more Layer-1 measurement reports to the RAN node while the execution condition is being evaluated.

28. The wireless terminal of claim 27, further comprising: means for performing a cell switch for the conditional LTM to one of the one or more candidate cells if the execution condition is met for the one of the one or more candidate cells after transmission of the one or more Layer 1 measurement reports; and means for determining a TCI state to be selected for the one candidate cell based on at least one of the one or more Layer 1 measurement reports.

29. The wireless terminal of claim 28, wherein the determining means is configured to select a best Transmission Configuration Indicator (TCI) state corresponding to a best reference signal beam of the one candidate cell reported in a predetermined number of most recent Layer 1 measurement reports.

30. The wireless terminal of claim 28, wherein the determining means is configured to select a best Transmission Configuration Indicator (TCI) state corresponding to a best reference signal beam of the one candidate cell reported by at least one Layer 1 measurement report within a recent predetermined time period.

31. The wireless terminal of claim 27, further comprising means for performing a cell switch to one of the one or more candidate cells if the execution condition is met for the one candidate cell after reporting the one or more Layer 1 measurement reports, wherein the means for performing the cell switch is configured to: perform a cell switch procedure that skips a random access procedure or a cell switch procedure using contention-free random access if the execution condition for the one candidate cell is met for a best reference signal beam reported in the one or more Layer 1 measurement reports; and perform a cell switch procedure using contention-based random access if the execution condition for the one candidate cell is met for a reference signal beam other than the best reference signal beam reported.

32. A wireless terminal according to any one of claims 27 to 31, wherein the Layer 1 measurement report indicates the best reference signal beam measured in any candidate cell included in the one or more candidate cells, or the best Transmission Configuration Indicator (TCI) status corresponding to the best reference signal beam.

33. The wireless terminal of claim 32, wherein the reference signal beam is a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) beam or a Channel State Information (CSI) Reference Signal (CSI-RS) beam.

34. A method performed by a wireless terminal, comprising: receiving from a radio access network (RAN) node a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered mobility (LTM); after receiving the configuration, evaluating an execution condition for the conditional LTM for each of the one or more candidate cells; and transmitting one or more Layer-1 measurement reports to the RAN node while the execution condition is being evaluated.

35. A program for causing a computer to perform a method for a wireless terminal, the method comprising: receiving, from a radio access network (RAN) node, a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered mobility (LTM); after receiving the configuration, evaluating an execution condition for the conditional LTM for each of the one or more candidate cells; and transmitting one or more Layer-1 measurement reports to the RAN node while the execution condition is being evaluated.

36. A radio access network (RAN) node comprising: means for transmitting a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered mobility (LTM) to a wireless terminal; and means for receiving one or more Layer-1 measurement reports from the wireless terminal after transmitting the configuration while the wireless terminal is evaluating conditions for executing the conditional LTM for each of the one or more candidate cells.

37. The RAN node of claim 36, further comprising: means for determining, if a cell switch for the conditional LTM is performed by the radio terminal to one of the one or more candidate cells after receiving the one or more Layer 1 measurement reports, a TCI state expected to be selected by the radio terminal for the one candidate cell based on at least one of the one or more Layer 1 measurement reports.

38. The RAN node of claim 37, wherein the means for determining is configured to select a best Transmission Configuration Indicator (TCI) state corresponding to a best reference signal beam of the one candidate cell reported in a predetermined number of most recent Layer 1 measurement reports.

39. The RAN node of claim 37, wherein the means for determining is configured to select a best Transmission Configuration Indicator (TCI) state corresponding to a best reference signal beam of the one candidate cell reported by at least one Layer 1 measurement report within a recent predetermined time period.

40. A RAN node as claimed in any one of claims 36 to 39, wherein the Layer 1 measurement report indicates the best reference signal beam measured in any candidate cell included in the one or more candidate cells, or the best Transmission Configuration Indicator (TCI) status corresponding to the best reference signal beam.

41. The RAN node of claim 40, wherein the reference signal beam is a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) beam or a Channel State Information (CSI) Reference Signal (CSI-RS) beam.

42. The RAN node of any one of claims 36 to 41, wherein the RAN node includes a central unit (CU) and one or more distributed units (DU).

43. A method performed by a Radio Access Network (RAN) node, comprising: transmitting a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM) to a wireless terminal; and receiving one or more Layer-1 measurement reports from the wireless terminal after transmitting the configuration while the wireless terminal is evaluating conditions for executing the conditional LTM for each of the one or more candidate cells.

44. A program for causing a computer to perform a method for a Radio Access Network (RAN) node, comprising: transmitting to a wireless terminal a configuration for each of one or more candidate cells for conditional Layer-1 / Layer-2 triggered Mobility (LTM); and receiving, after transmitting the configuration, one or more Layer-1 measurement reports from the wireless terminal while the wireless terminal is evaluating conditions for executing the conditional LTM for each of the one or more candidate cells.

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