Configuring low-layer triggered mobility

Abstract

A distributed unit (DU) of a distributed base station receives (1012) a CU-to-DU message from a central unit (CU) of the distributed base station, the CU-to-DU message including (i) a request for a reference low layer triggered mobility (LTM) configuration for a candidate cell and (ii) an LTM channel state information (CSI) resource configuration; generates (1014) a reference LTM DU configuration in response to the CU-to-DU message; generates (1006) a serving DU configuration based on the LTM CSI resource configuration; and sends (1019) the reference LTM DU configuration and the serving DU configuration to the CU.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Provisional U.S. Patent Application No. 63 / 595,750, filed November 2, 2023, entitled "Configuring Lower Layer Mobility". The entire contents of the provisional application are hereby expressly incorporated herein by reference. Technical Field

[0003] This disclosure relates to wireless communications, and more specifically, to configuring low-layer (e.g., layer 1 and / or layer 2) mobility (LTM) for user equipment (UE). Background Technology

[0004] This background description is provided for the purpose of presenting the general context of this disclosure. The work of the currently attributed inventors (to the extent described in this background section) and aspects of the specification that might not have been considered prior art at the time of filing are neither expressly nor impliedly acknowledged as prior art relative to this disclosure.

[0005] In telecommunications systems, the Packet Data Convergence Protocol (PDCP) sublayer of the radio protocol stack provides services such as user plane data delivery, encryption, and integrity protection. For example, the PDCP sublayer defined for the Evolved Universal Terrestrial Radio Access (EUTRA) radio interface (see 3GPP specification TS 36.323) and New Radio (NR) (see 3GPP specification TS 38.323) provides the ordering of Protocol Data Units (PDUs) in the uplink direction (from the user equipment, also known as the User Equipment (UE), to the base station) and in the downlink direction (from the base station to the UE). Additionally, the PDCP sublayer provides Signaling Radio Bearers (SRBs) and Data Radio Bearers (DRBs) to the Radio Resource Control (RRC) sublayer. Generally, the UE and base station can use SRBs to exchange RRC messages and Non-Access Stratum (NAS) messages, and can use DRBs to transmit data on the user plane.

[0006] UEs can use several types of SRBs and DRBs. When operating in dual connectivity (DC), the cell associated with the base station operating as the primary node (MN) defines the primary cell group (MCG), and the cell associated with the base station operating as the secondary node (SN) defines the secondary cell group (SCG). The so-called SRB1 resource carries RRC messages that, in some cases, include NAS messages on the dedicated control channel (DCCH), while the SRB2 resource supports RRC messages that include recorded measurement information or NAS messages, also on the DCCH but with a lower priority than the SRB1 resource. More generally, SRB1 and SRB2 resources allow the UE and MN to exchange MN-related RRC messages and embed SN-related RRC messages, and can also be referred to as MCG SRBs. SRB3 resources allow the UE and SN to exchange SN-related RRC messages and can be referred to as SCG SRBs. Split SRBs allow the UE to exchange RRC messages directly with the MN via lower-layer resources of the MN and SN. Additionally, a DRB that uses only the low-level resources of MN can be called an MCG DRB, a DRB that uses only the low-level resources of SN can be called an SCG DRB, and a DRB that uses the low-level resources of both MCG and SCG can be called a split DRB.

[0007] In some scenarios, a UE can concurrently utilize the resources of multiple Radio Access Network (RAN) nodes (e.g., components of a base station or distributed base station) interconnected via backhaul. This type of connection is called Multiple Radio Dual Connectivity (MR-DC) when these network nodes support different Radio Access Technologies (RATs). When the UE operates in MR-DC, one base station operates as the primary node (MN) covering the primary cell (PCell), and another base station operates as the secondary node (SN) covering the primary secondary cell (PSCell). The UE communicates with the MN (via the PCell) and the SN (via the PSCell). In other scenarios, the UE utilizes the resources of one base station at a time. One base station and / or the UE determines that the UE should establish a radio connection with another base station. For example, one base station may determine to hand over the UE to a second base station and initiate a handover process.

[0008] When a UE moves within the RAN from the coverage area of ​​one cell to the coverage area of ​​another, a serving cell change must be performed at some point. To perform the serving cell change, the RAN configures the UE to send Layer 3 (L3) measurements. Based on the L3 measurements received from the UE, the RAN sends an RRC reconfiguration message with Reconfiguration with Synchronization (e.g., the RRC reconfiguration message includes ReconfigurationWithSync IE) for the change of serving cell (e.g., PCell or PSCell). When the UE operates with at least one secondary cell (SCell) and carrier aggregation (CA) with the PCell or PSCell, the RAN must release at least one SCell due to the change of the PCell or PSCell. Serving cell changes involve a full L2 (and L1) reset, resulting in longer latency, greater overhead, and longer downtime. Therefore, 3GPP recently proposed new mobility techniques for serving cell changes. These techniques, known as Layer-Triggered Mobility (LTM) or “faster serving cell handover,” aim to reduce latency and overhead.

[0009] When the RAN communicates with the UE via the serving cell, the RAN receives one or more Layer 3 (e.g., RRC) measurement results from the UE. Based on the Layer 3 (L3) measurement results, the RAN determines a candidate cell for LTM cell handover, hereinafter also referred to as an "LTM candidate cell". To configure the LTM candidate cell for the UE, the RAN sends the LTM configuration for the LTM candidate cell to the UE via RRC signaling. The RAN then receives one or more Layer 1 (L1) measurement results from the UE. Based on the one or more L1 measurement results, the RAN determines that the LTM candidate cell is eligible to become the UE's serving cell. Therefore, the RAN sends an LTM cell handover command to the UE to instruct the UE to perform an LTM cell handover to the LTM candidate cell. In response to the LTM cell handover command, the UE performs a cell change from the serving cell to the LTM candidate cell. In response to the cell change, the UE disconnects from the serving cell and accesses the LTM candidate cell. After the UE successfully accesses the LTM candidate cell, the UE communicates with the RAN via the LTM candidate cell, and the LTM candidate cell becomes the UE's new serving cell.

[0010] It has been proposed that by sending a UE context modification request message to the DU, the RAN's CU can initiate a single CU-initiated UE context modification procedure to prepare the UE for LTM in the case of LTM within the gNB-DU. In response, the DU sends a UE context modification response including the generated low-layer RRC configuration. However, a single UE context modification procedure may not be sufficient to prepare the UE for LTM. Furthermore, it is unclear what the generated low-layer RRC configuration should include. According to one approach, the UE context modification response includes DU-to-CU RRC information, and this information can be used to include the generated low-layer RRC configuration. As specified in 3GPP specification 38.473, the DU-to-CU RRC information includes a single CellGroupConfig IE. In some scenarios, the RAN needs to provide more than one CellGroupConfig IE for different LTM subfunctions to prepare the UE for LTM. Therefore, the existing content of the UE context modification response message cannot properly enable LTM preparation. More generally, it is unclear how the CU and DU should combine LTM procedure communication or apply information such as channel state information. Summary of the Invention

[0011] An example embodiment of the technology disclosed herein is a method implemented in a distributed unit (DU) of a distributed base station. The method includes: receiving a CU-DU message from a central unit (CU) of the distributed base station, the CU-DU message including (i) a request for a reference lower-layer triggered mobility (LTM) configuration for a candidate cell and (ii) an LTM channel state information (CSI) resource configuration; generating a reference LTM DU configuration in response to the CU-DU message; generating a serving DU configuration based on the LTM CSI resource configuration; and sending the reference LTM DU configuration and the serving DU configuration to the CU.

[0012] Another example embodiment of the technology disclosed herein is a method implemented in a CU of a distributed base station. The method includes: sending a CU-DU message to a DU of the distributed base station, the CU-DU message including (i) a request for a reference LTM configuration for a candidate cell and (ii) an LTM CSI resource configuration; and receiving, from the DU and in response to the CU-DU message, a serving DU configuration and a reference LTM DU configuration based on the LTM CSI resource configuration.

[0013] Another example embodiment of these technologies is a method implemented in a DU of a distributed base station. The method includes: receiving a CU-DU message from a CU requesting LTM configuration for a candidate cell; generating an LTM DU configuration and a service DU configuration in response to the CU-DU message; and sending the LTM DU configuration and the service DU configuration to the CU.

[0014] Another example embodiment of these technologies is a radio access network (RAN) node, which includes a transceiver and processing hardware. The RAN is configured to implement one of the methods described above. Attached Figure Description

[0015] Figure 1A This is a block diagram of an example system in which the radio access network (RAN) and user equipment can implement the techniques disclosed herein for managing LTM configurations.

[0016] Figure 1B It is possible Figure 1A A block diagram of an example base station operating in the system, including centralized units (CU) and distributed units (DU);

[0017] Figure 2A This is a block diagram of an example protocol stack. Figure 1A The UE communicates with the base station according to the protocol stack;

[0018] Figure 2B This is a block diagram of an example protocol stack. Figure 1A The UE communicates with the CU and DU according to the protocol stack;

[0019] Figure 3 This is a message passing diagram of an example scenario in which the UE receives LTM configuration from the distributed unit (DU) of the distributed base station and accesses the candidate cell of the DU according to the LTM configuration;

[0020] Figure 4 Is with Figure 3 The message passing diagram is largely similar to the example scenario, but in this case, the candidate cell is associated with another DU of the distributed base station;

[0021] Figure 5A Is with Figure 3 The message passing diagram is largely similar to the example scenario, but the UE operates with dual connectivity and the candidate cell is associated with the secondary node (SN).

[0022] Figure 5B Is with Figure 5A The message passing graph is largely similar to the example scenario, but the SN is configured via the master node (MN) instead of directly performing LTM.

[0023] Figure 6A Is with Figure 3 The message passing diagram is largely similar to the example scenario, but the UE operates with dual connectivity and the candidate cell is associated with the secondary node (SN).

[0024] Figure 6B Is with Figure 6AThe message passing graph is largely similar to the example scenario, but the SN is configured via MN instead of directly using LTM.

[0025] Figure 7A Is with Figure 4 The message passing diagram is largely similar to the example scenario, but MN and SN are implemented in the same base station;

[0026] Figure 7B Is with Figure 7A The message passing diagram is largely similar to the example scenario, but the SN is configured via MN DU (M-DU) instead of directly performing LTM.

[0027] Figure 8A Is with Figure 3 The scenario is largely similar to the message passing diagram of the example scenario, but in which MN and SN are implemented in different corresponding DUs of the same base station, and the candidate cell is associated with another DU of the distributed base station;

[0028] Figure 8B Is with Figure 9A The message passing diagram is largely similar to that of the example scenario, but the SN is configured via M-DU instead of directly performing LTM.

[0029] Figure 9A This is a flowchart of an example method that can be implemented in a DU to generate LTM DU configuration and service DU configuration and send the configuration to the CU in different corresponding messages;

[0030] Figure 9B Is with Figure 9A The method is largely similar to the flowchart of the example method, but according to Figure 9B The method is that DU sends two configurations in the same message;

[0031] Figure 10A This is a flowchart of an example method that can be implemented in a DU to generate an LTM DU configuration and use an LTM CSI resource configuration from a CU to generate a service DU configuration and send the configuration to the CU in different response messages;

[0032] Figure 10B Is with Figure 10A The method is largely similar to the flowchart of the example method, but according to Figure 10B The method is that DU sends two configurations in the same message;

[0033] Figure 10C Is with Figure 10A The method is largely similar to the flowchart of the example method, but according to Figure 10CThe method is that the DU receives LTM CSI resource configuration, but does not receive an indication from the CU to request the configuration of LTM candidate cells;

[0034] Figure 10D Is with Figure 10C The method is largely similar to the flowchart of the example method, but according to Figure 10D The method is that DU sends two configurations in the same message;

[0035] Figure 10E Is with Figure 10A The method is largely similar to the flowchart of the example method, but according to Figure 10E The method is that the DU receives an indication of a request for a reference LTM DU configuration, rather than an indication of a request for a candidate LTM cell configuration.

[0036] Figure 10F Is with Figure 10D The method is largely similar to the flowchart of the example method, but according to Figure 10F The method is that DU sends two configurations in the same message;

[0037] Figure 11A This is a flowchart of an example method that can be implemented in the DU to generate an LTM DU configuration in response to an instruction from the CU to configure an LTM candidate cell and to generate a reference LTM DU configuration in response to an instruction from the CU to reference an LTM configuration;

[0038] Figure 11B Is with Figure 11A The method is largely similar to the flowchart of the example method, but according to Figure 11B The method is that DU sends two configurations in the same message;

[0039] Figure 12A Is with Figure 11A The method is largely similar to the flowchart of the example method, but according to Figure 12A In this method, the DU also receives LTM CSI resource configuration from the CU and sends (i) LTM DU configuration, (ii) reference LTM DU configuration and (iii) service DU configuration to the CU in the corresponding message;

[0040] Figure 12B Is with Figure 12A The method is largely similar to the flowchart of the example method, but according to Figure 12B The method involves the DU sending the LTM DU configuration and service DU configuration in the same message;

[0041] Figure 12C Is with Figure 12A The method is largely similar to the flowchart of the example method, but according to Figure 12CThe method involves the DU sending both the LTM DU configuration and the reference DU configuration in the same message;

[0042] Figure 12D Is with Figure 12A The method is largely similar to the flowchart of the example method, but according to Figure 12D The method involves the DU sending a reference LTM DU configuration and a service DU configuration in the same message;

[0043] Figure 13A This is a flowchart of an example method that can be implemented in the CU for receiving LTM DU configuration and service DU configuration from the DU in response to requests for LTM candidate cell configuration and LTM CSI resource configuration, respectively;

[0044] Figure 13B Is with Figure 13A The method is largely similar to the flowchart of the example method, but according to Figure 13B In addition, the CU also receives the reference LTM DU configuration from the DU in response to a request for the reference LTM DU configuration;

[0045] Figure 14 This is a flowchart of an example method for generating CU-DU messages based on whether the CU requests LTM candidate cell configuration and whether the CU sends LTM CSI resource configuration.

[0046] Figure 15A This is a flowchart of an example method for generating a CU-to-DU message based on whether the CU requests a non-reference LTM DU configuration or a reference LTM DU configuration;

[0047] Figure 15B This is a flowchart illustrating an example method for generating CU-DU messages based on whether the CU is requesting or serving LTM DU configuration; and

[0048] Figure 15C This is a flowchart of an example method for generating CU-DU messages based on whether the CU is requesting a reference LTM DU configuration or serving an LTM DU configuration. Detailed Implementation

[0049] Figure 1AAn example wireless communication system 100 is depicted, in which communication devices can implement these technologies. The wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106, and a core network (CN) 110. The UE 102 is initially connected to base station 104. In some scenarios, base station 104 can perform SN addition to configure the UE 102 to operate in dual connectivity (DC) with both base stations 104 and 106. Base stations 104 and 106 operate as the MN and SN of the UE 102, respectively.

[0050] In various configurations of the wireless communication system 100, base station 104 can be implemented as a primary eNB (MeNB) or primary gNB (MgNB), and base station 106 can be implemented as a secondary gNB (SgNB). UE 102 can communicate with base station 104 and base station 106 via the same RAT (such as EUTRA or NR) or different RATs. When base station 104 is a MeNB and base station 106 is an SgNB, UE 102 can be in EUTRA-NR DC (EN-DC) with both the MeNB and SgNB.

[0051] In some cases, the MeNB or SeNB is implemented as an ng-eNB instead of an eNB. When base station 104 is the primary ng-eNB (Mng-eNB) and base station 106 is the SgNB, UE 102 can be in a next-generation (NG) EUTRA-NRDC (NGEN-DC) with both the Mng-eNB and SgNB. When base station 104 is a MgNB and base station 106 is an SgNB, UE 102 can be in an NR-NR DC (NR-DC) with both the MgNB and SgNB. When base station 104 is a MgNB and base station 106 is a secondary ng-eNB (Sng-eNB), UE 102 can be in an NR-EUTRA DC (NE-DC) with both the MgNB and Sng-eNB.

[0052] In the scenario where UE 102 is handed over from base station 104 to base station 106, base stations 104 and 106 operate as the source base station (S-BS) and the target base station (T-BS), respectively. For example, before the handover, UE 102 can communicate with base station 104 and the additional base station (T-BS). Figure 1A (Not shown in the diagram) operates in DC mode. After the handover is completed, UE 102 can continue to operate in DC mode with base station 106 and the additional base station, or operate in single-connection (SC) mode with base station 106. In this case, base stations 104 and 106 operate as the source MN (S-MN) and the target MN (T-MN), respectively.

[0053] The core network (CN) 110 can be either the Evolved Packet Core (EPC) 111 or the 5th Generation Core (5GC) 160; both are... Figure 1A The base station 104 may be an eNB supporting an S1 interface for communication with EPC 111, an ng-eNB supporting an NG interface for communication with 5GC 160, or a gNB supporting an NR radio interface and an NG interface for communication with 5GC 160. To exchange messages directly with each other during the scenarios discussed below, base stations 104 and 106 may support X2 or Xn interfaces. Among other components, EPC 111 may include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. SGW 112 is generally configured to deliver user plane packets related to audio calls, video calls, Internet services, etc., and MME 114 is configured to manage authentication, registration, paging, and other related functions. PGW 116 provides connectivity from the UE to one or more external packet data networks (e.g., Internet networks and / or Internet Protocol (IP) Multimedia Subsystem (IMS) networks). 5GC 160 includes User Plane Functions (UPF) 162, Access and Mobility Management (AMF) 164, and / or Session Management Functions (SMF) 166. UPF 162 is generally configured to deliver user plane packets related to audio calls, video calls, Internet services, etc., AMF 164 is configured to manage authentication, registration, paging, and other related functions, and SMF 166 is configured to manage PDU sessions.

[0054] like Figure 1A As shown, base station 104 supports cell 124A, and base station 106 supports cell 126. Cells 124A and 126 can partially overlap, allowing UE 102 to communicate with base stations 104 and 106 via DC, where one of base stations 104 and 106 is MN and the other is SN. Base station 104 can support additional cells (such as cells 124B and 124C), and base station 106 can support additional cells (…). Figure 1A (Not shown in the diagram). Cells 124A, 124B, and 124C may partially overlap, allowing UE 102 to communicate with base station 104 via carrier aggregation (CA). Base station 104 may operate cells 124A, 124B, and 124C via one or more transmit and receive points (TRPs). More specifically, when UE 102 is in a DC configuration with base stations 104 and 106, one of base stations 104 and 106 operates as a MeNB, Mng-eNB, or MgNB, while the other operates as an SgNB or Sng-eNB.

[0055] Generally, the wireless communication network 100 may include any suitable number of base stations supporting NR cells and / or EUTRA cells. More specifically, the EPC 111 or 5GC 160 may be connected to any suitable number of base stations supporting NR cells and / or EUTRA cells. Although the examples below specifically refer to particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, the techniques disclosed herein can also be applied to other suitable radio access and / or core network technologies, such as sixth-generation (6G) radio access and / or 6G core networks or 5G NR-6G DC.

[0056] Processing hardware 130 may implement LTM controller 132 to support the LTM process. For example, LTM controller 132 may be implemented as a corresponding set of instructions executable by one or more processors. Processing hardware 130 may also implement additional components, such as a PHY controller (not shown), configured to transmit data and control signals with one or more user equipments (e.g., UE 102) via one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs on physical downlink (DL) channels and DL reference signals. PHY controller may be configured to receive data and control signals with one or more user equipments via one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs on physical uplink (UL) channels and / or UL reference signals. Processing hardware 130 may also implement a MAC controller (not shown), configured to perform MAC functions with one or more user equipments. MAC functions include random access (RA) procedures, managing UL timing advances for one or more user equipment (UEs), and / or communicating UL / DL MAC PDUs with one or more UEs. MAC functions include low-trigger mobility (LTM) related functions as described below. Processing hardware 130 may also include an RRC controller (not shown) to implement procedures and messaging at the RRC sublayer of the protocol communication stack. For example, the RRC controller may be configured to support RRC messaging associated with handover procedures, and / or support necessary operations when base station 104 operates as an MN relative to an SN or an SN relative to an MN. Base station 106 may include processing hardware 140 similar to processing hardware 130. Specifically, components 142, 144, and 146 may be similar to components 132 and 134, respectively.

[0057] UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or dedicated processing units. The processing hardware 150 may implement an LTM controller 152 to support LTM procedures in the serving cell and / or the target cell. For example, the LTM controller 152 may be implemented as a corresponding set of instructions executable by one or more processors.

[0058] The processing hardware 150 may also implement additional components, such as a PHY controller (not shown), configured to receive data and control signals with base station 104 or 106 on physical DL channels and / or DL ​​reference signals via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. The PHY controller may be configured to transmit data and control signals with base station 104 or 106 on physical UL channels and / or UL reference signals via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. In an example implementation, the processing hardware 150 includes a MAC controller (not shown) configured to perform MAC functions with base station 104 or 106. For example, MAC functions include random access procedures, managing UL timing advances for one or more user facilities, and communicating UL / DL MAC PDUs with base station 104 or 106. In another example, MAC functions include LTM-related functions as described below. The processing hardware 150 may also include an RRC controller (not shown) to implement process and message passing at the RRC sublayer of the protocol communication stack.

[0059] Figure 1BAn example distributed implementation of a base station (such as base station 104 or 106) is depicted. In this implementation, the base station may include a centralized unit (CU) 172 and one or more distributed units (DUs) 174. CU 172 is equipped with processing hardware, which may include one or more general-purpose processors (such as CPUs) and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or dedicated processing units. In one example, CU 172 is equipped with processing hardware 130. In another example, CU 172 is equipped with processing hardware 140. In the example implementation, processing hardware 140 includes an SN RRC controller 142 configured to manage or control one or more RRC configurations and / or RRC procedures when base station 106 operates as an SN. DU 174 is also equipped with processing hardware, which may include one or more general-purpose processors (such as CPUs) and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or dedicated processing units. In some examples, in the example implementation, the processing hardware includes: a Media Access Control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., random access procedures); and a Radio Link Control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station 106 operates as an MN or SN. The processing hardware may also include a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0060] Figure 2A An example protocol stack 200 is shown in a simplified manner, which UE 102 can use to communicate with an eNB / ng-eNB or gNB (e.g., one or more of base stations 104, 106).

[0061] In example stack 200, the EUTRA physical layer (PHY) 202A provides a transport channel to the EUTRA MAC sublayer 204A, which in turn provides a logical channel to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A then provides an RLC channel to the EUTRA PDCP sublayer 208 and, in some cases, to the NR PDCP sublayer 210. Similarly, the NRPHY 202B provides a transport channel to the NR MAC sublayer 204B, which in turn provides a logical channel to the NR RLC sublayer 206B. The NR RLC sublayer 206B then provides data delivery services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 can then provide data delivery services to the Serving Data Adaptation Protocol (SDAP) 212 or the Radio Resource Control (RRC) sublayer. Figure 2A (Not shown in the image) provides data transfer services. In some implementations, UE 102 supports both EUTRA and NR stacks, such as... Figure 2A As shown, this is to support the handover between EUTRA and NR base stations and / or support DCs via the EUTRA and NR interfaces. Additionally, as... Figure 2A As shown, UE 102 can support NR PDCP 210 layering on EUTRA RLC 206A, and SDAP sublayer 212 layering on NR PDCP sublayer 210.

[0062] EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 (e.g., from an Internet Protocol (IP) layer layered directly or indirectly on PDCP layers 208 or 210) receive packets that can be referred to as Service Data Units (SDUs), and (e.g., to RLC layers 206A or 206B) output packets that can be referred to as Protocol Data Units (PDUs). For simplicity, except where the difference between SDU and PDU is relevant, this disclosure refers to both SDU and PDU as "packets".

[0063] On the control plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 can provide signaling radio bearer (SRB) or RRC sublayer ( Figure 2A (Not shown) to exchange, for example, RRC messages or Non-Access Stratum (NAS) messages. On the user plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 can provide data radio bearers (DRBs) to support data exchange. The data exchanged on NR PDCP sublayer 210 can be SDAP PDUs, Internet Protocol (IP) packets, or Ethernet packets.

[0064] Figure 2BAn example protocol stack 250 is shown in a simplified manner, illustrating how UE 102 can communicate with DU (e.g., DU 174) and CU (e.g., CU 172). The radio protocol stack 200 is functionally split, as described by... Figure 2B The radio protocol stack 250 is shown in the diagram. At either base station 104 or 106, the CU can maintain all control and upper-layer functionality (e.g., RRC 214, SDAP 212, NR PDCP 210), while lower-layer operations (e.g., NR RLC 206B, NR MAC 204B, and NR PHY 202B) are delegated to the DU. To support connectivity to the 5GC, NR PDCP 210 provides SRBs to RRC 214, and NR PDCP 210 provides DRBs to SDAP 212 and SRBs to RRC 214.

[0065] Next is one of them Figure 1A This describes several example scenarios in which the base station operating in the system sends a configuration to the UE 102 and later activates the configuration for communication between the UE 102 and the base station. Generally speaking, Figures 3 to 7B Similar events are labeled with similar reference numerals (e.g., event 316 and...). Figure 4 A and Figure 4 Event 416 of B Figure 5A Event 516 Figure 5B Event 517 Figure 6A Event 616 Figure 6B Event 617 Figure 7A Event 716 and Figure 7B (Similar to event 717), where differences are discussed below where appropriate. Apart from the differences shown in the figures and discussed below, any of the alternative implementations discussed for specific events (e.g., those used for messaging and processing) can be applied to events labeled similarly in other figures.

[0066] First refer to Figure 3 In scenario 300, base station 104 includes CU 172 and DU 174, and DU 174 operates cell 124A. UE 102 initially communicates with DU 174 on cell 124A using the serving DU, and communicates with CU 172 via DU 174, for example, using the serving CU. In other words, DU 174 is the serving DU that is communicating with UE 102. In some implementations, UE 102 uses the serving DU to communicate in cell 124A and other cells (e.g., Figure 1AUE 102 communicates with DU 174 via carrier aggregation (CA) on cell 124A (not shown). DU 174 operates other cells. Cell 124A and / or other cells are the serving cells of UE 102. In other implementations, UE 102 communicates with DU 174 only on cell 124A. In some implementations, UE 102 communicates with DU 174 on cell 124A and / or other cells via one or more TRPs. In some implementations, cell 124A may be a PCell. In such cases, other cells include SCells and / or additional cells associated with a PCell or SCell. In other implementations, cell 124A may be an SCell, and one of the other cells is a PCell. In such cases, the remaining cells include SCells and / or additional cells associated with a PCell or SCell. In the following description, base station 104 may be DU 174, CU 172, or DU 174 and CU 172.

[0067] In event 302, UE 102 may transmit UL PDUs and / or UL control signals to base station 104 via one or more TRPs in cell 124A and / or other cells. In some implementations, UE 102 communicates UL PDUs and / or DL ​​PDUs with base station 104 via a radio bearer, which may include SRBs and / or DRBs. Base station 104 may configure the radio bearer for UE 102. In some implementations, the UL control signals include UL control information, channel state information, Hybrid Automatic Repeat Request (HARQ) acknowledgment (ACK), HARQ negative ACK, scheduling request, and / or probe reference signals. Similarly, UE 102 may receive DL PDUs and / or DL ​​control signals from base station 104 via one or more TRPs in cell 124A and / or other cells. In some implementations, the DL control signals include downlink control information (DCI) and reference signals (e.g., synchronization signal blocks, channel state information reference signals (CSI-RS), and / or tracking reference signals). Base station 104 can transmit DCI via one or more TRPs on the physical downlink control channel (PDCCH) monitored by UE 102 in cell 124A and / or other cells.

[0068] In some implementations, the serving DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some implementations, the serving DU configuration includes at least one first non-LTM TCI state configuration for the serving cell. In some implementations, DU 174 may send these configuration parameters and / or the first non-LTM TCI state configuration to CU 172. CU 172 generates one or more messages (e.g., RRC reconfiguration messages) including the configuration parameters and / or the first non-LTM TCI state configuration, and sends these messages to UE 102 via DU 174. In other implementations, DU 174 sends the configuration parameters and / or the first non-LTM TCI state configuration directly to UE 102. In some implementations, the serving DU configuration is a CellGroupConfig IE as defined in 3GPP specification 38.331. In other implementations, the serving DU configuration includes configuration parameters in the CellGroupConfig IE. In some implementations, the serving CU configuration includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, the serving CU configuration includes the MeasConfig IE and / or RadioBearerConfig IE as defined in 3GPP specification 38.331, or includes configuration parameters in the MeasConfig IE and / or RadioBearerConfig IE. In some implementations, the serving DU configuration includes the CSI-MeasConfig IE or configuration parameters for Channel State Information (CSI) measurement and reporting. In other implementations, the serving CU configuration includes the CSI-MeasConfig IE or configuration parameters for CSI measurement and reporting. In some implementations, UE 102 receives the serving CU configuration or configuration parameters in the serving CU configuration from CU 172 via DU 174. In other implementations, UE 102 receives a portion of the serving CU configuration and / or a portion of the serving DU configuration from a base station other than base station 104, and receives the remainder of these configuration parameters from base station 104.

[0069] In some implementations, UE 102 and DU 174 communicate with each other using a first non-LTM TCI state configuration, for example, in events 302, 318, 320, 324, 325, 330, and / or 331. In some implementations, DU 174 sends at least one first non-LTM TCI state activation / deactivation command to UE 102 to activate some of the first non-LTM TCI state configurations. UE 102 activates some of the first non-LTM TCI state configurations in response to the first non-LTM TCI state activation / deactivation command. In some implementations, DU 174 indicates the deactivation of some of the first non-LTM TCI state configurations in some of the first non-LTM TCI state activation / deactivation commands. UE 102 and DU 174 communicate with each other using the activated non-LTM TCI state configuration, for example, in events 302, 318, 320, 324, 325, 330, and / or 331.

[0070] In some implementations, each of the first non-LTM TCI state activation / deactivation commands is a MAC CE. MAC CEs may include one or more TCI state activation / deactivation commands for a UE-specific PDSCH MAC CE, one or more TCI state indications for a UE-specific PDCCH MAC CE, one or more PUCCH spatial relationship activation / deactivation MAC CEs, one or more enhanced TCI state activation / deactivation commands for a UE-specific PDSCH MAC CE, one or more enhanced PUCCH spatial relationship activation / deactivation MAC CEs, one or more enhanced TCI state indications for a UE-specific PDCCH MAC CE, one or more PUCCH spatial relationship activation / deactivation commands for multiple TRP PUCCH repeating MAC CEs, and / or one or more unified TCI state activation / deactivation MAC CEs.

[0071] In some implementations, DU 174 includes the serving cell ID (e.g., a serving cell index) in each of the first non-LTM TCI state activation / deactivation commands to identify the first non-LTM TCI state configuration. Each serving cell ID indicates the corresponding serving cell among the serving cells. In some implementations, the serving DU configuration includes the serving cell ID and configures the association between the serving cell ID and the first non-LTM TCI state configuration.

[0072] When communicating with base station 104, UE 102 sends at least one measurement report (304) to DU 174. In some implementations, the at least one measurement report includes a Layer 1 (L1) measurement report and / or a Layer 3 (L3) measurement report for at least one serving cell and / or for at least one non-serving cell of UE 102. For each of the L3 measurement reports, DU 174 sends a DU-to-CU message (306) including the L3 measurement report to CU 172. In some implementations, the DU-to-CU message of event 306 is an F1 Application Protocol (F1AP) message (e.g., a UL RRC messaging message). In some implementations, DU 174 does not send or avoids sending L1 measurement reports to CU 172. The at least one serving cell includes cell 124A and / or other cells, and the at least one non-serving cell includes cell 124B and / or cell 124C. In some implementations, the serving DU configuration or serving CU configuration includes at least one measurement configuration. In some implementations, in event 302, UE 102 receives one or more RRC messages (e.g., RRCReconfiguration messages) from CU 172 via DU 174, including at least one measurement configuration. Based on the at least one measurement configuration, UE 102 performs measurements and sends at least one measurement report to DU 174 in the form of 304. In some implementations, the at least one measurement configuration includes an L3 measurement configuration (e.g., MeasConfig IE) and / or an L1 measurement configuration. The L1 measurement configuration (e.g., CSI-MeasConfig IE) may include an L1 measurement resource configuration and / or an L1 measurement report configuration. The L1 measurement resource configuration can configure reference signals and / or resources of reference signals for UE 102 to measure and obtain L1 measurement results. In some implementations, the reference signals include CSI-RS and / or Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) Resource Block (SSB). For example, the L1 measurement resource configuration is CSI-ResourceConfig IE. In another example, the L1 measurement report configuration configures how UE 102 sends L1 measurement results / reports. For example, the L1 measurement report configuration is CSI-ReportConfig IE. For example, UE 102 sends an L3 measurement report to CU 172 via DU 174 according to the L3 measurement configuration. UE 102 sends an L1 measurement report to DU 174 according to either the L1 measurement configuration or the L1 measurement report configuration. In one implementation, DU 174 does not send an L1 measurement report to CU 172.

[0073] In some implementations, the L1 measurement configuration is a new RRC IE defined for low-layer triggered mobility (LTM) in 3GPP specification 38.331 v18.0.0 and / or later versions. In some implementations, the L1 measurement resource configuration is a new RRC IE defined for LTM in 3GPP specification 38.331 v18.0.0 and / or later versions. In some implementations, the L1 measurement report configuration is a new RRC IE defined for LTM in 3GPP specification 38.331 v18.0.0 and / or later versions. In some implementations, each of the L1 measurement report configurations may include a trigger event configuration that configures a trigger event to trigger UE 102 to send an L1 measurement report. If UE 102 detects the trigger event, UE 102 sends an L1 measurement report to DU 174.

[0074] In some implementations, each of the L1 measurement reports may include at least one L1 measurement result. In some implementations, at least one L1 measurement result includes at least one L1-reference received signal power (L1-RSRP) value and / or at least one L1-signal-to-interference-noise ratio (L1-SINR) value. In some implementations, for each of the L1 measurement reports, UE 102 sends a PUCCH transmission including the L1 measurement report to DU 174. That is, UE 102 sends each of the L1 measurement reports to DU 174 on the PUCCH. In other implementations, for each of the L1 measurement reports, UE 102 sends a PUSCH transmission including the L1 measurement report to DU 174. That is, UE 102 sends each of the L1 measurement reports to DU 174 on the PUSCH. In other implementations, UE 102 sends a portion of the L1 measurement report to DU 174 on the PUCCH and the remainder of the L1 measurement report to the DU on the Physical UL Shared Channel (PUSCH). That is, for each portion of the L1 measurement report, UE 102 sends a PUCCH transmission including the L1 measurement report to DU 174, and for each remainder of the L1 measurement report, UE 102 sends a PUSCH transmission including the L1 measurement report to DU 174. In some implementations, each of the L1 measurement reports is part of a CSI (i.e., a CSI component) or a CSI. In some implementations, UE 102 may include other CSI components in each of the PUCCH and / or PUSCH transmissions described above. In one implementation, other CSI components include, for example, the Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), CSI-RS Resource Indicator (CRI), SSB Resource Indicator (SSBRI), Layer Indicator (LI), and / or Rank Indicator (RI). In some implementations, UE 102 does not send L1 measurement reports to DU 174 in the format of an RRC message.

[0075] In some implementations, each of the L3 measurement reports may include at least one L3 measurement result. In some implementations, at least one L3 measurement result includes at least one RSRP (value) and / or at least one SINR (value). In one implementation, UE 102 sends each of the L3 measurement reports to CU 172 on the PUSCH via DU 174. In some implementations, each of the L3 measurement reports may be an RRC message (e.g., a MeasurementReport message). In some implementations, each of the L3 measurement configurations includes a specific measurement identifier (e.g., measId), and each of the L3 measurement reports includes a specific measurement identifier in a specific L3 measurement configuration. When CU 172 receives an L3 measurement report including a measurement identifier and an L3 measurement result from UE 102 via DU 174, CU 172 can determine that the L3 measurement report is associated with an L3 measurement configuration identified by the measurement identifier.

[0076] In some alternative implementations, for each of at least one measurement report (e.g., an L1 measurement report), in event 304, UE 102 sends a MAC control element (CE) including the measurement report to DU 174. In order to send the MAC CE, UE 102 generates one or more MAC PDUs, each MAC PDU including one or more of the MAC CEs sent to DU 174 in event 304.

[0077] In some implementations, UE 102 measures one or more reference signals according to at least one measurement configuration. The one or more reference signals may include one or more Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) Resource Blocks (SSBs) and / or one or more CSI-RSs. UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurement. DU 174 in cell 124A and other cells (e.g., cell 124B, cell 124C and / or Figure 1A One or more reference signals are transmitted on a cell (not shown in the diagram).

[0078] After receiving one or more of at least one measurement report from UE 102 (e.g., in response to receiving one or more of at least one measurement report from UE 102), base station 104 (i.e., CU 172 or DU 174) determines to prepare a first cell (e.g., cell 124B) for UE 102 for LTM. In some implementations, base station 104 determines to prepare the first cell for UE 102 because at least one measurement report indicates that the first cell can be used by base station 104 to communicate with UE 102. In some implementations, base station 104 determines to prepare the first cell for UE 102 because at least one measurement report indicates that the first cell is eligible to be a candidate cell that can be used for communication with UE 102. In some implementations, CU 172 determines to prepare the first cell for UE 102 if the L3 measurement report indicates that the signal strength and / or quality of the first cell is higher than a first predetermined threshold, better than the strength and / or quality of cell 124A, and / or better than the strength and / or quality of cell 124A by the first predetermined threshold. In other implementations, if the L1 measurement report indicates that the signal strength and / or quality of the first cell is higher than a first predetermined threshold, better than the signal strength and / or quality of cell 124A, and / or better than the signal strength and / or quality of cell 124A by the first predetermined threshold, then DU 174 determines that the first cell is ready for UE 102. Alternatively, regardless of whether a measurement report is received from UE 102, base station 104 determines that the first cell is ready for UE 102.

[0079] When CU 172 determines that a first cell is ready for LTM, CU 172 sends a 308 First CU to DU message to DU 174 to prepare the first cell for UE 102. In some implementations, CU 172 includes the cell identifier (ID) 1 of the first cell in the First CU to DU message to request DU 174 to prepare the first cell for LTM for UE 102. For example, cell ID 1 is the Cell Global Identifier (CGI). In another example, the cell ID is part of the CGI. In yet another example, the cell ID is the Physical Cell ID (PCI). In some implementations, CU 172 includes an LTM indicator in the First CU to DU message to instruct DU 174 to prepare the first cell for LTM. In some implementations, the LTM indicator is the LTM Information IE to be established or the LTM Information IE to be modified. In other implementations, CU 172 includes the LTM indicator in the LTM Information IE to be established and includes the LTM Information IE to be established in the First CU to DU message. In other implementations, CU 172 includes the LTM indicator in the LTM information IE to be modified, and also includes the LTM information IE to be modified in the first CU-DU message. In response to the first CU-DU message, DU 174 generates a first LTM DU configuration (hereinafter referred to as LTM DU configuration 1) for UE 102 for the first cell. DU 174 then sends a first DU-CU message including LTM DU configuration 1 to CU 172 in response to the first CU-DU message. In some implementations, DU 174 may include cell ID 1 along with LTM DU configuration 1 in the IE of the first DU-CU message to indicate that LTM DU configuration 1 is associated with the first cell (i.e., cell ID 1). Instead of responding to a CU-DU message received from CU 172, DU 174 initiates the transmission of the first DU-CU message to CU 172 when DU 174 determines that the first cell is ready.

[0080] In some implementations, DU 174 includes the cell ID of the first cell associated with LTM DU configuration 1 in the first DU to CU message to indicate that LTM DU configuration 1 is configured for or associated with the first cell. CU 172 identifies that LTM DU configuration 1 is configured for or associated with the first cell. In some scenarios and implementations, CU 172 may include additional cell IDs (e.g., cell ID 2, ..., N) in the first CU to DU message to prepare additional cells (e.g., cells 2, ..., N) for UE 102 for LTM, and DU 174 includes additional LTM DU configurations (e.g., LTM DU configuration 2, ..., N), each additional LTM DU configuration configuring a specific cell in the additional cells, as described below. In such cases, DU 174 includes the additional cell IDs associated with each additional LTM DU configuration in the first DU to CU message to indicate which LTM DU configuration is associated with which cell (ID). Cells 1 and / or 2, ..., N are candidate cells.

[0081] In some implementations, CU 172 does not include the (reference) LTM DU configuration in the first CU-DU message. In such cases, DU 174 generates a reference LTM DU configuration, generates LTM DU configurations 1 and / or 2, ..., N (i.e., non-reference LTM DU configurations) based on the reference LTM DU configuration, and includes the reference LTM DU configuration in the first DU-CU message. In other implementations, CU 172 includes the reference LTM DU configuration in the first CU-DU message. In such cases, DU 174 generates LTM DU configurations 1 and / or 2, ..., N, which are incremental configurations used to enhance the reference LTM DU configuration. In yet another implementation, CU 172 includes the reference LTM DU configuration (e.g., the first reference LTM DU configuration) in the first CU-DU message. In such cases, DU 174 generates a reference LTM DU configuration (e.g., a second reference LTM DU configuration) to replace the first reference LTM DU configuration, generates LTM DU configuration 1 and / or 2, ..., N based on the second reference LTM DU configuration, and includes the second reference LTM DU configuration in the first DU to CU message.

[0082] In some implementations, the reference LTM DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some implementations, the reference LTM DU configuration is the CellGroupConfig IE defined in 3GPP specification 38.331. In other implementations, the reference LTM DU configuration includes configuration parameters from the CellGroupConfig IE. In some implementations, the reference LTM DU configuration includes the CSI-MeasConfig IE or configuration parameters for Channel State Information (CSI) measurement and / or reporting.

[0083] In some implementations, the reference LTM DU configuration differs from the service DU configuration. In some implementations, a portion of the reference LTM DU configuration is identical to a portion of the service DU configuration, while the remainder of the reference LTM DU configuration differs from the remainder of the service DU configuration. In other implementations, the reference LTM DU configuration is identical to the service DU configuration.

[0084] After receiving the first DU to CU message, CU 172 generates an RRC reconfiguration message (e.g., an RRCReconfiguration message) that includes LTM DU configuration 1, and sends a second CU to DU message 316, which includes the RRC reconfiguration message, to DU 174. In some implementations, CU 172 includes the reference LTM DU configuration in the RRC reconfiguration message 316. In other implementations, CU 172 does not include the reference LTM DU configuration in the RRC reconfiguration message 316. In some implementations, if CU 172 sends the reference LTM DU configuration to UE 102 during event 302, then CU 172 does not include the reference LTM DU configuration in the RRC reconfiguration message 316. In other implementations, if CU 172 receives the reference LTM DU configuration from DU 174, then CU 172 includes the LTM DU configuration in the RRC reconfiguration message 316. Otherwise, if CU 172 does not receive the reference LTM DU configuration from DU 174, CU 172 will not include the reference LTM DU configuration in RRC reconfiguration message 316.

[0085] In some implementations, CU 172 includes LTM DU configuration 1 and / or LTM CU configuration 1 in a first container (e.g., the field / IE), and includes the first container (e.g., LTM configuration 1) in the RRC reconfiguration messages of events 316 and 318. In such cases, CU 172 generates the first container. The first container is used to indicate to UE 102 that LTM DU configuration 1 and / or LTM CU configuration 1 should not be applied immediately. In some scenarios or implementations, UE 102 receives an RRC reconfiguration message (e.g., the RRC reconfiguration message of event 318) that includes the configuration (e.g., LTM DU configuration 1). If the configuration is included in the first container, UE 102 avoids applying the configuration immediately. Otherwise, if the configuration is not included in the first container, UE 102 can apply the configuration immediately. In some implementations, the first container includes or includes a first add or modify list (e.g., the ltm-CandidateToAddModList field or LTM-CandidateToAddModList IE). CU 172 includes LTM DU configuration 1 and / or LTM CU configuration 1 in the first element (hereinafter referred to as element 1) of the first add or modify list. In some implementations, CU 172 generates an RRC message (e.g., an RRCRecConfiguration message) that includes LTM DU configuration 1 and / or LTM CU configuration 1, and includes the RRC message in element 1. In some implementations, element 1 is an add or modify IE (e.g., LTM-ConfigToAddMod IE, LTM-Candidate IE, LTM-CandidateToAddMod IE, or LTM-CandidateConfigToAddMod IE). When UE 102 receives the first add or modify list, UE 102 may store the first add or modify list in a variable, for example, in its random access memory (RAM). In other alternative implementations, DU 174 generates a first container and includes the first container in the first DU to CU message. In other alternative implementations, DU 174 generates element 1 and includes element 1 in the first DU to CU message.

[0086] In some implementations, CU 172 includes LTM CU configuration 1 in RRC reconfiguration message 316, the first container, or element 1, where LTM CU configuration 1 is associated with LTM DU configuration 1. To associate LTM CU configuration 1 with LTM DU configuration 1, CU 172 may include LTM CU configuration 1 and LTM DU configuration 1 in element 1. In some implementations, CU 172 includes LTM CU configurations 2, ..., N in RRC reconfiguration message 316 or the second container, where LTM CU configurations 2, ..., N are associated with LTM DU configurations 2, ..., N, respectively. To associate LTM CU configurations 2, ..., N with LTM DU configurations 2, ..., N, CU 172 may include LTM CU configurations 2, ..., N and LTM DU configurations in elements 2, ..., N, respectively. In other implementations, CU 172 includes the LTM CU configurations 2, ..., N associated with LTM DU configurations 2, ..., N in elements 2, ..., N, respectively. Alternatively, CU 172 does not include some or all of the LTM CU configurations for LTM DU configuration 1 and / or LTM DU configurations 2, ..., N in the RRC reconfiguration message 316.

[0087] Upon receiving RRC reconfiguration message 316, DU 174 sends RRC reconfiguration message 318 to UE 102. In response, UE 102 sends RRC reconfiguration complete message 320 (e.g., RRCReconfigurationComplete message) to DU 174, which in turn sends a second DU-to-CU message 322 including the RRC reconfiguration complete message to CU 172. In some implementations, CU 172 provides security protection for the RRC reconfiguration message (e.g., integrity protection and / or encryption). For example, CU 172 generates a Message Authentication Code (MAC-I) for integrity of the RRC reconfiguration message, encrypts the RRC reconfiguration message and the MAC-I to obtain an encrypted RRC reconfiguration message and an encrypted MAC-I, and in events 316 and 318, sends a PDCP PDU including the encrypted RRC reconfiguration message and the encrypted MAC-I to UE 102 via DU 174. When UE 102 receives a PDCP PDU from CU 172 via DU 174 (i.e., events 316 and 318), UE 102 decrypts the encrypted RRC reconfiguration and the encrypted MAC-I to obtain the RRC reconfiguration message and MAC-I, and verifies whether the MAC-I is valid. If UE 102 verifies that the MAC-I is invalid, UE 102 discards or ignores the RRC reconfiguration message. In some implementations, UE 102 may initiate an RRC connection reconstruction procedure in response to an invalid MAC-I. Otherwise, if UE 102 verifies that the MAC-I is valid, UE 102 may process the RRC reconfiguration. UE 102 avoids applying (i.e., executing) LTM DU configuration 1 until it receives an LTM command to activate LTM DU configuration 1, as described for events 330 and 350.

[0088] Events 308 (optional) and 310 in Figure 3 This is collectively referred to as LTM preparation process 390. Events 316, 318, 320, and 322 are... Figure 3 This is collectively referred to as the LTM configuration delivery process 394.

[0089] In some implementations, the first CU to DU message is a UE context establishment request message, and the first DU to CU message is a UE context establishment response message. In some implementations, the first CU to DU message is a UE context modification request message, and the first DU to CU message is a UE context modification response or a UE context modification request message. In the case of a UE context modification request message, CU 172 may send a UE context modification confirmation message to DU 174 in response to the UE context modification request message. In some implementations, the second CU to DU message is a DL RRC message passing message. In other implementations, the second CU to DU message is a UE context modification request message. In some implementations, the second DU to CU message is an ULRRC message passing message. In other implementations, the second DU to CU message is a UE context modification response message.

[0090] In some implementations, CU 172 may include the reference LTM CU configuration in RRC reconfiguration message 316 or the first container. In some implementations, CU 172 may generate LTM CU configuration 1 (i.e., the non-reference LTM CU configuration) as an incremental configuration to enhance the reference LTM CU configuration. Similarly, CU 172 may generate some or all of LTM CU configurations 2, ..., N as incremental configurations to enhance the reference LTM CU configuration. Alternatively, in RRC reconfiguration message 316 or the first container, CU 172 includes the reference LTM CU configuration but not the non-reference LTM CU configuration. In some implementations, CU 172 includes the reference LTM CU configuration and / or the reference LTM DU configuration in an additional container (e.g., the reference LTM DU configuration), and includes the additional container in RRC reconfiguration message 316.

[0091] In some implementations, the reference LTM CU configuration differs from the service CU configuration. In some implementations, a portion of the reference LTM CU configuration is identical to a portion of the service CU configuration, while the remainder of the reference LTM CU configuration differs from the remainder of the service CU configuration. In still other implementations, the reference LTM CU configuration is identical to the service LTM CU configuration.

[0092] In some implementations, CU 172 includes the first LTM ID (hereinafter referred to as ID 1) used to identify LTM DU configuration 1 or element 1 in the RRC reconfiguration message. In some implementations, CU 172 includes ID 1 in the first container or element 1. In some implementations, CU 172 assigns ID 1.

[0093] In some implementations, CU 172 may send ID 1 to DU 174, and DU 174 may associate ID 1 with LTM DU configuration 1 and / or cell ID 1. In some implementations, CU 172 may include ID 1 in a first CU-DU message. In other implementations, after receiving the first DU-CU message, CU 172 sends a third CU-DU message including ID 1 to DU 174, instead of including ID 1 in the first CU-DU message. In some implementations, in the third CU-DU message, CU 172 may include LTM DU configuration 1 and ID 1 and indicate the association between ID 1 and LTM DU configuration 1. Therefore, DU 174 may directly associate ID 1 with LTM DU configuration 1. In other implementations, in the third CU-DU message, CU 172 may include cell ID 1 and ID 1 (i.e., the first LTM ID) and indicate the association between cell ID 1 and ID 1. Therefore, DU 174 can associate ID 1 with LTM DU configuration 1 based on the association between cell ID 1 and ID 1, and the association between cell ID 1 and LTM DU configuration 1. In other implementations, CU 172 may include LTM DU configuration 1, cell ID 1, and / or ID 1 in the third CU to DU message and indicate the association between ID 1, LTM DU configuration 1, and / or cell ID 1. In some implementations, DU 174 may send a third DU to CU 172 in response to the third CU to DU message. In some implementations, the third CU to DU message and the third DU to CU message are a UE context modification request message and a UE context modification response message. In some implementations, CU 172 may include ID 1, cell ID 1, and / or LTM DU configuration 1 in the second CU to DU message, as described above. Therefore, the third CU to DU message may be omitted. In some implementations, the third DU to CU message is a UE context modification request message. In such cases, CU 172 sends a UE context modification confirmation message to DU 174 in response to the UE context modification request message.

[0094] In some implementations, events 312 (optional) and / or 314 (optional) are... Figure 3 This is collectively referred to as the LTMID assignment process 392.

[0095] If CU 172 includes ID 1 in the first CU to DU message, DU 174 may include ID 1 in LTM DU configuration 1, the first container, or element 1. Alternatively, DU 174 may not include ID 1 in LTM DU configuration 1, the first container, and / or element 1.

[0096] In some implementations, CU 172 includes the referenced LTM DU configuration in the first container. For example, CU 172 includes the referenced LTM DU configuration in a field of the first container that is different from the field of the first container that includes LTM DU configuration 1. In other implementations, CU 172 includes the referenced LTM DU configuration in the RRC reconfiguration message 316 and outside the first container. For example, CU 172 generates a third container (e.g., field / IE) to include the first container and the referenced LTM DU configuration, and includes the third container in the RRC reconfiguration message 316. In yet another implementation, DU 174 includes the referenced LTM DU configuration in the first container. For example, DU 174 includes the referenced LTM DU configuration in a field of the first container that is different from the field of the first container that includes LTM DU configuration 1. In yet another implementation, DU 174 generates a fourth container (e.g., field / IE) to include the first container and the referenced LTM DU configuration, and includes the fourth container in the first DU to CU message 310. In such cases, CU 172 includes the fourth container in RRC reconfiguration message 316. Alternatively, CU 172 retrieves reference LTM DU configuration and LTM DU configuration 1 from the fourth container and includes reference LTM DU configuration and LTM DU configuration 1, as described above.

[0097] In some implementations, neither CU 172 nor DU 174 is assigned an ID for identifying the reference LTM DU configuration.

[0098] In some implementations, LTM DU configuration 1 includes multiple configuration parameters for UE 102 to communicate with DU 174 on a first cell. In some implementations, these multiple configuration parameters include physical layer configuration parameters (e.g., PhysicalCellGroupConfig IE), MAC layer configuration parameters (e.g., MAC-CellGroupConfig IE), and / or RLC configuration parameters (e.g., RLC-BearerConfig IE). In some other implementations, these multiple configuration parameters include special cell configurations (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE). In some implementations, LTM DU configuration 1 is the CellGroupConfig IE defined in 3GPP specification 38.331. In other implementations, LTM DU configuration 1 includes configuration parameters from the CellGroupConfig IE.

[0099] In some implementations, LTM CU configuration 1 includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, LTM CU configuration 1 includes MeasConfigIE and / or RadioBearerConfigIE as defined in 3GPP specification 38.331, or includes configuration parameters from MeasConfigIE and / or RadioBearerConfigIE. In some implementations, LTM DU configuration 1 includes L1 measurement configuration 1 (e.g., CSI-MeasConfigIE) and / or at least one Configuration Indicator (TCI) status configuration. In other implementations, LTM CU configuration 1 includes L1 measurement configuration and / or TCI status configuration 1. In some implementations, the L1 measurement configuration includes at least one Reference Signal (RS) resource configuration 1 and / or at least one Reporting configuration 1. In some implementations, RS resource configuration 1 configures one or more RSs or one or more RS resources associated with cell 1. RSs include SSBs and / or CSI-RSs. RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of the RS resource configurations 1 includes an RS resource configuration ID. In some implementations, RS resource configuration 1 is a CSI-ResourceConfig IE (or similar). In some implementations, report configuration 1 configures one or more UL resources (e.g., PUCCH or PUSCH resources) on cell 1 for UE 102 to transmit measurement results. In some implementations, each of the report configurations 1 includes one or more RS resource configuration IDs that identify one or more RS resource configurations included in RS resource configuration 1. In some implementations, each configuration in TCI state configuration 1 associates one or two DL RSs with the corresponding quasi-co-located (QCL) type TCI state. The DL RS is associated with cell 1.

[0100] In some implementations, DU 174 includes L1 measurement configuration 1 and / or TCI state configuration 1 in the service DU configuration 1 (e.g., a non-LTM DU configuration). In some implementations, DU 174 includes the service DU configuration in the first DU-to-CU message. In other implementations, DU 174 sends an additional DU-to-CU message including the service DU configuration to CU 172. In some implementations, the additional DU-to-CU message is a UE context modification request message. In some implementations, CU 172 includes the service DU configuration 1 in RRC reconfiguration messages 316 and 318. In other implementations, CU 172 sends another RRC reconfiguration message including the service DU configuration to UE 102 via DU 174.

[0101] In some implementations, DU 174 includes the random access configuration in LTM DU configuration 1. In other implementations, DU 174 does not include the random access configuration in LTM DU configuration 1. In some implementations, if cell 124A and the first cell are not synchronized, DU 174 determines to include the random access configuration in LTM DU configuration 1. Otherwise, if cell 124A and the first cell are synchronized, DU 174 determines not to include the random access configuration in LTM DU configuration 1. In other implementations, if DU 174 determines that UE 102 and the first cell are not yet synchronized in the UL, DU 174 determines to include the random access configuration in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 and the first cell are already synchronized in the UL, DU 174 determines not to include the random access configuration in LTM DU configuration 1. If LTM DU configuration 1 includes a random access configuration, then UE 102 performs a random access procedure in event 332 according to the random access configuration, as described below. Otherwise, if LTM DU configuration 1 does not include a random access configuration or instructs UE 102 to skip the random access procedure in LTM, then UE 102 skips or avoids the random access procedure in event 332 in response to LTM DU configuration 1 excluding the random access configuration.

[0102] In some implementations, regardless of whether cell 124A and the first cell are synchronized, DU 174 includes the random access configuration parameters in LTM DU configuration 1 and / or reference LTM DU configuration. UE 102 performs the random access procedure based on the random access configuration parameters in event 332, as described below. In some implementations, the random access configuration parameters configure physical random access channel (PRACH) resources, the association between SSB and PRACH resources, and / or one or more PRACH timings.

[0103] In some implementations, if cell 124A and the first cell are synchronized, DU 174 determines to include a first indication in LTM DU configuration 1, the first indication configuring UE 102 not to perform a random access procedure on the first cell. Otherwise, if cell 124A and the first cell are not synchronized, DU 174 determines not to include the first indication in LTM DU configuration 1. In other implementations, if DU 174 determines that UE 102 is synchronized with the first cell in the UL, DU 174 determines to include the first indication in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 is not synchronized with the first cell in the UL, DU 174 determines not to include the first indication in LTM DU configuration 1. If LTM DU configuration 1 includes the first indication, UE 102 skips or avoids the random access procedure of event 332 according to or in response to the first indication. Otherwise, if LTMDU configuration 1 does not include the first indication, then UE 102 responds to LTMDU configuration 1 by excluding the first indication and performs a random access procedure in event 332 according to the random access configuration, as described below.

[0104] In some implementations, DU 174 includes reconfiguration with synchronization (e.g., ReconfigurationWithSync IE) in LTM DU configuration 1 or a special cell configuration. In other implementations, DU 174 does not include reconfiguration with synchronization (e.g., ReconfigurationWithSync IE) in LTM DU configuration 1 or a special cell configuration. In some implementations, DU 174 includes LTM cell handover information in the first LTM DU configuration 1. In some implementations, DU 174 includes random access configuration (parameters) in the LTM cell handover information (e.g., the ltm-CellSwitchInfo field or LTM-CellSwitchInfo IE). In some implementations, if cell 124A and the first cell are out of sync, DU 174 determines to include reconfiguration with synchronization in LTM DU configuration 1. Otherwise, if cell 124A is synchronized with the first cell, DU 174 determines not to include the reconfiguration configuration with synchronization in LTM DU configuration 1. In other implementations, if DU 174 determines that UE 102 is not yet synchronized with the first cell in the UL, DU 174 determines to include the reconfiguration configuration with synchronization in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 is already synchronized with the first cell in the UL, DU 174 determines not to include the reconfiguration configuration with synchronization in LTM DU configuration 1. In some implementations, if LTM DU configuration 1 includes the reconfiguration configuration with synchronization, UE 102 performs a random access procedure in event 332 in response to or based on the reconfiguration configuration with synchronization, as described below. Otherwise, if LTM DU configuration 1 does not include the reconfiguration configuration with synchronization, UE 102 skips or avoids the random access procedure in event 332. In some implementations, DU 174 includes the cell ID (i.e., cell ID 1) of cell 1 (i.e., the first cell) in LTM DU configuration 1. In one implementation, cell ID 1 can be a PCI. In another implementation, cell ID 1 is a CGI. In some implementations, cell ID 1 included in LTM DU configuration 1 is a PCI, while cell ID 1 included in the first CU to DU message is a CGI. In some further implementations, LTM DU configuration 1 includes cell index 1, which is an index of cell ID 1 or the first cell. Cell index 1 is not a cell ID. The cell index occupies fewer bits than the cell ID. In some implementations, CU 172 sets cell index 1 to a value and includes cell index 1 in the first CU to DU message of event 308.

[0105] In some implementations, after receiving one or more of the measurement reports for event 304 (e.g., in response to receiving one or more of the measurement reports for event 304), base station 104 (i.e., CU 172 or DU 174) determines additional cells (i.e., cells 2, ..., N) for LTM preparation of UE 102. In one implementation, base station 104 determines to prepare additional cells for LTM preparation of UE 102 because at least one measurement report indicates that the additional cell can be used by base station 104 to communicate with UE 102. The additional cell may include cell 124C and / or cells other than cells 124A, 124B, and 124C. In some implementations, if an L3 measurement report indicates that the signal strength and / or quality of a particular cell in the additional cells is higher than a corresponding predetermined threshold and / or better than cell 124A, then CU 172 determines to prepare said particular cell for LTM preparation of UE 102. In other implementations, if the L1 measurement report indicates that the signal strength and / or quality of a specific cell in the additional cells is higher than a first predetermined threshold and / or better than cell 124A, then DU 174 determines to prepare the specific cell for UE 102 for LTM. In one implementation, the corresponding predetermined threshold for the additional cell may be different from the first predetermined threshold. In another implementation, the corresponding predetermined threshold for the additional cell may be the same as the first predetermined threshold. In some implementations, the corresponding predetermined threshold for the additional cell may be the same or different. Alternatively, regardless of whether a measurement report is received from UE 102, base station 104 determines to prepare the additional cell for UE 102.

[0106] When CU 172 determines that an additional cell is to be prepared, CU 172 and DU 174 initiate and perform at least one additional LTM preparation procedure (LTM preparation procedure) to prepare the additional cell for LTM, wherein each of the LTM preparation procedures is similar to procedure 390. When DU 174 determines that an additional cell is to be prepared, DU 174 and CU 172 initiate and perform at least one additional LTM preparation procedure (LTM preparation procedure) to prepare the additional cell for LTM, wherein each of the LTM preparation procedures is similar to procedure 390.

[0107] In some implementations, CU 172 and DU 174 perform LTM preparation procedures 2, ..., N to prepare cells 2, ..., N respectively, similar to procedure 390. CU 172 may include cell IDs 2, ..., N in CU-DU messages 2, ..., N in LTM preparation procedures 2, ..., N respectively, similar to the first CU-DU message. In LTM preparation procedures 2, ..., N, DU 174 generates LTM DU configurations 2, ..., N for cells 2, ..., N, and includes LTM DU configurations 2, ..., N in DU-CU messages 2, ..., N respectively, as described for LTM DU configuration 1. Upon receiving CU-DU messages 2, ..., N, DU-CU messages 2, ..., N respond to CU-DU messages 2, ..., N respectively. "N" is an integer greater than one. For example, "N" is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16. In another example, the maximum number of "N" is 4, 8, 16, or 32. At least some of the examples and implementation options discussed in LTM DU Configuration 1 can also be applied to LTM DU Configuration 2, ..., N.

[0108] In other implementations, CU 172 and DU 174 perform a single LTM preparation process (i.e., LTM preparation process 390) to prepare cells 1, 2, ..., N. In this case, DU 174 includes LTM DU configurations 1, 2, ..., N for cells 1, 2, ..., N respectively in the first DU to CU message. In the first DU to CU message, DU 174 may include cell IDs 1, 2, ..., N associated with LTM DU configurations 1, 2, ..., N respectively to indicate that LTM DU configurations 1, 2, ..., N are configured for cell IDs 1, 2, ..., N respectively. If CU 172 determines to perform LTM preparation process 390, CU 172 includes cell IDs 1, 2, ..., N in the first CU to DU message to request DU 174 to prepare cells 1, 2, ..., N for LTM respectively.

[0109] After receiving LTM DU configurations 2, ..., N from DU 174, CU 172 may include LTM DU configurations 2, ..., N in a first container. In some implementations, CU 172 may include LTM DU configurations 2, ..., N in elements 2, ..., N respectively, and include elements 2, ..., N in the first container. In some implementations, CU 172 may include the LTM IDs (i.e., ID 2, ..., N) used to identify LTM DU configurations 2, ..., N in the RRC reconfiguration message. In some implementations, CU 172 may include ID 2, ..., N in the first container. For example, CU 172 may include ID 2, ..., N and LTM DU configurations 2, ..., N in elements 2, ..., N in a first add or modify list.

[0110] In some implementations, CU 172 assigns IDs 2, ..., N to LTM DUs respectively. In other implementations, CU 172 receives IDs 2, ..., N from DU 174 in the first DU to CU message of process 390. In yet another implementation, CU 172 receives IDs 2, ..., N from DU 174 in the DU to CU messages 2, ..., N of LTM preparation processes 2, ..., N respectively.

[0111] In some implementations, CU 172 and DU 174 can perform an LTM ID assignment process for each of LTM DU configurations 2, ..., N, similar to process 392. In other implementations, CU 172 can include IDs 2, ..., N and LTM DU configurations 2, ..., N in a third CU-DU message and indicate the association between IDs 2, ..., N and LTM DU configurations 2, ..., N respectively. Therefore, DU 174 can associate LTM DU configurations 2, ..., N with IDs 2, ..., N respectively. In yet another implementation, CU 172 can include cell IDs 2, ..., N and IDs 2, ..., N in a third CU-DU message and indicate the association between cell IDs 2, ..., N and IDs 2, ..., N respectively. Therefore, DU 174 can associate LTM DU configurations 2, ..., N with ID 2, ..., N respectively, based on the association between cell IDs 2, ..., N and ID 2, ..., N, and the association between cell IDs 2, ..., N and LTM DU configurations 2, ..., N. In other implementations, CU 172 can include IDs 2, ..., N, cell IDs 2, ..., N, and / or LTM DU configurations 2, ..., N in the second CU to DU message, as described above. Therefore, the third CU to DU message can be omitted. In yet another implementation, CU 172 can include IDs 2, ..., N in the first CU to DU message and indicate that IDs 2, ..., N are associated with cell IDs 2, ..., N respectively. In one implementation, DU 174 includes IDs 2, ..., N in LTM DU configurations 2, ..., N. Therefore, CU 172 does not include ID 2, ..., N in the RRC reconfiguration message, the first container, and / or elements 2, ..., N.

[0112] In some alternative implementations, DU 174 assigns IDs 2, ..., N. In some implementations, DU 174 includes IDs 2, ..., N in the first DU to CU message of process 390. In yet another implementation, DU 174 includes IDs 2, ..., N in DU to CU messages 2, ..., N of LTM preparation process 2, ..., N. CU 172 may include IDs 2, ..., N in the RRC reconfiguration message. In other implementations, DU 174 includes IDs 2, ..., N in LTMDU configuration 2, ..., N. Therefore, CU 172 does not include the ID (e.g., LTM ID) that identifies each of LTM DU configurations 2, ..., N in the RRC reconfiguration message, the first container, and / or element 1.

[0113] In some alternative implementations, CU 172 may generate a second container, including LTM DU configuration 2, ..., N or element 2, ..., N, instead of using the first container. CU 172 then sends an additional RRC reconfiguration message including the second container to UE 102 via DU 174, similar to events 316 and 318. In response, UE 102 sends an additional RRC reconfiguration complete message to CU 172 via DU 174, similar to events 320 and 322. In some implementations, the second container may be a second add-or-modify list (e.g., the ltm-ConfigToAddModList field, LTM-ConfigToAddModListIE, ltm-CandidateConfigToAddModList field, or LTM-CandidateConfigToAddModList IE), and each of elements 2, ..., N may be an add-or-modify IE (e.g., the ltm-ConfigToAddMod field, LTM-ConfigToAddMod IE, ltm-CandidateConfigToAddMod field, or LTM-CandidateConfigToAddMod IE). When UE 102 receives the second add-or-modify list, UE 102 may store the second add-or-modify list together with the first add-or-modify list in a variable, for example, in its random access memory (RAM).

[0114] In some implementations, DU 174 includes cell IDs 2, ..., N in LTM DU configurations 2, ..., N to identify cells 2, ..., N. In one implementation, each of cell IDs 2, ..., N is a PCI. In some other implementations, LTM DU configurations 2, ..., N include cell indices 2, ..., N indexed for cell IDs 2, ..., N or cells 2, ..., N respectively. When CU 172 prepares cells 2, ..., N for LTM in process 390, CU 172 may set cell indices 2, ..., N to different values ​​and include cell indices 2, ..., N in the first CU-to-CU-to-DU message of event 308. When CU 172 prepares cells 2, ..., N in an additional LTM preparation process, CU 172 may set cell indices 2, ..., N to different values ​​and include cell indices 2, ..., N in the CU-to-DU message of the additional LTM preparation process. CU 172 sets cell indices 1, ..., N to different values. In some implementations, the cell IDs 1, ..., N in the LTM DU configuration 1, ..., N are different from the cell IDs 1, ..., N in the CU to DU message described above.

[0115] In some implementations, each of the LTM DU configurations 1, ..., N includes physical configuration parameters, MAC configuration parameters, RLC configuration parameters, and / or L1 measurement configuration. In some implementations, each of the LTM DU configurations 1, ..., N may be a CellGroupConfig IE as defined in 3GPP specification 38.331. In other implementations, each of the LTM DU configurations 1, ..., N includes configuration parameters as defined in the CellGroupConfig IE in 3GPP specification 38.331. In still other implementations, multiple configuration parameters in each of the LTM DU configurations include specific cell configurations (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE). In some implementations, the LTM DU configurations 1, ..., N are CellGroupConfig IEs as defined in 3GPP specification 38.331. In other implementations, the LTM DU configurations 1, ..., N include configuration parameters from the CellGroupConfig IE.

[0116] In some implementations, CU 172 may include one or more additional LTM CU configurations in at least one of elements 2, ..., N, the first container, or the second container. Each of the additional LTM CU configurations is associated with a specific LTM DU configuration in LTM DU configurations 2, ..., N. Examples and implementations of the additional LTM CU configurations are similar to those of LTM CU configuration 1.

[0117] In some implementations, CU 172 determines to release LTM DU configuration M (or element M in element 1, ..., M) from LTM DU configurations 1, ..., N. 1 ≤ M ≤ N. In response to this determination, CU 172 sends an RRC reconfiguration message to UE 102 via DU 174 to instruct UE 102 to release LTM DU configuration M or element M. In one implementation, CU 172 generates a release list including an ID (i.e., LTM ID) M for releasing LTM DU configuration M or element M, and includes the release list in the RRC reconfiguration message. In response to the RRC reconfiguration message, UE 102 releases LTM DU configuration M or element M and sends an RRC reconfiguration complete message to CU 172 via DU 174. In response to this determination, CU 172 sends a CU-DU message to DU 174 to instruct DU 174 to release LTM DU configuration M. To instruct DU 174 to release the LTM DU configuration M, CU 172 can include the cell IDM or ID (i.e., LTM ID) M in the release indication (e.g., a field or IE) of the CU to DU message. In response, DU 174 releases the LTM DU configuration M and sends a DU to CU message to CU 172. In some implementations, the CU to DU message and the DU to CU message are respectively a UE context modification request message and a UE context modification response message.

[0118] In other implementations, DU 174 determines to release LTM DU configuration K. In response to this determination, DU 174 sends a DU-to-CU message to CU 172 to release LTM DU configuration K. To indicate that LTM DU configuration K is released, DU 174 may include the cell ID K or ID (i.e., LTM ID) K in the release indication (e.g., a field or IE) in the DU-to-CU message. 1 ≤ K ≤ N. After receiving the DU-to-CU message (e.g., in response to receiving the DU-to-CU message), CU 172 generates a release list including ID (i.e., LTMID) K to release LTM DU configuration K or element K, and sends an RRC reconfiguration message including the release list to UE 102 via DU 174. In response, UE 102 releases LTM DU configuration K or element K and sends an RRC reconfiguration complete message to UE 102 via DU 174. CU 172 may send a CU-to-DU message to DU 174 in response to the DU-to-CU message. In some implementations, the DU to CU message and the CU to DU message are respectively the UE context modification request message and the UE context modification confirmation message.

[0119] After receiving an RRC reconfiguration in event 318 or sending an RRC reconfiguration completion message in event 320, UE 102 sends at least one measurement report (324) to DU 174, similar to event 304. In some implementations, DU 174 may send a DU-CU message (326) including at least one measurement report to CU 172, similar to event 306. In other implementations, DU 174 does not send at least one measurement report to CU 172. In some implementations, at least one measurement report in event 324 includes an L1 measurement report or an L3 measurement report, as described for event 304. In some implementations, UE 102 sends at least one measurement report (324) to DU 174 on PUCCH and / or PUSCH, similar to event 304. In other implementations, UE 102 sends at least one MAC CE (324) including at least one measurement report to DU 174, similar to event 304. In some implementations, UE 102 does not send L1 measurement reports to DU 174 in the format of RRC messages.

[0120] In some implementations, UE 102 sends at least one measurement report (324) to DU 174 according to at least one measurement configuration. The at least one measurement configuration configures UE 102 to perform measurements and report measurement results. CU 172 sends at least one measurement configuration to UE 102 via DU 174. For example, in events 302 and / or 316 and / or after events 306 or 316, CU 172 may send one or more RRC messages (e.g., RRCReconfiguration messages) including at least one measurement configuration to UE 102 via DU 174. The one or more RRC messages may or may not include the RRC reconfiguration message of event 316. According to at least one measurement configuration, UE 102 performs measurements on one or more reference signals. The one or more reference signals may include one or more SSBs and / or one or more CSI-RSs. UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurements and includes the at least one L1 measurement result and / or at least one L3 measurement result in the at least one measurement report of event 324. DU 174 transmits one or more reference signals on cell 124A, cell 1, and / or cell 2, ..., N. The one or more reference signals may be CSI-RS or SSB.

[0121] In some implementations, at least one measurement configuration includes an L3 measurement configuration (e.g., a MeasConfig IE), as described for event 304. In other implementations, at least one measurement configuration includes or includes an L1 measurement configuration, as described above. In yet another implementation, the L1 measurement configuration may be a CSI-MeasConfig IE as defined in 3GPP specification 38.331 v18.0.0 and / or later versions. The L1 measurement configuration may include RS resource configuration and / or reporting configuration. UE 102 sends a 324 L1 measurement report to DU 174 on a UL resource (e.g., a PUCCH resource or a PUSCH resource) according to the reporting configuration. DU 174 receives the L1 measurement report on the UL resource according to the reporting configuration. In some implementations, the reporting configuration is a CSI-ReportConfig IE or similar. In other implementations, each of the reporting configurations is a new RRC IE. In some implementations, each of the reporting configurations configures periodic reporting and / or event-triggered reporting of L1 measurement results.

[0122] In some implementations, the L1 measurement report is a CSI report. In other implementations, the L1 measurement report is a MACCE. In some implementations, each of the measurement reports includes one or more RS resource indicators and / or one or more quantized measurement values. UE 102 measures the RS or RS resource according to the RS resource configuration and / or reporting configuration, and obtains quantized measurement values ​​from the measurements. In some implementations, the RS resource indicator indicates the RS or RS resource in which UE 102 performs measurements or obtains quantized measurement values. In some implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRI) and / or one or more CSI-RS resource indicators (CRI). Quantized measurement values ​​may include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0123] In other implementations, at least one measurement configuration includes a new type of measurement configuration (e.g., an LTM measurement configuration). The new type of measurement configuration may be newly defined in 3GPP specification v18.0.0 and / or later versions. In some implementations, the new type of measurement configuration includes a reference signal resource configuration that configures the resources in which DU 174 transmits reference signals. For example, the reference signal resource configuration includes CSI-RS and / or SSB. In one implementation, the reference signal resource configuration is a CSI-ResourceConfig IE. In another implementation, the new type of measurement configuration includes a measurement report configuration, as described above. UE 102 transmits a measurement report to DU 174 on the PUCCH or MAC CE according to the measurement report configuration. DU 174 receives the measurement report on the PUCCH or MAC CE according to the measurement report configuration. In such cases, the measurement report may be an L1 measurement report or a new type of measurement report (e.g., an LTM measurement report). In some implementations, the new type of measurement configuration includes configuration parameters newly defined in 3GPP specification v18.0.0 and / or later versions.

[0124] Upon receiving a measurement report in event 324 (e.g., in response to receiving a measurement report in event 324), DU 174 generates a first LTM command to activate LTM DU configuration 1 (i.e., the first LTM command instructs UE 102 to apply LTM DU configuration 1 or to make a change to the serving cell of cell 1). DU 174 then sends the first LTM command 330 to UE 102. In some implementations, DU 174 sends the first LTM command to UE 102 on cell 124A. In other implementations, DU 174 sends the first LTM command to UE 102 on cell 124D. In some implementations, DU 174 may include ID 1 in the first LTM command to indicate LTM DU configuration 1 or element 1, and UE 102 determines (e.g., identifies) LTM DU configuration 1 or element 1 based on ID 1.

[0125] In other implementations, DU 174 may include cell index 1, which is indexed to cell ID 1, in the first LTM command. UE 102 determines (e.g., identifies) LTM DU configuration 1 or element 1 based on cell index 1. Before receiving the first LTM command, UE 102 retrieves cell index 1 from LTM DU configuration 1 or element 1 and establishes association 1 between cell index 1 and LTM DU configuration 1 or element 1. In other words, before receiving the first LTM command, UE 102 decodes LTM DU configuration 1 or element 1 to obtain cell index 1. Therefore, UE 102 identifies LTM DU configuration 1 or element 1 based on cell index 1 and association 1. Before receiving the first LTM command, UE 102 retrieves cell indices 2, ..., N from LTM DU configurations or elements 2, ..., N, and establishes associations 2, ..., N between cell indices 2, ..., N and LTM DU configurations or elements 2, ..., N, respectively. In other words, before receiving the first LTM command, UE 102 decodes the LTM DU configuration or elements 2, ..., N to obtain cell indices 2, ..., N.

[0126] In other implementations, DU 174 includes cell ID 1 in the first LTM command, where cell ID 1 identifies cell 1. In some implementations, the cell ID 1 included in the first LTM command is the same as the cell ID 1 included in the first CU to DU message. In other implementations, DU 174 determines the cell ID 1 included in the first LTM command (e.g., PCI) from the cell ID 1 received in the first CU to DU message (e.g., CGI). UE 102 determines (e.g., identifies) LTM DU configuration 1 or element 1 based on cell ID 1. Before receiving the first LTM command, UE 102 retrieves cell ID 1 from LTM DU configuration 1 or element 1 and establishes an association 1 between cell ID 1 and LTM DU configuration 1 or element 1. In other words, before receiving the first LTM command, UE 102 decodes LTM DU configuration 1 or element 1 to obtain cell ID 1. Therefore, UE 102 identifies LTM DU configuration 1 or element 1 based on cell ID 1 and association 1 (received in the first LTM command). Before receiving the first LTM command, UE 102 retrieves cell IDs 2, ..., N from LTM DU configurations or elements 2, ..., N, and establishes associations 2, ..., N between cell IDs 2, ..., N and LTM DU configurations or elements 2, ..., N, respectively. In other words, before receiving the first LTM command, UE 102 decodes LTM DU configurations or elements 2, ..., N to obtain cell IDs 2, ..., N. In some implementations, DU 174 has a mapping table for storing mappings between PCI1, ..., N and CGI1, ..., N for cells 1, ..., N, respectively.

[0127] In other implementations, DU 174 may include a bitmap instead of ID 1 or cell index 1 in the first LTM command to activate LTM DU configuration 1. The number of bits in the bitmap is greater than or equal to "N". In one implementation, bits 1, ..., N correspond to the following: cell index 1, ..., N; ID 1, ..., N; LTM DU configuration 1, ..., N; or element 1, ..., N, and DU 174 sets the corresponding bit (e.g., bit 1) in the bitmap to a first value to indicate cell index 1, ID 1, LTM DU configuration 1, or element 1. Therefore, UE 102 can determine cell index 1, ID 1, LTM DU configuration 1, or element 1 based on bit 1 in the bitmap set to a first value. In another implementation, bits 0, ..., N-1 correspond to the following: cell index 1, ..., N; ID 1, ..., N; LTM DU configuration 1, ..., N; or element 1, ..., N, respectively, and DU174 sets the corresponding bit (e.g., bit 0) in the bitmap to a first value to indicate cell index 1, ID 1, LTM DU configuration 1, or element 1. Therefore, UE 102 can determine cell index 1, ID 1, LTM DU configuration 1, or element 1 based on bit 0 set to the first value in the bitmap. In this implementation, DU 174 sets the remaining bits in the bitmap to a second value to indicate that the remainder of LTM DU configuration 1, ..., N is not activated. In some implementations, the first value is one, and the second value is zero. In other implementations, the first value is zero, and the second value is one. Generally, if DU 174 determines that UE 102 is activating LTM DU configuration L or changing the serving cell to cell L, DU 174 may set the corresponding bit in the bitmap (e.g., bit L or bit L-1) to a first value and set the remaining bits to a second value, where 1 ≤ L ≤ N. In some implementations, DU 174 sets at most one bit in the bitmap to the first value.

[0128] After determining or identifying LTM DU configuration 1 or element 1, UE 102 then applies LTM DU configuration 1 and / or LTM CU configuration after receiving the first LTM command (e.g., in response to receiving the first LTM command).

[0129] In some implementations, at least one measurement report of event 324 (e.g., an L1 measurement report or a new type measurement report) includes at least one measurement result for the first cell, the TRP of the first cell, or a reference signal transmitted on the first cell. The reference signal may be CSI-RS or SSB. DU 174 determines to activate LTM DU Configuration 1 or send a first LTM command based on at least one measurement result. In some implementations, DU 174 determines to activate LTM DU Configuration 1 because at least one measurement result is higher than a second predetermined threshold, when at least one measurement result is higher than the second predetermined threshold, or if at least one measurement result is higher than the second predetermined threshold. In some implementations, at least one measurement result includes an L1-RSRP value, an L1-RSRQ value, and / or an L1-SINR value. In other implementations, at least one measurement result includes the RSRP value, RSRQ value, and / or SINR value of a new type measurement report. In some implementations, the second predetermined threshold is different from the first predetermined threshold. In one implementation, the second predetermined threshold is greater than the first predetermined threshold. In this scenario, at least one measurement indicates that the first cell is suitable for communication with UE 102. In another implementation, the second predetermined threshold is equal to the first predetermined threshold. In this case, at least one measurement indicates that the first cell consistently exceeds either the second or the first predetermined threshold. This indicates that the first cell is suitable for communication with UE 102. Therefore, for UE 102, DU 174 determines to activate LTM DU configuration 1 in response to the first cell's signal strength or quality exceeding the second predetermined threshold.

[0130] In some implementations, at least one measurement report (e.g., an L3 measurement report) for events 324 and 326 includes at least one measurement result for the first cell. CU 172 determines to activate LTM DU configuration 1 or send a first LTM command because at least one measurement result indicates that the signal strength or quality of the first cell is higher than a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In one implementation, the second predetermined threshold is greater than the first predetermined threshold. In this implementation, at least one measurement report for event 326 indicates that the signal strength or quality of the first cell is suitable for communication with UE 102. In another implementation, the second predetermined threshold is equal to the first predetermined threshold. In this implementation, at least one measurement report for event 326 indicates that the signal strength or quality of the first cell is consistently higher than either the second or first predetermined threshold. This also indicates that the first cell is suitable for communication with UE 102. Therefore, CU 172 determines to activate LTM DU configuration 1 in response to the signal strength or quality of the first cell being higher than the second predetermined threshold. In response to the determination, CU 172 sends a fourth CU-DU message (328) to DU 174 to activate LTM DU configuration 1 or trigger a serving cell change for UE 102 to cell 1. In some implementations, CU 172 includes ID 1 in the fourth CU-DU message. In other implementations, CU 172 includes cell index 1 in the fourth CU-DU message. In response to the fourth CU-DU message, DU 174 sends a first LTM command (330) to UE 102 and optionally sends a fourth DU-CU message to CU 172. In some implementations, CU 172 includes cell index 1 in the fourth CU-DU message. Therefore, DU 174 can determine the activation of LTM DU configuration 1 based on cell index 1. In other implementations, CU 172 may include cell ID 1 in the fourth CU-DU message. Therefore, DU 174 determines the activation of LTM DU configuration 1 based on cell ID 1. In other implementations, CU 172 may include ID 1 in the fourth CU to DU message. Therefore, DU 174 can determine the activation of LTM DU configuration 1 based on ID 1. In some implementations, the fourth CU to DU message and the fourth DU to CU message are the UE context modification request message and the UE context modification response message, respectively. In other implementations, the fourth CU to DU message and / or the fourth DU to CU message are new interface messages, such as the F1 Application Protocol (F1AP) message defined in 3GPP specification 38.473 v18.0.0 and / or later versions.

[0131] When it is determined that LTM DU configuration 1 is activated or the first LTM command 330 is sent, or in response to determining that LTM DU configuration 1 is activated or the first LTM command 330 is sent, DU 174 may send a DU-to-CU message 329 to CU 172 indicating that LTM is (being) executed. In some implementations, the DU-to-CU message is an LTM cell change notification message. In some implementations, DU 174 includes cell ID 1 or ID 1 (i.e., LTM ID) in the DU-to-CU message 329 to indicate that DU 174 will activate LTM DU configuration 1 or trigger a fast serving cell change (i.e., LTM serving cell change). The DU may send the DU-to-CU message 329 to CU 172 before or after sending the LTM command 330.

[0132] In some implementations, the first LTM command is the MAC CE included in the MAC PDU received by UE 102 from DU 174 in event 330. The MAC CE may be a new MAC CE defined in 3GPP specification 38.321 v18.0.0 and / or later versions. In one implementation, DU 174 includes a sub-header identifying the new MAC CE in the MAC PDU, and UE 102 identifies the new MAC CE in the MAC PDU based on the sub-header. The sub-header may include a logical channel ID or an extended logical channel ID defined in the 3GPP specification to identify the new MAC CE. For example, the logical channel ID or extended logical channel ID is newly defined in 3GPP specification 38.321 v18.0.0 and / or later versions. In other implementations, the first LTM command is the DCI received by UE 102 on the PDCCH from DU 174 in event 330. DU 174 generates a Cyclic Redundancy Check (CRC) for DCI, scrambles the CRC with the first C-RNTI of UE 102, and transmits the DCI and the scrambled CRC on the PDCCH in event 330. In one implementation, the DCI format can be an existing DCI format defined in the 3GPP specification (e.g., 38.212). In another implementation, the DCI format can be a new DCI format defined in the 3GPP specification (e.g., 38.212 v18.0.0 or later).

[0133] In some implementations, DU 174 does not provide security protection (e.g., integrity protection and / or encryption) for the first LTM command. This speeds up the processing of the first LTM command in UE 102 because UE 102 does not perform security checks (e.g., decryption and / or integrity checks) on the first LTM command.

[0134] In some implementations, after receiving the first LTM command, UE 102 may send a 331 acknowledgment to DU 174 on cell 124A or cell 124D to indicate that UE 102 has received the first LTM command. In some implementations, the acknowledgment is a HARQ ACK. In other implementations, the acknowledgment is a MAC CE. For example, the MAC CE is an existing MAC CE defined in 3GPP specification 38.321 v17.2.0 and / or later versions. In another example, the MAC CE is a new MAC CE defined in 3GPP specification 38.321 v18.0.0 and / or later versions. In yet another implementation, the acknowledgment is a PUCCH transmission.

[0135] In some implementations, CU 172 sends an RRC reconfiguration message 316 in response to an L3 measurement report 306 for the first cell. To configure UE 102 to send the L3 measurement report 306, CU 172 may send a first RRC reconfiguration message to UE 102 before event 306, including the L3 measurement configuration (e.g., MeasConfig IE). In some implementations, DU 174 sends a first LTM command 330 in response to an L1 measurement report 324 for the first cell. To configure UE 102 to send an L1 or new type measurement report 324, CU 172 may send a second RRC reconfiguration message to UE 102, including the L1 or new type measurement configuration. In some implementations, the first RRC reconfiguration message and the second RRC reconfiguration message may be the same message (i.e., the same instance). In other implementations, the first RRC reconfiguration message and the second RRC reconfiguration message are different messages. In some implementations, the second RRC reconfiguration message is the RRC reconfiguration message for event 316. In other implementations, the second RRC reconfiguration message is different from the RRC reconfiguration message for event 316.

[0136] Upon receiving the first LTM command (e.g., in response to receiving the first LTM command), UE 102 accesses the first cell 332. UE 102 identifies LTM DU configuration 1 based on ID 1, cell ID 1, or cell index 1 received in the first LTM command, and applies LTM DU configuration 1 to communicate with DU 174 on the first cell. In some implementations, UE 102 disconnects from cell 124A after receiving the first LTM command (e.g., in response to receiving the first LTM command) or after sending acknowledgment 331. In some implementations, UE 102 ceases communication on cell 124A after receiving acknowledgment 330 to the first LTM command or sending acknowledgment 331 (e.g., in response to receiving acknowledgment 330 to the first LTM command or sending acknowledgment 331). In some implementations, UE 102 accesses the first cell by performing a random access procedure with DU 174 on the first cell in response to receiving the first LTM command. In other implementations, after receiving the first LTM command (e.g., in response to receiving the first LTM command), UE 102 skips the random access procedure and sends a first transmission (e.g., a PUSCH transmission or a PUCCH transmission) to DU 174 on the first cell.

[0137] In some implementations, DU 174 configures UE 102's access to the first cell in LTM DU configuration 1, including whether UE 102 performs a random access procedure. When a first LTM command (e.g., a first LTM instruction) is received, UE 102 determines whether to perform a random access procedure on the first cell according to LTM DU configuration 1. If LTM DU configuration 1 configures UE 102 to perform a random access procedure, then in event 332, UE 102 performs a random access procedure on the first cell to connect to the first cell. For example, LTM DU configuration 1 includes a reconfiguration configuration with synchronization (e.g., ReconfigurationWithSyncIE) to configure UE 102 to perform a random access procedure when UE 102 receives an LTM command for the first cell. In other implementations, in LTM DU configuration 1, DU 174 configures UE 102 to skip the random access procedure for LTM serving cell change to the first cell. In this scenario, upon receiving the first LTM command, in event 332, UE 102 skips the random access procedure and sends a first transmission (e.g., a PUSCH transmission or a PUCCH transmission) to DU 174 on the first cell. In some implementations, DU 174 excludes a synchronized reconfiguration configuration in LTM DU configuration 1 to configure UE 102 to skip the random access procedure for LTM serving cell change to the first cell.

[0138] In other implementations, LTM DU configuration 1 includes a reconfiguration configuration with synchronization or a random access configuration. In such cases, DU 174 configures in the LTM command whether UE 102 performs a random access procedure on the first cell. Therefore, UE 102 determines whether to perform a random access procedure on the first cell in event 332 based on the first LTM command. In some implementations, DU 174 includes an indication (e.g., a field) indicating skipping the random access procedure in the first LTM command. In response to the indication or the first LTM command including the indication, UE 102 skips the random access procedure and directly transmits a first transmission (e.g., a PUSCH transmission or a PUCCH transmission) on the first cell to access the first cell. In other implementations, DU 174 excludes the indication in the first LTM command to configure UE 102 to perform a random access procedure. In response to the first LTM command excluding the indication, UE 102 performs a random access procedure on the first cell to access the first cell. In some other implementations, DU 174 includes a timing advance value in the first LTM command to indicate skipping the random access procedure. In response to receiving the timing advance value or a first LTM command including the timing advance value, UE 102 uses the timing advance value to skip the random access procedure and transmits a first transmission on the first cell to access the first cell. In yet another implementation, DU 174 excludes the timing advance value in the first LTM command to configure UE 102 to perform a random access procedure. In response to excluding the timing advance value in the first LTM command, UE 102 performs a random access procedure on the first cell to access the first cell.

[0139] In some implementations, the random access procedure is a four-step random access procedure. In other implementations, the random access procedure is a two-step random access procedure. In some implementations, the random access procedure is a contention-free random access procedure. In other implementations, the random access procedure is a contention-based random access procedure. In the case of a four-step random access procedure, UE 102 sends message 3, including the UE identifier, to DU 174 via the first cell during the random access procedure. DU 174 responds to message 3 by sending a contention resolution message (e.g., message 4) to UE 102. In the case of a two-step random access procedure, UE 102 sends message A, including the UE identifier, to DU 174 via the first cell during the random access procedure. DU 174 responds to message A by sending a contention resolution message (e.g., message B) to UE 102. In some implementations, when UE 102 receives a contention resolution message from DU 174 on the first cell, UE 102 determines that UE 102 has successfully completed the random access procedure (i.e., UE 102 has successfully accessed the first cell). In some implementations, LTM DU configuration 1 includes a second C-RNTI, and the UE identifier is the second C-RNTI of UE 102. In this type of implementation, the contention resolution message is a PDCCH transmission addressed to the second C-RNTI. In other implementations, LTM DU configuration 1 does not include a C-RNTI, and the UE identifier is the first C-RNTI. In this type of implementation, the contention resolution message is a PDCCH transmission addressed to the first C-RNTI. In some implementations, DU 174 includes the second C-RNTI in a reconfiguration configuration with synchronization. In other implementations, DU 174 includes the second C-RNTI in LTM cell handover information.

[0140] When LTM DU configuration 1 includes a dedicated random access preamble, the random access procedure is a contention-free random access procedure. In this case, UE 102 sends the dedicated random access preamble to DU 174 via the first cell. When UE 102 receives a random access response including the ID of the dedicated random access preamble from DU 174 on the first cell, UE 102 determines that UE 102 has successfully completed the random access procedure (i.e., UE 102 has successfully accessed the first cell).

[0141] If DU 174 configures UE 102 to perform a random access procedure on the first cell, as described above, then DU 174 will detect that UE 102 has accessed the first cell when it receives message 3, message A, or a special preamble during the random access procedure. If DU 174 configures UE 102 to skip the random access procedure, then DU 174 will detect that UE 102 has accessed the first cell when it receives the first transmission.

[0142] In some implementations, UE 102 transmits a first transmission (e.g., a PUSCH transmission) on the first cell using a UL grant. In some implementations, the first LTM command includes a UL grant. In other implementations, when UE 102 performs an LTM serving cell change to the first cell, in response to the first LTM command, UE 102 receives a first DCI including a UL grant on the PDCCH of the first cell. In some implementations, when UE 102 switches to the first cell in response to the first LTM command, UE 102 attempts to receive the first DCI or a UL grant by monitoring one or more PDCCHs on the first cell according to LTM DU configuration 1. While monitoring one or more PDCCHs on the first cell, UE 102 receives the first DCI and its CRC on the PDCCH. If LTM DU configuration 1 includes a second C-RNTI, UE 102 uses the CRC and the second C-RNTI to determine that the first DCI was transmitted to UE 102. In the case where LTM DU configuration 1 does not include a second C-RNT, UE 102 uses CRC and the first C-RNTI to determine that the first DCI is sent to UE 102.

[0143] In some implementations, CU 172 transmits at least one first TCI state configuration (e.g., LTM TCI state configuration) for the first cell to UE 102 via DU 174. In some implementations, each of the first TCI state configurations configures a TCI state for UE 102 to transmit and / or receive data and / or control signals on the first cell. Each TCI state associates or includes one or two DL RSs with a corresponding QCL type, and the DL RSs may be associated with a specific cell in cell 1, ..., N. DL RSs include SSBs and / or Tracking Reference Signals (TRS). In some implementations, CU 172 receives a DU-to-CU message including the first TCI state configuration from DU 174 and transmits an RRC message including the first TCI state configuration to UE 102 via DU 174. In other implementations, DU 174 includes the first TCI state configuration in a serving DU configuration (e.g., CellGroupConfig IE) and includes the serving DU configuration in the DU-to-CU message. In some implementations, the DU to CU message is either DU to CU message 310 or DU to CU message 314. In other implementations, the DU to CU message is a different message from messages 310 and 314. For example, the DU to CU message may be a UE context modification response message or a UE context modification request message.

[0144] In some implementations, DU 174 includes LTM DU configuration 1 in the first interface protocol IE / field of the DU to CU message 310, and includes the service DU configuration in the second interface protocol IE / field of the DU to CU message 314. In some implementations, events 312 (optional) and / or 314 (optional) in Figure 3 This is collectively referred to as the LTM TCI state configuration process 392.

[0145] In some implementations, CU 172 includes the service DU configuration in the RRC message. In some implementations, CU 172 avoids including the service DU configuration in the container used for LTM (e.g., the first container). In some implementations, CU 172 includes LTM ID 1 and the first LTM TCI state configuration in an element for LTM, an add-or-modify list for LTM, or a container similar to element 1, the first add-or-modify list for LTM, or the first container, respectively, and CU 172 includes said element, said add-or-modify list for LTM, or said container in the RRC message. In some implementations, the RRC message is RRC reconfiguration messages 316, 318. In such cases, CU 172 may include the first LTM TCI state configuration in element 1. In other implementations, RRC reconfiguration is another RRC reconfiguration message ( Figure 3 (Not shown in the image). In some implementations, DU 174 also includes the first TCI state configuration in LTM DU configuration 1. In other implementations, DU 174 avoids including the first TCI state configuration in LTM DU configuration 1.

[0146] In some implementations, the first interface protocol IE / field is the first F1AP IE / field, and the second interface protocol IE / field is the second F1AP IE / field. In some implementations, one of the first F1AP IE / field and the second F1AP IE / field is the F1AP CellGroupConfig IE / field, and the other is not the F1AP CellGroupConfig IE / field. In some implementations, DU 174 includes the first F1AP IE / field in the DU-to-CU RRC information IE in message 314, and includes the second F1AP IE / field in the DU-to-CU RRC information IE in the DU-to-CU message. In other implementations, neither the first F1AP IE / field nor the second F1AP IE / field is the F1AP CellGroupConfig IE / field. In other implementations, the second F1AP IE / field is the DU-to-CU RRC information IE, and the first F1AP IE / field is a new IE specifically for including LTM DU configuration.

[0147] In some implementations, DU 174 sends at least one first LTM TCI state activation / deactivation command to UE 102 to activate some of the first LTM TCI state configurations. UE 102 activates some of the first LTM TCI state configurations in response to the first LTM TCI state activation / deactivation command. In some implementations, DU 174 indicates the deactivation of some of the first LTM TCI state configurations in some of the first LTM TCI state activation / deactivation commands. In some implementations, DU 174 uses the activated LTM TCI state configuration or the first LTM TCI state configuration to transmit one or more DL RSs on the candidate cell. The DL RS may include one or more SSBs and / or one or more TRSs. In some implementations, UE 102 uses the activated LTM TCI state configuration to receive DL RSs. UE 102 can obtain L1 measurement results from the received DL RSs and send the L1 measurement results to DU 174. UE 102 can obtain L3 measurement results from the received DL RS and transmit the L3 measurement results to CU 172 via DU 174. In some implementations, DU 174 avoids using the first LTM TCI state configuration to communicate with UE 102 on the serving cell. In some implementations, UE 102 avoids using the first LTM TCI state configuration to communicate with DU 174 on the serving cell.

[0148] In some implementations, each of the first LTM TCI state activation / deactivation commands is a MAC CE (e.g., a candidate cell TCI state activation / deactivation command). In some implementations, DU 174 includes LTM ID 1 in each of the first LTM TCI state activation / deactivation commands to identify the first LTM TCI state configuration. In other implementations, DU 174 includes a candidate cell index (e.g., cell index 1) in each of the first LTM TCI state activation / deactivation commands to identify the first LTM TCI state configuration. In such cases, the candidate cell index is different from LTM ID 1. In some implementations, each of the first LTM TCI state configurations may include a candidate cell index. Alternatively, CU 172 includes the candidate cell index in an RRC message that includes the first LTM TCI state configuration. For example, CU 172 includes the candidate cell index in element 1. In some alternative implementations, UE 102 and DU 174 determine the candidate cell index from the PCI of the first cell. In such cases, base station 104 does not send the candidate cell index to UE 102.

[0149] In some implementations, upon receiving the first LTM command or accessing the first cell (e.g., in response to receiving the first LTM command or accessing the first cell), UE 102 uses some or all of the first LTM TCI state configuration in event 336 to perform DL reception (e.g., monitoring one or more PDCCHs) or UL transmission on the first cell. In other implementations, upon receiving the first LTM command or accessing the first cell (e.g., in response to receiving the first LTM command or accessing the first cell), UE 102 performs DL reception (e.g., monitoring one or more PDCCHs) or UL transmission on the first cell in event 336 without using the first LTM TCI state configuration.

[0150] In some implementations, each of the first LTM TCI state configurations includes a TCI state ID that identifies the corresponding TCI state configuration. For example, the first LTM TCI state configuration includes LTM TCI state configurations 1, ..., L, where L is a positive integer greater than zero. LTM TCI state configurations 1, ..., L include TCI state IDs 1, ..., L that respectively identify LTM TCI state configurations 1, ..., L. In some implementations, DU 174 includes TCI state ID 1 in the first LTM command to instruct UE 102 to activate LTM TCI state configuration 1 for communication on the first cell. UE 102 activates LTM TCI state configuration 1 in response to receiving TCI state ID 1 in the first LTM command. In some implementations, UE 102 uses (activated) LTM TCI state configuration 1 to access 332 on the first cell. In other implementations, UE 102 accesses 332 on the first cell without using the first LTM TCI state configuration. In some implementations, UE 102 uses (activated) LTM TCI state configuration 1 to communicate on the first cell 336. In some implementations, DU 174 uses activated LTM TCI state configuration 1 to communicate with UE 102 on the first cell 336.

[0151] In some implementations, in events 332 and / or 336, UE 102 uses LTM TCI state configuration 1 to monitor one or more PDCCHs, receive one or more DL RSs, receive one or more PDSCH transmissions, and / or send a first transmission and / or one or more additional transmissions. In some implementations, DU 174 detects 332 to UE 102 accessing a first cell and / or communicating with UE 102 on the first cell based on LTM TCI state configuration 1. In some implementations, DU 174 receives the first transmission 332 from UE 102 on the first cell and / or receives the additional transmission 336 based on TCI state configuration 1. In other implementations, in events 332 and / or 336, DU 174 sends one or more PDCCHs, one or more PDSCH transmissions, and / or one or more DL RSs based on LTM TCI state configuration 1.

[0152] In some implementations, in addition to TCI State ID 1, DU 174 also includes TCI State ID 2 in the first LTM command to instruct UE 102 to activate TCI State Configuration 2 for communication on the first cell. UE 102 activates LTM TCI State Configuration 1 in response to receiving TCI State ID 1 in the first LTM command, and activates LTM TCI State Configuration 2 in response to receiving TCI State ID 2 in the first LTM command. After receiving the first LTM command (e.g., in response to receiving the first LTM command), UE 102 uses activated LTM TCI State Configurations 1 and 2 to access 332 the first cell and / or communicate on the first cell 336. After sending the first LTM command or receiving an acknowledgment 331 (e.g., in response to sending the first LTM command or receiving an acknowledgment 331), DU 174 uses activated LTM TCI State Configurations 1 and 2 to communicate with UE 102 on the first cell in events 332 and / or 336.

[0153] In some implementations, after one or more TCI state configurations (e.g., TCI state configuration 1 and / or 2) indicated in the application LTM command (e.g., the first LTM command) are applied, UE 102 requires time (e.g., beam application time or cell handover delay) to acquire the TCI state configured in the TCI state configuration (e.g., synchronizing and / or receiving the DL RS configured in the TCI state configuration). The time used to acquire the TCI state is considered the handover delay. In such cases, DU 174 takes the handover delay into account when communicating with UE 102 on the first cell in events 332 and / or 336. For example, after sending the first LTM command or receiving acknowledgment 331, DU 174 begins communicating with UE 102 on the first cell using the activated LTM TCI state configuration 1 and / or 2 after the handover delay in events 332 and / or 336.

[0154] In some implementations, UE 102 uses LTM TCI state configuration 1 to monitor one or more PDCCHs, receive one or more DL RSs, and / or receive one or more PDSCH transmissions from DU 174 on the first cell, and uses LTM TCI state configuration 2 to send a first transmission and / or one or more additional transmissions to DU 174 on the first cell. In such implementations, DU 174 uses LTM TCI state configuration 1 to send one or more control signals, one or more PDCCHs, one or more DL RSs, and / or one or more PDSCH transmissions to UE 102 on the first cell, and uses LTM TCI state configuration 2 to receive a first transmission and / or one or more additional transmissions from UE 102 on the first cell. Each of the control signals includes DCI and a scrambled CRC for DCI.

[0155] In other implementations, UE 102 uses LTM TCI state configuration 1 to monitor one or more PDCCHs from DU 174 on the first cell, and uses LTM TCI state configuration 2 to receive one or more PDSCH transmissions from DU 174 on the first cell. Each of the control signals includes DCI and a scrambled CRC for DCI. In such implementations, DU 174 uses LTM TCI state configuration 1 to send one or more control signals to UE 102 on one or more PDCCHs on the first cell, and uses LTM TCI state configuration 2 to send one or more PDSCH transmissions to UE 102 on the first cell. In some implementations, UE 102 uses LTM TCI state configuration 1 to send a first transmission and / or one or more additional transmissions to DU 174 on the first cell. In such implementations, DU 174 uses LTM TCI state configuration 1 to receive a first transmission and / or one or more additional transmissions from UE 102 on the first cell. In other implementations, UE102 may use LTM TCI state configuration 2 to send a first transmission and / or one or more additional transmissions to DU 174 in the first cell. In such implementations, DU 174 may use LTM TCI state configuration 2 to receive the first transmission and / or one or more additional transmissions from UE 102 in the first cell.

[0156] In another implementation, UE 102 uses TCI state configuration 1 and TCI state configuration 2 to monitor one or more PDCCHs on the first cell, and uses one of TCI state configuration 1 and TCI state configuration 2 to transmit a first transmission and / or one or more additional transmissions on the first cell. In such an implementation, DU 174 uses LTM TCI state configuration 2 to transmit one or more control signals on one or more PDCCHs and to receive a first transmission and / or one or more additional transmissions from UE 102 on the first cell. Each of the control signals includes DCI and a scrambled CRC for DCI.

[0157] In some implementations, CU 172 receives a CN-BS message containing the UE capability IE of UE 102 from CN 110 (e.g., CN 110 or AMF 164), for example, during event 302. For example, the CN-BS message is an NG Application Protocol (NGAP) message. In other implementations, CU 172 receives a BS-BS message containing the UE capability IE from another base station (e.g., base station 106), for example, before event 302. In yet another implementation, CU 172 receives a UE capability information message containing the UE capability IE from UE 102 via DU 174 or another DU, for example, during event 302. In some implementations, DU 174 receives the UE capability IE of UE 102 (e.g., UE-NR-capability or UE-6G-capability) from CU 172, for example, during event 302.

[0158] In some implementations, the UE capability IE indicates that UE 102 supports RACH-less LTM. Therefore, based on the indication of supporting RACH-less LTM, DU 174 configures and / or activates one or more LTM TCI state configurations for UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support RACH-less LTM, DU 174 avoids configuring and / or activating LTM TCI state configurations for UE 102. For example, DU 174 avoids including the LTM TCI state configuration for UE 102 in the DU-to-CU message described above. Therefore, CU 712 does not send the LTM TCI state configuration to UE 102. For example, CU 172 does not include the LTM TCI state configuration in RRC reconfiguration messages 316, 318.

[0159] In other implementations, the UE capability IE indicates that the UE supports Early Timing Advance (TA) acquisition. Based on the indication of supporting Early TA acquisition, DU 174 configures and / or activates one or more LTM TCI state configurations for UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support Early TA acquisition, DU 174 avoids configuring and / or activating LTM TCI state configurations for UE 102. For example, DU 174 avoids including the LTM TCI state configuration for UE 102 in the DU to CU message described above. Therefore, CU 712 does not send the LTM TCI state configuration to UE 102. For example, CU 172 does not include the LTM TCI state configuration in RRC reconfiguration messages 316, 318.

[0160] In other implementations, the UE capability IE indicates that the UE supports UE-based TA acquisition (e.g., the UE acquires UL synchronization based on Reference Signal Time Difference (RSTD) measurements). Based on the indication of supporting UE-based TA acquisition, DU 174 configures and / or activates one or more LTM TCI state configurations for UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support UE-based TA acquisition, DU 174 avoids configuring and / or activating LTM TCI state configurations for UE 102. For example, DU 174 avoids including the LTM TCI state configuration for UE 102 in the DU-to-CU message described above. Therefore, CU 712 does not send the LTM TCI state configuration to UE 102. For example, CU 172 does not include the LTM TCI state configuration in RRC reconfiguration messages 316, 318.

[0161] In other implementations, the UE capability IE indicates that the UE supports the LTM TCI state. Based on the indication of LTM TCI state support, DU 174 configures and / or activates one or more LTM TCI state configurations for UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support the LTM TCI state, DU 174 avoids configuring and / or activating the LTM TCI state configuration for UE 102. For example, DU 174 avoids including the LTM TCI state configuration for UE 102 in the DU-to-CU message described above. Therefore, CU 712 does not send the LTM TCI state configuration to UE 102. For example, CU 172 does not include the LTM TCI state configuration in RRC reconfiguration messages 316, 318.

[0162] In other implementations, DU 174 is unsure whether to provide an LTM TCI state configuration for UE 102. DU 174 provides an LTM TCI state configuration for UE 102 to CU 172, as described above. CU 172 determines whether to send a first LTM TCI state configuration to UE 102. In some implementations, CU 172 sends a first LTM TCI state configuration to UE 102 based on an indication of support for RACH-less LTM, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support RACH-less LTM, CU 172 avoids sending an LTM TCI state configuration to UE 102. For example, CU 172 avoids sending a first LTM TCI state configuration to UE 102. For example, CU 172 avoids including the first LTM TCI state configuration in RRC reconfiguration messages 316, 318.

[0163] In other implementations, based on the indication that early TA acquisition is supported, CU 172 sends the first LTM TCI state configuration to UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support early TA acquisition, CU 172 avoids sending the LTM TCI state configuration to UE 102. For example, CU 172 avoids sending the first LTM TCI state configuration to UE 102. For example, CU 172 avoids including the first LTM TCI state configuration in RRC reconfiguration messages 316, 318.

[0164] In other implementations, based on an indication that UE-based TA acquisition is supported, CU 172 sends a first LTM TCI state configuration to UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support UE-based TA acquisition, CU 172 avoids sending the LTM TCI state configuration to UE 102. For example, CU 172 avoids sending the first LTM TCI state configuration to UE 102. For example, CU 172 avoids including the first LTM TCI state configuration in RRC reconfiguration messages 316, 318.

[0165] In other implementations, based on the indication of LTM TCI state support, CU 172 sends the first LTM TCI state configuration to UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support LTM TCI state, CU 172 avoids sending the LTM TCI state configuration to UE 102. For example, CU 172 avoids sending the first LTM TCI state configuration to UE 102. For example, CU 172 avoids including the first LTM TCI state configuration in RRC reconfiguration messages 316 and 318.

[0166] In some alternative implementations, DU 174 may not activate or may determine that the (LTM) TCI state configuration in the first LTM command is not activated. In such cases, DU 174 does not include the TCI state ID in the first LTM command. Therefore, when UE 102 receives a first LTM command that does not include the TCI state configuration, UE 102 avoids using the first LTM TCI configuration to access the first cell and / or communicate on the first cell.

[0167] In some implementations, if the UE capability IE indicates that UE 102 does not support RACH-less LTM, then DU 174 does not include the TCI state ID in the first LTM command or avoids including the TCI state ID in the first LTM command. Otherwise, if the UE capability IE indicates that UE 102 supports RACH-less LTM, then DU 174 includes one or more TCI state IDs (e.g., TCI state ID1 and / or TCI state ID2) in the first LTM command, as described above.

[0168] In other implementations, if DU 174 is not configured with an LTM TCI configuration for the first cell for UE 102, then DU 174 does not include the TCI status ID in the first LTM command or avoids including the TCI status ID in the first LTM command. Otherwise, if DU 174 is configured with one or more LTM TCI status configurations (e.g., a first LTM TCI status configuration), then DU 174 includes one or more LTM TCI status IDs (e.g., TCI status ID 1 and / or TCI status ID 2) in the first LTM command.

[0169] In other implementations, if the UE capability IE indicates that UE 102 does not support early TA acquisition, then DU 174 does not include the TCI state ID in the first LTM command or avoids including the TCI state ID in the first LTM command. Otherwise, if the UE capability indicates that UE 102 supports early TA acquisition, then DU 174 includes TCI state ID 1 and / or TCI state ID 2 in the first LTM command, as described above.

[0170] In other implementations, if the UE capability IE indicates that UE 102 does not support UE-based TA acquisition, then DU 174 does not include the TCI state ID in the first LTM command or avoids including the TCI state ID in the first LTM command. Otherwise, if the UE capability indicates that UE 102 supports early TA acquisition, then DU 174 includes TCI state ID 1 and / or TCI state ID 2 in the first LTM command, as described above.

[0171] In other implementations, if the UE capability IE indicates that UE 102 does not support LTM TCI state, then DU 174 does not include the TCI state ID in the first LTM command or avoids including the TCI state ID in the first LTM command. Otherwise, if the UE capability IE indicates that UE 102 supports LTM TCI state, then DU 174 includes TCI state ID 1 and / or TCI state ID 2 in the first LTM command, as described above.

[0172] In some implementations, after receiving the first LTM command, UE 102 stops using or disables the first non-LTMTCI configuration.

[0173] After successfully accessing the first cell, UE 102 uses LTM DU configuration 1 and / or references LTM DU configuration to communicate with DU 174 on the first cell 336, and communicates with CU 172 via DU 174. In this case, DU 174 uses LTM DU configuration 1 to communicate with UE 102 on the first cell 336. In some scenarios or implementations, UE 102 communicates with DU 174 on the first cell 336 via PUSCH transmission, PDSCH transmission, PUCCH transmission, PDCCH transmission, and / or sounding reference signal (SRS) transmission.

[0174] When UE 102 receives the reference LTM DU configuration as described above, UE 102 communicates with DU 174 on the first cell 336 according to LTM DU configuration 1 and at least a portion of the reference LTM DU configuration. In other words, UE 102 communicates with DU 174 according to the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration 336. Similarly, DU 174 communicates with UE 102 on the first cell 336 according to LTM DU configuration 1 and at least a portion of the reference LTM DU configuration. In other words, DU 174 communicates with UE 102 according to the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration 336.

[0175] If UE 102 receives neither LTM CU Configuration 1 nor Reference LTM CU Configuration, UE 102 communicates with CU 172 via DU 174 using the serving CU configuration 336. Correspondingly, if CU 172 neither sends LTM CU Configuration 1 nor Reference CU Configuration to UE 102, CU 172 communicates with UE 102 via DU 174 using the serving CU configuration 336. If UE 102 receives both LTM CU Configuration 1 and Reference LTM CU Configuration from CU 172, UE 102 communicates with CU 172 via DU 174 using LTMCU Configuration 1 and at least a portion of the reference LTM CU Configuration not enhanced by LTM CU Configuration 1 336. In this case, CU 172 communicates with UE 102 via DU 174 using LTM CU Configuration 1 and at least a portion of the reference LTMCU Configuration not enhanced by LTM CU Configuration 1 336.

[0176] If UE 102 receives LTM CU configuration 1 from CU 172 but does not receive a reference LTM CU configuration, UE 102 communicates with CU 172 via DU 174 using LTM CU configuration 1 336. In this case, CU 172 communicates with UE 102 via DU 174 using LTM CU configuration 1 336. If LTM CU configuration 1 is fully configured, UE 102 and CU 172 communicate with each other via DU 174 using LTM CU configuration 1 instead of the serving CU configuration 336. In some implementations, if UE 102 does not receive a reference LTM CU configuration from base station 104, UE 102 determines that LTM CU configuration 1 is fully configured. Correspondingly, if CU 172 determines to configure LTM CU configuration 1 as fully configured or to configure LTM CU configuration 1 as fully configured, CU 172 does not send a reference LTM CU configuration to UE 102. In other implementations, CU 172 includes a first indication (e.g., a field or IE) in LTM CU configuration 1, the first container, element 1, or the RRC reconfiguration message 316 to indicate that LTM CU configuration 1 is fully configured. If LTM CU configuration 1 is an incremental configuration for enhancing the service CU configuration, UE 102 and CU 172 communicate with each other via DU 174 336 using LTM CU configuration 1 and at least a portion of the service CU configuration not enhanced by LTM CU configuration 1. In some implementations, if UE 102 does not receive a reference LTM CU configuration from base station 104, UE 102 determines that LTM CU configuration 1 is an incremental configuration for enhancing the service CU configuration. Correspondingly, if CU 172 determines that LTM CU configuration 1 should be configured as an incremental configuration for enhancing the service CU configuration or configured as an incremental configuration for enhancing the service CU configuration, CU 172 does not send a reference LTM CU configuration to UE 102. In some implementations, CU 172 indicates that LTM CU Configuration 1 is an incremental configuration for enhancing service CU configuration by excluding the first indication in LTM CU Configuration 1, the first container, element 1, and / or RRC reconfiguration message 316. Alternatively, CU 172 includes a second indication (e.g., a field or IE) in LTM CU Configuration 1, the first container, element 1, or RRC reconfiguration message 316 to indicate that LTM CU Configuration 1 is an incremental configuration for enhancing service CU configuration. In some implementations, CU 172 indicates that LTM CU Configuration 1 is a full configuration by excluding the second indication in LTM CU Configuration 1, the first container, element 1, and / or RRC reconfiguration message 316.

[0177] If UE 102 receives a reference LTM CU configuration from CU 172 but does not receive LTM CU configuration 1, UE 102 communicates with CU 172 via DU 174 using the reference LTM CU configuration 336. In this case, CU 172 communicates with UE 102 via DU 174 using the reference LTM CU configuration 336. If the reference LTM CU configuration is fully configured, UE 102 and CU 172 communicate with each other via DU 174 using the reference LTM CU configuration instead of the serving CU configuration 336. In some implementations, UE 102 and CU 172 determine that reference LTM CU configuration 1 is fully configured, as specified in 3GPP specifications (e.g., 3GPP specification 38.331v18.0.0 or later). In other implementations, CU 172 includes a first indication (e.g., a field or IE) in the reference LTM CU configuration, the first container, or the RRC reconfiguration message 316 to indicate that the reference LTM CU configuration is a full configuration. If the reference LTM CU configuration is an incremental configuration for enhancing the service CU configuration, then UE 102 and CU 172 communicate with each other via DU 174 336 using the reference LTM CU configuration and at least a portion of the service CU configuration not enhanced by the reference LTM CU configuration. In some implementations, CU 172 indicates that the reference LTM CU configuration is an incremental configuration for enhancing the service CU configuration by excluding the first indication in the reference LTM CU configuration, the first container, element 1, and / or the RRC reconfiguration message 316. Alternatively, CU 172 includes a second indication (e.g., a field or IE) in the reference LTM CU configuration, the first container, element 1, or the RRC reconfiguration message 316 to indicate that the reference LTM CU configuration is an incremental configuration for enhancing the service CU configuration. In some implementations, CU 172 indicates that the reference LTM CU configuration is fully configured by excluding the second indication in the reference LTM CU configuration, the first container, element 1, and / or RRC reconfiguration message 316.

[0178] If UE 102 neither receives the reference LTM CU configuration from CU 172 nor LTM CU configuration 1, UE 102 communicates with CU 172 via DU 174 using the serving LTM CU configuration 336. In this case, CU 172 communicates with UE 102 via DU 174 using the serving LTM CU configuration 336.

[0179] In some implementations, DU 174 includes or configures at least one second non-LTM TCI state configuration for the first cell in LTM DU configuration 1. When communicating with UE 102 at event 332 or 336, DU 174 may send a second non-LTM TCI state activation / deactivation command to UE 102 on the first cell to activate the second non-LTM TCI state configuration and / or deactivate the activated LTM TCI state configuration. In some implementations, DU 174 includes the serving cell index of the first cell in the second non-LTM TCI state activation / deactivation command. DU 174 includes the serving cell index in LTM DU configuration 1. In some implementations, UE 102 stops using or deactivates (activated) LTM TCI state configuration in response to receiving the second non-LTM TCI state activation / deactivation command. In some implementations, the second non-LTM TCI state activation / deactivation command is a MAC CE. MAC CE can be a TCI status activation / deactivation for a UE-specific PDSCH MAC CE, a TCI status indication for a UE-specific PDCCH MAC CE, a PUCCH spatial relationship activation / deactivation MAC CE, an enhanced TCI status activation / deactivation for a UE-specific PDSCH MAC CE, an enhanced PUCCH spatial relationship activation / deactivation MAC CE, an enhanced TCI status indication for a UE-specific PDCCH MAC CE, a PUCCH spatial relationship activation / deactivation for multiple TRP PUCCH duplicate MAC CEs, or a unified TCI status activation / deactivation MAC CE.

[0180] In some implementations, the second non-LTM state configuration can be a Rel-15 / 16 TCI state configuration (i.e., not a unified joint / DL / UL TCI state). This implies that BS 104 can configure a Rel-15 / 16 beam indication framework for the first cell. The non-LTM TCI state configuration activated / indicated by the second non-LTM TCI state activation / deactivation command may only apply to a channel or RS (PDSCH / PDCCH / CSI-RS / PUCCH / SRS). In such implementations, if UE 102 receives a second non-LTM TCI state activation / deactivation command, the UE will deactivate or use the first LTM TCI state for the channel or RS that shares / follows / applies the unified TCI state. For example, if UE 102 receives an enhanced TCI state indication for a UE-specific PDCCH MAC CE, UE 102 will deactivate or use the first LTM TCI state for at least one of other channels that also share / follow / apply a unified TCI state (e.g., PDSCH, PUSCH, PUCCH, CSI-RS, or SRS). If UE 102 receives a second non-LTM TCI state activation / deactivation command, UE 102 can deactivate the activated first LTM TCI state configuration.

[0181] In some implementations, the second non-LTM TCI state configuration includes at least one TCI state configured in the first LTM TCI state configuration. In other implementations, the TCI states in the second non-LTM TCI state configuration are different from the TCI states in the first LTM TCI state configuration. In some implementations, the second non-LTM TCI state configuration configures more TCI states than the first LTM TCI state configuration. In some other implementations, the TCI states in the second non-LTM TCI state configuration are the same as the TCI states in the first LTM TCI state configuration. BS 104 / CU 172 / DU 174 may notify UE 102 in an RRC message or signal whether the first LTM TCI state configuration is the same as or different from the second non-LTM TCI state configuration, or whether it is a subset of the second non-LTM TCI state configuration.

[0182] In some implementations, the first LTM TCI state configuration for the first cell is a subset of the second non-LTM TCI state configuration for the first cell. In some implementations, the TCI state ID of the first LTM TCI state configuration for the first cell does not overlap with or is the same as those TCI state IDs of the second non-LTM TCI state configuration for the first cell. This may imply that when UE 102 receives a second non-LTM TCI state activation / deactivation command, UE 102 considers / determines that the TCI state ID indicated in the second non-LTM TCI state activation / deactivation command refers to either the first LTM TCI state configuration or the second non-LTM TCI state configuration for the first cell. For example, the TCI state ID of the first LTM TCI state configuration for the first cell is in the range #000 to #007; the TCI state ID of the second non-LTM TCI state configuration for the first cell is in the range #008 to #015. In this example, if the second non-LTM TCI state activation / deactivation command indicates TCI state ID #001, then UE 102 activates the first LTM TCI state configuration identified by TCI state ID #001; if the second non-LTM TCI state activation / deactivation command indicates TCI state ID #012, then UE 102 activates the second non-LTM TCI state configuration identified by TCI state ID #012. In some implementations, UE 102 combines or catenates the first LTM TCI state configuration for the first cell and the second non-LTM TCI state configuration for the first cell for non-LTM TCI state activation / indication purposes. In some implementations, UE 102 recognizes or determines the first LTM TCI state configuration for the first cell as or identifies it as a non-LTM TCI state configuration for the first cell.

[0183] In some implementations, DU 174 may not include or configure at least one second non-LTM TCI state configuration for the first cell in LTM DU configuration 1. In such cases, UE 102 recognizes or determines at least one first TCI state configuration (e.g., LTM TCI state configuration) for the first cell as a non-LTM TCI state configuration for the first cell. This may imply that when UE 102 receives a second non-LTM TCI state activation / deactivation command, UE 102 considers / determines that the TCI state ID indicated in the second non-LTM TCI state activation / deactivation command refers to a first LTM TCI state configuration for the first cell. For example, if the second non-LTM TCI state activation / deactivation command indicates TCI state ID #000, then UE 102 activates and / or applies the first TCI state configuration (e.g., LTM TCI state configuration) identified by TCI state ID #000 and performs non-LTM communication in the first cell.

[0184] In some implementations, if the first LTM TCI state configuration is associated with or includes an SSB corresponding to QCL type A, UE 102 avoids using this TCI state configuration for non-LTM purposes or for communication in the first cell. In some implementations, UE 102 may recognize or determine the first LTM TCI state configuration for the first cell as a non-LTM TCI state configuration for the first cell, unless it includes or is associated with an SSB corresponding to QCL type A.

[0185] In some implementations, when DU 174 is communicating with UE 102 on the first cell (332, 336), DU 174 avoids sending an LTM TCI state activation / deactivation command to UE 102 to activate the LTM TCI state configuration for the first cell or associated with LTM ID 1. In other implementations, when DU 174 is communicating with UE 102 on the first cell (332, 336), DU 174 sends a second LTM TCI state activation / deactivation command to UE 102 to activate at least one LTM TCI state configuration from the first LTM TCI state configuration that was not activated by the first LTM command. In response to the second LTM TCI state activation / deactivation command, UE 102 activates the LTM TCI state configuration indicated in the second LTM TCI state activation / deactivation command. In some implementations, in the second LTM TCI state activation / deactivation command, DU 174 may deactivate the LTM TCI state configuration activated in the first LTM command. In such cases, in response, UE 102 deactivates the LTM TCI state configuration activated in the first LTM command. UE 102 and DU 174 use the LTM TCI state configuration activated by the second LTM TCI state activation / deactivation command to communicate with each other on the first cell, as described above.

[0186] In some implementations, UE 102 sends an RRC message (e.g., an RRC reconfiguration complete message) to CU 172 via DU 174 and the first cell to instruct UE 102 to apply LTM DU configuration 1. If UE 102 is performing random access procedure 332, UE 102 may include the RRC message in message 3 or message A. Alternatively, UE 102 sends the RRC message after completing the random access procedure. If UE 102 skips random access procedure 332, UE 102 includes the RRC message in a PUSCH transmission within at least one PUSCH transmission. In some implementations, if UE 102 maintains communication with base station 104 on cell 124A (i.e., UE 102 is not disconnected from cell 124A), UE 102 may send the RRC message to base station 104 via cell 124A. When DU 174 receives the RRC message, DU 174 sends the RRC message to CU 172.

[0187] In other implementations, UE 102 avoids sending an RRC message to base station 104 in response to applying LTM DU configuration 1 or receiving a first LTM command. In such cases, UE 102 may include or send data in message 3, message A, or PUSCH transmission, as described above. UE 102 may generate a MAC PDU and / or RLC PDU that includes the data, and send or include the MAC PDU and / or RLC PDU in PUSCH transmission. For example, the data may be a PDCP PDU, SDAP PDU, LTE Positioning Protocol (LPP) PDU, RRC PDU, and / or NAS PDU. The RRC PDU includes a UL-DCCH- message that excludes the RRC reconfiguration completion message. The NAS PDU includes a Mobility Management (MM) message or a Session Management (SM) message. The MM message may be a 5G MM message or a 6G MM message, and the SM message may be a 5G SM message or a 6G SM message. When DU 174 receives the data, DU 174 sends the data to CU 172.

[0188] When DU 174 determines in event 332 or 336 that UE 102 has successfully connected to the first cell, DU 174 may send a 334 DU to CU message (e.g., access success message) to CU 172 (e.g., the CP of CU 172). In some implementations, DU 174 may include the cell ID 1 of the first cell in the DU to CU message of event 334. The cell ID may be PCI or CGI. Therefore, CU 172 determines that UE 102 is connected to the first cell after receiving the DU to CU message of event 334. When DU 174 determines in event 332 or 336 that UE 102 has successfully connected to the first cell, DU 174 may send a DL data delivery status message or frame to CU 172 (e.g., the UP of CU 172). In some implementations, upon or after receiving the DU-to-CU message 329, CU 172 may stop or suspend sending DL data for UE 102 to DU 174 until receiving the DU-to-CU message 334. CU 172 may do this because DU 174 is unable to buffer DL data for UE 102 during LTM execution in events 330 and / or 332. After receiving the DU-to-CU message 334, CU 172 resumes or continues sending DL data for UE 102 to DU 174. In other implementations, when CU 172 receives the DU-to-CU message 329, CU 172 may continue sending DL data for UE 102 to DU 174. CU 172 may do this because DU 174 may buffer DL data for UE 102 during LTM execution in events 330 and / or 332. When or after DU 174 detects that UE 102 has accessed cell 1, DU 174 sends DL data to UE 102 via cell 1.

[0189] In some implementations, when it is determined that UE 102 is connected to the first cell, sends the first LTM command 330, or receives an acknowledgment 331, DU 174 may stop communicating with UE 102 on cell 124A and / or release the resources of cell 124A configured for UE 102.

[0190] In some implementations, DU 174 may generate some or all of LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as a complete configuration to replace the serving DU configuration. If LTM DU configuration 1 is a complete configuration, then UE 102 and DU 174 communicate with each other based on LTM DU configuration 1 instead of the serving DU configuration 336. In some implementations, DU 174 includes an indication that LTM DU configuration 1 is a complete configuration in LTM DU configuration 1. In each of LTM DU configurations 2, ..., N, DU 174 may include an indication that the corresponding DU configuration is a complete configuration. Each of the indications in LTM DU configurations 1, ..., N may be a field or IE (i.e., the same field or IE). In other implementations, CU 172 may include a single indication that LTM DU configuration 1 and / or 2, ..., N is a complete configuration in the RRC reconfiguration message of events 316, 318. In the case of the second container, CU 172 may include a single indication indicating that LTM DU configurations 2, ..., N are fully configured in the additional RRC reconfiguration message. In yet another implementation, CU 172 may include a single indication indicating that LTM DU configurations 1 and / or 2, ..., N are fully configured in the first container. In yet another implementation, for each of LTM DU configurations 2, ..., N, CU 172 may include a specific indication indicating that the corresponding LTM DU configuration is fully configured in the first container. In the case of the second container, CU 172 may include a single indication indicating that LTM DU configurations 2, ..., N are fully configured in the second container. In yet another implementation, CU 172 may include an indication indicating that LTM DU configuration 1 is fully configured in element 1. In each of elements 2, ..., N, CU 172 may include an indication indicating that the corresponding LTM DU configuration is fully configured. UE 102 can determine whether LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are fully configured based on the above indications. In some implementations, each of the above indications differs from the fullConfig field defined in the current 3GPP specification. In some implementations, each of the above indications is the fullConfig field defined in the current 3GPP specification. If LTM DU configuration 1 is fully configured, and a reference LTM DU configuration is received from base station 104, for example, in RRC reconfiguration message 318, then UE 102 does not apply the reference LTM DU configuration in event 336. In such a case, DU 174 may not include the reference LTM DU configuration in the first DU to CU message 310.

[0191] In other implementations, DU 174 may generate LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as incremental configurations that enhance a portion of the reference LTM DU configuration. In other words, DU 174 generates LTM DU configuration 1, ..., N based on the reference LTM DU configuration. For example, if LTM DU configuration 1 is an incremental configuration, then UE 102 and DU 174 enhance the aforementioned portion of the reference LTM DU configuration with LTM DU configuration 1. Therefore, UE 102 and DU 174 communicate with each other 336 according to LTM DU configuration 1 and do not enhance a portion of the reference LTM DU configuration. In some implementations, LTM DU configuration 1 and / or 2, ..., N, the first container, the second container, or element 1, ..., N excludes indications that LTM DU configuration 1 and / or 2, ..., N is a full configuration to indicate that LTM DU configuration 1 and / or 2, ..., N is an incremental configuration. UE 102 can determine that each of LTM DU configurations 1 and / or 2, ..., N is an incremental configuration based on excluding the indication in LTM DU configurations 1 and / or 2, ..., N, first container, second container, or element 1 and / or 2, ..., N.

[0192] In some implementations, if UE 102 does not receive a reference LTM DU configuration for LTM DU configuration 1 and / or LTM DU configuration 2, ..., N, then UE 102 determines that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are complete configurations. Correspondingly, if DU 174 does not obtain a reference LTM DU configuration for UE 102 (i.e., DU 174 does not generate a reference LTM DU configuration for UE 102 and / or does not receive a reference LTM DU configuration for UE 102 from CU 172), then DU 174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as complete configurations.

[0193] In other implementations, if UE 102 does not receive a reference LTM DU configuration for LTM DU configuration 1 and / or LTM DU configuration 2, ..., N, then UE 102 determines that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are incremental configurations for enhancing the service DU configuration. In this case, UE 102 communicates with DU 174 336 based on LTM DU configuration 1 and at least a portion of the service DU configuration that is not enhanced by LTM DU configuration 1. Correspondingly, if DU 174 does not obtain a reference LTM DU configuration for UE 102 (i.e., DU 174 does not generate a reference LTM DU configuration for UE 102 and / or does not receive a reference LTM DU configuration for UE 102 from CU 172), then DU 174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as incremental configurations for enhancing the service DU configuration. In such cases, DU 174 communicates with UE 102 336 according to at least a portion of LTM DU configuration 1 and service DU configuration.

[0194] In some implementations, UE 102 uses a UE MAC entity (e.g., MAC 204B) to communicate with the DUMAC entity (e.g., MAC 204B) of DU 174 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). In some implementations, UE 102 resets the UE MAC entity after receiving a first LTM command or in response to receiving a first LTM command and before performing a random access procedure 332 or communicating with DU 174 via the first cell 336. In some implementations, DU 174 resets the DU MAC entity after sending a first LTM command, receiving an acknowledgment 331, or determining that UE 102 is connected to the first cell (e.g., in response to sending a first LTM command, receiving an acknowledgment 331, or determining that UE 102 is connected to the first cell).

[0195] In some implementations, when UE 102 resets the UE MAC entity, UE 102 performs at least one of the following actions on the UE MAC entity (i.e., UE MAC reset or full UE MAC reset):

[0196] • Initialize the configured logical channel's Bj to zero;

[0197] • Stop one or more timers;

[0198] • If UE 102 is configured to perform a random access procedure (e.g., event 332) with a configuration (e.g., configuration 1), then timeAlignmentTimer is considered to have expired;

[0199] • Set the New Data Indicator (NDI) used in the UL HARQ process to a value of 0;

[0200] • Set the NDI used for HARQ process ID to a value of 0 to monitor PDCCH in sidelink resource allocation mode 1;

[0201] • Refresh the Msg3 buffer;

[0202] • Refresh the MSGA buffer;

[0203] • Cancel (if any) the triggered scheduling request process;

[0204] • Cancel (if any) the triggered buffer status reporting process;

[0205] • Cancel (if any) the triggered power margin reporting process;

[0206] • Cancel any consistency LBT failures triggered (if any);

[0207] • Cancel any triggered BFRs;

[0208] • Cancel (if any) the sidelink buffer status reporting process that was triggered;

[0209] • Cancel (if any) the preemptive buffer status reporting process that was triggered;

[0210] • Cancel any triggered advance reporting processes;

[0211] • Cancel (if any) the referral rate query process that was triggered;

[0212] • Cancel (if any) the configured uplink authorization confirmation triggered;

[0213] • Cancel (if any) the configured sidelink authorization verification triggered;

[0214] • Cancel any expected protection symbol queries triggered (if any);

[0215] • Cancel (if any) the triggered positioning measurement gap activation / deactivation request process;

[0216] • Flush the soft buffer used for the DL HARQ process;

[0217] • For each of the DL HARQ processes, the next received transmission used for TB is regarded as the first transmission;

[0218] • Release (if any) temporary C-RNTI;

[0219] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0220] In some implementations, when DU 174 resets the DU MAC entity, DU 174 performs at least one of the following actions on the DU MAC entity (i.e., DU MAC reset or full DU MAC reset):

[0221] • Stop one or more timers;

[0222] • If UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), then the timeAlignmentTimer initiated and / or maintained by DU 174 for UE 102 is considered to have expired;

[0223] • Set the NDI used for the DL HARQ process to a value of 0;

[0224] • Refresh the soft buffer used for the UL HARQ process;

[0225] • For each of the UL HARQ processes, the next received transmission for the TB is considered the first transmission;

[0226] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER)

[0227] Depending on the implementation, UE 102 may determine whether to partially or completely reset the UE MAC entity. In some implementations, when UE 102 resets the UE MAC entity as described above, UE 102 completely resets the UE MAC entity (i.e., a full UE MAC reset). In a full UE MAC reset, UE 102 performs some or all of the actions described above. In other implementations, when UE 102 resets the UE MAC entity as described above, UE 102 partially resets the UE MAC entity (i.e., a partial UE MAC reset). In a partial UE MAC reset, UE 102 performs some or a subset or part of the actions in a full UE MAC reset.

[0228] In some implementations, a partial UE MAC reset includes at least one of the following actions:

[0229] • If UE 102 is configured to perform a random access procedure (e.g., event 332) with a configuration (e.g., configuration 1), then UE 102's timeAlignmentTimer is considered to have expired;

[0230] • Refresh the Msg3 buffer;

[0231] • Refresh the MSGA buffer;

[0232] • Release (if any) temporary C-RNTI;

[0233] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0234] In some implementations, partial UE MAC resets also include at least one of the following actions:

[0235] • Cancel (if any) the triggered scheduling request process;

[0236] • Cancel (if any) the triggered buffer status reporting process;

[0237] • Cancel (if any) the triggered power margin reporting process;

[0238] • Cancel any consistency LBT failures triggered (if any);

[0239] • Cancel any triggered BFRs;

[0240] • Cancel (if any) the sidelink buffer status reporting process that was triggered;

[0241] • Cancel (if any) the preemptive buffer status reporting process that was triggered;

[0242] • Cancel any triggered advance reporting processes;

[0243] • Cancel (if any) the referral rate query process that was triggered;

[0244] • Cancel (if any) the configured uplink authorization confirmation triggered;

[0245] • Cancel (if any) the configured sidelink authorization verification triggered;

[0246] • Cancel any expected protection symbol queries triggered (if any);

[0247] • Cancel (if any) the triggered positioning measurement gap activation / deactivation request process;

[0248] In some implementations, partial UE MAC resets also include at least one of the following actions:

[0249] • Stop the first part of one or more timers and keep the rest of one or more timers running;

[0250] • Set the New Data Indicator (NDI) used in the UL HARQ process to a value of 0;

[0251] • Set the NDI used for HARQ process ID to a value of 0 to monitor PDCCH in sidelink resource allocation mode 1;

[0252] • Flush the soft buffer used for the DL HARQ process;

[0253] • For each of the DL HARQ processes, the next received transmission used for TB is regarded as the first transmission;

[0254] Depending on the implementation, DU 174 may determine whether to partially or completely reset the DU MAC entity. In some implementations, when DU 174 resets the DU MAC entity as described above, DU 174 completely resets the DU MAC entity (i.e., a full DU MAC reset). In a full DU MAC reset, DU 174 performs some or all of the actions described above. In other implementations, when DU 174 resets the DU MAC entity as described above, DU 174 partially resets the DU MAC entity (i.e., a partial DU MAC reset). In a partial DU MAC reset, DU 174 performs some or a subset or part of the actions in a full DU MAC reset.

[0255] In some implementations, a partial DU MAC reset includes at least one of the following actions in a partial MAC reset:

[0256] • If UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), then the timeAlignmentTimer initiated and / or maintained by DU 174 for UE 102 is considered to have expired;

[0257] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER)

[0258] In some implementations, a partial DU MAC reset includes at least one of the following actions for a MAC entity (i.e., a DU MAC reset):

[0259] • Stop the first part of one or more timers and keep the rest of one or more timers running;

[0260] • Set the NDI used for the DL HARQ process to a value of 0;

[0261] • Refresh the soft buffer used for the UL HARQ process;

[0262] • For each of the UL HARQ processes, the next received transmission for the TB is considered the first transmission;

[0263] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER)

[0264] In other implementations, UE 102 avoids resetting the UE MAC entity in response to receiving the first LTM command. Similarly, DU 174 avoids resetting the DUMAC entity after sending the first LTM command, receiving acknowledgment 331, or determining that UE 102 is connected to the first cell (e.g., in response to sending the first LTM command, receiving acknowledgment 331, or determining that UE 102 is connected to the first cell). In other words, UE 102 communicates with DU 174 on the first cell using the UE MAC entity (not reset). Similarly, DU 174 communicates with UE 102 on the first cell using the DU MAC entity (not reset) during or after random access procedure 332, or after determining that UE 102 is connected to the first cell.

[0265] In some implementations, UE 102 uses at least one UE RLC entity (e.g., RLC 206B) to communicate RLC PDUs (e.g., events 302, 304, 318, 320, 324, 330, and / or 331) with at least one DU RLC entity (e.g., RLC 206B) of DU 174. In some implementations, UE 102 reconstructs some or all of the at least one UE RLC entity after receiving a first LTM command or in response to receiving a first LTM command and before performing a 332 random access procedure or communicating 336 with DU 174 via the first cell. In some implementations, DU 174 reconstructs some or all of the at least one DU RLC entity after sending a first LTM command, receiving an acknowledgment 331, or determining that UE 102 is connected to the first cell (e.g., in response to sending a first LTM command, receiving an acknowledgment 331, or determining that UE 102 is connected to the first cell).

[0266] In some implementations, LTM DU configuration 1 may or may not include one or more RLC reconstruction indications (e.g., a reestablishRLC field) that configure UE 102 to rebuild some or all of at least one UE RLC entity. If LTM DU configuration 1 includes an RLC reconstruction indication that configures UE 102 to rebuild the first UE RLC entity among at least one UE RLC entity used by UE 102 to communicate with DU 174 using the RLC PDU, then UE 102 rebuilds the first UE RLC entity in response to the RLC reconstruction indication and the first LTM command. In some implementations, UE 102 may rebuild the first UE RLC entity before performing the 332 random access procedure or before communicating with DU 174 via the first cell 336. In other implementations, UE 102 may rebuild the first UE RLC entity during or after the 332 random access procedure. Otherwise, if LTM DU configuration 1 does not include an RLC reconstruction indication, UE 102 avoids rebuilding the first UE RLC entity in response to the first LTM command.

[0267] In some implementations, when UE 102 reconstructs the first UE RLC entity, UE 102 performs at least one of the following actions on the first UE RLC entity:

[0268] • Discard RLC SDU, RLC SDU segments, and RLC PDU (if any);

[0269] • Stop and reset the timer (if it is running);

[0270] • Reset the state variable to its initial value.

[0271] In some implementations, state variables and timers are defined in 3GPP specification 38.322.

[0272] Otherwise, if LTM DU configuration 1 does not include an RLC reconstruction indication for the first UE RLC entity, UE 102 avoids reconstructing the first UE RLC entity upon receiving the first LTM command. In other words, UE 102 avoids the action of reconstructing the first UE RLC entity of UE 102 upon receiving the first LTM command. In some implementations, if LTM DU configuration 1 or element 1 does not include an RLC reconstruction indication but includes an indication that configuration 1 is fully configured, UE 102 may reconstruct the first UE RLC entity of UE 102 upon receiving the first LTM command. Otherwise, if LTM DU configuration 1 or element 1 does not include an RLC reconstruction indication and an indication that configuration 1 is fully configured, UE 102 avoids reconstructing the first UE RLC entity upon receiving the first LTM command.

[0273] Similarly, DU 174 reconstructs some or all of at least one DU RLC entity (e.g., NR RLC 206B) used by DU 174 to communicate with at least one UERLC entity of UE 102 (e.g., events 302, 304, 318, 320, 324, 330 and / or 331) in response to an RLC reconstruction instruction. In some implementations, DU 174 reconstructs the first DU RLC entity among at least one DURLC entity after sending a first LTM command, receiving an acknowledgment from UE 102 for the first LTM command, or determining that UE 102 is connected to the first cell. In some implementations, the acknowledgment is a HARQ ACK. In other implementations, the acknowledgment is a MAC CE. In still other implementations, the acknowledgment is a PUCCH transmission. In some implementations, when base station 104 reconstructs the first DU RLC entity, DU 174 performs at least one of the following actions for the first DU RLC entity:

[0274] • Discard RLC SDU, RLC SDU segments, and RLC PDU (if any);

[0275] • Stop and reset the timer (if it is running);

[0276] • Reset the state variable to its initial value.

[0277] In some implementations, state variables and timers are defined in 3GPP specification 38.322.

[0278] In other implementations, UE 102 avoids rebuilding some or all of at least one UERLC entity in response to receiving a first LTM command. Similarly, DU 174 avoids rebuilding some or more of at least one DU RLC entity after sending the first LTM command, receiving acknowledgment 331, or determining that UE 102 is connected to the first cell (e.g., in response to sending the first LTM command, receiving acknowledgment 331, or determining that UE 102 is connected to the first cell). In other words, UE 102 communicates with DU 174 on the first cell using some or all of at least one UE RLC entity (not rebuilt). For example, some or all of at least one UERLC entity includes a first UE RLC entity and / or a second UE RLC entity. Similarly, DU 174 communicates with UE 102 on the first cell during or after random access procedure 332 or after determining that UE 102 is connected to the first cell using some or all of at least one DU RLC entity (not rebuilt). For example, some or all of at least one DU RLC entity includes a first DU RLC entity and / or a second DU RLC entity.

[0279] In some implementations, in event 302, UE 102 uses at least one UE PDCP entity (e.g., PDCP 210) to communicate UL PDCP PDUs and / or DL ​​PDCPPDUs with at least one CU PDCP entity (e.g., PDCP 210) of CU 172. In some implementations, UE 102 performs a PDCP recovery procedure for some or all of the at least one UE PDCP entity after receiving a first LTM command or in response to receiving a first LTM command. For example, UE 102 performs a PDCP recovery procedure for the first UE PDCP entity among the at least one UE PDCP entities after receiving a first LTM command or in response to receiving a first LTM command. During the PDCP recovery procedure, UE 102 may or may not rebuild the first UE PDCP entity. After performing the PDCP recovery procedure or in response to performing the PDCP recovery procedure, in event 336, UE 102 may retransmit at least a portion of the UL PDCP PDU to CU 172 via DU 174 and the first cell. Similarly, CU 172 performs a PDCP recovery procedure for some or all of at least one CU PDCP entity after sending the first LTM command or in response to sending the first LTM command. For example, CU 172 performs a PDCP recovery procedure for the first CU PDCP entity among at least one CU PDCP entity after sending the first LTM command or in response to sending the first LTM command. In some implementations, CU 172 performs a PDCP recovery procedure for the first CU PDCP entity in response to receiving a DU to CU message 329 or 334. In other implementations, CU 172 performs a PDCP recovery procedure for the first CU PDCP entity in response to receiving a DL data delivery status message. During the PDCP recovery procedure, CU 172 may or may not rebuild the first CU PDCP entity. After performing the PDCP recovery procedure or in response to performing the PDCP recovery procedure, in event 336, CU 172 may retransmit at least a portion of the DL PDCP PDU to UE 102 via DU 174 and the first cell.

[0280] In other implementations, UE 102 avoids rebuilding some or all of at least one UE PDCP entity in response to receiving a first LTM command. For example, some or all of the at least one UE PDCP entity includes a first UE PDCP entity and / or a second UE PDCP entity. Similarly, CU 172 avoids rebuilding some or more of at least one CU PDCP entity after receiving a DU to CU message 329 or 340 (e.g., in response to receiving a DU to CU message 329 or 340) or after receiving a DL data delivery status message (e.g., in response to receiving a DL data delivery status message). In other words, UE 102 communicates with CU 172 via DU 174 and the first cell using some or all of at least one UE PDCP entity (not rebuilt). For example, some or all of the at least one UE PDCP entity includes a first UE PDCP entity and / or a second UE PDCP entity. Similarly, CU 172 communicates with UE 102 via DU 174 and the first cell using some or all of at least one CU PDCP entity (not rebuilt). For example, some or all of at least one CU PDCP entity includes a first CU PDCP entity and / or a second CU PDCP entity.

[0281] In some implementations, after determining that UE 102 is connected to the first cell, CU 172 may send a 338 CU to DU message (e.g., a UE context modification request message) to DU 174 to instruct DU 174 to stop communicating with UE 102 and / or release or suspend resources of cell 124A configured for UE 102. In response, DU 174 may stop communicating with UE 102 on cell 124A and / or release or suspend resources of cell 124A configured for UE 102, and send a 340 DU to CU 172 (e.g., a UE context modification response message). Events 338 (optional) and 340 (optional) in... Figure 3 This is collectively referred to as the resource release or modification process 396.

[0282] After or during communication with DU 174 on the first cell, events 344, 346, 348, 350, 351, 352, 354, and / or 356 may occur, similar to events 324, 326, 328, 330, 331, 332, 334, and / or 336, respectively. UE 102 sends at least one measurement report (344) to DU 174. The at least one measurement report includes at least one measurement result for the second cell (i.e., cell 2). The at least one measurement result indicates that the second cell is suitable for communication with UE 102 and / or the first cell is not suitable for communication with UE 102. Upon receiving at least one measurement report (e.g., in response to receiving at least one measurement report), DU 174 determines to activate LTM DU configuration 2 and generates a second LTM command to activate LTM DU configuration 2 (i.e., the second LTM command instructs UE 102 to apply LTM DU configuration 2). Then, DU 174 sends a second LTM command (350) to UE 102 on the first cell.

[0283] When it is determined that LTM DU configuration 2 is activated or a second LTM command is sent, or in response to activating LTM DU configuration 2 or sending a second LTM command, DU 174 may send a DU-to-CU message 349 to CU 172 indicating that LTM is (being) executed. In some implementations, DU 174 includes cell ID 2 or ID 2 (i.e., LTM ID) in the DU-to-CU message 349 to indicate that DU 174 wants to activate LTM DU configuration 2. DU may send the DU-to-CU message 349 to CU 172 before or after sending the LTM command 350.

[0284] The discussion of events 324, 326, 328, 330, 331, 332, 334 and / or 336 can also be applied to events 344, 346, 348, 350, 351, 352, 354 and / or 356 with simple modifications. For example, replace “Cell 124A”, “First LTM Command”, “First Cell”, “ID 1”, “LTM DU Configuration 1” and / or “LTM CU Configuration 1” with “First Cell”, “Second LTM Command” and “Second Cell”, “ID 2”, “LTM DU Configuration 2” and / or “LTM CU Configuration 2” respectively.

[0285] Events 344, 346, 348, 350, 351, 352, and 354 are in Figure 3 These are collectively referred to as LTM execution process 398. Events 304, 306, 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, and 356 are in... Figure 3This is collectively referred to as the LTM DU configuration and / or activation process 380.

[0286] Next reference Figure 4 In scenario 400, base station 104 includes CU 172, source DU (S-DU) 174A, and target DU (T-DU) 174B. S-DU 174A operates cell 124A and optionally additional cells, while T-DU 174B operates a first cell (e.g., cell 124C). Scenario 400 is similar to scenario 300. Therefore, the description of scenario 300 can be largely applied to scenario 400. The differences between scenarios 300 and 400 are described below.

[0287] Initially, UE 102 uses the serving DU to communicate with S-DU 174A 402 on cell 124A and communicates with CU 172 via S-DU 174A. S-DU 174A is the serving DU, and... Figure 3Similar to DU 174 in A. During communication 402, UE 102 sends at least one measurement report (e.g., L3 measurement report) via S-DU 174A to CU 172, numbers 404 and 406. Based on at least one measurement report, CU 172 determines to prepare cell 1, ..., N for LTM for UE 102 (operated by T-DU 174B), where N is a positive integer greater than 0 or 1. Cell 1, ..., N are identified by cell IDs 1, ..., N, respectively. In response to the determination, CU 172 and T-DU 174B perform a 490 LTM preparation procedure to (request T-DU 174B) prepare cell 1, ..., N for LTM for UE 102. N can be a positive integer greater than zero or 1. In LTM preparation procedure 490, CU 172 sends a CU-DU message including cell IDs 1, ..., N to T-DU 174B to request T-DU 174B to prepare cells 1, ..., N for UE 102 for LTM, similar to event 308. In response, T-DU 174B sends a DU-DU message including LTM DU configurations 1, ..., N to CU 172, similar to event 310. LTM DU configurations 1, ..., N configure cells 1, ..., N for LTM, respectively. Specifically, LTM DU configurations 1, ..., N include configuration parameters for communication on cells 1, ..., N, respectively. In some implementations, the CU-DU message and DU-CU message in procedure 490 are the UE context establishment request message and UE context establishment response message, respectively. CU 172 then sends LTM DU configurations 1, ..., N in an RRC reconfiguration message in LTM configuration delivery procedure 494, similar to LTM configuration delivery procedure 394. In some implementations, the T-DU 174B can include cell indices 1, ..., N in LTM DU configurations 1, ..., N, respectively. In some implementations, the CU 172 can set cell indices 1, ..., N to different values ​​and include cell indices 1, ..., N in the CU to DU message of procedure 490.

[0288] After LTM preparation procedure 490, CU 172 may perform an additional LTM preparation procedure with T-DU 174B to prepare cells N+1, ..., N+M for UE 102 for LTM, similar to procedure 490. M is a positive integer greater than zero. CU 172 may determine to do so based on one or more measurement reports received from UE 102 via S-DU 174A, similar to events 404 and 406. During the additional LTM preparation procedure, CU 172 sends a CU-DU message to T-DU 174B including cell IDs N+1, ..., N+M to request T-DU 174B to prepare cells N+1, ..., N+M for UE 102 for LTM. Cell IDs N+1, ..., N+M identify cell IDs N+1, ..., N+M, respectively. In response to the CU-DU message, T-DU 174B sends a DU-DU message to CU 172 including LTM DU configurations N+1, ..., N+M. The LTM DU configurations N+1, ..., N+M are for LTM configuration cells N+1, ..., N+M, respectively. Specifically, the LTM DU configurations N+1, ..., N+M include configuration parameters for communication on cells N+1, ..., N+M. CU 172 then sends the LTM DU configurations N+1, ..., N+M in an RRC reconfiguration message during the additional LTM DU configuration delivery process, similar to LTM configuration delivery process 394 or 494.

[0289] In some implementations, LTM preparation procedure 490 is a UE context establishment procedure, and the additional LTM preparation procedure is a UE context modification procedure. In other implementations, LTM procedure 490 and the additional LTM preparation procedure are both UE context establishment procedures. In yet another implementation, LTM procedure 490 and the additional LTM preparation procedure are both UE context modification procedures.

[0290] In some implementations, CU 172 and S-DU 174A can perform process 380 with UE 102, such as for Figure 3 As described. In procedure 380, CU 172 and S-DU 174A perform procedures 390 and / or 392 to prepare the S-DU 174A cell for UE 102 for LTM. It should be noted that in procedure 380 or for... Figure 3 The described value N can be related to... Figure 4The described value N may be the same or different. In procedure 390, CU 172 may receive a first DU-to-CU message including the reference LTM DU configuration from S-DU 174A in event 310. In other implementations, CU 172 and S-DU 174A do not perform procedure 380 with UE 102. In such cases, CU 172 may perform a 488 reference LTM DU configuration query procedure with S-DU 174A to obtain the reference LTM DU configuration. In procedure 488, CU 172 sends a 460 CU-to-DU message to S-DU 174A to request or query the reference LTM DU configuration. In some implementations, CU 172 may include an indication of requesting or querying the reference LTM DU configuration in the CU-to-DU message. In response to the indication or CU-to-DU message 460, S-DU 174A sends a 462 DU-to-CU message including the reference LTM DU configuration to CU 172. In some implementations, the indication is a reference LTM DU configuration query indication. In other implementations, the indication is an LTM indication, and CU 172 may include the query indication (e.g., GNB-DU configuration query IE) in the CU-DU message. After receiving the reference LTM DU configuration (i.e., in process 390 or process 488), CU 172 includes the reference LTM DU configuration (received from S-DU 174A) in the CU-DU message in LTM preparation process 490. T-DU 174B generates LTM DU configurations 1, ..., N based on the reference LTM DU configuration received from CU 172. In such cases, T-DU 174B does not include the reference LTM DU configuration in the DU-CU message in process 490. In the case of an additional LTM preparation process, T-DU 174B does not include the reference LTM DU configuration in the DU-CU message in the additional LTM preparation process. CU 172 may omit the reference LTM DU configuration from the CU-DU message during the additional LTM preparation process with T-DU 174B. In the case of the additional LTM preparation process, T-DU 174B generates LTM DU configurations N+1, ..., N+M based on the reference LTM DU configuration received from CU 172.

[0291] In some implementations, CU 172 does not provide a reference LTM DU configuration to T-DU 174B during LTM preparation procedure 490. In this case, T-DU 174B generates a reference LTM DU configuration and generates LTM DU configurations 1, ..., N based on the reference LTM DU configuration. In this case, T-DU 174B includes the reference LTM DU configuration in the DU-to-CU message in procedure 490. CU 172 sends the reference LTM DU configuration in the RRC reconfiguration message in procedure 490. In the case of an additional LTM preparation procedure, T-DU 174B generates LTM DU configurations N+1, ..., N+M based on the reference LTM DU configuration. In this case, T-DU 174B may not include the reference LTM DU configuration in the DU-to-CU message during the additional LTM preparation procedure. In some implementations, the reference LTM DU configuration generated by T-DU 174B differs from the reference LTM DU configuration generated by S-DU 174A. In other implementations, the reference LTM DU configuration generated by T-DU 174B is the same as the reference LTM DU configuration generated by S-DU 174A.

[0292] In some implementations, CU 172 includes the LTM DU configurations 1, ..., N of process 380 in the CU to DU message of process 490, and T-DU 174B generates LTM DU configurations 1, ..., N and / or N+1, ..., N+M taking into account or based on the configurations in the LTM DU configurations of process 380.

[0293] In some implementations, the LTM DU configuration X of process 380 includes at least one reference signal (RS) resource configuration X, where 1 ≤ X ≤ N. Each configuration in RS resource configuration X is associated with one or more RSs or one or more RS resources of cell X of S-DU 174A. RSs include SSBs and / or CSI-RSs. RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of RS resource configurations X includes an RS resource configuration ID. In some implementations, RS resource configuration X is a CSI-ResourceConfig IE (or similar). In some implementations, LTM DU configuration X includes a CSI-MeasConfig IE, and the CSI-MeasConfig IE includes a CSI-ResourceConfig IE. T-DU 174B generates at least one report configuration 1 for reporting measurement results of RSs or RS resources on cell 1 of T-DU 174B, and includes report configuration 1 in LTM DU configuration 1. In some implementations, report configuration 1 is a CSI-ReportConfig IE (or similar). In some implementations, the T-DU 174B generates at least one RS resource configuration 1 considering or based on RS resource configuration X, and includes RS resource configuration 1 in LTM DU configuration 1. In some implementations, the T-DU 174B includes RS resource configuration X in RS resource configuration 1. In other implementations, the T-DU 174B includes each of RS resource configurations X in RS resource configuration 1, except for the RS resource configuration ID in RS resource configuration X. The T-DU 174B assigns an RS resource configuration ID as a value for each of RS resource configurations 1 (including RS resource configuration X), and includes the RS resource configuration ID in the corresponding RS resource configuration.

[0294] In some implementations, Report Configuration 1 configures one or more UL resources (e.g., PUCCH or PUSCH resources) on Cell 1 for UE 102 to transmit measurement results. In some implementations, each of Report Configuration 1 includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in RS Resource Configuration 1. After UE 102 performs an LTM serving cell change from Cell 124A to Cell 1, UE 102 communicates with S-DU 174B (i.e., T-DU 17B becomes UE 102's S-DU) and transmits measurement results on the UL resources to S-DU 174B via Cell 1 according to Report Configuration 1. Correspondingly, S-DU 174B receives measurement results on the UL resources from UE 102 via Cell 1 according to Report Configuration 1. In some implementations, each of the measurement results includes one or more RS resource indicators and / or one or more quantized measurement values. UE 102 measures the RS or RS resource according to RS resource configuration 1 and / or reporting configuration 1, and obtains quantized measurement values ​​from the measurements. In some implementations, an RS resource indicator indicates the RS or RS resource in which UE 102 performs measurements or obtains quantized measurement values. In some implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRI) and / or one or more CSI-RS resource indicators (CRI). Quantized measurement values ​​may include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0295] In some implementations, the T-DU 174B also includes additional RS resource configurations in LTM DU configuration 1. Each configuration in the additional RS resource configurations is associated with one or more additional RSs or one or more additional RS resources in cell 1. Additional RSs include SSBs and / or CSI-RSs. Additional RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of the additional RS resource configurations includes an RS resource configuration ID. In some implementations, the additional RS resource configuration is a CSI-ResourceConfig IE (or similar). In some implementations, the T-DU 174B includes a CSI-ResourceConfig IE in a CSI-MeasConfig IE. The T-DU 174B generates at least one additional reporting configuration for reporting measurement results of RSs or RS resources on cell 1 of the T-DU 174B, and includes the additional reporting configuration in LTMDU configuration 1. In some implementations, the additional reporting configuration is a CSI-ReportConfig IE (or similar).

[0296] In some implementations, the additional report configuration configures one or more UL resources (e.g., PUCCH or PUSCH resources) on cell 1 for UE 102 to transmit measurement results. In some implementations, each of the additional report configurations includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the additional RS resource configuration. After UE 102 performs an LTM serving cell change from cell 124A to cell 1, UE 102 communicates with S-DU 174B 436 and transmits measurement results on the UL resources to S-DU 174B via cell 1 according to the additional report configuration. Correspondingly, S-DU 174B receives measurement results on the UL resources from UE 102 via cell 1 according to the additional report configuration. In some implementations, each of the measurement results includes one or more RS resource indicators and / or one or more quantized measurement values. UE 102 measures the additional RS or additional RS resources according to the additional RS resource configuration and / or the additional report configuration, and obtains quantized measurement values ​​from the measurements. In some implementations, the RS resource indicator indicates to the UE 102 an additional RS or RS resource in which it performs a measurement or obtains a quantized measurement value. In some implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRI) and / or one or more CSI-RS resource indicators (CRI). The quantized measurement value may include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0297] Similarly, the T-DU 174B can generate RS resource configurations 2, ..., N and / or N+1, ..., N+M and / or report configurations 2, ..., N and / or N+1, ..., N+M based on RS resource configuration X, and respectively include RS resource configurations 2, ..., N and / or N+1, ..., N+M and / or report configurations 2, ..., N and / or N+1, ..., N+M in LTM DU configurations 2, ..., N and / or N+1, ..., N+M, as described above.

[0298] In other implementations, the LTM DU configuration X of procedure 380 includes at least one TCI state configuration X, where 1 ≤ X ≤ N. Each configuration in the TCI state configuration X associates one or two DL RSs with or includes together with the TCI states of the corresponding QCL type. In some implementations, the DL RS may be associated with a cell X operated by S-DU 174A. In some implementations, each of the TCI state configuration X includes a TCI state ID. In some implementations, each of the TCI state configuration X is a TCI-State IE. In some implementations, the TCI state configuration X includes / is the ul-TCI-ToAddModList-r17 field, one or more TCI-UL-State-r17 IEs, the dl-OrJointTCI-StateToAddModList-r17 field, one or more TCI-State IEs, the TCI-ActivatedConfig IE, and / or the tci-StatesToAddModList field. In some implementations, LTM DU configuration X includes PDSCH-Config IE, and PDSCH-Config IE includes TCI state configuration X. In some implementations, T-DU 174B generates at least one TCI state configuration 1 taking into account or based on TCI state configuration X, and includes TCI state configuration 1 in LTM DU configuration 1. In some implementations, TCI state configuration 1 includes TCI state configuration X. In other implementations, T-DU 174B includes each of TCI state configurations X in TCI state configuration 1, except for the TCI state ID in TCI state configuration X. T-DU 174B assigns the TCI state ID as a value for each of TCI state configuration 1 (including TCI state configuration X), and includes the TCI state ID in the corresponding TCI state configuration. When UE 102 and S-DU 174B are communicating with each other 436, S-DU 174B can send an LTM command to UE 102 to instruct UE 102 to perform a fast serving cell change to cell X. S-DU 174B includes a TCI state ID in the LTM command to instruct UE 102 to apply a TCI state configuration identified by the TCI state ID to communicate on cell X, wherein the TCI state configuration is one of TCI state configurations X, or a configuration that includes one of TCI state configurations X.

[0299] Similarly, T-DU 174B may generate TCI state configurations 2, ..., N based on RS resource configuration X, and include TCI state configurations 2, ..., N and / or N+1, ..., N+M in LTM DU configurations 2, ..., N and / or N+1, ..., N+M respectively, as described above.

[0300] In some implementations, when CU 172 performs process 380 after process 490, CU 172 includes the LTM DU configuration 1, ..., N of process 490 in the CU to DU message of process 380, and S-DU 174A generates the LTM DU configuration 1, ..., N of process 380 in a manner similar to that described above, taking into account or based on the configuration in the LTM DU configuration of process 490.

[0301] In some implementations, CU 172 assigns to identify (received from T-DU 174B) the IDs 1, ..., N of LTM DU configurations 1, ..., N, and performs procedure 492 with T-DU 174B to provide IDs 1, ..., N and / or cell IDs 1, ..., N, similar to procedure 392. Therefore, T-DU 174B associates IDs 1, ..., N with LTM DU configurations 1, ..., N and / or cell IDs 1, ..., N, respectively. In other implementations, T-DU 174B assigns to identify (generated by T-DU 174B) the IDs 1, ..., N of LTM DU configurations 1, ..., N, and includes IDs 1, ..., N in the DU-to-CU message of procedure 490, similar to event 310. In some implementations, CU 172 is assigned to identify the IDs N+1, ..., N+M of the LTM DU configurations N+1, ..., N+M respectively, and performs a procedure (similar to procedure 492) with T-DU 174B to provide the IDs N+1, ..., N+M and / or cell IDs N+1, ..., N+M, similar to procedure 392. Therefore, T-DU 174B associates the IDs N+1, ..., N+M with the LTM DU configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M respectively. In other implementations, T-DU 174B is assigned to identify the IDs N+1, ..., N+M of the LTM DU configurations N+1, ..., N+M respectively, and includes the IDs 1, ..., N in the DU-to-CU message with the additional LTM preparation procedure, similar to event 310.

[0302] In some implementations, CU 172 sends a CU-DU message 412, including IDs 1, ..., N, to S-DU 174A, and in response, receives a DU-CU message 414 from S-DU 174A. The CU-DU message 412 and the DU-CU message 414 are... Figure 4 These are collectively referred to as LTM ID transfer procedure 493 or LTM cell index transfer procedure 493. In some implementations, messages 412 and 414 can be a UE context modification request message and a UE context modification response message, respectively. In some implementations, CU 172 includes LTM DU configuration 1, ..., N and / or cell ID 1, ..., N in CU to DU message 412. In one implementation, CU 172 includes ID 1, ..., N in CU to DU message 412. In another implementation, CU 172 includes cell index 1, ..., N in CU to DU message 412. In some alternative implementations, CU 172 can perform multiple LTM ID transfer procedures to send ID 1, ..., N; cell ID 1, ..., N; and / or LTM DU configuration 1, ..., N to S-DU 174A. In each of the above processes, CU 172 includes the following specific portions in a CU-DU message similar to message 412: ID 1, ..., N; Cell ID 1, ..., N; and / or LTM DU configuration 1, ..., N. Therefore, S-DU 174A associates ID 1, ..., N with LTM DU configuration 1, ..., N and / or Cell ID 1, ..., N, respectively. In other alternative implementations, CU 172 may perform multiple LTM cell index transfer processes to send cell index 1, ..., N; cell ID 1, ..., N; and / or LTM DU configuration 1, ..., N to S-DU 174A. In each of the above processes, CU 172 includes the following specific portions in a CU-DU message similar to message 412: Cell index 1, ..., N; Cell ID 1, ..., N; and / or LTM DU configuration 1, ..., N. Therefore, S-DU 174A associates cell indices 1, ..., N with LTM DU configurations 1, ..., N and / or cell IDs 1, ..., N, respectively.

[0303] In some implementations, S-DU 174A generates a first service DU configuration based on LTM DU configurations 1, 2, ..., and / or N, and includes the first service DU configuration in the DU-to-CU message 414. In some implementations, the first service DU configuration includes a configuration that updates (e.g., enhances, modifies, or replaces) service DU configuration 402. In other implementations, the first service DU configuration includes configurations not included in service DU configuration 402. CU 172 sends an RRC reconfiguration message including the first service DU configuration to UE 102. Upon receiving the RRC reconfiguration message, UE 102 applies the first service DU configuration to communicate with the service DU. For example, the RRC reconfiguration message is the RRC reconfiguration message in procedure 494 or similar. Depending on the implementation, UE 102 uses a configuration included in service DU configuration 402 that has not been updated by the first service DU configuration to communicate with S-DU 174A. The following are example implementations of generating the first service DU configuration based on LTM DU configurations 1, ..., N.

[0304] In some implementations, the LTM DU configuration Y of process 490 includes at least one RS resource configuration Y, where 1 ≤ Y ≤ N. Each configuration in RS resource configuration Y is associated with one or more RSs or one or more RS resources of cell Y of T-DU 174B. RSs include SSBs and / or CSI-RSs. RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of RS resource configurations Y includes an RS resource configuration ID. In some implementations, RS resource configuration Y is a CSI-ResourceConfig IE (or similar). In some implementations, LTM DU configuration Y includes a CSI-MeasConfig IE, and the CSI-MeasConfig IE includes a CSI-ResourceConfig IE. S-DU 174A generates at least one service report configuration for reporting measurement results of RSs or RS resources on cell 124A, and includes the service report configuration in the first service DU configuration. In some implementations, the service report configuration is a CSI-ReportConfig IE (or similar). In some implementations, S-DU 174A generates at least one service RS resource configuration considering or based on RS resource configuration Y, and includes the service RS resource configuration in the first service DU configuration. In some implementations, S-DU 174A includes RS resource configuration Y in the service RS resource configuration. In other implementations, S-DU 174A includes each of RS resource configurations Y in the service RS resource configuration, except for the RS resource configuration ID in RS resource configuration Y. S-DU 174A assigns the RS resource configuration ID as a value for each of the service RS resource configurations (including RS resource configuration Y), and includes the RS resource configuration ID in the corresponding service RS resource configuration.

[0305] In some implementations, the service report configuration configures one or more UL resources (e.g., PUCCH or PUSCH resources) on cell 124A for UE 102 to transmit measurement results. In some implementations, each of the service report configurations includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the service RS resource configuration. When UE 102 communicates with S-DU 174A, UE 102 transmits measurement results on the UL resources (e.g., event 424) to S-DU 174A via cell 124A according to the service report configuration. Correspondingly, S-DU 174A receives measurement results on the UL resources from UE 102 via cell 124A according to the service report configuration. In some implementations, each of the measurement results includes one or more RS resource indicators and / or one or more quantized measurement values. UE 102 measures the RS or RS resources according to the service RS resource configuration and / or service report configuration, and obtains quantized measurement values ​​from the measurements. In some implementations, the RS resource indicator indicates to the UE 102 where to perform a measurement or obtain a quantized measurement of an RS or RS resource. In some implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRIs) and / or one or more CSI-RS resource indicators (CRIs). The quantized measurement may include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0306] In other implementations, the LTM DU configuration Y of procedure 490 includes at least one TCI state configuration Y, where 1 ≤ Y ≤ N. Each configuration in the TCI state configuration Y associates one or two DL RSs with or includes together with the TCI states of the corresponding QCL type. In some implementations, the DL RSs may be associated with a cell Y operated by T-DU 174B. In some implementations, each of the TCI state configuration Y includes a TCI state ID. In some implementations, each of the TCI state configuration Y is a TCI-State IE. In some implementations, the TCI state configuration Y includes / is the ul-TCI-ToAddModList-r17 field, one or more TCI-UL-State-r17 IEs, the dl-OrJointTCI-StateToAddModList-r17 field, one or more TCI-State IEs, the TCI-ActivatedConfig IE, and / or the tci-StatesToAddModList field. In some implementations, LTM DU configuration Y includes PDSCH-Config IE, and PDSCH-Config IE includes TCI state configuration Y. In some implementations, S-DU 174A generates at least one service TCI state configuration considering or based on TCI state configuration Y, and includes the service TCI state configuration in the first service DU configuration. In some implementations, service TCI state configuration 1 includes TCI state configuration Y. In other implementations, S-DU 174A includes each of TCI state configurations Y in the service TCI state configuration, except for the TCI state ID in TCI state configuration Y. S-DU 174A assigns the TCI state ID as a value for each of the service TCI state configurations (including TCI state configuration Y), and includes the TCI state ID in the corresponding service TCI state configuration. When S-DU 174A communicates with UE 102 436, S-DU 174A can send an LTM command to UE 102 to instruct UE 102 to perform a fast serving cell change to cell Y. S-DU 174A includes a TCI state ID in the LTM command to instruct UE 102 to apply a TCI state configuration identified by the TCI state ID to communicate on cell Y, wherein the TCI state configuration is one of the TCI state configurations Y, or a configuration that includes one of the TCI state configurations Y.

[0307] In some implementations, CU 172 sends a CU-DU message including IDs N+1, ..., N+M to S-DU 174A, and in response, receives a DU-CU message from S-DU 174A, similar to CU-DU message 412 and DU-CU message 414, respectively. In some implementations, CU 172 includes LTM DU configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M in the CU-DU message. In some alternative implementations, CU 172 may perform multiple LTM ID transfer procedures to send IDs N+1, ..., N+M; cell IDs N+1, ..., N+M; and / or LTM DU configurations N+1, ..., N+M to S-DU 174A. In each of the processes described, CU 172 includes the following specific portions in a CU-DU message similar to message 412: IDs N+1, ..., N+M; cell IDs N+1, ..., N+M; and / or LTM DU configurations 1, ..., N. Therefore, S-DU 174A associates IDs N+1, ..., N+M with LTM DU configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M, respectively. In some implementations, S-DU 174A generates a second service DU configuration based on LTM DU configurations N+1, N+2, ..., and / or N+M, and includes the second service DU configuration in the DU-CU message. In some implementations, the second service DU configuration includes configurations that update (e.g., enhance, modify, or replace) the first service DU configuration and / or update configurations included in service DU configuration 402 that have not been updated by the first service DU configuration. In other implementations, the second service DU configuration includes configurations not included in the first service DU configuration. CU 172 sends an RRC reconfiguration message including the second service DU configuration to UE 102 via S-DU 174A. Upon receiving the RRC reconfiguration message, UE 102 applies the second service DU configuration to communicate with the service DU. For example, the RRC reconfiguration message is the RRC reconfiguration message in procedure 494 or similar. Depending on the implementation, UE 102 communicates with S-DU 174A using a configuration included in service DU configuration 402 and / or the first service DU configuration and not updated by the second service DU configuration. In some implementations, S-DU 174A generates one or more new L1 measurement configurations based on L1 measurement configurations in LTM DU configurations N+1, N+2, ..., and / or N+M, and includes the new L1 measurement configurations in the second service DU configuration.In some implementations, the S-DU 174A generates one or more new TCI state configurations based on the TCI state configurations in LTM DU configurations N+1, N+2, ..., and / or N+M, and includes the new TCI state configurations in the second service DU configuration.

[0308] In some implementations, when CU 172 and S-DU 174A perform procedure 380 with UE 102, the values ​​of ID 1, ..., N in procedure 380 are different from the values ​​of ID 1, ..., N and ID N+1, ..., N+M described for scenario 400. In some implementations, when CU 172 and S-DU 174A perform procedure 380 with UE 102, the values ​​of cell ID 1, ..., N in procedure 380 are different from the values ​​of cell ID 1, ..., N and cell ID N+1, ..., N+M described for scenario 400. In some implementations, when CU 172 and S-DU 174A perform procedure 380 with UE 102, the values ​​of cell index 1, ..., N in procedure 380 are different from the values ​​of cell index 1, ..., N and cell index N+1, ..., N+M described for scenario 400.

[0309] At a later time, UE 102 may send at least one measurement report (424) to S-DU 174A, similar to event 324. The at least one measurement report (e.g., an L1 measurement report) includes an event ID, a first measurement result for cell 1 of T-DU 174B, and / or includes a second measurement result for cell 124A. In some implementations, the first measurement result may be or includes RSRP, RSRQ, and / or SINR obtained by UE 102 from a reference signal transmitted on cell 1. Similarly, the second measurement result may be or includes RSRP, RSRQ, and / or SINR obtained by UE 102 from a reference signal transmitted on cell 124A. In some implementations, the event ID, RSRP, RSRQ, and / or SINR are L1-Event ID, L1-RSRP, L1-RSRQ, and / or L1-SINR, respectively. Based on the first measurement result and / or the second measurement result, S-DU 174A can send a first LTM command (i.e., LTM command 1) including ID 1 to UE 102, instructing UE 102 to perform a serving cell change to cell 1 of T-DU 174B. In some implementations, the first LTM command includes ID 1 (i.e., LTM ID). In other implementations, the first LTM command includes cell index 1. When UE 102 receives the first LTM command, UE 102 performs a serving cell change from serving cell to serving cell 1 according to LTM DU configuration 1. After receiving the first LTM command (e.g., in response to receiving the first LTM command), UE 102 may or may not perform the random access procedure with T-DU 174B as in event 332. Upon receiving the first LTM command or completing random access procedure 432 (e.g., in response to receiving the first LTM command or completing random access procedure 432), UE 102 can communicate with T-DU 174B on the first cell using LTM DU configuration 1 and / or referencing LTM DU configuration 436, and communicate with CU 172 via T-DU 174B, similar to event 336. If a serving cell change occurs during procedure 380, the serving cell can be cell 1 or cell 2 of S-DU 174A. Otherwise, if no serving cell change occurs during procedure 380 or procedure 380 is not performed, the serving cell is cell 124A. If the first LTM command includes LTM ID 1, UE 102 identifies LTM DU configuration 1 and / or cell ID 1 (i.e., cell 1) based on LTM ID 1, as for Figure 3 As described. If the first LTM command includes cell index 1, then UE 102 identifies LTM DU configuration 1, cell ID 1 (i.e., cell 1), and / or LTM ID 1 based on cell index 1, as for... Figure 3 As described. After receiving the first LTM command or successfully accessing cell 1 (e.g., in response to receiving the first LTM command or successfully accessing cell 1), UE102 applies LTM DU configuration 1 to communicate with T-DU 174B.

[0310] When it is determined that LTM DU configuration 1 is activated or the first LTM command 430 is sent, or in response to determining that LTM DU configuration 1 is activated or the first LTM command 430 is sent, the S-DU 174A may send a DU-to-CU message 429 to the CU 172 indicating that LTM is (being) executed. In some implementations, the S-DU 174A includes cell ID 1 or LTM ID 1 in the DU-to-CU message 429 to indicate that the S-DU 174A will activate LTM DU configuration 1 or trigger an LTM serving cell change. The S-DU 174A may send the DU-to-CU message 429 to the CU 172 before or after sending the LTM command 430. In some implementations, when or after the CU 172 receives the DU-to-CU message 429, the CU 172 may stop or suspend sending DL data for UE 102 to the S-DU 174A until it receives the DU-to-CU message 434. After receiving DU to CU message 434, CU 172 starts, continues, or resumes sending DL data for UE 102 to T-DU174B. When or after T-DU 174B detects UE 102 accessing cell 1, T-DU 174B sends DL data to UE 102 via cell 1.

[0311] The resource release procedure 496 can be similar to procedure 396. Alternatively, in the resource release procedure 496, CU 172 can send a CU-DU message (e.g., a UE context release command message) to S-DU 174A to release the UE context of UE 102. In response, S-DU 174A releases the UE context of UE 102 and sends a 440 DU-CU message (e.g., a UE context release complete message) to CU-172.

[0312] Events 380, 404, 406, 490, 492, 494, 494, 424, 426, 428, 429, 430, 431, 432, 434, 436, 496, 498, and 456 are in Figure 4 This is collectively referred to as the LTM configuration and / or activation process 480.

[0313] Next reference Figure 5AIn scenario 500A, base station 106 operates as the MN, and base station 104 operates as the SN. SN 104 includes CU 172 and DU 174. Scenario 500A is similar to scenario 300, except that scenario 500A is a DC scenario, while scenario 300 is a single-connectivity (SC) scenario. MN 106 can include CU and DU, and... Figure 3 It is similar to base station 104.

[0314] Initially, UE 102 communicates with MN 106 and SN 104 via DC. In event 502, UE 102 uses the serving DU configuration to communicate with DU 174 on cell 124A and uses the serving CU configuration to communicate with CU 172 via DU 174, similar to event 302. In some alternative implementations, UE 102 does not communicate with CU 172 via DU 174 in event 302. In some implementations, UE 102 may communicate with MN 106 and / or SN 104 via a radio bearer (502 UL PDU and / or DLPDU) via DC, the radio bearer including SRB and / or DRB. MN 106 and / or SN 104 may configure the radio bearer for UE 102. UE 102 communicates with SN 104 via DC on the SCG (i.e., SCG radio resources) configured for communication with UE 102, delivering 502 UL PDUs and / or DL ​​PDUs. UE 102 communicates with MN 106 via DC on the MCG (i.e., MCG radio resources) according to the MN configuration (i.e., MCG configuration). In some implementations, the serving DU configuration is the SN configuration (i.e., SCG configuration). In the MN configuration, MN 106 configures the MCG, which includes at least one serving cell (e.g., cell 126 and / or other cells) operated by MN 106. In the serving DU configuration, SN 106A configures the SCG, which includes at least one serving cell (e.g., cell 124A and / or other cells) operated by SN 104. In some implementations, the MN configuration includes multiple configuration parameters, and UE 102 receives the configuration parameters from MN 106 in one or more RRC messages. Figure 3 As described, the service DU configuration includes multiple configuration parameters. In some implementations, UE 102 receives these configuration parameters from SN 104 in one or more RRC messages, for example, via MN 106 and / or on an SRB (e.g., SRB3) configured to exchange RRC messages between UE 102 and SN 104 in MN 106 or SN 104.

[0315] When UE 102 communicates with MN 106 and SN 104 via DC, MN 106 may perform a 580 LTM DU configuration and / or activation procedure with UE 102, similar to procedures 380 and / or 480. In some implementations, when communicating with MN 106 and SN 104 via DC, UE 102 may send at least one measurement report to CU 172 via DU 174 and cell 124A in events 504 and 506, respectively, similar to events 304 and 306. In other implementations, when communicating with MN 106 and SN 104 via DC, UE 102 may send at least one measurement report (505) to MN 106 via cell 126. MN 106 then sends at least one measurement report (507) to CU 172. In some implementations, MN 106 generates at least one SN message including at least one measurement report and sends at least one SN message to CU 172 in event 507. In one implementation, at least one SN message includes an RRC delivery message and / or an SN modification request message.

[0316] Upon receiving at least one measurement report (e.g., in response to receiving at least one measurement report) or during communication between SN104 and UE102, SN104 determines to prepare a first cell for UE102, as for... Figure 3 As described. Events 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are similar to events 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, and 356, respectively. After receiving the first LTM command 530, sending an acknowledgment 531, or confirming that UE 102 has successfully connected to the first cell 532 or 536, UE 102, operating in DC mode with MN 106 and SN 104, communicates 536 with DU 174 on the first cell according to LTM DU configuration 1 and communicates 536 with CU 172 via DU 174, similar to event 336. At a later time, DU 174 and / or CU 172 may perform an LTM execution procedure 598 with UE 102 to command UE 102 to perform a cell change from the first cell to the second cell, similar to procedures 398 or 498. As a result of procedure 598, UE 102, operating in DC mode with MN 106 and SN 104, communicates 556 with DU 174 on the second cell according to LTM DU configuration 2 and via DU 174 with CU 172, similar to event 356.

[0317] Events 504, 506, 505, 507, 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are in Figure 5A This is collectively referred to as the LTM DU configuration and / or activation process 581.

[0318] Next reference Figure 5B Scenario 500B is largely similar to Scenario 500A, except that SN 104 sends RRC reconfiguration messages 517 and 519 to UE 102 via MN 106 and receives RRC reconfiguration completion messages 521 and 523 from UE 102 via MN 106. RRC reconfiguration messages 517 and 519 are similar to RRC reconfiguration messages 316 and 318. RRC reconfiguration completion messages 521 and 523 are similar to RRC reconfiguration messages 320 and 322. In some implementations, SN 104 generates a first SN message including the RRC reconfiguration message (e.g., an SN modification request message, an SN modification request message, or an RRC delivery message) and sends the first SN message to MN 106 in event 517. MN 106 generates an MN RRC message including the RRC reconfiguration message and sends the MN RRC message described in 519 to UE 102. In response, UE 102 generates an MN RRC response message including an RRC reconfiguration complete message and sends the MN RRC response message described in 521 to MN 106. In some implementations, MN 106 generates a second SN message including an RRC reconfiguration complete message (e.g., an SN reconfiguration complete message or an RRC delivery message) and sends the second SN message to SN 104 in event 523. In some implementations, the MN RRC message and the MN RRC response message can be an RRC reconfiguration message and an RRC reconfiguration complete message, respectively.

[0319] Events 504, 506, 505, 507, 590, 592, 594, 517, 519, 521, 523, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are... Figure 5B This is collectively referred to as the LTM DU configuration and / or activation process 582.

[0320] Next reference Figure 6AIn scenario 600A, base station 106 operates as the MN and base station 104 operates as the SN, similar to scenarios 300 to 500B. SN 104 includes CU 172, S-DU 174A, and T-DU 174B, similar to base station 104 in scenario 400. When UE 102 communicates with MN 106 and SN 104 via DC, MN 106 can perform a 680 LTM DU configuration and / or activation procedure with UE 102, similar to procedures 380 and / or 480. When UE 102 communicates with M-DU 174A and S-DU 174B via DC, CU 172 can perform a 681 LTM DU configuration and / or activation procedure with UE 102 via M-DU 174A or S-DU 174B, similar to procedures 581 or 582.

[0321] Next reference Figure 6B Scenario 600B is similar to scenarios 300 to 500B and 600A, except that SN 104 sends RRC reconfiguration messages 617 and 619 to UE 102 via MN106 and receives RRC reconfiguration completion messages 621 and 623 from UE 102 via MN106.

[0322] Next reference Figure 7A In scenario 700A, base station 104 operates as both MN and SN, similar to scenarios 300 to 600B. Base station 104 includes CU 172, main DU (M-DU) 174A, and auxiliary DU (S-DU) 174B. CU 172, together with M-DU 174A, operates as MN. Figure 3 Base station 104 or Figures 5A to 6B Similar to MN 106, and CU 172 together with S-DU 174B as SN operation, and Figures 5A to 6B Similar to SN 104 in the example.

[0323] In scenario 700A, UE 102 initially communicates with M-DU 174A and S-DU 174B via DC 702 and with CU 172 via M-DU 174A and S-DU 174B 702. In event 702, UE 102 uses the serving DU configuration to communicate with S-DU 174B on cell 124A and uses the serving CU configuration to communicate with CU 172 via S-DU 174B, similar to event 302. Events 704 and 706 are similar to events 304 and 306. In some implementations, UE 102 may send 705 at least one measurement report to M-DU 174A, similar to event 304. M-DU 174A then sends 707 at least one DU-to-CU message including at least one measurement report to CU 172, similar to event 306. When UE 102 communicates with M-DU 174A and S-DU 174B via DC, CU172 can perform a 780 LTM DU configuration and / or activation procedure with UE 102 via M-DU 174A, similar to procedure 380.

[0324] Events 704, 706, 705, 707, 790, 792, 794, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, and 756 are in Figure 7A This is collectively referred to as the LTM configuration and / or activation process 781.

[0325] Next reference Figure 7B Scenario 700B is similar to scenarios 300 to 600B and 700A, except that CU 172 sends 717 and 719 RRC reconfiguration messages to UE 102 via M-DU 174A and receives 721 and 723 RRC reconfiguration completion messages from UE 102 via M-DU 174A.

[0326] Events 704, 706, 705, 707, 790, 792, 794, 717, 719, 721, 723, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, and 756 are in Figure 7B This is collectively referred to as the LTM DU configuration and / or activation process 782.

[0327] Next reference Figure 8AIn scenario 800A, base station 104 operates as both MN and SN, similar to scenarios 300 to 700B. Base station 104 includes CU 172, primary DU (M-DU) 174A, secondary DU (S-DU) 174B, and target secondary DU (T-DU) 174C. CU 172 operates as MN together with M-DU 174A and as SN together with S-DU 174B. When UE 102 communicates with M-DU 174A and S-DU 174B via DC, CU 172 can perform an 880 LTM DU configuration and / or activation process with UE 102 via M-DU 174A, similar to process 380. When UE 102 communicates with M-DU 174A and S-DU 174B via DC, CU 172 can perform the 881 LTM DU configuration and / or activation procedure with UE 102 via S-DU 174A, similar to procedure 581 or 582.

[0328] Next reference Figure 8B Scenario 800B is similar to scenarios 300 to 700B and 800A, except that CU 172 sends 817 and 819 RRC reconfiguration messages to UE 102 via M-DU 174A and receives 821 and 823 RRC reconfiguration completion messages from UE 102 via M-DU 174A.

[0329] Next, refer to Figures 9A to 15C Several example methods for configuring and / or activating one or more TCI state configurations for LTM candidate cells (i.e., cells for LTM) are discussed, which can be implemented in RAN nodes (e.g., base stations, DUs, or CUs) or UEs. Figures 3 to 8B At least some of the points discussed can also be applied. Figures 9A to 15C .

[0330] Figure 9A This shows that it can be generated by DU (e.g., Figures 3 to 8B Example method 900A is implemented using DU 174, DU 174A, DU 174B or DU174C.

[0331] Method 900A begins at block 902, where the DU receives a first CU-DU message from the CU requesting configuration of candidate cells for LTM for the UE (e.g., events 308, 390, 490, 590, 690, 790, 890). At block 904, the DU generates an LTM DU configuration for the UE in response to receiving the first CU-DU message. At block 906, the DU generates a serving DU configuration for the UE in response to receiving the first CU-DU message. At block 908, the DU sends a first DU-CU message to the CU including the LTM DU configuration (e.g., events 310, 390, 490, 590, 690, 790, 890). At block 910, the DU sends a second DU-CU message to the CU including the serving DU configuration.

[0332] In some implementations, the DU is a service DU or a source DU. In some implementations, the LTM DU configuration is a non-referenced LTM DU configuration (e.g., LTM DU configuration 1 described above). In such implementations, the DU avoids including a referenced LTM DU configuration in the first DU-CU message or does not include a referenced LTM DU configuration in the first DU-CU message. Alternatively, the DU includes a referenced LTM DU configuration in the first DU-CU message, as described above. In some implementations, the DU avoids including a service DU configuration in the first DU-CU message or does not include a service DU configuration in the first DU-CU message. In some implementations, the DU avoids including an LTM DU configuration in the second DU-CU message or does not include an LTM DU configuration in the second DU-CU message.

[0333] In other implementations, the LTM DU configuration is referenced, as described above. In such implementations, the DU may not include the non-referenced LTM DU configuration in the first DU to CU message. Alternatively, the DU may include the non-referenced LTM DU configuration in the first DU to CU message.

[0334] In some implementations, the CU sends an RRC message (e.g., events 316, 318, 394, 494, 594, 517, 519, 694, 617, 619, 694, 794, 717, 719, 894, 817, 819) to the UE via the RAN node. In some implementations, the CU includes at least one LTM CSI resource configuration in the RRC message. The CU may include the LTM CSI resource configuration in a first CU-DU message. In other implementations, the CU includes the LTM DU configuration and the service DU configuration in a first RRC message and a second RRC message, respectively, and sends both messages to the UE via the RAN node. In some implementations, the CU includes the LTM CSI resource configuration in the first CU-DU message. In some implementations, the CU may include the LTM CSI resource configuration in either the first or second RRC message. In other implementations, the CU includes a portion of the LTM CSI resource configuration in the first RRC message and the remainder of the LTM CSI resource configuration in the second RRC message. In some implementations, the CU sends the second RRC message after sending the first RRC message to ensure that the UE receives the first RRC message before receiving the second RRC message. For example, the first RRC message is an RRC reconfiguration message in events 316, 318, 394, 494, 594, 517, 519, 694, 617, 619, 694, 794, 717, 719, 894, 817, 819. The second RRC message is another RRC reconfiguration message. In some implementations, the RAN node is a DU. In other implementations, the RAN node is another DU or a base station.

[0335] In some implementations, the DU sends a first DU to CU message in response to a first CU to DU message. In some implementations, the first CU to DU message and the first DU to CU message are respectively a UE context establishment request message and a UE context establishment response message. In other implementations, the first CU to DU message and the first DU to CU message are respectively a UE context modification request message and a UE context modification response message.

[0336] In other implementations, the DU initiates the transmission of a first DU-to-CU message to send LTM DU configuration to the CU. For example, the first DU-to-CU message may be a UE context modification request message. In such cases, the DU may respond to the first CU-to-DU message by sending an additional DU-to-CU message to the CU. In this case, the first CU-to-DU message and the additional DU-to-CU message may be a UE context establishment request message and a UE context establishment response message, respectively.

[0337] In some implementations, the DU initiates the transmission of a second DU-to-CU message to send the service DU configuration to the CU. For example, the second DU-to-CU message is a UE context modification request message. In response to the UE context modification request message, the DU receives a UE context modification confirmation message from the CU.

[0338] In some implementations, the LTM DU configuration and the Serving DU configuration are cell group configurations. For example, each in the cell group configuration is an RRC IE (e.g., CellGroupConfig IE) defined in 3GPP specification 38.331. After the CU sends a (second) RRC message including the Serving DU configuration to the UE, the DU uses the Serving DU configuration to communicate with the UE. In some implementations, the DU uses a first Serving DU configuration to communicate with the UE via the serving cell (e.g., events 302, 402, 502, 602, 702, 802). The Serving DU configuration at blocks 906 and 910 is a second Serving DU configuration. In some implementations, the second Serving DU configuration updates (e.g., replaces, modifies, or enhances) the first Serving DU configuration and / or includes configuration parameters not included in the first Serving DU configuration. Therefore, the DU uses the second Serving DU configuration and / or configuration parameters included in the first Serving DU configuration but not updated by the second Serving DU configuration to communicate with the UE. In some implementations, the first Serving DU configuration is or includes a cell group configuration (e.g., CellGroupConfig IE). In some implementations, the first service DU configuration includes or contains multiple configuration parameters (e.g., physical layer configuration parameters, one or more CSI resource configurations, one or more CSI report configurations, MAC configuration parameters, and / or RLC configuration parameters). In some implementations, the first service DU configuration includes configuration parameters included in the CellGroupConfig IE defined in 3GPP specification 38.331. In some implementations, the second service DU configuration includes one or more CSI report configurations. The DU uses the CSI report configuration to communicate with the UE (e.g., events 324, 424, 524, 624, 724, 824). In some implementations, the CSI report configuration includes the CSI-ReportConfig IE and / or the LTM-CSI-Report Configuration IE.

[0339] In some implementations, the CU includes the cell ID (e.g., CGI) of the candidate cell in the first CU-DU message to request it as a candidate cell (e.g., for...). Figures 3 to 8B The first cell described is preparing for LTM. In some implementations, the first CU to DU message is as follows: Figures 10A to 12D As described.

[0340] Method 900A prevents the DU from including LTM DU configuration and service DU configuration in a DU-to-CU message that cannot accommodate both LTM DU configuration and service DU configuration. Furthermore, the CU can use Method 900A to identify whether the received DU configuration is an LTM DU configuration or a service DU configuration.

[0341] Figure 9B The flowchart below shows an example method 900B, similar to method 900A, except that method 900B includes block 909 instead of blocks 908 and 910. At block 909, the DU sends a first DU-to-CU message to the CU, including both the LTM DU configuration and the service DU configuration. In this way, the CU simultaneously receives both the LTM DU configuration and the service DU configuration. Therefore, the CU can send an RRC message, including both the LTM DU configuration and the service DU configuration, to the UE via the RAN node, as described above. Method 900B simplifies the implementation complexity of the CU because the CU does not need to handle (e.g., wait for) the reception of a second DU-to-CU message.

[0342] In some implementations, the DU includes the LTM DU configuration and the service DU configuration in both the first IE and the second IE of the interface protocol, and includes both the first and second IEs in the first DU-to-CU message. For example, the interface protocol is F1AP as defined in 3GPP specification 38.473. In some implementations, the first IE is a new IE defined in 3GPP specification 38.473 from 3GPP release 18. In some implementations, the second IE is the DU-to-CU RRC information IE specified in 3GPP specification 38.473 from 3GPP release 15. In other implementations, the second IE is the CellGroupConfig IE specified in 3GPP specification 38.473 from 3GPP release 15. In such cases, the DU includes the second IE included in the DU-to-CU RRC information IE, and includes the DU-to-CU RRC information IE in the first DU-to-CU message. In such cases, the DU may include the first IE in the DU-to-CU RRC information IE.

[0343] Figure 10A It shows that it can be done in DU (e.g., Figures 3 to 8B Example method 1000A is implemented in DU 174, DU 174A, DU 174B or DU174C. Boxes 1002, 1004, 1006, 1008 and 1010 are similar to boxes 902, 904, 906, 908 and 910 respectively.

[0344] Method 1000A begins at box 1002. At box 1002, the DU receives a first CU-DU message (e.g., events 308, 390, 490, 590, 690, 790, 890) from the CU, including a first indication and at least one LTMCSI resource configuration, wherein the first indication requests configuration of LTM candidate cells. In some implementations, the first indication is an LTM indicator field or IE. At box 1004, the DU generates an LTM DU configuration in response to the first indication. At box 1006, the DU generates a serving DU configuration based on the LTM CSI resource configuration. At box 1008, the DU sends a first DU-CU message (e.g., events 310, 390, 490, 590, 690, 790, 890) to the CU, including the LTM DU configuration. At box 1010, the DU sends a second DU-CU message to the CU, including the serving DU configuration.

[0345] Figure 10B This is a flowchart of an example method 1000B, similar to method 1000A, except that method 1000B includes block 1009 instead of blocks 1008 and 1010. At block 1009, the DU sends a first DU-to-CU message (e.g., events 310, 390, 490, 590, 690, 790, 890) to the CU, including the LTM DU configuration and the service DU configuration. Block 1009 is similar to block 909.

[0346] Figure 10C This is a flowchart of an example method 1000C, similar to method 1000A, except that method 1000C includes blocks 1001 and 1003 instead of blocks 1002 and 1004. At block 1001, the DU receives a first CU-DU message (e.g., events 308, 390, 490, 590, 690, 790, 890) from the CU, including at least one LTM CSI resource configuration and excluding a first indication. At block 1003, the DU generates an LTM DU configuration in response to receiving the LTM CSI resource configuration. In some implementations, the DU generates configuration parameters based on the LTM CSI resource configuration and includes these parameters in the LTM DU configuration.

[0347] Figure 10D This is a flowchart of an example method 1000D, similar to method 1000C, except that method 1000D includes block 1009 instead of blocks 1008 and 1010. At block 1009, the DU sends a first DU-to-CU message (e.g., events 310, 390, 490, 590, 690, 790, 890) to the CU, which includes the LTM DU configuration and the service DU configuration.

[0348] Figure 10EThis is a flowchart of an example method 1000E, similar to method 1000A, except that method 1000E includes blocks 1012, 1014, and 1018 instead of blocks 1002, 1004, and 1008. At block 1012, the DU receives a first CU-DU message (e.g., events 308, 390, 490, 590, 690, 790, 890) from the CU, including a second indication and at least one LTM CSI resource configuration, wherein the second indication requests (e.g., queries) a reference to the LTM DU configuration. In some implementations, the second indication is an IE request for a lower-level configuration. At block 1014, the DU generates a reference LTM DU configuration in response to the second indication. At block 1018, the DU sends a first DU-CU message (e.g., events 310, 390, 490, 590, 690, 790, 890) to the CU, including the reference LTM DU configuration.

[0349] Figure 10F This is a flowchart of an example method 1000F, similar to method 1000E, except that method 1000F includes block 1019 instead of blocks 1018 and 1010. At block 1019, the DU sends a first DU-to-CU message (e.g., events 310, 390, 490, 590, 690, 790, 890) to the CU, which includes a reference LTM DU configuration and a service DU configuration.

[0350] Combination Figures 9A to 9B At least some of the examples and implementation options discussed can also be applied. Figures 10A to 10F .

[0351] Figure 11A This shows that it can be generated by DU (e.g., Figures 3 to 8B Example method 1100A is implemented by DU 174, DU 174A, DU 174B or DU174C. Boxes 1102, 1106 and 1110 are similar to boxes 902, 906 and 910, respectively.

[0352] Method 1100A begins at block 1102. At block 1102, the DU receives a first CU-DU message (e.g., events 308, 390, 490, 590, 690, 790, 890) from the CU, including a first indication and a second indication, wherein the first indication requests configuration of LTM candidate cells, and the second indication requests reference to the LTM DU configuration. The process proceeds to block 1004. At block 1106, the DU generates a reference LTM DU configuration in response to the second indication. The process proceeds to block 1008. At block 1110, the DU sends a second DU-CU message (e.g., events 310, 390, 490, 590, 690, 790, 890) to the CU, including the reference LTM DU configuration.

[0353] In some implementations, a DU is a service DU or a source DU. In other implementations, a DU is a candidate DU (e.g., Figure 4 , Figure 6A , Figure 6B , Figure 8A and Figure 8B (T-DU in the context of this implementation). In some implementations, the DU avoids including the service DU configuration in the first DU to CU message and / or the second DU to CU message, or does not include the service DU configuration in the first DU to CU message and / or the second DU to CU message. In some implementations, the DU avoids including the non-reference LTM DU configuration in the second DU to CU message, or does not include the non-reference LTM DU configuration in the second DU to CU message.

[0354] Figure 11B This is a flowchart of an example method 1100B, similar to method 1100A, except that method 1100B includes block 1109 instead of blocks 1008 and 1110. At block 1109, the DU sends a first DU-to-CU message (e.g., events 310, 390, 490, 590, 690, 790, 890) to the CU, including the LTM DU configuration (i.e., a non-reference LTM DU configuration) and the reference LTM DU configuration.

[0355] In some implementations, the DU includes both reference LTM DU configuration and non-reference LTM DU configuration in the first IE and second IE of the interface protocol, and includes both the first IE and the second IE in the first DU-to-CU message. For example, the interface protocol is F1AP as defined in 3GPP specification 38.473. In some implementations, the first IE is a new IE defined in 3GPP specification 38.473 from 3GPP release 18. In some implementations, the second IE is the DU-to-CU RRC information IE defined in 3GPP specification 38.473 from 3GPP release 15. In other implementations, the second IE is the CellGroupConfig IE specified in 3GPP specification 38.473 from 3GPP release 15. In such cases, the DU includes the second IE included in the DU-to-CU RRC information IE, and includes the DU-to-CU RRC information IE in the first DU-to-CU message. In such cases, the DU may include the first IE in the DU-to-CU RRC information IE.

[0356] In other implementations, the second IE is a new IE defined in 3GPP specification 38.473 from 3GPP Release 18. In some implementations, the first and second IEs can be grouped within a parent IE (e.g., an LTM information IE). In other implementations, the first and second IEs are included in the first DU to CU message without a parent IE.

[0357] Combination Figures 9A to 9B At least some of the examples and implementation options discussed can also be applied. Figures 11A to 11B .

[0358] Figure 12A This shows that it can be generated by DU (e.g., Figures 3 to 8B Example method 1200A is implemented using DU 174, DU 174A, DU 174B or DU174C. Box 1202 is similar to box 902.

[0359] Method 1200A begins at block 1202. At block 1202, the DU receives a first CU-DU message (e.g., events 308, 390, 490, 590, 690, 790, 890) from the CU, including a first indication, a second indication, and at least one LTM CSI resource configuration, wherein the first indication requests configuration of LTM candidate cells, and the second indication requests reference to the DU configuration. The process then proceeds to blocks 1004, 1106, and 1006. The process proceeds to blocks 1008 and 1110. At block 1204, the DU sends a third DU-CU message to the CU, including the serving DU configuration.

[0360] According to method 1200A, the DU includes the LTM DU configuration (i.e., the non-reference LTM DU configuration), the reference LTM DU configuration, and the service DU configuration in the corresponding DU-to-CU message. The DU avoids including any two of the LTM DU configuration, the reference LTM DU configuration, and the service DU configuration in the DU-to-CU message.

[0361] In some implementations, the DU responds to the first CU to DU message by sending a third DU to CU message. In such cases, combined with Figure 9A At least some of the examples and implementation options discussed in the first DU to CU message can also be applied to the third DU to CU message. In other implementations, box 1204 is similar to box 910.

[0362] Figure 12BThis is a flowchart of an example method 1200B, similar to method 1200A, except that method 1200B includes blocks 1009 and 1205 instead of blocks 1008, 1110, and 1204. At block 1205, the DU sends a second DU-to-CU message to the CU, including a reference to the LTM DU configuration.

[0363] In some implementations, the DU avoids including the reference LTM DU configuration in the first DU to CU message or does not include the reference LTM DU configuration in the first DU to CU message. In some implementations, the DU avoids including the LTM DU configuration (i.e., non-reference LTM DU configuration) and / or service DU configuration in the second DU to CU message or does not include the LTM DU configuration (i.e., non-reference LTM DU configuration) and / or service DU configuration in the second DU to CU message. In some implementations, at least some of the examples and implementation options discussed in box 910 may also be applicable to box 1205.

[0364] Figure 12C This is a flowchart of an example method 1200C, similar to method 1200A, except that method 1200C includes block 1109 instead of blocks 1008 and 1110. In some implementations, the DU avoids including the service DU configuration in the first DU-to-CU message or does not include the service DU configuration in the first DU-to-CU message. In some implementations, the DU avoids including the LTM DU configuration (i.e., non-referenced LTM DU configuration) and / or referenced LTM DU configuration in the second DU-to-CU message or does not include the LTM DU configuration (i.e., non-referenced LTM DU configuration) and / or referenced LTM DU configuration in the second DU-to-CU message.

[0365] Figure 12D This is a flowchart of an example method 1200D, similar to method 1200A, except that method 1200D includes blocks 1008 and 1207 instead of blocks 1008, 1110, and 1204. At block 1207, the DU sends a second DU-to-CU message to the CU, including the reference LTM DU configuration and the service DU configuration. In some implementations, the DU avoids including the LTM DU configuration (i.e., a non-reference LTM DU configuration) in the second DU-to-CU message or does not include the LTM DU configuration (i.e., a non-reference LTM DU configuration) in the second DU-to-CU message. In some implementations, the DU avoids including the reference LTM DU configuration and / or the service DU configuration in the first DU-to-CU message or does not include the reference LTM DU configuration and / or the service DU configuration in the first DU-to-CU message.

[0366] Combination Figures 9A to 9B , Figures 10A to 10F and Figures 11A to 11B At least some of the examples and implementation options discussed can also be applied. Figures 12A to 12D .

[0367] Figure 13A It shows that it can be generated by CU (e.g., Figures 3 to 8B Example method 1300A is implemented in CU 172.

[0368] Method 1300A begins at block 1302, where the CU sends a first CU-DU message (e.g., events 308, 390, 490, 590, 690, 790, 890) to a first DU, wherein the first indication requests configuration of an LTM candidate cell. At block 1304, the CU receives from the CU a first DU-CU message (e.g., events 310, 390, 490, 590, 690, 790, 890) including an LTM DU configuration. In some implementations, the LTM DU configuration is a non-LTM DU configuration (e.g., LTM DU configuration 1 described above). At block 1306, the CU sends a second CU-DU message to the first DU including at least one LTM CSI resource configuration. At block 1308, the CU receives from the DU a second DU-CU message including a serving DU configuration.

[0369] Method 1300A prevents the CU from including the first indication and LTM CSI resource configuration in the CU-DU message, which solves the problem that the DU-CU message cannot contain LTM DU configuration and service DU configuration. Method 1300A also solves the problem that the CU cannot identify whether the received DU configuration is an LTM DU configuration or a service DU configuration.

[0370] In some implementations, the CU includes a second instruction in the first CU-DU message, wherein the second instruction requests reference to the LTM DU configuration. In response to the second instruction, the DU may include the referenced LTM DU configuration in the first DU-CU message. In other implementations, the CU avoids including the second instruction in the first CU-DU message.

[0371] Figure 13B This is a flowchart of an example method 1300B, similar to method 1300A, except that method 1300B includes blocks 1312 and 1314. At block 1312, the CU sends a third CU-DU message to the first DU, including a second indication requesting reference to the LTM DU configuration. At block 1314, the CU receives a third DU-CU message destined for the CU, including reference to the LTM DU configuration.

[0372] Method 1300B prevents the CU from including the first instruction, the second instruction, and the LTM CSI resource configuration in the CU-DU message. This resolves the issue that the DU-CU message cannot accommodate LTM DU configuration, reference LTM DU configuration, and service DU configuration. Method 1300B also resolves the issue that the CU cannot identify whether the received DU configuration is a non-reference LTM DU configuration, a reference LTM DU configuration, or a service DU configuration.

[0373] In some implementations, the CU receives a third DU to CU message in response to a third CU to DU message. For example, the third CU to DU message and the third DU to CU message are the UE context establishment request message and the UE context establishment response message, respectively. In another example, the third CU to DU message and the third DU to CU message are the UE context modification request message and the UE context modification response message, respectively.

[0374] Combination Figures 9A to 9B , Figures 10A to 10F , Figures 11A to 11B and Figures 12A to 12D At least some of the examples and implementation options discussed can also be applied. Figures 13A to 13B .

[0375] Figure 14 It shows that it can be generated by CU (e.g., Figures 3 to 8B Example method 1400 is implemented in CU 172.

[0376] Method 1400 begins at box 1402, where the CU determines to send a CU-DU message for LTM. At box 1404, the CU determines whether to request LTM candidate cell configuration. If at box 1404 the CU determines to request LTM DU configuration, the process proceeds to box 1406. At box 1406, the CU includes a first indication in the CU-DU message, where the first indication requests a non-reference LTM DU configuration. Otherwise, if at box 1404 the CU determines not to request LTM candidate cell configuration, the process proceeds to box 1408. At box 1408, the CU determines whether to send LTM CSI resource configuration. If at box 1408 the CU determines to send LTM CSI resource configuration, the process proceeds to box 1410. At box 1410, the CU includes at least one LTM CSI resource configuration in the CU-DU message. At box 1412, the CU sends a CU-DU message to the DU (e.g., events 308, 394, 494, 594, 694, 794, 894). The process proceeds from boxes 1410 and 1406 to box 1412. Otherwise, if at box 1408 the CU determines not to send the LTM CSI resource configuration, the process proceeds to box 1414, where it ends.

[0377] Combination Figures 9A to 9B , Figures 10A to 10F , Figures 11A to 11B , Figures 12A to 12D and Figures 13A to 13B At least some of the examples and implementation options discussed can also be applied. Figure 14 For example, DU is... Figures 3 to 13B The DU.CU application described herein is used for UE (e.g., Figures 3 to 13B Method 1400 for configuring LTM in UE).

[0378] Figure 15A It shows that it can be generated by CU (e.g., Figures 3 to 8B Example method 1500A is implemented in CU 172.

[0379] Method 1500A begins at box 1502, where the CU determines to send a CU-to-DU message for LTM. At box 1504, the CU determines whether to request a non-reference LTM DU configuration or a reference LTM DU configuration. If at box 1504 the CU determines to request a non-reference LTM DU configuration, the process proceeds to box 1506. Otherwise, if at box 1504 the CU determines to request a reference LTM DU configuration, the process proceeds to box 1508. At box 1508, the CU includes a second indication in the CU-to-DU message, where the second indication requests a reference LTM DU configuration. The process proceeds from boxes 1508 and 1506 to box 1512. The CU applies [the following] for the UE (e.g., Figures 3 to 13B Method 1500A for configuring LTM in UE).

[0380] Figure 15B This is a flowchart of an example method 1500B, similar to method 1500A, except that method 1500B includes blocks 1503, 1506, and 1510 instead of blocks 1504, 1506, and 1508. At block 1503, the CU determines whether to request LTM DU configuration or service DU configuration. If the CU determines to request LTM DU configuration, the process proceeds to block 1506. At block 1506, the CU includes an indication in the CU-DU message that requests LTM DU configuration. In some implementations, this indication is the first indication described above. In other implementations, this indication is the second indication described above. Otherwise, if at block 1503 the CU determines to request service DU configuration (e.g., requesting configuration of one or more CSI report configurations), the process proceeds to block 1510. The process proceeds from blocks 1506 and 1510 to block 1512.

[0381] Figure 15BThis is a flowchart of example method 1500B, similar to method 1500A, except that method 1500C includes block 1505. At block 1505, the CU determines whether a non-reference LTM DU configuration, a reference LTM DU configuration, or a service DU configuration is requested. If at block 1505 the CU determines a non-reference LTM DU configuration is requested, the process proceeds to block 1406. If at block 1505 the CU determines a reference LTM DU configuration is requested, the process proceeds to block 1508. Otherwise, if at block 1505 the CU determines a service DU configuration is requested, the process proceeds to block 1410. The process proceeds from block 1510 and either block 1508 or 1506 to block 1512.

[0382] The following list of examples reflects various embodiments explicitly contemplated in this disclosure.

[0383] Example 1. A method implemented in a DU of a distributed base station, comprising: receiving a CU-DU message requesting LTM configuration for a candidate cell from a CU; generating an LTM DU configuration and a service DU configuration in response to the CU-DU message; and sending the LTM DU configuration and the service DU configuration to the CU.

[0384] Example 2. The method as described in Example 1, wherein the LTM DU configuration and the service DU configuration are sent in a single DU to CU message.

[0385] Example 3. The method as described in Example 1, wherein the LTM DU configuration and the service DU configuration are sent in separate corresponding DU to CU messages.

[0386] Example 4. The method as described in any of the preceding examples, wherein the LTM DU configuration includes a reconfiguration configuration with synchronization.

[0387] Example 5. The method as described in any of the preceding examples, wherein the LTM DU configuration includes a random access configuration.

[0388] Example 6. The method as described in any of the preceding examples, wherein the service DU configuration includes the CellGroupConfig information element (IE).

[0389] Example 7. The method as described in any of the preceding examples, wherein the CU to DU message includes LTM Channel State Information (CSI) resource configuration.

[0390] Example 8. The method as described in Example 7, wherein the generation of the service DU configuration is based on the LTMSCI resource configuration.

[0391] Example 9. The method as described in Example 7, wherein the generation of the LTM DU configuration is in response to receiving the LTM SCI resource configuration.

[0392] Example 10. The method as described in any of the preceding examples, wherein the CU to DU message includes an indication that the DU will generate the LTM DU configuration.

[0393] Example 11. The method as described in any of the preceding examples, wherein the CU to DU message includes an indication to request a reference LTM DU configuration; and the generated LTM DU configuration is the reference LTM DU configuration.

[0394] The following descriptions can be applied to the descriptions above.

[0395] Generally, a description of one of the above figures can be applied to another. If there is no conflict, the examples, implementations, and methods described above can be combined. The events or boxes described above can be optional or omitted. For example, events or boxes with dashed lines in the figures can be optional. Descriptions from the perspective of the receiving node also apply to the sending node. For example, a description of the receiving node (e.g., DU) receiving a message from the sending node (e.g., CU) can be used instead of the description of the sending node sending a message to the receiving node.

[0396] In some implementations, "message" is used, and "information element (IE)" can be used instead of "message," and vice versa. In some implementations, "IE" is used, and "field" can be used instead of "IE," and vice versa. In some implementations, "configurations" or "configuration parameters" can be used instead of "configuration," and vice versa. In some implementations, "serving cell change command," "Layer 1 / Layer 2 LTM cell handover command," "lower layer handover command," or "lower layer serving cell change command" can be used instead of "LTM command." In some implementations, "some" means "one or more." In some implementations, "at least one" means "one or more." In some implementations, "cell group configuration" can be used instead of "DU configuration." In some implementations, "serving cell index," "LTM cell index," "special cell (SpCell) index," "PCell index," or "PSCell index" can be used instead of "cell index." In some implementations, "source" can be used instead of "service." In some implementations, "measurement results" can be used instead of "measurement report." In some implementations, "early UL timing synchronization" or "early UL synchronization" can be used instead of "early TA acquisition". In some implementations, "early UL timing synchronization with candidate cell / the candidate cell" or "early UL synchronization with candidate cell / the candidate cell" can be used instead of "early TA acquisition on candidate cell / the candidate cell".

[0397] User devices (e.g., UE 102) that can implement the technologies disclosed herein can be any suitable device capable of wireless communication, such as smartphones, tablets, laptops, mobile game consoles, point-of-sale (POS) terminals, health monitoring devices, drones, cameras, media streaming dongles or other personal media devices, wearable devices (such as smartwatches), Wi-Fi hotspots, femtocells, or broadband routers. Additionally, in some cases, the user device can be embedded in electronic systems (such as the main unit of a vehicle or an advanced driver assistance system (ADAS)). Furthermore, the user device can operate as an Internet of Things (IoT) device or a mobile internet device (MID). Depending on the type, the user device may include one or more general-purpose processors, computer-readable storage, a user interface, one or more network interfaces, one or more sensors, etc.

[0398] Some embodiments described in this disclosure include logic or multiple components or modules. A module can be a software module (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing certain operations and can be configured or arranged in a certain way. A hardware module may include a dedicated circuit system or logic that is persistently configured (e.g., as a dedicated processor, such as a field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC), digital signal processor (DSP), etc.) to perform certain operations. A hardware module may also include programmable logic or circuit systems (e.g., as encompassed within a general-purpose processor or other programmable processor) that are temporarily configured by software to perform certain operations. The decision to implement a hardware module in a dedicated and persistently configured circuit system or in a temporarily configured circuit system (e.g., configured by software) may be driven by cost and time considerations.

[0399] When implemented in software, the technology can be provided as part of an operating system, a library used by multiple applications, a specific software application, etc. The software can be executed by one or more general-purpose processors or one or more dedicated processors.

[0400] Upon reading this disclosure, those skilled in the art will understand the additional and alternative structural and functional designs used to address mobility between base stations through the principles disclosed herein. Therefore, while specific embodiments and applications have been shown and described, it should be understood that the disclosed embodiments are not limited to the precise constructions and components disclosed herein. Various modifications, alterations, and variations that will be apparent to those skilled in the art may be made to the arrangement, operation, and details of the methods and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.

Claims

1. A method implemented in a distributed unit (DU) of a distributed base station, the method comprising: The central unit (CU) of the distributed base station receives a CU-DU message, the CU-DU message including (i) a request for a reference lower layer triggered mobility (LTM) configuration for a candidate cell and (ii) LTM channel state information (CSI) resource configuration; A reference LTM DU configuration is generated in response to the CU-DU message; The service DU configuration is generated based on the LTM CSI resource configuration. as well as Send the reference LTM DU configuration and the service DU configuration to the CU.

2. The method of claim 1, wherein: The CU to DU message includes a UE context establishment request message; and The reference LTM DU configuration and the service DU configuration are sent in the UE context establishment response message.

3. The method of claim 1, wherein: The CU to DU message includes a UE context modification request message; and The reference LTM DU configuration and the service DU configuration are sent in the UE context modification response message.

4. The method as claimed in any of the preceding claims, wherein the request for the reference LTM configuration includes a request information element (IE) for the lower-level configuration.

5. The method as described in any of the preceding claims, wherein the reference LTM DU configuration includes CellGroupConfig IE.

6. The method as described in any of the preceding claims, wherein the service DU configuration includes service report configuration.

7. The method of claim 6, wherein the service report configuration includes CSI-ReportConfig IE.

8. A method implemented in a central unit (CU) of a distributed base station, the method comprising: Send a CU to DU message to the distributed unit (DU) of the distributed base station, the CU to DU message including (i) a request for reference lower layer triggered mobility (LTM) configuration for candidate cells and (ii) LTM channel state information (CSI) resource configuration; as well as The service DU configuration and reference LTM DU configuration are received from the DU and in response to the CU to DU message, based on the LTM CSI resource configuration.

9. The method of claim 8, wherein: The CU to DU message includes a UE context establishment request message; and The reference LTM DU configuration and the service DU configuration are sent in the UE context establishment response message.

10. The method of claim 8, wherein: The CU to DU message includes a UE context modification request message; and The reference LTM DU configuration and the service DU configuration are sent in the UE context modification response message.

11. The method of any one of claims 8 to 10, wherein the request for the reference LTM configuration includes a request information element (IE) for the lower-level configuration.

12. The method of any one of claims 8 to 11, wherein the reference LTM DU configuration includes CellGroupConfig IE.

13. The method of any one of claims 8 to 12, wherein the service DU configuration includes service report configuration.

14. The method of claim 13, wherein the service report configuration includes CSI-ReportConfig IE.

15. A radio access network (RAN) node, comprising: transceiver; as well as Processing hardware, wherein the RAN is configured to implement the method as described in any of the preceding claims.

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