Random access configured for low layer triggered mobility cell handover

Abstract

A method implemented in a distributed unit (DU) of a distributed base station. The method can include receiving, from a central unit (CU) of the distributed base station, a request to prepare a candidate cell for low layer triggered mobility (LTM) of a user equipment (UE). The method can further include transmitting, to the CU in response to the request, LTM contention exempt random access (CERA) configuration parameters for accessing the candidate cell. Other methods and systems are described.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to U.S. Provisional Patent Application No. 63 / 571,598, filed March 29, 2024, entitled "Configuring Random Access for Lower Layer Triggered Mobility Cell Switch". The entire contents of that provisional application are hereby expressly incorporated by reference. Technical Field

[0003] This disclosure relates to wireless communications, and more specifically, to configuring random access for low-level triggered mobility (LTM) cell handover between central units (CUs). 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 would not have been considered prior art at the time of filing are neither expressly nor impliedly acknowledged as prior art to this disclosure.

[0005] Generally, base stations operating a cellular radio access network (RAN) use a specific radio access technology (RAT) and multiple layers of the radio protocol stack to communicate with user equipment (UE). For example, the physical layer (PHY) of the RAT provides a transport channel to the media access control (MAC) sublayer, which in turn provides a logical channel to the radio link control (RLC) sublayer, and the RLC sublayer in turn provides data transmission services to the packet data convergence protocol (PDCP) sublayer.

[0006] The PDCP sublayer of the radio protocol stack provides services such as user plane data transmission, 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). Furthermore, the PDCP sublayer provides Signaling Radio Bearers (SRBs) and Data Radio Bearers (DRBs) to the Radio Resource Control (RRC) sublayer. Generally, the UE and the 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.

[0007] In some scenarios, a UE can simultaneously utilize the resources of multiple RAN nodes (e.g., base stations or components of distributed base stations) interconnected via backhaul. When these multiple RAN nodes support different Radio Access Technologies (RATs), this type of connection is called Multiple Radio Dual Connectivity (MR-DC). When the UE operates under 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 with the SN (via the PSCell). In other scenarios, the UE utilizes the resources of one base station at a time. A base station and / or the UE can determine that the UE should establish a radio connection with the second base station. For example, a base station can determine to hand over the UE to the second base station, and the base station can initiate the handover process.

[0008] When a UE moves from the coverage area of ​​one cell in the RAN to another, the RAN performs a serving cell change by configuring the UE to send Layer 3 (L3) measurement results. Based on the L3 measurement results received from the UE, the RAN sends an RRC reconfiguration message, which configures reconfiguration with synchronization (e.g., the RRC reconfiguration message includes...). ReconfigurationWithSync IE) for changes to the serving cell (e.g., PCell or PSCell). When a UE operates with at least one secondary cell (SCell) and carrier aggregation (CA) with a PCell or PSCell, the RAN releases at least one SCell due to the change of the PCell or PSCell. Serving cell changes involve a complete L2 (and L1) reset, resulting in longer latency, greater overhead, and longer outage times. To address these issues, 3GPP recently proposed a procedure called Low Layer Triggered Mobility (LTM).

[0009] When the RAN communicates with the UE via the serving cell associated with the base station, the base station receives one or more Layer 3 (e.g., RRC) measurement results from the UE. Based on the Layer 3 (L3) measurement results, the base station determines to configure an LTM candidate cell for LTM cell handover. To configure an LTM candidate cell for the UE, the base station sends the LTM candidate configuration to the UE via RRC signaling. Subsequently, the base station receives one or more Layer 1 (L1) measurement results from the UE. Based on the one or more L1 measurement results, the base station determines that the LTM candidate cell is eligible to become the UE's serving cell. After making this determination, the base station sends an LTM cell handover command to the UE, instructing 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. The base station includes a central unit (CU) and distributed units (DUs). The one operating the serving cell in the DU is called the serving DU. If the LTM candidate cell is operated by the serving DU, the LTM cell handover is an intra-CU, intra-DU LTM cell handover. If an LTM candidate cell is operated by a candidate DU (C-DU) within a DU, then the LTM cell handover is an intra-CU inter-DU LTM cell handover. 3GPP enabled intra-CU intra-DU LTM cell handover and intra-CU inter-DU LTN cell handover in Release 18. However, it is currently unclear how equipment should handle inter-CU LTM cell handover.

[0010] Additionally, when the UE receives an LTM cell handover command from the RAN, the UE will perform an LTM cell handover to an LTM candidate cell according to the LTM candidate configuration. However, in inter-CU scenarios, how random access should be performed after an LTM cell handover is unclear. The RAN may include parameters such as the random access preamble index, synchronization signal block (SSB) index, physical random access channel (PRACH) mask index, and UL / SUL indicator in the LTM cell handover command, as described in 3GPP specification 38.321 v18.0.0. However, it is currently unclear how the RAN configures these parameters. Summary of the Invention

[0011] A method that can be implemented in a distributed unit (DU) of a distributed base station. The method may include receiving a request from the central unit (CU) of the distributed base station for preparing candidate cells for low-level triggered mobility (LTM) of a user equipment (UE). The method may include, in response to the request, sending LTM contention-free random access (CFRA) configuration parameters for accessing the candidate cells to the CU.

[0012] In another implementation, a method can be implemented in the central unit (CU) of a distributed base station. This method may include sending a request to the distributed unit (DU) to prepare a candidate cell for low-layer triggered mobility (LTM) for a user equipment (UE). The method may also include, in response to the request, receiving LTM contention-free random access (CFRA) configuration parameters from the DU for accessing the candidate cell.

[0013] In yet another implementation, a base station includes a transceiver and processing hardware, which can implement any of the methods described herein. Attached Figure Description

[0014] Figure 1A This is a block diagram of an example system in which the radio access network (RAN) and user equipment (UE) can implement the techniques of this disclosure for managing LTM between CUs;

[0015] Figure 1B This is another block diagram of an example system in which the RAN and UE can implement the techniques disclosed herein for managing LTM between CUs;

[0016] Figure 1C This is a block diagram of an example base station, which includes a CU (Combined Unit) and a Distributed Unit (DU). The CU and DU can be... Figure 1A or Figure 1B Operating within the system;

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

[0019] Figure 3 This is a message sequence diagram for an example scenario, in which the UE executes the LTM procedure within the CU and DU.

[0020] Figure 4 This is a message sequence diagram of an example scenario, in which the UE performs an intra-CU inter-DU LTM procedure;

[0021] Figure 5 This is a message sequence diagram for an example scenario, in which the UE performs an inter-CU LTM procedure;

[0022] Figure 6A This is a message sequence diagram of an example scenario with dual connections;

[0023] Figure 6B This is the message sequence diagram for the second example scenario of dual-connectivity;

[0024] Figure 6C This is the message sequence diagram for the third example scenario of dual-connectivity;

[0025] Figure 6D This is the message sequence diagram for the fourth example scenario of dual-connectivity;

[0026] Figure 7A This is a flowchart of the first example method that can be implemented by DU;

[0027] Figure 7B This is a flowchart of a second example method that can be implemented by DU;

[0028] Figure 7C This is a flowchart of a third example method that can be implemented by DU;

[0029] Figure 7D This is a flowchart of the fourth example method that can be implemented by DU;

[0030] Figure 7E This is a flowchart of the fifth example method that can be implemented by DU;

[0031] Figure 8A This is a flowchart of the first example method that can be implemented by C-DU;

[0032] Figure 8B This is a flowchart of a second example method that can be implemented by C-DU;

[0033] Figure 8C This is a flowchart of a third example method that can be implemented by C-DU;

[0034] Figure 8D This is a flowchart of the fourth example method that can be implemented by C-DU;

[0035] Figure 9A This is a flowchart of the first example method that can be implemented by S-DU;

[0036] Figure 9B This is a flowchart of a second example method that can be implemented by S-DU;

[0037] Figure 9C This is a flowchart of a third example method that can be implemented by S-DU;

[0038] Figure 9D This is a flowchart of the fourth example method that can be implemented by S-DU;

[0039] Figure 9E This is a flowchart of the fifth example method that can be implemented by S-DU;

[0040] Figure 9FThis is a flowchart of the sixth example method that can be implemented by S-DU;

[0041] Figure 9G This is a flowchart of the seventh example method that can be implemented by S-DU;

[0042] Figure 9H This is a flowchart of the eighth example method that can be implemented by S-DU;

[0043] Figure 9I This is a flowchart of the ninth example method that can be implemented by S-DU;

[0044] Figure 10A This is a flowchart of the first example method that can be implemented by CU;

[0045] Figure 10B This is a flowchart of a second example method that can be implemented by CU;

[0046] Figure 10C This is a flowchart of a third example method that can be implemented by CU;

[0047] Figure 10D This is a flowchart of the fourth example method that can be implemented by CU; and

[0048] Figure 11 This is a flowchart of an example method for LTM between CUs that can be implemented by a DU of a distributed base station. Detailed Implementation

[0049] The technology disclosed herein relates to Low Layer Triggered Mobility (LTM). LTM enables serving cell changes via L1 / L2 signaling while preserving upper-layer configurations and minimizing lower-layer configuration changes. These procedures can be used to perform LTM cell handovers (e.g., inter-CU LTM) between cells served by different base stations, where the UE can be with two base stations under a DC. Some aspects of this disclosure further provide techniques for configuring random access parameters in inter-CU LTM cell handovers.

[0050] First refer to Figure 1A Example wireless communication system 100 may implement one or more of these technologies. Wireless communication system 100 includes UE 102, base station (BS) 104A, base station 106A, and core network (CN) 110. Base stations 104A and 106A may operate in radio access network (RAN) 105. UE 102 is initially connected to base station 104A. In some scenarios, base station 104A may perform SN addition to configure UE 102 to operate with both base stations 104A and 106A in dual connectivity (DC). Base stations 104A and 106A operate as the MN and SN of UE 102, respectively.

[0051] In various configurations of the wireless communication system 100, base station 104A can operate as a primary eNB (MeNB) or primary gNB (MgNB), and base station 106A can operate as a secondary gNB (SgNB). UE 102 can communicate with base station 104A and base station 106A via the same RAT (such as EUTRA or NR) or different RATs. When base station 104A is a MeNB and base station 106A is an SgNB, UE 102 can be in EUTRA-NR DC (EN-DC) with both the MeNB and SgNB.

[0052] In some cases, the MeNB or SeNB is implemented as an ng-eNB instead of an eNB. When base station 104A is the primary ng-eNB (Mng-eNB) and base station 106A is the SgNB, UE 102 can be in a next-generation (NG) EUTRA-NR DC (NGEN-DC) with both the Mng-eNB and SgNB. When base station 104A is a MgNB and base station 106A is an SgNB, UE 102 can be in an NR-NR DC (NR-DC) with both the MgNB and SgNB. When base station 104A is a MgNB and base station 106A 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.

[0053] In the scenario where UE 102 is handed over from base station 104A to base station 106A, base stations 104A and 106A 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 104A and the additional base station (T-BS). Figure 1A (Not shown in the diagram) operates under DC. After the handover is completed, UE 102 can continue to operate under DC with base station 106A and the additional base station, or UE can operate under single connection (SC) with base station 106A. In this case, base stations 104A and 106A operate as the source MN (S-MN) and the target MN (T-MN), respectively.

[0054] The core network (CN) 110 can be either the Evolved Packet Core (EPC) 111 or the 5th Generation Core (5GC) 160; both are... Figure 1AAs described, although the CN can support other cores. Base station 104A can be an eNB supporting the S1 interface for communication with EPC 111, an ng-eNB supporting the NG interface for communication with 5GC 160, or a gNB supporting the NR radio interface and the NG interface for communication with 5GC 160. In order to exchange messages directly with each other during the scenarios discussed below, base stations 104A and 106A can support the X2 or Xn interface.

[0055] like Figure 1A As shown, base station 104A supports cell 124A, and base station 106A supports cell 126A. Cells 124A and 126A can partially overlap, allowing UE 102 to communicate with both base stations 104A and 106A under DC, where one of base stations 104A and 106A is MN and the other is SN. Base station 104A can support additional cells (such as cell 124B), and base station 106A can support additional cells (such as cell 124B). Figure 1A (Not shown in the diagram). Cells 124A and 124B may partially overlap, allowing UE 102 to communicate with base station 104A via carrier aggregation (CA). Base station 104A may operate cells 124A and 124B via one or more transmit and receive points (TRPs). More specifically, when UE 102 is in DC with base stations 104A and 106A, one of base stations 104A and 106A operates as a MeNB, Mng-eNB, or MgNB, while the other operates as an SgNB or Sng-eNB.

[0056] Generally, RAN 105 can include any suitable number of base stations supporting NR cells and / or EUTRA cells. More specifically, EPC 111 or 5GC 160 can connect to any suitable number of base stations supporting NR cells and / or EUTRA cells. See references below. Figure 1B An example configuration of CN 110 connected to an additional base station is discussed. 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.

[0057] Continue to refer to Figure 1ABase station 104A includes processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and non-transitory computer-readable storage of instructions executed by the one or more general-purpose processors. Additionally or alternatively, processing hardware 130 may include dedicated processing units. Processing hardware 130 may include a PHY controller 132 configured to transmit data and control signals and DL reference signals on a physical downlink (DL) channel to one or more user equipments (e.g., UE 102) via one or more cells (e.g., cells 124A, 124B) and / or one or more TRPs. PHY controller 132 is also configured to receive data and control signals and / or UL reference signals on a physical uplink (UL) channel from one or more user equipments via one or more cells (e.g., cells 124A, 124B) and / or one or more TRPs. In an example implementation, processing hardware 130 includes a MAC controller 134 configured to perform MAC functions with one or more user equipments. MAC functions include random access (RA) procedures, managing UL timing advance (TA) for one or more user equipments, and / or communicating UL / DL MACPDUs with one or more user equipments. MAC functions include Low Layer Triggered Mobility (LTM, also referred to herein as L1 / L2 triggered mobility or low layer triggered mobility) related functions as described below. In the example, LTM controller 137 may implement LTM functions in cooperation with MAC controller 134 or via signaling to the MAC controller. Processing hardware 130 may further include an RRC controller 136 for implementing procedures and messaging at the RRC sublayer of the protocol communication stack. For example, RRC controller 132 may be configured to support RRC messaging associated with handover procedures, and / or support necessary operations when base station 104A operates as an MN relative to the SN or as an SN relative to the MN. When base station 104A is a distributed base station, CU LTM controller 137A may operate in the CU, and DU LTM controller 137B may operate in the DU (see [link to CU]). Figure 1C Base station 106 may include processing hardware 140 similar to processing hardware 130. In particular, components 142, 144, 146, and 147 may be similar to components 132, 134, 136, and 137, respectively.

[0058] UE 102 includes processing hardware 150, which may include one or more general-purpose processors (such as a CPU), and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or dedicated processing units. PHY controller 152 is also configured to receive data and control signals and / or DL ​​reference signals on the physical DL channel from base station 104A or 106A via one or more cells (e.g., cells 124A, 124B, and / or 126) and / or one or more TRPs. PHY controller 152 is also configured to transmit data and control signals and / or UL reference signals on the physical UL channel to base station 104A or 106A via one or more cells (e.g., cells 124A, 124B, and / or 126) and / or one or more TRPs. In an example implementation, processing hardware 150 includes a MAC controller 154 configured to perform MAC functions with base station 104A or 106A. For example, MAC functions include random access procedures, managing UL timing advances for one or more user equipment, and communicating UL / DL MAC PDUs with base station 104A or 106A. In another example, MAC functions include LTM-related functions as described below. Processing hardware 150 may further include RRC controller 156 to implement procedures and message passing at the RRC sublayer of the protocol communication stack.

[0059] In operation, UE 102 can use radio bearers (e.g., DRBs or SRBs) that terminate at different times on MN 104A or SN 106A under DC. When communicating on radio bearers in the uplink (UL) (from UE 102 to the base station) and / or downlink (from the base station to UE 102) directions, UE 102 can apply one or more security keys. The UE can use several types of SRBs and DRBs. When operating under DC, a primary cell group (MCG) is defined with the base station operating as MN, and a secondary cell group (SCG) is defined with the base station operating as SN. For example, a first type of SRB resource (referred to as SRB1 resource) carries RRC messages, which in some cases include NAS messages on the dedicated control channel (DCCH). A second type of SRB resource (referred to as SRB2 resource) supports RRC messages including recorded measurement information or NAS messages, which are also on the DCCH but have a lower priority than SRB1 resources. More generally, SRB1 and SRB2 resources allow the UE and MN to exchange MN-related RRC messages and embed SN-related RRC messages. SRB1 and SRB2 can 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 the lower-level resources of the MN and SN. Further, a DRB using only the lower-level resources of the MN can be referred to as an MCG DRB, a DRB using only the lower-level resources of the SN can be referred to as an SCG DRB, and a DRB using both MCG and SCG lower-level resources can be referred to as a split DRB.

[0060] Figure 1B This is another block diagram of example system 100B, in which the RAN and UE can implement the techniques disclosed herein for managing LTM between CUs. Figure 1B Similar to Figure 1A . Figure 1B CN 110 is depicted, which connects to additional base stations 104A, 104B, 106A, and 106B communicating in cells 124A, 124B, 126A, and 126B. Cell 125 may overlap with one of cells 124A, 124B, 126A, and 126B or other cells.

[0061] Figure 1C Depicting Figure 1AExamples of distributed or decomposed implementations of any one or more of the base stations shown (e.g., base station 104A or 106A). In this implementation, the base station includes a central unit (CU) 172 and one or more DUs 174. CU 172 includes processing hardware, such as one or more general-purpose processors (e.g., CPUs) and 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 includes processing hardware 130 ( Figure 1A In another example, CU 172 includes processing hardware 140 (). Figure 1A In the example implementation, processing hardware 140 includes an SN RRC controller, which may be similar to RRC controller 146. Figure 1A The RRC controller is configured to manage or control one or more RRC configurations and / or RRC procedures when the base station 106A is operating as an SN.

[0062] Each of the DU 174A also includes processing hardware, which may include one or more general-purpose processors (e.g., CPUs) and 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, the processing hardware includes: a MAC controller (e.g., MAC controller 134, 144...). Figure 1A The MAC controller is configured to manage or control one or more MAC operations or procedures (e.g., random access procedures); and the Radio Link Control (RLC) controller is configured to manage or control one or more RLC operations or procedures when the base station 106A 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.

[0063] In some implementations, CU 172 may include a logical node CU-CP 172A, which hosts the control plane of CU 172. CU 172 may also include a logical node CU-UP 172B, which hosts the user plane of CU 172. CU-CP 172A may send control information (e.g., RRC messages, F1 application protocol messages), and CU-UP 172B may send data packets (e.g., SDAP PDUs or Internet Protocol packets).

[0064] A CU-CP 172A can connect to multiple CU-UP 172Bs via an E1 interface. The CU-CP 172A selects the appropriate CU-UP 172B for the requested service of UE 102. In some implementations, a single CU-UP 172B can connect to multiple CU-CP 172As via an E1 interface. A CU-CP 172A can connect to one or more DU 174s via an F1-C or W1-C interface. A CU-UP 172B can connect to one or more DU 174s via an F1-U or W1-U interface under the control of the same CU-CP 172A. In some implementations, a DU 174 can connect to multiple CU-UP 172Bs under the control of the same CU-CP 172A. In such implementations, the connection between the CU-UP 172B and the DU 174 is established by the CU-CP 172A using bearer context management functions.

[0065] Figure 2A The example protocol stack 200 is shown in a simplified manner. UE 102 can use this protocol stack to communicate with eNB / ng-eNB 230 or gNB 232 (e.g., one or more of base stations 104A, 104B, 106A, 106B). Figures 1A to 1B ))communication.

[0066] 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 further 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 transmission services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 can then provide data transmission 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 transmission services. In some implementations, UE 102 supports both EUTRA and NR stacks (e.g., ...). Figure 2A As shown), to support handover between EUTRA and NR base stations and / or support DC on the EUTRA and NR interfaces. Further, as... Figure 2AAs shown, UE102 can support NR PDCP 210 layering on EUTRA RLC 206A, and SDAP sublayer 212 layering on NR PDCP sublayer 210.

[0067] 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".

[0068] 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.

[0069] Figure 2B An 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 broken down as follows: Figure 2B The radio protocol stack 250 is shown in the diagram. At either base station 104A or 106A, the CU can retain 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.

[0070] Next, refer to Figures 3 to 5 Several example scenarios are among them. Figure 1A Several example scenarios illustrate how a base station operating in a system sends a configuration to UE 102 and later activates the configuration for communication between UE 102 and the base station. Generally speaking, Figures 3 to 5Similar events are labeled with similar reference numerals that share two least significant digits, where the differences are discussed below where appropriate. For example, event 302 is similar to... Figure 4 Event 402 and Figure 5 Event 502, and event 390 are similar. Figure 4 Event 490 and Figure 5 Event 590. Apart from the differences shown in the figures and discussed below, any other implementations discussed for a particular event (e.g., for messaging and processing) may be applied to events in other figures labeled with similar reference numerals.

[0071] First refer to Figure 3 In scenario 300, base station 104A includes CU 172 and DU 174, and DU 174 operates in cell 124A. UE 102 is initially configured to communicate with DU 174 on the serving cell (e.g., cell 124A) using the serving DU 302, and to communicate with CU 172 via DU 174 using the serving CU 174 302. DU 174 is the serving or source DU (S-DU) of UE 102. In other words, DU 174 is the serving DU (S-DU) that communicates with UE 102. In some implementations, UE 102 uses the serving DU to configure communication with CU 172 on cell 124A and other cells (e.g., cell 124A). Figure 1A UE 102 communicates with DU 174 via carrier aggregation (CA) on a cell (not shown). DU 174 operates on 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 (e.g., not on other cells). In some implementations, UE 102 communicates with DU 174 via one or more TRPs on cell 124A and / or other cells (i.e., the serving cells). In the following description, events 394, 324, 350, 352, 354, and 326 occur on the serving cell. 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, additional cells include SCells and / or additional cells associated with a PCell or Scell. In the following description, base station 104A may include DU 174, CU 172, or both DU 174 and CU 172.

[0072] In event 302, UE 102 may transmit UL PDUs and / or UL control signals to base station 104A 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 104A via radio bearers, which may include SRBs and / or DRBs. Base station 104A may configure the radio bearers for UE 102. In some implementations, UL control signals include UL control information, channel state information, Hybrid Automatic Repeat Request (HARQ) acknowledgment (ACK), HARQ negation ACK, scheduling request, and / or probe reference signals. Similarly, UE 102 may receive DL PDUs and / or DL ​​control signals from base station 104A via one or more TRPs in cell 124A and / or other cells. In some implementations, 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 104A 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.

[0073] 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 Transport Configuration Indicator (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 these configuration parameters and / or the first non-LTM TCI state configuration, and CU 172 sends these one or more 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 as defined in 3GPP specification 38.331. CellGroupConfig IE. In other implementations, the service DU configuration includes... CellGroupConfig Configuration parameters in 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 those defined in 3GPP specification 38.331. MeasConfig IE and / or RadioBearerConfig IE, or the CU service configuration includes MeasConfig IE and / or RadioBearerConfigConfiguration parameters in IE. Radio configuration parameters or RadioBearerConfig IE configures one or more DRBs. In some implementations, the service DU configuration includes... CSI-MeasConfig IE or configuration parameters used for Channel State Information (CSI) measurement and reporting. In other implementations, the service CU configuration includes... CSI-MeasConfig IE or configuration parameters used for CSI measurement and reporting. In some implementations, UE 102 receives the service CU configuration or configuration parameters in the service CU configuration from CU 172 via DU 174. In other implementations, UE 102 receives a portion of the service CU configuration and / or a portion of the service DU configuration from a base station other than base station 104A, and the UE receives the remainder of these configuration parameters from base station 104A.

[0074] In some implementations, DU 174 and UE 102 communicate with each other using a first non-LTM TCI state configuration, for example, in events 302, 318, 320, 324, 350, 354, and / or 326. In some implementations, DU 174 sends at least one first non-LTM TCI state activation / deactivation command (e.g., MAC control element (CE)) to UE 102 to activate the first non-LTM TCI state configuration. UE 102 activates the first non-LTM TCI state configuration in response to the first non-LTM TCI state activation / deactivation command. In some implementations, DU 174 includes a 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 the serving DU configuration establishes an association between the serving cell ID and the first non-LTM TCI state configuration.

[0075] When communicating with base station 104A, UE 102 sends at least one measurement report (304) to DU 174. In some implementations, the measurement report includes measurement results of UE 102's serving cell (e.g., cell 124A) and / or at least one non-serving cell. For each of the measurement reports, DU 174 sends a DU-to-CU message (306) including the 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 message delivery message). At least one serving cell includes cell 124A and / or other cells, and at least one non-serving cell includes cell 124B and / or an additional cell. In some implementations, the serving CU configuration includes at least one measurement configuration. Based on the measurement configuration, UE 102 performs measurements and sends a measurement report (304) to DU 174. In some implementations, the measurement configuration includes a Layer 3 (L3) measurement configuration (e.g., ... MeasConfig (IE), and the measurement report includes the L3 measurement report.

[0076] Upon receiving one or more measurement reports from UE 102 (e.g., in response to this), CU 172 determines to prepare a first cell (e.g., cell 1, such as cell 124B) as an LTM candidate cell for UE 102. In some implementations, base station 104A determines to prepare the first cell for UE 102 because the measurement report indicates that the first cell can be used by base station 104A to communicate with UE 102. In some implementations, base station 104A determines to prepare the first cell for UE 102 because the measurement report indicates that the first cell is eligible to be an LTM 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 signal strength and / or quality of the serving cell (e.g., cell 124A, as determined by a comparison operation), and / or better than the signal strength and / or quality of the serving cell by more than a first predetermined threshold. Alternatively, CU 172 determines whether to prepare the first cell for UE 102, regardless of whether a measurement report is received from UE 102.

[0077] In response to determining that the 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 of UE 102. For example, cell ID 1 includes 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, CU 172 includes the LTM indicator in the LTM Information Establishment IE, and CU 172 includes the LTM Information Establishment IE in the First CU to DU message. In other implementations, CU172 includes the LTM indicator in the LTM information modification IE, and CU172 includes the LTM information modification IE in the first CU to DU message.

[0078] In response to the first CU to DU message, DU 174 generates a first LTMDU configuration (hereinafter referred to as LTM DU configuration 1) for UE 102, which uses the first cell configuration for LTM. In some implementations, CU 172 includes the first LTM configuration ID (hereinafter referred to as LTM ID 1) in the first CU to DU message, and DU 174 associates LTM ID 1 and / or cell ID 1 with LTMDU configuration 1. DU 174 then sends a first DU to CU message 310 including LTM DU configuration 1 to CU 172 in response to the first CU to DU message.

[0079] Events 308 and 310 Figure 3 This process is collectively referred to as the LTM preparation process 390.

[0080] In some implementations, DU 174 includes the cell ID 1 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. When CU 172 and DU 174 perform multiple LTM preparation procedures (e.g., procedures 390 and LTM preparation procedures 2, ..., N described below) to prepare multiple LTM candidate cells, CU 172 can determine whether LTM DU configuration 1 is configured for or associated with the first cell based on the cell ID 1 in the first DU to CU message.

[0081] In some implementations, CU 172 does not include the LTM reference DU configuration in the first CU-DU message. In such cases, DU 174 generates the LTM reference DU configuration and includes it in the first DU-CU message. In some implementations, DU 174 generates LTM DU configuration 1 as an incremental configuration to enhance the LTM reference DU configuration. In other implementations, DU 174 generates LTM DU configuration 1 as a complete configuration, i.e., not just an enhanced LTM reference DU configuration.

[0082] In some implementations, CU 172 includes an LTM reference DU configuration request in a first CU-DU message, and DU 174 generates an LTM reference DU configuration, and DU 174 includes the LTM reference DU configuration in the first DU-CU message in response to the request. In some implementations, CU 172 determines whether UE 102 supports the LTM reference configuration. In the context of the implementation and as described in 3GPP specification 38.331, the reference configuration is a configuration provided to the UE by the network that is shared with a set of configured incomplete candidate configurations within the same cell group. Candidate configurations may include complete candidate configurations or incremental configurations relative to the reference configuration. If CU 172 determines that UE 102 supports the LTM reference configuration, CU 172 includes an LTM reference DU configuration request in the first CU-DU message. In response to the LTM reference DU configuration request, DU 174 includes the LTM reference DU configuration in the first DU-CU message. Otherwise, if CU 172 determines that UE 102 does not support the LTM reference configuration, CU 172 does not include the LTM reference DU configuration request in the first CU-DU message. In this case, DU 174 can generate LTMDU configuration 1 as the complete configuration, and DU 174 may not include the LTM reference DU configuration in the first DU-CU message. In other implementations, instead of sending the LTM reference DU configuration request in the first CU-DU message, CU 172 sends an additional CU-DU message to DU 174 including the LTM reference DU configuration request. In response, DU 174 sends an additional DU-CU message to CU 172 including the LTM reference DU configuration. In yet another implementation, DU 174 determines whether UE 102 supports the LTM reference configuration. If DU 174 determines that UE 102 supports the LTM reference configuration, DU 174 includes the LTM reference DU configuration in the first DU-CU message. Otherwise, if DU 174 determines that UE 102 does not support the LTM reference configuration, then DU 174 will not include the LTM reference DU configuration in the first DU to CU message.

[0083] In some implementations, CU 172 includes the LTM reference DU configuration in the first CU-DU message. In some implementations, CU 172 references the above... Figure 4 During the LTM preparation process, an LTM reference DU configuration is received from the additional DU. In other implementations, CU 172 is pre-configured with an LTM reference DU configuration. In some implementations, DU 174 generates LTM DU configuration 1 as an incremental configuration to enhance the LTM reference DU configuration. In other implementations, DU 174 ignores the LTM reference DU configuration and generates LTM DU configuration 1 as a complete configuration, i.e., not just an enhanced LTM reference DU configuration.

[0084] If DU 174 generates LTM DU configuration 1 as a complete configuration, DU 174 can include a complete configuration indication in the first DU to CU message to indicate that LTM DU configuration 1 is a complete configuration. In some implementations, if the first CU to DU message does not include the LTM reference DU configuration, then CU 172 can determine that LTM DU configuration 1 is a complete configuration. Otherwise, if the first CU to DU message includes the LTM reference DU configuration, then CU 172 can determine that LTM DU configuration 1 is an incremental configuration.

[0085] In some implementations, the LTM reference DU configuration differs from the service DU configuration. In some implementations, a portion of the LTM reference DU configuration is identical to a portion of the service DU configuration, while the remainder of the LTM reference DU configuration differs from the rest of the service DU configuration. In still other implementations, the LTM reference DU configuration is identical to the service DU configuration.

[0086] In some implementations, the LTM reference DU configuration differs from the service DU configuration. In some implementations, a portion of the LTM reference DU configuration is identical to a portion of the service DU configuration, while the remainder of the LTM reference DU configuration differs from the rest of the service DU configuration. In other implementations, the LTM reference DU configuration is identical to the service DU configuration.

[0087] To prepare the first cell as an LTM candidate cell for UE 102, CU 172 may send a second CU-DU message (312) to DU 174. This message includes CSI resource configuration (e.g., CSI resource configuration 1) and / or LTM synchronization signal block (SSB) configuration (i.e., LTM SSB configuration 1) to request DU 174 to generate one or more CSI report configurations (e.g., (LTM) CSI report configuration 1). The CSI resource configuration (e.g., (LTM) CSI resource configuration 1) includes configuration parameters for at least one reference signal (RS) transmitted on the first cell. The RS includes SSB and / or CSI-RS. The LTM SSB configuration includes SSB configuration parameters that configure the SSB frequency, subcarrier spacing, SSB period, SSB location, and / or SSB power of the SSB transmitted on the first cell.

[0088] Upon receiving the CSI resource configuration (e.g., in response to it), DU 174 generates one or more CSI report configurations based on the CSI resource configuration and includes the CSI report configuration in the service DU configuration (referred to as the second service DU configuration to distinguish it from the service DU configuration in event 302). In some implementations, the CSI report configuration configures UE 102 to send CSI reports based on RS measurement results. DU 174 sends a second DU to CU message 314, which includes the second service DU configuration, to CU 172. In some implementations, the CSI resource configuration includes (e.g., is or includes) one or more LTM-CSI- ResourceConfig-r18 IE. In other implementations, CSI resource configuration includes... ltm-CSI- ResourceConfigToAddModList Field / IE. In some implementations, the second service DU configuration is... CellGroupConfig IE.

[0089] In some implementations, CU 172 includes cell ID 1 and / or LTM ID 1 in the second CU-DU message (e.g., at event 312). In one implementation, CU 172 includes cell ID 1 and / or LTM ID 1 in the second CU-DU message to indicate that the CSI resource configuration is associated with the first cell. In another implementation, CU 172 includes cell ID 1 and / or LTM ID 1 in the second CU-DU message to allow DU 174 to associate LTM ID 1 with the first cell, cell ID 1, LTM DU configuration 1, and / or CSI reporting configuration. Based on the above implementations, DU 174 can associate LTM ID 1 and / or cell ID 1 with configurations associated with the first cell (e.g., LTM DU configuration 1, CSI resource configuration, and / or CSI reporting configuration). In some implementations, CU 172 includes LTM ID 1 in the first CU to DU message, while in others, CU 172 does not include LTM ID 1 in the first CU to DU message.

[0090] In some alternative implementations, CU 172 includes CSI resource configuration in the first CU to DU message, and DU 174 includes CSI report configuration in the first DU to CU message.

[0091] In some implementations, DU 174 sends LTM SSB configuration or SSB configuration parameters to CU 172, for example, in a first DU to CU message, a second DU to CU message, or an additional DU to CU message. In some implementations, DU 174 sends an additional DU to CU message in response to receiving an additional CU to DU message from CU 172. In other implementations, DU 174 sends a fourth DU to CU message in response to receiving a first CU to DU message or a second CU to DU message (e.g., ...). UE context modification beg information).

[0092] Events 312 and 314 Figure 3 This is collectively referred to as the LTM CSI report configuration and / or LTM ID configuration process 392.

[0093] After receiving the first DU to CU message, CU 172 generates a first LTM candidate configuration (i.e., LTM candidate configuration 1) including LTM DU configuration 1, and generates a first RRC reconfiguration message including LTM candidate configuration 1 and LTM ID 1. In some implementations, CU 172 includes LTM CU configuration 1 in LTM candidate configuration 1. In other implementations, CU 172 does not include LTM CU configuration in LTM candidate configuration 1. CU 172 sends a third CU to DU message 316, including the first RRC reconfiguration message, to DU 174. Then, DU 174 sends a first RRC reconfiguration message 318 to UE 102. In response, UE 102 sends a first RRC reconfiguration completion message 320 to DU 174. Then, DU 174 sends a third DU to CU message 322, including the first RRC reconfiguration completion message, to CU 172.

[0094] If the first DU to CU message includes an LTM reference DU configuration, then CU 172 generates an LTM reference configuration that includes the LTM reference DU configuration. In this case, CU 172 can include the LTM reference configuration in the first RRC reconfiguration message. In some implementations, CU 172 includes the LTM reference CU configuration in the LTM reference configuration. In this case, CU 172 can generate LTM CU configuration 1 as an incremental configuration based on the LTM reference CU configuration. In other implementations, CU 172 does not include the LTM reference CU configuration in the LTM reference configuration. In this case, CU 172 can generate LTM CU configuration 1 as a complete configuration. Alternatively, CU 172 sends a second RRC reconfiguration message including the LTM reference configuration to UE 102 via DU 174, similar to events 316 and 318. In response, UE 102 sends a second RRC reconfiguration complete message to CU 172 via DU 174, similar to events 320 and 322. In some implementations, if CU 172 does not receive the LTM reference DU configuration, CU 172 can generate an LTM reference configuration that includes only the LTM reference CU configuration. In other implementations, if CU 172 does not receive the LTM reference DU configuration, CU 172 may not generate an LTM reference configuration.

[0095] In some implementations, if the first DU to CU message includes a complete configuration indication, then CU 172 can determine that LTM DU configuration 1 is a complete configuration. Otherwise, if the first DU to CU message does not include a complete configuration indication, then CU 172 can determine that LTM DU configuration 1 is an incremental configuration. In some implementations, if LTM DU configuration 1 is a complete configuration, then CU 172 generates LTM candidate configuration 1 as a complete configuration. Otherwise, if LTM DU configuration 1 is an incremental configuration, then CU 172 generates LTM candidate configuration 1 as an incremental configuration. If LTM candidate configuration 1 is a complete configuration, then CU 172 includes the complete configuration indication in the first RRC reconfiguration message to indicate that LTM candidate configuration 1 is a complete configuration. If LTM candidate configuration 1 is an incremental configuration, then CU 172 excludes the complete configuration indication from the first RRC reconfiguration message to indicate that LTM candidate configuration 1 is an incremental configuration.

[0096] When CU 172 executes procedure 392, CU 172 may include the second service DU configuration in the first RRC reconfiguration message. Alternatively, in events similar to 316 and 318, CU 172 sends a third RRC reconfiguration message including the second service DU configuration to UE 102 via DU 174. In response, UE 102 sends a third RRC reconfiguration complete message to CU 172 via DU 174 in events similar to 320 and 322.

[0097] In some implementations, CU 172 includes the CSI resource configuration in the first, second, or third RRC reconfiguration message. In other implementations, in events similar to 316 and 318, CU 172 sends a fourth RRC reconfiguration message including the CSI resource configuration to UE 102 via DU 174. In response, UE 102 sends a fourth RRC reconfiguration complete message to UE 102 via DU 174 in events similar to 320 and 322.

[0098] In some implementations, DU 174 sends a DU-to-CU message to CU 172, which includes early synchronization information for UE 102. The DU-to-CU message can be a first DU-to-CU message, a second DU-to-CU message, or a fourth DU-to-CU message. In some implementations, DU 174 sends a fourth DU-to-CU message in response to receiving a fourth CU-to-DU message from CU 172. In other implementations, DU 174 sends a fourth DU-to-CU message in response to receiving a first CU-to-DU message or a second CU-to-DU message (e.g., ...). UE context modification requirementsIn one implementation, if DU 174 determines that UE 102 supports (i.e., is able to) early UL synchronization with the LTM candidate cell (e.g., early TA acquisition with the LTM candidate cell, early RA on the LTM candidate cell, or TA measured by the UE), then DU 174 sends a fourth DU to CU message. Otherwise, if DU 174 determines that UE 102 does not support early UL synchronization with the LTM candidate cell, then DU 174 does not send early synchronization information to CU 172. In other implementations, CU 172 sends a CU to DU message including an early synchronization information request (e.g., IE) to DU 174, and DU 174 includes the early synchronization information in the DU to CU message in response to the early synchronization information request. The CU to DU message can be a first CU to DU message, a second CU to DU message, or a fourth CU to DU message. In one implementation, if CU 172 determines that UE 102 supports early UL synchronization with the LTM candidate cell, then CU 172 may send an early synchronization information request. Otherwise, if CU 172 determines that UE 102 does not support early UL synchronization with the LTM candidate cell, CU 172 does not request DU 174 to provide early synchronization information for UE 102. If CU 172 receives early synchronization information, CU 172 includes the early synchronization information in the first, second, third, or fourth RRC reconfiguration message. Alternatively, in events similar to 316 and 318, CU 172 sends a fifth RRC reconfiguration message including early synchronization information to UE 102 via DU 174. In response, in events similar to 320 and 322, UE 102 sends a fifth RRC reconfiguration complete message to CU 172 via DU 174.

[0099] In some implementations, the early synchronization information includes a Random Access Channel (RACH) configuration (i.e., RACH configuration 1) and / or one or more TCI state configurations (i.e., TCI state configuration 1). In some implementations, the early synchronization request may include a request for RACH configuration. If the early synchronization request includes a request for RACH configuration, then DU 174 includes the RACH configuration in the early synchronization information or the DU-to-CU message (e.g., the first, second, or fourth DU-to-CU message). Otherwise, if the early synchronization request does not include a request for RACH configuration, then DU 174 does not include the RACH configuration in either the early synchronization information or the DU-to-CU message.

[0100] In some implementations, CU 172 includes one or more other LTM-related configurations of the first cell in the first, second, third, fourth, and / or fifth RRC reconfiguration messages. For example, other LTM-related configurations include the PCI and / or LTM SSB configurations of the first cell.

[0101] Events 316, 318, 320, and 322 are in Figure 3 This is collectively referred to as LTM configuration delivery process 394. LTM configuration delivery process 394 may further include second, third, fourth, and / or fifth RRC reconfiguration messages and second, third, fourth, and / or fifth RRC reconfiguration completion messages, related CU-to-DU messages, and / or related DU-to-CU messages. In some implementations, the aforementioned RRC reconfiguration messages and RRC reconfiguration completion messages are respectively... RRCReconfiguration Messages and RRCReconfigurationComplete information.

[0102] In some implementations, the first CU to DU message is UE Context Modification Request The message, and the first DU to CU message is UE context modification response Message. In some implementations, the second CU to DU message is UE Context Modification Request The message, and the second DU to CU message is UE context modification response Message or UE context modification requirements Message. In UE top and bottom Document revision requirements In the case of a message, CU 172 can respond to UE context modification requirements Message sent to DU 174 UE The following text has been revised and confirmed. Message. In some implementations, the third CU to DU message is DL RRC message transmission In other implementations, the third CU to DU message is a UE context modification request message. In some implementations, the third DU to CU message is... UL RRC message transmission Message. In other implementations, the third DU to CU message is a UE context modification response message.

[0103] In some implementations, the LTM reference CU configuration differs from the service CU configuration. In some implementations, a portion of the LTM reference CU configuration is identical to a portion of the service CU configuration, and the remainder of the LTM reference CU configuration differs from the remainder of the service CU configuration. In other implementations, the LTM reference CU configuration is identical to the service CU configuration.

[0104] In some implementations, the LTM reference CU configuration includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, LTM CU configuration 1 includes those defined in 3GPP specification 38.331. MeasConfigIE and / or RadioBearerConfig IE, or LTM CU configuration 1 includes MeasConfig IE and / or RadioBearerConfig Configuration parameters in Internet Explorer.

[0105] In some implementations, LTM CU Configuration 1 and / or LTM Reference CU Configuration include PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, LTM CU Configuration 1 or LTM Reference CU Configuration includes those defined in 3GPP specification 38.331. MeasConfig IE and / or RadioBearerConfig IE, or LTM CU configuration 1 or LTM reference CU configuration including MeasConfig IE and / or RadioBearerConfig Configuration parameters in Internet Explorer.

[0106] In some implementations, LTM DU configuration 1 includes multiple configuration parameters for UE 102 to communicate with DU 174 on the 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 further 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 defined in 3GPP specification 38.331. CellGroupConfig IE. In other implementations, LTM DU configuration 1 includes... CellGroupConfig Configuration parameters in Internet Explorer.

[0107] In some implementations, LTM DU configuration 1 includes a first L1 measurement configuration (e.g., CSI-MeasConfig The first L1 measurement configuration includes at least one first RS resource configuration and / or at least one first reporting configuration. In some implementations, the LTM CU configuration 1 includes a first TCI status configuration. In some implementations, the first L1 measurement configuration includes at least one first RS resource configuration and / or at least one first reporting configuration. In some implementations, the first RS resource configuration 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 first RS resource configurations includes an RS resource configuration ID. In some implementations, the first RS resource configuration is (similar to) CSI-ResourceConfig IE. In some implementations, the first report configuration configures one or more UL resources (e.g., PUCCH resources or PUSCH resources) on the first cell for UE 102 to transmit measurement results (e.g., CSI reports or LTM CSI reports). In some implementations, each of the first report configurations includes one or more RS resource configuration IDs that identify one or more RS resource configurations included in the first RS resource configuration. In some implementations, each of the first TCI state configurations configures a TCI state that associates one or two DL RSs with the corresponding Quasi-Co-located (QCL) type. The DL RS is associated with cell 1.

[0108] After receiving the LTM-related configuration and the second service DU configuration, or after receiving the aforementioned RRC reconfiguration message, UE 102 performs measurements on at least one first RS, generates at least one first L1 measurement result based on the measurements, and sends at least one first L1 measurement report including the first L1 measurement result to DU 174. The first RS may include an SSB and / or a CSI-RS. In some implementations, the transmission mode of the first RS and / or the first RS is configured in the CSI report configuration, LTM SSB configuration, and / or CSI resource configuration. UE 102 performs measurements on the first RS according to the CSI report configuration, LTM SSB configuration, and / or CSI resource configuration.

[0109] After receiving the LTM-related configuration and the second service DU configuration, or after receiving the aforementioned RRC reconfiguration message, UE 102 performs measurements on at least one second RS, generates at least one second L1 measurement result based on the measurements, and sends at least one second L1 measurement report including the first L1 measurement result to DU 174. The second RS may include an SSB and / or a CSI-RS. In some implementations, the second RS and / or the transmission mode of the second RS are configured in one or more second CSI report configurations, and / or configured in one or more second CSI resource configurations, which are included in the service DU configuration and / or the second service DU configuration in event 302. UE 102 performs measurements on the second RS according to the second CSI report configuration and / or the second CSI resource configuration. The second CSI report configuration may include a non-LTM CSI report configuration and / or an LTM CSI report configuration. The second CSI resource configuration may include a non-LTM CSI resource configuration and / or an LTMCSI resource configuration.

[0110] After sending the RACH configuration to UE 102 via CU 172, DU 174 can send a 350 PDCCH command to UE 102 to instruct UE 102 to send an RA preamble on the first cell. In response to the PDCCH command, UE 102 sends the RA preamble on the first cell. DU 174 includes PDCCH command information in the PDCCH command. The PDCCH command information includes the RA preamble index, UL or supplementary (or supplementary) UL indicator, SSB index, and / or physical RACH mask index. In some implementations, DU 174 includes LTM ID 1 in the PDCCH command to indicate the first cell. UE 102 identifies the first cell based on LTMID 1 in the PDCCH command, and UE 102 sends a 352 RA preamble to DU 174 on the first cell using the PDCCH command information. Accordingly, DU 174 receives the 352 RA preamble based on the PDCCH command information. In some implementations, DU 174 may determine the SSB index based on L1 measurement report 324 and / or CSI resource configuration, CSI report configuration, and / or LTM SSB configuration. In some implementations, the L1 measurement report may include the SSB index. In other implementations, the L1 measurement report includes the SS / PBCH block resource indicator (SSBRI) corresponding to the SSB index. Therefore, DU 174 determines the SSB index based on the SSBRI.

[0111] In some implementations, DU 174 determines whether to send a PDCCH command based on L1 measurement result 324. In some implementations, if the L1 measurement result indicates that the first cell is eligible for UE 102 to perform RA for early UL synchronization, DU 174 sends a PDCCH command. Otherwise, if the L1 measurement result indicates that the first cell is not eligible for UE 102 to perform RA for early UL synchronization, DU 174 avoids sending a PDCCH command. In other implementations, if the L1 measurement result indicates that the first cell is eligible for UE 102 to access, DU 174 sends a PDCCH command. Otherwise, if the L1 measurement result indicates that the first cell is not eligible for UE 102 to access, DU 174 avoids sending a PDCCH command. In yet another implementation, DU 174 sends a PDCCH command after receiving the 320 RRC reconfiguration complete message, regardless of the L1 measurement result 324.

[0112] After sending a 324 L1 measurement report or a 352 RA preamble, UE 102 may send a 354 additional L1 measurement report to DU 174, similar to event 324. Based on the additional L1 measurement report and / or L1 measurement report 324, DU 174 determines that UE 102 should perform an LTM cell handover to the first cell. In response to the determination, DU 174 generates an LTM cell handover command (e.g., MAC CE) including LTM ID 1 and sends a 326 LTM cell handover command to UE 102. In response to the determination, DU 174 may send a 328 DU-CU cell handover notification message to CU 172. In response to the LTM cell handover command, UE 102 performs an LTM cell handover to the first cell. During the LTM cell handover, UE 102 accesses the first cell (332) and sends a 336 RRC reconfiguration complete message to DU 174 via the first cell. DU 174 sends a DU-CU message (e.g., a UL RRC message transmission message) to CU 172, including an RRC reconfiguration completion message. When UE 102 receives an LTM cell handover command, UE 102 identifies LTM candidate configuration 1 from LTM ID 1 and uses LTM candidate configuration 1 to access the first cell (332). Depending on the implementation, UE 102 may stop communicating on the serving cell in response to the LTM cell handover command. Then, DU 174 sends a fifth DU-CU message to CU 172, including an RRC reconfiguration completion message. When DU 174 detects that UE 102 has accessed the first cell in event 332, DU 174 may send an access success message (334) to CU 172 to indicate that UE 102 has accessed the first cell.

[0113] In some implementations, DU 174 includes the TA value used for UL synchronization with the first cell in the LTM cell handover command. In one implementation, DU 174 obtains the TA value based on the RA preamble (e.g., the timing of the RA preamble reception). In another implementation, DU 174 obtains the TA value from the UL transmission of UE 102 on the serving cell (e.g., cell 124A). UE 102 applies the TA value to synchronize with the first cell in the UL transmission. After applying the TA value, UE 102 transmits the first UL transmission on the first cell based on LTM Candidate Configuration 1 without performing the RA procedure on the first cell. In some implementations, UE 102 transmits the first UL transmission on the first cell using UL grant. In this case, the first UL transmission is a PUSCH transmission. In some implementations, the PUSCH transmission includes an RRC reconfiguration complete message 336. In some implementations, the UL grant is a configured grant, and LTM Candidate Configuration 1 or LTM DU Configuration 1 includes a configured grant configuration for configuring the configured grant. In other implementations, the UL grant is a dynamic grant received by UE 102 on the PDCCH of the first cell. After sending the first UL transmission, UE 102 receives the PDCCH transmission addressed to UE 102's C-RNTI and determines that the LTM cell handover has been successfully completed in response to the receipt of the PDCCH transmission.

[0114] PDCCH transmissions may include UL grants or DL ​​assignments. If a PDCCH transmission includes a UL grant, UE 102 uses the UL grant to send a PUSCH transmission to DU 174 on the first cell. If a PDCCH transmission includes a DL assignment, DU 174 sends a PDSCH transmission to UE 102 on the first cell according to the DL assignment. DU 174 may send an Access Success Message 334 to CU 172 after receiving (e.g., in response to) a first UL transmission, sending a PDCCH transmission, receiving a PUSH transmission, or sending a PDSCH transmission.

[0115] In other implementations, DU 174 does not include the TA value in the LTM cell handover command. If the LTM cell handover command does not include the TA value, UE 102 performs a 332 RA procedure on the first cell according to the RA configuration parameters. In some implementations, the RA configuration parameters are included in LTM Candidate Configuration 1, LTM DU Configuration 1, and / or the LTM cell handover command. In some implementations, the RA configuration parameters configure PRACH resources, the association between SSB and PRACH resources, and / or one or more PRACH timings. If UE 102 successfully completes the RA procedure, UE 102 determines that the LTM cell handover to the first cell has been successfully completed. Depending on the implementation and / or the RA configuration parameters, the RA procedure can be a four-step RA procedure or a two-step RA procedure. Depending on the implementation and / or the RA configuration parameters, the RA procedure can be a contention-free RA (CFRA) procedure or a contention-based RA (CBRA) procedure. During a four-step RA procedure, UE 102 transmits an RA preamble (i.e., message 1) on the first cell and receives an RA response (i.e., message 2) on the first cell from DU 174, which responds to the RA preamble. Then, the UE transmits message 3 on the first cell using the UL authorization in the RA response, and DU 174, in response, transmits message 4 to UE 102 on the first cell. In some implementations, message 4 is a DCI. If the RA procedure is a CBRA procedure, UE 102 determines that contention resolution was successful upon receiving message 4. If the RA procedure is a CBRA procedure, the RA preamble is a dedicated preamble, and UE 102 determines that contention resolution was successful upon receiving the RA response. During a two-step RA procedure, UE 102 transmits message A on the first cell, and DU 174, in response, transmits message B to UE 102 on the first cell. If the RA procedure is a CFRA or CBRA procedure, UE 102 determines that contention resolution was successful upon receiving message B. UE 102 may include the RRC reconfiguration complete message 336 in message 3 or message A. Alternatively, UE 102 sends the RRC reconfiguration complete message 336 after completing the RA procedure. After receiving message 3, message A, or the RRC reconfiguration complete message 336, or after sending message 4 or message B, DU 174 may send an access success message 334 to CU 172.

[0116] In some implementations, DU 174 includes a first set of LTM CFRA configuration parameters in the LTM cell handover command to configure UE 102 to perform a CFRA procedure to access the first cell. In some implementations, the first set of LTM CFRA configuration parameters includes a first RA preamble index, a first SSB index, a first PRACH mask index, and / or a first UL / supplementary (or supplementary) UL (SUL) indicator. In some implementations, the first UL / NUL indicator configures UE 102 to perform a CFRA procedure on a normal UL (NUL) or SUL. For example, if the first UL / SUL indicator indicates UL (e.g., if the first UL / SUL indicator is set to a first value), then UE 102 performs a CFRA procedure on UL. Otherwise, if the first UL / SUL indicator indicates SUL (e.g., if the first UL / SUL indicator is set to a second value), then UE 102 performs a CFRA procedure on SUL. UE102 performs a 332 CFRA procedure to access a first cell using LTM CFRA configuration parameters and at least one RACH configuration. LTM candidate configuration 1 includes a RACH configuration. The RACH configuration is not configured for early UL synchronization. In some implementations, the RACH configuration is configured for LTM cell handover. In some implementations, at least one RACH configuration includes a common RACH configuration (e.g., RACH-ConfigCommon IE) and / or a generic RACH configuration (e.g., RACH-ConfigGeneric IE). In some implementations, the RACH configuration does not include a dedicated RACH configuration (e.g., RACH-ConfigDedicated IE). In other implementations, the RACH configuration includes a dedicated RACH configuration (e.g., RACH-ConfigDedicated IE). DU 174 performs a CFRA procedure with UE 102 based on the first set of LTM CFRA configuration parameters and the RACH configuration.

[0117] In some implementations, DU 174 determines whether to include the first set of LTM CFRA configuration parameters in the LTM cell handover command based on the measurement report received at event 354. In some implementations, DU 174 obtains (e.g., retrieves, obtains, calculates, or determines) one or more measurement results from the measurement report. In some implementations, the measurement results include the measurement results of a first SSB identified by a first SSB index. The first SSB is transmitted by DU 174 on the first cell. In such cases, if the measurement result of the first SSB is higher than (or equal to) a second predetermined threshold, DU 174 includes the first set of LTM CFRA configuration parameters in the LTM cell handover command. Otherwise, if the measurement result of the first SSB is lower than (or equal to) the second predetermined threshold, DU 174 avoids including the first set of LTM CFRA configuration parameters in the LTM cell handover command.

[0118] In some implementations, the DU 174 is (pre)configured with a first set of LTM CFRA configuration parameters. The DU 174 may preconfigure at least one additional set of LTM CFRA configuration parameters, and each of the additional sets includes the RA preamble index, SSB index, PRACH mask index, and / or UL / SUL indicator for the first cell. In some implementations, the first set and / or additional sets are specifically configured for the first cell. In other implementations, the first set and / or additional sets are configured for any cell operated by the DU 174. In some implementations, the DU 174 preconfigures the first set and / or additional sets for one of UL (i.e., NUL) and SUL. In other implementations, the DU 174 preconfigures the first set for one of UL and SUL, and configures the additional sets for the other of UL and SUL.

[0119] In some implementations, when DU 174 identifies the first SSB index based on the aforementioned measurement report, DU 174 identifies the first set of LTM CFRA configuration parameters based on the first SSB index. In some implementations, DU 174 determines the value of the first UL / SUL indicator based on the measurement result of the first SSB. For example, if the measurement result is below (or equal to) a third predetermined threshold, DU 174 sets the first UL / SUL indicator to a first value indicating UL (i.e., NUL). Otherwise, if the measurement result of the first SSB is above (or equal to) the third predetermined threshold, DU 174 sets the first UL / SUL indicator to a second value indicating SUL. In other implementations, DU 174 determines the value of the first UL / SUL indicator based on LTM DU configuration 1. For example, if LTM DU configuration 1 includes a RACH configuration for UL but does not include a RACH configuration for SUL, DU 174 sets the first UL / SUL indicator to a first value. Otherwise, if LTM DU configuration 1 includes a RACH configuration for SUL (wherein, in some implementations, LTM DU configuration 1 includes a RACH configuration for UL, while in others, LTM DU configuration 1 does not include a RACH configuration for UL), then DU 174 may set the first UL / SUL indicator to a second value, or determine the value of the first UL / SUL indicator based on the measurement result of the first SSB as described above. In yet another implementation, DU 174 sets the first UL / SUL indicator to a pre-configured value (e.g., a first value), for example, because DU 174 does not support SUL. In yet another implementation, DU 174 sets the first UL / SUL indicator to a pre-configured value (e.g., a second value), for example, because DU 174 is pre-configured to set the first UL / SUL indicator to that pre-configured value.

[0120] In some implementations, the first, second, and third predetermined thresholds are the same threshold. In other implementations, at least two of the first, second, and third predetermined thresholds are different or set to different values.

[0121] After successfully completing the LTM cell handover to the first cell as described above, UE 102 communicates with DU 174 and CU 172 via the first cell using LTM candidate configuration 1 340. In the case of the LTM reference configuration, UE 102 first applies the LTM reference configuration, and then applies LTM candidate configuration 1 to enhance the LTM reference configuration.

[0122] In some implementations, each of the TCI state configurations includes a TCI state ID. In some implementations, DU 174 includes the first TCI state ID indicating the first in the TCI state configuration in the DU-CU cell handover notification message and / or LTM cell handover command. UE 102 identifies the first in the TCI state configuration based on the first TCI state ID and applies the first TCI state configuration to communicate UL and / or DL ​​transmissions with DU 174 in events 332, 336, and / or 340. DU 174 applies the first TCI state configuration to communicate UL and / or DL ​​transmissions with UE 102 in events 332, 336, and / or 340. In other implementations, where separate TCI states are used, the DL TCI state and the UL TCI state use different TCI state IDs. In this scenario, DU 174 will include the first TCI state ID for DL ​​and / or the second TCI state ID for UL, respectively, in the DU-CU cell handover notification message and / or LTM cell handover command. UE 102 identifies the first TCI state configuration and the second TCI state configuration based on the first TCI state ID and the second TCI state ID, respectively. UE 102 applies the first TCI state configuration and the second TCI state configuration to communicate DL and UL transmissions to DU 174 in events 332, 336, and / or 340, respectively. DU 174 identifies the first TCI state configuration and the second TCI state configuration based on the first TCI state ID and the second TCI state ID, respectively. DU 174 applies the first TCI state configuration and the second TCI state configuration to communicate DL and UL transmissions to UE 102 in events 332, 336, and / or 340, respectively.

[0123] In some implementations, CU 172 may prepare additional cells (i.e., cells 2, ..., N) as LTM candidate cells for UE 102 before or after sending the LTM cell handover command, or during or after procedures 390 or 392, in conjunction with DU 174, as described above. N is an integer and greater than 1. For example, CU 172 and DU 174 perform additional LTM preparation procedures 2, ..., N to prepare cells 2, ..., N respectively. Each of LTM preparation procedures 2, ..., N is similar to procedure 390. In LTM preparation procedures 2, ..., N, CU 172 receives LTM DU configurations 2, ..., N, thereby configuring cells 2, ..., N for LTM respectively. CU 172 generates LTM candidate configurations 2, ..., N, each including LTM DU configurations 2, ..., N. CU 172 assigns LTM IDs 2, ..., N to identify LTM DU configurations 2, ..., N and LTM candidate configurations 2, ..., N respectively. CU 172 can acquire CSI resource configurations 2, ..., N, and, together with DU 174, perform CSI report configuration and / or LTM ID configuration procedures 2, ..., N to acquire CSI report configurations 2, ..., N, as described for CSI resource configuration 1 and CSI report configuration 1, respectively. CU 172 can acquire RACH configurations 2, ..., N for cells 2, ..., N, as described for RACH configuration 1, respectively. CU 172 can acquire TCI status configurations 2, ..., N for cells 2, ..., N, as described for TCI status configuration 1, respectively. Each of the CSI report configuration and / or LTM ID configuration procedures 2, ..., N is similar to procedure 392. CU 172 can acquire LTM SSB configurations 2, ..., N for cells 2, ..., N, as described for LTM SSB configuration 1, respectively. In some implementations, CU 172 may perform LTM configuration delivery procedures 2, ..., N with UE 102 to send to UE 102 lists including the following: {LTM ID 2, LTM candidate configuration 2, CSI resource configuration 2 (if obtained), TCI state configuration 2 (if obtained), RACH configuration 2 (if obtained), LTM SSB configuration 2 (if obtained)}, ..., {LTM ID N, LTM candidate configuration N, CSI resource configuration N, TCI state configuration N (if obtained), RACH configuration N (if obtained), LTM SSB configuration N (if obtained)}. Each of LTM configuration delivery procedures 2, ..., N is similar to procedure 394. In other implementations, CU 172 includes the list in the first RRC reconfiguration message.

[0124] In some implementations, after receiving the 334 Access Success Message or the 338 DU to CU Message, CU172 may send a 342 CU to DU 174. In one implementation, CU 172 sends the 342 CU to DU Message to release the radio resources and / or configuration of the serving cell configured for UE 102. In another implementation, CU 172 sends the 342 CU to DU Message to release some of LTM candidate cells 2, ..., N. In this case, CU 172 sends a message to release the resources and configuration of the candidate cells. In response to the CU to DU Message 342, DU 174 sends a 344 DU to CU 172. In some implementations, the CU to DU Message 342 and the DU to CU Message 344 are respectively... UE Context Modification Request Messages and UE context modification response information.

[0125] In some implementations, the LTM ID is provided in different formats depending on which command or message provides it. For example, the LTM ID can be provided differently in PDCCH commands, LTM cell handover commands, and RRC reconfiguration messages. For instance, a PDCCH command or LTM cell handover command includes a first field for including LTM ID 1, and a first RRC reconfiguration message includes a second field for including LTM ID 1. In some implementations, the first and second fields have different formats or encoding schemes. For example, the first field uses a binary format (i.e., 3 bits) with values ​​ranging from 0 to 7, and the second field uses an integer format with values ​​ranging from 1 to 8. In this example, a first field with a binary value of 000b is equivalent to a second field with an integer value of 1, a first field with a binary value of 001b is equivalent to a second field with an integer value of 2, and so on, and a first field with a binary value of 111b is equivalent to a second field with an integer value of 8.

[0126] Events 304, 306, 390, 392, 394, and 324 are collectively referred to as CU-DU-LTM configuration process 396. Events 304, 306, 390, 392, 394, 324, 350, 352, 354, 326, 328, 332, 334, 336, 338, and 340 are collectively referred to as CU-DU-LTM process 380.

[0127] Next reference Figure 4In scenario 400, base station 104A includes CU 172, S-DU 174A, and candidate DU (C-DU) 174B. S-DU 174A operates cell 124A and optionally additional cells, while C-DU 174B operates different cells (e.g., cell 124B or cell 126A). Figure 1A Scene 400 is a scene between DUs within a CU, similar to Scene 300. Therefore, the description of Scene 300 can be largely applied to Scene 400. Figure 3 Some descriptions of DU 174 in the document can be applied to Figure 4 S-DU 174A in, and for Figure 3 Some descriptions of DU 174 in the document can be applied to C-DU 174B. The differences between scenarios 300 and 400 are described below.

[0128] Initially, UE 102 uses the serving DU to configure communication 402 with S-DU 174A on one or more serving cells (e.g., cell 124A and / or other cells), and UE 102 uses the serving CU to configure communication with CU 172 via S-DU 174A. In some implementations, CU 172 and S-DU 174A may perform LTM configuration procedure 496 or LTM procedure 480 with UE 102, similar to procedures 396 and 380 respectively, as referenced. Figure 3 As described. In the case of procedure 380, UE 102 can perform an LTM cell handover to the first cell (e.g., cell 124B), as described in the reference. Figure 3As described. After a successful LTM cell handover, the first cell becomes the serving cell, and cell 124A and / or other cells are no longer serving cells for UE 102. In the case of procedure 496, UE 102 does not perform an LTM cell handover. During communication 402, UE 102 sends at least one measurement report (e.g., an L3 measurement report) via S-DU 174A to CU 172 in steps 404 and 406. Based on the measurement report, CU 172 determines that cell 1 (e.g., cell 126A operated by C-DU 174B) is ready for LTM for UE 102. Cell 1 is identified by a cell ID (i.e., cell ID 1). In response to the determination, CU 172 and C-DU 174B perform LTM preparation procedure 490 to prepare or request C-DU 174B to prepare cell 1 as an LTM candidate cell for UE 102. In LTM preparation process 490, CU 172 sends a first CU-DU message to C-DU 174B, including cell ID 1 of cell 1, to request C-DU 174B to prepare cell 1 as an LTM candidate cell for UE 102, similar to event 308. In response, C-DU 174B sends a first DU-CU message to CU 172, including the LTM DU configuration (e.g., LTM DU configuration 1), similar to event 310. In some implementations, CU 172 requests an LTM reference DU configuration in the first CU-DU message, such as a reference... Figure 3 As described, in other implementations, CU 172 does not request the LTM reference DU configuration in the first CU to DU message. In some implementations, C-DU 174B includes the LTM reference DU configuration in the first DU to CU message, as reference Figure 3 As described, in other implementations, the C-DU 174B does not include the LTM reference DU configuration in the first DU to CU message.

[0129] In some implementations, if CU 172 receives LTM reference DU configuration from S-DU 174A, such as reference... Figure 3 As described, CU 172 can include the LTM reference DU configuration in the first CU-DU message, and C-DU 174B can generate an LTM DU configuration as an incremental configuration based on the LTM reference DU configuration. In this case, C-DU 174B does not send the LTM reference DU configuration of UE 102 to CU 172. In other implementations, CU 172 receives the LTM reference DU configuration from C-DU 174B, for example, in the first DU-CU message or an appended DU-CU message, such as the reference DU configuration. Figure 3As described. In such cases, CU 172 can generate an LTM reference configuration that includes the LTM reference DU configuration. In some implementations, CU 172 includes the LTM reference CU configuration in the LTM reference configuration, while in other implementations, CU 172 does not include the LTM reference CU configuration in the LTM reference configuration.

[0130] To prepare cell 1 for LTM, CU 172 can perform LTM CSI report configuration and / or LTM ID configuration procedure 492 with S-DU 174A. In procedure 492, CU 172 sends a second CU-DU message to S-DU 174A, including a CSI resource configuration (e.g., CSI resource configuration 1) and / or an LTM SSB configuration (i.e., LTM SSB configuration 1), similar to event 312. In response, S-DU 174A sends a second DU-CU message to CU 172, including one or more CSI report configurations (e.g., CSI report configuration 1). In some implementations, CU 172 generates an LTM candidate configuration (e.g., LTM candidate configuration 1) including an LTM DU configuration, and CU 172 assigns an LTM ID (e.g., LTM ID 1) to identify the LTM DU configuration and / or LTM candidate configuration, as referenced. Figure 3 As described. In some implementations, CU 172 includes {LTM ID 1, Cell ID 1} as a tuple in the second CU to DU message.

[0131] To prepare cell 1 as an LTM candidate cell for UE 102, CU 172 can receive early synchronization information for cell 1 from C-DU 174B in DU-CU messages (e.g., the first DU-CU message or an additional DU-CU message), similar to the reference. Figure 3 The DU to CU message is described.

[0132] In some implementations, CU 172 can receive LTM SSB configuration or SSB configuration parameters in the LTM SSB configuration from C-DU 174B, for example, in the first DU to CU message or in the additional DU to CU message. In some implementations, CU 172 can receive the PCI of cell 1 from C-DU 174B in the first DU to CU message or in the additional DU to CU message. In some implementations, C-DU 174B sends an additional DU to CU message in response to receiving the additional CU to DU message from CU 172. In other implementations, C-DU 174B sends an additional DU to CU message in response to receiving the first CU to DU message (e.g., UE context modification requirements information).

[0133] In some implementations, C-DU 174B includes a first set of LTM CFRA configuration parameters in the first DU to CU message of process 490. In some implementations, the first set of LTM CFRA configuration parameters includes a first RA preamble index, a first SSB index, a first PRACH mask index, and / or a first UL / SUL indicator. In such cases, CU 172 includes the first set of LTM CFRA configuration parameters in the second CU to DU message of process 492. C-DU 174B may include at least one additional set of LTM CFRA configuration parameters in the first DU to CU message of process 490. Each of the additional set of LTM CFRA configuration parameters includes an RA preamble index, an SSB index, a PRACH mask index, and / or a UL / SUL indicator. In such cases, CU 172 includes the additional set of LTM CFRA configuration parameters in the second CU to DU message of process 492. In some implementations, the C-DU 174B configures the first group and / or supplementary group LTM CFRA configuration parameters for UE 102. In some implementations, the first group and / or supplementary group LTM CFRA configuration parameters are specifically configured for cell 1. In other implementations, the first group and / or supplementary group LTM CFRA configuration parameters are configured for any LTM candidate cells configured by the C-DU 174B for UE 102.

[0134] In some implementations, the first and supplementary group LTM CFRA configuration parameters do not include a separate UL / SUL indicator. In some implementations, C-DU 174B configures the first and / or supplementary group LTM CFRA configuration parameters for one of UL (i.e., NUL) and SUL (e.g., UL / NUL or SUL), and C-DU 174B includes a single UL / SUL indicator in the first DU to CU message, which indicates that the first and / or supplementary group LTM CFRA configuration parameters are configured for UL / NUL or SUL. In such cases, CU 172 includes a single UL / SUL indicator in the second CU to DU message, which indicates that the first and / or supplementary group LTM CFRA configuration parameters are configured for UL / NUL or SUL. In other implementations, if C-DU 174B configures the first group and / or additional group LTM CFRA configuration parameters for UL, then C-DU 174B includes the first group and / or additional group in the first field / IE of the first DU to CU message. Otherwise, if C-DU 174B configures the first group and / or additional group LTM CFRA configuration parameters for SUL, then C-DU 174B includes the first group and / or additional group in the second field / IE of the first DU to CU message. In such cases, the first field / IE and the second field / IE are defined for UL and SUL, respectively. In some implementations, if the first DU to CU includes the first group and / or additional group LTM CFRA configuration parameters in the first field / IE, then CU 172 includes the first group and / or additional group in the first field / IE of the second CU to DU message. Otherwise, if the first DU to CU includes the first group and / or additional group LTM CFRA configuration parameters in the second field / IE, then CU 172 includes the first group and / or additional group in the second field / IE of the second CU to DU message. In this case, the first field / IE and the second field / IE are defined for UL and SUL, respectively.

[0135] In some implementations, C-DU 174B configures a first set of LTM CFRA configuration parameters for one of UL and SUL (e.g., UL or SUL), and C-DU 174B configures an additional group for the other of UL and SUL. In some implementations, C-DU 174B sets a first UL / SUL indicator to a value indicating one of UL and SUL, and sets the UL / SUL indicator in the additional group to a value indicating the other of UL and SUL. In other implementations, if C-DU 174B configures the first group for one of UL and SUL and the additional group for the other of UL and SUL, then C-DU 174B includes the first group and the additional group in one and the other of the first field / IE and the second field IE in the first DU to CU message, respectively. In such cases, CU 172 includes the first group and the additional group in one and the other of the first field / IE and the second field IE in the second CU to DU message, respectively.

[0136] For reference Figure 3 As described, CU 172 performs LTM configuration delivery procedure 494 with UE 102 to send LTM ID 1 and LTM candidate configuration to UE 102. In some implementations, CU 172 sends {LTM ID, LTM candidate configuration} as a tuple in the first RRC reconfiguration message in procedure 494. Depending on the implementation, CU 172 may include the LTM reference configuration, CSI report configuration, CSI resource configuration, RACH configuration, TCI state configuration, LTM SSB configuration, and / or the PCI of cell 1 in the first RRC reconfiguration message to UE 102 and / or in other RRC reconfiguration messages sent to UE 102, such as the reference configuration. Figure 3 As described, CU 172 includes the LTM ID in the first RRC reconfiguration or other RRC reconfiguration messages to indicate that the CSI resource configuration, RACH configuration, TCI state configuration, LTM SSB configuration, and / or the PCI of cell 1 are associated with cell 1. For example, CU 172 includes the CSI resource configuration, RACH configuration, TCI state configuration, LTM SSB configuration, and / or the PCI of cell 1 in a tuple. In another example, CU 172 includes {LTM ID, CSI resource configuration, RACH configuration, TCI state configuration, LTM SSB configuration, and / or the PCI of cell 1} as a tuple in other RRC reconfiguration messages. In response to each of the other RRC reconfiguration messages, UE 102 sends an RRC reconfiguration complete message to CU 172 via S-DU 174A.

[0137] In some implementations, the PDCCH command information includes frequency domain resource assignment, RA preamble index, UL or supplementary (or supplementary) UL indicator, SSB index, and / or physical RACH mask index. CU 172 can send a CU-DU message (e.g., a second CU-DU message or an additional CU-DU message) including the PDCCH command information to S-DU 174A. In some implementations, CU 172 includes LTM ID 1 or cell ID 1 in the CU-DU message to indicate that the PDCCH command information is associated with LTM ID 1 or cell ID 1. For example, when CU 172 sends the PDCCH command information in a second CU-DU message, CU 172 includes {cell ID 1, PDCCH command information} as a tuple in the CU-DU message. When CU 172 sends an additional CU-DU message, S-DU 174A can send an additional DU-CU message in response. The S-DU 174A sends a 450 PDCCH command to UE 102 based on the PDCCH command information. For example, the S-DU 174A sends a 450 PDCCH command including the PDCCH command information to UE 102. In some implementations, the S-DU 174A may determine the SSB index to be included in the PDCCH command based on L1 Measurement Report 424 and / or CSI resource configuration, CSI report configuration, and / or LTM SSB configuration. In some implementations, the S-DU 174A includes LTM ID 1 in the PDCCH command to indicate cell 1. When CU 172 sends the PDCCH command information in an appended CU to DU message, the S-DU 174A may send an appended DU to CU message in response. UE 102 sends a 452 RA preamble to C-DU 174B on cell 1 using RACH configuration and / or the PDCCH command information. C-DU 174B obtains the TA value based on the RA preamble. C-DU 174B sends DU-CU TA information transmission message 456, including the TA value, to CU 172. CU 172 then sends CU-DU TA information transmission message 458, including the TA value, to S-DU 174A. In some implementations, C-DU 174B includes cell ID 1, RA preamble index, RA radio network temporary identifier (RA-RNTI), and / or the DU ID of S-DU 174A in message 456. In such cases, CU 172 includes cell ID 1, RA preamble index, RA-RNTI, and / or the DU ID of S-DU 174A in message 458. In response to the determination command UE 102 to perform an LTM cell handover to cell 1, S-DU 174A sends an LTM cell handover command 456, including LTM ID 1, to UE 102.If the S-DU 174A receives the TA value as described above, it can include the TA value in the LTM cell handover command. The S-DU 174A can also include the first TCI status ID in the LTM cell handover command. The first TCI status ID indicates the first one in the TCI status configuration.

[0138] In some implementations, the C-DU 174B determines the RA-RNTI based on the PRACH timing of the RA preamble 452 received by the C-DU 174B. In some implementations, the C-DU 174B calculates the RA-RNTI as follows:

[0139] RA-RNTI = 1 + s_id + 14 × t_id + 14 × 80 × f_id + 14 × 80 × 8 ×ul_carrier_id

[0140] Wherein, s_id is the index of the first OFDM symbol of the PRACH timing (0≤s_id < 14), t_id is the index of the first slot of the PRACH timing in the system frame (0≤t_id < 80), wherein the subcarrier spacing used to determine t_id is based on the μ value specified in Clause 5.3.2 of 3GPP TS 38.211 for μ={0, 1, 2, 3}, and for μ={5, 6}, t_id is the index of the 120 kHz slot in the system frame containing the PRACH timing (0≤t_id < 80), f_id is the index of the PRACH timing in the frequency domain (0≤f_id < 8), and ul_carrier_id is the UL carrier used for RA preamble transmission (0 for NUL carrier, 1 for SUL carrier).

[0141] In response to the determination command UE 102 to perform an LTM cell handover or to send the 426 LTM cell handover command, S-DU174A sends a 428 DU-CU cell handover notification message to CU 172 to instruct UE 102 to perform an LTM cell handover to cell 1. In response, CU 172 sends a 430 CU-DU cell handover notification message to C-DU 174B to instruct UE 102 to perform an LTM cell handover to cell 1. UE 102 accesses cell 1 in response to the LTM cell handover command. In some implementations, S-DU 174A determines that the first set of LTM CFRA configuration parameters are included and / or included in the LTM cell handover command to configure UE 102 to perform the CFRA procedure to access cell 1, as shown in the reference. Figure 3 As described, UE 102 uses LTM CFRA configuration parameters and at least one RACH configuration to perform the CFRA procedure to access cell 1, as referenced. Figure 3 As described. The C-DU 174B performs the CFRA procedure with UE 102 based on the LTM CFRA configuration parameters and RACH configuration, as referenced. Figure 3 As described.

[0142] In some implementations, the S-DU 174A determines whether to include the first set of LTM CFRA configuration parameters in the LTM cell handover command based on the measurement report received at event 454. In some implementations, the S-DU 174A obtains (e.g., retrieves, obtains, calculates, or determines) one or more measurement results from the measurement report. In some implementations, the measurement results include the measurement results of a first SSB identified by a first SSB index. The first SSB is transmitted by the C-DU 174B on cell 1. In such cases, if the measurement result of the first SSB is higher than (or equal to) a second predetermined threshold, the S-DU 174A includes the first set of LTM CFRA configuration parameters in the LTM cell handover command. Otherwise, if the measurement result of the first SSB is lower than (or equal to) the second predetermined threshold, the S-DU 174A avoids including the first set of LTM CFRA configuration parameters in the LTM cell handover command.

[0143] In some implementations, where the first set of LTM CFRA configuration parameters includes a first UL / SUL indicator, the S-DU 174A includes the first UL / SUL indicator in the LTM cell handover command, as shown in the reference. Figure 3 As described. In other implementations, where the first set of LTM CFRA configuration parameters does not include the UL / SUL indicator, the S-DU 174A can determine the value of the UL / SUL indicator and include it in the LTM cell handover command, as described below and / or referenced. Figure 3As described. In some implementations, if the second CU-to-DU message includes the first set of LTM CFRA configuration parameters in the first field / IE for UL, then the S-DU 174A sets the UL / SUL indicator to the first value for UL. Otherwise, if the second CU-to-DU message includes the first set of LTM CFRA configuration parameters in the second field / IE for UL, then the S-DU 174A sets the UL / SUL indicator to the second value for SUL. In other implementations, the S-DU 174A determines the value of the UL / SUL indicator in the LTM cell handover command based on the measurement result of the first SSB obtained by the S-DU 174A from the measurement report at event 454. In one implementation, if the measurement result is higher than (or equal to) a predetermined threshold, the S-DU 174A sets the UL / SUL indicator to the first value and includes the first set in the LTM cell handover command. Otherwise, if the measurement result is below (or equal to) a predetermined threshold, the S-DU 174A sets the UL / SUL indicator to a second value and includes the additional group instead of the first group in the LTM cell handover command. In other implementations, the S-DU 174A sets the UL / SUL indicator to a pre-configured value (e.g., the first value) because the C-DU 174B does not support SUL. In yet another implementation, the S-DU 174A sets the UL / SUL indicator to a pre-configured value (e.g., the second value) because the S-DU 174A is pre-configured to set the UL / SUL indicator to a pre-configured value.

[0144] In some implementations, S-DU 174A includes the first TCI state ID in the DU-CU cell handover notification message, and CU 172 further includes the first TCI state ID in the CU-DU cell handover notification message. UE 102 and C-DU174B identify the first in the TCI state configuration based on the first TCI state ID, and apply the first TCI state configuration to communicate UL transmissions and / or DL ​​transmissions in events 432, 436, and / or 440.

[0145] In other implementations, if separate TCI states are used, the DL TCI state and the UL TCI state use different TCI state IDs. In such cases, the S-DU 174A will include the first TCI state ID for DL ​​and the second TCI state ID for UL, respectively, configured for the first and second TCI states, in the DU-CU cell handover notification message and / or LTM cell handover command. In response to DU-CU cell handover notificationThe CU 172 then includes the first TCI state ID and the second TCI state ID in the CU-DU cell handover notification message to the C-DU 174B. The UE 102 identifies the first TCI state configuration and the second TCI state configuration based on the first TCI state ID and the second TCI state ID, respectively. The UE 102 applies the first TCI state configuration and the second TCI state configuration to receive DL transmissions and send UL transmissions with the C-DU 174B in events 432, 436, and / or 440, respectively. The C-DU 174B identifies the first TCI state configuration and the second TCI state configuration based on the first TCI state ID and the second TCI state ID, respectively. The C-DU 174B applies the first TCI state configuration and the second TCI state configuration to communicate DL transmissions and UL transmissions to the UE 102 in events 432, 436, and / or 440, respectively.

[0146] In some implementations, each of the TCI state configurations includes or is associated with a TCI state ID. In some implementations, CU 172 may send a CU-DU message (e.g., a second CU-DU message or an additional CU-DU message) to S-DU 174A that includes the TCI state configuration and / or the associated TCI state ID. In some implementations, CU 172 includes LTMID 1 or Cell ID 1 in the CU-DU message to indicate that the TCI state configuration is associated with LTM ID 1 or Cell ID 1. For example, when CU 172 sends the TCI state configuration and / or the associated TCI state ID in a second CU-DU message, CU 172 includes {Cell ID 1, TCI state configuration} as a tuple in the CU-DU message. When CU 172 sends an additional CU-DU message, S-DU 174A may send an additional DU-CU message in response. In some implementations, the S-DU174A includes the first TCI state ID, indicating the first in the TCI state configuration, in the LTM cell handover command 426. In some implementations, the S-DU 174A determines either the first TCI state configuration or the first TCI state ID. The UE 102 identifies one of the TCI state configurations based on the first TCI state ID and applies the first TCI state configuration in UL transmission and / or DL ​​reception in events 432, 436, and / or 440.

[0147] In some implementations, CU 172 may prepare additional cells (i.e., cells 2, ..., N) as LTM candidate cells for UE 102 before or after sending the LTM cell handover command, or during or after procedures 490 or 492, in conjunction with C-DU 174B, as referenced. Figure 3 As described.

[0148] In some implementations, the first CU to DU message and the first DU to CU message are UE Context Establishment Request Messages and UE Context Establishment Response Messages. In some implementations, the first CU to DU message and the first DU to CU message are... UE Request for amendments Messages and UE context modification response 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.

[0149] Events 404, 406, 490, 492, 494, and 424 are collectively referred to as CU-DU inter-LTM configuration procedure 497. Events 404, 406, 490, 492, 494, 424, 450, 452, 454, 456, 458, 426, 428, 430, 432, 434, 436, 438, 440, 442, and 444 are collectively referred to as CU-DU inter-LTM procedure 480.

[0150] Next reference Figure 5 In scenario 500, base station 104A operates as a serving base station or source base station (S-BS), and base station 106A operates as a candidate base station (C-BS). C-BS 106A includes CU 172 and DU 174. Scenario 500 is similar to scenarios 300 and 400, except that scenario 500 is an inter-CU scenario (i.e., an inter-base station scenario), while scenarios 300 and 400 are intra-CU scenarios (i.e., intra-base station scenarios). S-BS 104A may include CU and DU (… Figure 5 (not shown in the image), similar to Figure 3 and Figure 4 The base station 104A. Initially, UE 102 communicates with S-BS 104A via the serving cell using the service configuration 502. In some implementations, S-BS 104A includes S-DU and CU, and the service configuration may include a service CU configuration and a service DU configuration, as shown in reference [reference missing]. Figure 3 and Figure 4 As described. When communicating with UE 102 502, S-BS 104A can perform 580 in-CU LTM procedures with UE 102, similar to procedures 380 and / or 480. Alternatively, when communicating with UE 102 502, S-BS 104A can perform 596 in-CU LTM configuration procedures with UE 102, similar to procedures 396 and / or 496.

[0151] When communicating with S-BS 104A, UE 102 sends at least one measurement report (504) to S-BS 104A. The measurement report includes measurement results for UE 102's serving cell and / or at least one non-serving cell (e.g., cell 126A). Based on the measurement report, S-BS 104A determines a first cell (e.g., cell 126A) to be prepared as an LTM candidate cell for UE 102. For example, the measurement report includes the PCI of the first cell and the measurement results for cell 126A. S-BS 104A identifies the first cell as being operated by base station 106A based on the PCI and determines the first cell is eligible for LTM preparation based on the measurement results.

[0152] After determining the first cell to be prepared as the LTM candidate cell for UE 102 (e.g., in response to this), S-BS 104A (e.g., the CU of S-BS 104A) generates a handover request message including the first cell ID (i.e., cell ID 1) of the first cell (i.e., cell 1). S-BS 104A sends a 505 handover request message to CU 172. In some implementations, Transfer Request The message includes an LTM indicator, which indicates... Transfer Request The message involves the LTM of the first cell ID. Upon receiving... transfer ask Following the message (e.g., in response to this), CU 172 and DU 174 perform LTM preparation procedure 590 to prepare a first cell as an LTM candidate cell for UE 102, similar to procedure 390 or 490. In procedure 590, CU 172 sends a first CU-DU message including the first cell ID to DU 174 to request preparation of the first cell, similar to event 308. In response, CU 172 can receive a first DU-CU message including LTM DU configuration 1 from DU 174, similar to event 310. CU 172 generates a first LTM candidate configuration (LTM candidate configuration 1). In response to Transfer Request Message: CU 172 sends 507 to S-BS 104A, including the first LTM candidate configuration. Confirmation of transfer request Message. In some implementations, CU 172 includes the first cell ID. Transfer request confirmed recognize The message indicates that a first LTM candidate configuration is provided for or associated with a first cell (ID).

[0153] Events 505, 590, and 507 are in Figure 5 This is collectively referred to as the CU-inter-LTM preparation process (or alternatively, the MN-inter-LTM preparation process) 582.

[0154] In some implementations, Transfer Request The message includes the DU ID of the S-DU of S-BS 104A. In such cases, CU 172 includes the DU ID in the first CU-to-DU message. In some implementations, Transfer Request The message includes the BS ID of S-BS104A. When the BS ID is received, CU 172 can include the BS ID in the first CU to DU message. For example, the BS ID could be the gNB ID.

[0155] In some implementations, CU 172 requests the LTM reference DU configuration in procedure 590, such as the reference... Figure 3 and Figure 4 As described, in other implementations, CU 172 does not request the LTM reference DU configuration. In some implementations, DU 174 sends the LTM reference DU configuration to CU 172 in procedure 590, such as the reference... Figure 3 and Figure 4 As described, in other implementations, DU 174 does not send the LTM reference DU configuration to CU 172. In some implementations, S-BS 104A (e.g., the CU of S-BS 104A) can obtain the LTM reference configuration, such as the reference... Figure 3 and Figure 4 As described. In other implementations, the S-BS 104A can be transferred from another BS (during the LTM preparation process between another CU) Figure 5 (Not shown in the text) Receives the LTM reference configuration, as described above and later in this document. If the S-BS 104A acquires the LTM reference configuration, the S-BS 104A can include the LTM reference configuration (the LTM reference configuration generated by the S-BS) in... Transfer Request In some implementations, S-BS 104A includes the LTM reference configuration in the inter-node RRC message. HandoverPreparationInformation Alternatively, it can be used as an Xn Application Protocol (XnAP) IE or field, and include inter-node RRC messages or XnAP IEs. Transfer Request The message states that, alternatively, S-BS 104A determines the request or causes C-BS 106A to provide a complete LTM candidate configuration, in which case S-BS 104A does not include the LTM reference configuration. Transfer Request The message states that if the S-BS 104A does not obtain the LTM reference configuration, then the S-BS 104A will not include the LTM reference configuration in the message. Transfer Request In the message. If Transfer RequestIf the message includes an LTM reference configuration, CU 172 can include the LTM reference configuration in the first CU-DU message. DU 174 can extract the LTM reference DU configuration from the LTM reference configuration. Alternatively, CU 172 extracts the LTM reference DU configuration from the LTM reference configuration and includes the LTM reference DU configuration in the first CU-DU message. DU 174 can generate an LTM DU configuration as an incremental configuration based on the LTM reference DU configuration, such as a reference... Figure 3 As described. Alternatively, DU 174 can ignore the LTM reference (DU) configuration and generate an LTM DU configuration as the complete configuration, as described in the reference. Figure 3 As described.

[0156] Otherwise, if Transfer Request In some implementations, the CU 172 receives the LTM reference DU configuration from the DU 174, such as the reference DU configuration. Figure 3 As described, in other implementations, CU 172 does not receive the LTM reference DU configuration from DU 174. If CU 172 receives the LTM reference DU configuration (e.g., in the first DU to CU message), then CU 172 generates an LTM reference configuration that includes the LTM reference DU configuration (the LTM reference configuration generated by the C-BS). CU 172 may also include an LTM reference CU configuration (the LTM reference CU configuration generated by the candidate CU (C-CU)). Otherwise, if CU 172 does not receive the LTM reference DU configuration as described... Figure 3 If an LTM reference DU configuration is received from DU 174 as described, then CU 172 does not generate an LTM reference configuration. Instead, CU 172 generates an LTM reference configuration (C-BS generated LTM reference configuration) that includes only the LTM reference CU configuration generated by C-CU. When CU 172 generates an LTM reference configuration (C-BS generated LTM reference configuration), CU 172 includes the C-BS generated LTM reference configuration... Confirmation of transfer request In the message.

[0157] In some implementations, if LTM DU configuration 1 is a complete configuration, then CU 172 generates LTM candidate configuration 1 as the complete configuration. CU 172 may include the complete configuration indication (e.g., BS-to-BS interface protocol field / IE) in... Transfer Request confirmThe message indicates that LTM candidate configuration 1 is a complete configuration. In some implementations, the BS-to-BS interface protocol is the Xn application protocol defined in 3GPP specification 38.423. In some implementations, the complete configuration indication is a dedicated field / IE (e.g., LTM-specific) to reduce or eliminate the impact on non-LTM configurations. In other implementations, the complete configuration indication is an existing field / IE defined in 3GPP specification 38.423. Otherwise, if LTM DU configuration 1 is an incremental configuration, CU 172 generates LTM candidate configuration 1 as an incremental configuration. CU 172 can obtain... Confirmation of transfer request The message excludes the full configuration indication to indicate that LTM candidate configuration 1 is an incremental configuration. Alternatively, CU 172 may include the incremental configuration indication (e.g., the BS-to-BS interface protocol field / IE) in the message. Confirmation of transfer request The message indicates that LTM candidate configuration 1 is an incremental configuration. In some implementations, the BS-to-BS interface protocol is the Xn application protocol defined in 3GPP specification 38.423. In some implementations, the incremental configuration indication is a dedicated field / IE (e.g., LTM-specific) to reduce or eliminate the impact on non-LTM configurations. In other implementations, the incremental configuration indication is an existing field / IE defined in 3GPP specification 38.423. In some implementations, the BS-to-BS interface protocol field / IE can have one of at least two possible values ​​(i.e., a first value and a second value). The first value of the BS-to-BS interface protocol field / IE can indicate a full configuration, and the second value of the BS-to-BS interface protocol field / IE can indicate an incremental configuration.

[0158] In some implementations, the S-BS 104A is pre-configured with CSI resource configuration (e.g., CSI resource configuration 1 or LTM CSI resource configuration 1) and / or LTM SSB configuration (LTM SSB configuration 1) for the first cell. In other implementations, the S-BS 104A receives the CSI resource configuration and / or LTM SSB configuration from the OAM (Operation, Administration, and Maintenance) node. In yet another implementation, the S-BS 104A receives the CSI resource configuration and / or LTM SSB configuration from the CU 172. For example, the CU 172 includes the CSI resource configuration and / or LTM SSB configuration in... Confirmation of transfer request The message states that in some implementations, CU 172 includes the PCI (PCI 1) of the first cell. Confirmation of transfer request In the message, to prepare the first cell as a candidate LTM cell for UE 102, the CU of S-BS 104A uses the S-DU of S-BS 104A to perform the LTM CSI report configuration and / or LTM ID configuration procedures. Figure 5(Not shown in the diagram), similar to procedure 392. During the LTM CSI report configuration and / or LTM ID configuration process, the CU of S-BS104A sends the CSI resource configuration and / or LTM SSB configuration to the S-DU of S-BS104A. In response, the CU of S-BS104A receives one or more CSI report configurations of UE 102 from the S-DU of S-BS104A. In some implementations, the CU of S-BS104A receives the CSI report configuration from the second service DU configuration of the S-DU.

[0159] To prepare the first cell as an LTM candidate cell for UE 102, CU 172 can receive early synchronization information (e.g., early synchronization information 1) of the first cell from DU 174 in a DU-CU message (e.g., a first DU-CU message or an additional DU-CU message). In some implementations, DU 174 sends an additional DU-CU message in response to receiving an additional CU-DU message from CU 172. In other implementations, DU 174 sends an additional DU-CU message in response to receiving a first CU-DU message (e.g., ...). UE context modification request message ). CU 172 includes early synchronization information. Confirmation of transfer request The message includes early synchronization information, such as RACH configuration (e.g., RACH configuration 1) and / or at least one TCI state configuration (e.g., TCI state configuration 1). In some implementations, DU 174 includes PDCCH command information for early UL synchronization with the first cell in the early synchronization information or DU to CU message. CU 172 includes PDCCH command information in... Confirmation of transfer request In the message.

[0160] In some implementations, CU 172 assigns an LTM ID (e.g., LTMID 1) to identify the first LTM candidate configuration, and CU 172 includes the LTM ID in... Confirmation of transfer request In the message. In other implementations, S-BS 104A assigns an LTM ID (e.g., LTM ID 1) to identify the first LTM candidate configuration.

[0161] Received Confirmation of transfer request Following the message (e.g., in response to this), S-BS 104A (e.g., the CU of S-BS 104A) sends a first RRC reconfiguration message 518 to UE 102, which includes {LTM ID 1, LTM candidate configuration 1} as a tuple, similar to event 318. If Confirmation of transfer request If the message includes the LTM reference configuration, the S-BS104A can include the LTM reference configuration in the first RRC reconfiguration message. If the S-BS 104A receives... Transfer request confirmed recognize If the message contains CSI resource configuration 1, TCI state configuration 1, RACH configuration 1, and / or LTM SSB configuration 1, then the S-BS 104A may include this information in the tuple. Alternatively, the S-BS 104A sends one or more additional RRC reconfiguration messages to the UE 102, including CSI resource configuration 1, TCI state configuration 1, RACH configuration 1, LTM SSB configuration 1, and / or the PCI of the first cell. In each of the additional RRC reconfiguration messages, the S-BS 104A includes LTM ID 1 to indicate that CSI resource configuration 1, TCI state configuration 1, RACH configuration 1, LTM SSB configuration 1, and / or the PCI of the first cell are associated with or configured for the first cell. In response to the first RRC reconfiguration message, the UE 102 sends a 520 First RRC Reconfiguration Complete Message to the S-BS 104A. UE 102 sends an additional RRC reconfiguration complete message to S-BS 104A in response to each additional RRC reconfiguration complete message. The RRC reconfiguration messages (i.e., the first RRC reconfiguration message and / or the additional RRC reconfiguration messages) and the RRC reconfiguration complete messages (i.e., the first RRC reconfiguration complete message and / or the additional RRC reconfiguration complete messages) form the LTM configuration delivery process. S-BS 104A may include the second service DU configuration in the first RRC reconfiguration message or in one of the additional RRC reconfiguration messages.

[0162] In some implementations, if Confirmation of transfer request If the message includes a complete configuration indication indicating that LTM candidate configuration 1 is a complete configuration, then S-BS 104A will include the complete configuration indication (e.g., the RRC field / IE) in the first RRC reconfiguration message to indicate that LTM candidate configuration 1 is a complete configuration. Otherwise, if Confirmation of transfer request The message does not include a complete configuration instruction, or if Confirmation of transfer request If the message includes an incremental configuration indication to indicate that LTM candidate configuration 1 is an incremental configuration, then S-BS 104A will exclude or not include the full configuration indication (e.g., RRC field / IE) in the first RRC reconfiguration message to indicate that LTM candidate configuration 1 is an incremental configuration.

[0163] if Confirmation of transfer requestIf the message includes PDCCH command information (e.g., PDCCH command information 1), then the S-BS104A sends a 550 PDCCH command based on the PDCCH command information. If the S-BS104A is a distributed base station, the CU of the S-BS104A can send the PDCCH command information to the S-DU of the S-BS104A. For example, the S-BS104A or its S-DU sends a 550 PDCCH command to UE 102, including the PDCCH command information. In some implementations, the S-BS104A or its S-DU can determine the SSB index to be included in the PDCCH command based on L1 Measurement Report 524 and / or CSI resource configuration, CSI report configuration, and / or LTM SSB configuration. In some implementations, the S-DU or S-BS104A includes LTM ID 1 in the PDCCH command to indicate the first cell. UE 102 uses RACH configuration and / or PDCCH command information to send a 552 RA preamble to DU 174 on the first cell. S-DU or S-BS 104A obtains the TA value based on the RA preamble. DU 174 then sends a 556 DU-CU TA containing the TA value to CU172. Information transmission Message. CU 172 sends a CU-CU TA information transmission message 558, including the TA value, to S-BS 104A (e.g., the CU of S-BS 104A). In some implementations, DU 174 includes cell ID 1, RA preamble index, RA-RNTI, DU ID of S-DU of S-BS 104A, and / or BS ID of S-BS 104A in message 556. In some implementations, DU 174 does not include the BS ID in message 556. In some implementations, CU 172 includes cell ID 1, RA preamble index, RA-RNTI, DU ID of S-DU, and / or BS ID of S-BS 104A in message 558. In some implementations, CU 172 does not include the BS ID in message 558. The CU of S-BS 104A sends to the S-DU of S-BS 104A a message including the TA value, cell ID 1, RA preamble index, RA-RNTI, and / or the DU ID of the S-DU, and / or the BS ID of S-BS104A. CU-DU TA Information Transmission Message. In some implementations, the CU of S-BS 104A does not include the BS ID. CU-DU TA Information Transmission In the message.

[0164] In some implementations, CU 172 determines the address (e.g., IP address) of the S-BS 104A or its CU based on the BS ID of the S-BS 104A. In other implementations, CU 172 determines the address (e.g., IP address) of the S-BS 104A or its CU based on the DU ID of the S-DU of the S-BS 104A. Through these implementations, CU 172 sends data to the S-BS 104A or its CU according to the address. CU-CU TA Information Transmission information.

[0165] In response to, for example, determining a command for UE 102 to perform an LTM cell handover to a first cell based on measurement reports 524 and / or 554, S-DU or S-BS 104A sends an LTM cell handover command 526, including LTM ID 1 (e.g., a configuration identifier), to UE 102. In response to the LTM cell handover command, UE 102 may cease communication on the serving cell. In response to the LTM cell handover command, UE 102 accesses the first cell 532 and sends an RRC reconfiguration complete message 536 to DU 174. DU 174 then sends a DU-CU message 538, including the RRC reconfiguration complete message, to CU 172. Upon receiving the DU-CU message 538 or the RRC reconfiguration complete message, C-BS 106A communicates with UE 102 540 according to the first LTM candidate configuration and / or LTM reference configuration. In some implementations, UE 102 sends an RRC reconfiguration complete message (536) including LTM ID 1 to instruct UE 102 to apply the first LTM candidate configuration. Based on LTM ID 1, CU 172 identifies the first LTM candidate configuration and / or the LTM reference configuration. In other implementations, CU 172 is based on the configuration included in... Connection successful The first cell ID in message 534 identifies the first LTM candidate configuration and / or LTM reference configuration. In this implementation, CU 172 maintains or stores the association information between the first cell ID and the first LTM candidate configuration and / or between the first cell ID and the LTM reference configuration. When CU 172 receives 534... catch Successful entry When the message contains the first cell ID, CU 172 identifies the first LTM candidate configuration and / or LTM reference configuration based on the first cell ID and associated information.

[0166] In some implementations, UE 102 may perform an RA procedure in event 532 to access the first cell. The RA procedure may be a four-step RA procedure or a two-step RA procedure. The RA procedure may be a CBRA procedure or a CFRA procedure. In some implementations, S-BS 104A includes the first set of LTM CFRA configuration parameters in the LTM cell handover command to configure UE 102 to perform a CFRA procedure to access the first cell. UE 102 uses the first set of LTM CFRA configuration parameters to perform the CFRA procedure. In some implementations, DU 174 includes the first set of LTM CFRA configuration parameters in the first DU to CU message of procedure 590, as described for procedure 490. CU 172 then includes the first set of LTM CFRA configuration parameters in... Confirmation of transfer request In some implementations, DU 174 includes at least one additional group LTM CFRA configuration parameter in the first DU to CU message, as described for procedure 490. CU 172 then includes the additional group LTM CFRA configuration parameter in... Confirmation of transfer request In the message.

[0167] In some implementations, DU 174 configures the first group and / or the additional group for UL (i.e., NUL) or SUL, and indicates this configuration in the first DU to CU message, as for Figure 4 As described in C-DU 174B. When the first group and / or supplementary group are configured for either UL or SUL, CU 172 includes a single UL / SUL indicator. Please hand over Please confirm. In the message, the single UL / SUL indicator indicates that the first group and / or the supplementary group are configured for either UL or SUL. When the first group and / or the supplementary group are configured for UL, CU 172 includes the first group and / or the supplementary group... shift Submit a request for confirmation The first field in the message is / IE. When the first group and / or supplementary groups are configured for SUL, the CU172 will include the first group and / or supplementary groups. Confirmation of transfer request In the second field / IE of the message. In such cases, the first field / IE and the second field / IE are defined for UL and SUL, respectively.

[0168] In some implementations, DU 174 uses a first set of configurations for one of UL and SUL, and an additional set of configurations for the other of UL and SUL, and DU 174 indicates such configurations in the first DU to CU message, as referenced. Figure 4As described in C-DU 174B. In such cases, CU 172 sets the UL / SUL indicator in the first group to a value indicating either UL or SUL, and CU 172 sets the UL / SUL indicator in the supplementary group to a value indicating the other of UL and SUL. Alternatively, CU 172 includes the first group and the supplementary group separately. Confirmation of transfer request The message contains one of the first field / IE and the second field IE, and the other.

[0169] In some implementations, if the S-DU or S-BS 104A receives the TA value as described above, the S-DU or S-BS 104A may include the TA value in the LTM cell handover command. In some implementations, the S-DU or S-BS 104A may include the first TCI state ID in the LTM cell handover command. The first TCI state ID indicates the first one in the TCI state configuration. If the LTM cell handover command includes the TA value, UE 102 may skip performing the RA procedure in event 532 to access the first cell. Otherwise, UE 102 may perform the RA procedure in event 532 as described above to access the first cell.

[0170] In response to the confirmation command UE 102 to perform an LTM cell handover or to send the 526 LTM cell handover command, the S-DU of S-BS104A sends a DU-CU cell handover notification message to the CU of S-BS 104A to instruct UE 102 to perform or be performing an LTM cell handover to the first cell. In response to receiving... DU-CU cell handover notification Message: CU of S-BS 104A sends 527 to CU172 CU-CU cell handover notification The message instructs UE 102 to perform an LTM cell handover to the first cell. In response, CU 172 sends a 530 message to DU 174. CU-DU Cell Handover Notification The message instructs UE 102 to perform an LTM cell handover to the first cell. In some implementations, S-BS 104A includes the first TCI state ID. CU-CU cell handover notification In the message, CU 172 then includes the first TCI status ID. CU-DU Cell Handover NotificationIn the message, UE 102 and DU 174 identify the first TCI state configuration based on the first TCI state ID, and UE 102 and DU 174 apply the first TCI state configuration to communicate UL and / or DL ​​transmissions in events 532, 536, and / or 540. In other implementations, when using separate TCI states, the DL TCI state and the UL TCI state use different TCI state IDs. In such cases, the S-DU of S-BS104A will include the first TCI state ID for DL ​​and / or the second TCI state ID for UL in the first and second TCI state configurations, respectively. DU-CU cell handover notification In messages and / or LTM cell handover commands. In response to DU-CU small Zone switch notification The message states that the S-BS 104A CU will include the first TCI status ID and the second TCI status ID in the CU 172. CU- CU cell handover notification In the message. Then, CU 172 includes the first TCI status ID and the second TCI status ID in the message to DU 174. CU-DU Cell Handover Notification In the message, UE 102 identifies the first TCI state configuration and the second TCI state configuration based on the first TCI state ID and the second TCI state ID, respectively. UE 102 applies the first TCI state configuration and the second TCI state configuration to receive DL transmissions and transmit UL transmissions with DU 174 in events 532, 536, and / or 540, respectively. DU 174 identifies the first TCI state configuration and the second TCI state configuration based on the first TCI state ID and the second TCI state ID, respectively. DU 174 applies the first and / or second TCI state configurations to communicate DL transmissions and / or UL transmissions with UE 102 in events 532, 536, and / or 540, respectively.

[0171] In some implementations, the determination is made when UE 102 executes LTM cell handover, sends LTM cell handover command 526, or receives LTM cell handover command 527. DU-CU cell handover notification Following the message (e.g., in response to this), S-BS 104A (e.g., the CU of S-BS 104A) sends one or more 531s to CU 172. Early state transfer Each early state transmission message includes the DL COUNT value of the DRB or the DISCARD DL COUNT value of the data communicated between UE 102 and S-BS 104A via 502 data. In some implementations, upon receiving 534... Connection successfulFollowing the message, or after receiving the 538 DU to CU message or the RRC reconfiguration complete message, CU 172 sends a 539 LTM success message to S-BS 104A (e.g., the CU of S-BS 104A) to indicate that the LTM cell handover has been successfully completed. In some implementations, the LTM success message is... Successful handover In some implementations, CU 172 includes the first cell ID in the LTM success message. In other implementations, CU 172 does not send a BS-to-BS message to S-BS 104A (e.g., the CU of S-BS 104A) to indicate that the LTM cell handover has been successfully completed.

[0172] In some implementations, the process involves determining whether UE 102 is performing an LTM cell handover, sending the 526 LTM cell handover command, and receiving the 527 command. DU-CU cell handover notification Upon receiving a 539 LTM success message (e.g., in response to this), S-BS 104A (e.g., the CU of S-BS 104A) sends 541 to CU 172. SN status transfer The message includes the DL COUNT value and / or UL COUNT value of the DRB of the UE 102 and S-BS 104A communicating with each other via the 502 data.

[0173] In some implementations, upon receiving 534 Connection successful Messages received include 538 DU to CU message or RRC reconfiguration complete message, or 541 SN status transfer Following the message (e.g., in response to this), CU 172 sends 543 to S-BS 104A. UE context release Message. Response to UE context release The message indicates that S-BS 104A releases the UE context of UE 102.

[0174] In some implementations, the S-BS 104A (e.g., the CU of the S-BS 104A) may prepare additional cells (i.e., cells 2, ..., N) as LTM candidate cells for UE 102 before or after sending the LTM cell handover command, or during, before or after procedure 582, with CU 172, as described above. Cells 2, ..., N are identified by cell IDs 2, ..., N, respectively, and are operated by DU 174 and / or other DUs of the C-BS 106A. N is an integer and greater than 1. For example, the S-BS 104A and CU 172 perform additional CU-to-CU LTM preparation procedures 2, ..., N to prepare cells 2, ..., N, respectively. Each of the CU-to-CU LTM preparation procedures 2, ..., N is similar to procedure 582. In the CU-to-CU LTM preparation procedures 2, ..., N, the S-BS 104A receives LTM candidate configurations 2, ..., N, thereby configuring cells 2, ..., N for LTM, respectively. As described above, S-BS 104A or C-BS106A assigns LTM IDs 2, ..., N to identify LTM candidate configurations 2, ..., N, respectively. S-BS 104A can obtain CSI resource configurations 2, ..., N for cells 2, ..., N, as described for CSI resource configuration 1. S-BS 104A can obtain CSI report configurations 2, ..., N or cells 2, ..., N, as described for CSI report configuration 1. S-BS 104A can obtain RACH configurations 2, ..., N for cells 2, ..., N, as described for RACH configuration 1. S-BS 104A can obtain TCI status configurations 2, ..., N for cells 2, ..., N, as described for TCI status configuration 1. S-BS 104A can obtain LTM SSB configurations 2, ..., N for cells 2, ..., N, as described for LTM SSB configuration 1. S-BS 104A can obtain PCI 2, ..., N for cells 2, ..., N respectively, as described for PCI 1. In some implementations, S-BS 104A can perform LTM configuration delivery procedures 2, ..., N with UE 102 to send the following lists to UE 102 respectively: {LTM ID 2, LTM candidate configuration 2, CSI resource configuration 2 (if obtained), TCI state configuration 2 (if obtained), RACH configuration 2 (if obtained), LTM SSB configuration 2 (if obtained), PCI 2 (if obtained)}, ..., {LTM ID N, LTM candidate configuration N, CSI resource configuration N, TCI state configuration N (if obtained), RACH configuration N (if obtained), LTM SSB configuration N (if obtained), PCI N (if obtained)}.Each of the LTM configuration delivery procedures 2, ..., N is similar to procedure 394 and / or 494. In other implementations, S-BS 104A includes the list in the first RRC reconfiguration message.

[0175] In other implementations, S-BS 104A and CU 172 perform procedure 582 to prepare one or more of cells 1, ..., N as LTM candidate cells for UE 102. In such implementations, S-BS 104A includes cell ID 1 in the LTM... Transfer Request In message 505, ..., N, as described for cell ID 1. In some implementations, upon receiving... Transfer Request When a message is received, CU 172 determines or selects cells 1, ..., N as LTM candidate cells. M is a positive integer and M ≤ N. In other implementations, CU 172 inputs... Transfer Request The message requests the preparation of cells 1, ..., N for LTM. CU 172 and DU 174 perform LTM preparation procedures 2, ..., M to prepare cells 2, ..., M as LTM candidate cells for UE 102, respectively. LTM preparation procedures 2, ..., M are similar to procedure 590 performed by CU 172 and DU 174 to prepare cell 1. CU 172 obtains LTM candidate configurations 2, ..., M for cells 2, ..., M as the results of LTM preparation procedures 2, ..., M, similar to obtaining LTM candidate configuration 1. C-BS 106A can generate LTM candidate configurations 2, ..., M as a complete configuration, or generate incremental configurations based on the LTM reference configuration, as described for LTM candidate configuration 1. CU 172 includes LTM candidate configurations 2, ..., M in... Confirmation of transfer request In some implementations, CU 172 or S-BS 104A assigns LTM IDs 2, ..., M to identify LTM preparation processes 2, ..., M, as described for LTM ID 1. When CU 172 assigns LTM IDs 1, ..., M, CU 172 includes LTM IDs 1, ..., M along with LTM candidate configurations 1, ..., M in the handover request confirmation message, as described for LTM ID 1 and LTM candidate configuration 1.

[0176] In some implementations, CU 172 acquires the early synchronization information 2, ..., M of cells 2, ..., M respectively, as described for early synchronization information 1. CU 172 includes the early synchronization information 2, ..., M... Confirmation of transfer requestIn some implementations, CU 172 or S-BS 104A obtains the CSI resource configurations 2, ..., M of cells 2, ..., M respectively, as described for CSI resource configuration 1. When CU 172 obtains CSI resource configurations 2, ..., M, CU 172 includes CSI resource configurations 2, ..., M in... Confirmation of transfer request In the message.

[0177] In some implementations, CU 172 or S-BS 104A obtains the LTM SSB configurations 2, ..., M of cells 2, ..., M respectively, as described for LTM SSB configuration 1. When CU 172 obtains LTM SSB configurations 2, ..., M, CU 172 includes LTM SSB configurations 2, ..., M in... Confirmation of transfer request In some implementations, CU 172 or S-BS 104A obtains PCI 2, ..., M for cells 2, ..., M respectively, as described for PCI 1. When CU 172 obtains PCI 2, ..., M, CU 172 includes PCI 2, ..., M in... Confirmation of transfer request In the message.

[0178] In some implementations, CU 172 includes the following list. Confirmation of transfer request The message contains: {Cell ID1, LTM ID1 (if obtained or optional), LTM candidate configuration1, CSI resource configuration1 (if obtained or optional), TCI status configuration1 (if obtained or optional), early synchronization information1 (if obtained or optional), LTM SSB configuration1 (if obtained or optional), PCI 1 (if obtained or optional)}, ..., {Cell ID M, LTM ID M (if obtained or optional), LTM candidate configuration M, CSI resource configuration M (if obtained or optional), TCI status configuration M (if obtained or optional), early synchronization information M (if obtained or optional), LTM SSB configuration M (if obtained or optional), PCI M (if obtained or optional)}.

[0179] In some implementations, CU 172 acquires PDCCH command information 2, ..., M from cells 2, ..., M respectively, as described with reference to PDCCH command information 1. In one implementation, CU 172 includes PDCCH command information 2, ..., M in... Confirmation of transfer request In another implementation, CU 172 includes PDCCH command information 2, ..., M in the early synchronization information 2, ..., M respectively. S-BS 104A can retrieve the information from the early synchronization information 2, ..., M or from... Transfer Request confirm The message contains RACH configuration 2, TCI status configuration 2, and / or PDCCH command information 2, ..., RACH configuration M, TCI status configuration M, and / or PDCCH command information M.

[0180] In some implementations, S-BS 104A may perform LTM configuration delivery procedures 2, ..., M with UE 102 to send to UE 102 lists including the following: {LTM ID 2, LTM candidate configuration 2, CSI resource configuration 2 (if obtained), TCI state configuration 2 (if obtained), RACH configuration 2 (if obtained), LTM SSB configuration 2 (if obtained), PCI 2 (if obtained)}, ..., {LTM ID M, LTM candidate configuration M, CSI resource configuration M, TCI state configuration M (if obtained), RACH configuration M (if obtained), LTM SSB configuration M (if obtained), PCI M (if obtained)}. Each of LTM configuration delivery procedures 2, ..., M is similar to procedures 394 and / or 494. In other implementations, S-BS 104A includes the list in the first RRC reconfiguration message.

[0181] In some implementations, S-BS 104A can include the measurement results 1, ..., N of cells 1, ..., N separately. Transfer Request In the message, S-BS 104A receives measurement results from UE 102. C-BS 106A can select or determine cell 1, ..., M based on measurement results 1, ..., N. In other implementations, C-BS 106A can select or determine cell 1, ..., M based on one or more other factors (e.g., the capacity or load of cell 1, ..., N and / or the maximum number of LTM candidate cells). In one implementation, the maximum number is included... Transfer Request The message states that in another implementation, the maximum quantity is the predetermined quantity.

[0182] Figures 6A to 6D This is a message sequence diagram for an LTM scenario between CUs, where the UE is under the DC. First, refer to... Figure 6A In scenario 600A, base station 104B operates as the MN, base station 106A operates as a candidate SN (C-SN), and base station 104A operates as a serving or source SN (S-SN). C-SN 106A includes CU 172 and DU 174. MN 104B may include CU and DU (…). Figure 6A (not shown in the image), similar to Figure 3 BS 104A in S-SN 104A. S-SN 104A may include CU and DU ( Figure 6A(Not shown in the image), similar to C-SN106A. Scene 600A is similar to Scene 500, the difference being that Scene 600A is a DC scene while Scene 500 is not a DC scene.

[0183] Initially, UE 102 communicates with MN 104B and S-SN 104A under DC 602. In some implementations, UE 102 is configured to communicate with the DU of S-SN 104A on cell 124A using a serving DU, and to communicate with the CU of S-SN 104A via the DU of S-SN 104A using a serving CU, similar to event 302. In some implementations, UE 102 may communicate with MN 104B and / or S-SN 104A under DC via radio bearers 602 UL PDU and / or DL ​​PDU, which may include SRB and / or DRB. MN 104B and / or S-SN 104A may configure radio bearers for UE 102. UE 102 communicates 602 UL PDUs and / or DL ​​PDUs to S-SN 104A on the SCG (i.e., SCG radio resources) configured for communication with UE 102 under DC. UE 102 also communicates UL PDUs and / or DL ​​PDUs to MN 104B on the MCG (i.e., MCG radio resources) under DC according to the MN configuration (i.e., MCG configuration). In some implementations, the serving DU configuration is an SN configuration (i.e., SCG configuration). In the MN configuration, MN 104B configures an MCG that includes at least one serving cell (e.g., cell 124B and / or other cells) operated by MN 104B. In the serving DU configuration, S-SN 104A configures an SCG that includes at least one serving cell (e.g., cell 124A and / or other cells) operated by S-SN 104A. In some implementations, the MN configuration includes multiple configuration parameters, and UE 102 receives these configuration parameters from MN 104B in one or more RRC messages. (See reference...) Figure 3 As described, the service DU configuration includes multiple configuration parameters. In some implementations, UE 102 receives these configuration parameters from S-SN 104A, for example, via MN104B and / or on an SRB (e.g., SRB3) configured on MN 104B or S-SN 104A to exchange RRC messages between UE 102 and S-SN 104A.

[0184] When communicating with UE 102 under the DC along with MN 104B and S-SN 104A, S-SN 104A can perform the CU-in-LTM configuration procedure 696 with UE 102, similar to procedures 396 and / or 496. When communicating with UE 102 under the DC along with MN 104B and S-SN 104A, S-SN 104A can perform the CU-in-LTM procedure 680 with UE 102, similar to procedures 380 and / or 480. In procedure 696 or 680, the CU of S-SN 104A can send one or more RRC reconfiguration messages to UE 102 via SRB3, each RRC reconfiguration message including one or more LTM candidate configurations, similar to procedures 394 or 494. Alternatively, the CU of S-SN 104A may send one or more RRC reconfiguration messages to UE 102 via MN 104B, each RRC reconfiguration message including one or more LTM candidate configurations. In response to each of the RRC reconfiguration messages, UE 102 sends an RRC reconfiguration complete message to S-SN 104A via MN 104B.

[0185] When communicating with MN 104B and S-SN 104A under DC, UE 102 can, for example, send at least one measurement report (604A) to S-SN 104A directly via SRB3, similar to events 304 / 306, 404 / 406, and 504. Alternatively, UE 102 can send the measurement report to MN 104B. MN 104B generates at least one SN message including the measurement report and sends the SN message to CU 172. In one implementation, the SN message includes... RRC transmission Messages and / or SN Modification Request The S-SN 104A (e.g., the CU of the S-SN 104A) generates a measurement configuration that enables the UE 102 to send measurement reports, and sends the measurement reports to the UE 102 directly (e.g., via the S-DU of the S-SN 104A) or via the MN 104B.

[0186] After receiving one or more measurement reports from UE 102 (e.g., in response to this), S-SN 104A (e.g., the CU of S-SN 104A) determines to prepare a first cell (e.g., cell 126A) as an LTM candidate cell for UE 102. In response to this determination, S-SN 104A generates an SN request message (first SN request message) including a first cell ID (e.g., cell ID 1) of the first cell (e.g., cell 1) and / or an indication of a target SN ID for C-SN 106A. In some implementations, the SN request message includes an LTM indicator indicating that the SN request message pertains to the LTM of the first cell ID. S-SN 104A sends a 603 SN request message to MN 104B. Upon receiving the SN request message (e.g., in response to this), MN 104B sends a 605 SN request message (first SN request message) including the first cell ID to CU 172 to request the preparation of the first cell as an LTM candidate cell for UE 102. In response to the SN request message, CU 172 and DU 174 perform LTM preparation procedure 690 to prepare a first cell as an LTM candidate cell for UE 102, similar to procedures 390, 490, or 590. In procedure 690, CU 172 sends a first CU-DU message including the first cell ID to DU 174 to request preparation of the first cell, similar to event 308. In response, CU 172 can receive a first DU-CU message including LTM DU configuration 1 from DU 174, similar to event 310. CU 172 generates a first LTM candidate configuration (LTM candidate configuration 1). In response to the SN request message, CU 172 sends an SN request confirmation message 607 including the first LTM candidate configuration (first SN request confirmation message) to MN 104B. In some implementations, CU 172 includes the first cell ID in the SN request confirmation message to indicate that the first LTM candidate configuration is provided for or associated with the first cell (ID). MN 104B sends a 609A SN confirmation message (e.g., a first SN confirmation message) to S-SN 104A, which includes the first LTM candidate configuration. In some implementations, MN 104B includes the first cell ID in the SN confirmation message to indicate that the first LTM candidate configuration is provided for or associated with the first cell (ID).

[0187] Events 603, 605, 690, 607, and 609A are in Figure 6A The process is collectively referred to as the SN-initiated SN-to-SN LTM preparation process 698A.

[0188] In some implementations, the SN requires the message and the SN acknowledges the message. These are the SN change requirements. Messages and SN change confirmed recognize Message. In other implementations, the SN requirement message and the SN acknowledgment message are respectively SN Modification Request message and SN modification confirmed recognize In some implementations, the SN request message and the SN request confirmation message are the SN add request message and the SN add request confirmation message, respectively. In other implementations, the SN request message and the SN request confirmation message are the SN modify request message and the SN modify request confirmation message, respectively.

[0189] In some implementations, the SN request message includes the DU ID of the S-DU of S-SN 104A. In this case, MN104B may include the DU ID in the SN request message, and CU 172 may include the DU ID in the first CU to DU message. In other implementations, the SN request message includes the first BS ID of S-SN 104A. In some implementations, MN104B may include the first BS ID in the SN request message. When the first BS ID is received, CU 172 may include the first BS ID in the first CU to DU message. In some implementations, MN 104B may include its second BS ID in the SN request message. When the second BS ID is received, CU 172 may include the second BS ID in the first CU to DU message. In some implementations, the first BS ID and the second BS ID are gNB IDs.

[0190] In some implementations, CU 172 requests the LTM reference DU configuration in procedure 690, such as for... Figure 3 , Figure 4 ,as well as Figure 5 As described, in other implementations, CU 172 does not request the LTM reference DU configuration. In some implementations, DU 174 sends the LTM reference DU configuration to CU 172 in process 690, such as for... Figure 3 , Figure 4 ,as well as Figure 5 As described, in other implementations, DU 174 does not send the LTM reference DU configuration to CU 172. In some implementations, S-SN 104A (e.g., the CU of S-SN 104A) can obtain the LTM reference configuration, such as for... Figure 3 and Figure 4 As described. In other implementations, S-SN 104A can be from MN 106B during the LTM preparation process between another SN ( Figure 6A(Not shown) MN 104A receives the LTM reference configuration as described above and below. If S-SN 104A acquires the LTM reference configuration, S-SN 104A may include the LTM reference configuration (the LTM reference configuration generated by S-SN) in the SN request message. Then, MN 104B includes the LTM reference configuration in the SN request message. Alternatively, S-SN 104A determines to request or cause C-SN 106A to provide a complete LTM candidate configuration, such that S-SN 104A does not send the LTM reference configuration to C-SN 106A. If S-SN 104A does not acquire the LTM reference configuration, S-SN 104A does not include the LTM reference configuration in the SN request message. If the SN request message includes the LTM reference configuration, MN 104B includes the LTM reference configuration in the SN request message. Otherwise, if the SN request message does not include the LTM reference configuration, MN 104B may not include the LTM reference configuration in the SN request message.

[0191] If the SN request message includes the LTM reference configuration as described above, then CU 172 may include the LTM reference configuration in the first CU-DU message. Alternatively, CU 172 may extract the LTM reference DU configuration from the LTM reference configuration and include the LTM reference DU configuration in the first CU-DU message. Otherwise, if the SN request message does not include the LTM reference configuration, then in some implementations, CU 172 receives the LTM reference DU configuration from DU 174, as described above. Figure 3 As described, in other implementations, CU 172 does not receive the LTM reference DU configuration from DU 174. If CU 172 receives the LTM reference DU configuration (e.g., in the first DU to CU message), then CU 172 generates an LTM reference configuration that includes the LTM reference DU configuration (the LTM reference configuration generated by the C-SN). CU 172 may include an LTM reference CU configuration (the LTM reference CU configuration generated by the candidate CU (C-CU)). Otherwise, if CU 172 does not receive the LTM reference DU configuration as described... Figure 3 If an LTM reference DU configuration is received from DU 174 as described, then CU 172 does not generate an LTM reference configuration. Instead, CU 172 generates an LTM reference configuration (C-SN generated LTM reference configuration) that only includes the LTM reference CU configuration generated by C-CU. When CU 172 generates an LTM reference configuration (C-SN generated LTM reference configuration), CU 172 includes the C-SN generated LTM reference configuration in the SN request confirmation message.

[0192] In some implementations, if LTM DU configuration 1 is a complete configuration, CU 172 generates LTM candidate configuration 1 as a complete configuration. CU 172 may include a complete configuration indication (e.g., a BS-to-BS interface protocol field / IE) in the SN request confirmation message to indicate that LTM candidate configuration 1 is a complete configuration. In some implementations, the BS-to-BS interface protocol is the Xn application protocol defined in 3GPP specification 38.423. In some implementations, the complete configuration indication is a dedicated field / IE (e.g., LTM-specific) to reduce or eliminate the impact on non-LTM configurations. In other implementations, the complete configuration indication is an existing field / IE defined in 3GPP specification 38.423. Otherwise, if LTM DU configuration 1 is an incremental configuration, CU 172 generates LTM candidate configuration 1 as an incremental configuration. CU 172 may exclude the complete configuration indication from the SN request confirmation message to indicate that LTM candidate configuration 1 is an incremental configuration. Alternatively, CU 172 may include an incremental configuration indication (e.g., a BS-to-BS interface protocol field / IE) in the SN request confirmation message to indicate that LTM candidate configuration 1 is an incremental configuration. In some implementations, the BS-to-BS interface protocol is the Xn application protocol defined in 3GPP specification 38.423. In some implementations, the incremental configuration indication is a dedicated field / IE (e.g., LTM-specific) to reduce or eliminate the impact on non-LTM configurations. In other implementations, the incremental configuration indication is an existing field / IE defined in 3GPP specification 38.423. In some implementations, the BS-to-BS interface protocol field / IE may have one of at least two possible values ​​(i.e., a first value and a second value). The first value of the BS-to-BS interface protocol field / IE may indicate a full configuration, and the second value of the BS-to-BS interface protocol field / IE may indicate an incremental configuration.

[0193] In some implementations, the S-SN 104A is pre-configured with CSI resource configuration (e.g., CSI resource configuration 1 or LTM CSI resource configuration 1) and / or LTM SSB configuration (LTM SSB configuration 1) for the first cell. In yet another implementation, the CU 172 receives the CSI resource configuration and / or LTM SSB configuration from the OAM (Operation, Administration, and Maintenance) node. In yet another implementation, the S-SN 104A receives the CSI resource configuration and / or LTM SSB configuration from the CU 172. For example, the CU 172 includes the CSI resource configuration and / or LTM SSB configuration in the SN request confirmation message. In this case, the MN 104B may include the CSI resource configuration and / or LTM SSB configuration in the SN confirmation message. In some implementations, the CU 172 includes the PCI of the first cell in the SN request confirmation message. In this case, the MN 104B may include the PCI of the first cell in the SN confirmation message. To prepare the first cell as a candidate LTM cell for UE 102, the CU of S-SN 104A uses the S-DU of S-SN 104A to perform the LTM CSI report configuration and / or LTM ID configuration procedures. Figure 6A (Not shown in the diagram), similar to procedures 392 or 492. During the LTM CSI report configuration and / or LTM ID configuration process, the CU of S-SN 104A sends the CSI resource configuration and / or LTM SSB configuration to the S-DU of S-SN 104A. In response, the CU of S-SN 104A receives one or more CSI report configurations of UE 102 from the S-DU of S-SN 104A. In some implementations, S-SN 104A receives a second service DU configuration including the CSI report configuration.

[0194] In some implementations, CU 172 receives early synchronization information and / or PDCCH command information of the first cell from DU 174, as shown in the reference. Figure 5 As described. In some implementations, early synchronization information includes RACH configuration (e.g., RACH configuration 1) and / or at least one TCI state configuration (e.g., TCI state configuration 1). CU 172 includes early synchronization information and / or PDCCH command information in the SN request acknowledgment message. MN 104B includes early synchronization information and / or PDCCH command information in the SN acknowledgment message.

[0195] In some implementations, CU 172 assigns an LTM ID (e.g., LTMID 1) to identify the first LTM candidate configuration and includes the LTM ID and / or its associated (or mapped) cell ID in the SN request confirmation message. MN 104B includes the LTM ID and / or its associated (or mapped) cell ID in the SN confirmation message. In other implementations, S-SN 104A assigns an LTM ID (e.g., LTM ID 1) to identify the first LTM candidate configuration. In yet another implementation, MN 104B assigns an LTM ID (e.g., LTM ID 1) to identify the first LTM candidate configuration. In such cases, MN 104B may include the LTM ID in the SN confirmation message. After receiving or assigning the LTM ID, the CU of S-SN 104A sends the LTM ID and the first cell ID to the S-DU during the LTM ID configuration process, similar to procedures 390, 392, or 492.

[0196] Upon receiving the SN confirmation message (e.g., in response to this), S-SN 104A (e.g., the CU of S-SN 104A) performs LTM configuration delivery procedure 694 with UE 102 to send the LTM ID and LTM candidate configuration to UE 102. In some implementations, S-SN 104A sends {LTM ID, LTM candidate configuration} as a tuple in the first RRC reconfiguration message in procedure 694. Depending on the implementation, S-SN 104A may include the LTM reference configuration, CSI report configuration, CSI resource configuration, RACH configuration, TCI state configuration, LTM SSB configuration, and / or the PCI from the first cell to UE 102 in the first RRC reconfiguration message and / or other RRC reconfiguration messages sent to UE 102, such as the reference configuration. Figure 3 and Figure 4As described, S-SN 104A includes the LTMID in the first RRC reconfiguration or other RRC reconfiguration messages to indicate that the CSI resource configuration, RACH configuration, TCI state configuration, LTM SSB configuration, and / or the PCI of the first cell are associated with the first cell. For example, S-SN 104A includes the CSI resource configuration, RACH configuration, TCI state configuration, LTM SSB configuration, and / or the PCI of cell 1 in a tuple. In another example, S-SN 104A includes {LTM ID 1, CSI resource configuration, RACH configuration, TCI state configuration, LTM SSB configuration, and / or the PCI of cell 1} as a tuple in other RRC reconfiguration messages. In response to each of the other RRC reconfiguration messages, UE 102 sends an RRC reconfiguration complete message to CU 172 via S-DU 174A.

[0197] In some implementations, if the SN request message includes a full configuration indication indicating that LTM candidate configuration 1 is a full configuration, then S-SN 104A includes the full configuration indication (e.g., the RRC field / IE) in the first RRC reconfiguration message to indicate that LTM candidate configuration 1 is a full configuration. Otherwise, if the SN request message does not include a full configuration indication, or includes an incremental configuration indication to indicate that LTM candidate configuration 1 is an incremental configuration, then S-SN 104A excludes or does not include the full configuration indication (e.g., the RRC field / IE) in the first RRC reconfiguration message to indicate that LTM candidate configuration 1 is an incremental configuration.

[0198] If the SN confirmation message includes PDCCH command information (PDCCH command information 1), then S-SN 104A can send a 650A PDCCH command to UE 102 based on the PDCCH command information. If S-SN 104A is a distributed base station, then the CU of S-SN 104A can send the PDCCH command information to the S-DU of S-SN 104A, and the S-DU can send a 650A PDCCH command to UE 102. For example, S-SN 104A or its S-DU sends a 650A PDCCH command to UE 102, including the PDCCH command information. In some implementations, S-SN 104A or its S-DU can determine whether to send the PDCCH command based on (e.g., in response to) measurement report 624A. In some implementations, the S-SN 104A or S-DU can determine the SSB index to be included in the PDCCH command based on the L1 Measurement Report 624A and / or CSI resource configuration, CSI report configuration, and / or LTM SSB configuration. In some implementations, the S-DU or S-SN 104A includes LTM ID 1 in the PDCCH command to indicate the first cell. UE102 sends a 652 RA preamble to DU 174 on the first cell using RACH configuration and / or PDCCH command information. The S-DU or S-SN 104A obtains the TA value based on the RA preamble. DU 174 sends a 656 DU-CU TA command, including the TA value, to CU 172. Information transmission Message. CU 172 sends a CU-CU TA information transmission message 657, including the TA value, to MN 104B (e.g., the CU of MN 104B). MN 104B sends a CU-CU TA information transmission message 658, including the TA value, to S-SN 104A. In some implementations, DU 174 includes cell ID 1, RA preamble index, RA-RNTI, and / or the DU ID of the S-DU of S-SN 104A in message 656. DU 174 may additionally include a first BS ID and / or a second BS ID in message 656. In some implementations, CU 172 includes cell ID 1, RA preamble index, RA-RNTI, and / or the DU ID of the S-DU in message 657. In some implementations, CU 172 may additionally include a first BS ID and / or a second BS ID in message 657. Then, the MN104B includes the S-DU's cell ID 1, RA preamble index, RA-RNTI, and / or DU ID in message 658. In some implementations, the MN104B may additionally include the first BS ID and / or the second BS ID in message 658.

[0199] In some implementations, CU 172 determines the address (e.g., IP address) of MN 104B or its CU based on a second BS ID. Therefore, CU 172 sends message 657 to MN 104B according to the address. In some implementations, MN 104B determines the address (e.g., IP address) of S-SN 104A or its CU based on a first BS ID. In other implementations, MN 104B determines the address (e.g., IP address) of S-SN 104A or its CU based on the DU ID of S-DU of S-SN 104A. Through these implementations, MN 104B transmits message 658 (CU-CU TA information transmission message) to the CU of S-SN 104A or its CU based on the address.

[0200] In response to, for example, a command to UE 102 to perform an LTM cell handover to a first cell based on L1 measurement reports 624A and / or 654A, S-DU or S-SN 104A sends an LTM cell handover command 626A, including LTM ID 1, to UE 102. In response to the LTM cell handover command, UE 102 may cease communication on the serving cell. In response to the LTM cell handover command, UE 102 accesses the first cell 632. When UE 102 is detected in event 632, DU 174 sends an access success message 634 to CU 172. UE 102 sends an RRC reconfiguration complete message 636A to DU 174 during or after access 632. DU 174 then sends a DU-CU message 638, including the RRC reconfiguration complete message, to CU 172. In some alternative implementations, UE 102 sends the RRC reconfiguration complete message to C-SN 106A via MN 104B instead of via DU 174.

[0201] In some implementations, UE 102 may perform an RA procedure in event 632 to access the first cell. The RA procedure may be a four-step RA procedure or a two-step RA procedure. The RA procedure may be a CBRA procedure or a CFRA procedure. In some implementations, S-SN 104A includes a first set of LTM CFRA configuration parameters in the LTM cell handover command to configure UE 102 to perform a CFRA procedure to access the first cell. UE 102 uses the first set of LTM CFRA configuration parameters to perform the CFRA procedure. In some implementations, DU 174 includes the first set of LTM CFRA configuration parameters in the first DU to CU message of procedure 690, as described for procedure 490. CU 172 then includes the first set of LTM CFRA configuration parameters in the SN request confirmation message. In some implementations, DU 174 includes at least one additional set of LTM CFRA configuration parameters in the first DU to CU message, as described for procedure 490. CU 172 then includes the additional group LTM CFRA configuration parameters in the SN request confirmation message.

[0202] In some implementations, DU 174 configures the first group and / or the additional group for UL (i.e., NUL) or SUL, and indicates this configuration in the first DU to CU message, as for Figure 4 As described in C-DU 174B. When the first group and / or the supplementary group are configured for either UL or SUL, CU 172 includes a single UL / SUL indicator in the SN request confirmation message, indicating that the first group and / or the supplementary group are configured for either UL or SUL. When the first group and / or the supplementary group are configured for UL, CU 172 includes the first group and / or the supplementary group in the first field / IE of the SN request confirmation message. When the first group and / or the supplementary group are configured for SUL, CU 172 includes the first group and / or the supplementary group in the second field / IE of the SN request confirmation message. In such cases, the first field / IE and the second field / IE are defined for UL and SUL, respectively.

[0203] In some implementations, DU 174 uses the first set of configurations for one of UL and SUL, and the additional set of configurations for the other of UL and SUL, and indicates such configurations in the first DU to CU message, as referenced. Figure 4As described in C-DU174B. In such cases, CU 172 sets the UL / SUL indicator in the first group to a value indicating either UL or SUL, and sets the UL / SUL indicator in the supplementary group to a value indicating the other of UL and SUL. Alternatively, CU 172 includes the first group and the supplementary group in one and the other of the first field / IE and the second field IE in the SN request confirmation message, respectively.

[0204] Upon receiving a 634 Access Success Message, a 638 DU to CU Message, or a 636A RRC Reconfiguration Complete Message, C-SN 106A communicates 640 with MN 104B and C-SN 106A under DC according to a first LTM candidate configuration and / or LTM reference configuration. In some implementations, UE 102 includes LTM ID 1 in the RRC Reconfiguration Complete Message 636A to instruct UE 102 to apply the first LTM candidate configuration. Based on LTM ID 1, CU 172 identifies the first LTM candidate configuration and / or LTM reference configuration. In other implementations, CU 172 identifies the first LTM candidate configuration and / or LTM reference configuration based on the LTM ID 1. Connection successful The first cell ID in message 634 is used to identify the first LTM candidate configuration and / or LTM reference configuration. In this implementation, CU 172 maintains or stores the association information between the first cell ID and the first LTM candidate configuration and / or LTM reference configuration. When CU 172 receives... Access success When the message contains the first cell ID, CU 172 identifies the first LTM candidate configuration and / or LTM reference configuration based on the first cell ID and associated information.

[0205] In some implementations, if the S-DU or S-SN 104A receives the TA value as described above, the S-DU or S-SN 104A may include the TA value in the LTM cell handover command. In some implementations, the S-DU or S-SN 104A may include the first TCI state ID in the LTM cell handover command. The first TCI state ID indicates the first one in the TCI state configuration.

[0206] In response to the determination command UE 102 to perform LTM cell handover or send the 626A LTM ​​cell handover command, the S-DU of S-SN 104A sends a DU-CU cell handover notification message to the CU of S-SN 104A to instruct UE 102 to perform LTM cell handover to the first cell. In response to receiving DU-CU cell handover notificationIn this message, the CU of S-SN 104A sends a 627A CU-CU cell handover notification message to MN 104B to instruct UE 102 to perform or be performing an LTM cell handover to the first cell. In response, MN 104B sends a 629 CU-CU cell handover notification message to CU 172 to instruct UE 102 to perform or be performing an LTM cell handover to the first cell. In response, CU 172 sends a 630 CU-DU cell handover notification message to DU 174 to instruct UE 102 to perform or be performing an LTM cell handover to the first cell. In some implementations, S-SN 104A includes the first TCI state ID. CU-CU cell handover notification In message 627A. In this case, MN 104B includes the first TCI state ID. CU-CU cell handover notification In message 629, CU 172 then includes the first TCI status ID. CU-DU Cell Handover Notification In the message, UE 102 and DU 174 identify the first TCI state configuration based on the first TCI state ID and apply the first TCI state configuration to communicate UL and / or DL ​​transmissions in events 632, 636A, and / or 640. In other implementations, where separate TCI states are used, the DL TCI state and the UL TCI state use different TCI state IDs. In such cases, the S-DU of S-SN 104A will include the first TCI state ID for DL ​​and the second TCI state ID for UL in the TCI state configurations, respectively. DU-CU cell handover notification In messages and / or LTM cell handover commands. In response to DU-CU cell handover notification The message states that the CU of S-SN 104A will then include the first TCI status ID and the second TCI status ID in the MN 104B. CU-CU cell handover notification The message states that MN 104B includes the first TCI status ID and the second TCI status ID in the data sent to CU 172. CU-CU cell handover notification In the message. Then, CU 172 includes the first TCI status ID and the second TCI status ID in the message to DU 174. CU-DU Cell Handover NotificationIn the message, UE 102 identifies the first TCI state configuration and the second TCI state configuration based on the first TCI state ID and / or the second TCI state ID, respectively. UE 102 applies the first TCI state configuration and the second TCI state configuration to communicate DL transmission and UL transmission with DU 174 in events 632, 636A, and / or 640, respectively. DU 174 identifies the first TCI state configuration and the second TCI state configuration based on the first TCI state ID and the second TCI state ID, respectively. DU 174 applies the first and / or second TCI state configurations to communicate DL transmission and / or UL transmission with UE 102 in events 632, 636A, and / or 640, respectively.

[0207] In some implementations, after determining that UE 102 should perform an LTM cell handover or send an LTM cell handover command (e.g., in response to this), S-SN 104A sends one or more early status transmission messages (631) to MN 104B. Each early status transmission message includes the DLCOUNT value or DISCARD DL COUNT value of the DRB of the data (602) communicated between UE 102 and S-SN 104A. MN 104B sends one or more early status transmission messages to CU 172, each early status transmission message including the DL COUNT value or DISCARD DL COUNT value of the DRB of the data (602) communicated between UE 102 and S-SN 104A.

[0208] In some implementations, upon receiving 634 Connection successful After receiving either a 638 DU to CU message or an RRC reconfiguration complete message, CU 172 sends a 639 LTM success message to MN 104B (e.g., the CU of MN 104B) to indicate that the LTM cell handover was successfully completed. In some implementations, the LTM success message is... SN Modification Requirements The message is either a BS-to-BS access success message. In some implementations, CU 172 includes the first cell ID in the LTM success message. In other implementations, CU 172 does not send a BS-to-BS message to MN 104B (e.g., the CU of MN 104B) to indicate successful LTM cell handover. In some implementations, after receiving the LTM success message or receiving the RRC reconfiguration completion message from UE 102 (e.g., in response to this), MN 104B may send an SN message to S-SN 104A (e.g., ...). Figure 6C(As shown in event 645). The SN message can indicate that the LTM cell handover has been successfully completed, instruct S-SN 104A to suspend communication with UE 102, or instruct S-SN 104A to release the UE context of UE 102 and the resources configured for UE 102. MN 104B can include the first cell ID in the SN message. In some implementations, the SN message is... SN Modification Request information, SN release request Messages, SN access success messages, etc.

[0209] In some implementations, after determining that UE 102 performs an LTM cell handover, sends a 626A LTM ​​cell handover command, receives a DU-CU cell handover notification message from the S-DU, or receives an SN message handover (e.g., in response to this), S-SN 104A (e.g., the CU of S-SN 104A) sends a 641 to MN 104B. SN status transfer The message includes the DL COUNT and / or UL COUNT values ​​of the DRB for the 602 data communicated between UE102 and S-SN 104A. Upon receiving... SN status transfer Following message 641 (e.g., in response to this). MN 104B Send a 625 SN status transmission message to CU 172, including the DL COUNT value and / or UL COUNT value.

[0210] In some implementations, as described above, S-SN 104A (e.g., the CU of S-SN 104A) may prepare additional cells (i.e., cells 2, ..., N) as LTM candidate cells for UE 102 and MN 104B and one or more C-SNs (including C-SN 106A) before or after sending the LTM cell handover command, or during, before or after procedure 698A. N is an integer and greater than 1. Cells 2, ..., N can be operated by the C-SNs. For example, S-SN 104A uses MN 104B to perform additional inter-SN LTM preparation procedures 2, ..., N to prepare cells 2, ..., N respectively. Each of the one or more inter-SN LTM preparation procedures 2, ..., N is similar to procedure 698A. In the inter-SN LTM preparation procedures 2, ..., N, S-SN 104A receives LTM candidate configurations 2, ..., N, thereby configuring cells 2, ..., N for LTM respectively. As described above, MN 104B, S-SN 104A, or C-SN are assigned LTM IDs 2, ..., N to identify LTM candidate configurations 2, ..., N, respectively. S-SN 104A can obtain CSI resource configurations 2, ..., N for cells 2, ..., N, as described for CSI resource configuration 1. S-SN 104A can obtain CSI report configurations 2, ..., N or cells 2, ..., N, as described for CSI report configuration 1. S-SN 104A can obtain RACH configurations 2, ..., N for cells 2, ..., N, as described for RACH configuration 1. S-SN 104A can obtain TCI status configurations 2, ..., N for cells 2, ..., N, as described for TCI status configuration 1. S-SN 104A can obtain LTM SSB configurations 2, ..., N for cells 2, ..., N, as described for LTM SSB configuration 1. In some implementations, S-SN 104A can perform LTM configuration delivery procedures 2, ..., N with UE 102 to send {LTM ID 2, LTM candidate configuration 2, CSI resource configuration 2 (if obtained), TCI state configuration 2 (if obtained), RACH configuration 2 (if obtained), LTM SSB configuration 2 (if obtained)}, ..., {LTM ID N, LTM candidate configuration N, CSI resource configuration N, TCI state configuration N (if obtained), RACH configuration N (if obtained), LTM SSB configuration N (if obtained)} to UE 102 respectively. Each of LTM configuration delivery procedures 2, ..., N is similar to procedures 394, 494, and / or 594. In other implementations, S-SN 104A includes the tuples in the first RRC reconfiguration message.

[0211] In some implementations, the SN request message and SN confirmation message in each of the inter-SN LTM preparation processes 2, ..., N are respectively the SN modification request message and the SN modification confirmation message. In other implementations, the SN request message and SN confirmation message in each of the inter-SN LTM preparation processes 2, ..., N are respectively the SN change request message and the SN change confirmation message. In some implementations, the SN request message and SN request confirmation message in each of the inter-SN LTM preparation processes 2, ..., N are respectively the SN add request message and the SN add request confirmation message. In other implementations, the SN request message and SN request confirmation message in each of the inter-SN LTM preparation processes 2, ..., N are respectively the SN modification request message and the SN modification request confirmation message. In some implementations, the information provided in the SN confirmation message (e.g., LTM candidate configuration, LTM reference configuration, first cell ID, or LTM ID) is alternatively provided in the SN modification request message from MN 104B to S-SN 104A (i.e., similar to event 609B, which will be described with reference to scenario 600B).

[0212] In other implementations, S-SN 104A and CU 172 perform procedure 698A to prepare cell 1 and cell 2, ..., N (one or more of them) as LTM candidate cells for UE 102. Cell 2, ..., N are identified by cell IDs 2, ..., N respectively, and are operated by DU 174 and / or other DU operations of C-SN 106A. In such implementations, S-SN 104A includes cell IDs 2, ..., N in the SN request message 603 for LTM, and MN 104B includes cell IDs 2, ..., N in the SN request message as described earlier for cell ID 1. In some implementations, upon receiving the SN request message, CU 172 determines or selects cell 1, ..., M from cells 1, ..., N as LTM candidate cells. M is a positive integer and M≤N. In other implementations, CU 172 prepares cells 1, ..., N for LTM as requested in the SN request message. CU 172 and DU 174 execute LTM preparation procedures 2, ..., M to prepare cells 2, ..., M as LTM candidate cells for UE 102, respectively. LTM preparation procedures 2, ..., M are similar to the procedure 690 executed by CU 172 and DU 174 to prepare cell 1. CU 172 obtains LTM candidate configurations 2, ..., M for cells 2, ..., M as the results of LTM preparation procedures 2, ..., M, similar to obtaining LTM candidate configuration 1. C-SN 106A can generate LTM candidate configurations 2, ..., M as a complete configuration, or generate incremental configurations based on the LTM reference configuration, as described for LTM candidate configuration 1. CU 172 includes LTM candidate configurations 2, ..., M in the SN request confirmation message. In some implementations, CU 172, MN 104B, or S-SN 104A assigns LTM IDs 2, ..., M to identify LTM preparation process 2, ..., M respectively, as described for LTM ID 1 and LTM candidate configuration 1. When CU 172 assigns LTM IDs 1, ..., M, CU 172 includes LTM IDs 1, ..., M and LTM candidate configurations 1, ..., M in the SN request confirmation message respectively, as described for LTM ID 1 and LTM candidate configuration 1.

[0213] In some implementations, CU 172 acquires the early synchronization information 2, ..., M of cells 2, ..., M respectively, as described for early synchronization information 1. CU 172 includes the early synchronization information 2, ..., M in the SN request confirmation message. In some implementations, CU 172 or S-SN 104A acquires the CSI resource configuration 2, ..., M of cells 2, ..., M respectively, as described for CSI resource configuration 1. When CU 172 acquires the CSI resource configuration 2, ..., M, CU 172 includes the CSI resource configuration 2, ..., M in the SN request confirmation message.

[0214] In some implementations, CU 172 or S-SN 104A acquires the LTM SSB configurations 2, ..., M for cells 2, ..., M, as described for LTM SSB configuration 1. When CU 172 acquires LTM SSB configurations 2, ..., M, CU 172 includes them in the SN request confirmation message. In some implementations, CU 172 or S-SN 104A acquires the PCI 2, ..., M for cells 2, ..., M, as described for PCI 1. When CU 172 acquires PCI 2, ..., M, CU 172 includes them in the SN request confirmation message.

[0215] In some implementations, CU 172 includes the following list in the SN request confirmation message: {Cell ID 1, LTM ID 1 (if acquired or optional), LTM candidate configuration 1, CSI resource configuration 1 (if acquired or optional), TCI status configuration 1 (if acquired or optional), Early synchronization information 1 (if acquired or optional), LTM SSB configuration 1 (if acquired or optional), PCI 1 (if acquired or optional)}, ..., {Cell ID M, LTM ID M (if acquired or optional), LTM candidate configuration M, CSI resource configuration M (if acquired or optional), TCI status configuration M (if acquired or optional), Early synchronization information M (if acquired or optional), LTM SSB configuration M (if acquired or optional), PCI M (if acquired or optional)}. MN 104B includes a list or a portion of a list in the SN confirmation message.

[0216] In some implementations, CU 172 obtains PDCCH command information 2, ..., M from cells 2, ..., M respectively, as described for PDCCH command information 1. In one implementation, CU 172 includes PDCCH command information 2, ..., M in the SN request acknowledgment message. In another implementation, CU 172 includes PDCCH command information 2, ..., M in the early synchronization information 2, ..., M respectively. MN 104B may include PDCCH command information 2, ..., M in the SN acknowledgment message, as described for PDCCH command information 1. S-SN 104A may obtain RACH configuration 2, TCI status configuration 2, and / or PDCCH command information 2, ..., RACH configuration M, TCI status configuration M, and / or PDCCH command information M from the early synchronization information 2, ..., M or from the SN acknowledgment message.

[0217] In some implementations, S-SN 104A can perform LTM configuration delivery procedures 2, ..., M with UE 102 to send tuples to UE 102 respectively: {LTM ID 2, LTM candidate configuration 2, CSI resource configuration 2 (if obtained), TCI state configuration 2 (if obtained), RACH configuration 2 (if obtained), LTM SSB configuration 2 (if obtained), PCI 2 (if obtained)}, ..., {LTM ID M, LTM candidate configuration M, CSI resource configuration M, TCI state configuration M (if obtained), RACH configuration M (if obtained), LTM SSB configuration M (if obtained), PCI M (if obtained)}. Each of LTM configuration delivery procedures 2, ..., M is similar to procedures 394, 494, and / or 594. In other implementations, S-SN 104A includes the tuples in the first RRC reconfiguration message.

[0218] In some implementations, MN 104B can include the measurement results 1, ..., N of cells 1, ..., N in the SN request message, respectively. In some implementations, MN 104B can receive the measurement results from UE 102 and / or receive the measurement results in the SN request message from S-SN 104A. C-SN 106A can select or determine cells 1, ..., M based on measurement results 1, ..., N. In other implementations, C-SN 106A can select or determine cells 1, ..., M based on one or more other factors (e.g., the capacity or load of cells 1, ..., N and / or the maximum number of LTM candidate cells). In one implementation, the maximum number is included in the SN request message. In another implementation, the maximum number is a predetermined number.

[0219] Events 626A, 627A, 629, 630, 631, 632, 633, and 634 are in Figure 6A This is collectively referred to as LTM execution process 699.

[0220] Next reference Figure 6B Scenario 600B is generally similar to Scenario 600A, except that Scenario 600B includes events 604B, 609B, and 611 instead of events 603 and 609A. In Scenario 600B, MN 104B initiates the inter-SN LTM preparation procedure 698B, while in Scenario 600A, S-SN 104A initiates the inter-SN LTM preparation procedure 698A. When communicating with MN 104B and S-SN 104A under DC, UE 102 can send at least one measurement report 604B to MN 104B, for example via SRB1, similar to events 304 / 306, 404 / 406, and 504. If MN 104B is a distributed base station, then MN 104B includes CU and DU. The CU of MN 104B receives measurement reports from UE 102 via the DU of MN 104B. The MN 104B (e.g., the CU of the MN 104B) generates a measurement configuration that configures the UE 102 to send measurement reports, and sends the measurement configuration to the UE 102 (e.g., via the DU of the MN 104B).

[0221] After receiving one or more measurement reports from UE 102 (e.g., in response to this), MN 104B (e.g., the CU of MN 104B) determines to prepare a first cell (e.g., cell 124B) as an LTM candidate for UE 102. In response to this determination, MN 104B generates an SN request message (first SN request message) including the first cell ID (e.g., cell ID 1) of the first cell (e.g., cell 1) and sends a 605 SN request message to C-SN 106A. In response to the SN request message, CU 172 determines to perform LTM preparation procedure 690 with DU 174 and sends a 607 SN request confirmation message to MN 104B, as referenced. Figure 6AAs described. Upon receiving message 607 (e.g., in response to this), MN 104B sends a 609B SN Modification Request message to S-SN 104A, which includes a first LTM candidate configuration (e.g., LTM candidate configuration 1), an LTM reference configuration, and / or a first cell ID, similar to event 609A. If the SN Request Acknowledgment message includes LTM-related configurations for configuring the first cell as an LTM candidate cell, such as RACH configuration, TCI state configuration, CSI resource configuration, LTM SSB configuration, and / or the PCI of the first cell, then MN 104B includes the LTM-related configurations in the SN Modification Request message. In response to SN Modification Request In this message, S-SN 104A sends SN Modification Request Confirmation Message 611 to MN 104B, and performs LTM Configuration Delivery Procedure 694 with UE 102 to send the first LTM candidate configuration and / or LTM reference configuration to UE 102. Events 605, 690, 607, 609B, and 611... Figure 6B The process is collectively referred to as the MN-initiated SN-interval LTM preparation process 698B.

[0222] For reference Figure 6A As described, the SN request confirmation message 607 may include PDCCH command information. If the SN request confirmation message 607 includes PDCCH command information, then MN 104B will include the PDCCH command information in... SN Modification Request In the message. If SN Modification Request If the message includes PDCCH command information, then S-SN 104A can send a 650A PDCCH command to UE 102 based on the PDCCH command information, as shown in the reference. Figure 6A As described. If SN Modification Request If the message includes TCI status configuration, then S-SN 104A can include the first TCI status ID in the LTM cell handover command, as shown in the reference. Figure 6A As described.

[0223] In some implementations, MN 104B (e.g., the CU of MN 104B) may perform one or more LTM preparation procedures to prepare additional cells (i.e., cell 2, ..., N) as LTM candidate cells for UE 102 with CU 172 or other C-SNs, and each LTM preparation procedure is similar to procedure 698B. MN 104B may perform the LTM preparation procedure before or after sending the LTM cell handover command, or during, before, or after procedure 698B.

[0224] In other implementations, MN 104B and CU 172 perform procedure 698B to prepare one or more of cell 1 and cell 2, ..., N as LTM candidate cells for UE 102. N is an integer greater than 1. Cell 2, ..., N are identified by cell ID 2, ..., N respectively, and are operated by DU 174 and / or other DU operations of C-SN 106A. In such implementations, MN 104B includes cell ID 2, ..., N in SN request message 605, as described above with reference to cell ID 1.

[0225] Next reference Figure 6C Scenario 600C is generally similar to scenarios 600A and 600B, the difference being that scenario 600C includes events 694C, 636C, and 645 instead of events 694A, 636A, and 638. In scenario 600C, MN 104B, in an LTM configuration delivery procedure 694C (similar to procedures 394, 494, or 594), sends a second serving DU configuration (including CSI report configuration), LTM ID, first LTM candidate configuration, LTM reference configuration, CSI resource configuration, LTM SSB configuration, RACH configuration, TCI state configuration, and / or the PCI of the first cell to UE 102 in one or more RRC reconfiguration messages to configure the first cell as an LTM candidate cell. In some implementations, MN 104B generates the RRC reconfiguration message in procedure 694C, while S-SN 104A generates the RRC reconfiguration message in procedure 694A. In some implementations, MN 104B assigns LTMID in scenario 600C, while S-SN 104A assigns LTMID in scenarios 600A and 600B.

[0226] When UE 102 performs the 699 LTM execution procedure, UE 102 sends a 636C RRC reconfiguration message to MN 104B, similar to event 636A. In some implementations, UE 102 includes the LTM ID in the RRC reconfiguration completion message to indicate that UE 102 applies the first LTM candidate configuration. Upon receiving the RRC reconfiguration message (e.g., in response to this), MN 104B may send a 645 SN message to S-SN 104A, as referenced. Figure 6A As described. In some implementations, the MN 104B may include the first cell ID of the first cell in the SN message. The MN 104B may determine the first cell ID based on the LTM ID received in the RRC reconfiguration complete message.

[0227] Next reference Figure 6DScene 600D is generally similar to scenes 600A, 600B, and 600C, except that scene 600D includes events 624D, 650D, 654D, 626D, and 627D, instead of events 624A, 650A, 654A, 626A, and 627A. Events 624D, 650D, 654D, and 626D are similar to events 624A, 650A, 654A, and 626A, respectively. The difference is that MN 104B involves events 624D, 650D, 654D, and 626D, while S-SN 104A involves events 624A, 650A, 654A, and 626A. Event 627D differs from 627A in that, in event 627D, MN 104B can send a CU-CU cell handover notification message to S-SN 104A that may include a first TCI status ID and / or a second TCI status ID.

[0228] In some implementations, MN 104B can generate a CSI report configuration based on the CSI resource configuration, as described for S-SN 104A. The CSI resource configuration is configured in the RS transmitted on the first cell. In procedure 694C, MN 104B sends the CSI report configuration to UE 102. In some implementations, MN 104B has a pre-configured CSI resource configuration. In other implementations, MN 104B receives the CSI resource configuration from the OAM node. In yet another implementation, MN 104B receives the CSI resource configuration from CU 172 or S-SN 104A.

[0229] Next, refer to Figures 7A to 10D The discussion focused on the possibility of [doing something] at RAN nodes (e.g., CU 172). Figures 3 to 6D ), DU174 ( Figure 3 and Figures 5 to 6D )) and their configurations (e.g., C-DU 174B, S-DU 174A) Figure 4 Several example methods implemented in LTM (internal CU / internal DU). Generally speaking, Figures 3 to 6D Similar events in Figures 7A to 10D Similar reference numerals are used to denote operations in the figures, where reference numerals sharing two least significant digits correspond to similar operations, and differences are discussed hereinafter where appropriate. For example, operation 708 may be similar to operation 308, and operation 734 may be similar to operations 334, 434, and 534, and therefore separate descriptions are omitted.

[0230] Figure 7AAn example method 700A, which can be implemented by the DU, is shown. Method 700A begins at block 708, where the DU receives a CU-DU message from the CU requesting the preparation of a first cell as an LTM candidate cell for the UE. At block 710A, the DU sends a DU-CU message to the CU including a first set of LTM CFRA configuration parameters, wherein the first set of LTM CFRA configuration parameters is configured for the UE to access the UE's LTM candidate cell. At block 760A, the DU attempts to detect access on the first cell according to the first set of LTM CFRA configuration parameters. At block 732A, the DU can detect that the UE has accessed the first cell according to the first set of LTM CFRA configuration parameters. At block 734, the DU can send an access success message to the CU, notifying the UE that it has successfully accessed the first cell during LTM cell handover. At block 740, the DU can communicate with the UE via the first cell.

[0231] In some implementations, DU is either an S-DU or a C-DU. The descriptions of S-DU or C-DU above or below may apply to DU in method 700A. When the description of S-DU applies to DU in method 700A, the description of C-DU may apply to DU in some implementations, while in other implementations it may not apply to DU. When the description of C-DU applies to DU in method 700A, the description of S-DU may apply to DU in some implementations, while in other implementations it may not apply to DU.

[0232] In this implementation, the S-DU receives one or more measurement reports (e.g., CSI reports) from the UE (e.g., events 354, 454, 554, 654A, or 654D). The S-DU determines which LTM cell handover command to send based on the measurement reports. In some implementations, the measurement reports include one or more measurement results for one or more SSBs. The UE performs measurements on the SSBs and obtains the measurement results from the measurements. In some implementations, the S-DU determines which CFRA to configure in the LTM cell handover based on the measurement reports. The S-DU includes a first set of LTM CFRA configuration parameters in the LTM cell handover command and sends the LTM cell handover command to the UE (e.g., event 326).

[0233] In some implementations, the DU (e.g., S-DU or C-DU) attempts to detect access on the first cell after sending the first set of LTM CFRA configuration parameters (e.g., in response to this). In the case of a C-DU, the C-DU receives a CU-DU cell handover notification message from the CU, which triggers an LTM cell handover to the first cell (e.g., events 430, 530, 630). In some implementations, the C-DU attempts to detect access on the first cell before receiving the CU-DU cell handover notification message. In other implementations, the C-DU attempts to detect access on the first cell after receiving the CU-DU cell handover notification message (e.g., in response to this).

[0234] In some implementations, the first set of LTM CFRA configuration parameters includes a first RA preamble index, a first SSB index, a first PRACH mask index, and / or a first UL / SUL indicator. In some implementations, the DU receives the first set of LTM CFRA configuration parameters from the OAM node.

[0235] In some implementations, the DU includes at least one additional group LTM CFRA configuration parameter of the UE in the DU-CU message. In some implementations, the DU receives the additional group LTM CFRA configuration parameters from the OAM node. For example, each in the additional group includes an RA preamble index, an SSB index, a PRACH mask, and / or a UL / SUL indicator. In some implementations, the DU configures only the first group and / or the additional groups for the first cell (i.e., the LTM candidate cell) and the UE. In other implementations, the C-SN configures only the first group and / or the additional groups for the UE and any LTM candidate cells (i.e., the first cell and other LTM candidate cells). In yet another implementation, the C-SN configures only the first group and the additional groups for the UE and the first cell and other LTM candidate cells, respectively.

[0236] The LTM CFRA configuration parameters for the first group and the supplementary group include different values. In some implementations, the first SSB index (value) in the first group LTM CFRA configuration parameters differs from the SSB index (value) in the supplementary group LTM CFRA configuration parameters. In some implementations, the SSB index (value) in one of the supplementary group LTM CFRA configuration parameters differs from the SSB index (value) in the other supplementary group LTM CFRA configuration parameters. In some implementations, the first RA preamble index (value) in the first group LTM CFRA configuration parameters differs from the RA preamble index (value) in the supplementary group LTM CFRA configuration parameters. In some implementations, the RA preamble index (value) in one of the supplementary group LTM CFRA configuration parameters differs from the RA preamble index (value) in the other supplementary group LTM CFRA configuration parameters. In some implementations, the first PRACH mask index (value) in the first group LTM CFRA configuration parameters differs from the PRACH mask index (value) in the supplementary group LTM CFRA configuration parameters. In some implementations, the PRACH mask index (value) in one of the supplementary group LTM CFRA configuration parameters differs from the PRACH mask index (value) in the other supplementary group LTM CFRA configuration parameters. In some implementations, the first UL / SUL indicator (value) in the first group LTM CFRA configuration parameters differs from the UL / SUL indicator (value) in the supplementary group LTM CFRA configuration parameters. In other implementations, the first UL / SUL indicator (value) in the first group LTM CFRA configuration parameters is the same as the UL / SUL indicator (value) in the supplementary group LTM CFRA configuration parameters. In some implementations, the UL / SUL indicator (value) in one of the supplementary group LTM CFRA configuration parameters differs from the UL / SUL indicator (value) in the other supplementary group LTM CFRA configuration parameters. In other implementations, the UL / SUL indicator (value) in one of the LTM CFRA configuration parameters of the supplementary group is the same as the UL / SUL indicator (value) in the other of the LTM CFRA configuration parameters of the supplementary group.

[0237] In some implementations, the S-DU determines whether to include the first set of LTM CFRA configuration parameters in the LTM cell handover command based on the measurement report. In some implementations, the S-DU obtains (e.g., retrieves, obtains, calculates, or determines) one or more measurement results from the measurement report. In some implementations, the measurement results include the measurement results of a first SSB identified by a first SSB index. The first SSB is transmitted by the C-DU on the first cell. In some implementations, if the measurement result of the first SSB is higher than (or equal to) a predetermined threshold, the S-DU includes the first set of LTM CFRA configuration parameters in the LTM cell handover command. Otherwise, if the measurement result of the first SSB is less than or equal to the predetermined threshold, the S-DU avoids including the first set of LTM CFRA configuration parameters in the LTM cell handover command. In other implementations, the measurement results include the measurement results of a second SSB identified by a second SSB index, and do not include the measurement results of the first SSB. The second SSB is transmitted by the C-DU on the first cell. In one implementation, the S-DU does not receive the LTM CFRA configuration parameters, which include the UE and the second SSB index of the first cell. In another implementation, the measurement result of the second SSB is below (or equal to) a predetermined threshold. In such cases, the S-DU avoids including the (first set) LTM CFRA configuration parameters in the LTM cell handover command.

[0238] In some implementations, the DU includes the first set of LTM CFRA configuration parameters in a specific field / IE in the DU-CU message. If the specific field / IE (i.e., the first specific field / IE) is defined for or indicates UL, the S-DU sets the UL / SUL indicator in the LTM cell handover command to a first value indicating UL (i.e., normal UL (NUL)). Otherwise, if the specific field / IE (i.e., the second specific field / IE) is defined for or indicates SUL, the S-DU sets the UL / SUL indicator in the LTM cell handover command to a second value indicating SUL.

[0239] In some implementations, the DU indicates a first set of LTM CFRA configuration parameters for one of UL and SUL in the DU-CU message, and indicates an additional set of LTM CFRA configuration parameters for the other of UL and SUL. In some implementations, the C-DU sets the UL / SUL indicator in the first set of LTM CFRA configuration parameters to a value indicating one of UL and SUL, and sets the UL / SUL indicator in the additional set of LTM CFRA configuration parameters to a value indicating the other of UL and SUL.

[0240] In other implementations, the DU includes a first set of LTM CFRA configuration parameters in a first specific field / IE for one of UL and SUL in the DU-CU message, and includes an additional set of LTM CFRA configuration parameters in a second specific field / IE for the other of UL and SUL. In such cases, the first set of LTM CFRA configuration parameters and the additional set of LTM CFRA configuration parameters may not include the UL / SUL indicator. In some implementations, the S-DU determines the value of the UL / SUL indicator in the LTM cell handover command based on the measurement results of the first SSB (index) obtained (e.g., identified or determined) by the S-DU from the measurement report. In one implementation, if the measurement result is higher than (or equal to) a predetermined threshold, the S-DU sets the UL / SUL indicator to a first value and includes the first set of LTM CFRA configuration parameters in the LTM cell handover command. Otherwise, if the measurement result is below (or equal to) a predetermined threshold, the S-DU sets the UL / SUL indicator to the second value and includes the additional group of LTM CFRA configuration parameters instead of the first group of LTM CFRA configuration parameters in the LTM cell handover command.

[0241] In other implementations, the DU indicates the first set of LTM CFRA configuration parameters and / or the additional set of LTM CFRA configuration parameters for UL or SUL in the DU-CU message. In some implementations, the DU includes the first set of LTM CFRA configuration parameters and / or the additional set of LTM CFRA configuration parameters in a specific IE defined for UL or SUL in the DU-CU message. In other implementations, the DU includes a single UL / SUL indicator in the DU-CU message, which indicates the first set of LTM CFRA configuration parameters and the additional set of LTM CFRA configuration parameters for UL or SUL.

[0242] In some implementations, the first set of LTM CFRA configuration parameters includes a first RA preamble index and may exclude the SSB index, PRACH mask index, and UL / SUL indicator. In some implementations, the S-DU determines the SSB index, PRACH mask index, and / or UL / SUL indicator and includes the first RA preamble, SSB index, PRACH mask index, and UL / SUL indicator in the LTM cell handover command. In one implementation, the S-DU determines the SSB index based on the measurement report described above. The SSB index indicates the SSB transmitted on the first cell. In some implementations, the measurement result is associated with the SSB identified by the SSB index. In some implementations, the SSB measurement result is higher than or equal to a predetermined threshold. In some implementations, the S-DU determines the PRACH mask index based on the first RACH configuration. In some implementations, the CU-DU message can include the first RACH configuration (e.g., such as...). RACH-ConfigGeneric The general RACH configuration (such as the IE) is included in, for example, a specific field / IE. In some implementations, the specific field / IE is a first specific field / IE indicating that the first RACH configuration is used for UL. In other implementations, the specific field / IE is a second specific field / IE indicating that the first RACH configuration is used for SUL. In such cases, the CU may include the UL / SUL indicator indicating the first RACH configuration for UL or SUL in the CU-DU message. In other implementations, the S-DU receives the first RACH configuration from the OAM node. In some implementations, the first RACH configuration is configured for CFRA only, for CBRA, or for both CFRA and CBRA. In some implementations, the S-DU is set or pre-configured to set the UL / SUL indicator to a first value indicating UL (i.e., NUL). In other implementations, the S-DU is set or pre-configured to set the UL / SUL indicator to a second value indicating SUL. In yet another implementation, the S-DU sets the UL / SUL indicator to either a first or second value based on the first RACH configuration. For example, if the first RACH configuration is associated with UL (i.e., NUL), the S-DU sets the UL / SUL indicator to a first value. If the first RACH configuration is associated with SUL, the S-DU sets the UL / SUL indicator to a second value. The CU can indicate the first RACH configuration for UL or SUL in the CU-DU message. In other implementations, the S-DU determines the UL / SUL indicator based on measurement results in a measurement report. In one implementation, if the measurement result is higher than (or equal to) a predetermined threshold, the S-DU sets the UL / SUL indicator to a first value. Otherwise, if the measurement result is lower than (or equal to) the predetermined threshold, the S-DU sets the UL / SUL indicator to a second value.

[0243] In some implementations, the DU can receive a second CU-DU message from the CU requesting the preparation of a second cell for the C-SN as the UE's LTM candidate cell. In response, the DU sends a second DU-CU message to the CU, which includes the second LTM candidate configuration and / or a second set of LTM CFRA configuration parameters for the second cell, as described above. In some implementations, the second set of LTM CFRA configuration parameters includes a second RA preamble index, a second SSB index, a second PRACH mask index, and / or a second UL / SUL indicator. The description of the first set can be adapted to the second set by replacing "first" with "second". In some implementations, the first and second sets are identical. In other implementations, the first and second sets are different. In some alternative implementations, when preparing a second cell as the UE's LTM candidate cell, the DU does not include the UE's second set of LTM CFRA configuration parameters in the second DU-CU message. In such cases, if the S-DU determines that it commands the UE to perform an LTM cell handover to the second cell, the S-DU sends an LTM cell handover command to the UE, instructing the UE to perform an LTM cell handover to the second cell. In some implementations, the S-DU includes a first set of LTM CFRA configuration parameters in the LTM cell handover command. In this case, the first set of LTM CFRA configuration parameters can be configured for the UE to access any LTM candidate cell operated by the C-DU. The above description of the first cell can be applied to the second cell by replacing the phrase "first cell" with the phrase "second cell". In other implementations, the S-DU avoids including the first set of LTM CFRA configuration parameters in the LTM cell handover command. In this case, the first set of LTM CFRA configuration parameters can be configured for the UE to access only the first cell.

[0244] Figure 7B This is a flowchart of an example method 700B, similar to method 700A, except that method 700B includes blocks 710B, 760B, and 732B instead of blocks 710A, 760A, and 732A. At block 710B, the DU sends a DU-CU message to the CU including a first dedicated RACH configuration, wherein the first dedicated RACH configuration is configured for the UE to access the UE's LTM candidate cell. At block 760B, the DU attempts to detect access on the first cell according to the first dedicated RACH configuration. At block 732B, the DU can detect that the UE has accessed the first cell according to the first dedicated RACH configuration.

[0245] refer to Figure 7A The described examples and implementation methods can be applied to Figure 7B .

[0246] In some implementations, the first dedicated RACH configuration includes one or more sets of LTM CFRA configuration parameters {RA preamble index, SSB index, PRACH mask, and / or UL / SUL indicator} (e.g., see reference). Figure 7A The first group, the supplementary group, and / or the second group described. In some implementations, the first dedicated RACH configuration is defined in 3GPP specification 38.331. RACH-ConfigDedicated IE.

[0247] In some implementations, the DU indicates in the DU-CU message whether the first dedicated RACH configuration is for UL or SUL. The DU implicitly or explicitly indicates in the DU-CU message whether the first dedicated RACH configuration is for UL or SUL. In some implementations, if the DU generates a first dedicated RACH configuration configured for UL (i.e., NUL), the DU includes the first dedicated RACH configuration in the first field / UE of the DU-CU message. Otherwise, if the DU generates a first dedicated RACH configuration configured for SUL, the DU includes the first dedicated RACH configuration in the second field / UE of the DU-CU message. In such cases, the first field / IE and the second field / IE are defined for UL and SUL, respectively.

[0248] In other implementations, the DU includes the first dedicated RACH configuration in the DU-CU message. In one implementation, if the DU generates a first dedicated RACH configuration for UL, the DU sets the UL / SUL indicator to a first value and includes the UL / SUL indicator in the DU-CU message. Otherwise, if the DU generates a first dedicated RACH configuration configured for SUL, the DU sets the UL / SUL indicator to a second value and includes the UL / SUL indicator in the DU-CU message. The UL / SUL indicator set to the first value indicates the first dedicated RACH configuration for UL. The UL / SUL indicator set to the second value indicates the first dedicated RACH configuration for SUL. In another implementation, if the DU generates a first dedicated RACH configuration for UL, the DU includes the UL indicator in the DU-CU message. Alternatively, the DU indicates the first dedicated RACH configuration for UL by excluding the SUL indicator from the DU-CU message. Otherwise, if the DU generates a first dedicated RACH configuration configured for SUL, the DU includes the SUL indicator in the DU-CU message. Alternatively, the DU indicates the first dedicated RACH configuration for SUL by excluding the SUL indicator in the DU-to-CU message. The UL indicator indicates the first dedicated RACH configuration for UL. The SUL indicator indicates the first dedicated RACH configuration for SUL.

[0249] In some implementations, if a first dedicated RACH configuration is indicated or configured for UL, the S-DU can set the UL / SUL indicator in the LTM cell handover command to a first value. Otherwise, if a first dedicated RACH configuration is indicated or configured for SUL, the S-DU can set the UL / SUL indicator in the LTM cell handover command to a second value.

[0250] The UE described above is the first UE. In some implementations, when preparing the first cell as the LTM candidate cell for the second UE, the DU can configure a second dedicated RACH configuration for the second UE, similar to the description above regarding preparing the first cell as the LTM candidate cell for the first UE. The second dedicated RACH configuration differs from the first dedicated RACH configuration.

[0251] Figure 7C This is a flowchart of an example method 700C, similar to method 700A, except that method 700C includes blocks 774C, 760C-1, and 760C-2 instead of block 760A. At block 774C, the DU determines whether the first set of LTM CFRA configuration parameters is configured for UL or SUL. If the first set of LTM CFRA configuration parameters is configured for UL (i.e., the "UL" branch of block 774C), the process proceeds to block 760C-1. At block 760C-1, the DU attempts to detect access on the UL of the first cell according to the first set of LTM CFRA configuration parameters. Otherwise, if the first set of LTM CFRA configuration parameters is configured for SUL (i.e., the "SUL" branch of block 774C), the process proceeds to block 760C-2. At block 760C-2, the DU attempts to detect access on the SUL of the first cell according to the first set of LTM CFRA configuration parameters. The process proceeds from boxes 760C-1 and 760C-2 to box 732A.

[0252] Figure 7DThis is a flowchart of an example method 700D, similar to method 700B, except that method 700D includes blocks 774D, 760D-1, and 760D-2 instead of block 760B. At block 774D, the DU determines whether the first dedicated RACH configuration is configured for UL or SUL. If the first dedicated RACH configuration is configured for UL (i.e., the "UL" branch of block 774D), the process proceeds to block 760D-1. At block 760D-1, the DU attempts to detect access on the UL of the first cell according to the first dedicated RACH configuration. Otherwise, if the first dedicated RACH configuration is configured for SUL (i.e., the "SUL" branch of block 774D), the process proceeds to block 760D-2. At block 760D-2, the DU attempts to detect access on the SUL of the first cell according to the first dedicated RACH configuration. The process proceeds from blocks 760D-1 and 760D-2 to block 732B.

[0253] Figure 7E This is a flowchart of an example method 700E, similar to method 700A, except that method 700E includes blocks 710E and 760E instead of blocks 710A and 760A. At block 710E, the DU sends a DU-CU message to the CU including a first set of LTM CFRA configuration parameters and an additional set of LTM CFRA configuration parameters, wherein the first set and the additional set are configured for the UE to access the UE's LTM candidate cell. At block 760E, the DU attempts to detect access on the first cell according to the first set of LTM CFRA configuration parameters and the additional set of LTM CFRA configuration parameters.

[0254] refer to Figure 7A The described examples and implementation methods can be applied to Figures 7C to 7E .

[0255] In some implementations, the DU includes the first group and the supplementary group in a dedicated RACH configuration, and includes the dedicated RACH configuration in the DU-CU message. In other implementations, the DU includes the first group and the supplementary group in a first dedicated RACH configuration for one of UL and SUL and a second dedicated RACH configuration for the other of UL and SUL, and includes the first dedicated RACH configuration and the second dedicated RACH configuration in the DU-CU message.

[0256] Figure 8AAn example method 800A, which can be implemented by the C-DU, is shown. Method 800A begins at box 808, where the C-DU receives a CU-to-DU message requesting the preparation of a first cell as the LTM candidate cell for the UE. At box 868A, the C-DU determines whether to configure or configure at least one set of LTM CFRA configuration parameters for the UE. At box 874A, the DU determines whether this set of LTM CFRA configuration parameters is configured for UL or SUL. If the set of LTM CFRA configuration parameters is configured for UL (i.e., the “UL” branch of box 874A), the process proceeds to box 878A. At box 878A, the DU includes this set of LTM CFRA configuration parameters in the first field / IE of the DU-to-CU message. Otherwise, if the set of LTM CFRA configuration parameters is configured for SUL (i.e., the “SUL” branch of box 874A), the process proceeds to box 879A. At box 879A, the DU includes the set of LTM CFRA configuration parameters in the second field / IE of the DU to CU message. The process proceeds from boxes 878A and 879A to box 810. At box 810, the DU sends a DU to CU message to the CU.

[0257] refer to Figure 7A The description can be applied to Figure 8A .

[0258] Figure 8B This is a flowchart of an example method 800B, similar to method 800A, except that method 800B includes boxes 868B, 874B, 878B, and 879B instead of boxes 868A, 874A, 878A, and 879A. At box 868B, the C-DU determines whether the dedicated RACH configuration is configured for LTM and UE. At box 874B, the DU determines whether the dedicated RACH configuration is configured for UL or SUL. If the dedicated RACH configuration is configured for UL (i.e., the "UL" branch of box 874B), the process proceeds to box 878B. At box 878B, the DU includes the dedicated RACH configuration in the first field / IE of the DU-to-CU message. Otherwise, if the dedicated RACH configuration is configured for SUL (i.e., the "SUL" branch of box 874B), the process proceeds to box 879B. At box 879B, the DU includes the dedicated RACH configuration in the second field / IE of the DU-to-CU message. The process proceeds from boxes 878B and 879B to box 810.

[0259] Figure 8CThis is a flowchart of an example method 800C, similar to method 800A, except that method 800C includes blocks 878C, 813, and 883 instead of blocks 878A and 879A. At block 878C, the DU includes the group LTM CFRA configuration parameters in the DU-CU message. The process proceeds to block 874A. If the cell or node has already configured the group LTM CFRA configuration parameters for UL (i.e., the “UL” branch of block 874A), the process proceeds to block 813. At block 813, the DU sets the UL / SUL indicator to a first value and includes the UL / SUL indicator in the DU-CU message. Otherwise, if the group LTM CFRA configuration parameters are configured for SUL (i.e., the “SUL” branch of block 874A), the process proceeds to block 883. At block 883, the DU sets the UL / SUL indicator to a second value and includes the UL / SUL indicator in the DU-CU message. The process proceeds from box 813 and box 883 to box 810.

[0260] In some alternative implementations of box 813, the DU includes the UL indicator instead of the UL / SUL indicator in the DU-CU message. In some alternative implementations of box 883, the DU includes the SUL indicator instead of the UL / SUL indicator in the DU-CU message. In other alternative implementations, the DU excludes the SUL indicator in the DU-CU message to indicate that the set of LTM CFRA configuration parameters is configured for UL. In other alternative implementations, the DU excludes the UL indicator in the DU-CU message to indicate that the set of LTM CFRA configuration parameters is configured for SUL.

[0261] Figure 8D This is a flowchart of example method 800D, similar to methods 800B and 800C, except that method 800D includes box 878D instead of box 878C. At box 878D, the DU includes the dedicated RACH configuration in the DU-CU message. The process proceeds to box 874B. If the cell or node has already configured the dedicated RACH configuration for UL (i.e., the “UL” branch of box 874B), the process proceeds to box 813. Otherwise, if the dedicated RACH configuration is configured for SUL (i.e., the “SUL” branch of box 874B), the process proceeds to box 883.

[0262] refer to Figure 7A and Figure 7B The description can be applied to Figures 8B to 8D .

[0263] Figure 9AAn example method 900A, which can be implemented by the S-DU, is shown. Method 900A begins at block 912A, where the DU receives a CU-DU message from the CU including a first set of LTM CFRA configuration parameters and an additional set of LTM CFRA configuration parameters, wherein the first set and the additional set are configured for the UE to access an LTM candidate cell. At block 954, the S-DU receives one or more measurement reports from the UE. At block 915, the S-DU, for example, determines, based on the measurement reports, to command the UE to perform an LTM cell handover to the first cell (i.e., the LTM candidate cell). At block 963A, in response to the determination, the S-DU selects the first set of LTM CFRA configuration parameters based on the measurement reports. At block 964, the S-DU includes the first set of LTM CFRA configuration parameters in an LTM cell handover command for LTM cell handover. At block 926, the S-DU sends the LTM cell handover command to the UE.

[0264] Figure 9B This is a flowchart of an example method 900B, similar to method 900A, except that method 900B includes blocks 962 and 965 instead of block 963A. At block 962, the S-DU determines whether to configure the UE to perform the CFRA procedure on the first cell using either the first set of LTM CFRA configuration parameters or the supplementary set of LTM CFRA configuration parameters. If the S-DU determines to configure the UE to perform the CFRA procedure on the first cell using the first set of LTM CFRA configuration parameters (i.e., the "first set" branch of block 962), the process proceeds to block 964. At block 964, the S-DU includes the first set of LTM CFRA configuration parameters in the LTM cell handover command. Otherwise, if the S-DU determines to configure the UE to perform the CFRA procedure on the first cell using the supplementary set of LTM CFRA configuration parameters (i.e., the "supplementary set" branch of block 962), the process proceeds to block 965. At block 965, the S-DU includes the supplementary set of LTM CFRA configuration parameters in the LTM cell handover command. The process proceeds from boxes 964 and 965 to box 926. At box 926, the S-DU sends an LTM cell handover command to the UE.

[0265] Figure 9CThis is a flowchart of example method 900C, similar to methods 900A and 900B, except that method 900C includes blocks 912C, 970C, and 966 instead of blocks 912A, 962, and 966. At block 912C, the S-DU receives a CU-DU message from the CU including a first set of LTM CFRA configuration parameters, where the first set of LTM CFRA configuration parameters is configured for the UE to access an LTM candidate cell. At block 970C, the S-DU determines whether the UE is eligible to use the first set of LTM CFRA configuration parameters for LTM cell handover. If the UE is eligible to use the first set of LTM CFRA configuration parameters for LTM cell handover (i.e., the "Yes" branch of block 970C), the process proceeds to block 964. Otherwise, if the UE is not eligible to use the first set of LTM CFRA configuration parameters (i.e., the "No" branch of block 970C), the process proceeds to block 966. At box 966, the S-DU avoids including the first set of LTM CFRA configuration parameters in the LTM cell handover command. The process proceeds from boxes 964 and 966 to box 926.

[0266] Figure 9D This is a flowchart of example method 900D, similar to methods 900A, 900B, and 900C, except that method 900D includes blocks 974D, 976, and 977 instead of blocks 970C, 964, 965, and 966. At block 974D, the S-DU determines whether the first set of LTM CFRA configuration parameters is configured for UL or SUL. If the first set of LTM CFRA configuration parameters is configured for UL (i.e., the “UL” branch of block 974D, or Normal Uplink (NUL)), the process proceeds to block 976. At block 976, the S-DU sets the UL / SUL indicator in the LTM cell handover command to a first value. Otherwise, if the first set of LTM CFRA configuration parameters is configured for SUL (i.e., the “SUL” branch of block 974C), the process proceeds to block 977. At block 977, the S-DU sets the UL / SUL indicator in the LTM cell handover command to a second value. The process proceeds from boxes 976 and 977 to box 926.

[0267] Figure 9EThis is a flowchart for example method 900E, similar to methods 900A to 900D, except that method 900E includes box 974E instead of box 974C. At box 974E, the S-DU determines whether the first set of LTM CFRA configuration parameters is included in the first field / IE or the second field / IE in the CU to DU message. If the first set of LTM CFRA configuration parameters is included in the first field / IE (i.e., the "First Field / IE" branch of box 974E), the process proceeds to box 976. Otherwise, if the first set of LTM CFRA configuration parameters is included in the second field / IE (i.e., the "Second Field / IE" branch of box 974E), the process proceeds to box 977.

[0268] Figure 9F This is a flowchart of an example method 900F, similar to method 900A, except that method 900F includes blocks 912F and 963F instead of blocks 912A and 963A. At block 912F, the S-DU receives a CU-DU message from the CU including a first dedicated RACH configuration, where the first dedicated RACH configuration is configured for UE access to LTM candidate cells. At block 963F, the S-DU selects a first set of LTM CFRA configuration parameters from the first dedicated RACH configuration based on a measurement report.

[0269] Figure 9G This is a flowchart of example method 900G, similar to methods 900F and 900C, except that method 900G includes block 970G instead of block 970C. At block 970G, the S-DU determines whether the UE is eligible to use the first set of LTM CFRA configuration parameters in the first dedicated RACH configuration for LTM cell handover. If the UE is eligible to use the first set of LTM CFRA configuration parameters for LTM cell handover (i.e., the "Yes" branch of block 970G), the process proceeds to block 964. Otherwise, if the UE is not eligible to use the first set of LTM CFRA configuration parameters (i.e., the "No" branch of block 970G), the process proceeds to block 966.

[0270] Figure 9H This is a flowchart of example method 900H, similar to methods 900F and 900D, except that method 900H includes block 974H instead of block 974H. At block 974H, the S-DU determines whether the first dedicated RACH configuration is configured for UL or SUL. If the first dedicated RACH configuration is configured for UL (i.e., the "UL" branch of block 974H), the process proceeds to block 966. Otherwise, if the first dedicated RACH configuration is configured for SUL (i.e., the "SUL" branch of block 974D), the process proceeds to block 967.

[0271] Figure 9I This is a flowchart of example method 900I, similar to methods 900F, 900D, and 900H, except that method 900I includes box 974I instead of box 974D. At box 974I, the S-DU determines whether the first dedicated RACH configuration is included in the first field / IE or the second field / IE of the CU-DU message. If the first dedicated RACH configuration is included in the first field / IE (i.e., the "First Field / IE" branch of box 974I), the process proceeds to box 966. Otherwise, if the first dedicated RACH configuration is included in the second field / IE (i.e., the "Second Field / IE" branch of box 974I), the process proceeds to box 967.

[0272] refer to Figure 7A and Figure 7B The description can be applied to Figures 9A to 9I .

[0273] Figure 10A An example method 1000A, which can be implemented by the CU, is shown. Method 1000A begins at box 1010A, where the CU receives a DU-to-CU message from a first DU, including a first set of LTM CFRA configuration parameters configured for UE access to an LTM candidate cell. At box 1074A, the CU determines whether the first set of LTM CFRA configuration parameters is configured for UL or SUL. If the first set of LTM CFRA configuration parameters is configured for UL (i.e., the “UL” branch of box 1074A), the process proceeds to box 1095A. At box 1095A, the CU includes the first set of LTM CFRA configuration parameters in the first field / IE of the CU-to-DU message. Otherwise, if the first set of LTM CFRA configuration parameters is configured for SUL (i.e., the “SUL” branch of box 1074C), the process proceeds to box 1097A. At box 1097A, the CU includes the first set of LTM CFRA configuration parameters in the second field / IE of the CU-DU message. The process proceeds from boxes 1095A and 1097A to box 1012.

[0274] In some implementations, if the DU to CU message includes the first set of LTM CFRA configuration parameters in the first field / IE, the CU determines that the first set of LTM CFRA configuration parameters is configured for UL. Otherwise, if the DU to CU message includes the first set of LTM CFRA configuration parameters in the second field / IE, the CU determines that the first set of LTM CFRA configuration parameters is configured for SUL.

[0275] Figure 10BThis is a flowchart of an example method 1000B, similar to method 1000A, except that method 1000B includes blocks 1073B, 1086, 1083, and 1088 instead of blocks 1095A and 1097A. At block 1073B, the CU includes the first set of LTM CFRA configuration parameters in the CU-DU message. If the first set of LTM CFRA configuration parameters is configured for UL (i.e., the “UL” branch of block 1074C), the process proceeds to block 1086. At block 1086, the CU sets the UL / SUL indicator to a first value. Otherwise, if the first set of LTM CFRA configuration parameters is configured for SUL (i.e., the “SUL” branch of block 1074C), the process proceeds to block 1087. At block 1087, the CU includes setting the UL / SUL indicator to a second value. The process proceeds from blocks 1086 and 1087 to block 1088. The process proceeds from box 1088 to box 1012.

[0276] In some alternative implementations, if the first set of LTM CFRA configuration parameters is configured for UL (i.e., the "UL" branch of box 1074C), the CU includes a UL indicator instead of a UL / SUL indicator in the CU-DU message. The UL indicator indicates that the first set of LTM CFRA configuration parameters is configured for UL. Alternatively, the CU excludes an indicator (e.g., a UL / SUL indicator or a UL indicator) from the CU-DU message to indicate that the first set of LTM CFRA configuration parameters is configured for UL. In some alternative implementations, if the first set of LTM CFRA configuration parameters is configured for SUL (i.e., the "SUL" branch of box 1074C), the CU includes a SUL indicator instead of a UL / SUL indicator in the CU-DU message. The SUL indicator indicates that the first set of LTM CFRA configuration parameters is configured for SUL. Alternatively, the CU excludes indicators (e.g., UL / SUL indicator or SUL indicator) in the CU-DU message to indicate that the first set of LTM CFRA configuration parameters is configured for SUL.

[0277] Figure 10CThis is a flowchart of an example method 1000C, similar to method 1000A, except that method 1000C includes blocks 1010C, 1074D, 1095C, and 1097C instead of blocks 1010A, 1074C, 1095A, and 1097A. At block 1010C, the CU receives a DU-to-CU message from a first DU, including a first dedicated RACH configuration configured for UE access to an LTM candidate cell. At block 1074D, the CU determines whether the first dedicated RACH configuration is configured for UL or SUL. If the first dedicated RACH configuration is configured for UL (i.e., the "UL" branch of block 1074D), the process proceeds to block 1095C. At block 1095C, the CU includes the first dedicated RACH configuration in the first field / IE of the CU-to-DU message. Otherwise, if the first dedicated RACH configuration is configured for SUL (i.e., the “SUL” branch of box 1074D), the process proceeds to box 1097C. At box 1097C, the CU includes the first dedicated RACH configuration in the second field / IE of the CU to DU message. The process proceeds from box 1095C and box 1097C to box 1012.

[0278] In some implementations, if the DU to CU message includes the first dedicated RACH configuration in the first field / IE, then the CU determines that the first dedicated RACH configuration is configured for UL. Otherwise, if the DU to CU message includes the first dedicated RACH configuration in the second field / IE, then the CU determines that the first dedicated RACH configuration is configured for SUL.

[0279] Figure 10D This is a flowchart of example method 1000D, similar to methods 1000C and 1000B, except that method 1000D includes box 1073D instead of box 1073B. At box 1073D, the CU includes the first RACH-specific configuration in the CU-DU message.

[0280] refer to Figure 7A and Figure 7B The description can be applied to Figures 10A-10D .

[0281] Figure 11 The flowchart shows an example method 1100 for LTM between CUs, which can be implemented by distributed units (DUs) of distributed base stations (e.g., DU 174, S-DU 174A, C-DU 174B, etc.).

[0282] Method 1100 begins at block 1108, where the DU receives a request (e.g., event 708 or 808) related to low-level triggered mobility (LTM) of the user equipment (UE) from the centralized unit (CU) of the distributed base station.

[0283] Method 1100 may continue to box 1110, wherein the DU responds to the request by sending random access (RA) configuration parameters for accessing the LTM candidate cell to the CU (e.g., events 710A, 710B, 710E, or 810).

[0284] The DU can be a source DU (S-DU). Method 1100 may include receiving measurement reports of LTM candidate cells from the S-DU.

[0285] A measurement report can be received from the UE. Method 1100 may further include sending a cell handover command if the measurement report indicates that the UE should perform a cell handover. The S-DU may determine, based on the measurement report, which of the multiple sets of RA configuration parameters to provide in the cell handover command. The S-DU may determine, based on the UE's capability information regarding each of the multiple sets of RA configuration parameters or based on the measurement report, which of the multiple sets of RA configuration parameters to provide in the cell handover command (e.g., events 912A, 912C, 912F, 963A, or 963F).

[0286] Measurement reports can be received from the LTM C-DU, which is separate from the S-DU. Measurement reports may include measurement results for the Synchronization Signal Block (SSB). If the SSB measurement result is below a threshold, the S-DU can avoid providing RA configuration parameters in the cell handover command.

[0287] The RA configuration can be received from the CU or another CN node. The CN node may include an OAM node. For example, method 1100 may include receiving a generic RA channel (RACH) configuration from the CU or another CN node. The generic RACH configuration may be included in a message having a field indicating whether the generic RACH configuration is for uplink (UL or normal uplink (NUL)) communication or supplementary uplink (SUL) communication. The generic RACH configuration may be configured for either CFRA or CBRA, or both.

[0288] The RA configuration parameters may include at least one set of CFRA configuration parameters (e.g., event 868A). The at least one set of CFRA configuration parameters may include individual or combined NUL and SUL indicators. Method 1100 may include: if the at least one set of CFRA configuration parameters is configured for NUL, then sending the at least one set in a first field of the DU-to-CU message, and otherwise sending the at least one set in a second field of the DU-to-CU message (e.g., events 774C, 774D, 874A, 878A, or 879A). Method 1100 may include setting the indicator to have a first value or a second value (e.g., events 874A, 813, or 883) based on whether the at least one set of CFRA configuration parameters is configured for NUL or SUL.

[0289] Method 1100 may include sending NUL and SUL indicators in the LTM cell handover command. The DU may determine the values ​​of the NUL and SUL indicators based on a measurement report. The measurement report may include the measurement results of the SSB sent by the C-DU. If the SSB measurement result is below a threshold, the DU may avoid sending RA configuration parameters. The S-DU may set the values ​​for the NUL and SUL indicators based on whether the LTMC-DU supports SUL.

[0290] Method 1100 may include detecting UE access on an LTM candidate cell, the access being performed according to RA configuration parameters (e.g., events 760A, 732A, or 732B). Access may be based on a dedicated RACH configuration (e.g., events 760B, 760D-1, 760D-2, or 868B) or a CFRA configuration. If access is based on a dedicated RACH configuration, method 1100 may include: if the dedicated RACH configuration is configured for NUL, sending the dedicated RACH configuration in a first field of the DU-to-CU message; otherwise, sending the dedicated RACH configuration in a second field of the DU-to-CU message (e.g., events 874B, 878B, or 879B). Alternatively, method 1100 may include setting an indicator to have a first value or a second value based on whether the dedicated RACH configuration is configured for NUL or SUL. Method 1100 may include detecting UE access on NUL or SUL according to a dedicated RACH configuration (e.g., event 774D).

[0291] When the DU is a C-DU, method 1100 may include the C-DU sending a measurement report of the LTM candidate cell to the CU and / or S-DU. Method 1100 may include sending at least one set of CFRA parameters including the RA preamble index, SSB index, PRACH mask index, and / or UL / SUL indicator. The measurement report may include the measurement results of the SSB. Figure 12 is a flowchart of an example method 1100 for inter-CU LTM that can be implemented by the CUs of a distributed base station.

[0292] Method 1200 begins at block 1210, where the CU receives from the first DU RA configuration parameters (e.g., event 1010A or 1010C) for configuring the UE to access the LTM candidate cell.

[0293] Method 1200 may include sending RA configuration parameters to the second DU in block 1212 (e.g., event 1012).

[0294] Method 1200 may include receiving CFRA parameters or dedicated RACH parameters. At operation 1274, the CU may determine whether the RA configuration parameter configures a regular uplink (e.g., NUL or UL) or a supplementary uplink (e.g., SUL) (e.g., event 1074A or 1074C). If the RA configuration parameter configures UL, method 1200 may include box 1295, where the CU configures the RA configuration parameter in a first field of the CU-DU message. Otherwise, in operation 1297, the CU may configure the RA configuration parameter in a second field of the CU-DU message.

[0295] The following list of examples reflects the various implementations explicitly envisioned in this disclosure.

[0296] Example 1. A method implemented in a distributed unit (DU) of a distributed base station. The method includes: receiving a request related to low-layer triggered mobility (LTM) of a user equipment (UE) from a centralized unit (CU) of the distributed base station; and in response to the request, sending random access (RA) configuration parameters for accessing an LTM candidate cell to the CU.

[0297] Example 2. The method as described in Example 1, wherein: the DU is a source DU (S-DU), and wherein the LTM candidate cell is associated with a DU of a distributed base station that is different from the S-DU.

[0298] Example 3. The method as described in Example 2 further includes: receiving a measurement report of the LTM candidate cell by the S-DU.

[0299] Example 4. The method as described in any one of Examples 2 to 3, wherein receiving the measurement report includes receiving the measurement report from the UE.

[0300] Example 5. The method of any one of Examples 2 to 4 further includes: sending a cell handover command if the measurement report indicates that the UE should perform a cell handover.

[0301] Example 6. The method as described in Example 5, wherein: the S-DU determines, based on the measurement report, which of the multiple sets of RA configuration parameters to provide in the cell handover command.

[0302] Example 7. The method as described in Example 5, wherein the S-DU determines which set of RA configuration parameters to provide in the cell handover command based on the UE's capability information about each of the multiple sets of RA configuration parameters.

[0303] Example 8. The method of any one of Examples 3 to 7 further includes: receiving a first set of RA configuration parameters and an additional set of RA configuration parameters from the CU; and sending the first set or the additional set to the UE based on the measurement report.

[0304] Example 9. The method as described in Example 8, wherein sending the first group or the additional group includes sending an LTM cell handover command.

[0305] Example 10. The method as described in Example 3, wherein: the measurement report includes the measurement results of the synchronization signal block (SSB) sent by the LTM candidate DU (C-DU) separate from the S-DU.

[0306] Example 11. The method as described in Example 10, wherein: if the measurement result of the SSB is below a threshold, the S-DU avoids providing the RA configuration parameters in the cell handover command.

[0307] Example 12. The method of any one of Examples 2 to 11 further includes: receiving a general RA channel (RACH) configuration.

[0308] Example 13. The method as described in Example 12, wherein: the general RACH configuration is included in a message having a field indicating whether the general RACH configuration is used for uplink communication or supplemental uplink communication.

[0309] Example 14. The method of any one of Examples 12 to 13 further includes: receiving the general RACH configuration from a core network (CN) node or the CU.

[0310] Example 15. The method as described in Example 14, wherein the CN node includes an Operations Management and Maintenance (OAM) node.

[0311] Example 16. The method as described in Example 12, wherein: the general RACH configuration is configured for contention-free RA (CFRA), contention-based RA, or both CFRA and CBRA.

[0312] Example 17. The method as described in any one of Examples 1 to 16, wherein: the RA configuration parameters include at least one set of contention-free random access (CFRA) configuration parameters.

[0313] Example 18. The method as described in Example 17, wherein: the at least one set of CFRA configuration parameters includes separate Normal Uplink (NUL) indicators and Supplemental Uplink (SUL) indicators.

[0314] Example 19. The method as described in Example 17, wherein: the at least one set of CFRA configuration parameters does not include separate Normal Uplink (NUL) indicators and Supplemental Uplink (SUL) indicators.

[0315] Example 20. The method of any one of Examples 17 to 19 further includes: if the at least one set of CFRA configuration parameters is configured for NUL, then sending the at least one set in a first field of the DU to CU message; otherwise, sending the at least one set in a second field of the DU to CU message.

[0316] Example 21. The method of any one of Examples 17 to 19, further comprising: setting an indicator to have a first value or a second value based on whether the at least one set of CFRA configuration parameters are configured for NUL or SUL; and sending the indicator to the CU.

[0317] Example 22. The method of any one of Examples 17 to 21, wherein when the DU is a source DU (S-DU), the method includes: sending a NUL indicator and a SUL indicator in an LTM cell handover command.

[0318] Example 23. The method as described in Example 22, wherein: the S-DU determines the values ​​of the NUL indicator and the SUL indicator based on the measurement report.

[0319] Example 24. The method as described in Example 23, wherein: the measurement report includes the measurement results of the synchronization signal block (SSB) sent by the LTM candidate DU (C-DU) separate from the S-DU.

[0320] Example 25. The method as described in Example 24, wherein: if the measurement result of the SSB is below a threshold, the S-DU avoids sending RA configuration parameters.

[0321] Example 26. The method as described in Example 24, wherein: the S-DU sets the values ​​of the NUL indicator and the SUL indicator based on whether the LTM C-DU supports SUL.

[0322] Example 27. The method of any one of Examples 1 to 26 further includes: detecting access of the UE on the LTM candidate cell, the access being based on the RA configuration parameters.

[0323] Example 28. The method as described in Example 27, wherein the access is configured according to a dedicated RA channel (RACH).

[0324] Example 29. The method of Example 28 further includes: if the dedicated RACH configuration is configured for normal uplink (NUL), then sending the dedicated RACH configuration in a first field of the DU to CU message; otherwise, sending the dedicated RACH configuration in a second field of the DU to CU message.

[0325] Example 30. The method of Example 28 further includes: setting an indicator to have a first value or a second value based on whether the dedicated RACH configuration is configured for NUL or SUL; and sending the indicator to the CU.

[0326] Example 31. The method of Example 30 further includes: if the dedicated RACH is configured for NUL, then detecting the UE's access on the NUL, and otherwise detecting the UE's access on the SUL.

[0327] Example 32. The method as described in Example 28, wherein the access is configured according to contention-free random access (CFRA).

[0328] Example 33. The method as described in Example 1, wherein: the DU is a candidate DU (C-DU); and the method further includes sending a measurement report of the LTM candidate cell to the source DU or the CU.

[0329] Example 34. The method of Example 33 further includes: sending at least one set of LTM contention-free RA (CFRA) configuration parameters, said at least one set including an RA preamble index, a synchronization signal block (SSB) index, a physical RA channel (PRACH) mask index, or an uplink / supplementary uplink (UL / SUL) indicator.

[0330] Example 35. The method as described in Example 33, wherein: the measurement report includes at least the measurement results of the synchronization signal block (SSB).

[0331] Example 36. The method as described in Example 1, wherein: the RA configuration parameters indicate whether the subsequent RA process should include a two-step RA process or a four-step RA process.

[0332] Example 37. The method as described in Example 36, wherein the RA configuration parameters indicate whether subsequent RA processes should be contention-free or contention-based.

[0333] Example 38. The method as described in Example 1, wherein the RA configuration parameters are included in the LTM candidate configuration.

[0334] Example 39. The method as described in Example 1, wherein the RA configuration parameters are included in the LTM DU configuration.

[0335] Example 40. A method implemented in a centralized unit (CU) of a distributed base station, the method comprising: receiving random access (RA) configuration parameters from a first distributed unit (DU), the random access configuration parameters being used to configure a user equipment (UE) to access a lower layer triggered mobility (LTM) candidate cell; and sending the RA configuration parameters to a second DU.

[0336] Example 41. The method as described in Example 40, wherein: the RA configuration parameters include at least one set of contention-free random access (CFRA) configuration parameters.

[0337] Example 42. The method as described in Example 41, wherein: the at least one set of CFRA configuration parameters includes separate Normal Uplink (NUL) indicators and Supplemental Uplink (SUL) indicators.

[0338] Example 43. The method as described in Example 41, wherein: the at least one set of CFRA configuration parameters does not include separate Normal Uplink (NUL) indicators and Supplemental Uplink (SUL) indicators.

[0339] Example 44. The method of any one of Examples 41 to 43 further includes: if the at least one set of CFRA configuration parameters is configured for NUL, then sending the at least one set in a first field of the CU to DU message; otherwise, sending the at least one set in a second field of the CU to DU message.

[0340] Example 45. The method of any one of Examples 41 to 43 further includes: setting an indicator to have a first value or a second value based on whether the at least one set of CFRA configuration parameters are configured for NUL or SUL; and sending the indicator to the second DU.

[0341] Example 46. The method as described in Example 40, wherein: the RA configuration parameters include at least one set of dedicated RA channel (RACH) parameters.

[0342] Example 47. The method of Example 46 further includes: if the dedicated RACH configuration is configured for normal uplink (NUL), then sending the dedicated RACH configuration in a first field of the CU to DU message; otherwise, sending the dedicated RACH configuration in a second field of the CU to DU message.

[0343] The following description applies to the description above.

[0344] In some implementations, the SN requirement message and the SN acknowledgment message are respectively SN Change Requirements Messages and SN change confirmed recognize Message. In other implementations, the SN requirement message and the SN acknowledgment message are respectively SN Modification Request message and SN modification confirmed recognize Messages. In some implementations, the SN request message and the SN request acknowledgment message are respectively... SN Add Request Messages and SN Add Add confirmation request Messages. In other implementations, the SN request message and the SN request confirmation message are respectively SN Modification Request Messages and SN modification request confirmation information.

[0345] Generally, a description of one of the above figures can be applied to another. Examples, implementations, and methods described above can be combined if there is no conflict. Events or boxes described above can be optional or omitted. For example, events or boxes marked 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 a receiving node (e.g., DU) receiving a message from a sending node (e.g., CU) can be replaced with a description of the sending node sending a message to the receiving node. Similarly, a description of a receiving node (e.g., CU) receiving a message from a sending node (e.g., DU) can be replaced with a description of the sending node sending a message to the receiving node.

[0346] In some implementations, "message" is used and can be replaced with "information element (IE)" and vice versa. In some implementations, "IE" is used and can be replaced with "field" and vice versa. In some implementations, "configurations" or "configuration parameters" can be used to replace "configuration" and vice versa. In some implementations, "LTM command" can be replaced with "serving cell change command," "Layer 1 / Layer 2 LTM cell handover command," "lower layer handover command," or "lower layer serving cell change command." In some implementations, "some" means "one or more." In some implementations, "at least one" means "one or more." In some implementations, "DU configuration" can be replaced with "cell group configuration." In some implementations, "serving cell index," "LTM cell index," "special cell (SpCell) index," "PCell index," or "PSCell index" can be used to replace "cell index." In some implementations, "service" can be replaced with "source." In some implementations, "measurement report" can be replaced with "measurement result" or "CSI report". In some implementations, "early TA acquisition" can be replaced with "early UL timing synchronization" or "early UL synchronization". In some implementations, "early TA acquisition on candidate cells" can be replaced with "early UL timing synchronization with candidate cells" or "early UL synchronization with candidate cells". In some implementations, "include" can be replaced with "comprise". In some implementations, "exclude" can be replaced with "avoid including". In some implementations, the "handover request" and "handover request confirmation" described above are for illustrative purposes and can be replaced by messages with generic names. For example, "handover request" and "handover request confirmation" can be replaced by a first CU to CU message and a second CU to CU message, respectively. In another example, Transfer Request "and" Confirmation of transfer request "This can be replaced by the first interface message and the second interface message, respectively. In yet another example," Transfer Request "and" Confirmation of transfer request "These can be replaced by a first BS to BS message and a second BS to BS message, respectively. In some implementations, the terms "SN request," "SN confirmation," "SN request," and "SN request confirmation" described above are for illustrative purposes and can be replaced by messages with generic names. For example, "SN request message" can be replaced by an SN to MN message. In another example, "SN confirmation message" can be replaced by an MN to SN message."

[0347] The user device (e.g., UE 102) that can implement the technology of this disclosure can be any suitable device capable of wireless communication, such as a smartphone, tablet computer, laptop computer, mobile game console, point-of-sale (POS) terminal, health monitoring device, drone, camera, media streaming dongle or other personal media device, wearable device such as a smartwatch, wireless hotspot, femtocell or broadband router. 。 Furthermore, in some cases, the user device can be embedded in electronic systems such as the vehicle's main unit or advanced driver assistance systems (ADAS). Even further, 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.

[0348] Some implementations 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 to perform certain operations (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.). A hardware module may also include programmable logic or circuit systems that are temporarily configured by software to perform certain operations (e.g., as encompassed within a general-purpose processor or other programmable processor). 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.

[0349] When implemented in software, these technologies can be provided as part of an operating system, as a library used by multiple applications, or as a specific software application. The software can be executed by one or more general-purpose processors or one or more dedicated processors.

[0350] 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 using the principles disclosed herein. Therefore, while particular implementations and applications have been shown and described, it should be understood that the disclosed implementations 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 can be made in 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 request for candidate cells to prepare for low-layer triggering of mobility LTM for user equipment (UE). as well as In response to the request, LTM contention-free random access (CFRA) configuration parameters for accessing the candidate cell are sent to the CU.

2. The method of claim 1, wherein: The transmission includes sending a UE CONTEXT SETUP RESPONSE containing the CFRA configuration parameters.

3. The method of claim 1, wherein: The transmission includes sending a UE CONTEXT MODIFICATION RESPONSE that includes the CFRA configuration parameters.

4. The method according to any one of claims 1 to 3, wherein: LTM CFRA configuration parameters include resource configurations used to supplement uplink SUL.

5. The method according to any one of claims 1 to 4, wherein: LTM CFRA configuration parameters are included in the dedicated information element (IE) for Random Access Channel (RACH) configuration.

6. The method according to any one of claims 1 to 5, further comprising: Send an access success message to the CU notifying the UE that it has successfully accessed the candidate cell.

7. The method of claim 1, wherein: The DU is the source DU S-DU, and The candidate cell is associated with a DU of a distributed base station that is different from the S-DU.

8. The method of claim 7, further comprising: The LTM cell handover command to be sent to the UE is determined based on the measurement report received from the UE.

9. The method of claim 8, wherein: The DU determines, based on the measurement report, which of the multiple sets of random access RA configuration parameters to provide in the LTM cell handover command.

10. The method of claim 8, wherein: The DU determines which set of RA configuration parameters to provide in the LTM cell handover command based on the UE's capability information for each of the multiple sets of random access RA configurations.

11. The method of any one of claims 1 to 10, further comprising: The system detected that the UE accessed the candidate cell according to the LTM CFRA configuration parameters.

12. The method according to any one of claims 1 to 10, wherein: The candidate cells are associated with the second DU of different distributed base stations.

13. A method implemented in the central unit (CU) of a distributed base station, the method comprising: Send a request to the Distributed Unit (DU) to prepare candidate cells for Low Layer Triggered Mobility TM (LTM) for User Equipment (UE). as well as In response to the request, LTM contention-free random access (CFRA) configuration parameters for accessing the candidate cell are received from the DU.

14. The method of claim 13, further comprising: Send LTM CFRA configuration parameters to the second DU.

15. A base station comprising a transceiver and processing hardware, the base station being configured to implement the method as described in any one of claims 1 to 14.

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