Managing inter-central unit low layer triggered mobility

Abstract

Methods and apparatuses for managing inter-central unit low layer triggered mobility (LTM) are described herein. A method implemented in a source base station can include receiving, from the source base station, a handover request related to a cell associated with a distributed unit (DU) of a candidate base station. The method can further include obtaining a low layer triggered mobility (LTM) reference configuration. The method can further include generating an LTM configuration for the cell using the LTM reference configuration. The method can further include transmitting, to the source base station, a handover request acknowledgement including the LTM configuration. Other methods and apparatuses are described.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Provisional U.S. Patent Application No. 63 / 563,258, filed March 8, 2024, entitled “Managing Inter-Central Unit Lower Layer Triggered Mobility,” the entire contents of which are hereby expressly incorporated herein by reference.

[0003] This disclosure relates to wireless communications, and more specifically, to managing low-level triggered mobility (LTM) 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 named inventors (with respect to the work described in this background section) and aspects of the description that may not be otherwise 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 radio access technology (RAT) and multiple layers of a 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 layer 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 Protocol Data Unit (PDU) sequencing in the uplink direction (from 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 base station can use SRBs to exchange RRC messages and Non-Access Stratum (NAS) messages, and the UE and base station can use DRBs to transmit data on the user plane.

[0007] A UE can concurrently utilize the resources of multiple RAN nodes (e.g., components of a base station or distributed base station) interconnected via backhaul. Multiple Radio Dual Connectivity (MR-DC) refers to a connectivity scenario where these multiple RAN nodes support different Radio Access Technologies (RATs). When a 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 PCell) and the SN (via 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 a handover procedure.

[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) is used for changes in 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 must release at least one SCell due to the change in the PCell or PSCell. Serving cell changes involve a full L2 (and L1) reset, resulting in longer latency, greater overhead, and longer downtime. To address these issues, 3GPP recently proposed a low-layer triggered mobility (LTM) procedure.

[0009] During communication between the RAN and 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 LTM candidate cells to be configured for LTM cell switching. To configure LTM candidate cells for the UE, the base station sends an 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 switching command to the UE, instructing the UE to perform an LTM cell switching to the LTM candidate cell. In response to the LTM cell switching command, the UE performs a cell change from the serving cell to the LTM candidate cell. The base station includes a central cell (CU) and one or more distributed cells (DUs). One of the DUs operating the serving cell is called the serving DU. If the serving DU operates the LTM candidate cell, the LTM cell switching is an intra-CU, intra-DU LTM cell switching. If a candidate DU (C-DU) within a DU operates as an LTM candidate cell, then the LTM cell handover is an inter-DU LTM cell handover within a CU. 3GPP has enabled both intra-CU and inter-CU LTM cell handovers in Release 18 of the specification. However, it is unclear how the device should handle inter-CU LTM cell handovers. For example, it is unclear how the device should handle situations where an LTM candidate cell operates within candidate DUs in different CUs. Summary of the Invention

[0010] Example embodiments of these technologies are methods implemented in the central unit (CU) of a candidate base station, which includes a central unit (CU) and a distributed unit (DU). The method includes: receiving a cell-related handover request associated with the distributed unit (DU) of the candidate base station from a source base station; obtaining a low-layer triggered mobility (LTM) reference configuration; using the LTM reference configuration to generate an LTM configuration for the cell; and sending a handover request confirmation including the LTM configuration to the source base station.

[0011] Another example embodiment of these technologies is a method implemented in a source base station, the method comprising: sending a handover request to a candidate base station, the handover request including a request for preparing a cell for lower layer triggered mobility (LTM) for a user equipment (UE); receiving a handover request confirmation from the candidate base station; determining, based on the handover request or the handover request confirmation, whether to include an indicator that the LTM configuration is a complete configuration in the LTM configuration; and sending the LTM configuration to the UE.

[0012] Another example embodiment of these technologies is a base station that includes processing hardware and is configured to implement one of the methods described above. Attached Figure Description

[0013] 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;

[0014] Figure 1B It is possible Figure 1A A block diagram of an example base station operating in the system, including a central unit (CU) and a distributed unit (DU);

[0015] 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;

[0016] 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;

[0017] Figure 3 This is a message sequence diagram of an example scenario in which the UE executes the LTM procedure within the CU and DU.

[0018] Figure 4 This is a message sequence diagram of an example scenario in which the UE performs the LTM procedure between DUs within the CU;

[0019] Figure 5 This is a message sequence diagram of an example scenario in which the UE performs the inter-CU LTM procedure;

[0020] Figure 6A This is a flowchart of an example method that can be implemented by the source base station;

[0021] Figure 6B Apart from S-BS generating the LTM reference configuration, it is generally similar to Figure 6A A flowchart of the example methods;

[0022] Figure 7 This is a flowchart of an example method that can be implemented by the CU of the source base station;

[0023] Figure 8A This is a flowchart of an example method that can be implemented by a candidate base station (C-BS);

[0024] Figure 8B Aside from the C-BS generating reference LTM configuration, it is generally similar to Figure 8A A flowchart of the example methods;

[0025] Figure 9AThis is a flowchart of an example method that can be implemented by the CU of a candidate base station;

[0026] Figure 9B This is a flowchart of a second example method that can be implemented by the CU of C-BS;

[0027] Figure 9C This is a flowchart of a third example method that can be implemented by the CU of C-BS;

[0028] Figure 9D This is a flowchart of the fourth example method that can be implemented by the CU of C-BS;

[0029] Figure 10A This is a flowchart of an example method that can be implemented by the CU of C-BS;

[0030] Figure 10B Besides the CU retrieval LTM reference DU configuration, it is similar to Figure 10A A flowchart of the example methods;

[0031] Figure 11A This is a flowchart of an example method that can be implemented by the source base station;

[0032] Figure 11B Besides the switch request, including the LTM reference configuration, it is similar to Figure 11A A flowchart of the example methods;

[0033] Figure 12 This is a flowchart of an example method that can be implemented by a candidate base station;

[0034] Figure 13A This is a flowchart of an example method that can be implemented by the source base station;

[0035] Figure 13B Aside from whether the confirmation of the handover request by the source base station includes the LTM reference configuration, it is generally similar to... Figure 13A A flowchart of an example method;

[0036] Figure 13C Aside from the source base station confirming whether the LTM candidate configuration is a complete configuration, it is generally similar to... Figure 13A A flowchart of an example method;

[0037] Figure 14 This is a flowchart of an example method that can be implemented by a distributed unit (DU);

[0038] Figure 15 This is a flowchart of another example method that can be implemented by the source base station;

[0039] Figure 16Here is a flowchart of another example method that can be implemented using C-BS; and

[0040] Figure 17 This is a flowchart of another example method that can be implemented by a distributed unit (DU). Detailed Implementation

[0041] The source base station or candidate base station can implement the technology of this disclosure to perform LTM cell switching from one base station to a different base station, or LTM cell switching from a DU in a first CU to a DU in a different CU.

[0042] 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) 104, base station 106, and core network (CN) 110. Base stations 104 and 106 operate in radio access network (RAN) 105. UE 102 is initially connected to base station 104. In some scenarios, base station 104 may perform SN addition to configure UE 102 to operate with both base stations 104 and 106 in dual connectivity (DC). Base stations 104 and 106 operate as MN and SN of UE 102, respectively.

[0043] In various configurations of the wireless communication system 100, base station 104 can operate as a primary eNB (MeNB) or primary gNB (MgNB), and base station 106 can operate as a secondary gNB (SgNB). UE 102 can communicate with base station 104 and base station 106 via the same RAT (such as EUTRA or NR) or different RATs. When base station 104 is a MeNB and base station 106 is an SgNB, UE 102 can be in EUTRA-NR DC (EN-DC) mode with both the MeNB and SgNB.

[0044] In some cases, the MeNB or SeNB is implemented as an ng-eNB instead of an eNB. When base station 104 is the primary ng-eNB (Mng-eNB) and base station 106 is the SgNB, UE 102 can be under a next-generation (NG) EUTRA-NR DC (NGEN-DC) with both the Mng-eNB and SgNB. When base station 104 is a MgNB and base station 106 is an SgNB, UE 102 can be under an NR-NR DC (NR-DC) with both the MgNB and SgNB. When base station 104 is a MgNB and base station 106 is a secondary ng-eNB (Sng-eNB), UE 102 can be under an NR-EUTRA DC (NE-DC) with both the MgNB and Sng-eNB.

[0045] In the scenario where UE 102 switches from base station 104 to base station 106, base stations 104 and 106 operate as the source base station (S-BS) and the target base station (T-BS), respectively. For example, before the handover, UE 102 can communicate with base station 104 and the auxiliary base station (T-BS). Figure 1A (Not shown in the diagram) operates in DC mode. After the handover is completed, UE 102 can continue to operate in DC mode with base station 106 and the additional base station, or UE can operate in single-connection (SC) mode with base station 106. In the latter case, base stations 104 and 106 operate as the source MN (S-MN) and the target MN (T-MN), respectively.

[0046] The core network (CN) 110 can be either the Evolved Packet Core (EPC) 111 or the 5th Generation Core (5GC) 160; both are... Figure 1A The CN 110 may support other cores (not shown). Base station 104 may be an eNB supporting an S1 interface for communication with EPC 111, an ng-eNB supporting an NG interface for communication with 5GC 160, or a gNB supporting an NR radio interface and an NG interface for communication with 5GC 160. To exchange messages directly with each other during the scenarios discussed below, base stations 104 and 106 may support X2 or Xn interfaces.

[0047] like Figure 1A As shown, base station 104 supports cell 124A, and base station 106 supports cell 126. Cells 124A and 126 can partially overlap, allowing UE 102 to communicate with base stations 104 and 106 via DC, where one of base stations 104 and 106 is MN and the other is SN. Base station 104 can support additional cells such as cell 124B, and base station 106 can support additional cells (…). Figure 1A (Not shown in the diagram). Cells 124A, 124B, and 126 may partially overlap, allowing UE 102 to communicate with associated base stations 104 and 106 via carrier aggregation (CA). Base station 104 may operate cells 124A and 124B via one or more transmit and receive points (TRPs). More specifically, when UE 102 is in a DC configuration with base stations 104 and 106, one of base stations 104 and 106 operates as a MeNB, Mng-eNB, or MgNB, and the other operates as an SgNB or Sng-eNB.

[0048] Generally, RAN 105 may include any suitable number of base stations supporting NR cells and / or EUTRA cells. More specifically, EPC 111 or 5GC 160 may connect to any suitable number of base stations supporting NR cells and / or EUTRA cells. Although the examples below specifically refer to particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, the techniques disclosed herein can also be applied to other suitable radio access technologies and / or core network technologies, such as sixth-generation (6G) radio access and / or 6G core networks or 5G NR-6G DC.

[0049] Continue to refer to Figure 1ABase station 104 includes processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and a non-transitory computer-readable storage medium for storing instructions, the one or more general-purpose processors executing these instructions. 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 from one or more user equipments (e.g., UE 102) on a physical downlink (DL) channel and a DL reference signal 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 from the one or more user equipments on a physical uplink (UL) channel and / or a UL reference signal 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. The MAC function includes performing random access (RA) procedures, managing UL timing advance (TA) for one or more user equipment (UEs), and / or communicating UL / DLMAC PDUs with one or more UEs. The MAC function includes functions related to lower layer triggered mobility (LTM, also referred to herein as L1 / L2 triggered mobility or lower layer triggered mobility). In the example, the LTM function receives control via LTM controller 137 in cooperation with MAC controller 134 or via signaling to MAC controller 134. The processing hardware 130 may further include an RRC controller 136 to implement procedures and messaging at the RRC sublayer of the protocol communication stack. For example, the RRC controller 136 may be configured to support RRC messaging associated with handover procedures and / or support necessary operations when base station 104 operates as MN relative to SN or as SN relative to MN. When base station 104 is a distributed base station, CU LTM controller 137A can operate in the CU, and DU LTM controller 137B can operate in the DU (see [link to CU]). Figure 1B 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.

[0050] 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 from base station 104 or 106 on physical DL channels and / or DL ​​reference signals 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 to base station 104 or 106 on physical UL channels and / or UL reference signals 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 MAC controller 154, which is configured to perform MAC functions with base station 104 or 106. For example, MAC functions include performing random access procedures, managing UL timing advances for one or more user facilities, and communicating UL / DL MAC PDUs with base stations 104 or 106. In another example, MAC functions include LTM-related functions as described below. Processing hardware 150 may further include an RRC controller 156 to implement procedures and message passing at the RRC sublayer of the protocol communication stack.

[0051] In operation, UE 102 can use radio bearers (e.g., DRBs or SRBs) that terminate at different times on MN 104 or SN 106 under DC. UE 102 can apply one or more security keys when communicating on these radio bearers in the uplink (UL) direction (from UE 102 to the base station) and / or downlink direction (from the base station to UE 102). The UE can use several types of SRBs and DRBs. 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, which include recorded measurement information or NAS messages also on the DCCH but with a lower priority than SRB1 resources. More generally, SRB1 and SRB2 resources allow the UE and MN to exchange RRC messages related to the MN and embedded RRC messages related to the SN. 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 SRB. Split SRBs allow the UE to exchange RRC messages directly with the MN via the lower-layer resources of the MN and SN. Furthermore, a DRB that uses only the lower-layer resources of the MN can be referred to as MCG DRB, a DRB that uses only the lower-layer resources of the SN can be referred to as SCG DRB, and a DRB that uses both MCG and SCG lower-layer resources can be referred to as a split DRB.

[0052] Figure 1B Depicting Figure 1A Exemplary distributed or decomposed implementations of any one or more base stations shown (e.g., base station 104 or base station 106). In this implementation, base stations 104, 106 include a central unit (CU) 172 and one or more distributed units (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 SNRRC controller, which can be similar to RRC controller 146. Figure 1A It is configured to manage or control one or more RRC configurations and / or RRC procedures when the base station 106 is operating as an SN.

[0053] Each of DU 174 includes processing hardware that 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 media access control (MAC) controller (e.g., MAC controllers 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 106 operates as an MN or SN. The processing hardware may also include a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0054] In some implementations, CU 172 may include a logical node CU-CP172A that hosts the control plane of CU 172. CU 172 may also include a logical node CU-UP 172B that 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).

[0055] 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.

[0056] Figure 2A An example protocol stack 200 is shown in a simplified manner, which UE 102 can use to communicate with eNB / ng-eNB 230 or gNB 232 (e.g., one or more of base stations 104, 106).

[0057] 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 2A As shown, UE102 can support NR PDCP 210 layering on EUTRA RLC 206A, and SDAP sublayer 212 layering on NR PDCP sublayer 210.

[0058] 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".

[0059] 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.

[0060] Figure 2BAn example protocol stack 250 is shown in a simplified manner on which UE 102 can communicate with DU (e.g., DU 174) and CU (e.g., CU 172). The radio protocol stack 200 is functionally split, as follows: Figure 2B The radio protocol stack 250 is shown in the diagram. At either base station 104 or 106, the CU can maintain all control and upper-layer functionality (e.g., RRC214, SDAP 212, NR PDCP 210), while lower-layer operations (e.g., NR RLC 206B, NR MAC 204B, and NR PHY202B) 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.

[0061] Next, refer to Figures 3 to 5 It describes several example scenarios in which the base station (e.g., in) Figure 1A The base stations 104 and 106 operating in the system send configuration to the UE 102 and later activate the configuration for communication between the UE 102 and the base stations 104 and 106. Generally speaking, Figures 3 to 5 Similar events in the diagram are labeled with similar reference numerals that share two least significant figures, 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 figure and discussed below, any of the other implementations discussed for a particular event (e.g., for messaging and processing) can be applied to other events in the figure marked with similar reference numerals.

[0062] First refer to Figure 3In scenario 300, base station 104 includes CU 172 and DU 174, and DU 174 operates cell 124A. UE 102 initially uses a serving DU to communicate with DU 174 on the serving cell (e.g., cell 124A) 302, and UE 102 uses a serving CU to communicate with CU 172 via DU 174 302. DU 174 is a serving DU or source DU (S-DU) for UE 102. In other words, DU 174 is a serving DU (S-DU) communicating with UE 102. In some implementations, UE 102 uses a serving DU to communicate with DU 174 via carrier aggregation (CA) on cell 124A and other cells (e.g., cells not shown in FIG. 1A). DU 174 operates on the other cells. Cell 124A and / or the other cells are serving cells for 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 cell). 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 104 may include DU 174, CU 172, or both DU 174 and CU 172.

[0063] In event 302, UE 102 may transmit UL PDUs and / or UL control signals to base station 104 via one or more TRPs in cell 124A and / or other cells. In some implementations, UE 102 communicates UL PDUs and / or DL ​​PDUs with base station 104 via a radio bearer, which may include SRBs and / or DRBs. Base station 104 may configure the radio bearer for UE 102. In some implementations, UL control signals include UL control information, channel state information, Hybrid Automatic Repeat Request (HARQ) acknowledgment (ACK), HARQ negative ACK, scheduling request, and / or probe reference signals. Similarly, UE 102 may receive DL PDUs and / or DL ​​control signals from base station 104 via one or more TRPs in cell 124A and / or other cells. In some implementations, DL control signals include downlink control information (DCI) and reference signals (e.g., synchronization signal blocks, channel state information reference signals (CSI-RS), and / or tracking reference signals). Base station 104 can transmit DCI via one or more TRPs on the physical downlink control channel (PDCCH) monitored by UE 102 in cell 124A and / or other cells.

[0064] In some implementations, the serving DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some implementations, the serving DU configuration includes at least one first non-LTM TCI state configuration for the serving cell. In some implementations, DU 174 may send these configuration parameters and / or the first non-LTM TCI state configuration to CU 172. CU 172 generates one or more messages (e.g., RRC reconfiguration messages) that include the configuration parameters and / or the first non-LTM TCI state configuration. 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 RadioBearerConfig Configuration parameters in IE. Radio configuration parameters or RadioBearerConfigIE 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 104, and the UE receives the remainder of these configuration parameters from base station 104.

[0065] 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., 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 serving cells. In some implementations, the serving DU configuration includes the serving cell ID and configures the association between the serving cell ID and the first non-LTM TCI state configuration.

[0066] When communicating with base station 104, UE 102 sends at least one measurement report (304) to DU 174. In some implementations, the measurement report includes measurement results for the serving cell (e.g., cell 124A) and / or at least one non-serving cell for UE 102. 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 is an F1 Application Protocol (F1AP) message (e.g., UL RRC message transmission (Message). At least one serving cell includes cell 124A and / or other cells, and at least one non-serving cell includes cell 126 or cell 124B and / or Figure 1AAdditional cells are not shown. 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 304 measurement report 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.

[0067] After receiving one or more measurement reports from UE 102 (e.g., in response to receiving one or more measurement reports from UE 102), 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 104 determines to prepare the first cell for UE 102 because the measurement reports indicate that the first cell can be used by base station 104 to communicate with UE 102. In some implementations, base station 104 determines to prepare the first cell for UE 102 because the measurement reports indicate 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 reports indicate that the signal strength and / or quality of the first cell is higher than a first predetermined threshold, better than the strength and / or quality of the serving cell (e.g., cell 124A), and / or better than the strength and / or quality of the serving cell by a first predetermined threshold. Alternatively, CU 172 determines to prepare the first cell for UE 102, regardless of whether a measurement report is received from UE 102.

[0068] In response to determining that the first cell is ready for LTM, CU 172 sends a 385 First CU to DU message to DU 174 to prepare the first cell for UE 102. In some implementations, CU 172 includes the cell identifier (ID) 1 of the first cell in the First CU to DU message to request DU 174 to prepare the first cell for LTM for UE 102. In one 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 indicate to DU 174 that the first cell is to be prepared for LTM. LTM Information establishment In IE, and will LTM Information Establishment The IE is included in the first CU to DU message. In other implementations, the CU172 includes the LTM indicator. LTM Information Modification In IE, and will LTM Information ModificationThe IE is included in the first CU to DU message.

[0069] 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 for the first cell of the LTM configuration. 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 LTM DU 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.

[0070] Events 385 and 310 in Figure 3 This process is collectively referred to as the LTM preparation process 390.

[0071] 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 performs multiple LTM preparation procedures with DU 174 (e.g., procedures 390 and LTM preparation procedures 2, ..., N described below) to prepare multiple LTM candidate cells, CU 172 can determine that 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.

[0072] 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 only for enhancing the LTM reference DU configuration.

[0073] In some implementations, CU 172 includes an LTM reference DU configuration request in a first CU-DU message, and DU 174, in response to the request, generates an LTM reference DU configuration and includes it in a first DU-CU message. In some implementations, CU 172 determines whether UE 102 supports the LTM reference configuration. In the context of this embodiment, and as described in 3GPP specification 38.331, the reference configuration is a configuration provided by the network to the UE that is common to 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 a first CU-DU message. DU 174, in response to the LTM reference DU configuration request, includes the LTM reference DU configuration in a 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 LTM DU configuration 1 as the complete configuration and may not include the LTM reference DU configuration in the first DU-CU message. In other implementations, CU 172 sends an additional CU-DU message to DU 174 including the LTM reference DU configuration request, instead of sending the LTM reference DU configuration request in the first CU-DU message. 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.

[0074] In some implementations, CU 172 includes the LTM reference DU configuration in the first CU-DU message. In some implementations, CU 172, as described above and referencing... Figure 4During 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 merely an extension of the LTM reference DU configuration.

[0075] 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.

[0076] 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, and 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. In some implementations, the LTM reference DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some implementations, the LTM reference DU configuration is as defined in 3GPP specification 38.331. CellGroupConfig IE. In other implementations, the LTM reference DU configuration includes... CellGroupConfig Configuration parameters in IE. In some implementations, the LTM reference DU configuration includes... CSI-MeasConfig IE or configuration parameters used for Channel State Information (CSI) measurement and / or reporting.

[0077] 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, and 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.

[0078] 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, including CSI resource configuration (e.g., CSI resource configuration 1) and / or LTM 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) to be transmitted on the first cell. The RS includes an SSB and / or a CSI-RS. The LTM SSB configuration includes SSB configuration parameters that configure the SSB frequency, subcarrier spacing, SSB periodicity, SSB location, and / or SSB power for the SSB to be transmitted on the first cell.

[0079] Upon receiving the CSI resource configuration (e.g., in response to receiving the CSI resource configuration), 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 in event 302 to distinguish it from the service DU configuration). In some implementations, the CSI report configuration configures UE 102 to send CSI reports based on RS measurements. DU 174 sends a second DU to CU message 314, including 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.

[0080] In some implementations, CU 172 includes cell ID 1 and / or LTM ID 1 in the second CU-DU message (e.g., in 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 so that DU 174 can 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 such implementations, CU 172 includes LTM ID 1 in the first CU-DU message. In other implementations, CU 172 does not include LTM ID 1 in the first CU to DU message.

[0081] 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.

[0082] In some implementations, DU 174 sends LTM SSB configuration or SSB configuration parameters to CU 172 in, for example, 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).

[0083] Events 312 and 314 Figure 3 This is collectively referred to as the LTM CSI report configuration and / or LTM ID configuration process 392.

[0084] 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.

[0085] 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, similar to events 316 and 318, CU 172 sends a second RRC reconfiguration message including the LTM reference configuration to UE 102 via DU 174. In response, similar to events 320 and 322, UE 102 sends a second RRC reconfiguration complete message to CU 172 via DU 174. 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.

[0086] 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 a 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.

[0087] 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, in events similar to 320 and 322, UE 102 sends a third RRC reconfiguration completion message to CU 172 via DU 174.

[0088] In some implementations, CU 172 includes the CSI resource configuration in the first, second, or third RRC reconfiguration message. In other implementations, similar to events 316 and 318, CU 172 sends a fourth RRC reconfiguration message including the CSI resource configuration to UE 102 via DU 174. In response, similar to events 320 and 322, UE 102 sends a fourth RRC reconfiguration complete message to CU 172 via DU 174.

[0089] In some implementations, DU 174 sends a DU-CU message to CU 172, including early synchronization information for UE 102. The DU-CU message can be a first DU-CU message, a second DU-CU message, or a fourth DU-CU message. In some implementations, DU 174 sends a fourth DU-CU message in response to receiving a fourth CU-DU message from CU 172. In other implementations, DU 174 sends a fourth DU-CU message in response to receiving a first CU-DU message or a second CU-DU message (e.g., ...). UE context modification requirementsIn one implementation, if DU 174 determines that UE 102 supports (i.e., is capable of) 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 that includes an early synchronization information request (e.g., IE), 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 CU172 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 a first RRC reconfiguration message, a second RRC reconfiguration message, a third RRC reconfiguration message, or a fourth RRC reconfiguration message. Alternatively, similar to events 316 and 318, CU 172 sends a fifth RRC reconfiguration message including the early synchronization information to UE 102 via DU 174. In response, similar to events 320 and 322, UE 102 sends a fifth RRC reconfiguration complete message to CU 172 via DU 174.

[0090] 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 in the DU-CU message (e.g., in the first DU-CU message, the second DU-CU message, or the fourth DU-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 the early synchronization information or in the DU-CU message.

[0091] In some implementations, CU 172 includes one or more other LTM-related configurations for the first cell in the first RRC reconfiguration message, the second RRC reconfiguration message, the third RRC reconfiguration message, the fourth RRC reconfiguration message, and / or the fifth RRC reconfiguration message. For example, other LTM-related configurations include the PCI of the first cell and / or the LTM SSB configuration.

[0092] 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 a second RRC reconfiguration message, a third RRC reconfiguration message, a fourth RRC reconfiguration message and / or a fifth RRC reconfiguration message, as well as a second RRC reconfiguration completion message, a third RRC reconfiguration completion message, a fourth RRC reconfiguration completion message and / or a fifth RRC reconfiguration completion message, related CU to DU messages and / or related DU to CU messages. In some implementations, the aforementioned RRC reconfiguration message and RRC reconfiguration completion message are respectively... RRCReconfiguration Messages and RRCReconfigurationComplete information.

[0093] 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 Message. In other implementations, the third CU to DU message is 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 UE context modification response information.

[0094] 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, while 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.

[0095] 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. MeasConfig IE and / or RadioBearerConfig IE, or LTM CU configuration 1 includes MeasConfig IE and / or RadioBearerConfig Configuration parameters in Internet Explorer.

[0096] 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, will include the configuration parameters in MeasConfig IE and / or RadioBearerConfig in IE.

[0097] 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.

[0098] In some implementations, LTM DU configuration 1 includes a first L1 measurement configuration (e.g., CSI-MeasConfigThe first L1 measurement configuration includes at least one first RS resource configuration and / or at least one first reporting configuration. In other implementations, 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-location (QCL) type. The DL RS is associated with cell 1.

[0099] 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 first RS and / or the transmission mode of the first RS are 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.

[0100] 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 the service DU configuration in event 302 and / or in one or more second CSI report configurations and / or one or more second CSI resource configurations included in the second service DU configuration. 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 LTM CSI resource configuration.

[0101] 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 an RA preamble index, a UL or supplementary UL indicator, an SSB index, and / or a 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 LTM ID 1 in the PDCCH command and sends a 352 RA preamble to DU 174 on the first cell using the PDCCH command information. Correspondingly, DU 174 receives the 352 RA preamble according to the PDCCH command information. In some implementations, DU 174 may determine the SSB index based on L1 measurement report 324, 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.

[0102] 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.

[0103] After sending a 324 L1 measurement report or a 352 RA preamble, similar to event 324, UE 102 may send a 354 additional L1 measurement report to DU 174. Based on the additional L1 measurement report and / or based on L1 measurement report 324, DU 174 determines a command for UE 102 to perform an LTM cell handover to the first cell. In response to this 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 this 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., 338) to CU 172, which includes an RRC reconfiguration completion message. UL RRC message transmission (Message). When UE 102 receives an LTM cell switching 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, in response to the LTM cell switching command, UE 102 may stop communicating on the serving cell. 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.

[0104] In some implementations, DU 174 includes a TA value in the LTM cell transition command for UL synchronization with the first cell. In one implementation, DU 174 derives the TA value based on an RA preamble (e.g., the timing of the RA preamble reception). In another implementation, DU 174 derives the TA value from a UL transmission from the serving cell (e.g., cell 124A) of UE 102. UE 102 applies the TA value to synchronize with the first cell in the UL transmission. After applying the TA value, UE 102 transmits a first UL transmission on the first cell based on LTM candidate configuration 1 without performing an RA procedure on the first cell. In some implementations, UE 102 transmits the first UL transmission on the first cell using UL authorization. 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 the configured grant configuration that configures 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 a PDCCH transmission addressed to UE 102's C-RNTI and determines that the LTM cell transition has been successfully completed in response to receiving the PDCCH transmission.

[0105] PDCCH transmissions may include UL grants or DL ​​assignments. If the 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 the PDCCH transmission includes a DL assignment, DU 174 sends a PDSCH transmission to UE 102 on the first cell according to the DL assignment. After receiving a first UL transmission, sending a PDCCH transmission, receiving a PUSH transmission, or sending a PDSCH transmission (e.g., in response to receiving a first UL transmission, sending a PDCCH transmission, receiving a PUSH transmission, or sending a PDSCH transmission), DU 174 may send an Access Success Message 334 to CU 172.

[0106] 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 or in LTM DU configuration 1. In some implementations, the RA configuration parameters configure the association between PRACH resources, 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. During a four-step RA procedure, in response, UE 102 sends message 3 on the first cell, and DU 174 sends message 4 to UE 102 on the first cell. During the two-step RA procedure, in response, UE 102 sends message A on the first cell, and DU 174 sends message B to UE 102 on the first cell. UE 102 may include an RRC reconfiguration complete message 336 in message 3 or message A. Alternatively, UE 102 sends an RRC reconfiguration complete message 336 after completing the RA procedure. After receiving message 3, message A, or 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.

[0107] 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.

[0108] In some implementations, each TCI state configuration in the TCI state configuration includes a TCI state ID. In some implementations, DU 174 includes a first TCI state ID in the LTM cell handover command, indicating a first TCI state configuration in the TCI state configuration. In events 332, 336, and / or 340, UE 102 identifies the first TCI state configuration in the TCI state configuration based on the first TCI state ID and applies the first TCI state configuration to transmit UL and / or DL ​​transmissions with DU 174. In events 332, 336, and / or 340, DU 174 applies the first TCI state configuration to transmit UL and / or DL ​​transmissions with UE 102.

[0109] In some implementations, before or after sending the LTM cell switching command, or during or after procedures 390 or 392, CU 172 may utilize DU 174 to prepare additional cells (i.e., cells 2, ..., N) as LTM candidate cells for UE 102, as described above. N is an integer greater than 1. For example, CU 172 performs additional LTM preparation procedures 2, ..., N with DU 174 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 for LTM, respectively. CU 172 generates LTM candidate configurations 2, ..., N, respectively, 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 obtain CSI resource configurations 2, ..., N and execute CSI report configuration and / or LTM ID configuration procedures 2, ..., N with DU 174 to obtain CSI report configurations 2, ..., N respectively, as described for CSI resource configuration 1 and CSI report configuration 1. CU 172 can obtain RACH configurations 2, ..., N for cells 2, ..., N respectively, as described for RACH configuration 1. CU 172 can obtain TCI status configurations 2, ..., N for cells 2, ..., N respectively, as described for TCI status configuration 1. Each of the CSI report configuration and / or LTM ID configuration procedures 2, ..., N is similar to procedure 392. CU 172 can obtain LTM SSB configurations 2, ..., N for cells 2, ..., N respectively, as described for LTM SSB configuration 1. In some implementations, CU 172 may execute LTM configuration delivery procedures 2, ..., N with UE 102 to send to UE 102 a list 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.

[0110] In some implementations, after receiving the 334 Access Success Message or the 338 DU to CU Message, CU 172 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 LTM candidate cells from 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.

[0111] In some implementations, the LTM ID is provided in different formats depending on which command or message provides it. For example, the LTM ID may be provided differently in a PDCCH command, an LTM cell switching command, and an RRC reconfiguration message. For instance, a PDCCH command or LTM cell switching 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 code processing 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.

[0112] Events 304, 306, 390, 392, 394, and 324 are in Figure 3 This is collectively referred to as the 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 in... Figure 3 This is collectively referred to as the CU-internal DU-internal LTM process 380.

[0113] Next reference Figure 4 In scenario 400, base station 104 includes CU 172, S-DU 174A, and candidate DU (C-DU) 174B. S-DU 174A operates cell 124A (… Figure 1A It can optionally operate additional cells, while C-DU 174B operates the first cell (e.g., cell 126). Scenario 400 is an intra-CU inter-DU scenario, similar to scenario 300. Therefore, the description for scenario 300 can generally be applied to scenario 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.

[0114] Initially, UE 102 uses the serving DU configuration to communicate with S-DU 174A on one or more serving cells (e.g., cell 124A and / or other cells) 402, and UE 102 uses the serving CU configuration to communicate 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 above. In the case of process 480, as referenced... Figure 3The UE 102 may perform an LTM cell transition to a first cell (e.g., cell 124B). After a successful LTM cell transition, the first cell becomes the serving cell, and cell 124A and / or other cells cease to be the serving cells of UE 102. In the case of procedure 496, UE 102 does not perform an LTM cell transition. 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 cell 1 (e.g., cell 126 operated by C-DU 174B) to be prepared for LTM by UE 102. Cell 1 is identified by a cell ID (i.e., cell ID 1). In response to this determination, CU 172 performs step 490 of the LTM preparation procedure with C-DU 174B 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, requesting C-DU 174B to prepare cell 1 as an LTM candidate cell for UE 102, similar to event 385. 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 the LTM reference DU configuration in the first CU-DU message, such as reference... Figure 3 As described above. In other implementations, CU 172 does not request the LTM reference DU configuration in the first CU-DU message. In some implementations, C-DU 174B includes the LTM reference DU configuration in the first DU-CU message, such as reference... Figure 3 As described above. In other implementations, the C-DU 174B does not include the LTM reference DU configuration in the first DU to CU message.

[0115] In some implementations, if CU 172 receives LTM reference DU configuration from S-DU 174A, such as reference... Figure 3 As described above, CU 172 may include an LTM reference DU configuration in the first CU to DU message, and C-DU 174B may 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 for 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 to CU message or as a reference Figure 3The additional DU is received in the CU message. In this case, 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. In other implementations, CU 172 does not include the LTM reference CU configuration in the LTM reference configuration.

[0116] To prepare cell 1 for LTM, CU 172 can execute procedure 492 with S-DU 174A for LTM CSI report configuration and / or LTM ID configuration. 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 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 above. In some implementations, CU 172 includes {LTM ID 1, Cell ID 1} as a tuple in the second CU to DU message.

[0117] 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 a DU-CU message (e.g., a first DU-CU message or an additional DU-CU message). In some implementations, C-DU 174B sends an additional DU-CU message in response to receiving an additional CU-DU message from CU 172. In other implementations, C-DU 174B sends an additional DU-CU message in response to receiving a first CU-DU message (e.g., ...). UE context modification requirements Message). 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), as referenced. Figure 3 As described above. In some implementations, the C-DU 174B includes PDCCH command information (PDCCH command information 1) for early UL synchronization with the first cell in the early synchronization information or in the DU to CU message.

[0118] 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 a first DU-to-CU message or in an additional DU-to-CU message. In some implementations, CU 172 can receive the PCI of cell 1 from C-DU 174B in a first DU-to-CU message or in an additional DU-to-CU message. In some implementations, C-DU 174B sends an additional DU-to-CU message in response to receiving the additional DU-to-CU 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).

[0119] 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, in procedure 494, CU 172 sends {LTM ID, LTM candidate configuration} as a tuple in the first RRC reconfiguration message. 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 The CU 172 includes an LTM ID in the first RRC reconfiguration message 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, the 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, the 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 RRC reconfiguration message in the other RRC reconfiguration messages, the UE 102 sends an RRC reconfiguration complete message to the CU 172 via the S-DU 174A.

[0120] In some implementations, the PDCCH command information includes frequency domain resource assignment, RA preamble index, UL 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 PDCCH command information. For example, the S-DU 174A sends a 450 PDCCH command to UE 102 including PDCCH command information. In some implementations, the S-DU 174A may determine the SSB index 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 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 PDCCH command information. C-DU 174B derives the TA value based on the RA preamble. C-DU 174B sends a DU-CU TA information transmission message (456) including the TA value to CU 172. CU 172 then sends a CU-DU TA information transmission message (458) including the TA value to S-DU174A. In some implementations, C-DU 174B includes cell ID 1, RA preamble index, RA radio network temporary identifier (RA-RNTI), and / or S-DU 174A's DUID in message 456. In such cases, CU 172 includes cell ID 1, RA preamble index, RA-RNTI, and / or S-DU174A's DU ID 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, the S-DU 174A can include the TA value in the LTM cell transition command. The S-DU 174A can also include the first TCI state ID in the LTM cell transition command. The first TCI state ID indicates the first TCI state configuration in the TCI state configuration.

[0121] In some implementations, the C-DU 174B determines the RA-RNTI based on the PRACH timing of the 452 RA preamble received by the C-DU 174B. In some implementations, the C-DU 174B calculates the RA-RNTI as follows:

[0122] RA-RNTI = 1 + s_id + 14 × t_id + 14 × 80 × f_id + 14 × 80 × 8 ×ul_carrier_id

[0123] 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 values ​​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 carriers and 1 for SUL carriers).

[0124] In response to the confirmation command UE 102 to perform LTM cell handover or send LTM cell handover command 426, S-DU174A sends command 428 to CU 172. DU-CU Cell Switching Notice The message instructs UE 102 to perform an LTM cell handover to cell 1. In response, CU 172 sends a 430 message to C-DU 174B. CU-DU Cell Switching Notice The message instructs UE 102 to perform an LTM cell handover to cell 1. In some implementations, the S-DU 174A... DU-CU Cell Switching Notice The message includes the first TCI status ID, and CU 172 then... CU-DU Cell Switching NoticeThe message includes a first TCI state ID. In events 432, 436, and / or 440, UE 102 and C-DU 174B identify the first TC state configuration in the TC state configuration based on the first TCI state ID, and apply the first TCI state configuration to transmit UL and / or DL ​​transmissions.

[0125] In some implementations, each TCI state configuration in the TCI state configuration includes a TCI state ID or is associated with that 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 LTM ID 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 to CU 172 in response. In some implementations, the S-DU 174A includes a first TCI state ID in the LTM cell transition command 426, indicating a first TCI state configuration in the TCI state configuration. In some implementations, the S-DU 174A determines either the first TCI state configuration or the first TCI state ID. In events 432, 436, and / or 440, the UE 102 identifies a TCI state configuration in the TCI state configuration based on the first TCI state ID and applies the first TCI state configuration in UL transmission and / or DL ​​reception.

[0126] In some implementations, before or after sending the LTM cell switching command, or during or after procedures 490 or 492, CU 172 may use C-DU 174B to prepare additional cells (i.e., cells 2, ..., N) as LTM candidate cells for UE102, as shown in reference [reference]. Figure 3 As described.

[0127] 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 can be... UE Context Modification Request Messages and UE context modification responseIn 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.

[0128] Events 404, 406, 490, 492, 494, and 424 are in Figure 4 This is collectively referred to as the CU-DU inter-LTM configuration process 496. Events 404, 406, 490, 492, 494, 494, 424, 450, 452, 454, 456, 458, 426, 428, 430, 432, 434, 436, 438, 440, 442, and 444 are in... Figure 4 This is collectively referred to as the LTM process between CU and DU.480.

[0129] Next reference Figure 5 In scenario 500, base station 104 operates as a serving or source base station (S-BS), and base station 106 operates as a candidate base station (C-BS). C-BS 106 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). Similar to... Figure 3 and Figure 4 The base station 104 shown in the figure, S-BS 104 may include CU and DU ( Figure 5 (Not shown in the image). Initially, UE102 communicates with S-BS 104 via the serving cell using the service configuration 502. In some implementations, S-BS 104 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. During communication 502 with UE 102, S-BS 104 may perform an in-CU LTM procedure 580 with UE 102, similar to procedures 380 and / or 480. Alternatively, during communication 502 with UE 102, S-BS 104 may perform an in-CU LTM configuration procedure 596 with UE 102, similar to procedures 396 and / or 496.

[0130] When communicating with S-BS 104, UE 102 sends at least one measurement report (504) to S-BS 104. The measurement report includes information about the serving cell and / or at least one non-serving cell (e.g., cell 126) for UE 102. Figure 1AThe S-BS 104 uses the measurement report to determine which first cell (e.g., cell 126) is 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 of cell 126. The S-BS 104 uses the PCI to identify the first cell operated by base station 106 and uses the measurement results to determine whether the first cell is eligible for LTM preparation.

[0131] After determining that a first cell is to be prepared as an LTM candidate cell for UE 102 (e.g., in response to preparing a first cell as an LTM candidate cell for UE 102), S-BS 104 (e.g., the CU of S-BS 104) generates a first cell ID (i.e., cell ID 1) including the first cell (i.e., cell 1). Switching requests Message. S-BS 104 sends 505 to CU 172. Switching requests Message. In some implementations, Switching requests The message includes instructions Switching requests The message contains an LTM indicator for the LTM used for the first cell ID. Upon receiving... Switching requests After the message (e.g., in response to receiving) Switching requests In the event of event 385, CU 172 and DU 174 execute 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 385. 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). Switching requests Message 507 from CU 172 to S-BS 104, including the first LTM candidate configuration. Switch request confirmation Message. In some implementations, CU 172 in Switch request confirmation The message includes a first cell ID to indicate that a first LTM candidate configuration is provided for or associated with the first cell (ID).

[0132] 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) 598.

[0133] In some implementations, Switching requestsThe message includes the DU ID of the S-DU from S-BS 104. In such cases, CU 172 includes the DU ID in the first CU-DU message. In some implementations, Switching requests The message includes the BS ID of S-BS 104. When the BS ID is received, CU 172 may include the BS ID in the first CU to DU message. For example, the BS ID may be the gNB ID.

[0134] 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 procedure 590. In some implementations, DU 174 sends the LTM reference DU configuration to CU 172 in procedure 590, as 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 process 590. In some implementations, S-BS 104 (e.g., the CU of S-BS 104) can obtain the LTM reference configuration, such as reference Figure 3 and Figure 4 As described. In other implementations, S-BS 104 can be transferred from another BS during another CU-to-CU LTM preparation process, as described above and later herein. Figure 5 (Not shown in the image) Receives the LTM reference configuration. If the S-BS 104 obtains the LTM reference configuration, the S-BS 104 can... Switching requests The message includes the LTM reference configuration (the LTM reference configuration generated by S-BS). In some implementations, S-BS 104 includes the LTM reference configuration in the inter-node RRC message. HandoverPreparationInformation In, or include as an Xn Application Protocol (XnAP) IE or field, and include inter-node RRC messages or XnAP IEs. Switching requests In the message. Alternatively, S-BS 104 determines the request or causes C-BS 106 to provide a complete LTM candidate configuration, in which case S-BS 104 in Please switch beg The message does not include the LTM reference configuration. If the S-BS 104 does not obtain the LTM reference configuration, then the S-BS 104 is not... Switch ask The message includes the LTM reference configuration. If Switching requestsIf the message includes an LTM reference configuration, then 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 Alternatively, DU 174 can ignore the LTM reference (DU) configuration and generate an LTM DU configuration as the complete configuration, as described above. Figure 3 As stated above.

[0135] Otherwise, if Switching requests In some implementations, the CU 172 receives the LTM reference DU configuration from the DU 174, such as the reference DU configuration. Figure 3 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 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 from DU 174, as in the reference... Figure 3 In this case, CU 172 does not generate an LTM reference configuration. Instead, CU 172 generates an LTM reference configuration (C-BS 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-BS generated LTM reference configuration), CU 172 includes the C-BS generated LTM reference configuration in... Switch request confirmation In the message.

[0136] 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 can... Switch request confirmationThe message includes a full configuration indication (e.g., the BS-to-BS interface protocol field / IE) to indicate that LTM candidate configuration 1 is a full 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 full configuration indication is a dedicated field / IE (e.g., LTM-specific) used to reduce or eliminate the impact on non-LTM configurations. In other implementations, the full 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... Switch request confirmation The message excludes the full configuration indication to indicate that LTM candidate configuration 1 is an incremental configuration. Alternatively, CU 172 can... Switch request confirmation The message includes an incremental configuration indication (e.g., a BS-to-BS interface protocol field / IE) 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) used 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 at least two possible values ​​(i.e., a first value and a second value). The BS-to-BS interface protocol field / IE can have a first value to indicate a complete configuration, while the BS-to-BS interface protocol field / IE can have a second value to indicate an incremental configuration.

[0137] In some implementations, for the first cell, the S-BS 104 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). In other implementations, the S-BS 104 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 104 receives the CSI resource configuration and / or LTM SSB configuration from the CU 172. For example, the CU 172 in... Please switch Please confirm. The message includes CSI resource configuration and / or LTM SSB configuration. In some implementations, CU 172 in Switching requests confirmThe message includes the PCI (PCI 1) of the first cell. To prepare the first cell as a candidate LTM cell for UE 102, the CU and S-DU of S-BS 104 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-BS 104 sends the CSI resource configuration and / or LTM SSB configuration to the S-DU of S-BS 104. In response, the CU of S-BS 104 receives one or more CSI report configurations for UE 102 from the S-DU of S-BS 104. In some implementations, the CU of S-BS 104 receives the CSI report configuration from the second service DU configuration of the S-DU.

[0138] To prepare a first cell as an LTM candidate cell for UE 102, CU 172 can receive early synchronization information (e.g., early synchronization information 1) for 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 requirements (Message). CU 172 in Switch request confirmation The message includes early synchronization information. This 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). In some implementations, DU 174 includes PDCCH command information for early UL synchronization with the first cell in the early synchronization information or in the DU-to-CU message. CU 172 in Switch request confirmation The message includes PDCCH command information.

[0139] In some implementations, CU 172 assigns an LTM ID (e.g., LTMID 1) to identify the first LTM candidate configuration, and in Switch request confirmation The message includes an LTM ID. In other implementations, S-BS 104 assigns an LTM ID (e.g., LTM ID 1) to identify the first LTM candidate configuration.

[0140] Received Switch request confirmationFollowing the message (e.g., in response to receiving a handover request confirmation message), S-BS104 (e.g., the CU of S-BS104) sends a first RRC reconfiguration message 518 to UE 102, including {LTM ID1, LTM candidate configuration1} as tuples, similar to event 318. If Switch request confirmation If the message includes the LTM reference configuration, then S-BS 104 can include the LTM reference configuration in the first RRC reconfiguration message. If S-BS 104 in Switch request confirmation Upon receiving this information in the message, S-BS 104 may include CSI Resource Configuration 1, TCI State Configuration 1, RACH Configuration 1, and / or LTM SSB Configuration 1 in the tuple. Alternatively, S-BS 104 sends one or more additional RRC reconfiguration messages to 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 additional RRC reconfiguration message, S-BS 104 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. UE 102 responds to the first RRC reconfiguration message by sending a 520 First RRC Reconfiguration Complete Message to S-BS 104. In response to each RRC reconfiguration completion message in the supplementary RRC reconfiguration completion messages, UE 102 sends an additional RRC reconfiguration completion message to S-BS 104. The RRC reconfiguration messages (i.e., the first RRC reconfiguration message and / or the supplementary RRC reconfiguration messages) and the RRC reconfiguration completion messages (i.e., the first RRC reconfiguration completion message and / or the supplementary RRC reconfiguration completion messages) form the LTM configuration delivery process. S-BS 104 may include the second service DU configuration in the first RRC reconfiguration message or in one of the supplementary RRC reconfiguration messages.

[0141] In some implementations, if Switch request confirmation If the message includes a full configuration indication to indicate that LTM candidate configuration 1 is a full configuration, then S-BS 104 includes a 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 Switch request confirmation The message does not include a complete configuration instruction (or if) Switch request confirmation If the message includes an incremental configuration indication to indicate that LTM candidate configuration 1 is an incremental configuration, then S-BS104 indicates that LTM candidate configuration 1 is an incremental configuration by excluding the complete configuration indication (e.g., the RRC field / IE) from the first RRC reconfiguration message.

[0142] if Switch request confirmation If the message includes PDCCH command information (PDCCH command information 1), then S-BS 104 sends a 550 PDCCH command based on the PDCCH command information. If S-BS 104 is a distributed base station, then the CU of S-BS 104 can send the PDCCH command information to the S-DU of S-BS 104. For example, S-BS 104 or its S-DU sends a 550 PDCCH command including the PDCCH command information to UE 102. In some implementations, S-BS 104 or its S-DU can determine the SSB index 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, S-DU or S-BS 104 includes LTM ID 1 in the PDCCH 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 104 derives the TA value based on the RA preamble. DU 174 then sends a 556 RA preamble containing the TA value to CU 172. DU-CU TA information transmission Message. CU 172 sends a CU-CU TA information transmission message 558, including the TA value, to S-BS 104 (e.g., the CU of S-BS 104). In some implementations, DU 174 includes cell ID 1, RA preamble index, RA-RNTI, DU ID of S-DU of S-BS 104, and / or BS ID of S-BS 104 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 104 in message 558. In some implementations, CU 172 does not include the BS ID in message 558. The CU of S-BS 104 sends the following information to the S-DU of S-BS 104: 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-BS 104. CU-DU TA Information Transmission Message. In some implementations, the S-BS 104's CU is in CU-DU TA Information Transmission The message does not include the BS ID.

[0143] In some implementations, CU 172 determines the address (e.g., IP address) of S-BS 104 or its CU based on the BS ID of S-BS 104. In other implementations, CU 172 determines the address (e.g., IP address) of S-BS 104 or its CU based on the DU ID of S-DU of S-BS 104. Using these implementations, CU 172 sends data to S-BS 104 or its CU based on the address. CU-CU TA Information Transmission information.

[0144] In response to, for example, determining a command for UE 102 to perform an LTM cell switch to a first cell based on measurement reports 524 and / or 554, S-DU or S-BS 104 sends an LTM cell switch command 526, including LTM ID 1 (e.g., a configuration identifier), to UE 102. In response to the LTM cell switch command, UE 102 may cease communication on the serving cell. In response to the LTM cell switch 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 106 communicates with UE 102 540 according to a 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 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... Connection successful When the message receives the first cell ID 534, CU 172 identifies the first LTM candidate configuration and / or LTM reference configuration based on the first cell ID and associated information.

[0145] In some implementations, if the S-DU or S-BS 104 receives a TA value, as described above, the S-DU or S-BS 104 may include the TA value in the LTM cell handover command. In some implementations, the S-DU or S-BS 104 includes a first TCI state ID in the LTM cell handover command. The first TCI state ID indicates the first TCI state configuration in the TCI state configuration.

[0146] In response to the determination command UE 102 to perform LTM cell handover or subsequently send LTM cell handover command 526, the S-DU of S-BS 104 sends to the CU of S-BS 104. DU-CU Cell Switching Notice The message instructs UE 102 to perform or be performing an LTM cell handover to the first cell. In response to receiving... DU-CU Cell Switching Notice Message: CU on S-BS 104 sends 527 to CU 172 CU-CU Cell Switching 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 Switching Notice The message instructs UE 102 to perform an LTM cell handover to the first cell. In some implementations, S-BS 104... CU-CU Cell Switching Notification The message includes the first TCI status ID, and CU 172 then... CU-DU Cell Switching Notice The message includes a first TCI state ID. In events 532, 536, and / or 540, UE 102 and DU 174 identify the first TC state configuration in the TC state configuration based on the first TCI state ID, and UE 102 and DU 174 apply the first TCI state configuration to transmit UL transmissions and / or DL ​​transmissions.

[0147] In some implementations, the UE 102 determines whether to execute an LTM cell handover, send an LTM cell handover command (526), ​​or receive a command (527). DU-CU Cell Switching Notice Following the message (e.g., in response to command UE 102 to perform LTM cell switching, sending LTM cell switching command 526, or receiving LTM cell switching command 527), DU-CU Cell Switching Notice Message), S-BS 104 (e.g., the CU of S-BS 104) sends one or more 531 messages to CU 172. Early state transfer Each early state transmission message includes the DL count value of the DRB used by UE 102 and S-BS 104 to transmit 502 data to each other, or the discarded DL count value. 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 104 (e.g., the CU of S-BS 104) to indicate that the LTM cell transition was successfully completed. In some implementations, the LTM success message is... Switching successful 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 104 (e.g., the CU of S-BS 104) to indicate that the LTM cell transition has been successfully completed.

[0148] In some implementations, after determining that UE 102 should perform an LTM cell switch, sending the 526 LTM cell switch command, receiving the 527 DU-CU cell switch notification message, or receiving the 539 LTM success message (e.g., in response to determining that UE 102 should perform an LTM cell switch, sending the 526 LTM cell switch command, receiving the 527 DU-CU cell switch notification message, or receiving the 539 LTM success message), DU-CU Cell Switching Notice Upon receiving a 539 LTM success message, S-BS 104 (e.g., the CU of S-BS 104) sends 541 to CU 172. SN status transfer The SN status transmission message includes the DL count value and / or UL count value of the DRB used by UE 102 and S-BS 104 to transmit 502 data to each other.

[0149] In some implementations, when receiving 534 Connection successful Message, receive 538 DU to CU message or RRC reconfiguration complete message or receive 541 SN status transfer Following the message (e.g., in response to receiving a 534 access success message, a 538 DU to CU message, an RRC reconfiguration complete message, or a 541 SN status transmission message), CU 172 sends 543 to S-BS 104. UE context release Message. Response to UE context release The message indicates that S-BS 104 is releasing the UE context of UE 102.

[0150] In some implementations, before or after sending the LTM cell transition command, or during or after procedure 598, S-BS 104 (e.g., the CU of S-BS 104) may utilize CU 172 to prepare additional cells (i.e., cells 2, ..., N) as LTM candidate cells for UE 102, 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 C-BS 106. N is an integer greater than 1. For example, S-BS 104 performs additional inter-CU LTM preparation procedures 2, ..., N with CU 172 to prepare cells 2, ..., N. Each of the inter-CU LTM preparation procedures 2, ..., N is similar to procedure 598. In the inter-CU LTM preparation procedures 2, ..., N, S-BS 104 receives LTM candidate configurations 2, ..., N for LTM, respectively. As described above, S-BS 104 or C-BS 106 assigns LTM IDs 2, ..., N to identify LTM candidate configurations 2, ..., N, respectively. S-BS 104 can obtain CSI resource configurations 2, ..., N for cells 2, ..., N, as described for CSI resource configuration 1. S-BS 104 can obtain CSI reporting configurations 2, ..., N for cells 2, ..., N, as described for CSI reporting configuration 1. S-BS 104 can obtain RACH configurations 2, ..., N for cells 2, ..., N, as described for RACH configuration 1. S-BS 104 can obtain TCI status configurations 2, ..., N for cells 2, ..., N, as described for TCI status configuration 1. S-BS 104 can obtain LTM SSB configurations 2, ..., N for cells 2, ..., N, as described for LTM SSB configuration 1. S-BS 104 can obtain PCI 2, ..., N for cells 2, ..., N, as described for PCI 1. In some implementations, S-BS 104 can perform LTM configuration delivery procedures 2, ..., N with UE 102 to send the following lists to UE 102 respectively: {LTMID 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 procedures 394 and / or 494. In other implementations, S-BS104 includes a list in the first RRC reconfiguration message.

[0151] In other implementations, S-BS 104 performs the same process 598 as CU 172 to prepare one or more cells from cell 1, ..., N as LTM candidate cells for UE 102. In this type of implementation, S-BS 104 uses LTM... Switching requests Message 505 includes cell ID 1, ..., N, as described for cell ID 1. In some implementations, upon receiving... Switching requests 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... Switching requests The message requests the preparation of cells 1, ..., N for LTM. CU 172 performs LTM preparation procedures 2, ..., M with DU 174 to prepare cells 2, ..., M as LTM candidate cells for UE 102. 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 result of LTM preparation procedures 2, ..., M, similar to obtaining LTM candidate configuration 1. C-BS 106 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 in Switch request confirmation The message includes LTM candidate configurations 2, ..., M. In some implementations, CU172 or S-BS 104 assigns LTM IDs 2, ..., M to identify LTM preparation processes 2, ..., M respectively, as described for LTM ID 1. When CU 172 assigns LTM IDs 1, ..., M, CU 172... Switch request confirmation The messages include LTM ID1, ..., M and LTM candidate configuration 1, ..., M, as described in references to LTM ID1 and LTM candidate configuration 1.

[0152] In some implementations, CU 172 obtains early synchronization information 2, ..., M for cells 2, ..., M respectively, as described with reference to early synchronization information 1. CU 172 in Switch request confirmationThe message includes early synchronization information 2, ..., M. In some implementations, CU 172 or S-BS 104 obtains CSI resource configurations 2, ..., M for cells 2, ..., M, respectively, as described with reference to CSI resource configuration 1. When CU 172 obtains CSI resource configurations 2, ..., M, CU 172... Switch request confirmation The message includes CSI resource configuration 2, ..., M.

[0153] In some implementations, CU 172 or S-BS 104 obtains LTM SSB configurations 2, ..., M for cells 2, ..., M, respectively, as described with reference to LTM SSB configuration 1. When CU 172 obtains LTM SSB configurations 2, ..., M, CU 172... Switch request confirmation The message includes LTM SSB configuration 2, ..., M. In some implementations, CU 172 or S-BS 104 obtains PCI 2, ..., M for cell 2, as described in PCI 1. When CU 172 obtains PCI 2, ..., M, CU 172... Switch request confirmation The message includes PCI 2, ..., M.

[0154] In some implementations, CU 172 is... Switch request confirmation The message includes a list containing the following: {Cell ID 1, LTM ID 1 (if available or optional), LTM candidate configuration 1, CSI resource configuration 1 (if available or optional), TCI status configuration 1 (if available or optional), early synchronization information 1 (if available or optional), LTM SSB configuration 1 (if available or optional), PCI 1 (if available or optional)}, ..., {Cell ID M, LTM ID M (if available or optional), LTM candidate configuration M, CSI resource configuration M (if available or optional), TCI status configuration M (if available or optional), early synchronization information M (if available or optional), LTM SSB configuration M (if available or optional), PCI M (if available or optional)}.

[0155] In some implementations, CU 172 obtains PDCCH command information 2, ..., M for cells 2, ..., M respectively, as described for PDCCH command information 1. In one implementation, CU 172 in Switch request confirmationThe message includes PDCCH command information 2, ..., M. In another implementation, CU 172 includes PDCCH command information 2, ..., M in the early synchronization information 2, ..., M respectively. S-BS 104 can retrieve the early synchronization information 2, ..., M or from... Switch request confirmation The message obtains 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.

[0156] In some implementations, S-BS 104 may execute LTM configuration delivery procedures 2, ..., M with UE 102 to send a list to UE 102 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 104 includes the list in the first RRC reconfiguration message.

[0157] In some implementations, S-BS 104 can... Switching requests The message includes measurement results 1, ..., N for cells 1, ..., N. S-BS 104 receives the measurement results from UE 102. C-BS 106 can select or determine cells 1, ..., M based on measurement results 1, ..., N. In other implementations, C-BS 106 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 of LTM candidate cells is included... Switching requests The message states that in another implementation, the maximum number of LTM candidate cells is a predetermined number.

[0158] Next, refer to Figures 6A to 16 Several example methods for implementing inter-CU LTM in RAN nodes (e.g., base stations, DUs, or CUs) are discussed. References Figures 3 to 5 The provided description may be applicable Figures 6A to 16 Generally speaking, Figures 6A to 17Similar events in the figures are labeled with similar reference numerals that share two least significant digits, and differences are discussed where appropriate. For example, event 302 is similar to event 602. Apart from the differences shown in the figures and discussed below, any other implementations of the other implementations discussed for specific events (e.g., those used for messaging and processing) can be applied to other events labeled with similar reference numerals in the figures.

[0159] Figure 6A It can be generated by the first base station (BS) (for example, Figure 5 The flowchart shows an example method 600A implemented by S-BS 104. Method 600A begins at block 602, where the first BS communicates with the UE using a service configuration. In block 605A, the first BS sends a first... Switching requests The message configures the first cell for LTM. For example, the second BS is... Figure 5 C-BS 106 in block 607A. In block 607A, the first BS receives from the second BS a first LTM candidate configuration and an LTM reference configuration. Switch request confirmation In box 617, the first BS generates a first RRC message including a first LTM candidate configuration and an LTM reference configuration. In box 618, the first BS sends the first RRC message to the UE. In box 675, the first BS sends a second RRC message including the LTM reference configuration to the third BS. Please switch beg The message is used to configure a second cell for LTM (e.g., event 505). In box 677, the first BS receives a second LTM candidate configuration from the third BS. Switch request confirmation Message (e.g., event 507). In box 687, the first BS generates a second RRC message including a second LTM candidate configuration. In box 688, the first BS sends the second RRC message to the UE (e.g., event 518).

[0160] Figure 6B This is a flowchart of an example method 600B, similar to method 600A, except that method 600B includes blocks 660, 605B, and 607B instead of blocks 605A and 607A. In block 660, the first BS generates an LTM reference configuration. In block 605B, the first BS sends a first LTM reference configuration to a second BS. Switching requests The message is used to configure the first cell for LTM. In box 607B, the first BS receives a first LTM candidate configuration from the second BS. Switch request confirmation information.

[0161] Figure 7 This shows that it can be generated by S-BS (e.g., Figure 5Example method 700 is implemented by the CU of the S-BS 104. Method 700 begins at block 702, where the CU communicates with the UE via the S-DU. At block 708, the CU sends a CU-DU message to a first DU. At block 710, the CU receives a DU-CU message from the first DU including an LTM reference DU configuration. At block 760, the CU generates an LTM reference configuration including the LTM reference DU configuration. The process proceeds to blocks 605B, 607B, and 617. At block 718, the CU sends a first RRC message to the UE via the S-DU. The process proceeds to blocks 675, 677, and 687. At block 788, the CU sends a second RRC message to the UE via the S-DU (e.g., event 518).

[0162] Figure 8A It shows that it can be generated by the first BS (e.g., Figure 5 Example method 800A is implemented using C-BS 106. Method 800A begins at block 805A, where the first BS receives data from the second BS. Switching requests The message requests that a first cell be prepared for the UE as an LTM candidate cell, in which... Switching requests The message includes the LTM reference configuration. For example, the second BS is... Figure 5 S-BS 104 in block 864. In block 864, the first BS generates a first LTM candidate configuration based on the LTM reference configuration. In block 807A, the first BS sends a configuration including the first LTM candidate configuration to the second BS. Switch request confirmation Message. In box 827, the first BS receives from the second BS. CU-CU cell switching notify Message. In box 831, the first BS receives from the second BS. Early state transfer In box 832, the first BS detects that the UE has accessed the first cell. In box 839, the first BS sends an LTM success message to the second BS. In box 841, the first BS receives a message from the second BS. SN Status transfer Message. In frame 840, the first BS communicates with the UE via the first cell.

[0163] Figure 8B This is a flowchart of an example method 800B, similar to method 800A, except that method 800B includes boxes 805B, 862, and 807B instead of boxes 805A and 807A. In box 805B, the first BS receives from the second BS. Switching requests The message requests the preparation of a first cell as an LTM candidate cell for the UE. In box 862, the first BS generates an LTM reference configuration. In box 807B, the first BS sends a message to the second BS including the first LTM candidate configuration and the LTM reference configuration. Switch request confirmation information.

[0164] Figure 9AIt shows that it can be generated by the first BS (e.g., Figure 5 Example method 900A is implemented by the CU of C-BS 106. Method 900A begins at block 905A. In block 908A, the CU sends a CU-DU message including an LTM reference configuration to the DU to request preparation of a first cell for LTM. In some implementations, the CU avoids requesting the DU to provide an LTM reference DU configuration. In block 910A, the CU receives a DU-CU message from the DU including a first LTM DU configuration. In block 913, the CU generates a first LTM candidate configuration including the first LTM DU configuration. The process proceeds to block 907A, and then to blocks 827, 831, 934, 839, 841, and / or 940. In block 934, the CU receives an access success message from the DU indicating that the UE has (successfully) accessed the first cell. In block 940, the CU communicates with the UE via the DU and the first cell.

[0165] Figure 9B This is a flowchart of an example method 900B, similar to method 900A, except that method 900B includes blocks 805B, 908B, 910B, 915, and 807B instead of blocks 905A, 908A, 910A, and 907A. In block 908B, the CU sends a CU-DU message to the DU to request preparation of a first cell for LTM. In block 910B, the CU receives a DU-CU message from the DU including an LTM reference DU configuration and a first LTM DU configuration. In block 913, the CU generates a first LTM candidate configuration including the first LTM DU configuration. In block 915, the CU generates a first LTM reference configuration including the LTM reference DU configuration. In block 907B, the CU sends a handover request confirmation message to the second BS including the first LTM candidate configuration and the LTM reference configuration.

[0166] Figure 9C This is a flowchart of an example method 900C, similar to method 900A, except that method 900C includes blocks 966 and 908C instead of block 908A. In block 966, the CU retrieves the LTM reference DU configuration from the LTM reference configuration. In block 908C, the CU sends a CU-DU message including the LTM reference DU configuration to the DU to request preparation of the first cell for LTM.

[0167] Figure 9DThis is a flowchart of example method 900D, similar to methods 900A and 900B, except that method 900D includes blocks 908D-1, 910D-1, 908D-2, and 910D-2 instead of blocks 908B and 910B. In block 908D-1, the CU sends a CU-DU message to the DU to request an LTM reference DU configuration. In block 910D-1, the CU receives a DU-CU message from the DU including the LTM reference DU configuration. In block 908D-2, the CU sends a CU-DU message to the DU to request preparation of a first cell for LTM. In block 910D-2, the CU receives a DU-CU message from the DU including a first LTM DU configuration. In some implementations, the CU includes the LTM reference DU configuration in the DU-CU message of block 908D-2. The DU can generate the first LTM DU configuration as an incremental configuration based on the LTM reference DU configuration.

[0168] Figure 10A It shows that it can be generated by the first BS (e.g., Figure 5 Example method 1000A is implemented by the CU of the C-BS 106. Method 1000A begins at box 1005, where the CU is implemented from the second BS (e.g., Figure 5 S-BS 104) receiving Switching requests The CU sends a message requesting the preparation of a cell for the UE. In box 1068, the CU includes the cell ID of the cell in the CU-DU message. In some implementations, Switching requests The message includes the cell ID. In box 1070, the CU is determined. Switching requests Does the message include the LTM reference configuration? If so... Switching requests If the message includes the LTM reference configuration (i.e., the "Yes" branch of box 1070), the process proceeds to box 1072. In box 1072, the CU includes the LTM reference configuration in the CU-DU message. The process then proceeds from box 1072 to box 1008. Otherwise, if the CU determines... Switch ask If the message does not include the LTM reference configuration (i.e., the "No" branch of box 1070), the process proceeds to box 1008. In box 1008, the CU sends a CU-DU message to the DU. In box 1010, the CU receives a DU-CU message from the DU including the DU configuration. In box 1011, the CU generates an RRC reconfiguration message including the DU configuration. In box 1007, the CU sends a message including the RRC reconfiguration message to the second BS. Switching requests confirm information.

[0169] In some implementations, the DU configuration is an LTM DU configuration. In one implementation, the LTM DU configuration is an incremental configuration based on the LTM reference DU configuration in the LTM reference configuration. In another implementation, the LTM DU is a complete configuration.

[0170] Figure 10B This is a flowchart of an example method 1000B, similar to method 1000A, except that method 1000B includes boxes 966 and 1073 instead of box 1072. If Switching requests If the message includes the LTM reference configuration (i.e., the "Yes" branch of box 1070), then the process proceeds to... Figure 9C Box 966 is described in section 1. The process proceeds from box 966 to box 1073. In box 1073, the C-CU includes the LTM reference DU configuration in the CU-DU message. The process proceeds from box 1073 to box 1008.

[0171] In some implementations, the DU configuration is an LTM DU configuration. In one implementation, the LTM DU configuration is an incremental configuration based on an LTM reference DU configuration. In another implementation, the LTM DU is a complete configuration.

[0172] Figure 11A This shows that it can be generated by a first base station (BS) (e.g., Figure 5 Example method 1100A is implemented by S-BS 104. Method 1100A begins at box 1102. In box 1174, the first BS initiates a handover preparation procedure to prepare the cell for the UE. In box 1176, the first BS determines whether to initiate a handover preparation procedure for LTM. If no handover preparation procedure is initiated for LTM (i.e., the "No" branch of box 1176), the process proceeds to box 1178. In box 1178, the first BS includes the service configuration in... Switch ask In the message. Otherwise, if a handover preparation process is initiated for LTM (i.e., the "Yes" branch of box 1176), the process proceeds to box 1182. In box 1182, the first BS avoids in Switching requests The message includes service configuration. In other words, if a handover preparation process is initiated for reasons related to LTM, the first BS will avoid [the process / event]. Switching requests The message includes service configuration. In box 1105, the first BS sends a message to the second BS. Switching requests Message. The process proceeds from boxes 1182 and 1178 to box 1105.

[0173] In some implementations, if a handover is initiated for LTM, the first BS is in Switching requests The message includes the LTM indicator.

[0174] Figure 11BThe flowchart is similar to that of Method 1100A, but Method 1100B includes box 1183 instead of box 1182. If a switchover preparation process is initiated for LTM (i.e., the "Yes" branch of block 1176), the process proceeds to box 1183. In box 1183, the first BS includes the LTM reference configuration. Switching requests The message indicates that the process proceeds from box 1183 to box 1105.

[0175] Figure 12 It shows that it can be generated by the first BS (e.g., Figure 5 Example method 1200 is implemented using C-BS 106. Method 1200 begins in boxes 1005 and 1070. If Switching requests If the message includes the LTM reference configuration (i.e., the "Yes" branch of box 1070), the process proceeds to box 1264. In box 1264, the first BS generates an LTM candidate configuration as an incremental configuration based on the LTM reference configuration. Otherwise, if the first BS determines... Switching requests If the message does not include the LTM reference configuration (i.e., the "NOT branch of box 1070"), the process proceeds to box 1265. In box 1265, the first BS generates an LTM candidate configuration as the complete configuration. In box 1207, the C-BS sends a message including the LTM candidate configuration to the second BS. Switch request confirmation Message. The process proceeds from boxes 1264 and 1265 to box 1207.

[0176] If the first BS generates an LTM candidate configuration as the complete configuration, then the first BS in Switch request confirmation The message includes a first complete configuration indicator (e.g., the BS-to-BS interface protocol field / IE) to indicate that the LTM candidate configuration is a complete configuration. For example, the BS-to-BS interface protocol field / IE is the XnAP field / IE. If the first BS generates an LTM candidate configuration as an incremental configuration, then the first BS in Switch request confirmation The message excludes the first complete configuration indicator to indicate that the LTM candidate configuration is an incremental configuration. Alternatively, the first BS in Switch request confirmation The message includes an incremental configuration indicator to indicate that the LTM candidate configuration is an incremental configuration.

[0177] When the second BS is Switch request confirmation When an LTM candidate configuration is received in the message, the second BS sends an RRC message including the LTM candidate configuration to the UE (e.g., event 518). If Switch request confirmation If the message includes a first complete configuration indicator, then the second BS includes a second complete configuration indicator (e.g., the RRC field / IE) in the RRC message to indicate to the UE that the LTM candidate configuration is a complete configuration. Otherwise, if Switch request confirmationIf the message does not include a first complete configuration indicator or includes an incremental configuration indicator, the second BS excludes the second complete configuration indicator in the RRC message to indicate that the LTM candidate configuration is an incremental configuration based on the LTM reference configuration. In some implementations, the second BS includes the LTM reference configuration in the RRC message. In another implementation, the second BS sends another RRC message (e.g., an RRC reconfiguration message) to the UE that includes the LTM reference configuration, similar to event 518.

[0178] Figure 13A This shows that it can be generated by a first base station (BS) (e.g., Figure 5 Example method 1300A is implemented by S-BS 104 in the example. Method 1300A begins at block 1305, where the first BS sends a request to the second BS to prepare the cell for LTM for the UE. Switching requests Message. In box 1307, the first BS receives from the second BS a message including the LTM candidate configuration. Switch request confirmation Message. In box 1317, the first BS includes an LTM candidate configuration in its LTM configuration. The process proceeds to box 1370. If Switching requests If the message does not include the LTM reference configuration (i.e., the "No" branch of box 1370), the process proceeds to box 1384. In box 1384, the first BS includes a full configuration indicator in the LTM configuration to indicate that the LTM candidate configuration is a full configuration. Otherwise, if Switching requests If the message includes the LTM reference configuration (i.e., the "Yes" branch of box 1370), the process proceeds to box 1386. In box 1386, the first BS excludes the complete configuration indicator from the LTM configuration. In box 1318, the first BS sends an RRC message including the LTM configuration to the UE. The process proceeds from boxes 1386 and 1384 to box 1318.

[0179] Figure 13B This is a flowchart of an example method 1300B, similar to method 1300A, except that method 1300B includes block 1371 instead of block 1070. In block 1371, S-BS is determined. Switch request confirmation Does the message include the LTM reference configuration? If so... Please switch Please confirm. If the message does not include the LTM reference configuration (i.e., the "No" branch of box 1371), the process proceeds to box 1384. Otherwise, if S-BS is determined... Switching requests If the confirmation message includes the LTM reference configuration (i.e., the "Yes" branch of box 1371), the process proceeds to box 1386.

[0180] Figure 13CThis is a flowchart of an example method 1300C, similar to method 1300A, except that method 1300C includes box 1369 instead of box 1370. In box 1369, S-BS is determined. Switch request confirmation The message indicates whether the LTM candidate configuration is a complete configuration. If the switch request confirmation message indicates... LTM candidate configurations If it's a complete configuration (i.e., the "Yes" branch of box 1369), the process proceeds to box 1384. Otherwise, if Switch request confirmation If the message indicates that the LTM candidate configuration is an incremental configuration (i.e., the "No" branch of box 1369), then the process proceeds to box 1385.

[0181] Figure 14 It shows that it can be generated by DU (e.g., Figure 5 Example method 1400 is implemented by DU 174 in the example. Method 1400 begins at block 1408, where the DU receives from the CU handover information preparation for LTM (e.g., HandoverPreparationInformation In box 1470, the DU determines whether the handover preparation information includes the LTM reference configuration. If the handover preparation information includes the LTM reference configuration (i.e., the "Yes" branch of box 1470), the process proceeds to box 1464. In box 1464, the DU generates an LTM DU configuration as an incremental configuration based on the LTM reference DU configuration in the LTM reference configuration. Otherwise, if the handover preparation information does not include the LTM reference configuration (i.e., the "No" branch of box 1470), the process proceeds to box 1465. In box 1465, the DU generates an LTM DU configuration as a complete configuration. In box 1410, the DU sends a DU-CU message to the CU including the LTM DU configuration. The process proceeds from boxes 1465 and 1464 to box 1410.

[0182] If the DU generates an LTM DU configuration as a complete configuration, the DU includes a first configuration completeness indicator (e.g., the CU-DU interface protocol field / IE) in the DU-to-CU message to indicate that the LTM DU configuration is a complete configuration. For example, the CU-DU interface protocol field / IE is the F1AP field / IE. If the DU generates an LTM DU configuration as an incremental configuration based on an LTM reference DU configuration, the DU excludes the first complete configuration indicator in the DU-to-CU message.

[0183] When the CU receives the LTM DU configuration in the DU-to-CU message, the CU generates an LTM candidate configuration that includes the LTM DU configuration and sends it to the BS (e.g., Figure 5 The S-BS 104 or the CU of the S-BS 104 sends a message including the LTM candidate configuration. Switching request confirmed recognize Message. If the DU to CU message includes the first complete configuration indicator, then the CU is in Switch request confirmation The message includes a second complete configuration indicator (e.g., BS to BS field / IE) to indicate that the LTM candidate configuration is a complete configuration. Otherwise, if the DU to CU message does not include the first complete configuration indicator, then the CU is in... Switch request confirmation The message excludes the second complete configuration indicator to indicate that the LTM candidate configuration is an incremental configuration based on the LTM reference configuration. Alternatively, the CU in Switch request confirmation The message includes an incremental configuration indicator to indicate that the LTM candidate configuration is an incremental configuration based on the LTM reference configuration.

[0184] Figure 15 It can be generated by the source base station (S-BS) (e.g., base station 104). Figure 1A , Figure 5 The flowchart of example method 1500 for LTM between CUs is shown.

[0185] Method 1500 begins at block 1505, where the source base station sends a handover request to the candidate base station, the handover request including a request to prepare a cell of the candidate base station for low-layer triggered mobility (LTM) cell handover for user equipment (UE) (e.g., event 1305).

[0186] In box 1507, the S-BS receives a handover request confirmation from the C-BS (e.g., event 1307). In box 1570, the S-BS determines, based on the handover request or handover request confirmation, whether to include an indicator that the LTM configuration is complete in the LTM configuration (e.g., events 1370, 1371, or 1369).

[0187] In box 1518, the S-BS can send LTM configuration to the UE (e.g., event 1318).

[0188] Method 1500 may further include: including an indicator in the LTM configuration in response to determining that the handover request includes an LTM reference configuration (e.g., event 1370). Method 1500 may further include: including an indicator in the LTM configuration in response to determining that the handover request confirms the inclusion of an LTM reference configuration (e.g., event 1371). Method 1500 may further include: including an indicator in the LTM configuration (e.g., event 1369) in response to determining that the handover request confirms the inclusion of an LTM candidate configuration containing an indication that the LTM candidate configuration is a complete configuration.

[0189] Figure 16 It can be made by C-BS (e.g., base station 106) Figure 1A , Figure 5 The flowchart of example method 1600 for CU-to-CU LTM is shown.

[0190] Method 1600 begins at box 1605, where the C-BS receives from the source base station (S-BS) a cell-related handover request associated with the DU of the candidate base station (e.g., events 805A, 805B, 905A, 905B, 1005, or 1205).

[0191] In box 1697, the C-BS can obtain a Low-Layer Triggered Mobility (LTM) reference configuration. The C-BS can obtain the LTM reference configuration by receiving it in a handover request. The LTM reference configuration can be an LTM reference DU configuration. Obtaining the LTM reference DU configuration can include receiving the LTM reference DU configuration from the DU. When the LTM configuration is an LTM reference configuration, method 1600 can include sending a request to the DU to prepare a cell for LTM; receiving the LTM reference DU configuration from the DU; and using the LTM reference DU configuration to generate an LTM reference configuration. Method 1600 can further include receiving the LTM DU configuration from the DU; using the LTM DU configuration to generate an LTM candidate configuration; and sending the LTM candidate configuration and the LTM reference configuration to the source base station in a handover request confirmation. The LTM reference DU configuration and the LTM DU configuration are received in the same or different DU-to-CU message.

[0192] At box 1699, the C-BS can use an LTM reference configuration to generate an LTM configuration for the cell. The LTM configuration may include or contain LTM candidate configurations. At least in these cases, in the first example, method 1600 may include sending an LTM reference configuration to the DU; receiving an LTM DU configuration for the cell from the DU in response to the sending of the LTM reference configuration; and using the LTM DU configuration to generate an LTM candidate configuration. Alternatively, in these cases and in the second example, method 1600 may include retrieving an LTM reference DU configuration from the LTM reference configuration; sending the LTM reference DU configuration to the DU; receiving an LTM DU configuration for the cell from the DU in response to the sending of the LTM reference DU configuration; and using the LTM DU configuration to generate an LTM candidate configuration. In either the first or second example alternative, method 1600 may include generating a CU-DU message including the cell's identifier; and including the LTM reference configuration in the CU-DU message in response to determining that a handover request includes the LTM reference configuration. Generating an LTM configuration for a cell may further include: in response to determining that the handover request does not include an LTM reference configuration, generating an LTM configuration as a complete configuration.

[0193] Generating an LTM configuration for a cell may include: in response to determining a handover request, including an LTM reference configuration, and generating an LTM configuration as an incremental configuration based on the LTM reference configuration.

[0194] In box 1607, the C-BS can send a handover request confirmation, including the LTM configuration, to the S-BS.

[0195] Method 1600 may include performing an LTM preparation process using a distributed unit (DU) associated with the C-BS (e.g., event 590). Method 1600 may further include sending a request for an LTM reference DU configuration to the DU (e.g., event 908D-1); receiving the LTM reference DU configuration in response to the request (e.g., event 910D-1); and sending the LTM reference DU configuration to a second DU in a request to prepare candidate cells for LTM (e.g., event 910D-2). Method 1600 may include receiving a handover request from the S-BS that does not include the LTM reference configuration (e.g., events 1070 or 1270), and during handover, sending a Central Unit (CU) to Distributed Unit (DU) message excluding LTM information (e.g., events 1008, 1066, 1073, or 1205). Method 1600 may further include: sending a CU-DU message including the LTM reference configuration if the handover request includes the LTM reference configuration (e.g., event 1072); avoiding the generation of an LTM candidate configuration as an incremental configuration (e.g., event 1264); and sending the LTM candidate configuration as a complete configuration in the handover confirmation (e.g., events 1265 or 1207). The LTM cell transition command may include a CU-CU cell transition notification message. Any subsequent cell transition notifications and follow-up messages may be related to previous messages regarding... Figures 8A to 10B and Figure 12 The messages described are the same or similar. Figure 17 The DU (e.g.) is shown. Figure 5 Another example method 1700 can be implemented by DU 174 in the diagram. Method 1700 begins at block 1708, where the DU receives a handover preparation message from the CU. The handover preparation message may include LTM information (of the UE) (e.g., event 1408). If the handover preparation message includes an LTM reference configuration, then method 1700 includes generating an LTM DU configuration as an incremental configuration based on the LTM reference configuration (e.g., event 1470).

[0196] In box 1710, the DU can send a response to the handover readiness message. The response may include LTM DU configuration information (e.g., event 1710). The LTM DU configuration information may include an indicator of whether the LTM DU configuration is complete (e.g., event 1465).

[0197] Method 1600 may include performing an LTM preparation process using a distributed unit (DU) associated with the C-BS (e.g., event 590). Method 1600 may further include sending a request for an LTM reference DU configuration to the DU (e.g., event 908D-1); receiving the LTM reference DU configuration in response to the request (e.g., event 910D-1); and sending the LTM reference DU configuration to a second DU in a request to prepare candidate cells for LTM (e.g., event 910D-2). Method 1600 may include receiving a handover request from the S-BS that does not include the LTM reference configuration (e.g., event 1070 or event 1270), and during handover, sending a Central Unit (CU) to Distributed Unit (DU) message excluding LTM information (e.g., events 1008, 1066, 1073, or 1205). Method 1600 may further include: sending a CU-DU message including the LTM reference configuration if the handover request includes the LTM reference configuration (e.g., event 1072); avoiding the generation of an LTM candidate configuration as an incremental configuration (e.g., event 1264); and sending the LTM candidate configuration as a complete configuration in the handover confirmation (e.g., events 1265 or 1207). The LTM cell transition command may include a CU-CU cell transition notification message. Any subsequent cell transition notifications and follow-up messages may be related to previous messages regarding... Figures 8A to 10B and Figure 12 The messages described are the same or similar.

[0198] The following list of examples illustrates various embodiments explicitly contemplated in this disclosure.

[0199] Example 1. A method implemented in a source base station (S-BS), the method comprising: sending a handover request to a candidate base station (C-BS) to configure a candidate cell associated with the C-BS for low-level triggered mobility (LTM) configuration for a user equipment (UE); receiving a response to the handover request from the C-BS, one of the response or the handover request including an LTM reference configuration; and sending the LTM reference configuration to the UE.

[0200] Example 2. The method as described in Example 1, further comprising: generating the LTM reference configuration prior to the transmission of the handover request, wherein the handover request includes the LTM reference configuration.

[0201] Example 3. The method as described in Example 2, wherein: the LTM reference configuration is received from a BS different from the C-BS or the S-BS.

[0202] Example 4. The method as described in Example 2, wherein: the LTM reference configuration includes an LTM reference distributed unit (DU) configuration.

[0203] Example 5. The method as described in Example 4, wherein: the S-BS includes a central unit (CU); and the method further includes sending a CU-to-DU message to the DU, and receiving an LTM reference DU configuration in response to sending the CU-to-DU message.

[0204] Example 6. The method as described in Example 5, wherein the method further includes sending the LTM reference configuration to the UE via the service DU of the S-BS.

[0205] Example 7. The method as described in Example 1 further includes sending an additional request for configuring additional candidate cells for LTM.

[0206] Example 8. The method described in Example 7, wherein: at least one additional request is provided to different C-BSs.

[0207] Example 9. The method as described in Example 7, wherein: at least one additional request includes the LTM reference configuration.

[0208] Example 10. The method of Example 7 further includes receiving a response to the additional request, the response to the additional request including a second LTM candidate configuration.

[0209] Example 11. The method of Example 10 further includes generating a Radio Resource Control (RRC) message including the second LTM candidate configuration, and sending the RRC message to the UE.

[0210] Example 12. The method as described in Example 1, wherein the response includes a switch confirmation.

[0211] Example 13. The method as described in Example 12, wherein the switching confirmation includes an LTM candidate configuration and an indication of whether the LTM candidate configuration is a complete configuration.

[0212] Example 14. The method of Example 13 further includes: sending the LTM candidate configuration and an indication of whether the LTM candidate configuration is complete to the UE.

[0213] Example 15. The method as described in Example 13 further includes excluding the indication if the switching request includes the LTM reference configuration.

[0214] Example 16. The method as described in Example 13, wherein: the indication indicates that the LTM candidate configuration is an incremental configuration.

[0215] Example 17. The method as described in Example 1, wherein sending the LTM reference configuration includes sending a Radio Resource Control (RRC) message.

[0216] Example 18. The method as described in Example 17, wherein: the RRC message includes at least one of an LTM identifier or an LTM candidate configuration for at least one candidate cell.

[0217] Example 19. The method as described in Example 17, wherein: the RRC message includes a tuple containing an LTM identifier and the LTM configuration.

[0218] Example 20. The method as described in Example 17, wherein: sending the LTM reference configuration includes sending one or more RRC messages, the one or more RRC messages including at least one of Channel State Information (CSI), LTM Synchronization Signal Block (SSB) information, Random Access Channel (RACH) configuration, or Transport Configuration Indicator (TCI) status configuration for the candidate cell.

[0219] Example 21. The method of Example 17 further includes: sending a second RRC configuration message including a second LTM reference configuration.

[0220] Example 22. The method as described in Example 21, wherein: the second LTM reference configuration is used for a cell associated with a base station different from the C-BS.

[0221] Example 23. The method described in Example 1 further includes avoiding including service configuration in the switching request.

[0222] Example 24. The method as described in Example 23, wherein: if the handover request is for LTM, the S-BS includes an LTM reference configuration in the handover request.

[0223] Example 25. The method of Example 1 further includes: receiving measurement information from the UE; and identifying the candidate cell based on the measurement information.

[0224] Example 26. The method of Example 1 further includes: sending another handover request to the C-BS or to a different candidate base station, the other handover request not being for LTM and the other handover request including service configuration.

[0225] Example 27. A method implemented in a candidate base station (C-BS), the method comprising: receiving a handover request from a source base station (S-BS) to configure a candidate cell associated with the C-BS for low-layer triggered mobility (LTM) for a user equipment (UE); and sending an LTM candidate configuration to the S-BS in response to the handover request, the LTM candidate configuration being based on an LTM reference configuration.

[0226] Example 28. The method as described in Example 27, wherein the LTM reference configuration is included in the switching request.

[0227] Example 29. The method as described in Example 28, wherein the C-BS generates the LTM reference configuration.

[0228] Example 30. The method as described in Example 28, wherein the sending includes sending a switch confirmation.

[0229] Example 31. The method as described in Example 30, wherein: the switching confirmation includes an indication of whether the LTM configuration is a complete configuration.

[0230] Example 32. The method as described in Example 31, wherein: the indication indicates that the LTM configuration is an incremental configuration.

[0231] Example 33. The method described in Example 27 further includes sending an LTM success indication indicating that the LTM cell transition has been successfully completed.

[0232] Example 34. The method as described in Example 34, wherein: the LTM success indication is sent in response to receiving a success indication from a distributed unit (DU) associated with the C-BS.

[0233] Example 35. The method of Example 34 further includes detecting UE access in the candidate cell.

[0234] Example 36. The method as described in Example 34, wherein: the LTM success indication includes the LTM identifier of the candidate cell.

[0235] Example 37. The method as described in Example 34, wherein: the LTM success indication includes a switch success message.

[0236] Example 38. The method of Example 34 further includes: receiving an LTM DU configuration in response to sending the LTM success indication.

[0237] Example 39. The method of Example 38 further includes: receiving an LTM reference DU configuration in response to sending the LTM success indication.

[0238] Example 40. The method of Example 27 further includes receiving downlink data radio bearer (DRB) information from the S-BS in an early state transmission message.

[0239] Example 41. A method implemented in a distributed unit (DU) associated with a central unit (CU), the method comprising: receiving a handover preparation message from the CU, the handover preparation message including lower layer triggered mobility (LTM) information of a user equipment (UE); and sending a response to the handover preparation message, the response including LTM DU configuration information.

[0240] Example 43. The method as described in Example 42, wherein: the LTM DU configuration information includes an indicator of whether the LTM DU configuration is a complete configuration.

[0241] Example 44. The method as described in Example 42, wherein: if the handover preparation message includes an LTM reference configuration, the method includes generating the LTM DU configuration as an incremental configuration based on the LTM reference configuration.

[0242] Example 47. An apparatus for a base station, comprising a circuitry system for performing any one or more of the processing described in Examples 1 to 46.

[0243] 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. The events or boxes described above can be optional or omitted. For example, events or boxes marked with dashed lines in the figures may 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 a sending node sending a message to a 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 a sending node sending a message to a receiving node.

[0244] 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, "DU configuration" can be replaced with "cell group configuration". 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 timed synchronization" or "early UL synchronization". In some implementations, "early TA acquisition on candidate cells" can be replaced with "early UL timed synchronization with candidate cells" or "early UL synchronization with candidate cells". The above-described " Switch request and" Switch request confirmation "This is for illustrative purposes and can be replaced with a message having a generic name. For example, " Switching requests "and" Switch request confirmation "This can be replaced with the first CU-to-CU message and the second CU-to-CU message, respectively. In another example, " Switching requests "and" Switching request confirmed recognize "This can be replaced with the first interface message and the second interface message, respectively. In another example, " Switching requests "and" Please switch Please confirm. "Can be replaced with the first BS to BS message and the second BS to BS message respectively. In some implementations, "include" can be replaced with "contain". In some implementations, "exclude" can be replaced with "avoid including".

[0245] The user device in which the technologies of this disclosure are implemented (e.g., UE 102) 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. Further, in some cases, the user device can be embedded in an electronic system (such as the main unit of a vehicle or an advanced driver assistance system (ADAS)). Further still, 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.

[0246] Some embodiments described in this disclosure include logic or multiple components or modules. A module can be a software module (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing certain operations and can be configured or arranged in a certain way. A hardware module may include a dedicated circuit system or logic (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.) that is persistently configured to perform certain operations. A hardware module may also include programmable logic or circuit systems (e.g., as contained within a general-purpose processor or other programmable processor) that are temporarily configured by software to perform certain operations. The decision to implement a hardware module in a dedicated and persistently configured circuit system or in a temporarily configured circuit system (e.g., configured by software) may be driven by cost and time considerations.

[0247] When implemented in software, these technologies can be provided as part of an operating system, a library used by multiple applications, or a specific software application. The software can be executed by one or more general-purpose processors or one or more dedicated processors.

[0248] Upon reading this disclosure, those skilled in the art will understand additional and alternative structural and functional designs for handling mobility between base stations using the principles disclosed herein. Therefore, while specific embodiments and applications have been shown and described, it should be understood that the disclosed embodiments are not limited to the precise constructions and components disclosed herein. Various modifications, alterations, and variations that will be apparent to those skilled in the art 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 the central unit (CU) of a candidate base station, the method comprising: Receive a handover request related to the cell associated with the Distributed Unit (DU) of the candidate base station from the source base station; Obtain the low-level triggered mobility LTM reference configuration; Use the LTM reference configuration to generate the LTM configuration for the cell; as well as Send a handover request confirmation, including the LTM configuration, to the source base station.

2. The method of claim 1, wherein: The acquisition of the LTM reference configuration includes receiving the LTM reference configuration in the handover request.

3. The method as described in claim 2, wherein, The LTM configuration is an LTM candidate configuration, and the method further includes: Send the LTM reference configuration to the DU; In response to the transmission of the LTM reference configuration, receive the LTM DU configuration for the cell from the DU; and The LTM DU configuration is used to generate the LTM candidate configuration.

4. The method of claim 2, wherein, The LTM configuration is an LTM candidate configuration, and the method further includes: Retrieve the LTM reference DU configuration from the LTM reference configuration; Send the LTM reference DU configuration to the DU; In response to the transmission of the LTM reference DU configuration, receive the LTM DU configuration for the cell from the DU; and The LTM DU configuration is used to generate the LTM candidate configuration.

5. The method of claim 3 or 4, further comprising: Generate a CU-DU message including the identifier of the cell; as well as In response to determining that the handover request includes the LTM reference configuration, the LTM reference configuration is included in the CU to DU message.

6. The method according to any one of claims 2 to 5, wherein, The generation of the LTM configuration for the cell includes: In response to determining that the switching request includes the LTM reference configuration, the LTM configuration is generated as an incremental configuration based on the LTM reference configuration.

7. The method of claim 1, wherein: The LTM reference configuration is the LTM reference DU configuration, and The acquisition of the LTM reference DU configuration includes receiving the LTM reference DU configuration from the DU.

8. The method of claim 7, wherein, The LTM configuration is an LTM reference configuration, and the method further includes: Send a request to the DU to prepare the cell for LTM; Receive the LTM reference DU configuration from the DU; and The LTM reference configuration is generated using the LTM reference DU configuration.

9. The method of claim 8, further comprising: Receive LTM DU configuration from the DU; Use the LTM DU configuration to generate LTM candidate configurations; as well as In the handover request confirmation, the LTM candidate configuration and the LTM reference configuration are sent to the source base station.

10. The method of claim 9, wherein: The LTM reference DU configuration and the LTM DU configuration are received in the same DU to CU message.

11. The method of claim 1, wherein: The LTM reference DU configuration and the LTM DU configuration are received in separate corresponding DU-to-CU messages.

12. The method according to any one of claims 7 to 11, wherein, The generation of the LTM configuration for the cell includes: In response to determining that the switching request does not include the LTM reference configuration, the LTM configuration is generated as a complete configuration.

13. The method as described in any of the preceding claims, wherein: The handover request indicates the cell associated with the DU; and The request to the DU includes a request to prepare the cell for LTM.

14. A method implemented in a source base station, the method comprising: Send a handover request to a candidate base station, the handover request including a request to prepare a cell of the candidate base station for low-layer mobility LTM for the user equipment (UE); Receive handover request confirmation from the candidate base station; Whether to include an indicator that the LTM configuration is a complete configuration in the LTM configuration is determined based on the switching request or the confirmation of the switching request; as well as Send the LTM configuration to the UE.

15. The method of claim 14, further comprising: In response to determining that the switching request includes an LTM reference configuration, the indicator is included in the LTM configuration.

16. The method of claim 14, further comprising: In response to determining that the handover request confirms the inclusion of the LTM reference configuration, the indicator is included in the LTM configuration.

17. The method of claim 14, further comprising: In response to determining that the switching request confirms an LTM candidate configuration including an indication that the LTM candidate configuration is a complete configuration, the indication is included in the LTM configuration.

18. An apparatus comprising processing hardware and configured to implement the method as described in any of the preceding claims.

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