Managing early timing advance acquisition

Abstract

One or more distributed units (DUs) of a distributed base station also including a central unit (CU), the method comprising: transmitting, from a candidate DU to the CU, a configuration parameter for early timing advance (TA) acquisition by a user equipment (UE) in a target cell; receiving, in the target cell and according to the configuration parameters, a random access preamble from the UE at the candidate DU; and transmitting the TA value from the candidate DU to the CU based on the reception of the random access preamble.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Provisional U.S. Patent Application No. 63 / 516,136, filed July 27, 2024, entitled “Managing Early Timing Advance Acquisition.” The entire contents of that provisional application are hereby expressly incorporated herein by reference. Technical Field

[0003] This disclosure relates to wireless communications, and more particularly, to managing early timing acquisition for early uplink timing synchronization of the UE with the target cell prior to the UE connecting to the target cell. Background Technology

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

[0005] In telecommunications systems, the Packet Data Convergence Protocol (PDCP) sublayer of the radio protocol stack provides services such as user plane data delivery, encryption, and integrity protection. For example, the PDCP 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 Signal Transmission Radio Bearers (SRBs) and Data Radio Bearers (DRBs) to the Radio Resource Control (RRC) sublayer. Generally, the UE and base station can use SRBs to exchange RRC messages and Non-Access Stratum (NAS) messages, and can use DRBs to transmit data on the user plane.

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

[0007] In some scenarios, a UE can simultaneously utilize the resources of multiple Radio Access Network (RAN) nodes (e.g., base stations, or components of distributed base stations) interconnected via backhaul. This type of connection is called Multiple Radio Dual Connectivity (MR-DC) when these network nodes support different Radio Access Technologies (RATs). When the UE operates under MR-DC, one base station operates as the primary node (MN) covering the primary cell (PCell), while 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. One base station and / or the UE determines that the UE should establish a radio connection with another base station. For example, a base station may determine to transfer the UE to a second base station and initiate a transfer procedure.

[0008] When a UE moves from the coverage area of ​​one cell in the RAN to the coverage area of ​​another cell, the UE and the RAN must perform a serving cell change at some point. For this purpose, the RAN configures the UE to send Layer 3 (L3) measurements. Using the L3 measurements from the UE, the RAN sends an RRC reconfiguration message that configures a synchronous reconfiguration (e.g., the RRC reconfiguration message includes a ReconfigurationWithSync IE) for the change of serving cell (e.g., PCell or PSCell). When the UE operates with at least one secondary cell (SCell) and carrier aggregation (CA) with the PCell or PSCell, the RAN must release at least one SCell due to the change of the PCell or PSCell. Serving cell changes involve a full L2 (and L1) reset, resulting in longer latency, greater overhead, and longer downtime. For these reasons, the 3rd Generation Partnership Project (3GPP) proposed developing new mobility technologies for serving cell changes. These technologies aim to reduce latency and overhead and are known as Lower Layer Triggered Mobility (LTM) or faster serving cell handover.

[0009] When a UE performs a serving cell change from its serving cell to a target cell within the RAN, the UE executes a random access procedure to synchronize with the target cell in the uplink direction (i.e., from the UE to the RAN). Only after the UE successfully completes the random access procedure can it begin data communication with the RAN via the target cell. Therefore, data communication is interrupted during the serving cell handover.

[0010] To avoid interruptions, the RAN can instruct the UE to send a random access preamble in the target cell while the UE is connecting to the serving cell. For example, the RAN can send a PDCCH command to the UE to trigger the UE to send the random access preamble in the target cell. In response, the UE sends the random access preamble in the target cell. The RAN can then use this random access preamble to obtain a timing advance (TA) value for synchronization with the target cell. When handing over to the target cell, the UE applies this TA value to communicate directly in the target cell without performing a random access procedure. In this way, both the UE and the RAN avoid interruptions.

[0011] However, it remains unclear how the RAN enables the UE to transmit the random access preamble in the target cell. Furthermore, in some scenarios, after the RAN obtains the TA value but before it sends it to the UE, the UE can move from one geographic area to another. Currently, the UE and / or RAN do not consider whether the TA value is valid. If the RAN sends an invalid TA value to the UE and the UE applies that invalid TA value, transmissions from the UE in the target cell will be out of sync with the RAN, causing interference to other UEs. Summary of the Invention

[0012] An example embodiment of the technology disclosed herein is a method implemented in one or more distributed units (DUs) of a distributed base station that also includes a central unit (CU). The method includes: sending configuration parameters from a candidate DU to the CU for early timing advance (TA) acquisition by a user equipment (UE) in a target cell; receiving a random access preamble from the UE at the candidate DU in the target cell and according to the configuration parameters; and sending a TA value from the candidate DU to the CU based on the reception of the random access preamble.

[0013] Another example embodiment of these technologies is a method implemented in the central unit (CU) of a distributed base station. The method includes: receiving configuration parameters from a candidate DU of the distributed base station for early timing advance (TA) acquisition by a user equipment (UE) in a target cell; sending the configuration parameters to the UE; and receiving from the candidate DU a TA value generated for the UE in the target cell.

[0014] Another example embodiment of these technologies is a node in a distributed base station, the node including processing hardware and configured to implement the method described in any of the preceding claims. Attached Figure Description

[0015] FIG. 1A This is a block diagram of an example system in which the radio access network (RAN) and user equipment can implement the technology for managing early timing advance acquisition disclosed herein;

[0016] FIG. 1B It includes being able to FIG. 1A A block diagram of an example base station for centralized unit (CU) and distributed unit (DU) operations in the system;

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

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

[0019] FIG. 3 This is a message passing diagram of an example scenario where a base station initiates an LTM cell change within a DU;

[0020] FIG. 4 This is a message passing diagram of an example scenario where a base station initiates an inter-DU LTM cell change.

[0021] FIG. 5A to FIG. 5B This is a message passing diagram of an example scenario where MN operates together with SN under DC and SN performs LTM cell changes within DU;

[0022] FIG. 6A to FIG. 6B This is a message passing diagram of an example scenario where MN operates together with SN under DC and SN performs LTM cell change between DU;

[0023] FIG. 7A and FIG. 7B This is a message passing diagram of an example scenario in which one DU in a distributed base station acts as MN, another DU in the distributed base station acts as SN, and the SN performs LTM cell change within the DU.

[0024] FIG. 8A and FIG. 8B This is a message passing diagram of an example scenario in which one DU in a distributed base station acts as the MN, another DU in the distributed base station acts as the SN, and the SN performs LTM cell change between DUs.

[0025] FIG. 9A This is a flowchart of an example method in DU for obtaining random access configuration parameters from CU for early timing advance acquisition;

[0026] FIG. 9B It is similar to FIG. 9A The example method is shown in the flowchart, but in it the DU sends the cell index to the CU instead of the cell ID to request random access configuration parameters;

[0027] FIG. 9C It is similar to FIG. 9A The example method is shown in the flowchart, but in it the DU sends the LTM ID to the CU instead of the cell ID to request random access configuration parameters;

[0028] FIG. 10 This is a flowchart of an example method in DU used to determine whether to perform an early timing advance acquisition process based on measurement results from the UE;

[0029] FIG. 11 This is a flowchart of an example method in DU used to determine whether the early timing advance fetch process should be executed based on whether the UE supports early timing advance fetch;

[0030] FIG. 12A This is a flowchart of an example method in DU for determining whether to include an early timing advance value in an LTM command based on whether DU receives a timing advance value;

[0031] FIG. 12B This is a flowchart of an example method in DU for determining whether to include an early timing advance value in an LTM command based on whether the timing advance value is valid;

[0032] FIG. 13 This is a flowchart of an example method in DU used to operate the timing advance validity timer;

[0033] FIG. 14A This is a flowchart of an example method in a DU for determining whether to include an early timing advance value in an LTM command based on the cell in which the DU has obtained a timing advance value;

[0034] FIG. 14A It is similar to FIG. 14A The example method is a flowchart, but it is in which DU determines whether the timing advance value is valid;

[0035] FIG. 15 It is similar to FIG. 14A or FIG. 14B The flowchart of the example method is shown, but DU also operates on the timing advance validity timer;

[0036] FIG. 16A This is a flowchart of an example method in the CU for providing random access configuration parameters to the DU for early timing acquisition;

[0037] FIG. 16B It is similar to FIG. 16A The example method is shown in the flowchart, but in which the CU receives the cell index from the DU instead of the cell ID in the request for random access configuration parameters;

[0038] FIG. 16C It is similar to FIG. 16B The example method is shown in the flowchart, but in which the CU receives the LTM ID from the DU instead of the cell ID in the request for random access configuration parameters;

[0039] FIG. 17 This is a flowchart of an example method in DU used to configure the UE for early timing advance acquisition;

[0040] FIG. 18 This is a flowchart of an example method in DU for providing random access configuration parameters to CU for early timing acquisition;

[0041] FIG. 19 This is a flowchart of an example method in DU for deriving timing advance values ​​based on random access preambles and providing those timing advance values ​​to CU; and

[0042] FIG. 20 This is a flowchart of an example method in the UE for receiving and applying timing advance for early timing advance acquisition. Detailed Implementation

[0043] FIG. 1A An example wireless communication system 100 in which communication devices can implement these technologies is depicted. The wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106, and a core network (CN) 110. The UE 102 is initially connected to base station 104. In some scenarios, base station 104 can perform SN addition to configure the UE 102 to operate in dual connectivity (DC) with both base stations 104 and 106. Base stations 104 and 106 operate as the MN and SN of the UE 102, respectively.

[0044] In various configurations of the wireless communication system 100, base station 104 can be implemented as a primary eNB (MeNB) or primary gNB (MgNB), and base station 106 can be implemented as a secondary gNB (SgNB). UE 102 can communicate with base station 104 and base station 106 via the same RAT (such as EUTRA or NR) or different RATs. When base station 104 is a MeNB and base station 106 is an SgNB, UE 102 can be in EUTRA-NR DC (EN-DC) with both the MeNB and SgNB.

[0045] In some cases, the MeNB or SeNB is implemented as an ng-eNB instead of an eNB. When base station 104 is the primary ng-eNB (Mng-eNB) and base station 106 is the SgNB, UE 102 can be in a next-generation (NG) EUTRA-NRDC (NGEN-DC) with both the Mng-eNB and SgNB. When base station 104 is a MgNB and base station 106 is an SgNB, UE 102 can be in an NR-NR DC (NR-DC) with both the MgNB and SgNB. When base station 104 is a MgNB and base station 106 is a secondary ng-eNB (Sng-eNB), UE 102 can be in an NR-EUTRA DC (NE-DC) with both the MgNB and Sng-eNB.

[0046] 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 destination base station (T-BS), respectively. UE 102 can, for example, communicate with base station 104 and the auxiliary base station (T-BS) under DC before the switch.FIG. 1A (Not shown in the diagram) Operation. After the handover is completed, UE 102 can continue to operate with base station 106 and the additional base station under DC or with base station 106 under single connection (SC). In this case, base stations 104 and 106 operate as the source MN (S-MN) and the target MN (T-MN), respectively.

[0047] The core network (CN) 110 can be either the Evolved Packet Core (EPC) 111 or the fifth-generation core (5GC) 160; both are... FIG. 1A The following description is provided. 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. Base stations 104 and 106 may support X2 or Xn interfaces to directly exchange messages with each other during the scenarios discussed below. Among other components, EPC 111 may include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. SGW 112 is generally configured to transmit user plane packets related to audio calls, video calls, Internet services, etc., and MME 114 is configured to manage authentication, registration, paging, and other related functions. PGW 116 provides connectivity from the UE to one or more external packet data networks (e.g., Internet networks and / or Internet Protocol (IP) Multimedia Subsystem (IMS) networks). 5GC 160 includes User Plane Functions (UPF) 162, Access and Mobility Management (AMF) 164, and / or Session Management Functions (SMF) 166. UPF 162 is generally configured to transmit user plane packets related to audio calls, video calls, Internet services, etc., AMF 164 is configured to manage authentication, registration, paging, and other related functions, and SMF 166 is configured to manage PDU sessions.

[0048] like FIG. 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 under DC, where one of base stations 104 and 106 is MN and the other is SN. Base station 104 can support additional cells such as cells 124B and 124C, and base station 106 can support additional cells (…). FIG. 1A(Not shown in the diagram). Cells 124A, 124B, and 124C may partially overlap, allowing UE 102 to communicate with base station 104 via carrier aggregation (CA). Base station 104 may operate cells 124A, 124B, and 124C via one or more transmit and receive points (TRPs). More specifically, when UE 102 is in a DC configuration with base stations 104 and 106, one of base stations 104 and 106 operates as a MeNB, Mng-eNB, or MgNB, while the other operates as an SgNB or Sng-eNB.

[0049] Generally, the wireless communication network 100 may include any suitable number of base stations supporting NR cells and / or EUTRA cells. More specifically, the EPC 111 or 5GC 160 may 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 and / or core network technologies, such as sixth-generation (6G) radio access and / or 6G core networks or 5G NR-6G DC.

[0050] Continue to refer to FIG. 1A The base station 104 is equipped with processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and non-transitory computer-readable storage of instructions executed by the one or more general-purpose processors. Alternatively, the processing hardware 130 may include dedicated processing units.

[0051] The processing hardware 130 may implement an LTM controller 132 to support the LTM process and an early TA acquisition controller 134 to support early TA acquisition at the UE. For example, the LTM controller 132 and the early TA acquisition controller 134 may be implemented as corresponding instruction sets executable by one or more processors.

[0052] The processing hardware 130 may also implement additional components, such as a PHY controller (not shown), configured to transmit data and control signals with one or more user equipments (e.g., UE 102) via one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs on physical downlink (DL) channels and DL reference signals. The PHY controller may be configured to receive data and control signals with one or more user equipments via one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs on physical uplink (UL) channels and / or UL reference signals. The processing hardware 130 may also implement a MAC controller (not shown), configured to perform MAC functions with one or more user equipments. MAC functions include random access (RA) procedures, managing UL timing advances for one or more user equipments, and / or communicating UL / DL MAC PDUs with one or more user equipments. MAC functions include lower-layer triggered mobility (LTM) related functions as described below. Processing hardware 130 may further include an RRC controller (not shown) to implement procedures and message passing at the RRC sublayer of the protocol communication stack. For example, the RRC controller may be configured to support RRC message passing 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. Base station 106 may include processing hardware 140 similar to processing hardware 130. Specifically, components 142, 144, and 146 may be similar to components 132 and 134, respectively.

[0053] UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors such as a CPU and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or dedicated processing units. Processing hardware 150 may implement an LTM controller 152 to support the LTM process, and an early TA acquisition controller 154 to support early TA acquisition in the serving cell and / or the target cell. For example, LTM controller 152 and TA acquisition controller 154 may be implemented as corresponding instruction sets executable by one or more processors.

[0054] In operation, UE 102 can use radio bearers (e.g., DRB or SRB) that terminate at MN 104 or SN 106 at different times under DC. When communicating on radio bearers in the uplink (UL) (from UE 102 to the base station) and / or downlink (from the base station to UE 102) directions, UE 102 can apply one or more security keys.

[0055] FIG. 1BAn example distributed implementation of a base station, such as base station 104 or 106, is depicted. In this implementation, the base station may include a centralized unit (CU) 172 and one or more distributed units (DUs) 174. CU 172 is equipped with processing hardware that may include one or more general-purpose processors (such as 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 is equipped with processing hardware 130. In another example, CU 172 is equipped with processing hardware 140. In the example implementation, processing hardware 140 includes an SN RRC controller 142 configured to manage or control one or more RRC configurations and / or RRC procedures when base station 106 operates as an SN. DU 174 is also equipped with processing hardware that may include one or more general-purpose processors (such as 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, in the example implementation, the processing hardware includes: a Media Access Control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., random access procedures); and a Radio Link Control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station 106 operates as an MN or SN. The processing hardware may further include a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0056] FIG. 2A An example protocol stack 200 is shown in a simplified manner, which UE 102 can use to communicate with eNB / ng-eNB or gNB (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 then provides an RLC channel to the EUTRA PDCP sublayer 208 and, in some cases, to the NR PDCP sublayer 210. Similarly, the NRPHY 202B provides a transport channel to the NR MAC sublayer 204B, which in turn provides a logical channel to the NR RLC sublayer 206B. The NR RLC sublayer 206B then provides data 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. FIG. 2A (Not shown in the image) provides data transmission services. In some implementations, UE 102 supports both EUTRA and NR stacks, such as... FIG. 2A As shown, this supports switching between EUTRA and NR base stations and / or supports DCs via EUTRA and NR interfaces. Further, as... FIG. 2A As illustrated, UE 102 can support layering of NR PDCP 210 over EUTRA RLC 206A, and layering of SDAP sublayer 212 over NR PDCP sublayer 210.

[0058] EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 receive packets that can be referred to as Service Data Units (SDUs) (e.g., from Internet Protocol (IP) layers that are directly or indirectly layered on PDCP layers 208 or 210), and output packets that can be referred to as Protocol Data Units (PDUs) (e.g., output to RLC layers 206A or 206B). Except where the difference between SDU and PDU is relevant, for simplicity, 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 signal transmission radio bearer (SRB) or RRC sublayer ( FIG. 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] FIG. 2BAn example protocol stack 250 is shown in a simplified manner, illustrating how UE 102 can communicate with DU (e.g., DU 174) and CU (e.g., CU 172). The radio protocol stack 200 is functionally split, as described by... FIG. 2B The radio protocol stack 250 is shown in the diagram. The CU at either base station 104 or 106 can retain all control and upper-layer functionality (e.g., RRC 214, SDAP 212, NR PDCP 210), while lower-layer operations (e.g., NR RLC 206B, NR MAC 204B, and NR PHY 202B) are delegated to the DU. To support connectivity to the 5GC, NR PDCP 210 provides SRBs to RRC 214, and NR PDCP 210 provides DRBs to SDAP 212 and SRBs to RRC 214.

[0061] Next is one of them FIG. 1A The system includes several example scenarios where the base station operating in the system sends a configuration to the UE 102 and later activates the configuration for communication between the UE 102 and the base station. Generally, FIG. 3 to FIG. 20 Similar events in the figures are labeled with similar reference numerals (sharing two least significant digits), where differences are discussed below where appropriate. For example, event 304 is similar to events 404, 505, 604, 704, and 804; event 330 is similar to events 430, 530, 630, 730, and 830, as well as boxes 930, 1030, and 1230; differences will be discussed below where appropriate. Apart from the differences shown in the figures and discussed below, any of the alternative implementations discussed regarding specific events (e.g., those used for messaging and processing) can be applied to other events labeled with similar reference numerals in the figures.

[0062] First refer to FIG. 3 In scenario 300, base station 104 includes CU 172 and DU 174, and DU 174 operates cell 124A. UE 102 initially uses the serving DU to communicate with DU 174 on cell 124A 302, and, for example, uses the serving CU to communicate with CU 172 via DU 174. In other words, DU 174 is the serving DU that is communicating with UE 102. In some implementations, UE 102 uses the serving DU in carrier aggregation (CA) configuration on cell 124A and other cells (e.g., FIG. 1AUE 102 communicates with DU 174 on cell 124A (not shown). DU 174 operates other cells. In other implementations, UE 102 communicates with DU 174 only on cell 124A. In some implementations, UE 102 communicates with DU 174 on cell 124A and / or other cells via one or more TRPs. In some implementations, cell 124A may be a PCell. In such cases, other cells include SCells and / or additional cells associated with a PCell or SCell. In other implementations, cell 124A may be an SCell, and one of the other cells is a PCell. In such cases, the remaining cells include SCells and / or additional cells associated with a PCell or SCell. In the following description, base station 104 may be DU 174, CU 172, or DU 174 and CU 172.

[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 to base station 104 via a radio bearer that may include SRBs and / or DRBs. Base station 104 may be configured to the radio bearer of UE 102. In some implementations, UL control signals include UL control information, channel state information, Hybrid Automatic Repeat Request (HARQ) acknowledgment (ACK), HARQ negation ACK, scheduling request, and / or probe reference signals. Similarly, UE 102 may receive DL PDUs and / or DL ​​control signals from base station 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, DU 174 can send these configuration parameters to CU 172. CU 172 generates one or more messages (e.g., an RRC reconfiguration message) including the configuration parameters and sends these messages to UE 102 via DU 174. In other implementations, DU 174 sends the configuration parameters directly to UE 102. In some implementations, the serving DU configuration is the CellGroupConfig IE defined in 3GPP specification 38.331. In other implementations, the serving DU configuration includes configuration parameters in the CellGroupConfig IE. In some implementations, the serving CU configuration includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, the serving CU configuration includes the MeasConfig IE and / or RadioBearerConfig IE as defined in 3GPP specification 38.331, or includes configuration parameters in the MeasConfig IE and / or RadioBearerConfig IE. In some implementations, the serving DU configuration includes the CSI-MeasConfig IE or configuration parameters for Channel State Information (CSI) measurement and reporting. In other implementations, the serving CU configuration includes the CSI-MeasConfig IE or configuration parameters for CSI measurement and reporting. In some implementations, UE 102 receives the serving CU configuration or configuration parameters in the serving CU configuration from CU 172 via DU 174. In other implementations, UE 102 receives a portion of the serving CU configuration and / or a portion of the serving DU configuration from a base station other than base station 104, and receives the remainder of these configuration parameters from base station 104.

[0065] When communicating with base station 104, UE 102 sends at least one measurement report (304) to DU 174. In some implementations, the at least one measurement report includes a Layer 1 (L1) measurement report and / or a Layer 3 (L3) measurement report for at least one serving cell and / or for at least one non-serving cell of UE 102. For each of the L3 measurement reports, DU 174 sends a DU-to-CU message (306) including the L3 measurement report to CU 172. In some implementations, the DU-to-CU message of event 306 is an F1 Application Protocol (F1AP) message (e.g., a UL RRC message delivery message). In some implementations, DU 174 does not send or avoids sending L1 measurement reports to CU 172. At least one serving cell includes cell 124A and / or other cells, and at least one non-serving cell includes cell 124B and / or cell 124C. In some implementations, the serving DU configuration or serving CU configuration includes at least one measurement configuration. In some implementations, in event 302, UE 102 receives one or more RRC messages (e.g., RRCReconfiguration messages) from CU 172 via DU 174, including at least one measurement configuration. Based on the at least one measurement configuration, UE 102 performs a measurement and sends at least one measurement report (304) to DU 174. In some implementations, the at least one measurement configuration includes an L3 measurement configuration (e.g., MeasConfig IE) and / or an L1 measurement configuration. The L1 measurement configuration (e.g., CSI-MeasConfig IE) may include an L1 measurement resource configuration and / or an L1 measurement report configuration. The L1 measurement resource configuration may configure a reference signal and / or resources of the reference signal for UE 102 to measure and obtain L1 measurement results. In some implementations, the reference signal includes CSI-RS and / or Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) Resource Block (SSB). For example, the L1 measurement resource configuration is CSI-ResourceConfig IE. In another example, the L1 measurement report configuration configures how UE 102 sends L1 measurement results / reports. For example, the L1 measurement report configuration is CSI-ReportConfig IE. For instance, UE 102 sends an L3 measurement report to CU 172 via DU 174 according to the L3 measurement configuration. UE 102 sends an L1 measurement report to DU 174 according to either the L1 measurement configuration or the L1 measurement report configuration. In one implementation, DU 174 does not send L1 measurement reports to CU 172.

[0066] In some implementations, the L1 measurement configuration is the new RRC IE defined in 3GPP specification 38.331 v18.0.0 and / or later for lower-layer triggered mobility (LTM). In some implementations, the L1 measurement resource configuration is the new RRC IE defined in 3GPP specification 38.331 v18.0.0 and / or later for LTM. In some implementations, the L1 measurement reporting configuration is the new RRC IE defined in 3GPP specification 38.331 v18.0.0 and / or later for LTM. In some implementations, each of the L1 measurement reporting configurations may include a trigger event configuration that configures a trigger event to trigger UE 102 to send an L1 measurement report. If UE 102 detects the trigger event, UE 102 sends an L1 measurement report to DU 174.

[0067] In some implementations, each of the L1 measurement reports may include at least one L1 measurement result. In some implementations, at least one L1 measurement result includes at least one L1 reference received signal power (L1-RSRP) value and / or at least one L1 signal-to-interference-noise ratio (L1-SINR) value. In some implementations, for each of the L1 measurement reports, UE 102 sends a PUCCH transmission including the L1 measurement report to DU 174. That is, UE 102 sends each of the L1 measurement reports to DU 174 on the PUCCH. In other implementations, for each of the L1 measurement reports, UE 102 sends a PUSCH transmission including the L1 measurement report to DU 174. That is, UE 102 sends each of the L1 measurement reports to DU 174 on the PUSCH. In yet another implementation, UE 102 sends a portion of the L1 measurement report to DU 174 on the PUCCH and the remainder of the L1 measurement report to that DU on the Physical UL Shared Channel (PUSCH). In other words, for each portion of the L1 measurement report, UE 102 sends a PUCCH transmission including the L1 measurement report to DU 174, and for each remaining portion of the L1 measurement report, UE 102 sends a PUSCH transmission including the L1 measurement report to DU 174. In some implementations, each of the L1 measurement reports is a part of a CSI (i.e., a CSI component) or a CSI. In some implementations, UE 102 may include other CSI components in each of the aforementioned PUCCH and / or PUSCH transmissions. In one implementation, other CSI components include, for example, a Channel Quality Indicator (CQI), a Precoding Matrix Indicator (PMI), a CSI-RS Resource Indicator (CRI), an SSB Resource Indicator (SSBRI), a Layer Indicator (LI), and / or a Rank Indicator (RI). In some implementations, UE 102 does not send the L1 measurement report to DU 174 in the format of an RRC message.

[0068] In some implementations, each of the L3 measurement reports may include at least one L3 measurement result. In some implementations, at least one L3 measurement result includes at least one RSRP (value) and / or at least one SINR (value). In one implementation, UE 102 sends each of the L3 measurement reports to CU 172 via DU 174 on the PUSCH. In some implementations, each of the L3 measurement reports may be an RRC message (e.g., a MeasurementReport message). In some implementations, each of the L3 measurement configurations includes a specific measurement identifier (e.g., measId), and each of the L3 measurement reports includes a specific measurement identifier in a specific L3 measurement configuration. When CU 172 receives an L3 measurement report including a measurement identifier and an L3 measurement result from UE 102 via DU 174, CU 172 may determine that the L3 measurement report is associated with the L3 measurement configuration identified by the measurement identifier.

[0069] In some alternative implementations, for each of at least one measurement report (e.g., an L1 measurement report), UE 102 sends a MAC control element (CE) including the measurement report to DU 174 in event 304. In order to send the MAC CE, UE 102 generates one or more MAC PDUs to DU 174 in event 304, each MAC PDU including one or more of the MAC CEs.

[0070] In some implementations, UE 102 performs measurements on one or more reference signals according to at least one measurement configuration. These one or more reference signals may include one or more Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) Resource Blocks (SSBs) and / or one or more CSI-RSs. UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurements. DU 174 in cell 124A and other cells (e.g., cell 124B, cell 124C and / or FIG. 1A One or more reference signals are transmitted on a cell (not shown in the diagram).

[0071] Upon receiving one or more of at least one measurement report from UE 102 (e.g., in response to this), base station 104 (i.e., CU 172 or DU 174) determines a first cell (e.g., cell 124B) for UE 102 to prepare for LTM. In some implementations, base station 104 determines to prepare the first cell for UE 102 because at least one measurement report indicates that the first cell can be used by base station 104 to communicate with UE 102. In some implementations, base station 104 determines to prepare the first cell for UE 102 because at least one measurement report indicates that the first cell is eligible to be a candidate cell for communication with UE 102. In some implementations, CU 172 determines to prepare the first cell for UE 102 if an L3 measurement report indicates that the signal strength and / or quality of the first cell is higher than a first predetermined threshold, better than the signal strength and / or quality of cell 124A, and / or better than the signal strength and / or quality of cell 124A by a first predetermined threshold. In other implementations, if the L1 measurement report indicates that the signal strength and / or quality of the first cell is higher than a first predetermined threshold, better than the signal strength and / or quality of cell 124A, and / or better than the signal strength and / or quality of cell 124A by a first predetermined threshold, then DU 174 determines to prepare the first cell for UE 102. Alternatively, base station 104 determines to prepare the first cell for UE 102 regardless of whether a measurement report is received from UE 102.

[0072] When CU 172 determines that a first cell is ready for LTM, CU 172 sends a 308 First CU to DU message to DU 174 to prepare the first cell for UE 102. In some implementations, CU 172 includes the cell identifier (ID) 1 of the first cell in the First CU to DU message to request DU 174 to prepare the first cell for LTM for UE 102. For example, cell ID 1 is the Cell Global Identifier (CGI). In another example, the cell ID is part of the CGI. In yet another example, the cell ID is the Physical Cell ID (PCI). In response to the First CU to DU message, DU 174 generates a first LTM DU configuration (hereinafter referred to as LTM DU configuration 1) for UE 102, which configures the first cell for LTM. DU 174 then sends a 310 First DU to CU message including LTM DU configuration 1 to CU 172 in response to the First CU to DU message. In some implementations, DU 174 may include cell ID 1 along with LTM DU configuration 1 in the IE of the first DU to CU message to indicate that LTM DU configuration 1 is associated with the first cell (i.e., cell ID 1). Instead of responding to a CU to DU message received from CU 172, DU 174 initiates the sending of the first DU to CU message to CU 172 when it determines that the first cell is ready.

[0073] In some implementations, DU 174 includes cell ID 1 in the first DU to CU message to indicate that LTM DU configuration 1 is configured for or associated with the first cell. CU 172 identifies that LTM DU configuration 1 is configured for or associated with the first cell. In some scenarios and implementations, CU 172 may include additional cell IDs (e.g., cell ID 2, ..., N) in the first CU to DU message to prepare additional cells (e.g., cells 2, ..., N) for LTM use by UE 102, and DU 174 includes additional LTM DU configurations (e.g., LTM DU configuration 2, ..., N), each additional LTM DU configuration configuring a specific cell in the additional cells, as described below. In such cases, DU 174 includes the additional cell IDs associated with each additional LTM DU configuration in the first DU to CU message to indicate which LTM DU configuration is associated with which cell (ID). Cells 1 and / or 2, ..., N are candidate cells. In some implementations, CU 172 associates LTM DU configurations 1, ..., N with cell IDs 1, ..., N, respectively.

[0074] In some implementations, DU 174 includes UE ID 1 in the first DU to CU message to indicate that DU 174 configures UE ID 1 for communication with UE 102 in the first cell. When preparing additional cells (e.g., cells 2, ..., N) for LTM for UE 102 in the first CU to DU message, DU 174 may include UE ID 2, ..., N for communication with UE 102 on cells 2, ..., N, respectively, in the first DU to CU message. In some implementations, UE ID 1, ..., N are Cell Radio Network Temporary Identifiers (C-RNTI). In some implementations, DU 174 includes UE ID 1, ..., N in LTM DU configurations 1, ..., N, respectively. In some implementations, DU 174 includes UE ID 1, ..., N in the first DU to CU message and also includes UE ID 1, ..., N in LTM DU configurations 1, ..., N, respectively. In some implementations, CU 172 stores UE IDs 1, ..., N and associates UE IDs 1, ..., N with LTM DU configurations 1, ..., N and / or cell IDs 1, ..., N respectively.

[0075] In some implementations, CU 172 does not include the (reference) LTM DU configuration in the first CU-DU message. In such cases, DU 174 generates a reference LTM DU configuration, generates LTM DU configurations 1 and / or 2, ..., N (i.e., non-reference LTM DU configurations) based on the reference LTM DU configuration, and includes the reference LTM DU configuration in the first DU-CU message. In other implementations, CU 172 includes the reference LTM DU configuration in the first CU-DU message. In such cases, DU 174 generates LTM DU configurations 1 and / or 2, ..., N, which are incremental configurations used to enhance the reference LTM DU configuration. In yet another implementation, CU 172 includes the reference LTM DU configuration (e.g., the first reference LTM DU configuration) in the first CU-DU message. In such cases, DU 174 generates a reference LTM DU configuration (e.g., a second reference LTM DU configuration) that replaces the first reference LTM DU configuration, generates LTM DU configuration 1 and / or 2, ..., N based on the second reference LTM DU configuration, and includes the second reference LTM DU configuration in the first DU to CU message.

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

[0077] In some implementations, the reference LTM DU configuration differs from the service DU configuration. In some implementations, a portion of the reference LTM DU configuration is identical to a portion of the service DU configuration, and the remainder of the reference LTM DU configuration differs from the remainder of the service DU configuration. In other implementations, the reference LTM DU configuration is identical to the service DU configuration.

[0078] After receiving the first DU to CU message, CU 172 generates an RRC reconfiguration message (e.g., an RRCReconfiguration message) that includes LTM DU configuration 1, and sends a second CU to DU message 316, which includes the RRC reconfiguration message, to DU 174. In some implementations, CU 172 includes the reference LTM DU configuration in the RRC reconfiguration message 316. In other implementations, CU 172 does not include the reference LTM DU configuration in the RRC reconfiguration message 316. In some implementations, if CU 172 sends the reference LTM DU configuration to UE 102 during event 302, then CU 172 does not include the reference LTM DU configuration in the RRC reconfiguration message 316. In other implementations, if CU 172 receives the reference LTM DU configuration from DU 174, then CU 172 includes the LTM DU configuration in the RRC reconfiguration message 316. Otherwise, if CU 172 does not receive the reference LTM DU configuration from DU 174, CU 172 will not include the reference LTM DU configuration in RRC reconfiguration message 316.

[0079] In some implementations, CU 172 includes LTM DU configuration 1 and / or LTM CU configuration 1 in a first container (e.g., field / IE), and includes the first container (e.g., LTM configuration 1) in the RRC reconfiguration messages of events 316 and 318. In such cases, CU 172 generates the first container. The first container is used to instruct UE 102 not to immediately apply LTM DU configuration 1 and / or LTM CU configuration 1. In some scenarios or implementations, UE 102 receives an RRC reconfiguration message (e.g., the RRC reconfiguration message of event 318) that includes the configuration (e.g., LTM DU configuration 1). If the configuration is included in the first container, UE 102 avoids immediately applying the configuration. Otherwise, if the configuration is not included in the first container, UE 102 can apply the configuration immediately. In some implementations, the first container includes or is a first add or modify list (e.g., the ltm-ConfigToAddModList field, the ltm-CandidateToAddModList field, or the ltm-CandidateConfigToAddModList field). CU 172 includes LTM DU configuration 1 and / or LTM CU configuration 1 in the first element (hereinafter referred to as element 1) of the first add or modify list. In some implementations, CU 172 generates an RRC message (e.g., an RRCReconfiguration message) that includes LTM DU configuration 1 and / or LTM CU configuration 1 and includes the RRC message in element 1. In some implementations, element 1 is an add or modify IE (e.g., LTM-ConfigToAddMod IE, LTM-Candidate IE, LTM-CandidateToAddMod IE, or LTM-CandidateConfigToAddMod IE). When UE 102 receives the first add or modify list, UE 102 may store the first add or modify list (e.g., in a variable stored in random access memory (RAM)). In other alternative implementations, DU 174 generates a first container and includes the first container in the first DU to CU message. In yet another alternative implementation, DU 174 generates element 1 and includes element 1 in the first DU to CU message.

[0080] In some implementations, CU 172 includes LTM CU configuration 1 in RRC reconfiguration message 316, the first container, or element 1, where LTM CU configuration 1 is associated with LTM DU configuration 1. To associate LTM CU configuration 1 with LTM DU configuration 1, CU 172 may include LTM CU configuration 1 and LTM DU configuration 1 in element 1. In some implementations, CU 172 includes LTM CU configurations 2, ..., N in RRC reconfiguration message 316 or the second container, where LTM CU configurations 2, ..., N are associated with LTM DU configurations 2, ..., N, respectively. To associate LTM CU configurations 2, ..., N with LTM DU configurations 2, ..., N, CU 172 may include LTM CU configurations 2, ..., N and LTM DU configurations in elements 2, ..., N, respectively. In other implementations, CU 172 includes the LTM CU configurations 2, ..., N associated with LTM DU configurations 2, ..., N in elements 2, ..., N, respectively. Alternatively, CU 172 does not include some or all of the LTM CU configurations for LTM DU configuration 1 and / or LTM DU configurations 2, ..., N in the RRC reconfiguration message 316.

[0081] Upon receiving RRC reconfiguration message 316, DU 174 sends RRC reconfiguration message 318 to UE 102. In response, UE 102 sends RRC reconfiguration complete message 320 (e.g., RRCReconfigurationComplete message) to DU 174, and DU 174 then sends a second DU-to-CU message 322, including the RRC reconfiguration complete message, to CU 172. In some implementations, CU 172 performs security protection on the RRC reconfiguration message (e.g., integrity protection and / or encryption). For example, CU 172 generates an integrity message authentication code (MAC-I) for the RRC reconfiguration message, encrypts the RRC reconfiguration message and the MAC-I to obtain an encrypted RRC reconfiguration message and an encrypted MAC-I, and sends a PDCP PDU including the encrypted RRC reconfiguration message and the encrypted MAC-I to UE 102 via DU 174 in events 316 and 318. When UE 102 receives a PDCP PDU from CU 172 via DU 174 (i.e., events 316 and 318), UE 102 decrypts the encrypted RRC reconfiguration and encrypted MAC-I to obtain the RRC reconfiguration message and MAC-I, and verifies the validity of the MAC-I. If UE 102 verifies that the MAC-I is invalid, UE 102 discards or ignores the RRC reconfiguration message. In some implementations, UE 102 may perform an RRC connection reconstruction procedure in response to an invalid MAC-I. Otherwise, if UE 102 verifies that the MAC-I is valid, UE 102 may process the RRC reconfiguration. UE 102 avoids applying (i.e., executing) LTM DU configuration 1 until it receives an LTM command to activate LTM DU configuration 1, as described for events 330 and 350.

[0082] Events 308 (optional) and 310 in FIG. 3 This is collectively referred to as LTM preparation process 390. Events 316, 318, 320, and 322 are... FIG. 3 This is collectively referred to as the LTM configuration delivery process 394.

[0083] In some implementations, the first CU to DU message is a UE context modification request message, and the first DU to CU message is a UE context modification response message or a UE context modification request message. In the case of a UE context modification request message, CU 172 may send a UE context modification confirmation message to DU 174 in response to the UE context modification request message. In some implementations, the second CU to DU message is a DL RRC message transmission message. In other implementations, the second CU to DU message is a UE context modification request message, and DU 174 may send a second DU to CU message (e.g., a UE context modification response message) to CU 172 in response to the second CU to DU message.

[0084] In some implementations, CU 172 may include the reference LTM CU configuration in RRC reconfiguration message 316 or the first container. In some implementations, CU 172 may generate LTM CU configuration 1 (i.e., the non-reference LTM CU configuration) as an incremental configuration to enhance the reference LTM CU configuration. Similarly, CU 172 may generate some or all of LTM CU configurations 2, ..., N as incremental configurations to enhance the reference LTM CU configuration. Alternatively, in RRC reconfiguration message 316 or the first container, CU 172 includes the reference LTM CU configuration but not the non-reference LTM CU configuration. In some implementations, CU 172 includes the reference LTM CU configuration and / or the reference LTM DU configuration in an additional container (e.g., the reference LTM configuration) and includes this additional container in RRC reconfiguration message 316.

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

[0086] In some implementations, CU 172 includes the first LTM ID (hereinafter referred to as ID 1) used to identify LTM DU configuration 1 or element 1 in the RRC reconfiguration message. In some implementations, CU 172 includes ID 1 in the first container or element 1. In some implementations, CU 172 assigns ID 1.

[0087] In some implementations, CU 172 may send ID 1 to DU 174, and DU 174 associates ID 1 with LTM DU configuration 1 and / or cell ID 1. In some implementations, CU 172 includes ID 1 in the first CU-DU message. In other implementations, after receiving the first DU-CU message, CU 172 sends a third CU-DU message including ID 1 to DU 174, instead of including ID 1 in the first CU-DU message. In some implementations, in the third CU-DU message, CU 172 may include LTM DU configuration 1 and ID 1, and indicate the association between ID 1 and LTM DU configuration 1. Therefore, DU 174 may directly associate ID 1 with LTM DU configuration 1. In other implementations, in the third CU-DU message, CU 172 may include cell ID 1 and ID 1 (i.e., the first LTM ID), and indicate the association between cell ID 1 and ID 1. Therefore, DU 174 can associate ID 1 with LTM DU configuration 1 based on the association between cell ID 1 and ID 1, and the association between cell ID 1 and LTM DU configuration 1. In other implementations, CU 172 may include LTM DU configuration 1, cell ID 1, and / or ID 1 in the third CU to DU message, and indicate the association between ID 1, LTM DU configuration 1, and / or cell ID 1. In some implementations, DU 174 may send a third DU to CU 172 in response to the third CU to DU message. In some implementations, the third CU to DU message and the third DU to CU message are a UE context modification request message and a UE context modification response message. Events 312 (optional) and 314 (optional) in FIG. 3 This is collectively referred to as LTM ID assignment procedure 392. In other implementations, CU 172 may include ID 1, cell ID 1, and / or LTM DU configuration 1 in the second CU to DU message, as described above. Therefore, the third CU to DU message can be omitted.

[0088] If CU 172 includes ID 1 in the first CU to DU message, DU 174 may include ID 1 in LTM DU configuration 1, the first container, or element 1. Alternatively, DU 174 may not include ID 1 in LTM DU configuration 1, the first container, and / or element 1.

[0089] In some implementations, CU 172 includes the referenced LTM DU configuration in a first container. For example, CU 172 includes the referenced LTM DU configuration in fields of a first container that are different from the fields of the first container that includes LTM DU configuration 1. In other implementations, CU 172 includes the referenced LTM DU configuration in RRC reconfiguration message 316 and outside the first container. For example, CU 172 generates a third container (e.g., field / IE) to include the first container and the referenced LTM DU configuration, and includes the third container in RRC reconfiguration message 316. In yet another implementation, DU 174 includes the referenced LTM DU configuration in a first container. For example, DU 174 includes the referenced LTM DU configuration in fields of a first container that are different from the fields of the first container that includes LTM DU configuration 1. In yet another implementation, DU 174 generates a fourth container (e.g., field / IE) to include the first container and the referenced LTM DU configuration, and includes the fourth container in the first DU to CU message 310. In this case, CU 172 includes the fourth container in the RRC reconfiguration message 316. Alternatively, CU 172 retrieves the reference LTM DU configuration and LTM DU configuration 1 from the fourth container, and includes the reference LTM DU configuration and LTM DU configuration 1, as described above.

[0090] In some implementations, neither CU 172 nor DU 174 is assigned an ID to identify the reference LTM DU configuration.

[0091] In some implementations, LTM DU configuration 1 includes multiple configuration parameters for UE 102 to communicate with DU 174 in 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 the CellGroupConfig IE defined in 3GPP specification 38.331. In other implementations, LTM DU configuration 1 includes configuration parameters from the CellGroupConfig IE.

[0092] In some implementations, LTM CU configuration 1 includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, LTM CU configuration 1 includes MeasConfig IE and / or RadioBearerConfig IE as defined in 3GPP specification 38.331, or includes configuration parameters from MeasConfig IE and / or RadioBearerConfig IE. In some implementations, LTM DU configuration 1 includes L1 measurement configuration 1 (e.g., CSI-MeasConfig IE) and / or at least one Configuration Indicator (TCI) status configuration. In other implementations, LTM CU configuration 1 includes L1 measurement configuration and / or TCI status configuration 1. In some implementations, the L1 measurement configuration includes at least one Reference Signal (RS) resource configuration 1 and / or at least one Reporting configuration 1. In some implementations, RS resource configuration 1 configures one or more RSs or one or more RS resources associated with cell 1. RSs include SSBs and / or CSI-RSs. RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of the RS resource configurations 1 includes an RS resource configuration ID. In some implementations, RS resource configuration 1 is (similar to) a CSI-ResourceConfig IE. In some implementations, report configuration 1 configures one or more UL resources (e.g., PUCCH or PUSCH resources) on cell 1 for UE 102 to transmit measurement results. In some implementations, each of the report configurations 1 includes one or more RS resource configuration IDs that identify one or more RS resource configurations included in RS resource configuration 1. In some implementations, each configuration in TCI state configuration 1 associates one or two DL RSs with the corresponding Quasi-Co-location (QCL) type of TCI state. The DL RS is associated with cell 1.

[0093] In some implementations, DU 174 includes L1 measurement configuration 1 and / or TCI state configuration 1 in the service DU configuration 1 (e.g., a non-LTM DU configuration). In some implementations, DU 174 includes the service DU configuration in the first DU to CU message. In other implementations, DU 174 sends an additional DU to CU 172 including the service DU configuration. In some implementations, the additional DU to CU message is a UE context modification request message. In some implementations, CU 172 includes the service DU configuration 1 in RRC reconfiguration messages 316, 318. In other implementations, CU 172 sends another RRC reconfiguration message including the service DU configuration to UE 102 via DU 174.

[0094] In some implementations, DU 174 includes the random access configuration in LTM DU configuration 1. In other implementations, DU 174 does not include the random access configuration in LTM DU configuration 1. In some implementations, if cell 124A and the first cell are not synchronized, DU 174 determines to include the random access configuration in LTM DU configuration 1. Otherwise, if cell 124A and the first cell are synchronized, DU 174 determines not to include the random access configuration in LTM DU configuration 1. In other implementations, if DU 174 determines that UE 102 has not yet synchronized with the first cell in the UL, DU 174 determines to include the random access configuration in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 is already synchronized with the first cell in the UL, DU 174 determines not to include the random access configuration in LTM DU configuration 1. If LTM DU configuration 1 includes a random access configuration, then UE 102 can perform a random access procedure in event 332 according to the random access configuration, as described below. Otherwise, if LTM DU configuration 1 does not include a random access configuration or instructs UE 102 to skip the random access procedure in LTM, then UE 102 skips or avoids performing the random access procedure in event 332 in response to LTM DU configuration 1 excluding the random access configuration.

[0095] In some implementations, DU 174 includes random access configuration parameters in LTM DU configuration 1 and / or reference LTM DU configuration, regardless of whether cell 124A and the first cell are synchronized. In some implementations, UE 102 performs the random access procedure in event 332 according to the random access configuration parameters, as described below. In some implementations, the random access configuration parameters configure physical random access channel (PRACH) resources, the association between SSB and PRACH resources, and / or one or more PRACH occasions.

[0096] In some implementations, if cell 124A and the first cell are synchronized, DU 174 determines to include a first indication in LTM DU configuration 1, which configures UE 102 not to perform a random access procedure in the first cell. Otherwise, if cell 124A and the first cell are not synchronized, DU 174 determines not to include the first indication in LTM DU configuration 1. In other implementations, if DU 174 determines that UE 102 is already synchronized with the first cell in the UL, DU 174 determines to include the first indication in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 is not yet synchronized with the first cell in the UL, DU 174 determines not to include the first indication in LTM DU configuration 1. If LTM DU configuration 1 includes the first indication, UE 102 skips or avoids performing the random access procedure of event 332 according to or in response to the first indication. Otherwise, if LTMDU configuration 1 excludes the first indication, then in response to LTMDU configuration 1 not including the first indication, UE 102 performs a random access procedure in event 332 according to the random access configuration, as described below.

[0097] In some implementations, DU 174 includes reconfigurations with synchronized configurations (e.g., ReconfigurationWithSync IE) in LTM DU configuration 1 or a special cell configuration. In other implementations, DU 174 does not include reconfigurations with synchronized configurations (e.g., ReconfigurationWithSync IE) in LTM DU configuration 1 or a special cell configuration. In some implementations, if cell 124A and the first cell are not synchronized, DU 174 determines to include reconfigurations with synchronized configurations in LTM DU configuration 1. Otherwise, if cell 124A and the first cell are synchronized, DU 174 determines not to include reconfigurations with synchronized configurations in LTM DU configuration 1. In other implementations, if DU 174 determines that UE 102 has not yet synchronized with the first cell in the UL, DU 174 determines to include reconfigurations with synchronized configurations in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 is already synchronized with the first cell in the UL, then DU 174 determines not to include the reconfiguration with synchronization configuration in LTM DU configuration 1. In some implementations, if LTM DU configuration 1 includes the reconfiguration with synchronization configuration, then UE 102 performs a random access procedure in event 332 in response to or based on the reconfiguration with synchronization configuration, as described below. Otherwise, if LTM DU configuration 1 does not include the reconfiguration with synchronization configuration, then UE 102 skips or avoids performing the random access procedure in event 332.

[0098] In some implementations, DU 174 includes the cell ID (i.e., cell ID 1) of cell 1 (i.e., the first cell) in LTM DU configuration 1. In one implementation, cell ID 1 may be a PCI. In another implementation, cell ID 1 is a CGI. In some implementations, cell ID 1 included in LTM DU configuration 1 is a PCI, while cell ID 1 included in the first CU to DU message is a CGI. In some further implementations, LTM DU configuration 1 includes cell index 1 indexed to cell ID 1 or the first cell. Cell index 1 is not a cell ID. The cell index occupies fewer bits than the cell ID. In some implementations, CU 172 sets cell index 1 to a value and includes cell index 1 in the first CU to DU message of event 308.

[0099] In some implementations, upon receiving one or more of the measurement reports for event 304 (e.g., in response to this), base station 104 (i.e., CU 172 or DU 174) determines to prepare an additional cell (i.e., cell 2, ..., N) for LTM for UE 102. In one implementation, base station 104 determines to prepare an additional cell for LTM for UE 102 because at least one measurement report indicates that the additional cell can be used by base station 104 to communicate with UE 102. The additional cell may include cell 124C and / or cells other than cells 124A, 124B, and 124C. In some implementations, CU 172 determines to prepare that particular cell for LTM for UE 102 if an L3 measurement report indicates that the signal strength and / or quality of a particular cell in the additional cells is higher than a corresponding predetermined threshold and / or better than cell 124A. In other implementations, if the L1 measurement report indicates that the signal strength and / or quality of a particular cell in the additional cells is higher than a first predetermined threshold and / or better than cell 124A, then DU 174 determines that particular cell to be prepared for LTM by UE 102. In one implementation, the corresponding predetermined threshold for the additional cell may be different from the first predetermined threshold. In another implementation, the corresponding predetermined threshold for the additional cell may be the same as the first predetermined threshold. In some implementations, the corresponding predetermined threshold for the additional cell may be the same or different. Alternatively, base station 104 determines to prepare the additional cell for UE 102 regardless of whether a measurement report is received from UE 102.

[0100] When CU 172 determines that an additional cell is to be prepared, CU 172 initiates and executes at least one additional LTM preparation procedure (LTM preparation procedure) with DU 174 to prepare the additional cell for LTM, wherein each of the LTM preparation procedures is similar to procedure 390. When DU 174 determines that an additional cell is to be prepared, DU 174 initiates and executes at least one additional LTM preparation procedure (LTM preparation procedure) with CU 172 to prepare the additional cell for LTM, wherein each of the LTM preparation procedures is similar to procedure 390.

[0101] In some implementations, CU 172 and DU 174 perform LTM preparation procedures 2, ..., N similar to procedure 390 to prepare cells 2, ..., N, respectively. CU 172 may include cell IDs 2, ..., N in CU-DU messages 2, ..., N in LTM preparation procedures 2, ..., N, similar to the first CU-DU message. In LTM preparation procedures 2, ..., N, DU 174 generates LTM DU configurations 2, ..., N for cells 2, ..., N, and includes LTM DU configurations 2, ..., N in DU-CU messages 2, ..., N, as described for LTM DU configuration 1. Upon receiving CU-DU messages 2, ..., N, DU-CU messages 2, ..., N respond to CU-DU messages 2, ..., N, respectively. "N" is an integer greater than one. For example, "N" is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16. In another example, the maximum number of "N" is 4, 8, 16, or 32. At least some of the descriptions in LTM DU Configuration 1 can also be applied to LTM DU Configuration 2, ..., N.

[0102] In other implementations, CU 172 and DU 174 perform a single LTM preparation procedure (i.e., LTM preparation procedure 390) to prepare cells 1, 2, ..., N. In this case, DU 174 includes the LTM DU configurations 1, 2, ..., N for cells 1, 2, ..., N in the first DU to CU message. In the first DU to CU message, DU 174 may include cell IDs 1, 2, ..., N associated with LTM DU configurations 1, 2, ..., N respectively, to indicate that LTM DU configurations 1, 2, ..., N are configured for cell IDs 1, 2, ..., N respectively. When CU 172 determines to perform LTM preparation procedure 390, CU 172 includes cell IDs 1, 2, ..., N in the first CU to DU message to request DU 174 to prepare cells 1, 2, ..., N for LTM respectively.

[0103] After receiving LTM DU configurations 2, ..., N from DU 174, CU 172 may include LTM DU configurations 2, ..., N in a first container. In some implementations, CU 172 may include LTM DU configurations 2, ..., N in elements 2, ..., N respectively, and include elements 2, ..., N in the first container. In some implementations, CU 172 may include the LTM IDs (i.e., ID 2, ..., N) used to identify LTM DU configurations 2, ..., N respectively in the RRC reconfiguration message. In some implementations, CU 172 may include ID 2, ..., N in the first container. For example, CU 172 may include ID 2, ..., N and LTM DU configurations 2, ..., N in elements 2, ..., N in a first add or modify list.

[0104] In some implementations, CU 172 assigns IDs 2, ..., N to LTM DUs respectively. In other implementations, CU 172 receives IDs 2, ..., N from the first DU to CU message in process 390 of DU 174. In yet another implementation, CU 172 receives IDs 2, ..., N from DU to CU messages 2, ..., N in LTM preparation processes 2, ..., N respectively from DU 174.

[0105] In some implementations, CU 172 can perform an LTM ID assignment procedure similar to procedure 392 with DU 174 for each of LTM DU configurations 2, ..., N. In other implementations, CU 172 can include IDs 2, ..., N and LTM DU configurations 2, ..., N in a third CU-DU message, indicating the association between IDs 2, ..., N and LTM DU configurations 2, ..., N respectively. Therefore, DU 174 can associate LTM DU configurations 2, ..., N with IDs 2, ..., N respectively. In yet another implementation, CU 172 can include cell IDs 2, ..., N and IDs 2, ..., N in a third CU-DU message, indicating the association between cell IDs 2, ..., N and IDs 2, ..., N respectively. Therefore, DU 174 can associate LTM DU configurations 2, ..., N with ID 2, ..., N based on the associations between cell IDs 2, ..., N and ID 2, ..., N respectively, and the associations between cell IDs 2, ..., N and LTM DU configurations 2, ..., N respectively. In other implementations, CU 172 can include IDs 2, ..., N, cell IDs 2, ..., N, and / or LTM DU configurations 2, ..., N in the second CU to DU message, as described above. Therefore, the third CU to DU message can be omitted. In yet another implementation, CU 172 can include IDs 2, ..., N in the first CU to DU message and indicate that IDs 2, ..., N are associated with cell IDs 2, ..., N respectively. In one implementation, DU 174 includes IDs 2, ..., N in LTM DU configurations 2, ..., N. Therefore, CU 172 does not include ID 2, ..., N in the RRC reconfiguration message, the first container, and / or element 2, ..., N.

[0106] In some alternative implementations, DU 174 assigns IDs 2, ..., N. In some implementations, DU 174 includes IDs 2, ..., N in the first DU to CU message of process 390. In yet another implementation, DU 174 includes IDs 2, ..., N in DU to CU messages 2, ..., N of LTM preparation process 2, ..., N. CU 172 may include IDs 2, ..., N in the RRC reconfiguration message. In other implementations, DU 174 includes IDs 2, ..., N in LTMDU configuration 2, ..., N. Therefore, CU 172 does not include the ID (e.g., LTM ID) identifying each of LTM DU configurations 2, ..., N in the RRC reconfiguration message, the first container, and / or element 1.

[0107] In some alternative implementations, CU 172 may generate a second container, including LTM DU configuration 2, ..., N or element 2, ..., N, instead of using the first container. Then, similar to events 316 and 318, CU 172 sends an additional RRC reconfiguration message including the second container to UE 102 via DU 174. In response, similar to events 320 and 322, UE 102 sends an additional RRC reconfiguration complete message to CU 172 via DU 174. In some implementations, the second container may be a second add-or-modify list (e.g., the ltm-ConfigToAddModList field, LTM-ConfigToAddModList IE, ltm-CandidateConfigToAddModList field, or LTM-CandidateConfigToAddModList IE), and each of elements 2, ..., N may be an add-or-modify IE (e.g., the ltm-ConfigToAddMod field, LTM-ConfigToAddMod IE, ltm-CandidateConfigToAddMod field, or LTM-CandidateConfigToAddMod IE). When UE 102 receives the second add-or-modify list, UE 102 may store the second add-or-modify list together with the first add-or-modify list (e.g., in a variable in its random access memory (RAM)).

[0108] In some implementations, DU 174 includes cell IDs 2, ..., N in LTM DU configurations 2, ..., N to identify cells 2, ..., N. In one implementation, each of cell IDs 2, ..., N is a PCI. In some further implementations, LTM DU configurations 2, ..., N include cell indices 2, ..., N indexed for cell IDs 2, ..., N or cells 2, ..., N respectively. When CU 172 prepares cells 2, ..., N for LTM in process 390, CU 172 may set cell indices 2, ..., N to different values ​​and include cell indices 2, ..., N in the first CU-to-DU message of event 308. When CU 172 prepares cells 2, ..., N in the additional LTM preparation process, CU 172 may set cell indices 2, ..., N to different values ​​and include cell indices 2, ..., N in the CU-to-DU message of the additional LTM preparation process. CU 172 sets cell indices 1, ..., N to different values. In some implementations, the cell IDs 1, ..., N in the LTM DU configuration 1, ..., N are different from the cell IDs 1, ..., N in the CU to DU message described above.

[0109] In some implementations, each of the LTM DU configurations 1, ..., N includes physical configuration parameters, MAC configuration parameters, RLC configuration parameters, and / or L1 measurement configuration. In some implementations, each of the LTM DU configurations 1, ..., N may be a CellGroupConfig IE as defined in 3GPP specification 38.331. In other implementations, each of the LTM DU configurations 1, ..., N includes configuration parameters included in a CellGroupConfig IE as defined in 3GPP specification 38.331. In some further implementations, multiple configuration parameters in each of the LTM DU configurations include specific cell configurations (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE). In some implementations, the LTM DU configurations 1, ..., N are CellGroupConfig IEs as defined in 3GPP specification 38.331. In other implementations, the LTM DU configurations 1, ..., N include configuration parameters from a CellGroupConfig IE.

[0110] In some implementations, CU 172 may include one or more additional LTM CU configurations in at least one of elements 2, ..., N, the first container, or the second container. Each of the additional LTM CU configurations is associated with a specific LTM DU configuration in LTM DU configurations 2, ..., N. At least some of the descriptions of the additional LTM CU configurations are similar to LTM CU configuration 1.

[0111] In some implementations, CU 172 determines to release LTM DU configuration M (or element M in element 1, ..., M) from LTM DU configurations 1, ..., N. 1 ≤ M ≤ N. In response to this determination, CU 172 sends an RRC reconfiguration message to UE 102 via DU 174, instructing UE 102 to release LTM DU configuration M or element M. In one implementation, CU 172 generates a release list including an ID (i.e., LTM ID) M for releasing LTM DU configuration M or element M, and includes the release list in the RRC reconfiguration message. In response to the RRC reconfiguration message, UE 102 releases LTM DU configuration M or element M and sends an RRC reconfiguration complete message to CU 172 via DU 174. In response to this determination, CU 172 sends a CU-DU message to DU 174, instructing DU 174 to release LTM DU configuration M. To instruct DU 174 to release the LTM DU configuration M, CU 172 can include the cell IDM or ID (i.e., LTM ID) M in the release instruction (e.g., a field or IE) in the CU-DU message. In response, DU 174 releases the LTM DU configuration M and sends a DU-CU message to CU 172. In some implementations, the CU-DU message and the DU-CU message are respectively a UE context modification request message and a UE context modification response message.

[0112] In other implementations, DU 174 determines to release LTM DU configuration K. In response to this determination, DU 174 sends a DU-to-CU message to CU 172 to release LTM DU configuration K. To indicate that LTM DU configuration K has been released, DU 174 may include the cell ID K or ID (i.e., LTM ID) K in the release indication (e.g., a field or IE) in the DU-to-CU message. 1 ≤ K ≤ N. After receiving the DU-to-CU message (e.g., in response to this), CU 172 generates a release list including ID (i.e., LTM ID) K for releasing LTM DU configuration K or element K, and sends an RRC reconfiguration message including this release list to UE 102 via DU 174. In response, UE 102 releases LTM DU configuration K or element K and sends an RRC reconfiguration complete message to UE 102 via DU 174. CU 172 may send a CU-to-DU message to DU 174 in response to the DU-to-CU message. In some implementations, the DU to CU message and the CU to DU message are respectively the UE context modification request message and the UE context modification confirmation message.

[0113] After receiving an RRC reconfiguration in event 318 or sending an RRC reconfiguration completion message in event 320, similar to event 304, UE 102 sends at least one measurement report (324) to DU 174. In some implementations, similar to event 306, DU 174 may send a DU-CU message (326) including at least one measurement report to CU 172. In other implementations, DU 174 does not send at least one measurement report to CU 172. In some implementations, at least one measurement report in event 324 includes an L1 measurement report or an L3 measurement report, as described for event 304. In some implementations, similar to event 304, UE 102 sends at least one measurement report (324) to DU 174 on PUCCH and / or PUSCH. In other implementations, similar to event 304, UE 102 sends at least one MAC CE (324) including at least one measurement report to DU 174. In some implementations, UE 102 does not send L1 measurement reports to DU 174 in the format of RRC messages.

[0114] In some implementations, UE 102 sends at least one measurement report (324) to DU 174 according to at least one measurement configuration. The at least one measurement configuration configures UE 102 to perform measurements and report measurement results. CU 172 sends at least one measurement configuration to UE 102 via DU 174. For example, CU 172 may send one or more RRC messages (e.g., RRCReconfiguration messages) including at least one measurement configuration to UE 102 via DU 174 during and / or after events 302 and / or 316. The one or more RRC messages may or may not include the RRC reconfiguration message of event 316. According to at least one measurement configuration, UE 102 performs measurements on one or more reference signals. The one or more reference signals may include one or more SSBs and / or one or more CSI-RSs. UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurements and includes the at least one L1 measurement result and / or at least one L3 measurement result in the at least one measurement report (324). DU 174 transmits one or more reference signals on cell 124A, cell 1, and / or cell 2, ..., N. The one or more reference signals may be CSI-RS or SSB.

[0115] In some implementations, the at least one measurement configuration includes an L3 measurement configuration (e.g., a MeasConfigIE), as described for event 304. In other implementations, the at least one measurement configuration includes or is an L1 measurement configuration, as described above. In yet another implementation, the L1 measurement configuration may be a CSI-MeasConfigIE defined in 3GPP specification 38.331 v18.0.0 and / or later. The L1 measurement configuration may include RS resource configuration and / or reporting configuration. UE 102 sends a 324 L1 measurement report to DU 174 on a UL resource (e.g., a PUCCH resource or a PUSCH resource) according to the reporting configuration. DU 174 receives the L1 measurement report on the UL resource according to the reporting configuration. In some implementations, the reporting configuration is or is similar to a CSI-ReportConfigIE. In other implementations, each of the reporting configurations is a new RRCIE. In some implementations, each of the reporting configurations periodically configures the reporting of L1 measurement results and / or event-triggered reporting.

[0116] In some implementations, the L1 measurement report is a CSI report. In other implementations, the L1 measurement report is a MACCE. In some implementations, each of the measurement reports includes one or more RS resource indicators and / or one or more quantized measurement values. UE 102 performs measurements on the RS or RS resource according to the RS resource configuration and / or reporting configuration, and obtains quantized measurement values ​​from the measurements. In some implementations, the RS resource indicator indicates the RS or RS resource in which UE 102 performs measurements or obtains quantized measurement values. In some implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRI) and / or one or more CSI-RS resource indicators (CRI). Quantized measurement values ​​may include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0117] In other implementations, the at least one measurement configuration includes a novel measurement configuration (e.g., an LTM measurement configuration). The novel measurement configuration may be newly defined in 3GPP specification v18.0.0 and / or later. In some implementations, the novel measurement configuration includes a reference signal resource configuration that configures the resources in which DU 174 transmits reference signals. For example, the reference signal resource configuration includes CSI-RS and / or SSB. In one implementation, the reference signal resource configuration is CSI-ResourceConfig IE. In another implementation, as described above, the novel measurement configuration includes a measurement report configuration. UE 102 transmits a measurement report to DU 174 on the PUCCH or MAC CE according to the measurement report configuration. DU 174 receives the measurement report on the PUCCH or MAC CE according to the measurement report configuration. In such cases, the measurement report may be an L1 measurement report or a novel measurement report (e.g., an LTM measurement report). In some implementations, the novel measurement configuration includes configuration parameters newly defined in 3GPP specification v18.0.0 and / or later.

[0118] Upon receiving at least one measurement report in event 324 (e.g., in response to this), DU 174 generates a first LTM command to activate LTM DU configuration 1 (i.e., the first LTM command instructs UE 102 to apply LTM DU configuration 1 or perform a serving cell change for cell 1). DU 174 then sends the first LTM command to UE 102 at 330. In some implementations, DU 174 sends the first LTM command to UE 102 on cell 124A. In other implementations, DU 174 sends the first LTM command to UE 102 on cell 124D. In some implementations, DU 174 may include ID 1 in the first LTM command to indicate LTM DU configuration 1 or element 1, and UE 102 determines (e.g., identifies) LTM DU configuration 1 or element 1 based on ID 1.

[0119] In other implementations, DU 174 may include cell index 1, which is indexed to cell ID 1, in the first LTM command. UE 102 determines (e.g., identifies) LTM DU configuration 1 or element 1 based on cell index 1. Before receiving the first LTM command, UE 102 retrieves cell index 1 from LTM DU configuration 1 or element 1 and establishes association 1 between cell index 1 and LTM DU configuration 1 or element 1. In other words, UE 102 decodes LTM DU configuration 1 or element 1 to obtain cell index 1 before receiving the first LTM command. Therefore, UE 102 identifies LTM DU configuration 1 or element 1 based on cell index 1 and association 1. Before receiving the first LTM command, UE 102 retrieves cell indices 2, ..., N from LTM DU configurations or elements 2, ..., N, and establishes associations 2, ..., N between cell indices 2, ..., N and LTM DU configurations or elements 2, ..., N, respectively. In other words, before receiving the first LTM command, UE 102 decodes the LTM DU configuration or elements 2, ..., N to obtain cell indices 2, ..., N.

[0120] In other implementations, DU 174 includes cell ID 1 in the first LTM command, where cell ID 1 identifies cell 1. In some implementations, the cell ID 1 included in the first LTM command is the same as the cell ID 1 included in the first CU to DU message. In other implementations, DU 174 determines the cell ID 1 (e.g., PCI) included in the first LTM command from the cell ID 1 (e.g., CGI) received in the first CU to DU message. UE 102 determines (e.g., identifies) LTM DU configuration 1 or element 1 based on cell ID 1. Before receiving the first LTM command, UE 102 retrieves cell ID 1 from LTM DU configuration 1 or element 1 and establishes an association 1 between cell ID 1 and LTM DU configuration 1 or element 1. In other words, UE 102 decodes LTM DU configuration 1 or element 1 to obtain cell ID 1 before receiving the first LTM command. Therefore, UE 102 identifies LTM DU configuration 1 or element 1 based on cell ID 1 (received in the first LTM command) and association 1. Before receiving the first LTM command, UE 102 retrieves cell IDs 2, ..., N from LTM DU configurations or elements 2, ..., N, and establishes associations 2, ..., N between cell IDs 2, ..., N and LTM DU configurations or elements 2, ..., N respectively. In other words, UE 102 decodes LTM DU configurations or elements 2, ..., N to obtain cell IDs 2, ..., N before receiving the first LTM command. In some implementations, DU 174 has a mapping table for storing mappings of PCI 1, ..., N to CGI 1, ..., N for cells 1, ..., N respectively.

[0121] In other implementations, DU 174 may include a bitmap in the first LTM command to activate LTM DU configuration 1 instead of ID 1 or cell index 1. The number of bits in the bitmap is greater than or equal to "N". In one implementation, bits 1, ..., N correspond to cell index 1, ..., N, ID 1, ..., N, LTM DU configuration 1, ..., N, or element 1, ..., N, respectively, and DU 174 sets the corresponding bit (e.g., bit 1) in the bitmap to a first value to indicate cell index 1, ID 1, LTM DU configuration 1, or element 1. Therefore, UE 102 can determine cell index 1, ID 1, LTM DU configuration 1, or element 1 based on bit 1 in the bitmap that is set to a first value. In another implementation, bits 0, ..., N-1 correspond to cell index 1, ..., N, ID 1, ..., N, LTM DU configuration 1, ..., N, or element 1, ..., N, respectively, and DU 174 sets the corresponding bit (e.g., bit 0) in the bitmap to a first value to indicate cell index 1, ID 1, LTM DU configuration 1, or element 1. Therefore, UE 102 can determine cell index 1, ID 1, LTM DU configuration 1, or element 1 based on bit 0 set to the first value in the bitmap. In this implementation, DU 174 sets the remaining bits in the bitmap to a second value to indicate that the remaining portions of LTM DU configuration 1, ..., N are not activated. In some implementations, the first value is one, and the second value is zero. In other implementations, the first value is zero, and the second value is one. Generally, if DU 174 determines that LTM DU configuration L is activated or that the serving cell for UE 102 is changed to cell L, DU 174 may set the corresponding bit in the bitmap (e.g., bit L or bit L-1) to a first value and set the remaining bits to a second value, where 1 ≤ L ≤ N. In some implementations, DU 174 sets at most one bit in the bitmap to the first value.

[0122] After identifying or identifying LTM DU configuration 1 or element 1, UE 102 then applies LTM DU configuration 1 and / or LTM CU configuration after receiving the first LTM command (e.g., in response to this).

[0123] In some implementations, at least one measurement report of event 324 (e.g., an L1 measurement report or a novel measurement report) includes at least one measurement result of the first cell, the TRP of the first cell, or a reference signal transmitted in the first cell. The reference signal may be CSI-RS or SSB. DU 174 determines to activate LTM DU configuration 1 or send a first LTM command based on at least one measurement result. In some implementations, DU 174 determines to activate LTM DU configuration 1 because at least one measurement result is higher than a second predetermined threshold, when at least one measurement result is higher than the second predetermined threshold, or in the case where at least one measurement result is higher than the second predetermined threshold. In some implementations, the at least one measurement result includes an L1-RSRP value, an L1-RSRQ value, and / or an L1-SINR value. In other implementations, the at least one measurement result includes the RSRP value, RSRQ value, and / or SINR value of a novel measurement report. In some implementations, the second predetermined threshold is different from the first predetermined threshold. In one implementation, the second predetermined threshold is greater than the first predetermined threshold. In this case, at least one measurement indicates that the first cell is suitable for communication with UE 102. In another implementation, the second predetermined threshold is equal to the first predetermined threshold. In this case, the at least one measurement indicates that the first cell is consistently above either the second predetermined threshold or the first predetermined threshold. This indicates that the first cell is suitable for communication with UE 102. Therefore, in response to the signal strength or quality of the first cell being higher than the second predetermined threshold of UE 102, DU 174 determines to activate LTM DU configuration 1.

[0124] In some implementations, at least one measurement report (e.g., an L3 measurement report) of events 324 and 326 includes at least one measurement result of the first cell. CU 172 determines to activate LTM DU configuration 1 or send a first LTM command because at least one measurement result indicates that the signal strength or quality of the first cell is higher than a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In one implementation, the second predetermined threshold is greater than the first predetermined threshold. In such an implementation, at least one measurement report of event 326 indicates that the signal strength or quality of the first cell is suitable for communication with UE 102. In another implementation, the second predetermined threshold is equal to the first predetermined threshold. In such an implementation, at least one measurement report of event 326 indicates that the signal strength or quality of the first cell is consistently higher than either the second predetermined threshold or the first predetermined threshold. This also indicates that the first cell is suitable for communication with UE 102. Therefore, in response to the signal strength or quality of the first cell being higher than the second predetermined threshold, CU 172 determines to activate LTM DU configuration 1. In response to this determination, CU 172 sends a fourth CU-DU message (328) to DU 174 to activate LTM DU configuration 1 or trigger a serving cell change for UE 102 to cell 1. In some implementations, CU 172 includes ID 1 in the fourth CU-DU message. In other implementations, CU 172 includes cell index 1 in the fourth CU-DU message. In response to the fourth CU-DU message, DU 174 sends a first LTM command (330) to UE 102 and optionally sends a fourth DU-CU message to CU 172. In some implementations, CU 172 includes cell index 1 in the fourth CU-DU message. Therefore, DU 174 can determine the activation of LTM DU configuration 1 based on cell index 1. In other implementations, CU 172 may include cell ID 1 in the fourth CU-DU message. Therefore, DU 174 determines the activation of LTM DU configuration 1 based on cell ID 1. In other implementations, CU 172 may include ID 1 in the fourth CU to DU message. Therefore, DU 174 can determine the activation of LTM DU configuration 1 based on ID 1. In some implementations, the fourth CU to DU message and the fourth DU to CU message are the UE context modification request message and the UE context modification response message, respectively. In other implementations, the fourth CU to DU message and / or the fourth DU to CU message are new interface messages, such as F1 Application Protocol (F1AP) messages defined in 3GPP specification 38.473 v18.0.0 and / or later.

[0125] When LTM DU configuration 1 is activated or the first LTM command 330 is sent, or in response to this, DU 174 may send a DU-to-CU message 329 to CU 172 indicating that LTM is being performed. In some implementations, DU 174 includes cell ID 1 or ID 1 (i.e., LTM ID) in the DU-to-CU message 329 to indicate that DU 174 wants to activate LTM DU configuration 1 or trigger a fast serving cell change (i.e., LTM serving cell change). DU sends the DU-to-CU message 329 to CU 172 before or after sending the LTM command 330.

[0126] In some implementations, the first LTM command is the MAC CE included in the MAC PDU received by UE 102 from DU 174 in event 330. The MAC CE may be a new MAC CE defined in 3GPP specification 38.321 v18.0.0 and / or later. In one implementation, DU 174 includes a subheader identifying the new MAC CE in the MAC PDU, and UE 102 identifies the new MAC CE in the MAC PDU based on this subheader. The subheader includes a logical channel ID or an extended logical channel ID defined in the 3GPP specification to identify the new MAC CE. For example, the logical channel ID or extended logical channel ID is newly defined in 3GPP specification 38.321 v18.0.0 and / or later. In other implementations, the first LTM command is the DCI received by UE 102 on the PDCCH from DU 174 in event 330. DU 174 generates a CRC for the DCI, scrambles the CRC using the first C-RNTI of UE 102, and transmits the DCI and the scrambled CRC on the PDCCH in event 330. In one implementation, the DCI format can be an existing DCI format defined in a 3GPP specification (e.g., 38.212). In another implementation, the DCI format can be a new DCI format defined in a 3GPP specification (e.g., 38.212 v18.0.0 or later). In some implementations, DU 174 assigns the first C-RNTI for communication with UE 102 on cell 124A.

[0127] In some implementations, DU 174 does not perform security protection (e.g., integrity protection and / or encryption) on the first LTM command. This speeds up the processing of the first LTM command in UE 102 because UE 102 does not perform security checks (e.g., decryption and / or integrity checks) on the first LTM command.

[0128] In some implementations, after receiving the first LTM command, UE 102 may send a 331 acknowledgment to DU 174 on cell 124A or cell 124D to indicate that UE 102 has received the first LTM command. In some implementations, the acknowledgment is a HARQ ACK. In other implementations, the acknowledgment is a MAC CE. For example, the MAC CE is an existing MAC CE defined in 3GPP specification 38.321 v17.2.0 and / or later. In another example, the MAC CE is a new MAC CE defined in 3GPP specification 38.321 v18.0.0 and / or later. In yet another implementation, the acknowledgment is a PUCCH transmission.

[0129] In some implementations, CU 172 sends an RRC reconfiguration message 316 in response to an L3 measurement report 306 for the first cell. To configure UE 102 to send the L3 measurement report 306, CU 172 may send a first RRC reconfiguration message to UE 102 before event 306, including the L3 measurement configuration (e.g., MeasConfig IE). In some implementations, DU 174 sends a first LTM command 330 in response to an L1 measurement report 324 for the first cell. To configure UE 102 to send an L1 or new measurement report 324, CU 172 may send a second RRC reconfiguration message to UE 102, including the L1 or new measurement configuration. In some implementations, the first RRC reconfiguration message and the second RRC reconfiguration message may be the same message (i.e., the same instance). In other implementations, the first RRC reconfiguration message and the second RRC reconfiguration message are different messages. In some implementations, the second RRC reconfiguration message is the RRC reconfiguration message for event 316. In other implementations, the second RRC reconfiguration message differs from the RRC reconfiguration message for event 316.

[0130] Upon receiving the first LTM command (e.g., in response to this), UE 102 accesses the first cell 332. UE 102 identifies LTM DU configuration 1 based on LTM ID 1, cell ID 1, or cell index 1 received in the first LTM command, and applies LTM DU configuration 1 to communicate with DU 174 in the first cell. In some implementations, UE 102 disconnects from cell 124A after receiving the first LTM command or after sending acknowledgment 331 (e.g., in response to this). In some implementations, UE 102 ceases communication on cell 124A after receiving the first LTM command 330 or sending acknowledgment 331 (e.g., in response to this). In some implementations, UE 102 accesses the first cell 332 by performing a random access procedure with DU 174 in the first cell in response to receiving the first LTM command. In other implementations, upon receiving the first LTM command (e.g., in response to this), UE 102 skips the random access procedure in event 332 and sends a first transmission (e.g., a PUSCH transmission or a PUCCH transmission) to DU 174 in the first cell. In some implementations, UE 102 uses configuration parameters included in LTM DU configuration 1 to send the first transmission. In some implementations, these configuration parameters include PUSCH configuration, PUCCH configuration, and / or UL authorization.

[0131] In some implementations, DU 174 configures UE 102's access to the first cell in LTM DU configuration 1, including whether UE 102 performs a random access procedure. When a first LTM command is received, UE 102 determines whether to perform a random access procedure in the first cell according to LTM DU configuration 1. If LTM DU configuration 1 configures UE 102 to perform a random access procedure, then UE 102 performs a random access procedure on the first cell in event 332 to connect to the first cell. For example, LTM DU configuration 1 includes a reconfiguration with synchronization configuration (e.g., ReconfigurationWithSync IE) to configure UE 102 to perform a random access procedure when UE 102 receives an LTM command for the first cell. In other implementations, in LTM DU configuration 1, DU 174 configures UE 102 to skip the random access procedure for LTM serving cell changes to the first cell. In this scenario, after receiving the first LTM command, UE 102 skips the random access procedure in event 332 and sends a first transmission (e.g., a PUSCH transmission or a PUCCH transmission) to DU 174 in the first cell. In some implementations, DU 174 excludes reconfiguration with synchronization configuration in LTM DU configuration 1 to configure UE 102 to skip the random access procedure for LTM serving cell change to the first cell. In other implementations, DU 174 includes an indication in LTM DU configuration 1 to indicate skipping the random access procedure for LTM serving cell change to the first cell.

[0132] In other implementations, LTM DU configuration 1 includes a reconfiguration or random access configuration with synchronized configuration for LTM serving cell changes to the first cell. In this case, DU 174 configures in the LTM command whether UE 102 performs a random access procedure in the first cell. Therefore, UE 102 determines in event 332 whether to perform a random access procedure in the first cell based on the first LTM command. In some implementations, DU 174 includes an indication (e.g., a field) indicating skipping the random access procedure in the first LTM command. In response to this indication or the first LTM command including the indication, UE 102 skips the random access procedure and directly sends a first transmission (e.g., a PUSCH transmission or a PUCCH transmission) in the first cell to access the first cell. In other implementations, DU 174 excludes this indication in the first LTM command to configure UE 102 to perform a random access procedure. In response to the first LTM command excluding the indication, UE 102 performs a random access procedure in the first cell to access the first cell. In some other implementations, DU 174 includes a timing advance (TA) value in the first LTM command to indicate skipping the random access procedure. In response to receiving the TA value or a first LTM command including the TA value, UE 102 skips the random access procedure and transmits a first transmission in the first cell using the timing advance value to access the first cell. In yet another implementation, DU 174 excludes the timing advance value in the first LTM command to configure UE 102 to perform a random access procedure. In response to the first LTM command excluding the timing advance value, UE 102 performs a random access procedure in the first cell to access the first cell.

[0133] In some implementations, the random access procedure is a four-step random access procedure. In other implementations, the random access procedure is a two-step random access procedure. In some implementations, the random access procedure is a contention-free random access procedure. In other implementations, the random access procedure is a contention-based random access procedure. In the case of a four-step random access procedure, UE 102 sends message 3, including the UE ID, to DU 174 via the first cell during the random access procedure. DU 174 responds to message 3 by sending a contention resolution message (e.g., message 4) to UE 102. In the case of a two-step random access procedure, UE 102 sends message A, including the UE ID, to DU 174 via the first cell during the random access procedure. DU 174 responds to message A by sending a contention resolution message (e.g., message B) to UE 102. In some implementations, when UE 102 receives a contention resolution message from DU 174 in the first cell, UE 102 determines that UE 102 has successfully completed the random access procedure (i.e., UE 102 has successfully accessed the first cell). In some implementations, LTM DU configuration 1 includes a second C-RNTI, and the UE ID is the second C-RNTI of UE 102. In this type of implementation, the contention resolution message is a PDCCH transmission addressed to the second C-RNTI. In other implementations, LTM DU configuration 1 does not include a C-RNTI, and the UE ID is the first C-RNTI. In this type of implementation, the contention resolution message is a PDCCH transmission addressed to the first C-RNTI.

[0134] When LTM DU configuration 1 includes a dedicated random access preamble, the random access procedure is a contention-free random access procedure. In this case, UE 102 sends the dedicated random access preamble to DU 174 via the first cell. When UE 102 receives a random access response including the ID of the dedicated random access preamble from DU 174 in the first cell, UE 102 determines that UE 102 has successfully completed the random access procedure (i.e., UE 102 has successfully accessed the first cell).

[0135] If DU 174 configures UE 102 to perform a random access procedure in the first cell as described above, then DU 174 will detect that UE 102 has accessed the first cell when it receives message 3, message A, or a special preamble during the random access procedure. If DU 174 configures UE 102 to skip the random access procedure, then DU 174 will detect that UE 102 has accessed the first cell when it receives the first transmission.

[0136] In some implementations, UE 102 transmits a first transmission (e.g., a PUSCH transmission) in the first cell using a UL grant. In some implementations, the first LTM command includes a UL grant. In other implementations, when UE 102 performs an LTM serving cell change to the first cell in response to the first LTM command, UE 102 receives a first DCI including a UL grant on the PDCCH in the first cell. In some implementations, when UE 102 switches to the first cell in response to the first LTM command, UE 102 attempts to receive the first DCI or a UL grant by monitoring one or more PDCCHs in the first cell according to LTM DU configuration 1. When one or more PDCCHs in the first cell are detected, UE 102 receives the first DCI and its CRC on the PDCCH. When LTM DU configuration 1 includes a second C-RNTI, UE 102 uses the CRC and the second C-RNTI to confirm that the first DCI was transmitted for UE 102. In the absence of a second C-RNT in LTM DU configuration 1, UE 102 uses CRC and the first C-RNTI to determine that the first DCI was sent for UE 102.

[0137] / / TCI status configuration

[0138] In some implementations, CU 172 sends at least one first TCI state configuration to UE 102 via DU 174. In some implementations, each first TCI state configuration configures a TCI state for UE 102 to send and / or receive data and / or control signals in a first cell. Each TCI state associates one or two DL RSs with a corresponding QCL type, and the DL RSs may be associated with a specific cell in cell 1, ..., N. In some implementations, CU 172 receives a DU-to-CU message including the first TCI state configuration from DU 174 and sends an RRC message including the first TCI state configuration to UE 102 via DU 174. In a further implementation, DU 174 includes the first TCI state configuration in a serving DU configuration (e.g., CellGroupConfig IE) and includes the serving DU configuration in the DU-to-CU message. In some implementations, DU 174 includes LTM DU configuration 1 in the first interface protocol IE / field of message 312, and includes service DU configuration in the second interface protocol IE / field of the DU to CU message.

[0139] In some implementations, the first interface protocol IE / field is defined as part of the format of the DU to CU message. CU 172 includes the service DU configuration in the RRC message. In some implementations, CU 172 avoids including the service DU configuration in the LTM container (e.g., the first container). In other implementations, CU 172 includes the first TCI state configuration in an LTM element, an LTM add or modify list, or a container similar to element 1, the first add or modify list, or the first container. In some implementations, the RRC message is an RRC reconfiguration message 316, 318, or another RRC reconfiguration message (…). FIG. 3 (Not shown in the image). In some implementations, the DU to CU message is message 312, message 314, UE context modification response message, or UE context modification request message. In some implementations, DU 174 also includes the first TCI state configuration in LTMDU configuration 1. In other implementations, DU 174 avoids including the first TCI state configuration in LTM DU configuration 1.

[0140] In some implementations, the first interface protocol IE / field is the first F1AP IE / field, and the second interface protocol IE / field is the second F1AP IE / field. In some implementations, one of the first F1AP IE / field and the second F1AP IE / field is the F1AP CellGroupConfig IE / field, and the other is not the F1AP CellGroupConfig IE / field. In some implementations, DU 174 includes the first F1AP IE / field in the DU to CU RRC information IE in message 312, and includes the second F1AP IE / field in the DU to CU RRC information IE in the DU to CU message. In other implementations, neither the first F1AP IE / field nor the second F1AP IE / field is the F1AP CellGroupConfig IE / field. In other implementations, the second F1AP IE / field is the DU to CU RRC information IE, and the first F1AP IE / field is a new IE specifically for including LTM DU configuration.

[0141] In some implementations, upon receiving a first LTM command (e.g., in response to this) or upon accessing the first cell 332, UE 102 uses some or all of the first TCI state configurations to monitor one or more PDCCHs in the first cell. In some implementations, each of the first TCI state configurations includes a TCI state ID identifying the corresponding TCI state configuration. For example, the first TCI state configurations include TCI state configurations 1, ..., L, where L is a positive integer greater than zero. TCI state configurations 1, ..., L include TCI state IDs 1, ..., L, respectively identifying TCI state configurations 1, ..., L. DU 174 includes TCI state ID 1 in the first LTM command to instruct UE 102 to apply TCI state configuration 1 for communication in the first cell. Upon receiving the first LTM command (e.g., in response to this), UE 102 uses TCI state configuration 1 to access and / or communicate in the first cell based on TCI state ID 1. For example, UE 102 uses TCI state configuration 1 to monitor one or more PDCCHs and / or send a first transmission. In some implementations, DU 174 detects that UE 102 has accessed the first cell based on TCI state configuration 1 and communicates with UE 102 in the first cell. For example, DU 174 receives a first transmission from UE 102 in the first cell based on TCI state configuration 1.

[0142] In some implementations, DU 174 includes TCI State ID 2 in the first LTM command to instruct UE 102 to apply TCI State Configuration 2 in addition to TCI State ID 1 for communication in the first cell. Upon receiving the first LTM command (e.g., in response to it), UE 102 uses TCI State Configurations 1 and 2 to access and / or communicate in the first cell based on TCI State ID 1 and TCI State ID 2. For example, UE 102 uses TCI State Configuration 1 to monitor one or more PDCCHs in the first cell and uses TCI State Configuration 2 to send a first transmission in the first cell. In another example, UE 102 uses both TCI State Configuration 1 and TCI State Configuration 2 to monitor one or more PDCCHs in the first cell and sends a first transmission in the first cell using either TCI State Configuration 1 or TCI State Configuration 2. In some implementations, DU 174 detects that UE 102 has accessed the first cell and is communicating with UE 102 in the first cell based on TCI State Configuration 1 and / or TCI State Configuration 2. For example, DU 174 receives a first transmission from UE 102 in a first cell based on either TCI state configuration 1 or TCI state configuration 2.

[0143] In some alternative implementations, DU 174 may not include the TCI state ID in the first LTM command. In such cases, UE 10, upon receiving the first LTM command (e.g., in response to it), communicates with the first DU in the first cell using at least one first TCI state. In some implementations, DU 174 is configured to detect UE 102 accessing the first cell based on the first TCI state and communicate with UE 102 in the first cell.

[0144] In some implementations, before sending the first LTM command, DU 174 may send one or more activation commands to activate some or all of the first TCI state configurations in the first TCI state configuration. In some implementations, each activation command in the activation commands is a MAC CE. In other implementations, each activation command in the activation commands is a DCI. In some implementations, DU 174 includes TCI state ID 1 and / or TCI state ID 2 in the activation command to activate TCI state configuration 1 and / or TCI state configuration 2, respectively. Therefore, when UE 102 receives the activation command, it determines or identifies that TCI state configuration 1 and / or TCI state configuration 2 are active. In other implementations, DU 174 includes all TCI state IDs used for the first TCI state configuration in the activation command. Therefore, when UE 102 receives the activation command, it determines or identifies that the first TCI state configuration is active. In some implementations, DU 174 avoids including TCI state IDs of TCI state configurations that DU 174 has not yet activated for UE 102 in the first LTM command. In some implementations, DU 174 includes cell ID1 or cell index1 in the activation command. Based on cell ID1 or cell index1 and one or more TCI state IDs in the activation command, UE 102 determines that the activation command activates one or more TCI state configurations in the first TCI state configuration, wherein each of the TCI state IDs identifies a specific TCI state configuration in the TCI state configuration.

[0145] In some implementations, UE 102 uses one or more TCI state configurations to communicate with DU 174 on cell 124A (e.g., events 302, 304, 318, 320, 324, 330). In some implementations, each of the TCI state configurations configures a TCI state for UE 102 to transmit and / or receive data and / or control signals on cell 124A. In some implementations, UE 102 stops using the TCI configuration upon receiving a first LTM command.

[0146] After successfully accessing the first cell, UE 102 communicates 336 with DU 174 in the first cell using LTM DU configuration 1 and / or a reference LTM DU configuration, and communicates with CU 172 via DU 174. In this case, DU 174 communicates 336 with UE 102 in the first cell using LTM DU configuration 1. In some scenarios or implementations, UE 102 communicates 336 PUSCH transmissions, PDSCH transmissions, PUCCH transmissions, PDCCH transmissions, and / or sounding reference signals (SRS) transmissions with DU 174 in the first cell. In some implementations, UE 102 uses some or all of the first TCI state configurations to perform 336 communication with DU 174. Similarly, DU 174 uses some or all of the first TCI state configurations to perform 336 communication with UE 102. In some implementations, DU 174 includes one or more additional TCI state configurations in LTM DU configuration 1. In this scenario, DU 174 may send one or more activation commands to UE 102 via the first cell in event 336 to activate the additional TCI state configuration. Upon receiving the activation commands, UE 102 determines that the additional TCI state configuration is active. In some implementations, each activation command in the activation commands is a MAC CE. In other implementations, each activation command in the activation commands is a DCI. After receiving the activation commands, UE 102 communicates with DU 174 in the first cell using the additional TCI state configuration. Similarly, after sending the activation commands, DU 174 communicates with UE 102 in the first cell using the additional TCI state configuration.

[0147] When UE 102 receives the reference LTM DU configuration as described above, UE 102 communicates with DU 174 in the first cell 336 according to at least a portion of LTM DU configuration 1 and the reference LTM DU configuration. In other words, UE 102 communicates with DU 174 336 according to the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration. Similarly, DU 174 communicates with UE 102 in the first cell 336 according to at least a portion of LTM DU configuration 1 and the reference LTM DU configuration. In other words, DU 174 communicates with UE 102 336 according to the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration.

[0148] If UE 102 receives neither LTM CU Configuration 1 nor Reference LTM CU Configuration, UE 102 communicates with CU 172 via DU 174 using the serving CU configuration 336. Correspondingly, if CU 172 neither sends LTM CU Configuration 1 nor Reference CU Configuration to UE 102, CU 172 communicates with UE 102 via DU 174 using the serving CU configuration 336. If UE 102 receives both LTM CU Configuration 1 and Reference LTM CU Configuration from CU 172, UE 102 communicates with CU 172 via DU 174 using LTM CU Configuration 1 and at least a portion of the reference LTM CU Configuration not enhanced by LTM CU Configuration 1 336. In this case, CU 172 communicates with UE 102 via DU 174 using LTM CU Configuration 1 and at least a portion of the reference LTM CU Configuration not enhanced by LTM CU Configuration 1 336.

[0149] If UE 102 receives LTM CU configuration 1 from CU 172 but does not receive a reference LTM CU configuration, UE 102 communicates with CU 172 via DU 174 using LTM CU configuration 1 336. In this case, CU 172 communicates with UE 102 via DU 174 using LTM CU configuration 1 336. If LTM CU configuration 1 is a complete configuration, UE 102 and CU 172 communicate with each other via DU 174 using LTM CU configuration 1 instead of the serving CU configuration 336. In some implementations, if UE 102 does not receive a reference LTM CU configuration from base station 104, UE 102 determines that LTM CU configuration 1 is a complete configuration. Correspondingly, if CU 172 determines to configure LTM CU configuration 1 as a complete configuration, CU 172 does not send a reference LTM CU configuration to UE 102. In other implementations, CU 172 includes a first indication (e.g., a field or IE) in LTM CU configuration 1, the first container, element 1, or the RRC reconfiguration message 316 to indicate that LTM CU configuration 1 is a complete configuration. If LTM CU configuration 1 is an incremental configuration for enhancing the service CU configuration, UE 102 and CU 172 communicate with each other via DU 174 336 using LTM CU configuration 1 and at least a portion of the service CU configuration not enhanced by LTM CU configuration 1. In some implementations, if UE 102 does not receive a reference LTM CU configuration from base station 104, UE 102 determines that LTM CU configuration 1 is an incremental configuration for enhancing the service CU configuration. Correspondingly, if CU 172 determines that it wants to configure LTM CU configuration 1 as an incremental configuration for enhancing the service CU configuration, CU 172 does not send the reference LTM CU configuration to UE 102. In some implementations, CU 172 indicates that LTM CU Configuration 1 is an incremental configuration for enhancing service CU configuration by excluding a first indication in LTM CU Configuration 1, the first container, element 1, and / or RRC reconfiguration message 316. Alternatively, CU 172 includes a second indication (e.g., a field or IE) in LTM CU Configuration 1, the first container, element 1, or RRC reconfiguration message 316 to indicate that LTM CU Configuration 1 is an incremental configuration for enhancing service CU configuration. In some implementations, CU 172 indicates that LTM CU Configuration 1 is a complete configuration by excluding a second indication in LTM CU Configuration 1, the first container, element 1, and / or RRC reconfiguration message 316.

[0150] If UE 102 receives a reference LTM CU configuration from CU 172 but does not receive LTM CU configuration 1, UE 102 communicates with CU 172 via DU 174 using the reference LTM CU configuration 336. In this case, CU 172 communicates with UE 102 via DU 174 using the reference LTM CU configuration 336. If the reference LTM CU configuration is a complete configuration, UE 102 and CU 172 communicate with each other via DU 174 using the reference LTM CU configuration instead of the serving CU configuration 336. In some implementations, UE 102 and CU 172 determine that reference LTM CU configuration 1 is the complete configuration specified in the 3GPP specification (e.g., 3GPP specification 38.331 v18.0.0 or later). In other implementations, CU 172 includes a first indication (e.g., a field or IE) in the reference LTM CU configuration, the first container, or the RRC reconfiguration message 316 to indicate that the reference LTM CU configuration is a complete configuration. If the reference LTM CU configuration is an incremental configuration for enhancing the service CU configuration, UE 102 and CU 172 communicate with each other via DU 174 336 using the reference LTM CU configuration and at least a portion of the service CU configuration not enhanced by the reference LTM CU configuration. In some implementations, CU 172 indicates that the reference LTM CU configuration is an incremental configuration for enhancing the service CU configuration by excluding the first indication in the reference LTM CU configuration, the first container, element 1, and / or the RRC reconfiguration message 316. Alternatively, CU 172 includes a second indication (e.g., a field or IE) in the reference LTM CU configuration, the first container, element 1, or the RRC reconfiguration message 316 to indicate that the reference LTM CU configuration is an incremental configuration for enhancing the service CU configuration. In some implementations, CU 172 indicates that the reference LTM CU configuration is complete by excluding the second indication in the reference LTM CU configuration, the first container, element 1, and / or RRC reconfiguration message 316.

[0151] If UE 102 receives neither the reference LTM CU configuration nor LTM CU configuration 1 from CU 172, UE 102 communicates with CU 172 via DU 174 using the serving LTM CU configuration 336. In this case, CU 172 communicates with UE 102 via DU 174 using the serving LTM CU configuration 336.

[0152] In some implementations, UE 102 sends an RRC message to CU 172 via DU 174 and the first cell to instruct UE 102 to apply LTM DU configuration 1. If UE 102 performs random access procedure 332, UE 102 may include the RRC message in message 3 or message A. Alternatively, UE 102 sends the RRC message after completing the random access procedure. If UE 102 skips random access procedure 332, UE 102 includes the RRC message in the first PUSCH transmission. In some implementations, if UE 102 maintains communication with base station 104 on cell 124A (i.e., UE 102 has not disconnected from cell 124A), UE 102 may send the RRC message to base station 104 via cell 124A. When DU 174 receives the RRC message, DU 174 sends the RRC message to CU 172.

[0153] In some implementations, UE 102 includes LTM ID 1 in the RRC message. Upon receiving an RRC message including LTM ID 1, CU 172 determines that UE 102 is performing an LTM cell handover to cell 1 and is communicating with base station 104 using LTM DU configuration 1 and / or LTM CU configuration 1. In other implementations, UE 102 includes UE ID 1 in the RRC message. Upon receiving an RRC message including UE ID 1, CU 172 determines that UE 102 is performing an LTM cell handover to cell 1 and is communicating with base station 104 using LTM DU configuration 1 and / or LTM CU configuration 1. In some implementations, the RRC message is an RRC reconfiguration complete message (e.g., an RRCReconfigurationComplete message). In other implementations, UE 102 neither includes the LTM ID nor the UE ID in the RRC message.

[0154] In other implementations, UE 102 avoids sending an RRC message to base station 104 in response to applying LTM DU configuration 1 or receiving a first LTM command. In such cases, UE 102 may include or send data in message 3, message A, or PUSCH transmission as described above. UE 102 may generate a MAC PDU and / or RLC PDU that includes data, and send or include the MAC PDU and / or RLC PDU in PUSCH transmission. For example, the data may be a PDCP PDU, SDAP PDU, LTE Positioning Protocol (LPP) PDU, RRC PDU, and / or NAS PDU. The RRC PDU includes a UL-DCCH-Message that excludes the RRC reconfiguration completion message. The NAS PDU includes a Mobility Management (MM) message or a Session Management (SM) message. The MM message may be a 5G MM message or a 6G MM message, and the SM message may be a 5G SM message or a 6G SM message. When DU 174 receives the data, DU 174 sends the data to CU 172.

[0155] When DU 174 determines in event 332 or 336 that UE 102 has successfully connected to the first cell, DU 174 may send a 334 DU to CU 172 (e.g., the CP of CU 172) message (e.g., an access success message). In some implementations, DU 174 may include the cell ID 1 of the first cell in the DU to CU message of event 334. The cell ID may be PCI or CGI. Therefore, CU 172 determines that UE 102 is connected to the first cell upon receiving the DU to CU message of event 334. When DU 174 determines in event 332 or 336 that UE 102 has successfully connected to the first cell, DU 174 may send a DL data delivery status message or frame to CU 172 (e.g., the UP of CU 172). In some implementations, upon or after receiving the DU-to-CU message 329, CU 172 may stop or suspend sending DL data for UE 102 to DU 174 until receiving the DU-to-CU message 334. CU 172 can do this because DU 174 is unable to buffer DL data for UE 102 during the LTM execution in events 330 and / or 332. After receiving the DU-to-CU message 334, CU 172 continues or resumes sending DL data for UE 102 to DU 174. In other implementations, when CU 172 receives the DU-to-CU message 329, CU 172 may continue sending DL data for UE 102 to DU 174. CU 172 can do this because DU 174 can buffer DL data for UE 102 during the LTM execution in events 330 and / or 332. When or after DU 174 detects that UE 102 has accessed cell 1, DU 174 sends DL data to UE 102 via cell 1.

[0156] In some implementations, when it is determined that UE 102 is connected to the first cell, sends the first LTM command 330, or receives the acknowledgment 331, DU 174 may stop communicating with UE 102 on cell 124A and / or release the resources of cell 124A configured for UE 102.

[0157] In some implementations, DU 174 may generate some or all of LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as a complete configuration to replace the serving DU configuration. If LTM DU configuration 1 is a complete configuration, then UE 102 and DU 174 communicate with each other based on LTM DU configuration 1 instead of the serving DU configuration 336. In some implementations, DU 174 includes an indication in LTM DU configuration 1 that LTM DU configuration 1 is a complete configuration. In each of LTM DU configurations 2, ..., N, DU 174 may include an indication indicating that the corresponding DU configuration is a complete configuration. Each of the indications in LTM DU configurations 1, ..., N may be a field or IE (i.e., the same field or IE). In other implementations, CU 172 may include a single indication indicating that LTM DU configuration 1 and / or 2, ..., N is a complete configuration in the RRC reconfiguration message of events 316, 318. In the case of a second container, CU 172 may include a single indication indicating that LTM DU configurations 2, ..., N are complete configurations in an additional RRC reconfiguration message. In yet another implementation, CU 172 may include a single indication indicating that LTM DU configurations 1 and / or 2, ..., N are complete configurations in a first container. In yet another implementation, for each of LTM DU configurations 2, ..., N, CU 172 may include a specific indication indicating that the corresponding LTM DU configuration is complete in the first container. In the case of a second container, CU 172 may include a single indication indicating that LTM DU configurations 2, ..., N are complete configurations in a second container. In yet another implementation, CU 172 may include an indication indicating that LTM DU configuration 1 is complete in element 1. In each of elements 2, ..., N, CU 172 may include an indication indicating that the corresponding LTM DU configuration is complete. Based on the above indications, UE 102 can determine that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are complete configurations. In some implementations, each of the above indications differs from the fullConfig field defined in the current 3GPP specification. In some implementations, each of the above indications is the fullConfig field defined in the current 3GPP specification. If LTM DU configuration 1 is a complete configuration, and if it is received from base station 104, for example, in RRC reconfiguration message 318, then UE 102 does not apply the reference LTM DU configuration in event 336. In such cases, DU 174 may not include the reference LTM DU configuration in the first DU to CU message 310.

[0158] In other implementations, DU 174 can generate LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as incremental configurations that enhance a portion of the reference LTM DU configuration. In other words, DU 174 generates LTM DU configuration 1, ..., N based on the reference LTM DU configuration. For example, if LTM DU configuration 1 is an incremental configuration, then UE 102 and DU 174 utilize LTM DU configuration 1 to enhance a portion of the reference LTM DU configuration. Therefore, UE 102 and DU 174 communicate with each other based on LTM DU configuration 1 and the unenhanced portion of the reference LTM DU configuration 336. In some implementations, LTM DU configuration 1 and / or 2, ..., N, the first container, the second container, or element 1, ..., N excludes indications that LTM DU configuration 1 and / or 2, ..., N is a complete configuration, instead indicating that LTM DU configuration 1 and / or 2, ..., N is an incremental configuration. UE 102 can determine that each of LTM DU configurations 1 and / or 2, ..., N is an incremental configuration based on the indication that LTM DU configurations 1 and / or 2, ..., N are excluded.

[0159] In some implementations, if UE 102 does not receive a reference LTM DU configuration for LTM DU configuration 1 and / or LTM DU configuration 2, ..., N, then UE 102 determines that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are complete configurations. Correspondingly, if DU 174 does not obtain a reference LTM DU configuration for UE 102 (i.e., DU 174 does not generate a reference LTM DU configuration for UE 102 and / or does not receive a reference LTM DU configuration for UE 102 from CU 172), then DU 174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as complete configurations.

[0160] In other implementations, if UE 102 does not receive a reference LTM DU configuration for LTM DU configuration 1 and / or LTM DU configuration 2, ..., N, then UE 102 determines that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are incremental configurations for enhancing the service DU configuration. In such cases, UE 102 communicates with DU 174 336 based on at least a portion of the service DU configuration that is not enhanced by LTM DU configuration 1. Correspondingly, if DU 174 does not obtain a reference LTM DU configuration for UE 102 (i.e., DU 174 does not generate a reference LTM DU configuration for UE 102 and / or receives a reference LTM DU configuration for UE 102 from CU 172), then DU 174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as incremental configurations for enhancing the service DU configuration. In such cases, DU 174 communicates with UE 102 336 based on at least a portion of LTM DU configuration 1 and service DU configuration.

[0161] In some implementations, UE 102 uses a UE MAC entity (e.g., MAC 204B) to communicate with the DUMAC entity (e.g., MAC 204B) of DU 174 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). In some implementations, UE 102 resets the UE MAC entity after receiving a first LTM command or in response to it, and before performing the 332 random access procedure or communicating 336 with DU 174 via the first cell. In some implementations, DU 174 resets the DU MAC entity after sending the first LTM command, receiving an acknowledgment 331, or determining that UE 102 is connected to the first cell (e.g., in response to it).

[0162] In some implementations, when UE 102 resets the UE MAC entity, UE 102 performs at least one of the following actions on the UE MAC entity (i.e., UE MAC reset or full UE MAC reset):

[0163] • Initialize Bj for the configured logical channel to zero;

[0164] • Stop one or more timers;

[0165] • If UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), then timeAlignmentTimer is considered to have expired;

[0166] • Set the New Data Indicator (NDI) used in the UL HARQ process to a value of 0;

[0167] • Set the NDI used for HARQ process ID to a value of 0 to monitor PDCCH in sidelink resource allocation mode 1;

[0168] • Refresh the Msg3 buffer;

[0169] • Refresh the MSGA buffer;

[0170] • Cancel the scheduling request process (if any);

[0171] • Cancel (if any) the triggered buffer status reporting procedure;

[0172] • Cancel (if any) the triggered power margin reporting process;

[0173] • Cancel any consistency LBT failures triggered (if any);

[0174] • Cancel any triggered BFRs;

[0175] • Cancel (if any) the side-link buffer status reporting procedure that was triggered;

[0176] • Cancel (if any) the preemptive buffer status reporting process that was triggered;

[0177] • Cancel (if any) the timed advance reporting process that was triggered;

[0178] • Cancel (if any) the triggered referral rate query process;

[0179] • Cancel (if any) the uplink authorization confirmation triggered by the configuration;

[0180] • Cancel (if any) the sidelink authorization confirmation triggered by the configuration;

[0181] • Cancel any expected protection symbol queries triggered (if any);

[0182] • Cancel (if any) the triggered positioning measurement gap activation / deactivation request process;

[0183] • Refresh the soft buffer used for the DL HARQ process;

[0184] • For each of the DL HARQ processes, the next received transmission for TB is considered the first transmission.

[0185] • Release (if any) temporary C-RNTI;

[0186] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0187] In some implementations, when DU 174 resets the DU MAC entity, DU 174 performs at least one of the following actions on the DU MAC entity (i.e., DU MAC reset or full DU MAC reset):

[0188] • Stop one or more timers;

[0189] • If UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), then the timeAlignmentTimer initiated and / or maintained by DU 174 for UE 102 is considered expired;

[0190] • Set the NDI used for the DL HARQ process to a value of 0;

[0191] • Refresh the soft buffer used in the UL HARQ process;

[0192] • For each of the UL HARQ processes, the next received transmission for the TB is considered the first transmission;

[0193] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0194] Depending on the implementation, UE 102 may determine whether to partially or completely reset the UE MAC entity. In some implementations, when UE 102 resets the UE MAC entity as described above, UE 102 completely resets the UE MAC entity (i.e., a full UE MAC reset). In a full UE MAC reset, UE 102 performs some or all of the actions described above. In other implementations, when UE 102 resets the UE MAC entity as described above, UE 102 partially resets the UE MAC entity (i.e., a partial UE MAC reset). In a partial UE MAC reset, UE 102 performs a subset or part of some or all of the actions in a full UE MAC reset.

[0195] In some implementations, a partial UE MAC reset includes at least one of the following actions:

[0196] • If UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), then UE 102's timeAlignmentTimer is considered to have expired;

[0197] • Refresh the Msg3 buffer;

[0198] • Refresh the MSGA buffer;

[0199] • Release (if any) temporary C-RNTI;

[0200] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0201] In some implementations, a partial UE MAC reset further includes at least one of the following actions:

[0202] • Cancel the scheduling request process (if any);

[0203] • Cancel (if any) the triggered buffer status reporting procedure;

[0204] • Cancel (if any) the triggered power margin reporting process;

[0205] • Cancel any consistency LBT failures triggered (if any);

[0206] • Cancel any triggered BFRs;

[0207] • Cancel (if any) the side-link buffer status reporting procedure that was triggered;

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

[0209] • Cancel (if any) the timed advance reporting process that was triggered;

[0210] • Cancel (if any) the triggered referral rate query process;

[0211] • Cancel (if any) the uplink authorization confirmation triggered by the configuration;

[0212] • Cancel (if any) the sidelink authorization confirmation triggered by the configuration;

[0213] • Cancel any expected protection symbol queries triggered (if any);

[0214] • Cancel (if any) the triggered positioning measurement gap activation / deactivation request process;

[0215] In some implementations, a partial UE MAC reset further includes at least one of the following actions:

[0216] • Stop the first part of one or more timers and keep the rest of one or more timers;

[0217] • Set the New Data Indicator (NDI) used in the UL HARQ process to a value of 0;

[0218] • Set the NDI used for HARQ process ID to a value of 0 to monitor PDCCH in sidelink resource allocation mode 1;

[0219] • Refresh the soft buffer used for the DL HARQ process;

[0220] • For each of the DL HARQ processes, the next received transmission for TB is considered the first transmission.

[0221] Depending on the implementation, DU 174 may determine whether to partially or completely reset the DU MAC entity. In some implementations, when DU 174 resets the DU MAC entity as described above, DU 174 completely resets the DU MAC entity (i.e., a full DU MAC reset). In a full DU MAC reset, DU 174 performs some or all of the actions described above. In other implementations, when DU 174 resets the DU MAC entity as described above, DU 174 partially resets the DU MAC entity (i.e., a partial DU MAC reset). In a partial DU MAC reset, DU 174 performs a subset or part of some or all of the actions in a full DU MAC reset.

[0222] In some implementations, a partial DU MAC reset includes at least one of the following actions in a partial MAC reset:

[0223] • If UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), then the timeAlignmentTimer initiated and / or maintained by DU 174 for UE 102 is considered expired;

[0224] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0225] In some implementations, a partial DU MAC reset includes at least one of the following actions for a MAC entity (i.e., a DU MAC reset):

[0226] • Stop the first part of one or more timers and keep the rest of one or more timers;

[0227] • Set the NDI used for the DL HARQ process to a value of 0;

[0228] • Refresh the soft buffer used in the UL HARQ process;

[0229] • For each of the UL HARQ processes, the next received transmission for the TB is considered the first transmission;

[0230] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0231] In other implementations, UE 102 avoids resetting the UE MAC entity in response to receiving the first LTM command. Similarly, DU 174 avoids resetting the DU MAC entity after sending the first LTM command, receiving acknowledgment 331, or determining that UE 102 is connected to the first cell (e.g., in response to this). In other words, UE 102 uses the UE MAC entity (not reset) to communicate with DU 174 in the first cell. Similarly, DU 174 uses the DU MAC entity (not reset) to communicate with UE 102 in the first cell during or after random access procedure 332, or after determining that UE 102 is connected to the first cell.

[0232] In some implementations, UE 102 uses at least one UE RLC entity (e.g., RLC 206B) to communicate RLC PDUs (e.g., events 302, 304, 318, 320, 324, 330, and / or 331) to at least one DU RLC entity (e.g., RLC 206B) of DU 174. In some implementations, UE 102 reconstructs some or all of the at least one UE RLC entity after receiving a first LTM command or in response to it, and before performing the 332 random access procedure or communicating 336 with DU 174 via the first cell. In some implementations, DU 174 reconstructs some or all of the at least one DU RLC entity after sending the first LTM command, receiving acknowledgment 331, or determining that UE 102 is connected to the first cell (e.g., in response to it).

[0233] In some implementations, LTM DU configuration 1 may or may not include one or more RLC reconstruction indications (e.g., a reestablishRLC field) that configure UE 102 to rebuild some or all of at least one UE RLC entity. If LTM DU configuration 1 includes an RLC reconstruction indication that configures UE 102 to rebuild a first UE RLC entity among at least one UE RLC entity used by UE 102 to communicate an RLC PDU to DU 174, then UE 102 rebuilds the first UE RLC entity in response to the RLC reconstruction indication and the first LTM command. In some implementations, UE 102 may rebuild the first UE RLC entity before performing the 332 random access procedure or before communicating 336 with DU 174 via the first cell. In other implementations, UE 102 may rebuild the first UE RLC entity concurrently with or after performing the 332 random access procedure. Otherwise, if LTM DU configuration 1 does not include an RLC reconstruction indication, UE 102 avoids rebuilding the first UE RLC entity in response to the first LTM command.

[0234] In some implementations, when UE 102 reconstructs the first UE RLC entity, UE 102 performs at least one of the following actions on the first UE RLC entity:

[0235] • Discard RLC SDU, RLC SDU segments, and RLC PDU (if any);

[0236] • Stop and reset the timer (if it is running);

[0237] • Reset the state variable to its initial value.

[0238] In some implementations, state variables and timers are defined in 3GPP specification 38.322.

[0239] Otherwise, if LTM DU configuration 1 does not include an RLC reconstruction indication for the first UE RLC entity, then UE 102 avoids reconstructing the first UE RLC entity upon or when the first LTM command is received. In other words, UE 102 avoids performing the action for reconstructing the first UE RLC entity of UE 102 upon or when the first LTM command is received. In some implementations, if LTM DU configuration 1 or element 1 does not include an RLC reconstruction indication but includes an indication that configuration 1 is fully configured, then UE 102 may reconstruct the first UE RLC entity of UE 102 upon or when the first LTM command is received. Otherwise, if LTM DU configuration 1 or element 1 does not include an RLC reconstruction indication and an indication that configuration 1 is fully configured, then UE 102 avoids reconstructing the first UE RLC entity upon or when the first LTM command is received.

[0240] Similarly, DU 174 reconstructs some or all of at least one DU RLC entity (e.g., NR RLC 206B) used by DU 174 to communicate with at least one UERLC entity of UE 102 (e.g., events 302, 304, 318, 320, 324, 330 and / or 331) in response to an RLC reconstruction instruction. In some implementations, DU 174 reconstructs the first DU RLC entity among at least one DURLC entity after sending a first LTM command, receiving an acknowledgment of the first LTM command from UE 102, or determining that UE 102 is connected to the first cell. In some implementations, the acknowledgment is a HARQ ACK. In other implementations, the acknowledgment is a MAC CE. In yet another implementation, the acknowledgment is a PUCCH transmission. In some implementations, when base station 104 reconstructs the first DU RLC entity, DU 174 performs at least one of the following actions for the first DU RLC entity:

[0241] • Discard RLC SDU, RLC SDU segments, and RLC PDU (if any);

[0242] • Stop and reset the timer (if it is running);

[0243] • Reset the state variable to its initial value.

[0244] In some implementations, state variables and timers are defined in 3GPP specification 38.322.

[0245] In other implementations, UE 102 avoids rebuilding some or all of at least one UERLC entity in response to receiving a first LTM command. Similarly, DU 174 avoids rebuilding some or more of at least one DU RLC entity after sending the first LTM command, receiving acknowledgment 331, or determining that UE 102 is connected to the first cell (e.g., in response to this). In other words, UE 102 uses some or all of at least one UE RLC entity (not rebuilt) to communicate with DU 174 in the first cell. For example, some or all of at least one UE RLC entity includes a first UE RLC entity and / or a second UERLC entity. Similarly, DU 174 uses some or all of at least one DU RLC entity (not rebuilt) to communicate with UE 102 in the first cell during or after random access procedure 332 or after determining that UE 102 is connected to the first cell. For example, some or all of at least one DU RLC entity includes a first DU RLC entity and / or a second DU RLC entity.

[0246] In some implementations, UE 102 uses at least one UE PDCP entity (e.g., PDCP 210) in event 302 to communicate UL PDCP PDUs and / or DL ​​PDCPPDUs to at least one CU PDCP entity (e.g., PDCP 210) of CU 172. In some implementations, UE 102 performs a PDCP recovery procedure for some or all of the at least one UE PDCP entity after receiving or in response to a first LTM command. For example, UE 102 performs a PDCP recovery procedure for the first UE PDCP entity among the at least one UE PDCP entities after receiving or in response to receiving a first LTM command. During the PDCP recovery procedure, UE 102 may or may not rebuild the first UE PDCP entity. After performing or in response to performing the PDCP recovery procedure, UE 102 may retransmit at least a portion of the UL PDCP PDUs to CU 172 via DU 174 and the first cell in event 336. Similarly, after sending the first LTM command or in response to sending the first LTM command, CU 172 performs some or all of the PDCP recovery procedures for at least one CU PDCP entity. For example, after sending the first LTM command or in response to sending the first LTM command, CU 172 performs the PDCP recovery procedure for the first CU PDCP entity among at least one CU PDCP entity. In some implementations, CU 172 performs the PDCP recovery procedure for the first CU PDCP entity in response to receiving a DU to CU message 329 or 334. In other implementations, CU 172 performs the PDCP recovery procedure for the first CU PDCP entity in response to receiving a DL data delivery status message. During the PDCP recovery procedure, CU 172 may or may not rebuild the first CU PDCP entity. After performing the PDCP recovery procedure or in response to performing the PDCP recovery procedure, CU 172 may retransmit at least a portion of the DL PDCP PDU to UE 102 via DU 174 and the first cell in event 336.

[0247] In other implementations, UE 102 avoids rebuilding some or all of at least one UE PDCP entity in response to receiving a first LTM command. For example, some or all of the at least one UE PDCP entity includes a first UE PDCP entity and / or a second UE PDCP entity. Similarly, after receiving a DU to CU message 329 or 340 (e.g., in response to this) or after receiving a DL data delivery status message (e.g., in response to this), CU 172 avoids rebuilding some or more of at least one CU PDCP entity. In other words, UE 102 uses some or all of at least one UE PDCP entity (not rebuilt) to communicate with CU 172 via DU 174 and the first cell. For example, some or all of the at least one UE PDCP entity includes a first UE PDCP entity and / or a second UE PDCP entity. Similarly, CU 172 uses some or all of at least one CU PDCP entity (not rebuilt) to communicate with UE 102 via DU 174 and the first cell. For example, some or all of at least one CU PDCP entity includes a first CU PDCP entity and / or a second CU PDCP entity.

[0248] In some implementations, after determining that UE 102 is connected to the first cell, CU 172 may send a 338 CU to DU message (e.g., a UE context modification request message) to DU 174 to instruct DU 174 to stop communicating with UE 102 and / or release or suspend resources configured for UE 102 in cell 124A. In response, DU 174 may stop communicating with UE 102 on cell 124A and / or release or suspend resources configured for UE 102 in cell 124A, and send a 340 DU to CU message (e.g., a UE context modification response message) to CU 172. Events 338 (optional) and 340 (optional) in... FIG. 3 This is collectively referred to as the resource release process 396.

[0249] After communicating with DU 174 in the first cell, or simultaneously with communicating with DU 174 in the first cell, events 344, 346, 348, 350, 351, 352, 354, and / or 356, respectively, similar to events 324, 326, 328, 330, 331, 332, 334, and / or 336, may occur. UE 102 sends at least one measurement report (344) to DU 174. The at least one measurement report includes at least one measurement result for the second cell (i.e., cell 2). The at least one measurement result indicates that the second cell is suitable for communicating with UE 102 and / or the first cell is not suitable for communicating with UE 102. Upon receiving at least one measurement report (e.g., in response to this), DU 174 determines to activate LTM DU configuration 2 and generates a second LTM command to activate LTM DU configuration 2 (i.e., the second LTM command instructs UE 102 to apply LTM DU configuration 2). Then, DU 174 sends 350 second LTM commands to UE 102 in the first cell.

[0250] When it is determined that LTM DU configuration 2 is activated or a second LTM command is sent, or in response to this, DU 174 may send a DU-to-CU message 349 to CU 172 indicating that LTM is being performed. In some implementations, DU 174 includes cell ID 2 or ID2 (i.e., LTM ID) in the DU-to-CU message 349 to indicate that DU 174 will activate LTM DU configuration 2. The DU may send the DU-to-CU message 349 to CU 172 before or after sending the LTM command 350.

[0251] At least some of the descriptions in events 324, 326, 328, 330, 331, 332, 334 and / or 336 may also be applied to events 344, 346, 348, 350, 351, 352, 354 and / or 356 with simple modifications. For example, “Cell 124A”, “First LTM Command”, “First Cell”, “ID 1”, “LTM DU Configuration 1” and / or “LTM CU Configuration 1” are replaced with “First Cell”, “Second LTM Command” and “Second Cell”, “ID 2”, “LTM DU Configuration 2” and / or “LTM CU Configuration 2”, respectively.

[0252] Events 344, 346, 348, 350, 351, 352, and 354 are in FIG. 3 These are collectively referred to as LTM execution process 398. Events 304, 306, 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, and 356 are in... FIG. 3This is collectively referred to as the LTM DU configuration and / or activation process 380.

[0253] Next reference FIG. 4 In scenario 400, base station 104 includes CU 172, source DU (S-DU) 174A, and target DU (T-DU) 174B. S-DU 174A operates cell 124A and optionally additional cells, while T-DU 174B operates a first cell (e.g., cell 124C). Scenario 400 is similar to scenario 300. Therefore, the description of scenario 300 can generally be applied to scenario 400. The differences between scenarios 300 and 400 are described below.

[0254] Initially, UE 102 uses the serving DU to communicate with S-DU 174A on cell 124A 402, and communicates with CU 172 via S-DU 174A. S-DU 174A is the serving DU, similar to... FIG. 3In communication 402, UE102 sends at least one measurement report (e.g., an L3 measurement report) via S-DU 174A to CU 172, numbers 404 and 406. Based on the at least one measurement report, CU 172 determines (operated by T-DU 174B) cells 1, ..., N prepared for LTM by UE 102, where N is a positive integer greater than 0 or 1. Cells 1, ..., N are identified by cell IDs 1, ..., N, respectively. In response to this determination, CU 172 and T-DU 174B perform LTM preparation procedure 490 to (request T-DU 174B) prepare cells 1, ..., N for LTM by UE 102. N can be a positive integer greater than zero or 1. In LTM preparation procedure 490, similar to event 308, CU 172 sends a CU-DU message including cell IDs 1, ..., N to T-DU 174B to request T-DU 174B to prepare cells 1, ..., N for LTM for UE 102. In response, similar to event 310, T-DU 174B sends a DU-DU message including LTM DU configurations 1, ..., N to CU 172. LTM DU configurations 1, ..., N configure cells 1, ..., N for LTM, respectively. Specifically, LTM DU configurations 1, ..., N include configuration parameters for communication on cells 1, ..., N, respectively. In some implementations, the CU-DU message and DU-CU message in procedure 490 are respectively a UE context establishment request message and a UE context establishment response message. Similar to LTM configuration delivery procedure 394, CU 172 then sends LTM DU configurations 1, ..., N in an RRC reconfiguration message in LTM configuration delivery procedure 494. In some implementations, the T-DU 174B can include cell indices 1, ..., N in the LTM DU configurations 1, ..., N respectively. In some implementations, the CU 172 can set cell indices 1, ..., N to different values ​​and include cell indices 1, ..., N in the CU to DU message of procedure 490.

[0255] After performing LTM preparation procedure 490, CU 172 may perform an additional LTM preparation procedure with T-DU 174B to prepare cells N+1, ..., N+M for LTM for UE 102, similar to procedure 490. M is a positive integer greater than zero. Similar to events 404 and 406, CU 172 may determine to do so based on one or more measurement reports received from UE 102 via S-DU 174A. During the additional LTM preparation procedure, CU 172 sends a CU-DU message to T-DU 174B including cell IDs N+1, ..., N+M to request T-DU 174B to prepare cells N+1, ..., N+M for LTM for UE 102. Cell IDs N+1, ..., N+M identify cell IDs N+1, ..., N+M, respectively. In response to the CU-DU message, T-DU 174B sends a DU-DU message to CU 172 including LTMDU configurations N+1, ..., N+M. The LTM DU configurations N+1, ..., N+M configure the cells N+1, ..., N+M for LTM, respectively. Specifically, the LTM DU configurations N+1, ..., N+M include configuration parameters for communication on cells N+1, ..., N+M. Similar to LTM configuration delivery procedures 394 or 494, CU 172 then sends the LTM DU configurations N+1, ..., N+M in an RRC reconfiguration message during an additional LTM configuration delivery procedure.

[0256] In some implementations, LTM preparation procedure 490 is a UE context establishment procedure, and the additional LTM preparation procedure is a UE context modification procedure. In other implementations, both LTM preparation procedure 490 and the additional LTM preparation procedure are UE context establishment procedures. The UE context establishment procedures can occur in parallel between the CU and DU, and these procedures can be distinguished by the SpCell ID IE and the requested target cell ID IE in the UE context establishment request message and UE context establishment request confirmation message, respectively.

[0257] In some implementations, CU 172 and S-DU 174A can execute procedure 380 with UE 102, such as for... FIG. 3 As described above. In procedure 380, CU 172 and S-DU 174A perform procedures 390 and / or 392 to prepare the S-DU 174A cell for LTM for UE 102. Note that in procedure 380 or for FIG. 3 The described value N can be related to... FIG. 4The described value N may be the same or different. In procedure 390, CU 172 may receive a first DU-to-CU message including the reference LTM DU configuration from S-DU 174A in event 310. In other implementations, CU 172 and S-DU 174A do not perform procedure 380 with UE 102. In such cases, CU 172 may perform a 488 reference LTM DU configuration query procedure with S-DU 174A to obtain the reference LTM DU configuration. In procedure 488, CU 172 sends a 460 CU-to-DU message to S-DU 174A to request or query the reference LTM DU configuration. In some implementations, CU 172 may include an indication in the CU-to-DU message to request or query the reference LTM DU configuration. In response to the indication or CU-to-DU message 460, S-DU 174A sends a 462 DU-to-CU message including the reference LTM DU configuration to CU 172. In some implementations, the indication is a reference LTM DU configuration query indication. In other implementations, the indication is an LTM indication, and CU 172 may include the query indication (e.g., GNB-DU configuration query IE) in the CU-DU message. After receiving the reference LTM DU configuration (i.e., in process 390 or process 488), CU 172 includes the reference LTM DU configuration (received from S-DU 174A) in the CU-DU message in LTM preparation process 490. T-DU 174B generates LTM DU configurations 1, ..., N based on the reference LTM DU configuration received from CU 172. In this case, T-DU 174B does not include the reference LTM DU configuration in the DU-CU message in process 490. In the case of an additional LTM preparation process, T-DU 174B does not include the reference LTM DU configuration in the DU-CU message in the additional LTM preparation process. CU 172 may omit the reference LTMDU configuration from the CU-DU message during the additional LTM preparation process with T-DU 174B. In the case of the additional LTM preparation process, T-DU 174B generates LTMDU configurations N+1, ..., N+M based on the reference LTMDU configuration received from CU 172.

[0258] In some implementations, CU 172 does not provide a reference LTM DU configuration to T-DU 174B during LTM preparation procedure 490. In this case, T-DU 174B generates a reference LTM DU configuration and generates LTM DU configurations 1, ..., N based on the reference LTM DU configuration. In this case, T-DU 174B includes the reference LTM DU configuration in the DU-to-CU message in procedure 490. CU 172 sends the reference LTM DU configuration in the RRC reconfiguration message in procedure 490. In the case of an additional LTM preparation procedure, T-DU 174B generates LTM DU configurations N+1, ..., N+M based on the reference LTM DU configuration. In this case, T-DU 174B may not include the reference LTM DU configuration in the DU-to-CU message during the additional LTM preparation procedure. In some implementations, the reference LTM DU configuration generated by T-DU 174B differs from the reference LTM DU configuration generated by S-DU 174A. In other implementations, the reference LTM DU configuration generated by T-DU 174B is the same as the reference LTM DU configuration generated by S-DU 174A.

[0259] In some implementations, CU 172 includes the LTM DU configurations 1, ..., N of process 380 in the CU to DU message of process 490, and T-DU 174B considers or generates LTM DU configurations 1, ..., N and / or N+1, ..., N+M based on the configurations in the LTM DU configurations of process 380.

[0260] / / RS resource configuration

[0261] In some implementations, the LTM DU configuration X of process 380 includes at least one Reference Signal (RS) resource configuration X, where 1 ≤ X ≤ N. Each of the RS resource configurations X configures one or more RSs or one or more RS resources associated with cell X of S-DU 174A. RSs include SSBs and / or CSI-RSs. RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of the RS resource configurations X includes an RS resource configuration ID. In some implementations, the RS resource configuration X is (similar to) a CSI-ResourceConfig IE. In some implementations, the LTM DU configuration X includes a CSI-MeasConfig IE, and the CSI-MeasConfig IE includes a CSI-ResourceConfig IE. T-DU 174B generates at least one report configuration 1 for reporting measurement results of RSs or RS resources on cell 1 of T-DU 174B, and includes report configuration 1 in LTM DU configuration 1. In some implementations, report configuration 1 is (similar to) a CSI-ReportConfig IE. In some implementations, the T-DU 174B considers or generates at least one RS resource configuration 1 based on RS resource configuration X, and includes the RS resource configuration 1 in the LTM DU configuration 1. In some implementations, the T-DU 174B includes RS resource configuration X in RS resource configuration 1. In other implementations, the T-DU 174B includes each of RS resource configurations X in RS resource configuration 1, except for the RS resource configuration ID in RS resource configuration X. The T-DU 174B assigns an RS resource configuration ID to the value of each of RS resource configurations 1 (including RS resource configuration X), and includes the RS resource configuration ID in the corresponding RS resource configuration.

[0262] In some implementations, Report Configuration 1 configures one or more UL resources (e.g., PUCCH or PUSCH resources) for UE 102 on cell 1 to transmit measurement results. In some implementations, each of Report Configuration 1 includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in RS resource configuration 1. After UE 102 performs an LTM serving cell change from cell 124A to cell 1, UE 102 communicates with S-DU 174B (i.e., T-DU 17B becomes the S-DU for UE 102) and transmits measurement results to S-DU 174B on UL resources via cell 1 according to Report Configuration 1. Correspondingly, S-DU 174B receives measurement results from UE 102 on UL resources via cell 1 according to Report Configuration 1. In some implementations, each of the measurement results includes one or more RS resource indicators and / or one or more quantized measurement values. UE 102 performs measurements on an RS or RS resource according to RS resource configuration 1 and / or reporting configuration 1, and obtains quantized measurement values ​​from the measurements. In some implementations, an RS resource indicator indicates the RS or RS resource in which UE 102 performs measurements or obtains quantized measurement values. In some implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRI) and / or one or more CSI-RS resource indicators (CRI). The quantized measurement values ​​may include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0263] In some implementations, the T-DU 174B also includes additional RS resource configurations in LTM DU configuration 1. Each configuration in the additional RS resource configurations is associated with one or more additional RSs or one or more additional RS resources in cell 1. Additional RSs include SSBs and / or CSI-RSs. Additional RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of the additional RS resource configurations includes an RS resource configuration ID. In some implementations, the additional RS resource configuration is (similar to) a CSI-ResourceConfig IE. In some implementations, the T-DU 174B includes the CSI-ResourceConfig IE in a CSI-MeasConfig IE. The T-DU 174B generates at least one additional reporting configuration for reporting measurement results of RSs or RS resources on cell 1 of the T-DU 174B, and includes this additional reporting configuration in LTM DU configuration 1. In some implementations, this additional reporting configuration is (similar to) a CSI-ReportConfig IE.

[0264] In some implementations, the additional report configuration allows UE 102 to configure one or more UL resources (e.g., PUCCH or PUSCH resources) on cell 1 to transmit measurement results. In some implementations, each of the additional report configurations includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the additional RS resource configuration. After UE 102 performs an LTM serving cell change from cell 124A to cell 1, UE 102 communicates with S-DU 174B 436 and transmits measurement results to S-DU 174B via cell 1 on UL resources according to the additional report configuration. Correspondingly, S-DU 174B receives measurement results from UE 102 via cell 1 on UL resources according to the additional report configuration. In some implementations, each of the measurement results includes one or more RS resource indicators and / or one or more quantized measurement values. UE 102 performs measurements on the additional RS or additional RS resources according to the additional RS resource configuration and / or additional report configuration, and obtains quantized measurement values ​​from the measurements. In some implementations, the RS resource indicator indicates an additional RS or RS resource in which the UE 102 performs a measurement or obtains a quantized measurement value. In some implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRIs) and / or one or more CSI-RS resource indicators (CRIs). The quantized measurement value may include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0265] Similarly, T-DU 174B may consider or generate RS resource configurations 2, ..., N and / or N+1, ..., N+M and / or report configurations 2, ..., N and / or N+1, ..., N+M based on RS resource configuration X, and include RS resource configurations 2, ..., N and / or N+1, ..., N+M and / or report configurations 2, ..., N and / or N+1, ..., N+M in LTM DU configurations 2, ..., N and / or N+1, ..., N+M, as described above.

[0266] / / TCI status configuration

[0267] In other implementations, the LTM DU configuration X of procedure 380 includes at least one TCI state configuration X, where 1 ≤ X ≤ N. Each configuration in the TCI state configuration X associates one or two DL RSs with the TCI state of the corresponding QCL type. In some implementations, the DL RS may be associated with a cell X operated by S-DU 174A. In some implementations, each of the TCI state configuration X includes a TCI state ID. In some implementations, each of the TCI state configuration X is a TCI state IE. In some implementations, the TCI state configuration X includes / is an ul-TCI-ToAddModList-r17 field, one or more TCI-UL-State-r17 IEs, a dl-OrJointTCI-StateToAddModList-r17 field, one or more TCI-State IEs, a TCI-ActivatedConfig IE, and / or a tci-StatesToAddModList field. In some implementations, LTM DU configuration X includes PDSCH-Config IE, and PDSCH-Config IE includes TCI state configuration X. In some implementations, T-DU 174B considers or is based on TCI state configuration X to generate at least one TCI state configuration 1, and includes TCI state configuration 1 in LTM DU configuration 1. In some implementations, TCI state configuration 1 includes TCI state configuration X. In other implementations, T-DU 174B includes each of TCI state configurations X in TCI state configuration 1, except for the TCI state ID in TCI state configuration X. T-DU 174B assigns a TCI state ID to the value of each of TCI state configurations 1 (including TCI state configuration X), and includes that TCI state ID in the corresponding TCI state configuration. When UE102 and S-DU 174B communicate with each other 436, S-DU 174B can send an LTM command to UE102 to instruct UE102 to perform a fast serving cell change to cell X. S-DU 174B includes the TCI state ID in the LTM command to instruct UE102 to apply the TCI state configuration identified by the TCI state ID to communicate on cell X, where the TCI state configuration is one of TCI state configurations X, or a configuration that includes one of TCI state configurations X.

[0268] Similarly, T-DU 174B may consider or generate TCI state configurations 2, ..., N based on RS resource configuration X, and include TCI state configurations 2, ..., N and / or N+1, ..., N+M in LTM DU configurations 2, ..., N and / or N+1, ..., N+M, as described above.

[0269] In some implementations, where CU 172 executes process 380 after executing process 490, CU 172 includes the LTM DU configurations 1, ..., N of process 490 in the CU-DU message of process 380 in a similar manner as described above, and S-DU 174A generates the LTM DU configurations 1, ..., N of process 380 by considering or based on the configurations in the LTM DU configurations of process 490.

[0270] In some implementations, similar to procedure 392, CU 172 assigns IDs 1, ..., N to identify LTM DU configurations 1, ..., N (received from T-DU 174B), and performs procedure 492 with T-DU 174B to provide IDs 1, ..., N and / or cell IDs 1, ..., N to T-DU 174B. Therefore, T-DU 174B associates IDs 1, ..., N with LTM DU configurations 1, ..., N and / or cell IDs 1, ..., N, respectively. In other implementations, T-DU 174B assigns IDs 1, ..., N to identify LTM DU configurations 1, ..., N (generated by T-DU 174B), and includes IDs 1, ..., N in the DU-to-CU message of procedure 490, similar to event 310. In some implementations, similar to procedure 392, CU 172 assigns IDs N+1, ..., N+M to identify LTM DU configurations N+1, ..., N+M respectively, and performs a procedure (similar to procedure 492) with T-DU 174B to provide IDs N+1, ..., N+M and / or cell IDs N+1, ..., N+M to T-DU 174B. Therefore, T-DU 174B associates IDs N+1, ..., N+M with LTM DU configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M respectively. In other implementations, T-DU 174B assigns IDs N+1, ..., N+M to identify LTM DU configurations N+1, ..., N+M respectively, and includes IDs 1, ..., N in the DU-to-CU message of the additional LTM preparation procedure, similar to event 310.

[0271] In some implementations, CU 172 sends a CU-DU message 412, including IDs 1, ..., N, to S-DU 174A, and receives a DU-CU message 414 from S-DU 174A in response. The CU-DU message 412 and the DU-CU message 414 are... FIG. 4These are collectively referred to as LTM ID transmission procedure 493 or LTM cell index transmission procedure 493. In some implementations, messages 412 and 414 can be a UE context modification request message and a UE context modification response message, respectively. In some implementations, CU 172 includes LTM DU configuration 1, ..., N and / or cell ID 1, ..., N in CU to DU message 412. In one implementation, CU 172 includes ID 1, ..., N in CU to DU message 412. In another implementation, CU 172 includes cell index 1, ..., N in CU to DU message 412. In some alternative implementations, CU 172 can perform multiple LTM ID transmission procedures to send ID 1, ..., N, cell ID 1, ..., N and / or LTM DU configuration 1, ..., N to S-DU 174A. In each of the procedures, CU 172 includes specific portions of ID 1, ..., N, cell ID 1, ..., N, and / or LTM DU configuration 1, ..., N in a CU-to-DU message similar to message 412. Therefore, S-DU 174A associates ID 1, ..., N with LTM DU configuration 1, ..., N, and / or cell ID 1, ..., N, respectively. In other alternative implementations, CU 172 may perform multiple LTM cell index transmission procedures to send cell index 1, ..., N, cell ID 1, ..., N, and / or LTM DU configuration 1, ..., N to S-DU 174A. In each of the procedures, CU 172 includes specific portions of cell index 1, ..., N, cell ID 1, ..., N, and / or LTM DU configuration 1, ..., N in a CU-to-DU message similar to message 412. Therefore, S-DU 174A associates cell indices 1, ..., N with LTM DU configurations 1, ..., N and / or cell IDs 1, ..., N, respectively.

[0272] / / RS resource configuration

[0273] In some implementations, S-DU 174A generates a first service DU configuration based on LTM DU configurations 1, 2, ..., and / or N, and includes the first service DU configuration in the DU-to-CU message 414. In some implementations, the first service DU configuration includes a configuration that updates (e.g., enhances, modifies, or replaces) service DU configuration 402. In other implementations, the first service DU configuration includes configurations not included in service DU configuration 402. CU 172 sends an RRC reconfiguration message including the first service DU configuration to UE 102. Upon receiving the RRC reconfiguration message, UE 102 applies the first service DU configuration to communicate with the service DU. For example, the RRC reconfiguration message is or is similar to the RRC reconfiguration message in procedure 494. Depending on the implementation, UE 102 communicates with S-DU 174A using a configuration included in service DU configuration 402 that has not been updated by the first service DU configuration. The following are example implementations of generating the first service DU configuration based on LTM DU configurations 1, ..., N.

[0274] In some implementations, the LTM DU configuration Y of process 490 includes at least one RS resource configuration Y, where 1 ≤ Y ≤ N. Each configuration in RS resource configuration Y is associated with one or more RSs or one or more RS resources of cell Y of T-DU 174B. RSs include SSBs and / or CSI-RSs. RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of RS resource configurations Y includes an RS resource configuration ID. In some implementations, RS resource configuration Y is (similar to) CSI-ResourceConfig IE. In some implementations, LTM DU configuration Y includes CSI-MeasConfig IE, and CSI-MeasConfig IE includes CSI-ResourceConfig IE. S-DU 174A generates at least one service report configuration for reporting measurement results of RSs or RS resources on cell 124A and includes this service report configuration in the first service DU configuration. In some implementations, the service report configuration is (similar to) CSI-ReportConfig IE. In some implementations, S-DU 174A considers or generates at least one service RS resource configuration based on RS resource configuration Y, and includes the service RS resource configuration in the first service DU configuration. In some implementations, S-DU 174A includes RS resource configuration Y in the service RS resource configuration. In other implementations, S-DU 174A includes each of RS resource configurations Y in the service RS resource configuration, except for the RS resource configuration ID in RS resource configuration Y. S-DU 174A assigns a configuration ID to the value of each of the service RS resource configurations (including RS resource configuration Y), and includes the RS resource configuration ID in the corresponding service RS resource configuration.

[0275] In some implementations, the service report is configured for UE 102 to configure one or more UL resources (e.g., PUCCH or PUSCH resources) on cell 124A to send measurement results. In some implementations, each of the service report configurations includes one or more RS resource configuration IDs that identify one or more RS resource configurations included in the service RS resource configuration. When UE 102 communicates with S-DU 174A, UE 102 sends measurement results (e.g., event 424) to S-DU 174A via cell 124A on the UL resources according to the service report configuration. Correspondingly, S-DU 174A receives measurement results from UE 102 via cell 124A on the UL resources according to the service report configuration. In some implementations, each of the measurement results includes one or more RS resource indicators and / or one or more quantized measurement values. UE 102 performs measurements on the RS or RS resources according to the service RS resource configuration and / or service report configuration, and obtains quantized measurement values ​​from the measurements. In some implementations, the RS resource indicator indicates the RS or RS resource in which the UE 102 performs a measurement or obtains a quantized measurement value. In some implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRI) and / or one or more CSI-RS resource indicators (CRI). The quantized measurement value may include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0276] / / TCI status configuration

[0277] In other implementations, the LTM DU configuration Y of procedure 490 includes at least one TCI state configuration Y, where 1 ≤ Y ≤ N. Each configuration in the TCI state configuration Y associates one or two DL RSs with the TCI state of the corresponding QCL type. In some implementations, the DL RS may be associated with a cell Y operated by T-DU 174B. In some implementations, each of the TCI state configuration Y includes a TCI state ID. In some implementations, each of the TCI state configuration Y is a TCI-State IE. In some implementations, the TCI state configuration Y includes / is the ul-TCI-ToAddModList-r17 field, one or more TCI-UL-State-r17 IEs, the dl-OrJointTCI-StateToAddModList-r17 field, one or more TCI-State IEs, the TCI-ActivatedConfig IE, and / or the tci-StatesToAddModList field. In some implementations, LTM DU configuration Y includes PDSCH-Config IE, and PDSCH-Config IE includes TCI state configuration Y. In some implementations, S-DU 174A considers or is based on TCI state configuration Y to generate at least one service TCI state configuration, and includes the service TCI state configuration in the first service DU configuration. In some implementations, service TCI state configuration 1 includes TCI state configuration Y. In other implementations, S-DU 174A includes each of TCI state configurations Y in the service TCI state configuration, except for the TCI state ID in TCI state configuration Y. S-DU 174A assigns a TCI state ID to the value of each of the service TCI state configurations (including TCI state configuration Y), and includes the TCI state ID in the corresponding service TCI state configuration. When S-DU 174A communicates with UE 102 436, S-DU 174A can send an LTM command to UE 102 to instruct UE 102 to perform a fast serving cell change to cell Y. S-DU 174A includes the TCI state ID in the LTM command to instruct UE 102 to apply the TCI state configuration identified by the TCI state ID to communicate on cell Y, where the TCI state configuration is one of the TCI state configurations in Y, or includes a configuration of one of the TCI state configurations in Y.

[0278] In some implementations, CU 172 sends a CU-DU message including IDs N+1, ..., N+M to S-DU 174A, and in response receives DU-CU messages from S-DU 174A that are similar to CU-DU message 412 and DU-CU message 414, respectively. In some implementations, CU 172 includes LTM DU configuration N+1, ..., N+M and / or cell IDs N+1, ..., N+M in the CU-DU message. In some alternative implementations, CU 172 may perform multiple LTM ID transmission procedures to send IDs N+1, ..., N+M, cell IDs N+1, ..., N+M, and / or LTM DU configurations N+1, ..., N+M to S-DU 174A. In each of the processes, CU 172 includes specific portions of IDs N+1, ..., N+M, cell IDs N+1, ..., N+M, and / or LTM DU configurations 1, ..., N in a CU-to-DU message similar to message 412. Therefore, S-DU 174A associates IDs N+1, ..., N+M with LTM DU configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M, respectively. In some implementations, S-DU 174A generates a second service DU configuration based on LTM DU configurations N+1, N+2, ..., and / or N+M, and includes the second service DU configuration in the DU-to-CU message. In some implementations, the second service DU configuration includes configurations that update (e.g., enhance, modify, or replace) the first service DU configuration and / or update configurations included in service DU configuration 402 that have not been updated by the first service DU configuration. In other implementations, the second service DU configuration includes configurations not included in the first service DU configuration. CU 172 sends an RRC reconfiguration message, including a second serving DU configuration, to UE 102 via S-DU 174A. Upon receiving the RRC reconfiguration message, UE 102 applies the second serving DU configuration to communicate with the serving DU. For example, the RRC reconfiguration message is or is similar to the RRC reconfiguration message in procedure 494. Depending on the implementation, UE 102 communicates with S-DU 174A using a configuration included in serving DU configuration 402 and / or the first serving DU configuration and not updated by the second serving DU configuration. In some implementations, S-DU 174A generates one or more new L1 measurement configurations based on the L1 measurement configurations in LTM DU configurations N+1, N+2, ... and / or N+M, and includes these new L1 measurement configurations in the second serving DU configuration. In some implementations, the S-DU 174A generates one or more new TCI state configurations based on the TCI state configurations in LTM DU configurations N+1, N+2, ... and / or N+M, and includes the new TCI state configurations in the second service DU configuration.

[0279] In some implementations, when CU 172 and S-DU 174A execute procedure 380 with UE 102, the values ​​of ID 1, ..., N in procedure 380 are different from the values ​​of ID 1, ..., N and ID N+1, ..., N+M described for scenario 400. In some implementations, when CU 172 and S-DU 174A execute procedure 380 with UE 102, the values ​​of cell ID 1, ..., N in procedure 380 are different from the values ​​of cell ID 1, ..., N and cell ID N+1, ..., N+M described for scenario 400. In some implementations, when CU 172 and S-DU 174A execute procedure 380 with UE 102, the values ​​of cell index 1, ..., N in procedure 380 are different from the values ​​of cell index 1, ..., N and cell index N+1, ..., N+M described for scenario 400.

[0280] Later, similar to event 324, UE 102 may send at least one measurement report (424) to S-DU 174A. The at least one measurement report (e.g., an L1 measurement report) includes an event ID, a first measurement result for cell 1 of T-DU 174B, and / or includes a second measurement result for cell 124A. In some implementations, the first measurement result may be or includes RSRP, RSRQ, and / or SINR obtained by UE 102 from a reference signal transmitted on cell 1. Similarly, the second measurement result may be or includes RSRP, RSRQ, and / or SINR obtained by UE 102 from a reference signal transmitted on cell 124A. In some implementations, the event ID, RSRP, RSRQ, and / or SINR are L1 event ID, L1-RSRP, L1-RSRQ, and / or L1-SINR, respectively. Based on the first measurement result and / or the second measurement result, S-DU 174A may send a first LTM command (i.e., LTM command 1) including ID 1 to UE 102, instructing UE 102 to perform a serving cell change to cell 1 of T-DU 174B. In some implementations, the first LTM command includes ID 1. In other implementations, the first LTM command includes cell index 1. When UE 102 receives the first LTM command, UE 102 performs a serving cell change from serving cell to cell 1 according to LTM DU configuration 1. After receiving the first LTM command (e.g., in response to this), UE 102 may or may not perform a random access procedure (432) with T-DU 174B, similar to event 332. Upon receiving the first LTM command or completing random access procedure 432 (e.g., in response to this), UE 102 can communicate with T-DU174B in the first cell using LTM DU configuration 1 and / or reference LTM DU configuration 436, and communicate with CU 172 via T-DU 174B, similar to event 336. If a serving cell change occurs in procedure 380, the serving cell can be cell 1 or cell 2 of S-DU 174A. Otherwise, if no serving cell change occurs in procedure 380 or procedure 380 is not executed, the serving cell is cell 124A. If the first LTM command includes ID 1, UE 102 identifies LTM DU configuration 1 and / or cell ID 1 (i.e., cell 1) based on ID 1, as for FIG. 3 As stated above. If the first LTM command includes cell index 1, then UE 102 identifies LTM DU configuration 1, cell ID 1 (i.e., cell 1), and / or LTM ID 1 based on cell index 1, as for... FIG. 3As described above. Upon receiving the first LTM command or successfully accessing cell 1 (e.g., in response to this), UE 102 applies LTM DU configuration 1 to communicate with T-DU 174B.

[0281] When LTM DU Configuration 1 is activated or the first LTM command 430 is sent, or in response to this, S-DU 174A may send a DU-to-CU message 429 to CU 172 indicating that LTM is being performed. In some implementations, S-DU 174A includes Cell ID 1 or ID 1 (i.e., LTM ID) in the DU-to-CU message 429 to indicate that S-DU 174A wants to activate LTM DU Configuration 1 or trigger an LTM serving cell change. S-DU 174A may send the DU-to-CU message 429 to CU 172 before or after sending the LTM command 430. In some implementations, upon or after CU 172 receives the DU-to-CU message 429, CU 172 may stop or suspend sending DL data for UE 102 to S-DU 174A until it receives the DU-to-CU message 434. After receiving DU to CU message 434, CU 172 starts, continues, or resumes sending DL data for UE 102 to T-DU 174B. When or after T-DU 174B detects UE 102 accessing cell 1, T-DU 174B sends DL data to UE 102 via cell 1.

[0282] The resource release procedure 496 can be similar to procedure 396. Alternatively, in the resource release procedure 496, CU 172 can send a CU-DU message (e.g., a UE context release command message) to S-DU 174A to release the UE context of UE 102. In response, S-DU 174A releases the UE context of UE 102 and sends a 440 DU-CU message (e.g., a UE context release complete message) to CU-172.

[0283] Events 380, 404, 406, 490, 492, 494, 494, 424, 426, 428, 429, 430, 431, 432, 434, 436, 496, 498, and 456 are in FIG. 4 This is collectively referred to as the LTM configuration and / or activation process 480.

[0284] Next reference FIG. 5AIn scenario 500A, base station 106 operates as the MN (Mean Access Provider) and base station 104 operates as the SN (Signal Provider). SN 104 includes CU 172 and DU 174. Scenario 500A is similar to scenario 300, except that scenario 500A is a DC (Distributed Access Provider) scenario, while scenario 300 is a Single Connectivity (SC) scenario. MN 106 may include components similar to... FIG. 3 The CU and DU of base station 104.

[0285] Initially, UE 102 communicates with MN 106 and SN 104 under DC. In event 502, UE 102 uses the serving DU configuration to communicate with DU 174 on cell 124A and uses the serving CU configuration to communicate with CU 172 via DU 174, similar to event 302. In some alternative implementations, UE 102 does not communicate with CU 172 via DU 174 in event 302. In some implementations, UE 102 may communicate 502UL PDUs and / or DL ​​PDUs with MN 106 and / or SN 104 under DC via a radio bearer, which may include SRBs and / or DRBs. MN 106 and / or SN 104 may be configured to communicate with the radio bearers of UE 102. UE 102 communicates 502 UL PDUs and / or DL ​​PDUs with SN 104 on the SCG (i.e., SCG radio resources) configured for communication with UE 102 under DC. UE 102 communicates UL PDUs and / or DL ​​PDUs with MN 106 on the MCG (i.e., MCG radio resources) according to the MN configuration (i.e., MCG configuration) under DC. In some implementations, the serving DU configuration is the SN configuration (i.e., SCG configuration). In the MN configuration, MN 106 configures the MCG, which includes at least one serving cell (e.g., cell 126 and / or other cells) operated by MN 106. In the serving DU configuration, SN 106A configures the SCG, which includes at least one serving cell (e.g., cell 124A and / or other cells) operated by SN 104. In some implementations, the MN configuration includes multiple configuration parameters, and UE 102 receives the configuration parameters in one or more RRC messages from MN 106. For example, regarding FIG. 3 The service DU configuration includes multiple configuration parameters. In some implementations, UE 102 receives these configuration parameters from SN 104, for example, via MN 106 and / or on an SRB (e.g., SRB3) configured to exchange RRC messages between UE 102 and SN 104.

[0286] When UE 102 communicates with MN 106 and SN 104 under DC, MN 106 may perform an LTM DU configuration and / or activation procedure similar to procedures 380 and / or 480 with UE 102. In some implementations, when communicating with MN 106 and SN 104 under DC, UE 102 may send at least one measurement report to CU 172 via DU 174 and cell 124A in events 504 and 506, respectively, similar to events 304 and 306. In other implementations, when communicating with MN 106 and SN 104 under DC, UE 102 may send at least one measurement report to MN 106 via cell 126. MN 106 then sends at least one measurement report to CU 172. In some implementations, MN 106 generates at least one SN message including at least one measurement report and sends at least one SN message to CU 172 in event 507. In one implementation, at least one SN message includes an RRC transmission message and / or an SN modification request message.

[0287] Upon receiving at least one measurement report (e.g., in response to this) or during communication between SN 104 and UE 102, SN 104 determines to prepare a first cell for UE 102, as for... FIG. 3 As described. Events 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are similar to events 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, and 356, respectively. After receiving the first LTM command 530, sending an acknowledgment 531, or confirming that UE 102 has successfully connected to the first cell 532 or 536, similar to event 336, UE 102, operating under DC with MN 106 and SN 104, communicates with DU 174 in the first cell according to LTM DU configuration 1 536, and communicates with CU 172 via DU 174 536. Later, DU 174 and / or CU 172 may perform an LTM execution procedure 598 with UE 102, similar to procedure 398 or 498, to command UE 102 to perform a cell change from the first cell to the second cell. Due to procedure 598, similar to event 356, UE 102, operating under DC with MN 106 and SN 104, communicates 556 with DU 174 in the second cell according to LTM DU configuration 2, and communicates 556 with CU 172 via DU 174.

[0288] Events 504, 506, 505, 507, 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are in FIG. 5A This is collectively referred to as the LTM DU configuration and / or activation process 581.

[0289] Next reference FIG. 5B Scenario 500B is generally similar to Scenario 500A, except that SN 104 sends RRC reconfiguration messages 517 and 519 to UE 102 via MN 106, and receives RRC reconfiguration completion messages 521 and 523 from UE 102 via MN 106. RRC reconfiguration messages 517 and 519 are similar to RRC reconfiguration messages 316 and 318. RRC reconfiguration completion messages 521 and 523 are similar to RRC reconfiguration messages 320 and 322. In some implementations, SN 104 generates a first SN message including the RRC reconfiguration message (e.g., an SN modification request message, an SN modification request message, or an RRC transmission message) and sends the first SN message to MN 106 in event 517. MN 106 generates an MN RRC message including the RRC reconfiguration message and sends the MN RRC message 519 to UE 102. In response, UE 102 generates an MN RRC response message including an RRC reconfiguration complete message and sends this MN RRC response message to MN 106 at event 521. In some implementations, MN 106 generates a second SN message (e.g., an SN reconfiguration complete message or an RRC transmission message) including an RRC reconfiguration complete message and sends the second SN message to SN 104 at event 523. In some implementations, the MN RRC message and the MN RRC response message can be an RRC reconfiguration message and an RRC reconfiguration complete message, respectively.

[0290] Events 504, 506, 505, 507, 590, 592, 594, 517, 519, 521, 523, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are... FIG. 5B This is collectively referred to as the LTM DU configuration and / or activation process 582.

[0291] Next reference FIG. 6AIn scenario 600A, similar to scenarios 300 to 500B, base station 106 operates as the MN, and base station 104 operates as the SN. Similar to base station 104 in scenario 400, SN 104 includes CU 172, S-DU 174A, and T-DU 174B. When UE 102 communicates with MN 106 and SN 104 under DC, MN 106 can perform LTM DU configuration and / or activation procedures similar to procedures 380 and / or 480 with UE 102 (680). When UE 102 communicates with M-DU 174A and S-DU 174B under DC, CU 172 can perform LTM DU configuration and / or activation procedures similar to procedures 581 or 582 with UE 102 via M-DU 174A or S-DU 174B (681).

[0292] Next reference FIG. 6B Scenario 600B is similar to scenarios 300-500B and 600A, except that SN 104 sends 617 and 619 RRC reconfiguration messages to UE 102 via MN 106, and receives 621 and 623 RRC reconfiguration complete messages from UE 102 via MN 106.

[0293] Next reference FIG. 7A In scenario 700A, base station 104 operates as both MN and SN, similar to scenarios 300-600B. Base station 104 includes CU 172, main DU (M-DU) 174A, and auxiliary DU (S-DU) 174B. Similar to... FIG. 3 Base station 104 or FIG. 5A to FIG. 6B MN 106, CU 172 operate together with M-DU 174A as MN and are similar FIG. 5A to FIG. 6B SN 104, CU 172 in the series operate together with S-DU 174B, which is an SN.

[0294] In scenario 700A, UE 102 initially communicates with M-DU 174A and S-DU 174B under DC 702 and communicates with CU 172 via M-DU 174A and S-DU 174B 702. In event 702, similar to event 302, UE 102 uses the serving DU configuration to communicate with S-DU 174B on cell 124A and uses the serving CU configuration to communicate with CU 172 via S-DU 174B. Events 704 and 706 are similar to events 304 and 306. In some implementations, similar to event 304, UE 102 may send 705 at least one measurement report to M-DU 174A. Similar to event 306, M-DU 174A then sends 707 at least one DU-to-CU message including at least one measurement report to CU 172. When UE 102 communicates with M-DU 174A and S-DU 174B under DC, CU 172 can perform LTM DU configuration and / or activation procedures similar to procedure 380 with UE 102 via M-DU 174A.

[0295] Events 704, 706, 705, 707, 790, 792, 794, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, and 756 are in FIG. 7A This is collectively referred to as the LTM configuration and / or activation process 781.

[0296] Next reference FIG. 7B Scenario 700B is similar to scenarios 300 to 600B and 700A, except that CU 172 sends 717 and 719 RRC reconfiguration messages to UE 102 via M-DU 174A and receives 721 and 723 RRC reconfiguration complete messages from UE 102 via M-DU 174A.

[0297] Events 704, 706, 705, 707, 790, 792, 794, 717, 719, 721, 723, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, and 756 are in FIG. 7B This is collectively referred to as the LTM DU configuration and / or activation process 782.

[0298] Next reference FIG. 8AIn scenario 800A, similar to scenarios 300 to 700B, base station 104 operates as both MN and SN. Base station 104 includes CU 172, primary DU (M-DU) 174A, secondary DU (S-DU) 174B, and target secondary DU (T-DU) 174C. CU 172 operates together with M-DU 174A as MN and with S-DU 174B as SN. When UE 102 communicates with M-DU 174A and S-DU 174B under DC, CU 172 can perform an LTM DU configuration and / or activation procedure similar to procedure 380 with UE 102 via M-DU 174A. When UE 102 communicates with M-DU 174A and S-DU 174B under DC, CU 172 can perform LTM DU configuration and / or activation procedures similar to procedures 581 or 582 together with UE 102 via S-DU 174A.

[0299] Next reference FIG. 8B Except that CU 172 sends RRC reconfiguration messages 817 and 819 to UE 102 via M-DU 174A and receives RRC reconfiguration completion messages 821 and 823 from UE 102 via M-DU 174A, scenario 800B is similar to scenarios 300-700B and 800A.

[0300] Next, refer to FIG. 9A to FIG. 20 The discussion covers several example methods for implementing LTM in RAN nodes such as base stations, DUs, CUs, or UEs. (Above) FIG. 3 to FIG. 8B At least some of the descriptions in the description can also be applied to FIG. 9A to FIG. 20 .

[0301] FIG. 9A It shows that it can be generated by DU (e.g., FIG. 3 to FIG. 8B Example method 900A for preparing and triggering early timing advance (TA) acquisition with a UE (e.g., UE 102), implemented by DU 174, S-DU 174A, M-DU 174A or S-DU 174B.

[0302] Method 900A begins at block 902, where the DU communicates with the UE via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, 881, 324, 344, 398, 424, 444, 498, 524, 598, 624, 698, 724, 798, 824, or 898). In block 910A, the DU sends a first DU-CU message to the CU, including a first cell ID, to request random access configuration parameters for the UE for early TA acquisition in the first cell, where the first cell ID identifies the first cell (e.g., event 310). In block 912, the DU receives a first CU-DU message from the CU, which includes random access configuration parameters for the UE for early TA acquisition in the first cell (e.g., event 312). In block 918, the DU sends a first command to the UE via the serving cell, wherein the first command includes random access configuration parameters (e.g., event 318). In block 928, the DU receives a second CU-DU message from the CU, which includes TA values ​​for uplink synchronization with the UE in the first cell. In block 930, the DU sends a first LTM command to the UE via the serving cell, wherein the first LTM command commands the UE to connect to the first cell (e.g., events 330, 350, 398, 430, 450, 498, 530, 598, 630, 698, 730, 798, 830, or 898).

[0303] In some implementations, the first DU to CU message, the first CU to DU message, and the second CU to DU message are F1 Application Protocol (F1AP) messages. In some implementations, the first DU to CU message is a UE context modification request message. In some implementations, the first CU to DU message is a UE context modification confirmation message or a UE context modification request message. In some implementations, the second CU to DU message is a UE context modification request message.

[0304] In some implementations, the DU communicates with the UE via the serving cell and other serving cells (e.g., the DU configures the UE under carrier aggregation). In such cases, the DU may send the first LTM command to the UE via one of the other serving cells. In some implementations, the DU sends the first command on the PDCCH. In some implementations, the first command is a PDCCH command or a DCI.

[0305] In some implementations, random access configuration parameters configure physical random access channel (PRACH) resources, the association between SSB and PRACH resources, and / or one or more PRACH timings. In some implementations, random access configuration parameters include a random access preamble index, an indicator indicating a UL or supplementary UL (SUL), an SSB index, and / or a PRACH mask index. The random access preamble index indicates, identifies, or indexes a random access preamble. In response to receiving a first command, the UE selects or generates a random access preamble based on the random access preamble index. In some implementations, the PRACH mask index configures one or more PRACH timings. The UE determines the PRACH timing for transmitting the random access preamble in the first cell based on the SSB index and / or the PRACH mask index. In some implementations, an indicator set to 0 indicates a UL, and an indicator set to 1 indicates a SUL. The UE transmits the random access preamble on the UL or SUL of the first cell based on this indicator. In some implementations, the first command includes an identifier for the DCI format and / or a frequency domain resource allocation field. In some implementations, the DU sets the identifier for the DCI format to zero. In some implementations, the DU sets all bits in the frequency domain resource allocation field to zero.

[0306] In some implementations, at block 902, the DU receives at least one first measurement result from the UE via the serving cell (e.g., events 324, 344, 398, 424, 444, 498, 524, 598, 624, 698, 724, 798, 824, 898). Based on the first measurement result, the DU determines the random access configuration parameters requested for the UE for early TA acquisition in the first cell. The DU sends a first DU-CU message in response to this determination. In some implementations, the DU determines to send a first LTM command based on the first measurement result. In other implementations, after blocks 910A, 912, 918, or 928, the DU receives at least one second measurement result from the UE via the serving cell (e.g., events 324, 344, 398, 424, 444, 498, 524, 598, 624, 698, 724, 798, 824, 898). In this implementation, the DU determines to send the first LTM command based on the second measurement result.

[0307] FIG. 9B This is a flowchart of an example method 900B, similar to method 900A, except that method 900B includes block 910B instead of block 910A. In block 910B, the DU sends a first DU-CU message to the CU, including a first cell index, to request random access configuration parameters for the UE for early TA acquisition, where the first cell index indicates a first cell.

[0308] FIG. 9C This is a flowchart of an example method 900C, similar to method 900A, except that method 900C includes block 910C instead of block 910A. In block 910C, the DU sends a first DU-CU message to the CU, including a first LTM ID, to request random access configuration parameters for the UE for early TA acquisition, where the first LTM ID identifies the first LTM configuration. In some implementations, the first LTM configuration includes an LTM CU configuration and / or an LTM DU configuration.

[0309] FIG. 10 It shows that it can be generated by DU (e.g., FIG. 3 to FIG. 8B Example method 1000 for preparing and triggering early timing advance (TA) acquisition with UE (e.g., UE 102), implemented by DU 174, S-DU 174A, M-DU 174A or S-DU 174B.

[0310] Method 1000 begins at block 1002, where the DU communicates with the UE via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, or 881). At block 1024, the DU receives from the UE at least one first measurement result for the first cell (e.g., events 324, 344, 398, 424, 444, 498, 524, 598, 624, 698, 724, 798, 824, 898). At block 1025A, the DU determines whether the first measurement result is higher than a first threshold or a second threshold. If the DU determines at block 1025A that the first measurement result is higher than the first threshold, the process proceeds to block 1010. In box 1010, the DU performs the action described in boxes 910A, 910B, or 910C. In box 1012, the DU performs the action described in boxes 912, 918, and 928. In box 1027, the DU receives at least one second measurement result from the UE (e.g., events 324, 344, 398, 424, 444, 498, 524, 598, 624, 698, 724, 798, 824, or 898). In box 1025B, the DU determines whether the second measurement result is higher than a second threshold. Otherwise, if the DU determines in box 1025A that the first measurement result is higher than the second threshold, the process proceeds to box 1016. In box 1016, the DU performs the action described for box 930.

[0311] If DU determines in box 1025B that the second measurement result is higher than the second threshold, the process proceeds to box 1030. The process proceeds from box 1025B and box 1025A to box 1030. Otherwise, if DU determines in box 1025B that the second measurement result is not higher than the second threshold, the process ends.

[0312] In some implementations, the first measurement result is associated with one or more reference signals transmitted in the first cell. In some implementations, the second measurement result is associated with one or more reference signals transmitted in the first cell. In some implementations, the reference signals include one or more SSBs and / or one or more CSI-RSs.

[0313] In some implementations, the first threshold is lower than the second threshold. In some implementations, the DU predetermines the first and second thresholds. In other implementations, the DU receives the first and second thresholds from the CU. In yet another implementation, the DU receives the first and second thresholds from the Operation, Administration, and Maintenance (OAM) node.

[0314] In some implementations, the DU receives the first measurement result from the UE on one or more PUCCHs. In other implementations, the DU receives the first measurement result in one or more PUSCH transmissions from the UE.

[0315] FIG. 9A to FIG. 9C At least some of the descriptions in the description can also be applied to FIG. 10 .

[0316] FIG. 11 It shows that it can be generated by DU (e.g., FIG. 3 to FIG. 8B Example method 1100 for preparing and triggering early timing advance (TA) acquisition with UE (e.g., UE 102), implemented by DU 174, S-DU 174A, M-DU 174A or S-DU 174B.

[0317] Method 1100 begins at box 1102, where the DU communicates with the UE via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, 881, 324, 344, 398, 424, 444, 498, 524, 598, 624, 698, 724, 798, 824, or 898). At box 1103, the DU determines whether the UE supports early TA acquisition. If the DU determines in box 1103 that the UE supports early TA acquisition, the process proceeds to box 1110. At box 1110, the DU performs the actions described in 910A, 910B, or 910C. Otherwise, if the DU determines in box 1103 that the UE does not support early TA acquisition, the process proceeds to box 1109. In box 1109, the DU avoids requesting the random access configuration parameters for the UE used for early TA acquisition.

[0318] FIG. 9A to FIG. 10 At least some of the descriptions in the description can also be applied to FIG. 11 .

[0319] FIG. 12A It shows that it can be generated by DU (e.g., FIG. 3 to FIG. 8B Example method 1200A for preparing and triggering early timing advance (TA) acquisition with a UE (e.g., UE 102), implemented by DU 174, S-DU 174A, M-DU 174A or S-DU 174B.

[0320] Method 1200A begins at box 1202, where the DU performs the actions described in box 902. At box 1210, the DU performs the actions described in boxes 910A, 910B, or 910C. At box 1212, the DU performs the actions described in boxes 912, 918, and 928. At box 1211, the DU determines to send an LTM command to instruct the UE to perform a serving cell change to the first cell. At box 1213, the DU includes an ID in the LTM command to indicate the first cell. At box 1233A, the DU determines whether it has received a TA value for uplink synchronization with the UE in the first cell. If the DU determines at box 1233A that it has received a TA value for performing uplink synchronization with the UE in the first cell, the procedure proceeds to box 1235. At box 1235, the DU includes the TA value in the LTM command. Otherwise, if the DU determines in box 1233A that it has not received the TA value for uplink synchronization with the UE in the first cell, the procedure skips box 1235 and proceeds to box 1230. In box 1230, the DU sends an LTM command to the UE via the serving cell (e.g., events 330, 350, 398, 430, 450, 498, 530, 598, 630, 698, 730, 798, 830, or 898).

[0321] In some implementations, ID is the cell ID (e.g., PCI) of the first cell. In other implementations, ID is the cell index indicating the first cell. In still other implementations, ID is the LTM ID that identifies the LTM configuration that sets the first cell as a candidate cell for LTM.

[0322] FIG. 12B This is a flowchart of an example method 1200B, similar to method 1200A, except that method 1200B includes box 1233B instead of box 1233A. In box 1233B, DU determines whether the TA value is valid. If DU determines that the TA value is valid in box 1233B, the process proceeds to box 1235. Otherwise, if DU determines that the TA value is invalid in box 1233B, the process skips box 1235 and proceeds to box 1216.

[0323] In some implementations, the DU starts a TA validity timer upon receiving a TA value. If the TA validity timer expires, the DU determines the TA value is invalid. Otherwise, if the TA validity timer is running, the DU determines the TA value is valid. In some implementations, the DU starts the TA validity timer using a timer value. In some implementations, the DU predetermines the timer value. In other implementations, the DU receives the timer value from the CU.

[0324] In some implementations, the DU receives one or more measurement results for a first cell from the UE after receiving the TA value. If the measurement result is higher than a threshold, the DU determines the TA value is invalid. Otherwise, if the measurement result is lower than or equal to the threshold, the DU determines the TA value is valid. In some implementations, the DU predetermines a threshold value for the threshold. In other implementations, the DU receives the threshold value for the threshold from the CU.

[0325] FIG. 9A to FIG. 10 At least some of the descriptions in the description can also be applied to FIG. 12A to FIG. 12B .

[0326] FIG. 13 It shows that it can be generated by DU (e.g., FIG. 3 to FIG. 8B Example method 1300 for preparing and triggering early timing advance (TA) acquisition with a UE (e.g., UE 102), implemented by DU 174, S-DU 174A, M-DU 174A or S-DU 174B.

[0327] Method 1300 begins at box 1302, where the DU performs the actions described for box 902. At box 1310, the DU performs the actions described for boxes 910A, 910B, or 910C. At box 1312, the DU performs the actions described for boxes 912, 918, and 928. At box 1361, the DU starts a TA validity timer to maintain the validity of the TA value. The process proceeds from box 1361 to box 1330 or box 1312. At box 1330, the DU performs the actions described for box 930. At box 1362, the DU detects that the TA validity timer has expired. The process proceeds from box 1330 or 1363 to box 1363. At box 1364, the DU discards the TA value. If the process proceeds from box 1363 to box 1364, the DU discards the TA value in response to the detection. If the process proceeds from box 1330 to box 1364, the DU discards the TA value after sending it in box 1330.

[0328] FIG. 9A to FIG. 10 At least some of the descriptions in the description can also be applied to FIG. 13 .

[0329] FIG. 14A It shows that it can be generated by DU (e.g., FIG. 3 to FIG. 8B Example method 1400A for preparing and triggering early timing advance (TA) acquisition with a UE (e.g., UE 102), implemented by DU 174, S-DU 174A, M-DU 174A or S-DU 174B.

[0330] Method 1400A begins at block 1402, where the DU communicates with the UE via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, 881, 324, 344, 398, 424, 444, 498, 524, 598, 624, 698, 724, 798, 824, or 898). At block 1418, the DU sends a first command to the UE via the serving cell, wherein the first command includes random access configuration parameters for obtaining an early TA in a first cell for the UE. At block 1465, the DU receives a random access preamble from the UE via the first cell for obtaining the early TA using the multiple random access configuration parameters. At block 1466, the DU obtains the TA value based on the random access preamble. In some implementations, the DU obtains the TA value based on the time when the DU receives the random access preamble.

[0331] In box 1411, the DU determines to send an LTM command to instruct the UE to perform a serving cell change to the first cell. In box 1413, the DU includes an ID in the LTM command to indicate the first cell. In box 1433A, the DU determines whether it has obtained a TA value for uplink synchronization with the UE in the first cell. If the DU determines in box 1433A that it has obtained a TA value for uplink synchronization with the UE in the first cell, the procedure proceeds to box 1435. In box 1435, the DU includes the TA value in the LTM command. Otherwise, if the DU determines that it has not obtained a TA value for uplink synchronization with the UE in the first cell, the procedure skips box 1435 and proceeds to box 1430. In box 1430, the DU sends an LTM command to the UE via the serving cell (e.g., events 330, 350, 398, 430, 450, 498, 530, 598, 630, 698, 730, 798, 830, or 898).

[0332] FIG. 14B This is a flowchart of example method 1400B, similar to method 1400A, except that method 1400B includes box 1433B instead of box 1433A. In box 1433B, DU determines whether the TA value is valid. If DU determines the TA value is valid in box 1433B, the process proceeds to box 1435. Otherwise, if DU determines the TA value is invalid in box 1434B, the process skips box 1435 and proceeds to box 1430.

[0333] FIG. 9A to FIG. 13 At least some of the descriptions in the description can also be applied to FIG. 14A to FIG. 14B .

[0334] FIG. 15It shows that it can be generated by DU (e.g., FIG. 3 to FIG. 8B Example method 1500 for preparing and triggering early timing advance (TA) acquisition with a UE (e.g., UE 102), implemented by DU 174, S-DU 174A, M-DU 174A or S-DU 174B.

[0335] Method 1500 begins at box 1502, where the DU performs the actions described in box 1402. At box 1518, the DU performs the actions described in boxes 1418, 1465, and 1466. At box 1561, the DU starts a TA validity timer to maintain the validity of the TA value. At box 1530, the DU sends a first LTM command to the UE via the serving cell, wherein the first LTM command instructs the UE to connect to the first cell. At box 1563, the DU detects that the TA validity timer has expired. The procedure proceeds from box 1561 to box 1530 or box 1563. At box 1564, the DU discards the TA value. The procedure proceeds from boxes 1530 and 1563 to box 1564.

[0336] FIG. 9A At least some of the descriptions in Figure 14 can also be applied. FIG. 15 .

[0337] FIG. 16A It shows that it can be generated by CU (e.g., FIG. 3 to FIG. 8B Example method 1600A, implemented in CU 172, for preparing and triggering early timing advance (TA) acquisition with UE (e.g., UE 102).

[0338] Method 1600A begins at box 1602, where the CU communicates with the UE via the serving DU (e.g., events 302, 304, 316, 318, 320, 322, 324, 326, 394, 402, 404, 494, 424, 426, 502, 504, 506, 505, 507, 594, 524, 526, 517, 519, 521, 523, 602, 604, 606, 605, 607, 694, 624, 626, 617, 619, 621, 62...). 3, 702, 704, 706, 705, 707, 794, 724, 726, 717, 719, 721, 723, 802, 804, 806, 805, 807, 804, 824, 826, 817, 819, 821, 823, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, or 881). In block 1610A, the CU receives a first DU-to-CU message from the serving DU, including a first cell ID. The first DU-to-CU message requests random access configuration parameters for early TA acquisition on the first cell for the UE, where the first cell ID identifies the first cell. In block 1671, the CU sends a first CU-to-DU message to the first DU operating the first cell to request random access configuration parameters for early TA acquisition in the first cell for the UE. In block 1672, the CU receives a second DU-to-CU message from the first DU, which includes random access configuration parameters for the UE for early TA acquisition in the first cell. In block 1612, the CU sends a second CU-to-DU message to the serving DU, which includes random access configuration parameters for the UE for early TA acquisition in the first cell. In block 1683, the CU receives a third DU-to-CU message from the first DU, which includes TA values ​​for the UE for uplink synchronization with the first cell. In block 1684, the CU sends a third CU-to-DU message including the TA values ​​from the CU. In block 1634, the CU receives a fourth DU-to-CU message from the first DU indicating successful UE access to the first cell (e.g., events 334, 354, 398, 434, 454, 498, 534, 598, 634, 698, 734, 798, 834, or 898). In box 1636, the CU communicates with the UE via the first DU and the first cell (e.g., events 336, 356, 436, 456, 536, 556, 636, 656, 736, 756, 836, or 856).

[0339] In some implementations, the CU sends a first CU-DU message to the first DU in response to receiving a first DU-CU message. In some implementations, the CU receives a second DU-CU message in response to the first CU-DU message.

[0340] In some implementations, the first CU to DU message, the second CU to DU message, the third CU to DU message, and the fourth CU to DU message are F1AP messages. In some implementations, the first DU to CU message, the second CU to DU message, and the third CU to DU message are F1AP messages. In some implementations, the first DU to CU message is a UE context modification request message. In some implementations, the first CU to DU message is a UE context modification request message. In some implementations, the second DU to CU message is a UE context modification response message. In other implementations, the second DU to CU message is a UE context modification request message. In some implementations, the second CU to DU message is a UE context modification request message. In some implementations, the third DU to CU message is a UE context modification request message. In some implementations, the third CU to DU message is a UE context modification request message. In some implementations, the fourth DU to CU message is an access success message.

[0341] FIG. 16B This is a flowchart of an example method 1600B, similar to method 1600A, except that method 1600B includes block 1610B instead of block 1610A. At block 1610B, the CU receives a first DU-to-CU message from the serving DU, which includes a first cell index, to request random access configuration parameters for the UE for early TA acquisition in the first cell, where the first cell index indicates the first cell.

[0342] FIG. 16C This is a flowchart of an example method 1600C, similar to method 1600A, except that method 1600C includes block 1604C instead of block 1604A. In block 1604C, the CU receives a first DU-to-CU message from the serving DU, including a first LTM ID, to request random access configuration parameters for the UE for early TA acquisition in the first cell, where the first LTM ID indicates the first LTM configuration.

[0343] FIG. 9A to FIG. 15 At least some of the descriptions in the description can also be applied to FIG. 16A to FIG. 16C .

[0344] FIG. 17 It shows that it can be generated by DU (e.g., FIG. 3 to FIG. 8BExample method 1700 for preparing and triggering early timing advance (TA) acquisition with a UE (e.g., UE 102), implemented in DU 174, S-DU 174A, T-DU 174B, M-DU174A, S-DU 174B or T-DU 174C.

[0345] Method 1700 begins at box 1710, where the DU sends an LTM DU configuration for the UE, wherein the LTM DU configuration is configured for the first cell for LTM (e.g., events 310, 390, 318, 394, 490, 494, 590, 594, 519, 690, 694, 619, 790, 794, 890, 894, 819). At box 1718, the DU sends random access configuration parameters for the UE for early TA acquisition in the first cell. At box 1765, the DU determines, based on the multiple random access configuration parameters, whether it has received a random access preamble for early TA acquisition from the UE in the first cell. If, based on the multiple random access configuration parameters, the DU determines that it has not received a random access preamble for early TA acquisition from the UE in the first cell, the process returns to boxes 1704-1718. Otherwise, if the DU determines in box 1765 that the DU has received a random access preamble from the UE in the first cell for early TA acquisition based on multiple random access configuration parameters, the process is complete.

[0346] In some implementations, if the DU is the serving DU, the DU sends multiple random access configuration parameters to the UE. In other implementations, if the DU is a candidate DU, the DU sends multiple random access configuration parameters to the CU.

[0347] In some implementations, when multiple random access configuration parameters are sent, the DU starts a timer. If, while the timer is running, the DU receives a random access preamble from the UE in the first cell using the multiple random access configuration parameters, the DU stops the timer. If the timer expires, the DU determines that it has not received a random access preamble for early TA acquisition from the UE in the first cell. In other implementations, the DU attempts to receive a random access preamble for early TA acquisition from the UE in the first cell for a predetermined number of times. If the DU does not receive a random access preamble for early TA acquisition from the UE in the first cell for the predetermined number of attempts, the DU determines that it has not received a random access preamble for early TA acquisition from the UE in the first cell.

[0348] In some implementations, the DU attempts to receive, or receives from the UE in the first cell for early TA acquisition, a random access preamble for the TA acquisition, based on multiple random access configuration parameters and the random access configuration parameters included in the LTM DU configuration.

[0349] FIG. 9A to FIG. 15 At least some of the descriptions in the description can also be applied to FIG. 17 .

[0350] FIG. 18 It shows that it can be generated by DU (e.g., FIG. 4 , FIG. 6A , FIG. 6B , FIG. 8A and FIG. 8B Example method 1800 implemented in T-DU 174B or T-DU174C for preparing and triggering early timing advance (TA) acquisition with UE (e.g., UE 102).

[0351] Method 1800 begins at block 1810, where the DU sends an LTM DU configuration for the UE to the CU, wherein the LTM DU configuration configures the first cell for LTM (e.g., events 310, 390, 318, 394, 490, 494, 590, 594, 519, 690, 694, 619, 790, 794, 890, 894, 819). At block 1818, the DU sends to the CU multiple random access configuration parameters for the UE for early TA acquisition in the first cell. At block 1878, the DU sends to the CU configuration parameters for the UE specifying the transmission time of the multiple random access configuration parameters.

[0352] In some implementations, the DU sends a first DU-CU message to the CU, which includes multiple random access configuration parameters, and a second DU-CU message to the CU, which includes configuration parameters. In other implementations, the DU sends a DU-CU message to the CU that includes multiple random access configuration parameters and configuration parameters.

[0353] In some implementations, when a CU sends multiple random access configuration parameters and configuration parameters to another DU (i.e., the second DU), for example, the second DU is... FIG. 4 , FIG. 6A , FIG. 6B , FIG. 8A and FIG. 8B The S-DU is either S-DU 174A or S-DU 174B. In some implementations, the CU sends a third CU-DU message including multiple random access configuration parameters to the second DU, and also sends a fourth CU-DU message including configuration parameters to the second DU. In other implementations, the CU sends a CU-DU message including multiple random access configuration parameters and configuration parameters to the second DU. The second DU sends a first command including multiple random access configuration parameters to the UE during the transmission time.

[0354] FIG. 9A to FIG. 15 andFIG. 17 At least some of the descriptions in the description can be applied to FIG. 18 .

[0355] FIG. 19 It shows that it can be generated by DU (e.g., FIG. 4 , FIG. 6A , FIG. 6B , FIG. 8A and FIG. 8B Example method 1900 for preparing and triggering early timing advance (TA) acquisition with UE (e.g., UE 102), implemented in T-DU 174B or T-DU174C.

[0356] Method 1900 begins at block 1910A, where the DU sends an LTM DU configuration for the UE to the CU, wherein the LTM DU configuration configures a first cell for LTM (e.g., events 310, 390, 318, 394, 490, 494, 590, 594, 519, 690, 694, 619, 790, 794, 890, 894, 819). In block 1910B, the DU sends to the CU multiple random access configuration parameters for the UE for early TA acquisition in the first cell. In block 1965, the DU receives a random access preamble from the UE in the first cell for early TA acquisition based on the multiple random access configuration parameters. In block 1985, the DU derives the TA value based on the random access preamble. In block 1987, the DU sends the TA value and one or more parameters to the CU, wherein the parameters control the validity of the TA value.

[0357] In some implementations, the CU sends the TA value and parameters to another DU (i.e., the second DU). For example, the second DU is... FIG. 12B The DU. In some implementations, the parameters include a timer value used to maintain the validity of the TA value, such as for... FIG. 12B As described above. In other implementations, the parameters include a threshold value used to maintain the validity of the TA value, such as for... FIG. 12B As stated above.

[0358] FIG. 9A to FIG. 15 , FIG. 17 and FIG. 18 At least some of the descriptions in the description can also be applied to FIG. 20 .

[0359] FIG. 3 to FIG. 8B It shows that it can be generated by the UE (e.g., FIG. 3 to FIG. 8B The UE 102 in the RAN (e.g., ) is used to determine whether to apply the RAN (e.g., FIG. 9A to FIG. 15Example method 2000 for receiving TA values ​​(RAN 105 or DU 174, S-DU 174A, M-DU 174A or S-DU 174B).

[0360] Method 2000 begins at block 2002, where the UE communicates with the RAN via the serving cell (e.g., events 302, 304, 316, 318, 320, 322, 324, 326, 394, 402+, 404, 494, 424, 426, 502, 504, 506, 505, 507, 594, 524, 526, 517, 519, 521, 523, 602, 604, 606, 605, 607, 694, ...). 624, 626, 617, 619, 621, 623, 702, 704, 706, 705, 707, 794, 724, 726, 717, 719, 721, 723, 802, 804, 806, 805, 807, 804, 824, 826, 817, 819, 821, 823, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, or 881. In box 2018A, the UE receives the LTM configuration for configuring the first cell from the RAN (e.g., events 318, 394, 494, 594, 519, 694, 619, 794, 894, or 819). In box 2018B, the UE receives a first command from the RAN on the serving cell, wherein the first command includes random access configuration parameters for early TA acquisition in the first cell. In box 2065, the UE sends a random access preamble to the RAN in the first cell in response to the first command. At box 2030, the UE receives an LTM command from the RAN on the serving cell, wherein the LTM command commands connection to the first cell and includes a TA value (e.g., event 330, 350, 398, 430, 450, 498, 530, 598, 630, 698, 730, 798, 830, or 898). In box 2033, the UE determines whether the TA value is valid. If the UE determines that the TA value is valid in box 2012, the procedure proceeds to box 2014. In box 2032A, the UE responds to an LTM command by using the TA value to access the first cell (e.g., events 332, 352, 398, 432, 452, 498, 532, 598, 632, 698, 732, 798, 832, or 898). Otherwise, if the UE determines in box 2012 that the TA value is invalid, the procedure proceeds to box 2016. In box 2032B, the UE responds to an LTM command by avoiding the application of the TA value and performs a random access procedure with the RAN in the first cell (e.g., events 332, 352, 398, 432, 452, 498, 532, 598, 632, 698, 732, 798, 832, or 898).

[0361] In some implementations, after receiving the TA value, the UE performs measurements on one or more reference signals in a first cell and obtains one or more measurement results for the first cell from the measurements. If the measurement result is higher than a threshold, the UE determines the TA value is invalid. Otherwise, if the measurement result is lower than or equal to the threshold, the UE determines the TA value is valid. In some implementations, the UE predetermines a threshold value for the threshold. In other implementations, the UE receives the threshold value for the threshold from the RAN. For example, the UE receives an RRC reconfiguration message (e.g., event 318, 394, 494, 594, 519, 694, 619, 794, 894, or 819) that includes the threshold value from the RAN. In some implementations, the LTM configuration includes the threshold value.

[0362] FIG. 17 , FIG. 18 and FIG. 20 At least some of the descriptions in the description can also be applied to ​ .

[0363] The following list of examples illustrates various embodiments explicitly contemplated in this disclosure.

[0364] Example 1. A method implemented in a distributed base station (DU) including a CU, the method comprising: sending a request to the CU for configuration parameters that a UE will use for early timing advance (TA) acquisition in a target cell, the request including an indication of the target cell; receiving the configuration parameters from the CU; and sending the configuration parameters to the UE in the serving cell.

[0365] Example 2. The method as described in Example 1, wherein the indication of the target cell includes the cell identifier of the target cell.

[0366] Example 3. The method as described in Example 1, wherein the indication of the target cell includes a cell index corresponding to the target cell.

[0367] Example 4. The method as described in Example 1, wherein the indication of the target cell includes an identifier of the LTM configuration associated with the target cell.

[0368] Example 5. The method as described in Example 4, wherein the LTM configuration includes an LTM CU configuration.

[0369] Example 6. The method as described in Example 4 or 5, wherein the LTM configuration includes an LTM DU configuration.

[0370] Example 7. The method as described in any of the preceding examples, wherein the configuration parameters include random access parameters for performing a random access procedure in the target cell.

[0371] Example 8. The method as described in any of the preceding examples further includes: receiving measurements related to the target cell from the UE; and sending an LTM command to the UE when the measurements meet a predefined threshold.

[0372] Example 9. The method as described in Example 8 further includes: including the TA value in the LTM command.

[0373] Example 10. The method as described in Example 9, wherein including the TA value in the LTM command is in response to determining that the DU receives the TA value from the CU.

[0374] Example 11. The method as described in Example 9, wherein including the TA value in the LTM command is in response to determining that the TA value is valid.

[0375] Example 12. The method as described in any of the preceding examples, wherein sending the configuration parameters to the UE is in response to determining that the UE supports the early TA acquisition.

[0376] Example 13. The method as described in any one of Examples 1 to 5 or 7 to 11, further comprising sending an LTM DU configuration for the target cell to the CU.

[0377] Example 14. A method implemented in a CU of a distributed base station including a DU, the method comprising: receiving from the CU a request for configuration parameters for a UE to use for early timing advance (TA) acquisition in a target cell, the request including an indication of the target cell; and sending the configuration parameters to the DU for transmission to the UE.

[0378] Example 15. The method as described in Example 14, wherein the indication of the target cell includes the cell identifier of the target cell.

[0379] Example 16. The method as described in Example 14, wherein the indication of the target cell includes a cell index corresponding to the target cell.

[0380] Example 17. The method as described in Example 14, wherein the indication of the target cell includes an identifier of the LTM configuration associated with the target cell.

[0381] Example 18. A radio access network (RAN) includes: a transceiver; and processing hardware configured to implement the method described in any of the preceding examples.

[0382] The following descriptions can be applied to the descriptions above.

[0383] Generally, a description of one of the above figures can be applied to another. If there is no conflict, the examples, implementations, and methods described above can be combined. The events or boxes described above can be optional or omitted. For example, events or boxes with dashed lines in the figures can be optional. In some implementations, "message" is used and can be replaced with "information element (IE)," and vice versa. In some implementations, "IE" is used and can be replaced with "field," and vice versa. In some implementations, "configurations" or "configuration parameters" can be used to replace "configuration," and vice versa. In some implementations, "LTM command" can be replaced with "serving cell change command," "Layer 1 / Layer 2 handover command," "lower layer handover command," or "lower layer serving cell change command." In some implementations, "some" means "one or more." In some implementations, "at least one" means "one or more." In some implementations, "DU configuration" can be replaced with "cell group configuration." In some implementations, "cell index" can be replaced with "serving cell index," "LTM cell index," "special cell (SpCell) index," "PCell index," or "PSCell index." In some implementations, "serving" can be replaced with "source." In some implementations, "measurement report" can be replaced with "measurement result." In some implementations, "early TA acquisition" can be replaced with "early timed synchronization," "early timed synchronization with the target cell," "early TA value acquisition," or "early TA value acquisition for the target cell." In some implementations, "early TA acquisition configuration" can be replaced with "early TA acquisition indication" or "early TA acquisition enable indication." In some implementations, "identifier" can be replaced with "OK," and vice versa.

[0384] The user device that can implement the technology of this disclosure (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. Furthermore, 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)). Even further, the user device can operate as an Internet of Things (IoT) device or a mobile internet device (MID). Depending on the type, the user device may include one or more general-purpose processors, computer-readable storage, a user interface, one or more network interfaces, one or more sensors, etc.

[0385] Some embodiments described in this disclosure include logic or multiple components or modules. A module can be a software module (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing certain operations and can be configured or arranged in a certain way. A hardware module may include a dedicated circuit system or logic that is persistently configured (e.g., as a dedicated processor, such as a field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC), digital signal processor (DSP), etc.) to perform certain operations. A hardware module may also include programmable logic or circuit systems that are temporarily configured by software to perform certain operations (e.g., as encompassed within a general-purpose processor or other programmable processor). The decision to implement a hardware module in a dedicated and persistently configured circuit system or in a temporarily configured circuit system (e.g., configured by software) may be driven by cost and time considerations.

[0386] 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.

[0387] 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 may be made to the arrangement, operation, and details of the methods and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.

Claims

1. A method implemented in one or more distributed units (DUs) of a distributed base station further comprising a central unit (CU), the method comprising: The candidate DU sends configuration parameters to the CU for early timing advance TA acquisition by the user equipment UE in the target cell; In the target cell and according to the configuration parameters, the random access preamble is received from the UE at the candidate DU; as well as The TA value is sent from the candidate DU to the CU based on the reception of the random access preamble.

2. The method of claim 1, further comprising: Prior to the reception of the random access preamble, the lower-layer triggered mobility LTM DU configuration associated with the target cell is sent from the candidate DU to the CU.

3. The method of claim 2, wherein: The transmission configured in the LTM DU includes sending a UE context establishment response message.

4. The method as described in any of the preceding claims, wherein: The configuration parameters used for early TA acquisition include physical random access channel (PRACH) resources.

5. The method as described in any of the preceding claims, wherein: The configuration parameters used for early TA acquisition include one or more PRACH timings.

6. The method as described in any one of the preceding claims, further comprising: Before the reception of the random access preamble: The source DU sends a command to the UE to instruct the UE to send the random access preamble in the target cell.

7. The method of claim 6, wherein, The command that the UE sends the random access preamble is a Physical Downlink Control Channel (PDCCH) command.

8. The method of claim 6 or 7, further comprising: Following the reception of the random access preamble: Receive a measurement report from the UE at the source DU; as well as The source DU sends an LTM command to the UE to instruct the UE to initiate an LTM cell handover to the target cell.

9. A method implemented in the central unit (CU) of a distributed base station, the method comprising: Receive configuration parameters from the candidate DU of the distributed base station for early timing advance TA acquisition by the user equipment UE in the target cell; Send the configuration parameters to the UE; as well as The candidate DU receives the TA value generated for the UE in the target cell.

10. The method of claim 9, wherein: Sending the configuration parameters to the UE includes sending the configuration parameters to the UE via the source DU of the distributed base station.

11. The method of claim 9 or 10, further comprising: Prior to the reception of the random access preamble, the lower-layer triggered mobility LTM DU configuration associated with the target cell is received from the candidate DU.

12. The method of claim 11, wherein: The receiving in the LTM DU configuration includes sending a UE context establishment response message.

13. The method according to any one of claims 9 to 12, wherein: The configuration parameters used for early TA acquisition include physical random access channel (PRACH) resources.

14. The method according to any one of claims 9 to 13, wherein: The configuration parameters used for early TA acquisition include one or more PRACH timings.

15. A node in a distributed base station, comprising processing hardware and configured to implement the method as described in any of the preceding claims.

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