Managing uplink synchronization in cell handover without random access channel

Abstract

A user equipment (UE) may implement a method for managing uplink synchronization during a cell handover without a random access channel triggered by lower-layer signaling. The method includes: communicating with a radio access network (RAN) via a serving cell; receiving a command to perform a lower-layer triggered mobility (LTM) handover to a candidate cell; applying a timing advance (TA) value to uplink (UL) synchronization with the candidate cell; and maintaining the UL synchronization based on the TA value after the LTM handover to the candidate cell is completed.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to U.S. Provisional Patent Application No. 63 / 605,468, filed December 1, 2023, entitled “Managing Uplink Synchronization in a Random Access Channel-Lless Cell Switch,” and U.S. Provisional Patent Application No. 63 / 680,559, filed August 7, 2024, entitled “Managing Uplink Synchronization in a Random Access Channel-Lless Cell Switch.” The entire contents of these provisional applications are hereby expressly incorporated by reference. Technical Field

[0003] This disclosure relates to wireless communications, and more specifically to managing uplink synchronization during cell handovers without a random access channel triggered by lower-layer signaling. Background Technology

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

[0005] 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, as defined for the Evolved Universal Terrestrial Radio Access (EUTRA) radio interface (see 3GPP Technical Specification (TS) 36.323) and New Radio (NR) (see 3GPP TS 38.323), provides the ordering of Protocol Data Units (PDUs) in the uplink direction (from the user equipment (UE) to the base station) and in the downlink direction (from the base station to the UE). Furthermore, the PDCP sublayer provides Signaling Radio Bearers (SRBs) and Data Radio Bearers (DRBs) to the Radio Resource Control (RRC) sublayer. Generally, the UE and base station can use SRBs to exchange RRC messages and Non-Access Stratum (NAS) messages. The UE and base station can further use DRBs to transmit data on the user plane.

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

[0007] In some scenarios, a UE simultaneously utilizes 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 a UE operates in MR-DC, one base station operates as the primary node (MN) covering the primary cell (PCell), and another base station operates as the secondary node (SN) covering the primary secondary cell (PSCell). The UE communicates with the MN (via the PCell) and the SN (via the PSCell). In other scenarios, the UE utilizes the resources of one base station at a time. One base station and / or the UE determines that the UE should establish a radio connection with another base station. For example, one base station determines to hand over the UE to a second base station and initiates a handover procedure.

[0008] When a UE moves from the coverage area of ​​one cell in the RAN to another, at some point, the RAN will perform a serving cell change for the UE. To perform the serving cell change, the RAN configures the UE to send Layer 3 (L3) measurements. Based on the L3 measurements received from the UE, the RAN sends an RRC reconfiguration message, which configures a reconfiguration with synchronization (e.g., the RRC reconfiguration message includes a ReconfigurationWithSync information element (IE)) for the change of the serving cell (e.g., PCell or PSCell). If the UE is operating under carrier aggregation (CA) with at least one secondary cell (SCell) and PCell or PSCell, the RAN releases that at least one SCell due to the change of PCell or PSCell. Serving cell changes involve a complete L2 (and L1) reset, resulting in longer latency, greater overhead, and longer downtime. Therefore, it is desirable to develop new mobility technologies for serving cell changes. These techniques, designed to reduce latency and overhead, are known as Lower Layer Triggered Mobility (LTM) cell handover (also called Lower Layer Triggered Mobility) or faster serving cell handover.

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

[0010] Various attempts have been made to enable LTM in the Media Access Control (MAC) sublayer (e.g., as described in 3GPP R2-2312410). In some cases, the LTM cell handover command is a MAC control element (CE) (e.g., as specified in 3GPP R2-2312410). In some cases, the RAN includes a timing advance (TA) command (i.e., containing a TA value) in the LTM cell handover command. In response to receiving the LTM cell handover command, the UE applies the TA value to UL synchronization with the LTM candidate cell and starts a time alignment timer to maintain (e.g., count) the validity period of the UL synchronization (e.g., as described in 3GPP R2-2312410). The UE performs a MAC reset in response to the LTM cell handover command. The UE assumes that all time alignment timers have expired and performs the corresponding action in the MAC reset (e.g., as described in 3GPP R2-2313410 or TS 38.321) (e.g., as described in 3GPP R2-2312410). Specifically, if the MAC entity reset is requested by an upper layer or if the MAC entity reset is triggered due to SCG deactivation (e.g., as defined in 3GPP R2-2313410 or TS38.321), the MAC entity should treat all timeAlignmentTimers, inactivePosSRS-TimeAlignmentTimer, and cg-SDT-TimeAlignmentTimer (if configured) as expired and perform the corresponding actions (e.g., as described in 3GPP R2-2312410). Therefore, the UE stops the time alignment timer during a MAC reset due to an LTM cell handover command.

[0011] When the timeAlignmentTimer associated with the TAG to which the serving cell belongs is not running, the UE does not perform any uplink transmissions on the serving cell other than random access preamble and MSGA transmissions (e.g., as described in 3GPP R2-2313410 or TS 38.321). Because the time alignment timer used for UL synchronization with the LTM candidate cell is not running, the UE does not send any uplink transmissions on the LTM candidate cell other than random access preamble and MSGA transmissions when switching to the LTM candidate cell. This results in UL data transmission being interrupted on the candidate cell. Summary of the Invention

[0012] An example embodiment of the technology disclosed herein is a method implemented in a user equipment (UE). The method includes: communicating with a radio access network (RAN) via a serving cell; receiving a command to perform a low-layer triggered mobility (LTM) handover to a candidate cell; applying a timing advance (TA) value to uplink (UL) synchronization with the candidate cell; and maintaining the UL synchronization based on the TA value after the LTM handover to the candidate cell is completed.

[0013] Another example embodiment of these technologies is a user equipment (UE) that includes a transceiver and / or processing hardware configured to implement the methods described above.

[0014] Another example embodiment of these technologies is a method implemented in a radio access network (RAN) node. The method includes: communicating with a user equipment (UE); sending a command to the UE to perform a lower-layer triggered mobility (LTM) handover to a candidate cell; and, in response to determining that the UE has accessed the candidate cell, sending a timing advance (TA) command to the UE, the TA command including a TA value for uplink synchronization with the candidate cell.

[0015] Another example embodiment of these technologies is a radio access network (RAN) node that includes transceivers and / or processing hardware configured to implement the methods described above. Attached Figure Description

[0016] Figure 1A This is a block diagram of an example system in which the radio access network (RAN) and user equipment can implement the techniques disclosed herein for managing conditional processes associated with secondary nodes (SNs);

[0017] Figure 1B It includes being able to Figure 1A A block diagram of an example base station for centralized unit (CU) and distributed unit (DU) operations in the system;

[0018] Figure 2A This is a block diagram of an example protocol stack. Figure 1A The UE communicates with the base station according to this protocol stack;

[0019] Figure 2B This is a block diagram of an example protocol stack. Figure 1A The UE communicates with the CU and DU according to this protocol stack;

[0020] Figure 3 It is a message passing graph used to manage low-level triggered mobility configuration and reconfiguration examples.

[0021] Figure 4 It is similar to Figure 3The example scenario is shown in the message passing diagram for the example scenario where the UE sends a measurement report to the target DU.

[0022] Figure 5A It is similar to Figure 3 The example scenario is shown in the message passing diagram of the example scenario in which the UE communicates with the MN and SN under the DC.

[0023] Figure 5B It is similar to Figure 5A The example scenario is shown in the message passing diagram of the example scenario in which the SN provides configuration information to the UE via the MN;

[0024] Figure 6A It is similar to Figure 3 The example scenario is shown in the message passing diagram of an example scenario in which the UE uses LTM configuration to communicate with the target DU.

[0025] Figure 6B It is similar to Figure 6A The example scenario is shown in the message passing diagram of the example scenario in which the SN provides configuration information to the UE via the MN;

[0026] Figure 7A It is similar to Figure 3 Example scenario, but the message passing diagram of the example scenario in which the UE communicates with the combined MN / SN;

[0027] Figure 7B It is similar to Figure 7A The example scenario is shown in the message passing diagram of the example scenario in which the S-DU provides configuration information to the UE via the M-DU;

[0028] Figure 8A It is similar to Figure 3 Example scenario, but in which the UE communicates with the combined MN / SN including the target DU, message passing diagram;

[0029] Figure 8B It is similar to Figure 8A The example scenario is shown in the message passing diagram of the example scenario in which the S-DU provides configuration information to the UE via the M-DU;

[0030] Figure 9A This is a flowchart of an example method implemented in the UE for performing a MAC reset in response to an LTM command and preventing the UL synchronization timer from expiring during the MAC reset;

[0031] Figure 9B It is similar to Figure 9A The flowchart shows an example method where the UE stops the timer while maintaining UL synchronization.

[0032] Figure 9C It is similar to Figure 9A The flowchart shows an example method where the UE starts an updated time alignment timer after performing a MAC reset.

[0033] Figure 10A It is similar to Figure 9A The example method, but in which the flowchart shows an example method for the UE to measure the TA value used for UL synchronization;

[0034] Figure 10B It is similar to Figure 9B The example method, but in which the flowchart shows an example method for the UE to measure the TA value used for UL synchronization;

[0035] Figure 10C It is similar to Figure 9C The example method, but in which the flowchart shows an example method for the UE to measure the TA value used for UL synchronization;

[0036] Figure 11A It is similar to Figure 9A The flowchart shows an example method where the UE starts a time alignment timer before receiving an LTM command from the RAN.

[0037] Figure 11B It is similar to Figure 9B The flowchart shows an example method where the UE starts a time alignment timer before receiving an LTM command from the RAN.

[0038] Figure 12A It is similar to Figure 11A The example method, but in which the flowchart shows an example method for the UE to measure the TA value used for UL synchronization;

[0039] Figure 12B It is similar to Figure 11B The example method, but in which the flowchart shows an example method for the UE to measure the TA value used for UL synchronization;

[0040] Figure 13 This is a flowchart of an example method implemented in the RAN node for detecting UE access candidate cells in response to sending an LTM command and / or performing a MAC reset; and

[0041] Figure 14 This is a flowchart of an example method implemented in DU for initializing a MAC entity to communicate with the UE on a candidate cell and sending a TA command including a second TA value to cause the UE to start a time alignment timer. Detailed Implementation

[0042] Figure 1AAn example wireless communication system 100 is depicted, in which communication devices can implement these technologies. The wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106, and a core network (CN) 110. The UE 102 is initially connected to base station 104. In some scenarios, base station 104 can perform SN addition to configure the UE 102 to operate in dual connectivity (DC) with both base stations 104 and 106. Base stations 104 and 106 operate as the MN and SN of the UE 102, respectively.

[0043] 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.

[0044] In some cases, the MeNB or SeNB is implemented as an ng-eNB instead of an eNB. When base station 104 is the primary ng-eNB (Mng-eNB) and base station 106 is the SgNB, UE 102 can be 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.

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

[0046] The core network (CN) 110 can be either the Evolved Packet Core (EPC) 111 or the 5th Generation Core (5GC) 160; both are... Figure 1A The base station 104 may be an eNB supporting an S1 interface for communication with EPC 111, an ng-eNB supporting an NG interface for communication with 5GC 160, or a gNB supporting an NR radio interface and an NG interface for communication with 5GC 160. To exchange messages directly with each other during the scenarios discussed below, base stations 104 and 106 may support X2 or Xn interfaces. Among other components, EPC 111 may include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. SGW 112 is generally configured to deliver user plane packets related to audio calls, video calls, Internet services, etc., and MME 114 is configured to manage authentication, registration, paging, and other related functions. PGW 116 provides connectivity from the UE to one or more external packet data networks (e.g., Internet networks and / or Internet Protocol (IP) Multimedia Subsystem (IMS) networks). 5GC 160 includes User Plane Functions (UPF) 162, Access and Mobility Management (AMF) 164, and / or Session Management Functions (SMF) 166. UPF 162 is generally configured to deliver user plane packets related to audio calls, video calls, Internet services, etc., AMF 164 is configured to manage authentication, registration, paging, and other related functions, and SMF 166 is configured to manage PDU sessions.

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

[0048] Generally, the wireless communication network 100 may include any suitable number of base stations supporting NR cells and / or EUTRA cells. More specifically, the EPC 111 or 5GC 160 may be connected to any suitable number of base stations supporting NR cells and / or EUTRA cells. Although the examples below specifically refer to particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, the techniques disclosed herein can also be applied to other suitable radio access and / or core network technologies, such as sixth-generation (6G) radio access and / or 6G core networks or 5G NR-6G DC.

[0049] Continue to refer to Figure 1A Base station 104 is equipped with processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and a non-transitory computer-readable storage memory for storing instructions, the one or more general-purpose processors executing these instructions. Alternatively, processing hardware 130 may include dedicated processing units. Processing hardware 130 may include a PHY controller 132 configured to transmit data and control signals 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 a physical downlink (DL) channel and a DL reference signal. PHY controller 132 is also 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 a physical uplink (UL) channel and / or a UL reference signal. In an example implementation, processing hardware 130 includes a MAC controller 134 configured to perform MAC functions with one or more user equipments. MAC functions include random access (RA) procedures, managing UL timing advance (TA) for one or more user equipment (UEs), and / or communicating UL / DL MAC PDUs with one or more UEs. MAC functions include Lower Triggered Mobility (LTM) related functions as described below. Processing hardware 130 may further include an RRC controller 136 to implement procedures and messaging at the RRC sublayer of the protocol communication stack. For example, RRC controller 132 may be configured to support RRC messaging associated with LTM configuration procedures, 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, 134, and 136, respectively.

[0050] UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors (such as a CPU), a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or dedicated processing units. PHY controller 152 is also configured to receive data and control signals with base station 104 or 106 on physical DL channels and / or DL ​​reference signals via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. PHY controller 152 is also configured to transmit data and control signals with base station 104 or 106 on physical UL channels and / or UL reference signals via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. In an example implementation, processing hardware 150 includes a MAC controller 154 configured to perform MAC functions with base station 104 or 106. For example, MAC functions include random access procedures, managing UL timing advances for one or more user facilities, and communicating UL / DL MAC PDUs with base stations 104 or 106. In another example, MAC functions include LTM-related functions as described below. Processing hardware 150 may further include an RRC controller 156 to implement procedures and message passing at the RRC sublayer of the protocol communication stack.

[0051] In operation, UE 102 can use radio bearers (e.g., 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.

[0052] Figure 1BAn example distributed implementation of a base station (such as base station 104 or 106) is depicted. In this implementation, the base station may include a centralized unit (CU) 172 and one or more distributed units (DUs) 174. CU 172 is equipped with processing hardware 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.

[0053] Figure 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).

[0054] In example stack 200, the EUTRA physical layer (PHY) 202A provides a transport channel to the EUTRA MAC sublayer 204A, which in turn provides a logical channel to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A then provides an RLC channel to the EUTRA PDCP sublayer 208 and, in some cases, to the NR PDCP sublayer 210. Similarly, the NRPHY 202B provides a transport channel to the NR MAC sublayer 204B, which in turn provides a logical channel to the NR RLC sublayer 206B. The NR RLC sublayer 206B then provides data delivery services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 can then provide data delivery services to the Serving Data Adaptation Protocol (SDAP) 212 or the Radio Resource Control (RRC) sublayer. Figure 2A (Not shown in the image) provides data transfer services. In some implementations, UE 102 supports both EUTRA and NR stacks, such as... Figure 2A As shown, this supports handover between EUTRA and NR base stations and / or supports DCs via EUTRA and NR interfaces. Further, as... Figure 2A As shown, UE102 can support NR PDCP 210 layering on EUTRA RLC 206A, and SDAP sublayer 212 layering on NR PDCP sublayer 210.

[0055] EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 (e.g., from an Internet Protocol (IP) layer layered directly or indirectly on PDCP layers 208 or 210) receive packets that can be referred to as Service Data Units (SDUs), and (e.g., to RLC layers 206A or 206B) output packets that can be referred to as Protocol Data Units (PDUs). For simplicity, except where the difference between SDU and PDU is relevant, this disclosure refers to both SDU and PDU as "packets".

[0056] On the control plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 can provide signaling radio bearer (SRB) or RRC sublayer ( Figure 2A (Not shown) to exchange, for example, RRC messages or Non-Access Stratum (NAS) messages. On the user plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 can provide data radio bearers (DRBs) to support data exchange. The data exchanged on NR PDCP sublayer 210 can be SDAP PDUs, Internet Protocol (IP) packets, or Ethernet packets.

[0057] Figure 2BAn example protocol stack 250 is shown in a simplified manner, illustrating how UE 102 can communicate with DU (e.g., DU 174) and CU (e.g., CU 172). The radio protocol stack 200 is functionally decomposed, as shown by... Figure 2B The radio protocol stack 250 is shown in the diagram. At either base station 104 or 106, the CU can maintain all control and upper-layer functionality (e.g., RRC 214, SDAP 212, NR PDCP 210), while lower-layer operations (e.g., NR RLC 206B, NR MAC 204B, and NR PHY 202B) are delegated to the DU. To support connectivity to the 5GC, NR PDCP 210 provides SRBs to RRC 214, and NR PDCP 210 provides DRBs to SDAP 212 and SRBs to RRC 214.

[0058] Next is one of them Figure 1A This describes several example scenarios in which the base station operating in the system sends a configuration to the UE 102 and later activates the configuration for communication between the UE 102 and the base station. Generally speaking, Figures 3 to 7B Similar events are labeled with similar reference numerals (e.g., event 316 and...). Figure 4 A and Figure 4 Event 416 of B Figure 5A Event 516 Figure 5B Event 517 Figure 6A Event 616 Figure 6B Event 617 Figure 7A Event 716 and Figure 7B (Similar to event 717), where differences are discussed below where appropriate. Apart from the differences shown in the figures and discussed below, any of the alternative implementations discussed for specific events (e.g., those used for messaging and processing) can be applied to events labeled similarly in other figures.

[0059] First refer to Figure 3 In scenario 300, base station 104 includes CU 172 and DU 174, and DU 174 operates cell 124A. UE 102 initially communicates with DU 174 on cell 124A using the serving DU configuration 302, and communicates with CU 172 via DU 174 (e.g., using the serving CU configuration). In other words, DU 174 is the serving DU that is communicating with UE 102. In some implementations, UE 102 uses the serving DU configuration on cell 124A and other cells (e.g., ...). Figure 1AUE 102 communicates with DU 174 via carrier aggregation (CA) on cell 124D (not shown). DU 174 operates other cells. Cell 124A and / or other cells are the serving cells of UE 102. In a further implementation, 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 is a PCell. In such cases, other cells include SCells and / or additional cells associated with a PCell or SCell. In a further implementation, cell 124A is 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 some implementations, for the following description, base station 104 is DU 174, CU 172, or DU 174 and CU 172.

[0060] In a further implementation, UE 102 transmits a 302 UL PDU and / or UL control signal to base station 104 via one or more TRPs in cell 124A and / or other cells. In some implementations, UE 102 communicates UL PDUs and / or DL ​​PDUs with base station 104 via a radio bearer, which includes SRBs and / or DRBs. In a further implementation, base station 104 configures the radio bearer for UE 102. In some implementations, the UL control signal includes UL control information, channel state information, Hybrid Automatic Repeat Request (HARQ) acknowledgment (ACK), HARQ negative ACK, scheduling request, and / or probe reference signal. In a further implementation, similarly, UE 102 receives DL PDUs and / or DL ​​control signals from base station 104 via one or more TRPs in cell 124A and / or other cells. In some implementations, the DL control signal includes downlink control information (DCI) and reference signals (e.g., synchronization signal block, channel state information reference signal (CSI-RS), and / or tracking reference signal). In a further implementation, base station 104 transmits the DCI via one or more TRPs on the physical downlink control channel (PDCCH) monitored by UE 102 in cell 124A and / or other cells.

[0061] In some implementations, the serving DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In a further implementation, the serving DU configuration includes at least one first non-LTM TCI state configuration for the serving cell. In an even further implementation, DU 174 sends these configuration parameters and / or the first non-LTM TCI state configuration to CU 172. CU 172 generates one or more messages (e.g., RRC reconfiguration messages) including these configuration parameters and / or the first non-LTM TCI state configuration and sends these messages to UE 102 via DU 174. In some implementations, DU 174 sends these configuration parameters and / or the first non-LTM TCI state configuration directly to UE 102. In a further implementation, the serving DU configuration is a CellGroupConfig IE (e.g., defined in 3GPP TS 38.331). In an even further implementation, 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 further implementations, the serving CU configuration includes a MeasConfig IE and / or a RadioBearerConfig IE (e.g., as defined in 3GPP TS 38.331), or includes configuration parameters within a MeasConfig IE and / or a RadioBearerConfig IE. In some implementations, the serving DU configuration includes a CSI-MeasConfig IE or configuration parameters for Channel State Information (CSI) measurement and reporting. In further implementations, the serving CU configuration includes a CSI-MeasConfig IE or configuration parameters for CSI measurement and reporting. In some implementations, UE 102 receives the serving CU configuration or configuration parameters within the serving CU configuration from CU 172 via DU 174. In further 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.

[0062] In some implementations, UE 102 and DU 174 communicate with each other using a first non-LTM TCI state configuration (e.g., in events 302, 318, 320, 324, 325, 330, and / or 331). In some implementations, DU 174 sends at least one first non-LTM TCI state activation / deactivation command to UE 102 to activate some state configurations in the first non-LTM TCI state configuration. UE 102 activates some state configurations in the first non-LTM TCI state configuration in response to the first non-LTM TCI state activation / deactivation command. In some implementations, DU 174 instructs to deactivate some state configurations in the first non-LTM TCI state activation / deactivation command. UE 102 and DU 174 communicate with each other using an active non-LTM TCI state configuration (e.g., in events 302, 318, 320, 324, 325, 330 and / or 331).

[0063] In some implementations, the first non-LTM TCI state activation / deactivation command is a MAC CE. In some implementations, a MAC CE includes one or more TCI state activation / deactivation commands for a UE-specific PDSCH MAC CE, one or more TCI state indications for a UE-specific PDCCH MAC CE, one or more PUCCH spatial relationship activation / deactivation MAC CEs, one or more enhanced TCI state activation / deactivation commands for a UE-specific PDSCH MAC CE, one or more enhanced PUCCH spatial relationship activation / deactivation MAC CEs, one or more enhanced TCI state indications for a UE-specific PDCCH MAC CE, one or more PUCCH spatial relationship activation / deactivation commands for multiple TRP PUCCH repeating MAC CEs, and / or one or more unified TCI state activation / deactivation MAC CEs.

[0064] In some implementations, DU 174 includes the serving cell ID (e.g., a serving cell index) in each of the first non-LTTM TCI state activation / deactivation commands to identify the first non-LTM TCI state configuration. Each serving cell ID indicates the corresponding serving cell among the serving cells. In some implementations, the serving DU configuration includes the serving cell ID and configures the association between the serving cell ID and the first non-LTM TCI state configuration.

[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 at least one non-serving cell for UE 102. For each of the L3 measurement reports, DU 174 sends a DU-to-CU message (306) including the L3 measurement report to CU 172. In some implementations, the DU-to-CU message of event 306 is an F1 Application Protocol (F1AP) message (e.g., a UL RRC messaging message). In some implementations, DU 174 does not send or avoids sending L1 measurement reports to CU 172. The at least one serving cell includes cell 124A and / or other cells, and the at least one non-serving cell includes cell 124B and / or cell 124C. In some implementations, the serving DU configuration or serving CU configuration includes at least one measurement configuration. In some implementations, UE 102 receives 302 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 304 at least one measurement report 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. In a further implementation, the L1 measurement configuration (e.g., CSI-MeasConfig IE) includes an L1 measurement resource configuration and / or an L1 measurement report configuration. In yet another implementation, the L1 measurement resource configuration configures reference signals and / or resources of reference signals for UE 102 to measure and obtain L1 measurement results. In some implementations, the reference signals include CSI-RS and / or Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) resource blocks (SSBs). 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. As another example, UE 102 sends an L3 measurement report to CU 172 via DU 174 according to the L3 measurement configuration. UE 102 sends the L1 measurement report to DU 174 according to either the L1 measurement configuration or the L1 measurement report configuration. In some implementations, DU 174 does not send L1 measurement reports to CU 172.

[0066] In some implementations, the L1 measurement configuration is a specially defined RRCIE (e.g., as defined in 3GPP TS 38.331) for low-layer triggered mobility (LTM). In some implementations, the L1 measurement resource configuration is a specially defined RRCIE (e.g., as defined in 3GPP TS 38.331) for LTM. In some implementations, the L1 measurement reporting configuration is a specially defined RRCIE (e.g., as defined in 3GPP TS 38.331) for LTM. In some implementations, each of the L1 measurement reporting configurations includes 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 includes at least one L1 measurement result. In some implementations, at least one L1 measurement result includes at least one L1-Reference Received 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 transmits a PUCCH transmission including the L1 measurement report to DU 174. That is, UE 102 transmits each of the L1 measurement reports to DU 174 on the PUCCH. In a further implementation, for each of the L1 measurement reports, UE 102 transmits a PUSCH transmission including the L1 measurement report to DU 174. That is, UE 102 transmits each of the L1 measurement reports to DU 174 on the PUSCH. In yet another further implementation, UE 102 transmits a portion of the L1 measurement report to DU 174 on the PUCCH and the remainder of the L1 measurement report to the DU on the Physical UL Shared Channel (PUSCH). 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 of the remaining portions of the L1 measurement report, UE 102 sends a PUSCH transmission including the L1 measurement report to DU 174. In some implementations, each portion of the L1 measurement report is part of a CSI report (i.e., a CSI component) or a CSI report. In some implementations, UE 102 includes other CSI components in the aforementioned PUCCH and / or PUSCH transmissions. In further implementations, these other CSI components include the Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), CSI-RS Resource Indicator (CRI), SSB Resource Indicator (SSBRI), Layer Indicator (LI), and / or Rank Indicator (RI). In some implementations, UE 102 does not send the L1 measurement report formatted as an RRC message to DU 174.

[0068] In some implementations, each of the L3 measurement reports includes at least one L3 measurement result. In further implementations, the at least one L3 measurement result includes at least one RSRP value and / or at least one SINR value. In some implementations, 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 is an RRC message (e.g., a MeasurementReport message). In some implementations, each of the L3 measurement configurations includes a specific measurement identifier (e.g., a measId), and each of the L3 measurement reports includes a specific measurement identifier in a specific L3 measurement configuration. In some implementations, 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 determines that the L3 measurement report is associated with the L3 measurement configuration identified by the measurement identifier.

[0069] In a further implementation, 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. To send the MAC CE, UE 102 generates one or more MAC PDUs to DU 174, 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. In a further implementation, the one or more reference signals include one or more synchronization signal (SS) / physical broadcast channel (PBCH) blocks (SSB) and / or one or more CSI-RS. 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 Figure 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 use 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 base station 104 can use the first cell 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 as a candidate cell for communicating 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 a further implementation, 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 some implementations, CU 172 includes an LTM indicator in the First CU to DU message to instruct DU 174 to prepare the first cell for LTM. In some implementations, the LTM indicator is the LTM Information to be Setup IE or the LTM Information to be Modified IE. In a further implementation, CU 172 includes the LTM indicator in the LTM information IE to be established, and includes the LTM information IE to be established in the first CU to DU message. In yet another implementation, CU 172 includes the LTM indicator in the LTM information IE to be modified, and includes the LTM information IE to be modified in the first CU to DU message. 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 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 includes cell ID 1 and LTM DU configuration 1 together 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). When DU 174 determines that the first cell is ready, DU 174 initiates the sending of the first DU to CU message to CU 172, instead of responding to the CU to DU message received from CU 172.

[0073] In some implementations, DU 174 includes the cell ID of the first cell associated with LTM DU configuration 1 in the first DU to CU message to indicate that LTM DU configuration 1 is configured for or associated with the first cell. CU 172 identifies that LTM DU configuration 1 is configured for or associated with the first cell. In some implementations, CU 172 includes 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 for 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.

[0074] In some implementations, CU 172 does not include the LTM DU configuration and / or 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 configurations in the first DU-CU message. In a further implementation, 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 further implementation, CU 172 includes the reference LTM DU configuration (e.g., a first reference LTM DU configuration) in the first CU-DU message. In this case, 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 configurations 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. In an additional implementation, CU 172 does not include the reference LTM DU configuration in the first CU to DU message. In this case, DU 174 generates LTM DU configurations 1 and / or 2, ..., N (i.e., non-reference LTM DU configurations) as the complete LTM DU configuration.

[0075] 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 (e.g., as defined in 3GPP TS 38.331) a CellGroupConfig IE. In further implementations, the reference LTM DU configuration includes configuration parameters in a CellGroupConfig IE. In some implementations, the reference LTM DU configuration includes a CSI-MeasConfig IE or configuration parameters for Channel State Information (CSI) measurement and / or reporting.

[0076] In some implementations, the reference LTM DU configuration differs from the service DU configuration. In some implementations, a portion of the reference LTM DU configuration is identical to a portion of the service DU configuration, while the remainder of the reference LTM DU configuration differs from the remainder of the service DU configuration. In a further implementation, the reference LTM DU configuration is identical to the service DU configuration.

[0077] 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 sent by CU 172. In a further implementation, 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 during event 316. In a further implementation, 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 of event 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 the RRC reconfiguration message of event 316.

[0078] 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 in events 316 and 318. In such cases, CU 172 generates the first container. The first container indicates to UE 102 not to immediately apply LTM DU configuration 1 and / or LTM CU configuration 1. In some implementations, UE 102 receives an RRC reconfiguration message (e.g., the RRC reconfiguration message in event 318) that includes the configuration (e.g., LTM DU configuration 1 and / or LTM CU configuration 1). If the first container includes the configuration and the RRC reconfiguration message includes the first container, UE 102 avoids immediately applying the configuration. Otherwise, in some implementations, if the configuration is not included in the first container, UE 102 applies the configuration immediately.

[0079] In some implementations, the first container includes or is a first add or modify list (e.g., an ltm-CandidateToAddModList field or an LTM-CandidateToAddModList IE). CU 172 includes LTM DU configuration 1 and / or LTM CU configuration 1 in the first element (hereinafter referred to as element 1) of the first add or modify list. In some implementations, CU 172 generates an RRC message (e.g., an RRCReconfiguration message) that includes LTM DU configuration 1 and / or LTM CU configuration 1, and includes that RRC message in element 1. In some implementations, element 1 is an add or modify IE (e.g., an LTM-ConfigToAddMod IE, an LTM-Candidate IE, an LTM-CandidateToAddMod IE, or an LTM-CandidateConfigToAddMod IE). In some implementations, when UE 102 receives the first add or modify list, UE 102 stores the first add or modify list (e.g., in a variable in random access memory (RAM)). In a further implementation, DU 174 generates a first container and includes the first container in the first DU to CU message. In yet another further 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 the RRC reconfiguration message of event 316, the first container, or element 1, where LTM CU configuration 1 is associated with LTM DU configuration 1. In a further implementation, to associate LTM CU configuration 1 with LTM DU configuration 1, CU 172 includes both LTM CU configuration 1 and LTM DU configuration in element 1. In some implementations, CU 172 includes LTM CU configurations 2, ..., N in the RRC reconfiguration message of event 316 or the second container, where LTM CU configurations 2, ..., N are associated with LTM DU configurations 2, ..., N, respectively. In some implementations, to associate LTM CU configurations 2, ..., N with LTM DU configurations 2, ..., N, CU 172 includes LTM CU configurations 2, ..., N and LTM DU configurations in elements 2, ..., N, respectively. In a further implementation, 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 of event 316.

[0081] Upon receiving the 316 RRC reconfiguration message, DU 174 sends the 318 RRC reconfiguration message to UE 102. In response, UE 102 sends the 320 RRC reconfiguration complete message (e.g., RRCReconfigurationComplete message) to DU 174, which in turn sends a second DU-to-CU message (322) including the RRC reconfiguration complete message to CU 172. In some implementations, CU 172 performs security protection on the RRC reconfiguration message (e.g., integrity protection and / or encryption). For example, CU 172 generates an integrity-based 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 the 316 and 318 PDCP PDUs including the encrypted RRC reconfiguration message and the encrypted MAC-I to UE 102 via DU 174. When UE 102 receives a PDCP PDU from CU 172 via DU 174 (i.e., events 316 and 318), UE 102 decrypts the encrypted RRC reconfiguration and encrypted MAC-I to obtain the RRC reconfiguration message and MAC-I, and verifies whether the MAC-I is valid. If UE 102 verifies that the MAC-I is invalid, UE 102 discards or ignores the RRC reconfiguration message. In some implementations, UE 102 performs an RRC connection reconstruction procedure in response to an invalid MAC-I. In a further implementation, if UE 102 verifies that the MAC-I is valid, UE 102 processes 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 Figure 3 This is collectively referred to as LTM preparation process 390. Events 316, 318, 320, and 322 are... Figure 3 This is collectively referred to as the LTM configuration delivery process 394.

[0083] In some implementations, the first CU to DU message is a UE context establishment request message, and the first DU to CU message is a UE context establishment response message. In some implementations, the first CU to DU message is a UE context modification request message, and the first DU to CU message is a UE context modification response message or a UE context modification request message. In the case of a UE context modification request message, CU 172 sends 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 a further implementation, the second CU to DU message is a UE context modification request message. In an even further implementation, the second DU to CU message is a UL RRC message transmission message. In yet another further implementation, the second DU to CU message is a UE context modification response message.

[0084] In some implementations, CU 172 includes the reference LTM CU configuration in the RRC reconfiguration message or the first container in event 316. In a further implementation, CU 172 generates LTM CU configuration 1 (i.e., the non-reference LTM CU configuration) as an incremental configuration to enhance the reference LTM CU configuration. Similarly, in still a further implementation, CU 172 generates some or all of LTM CU configurations 2, ..., N as incremental configurations to enhance the reference LTM CU configuration. Alternatively, CU 172 includes the reference LTM CU configuration in the RRC reconfiguration message or the first container in event 316, but does not include 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 the additional container in the RRC reconfiguration message in event 316.

[0085] In some implementations, the reference LTM CU configuration differs from the service CU configuration. In a further implementation, a portion of the reference LTM CU configuration is identical to a portion of the service CU configuration, while the remainder of the reference LTM CU configuration differs from the remainder of the service CU configuration. In still a further implementation, the reference LTM CU configuration is identical to the service 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 sends 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 a further implementation, 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 includes LTM DU configuration 1 and ID 1, and indicates the association between ID 1 and LTM DU configuration 1. Therefore, in some implementations, DU 174 directly associates ID 1 with LTM DU configuration 1. In a further implementation, in the third CU to DU message, CU 172 includes cell ID 1 and ID 1 (i.e., the first LTM ID) and indicates the association between cell ID 1 and ID 1. Therefore, in some such implementations, DU 174 associates 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 yet another further implementation, in the third CU to DU message, CU 172 includes LTM DU configuration 1, cell ID 1, and / or ID 1, and indicates the association between ID 1, LTM DU configuration 1, and / or cell ID 1. In some implementations, DU 174 sends a third DU to CU 172 in response to the third CU to DU message. In some implementations, the third CU to DU message and the third DU to CU message are a UE context modification request message and a UE context modification response message. In some implementations, CU 172 includes ID 1, Cell ID 1, and / or LTM DU Configuration 1 in the second CU-DU message, as described above. Therefore, the third CU-DU message is omitted. In a further implementation, the third DU-CU message is a UE context modification request message. In this case, CU 172 sends a UE context modification confirmation message to DU 174 in response to the UE context modification request message.

[0088] In some implementations, events 312 (optional) and / or 314 (optional) are... Figure 3 This is collectively referred to as the LTMID assignment process 392.

[0089] In some implementations, where CU 172 includes ID 1 in the first CU to DU message, DU 174 includes ID 1 in LTM DU configuration 1, the first container, or element 1. Alternatively, in some implementations, DU 174 does not include ID 1 in LTM DU configuration 1, the first container, and / or element 1.

[0090] In some implementations, CU 172 includes the referenced LTM DU configuration in the first container. For example, CU 172 includes the referenced LTM DU configuration in a field of a first container that is different from the field of the first container that includes LTM DU configuration 1. In a further implementation, CU 172 includes the referenced LTM DU configuration in the RRC reconfiguration message of event 316 and outside the first container. For example, CU 172 generates a third container (e.g., field / IE) to include the first container and the referenced LTM DU configuration, and includes the third container in the RRC reconfiguration message of event 316. In yet another further implementation, DU 174 includes the referenced LTM DU configuration in the first container. For example, DU 174 includes the referenced LTM DU configuration in a field of a first container that is different from the field of the first container that includes LTM DU configuration 1. In a further implementation, DU 174 generates a fourth container (e.g., field / IE) to include the first container and the reference LTM DU configuration, and includes the fourth container in the first DU to CU message of event 310. In this case, CU 172 includes the fourth container in the RRC reconfiguration message of event 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.

[0091] In some implementations, neither CU 172 nor DU 174 is assigned an ID to identify the reference LTM DU configuration.

[0092] In some implementations, LTM DU configuration 1 includes multiple configuration parameters for UE 102 to communicate with DU 174 on a first cell. In some implementations, these multiple configuration parameters include physical layer configuration parameters (e.g., PhysicalCellGroupConfig IE), MAC layer configuration parameters (e.g., MAC-CellGroupConfig IE), and / or RLC configuration parameters (e.g., RLC-BearerConfig IE). In further implementations, these multiple configuration parameters include specific 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 a CellGroupConfig IE (e.g., defined in 3GPP TS 38.331). In other implementations, LTM DU configuration 1 includes configuration parameters within a CellGroupConfig IE.

[0093] 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 (e.g., as defined in 3GPP TS 38.331) MeasConfig IE and / or RadioBearerConfig IE, 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 some 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-RS. RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of RS resource configurations 1 includes an RS resource configuration ID. In some implementations, RS resource configuration 1 is a CSI-ResourceConfig IE (or similar). In some implementations, reporting 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 reporting configurations 1 includes one or more RS resource configuration IDs identifying 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 TCI state of the corresponding Quasi-Co-location (QCL) type. The DL RS is associated with cell 1.

[0094] 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 a further implementation, DU 174 sends an additional DU-to-CU message including the service DU configuration to CU 172. In some implementations, the additional DU-to-CU message is a UE context modification request message. In some implementations, CU 172 includes the service DU configuration 1 in the RRC reconfiguration messages for events 316 and 318. In a further implementation, CU 172 sends another RRC reconfiguration message including the service DU configuration to UE 102 via DU 174.

[0095] In some implementations, DU 174 includes the random access configuration in LTM DU configuration 1. In further 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 some implementations, if DU 174 determines that UE 102 has not yet synchronized with the first cell in UL, DU 174 determines to include the random access configuration in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 is synchronized with the first cell in UL, DU 174 determines not to include the random access configuration in LTM DU configuration 1. If LTM DU configuration 1 includes the random access configuration, UE 102 performs the 332 random access procedure 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, UE 102 skips or avoids performing the 322 random access procedure in response to LTM DU configuration 1 excluding the random access configuration.

[0096] In some implementations, DU 174 includes random access configuration parameters in LTM DU configuration 1 and / or a reference LTM DU configuration, regardless of whether cell 124A and the first cell are synchronized. UE 102 performs the 332 random access procedure based on 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 timings.

[0097] 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 on the first cell. Otherwise, if cell 124A and the first cell are not synchronized, DU 174 determines not to include the first indication in LTM DU configuration 1. In a further implementation, if DU 174 determines that UE 102 is synchronized with the first cell in the UL, DU 174 determines to include the first indication in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 is not synchronized with the first cell in the UL, DU 174 determines not to include the first indication in LTM DU configuration 1. If LTM DU configuration 1 includes the first indication, UE 102 skips or avoids performing the 332 random access procedure based on or in response to the first indication. Otherwise, if LTM DU configuration 1 does not include the first indication, then in response to LTM DU configuration 1 excluding the first indication, UE 102 performs the 332 random access procedure according to the random access configuration, as described below.

[0098] In some implementations, DU 174 includes a synchronized reconfiguration configuration (e.g., ReconfigurationWithSync IE) in LTM DU Configuration 1 or a special cell configuration. In further implementations, DU 174 does not include a synchronized reconfiguration configuration (e.g., ReconfigurationWithSync IE) in LTM DU Configuration 1 or a special cell configuration. In some implementations, DU 174 includes LTM cell handover information in the first LTM DU Configuration 1. In further implementations, DU 174 includes random access configuration (parameters) in the LTM cell handover information (e.g., the ltm-CellSwitchInfo field or LTM-CellSwitchInfo IE). In some implementations, if cell 124A and the first cell are not synchronized, DU 174 determines to include a synchronized reconfiguration configuration in LTM DU Configuration 1. Otherwise, if cell 124A is synchronized with the first cell, DU 174 determines not to include a synchronized reconfiguration configuration in LTM DU Configuration 1. In other implementations, if DU 174 determines that UE 102 is not yet synchronized with the first cell in the UL, then DU 174 determines to include the reconfiguration configuration with synchronization in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 is already synchronized with the first cell in the UL, then DU 174 determines not to include the reconfiguration configuration with synchronization in LTM DU configuration 1. In some implementations, if LTM DU configuration 1 includes the reconfiguration configuration with synchronization, then UE 102 performs the 332 random access procedure in response to or based on the reconfiguration configuration with synchronization, as described below. Otherwise, if LTM DU configuration 1 does not include the reconfiguration configuration with synchronization, then UE 102 skips or avoids performing the 332 random access procedure. In some implementations, DU 174 includes the cell ID of cell 1 (i.e., the first cell) (i.e., cell ID 1) in LTM DU configuration 1. In a further implementation, cell ID 1 is a PCI. In a further 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 a further implementation, 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 304 to one or more of at least one measurement report (e.g., in response to this), base station 104 (i.e., CU 172 or DU 174) determines an additional cell (i.e., cell 2, ..., N) for LTM for UE 102. In a further implementation, base station 104 determines the additional cell for LTM for UE 102 because at least one measurement report indicates that base station 104 uses the additional cell to communicate with UE 102. In still a further implementation, the additional cell includes cell 124C and / or cells other than cells 124A, 124B, and 124C. In some implementations, CU 172 determines 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 a further implementation, 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 some implementations, the corresponding predetermined threshold for the additional cell is different from the first predetermined threshold. In a further implementation, the corresponding predetermined threshold for the additional cell is the same as the first predetermined threshold. In a further implementation, the corresponding predetermined threshold for the additional cell is 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 at least one additional LTM preparation procedure and executes at least one additional 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 at least one additional LTM preparation procedure and executes at least one additional 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 to prepare cells 2, ..., N respectively, similar to procedure 390. In a further implementation, CU 172 includes cell IDs 2, ..., N in CU-DU messages 2, ..., N, similar to the first CU-DU message, during LTM preparation procedures 2, ..., N. During 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" can be 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. The example and implementation of LTMDU configuration 1 can be applied to LTMDU configurations 2, ..., N.

[0102] In a further implementation, 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 LTM DU configurations 1, 2, ..., N for cells 1, 2, ..., N respectively in the first DU to CU message. In an even further implementation, in the first DU to CU message, DU 174 includes 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] In some implementations, after receiving LTM DU configurations 2, ..., N from DU 174, CU 172 includes LTM DU configurations 2, ..., N in a first container. In a further implementation, CU 172 includes LTM DU configurations 2, ..., N in elements 2, ..., N respectively, and includes elements 2, ..., N in the first container. In an even further implementation, CU 172 includes the LTM IDs (i.e., ID 2, ..., N) used to identify LTM DU configurations 2, ..., N in the RRC reconfiguration message. In yet another further implementation, CU 172 includes ID 2, ..., N in the first container. For example, CU 172 includes 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 a further implementation, CU 172 receives IDs 2, ..., N from the first DU to CU message of process 390 from DU 174. In an even further 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 performs an LTM ID assignment procedure similar to procedure 392 with DU 174 for each of LTM DU configurations 2, ..., N. In a further implementation, CU 172 includes IDs 2, ..., N and LTM DU configurations 2, ..., N in a third CU-DU message and indicates the association between IDs 2, ..., N and LTM DU configurations 2, ..., N, respectively. Therefore, in some such implementations, DU 174 associates LTM DU configurations 2, ..., N with IDs 2, ..., N, respectively. In yet another further implementation, CU 172 includes cell IDs 2, ..., N and IDs 2, ..., N in a third CU-DU message and indicates the association between cell IDs 2, ..., N and IDs 2, ..., N, respectively. Therefore, in some implementations, DU 174 associates LTM DU configurations 2, ..., N with ID2, ..., N based on the associations between cell IDs 2, ..., N and ID2, ..., N respectively, and the associations between cell IDs 2, ..., N and LTM DU configurations 2, ..., N respectively. In some implementations, CU 172 includes 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, in a further implementation, CU 172 omits the third CU-to-DU message. In yet another further implementation, CU 172 includes IDs 2, ..., N in the first CU-to-DU message and indicates that IDs 2, ..., N are associated with cell IDs 2, ..., N respectively. In some implementations, 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 implementations, DU 174 assigns IDs 2, ..., N. In a further implementation, DU 174 includes IDs 2, ..., N in the first DU to CU message of process 390. In still a further implementation, DU 174 includes IDs 2, ..., N in DU to CU messages 2, ..., N of LTM preparation process 2, ..., N. In some implementations, CU 172 includes IDs 2, ..., N in the RRC reconfiguration message. In some implementations, DU 174 includes IDs 2, ..., N in LTM DU configuration 2, ..., N. Therefore, CU 172 does not include the ID identifying each of LTM DU configurations 2, ..., N (e.g., LTM ID) in the RRC reconfiguration message, the first container, and / or element 1.

[0107] In some implementations, CU 172 generates 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 includes either 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 is an add or modify IE (e.g., the ltm-ConfigToAddMod field, LTM-ConfigToAddMod IE, ltm-CandidateConfigToAddMod field, or LTM-CandidateConfigToAddMod IE). In some implementations, when UE 102 receives the second add or modify list, UE 102 stores the second add or modify list together with the first add or modify list (e.g., as a variable in RAM).

[0108] In some implementations, DU 174 includes cell IDs 2, ..., N in LTM DU configurations 2, ..., N to identify cells 2, ..., N. In some implementations, each of cell IDs 2, ..., N is a PCI. In a further implementation, LTM DU configurations 2, ..., N include cell indices 2, ..., N indexed for cell IDs 2, ..., N or cells 2, ..., N respectively. In some cases where CU 172 prepares cells 2, ..., N for LTM in process 390, CU 172 sets cell indices 2, ..., N to different values ​​and includes cell indices 2, ..., N in the first CU to CU to DU message of event 308. In some cases where CU 172 prepares cells 2, ..., N in an additional LTM preparation process, cell indices 2, ..., N are set to different values, and cell indices 2, ..., N are included 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 a further implementation, each of the LTM DU configurations 1, ..., N is a CellGroupConfig IE (e.g., as defined in 3GPP TS 38.331). In still a further implementation, each of the LTM DU configurations 1, ..., N includes configuration parameters included in a CellGroupConfig IE (e.g., as defined in 3GPP TS 38.331). In still a further implementation, multiple configuration parameters in each of the LTM DU configurations include a specific cell configuration (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE). In some implementations, LTM DU configurations 1, ..., N are CellGroupConfig IEs (e.g., as defined in 3GPP TS 38.331). In a further implementation, LTM DU configuration 1, ..., N includes the configuration parameters in CellGroupConfig IE.

[0110] In some implementations, CU 172 includes 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 configuration 2, ..., N. Examples and implementations 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 to instruct UE 102 to release LTM DU configuration M or element M. In some implementations, CU 172 generates a release list including an ID (i.e., LTM ID) M for releasing LTM DU configuration M or element M, and includes the release list in the RRC reconfiguration message. In response to the RRC reconfiguration message, UE 102 releases LTM DU configuration M or element M, and sends an RRC reconfiguration complete message to CU 172 via DU 174. In response to this determination, CU 172 sends a CU-DU message to DU 174 to instruct DU 174 to release LTM DU configuration M. In some implementations, to instruct DU 174 to release the LTM DU configuration M, CU 172 includes the cell ID M 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, where 1 ≤ K ≤ N. In response to this determination, DU 174 sends a DU-to-CU message to CU 172 to release LTM DU configuration K. In some implementations, to indicate the release of LTM DU configuration K, DU 174 includes 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. Upon receiving the DU-to-CU message (e.g., in response to this), CU 172 generates a release list including the ID (i.e., LTM ID) K to release LTM DU configuration K or element K, and sends an RRC reconfiguration message including the release list to UE 102 via DU 174. In response, UE 102 releases LTM DU configuration K or element K, and sends an RRC reconfiguration complete message to UE 102 via DU 174. In some implementations, CU 172 sends a CU to DU message to DU 174 in response to a DU to CU message. In some implementations, the DU to CU message and the CU to DU message are respectively a UE context modification request message and a UE context modification confirmation message.

[0113] After receiving a 318 RRC reconfiguration message or sending a 320 RRC reconfiguration complete message, UE 102 sends a 324 message containing at least one measurement report to DU 174, similar to event 304. In some implementations, similar to event 306, DU 174 sends a DU-CU message containing at least one measurement report to CU 172. In a further implementation, DU 174 does not send at least one measurement report to CU 172. In some implementations, UE 102 sends a 324 message containing at least one measurement report, such as an L1 or L3 measurement report as described for event 304. In a further implementation, UE 102 sends a 324 message containing at least one measurement report to DU 174 on the PUCCH and / or PUSCH, similar to event 304. In still a further implementation, UE 102 sends a 324 message containing at least one MAC CE, similar to event 304, to DU 174. In a further implementation, 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. This 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. In some implementations, CU 172 sends 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. In some implementations, the one or more RRC messages include an RRC reconfiguration message for event 316. According to at least one measurement configuration, UE 102 performs measurements on one or more reference signals. In some implementations, the one or more reference signals 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 measurement, and includes at least one L1 measurement result and / or at least one L3 measurement result in at least one measurement report in event 324. DU 174 transmits one or more reference signals on cell 124A, cell 1, and / or cell 2, ..., N. In some implementations, the one or more reference signals are CSI-RS or SSB.

[0115] In some implementations, at least one measurement configuration includes an L3 measurement configuration (e.g., a MeasConfig IE), as described for event 304. In a further implementation, at least one measurement configuration includes or includes one or more L1 measurement configurations, as described above. In still a further implementation, the L1 measurement configuration is or includes a CSI-MeasConfig IE (e.g., as defined in 3GPP TS 38.331). In yet still a further implementation, the L1 measurement configuration includes an RS resource configuration and / or a 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-ReportConfig IE. In a further implementation, each of the reporting configurations is a specifically defined RRC IE (e.g., as defined in 3GPP TS 38.331). In some implementations, each of the reporting configurations configures periodic reporting and / or event-triggered reporting of L1 measurement results.

[0116] In some implementations, the L1 measurement report is a CSI report. In a further implementation, the L1 measurement report is a MAC CE. In still a further implementation, 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 RS or RS resources according to 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). In some implementations, the quantized measurement values ​​include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0117] In a further implementation, at least one measurement configuration includes a specially defined measurement configuration (e.g., an LTM measurement configuration as defined in 3GPP TS 38.331). In some implementations, the specially defined 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 some implementations, the reference signal resource configuration is a CSI-ResourceConfig IE. In a further implementation, as described above, the specially defined 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 some implementations, the measurement report is an L1 measurement report or a specially defined measurement report (e.g., an LTM measurement report). In some implementations, the specially defined measurement configuration includes specially defined configuration parameters (e.g., specifically defined in 3GPP TS 38.331).

[0118] Upon receiving measurement report 324 (e.g., in response to it), DU 174 generates a first LTM command to activate LTMDU configuration 1 (i.e., the first LTM command instructs UE 102 to apply LTMDU configuration 1 or perform a serving cell change to cell 1). DU 174 then sends the first LTM command 330 to UE 102. In some implementations, DU 174 sends the first LTM command to UE 102 on cell 124A. In a further implementation, DU 174 sends the first LTM command to UE 102 on cell 124D. In some implementations, DU 174 includes ID 1 in the first LTM command to indicate LTMDU configuration 1 or element 1, and UE 102 determines (e.g., identifies) LTMDU configuration 1 or element 1 based on ID 1.

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

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

[0121] In a further implementation, DU 174 includes 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 some implementations, 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, in some such implementations, UE 102 determines 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 a further 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, in some such implementations, UE 102 determines 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 such implementations, DU 174 sets the remaining bits in the bitmap to a second value to indicate that the remainder of LTM DU configuration 1, ..., N is not activated. In some implementations, the first value is one, and the second value is zero. In a further implementation, the first value is zero, and the second value is one. Generally, if DU174 determines that UE 102 is activating LTM DU configuration L or changing the serving cell to cell L, then DU 174 sets the corresponding bit in the bitmap (e.g., bit L or bit L-1) to a first value and sets 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 specially defined measurement report) includes at least one measurement result of the first cell, the TRP of the first cell, or a reference signal transmitted on the first cell. In some implementations, the reference signal is 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, at least one measurement result includes an L1-RSRP value, an L1-RSRQ value, and / or an L1-SINR value. In a further implementation, at least one measurement result includes an RSRP value, an RSRQ value, and / or a SINR value from a specially defined measurement report. In some implementations, the second predetermined threshold is different from the first predetermined threshold. In some implementations, the second predetermined threshold is greater than the first predetermined threshold. In this case, the at least one measurement indicates that the first cell is suitable for communication with UE 102. In a further implementation, the second predetermined threshold is equal to the first predetermined threshold. In this case, at least one measurement indicates that the first cell is consistently above either the second predetermined threshold or the first predetermined threshold, thereby indicating that the first cell is suitable for communication with UE 102. Therefore, in response to the signal strength or quality of the first cell exceeding 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 some implementations, the second predetermined threshold is greater than the first predetermined threshold. In such implementations, 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 a further implementation, the second predetermined threshold is equal to the first predetermined threshold. In such implementations, at least one measurement report of event 326 indicates that the signal strength or quality of the first cell has consistently been higher than either the second or the first predetermined threshold, further indicating that the first cell is suitable for communication with UE 102. Therefore, in response to the signal strength or quality of the first cell exceeding the second predetermined threshold, CU 172 determines to activate LTM DU configuration 1.

[0125] 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 UE 102 to change its serving cell to cell 1. In some implementations, CU 172 includes ID 1 in the fourth CU-DU message. In a further implementation, 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, in some further implementations, DU 174 determines to activate LTM DU configuration 1 based on cell index 1. In a further implementation, CU 172 includes cell ID 1 in the fourth CU-DU message. Therefore, DU 174 determines to activate LTM DU configuration 1 based on cell ID 1. In a further implementation, CU 172 includes ID 1 in the fourth CU to DU message. Therefore, in some implementations, DU 174 determines 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 a further implementation, the fourth CU to DU message and / or the fourth DU to CU message are specially defined interface messages (e.g., F1 Application Protocol (F1AP) messages as defined in 3GPP TS 38.473).

[0126] In some implementations, when it is determined that LTM DU configuration 1 is activated or the first LTM command 330 is sent, or in response to this, DU 174 sends a DU-to-CU message 329 to CU 172 indicating that LTM is being executed or is being executed. In some implementations, the DU-to-CU message is an LTM cell change notification message. In some implementations, DU 174 includes cell ID 1 or ID 1 (i.e., LTM ID) in the DU-to-CU message of event 329 to indicate that DU 174 will activate LTM DU configuration 1 or trigger a fast serving cell change (i.e., LTM serving cell change). In a further implementation, DU 174 sends the DU-to-CU message 329 to CU 172 before or after sending the LTM command 330.

[0127] 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. In some implementations, the MAC CE is a specially defined MAC CE (e.g., as defined in 3GPP TS 38.321). In some implementations, DU 174 includes a sub-header identifying the specially defined MAC CE in the MAC PDU, and UE 102 identifies the specially defined MAC CE in the MAC PDU based on this sub-header. In some implementations, the sub-header includes a logical channel ID or an extended logical channel ID (e.g., as defined in 3GPP TS 38.321) to identify the new MAC CE. In a further implementation, the first LTM command is the DCI received by UE 102 from DU 174 on the PDCCH in event 330. DU 174 generates a Cyclic Redundancy Check (CRC) for the DCI, scrambles the CRC using the first C-RNTI of UE 102, and transmits the 330 DCI and the scrambled CRC on the PDCCH. In some implementations, the DCI format is an existing DCI format (e.g., defined in 3GPP TS 38.212). In further implementations, the DCI format is a specially defined DCI format (e.g., as defined in 3GPP TS 38.212).

[0128] In some implementations, DU 174 does not perform security protection (e.g., integrity protection and / or encryption) on the first LTM command, which 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.

[0129] In some implementations, after receiving the first LTM command, UE 102 sends 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 HARQACK. In a further implementation, the acknowledgment is a MAC CE. For example, the MAC CE is an existing MAC CE (e.g., as defined in 3GPP TS 38.321). In another example, the MAC CE is a specially defined MAC CE (e.g., as defined in 3GPP TS 38.321). In yet another further implementation, the acknowledgment is a PUCCH transmission.

[0130] In some implementations, CU 172 sends an RRC reconfiguration message 316 in response to an L3 measurement report for event 306 of the first cell. To configure UE 102 to send an L3 measurement report for event 306, CU 172 sends 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 for event 324 of the first cell. In some implementations, to configure UE 102 to send an L1 or specially defined measurement report for event 324, CU 172 sends a second RRC reconfiguration message to UE 102, including the L1 or specially defined measurement configuration. In some implementations, the first RRC reconfiguration message and the second RRC reconfiguration message are the same message (i.e., the same instance). In further 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 a further implementation, the second RRC reconfiguration message is different from the RRC reconfiguration message for event 316.

[0131] 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 ID 1, cell ID 1, or cell index 1 received in the first LTM command, and applies LTM DU configuration 1 to communicate with DU 174 on the first cell. In some implementations, upon receiving the first LTM command 330 (e.g., in response to this) or after sending an acknowledgment 331, UE 102 disconnects from cell 124A. In some implementations, upon receiving the first LTM command 330 or sending an acknowledgment 331 (e.g., in response to this), UE 102 ceases communication on cell 124A. In some implementations, UE 102 accesses the first cell by performing a random access procedure with DU 174 on the first cell in response to receiving the first LTM command. In a further implementation, upon receiving the first LTM command (e.g., in response to this), UE 102 skips the random access procedure and sends an initial transmission (e.g., a PUSCH transmission or a PUCCH transmission) to DU 174 on the first cell.

[0132] 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 on the first cell according to LTM DU configuration 1. If LTM DU configuration 1 configures UE 102 to perform a random access procedure, then UE 102 performs a 332 random access procedure on the first cell to connect to the first cell. For example, LTM DU configuration 1 includes a reconfiguration configuration with synchronization (e.g., ReconfigurationWithSync IE) to configure UE 102 to perform a random access procedure when UE 102 receives an LTM command for the first cell. In some implementations, in LTM DU configuration 1, DU 174 configures UE 102 to skip the random access procedure for an LTM serving cell change for the first cell. In this scenario, after receiving the first LTM command, UE 102 skips the random access procedure and sends an initial transmission (e.g., a PUSCH transmission or a PUCCH transmission) to DU 174 on the first cell in event 332. In some implementations, DU 174 excludes the synchronized reconfiguration configuration in LTM DU configuration 1 to configure UE 102 to skip the random access procedure for LTM serving cell changes in the first cell.

[0133] In some implementations, LTM DU configuration 1 includes a reconfiguration configuration or random access configuration with synchronization. In such cases, DU 174 configures in the LTM command whether UE 102 performs a random access procedure on the first cell. Therefore, UE 102 determines whether to perform a 332 random access procedure on the first cell based on the first LTM command. In some implementations, DU 174 includes an indication (e.g., a field) to skip 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 an initial transmission (e.g., a PUSCH transmission or a PUCCH transmission) on the first cell to access the first cell. In some 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 on the first cell to access the first cell. In a further implementation, DU174 includes a timing advance value in the first LTM command to indicate skipping the random access procedure. In response to receiving the timing advance value or a first LTM command including the timing advance value, UE 102 uses the timing advance value to skip the random access procedure and transmits an initial transmission on the first cell to access the first cell. In yet another further 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 command, UE 102 performs a random access procedure on the first cell to access the first cell.

[0134] In some implementations, the random access procedure is a four-step random access procedure. In a further implementation, 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 still a further implementation, the random access procedure is a contention-based random access procedure. In the case of a four-step random access procedure, UE 102 sends message 3, including the UE identifier, to DU 174 via the first cell during the random access procedure. DU 174 responds to message 3 by sending a contention resolution message (e.g., message 4) to UE 102. In the case of a two-step random access procedure, UE 102 sends message A, including the UE identifier, to DU 174 via the first cell during the random access procedure. DU 174 responds to message A by sending a contention resolution message (e.g., message B) to UE 102. In some implementations, when UE 102 receives a contention resolution message from DU 174 on the first cell, UE 102 determines that UE 102 has successfully completed the random access procedure (i.e., UE 102 has successfully accessed the first cell). In some implementations, LTM DU configuration 1 includes a second C-RNTI, and the UE identifier is the second C-RNTI of UE 102. In this type of implementation, the contention resolution message is a PDCCH transmission addressed to the second C-RNTI. In a further implementation, LTM DU configuration 1 does not include a C-RNTI, and the UE identifier is the first C-RNTI. In this type of implementation, the contention resolution message is a PDCCH transmission addressed to the first C-RNTI. In some implementations, DU 174 includes the second C-RNTI in a reconfiguration configuration with synchronization. In a further implementation, DU 174 includes the second C-RNTI in LTM cell handover information.

[0135] In some implementations, LTM DU configuration 1 includes parameters for configuring contention-free random access resources, such as a dedicated random access preamble and / or PRACH timing as described below. In one implementation, LTM DU configuration 1 includes a RACH-ConfigDedicated IE containing parameters. In other implementations, the first LTM command includes parameters for configuring contention-free random access resources. The parameters in LTM DU configuration 1 or the first LTM command include a dedicated random access preamble (index), a PRACH mask index, an SSB index, and / or a repetition count. The dedicated random access preamble index indicates the dedicated random access preamble. In some implementations, the PRACH mask index indicates one or more allowed PRACH timings for UE 102 to transmit the dedicated random access preamble. In some implementations, the SSB index indicates the SSB used by UE 102 to determine at least one of the allowed PRACH timings. In such implementations, the random access procedure is a contention-free random access procedure. In random access procedure 332, UE 102 sends a dedicated random access preamble to DU 174 via the first cell at a (determined or permitted) PRACH timing. In some implementations, UE 102 sends the dedicated random access preamble at one or more times based on the number of repetitions. When UE 102 receives a random access response including the ID of the dedicated random access preamble from DU 174 on the first cell, UE 102 determines that UE 102 has successfully completed the random access procedure (i.e., UE 102 has successfully accessed the first cell). In response to this determination, UE 102 releases parameters or contention-free random access resources. In some implementations, in response to performing a MAC reset caused by LTM cell handover as described above, UE 102 maintains (e.g., retains or preserves) parameters or contention-free random access resources. Therefore, after performing a MAC reset, UE 102 uses parameters or contention-free random access resources to perform the contention-free random access procedure 332. In some implementations, UE 102 starts a timer (e.g., T304, T420, etc.) when performing (e.g., executing) an LTM cell handover to a first cell. Upon successful completion of the random access procedure, UE 102 determines that the LTM cell handover to the first cell was successful and stops the timer. If the timer expires (i.e., the LTM cell handover of UE 102 fails), UE 102 releases parameters or contention-free random access resources. In some implementations, the RRC entity of UE 102 (e.g., RRC 214) sends an indication to the MAC entity of UE 102 (e.g., MAC 204B) to instruct the MAC entity to release the contention-free random access resources. The MAC entity releases the contention-free random access resources in response to this indication.This implementation method prevents UE 102 from incorrectly using contention-free random access resources during subsequent random access procedures.

[0136] In some implementations, UE 102 may perform one or more actions if a timer for the MCG (e.g., T304 for reconfiguration with synchronization) or a timer for path switching (e.g., T420) expires, or if the indicated UE 102 (e.g., indicated by the targetRelayUE-Identity in the reconfigurationWithSync message containing an indication of path switching (e.g., as specified in 3GPP TS 38.331)) (e.g., a target L2 U2N relay UE). In some such implementations, UE 102 releases (i) a dedicated preamble provided in rach-ConfigDedicated (e.g., if configured) and / or (ii) a dedicated msgA PUSCH resource provided in Rach-ConfigDedicated (e.g., if configured). In a further implementation, if the timer (e.g., T304) is started due to LTM handover, UE 102 additionally or alternatively instructs the lower layer to release the dedicated preamble (if provided in the LTM cell handover command). In still a further implementation, if any DAPS bearer is configured and no radio link failure is detected in the source PCell (e.g., according to 3GPP TS 38.331), UE 102 additionally or alternatively resets the MAC of the target PCell and releases the MAC configuration of the target PCell.

[0137] In some implementations of this kind, UE 102 additionally or alternatively performs operations for each DAPS bearer, for each SRB, and / or for each non-DAPS bearer. In some implementations, for each DAPS bearer, UE 102 (i) releases one or more RLC entities (e.g., as specified in 3GPP TS 38.322) and the associated logical channel of the target PCell, and / or (ii) reconfigures the PDCP entity to release the DAPS (e.g., as specified in 3GPP TS 38.323). In a further implementation, for each SRB, UE 102 (i) if it does not receive masterKeyUpdate, configures state variable continuity for the PDCP entity of the source PCell (e.g., as specified in 3GPP TS 38.323), (ii) releases the PDCP entity of the target PCell, (iii) releases the RLC entity of the target PCell (e.g., as specified in 3GPP TS 38.322) and the associated logical channel, (iv) triggers the PDCP entity of the source PCell to perform SDU drop (e.g., as specified in 3GPP TS 38.323), and / or (v) rebuilds the RLC entity of the source PCell. In a still further implementation, for each non-DAPS bearer, UE 102 restores the UE configuration used for the DRB or multicast MRB in the source PCell, including the PDCP, RLC state variables, security configuration, and data stored in the transmit and receive buffers in the PDCP and RLC entities.

[0138] In a further implementation of this type, if any DAPS bearer is configured and no radio link failure is detected in the source PCell, UE 102 additionally or alternatively (i) releases the physical channel configuration of the target PCell, (ii) discards the key (e.g., K) used in the target PCell. gNB Key, K RRCenc Key, K RRCint Key, K UPint Key and / or K UPenc (iii) restore the suspended SRB in the source PCell, (iv) restore the UE measurement configuration used in the source PCell, (v) store the handover failure information in the VarRLF-Report (e.g., as described in 3GPP TS 38.331), and / or (vi) initiate a failure information procedure (e.g., as described in 3GPP TS 38.331) to report the DAPS handover failure.

[0139] In other implementations, UE 102 may perform additional functionalities if no DAPS bearer is configured or if a radio link failure is detected in the source PCell. In some such implementations, if attemptLTM-Switch is configured and the expiration of the MCG timer (e.g., T304) is caused by an LTM cell handover execution triggered by an indication from a lower layer (e.g., as described in 3GPP TS 38.331), UE 102 reverts to the UE configuration used in the source PCell, except for the PDCP state variables of the SRB associated with the MCG. Otherwise, in a further implementation, UE 102 reverts to the UE configuration used in the source PCell. If the associated timer (e.g., T304) was not initiated during a cell selection performed while another timer (e.g., T311) was running (e.g., as defined in 3GPP TS 38.331), UE 102 stores the handover failure information in a VarRLF-Report (e.g., as described in 3GPP TS 38.331). Furthermore, UE 102 initiates a connection re-establishment procedure (e.g., as specified in 3GPP TS 38.331). Depending on the implementation, UE configuration may include state variables and parameters for each radio bearer.

[0140] In a further implementation, if the timer for the secondary cell group (e.g., T304) expires, UE 102 performs additional and / or alternative functionality. In some implementations, if MCG transmission is not suspended, UE 102 (i) releases the dedicated preamble provided in rach-ConfigDedicated (if configured), (ii) releases the dedicated msgA PUSCH resource provided in rach-ConfigDedicated (if configured), (iii) if the timer (e.g., T304) was started due to LTM cell handover, instructs the lower layer to release the dedicated preamble (if provided in the LTM cell handover command), and / or (iv) initiates an SCG failure information procedure (e.g., as specified in 3GPP TS 38.331) to report a reconfiguration failure of the SCG with synchronization, after which the RRC reconfiguration procedure ends. In a further implementation (e.g., if MCG transmission is suspended), UE 102: (i) if the UE is in NR-DC, initiates a connection re-establishment procedure as specified in 3GPP TS 38.331, otherwise (ii) initiates a connection re-establishment procedure as specified in 3GPP TS 36.331 (e.g., if the UE is in (NG)EN-DC).

[0141] In a further implementation, if a timer (e.g., T304) expires while receiving RRCReconfiguration via another RAT (e.g., HO to NR failure), UE 102 resets the MAC and / or performs an action defined for this failure condition (e.g., as defined in the TS applicable to that other RAT). In some implementations, handover failure refers to a reconfiguration failure with synchronization.

[0142] If DU 174 configures UE 102 to perform the random access procedure as described above on the first cell, then when DU 174 receives message 3, message A, or a dedicated random access preamble during the random access procedure, DU 174 detects that UE 102 has accessed the first cell. If DU 174 configures UE 102 to skip the random access procedure, then when DU 174 receives the first transmission, DU 174 detects that UE 102 has accessed the first cell.

[0143] In some implementations, UE 102 sends the initial transmission (e.g., PUSCH transmission) on the first cell using a UL grant. In some implementations, the first LTM command includes a UL grant. In a further implementation, when UE 102 performs an LTM serving cell change to the first cell in response to a first LTM command, UE 102 receives a first DCI including a UL grant on the PDCCH of the first cell. In some implementations, when UE 102 switches to the first cell in response to a first LTM command, UE 102 attempts to receive the first DCI or a UL grant by monitoring one or more PDCCHs on the first cell according to LTM DU configuration 1. While monitoring one or more PDCCHs on the first cell, UE 102 receives the first DCI and its CRC on the PDCCH. If LTM DU configuration 1 includes a second C-RNTI, UE 102 uses the CRC and the second C-RNTI to determine that the first DCI was sent to UE 102. In the case where LTM DU configuration 1 does not include a second C-RNT, UE 102 uses CRC and the first C-RNTI to determine that the first DCI is sent to UE 102.

[0144] In some implementations, CU 172 transmits at least one first TCI state configuration (e.g., LTM TCI state configuration) of the first cell to UE 102 via DU 174. In some implementations, each of the first TCI state configurations configures the TCI state for UE 102 to transmit and / or receive data and / or control signals on the first cell. In some implementations, each TCI state associates or includes one or two DL RSs with a corresponding QCL type, and the DL RSs are associated with a specific cell in cells 1, ..., N. The DL RSs include SSBs and / or Tracking Reference Signals (TRS). In some implementations, CU 172 receives a DU-to-CU message including the first TCI state configuration from DU 174 and transmits an RRC message including the first TCI state configuration to UE 102 via DU 174. In some implementations, DU 174 includes the first TCI state configuration in a serving DU configuration (e.g., CellGroupConfig IE) and includes the serving DU configuration in the DU-to-CU message. In some implementations, the DU to CU message is either the DU to CU message of event 310 or the DU to CU message of event 314. In further implementations, the DU to CU message is a different message from the messages of events 310 and 314. For example, the DU to CU message is a UE context modification response message or a UE context modification request message.

[0145] In some implementations, DU 174 includes LTM DU configuration 1 in the first interface protocol IE / field of the DU-to-CU message in event 310, and includes the service DU configuration in the second interface protocol IE / field of the DU-to-CU message in event 314. In some implementations, if DU 174 includes the first TCI state configuration in the DU-to-CU message in event 314, events 312 (optional) and / or 314 (optional) in Figure 3 This is collectively referred to as the LTM TCI state configuration process 392.

[0146] In some implementations, CU 172 includes the service DU configuration in the RRC message. In a further implementation, CU 172 avoids including the service DU configuration in the container used for LTM (e.g., the first container). In still a further implementation, CU 172 includes LTM ID 1 and the first LTM TCI state configuration in an element used for LTM, an add or modify list used for LTM, or a container, and CU 172 includes this element, add or modify list used for LTM, or container in the RRC message, similar to element 1, the first add or modify list, or the first container, respectively. In some implementations, the RRC message is an RRC reconfiguration message for events 316 and / or 318. In some such cases, CU 172 includes the first LTM TCI state configuration in element 1. In a further implementation, the RRC reconfiguration is another RRC reconfiguration message ( Figure 3 (Not shown in the image). In some implementations, DU 174 also includes the first TCI state configuration in LTM DU configuration 1. In a further implementation, DU 174 avoids including the first TCI state configuration in LTM DU configuration 1.

[0147] 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 of a message (e.g., event 314), and includes the second F1AP IE / field in the DU to CU RRC information IE of the DU to CU message. In a further implementation, neither the first F1AP IE / field nor the second F1AP IE / field is the F1AP CellGroupConfig IE / field. In an even further implementation, 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.

[0148] In some implementations, DU 174 sends at least one first LTM TCI state activation / deactivation command (325) to UE 102 to activate some state configurations in the first LTM TCI state configuration. UE 102 activates some state configurations in the first LTM TCI state configuration in response to the first LTM TCI state activation / deactivation command. In some implementations, DU 174 instructs to deactivate some state configurations in the first LTM TCI state activation / deactivation command. In some implementations, DU 174 transmits one or more DL RSs on the candidate cell using the activated LTM TCI state configuration or the first LTM TCI state configuration. In some implementations, the DL RS includes one or more SSBs and / or one or more TRSs. In some implementations, UE 102 receives the DLRS using the activated LTM TCI state configuration. In a further implementation, UE 102 obtains L1 measurement results from the received DL RS and sends the L1 measurement results to DU 174. In a further implementation, UE 102 obtains the L3 measurement result from the received DL RS and transmits the L3 measurement result to CU 172 via DU 174. In some implementations, DU 174 avoids using the first LTM TCI state configuration to communicate with UE 102 on the serving cell. In some implementations, UE 102 avoids using the first LTM TCI state configuration to communicate with DU 174 on the serving cell.

[0149] In some implementations, each of the first LTM TCI state activation / deactivation commands is a MAC CE (e.g., a candidate cell TCI state activation / deactivation command). In some implementations, DU 174 includes LTM ID 1 in each of the first LTM TCI state activation / deactivation commands to identify the first LTM TCI state configuration. In a further implementation, DU 174 includes a candidate cell index (e.g., cell index 1) in each of the first LTM TCI state activation / deactivation commands to identify the first LTM TCI state configuration. In this case, the candidate cell index is different from LTM ID 1. In some implementations, each of the first LTM TCI state configurations includes a candidate cell index. Alternatively, CU 172 includes the candidate cell index in an RRC message that includes the first LTM TCI state configuration. For example, CU 172 includes the candidate cell index in element 1. In a further implementation, UE 102 and DU 174 determine the candidate cell index based on the PCI of the first cell. In such cases, base station 104 does not send candidate cell indexes to UE 102.

[0150] In some implementations, upon receiving the first LTM command or accessing the first cell (e.g., in response to this), UE 102 performs 336 DL reception (e.g., monitoring one or more PDCCHs) or UL transmission on the first cell using some or all of the first LTM TCI state configuration. In a further implementation, upon receiving the first LTM command or accessing the first cell (e.g., in response to this), UE 102 performs 336 DL reception (e.g., monitoring one or more PDCCHs) or UL transmission on the first cell without using the first LTM TCI state configuration.

[0151] In some implementations, each of the first LTM TCI state configurations includes a TCI state ID that identifies the corresponding TCI state configuration. For example, the first LTM TCI state configuration includes LTM TCI state configurations 1, ..., L, where L is a positive integer greater than zero. LTM TCI state configurations 1, ..., L include TCI state IDs 1, ..., L that respectively identify LTM TCI state configurations 1, ..., L. In some implementations, DU 174 includes TCI state ID 1 in the first LTM command to instruct UE 102 to activate LTM TCI state configuration 1 for communication on the first cell. UE 102 activates LTM TCI state configuration 1 in response to receiving TCI state ID 1 in the first LTM command. In some implementations, UE 102 uses (activated) LTM TCI state configuration 1 to access the first cell at event 332. In a further implementation, UE 102 accesses the first cell at event 332 without using the first LTM TCI state configuration. In some implementations, UE 102 communicates on the first cell using (activated) LTM TCI state configuration 1 at event 336. In some implementations, DU 174 communicates with UE 102 on the first cell using activated LTM TCI state configuration 1 at event 336.

[0152] In some implementations, at events 332 and / or 336, UE 102 uses LTM TCI state configuration 1 to monitor one or more PDCCHs, receive one or more DL RSs, receive one or more PDSCH transmissions, and / or send an initial transmission and / or one or more additional transmissions. In some implementations, DU 174 detects UE 102 accessing the first cell at event 332 and / or communicates with UE 102 on the first cell at event 336 based on LTM TCI state configuration 1. In a further implementation, at events 332 and / or 336, DU 174 receives an initial transmission and / or additional transmissions from UE 102 on the first cell based on TCI state configuration 1. In still a further implementation, at events 332 and / or 336, DU 174 sends one or more PDCCHs, one or more PDSCH transmissions, and / or one or more DL RSs based on LTM TCI state configuration 1.

[0153] In some implementations, in addition to TCI State ID 1, DU 174 also includes TCI State ID 2 in the first LTM command to instruct UE 102 to activate TCI State Configuration 2 for communication on the first cell. UE 102 activates LTM TCI State Configuration 1 in response to receiving TCI State ID 1 in the first LTM command, and activates LTM TCI State Configuration 2 in response to receiving TCI State ID 2 in the first LTM command. After receiving the first LTM command (e.g., in response to this), UE 102 uses the activated LTM TCI State Configurations 1 and 2 to access the first cell and / or communicate on the first cell (e.g., at events 332 and / or 336, respectively). After sending the first LTM command at 330 or receiving the acknowledgment at 331 (e.g., in response to this), DU 174 communicates with UE 102 on the first cell using the activated LTM TCI State Configurations 1 and 2 at events 332 and / or 336.

[0154] In some implementations, after applying one or more TCI state configurations (e.g., TCI state configuration 1 and / or 2) indicated in an LTM command (e.g., a first LTM command), UE 102 spends time (e.g., beam application time or cell handover delay) to acquire the TCI state configured in the TCI state configuration (e.g., synchronizing and / or receiving the DL RS configured in the TCI state configuration). The time for acquiring the TCI state is considered the handover delay. In such cases, DU 174 takes this handover delay into account when communicating with UE 102 on the first cell in events 332 and / or 336. For example, after sending the first LTM command 330 or receiving acknowledgment 331 331, DU 174, after the handover delay, uses the active LTM TCI state configuration 1 and / or 2 to begin communicating with UE 102 on the first cell in events 332 and / or 336.

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

[0156] In a further implementation, UE 102 uses LTM TCI state configuration 1 to monitor one or more PDCCHs from DU 174 on the first cell, and uses LTM TCI state configuration 2 to receive one or more PDSCH transmissions from DU 174 on the first cell. Each of the control signals includes a DCI and a scrambled CRC for that DCI. In this implementation, DU 174 uses LTM TCI state configuration 1 to send one or more control signals to UE 102 on one or more PDCCHs on the first cell, and uses LTM TCI state configuration 2 to send one or more PDSCH transmissions to UE 102 on the first cell. In some implementations, UE 102 uses LTM TCI state configuration 1 to send an initial transmission and / or one or more additional transmissions to DU 174 on the first cell. In this implementation, DU 174 uses LTM TCI state configuration 1 to receive an initial transmission and / or one or more additional transmissions from UE 102 on the first cell. In some further implementations, UE102 uses LTM TCI state configuration 2 to send an initial transmission and / or one or more additional transmissions to DU 174 on the first cell. In such implementations, DU 174 uses LTM TCI state configuration 2 to receive an initial transmission and / or one or more additional transmissions from UE 102 on the first cell.

[0157] In a further implementation, UE 102 monitors one or more PDCCHs on the first cell using TCI state configuration 1 and TCI state configuration 2, and transmits an initial transmission and / or one or more additional transmissions on the first cell using one of TCI state configuration 1 and TCI state configuration 2. In some such implementations, DU 174 transmits one or more control signals on one or more PDCCHs, and receives an initial transmission and / or one or more additional transmissions from UE 102 on the first cell using LTM TCI state configuration 2. Each of the control signals includes a DCI and a scrambled CRC for that DCI.

[0158] In some implementations, CU 172 receives a CN-to-BS message including the UE capability IE of UE 102 from a CN (e.g., CN 110 or AMF 164) (e.g., during event 302). For example, the CN-to-BS message is an NG Application Protocol (NGAP) message. In a further implementation, CU 172 receives a BS-to-BS message including the UE capability IE from another base station (e.g., base station 106) (e.g., before event 302). In still a further implementation, CU 172 receives a UE capability information message including the UE capability IE from UE 102 via DU 174 or another DU (e.g., during event 302). In some implementations, DU 174 receives the UE capability IE of UE 102 (e.g., UE-NR-Capability or UE-6G-Capability) from CU 172 (e.g., during event 302).

[0159] In some implementations, the UE capability IE indicates that UE 102 supports LTM without RACH. Therefore, based on the indication of supporting LTM without a random access channel (RACH), DU 174 configures and / or activates one or more LTM TCI state configurations for UE 102 as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support LTM without RACH, DU 174 avoids configuring and / or activating LTM TCI state configurations for UE 102. For example, DU 174 avoids including the LTM TCI state configuration of UE 102 in the aforementioned DU to CU message. Therefore, CU 712 does not send the LTM TCI state configuration to UE 102. For example, CU 712 does not include the LTM TCI state configuration in the RRC reconfiguration messages of events 316 and / or 318.

[0160] In a further implementation, the UE capability IE indicates that the UE supports Early Timing Advance (TA) acquisition. Based on the indication of supporting Early TA acquisition, DU 174 configures and / or activates one or more LTM TCI state configurations for UE 102 as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support Early TA acquisition, DU 174 avoids configuring and / or activating LTM TCI state configurations for UE 102. For example, DU 174 avoids including the LTM TCI state configuration of UE 102 in the aforementioned DU to CU message. Therefore, CU 712 will not send the LTM TCI state configuration to UE 102. For example, CU 172 does not include the LTM TCI state configuration in the RRC reconfiguration messages of events 316 and / or 318.

[0161] In a further implementation, the UE capability IE indicates that the UE supports UE-based TA acquisition (e.g., the UE acquires UL synchronization based on Reference Signal Time Difference (RSTD) measurements). Based on the indication of supporting UE-based TA acquisition, DU 174 configures and / or activates one or more LTM TCI state configurations for UE 102 as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support UE-based TA acquisition, DU 174 avoids configuring and / or activating LTM TCI state configurations for UE 102. For example, DU 174 avoids including the LTM TCI state configuration of UE 102 in the aforementioned DU to CU message. Therefore, CU 712 will not send the LTM TCI state configuration to UE 102. For example, CU 172 does not include the LTM TCI state configuration in the RRC reconfiguration messages of events 316 and / or 318.

[0162] In a further implementation, the UE capability IE indicates that the UE supports the LTM TCI state. Based on the indication of supporting the LTM TCI state, DU 174 configures and / or activates one or more LTM TCI state configurations for UE 102 as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support the LTM TCI state, DU 174 avoids configuring and / or activating the LTM TCI state configuration for UE 102. For example, DU 174 avoids including the LTM TCI state configuration of UE 102 in the aforementioned DU to CU message. Therefore, CU 712 will not send the LTM TCI state configuration to UE 102. For example, CU 172 does not include the LTM TCI state configuration in the RRC reconfiguration messages of events 316 and / or 318.

[0163] In some implementations, DU 174 is unsure whether to provide LTM TCI state configuration to UE 102. As described above, DU 174 provides LTM TCI state configuration for UE 102 to CU 172. CU 172 determines whether to send the first LTM TCI state configuration to UE 102. In some implementations, based on an indication that RACH-free LTM is supported, CU 172 sends the first LTM TCI state configuration to UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support RACH-free LTM, CU 172 avoids sending the LTM TCI state configuration to UE 102. For example, CU 172 avoids sending the first LTM TCI state configuration to UE 102. For example, CU 172 avoids including the first LTM TCI state configuration in the RRC reconfiguration messages of events 316 and / or 318.

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

[0165] In a further implementation, based on an indication that UE-based TA acquisition is supported, CU 172 sends a first LTM TCI state configuration to UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support UE-based TA acquisition, CU 172 avoids sending the LTM TCI state configuration to UE 102. For example, CU 172 avoids sending the first LTM TCI state configuration to UE 102. As a further example, CU 172 avoids including the first LTM TCI state configuration in the RRC reconfiguration messages of events 316 and / or 318.

[0166] In a further implementation, based on an indication that LTM TCI state is supported, CU 172 sends the first LTM TCI state configuration to UE 102, as described above. In some implementations, if the UE capability IE indicates that UE 102 does not support LTM TCI state, CU 172 avoids sending the LTM TCI state configuration to UE 102. For example, CU 172 avoids sending the first LTM TCI state configuration to UE 102. As a further example, CU 172 avoids including the first LTM TCI state configuration in the RRC reconfiguration messages of events 316 and / or 318.

[0167] In some alternative implementations, DU 174 does not activate or determines that the (LTM) TCI state configuration is inactive in the first LTM command. In such cases, DU 174 does not include the TCI state ID in the first LTM command. Therefore, when UE 102 receives a first LTM command that does not include the TCI state configuration, UE 102 avoids using the first LTM TCI configuration to access the first cell and / or communicate on the first cell.

[0168] In some implementations, if the UE capability IE indicates that UE 102 does not support LTM without RACH, then DU 174 does not include the TCI state ID in the first LTM command or avoids including the TCI state ID in the first LTM command. Otherwise, if the UE capability IE indicates that UE 102 supports LTM without RACH, then DU 174 includes one or more TCI state IDs (e.g., TCI state ID1 and / or TCI state ID2) in the first LTM command, as described above.

[0169] In a further implementation, if DU 174 does not configure the LTM TCI state configuration of the first cell for UE 102, then DU 174 does not include the TCI state ID in the first LTM command or avoids including the TCI state ID in the first LTM command. Otherwise, if DU 174 configures one or more LTM TCI state configurations (e.g., the first LTM TCI state configuration), then DU 174 includes one or more LTM TCI state IDs (e.g., TCI state ID 1 and / or TCI state ID 2) in the first LTM command.

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

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

[0172] In a further implementation, if the UE capability IE indicates that UE 102 does not support LTM TCI state, then DU 174 does not include the TCI state ID in the first LTM command or avoids including the TCI state ID in the first LTM command. Otherwise, if the UE capability indicates that UE 102 supports LTM TCI state, then DU 174 includes TCI state ID 1 and / or TCI state ID 2 in the first LTM command, as described above.

[0173] In some implementations, UE 102 stops using or disables the first non-LTMTCI configuration when it receives the first LTM command.

[0174] After successfully accessing the first cell, UE 102 communicates with DU 174 on the first cell at event 336 using LTM DU configuration 1 and / or referencing LTM DU configuration, and communicates with CU 172 via DU 174. In this case, DU 174 communicates with UE 102 on the first cell at event 336 using LTM DU configuration 1. In some implementations, UE 102 communicates PUSCH transmissions, PDSCH transmissions, PUCCH transmissions, PDCCH transmissions, and / or sounding reference signal (SRS) transmissions with DU 174 on the first cell at event 336.

[0175] When UE 102 receives the reference LTM DU configuration as described above, UE 102 communicates with DU 174 on the first cell at event 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 at event 336 according to the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration. Similarly, DU 174 communicates with UE 102 on the first cell at event 336 according to LTM DU configuration 1 and at least a portion of the reference LTM DU configuration. In other words, DU 174 communicates with UE 102 at event 336 according to the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration.

[0176] If UE 102 neither receives LTM CU Configuration 1 nor the reference LTM CU Configuration, UE 102 communicates with CU 172 via DU 174 at event 336 using the serving CU configuration. Correspondingly, if CU 172 neither sends LTM CU Configuration 1 nor the reference CU configuration to UE 102, CU 172 communicates with UE 102 via DU 174 at event 336 using the serving CU configuration. If UE 102 receives both LTM CU Configuration 1 and the reference LTM CU configuration from CU 172, UE 102 communicates with CU 172 via DU 174 at event 336 using LTM CU Configuration 1 and at least a portion of the reference LTM CU configuration not enhanced by LTM CU Configuration 1. In this case, CU 172 communicates with UE 102 via DU 174 at event 336 using LTM CU configuration 1 and at least a portion of a reference LTM CU configuration not enhanced by LTM CU configuration 1.

[0177] If UE 102 receives LTM CU Configuration 1 from CU 172 but does not receive the reference LTM CU Configuration, UE 102 communicates with CU 172 via DU 174 using LTM CU Configuration 1 at event 336. In this case, CU 172 communicates with UE 102 via DU 174 using LTM CU Configuration 1 at event 336. If LTM CU Configuration 1 is a full configuration (i.e., complete configuration), then UE 102 and CU 172 communicate with each other via DU 174 using LTM CU Configuration 1 instead of the serving CU configuration at event 336. In some implementations, if UE 102 does not receive the reference LTM CU Configuration from base station 104, then UE 102 determines that LTM CU Configuration 1 is a full configuration. Correspondingly, if CU 172 determines that it wants to configure LTM CU configuration 1 as a full configuration, then 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 (e.g., at event 316) to indicate that LTM CU configuration 1 is a full configuration. If LTM CU configuration 1 is an incremental configuration for enhancing the service CU configuration, then UE 102 and CU 172 communicate with each other via DU 174 at event 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, then UE 102 determines that LTM CU configuration 1 is an incremental configuration for enhancing the service CU configuration. Correspondingly, if CU 172 determines that LTM CU configuration 1 should be configured as an incremental configuration for enhanced service CU configuration, then CU 172 does not send a reference LTM CU configuration to UE 102. In some implementations, CU 172 indicates that LTM CU configuration 1 is an incremental configuration for enhanced service CU configuration by excluding a first indication in (e.g., the LTM CU configuration 1, first container, element 1, and / or RRC reconfiguration message of event 316). Alternatively, CU 172 includes a second indication (e.g., a field or IE) in (e.g., the LTM CU configuration 1, first container, element 1, or RRC reconfiguration message of event 316) to indicate that LTM CU configuration 1 is an incremental configuration for enhanced service CU configuration. In some implementations, CU 172 indicates that LTM CU configuration 1 is a full configuration by excluding a second indication in (e.g., the LTM CU configuration 1, first container, element 1, and / or RRC reconfiguration message of event 316).

[0178] 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 at event 336 using the reference LTM CU configuration. In this case, CU 172 communicates with UE 102 via DU 174 at event 336 using the reference LTM CU configuration. If the reference LTM CU configuration is a full configuration, UE 102 and CU 172 communicate with each other via DU 174 at event 336 using the reference LTM CU configuration instead of the serving CU configuration. In some implementations, UE 102 and CU 172 determine that reference LTM CU configuration 1 is a full configuration (e.g., as specified in 3GPP TS 38.331). In other implementations, CU 172 includes a first indication (e.g., a field or IE) in the reference LTM CU configuration (e.g., at event 316), the first container, or the RRC reconfiguration message to indicate that the reference LTM CU configuration is a full configuration. If the reference LTM CU configuration is an incremental configuration for enhancing the service CU configuration, then UE 102 and CU 172 communicate with each other via DU 174 at event 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 (e.g., at event 316), the first container, element 1, and / or the RRC reconfiguration message. Alternatively, CU 172 may include a second indication (e.g., a field or IE) in the reference LTM CU configuration, first container, element 1, or RRC reconfiguration message (e.g., for event 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 a full configuration by excluding the second indication in the reference LTM CU configuration, first container, element 1, and / or RRC reconfiguration message (e.g., for event 316).

[0179] 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 CU configuration at event 336. In this case, CU 172 communicates with UE 102 via DU 174 using the serving CU configuration at event 336.

[0180] In some implementations, DU 174 includes or configures at least one second non-LTM TCI state configuration of the first cell in LTM DU configuration 1. In some implementations, when communicating with UE 102 (e.g., at event 332 or 336), DU 174 sends a second non-LTM TCI state activation / deactivation command to UE 102 on the first cell to activate the second non-LTM TCI state configuration and / or deactivate the activated LTM TCI state configuration. In some implementations, DU 174 includes the serving cell index of the first cell in the second non-LTM TCI state activation / deactivation command. DU 174 includes the serving cell index in LTM DU configuration 1. In some implementations, UE 102 stops using or deactivates the (activated) LTM TCI state configuration in response to receiving the second non-LTM TCI state activation / deactivation command. In some implementations, the second non-LTM TCI state activation / deactivation command is a MAC CE. In a further implementation, the MAC CE can be a UE-specific PDSCH MAC CE TCI state activation / deactivation, a UE-specific PDCCH MAC CE TCI state indication, a PUCCH spatial relationship activation / deactivation MAC CE, a UE-specific PDSCH MAC CE enhanced TCI state activation / deactivation, an enhanced PUCCH spatial relationship activation / deactivation MAC CE, a UE-specific PDCCH MAC CE enhanced TCI state indication, a PUCCH spatial relationship activation / deactivation for multiple TRPPUCCH repeated MAC CEs, or a unified TCI state activation / deactivation MAC CE.

[0181] In some implementations, the second non-LTM state configuration is a Rel-15 / 16 TCI state configuration (i.e., not a unified joint / DL / UL TCI state). In some implementations, this means that BS 104 configures a Rel-15 / 16 beam indication frame for the first cell. In some implementations, the non-LTM TCI state configuration activated / indicated by the second non-LTM TCI state activation / deactivation command applies only to channels or RSs (PDSCH / PDCCH / CSI-RS / PUCCH / SRS). In such implementations, if UE 102 receives a second non-LTM TCI state activation / deactivation command, the UE stops or uses the first LTM TCI state for the channel or RS that is applicable to sharing / following / applying the unified TCI state. For example, if UE 102 receives an enhanced TCI state indication for a UE-specific PDCCH MAC CE, UE 102 stops or uses the first LTM TCI state for at least one of the other channels or RSs (e.g., PDSCH, PUSCH, PUCCH, CSI-RS, or SRS) that also apply the shared / followed / applied unified TCI state. In some implementations, if UE 102 receives a second non-LTM TCI state activation / deactivation command, UE 102 deactivates the activated first LTM TCI state configuration.

[0182] In some implementations, the second non-LTM TCI state configuration includes at least one TCI state configured in the first LTM TCI state configuration. In a further implementation, the TCI states in the second non-LTM TCI state configuration are different from the TCI states in the first LTM TCI state configuration. In some implementations, the second non-LTM TCI state configuration configures more TCI states than the first LTM TCI state configuration. In a further implementation, the TCI states in the second non-LTM TCI state configuration are the same as the TCI states in the first LTM TCI state configuration. In some implementations, BS 104 / CU 172 / DU 174 informs UE 102 in an RRC message or signal whether the first LTM TCI state configuration is the same as or different from the second non-LTM TCI state configuration, or whether it is a subset of the second non-LTM TCI state configuration.

[0183] In some implementations, the first LTM TCI state configuration of the first cell is a subset of the second non-LTTM TCI state configuration of the first cell. In some implementations, the TCI state ID of the first LTM TCI state configuration of the first cell does not overlap with or match the TCI state ID of the second non-LTTM TCI state configuration of the first cell. This means that in some implementations, when UE 102 receives a second non-LTTM TCI state activation / deactivation command, UE 102 considers / determines that the TCI state ID indicated in the second non-LTTM TCI state activation / deactivation command refers to either the first LTM TCI state configuration or the second non-LTTM TCI state configuration of the first cell. For example, the range of the TCI state ID of the first LTM TCI state configuration of the first cell is #000 to #007; the range of the TCI state ID of the second non-LTTM TCI state configuration of the first cell is #008 to #015. In such an example, if the second non-LTM TCI state activation / deactivation command indicates TCI state ID #001, then UE 102 activates the first LTM TCI state configuration identified by TCI state ID #001; if the second non-LTM TCI state activation / deactivation command indicates TCI state ID #012, then UE 102 activates the second non-LTM TCI state configuration identified by TCI state ID #012. In some implementations, for non-LTM TCI state activation / indication purposes, UE 102 combines or links the first LTM TCI state configuration and the second non-LTM TCI state configuration of the first cell. In some implementations, UE 102 considers or determines that the first LTM TCI state configuration of the first cell is the non-LTM TCI state configuration of the first cell.

[0184] In some implementations, DU 174 does not include or configure at least one second non-LTM TCI state configuration of the first cell in LTM DU configuration 1. In such cases, UE 102 considers or determines that at least one first TCI state configuration (e.g., LTM TCI state configuration) of the first cell is a non-LTM TCI state configuration of the first cell. In some such implementations, this means that when UE 102 receives a second non-LTM TCI state activation / deactivation command, UE 102 considers / determines that the TCI state ID indicated in the second non-LTM TCI state activation / deactivation command refers to the first LTM TCI state configuration of the first cell. For example, if the second non-LTM TCI state activation / deactivation command indicates TCI state ID #000, then UE 102 activates and / or applies the first TCI state configuration (e.g., LTM TCI state configuration) identified by TCI state ID #000 and performs non-LTM communication in the first cell.

[0185] In some implementations, if the first LTM TCI state configuration is associated with or includes an SSB corresponding to QCL type A, UE 102 avoids using this TCI state configuration for non-LTM purposes or communications in the first cell. In some implementations, UE 102 considers or determines that the first LTM TCI state configuration of the first cell is a non-LTM TCI state configuration of the first cell unless it includes or is associated with an SSB corresponding to QCL type A.

[0186] In some implementations, when DU 174 communicates with UE 102 on the first cell or simultaneously (e.g., at events 332 and / or 336), DU 174 avoids sending an LTM TCI state activation / deactivation command to UE 102 to activate the LTM TCI state configuration of the first cell or associated with LTM ID 1. In a further implementation, when DU 174 communicates with UE 102 on the first cell or simultaneously (e.g., at events 332 and / or 336), DU 174 sends a second LTM TCI state activation / deactivation command to UE 102 to activate at least one LTM TCI state configuration in the first LTM TCI state configuration that was not activated by the first LTM command. In response to the second LTM TCI state activation / deactivation command, UE 102 activates the LTM TCI state configuration indicated in the second LTM TCI state activation / deactivation command. In some implementations, DU 174 disables the LTM TCI state configuration activated in the first LTM command in the second LTM TCI state activation / deactivation command. In such cases, UE 102 disables the LTM TCI state configuration activated in the first LTM command in response. UE 102 and DU 174 communicate with each other on the first cell using the LTM TCI state configuration activated by the second LTM TCI state activation / deactivation command, as described above.

[0187] In some implementations, UE 102 sends an RRC message (e.g., an RRC reconfiguration complete message) to CU 172 via DU 174 and the first cell to instruct UE 102 to apply LTM DU configuration 1. In some implementations, when UE 102 performs the 332 random access procedure, UE 102 includes 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 the 332 random access procedure, UE 102 includes the RRC message in one of at least one PUSCH transmissions. 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 sends the RRC message to base station 104 via cell 124A. When DU 174 receives an RRC message, DU 174 sends the RRC message to CU 172.

[0188] In a further implementation, 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 some such implementations, UE 102 includes or sends data in message 3, message A, or PUSCH transmission as described above. In some implementations, UE 102 generates a MAC PDU and / or RLC PDU that includes data, and sends or includes the MAC PDU and / or RLC PDU in PUSCH transmission. For example, in some implementations, the data is 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. In some implementations, the MM message is a 5G MM message or a 6G MM message, and the SM message is a 5G SM message or a 6G SM message. When DU 174 receives data, it sends the data to CU 172.

[0189] In some implementations, when DU 174 determines in event 332 or 336 that UE 102 has successfully connected to the first cell, DU 174 sends 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 includes the cell ID 1 of the first cell in the DU to CU message of event 334. In some implementations, the cell ID is 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. In some implementations, when DU 174 determines in event 332 or 336 that UE 102 has successfully connected to the first cell, DU 174 sends a DL data delivery status message or frame to CU 172 (e.g., the UP of CU 172). In some implementations, when CU 172 receives message 329 (DU to CU), CU 172 stops or suspends sending DL data for UE 102 to DU 174 until it receives message 334 (DU to CU). In a further implementation, CU 172 stops or suspends sending because DU 174 cannot buffer DL data for UE 102 during LTM execution in events 330 and / or 332. After receiving message 334 (DU to CU), CU 172 resumes or continues sending DL data for UE 102 to DU 174. In some implementations, when CU 172 receives message 329 (DU to CU), CU 172 continues sending DL data for UE 102 to DU 174. In some implementations, CU 172 continues sending because DU 174 is able to buffer DL data for UE 102 during LTM execution in events 330 and / or 332. When or after DU 174 detects that UE 102 has accessed cell 1, DU 174 sends DL data to UE 102 via cell 1.

[0190] 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 stops communicating with UE 102 on cell 124A and / or releases the resources of cell 124A configured for UE 102.

[0191] In some implementations, DU 174 generates some or all of LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as a full configuration (i.e., a complete configuration without referencing the reference LTM DU configuration). If LTM DU configuration 1 is a full configuration, then UE 102 and DU 174 communicate with each other at event 336 based on LTM DU configuration 1 rather than the serving DU configuration. In some implementations, DU 174 includes an indication in LTM DU configuration 1 that it is a full configuration. In some implementations, in each of LTM DU configurations 2, ..., N, DU 174 includes an indication for indicating that the corresponding DU configuration is a full configuration. In some implementations, each of the indications in LTM DU configurations 1, ..., N is a field or IE (i.e., the same field or IE). In some implementations, CU 172 includes a single indication that LTM DU configurations 1 and / or 2, ..., N are fully configured in the RRC reconfiguration messages of events 316 and 318. In some implementations, in the case of a second container, CU 172 includes a single indication that LTM DU configurations 2, ..., N are fully configured in an additional RRC reconfiguration message. In a further implementation, CU 172 includes a single indication that LTM DU configurations 1 and / or 2, ..., N are fully configured in a first container. In still a further implementation, for each of LTM DU configurations 2, ..., N, CU 172 includes a specific indication that the corresponding LTM DU configuration is fully configured in the first container. In the case of a second container, in some implementations, CU 172 includes a single indication that LTM DU configurations 2, ..., N are fully configured in the second container. In a further implementation, CU 172 includes an indication in element 1 that LTM DU configuration 1 is fully configured. In some implementations, in each of elements 2, ..., N, CU 172 includes an indication that the corresponding LTM DU configuration is fully configured. In some implementations, UE 102 determines that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are fully configured based on the above indications. In some implementations, each of the above indications differs from the fullConfig field defined in the current 3GPP specification. In some implementations, each of the above indications is the fullConfig field defined in the current 3GPP specification. If LTM DU configuration 1 is fully configured, and a reference LTM DU configuration is received from base station 104 (e.g., in RRC reconfiguration message 318), then UE 102 (e.g., in event 336) does not apply the reference LTM DU configuration.In such cases, in some implementations, DU 174 does not include the reference LTMDU configuration in the first DU to CU message of event 310.

[0192] In some implementations, DU 174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as incremental configurations that enhance at least 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 at least a portion of the reference LTM DU configuration. Therefore, UE 102 and DU 174 communicate with each other at event 336 based on LTM DU configuration 1 and the unenhanced portion of the reference LTM DU configuration. In some implementations, LTM DU configuration 1 and / or 2, ..., N, the first container, the second container, or element 1, ..., N excludes indications that LTM DU configuration 1 and / or 2, ..., N is a full configuration to indicate that LTM DU configuration 1 and / or 2, ..., N is an incremental configuration. In some implementations, UE 102 determines that each of LTM DU configurations 1 and / or 2, ..., N, the first container, the second container, or elements 1 and / or 2, ..., N excludes this indication to determine that each of LTM DU configurations 1 and / or 2, ..., N is an incremental configuration.

[0193] 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 full 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 full configurations.

[0194] In a further implementation, if UE 102 does not receive a reference LTM DU configuration for LTM DU configuration 1 and / or LTM DU configuration 2, ..., N, then UE 102 determines that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are incremental configurations for enhancing the service DU configuration. In this case, UE 102 communicates with DU 174 at event 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 does not receive a reference LTM DU configuration for UE 102 from CU 172), then DU 174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as incremental configurations for enhancing the service DU configuration. In this case, DU 174 communicates with UE 102 at event 336 according to LTM DU configuration 1 and at least a portion of the service DU configuration.

[0195] In some implementations, UE 102 uses a UE MAC entity (e.g., MAC 204B) to communicate with the DUMAC entity (e.g., MAC 204B) of DU 174 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). In some implementations, UE 102 resets the UE MAC entity after receiving a first LTM command or in response to receiving a first LTM command and before performing a random access procedure (332) or communication with DU 174 via the first cell (336). In some implementations, DU 174 resets the DU MAC entity after sending a first LTM command, receiving 331 to acknowledge, or determining that UE 102 is connected to the first cell (e.g., in response to this).

[0196] In some implementations, when UE 102 resets the UE MAC entity, UE 102 performs at least one of the following actions (i.e., UE MAC reset or full UE MAC reset) on the UE MAC entity: (i) initializing the Bj of the configured logical channel to zero; (ii) stopping one or more timers; (iii) assuming that timeAlignmentTimer has expired if UE 102 is configured in a configuration (e.g., configuration 1) to perform a random access procedure (e.g., event 332); (iv) setting the New Data Indicator (NDI) of the UL HARQ process to a value of 0; (v) setting the NDI of the HARQ process ID to a value of 0 for monitoring the PDCCH in sidelink resource allocation mode 1; (vi) refreshing the message 3 (Msg3) buffer; (vii) refreshing message A. (MSGA) buffer; (viii) cancel (if any) the triggered scheduling request procedure; (ix) cancel (if any) the triggered buffer status report procedure; (x) cancel (if any) the triggered power headroom report procedure; (xi) cancel (if any) the triggered consistent LBT failure; (xii) cancel any triggered BFR; (xiii) cancel (if any) the triggered sidelink buffer status report procedure; (xiv) cancel (if any) the triggered preemptive buffer status report procedure; (xv) cancel (if any) the triggered timing advance report procedure; (xvi) cancel (if any) the triggered recommended bit rate query procedure; (xvii) cancel (if any) the triggered configured uplink grant acknowledgment; (xviii) cancel (if any) the triggered configured sidelink grant acknowledgment; (xix) cancel any triggered expected protection symbol query; (xx) cancel (if any) the triggered location measurement gap activation / deactivation request procedure; (xxi) refresh for DL (xxii) For each of the DL HARQ processes, treat the next received transmission for TB as the first transmission; (xxiii) Release (if any) the temporary C-RNTI; and / or (xxiv) reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0197] 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): (i) stopping one or more timers; (ii) assuming that the timeAlignmentTimer initiated and / or maintained by DU 174 for UE 102 has expired if UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1); (iii) setting the NDI of the DL HARQ process to a value of 0; (iv) flushing the soft buffer for the UL HARQ process; (v) for each of the UL HARQ processes, treating the next received transmission for the TB as the first transmission; and (vi) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0198] Depending on the implementation, UE 102 determines 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 a further implementation, when UE 102 resets the UE MAC entity as described above, UE 102 partially resets the UE MAC entity (i.e., a partial UE MAC reset). In a partial UE MAC reset, UE 102 performs some or a subset or part of the actions in a full UE MAC reset.

[0199] In a further implementation, a partial UE MAC reset includes at least one of the following actions: (i) 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 of UE 102 is considered to have expired; (ii) the Msg3 buffer is flushed; (iii) the MSGA buffer is flushed; (iv) the temporary C-RNTI is released (if any); and / or (v) one or more counters are reset (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0200] In further implementations, some UEs MAC reset further includes at least one of the following actions: (i) canceling (if any) the triggered scheduling request procedure; (ii) canceling (if any) the triggered buffer status report procedure; (iii) canceling (if any) the triggered power headroom report procedure; (iv) canceling (if any) the triggered consistent LBT failure; (v) canceling (if any) the triggered BFR; (vi) canceling (if any) the triggered sidelink buffer status report procedure; (vii) canceling (if any) the triggered preemptive buffer status report procedure; (viii) canceling (if any) the triggered timing advance report procedure; (ix) canceling (if any) the triggered recommended bit rate query procedure; (x) canceling (if any) the triggered configured uplink authorization confirmation; (xi) canceling (if any) the triggered configured sidelink authorization confirmation; (xii) canceling (if any) the triggered expected protection symbol query; and / or (xiii) canceling (if any) the triggered location measurement gap activation / deactivation request procedure.

[0201] In a further implementation, the partial UE MAC reset further includes at least one of the following actions: (i) stopping the first portion of one or more timers and retaining the remainder of one or more timers; (ii) setting the New Data Indicator (NDI) of the UL HARQ process to the value 0; (iii) setting the NDI of the HARQ process ID to the value 0 for monitoring the PDCCH in sidelink resource allocation mode 1; (iv) refreshing the soft buffer for the DL HARQ process; and / or (v) for each of the DL HARQ processes, treating the next received transmission for the TB as the first transmission.

[0202] Depending on the implementation, DU 174 determines 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 a further implementation, 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.

[0203] In a further implementation, a partial DU MAC reset includes at least one of the following actions in the partial MAC reset: (i) if UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), then the timeAlignmentTimer initiated and / or maintained by DU 174 for UE 102 is considered to have expired and / or (ii) one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0204] In a further implementation, a partial DU MAC reset includes at least one of the following actions (i.e., DU MAC reset) for the MAC entity: (i) stopping the first portion of one or more timers and retaining the remainder of one or more timers; (ii) setting the NDI of the DL HARQ process to the value 0; (iii) flushing the soft buffer for the UL HARQ process; (iv) for each of the UL HARQ processes, treating the next received transmission for the TB as the first transmission; and (v) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0205] In some 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 at 330 and receiving 331 to acknowledge or determine that UE 102 is connected to the first cell (e.g., in response to this). In other words, UE 102 communicates with DU 174 on the first cell using the UE MAC entity (e.g., not reset). Similarly, DU 174 communicates with UE 102 on the first cell during or after the random access procedure of event 332 or after determining that UE 102 is connected to the first cell.

[0206] In some implementations, UE 102 uses at least one UE RLC entity (e.g., RLC 206B) to communicate RLC PDUs (e.g., events 302, 304, 318, 320, 324, 330, and / or 331) with at least one DU RLC entity (e.g., RLC 206B) of DU 174. In some implementations, UE 102 reconstructs some or all of the at least one UE RLC entity after receiving a first LTM command or in response to receiving a first LTM command and before performing 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 330 first LTM command, receiving 331 to acknowledge or determine that UE 102 is connected to the first cell (e.g., in response to this).

[0207] In some implementations, LTM DU configuration 1 includes one or more RLC reconstruction indications (e.g., reestablishRLC fields) configuring UE 102 to rebuild some or all of at least one UE RLC entity. If LTM DU configuration 1 includes an RLC reconstruction indication for a first UE RLC entity among at least one UE RLC entity used by UE 102 to communicate with DU 174 using the RLC PDU, 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 rebuilds the first UE RLC entity before performing the 332 random access procedure or before performing the 336 communication with DU 174 via the first cell. In a further implementation, UE 102 rebuilds 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.

[0208] 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: (i) discarding the RLC SDU, RLC SDU segment, and RLC PDU (if any); (ii) stopping and resetting the timer (if it is running); and (iii) resetting the state variables to their initial values. In some implementations, the state variables and timers are predefined (e.g., defined in 3GPP TS 38.322).

[0209] 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 when 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 when 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 reconstructs the first UE RLC entity of UE 102 when 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 when or when the first LTM command is received.

[0210] 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 further implementations, the acknowledgment is a MAC CE. In some implementations, the acknowledgment is a PUCCH transmission. In some implementations, when base station 104 reconstructs the first DU RLC entity, DU 174 performs at least one of the following actions on the first DU RLC entity: (i) discarding the RLC SDU, RLC SDU segment, and RLC PDU (if any); (ii) stopping and resetting a timer (if it is running); and / or (iii) resetting the state variables to their initial values. In some implementations, the state variables and timers are predefined (e.g., in 3GPP TS 38.322).

[0211] In some implementations, UE 102 avoids rebuilding some or all of at least one UE RLC 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 331 to acknowledge or determine that UE 102 is connected to the first cell (e.g., in response to this). In other words, UE 102 communicates with DU 174 on the first cell using some or all of at least one UE RLC entity (e.g., not rebuilt). For example, some or all of at least one UE RLC entity includes a first UE RLC entity and / or a second UE RLC entity. Similarly, DU 174 communicates with UE 102 on the first cell during or after random access procedure 332 or after determining that UE 102 is connected to the first cell using some or all of at least one DU RLC entity (e.g., not rebuilt). For example, some or all of at least one DU RLC entity includes a first DU RLC entity and / or a second DU RLC entity.

[0212] In some implementations, at event 302, UE 102 uses at least one UE PDCP entity (e.g., PDCP 210) to communicate UL PDCP PDUs and / or DL ​​PDCPPDUs with at least one CU PDCP entity (e.g., PDCP 210) of CU 172. In some implementations, UE 102 performs a PDCP recovery procedure for some or all of the at least one UE PDCP entity after receiving or in response to receiving a first LTM command. For example, UE 102 performs a PDCP recovery procedure for the first UE PDCP entity among the at least one UE PDCP entities after receiving 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. In some implementations, after performing or in response to performing the PDCP recovery procedure, UE 102 retransmits at least a portion of the UL PDCP PDUs to CU 172 via DU 174 and the first cell at event 336. Similarly, CU 172 performs a PDCP recovery procedure for some or all of at least one CU PDCP entity after sending the first LTM command or in response to sending the first LTM command. For example, CU 172 performs a PDCP recovery procedure for the first CU PDCP entity among at least one CU PDCP entity after sending the first LTM command or in response to sending the first LTM command. In some implementations, CU 172 performs PDCP recovery procedure 329 or 334 for the first CU PDCP entity in response to receiving a DU to CU message. In a further implementation, CU 172 performs PDCP recovery procedure for the first CU PDCP entity in response to receiving a DL data delivery status message. In some implementations, CU 172 reconstructs the first CU PDCP entity during the PDCP recovery procedure. In a further implementation, after or in response to the execution of the PDCP recovery procedure, CU 172 retransmits at least a portion of the DL PDCP PDU to UE 102 via DU 174 and the first cell in event 336.

[0213] In some 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 (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 (329 or 340). In other words, UE 102 communicates with CU 172 via DU 174 and the first cell using some or all of at least one UE PDCP entity (e.g., not rebuilt). For example, some or all of the at least one UE PDCP entity includes a first UE PDCP entity and / or a second UE PDCP entity. Similarly, CU 172 communicates with UE 102 via DU 174 and the first cell using some or all of at least one CU PDCP entity (e.g., not rebuilt). For example, some or all of at least one CU PDCP entity includes a first CU PDCP entity and / or a second CU PDCP entity.

[0214] In some implementations, after determining that UE 102 is connected to the first cell, receiving a 329 DU to CU message, or receiving a 334 access success message, CU 172 sends a 338 CU to DU message (e.g., a UE context modification request message) to DU 174 to instruct DU 174 to stop communicating with UE 102 and / or release or suspend resources of cell 124A configured for UE 102. In some implementations, in response to event 338, DU 174 stops communicating with UE 102 on cell 124A and / or releases or suspends resources of cell 124A configured for UE 102, and sends a 340 DU to CU message (e.g., a UE context modification response message) to CU 172. Events 338 (optional) and 340 (optional) in... Figure 3 This is collectively referred to as the resource release or modification process 396.

[0215] In some implementations, events 344, 346, 348, 350, 351, 352, 354, and / or 356, respectively, occur after or during communication with DU 174 on the first cell. UE 102 sends at least one measurement report (344) to DU 174. The at least one measurement report includes at least one measurement result for the second cell (i.e., cell 2). The at least one measurement result indicates that the second cell is suitable for communication with UE 102 and / or the first cell is not suitable for communication with UE 102. Upon receiving at least one measurement report (e.g., in response to 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 a second LTM command (350) to UE 102 on the first cell.

[0216] In some implementations, 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 sends a DU-to-CU message 349 to CU 172 indicating that LTM is being performed and / or will be performed. In some implementations, DU 174 includes cell ID 2 or ID 2 (i.e., LTM ID) in the DU-to-CU message 349 to indicate that DU 174 is activating LTM DU configuration 2. In some implementations, the DU sends the DU-to-CU message 349 to CU 172 before or after sending the LTM command 350.

[0217] The descriptions for events 324, 326, 328, 330, 331, 332, 334, and / or 336 can be applied to events 344, 346, 348, 350, 351, 352, 354, and / or 356 with simple modifications. For example, replace “Cell 124A,” “First LTM Command,” “First Cell,” “ID 1,” “LTM DU Configuration 1,” and / or “LTM CU Configuration 1” with “First Cell,” “Second LTM Command,” and “Second Cell,” “ID 2,” “LTM DU Configuration 2,” and / or “LTM CU Configuration 2,” respectively.

[0218] Events 344, 346, 348, 350, 351, 352, and 354 are in Figure 3 These are collectively referred to as LTM execution process 398. Events 304, 306, 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, and 356 are in... Figure 3 This is collectively referred to as the LTM DU configuration and / or activation process 380.

[0219] Next reference Figure 4 In scenario 400, base station 104 includes CU 172, source DU (S-DU) 174A, and target DU (T-DU) 174B. S-DU 174A operates cell 124A and optionally additional cells, while T-DU 174B operates a first cell (e.g., cell 124C). Scenario 400 is similar to scenario 300. Therefore, the description for scenario 300 can generally be applied to scenario 400. The differences between scenarios 300 and 400 are described below.

[0220] Initially, UE 102 uses the serving DU configuration to communicate with S-DU 174A 402 on cell 124A and communicates with CU 172 via S-DU 174A. S-DU 174A is connected to... Figure 3Similar to DU 174 in A, during the communication at event 402, UE 102 sends at least one measurement report (e.g., L3 measurement report) via S-DU 174A to CU 172, numbers 404 and 406. Based on at least one measurement report, CU 172 determines (operated by T-DU 174B) cells 1, ..., N prepared for LTM for 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 the 490 LTM preparation procedure to (e.g., request T-DU 174B) prepare cells 1, ..., N for LTM for UE 102. In some implementations, N is 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, T-DU 174B sends a DU-DU message including LTM DU configurations 1, ..., N to CU 172, similar to event 310. LTM DU configurations 1, ..., N configure cells 1, ..., N for LTM respectively. Specifically, LTM DU configurations 1, ..., N include configuration parameters for communication on cells 1, ..., N respectively. In some implementations, the CU-DU message and DU-CU message in procedure 490 are the UE context establishment request message and UE context establishment response message, respectively. 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-DU174B includes cell indices 1, ..., N in the LTM DU configurations 1, ..., N, respectively. In some implementations, the CU 172 sets cell indices 1, ..., N to different values ​​and includes cell indices 1, ..., N in the CU-DU message of procedure 490.

[0221] In some implementations, after executing LTM preparation procedure 490, CU 172 and T-DU 174B perform an additional LTM preparation procedure to prepare cells N+1, ..., N+M for LTM for UE 102, similar to procedure 490. M is a positive integer greater than zero. In a further implementation, similar to events 404 and 406, CU 172 determines 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 LTM DU configurations N+1, ..., N+M. The LTM DU configurations N+1, ..., N+M configure 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 process.

[0222] 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 a further implementation, LTM procedure 490 and the additional LTM preparation procedure are both UE context establishment procedures. In still a further implementation, LTM procedure 490 and the additional LTM preparation procedure are both UE context modification procedures.

[0223] In some implementations, CU 172 and S-DU 174A execute procedure 380 with UE 102, such as for... Figure 3 As described above. In process 380, CU 172 and S-DU 174A execute processes 390 and / or 392 to prepare the S-DU174A cell for LTM for UE 102. Note that in some implementations, process 380 or as for... Figure 3 The described value N and the target Figure 4The described value N may be the same or different. In some implementations, in procedure 390, CU 172 receives 310 a first DU-to-CU message including a reference LTM DU configuration from S-DU 174A. In a further implementation, CU 172 and S-DU 174A do not perform procedure 380 with UE 102. In some such implementations, CU 172 and S-DU 174A perform a 488 reference LTM DU configuration query procedure 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 will include an indication in the CU-to-DU message to request or query the reference LTM DU configuration. In response to this indication or the CU-to-DU message of event 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 a further implementation, the indication is an LTM indication, and CU 172 includes 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 (e.g., 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. In some implementations, CU 172 and T-DU 174B do not include the reference LTM DU configuration in the CU-DU message during the additional LTM preparation process. In the case of the additional LTM preparation process, T-DU 174B generates LTM DU configurations N+1, ..., N+M based on the reference LTM DU configuration received from CU 172.

[0224] 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 some such implementations, T-DU 174B does 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 a further implementation, the reference LTM DU configuration generated by T-DU 174B is the same as the reference LTM DU configuration generated by S-DU 174A.

[0225] 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.

[0226] In some implementations, the LTM DU configuration X of process 380 includes at least one reference signal (RS) resource configuration X, where 1 ≤ X ≤ N. Each configuration in RS resource configuration X is associated with one or more RSs or one or more RS resources of cell X of S-DU 174A. RSs include SSBs and / or CSI-RSs. RS resources include SSB resources and / or CSI-RS resources. In some implementations, each of RS resource configurations X includes an RS resource configuration ID. In some implementations, RS resource configuration X is and / or similar to a CSI-ResourceConfig IE. In some implementations, LTM DU configuration X includes a CSI-MeasConfig IE, and the CSI-MeasConfig IE includes a CSI-ResourceConfig IE. T-DU 174B generates at least one reporting configuration 1 for reporting measurement results of RSs or RS resources on cell 1 of T-DU 174B, and includes reporting configuration 1 in LTM DU configuration 1. In some implementations, report configuration 1 is and / or similar to CSI-ReportConfig IE. In some implementations, T-DU 174B generates at least one RS resource configuration 1 considering or based on RS resource configuration X, and includes RS resource configuration 1 in LTM DU configuration 1. In some implementations, T-DU 174B includes RS resource configuration X in RS resource configuration 1. In a further implementation, 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. T-DU 174B assigns the RS resource configuration ID as a value for each of RS resource configurations 1 (e.g., including RS resource configuration X), and includes the RS resource configuration ID in the corresponding RS resource configuration.

[0227] In some implementations, Report Configuration 1 configures one or more UL resources (e.g., PUCCH or PUSCH resources) on Cell 1 for UE 102 to transmit measurement results. In some implementations, each of Report Configuration 1 includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in RS Resource Configuration 1. After UE 102 performs an LTM serving cell change from Cell 124A to Cell 1, UE 102 communicates with S-DU 174B (i.e., T-DU 17B becomes UE 102's S-DU) and transmits measurement results to S-DU 174B via Cell 1 on UL resources according to Report Configuration 1. Correspondingly, S-DU 174B receives measurement results from UE 102 via Cell 1 on UL resources 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). In some implementations, the quantized measurement values ​​include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0228] 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 configurations are and / or similar to a CSI-ResourceConfig IE. In some implementations, the T-DU 174B includes a CSI-ResourceConfig IE in a CSI-MeasConfig IE. The T-DU 174B generates at least one additional reporting configuration for reporting measurement results of RSs or RS resources on cell 1 of the T-DU 174B, and includes the additional reporting configuration in LTMDU configuration 1. In some implementations, the additional reporting configuration is and / or similar to a CSI-ReportConfig IE.

[0229] In some implementations, the additional report configuration configures one or more UL resources (e.g., PUCCH or PUSCH resources) on cell 1 for UE 102 to transmit measurement results. In some implementations, each of the additional report configurations includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the additional RS resource configuration. After UE 102 performs an LTM serving cell change from cell 124A to cell 1, UE 102 communicates with S-DU 174B 436 and transmits measurement results 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 to the UE 102 an additional RS or RS resource in which it performs a measurement or obtains a quantized measurement value. In some implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRI) and / or one or more CSI-RS resource indicators (CRI). In some implementations, the quantized measurement value includes one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0230] Similarly, in some implementations, the T-DU 174B considers or generates 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. In some such implementations, the T-DU 174B also includes 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.

[0231] In some implementations, the LTM DU configuration X of process 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 a corresponding QCL type or includes a TCI state of one or two DL RSs. In some implementations, the DL RSs are 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 further 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 generates at least one TCI state configuration 1 considering or based on TCI state configuration X and includes TCI state configuration 1 in LTM DU configuration 1. In some implementations, TCI state configuration 1 includes TCI state configuration X. In some 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 value for each of TCI state configurations 1 (e.g., including TCI state configuration X) and includes the TCI state ID in the corresponding TCI state configuration. In some implementations, when UE 102 and S-DU 174B are communicating with each other 436, S-DU 174B sends an LTM command to UE 102 to instruct UE 102 to perform a fast serving cell change to cell X. S-DU 174B includes a TCI state ID in the LTM command to instruct UE 102 to apply a TCI state configuration identified by the TCI state ID to communicate on cell X, wherein the TCI state configuration is one of TCI state configurations X, or a configuration that includes one of TCI state configurations X.

[0232] In some implementations, similarly, the T-DU 174B considers or generates TCI state configurations 2, ..., N based on RS resource configuration X, and includes 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.

[0233] 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 to DU message of process 380, and S-DU 174A generates the LTM DU configurations 1, ..., N of process 380 in a manner similar to that described above, taking into account or based on the configurations in the LTM DU configurations of process 490.

[0234] In some implementations, CU 172 assigns IDs 1, ..., N to LTM DU configurations 1, ..., N respectively (e.g., received from T-DU 174B), and performs procedure 492 with T-DU 174B to provide IDs 1, ..., N and / or cell IDs 1, ..., N, similar to procedure 392. Therefore, T-DU 174B associates IDs 1, ..., N with LTM DU configurations 1, ..., N and / or cell IDs 1, ..., N respectively. In some implementations, T-DU 174B assigns IDs 1, ..., N to LTM DU configurations 1, ..., N respectively (e.g., generated by T-DU 174B), and similar to event 310, includes IDs 1, ..., N in the DU-to-CU message of procedure 490. In some implementations, CU 172 assigns IDs N+1, ..., N+M that identify LTM DU configurations N+1, ..., N+M respectively, and performs a procedure (e.g., 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, similar to procedure 392. 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 a further implementation, T-DU 174B assigns IDs N+1, ..., N+M that identify LTM DU configurations N+1, ..., N+M respectively, and, similar to event 310, includes IDs 1, ..., N in the DU-to-CU message of the additional LTM preparation procedure.

[0235] In some implementations, CU 172 sends a CU-DU message (412) including IDs 1, ..., N to S-DU 174A, and in response, receives a DU-CU message (414) from S-DU 174A. The CU-DU message of event 412 and the DU-CU message of event 414... Figure 4 This is collectively referred to as LTM ID transmission procedure 493 or LTM cell index transmission procedure 493. In some implementations, the messages of event 412 and event 414 are the UE context modification request message and the UE context modification response message, respectively. In some implementations, CU 172 includes LTM DU configuration 1, ..., N and / or cell ID 1, ..., N in the CU to DU message of event 412. In some implementations, CU 172 includes ID 1, ..., N in the CU to DU message of event 412. In a further implementation, CU 172 includes cell index 1, ..., N in the CU to DU message of event 412. In still a further implementation, CU 172 performs 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 processes, CU 172 includes specific portions of ID1, ..., N, cell ID1, ..., N, and / or LTM DU configuration1, ..., N in a CU-to-DU message similar to message 412. Therefore, S-DU 174A associates ID1, ..., N with LTM DU configuration1, ..., N, and / or cell ID1, ..., N, respectively. In a further implementation, CU 172 performs multiple LTM cell index transmission processes to send cell index1, ..., N, cell ID1, ..., N, and / or LTM DU configuration1, ..., N to S-DU 174A. In each of the processes, CU 172 includes specific portions of cell index1, ..., N, cell ID1, ..., N, and / or LTM DU configuration1, ..., 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.

[0236] 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 of event 414. In some implementations, the first service DU configuration includes a configuration that updates (e.g., enhances, modifies, or replaces) the service DU configuration of event 402. In a further implementation, the first service DU configuration includes a configuration not included in the service DU configuration of event 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 S-DU 174A. 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 the service DU configuration of event 402 that has not been updated by the first service DU configuration. The following is an example implementation of generating the first service DU configuration based on LTM DU configuration 1, ..., N.

[0237] 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 and / or similar to a CSI-ResourceConfig IE. In some implementations, LTM DU configuration Y includes a CSI-MeasConfig IE, and the CSI-MeasConfig IE includes a CSI-ResourceConfig IE. S-DU 174A generates at least one service report configuration for reporting measurement results of RSs or RS resources on cell 124A and includes the service report configuration in the first service DU configuration. In some implementations, the service report configuration is (e.g., similar to) a CSI-ReportConfig IE. In some implementations, S-DU 174A generates at least one service RS resource configuration considering or based on RS resource configuration Y, and includes the service RS resource configuration in the first service DU configuration. In some implementations, S-DU 174A includes RS resource configuration Y in the service RS resource configuration. In a further implementation, 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 an RS resource configuration ID value for each of the service RS resource configurations (e.g., including RS resource configuration Y), and includes the RS resource configuration ID in the corresponding service RS resource configuration.

[0238] In some implementations, the service report configuration configures one or more UL resources (e.g., PUCCH or PUSCH resources) on cell 124A for UE 102 to transmit measurement results. In a further implementation, each of the service report configurations includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the service RS resource configuration. When UE 102 communicates with S-DU 174A, UE 102 transmits measurement results (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 the 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 to the UE 102 where it performs a measurement or obtains a quantized measurement value for an RS or RS resource. In further implementations, the RS resource indicator includes one or more SSB resource indicators (SSBRIs) and / or one or more CSI-RS resource indicators (CRIs). In some implementations, the quantized measurement value includes one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0239] 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 corresponding QCL type or includes the TCI state of one or two DL RSs. In some implementations, the DL RSs are associated with the cell Y operated by T-DU 174B. In some implementations, each of the TCI state configuration Y includes a TCI state ID. In some implementations, each of the TCI state configuration Y is a TCI-State IE. In some implementations, the TCI state configuration Y includes / is the ul-TCI-ToAddModList-r17 field, one or more TCI-UL-State-r17 IEs, the dl-OrJointTCI-StateToAddModList-r17 field, one or more TCI-State IEs, the TCI-ActivatedConfig IE, and / or the tci-StatesToAddModList field. In some implementations, LTM DU configuration Y includes PDSCH-Config IE, and PDSCH-Config IE includes TCI state configuration Y. In some implementations, S-DU 174A generates at least one service TCI state configuration taking into account or based on TCI state configuration Y, and includes the service TCI state configuration in the first service DU configuration. In some implementations, service TCI state configuration 1 includes TCI state configuration Y. In other implementations, S-DU 174A includes each of TCI state configurations Y in the service TCI state configuration, except for the TCI state ID in TCI state configuration Y. S-DU 174A assigns the TCI state ID as a value for each service TCI state configuration (e.g., including TCI state configuration Y), and includes the TCI state ID in the corresponding service TCI state configuration. In some implementations, when the S-DU174A communicates with UE 102 at event 436, the S-DU 174A sends an LTM command to UE 102 to instruct UE 102 to perform a fast serving cell change to cell Y. The S-DU 174A includes a TCI state ID in the LTM command to instruct UE 102 to apply a TCI state configuration identified by the TCI state ID to communicate on cell Y, wherein the TCI state configuration is one of TCI state configurations Y, or a configuration that includes one of TCI state configurations Y.

[0240] In some implementations, CU 172 sends a CU-DU message including IDs N+1, ..., N+M to S-DU 174A, and in response receives a DU-CU message from S-DU 174A, which is similar to the CU-DU message of event 412 and the DU-CU message of event 414, respectively. In some implementations, CU 172 includes LTM DU configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M in the CU-DU message. In a further implementation, CU 172 performs 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 event 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 the service DU configuration of event 402 but not updated by the first service DU configuration. In a further implementation, 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 service DU configuration, to UE 102 via S-DU 174A. Upon receiving the RRC reconfiguration message, UE 102 applies the second service DU configuration to communicate with the service DU. For example, the RRC reconfiguration message is 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 the service DU configuration of event 402 and / or the first service DU configuration that has not been updated by the second service 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 the new L1 measurement configurations in the second service DU configuration.In some implementations, the S-DU174A 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.

[0241] 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 a further implementation, 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 an even further implementation, 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.

[0242] In some implementations, similar to event 324, UE 102 later sends 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 a second measurement result for cell 124A. In some implementations, the first measurement result includes RSRP, RSRQ, and / or SINR obtained by UE 102 from a reference signal transmitted on cell 1. In some implementations, similarly, the second measurement result 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. In some implementations, based on the first measurement result and / or the second measurement result, S-DU 174A sends a first LTM command (i.e., LTM command 1) including ID 1 to UE 102, instructing UE 102 to perform a serving cell change to cell 1 of T-DU 174B. In some implementations, the first LTM command includes ID 1 (i.e., LTM ID). In a further implementation, 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 LTMDU configuration 1. In some implementations, after receiving the first LTM command (e.g., in response to this), UE 102 performs or does not perform a random access procedure (432) with T-DU 174B, similar to event 332. In some implementations, upon receiving the first LTM command or completing random access procedure 432 (e.g., in response to this), similar to event 336, UE 102 communicates with T-DU 174B on the first cell using LTM DU configuration 1 and / or referencing LTM DU configuration at event 436, and communicates with CU 172 via T-DU 174B. In some implementations, if a serving cell change occurs in procedure 380, the serving cell is 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 LTM ID 1, UE 102 identifies LTM DU configuration 1 and / or cell ID 1 (i.e., cell 1) based on LTM ID 1, as for Figure 3 As 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... Figure 3 As 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-DU174B.

[0243] In some implementations, upon determining that LTM DU configuration 1 is activated or sending the first LTM command (430), or in response to this, the S-DU 174A sends a DU-to-CU message (429) to the CU 172 indicating that LTM is being executed or is being executed. In some implementations, the S-DU 174A includes cell ID 1 or LTM ID 1 in the DU-to-CU message of event 429 to indicate that the S-DU 174A will activate LTM DU configuration 1 or trigger an LTM serving cell change. In a further implementation, the S-DU 174A sends a DU-to-CU message (429) to the CU 172 before or after sending the LTM command (430). In some implementations, when the CU 172 receives the DU-to-CU message (429), the CU 172 stops or suspends sending DL data for UE 102 to the S-DU 174A until it receives the DU-to-CU message (434). After receiving the 434 DU to CU message, CU 172 starts, continues, or resumes sending DL data for UE 102 to T-DU 174B. When T-DU 174B detects UE 102 accessing cell 1 or later, T-DU 174B sends DL data to UE 102 via cell 1.

[0244] In some implementations, the resource release procedure 496 is similar to procedure 396. In a further implementation, in the resource release procedure 496, CU 172 sends 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.

[0245] Events 380, 404, 406, 490, 492, 494, 494, 424, 426, 428, 429, 430, 431, 432, 434, 436, 496, 498, and 456 are in Figure 4 This is collectively referred to as the LTM configuration and / or activation process 480.

[0246] Next reference Figure 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 Data Center) scenario, while scenario 300 is a single-connectivity (SC) scenario. In some implementations, MN 106 includes components similar to... Figure 3 The CU and DU of base station 104.

[0247] Initially, UE 102 communicates with MN 106 and SN 104 under DC. In event 502, similar to event 302, 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. In some alternative implementations, UE 102 does not communicate with CU 172 via DU 174 in event 302. In some implementations, UE 102 under DC communicates UL PDUs and / or DL ​​PDUs with MN 106 and / or SN 104 via radio bearers at event 502, these radio bearers including SRBs and / or DRBs. In some implementations, MN 106 and / or SN 104 configure radio bearers for UE 102. At event 502, UE 102 communicates UL PDUs and / or DL ​​PDUs with SN 104 via DC on the SCG (i.e., SCG radio resources) configured for communication with UE 102. UE 102 then communicates UL PDUs and / or DLPDUs to MN 106 via 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 an SN configuration (i.e., SCG configuration). In the MN configuration, MN 106 configures an MCG that 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 an SCG that 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 these parameters from MN 106 in one or more RRC messages. For example, regarding... Figure 3 As described, the service DU configuration includes multiple configuration parameters. In some implementations, UE 102 receives these configuration parameters from SN 104 (e.g., via MN 106 and / or on SRB (e.g., SRB3)) in one or more RRC messages to exchange RRC messages between UE 102 and SN 104.

[0248] In a further implementation, when UE 102 communicates with MN 106 and SN 104 under DC, similar to procedures 380 and / or 480, MN 106 and UE 102 perform a 580 LTM DU configuration and / or activation procedure. In some implementations, when communicating with MN 106 and SN 104 under DC, UE 102 sends 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 a further implementation, when communicating with MN 106 and SN 104 under DC, UE 102 sends at least one measurement report 505 to MN 106 via cell 126. MN 106 then sends at least one measurement report 507 to CU 172. In some implementations, MN 106 generates at least one SN message including at least one measurement report and sends the at least one SN message to CU 172. In some implementations, the at least one SN message includes an RRC delivery message and / or an SN modification request message.

[0249] 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... Figure 3 As described. Events 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are similar to events 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, and 356, respectively. After receiving the first LTM command at 530, sending an acknowledgment at 531, or confirming that UE 102 has successfully connected to the first cell (e.g., at events 532 or 536), UE 102, operating in DC mode with MN 106 and SN 104, communicates with DU 174 on the first cell according to LTM DU configuration 1 at event 536 and communicates with CU 172 via DU 174 at event 536, similar to event 336. In some implementations, later, similar to procedures 398 or 498, DU174 and / or CU172, together with UE 102, perform LTM execution procedure 598 to command UE 102 to perform a cell change from the first cell to the second cell. As a result of procedure 598, UE 102, operating in DC mode with MN 106 and SN 104, communicates with DU 174 on the second cell at event 556 according to LTM DU configuration 2 and communicates with CU 172 via DU 174 at event 556, similar to event 356.

[0250] Events 504, 506, 505, 507, 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are in Figure 5A This is collectively referred to as the LTM DU configuration and / or activation process 581.

[0251] Next reference Figure 5B Scenario 500B is largely similar to Scenario 500A, except that SN 104 sends RRC reconfiguration messages 517 and 519 to UE 102 via MN 106 and receives RRC reconfiguration completion messages 521 and 523 from UE 102 via MN 106. The RRC reconfiguration messages of events 517 and 519 are similar to those of events 316 and 318. The RRC reconfiguration completion messages of events 521 and 523 are similar to those of events 320 and 322. In some implementations, SN 104 generates a first SN message (e.g., an SN modification request message, SN modification request message, or RRC transmission message) including the RRC reconfiguration message and sends the first SN message 517 to MN 106. 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. 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. In some implementations, the MN RRC message and the MN RRC response message are respectively an RRC reconfiguration message and an RRC reconfiguration complete message.

[0252] 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 in Figure 5B This is collectively referred to as the LTM DU configuration and / or activation process 582.

[0253] Next reference Figure 6AIn scenario 600A, base station 106 operates as the MN and base station 104 operates as the SN, similar to scenarios 300-500B. Similar to base station 104 in scenario 400, SN 104 includes CU 172, S-DU 174A, and T-DU 174B. In some implementations, when UE 102 communicates with MN 106 and SN 104 under DC, similar to procedures 380 and / or 480, MN 106 performs a 680 LTM DU configuration and / or activation procedure with UE 102. In a further implementation, when UE 102 communicates with M-DU 174A and S-DU 174B under DC, similar to procedures 581 and / or 582, CU 172 performs a 681 LTM DU configuration and / or activation procedure with UE 102 via M-DU 174A or S-DU 174B.

[0254] Next reference Figure 6B Scenario 600B is similar to scenarios 300-500B and 600A, except that SN 104 sends RRC reconfiguration messages 617 and 619 to UE 102 via MN 106, and receives RRC reconfiguration completion messages 621 and 623 from UE 102 via MN 106.

[0255] Next reference Figure 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... Figure 3 Base station 104 or Figures 5A to 6B MN 106, CU 172 operate together with M-DU 174A as MN, and are similar Figures 5A to 6B SN 104, CU 172 in the series operate together with S-DU 174B, which is an SN.

[0256] In scenario 700A, UE 102 initially communicates with M-DU 174A and S-DU 174B via DC at event 702 and communicates with CU 172 via M-DU 174A and S-DU 174B at event 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 sends at least one measurement report (705) to M-DU 174A. Similar to event 306, M-DU 174A then sends at least one DU-to-CU message (707) including at least one measurement report to CU 172. In some implementations, when UE102 communicates with M-DU 174A and S-DU 174B under DC, similar to procedure 380, CU 172 performs the 780 LTM DU configuration and / or activation procedure with UE102 via M-DU 174A.

[0257] Events 704, 706, 705, 707, 790, 792, 794, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, and 756 are in Figure 7A This is collectively referred to as the LTM configuration and / or activation process 781.

[0258] Next reference Figure 7B Scenario 700B is similar to scenarios 300-600B 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.

[0259] Events 704, 706, 705, 707, 790, 792, 794, 717, 719, 721, 723, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, and 756 are in Figure 7B This is collectively referred to as the LTM DU configuration and / or activation process 782.

[0260] Next reference Figure 8AIn scenario 800A, base station 104 operates as both MN and SN, similar to scenarios 300-700B. Base station 104 includes CU 172, primary DU (M-DU) 174A, secondary DU (S-DU) 174B, and target secondary DU (T-DU) 174C. CU 172 operates with M-DU 174A as MN and with S-DU 174B as SN. In some implementations, when UE 102 communicates with M-DU 174A and S-DU 174B under DC, similar to procedure 380, CU 172 performs the 880 LTM DU configuration and / or activation procedure with UE 102 via M-DU 174A. In a further implementation, when UE 102 communicates with M-DU 174A and S-DU 174B under DC, CU 172 performs an LTM DU configuration and / or activation procedure similar to procedure 581 or 582 together with UE 102 via S-DU 174A.

[0261] Next reference Figure 8B Scenario 800B is similar to scenarios 300-700B and 800A, 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.

[0262] Next, refer to Figures 9A to 14 Several example methods for LTM that can be implemented in RAN nodes (e.g., base stations, DUs, or CUs) or UEs are discussed. (Targeting...) Figures 3 to 8B The description described can be applied to Figures 9A to 14 .

[0263] Figure 9A An example method 900A that can be implemented by a UE (e.g., UE 102) is shown.

[0264] Method 900A begins at block 902, where the UE communicates with the RAN (e.g., RAN 105) via the serving cell (e.g., events 302, 402, 502, 602, 702, 802). In some implementations, the UE communicates with the RAN using a MAC entity at block 902, and the MAC entity performs the operation of MAC layer 204B. At block 904, the UE receives an LTM candidate configuration from the RAN, where the LTM candidate configuration configures candidate cells (e.g., events 316, 318, 394, 494, 594, 517, 519, 694, 617, 619, 794, 717, 719, 894, 817, or 819). In some implementations, the LTM candidate configuration includes an LTM DU configuration configuring the candidate cells, as described above. In some implementations, the serving cell is the serving PCell, and the candidate cell is the candidate PCell. In other implementations, the serving cell is the serving PSCell, and the candidate cell is the candidate PSCell. In some implementations, the LTM candidate configuration is the LTM-Candidate IE. In other implementations, the LTM candidate configuration is the LTM-CandidateConfig IE. In some implementations, the LTM candidate configuration includes an LTM ID (i.e., a configuration ID) that identifies the LTM candidate configuration or LTM DU configuration.

[0265] At box 906, the UE receives an LTM command (e.g., events 330, 430, 530, 630, 730, or 830) from the RAN via the serving cell, which includes a TA value. In some implementations, the LTM command includes an LTM ID, and the UE identifies the LTM candidate configuration based on the LTM ID. In other implementations, the LTM command includes an LTM configuration index derived from or mapped from the LTM ID. In some implementations, the LTM configuration index is the LTM ID minus one (e.g., LTM ID – 1). For example, if the LTM ID is set to the value N, then the value of the LTM configuration index is N-1. Therefore, the UE identifies the LTM candidate configuration based on the LTM configuration index and the mapping between the LTM configuration index and the LTM ID.

[0266] At box 908, the UE applies the TA value to UL synchronization with the candidate cell. At box 910, the UE starts a time alignment timer to maintain (e.g., count) the validity period of the UL synchronization. In some implementations, because the UE started the time alignment timer at box 902 to maintain the validity period of the UL synchronization with the serving cell, the time alignment timer is already running before a random access response is received. In such cases, the UE restarts the time alignment timer at box 910. In some implementations, the UE starts or restarts the time alignment timer at the MAC entity. At box 912, the UE performs a MAC reset in response to an LTM command. The UE performs a MAC reset for communication with the RAN on the candidate cell. In some implementations, when the UE performs a MAC reset at box 912, the MAC entity used for communication with the RAN on the candidate cell is reset. At box 914, when a MAC reset is performed (e.g., in response to this), the UE keeps the time alignment timer running. That is, the UE avoids stopping the time alignment timer in response to a MAC reset. At block 916, when a MAC reset is performed (e.g., in response to this), the UE determines that the timer alignment timer has not expired. At block 918, after performing the MAC reset, the UE communicates with the RAN via the candidate cell using the LTM candidate configuration (e.g., events 336, 436, 536, 636, 736, or 836). In some implementations, the UE communicates with the RAN using the MAC entity at block 918 after resetting the MAC entity.

[0267] Because the time alignment timer continues to run after the MAC reset, the UE sends UL transmissions (e.g., PUSCH and PUCCH transmissions) to the RAN on the candidate cell at box 918 without performing a random access procedure to synchronize with the candidate cell in the UL.

[0268] Figure 9BThis is a flowchart of an example method 900B, similar to method 900A, except that method 900B includes blocks 913, 915, and 917 instead of blocks 914 and 916. At block 913, the UE stops the time alignment timer when performing a MAC reset. At block 915, the UE determines that the time alignment timer has expired when performing a MAC reset. At block 917, the UE determines that it will maintain UL synchronization even when the time alignment timer is not running. That is, the UE maintains UL synchronization with the candidate cell even when the time alignment timer is not running. In other words, at block 917, the UE determines that UL synchronization is valid when the time alignment timer is stopped and / or when the time alignment timer is determined to have expired. Because UL synchronization is maintained after a MAC reset, the UE sends UL transmissions (e.g., PUSCH and PUCCH transmissions) to the RAN on the candidate cell at block 918 without performing a random access procedure to synchronize with the candidate cell in the UL.

[0269] Figure 9C This is a flowchart of an example method 900C, similar to method 900A, except that method 900C includes block 911 instead of blocks 910, 914, and 916. At block 911, after performing a MAC reset, the UE starts a time alignment timer to maintain the validity of UL synchronization. In some implementations, the UE applies the TA value before performing the MAC reset. In such cases, the UE maintains UL synchronization with the candidate cell during or after performing the MAC reset (e.g., in response to this). In other implementations, the UE applies the TA value after performing the MAC reset.

[0270] Because the time alignment timer is running after the MAC reset, the UE sends UL transmissions (e.g., PUSCH and PUCCH transmissions) to the RAN on the candidate cell at box 918 without performing a random access procedure to synchronize with the candidate cell in the UL.

[0271] Figure 10A This is a flowchart of an example method 1000A, similar to method 900A, except that method 1000A includes blocks 1006 and 1007 instead of block 906. At block 1006, the UE receives an LTM command (e.g., events 332, 432, 532, 632, 732, or 832) from the RAN via the serving cell. At block 1007, the UE measures the TA value used for UL synchronization with the candidate cell.

[0272] Figure 9A The examples and implementations described herein can be applied to Figure 10A ,Apart from Figure 10A The LTM command in the UE does not include the TA value, and the UE obtains the TA value from the measurement performed by the UE.

[0273] Figure 10B This is a flowchart of example method 1000B, similar to methods 1000A and 900B. (Targeting...) Figure 10A and Figure 9B The described examples and implementations can be applied to Figure 10B .

[0274] Figure 10C This is a flowchart of example method 1000C, similar to methods 1000A and 900C. (Targeting...) Figure 10A and Figure 9C The described examples and implementations can be applied to Figure 10C .

[0275] Figure 11A This is a flowchart of example method 1100A, similar to method 900A, except that method 1100A includes block 1103 instead of block 910. At block 1103, the UE initiates a time alignment timer to maintain the validity period of UL synchronization with the RAN on the serving cell. Figure 9A Unlike method 1100A, the UE does not start or restart the time alignment timer to maintain UL synchronization with the candidate cell when applying the TA value to UL synchronization with the candidate cell (e.g., in response to this).

[0276] In some implementations, if the time alignment timer is running when the LTM command is received, the UE continues to use the remaining time of the running time alignment timer to maintain UL synchronization with the candidate cell when the TA value is applied for UL synchronization with the candidate cell (e.g., in response to this). In the case where the time alignment timer expires before receiving the TA command from the RAN, as described below, the UE still maintains UL synchronization with the candidate cell and continues to communicate with the RAN via the candidate cell without performing a random access procedure to synchronize with the candidate cell in the UL. In other implementations, the UE does not use the running time alignment timer to maintain UL synchronization with the candidate cell when the TA value is applied for UL synchronization with the candidate cell (e.g., in response to this).

[0277] After the RAN determines that the UE has successfully accessed the candidate cell, or at the time of access, the RAN sends a TA command to the UE via the candidate cell to provide the TA value. In response to receiving the TA command, the UE applies the TA value to its UL synchronization with the candidate cell and starts or restarts the time alignment timer to maintain the validity of the UL synchronization. In some implementations, the TA command is a MAC CE, which is different from the LTM command.

[0278] against Figure 9A The examples and implementations described in the UE description can be applied to Figure 11A.

[0279] Figure 11B This is a flowchart of example method 1100B, similar to methods 1100A and 900B. (Targeting...) Figure 11A and Figure 9B The examples and implementations described in the UE description can be applied to Figure 11B The MAC entity in the document.

[0280] Figure 12A This is a flowchart of example method 1200A, similar to methods 900A, 1000A, and 1100A. (For...) Figure 9A , Figure 10A and Figure 11A The described examples and implementations can be applied to Figure 12A .

[0281] Figure 12B This is a flowchart of example method 1200B, similar to methods 900B, 1000B, and 1100B. (Targeting...) Figure 9B , Figure 10B and Figure 11B The described examples and implementations can be applied to Figure 12B .

[0282] Figure 13 An example method 1300 is shown that can be implemented by an RAN (e.g., RAN 105, base station 104 or 106, or DU 174).

[0283] Method 1300 begins at block 1302, where the RAN communicates with the UE (e.g., UE 102) via the serving cell (e.g., events 302, 402, 502, 602, 702, 802). In some implementations, the RAN uses a MAC entity to communicate with the UE at block 1302, and the MAC entity performs MAC layer 204B operations. At block 1304, the RAN sends an LTM candidate configuration to the UE, where the LTM candidate configuration configures a candidate cell (e.g., events 316, 318, 394, 494, 594, 517, 519, 694, 617, 619, 794, 717, 719, 894, 817, or 819). At block 1306, the RAN sends an LTM command including a first TA value to the UE via the serving cell (e.g., events 330, 430, 530, 630, 730, or 830).

[0284] At block 1308, the RAN performs a MAC reset in response to an LTM command to communicate with the UE on the candidate cell. In some implementations, the RAN resets the MAC entity used for communicating with the UE on the candidate cell when performing the MAC reset at block 1308. At block 1310, the RAN detects that the UE has accessed the candidate cell (e.g., events 332, 432, 532, 632, 732, or 832). In some implementations, the RAN performs a MAC reset before detection. In other implementations, the RAN performs a MAC reset in response to the detection. At block 1312, the RAN sends a TA command, including a second TA value, to the UE via the candidate cell to cause the UE to start a UE time alignment timer to maintain the validity period of UL synchronization with the candidate cell. In some implementations, the RAN uses a MAC entity to send the TA command to the UE. At block 1314, in response to sending the TA command, the RAN starts a RAN time alignment timer to maintain the validity period of UL synchronization between the UE and the candidate cell. After detecting that the UE has accessed a candidate cell, the RAN communicates with the UE via the candidate cell, for example, using a MAC entity (e.g., events 336, 436, 536, 636, 736, or 836).

[0285] In some alternative implementations, in response to an LTM command, the RAN initiates another MAC entity to communicate with the UE on a candidate cell, instead of resetting the MAC entity. The RAN uses this other MAC entity to send TA commands and communicate with the UE via the candidate cell.

[0286] The examples and implementations described above can be applied to Figure 13 .

[0287] Figure 14 Example method 1400 is shown, which can be derived from candidate DUs (C-DUs) (e.g., Figure 4 , Figure 6A and Figure 6B The T-DU 174B in the middle, and Figure 8A and Figure 8B The T-DU 174C is implemented in this system.

[0288] Method 1400 begins at block 1402, where the C-DU sends an LTM DU configuration to the UE (e.g., UE 102) via a CU (e.g., CU 172), wherein the LTM DU configuration configures candidate cells (e.g., events 310, 316, 318, 390, 394, 490, 494, 590, 594, 517, 519, 690, 694, 617, 619, 790, 794, 717, 719, 890, 894, 817, or 819). At block 1404, the C-DU sends a first TA value to the UE via the CU. In some implementations, the C-DU sends a DU-to-CU message including the first TA value to the CU, and the CU then sends a message to the serving DU (e.g., ...). Figure 4 , Figure 6A and Figure 6B S-DU 174A, or Figure 8A and Figure 8B The S-DU (174B) sends a CU-to-DU message including a first TA value. The serving DU sends an LTM command (e.g., event 430, 630, or 830) including the first TA value to the UE. In some implementations, the DU-to-CU message is an F1 Application Protocol (F1AP) message (e.g., a UE Context Modification Request message or a TA Info Notify message). In some implementations, the CU-to-DU message is an F1AP message (e.g., a UE Context Modification Request message or a TA Info Notify message). In other implementations, the C-DU sends a DU-to-DU message including the first TA value (e.g., a TA Info Notify message) to the serving DU via the CU (i.e., transparent to the CU) or directly to the serving DU.

[0289] At block 1406, the C-DU initiates a MAC entity to communicate with the UE on the candidate cell. At block 1408, the C-DU detects that the UE has accessed the candidate cell (e.g., events 432, 632, or 832). At block 1410, the C-DU sends a TA command including a second TA value to the UE via the candidate cell to cause the UE to start a time alignment timer. At block 1412, in response to sending the TA command, the C-DU starts a DU time alignment timer to maintain the validity period of UL synchronization between the UE and the candidate cell.

[0290] The examples and implementations described above can be applied to Figure 14 .

[0291] The following list of examples illustrates various embodiments explicitly contemplated in this disclosure:

[0292] Example 1. A method implemented in a user equipment (UE), the method comprising: communicating with a radio access network (RAN) node via a serving cell; receiving at the UE a command to perform a low-layer triggered mobility (LTM) handover to a candidate cell; applying a timing advance (TA) value at the UE to uplink (UL) synchronization with the candidate cell; and maintaining the UL synchronization at the UE based on the TA value after completing the LTM handover to the candidate cell.

[0293] Example 2. The method as described in Example 1 further includes: in response to applying the TA value, starting a time alignment timer to define the validity period of the UL synchronization; performing a media access control (MAC) reset in response to executing the command for the LTM switching; and preventing the time alignment timer from expiring in response to the MAC reset.

[0294] Example 3. The method as described in Example 1 further includes: in response to applying the TA value, starting a time alignment timer to define the validity period of the UL synchronization; performing a media access control (MAC) reset in response to executing the command for the LTM handover; determining the expiration of the time alignment timer in response to the MAC reset; and determining that the UE maintains the UL synchronization after the time alignment timer expires.

[0295] Example 4. The method as described in Example 3 further includes: sending a UL transmission to the RAN node without performing a random access procedure after the MAC reset is performed and while the time alignment timer is running.

[0296] Example 5. The method described in Example 4, wherein the UL transmission includes a Physical Uplink Shared Channel (PUSCH) transmission.

[0297] Example 6. The method as described in Example 4, wherein the UL transmission includes a Physical Uplink Control Channel (PUCCH) transmission.

[0298] Example 7. The method of any one of Examples 3 to 6 further includes: after determining that the UE maintains the UL synchronization, receiving a TA command in the candidate cell, the TA command including a new TA value.

[0299] Example 8. The method of Example 7 further includes: in response to receiving the new TA value, continuing to maintain the UL synchronization.

[0300] Example 9. The method of Example 1 further includes: performing a media access control (MAC) reset in response to the command to perform the LTM switching; and, in response to the MAC reset, starting a time alignment timer to define the validity period of the UL synchronization based on the TA value.

[0301] Example 10. The method of Example 1 further includes: prior to receiving the command, starting a time alignment timer to define the validity period of the UL synchronization.

[0302] Example 11. The method as described in any one of Examples 1 to 10, wherein the command for performing the LTM switching includes the TA value.

[0303] Example 12. The method of any one of Examples 1 to 10, wherein the command for performing the LTM handover does not include the TA value, the method further comprising: determining the TA value using one or more measurements at the UE.

[0304] Example 13. The method as described in any of the preceding examples further includes: receiving an LTM configuration for configuring the candidate cell before receiving the command.

[0305] Example 14. A user equipment (UE) includes a transceiver and processing hardware and is configured to implement the method according to any one of the foregoing examples.

[0306] Example 15. A method implemented in a radio access network (RAN) node, the method comprising: communicating with a user equipment (UE) at the RAN node; sending a command from the RAN node to the UE to perform a low-layer triggered mobility (LTM) handover to a candidate cell; and, in response to determining that the UE has accessed the candidate cell, sending a timing advance (TA) command from the RAN node to the UE, the TA command including a TA value for uplink synchronization (UL) with the candidate cell.

[0307] Example 16. The method as described in Example 15, wherein: the command for performing the LTM switching includes a first TA value; and the TA value included in the TA command is a second TA value.

[0308] Example 17. The method of any one of Examples 15 or 16 further includes: in response to sending the TA command, starting a RAN time alignment timer to define the validity period of the UL synchronization.

[0309] Example 18. The method of any one of Examples 15 to 17, further comprising: performing a Media Access Control (MAC) reset for the UE in response to the sending of the command to perform the LTM handover.

[0310] Example 19. The method of any one of Examples 15 to 18, further comprising: sending an LTM configuration for configuring the candidate cell to the UE before sending the command to perform the LTM handover.

[0311] Example 20. A method implemented in the distributed unit (DU) of the RAN node as described in Example 19, wherein: the transmission of the LTM configuration includes transmitting the LTM DU configuration via the central unit (CU) of the RAN node.

[0312] Example 21. A method implemented in a distributed unit (DU) of the RAN node as described in any one of Examples 15 to 19, wherein the RAN node includes a central unit (CU).

[0313] Example 22. The method as described in Example 21, wherein sending the command includes sending the command via the CU.

[0314] Example 23. The method of any one of Examples 21 or 22 further includes: initializing a MAC entity for communicating with the UE on the candidate cell.

[0315] Example 24. The method of any one of Examples 21 to 23 further includes: in response to sending the TA command, starting a DU time alignment timer to define the validity period of the UL synchronization.

[0316] Example 25. A radio access network (RAN) node, the RAN node comprising: a transceiver; and processing hardware configured to implement the method according to any one of Examples 15 to 24.

[0317] Example 26. A RAN node as described in Example 25, wherein the RAN node is a distributed unit (DU) of the RAN node.

[0318] The following descriptions can be applied to the descriptions above.

[0319] 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, the events or boxes with dashed lines in the figures can be optional. Descriptions from the perspective of the receiving node also apply to the sending node. For example, a description of a receiving node (e.g., DU) receiving a message from a sending node (e.g., CU) can be replaced with a description of the sending node sending a message to the receiving node. Similarly, a description of a receiving node (e.g., CU) receiving a message from a sending node (e.g., DU) can be replaced with a description of the sending node sending a message to the receiving node.

[0320] In some implementations, "message" is used and can be replaced by "information element (IE)" and vice versa. In some implementations, "IE" is used and can be replaced by "field" and vice versa. In some implementations, "configurations" or "configuration parameters" can be used to replace "configuration" and vice versa. In some implementations, "serving cell change command," "LTM cell handover command," "lower layer handover command," or "lower layer serving cell change command" can be used instead of "LTM command." In some implementations, "layer 1 / layer 2" can be used to replace "lower layer." In some implementations, "some" means "one or more." In some implementations, "at least one" means "one or more." In some implementations, "cell group configuration" can be used to replace "DU configuration." In some implementations, "serving cell index," "LTM cell index," "special cell (SpCell) index," "PCell index," or "PSCell index" can be used to replace "cell index." In some implementations, "source" can be used instead of "service". In some implementations, "measurement result" or "CSI report" can be used instead of "measurement report". In some implementations, "early UL timing synchronization" or "early UL synchronization" can be used instead of "early TA acquisition". In some implementations, "early TA acquisition on / on the candidate cell" can be replaced by "synchronization with the candidate cell / with the candidate cell's early UL timing" or "synchronization with the candidate cell / with the candidate cell's early UL".

[0321] The user device that implements 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. Further, in some cases, the user device can be embedded in an electronic system such as a vehicle headunit or advanced driver assistance system (ADAS). Still 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.

[0322] 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., by software configuration) may be driven by cost and time considerations.

[0323] When implemented in software, the technology can be provided as part of an operating system, a library used by multiple applications, a specific software application, etc. The software can be executed by one or more general-purpose processors or one or more dedicated processors.

[0324] 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 a user equipment (UE), the method comprising: Communicating with the Radio Access Network (RAN) node via the serving cell; The UE receives a command to perform a low-layer triggered mobility LTM handover to the candidate cell; At the UE, the timing advance TA value is applied to the uplink UL synchronization with the candidate cell; as well as After the LTM handover to the candidate cell is completed, the UL synchronization is maintained at the UE based on the TA value.

2. The method of claim 1, further comprising: In response to the application of the TA value, a time alignment timer is started to define the validity period of the UL synchronization; In response to the command to perform the LTM switch, a Media Access Control (MAC) reset is performed; and In response to the MAC reset, the time alignment timer is prevented from expiring.

3. The method of claim 1, further comprising: In response to the application of the TA value, a time alignment timer is started to define the validity period of the UL synchronization; In response to the command to perform the LTM switch, a Media Access Control (MAC) reset is performed; The expiration of the time alignment timer is determined in response to the MAC reset; as well as The UE is determined to maintain UL synchronization after the time alignment timer expires.

4. The method of claim 3, further comprising: After the MAC reset is performed and while the time alignment timer is running, a UL transmission is sent to the RAN node without performing a random access procedure.

5. The method of any one of claims 3 or 4, further comprising: After determining that the UE maintains the UL synchronization, a TA command is received in the candidate cell, the TA command including a new TA value.

6. The method of claim 1, further comprising: In response to the command to perform the LTM switch, a Media Access Control (MAC) reset is performed; In response to the MAC reset, a time alignment timer is started to define the validity period of the UL synchronization based on the TA value.

7. The method of claim 1, further comprising: Prior to receiving the command, a time alignment timer is started to define the validity period of the UL synchronization.

8. The method of any one of claims 1 to 7, wherein the command for performing the LTM switching does not include the TA value, the method further comprising: The TA value is determined using one or more measurements at the UE.

9. A user equipment (UE), comprising: transceiver; as well as Processing hardware, the processing hardware being configured to implement the method according to any one of the preceding claims.

10. A method implemented in a radio access network (RAN) node, the method comprising: Communicating with the User Equipment (UE) at the RAN node; The RAN node sends a command to the UE to perform a low-layer triggered mobility LTM handover to the candidate cell; In response to determining that the UE has accessed the candidate cell, the RAN node sends a timed advance TA command to the UE. The TA command includes a TA value for maintaining uplink UL synchronization with the candidate cell after the LTM handover is completed.

11. The method of claim 10, wherein: The command to execute the LTM switch includes a first TA value; and The TA value included in the TA command is the second TA value.

12. The method of any one of claims 10 or 11, further comprising: In response to sending the TA command, a RAN time alignment timer is started to define the validity period of the UL synchronization.

13. The method of any one of claims 10 to 12, further comprising: In response to the command to perform the LTM handover, a Media Access Control (MAC) reset is performed for the UE.

14. The method of any one of claims 10 to 13, further comprising: Before sending the command to perform the LTM handover, the LTM configuration for configuring the candidate cell is sent to the UE.

15. A radio access network (RAN) node, the RAN node comprising: transceiver; as well as Processing hardware, the processing hardware being configured to implement the method according to any one of claims 10 to 14.

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