Managing configurations for fast serving cell changes

Abstract

A user equipment (UE) receives a first reference lower layer triggered mobility (LTM) configuration from a radio access network (RAN) node. The UE further receives a second reference LTM configuration from the RAN node. The UE replaces the first reference LTM configuration with the second reference LTM configuration.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Provisional U.S. Patent Application No. 63 / 483,754, entitled “Managing Configurations for FastServing Cell Changes,” filed on February 7, 2023. The entire contents of this provisional application are hereby expressly incorporated herein by reference. Technical Field

[0003] The present disclosure relates to wireless communications, and more particularly, to managing configuration for fast serving cell changes for user equipment (UE). Background Art

[0004] This background description is provided for the purpose of generally presenting the context of the present disclosure. The work of the inventors named herein (to the extent that it is described in this background section) and aspects of the specification that may not have been considered prior art at the time of filing are neither explicitly nor implicitly admitted to be prior art to the present disclosure.

[0005] In telecommunications systems, the Packet Data Convergence Protocol (PDCP) sublayer of the radio protocol stack provides services such as user plane data transfer, encryption, integrity protection, etc. For example, the PDCP layer defined for the Evolved Universal Terrestrial Radio Access (EUTRA) radio interface (see 3GPP specification TS 36.323) and New Radio (NR) (see 3GPP specification TS 38.323) provides sequencing of protocol data units (PDUs) in the uplink direction (from a user device (also referred to as user equipment (UE)) to a base station) and in the downlink direction (from a base station to a UE). Furthermore, the PDCP sublayer provides signaling radio bearers (SRBs) and data radio bearers (DRBs) to the radio resource control (RRC) sublayer. Generally speaking, the UE and the base station can use SRBs to exchange RRC messages and non-access stratum (NAS) messages, and can use DRBs to transmit data on the user plane.

[0006] The UE can use several types of SRBs and DRBs. When operating in dual connectivity (DC), the cells associated with the base station operating the master node (MN) define a master cell group (MCG), and the cells associated with the base station operating as the secondary node (SN) define a secondary cell group (SCG). The so-called SRB1 resources carry RRC messages including NAS messages on the dedicated control channel (DCCH) in some cases, while SRB2 resources support RRC messages including logged measurement information or NAS messages also on the DCCH but with a lower priority than the SRB1 resources. More generally, SRB1 and SRB2 resources allow the UE and MN to exchange RRC messages related to the MN and embed RRC messages related to the SN, and may also be referred to as MCG SRBs. SRB3 resources allow the UE and SN to exchange RRC messages related to the SN, and may be referred to as SCG SRBs. Split SRBs allow the UE to exchange RRC messages directly with the MN via the lower layer resources of the MN and SN. Further, a DRB using only the lower layer resources of the MN may be referred to as an MCG DRB, a DRB using only the lower layer resources of the SN may be referred to as an SCG DRB, and a DRB using the lower layer resources of both the MCG and the SCG may be referred to as a split DRB.

[0007] In some scenarios, the UE can simultaneously utilize the resources of multiple radio access network (RAN) nodes (e.g., base stations, or components of distributed base stations) interconnected by backhaul. When these network nodes support different radio access technologies (RATs), this type of connection is called multi-radio dual connectivity (MR-DC). When the UE operates in MR-DC, one base station operates as a master node (MN) covering a primary cell (PCell), and the other base station operates as a secondary node (SN) covering a 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. A base station and / or the UE determines that the UE should establish a radio connection with another base station. For example, a base station may determine to hand over the UE to a second base station and initiate a handover process.

[0008] When a UE moves from the coverage area of ​​one cell in the RAN to the coverage area of ​​another cell, the UE and the network must perform a serving cell change at some point. To perform the serving cell change, the RAN configures the UE to send Layer 3 (L3) measurements. Based on the L3 measurements from the UE, the RAN sends an RRC reconfiguration message for reconfiguration with synchronization (e.g., the RRC reconfiguration message includes a ReconfigurationWithSync information element (IE)) for a serving cell change (e.g., PCell or PSCell). In the case where the UE operates with carrier aggregation (CA) of at least one secondary cell (SCell) with the PCell or PSCell, the RAN must release at least one SCell due to the PCell or PSCell change. A serving cell change involves a full L2 (and L1) reset, resulting in longer latency, greater overhead, and longer outage time.

[0009] To address these issues, 3GPP recently proposed developing mobility procedures for reducing latency and overhead for fast serving cell changes, as described in technical document RP-221799. However, it is unclear how the network (e.g., base station) and UE should configure and manage the configuration for these mobility procedures, especially when there are configuration updates. Summary of the Invention

[0010] An example embodiment of these techniques is a configuration method implemented in a user equipment (UE), the method comprising: receiving a first reference lower layer triggered mobility (LTM) configuration from a radio access network (RAN) node; receiving a second reference LTM configuration from the RAN node; and replacing the first reference LTM configuration with the second reference LTM configuration.

[0011] Another example embodiment of the techniques is a configuration method implemented in a radio access network (RAN) node, the method comprising: sending a first reference lower layer triggered mobility (LTM) configuration to a user equipment (UE); sending a second reference LTM configuration to the UE; and replacing the first reference LTM configuration with the second reference LTM configuration at the RAN node.

[0012] Yet another example embodiment of these techniques is an apparatus comprising a transceiver and processing hardware, wherein the apparatus is configured to implement one of the above methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1A is a block diagram of an example system in which a radio access network (RAN) and a user device may implement the disclosed techniques for managing conditional procedures related to a secondary node (SN);

[0014] Figure 1B It includes Figure 1A A block diagram of an example base station of a centralized unit (CU) and a distributed unit (DU) operating in a system;

[0015] Figure 2A is a block diagram of an example protocol stack, Figure 1A The UE communicates with the base station according to the protocol stack;

[0016] Figure 2B is a block diagram of an example protocol stack, Figure 1A The UE communicates with the CU and DU according to the protocol stack;

[0017] Figure 3 is a messaging diagram for an example scenario in which the CU provides a reference lower layer triggered mobility configuration to the DU for use in generating a configuration of the UE;

[0018] Figure 4 is similar to Figure 3 but a message passing diagram for an example scenario where the base station includes a source DU (S-DU) and a target DU (T-DU);

[0019] Figure 5A is similar to Figure 3 Message passing diagram for an example scenario where the UE communicates under DC with the MN and SN;

[0020] Figure 5B is similar to Figure 5A Message passing diagram for an example scenario where the CU provides configuration to the UE via the MN;

[0021] Figure 6A is similar to Figure 3 Message passing diagram for an example scenario of , but where the CU communicates with the S-DU and T-DU in the SN;

[0022] Figure 6B is similar to Figure 6A Message passing diagram of an example scenario of an example scenario of , but where the CU provides the configuration to the UE via the MN;

[0023] Figure 7A is similar to Figure 3 Message passing diagram of an example scenario of an example scenario of , but where the CU communicates with both the M-DU and the S-DU;

[0024] Figure 7B is similar to Figure 7A Message passing diagram for an example scenario of , but where the CU provides a reference lower layer triggered mobility configuration to the UE via an M-DU;

[0025] Figure 8A is similar to Figure 3 Message passing diagram for an example scenario of , but where the CU communicates with the M-DU, S-DU, and T-DU;

[0026] Figure 8B is similar to Figure 8A but a messaging diagram for an example scenario where the CU provides a reference to a lower layer triggering mobility configuration to the UE via an M-DU;

[0027] Figure 9 is a flow chart of an example method that may be implemented in a RAN of the present disclosure for configuring a UE with a reference LTM configuration and using the reference LTM configuration after the UE performs a serving cell change;

[0028] Figure 10A is a flow chart of an example method that may be implemented in the RAN of the present disclosure for configuring a UE with a first reference LTM configuration and a second reference LTM configuration that replaces the first reference LTM configuration;

[0029] Figure 10B is a flow chart of an example method that may be implemented in the RAN of the present disclosure for configuring a UE with a first reference LTM configuration and a second reference LTM configuration that modifies the first reference LTM configuration;

[0030] Figure 10C is a flow chart of an example method that may be implemented in the RAN of the present disclosure for configuring a UE with a first reference LTM configuration and a second reference LTM configuration that replaces or modifies the first reference LTM configuration;

[0031] Figure 11 is a flow chart of an example method that may be implemented in a RAN of the present disclosure for determining whether a subsequent DU configuration affects a previous reference LTM configuration to determine which LTM configuration to send to a UE;

[0032] Figure 12 is a flow chart of an example method that may be implemented in a UE of the present disclosure for receiving a reference LTM configuration and using the reference LTM configuration to communicate with a RAN after performing a serving cell change;

[0033] Figure 13A is a flow chart of an example method for processing multiple reference LTM configurations that may be implemented in a UE of the present disclosure;

[0034] Figure 13B is a flow chart of an example method that may be implemented in a UE of the present disclosure for determining whether a subsequent reference LTM configuration replaces or modifies a previous reference LTM configuration;

[0035] Figure 14is a flow chart of an example method that may be implemented in a UE of the present disclosure for determining how to utilize a reference LTM configuration based on whether the reference LTM configuration is a full configuration or an incremental configuration; and

[0036] Figure 15 is a flow chart of an example method that may be implemented in a UE of the present disclosure for determining how to utilize an LTM configuration based on whether the UE has a reference LTM configuration. DETAILED DESCRIPTION

[0037] Figure 1A An example wireless communication system 100 is depicted in which a communication device may implement these techniques. Wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106, and a core network (CN) 110. UE 102 initially connects to base station 104. In some scenarios, base station 104 may perform a SN add to configure UE 102 to operate in dual connectivity (DC) with base station 104 and base station 106. Base stations 104 and 106 operate as the mobile node and a network node, respectively, of UE 102.

[0038] In various configurations of the wireless communication system 100, the base station 104 can be implemented as a master eNB (MeNB) or a master gNB (MgNB), and the base station 106 can be implemented as a secondary gNB (SgNB). The UE 102 can communicate with the base station 104 and the base station 106 via the same RAT or different RATs such as EUTRA or NR. When the base station 104 is a MeNB and the base station 106 is an SgNB, the UE 102 can be in EUTRA-NR DC (EN-DC) with the MeNB and the SgNB.

[0039] In some cases, the MeNB or SeNB is implemented as an ng-eNB instead of an eNB. When the base station 104 is a master ng-eNB (Mng-eNB) and the base station 106 is an SgNB, the UE 102 can be in Next Generation (NG) EUTRA-NR DC (NGEN-DC) with the Mng-eNB and the SgNB. When the base station 104 is a MgNB and the base station 106 is an SgNB, the UE 102 can be in NR-NR DC (NR-DC) with the MgNB and the SgNB. When the base station 104 is a MgNB and the base station 106 is a secondary ng-eNB (Sng-eNB), the UE 102 can be in NR-EUTRA DC (NE-DC) with the MgNB and the Sng-eNB.

[0040] In a scenario where UE 102 is handed over from base station 104 to base station 106, base stations 104 and 106 operate as a source base station (S-BS) and a target base station (T-BS), respectively. For example, before the handover, UE 102 may communicate with base station 104 and an additional base station ( Figure 1A After the handover is completed, UE 102 may continue to operate in DC with base station 106 and the additional base station or operate in single connectivity (SC) with base station 106. In this case, base stations 104 and 106 operate as a source MN (S-MN) and a target MN (T-MN), respectively.

[0041] The core network (CN) 110 may be an evolved packet core (EPC) 111 or a fifth generation core (5GC) 160, both of which are Figure 1A 1. The base station 104 may be an eNB supporting an S1 interface for communicating with the EPC 111, an ng-eNB supporting an NG interface for communicating with the 5GC 160, or a gNB supporting both an NR radio interface and an NG interface for communicating with the 5GC 160. To exchange messages directly with each other during the scenarios discussed below, the base stations 104 and 106 may support an X2 or Xn interface. Among other components, the EPC 111 may include a serving gateway (SGW) 112, a mobility management entity (MME) 114, and a packet data network gateway (PGW) 116. The SGW 112 is generally configured to transport user plane packets associated with audio calls, video calls, internet services, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The PGW 116 provides connectivity from the UE to one or more external packet data networks, such as an internet network and / or an internet protocol (IP) multimedia subsystem (IMS) network. 5GC 160 includes a user plane function (UPF) 162 and an access and mobility management (AMF) 164 and / or a session management function (SMF) 166. UPF 162 is generally configured to transmit user plane packets related to audio calls, video calls, Internet services, etc., AMF 164 is configured to manage authentication, registration, paging and other related functions, and SMF 166 is configured to manage PDU sessions.

[0042] like Figure 1A As shown, base station 104 supports cell 124A, and base station 106 supports cell 126. Cells 124A and 126 may partially overlap, such that UE 102 may communicate with base station 104 and base station 106 in DC, where one of base stations 104 and 106 is a MN and the other is a SN. Base station 104 may support additional cells such as cells 124B and 124C, and base station 106 may support additional cells ( Figure 1A(not shown). Cells 124A, 124B, and 124C may partially overlap, allowing UE 102 to communicate with base station 104 using carrier aggregation (CA). Base station 104 may operate cells 124A, 124B, and 124C via one or more transmission and reception points (TRPs). More specifically, when UE 102 operates in DC with base station 104 and base station 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.

[0043] In general, 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 the 5GC 160 may be connected to any suitable number of base stations supporting NR cells and / or EUTRA cells. Although the examples below specifically relate to specific CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, the techniques of the present disclosure may also be applicable to other suitable radio access technologies and / or core network technologies, such as sixth generation (6G) radio access and / or 6G core network or 5G NR-6G DC.

[0044] Continue to refer Figure 1A, the base station 104 is equipped with processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and non-transitory computer-readable memory storing instructions, and the one or more general-purpose processors execute the instructions. Additionally or alternatively, the processing hardware 130 may include a dedicated processing unit. The processing hardware 130 may include a PHY controller (not shown) configured to send data and control signals on physical downlink (DL) channels and DL reference signals to one or more user devices (e.g., UE 102) via one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs. The PHY controller is also configured to receive data and control signals on physical uplink (UL) channels and / or UL reference signals to one or more user devices via one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs. In an example implementation, the processing hardware 130 includes a MAC controller 132, which is configured to perform MAC functions with one or more user devices. MAC functions include random access (RA) procedures, managing UL timing advance for one or more user devices, and / or communicating UL / DL MAC PDUs with one or more user devices. The processing hardware 130 may further include an RRC controller 134 to implement procedures and messaging at the RRC sublayer of the protocol communication stack. For example, the RRC controller 134 may be configured to support RRC messaging associated with a handover procedure and / or support necessary operations when the base station 104 operates as a MN relative to a SN or a SN relative to a MN. The base station 106 may include processing hardware 140 similar to the processing hardware 130. In particular, components 142, 144, and 146 may be similar to components 132, 134, and 136, respectively.

[0045] The processing hardware 130 may also include an LTM controller 136 configured to implement the following reference Figures 3 to 15 At least some of the techniques discussed.

[0046] UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors such as a CPU and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or dedicated processing units. A PHY controller (not shown) is further configured to receive data and control signals on physical DL channels and / or DL ​​reference signals with base station 104 or 106 via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. The PHY controller is further configured to send data and control signals on physical UL channels and / or UL reference signals with base station 104 or 106 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 152, which is configured to perform MAC functions with base station 104 or 106. For example, MAC functions include random access procedures, managing UL timing advance of one or more user devices, and communicating UL / DL MAC PDUs with base station 104 or 106. The processing hardware 150 may further include an RRC controller 154 to implement procedures and message delivery at the RRC sublayer of the protocol communication stack. Further, the processing hardware 150 may also include an LTM controller 156 configured to implement the following reference Figures 3 to 15 At least some of the techniques discussed.

[0047] In operation, UE 102 may use radio bearers (e.g., DRBs or SRBs) under DC that terminate at different times at MN 104 or SN 106. UE 102 may apply one or more security keys when communicating on the radio bearers in the uplink (UL) (from UE 102 to the base station) and / or downlink (from the base station to UE 102) directions.

[0048] Figure 1BAn example distributed implementation of a base station, such as base station 104 or 106, is depicted. In this implementation, the base station may include a centralized unit (CU) 172 and one or more distributed units (DUs) 174. CU 172 is equipped with processing hardware, which may include one or more general-purpose processors, such as CPUs, and 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 an example implementation, processing hardware 140 includes an SN RRC controller (not shown) configured to manage or control one or more RRC configurations and / or RRC procedures when base station 106 operates as an SN. DU 174 is also equipped with processing hardware, which may include one or more general-purpose processors, such as CPUs, and 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 an example implementation, the processing hardware includes: a medium 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 a MN or a SN. The processing hardware may further include a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0049] Figure 2A An example protocol stack 200 is shown in a simplified manner, according to which a UE 240 (e.g., which can be implemented as UE 102) can communicate with an eNB / ng-eNB 230 (e.g., which can be implemented as base station 104 or 106) or a gNB (e.g., which can be implemented as base station 104).

[0050] In the example stack 200, the EUTRA physical layer (PHY) 202A provides transport channels to the EUTRA MAC sublayer 204A, which in turn provides logical channels to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A in turn provides RLC channels to the EUTRA PDCP sublayer 208 and, in some cases, to the NR PDCP sublayer 210. Similarly, the NRRPHY 202B provides transport channels to the NR MAC sublayer 204B, which in turn provides logical channels to the NR RLC sublayer 206B. The NR RLC sublayer 206B in turn provides data transfer services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 can then provide data transfer services to the Service Data Adaptation Protocol (SDAP) 212 or the Radio Resource Control (RRC) sublayer ( Figure 2A In some implementations, the UE 102 supports both EUTRA and NR stacks, such as Figure 2A As shown, to support switching between EUTRA and NR base stations and / or support DC through EUTRA and NR interfaces. Figure 2A As shown, the UE 102 may support NR PDCP 210 layered on top of the EUTRA RLC 206A, and SDAP sublayer 212 layered on top of the NR PDCP sublayer 210.

[0051] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets, which may be referred to as service data units (SDUs) (e.g., from an Internet Protocol (IP) layer layered directly or indirectly on the PDCP layer 208 or 210), and output packets, which may be referred to as protocol data units (PDUs) (e.g., to the RLC layer 206A or 206B). For simplicity, this disclosure refers to both SDUs and PDUs as "packets," except where the difference between SDUs and PDUs is relevant.

[0052] On the control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 may provide signaling radio bearers (SRBs) or RRC sublayers ( Figure 2A The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 may exchange data (e.g., RRC messages or non-access stratum (NAS) messages) on the user plane. The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 may provide data radio bearers (DRBs) to support data exchange. The data exchanged on the NR PDCP sublayer 210 may be SDAP PDUs, Internet Protocol (IP) packets, or Ethernet packets.

[0053] Figure 2BAn example protocol stack 250 is shown in simplified form in which the UE 102 can communicate with a DU (e.g., DU 174) and a CU (e.g., CU 172). The radio protocol stack 200 is functionally split, as shown in FIG. Figure 2B 20. The CU at either base station 104 or 106 can maintain all control and upper layer functions (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.

[0054] Next is the Figure 1A Several example scenarios are provided in which a base station operating in a system sends a configuration to a UE 102 and later activates the configuration for communication between the UE 102 and the base station. Figures 3 to 7B Similar events are marked with similar reference numerals (e.g., event 316 is similar to Figure 4 A and Figure 4 B's event 416, Figure 5A Event 516, Figure 5B Event 517, Figure 6A Event 616, Figure 6B Event 617, Figure 7A Event 716 and Figure 7B 717), with differences discussed below where appropriate. In addition to the differences shown in the figures and discussed below, any of the alternative implementations discussed with respect to a particular event (e.g., for message delivery and processing) may apply to events labeled with similar reference numbers in other figures.

[0055] First reference Figure 3 In scenario 300, base station 104 includes CU 172 and DU 174, and DU 174 operates cell 124A. UE 102 initially communicates 302 with DU 174 on cell 124A using a serving DU configuration, and communicates with CU 172 via DU 174, for example, using a serving CU configuration. In some implementations, UE 102 communicates 306 with DU 174 in cell 124A and other cells (e.g., Figure 1A174 operates other cells. In other implementations, UE 102 communicates with DU 174 only on cell 124A. In some implementations, UE 102 communicates with DU 174 on cell 124A and / or other cells via one or more TRPs. In some implementations, cell 124A may be a PCell. In such cases, the other cells include SCells and / or additional cells associated with the PCell or SCell. In other implementations, cell 124A may be an SCell, and one of the other cells may be a PCell. In such cases, the remaining cells include SCells and / or additional cells associated with the PCell or SCell. In the following description, base station 104 may be DU 174, CU 172, or DU 174 and CU 172.

[0056] During operation 302, UE 102 may transmit UL PDUs and / or UL control signals to base station 104 on cell 124A and / or other cells via one or more TRPs. In some implementations, UE 102 communicates UL PDUs and / or DL ​​PDUs with base station 104 via radio bearers that may include SRBs and / or DRBs. Base station 104 may configure radio bearers to UE 102. In some implementations, the UL control signals include UL control information, channel state information, hybrid automatic repeat request (HARQ) acknowledgements (ACKs), HARQ negative ACKs, scheduling requests, and / or sounding reference signals. Similarly, UE 102 may receive DL PDUs and / or DL ​​control signals from base station 104 on cell 124A and / or other cells via one or more TRPs. In some implementations, the DL control signals include downlink control information (DCI) and reference signals (e.g., synchronization signal blocks, channel state information reference signals (CSI-RS), and / or tracking reference signals). Base station 104 may send DCI via one or more TRPs on a physical downlink control channel (PDCCH) on cell 124A and / or other cells monitored by UE 102.

[0057] In some implementations, the serving DU configuration includes physical layer configuration parameters, MAC layer configuration parameters, and / or RLC configuration parameters. In some implementations, DU 174 may send these configuration parameters to CU 172. CU 172 generates one or more messages (e.g., RRC reconfiguration messages) including the configuration parameters and sends the one or more messages to UE 102 via DU 174. In other implementations, DU 174 sends the configuration parameters directly to UE 102. In some implementations, the serving DU configuration is the CellGroupConfig IE defined in 3GPP specification 38.331. In other implementations, the serving DU configuration includes configuration parameters in the CellGroupConfig IE. In some implementations, the serving CU configuration includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, the serving CU configuration includes the MeasConfig IE and / or the RadioBearerConfig IE defined in 3GPP specification 38.331, or includes configuration parameters in the MeasConfig IE and / or the RadioBearerConfig IE. In some implementations, the serving DU configuration includes the CSI-MeasConfig IE or configuration parameters for channel state information (CSI) measurement and reporting. In other implementations, the serving CU configuration includes the CSI-MeasConfig IE or configuration parameters for channel state information (CSI) measurement and reporting. In some implementations, the UE 102 receives the serving CU configuration or the configuration parameters in the serving CU configuration from the CU 172 via the DU 174. In other implementations, the 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 the base station 104, and receives the remainder of these configuration parameters from the base station 104.

[0058] While communicating with base station 104, UE 102 sends 304 at least one measurement report 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 of UE 102. For each L3 measurement report, DU 174 sends 306 a DU-to-CU message to CU 172 including the L3 measurement report. In some implementations, the DU-to-CU message of event 306 is an F1 Application Protocol (F1AP) message (e.g., an UL RRC messaging message). In some implementations, DU 174 does not send or refrains from sending the L1 measurement report 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, a serving DU configuration or a serving CU configuration includes at least one measurement configuration. In some implementations, at event 302, UE 102 receives one or more RRC messages (e.g., RRCReconfiguration messages) from CU 172 via DU 174, including at least one measurement configuration. Based on the at least one measurement configuration, UE 102 performs measurements and sends 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., a MeasConfig IE) and / or an L1 measurement configuration. The L1 measurement configuration (e.g., a CSI-MeasConfig IE) may include an L1 measurement resource configuration and / or an L1 measurement report configuration. The L1 measurement resource configuration may configure the UE 102 with reference signal (e.g., CSI-RS) resources for measuring and obtaining L1 measurement results. For example, the L1 measurement resource configuration is a CSI-ResourceConfig IE. In another example, the L1 measurement report configuration configures the manner in which UE 102 sends L1 measurement results / reports. For example, the L1 measurement report configuration is a CSI-ReportConfig IE. For example, UE 102 sends an L3 measurement report to CU 172 via DU 174 according to the L3 measurement configuration. UE 102 sends an L1 measurement report to DU 174 according to the L1 measurement configuration or L1 measurement report configuration. In one implementation, DU 174 does not send an L1 measurement report to CU 172.

[0059] In some implementations, an L1 measurement configuration is an RRC IE defined specifically for and dedicated to Lower Layer Triggered Mobility (LTM) (e.g., in a relevant 3GPP specification such as TS 38.331). Further, in some implementations, an L1 measurement resource configuration is an RRC IE defined specifically for and dedicated to LTM. Still further, in some implementations, an L1 measurement report configuration is an RRC IE defined specifically for and dedicated to LTM. In some implementations, each of the L1 measurement report configurations may include a triggering event configuration that configures a triggering event to trigger UE 102 to send an L1 measurement report. If UE 102 detects a triggering event, UE 102 sends the L1 measurement report to DU 174.

[0060] In some implementations, (each of) the L1 measurement reports may include at least one L1 measurement result. In some implementations, at least the L1 measurement result includes at least one L1 reference signal received power (L1-RSRP) value, an L1 reference signal received quality (L1-RSRQ), and / or at least one L1 signal-to-interference and noise ratio (L1-SINR) value. In some implementations, for each of the L1 measurement reports, the UE 102 sends a PUCCH transmission including the L1 measurement report to the DU 174. That is, the UE 102 sends each of the L1 measurement reports to the DU 174 on the PUCCH. In other implementations, for each of the L1 measurement reports, the UE 102 sends a PUSCH transmission including the L1 measurement report to the DU 174. That is, the UE 102 sends each of the L1 measurement reports to the DU 174 on the PUSCH. In yet other implementations, the UE 102 transmits a portion of the L1 measurement report to the DU 174 on the PUCCH and transmits the remaining portion of the L1 measurement report on the physical UL shared channel (PUSCH). That is, for each portion of the L1 measurement report, the UE 102 transmits a PUCCH transmission including the L1 measurement report to the DU 174, and for each remaining portion of the L1 measurement report, the UE 102 transmits a PUSCH transmission including the L1 measurement report to the DU 174. In some implementations, each of the L1 measurement reports is a portion of channel state information (CSI) (i.e., a CSI component) or CSI. In some implementations, the UE 102 may include other CSI components in (each of) the aforementioned PUCCH transmission and / or PUSCH transmission. In one implementation, other CSI components include, for example, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a CSI-RS resource indicator (CRI), a synchronization signal (SS) / physical broadcast channel (PBCH) resource block indicator (SSBRI), a layer indicator (LI), and / or a rank indicator (RI). In some implementations, the UE 102 does not send the L1 measurement report to the DU 174 in the format of an RRC message. In some implementations, each of the L1 measurement reports includes an L1 event ID for identifying or indicating a triggered L1 event. Alternatively, each of the L1 measurement reports does not include an L1 event ID for identifying or indicating a triggered L1 event.

[0061] In some implementations, each L3 measurement report in the L3 measurement report may include at least one L3 measurement result. In some implementations, the at least one L3 measurement result includes at least one RSRP (value) and / or at least one SINR (value). In one implementation, the UE 102 sends each of the L3 measurement reports to the CU 172 via the DU 174 on the PUSCH. In some implementations, each of the L3 measurement reports may be an RRC message (e.g., a MeasurementReport message). In some implementations, each of the L3 measurement configurations includes a specific measurement identifier (e.g., measId), and each of the L3 measurement reports includes a specific measurement identifier in a specific L3 measurement configuration. When the CU 172 receives the L3 measurement report including the measurement identifier and the L3 measurement result from the UE 102 via the DU 174, the CU 172 may determine that the L3 measurement report is associated with the L3 measurement configuration identified by the measurement identifier.

[0062] In some alternative implementations, for each of at least one measurement report (e.g., an L1 measurement report), the UE 102 sends a MAC control element (CE) including the measurement report to the DU 174 at event 304. To send the MAC CE, the UE 102 generates one or more MAC PDUs to the DU 174 at event 304, each MAC PDU including one or more of the MAC CEs.

[0063] In some implementations, the UE 102 performs measurements on one or more reference signals according to at least one measurement configuration. The one or more reference signals may include one or more synchronization signal (SS) / physical broadcast channel (PBCH) resource blocks (SSBs) and / or one or more CSI-RSs. The UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurements. The DU 174 performs measurements on the cell 124A and other cells (e.g., cell 124B, cell 124C, and / or Figure 1A One or more reference signals are sent on a cell (not shown in the figure).

[0064] After receiving one or more of the at least one measurement report from UE 102 (e.g., in response thereto), base station 104 (i.e., CU 172 or DU 174) determines to prepare a first cell (e.g., cell 124B) for LTM for 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 can be used by base station 104 to communicate with UE 102. In some implementations, base station 104 determines to prepare the first cell for UE 102 because at least one measurement report indicates that the first cell qualifies as a candidate cell that can be used for communication with UE 102. In some implementations, CU 172 determines to prepare the first cell for UE 102 if the L3 measurement report indicates that the signal strength and / or quality of the first cell is above a first predetermined threshold, is better than the strength and / or quality of cell 124A, and / or is better than the strength and / or quality of cell 124A by a first predetermined threshold. In other implementations, if the L1 measurement report indicates that the signal strength and / or quality of the first cell is above a first predetermined threshold, is better than the signal strength and / or quality of cell 124A, and / or is 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.

[0065] If the CU 172 determines to prepare the first cell for LTM, the CU 172 sends 308 a first CU-to-DU message to the DU 174 to prepare the first cell for the UE 102. In some implementations, the CU 172 includes a cell identifier (ID) of the first cell in the first CU-to-DU message to request the DU 174 to prepare the first cell for LTM for the UE 102. For example, the cell ID is a cell global identifier (CGI). In another example, the cell ID is a portion of the CGI. In yet another example, the cell ID is a physical cell ID (PCI). In response to the first CU-to-DU message, the DU 174 generates a first LTM configuration (hereinafter referred to as LTM configuration 1) for the UE 102, which configures the first cell for LTM. The DU 174 then sends 310 a first DU-to-CU message including the LTM configuration 1 to the CU 172 in response to the first CU-to-DU message. In the event that DU 174 determines to prepare the first cell, DU 174 initiates sending a first DU-to-CU message to CU 172 rather than responding to a CU-to-DU message received from CU 172 .

[0066] In some implementations, DU 174 includes the cell ID of the first cell associated with LTM configuration 1 in the first DU-to-CU message to indicate that LTM configuration 1 is configured for or associated with the first cell. CU 172 identifies that LTM configuration 1 is configured for or associated with the first cell. In some scenarios and implementations, CU 172 may include additional cell IDs (e.g., cell IDs 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 configurations (e.g., LTM configurations 2, ..., N), each configuring a specific one of the additional cells, as described below. In such cases, DU 174 includes the additional cell IDs associated with each additional LTM configuration in the first DU-to-CU message to indicate which LTM configuration is associated with which cell (ID). Cells 1 and / or 2, ..., N are candidate cells.

[0067] In some implementations, CU 172 does not include a (reference) LTM configuration in the first CU-to-DU message. In such cases, DU 174 generates a reference LTM configuration, generates LTM configurations 1 and / or 2, ..., N (i.e., non-reference LTM configurations) based on the reference LTM configuration, and includes the reference LTM configuration in the first DU-to-CU message. In other implementations, CU 172 includes a reference LTM configuration in the first CU-to-DU message. In such cases, DU 174 generates LTM configurations 1 and / or 2, ..., N, which are incremental configurations to enhance the reference LTM configuration. In yet other implementations, CU 172 includes a reference LTM configuration (e.g., the first reference LTM configuration) in the first CU-DU message. In such cases, DU 174 generates a reference LTM configuration (e.g., a second reference LTM configuration) that replaces the first reference LTM configuration, generates LTM configurations 1 and / or 2, ..., N based on the second reference LTM configuration, and includes the second reference LTM configuration in the first DU-to-CU message.

[0068] In some implementations, the reference LTM configuration includes physical layer configuration parameters, MAC layer configuration parameters, and / or RLC configuration parameters. In some implementations, the reference LTM configuration is the CellGroupConfig IE defined in 3GPP specification 38.331. In other implementations, the reference LTM configuration includes configuration parameters in the CellGroupConfig IE. In some implementations, the reference LTM configuration includes the CSI-MeasConfig IE or configuration parameters for channel state information (CSI) measurement and / or reporting.

[0069] In some implementations, the reference LTM configuration is different from the serving DU configuration. In some implementations, a portion of the reference LTM configuration is identical to a portion of the serving DU configuration, and the remainder of the reference LTM configuration is different from the remainder of the serving DU configuration. In other implementations, the reference LTM configuration is identical to the serving DU configuration.

[0070] After receiving the first DU-to-CU message, CU 172 generates an RRC reconfiguration message (e.g., an RRCReconfiguration message) that includes LTM configuration 1 and sends 316 a second CU-to-DU message that includes the RRC reconfiguration message to DU 174. In some implementations, CU 172 includes a reference LTM configuration in RRC reconfiguration message 316. In other implementations, CU 172 does not include the reference LTM configuration in RRC reconfiguration message 316. In some implementations, if CU 172 sends a reference LTM configuration to UE 102 during event 302, CU 174 does not include the reference LTM configuration in RRC reconfiguration message 316. In other implementations, if CU 172 receives the reference LTM configuration from DU 174, CU 172 includes the LTM configuration in RRC reconfiguration message 316. Otherwise, if the CU 172 does not receive the reference LTM configuration from the DU 174 , the CU 172 does not include the reference LTM configuration in the RRC reconfiguration message 316 .

[0071] After receiving the RRC reconfiguration message 316, DU 174 sends 318 the RRC reconfiguration message to UE 102. In response, UE 102 sends 320 an RRC reconfiguration complete message (e.g., an RRCReconfigurationComplete message) to DU 174, which in turn sends 322 a second DU-to-CU message including the RRC reconfiguration complete message to CU 172. In some implementations, CU 172 performs security protection (e.g., integrity protection and / or encryption) on the RRC reconfiguration message. For example, CU 172 generates a message authentication code for integrity (MAC-I) for the RRC reconfiguration message, encrypts the RRC reconfiguration message and the MAC-I to obtain an encrypted RRC reconfiguration message and an encrypted MAC-I, and sends a PDCP PDU including the encrypted RRC reconfiguration message and the encrypted MAC-I to UE 102 via DU 174 at events 316 and 318. When UE 102 receives the PDCP PDU from CU 172 via DU 174 (i.e., events 316 and 318), UE 102 decrypts the encrypted RRC reconfiguration and the encrypted MAC-I to obtain the RRC reconfiguration message and the MAC-I and verifies whether the MAC-I is valid. If UE 102 verifies that the MAC-I is invalid, UE 102 discards or ignores the RRC reconfiguration message. In some implementations, UE 102 may perform an RRC connection reestablishment procedure in response to the invalid MAC-I. Otherwise, if UE 102 verifies that the MAC-I is valid, UE 102 may process the RRC reconfiguration. UE 102 avoids applying (i.e., executing) LTM configuration 1 until a configuration activation command is received to activate LTM configuration 1 (e.g., event 330).

[0072] Events 308 (optional) and 310 Figure 3 are collectively referred to as the LTM preparation process 390. Events 316, 318, 320, and 322 are Figure 3 are collectively referred to as the LTM configuration delivery process 394.

[0073] In some implementations, prior to receiving the first CU-to-DU message, the DU 174 sends the reference LTM configuration to the UE 102 in a process similar to processes 390 and 392. In such cases, the DU 174 does not include the reference LTM configuration in the first DU-to-CU message.

[0074] In some implementations, where the CU 172 performs multiple LTM preparation processes 390, the DU 174 includes the reference LTM configuration in the first DU-to-CU message in the first LTM preparation process of the LTM preparation process 390. In such cases, the DU 174 may not include the reference LTM configuration in the DU-to-CU messages in the remainder of the LTM preparation process 390.

[0075] 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 Required message. In the case of a UE Context Modification Required message, CU 172 may send a UE Context Modification Confirm message to DU 174 in response to the UE Context Modification Required message. In some implementations, the second CU-to-DU message is a DL RRC Message Transfer message. In other implementations, the second CU-to-DU message is a UE Context Modification Request message, and DU 174 may send a second DU-to-CU message (e.g., a UE Context Modification Response message) to CU 172 in response to the second CU-to-DU message.

[0076] In some implementations, CU 172 includes LTM configuration 1 in a first container (e.g., a field / IE) and includes the first container in the RRC reconfiguration message at events 316 and 318. In such cases, CU 172 generates the first container. The first container is used to indicate to UE 102 that LTM configuration 1 should not be immediately applied. In some scenarios and implementations, UE 102 receives an RRC reconfiguration message (e.g., the RRC reconfiguration message at event 318) that includes the configuration (e.g., LTM configuration 1). If the configuration is included in the first container, UE 102 avoids immediately applying the configuration. Otherwise, if the configuration is not included in the first container, UE 102 may immediately apply the configuration. In some implementations, the first container may be a first add or modify list (e.g., an ltm-ConfigToAddModList field, an LTM-ConfigToAddModList IE, an ltm-CandidateConfigToAddModList field, or an LTM-CandidateConfigToAddModList IE). CU 172 includes LTM configuration 1 in the first element of the first add or modify list (hereinafter referred to as element 1). For example, element 1 can be an add or modify IE (ltm-ConfigToAddMod field, LTM-ConfigToAddMod IE, ltm-CandidateConfigToAddMod field, or LTM-CandidateConfigToAddMod IE). When UE 102 receives the first add or modify list, UE 102 can store the first add or modify list (e.g., in a variable in random access memory (RAM)). In other alternative implementations, DU 174 generates a first container and includes the first container in a first DU-to-CU message. In still other alternative implementations, DU 174 generates element 1 and includes element 1 in the first DU-to-CU message.

[0077] 1) CU assigns an ID to LTM configuration 1

[0078] In some implementations, CU 172 includes a first LTM ID (referred to herein as ID 1) identifying LTM configuration 1 or element 1 in the RRC reconfiguration message. In some implementations, CU 172 includes ID 1 in a first container or element 1. In some implementations, CU 172 assigns ID 1. In other implementations, CU 172 receives ID 1 in a first DU-to-CU message from DU 174, as described below.

[0079] If CU 172 assigns or generates ID 1, CU 172 may send ID 1 to DU 174, and DU 174 may associate ID 1 with LTM configuration 1. In some implementations, in a first CU-to-DU message, CU 172 includes ID 1 and indicates that ID 1 is associated with LTM configuration 1. In other implementations, after receiving the first DU-to-CU message, CU 172 sends 312 a third CU-to-DU message including ID 1 to DU 174, instead of including ID 1 in the first CU-to-DU message. In some implementations, in the third CU-to-DU message, CU 172 may include LTM configuration 1 and ID 1 and indicate the association between ID 1 and LTM configuration 1. Thus, DU 174 may directly associate ID 1 with LTM configuration 1. In other implementations, in the third CU-to-DU message, CU 172 may include cell ID 1 and ID 1 (i.e., the first LTM ID), and indicate the association between cell ID 1 and ID 1. Therefore, DU 174 associates ID 1 with LTM configuration 1 based on the association between cell ID 1 and ID 1 and the association between cell ID 1 and LTM configuration 1. In still other implementations, in the third CU-to-DU message, CU 172 may include LTM configuration 1, cell ID 1, and ID 1, and indicate the association between ID 1, LTM configuration 1, and cell ID 1. In some implementations, DU 174 may send 314 a third DU-to-CU message to CU 172 in response to the third CU-to-DU message. In some implementations, the third CU-to-DU message and the third DU-to-CU message are a UE context modification request message and a UE context modification response message. Events 312 (optional) and 314 (optional) are performed at Figure 3 392. In other implementations, CU 172 may include ID 1, cell ID 1, and / or LTM configuration 1 in the second CU-to-DU message, as described above. Thus, the third CU-to-DU message may be omitted.

[0080] Where CU 172 includes ID 1 in the first CU-to-DU message, DU 174 may include ID 1 in LTM configuration 1, first container, or element 1. Alternatively, DU 174 does not include ID 1 in LTM configuration 1, first container, and / or element 1.

[0081] 2) DU assigns an ID to LTM configuration 1

[0082] In some alternative implementations, DU 174 assigns ID 1, which identifies LTM configuration 1. In some implementations, DU 174 includes ID 1 in the first DU-to-CU message. CU 172 may include ID 1 in the RRC reconfiguration message, as described above. In other implementations, DU 174 includes ID 1 in LTM configuration 1, the first container, or element 1. Thus, CU 172 does not include the ID identifying LTM configuration 1 in the RRC reconfiguration message, the first container, and / or element 1.

[0083] In some implementations, CU 172 includes the reference LTM configuration in the first container. For example, CU 172 includes the reference LTM configuration in a field of the first container that is different from the field of the first container that includes LTM configuration 1. In other implementations, CU 172 includes the reference LTM configuration in RRC reconfiguration message 316 and outside of the first container. For example, CU 172 generates a third container (e.g., a field / IE) to include the first container and the reference LTM configuration, and includes the third container in RRC reconfiguration message 316. In still other implementations, DU 174 includes the reference LTM configuration in the first container. For example, DU 174 includes the reference LTM configuration in a field of the first container that is different from the field of the first container that includes LTM configuration 1. In still other implementations, DU 174 generates a fourth container (e.g., a field / IE) to include the first container and the reference LTM configuration, and includes the fourth container in first DU-to-CU message 310. In such cases, CU 172 includes the fourth container in RRC reconfiguration message 316. Alternatively, the CU 172 retrieves the reference LTM configuration and LTM configuration 1 from the fourth container and includes the reference LTM DU configuration and LTM DU configuration 1 as described above.

[0084] In some implementations, neither the CU 172 nor the DU 174 assigns an ID for identifying a reference LTM configuration. In such cases, there is no ID for the reference LTM configuration.

[0085] In some implementations, LTM Configuration 1 includes multiple configuration parameters for UE 102 to communicate with DU 174 on the first cell. In some implementations, the multiple configuration parameters include physical layer configuration parameters (e.g., PhysicalCellGroupConfig IE), MAC layer configuration parameters (e.g., MAC-CellGroupConfig IE), and / or RLC configuration parameters (e.g., RLC-BearerConfig IE). In some further implementations, the multiple configuration parameters include special cell configuration (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE). In some implementations, LTM Configuration 1 is the CellGroupConfig IE defined in 3GPP specification 38.331. In other implementations, LTM Configuration 1 includes configuration parameters in the CellGroupConfig IE.

[0086] In some implementations, DU 174 includes the random access configuration in LTM configuration 1. In other implementations, DU 174 does not include the random access configuration in LTM 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 configuration 1. Otherwise, if cell 124A and the first cell are synchronized, DU 174 determines not to include the random access configuration in LTM configuration 1. In other implementations, if DU 174 determines that UE 102 has not yet synchronized with the first cell in the UL, DU 174 determines to include the random access configuration in LTM configuration 1. Otherwise, if DU 174 determines that UE 102 has already synchronized with the first cell in the UL, DU 174 determines not to include the random access configuration in LTM configuration 1. If LTM configuration 1 includes the random access configuration, UE 102 performs a random access procedure according to the random access configuration at event 332, as described below. Otherwise, if LTM configuration 1 does not include random access configuration, UE 102 skips or avoids performing the random access procedure of event 332 in response to LTM configuration 1 excluding random access configuration.

[0087] In some implementations, DU 174 includes the random access configuration parameters in LTM configuration 1 and / or the reference LTM configuration regardless of whether cell 124A and the first cell are synchronized. UE 102 performs a random access procedure in event 332 according to the random access configuration parameters, as described below.

[0088] In some implementations, if cell 124A is synchronized with the first cell, DU 174 determines to include a first indication in LTM configuration 1, which configures UE 102 not to perform a random access procedure on the first cell. Otherwise, if cell 124A is not synchronized with the first cell, DU 174 determines not to include the first indication in LTM configuration 1. In other implementations, if DU 174 determines that UE 102 is already synchronized with the first cell in the UL, DU 174 determines to include the first indication in LTM configuration 1. Otherwise, if DU 174 determines that UE 102 is not yet synchronized with the first cell in the UL, DU 174 determines not to include the first indication in LTM configuration 1. If LTM configuration 1 includes the first indication, UE 102 skips or avoids performing the random access procedure of event 332 based on or in response to the first indication. Otherwise, if LTM configuration 1 does not include the first indication, then in response to LTM configuration 1 excluding the first indication, UE 102 performs a random access procedure according to the random access configuration at event 332, as described below.

[0089] In some implementations, the DU 174 includes the reconfiguration with synchronization configuration (e.g., ReconfigurationWithSync IE) in LTM Configuration 1 or the special cell configuration. In other implementations, the DU 174 does not include the reconfiguration with synchronization configuration (e.g., ReconfigurationWithSync IE) in LTM Configuration 1 or the special cell configuration. In some implementations, if the cell 124A and the first cell are not synchronized, the DU 174 determines to include the reconfiguration with synchronization configuration in LTM Configuration 1. Otherwise, if the cell 124A and the first cell are synchronized, the DU 174 determines not to include the reconfiguration with synchronization configuration in LTM Configuration 1. In other implementations, if the DU 174 determines that the UE 102 has not yet synchronized with the first cell in the UL, the DU 174 determines to include the reconfiguration with synchronization configuration in LTM Configuration 1. Otherwise, if DU 174 determines that UE 102 is already synchronized with the first cell in the UL, DU 174 determines not to include the reconfiguration with synchronization configuration in LTM configuration 1. In some implementations, if LTM configuration 1 includes the reconfiguration with synchronization configuration, UE 102 performs a random access procedure at event 332 in response to or in accordance with the reconfiguration with synchronization configuration, as described below. Otherwise, if LTM configuration 1 does not include the reconfiguration with synchronization configuration, UE 102 skips or avoids performing the random access procedure of event 332. In some implementations, DU 174 includes the cell ID of cell 1 (i.e., the first cell) (i.e., cell ID 1) in LTM configuration 1. In one implementation, cell ID 1 may be a PCI. In another implementation, cell ID 1 is a CGI. In some further implementations, LTM configuration 1 includes cell index 1 (e.g., a serving cell index or an LTM cell index) that indexes cell ID 1 or the first cell. Cell index 1 is not a cell ID.

[0090] In some implementations, after receiving one or more of the at least one measurement report for event 304 (e.g., in response thereto), the base station 104 (i.e., the CU 172 or the DU 174) determines to prepare additional cells (i.e., cells 2, ..., N) of the base station 104 for LTM for the UE 102. In one implementation, the base station 104 determines to prepare the additional cells for the UE 102 for LTM because the at least one measurement report indicates that the additional cells can be used by the base station 104 to communicate with the UE 102. The additional cells can include cell 124C and / or cells other than cells 124A, 124B, and 124C. In some implementations, the CU 172 determines to prepare a particular cell of the additional cells for LTM for the UE 102 if the L3 measurement report indicates that the signal strength and / or quality of the particular cell is above a corresponding predetermined threshold and / or better than cell 124A. In other implementations, if the L1 measurement report indicates that the signal strength and / or quality of a particular cell among the additional cells is above a first predetermined threshold and / or better than cell 124A, DU 174 determines to prepare the particular cell for LTM for UE 102. In one implementation, the corresponding predetermined threshold for the additional cell may be different from the first predetermined threshold. In another implementation, the corresponding predetermined threshold for the additional cell may be the same as the first predetermined threshold. In some implementations, the corresponding predetermined threshold for the additional cell may be the same or different. Alternatively, base station 104 determines to prepare the additional cell for UE 102 regardless of whether a measurement report is received from UE 102.

[0091] In the event that CU 172 determines to prepare an additional cell, CU 172 initiates and performs at least one additional LTM preparation process (LTM preparation process) with DU 174 to prepare the additional cell for LTM, wherein each of the LTM preparation processes is similar to process 390. In the event that DU 174 determines to prepare an additional cell, DU 174 initiates and performs at least one additional LTM preparation process (LTM preparation process) with CU 172 to prepare the additional cell for LTM, wherein each of the LTM preparation processes is similar to process 390.

[0092] In some implementations, the CU 172 and the DU 174 perform LTM preparation processes 2, ..., N similar to process 390 to prepare cells 2, ..., N, respectively. During the LTM preparation processes 2, ..., N, the CU 172 may include the cell IDs 2, ..., N in CU-to-DU messages 2, ..., N, respectively, similar to the first CU-to-DU message. During the LTM preparation processes 2, ..., N, the DU 174 generates LTM configurations 2, ..., N that configure cells 2, ..., N and includes the LTM configurations 2, ..., N in DU-to-CU messages 2, ..., N, respectively, as described for LTM configuration 1. Upon receiving the CU-to-DU messages 2, ..., N, the DU-to-CU messages 2, ..., N, respectively, respond to the CU-to-DU messages 2, ..., N. "N" is an integer greater than one. For example, "N" is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16. In another example, the maximum number of "N" is 4, 8, 16, or 32. The examples and implementations of LTM configuration 1 may be applicable to LTM configurations 2, ..., N.

[0093] In other implementations, the CU 172 and the DU 174 perform a single LTM preparation process (i.e., the LTM preparation process 390) to prepare cells 1, 2, ..., N. In such cases, the DU 174 includes LTM configurations 1, 2, ..., N for cells 1, 2, ..., N, respectively, in a first DU-to-CU message. In the first DU-to-CU message, the DU 174 may include cell IDs 1, 2, ..., N associated with the LTM configurations 1, 2, ..., N, respectively, to indicate that the LTM configurations 1, 2, ..., N are configured for cell IDs 1, 2, ..., N, respectively. If the CU 172 determines to perform the LTM preparation process 390, the CU 172 includes the cell IDs 1, 2, ..., N in the first CU-to-DU message to request the DU 174 to prepare cells 1, 2, ..., N, respectively, for LTM.

[0094] After receiving LTM configurations 2, ..., N from DU 174, CU 172 may include LTM configurations 2, ..., N in a first container. In some implementations, CU 172 may include LTM configurations 2, ..., N in elements 2, ..., N, respectively, and include elements 2, ..., N in the first container. In some implementations, CU 172 includes LTM IDs (i.e., IDs 2, ..., N) used to identify LTM configurations 2, ..., N, respectively, in an RRC reconfiguration message. In some implementations, CU 172 includes IDs 2, ..., N in the first container. For example, CU 172 may include IDs 2, ..., N and LTM configurations 2, ..., N in elements 2, ..., N in a first addition or modification list.

[0095] In some implementations, the CU 172 assigns IDs 2, ..., N for LTM configurations 2, ..., N, respectively. In other implementations, the CU 172 receives the IDs 2, ..., N in the first DU-to-CU message of process 390 from the DU 174. In still other implementations, the CU 172 receives the IDs 2, ..., N in DU-to-CU messages 2, ..., N of LTM preparation processes 2, ..., N, respectively, from the DU 174.

[0096] In some implementations, CU 172 may perform an LTM ID assignment process similar to process 392 with DU 174 for each of LTM configurations 2, ..., N. In other implementations, CU 172 may include IDs 2, ..., N and LTM configurations 2, ..., N in a third CU-to-DU message and indicate the association between IDs 2, ..., N and LTM configurations 2, ..., N, respectively. Thus, DU 174 may associate LTM configurations 2, ..., N with IDs 2, ..., N, respectively. In still other implementations, CU 172 may include cell IDs 2, ..., N and IDs 2, ..., N in a third CU-to-DU message and indicate the association between cell IDs 2, ..., N and IDs 2, ..., N, respectively. Therefore, DU 174 may associate LTM configurations 2, ..., N with IDs 2, ..., N, respectively, based on the associations between cell IDs 2, ..., N and IDs 2, ..., N, respectively, and the associations between cell IDs 2, ..., N and LTM configurations 2, ..., N, respectively. In other implementations, CU 172 may include IDs 2, ..., N, cell IDs 2, ..., N, and / or LTM configurations 2, ..., N in the second CU-to-DU message, as described above. Therefore, the third CU-to-DU message may be omitted. In yet other implementations, CU 172 may include IDs 2, ..., N in the first CU-to-DU message and indicate that IDs 2, ..., N are associated with cell IDs 2, ..., N, respectively. In one implementation, DU 174 includes IDs 2, ..., N in LTM configurations 2, ..., N. Therefore, CU 172 does not include IDs 2, ..., N in the RRC reconfiguration message, the first container, and / or elements 2, ..., N.

[0097] In some alternative implementations, DU 174 assigns IDs 2, ..., N. In some implementations, DU 174 includes IDs 2, ..., N in the first DU-to-CU message of process 390. In still other implementations, DU 174 includes IDs 2, ..., N in DU-to-CU messages 2, ..., N of LTM preparation processes 2, ..., N. CU 172 may include IDs 2, ..., N in an RRC reconfiguration message. In other implementations, DU 174 includes IDs 2, ..., N in LTM configurations 2, ..., N. Thus, CU 172 does not include an ID identifying each of LTM configurations 2, ..., N (e.g., an LTM ID) in the RRC reconfiguration message, the first container, and / or element 1.

[0098] In some alternative implementations, instead of using the first container, CU 172 may generate a second container including LTM configurations 2, ..., N or elements 2, ..., N. Then, similar to events 316 and 318, CU 172 sends an additional RRC reconfiguration message including the second container to UE 102 via DU 174. In response, similar to events 320 and 322, UE 102 sends an additional RRC reconfiguration complete message to CU 172 via DU 174. In some implementations, the second container may be a second addition or modification list (e.g., a ltm-ConfigToAddModList field, a LTM-ConfigToAddModList IE, a ltm-CandidateConfigToAddModList field, or a LTM-CandidateConfigToAddModList IE), and each of elements 2, ..., N may be an addition or modification IE (e.g., a ltm-ConfigToAddMod field, a LTM-ConfigToAddMod IE, a ltm-CandidateConfigToAddMod field, or a LTM-CandidateConfigToAddMod IE). When the UE 102 receives the second addition or modification list, the UE 102 may store the second addition or modification list together with the first addition or modification list (e.g., in a variable in its random access memory (RAM)).

[0099] In some implementations, the DU 174 includes cell IDs 2, ..., N in LTM configurations 2, ..., N, respectively, to identify cells 2, ..., N. In one implementation, each of the cell IDs 2, ..., N is a PCI. In some further implementations, the LTM configurations 2, ..., N include (e.g., serving) cell indexes 2, ..., N that index the cell IDs 2, ..., N or the cells 2, ..., N, respectively. In some implementations, the cell IDs 1, ..., N in the LTM configurations 1, ..., N may be different from the cell IDs 1, ..., N in the CU-to-DU message described above.

[0100] In some implementations, each of LTM configurations 1, ..., N includes physical configuration parameters, MAC configuration parameters, RLC configuration parameters, and / or L1 measurement configuration. In some implementations, each of LTM configurations 1, ..., N may be a CellGroupConfig IE as defined in 3GPP specification 38.331. In other implementations, each of LTM configurations 1, ..., N includes configuration parameters included in a CellGroupConfig IE as defined in 3GPP specification 38.331. In some further implementations, the plurality of configuration parameters in each of the LTM configurations includes a specific special cell configuration (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE). In some implementations, LTM configurations 1, ..., N are CellGroupConfig IEs as defined in 3GPP specification 38.331. In other implementations, LTM configurations 1, ..., N include configuration parameters in a CellGroupConfig IE.

[0101] In some implementations, CU 172 determines to release LTM configuration M (or element M) in LTM configurations 1, ..., N (or element M in elements 1, ..., M). 1 ≤ M ≤ N. In response to the determination, CU 172 sends an RRC reconfiguration message to UE 102 via DU 174 to instruct UE 102 to release LTM configuration M or element M. In one implementation, CU 172 generates a release list for releasing LTM configuration M or element M, including ID (i.e., LTM ID) M, and includes the release list in the RRC reconfiguration message. In response to the RRC reconfiguration message, UE 102 releases LTM configuration M or element M and sends an RRC reconfiguration complete message to CU 172 via DU 174. In response to the determination, CU 172 sends a CU-to-DU message to DU 174 to instruct DU 174 to release LTM configuration M. To instruct DU 174 to release LTM configuration M, CU 172 may include cell ID M or ID (i.e., LTM ID) M in a release indication (e.g., a field or IE) in a CU-to-DU message. In response, DU 174 releases LTM configuration M and sends a DU-to-CU message to CU 172. In some implementations, the CU-to-DU message and the DU-to-CU message are a UE Context Modification Request message and a UE Context Modification Response message, respectively.

[0102] In other implementations, DU 174 determines to release LTM configuration K. In response to this determination, DU 174 sends a DU-to-CU message to CU 172 to release LTM configuration K. To indicate that LTM configuration K is released, DU 174 may include cell ID K or ID (i.e., LTM ID) K in a release indication (e.g., a field or IE) in the DU-to-CU message. 1 ≤ K ≤ N. After receiving the DU-to-CU message (e.g., in response thereto), CU 172 generates a release list for releasing LTM configuration K or element K, including ID (i.e., LTM ID) K, and sends an RRC reconfiguration message including the release list to UE 102 via DU 174. In response, UE 102 releases LTM configuration K or element K and sends an RRC reconfiguration complete message to UE 102 via DU 174. CU 172 may send a CU-to-DU message to DU 174 in response to the DU-to-CU message. In some implementations, the DU-to-CU message and the CU-to-DU message are a UE context modification required message and a UE context modification confirm message, respectively.

[0103] After receiving the RRC reconfiguration at event 318 or sending the RRC reconfiguration complete message at event 320, similar to event 304, UE 102 sends 324 at least one measurement report to DU 174. In some implementations, similar to event 306, DU 174 may send 326 a DU-to-CU message including the at least one measurement report to CU 172. In other implementations, DU 174 does not send the at least one measurement report to CU 172. In some implementations, the at least one measurement report of event 324 includes an L1 measurement report or an L3 measurement report, as described for event 304. In some implementations, similar to event 304, UE 102 sends 324 the at least one measurement report to DU 174 on the PUCCH and / or PUSCH. In other implementations, UE 102 sends 324 at least one MAC CE including the at least one measurement report to DU 174, similar to event 304. In some implementations, the UE 102 does not send the L1 measurement report to the DU 174 in the format of an RRC message.

[0104] In some implementations, UE 102 sends 324 at least one measurement report to DU 174 based on at least one measurement configuration. The at least one measurement configuration configures UE 102 to perform measurements and report the measurement results. CU 172 sends the at least one measurement configuration to UE 102 via DU 174. For example, CU 172 may send one or more RRC messages (e.g., RRCReconfiguration messages) including the at least one measurement configuration to UE 102 via DU 174 during and / or after events 302 and / or 316. The one or more RRC messages may or may not include the RRCReconfiguration message of event 316. Based on the at least one measurement configuration, UE 102 performs measurements on one or more reference signals. The one or more reference signals may include one or more SSBs and / or one or more CSI-RSs. UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurements and includes the at least one L1 measurement result and / or at least one L3 measurement result in at least the measurement report of event 324. DU 174 transmits one or more reference signals on cell 124A, cell 1, and / or cell 2, ..., N. The one or more reference signals may be CSI-RS or SSB.

[0105] In some implementations, the at least one measurement configuration includes an L3 measurement configuration (e.g., a MeasConfig IE), as described for event 304. In other implementations, the at least one measurement configuration includes an L1 measurement configuration, as described for event 304. For example, the L1 measurement configuration may be a CSI-MeasConfig IE, such as defined in 3GPP specification 38.331. The L1 measurement configuration may include a measurement report configuration. UE 102 sends an L1 measurement report to DU 174 on a PUCCH or MAC CE based on the measurement report configuration. DU 174 receives the L1 measurement report on a PUCCH or MAC CE based on the measurement report configuration. In some implementations, the measurement report configuration is a CSI-ReportConfig IE. In other implementations, each of the measurement report configurations is a dedicated RRC IE (defined specifically for and dedicated to conveying measurement report configurations related to LTM). In some implementations, (each of) the measurement report configurations configures periodic reporting and / or event-triggered reporting of L1 measurement results.

[0106] In yet other implementations, at least one measurement configuration includes a measurement configuration of a type defined specifically for and dedicated to LTM (e.g., an LTM measurement configuration). The LTM-type measurement configuration may be specifically defined in conjunction with LTM in relevant 3GPP specifications. In some implementations, the LTM-type measurement configuration includes a reference signal resource configuration that configures resources in which DU 174 transmits reference signals. For example, the reference signal resource configuration includes CSI-RS and / or SSB. In one implementation, the reference signal resource configuration is a CSI-ResourceConfig IE. In another implementation, as described above, the LTM-type measurement configuration includes a measurement report configuration. UE 102 sends a measurement report to DU 174 on a PUCCH or MAC CE based on the measurement report configuration. DU 174 receives the measurement report on a PUCCH or MAC CE based on the measurement report configuration. In such cases, the measurement report may be an L1 measurement report or an LTM-type measurement report (e.g., an LTM measurement report). In some implementations, the LTM-type measurement configuration includes configuration parameters specifically defined in conjunction with LTM in relevant 3GPP specifications.

[0107] After receiving the at least one measurement report at event 324 (e.g., in response thereto), DU 174 generates a first LTM command to activate LTM configuration 1 (i.e., the first LTM command instructs UE 102 to apply LTM configuration 1 or perform a serving cell change to cell 1). DU 174 then sends 330 the first LTM command to UE 102. In some implementations, DU 174 sends the first LTM command to UE 102 on cell 124A. In other implementations, DU 174 sends the first LTM command to UE 102 on cell 124D. In some implementations, DU 174 may include ID 1 in the first LTM command to indicate LTM configuration 1, and UE 102 determines (e.g., identifies) LTM configuration 1 or element 1 based on ID 1. In other implementations, DU 174 may include cell index 1, which indexes cell ID 1, in the first LTM command. The UE 102 determines (eg, identifies) LTM configuration 1 or element 1 based on cell index 1. After determining LTM configuration 1 or element 1, the UE 102 then applies LTM configuration 1 in response to receiving the first LTM command.

[0108] In yet other implementations, DU 174 may include a bitmap in the first LTM command to activate LTM configuration 1 instead of ID 1 or cell index 1. The number of bits in the bitmap is greater than or equal to "N." In one implementation, bits 1, ..., N correspond to LTM configurations 1, ..., N or elements 1, ..., N, respectively, and DU 174 sets the corresponding bit (e.g., bit 1) in the bitmap to a first value to indicate ID 1, LTM configuration 1, or element 1. Thus, UE 102 can determine ID 1, LTM configuration 1, or element 1 based on bit 1 in the bitmap being set to the first value. In another implementation, bits 0, ..., N-1 correspond to LTM configurations 1, ..., N or elements 1, ..., N, respectively, and DU 174 sets the corresponding bit (e.g., bit 0) in the bitmap to the first value to indicate ID 1 or LTM configuration 1. Thus, UE 102 can determine ID 1 or LTM configuration 1 based on bit 0 in the bitmap being set to the first value. In such implementations, DU 174 sets the remaining bits in the bitmap to a second value to indicate that the remaining LTM configurations 1, ..., N are not activated. In some implementations, the first value is one and the second value is zero. In other implementations, the first value is zero and the second value is one. Generally speaking, if DU 174 determines to activate LTM configuration L, DU 174 may set the corresponding bit in the bitmap (e.g., bit L or bit L-1) to the first value and the remaining bits to the second value, where 1 ≤ L ≤ N.

[0109] In some implementations, the at least one measurement report (e.g., an L1 measurement report or an LTM-type measurement report) of event 324 includes at least one measurement result of the first cell, a TRP of the first cell, or a reference signal transmitted on the first cell. The reference signal may be a CSI-RS or an SSB. DU 174 determines to activate LTM configuration 1 or to transmit a first LTM command based on the at least one measurement result. In some implementations, DU 174 determines to activate LTM configuration 1 because, when, or if the at least one measurement result is above a second predetermined threshold, the at least one measurement result includes an L1-RSRP value, an L1-RSRQ value, and / or an L1-SINR value. In other implementations, the at least one measurement result includes an RSRP value, an RSRQ value, and / or an SINR value of an LTM-type measurement report. In some implementations, the second predetermined threshold is different from the first predetermined threshold. In one implementation, the second predetermined threshold is greater than the first predetermined threshold. In this case, the at least one measurement result indicates that the first cell is suitable for communication with UE 102. In another implementation, the second predetermined threshold is equal to the first predetermined threshold. In this case, the at least one measurement result indicates that the first cell is continuously above the second predetermined threshold or the first predetermined threshold. This indicates that the first cell is suitable for communication with UE 102. Therefore, in response to the signal strength or quality of the first cell being above the second predetermined threshold for UE 102, DU 174 determines to activate LTM configuration 1.

[0110] In some implementations, at least one measurement report (e.g., L3 measurement report) of events 324 and 326 includes at least one measurement result for the first cell. CU 172 determines to activate LTM configuration 1 or send the first LTM command because the at least one measurement result indicates that the signal strength or quality of the first cell is above a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In one implementation, the second predetermined threshold is greater than the first predetermined threshold. In such an implementation, the at least one measurement report of event 326 indicates that the signal strength or quality of the first cell is suitable for communication with UE 102. In another implementation, the second predetermined threshold is equal to the first predetermined threshold. In such an implementation, the at least one measurement report of event 326 indicates that the signal strength or quality of the first cell is consistently above the second predetermined threshold or the first predetermined threshold. This also indicates that the first cell is suitable for communication with UE 102. Therefore, in response to the signal strength or quality of the first cell being above the second predetermined threshold, CU 172 determines to activate LTM configuration 1. In response to this determination, CU 172 sends 328 a fourth CU-to-DU message to DU 174 to activate LTM configuration 1. In response to the fourth CU-to-DU message, DU 174 sends 330 a first LTM command to UE 102 and, optionally, sends a fourth DU-to-CU message to CU 172. In some implementations, CU 172 includes cell index 1 in the fourth CU-to-DU message. Thus, DU 174 may determine to activate LTM configuration 1 based on cell index 1. In other implementations, CU 172 may include cell ID 1 in the fourth CU-to-DU message. Thus, DU 174 may determine to activate LTM configuration 1 based on cell ID 1. In yet other implementations, CU 172 may include ID 1 in the fourth CU-to-DU message. Thus, DU 174 may determine to activate LTM configuration 1 based on ID 1. In some implementations, the fourth CU-to-DU message and the fourth DU-to-CU message are a UE context modification request message and a UE context modification response message, respectively. In other implementations, the fourth CU-to-DU message and / or the fourth DU-to-CU message is an LTM interface message defined in relevant 3GPP specifications specifically for LTM (eg, TS 38.473), such as an F1 Application Protocol (F1AP) message.

[0111] Upon determining to activate LTM configuration 1 or sending the first LTM command, or in response thereto, the DU 174 may send 329 a DU-to-CU message to the CU 172 indicating that LTM is being executed. In some implementations, the DU 174 includes cell ID 1 or ID 1 (i.e., LTM ID) in the DU-to-CU message 329 to indicate that the DU 174 is activating LTM configuration 1. The DU may send the DU-to-CU message 329 to the CU 172 before or after sending the LTM command 330.

[0112] In some implementations, the first LTM command is a MAC CE included in a MAC PDU that UE 102 receives from DU 174 at event 330. The MAC CE can be a MAC CE specifically defined and dedicated in conjunction with the LTM command (e.g., in a relevant 3GPP specification such as TS 38.321). In one implementation, DU 174 includes a subheader that identifies a dedicated (e.g., dedicated for LTM purposes) MAC CE in the MAC PDU, and UE 102 identifies the dedicated (or LTM) MAC CE in the MAC PDU based on the subheader. The subheader includes a logical channel ID or an extended logical channel ID that identifies the LTM MAC CE defined in the 3GPP specification. For example, the logical channel ID or extended logical channel ID is defined for this purpose in a relevant 3GPP specification (e.g., TS 38.321). In other implementations, the first LTM command is a DCI that UE 102 receives from DU 174 on the PDCCH at event 330. DU 174 generates a CRC for the DCI, scrambles the CRC with the first C-RNTI of UE 102, and transmits the DCI and the scrambled CRC on the PDCCH at event 330. In one implementation, the format of the DCI may be a DCI format defined in a 3GPP specification (e.g., 38.212). In another implementation, the format of the DCI is a format defined specifically for and used with the LTM process in a relevant 3GPP specification (e.g., 38.212).

[0113] In some implementations, the DU 174 does not perform security protection (e.g., integrity protection and / or encryption) on the first LTM command. This speeds up processing of the first LTM command in the UE 102 because the UE 102 does not perform security checks (e.g., decryption and / or integrity checks) on the first LTM command.

[0114] In some implementations, after receiving the first LTM command, UE 102 may send 331 an acknowledgment to DU 174 on cell 124A or cell 124D to indicate that UE 102 received the first LTM command. In some implementations, the acknowledgment is a HARQ ACK. In other implementations, the acknowledgment is a MAC CE. For example, the MAC CE is a MAC CE defined in, for example, 3GPP specification 38.321. In another example, the MAC CE is a MAC CE defined and dedicated for LTM purposes in a relevant 3GPP specification, such as TS 38.321. In still other implementations, the acknowledgment is a PUCCH transmission.

[0115] In some implementations, the CU 172 sends 316 an RRC reconfiguration message in response to the L3 measurement report 306 for the first cell. To configure the UE 102 to send the L3 measurement report 306, the CU 172 may send a first RRC reconfiguration message including an L3 measurement configuration (e.g., a MeasConfig IE) to the UE 102 before event 306. In some implementations, the DU 174 sends 330 a first LTM command in response to the L1 measurement report 324 for the first cell. To configure the UE 102 to send an L1 or LTM type measurement report 324, the CU 172 may send a second RRC reconfiguration message including an L1 or LTM type measurement configuration to the UE 102. In some implementations, the first RRC reconfiguration message and the second RRC reconfiguration message may be the same message (i.e., the same instance). In other implementations, the first RRC reconfiguration message and the second RRC reconfiguration message are different messages. In some implementations, the second RRC reconfiguration message is the RRC reconfiguration message of event 316. In other implementations, the second RRC reconfiguration message is different from the RRC reconfiguration message of event 316.

[0116] After receiving the first LTM command (e.g., in response thereto), UE 102 identifies LTM configuration 1 based on ID 1 and applies LTM configuration 1. In some implementations, UE 102 may perform 332 a random access procedure on the first cell with DU 174 in response to applying LTM configuration 1 or receiving the first LTM command. In some implementations, UE 102 disconnects from cell 124A after receiving the first LTM command or after sending an acknowledgment (e.g., in response thereto). In other words, after receiving 330 the first LTM command or sending 331 an acknowledgment (e.g., in response thereto), UE 102 ceases communicating on cell 124A. In such cases, UE 102 performs 332 a random access procedure after disconnecting from cell 124A. UE 102 may determine whether to perform a random access procedure based on LTM configuration 1. In one implementation, if LTM configuration 1 configures UE 102 to perform a random access procedure, UE 102 performs a random access procedure in event 332. For example, LTM configuration 1 includes a reconfiguration with synchronization configuration (e.g., a ReconfigurationWithSync IE) to configure UE 102 to perform a random access procedure. Otherwise, if LTM configuration 1 does not configure UE 102 to perform a random access procedure or does not configure UE 102 to skip a random access procedure, UE 102 avoids performing a random access procedure with DU 174 upon receiving the first LTM command. In such a case, UE 102 skips event 316. For example, if LTM configuration 1 excludes a reconfiguration with synchronization configuration, LTM configuration 1 configures UE 102 not to perform a random access procedure. In some implementations, the random access procedure is a four-step random access procedure. In other implementations, the random access procedure is a two-step random access procedure. In some implementations, the random access procedure is a contention-free random access procedure. In other implementations, the random access procedure is a contention-based random access procedure.

[0117] When UE 102 performs 332 a random access procedure, UE 102 communicates 336 with DU 174 on a first cell using LTM configuration 1 and / or a reference LTM configuration, and communicates with CU 172 via DU 174 after successfully completing the random access procedure. In such cases, DU 174 communicates with UE 102 on the first cell using LTM configuration 1 at event 332 and / or event 336. In some scenarios or implementations, UE 102 communicates UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) with base station 104 at event 336. In some implementations, UE 102 determines that UE 102 has successfully completed the random access procedure when UE 102 receives contention resolution from DU 174. In the case where the random access procedure is a four-step random access procedure, UE 102 sends message 3 including a UE identity to DU 174 via the first cell during the random access procedure. If the random access procedure is a two-step random access procedure, UE 102 transmits a message A including a UE identity to DU 174 via the first cell during the random access procedure. In some implementations, if LTM configuration 1 includes a second C-RNTI, the UE identity is the second C-RNTI of UE 102. Otherwise, if LTM configuration 1 does not include a C-RNTI, the UE identity is the first C-RNTI. If the random access procedure is a contention-free random access procedure, UE 102 transmits a dedicated random access preamble to DU 174 via the first cell. In this case, LTM configuration 1 includes a dedicated random access preamble.

[0118] The DU 174 identifies or determines that the UE 102 is connected to the first cell upon receiving the UE identification or the dedicated preamble from the UE 102 in the random access procedure 332 .

[0119] In the event that UE 102 skips the random access procedure, UE 102, after receiving the first LTM command (e.g., in response thereto), directly communicates 336 with DU 174 on the first cell according to LTM configuration 1 and communicates with CU 172 via DU 174. For example, UE 102 directly communicates UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) with base station 104 at event 336. In some implementations, DU 174 may include configuration parameters in LTM configuration 1 that configure resources for UE 102 to transmit at least one PUCCH or PUSCH transmission, and UE 102 may use the configuration parameters to transmit at least one PUCCH or PUSCH transmission on the resources to indicate that UE 102 is connected to the first cell. In other implementations, DU 174 may send at least one DCI to UE 102 on the PDCCH on the first cell to instruct UE 102 to transmit at least one PUCCH or PUSCH transmission after sending the first LTM command. The at least one DCI configures resources for UE 102 to transmit at least one PUCCH or PUSCH transmission, and UE 102 transmits at least one PUCCH or PUSCH transmission on the resources. DU 174 identifies or determines that UE 102 is connected to the first cell upon receiving the PUCCH or PUSCH transmission. DU 174 identifies or determines that UE 102 is connected to the first cell upon receiving the PUCCH or PUSCH transmission on the resources configured in LTM configuration 1 or the at least one DCI.

[0120] In the event that UE 102 receives the reference LTM configuration as described above, UE 102 communicates 336 with DU 174 on the first cell in accordance with LTM configuration 1 and at least a portion of the reference LTM configuration. In other words, UE 102 communicates 336 with DU 174 in accordance with the configuration parameters in LTM configuration 1 and the reference LTM configuration. Similarly, DU 174 communicates 336 with UE 102 on the first cell in accordance with LTM configuration 1 and at least a portion of the reference LTM configuration. In other words, DU 174 communicates 336 with UE 102 in accordance with the configuration parameters in LTM configuration 1 and the reference LTM configuration.

[0121] In some implementations, the UE 102 sends an RRC message (e.g., an RRC reconfiguration complete message) to the CU 172 via the DU 174 and the first cell to instruct the UE 102 to apply LTM configuration 1. If the UE 102 performs the random access procedure 332, the UE 102 may include the RRC message in message 3 or message A. Alternatively, the UE 102 sends the RRC message after completing the random access procedure. If the UE 102 skips the random access procedure 332, the UE 102 includes the RRC message in a PUSCH transmission in at least one PUSCH transmission. In some implementations, if the UE 102 maintains communication with the base station 104 on the cell 124A (i.e., the UE 102 is not disconnected from the cell 124A), the UE 102 may send the RRC message to the base station 104 via the cell 124A. When the DU 174 receives the RRC message, the DU 174 sends the RRC message to the CU 172.

[0122] In other implementations, UE 102 refrains from sending an RRC message to base station 104 in response to applying LTM configuration 1 or receiving a first LTM command. In such cases, UE 102 may include or send data in Message 3, Message A, or a PUSCH transmission as described above. UE 102 may generate a MAC PDU and / or RLC PDU including the data and send or include the MAC PDU and / or RLC PDU in a PUSCH transmission. For example, the data may be a PDCP PDU, a SDAP PDU, an LTE Positioning Protocol (LPP) PDU, an RRC PDU, and / or a NAS PDU. The RRC PDU includes an UL-DCCH-Message excluding an RRC Reconfiguration Complete message. The NAS PDU includes a Mobility Management (MM) message or a Session Management (SM) message. The MM message may be a 5G MM message or a 6G MM message, and the SM message may be a 5G SM message or a 6G SM message. When DU 174 receives the data, DU 174 sends the data to CU 172.

[0123] When DU 174 determines at event 332 or 336 that UE 102 is successfully connected to the first cell, DU 174 may send 334 a DU-to-CU message (e.g., an access success message) to CU 172 (e.g., the CP of CU 172). In some implementations, DU 174 may include the cell ID 1 of the first cell in the DU-to-CU message at event 334. The cell ID may be a PCI or a CGI. Thus, CU 172 determines that UE 102 is connected to the first cell upon receiving the DU-to-CU message at event 334. When DU 174 determines at event 332 or 336 that UE 102 is successfully connected to the first cell, DU 174 may send a DL data delivery status message or frame to CU 172 (e.g., the UP of CU 172).

[0124] In some implementations, upon determining that UE 102 is connected to the first cell, sending 330 a first LTM command, or receiving 331 an acknowledgment, DU 174 may cease communicating with UE 102 on cell 124A and / or release resources of cell 124A configured for UE 102.

[0125] In some implementations, DU 174 may generate some or all of LTM configuration 1 and / or LTM configurations 2, ..., N as complete configurations to replace the serving DU configuration. If LTM configuration 1 is a complete configuration, UE 102 and DU 174 communicate 336 with each other based on LTM configuration 1 rather than the serving DU configuration. In some implementations, DU 174 includes an indication in LTM configuration 1 that LTM configuration 1 is a complete configuration. In each of LTM configurations 2, ..., N, DU 174 may include an indication indicating that the corresponding DU configuration is a complete configuration. Each of the indications in LTM configurations 1, ..., N may be a field or IE (i.e., the same field or IE). In other implementations, CU 172 may include a single indication in the RRC reconfiguration message for events 316 and 318 indicating that LTM configurations 1 and / or 2, ..., N are complete configurations. In the case of a second container, CU 172 may include a single indication in an additional RRC reconfiguration message indicating that LTM configurations 2, ..., N are complete configurations. In yet other implementations, CU 172 may include a single indication in the first container indicating that LTM configurations 1 and / or 2, ..., N are complete configurations. In yet other implementations, for each of LTM configurations 2, ..., N, CU 172 may include a specific indication in the first container indicating that the corresponding LTM configuration is a complete configuration. In the case of a second container, CU 172 may include a single indication in the second container indicating that LTM configurations 2, ..., N are complete configurations. In yet other implementations, CU 172 may include an indication in element 1 indicating that LTM configuration 1 is a complete configuration. In each of elements 2, ..., N, CU 172 may include an indication indicating that the corresponding LTM configuration is a complete configuration. Based on these indications, UE 102 may determine that LTM configuration 1 and / or LTM configurations 2, ..., N are complete configurations. In some implementations, each of the above indications is different from the fullConfig field defined in current 3GPP specifications. In some implementations, each of the above indications is the fullConfig field defined in current 3GPP specifications. In the case where LTM configuration 1 is a complete configuration, UE 102 in event 336 does not apply the reference LTM configuration if, for example, received from base station 104 in RRC reconfiguration message 318. In such a case, DU 174 may not include the reference LTM configuration in first DU to CU message 310.

[0126] In other implementations, DU 174 may generate LTM configuration 1 and / or LTM configuration 2, ..., N as incremental configurations that enhance (a portion of) a reference LTM configuration. In other words, DU 174 generates LTM configurations 1, ..., N based on the reference LTM configuration. For example, if LTM configuration 1 is an incremental configuration, UE 102 and DU 174 enhance (a portion of) the reference LTM configuration using LTM configuration 1. Thus, UE 102 and DU 174 communicate 336 with each other based on LTM configuration 1 and the unenhanced portion of the reference LTM configuration. In some implementations, LTM configurations 1 and / or 2, ..., N, the first container, the second container, or the elements 1, ..., N exclude the indication that LTM configurations 1 and / or 2, ..., N are complete configurations to indicate that LTM configurations 1 and / or 2, ..., N are incremental configurations. UE 102 may determine that each of LTM configurations 1 and / or 2, ..., N is an incremental configuration based on the indication being excluded in LTM configurations 1 and / or 2, ..., N, the first container, the second container, or elements 1 and / or 2, ..., N.

[0127] In some implementations, if the UE 102 does not receive a reference LTM configuration for LTM configuration 1 and / or LTM configuration 2, ..., N, the UE 102 determines that LTM configuration 1 and / or LTM configuration 2, ..., N are complete configurations. Correspondingly, if the DU 174 does not obtain a reference LTM configuration for the UE 102 (i.e., the DU 174 does not generate a reference LTM configuration for the UE 102 and / or receives a reference LTM configuration for the UE 102 from the CU 174), the DU 174 generates LTM configuration 1 and / or LTM configuration 2, ..., N as complete configurations.

[0128] In other implementations, if the UE 102 does not receive a reference LTM configuration for LTM configuration 1 and / or LTM configuration 2, ..., N, the UE 102 determines that LTM configuration 1 and / or LTM configuration 2, ..., N are delta configurations for enhancing the serving DU configuration. In such a case, the UE 102 communicates 336 with the DU 174 based on LTM configuration 1 and at least a portion of the serving DU configuration that is not enhanced by LTM configuration 1. Correspondingly, if the DU 174 does not obtain a reference LTM configuration for the UE 102 (i.e., the DU 174 does not generate a reference LTM configuration for the UE 102 and / or receives a reference LTM configuration for the UE 102 from the CU 174), the DU 174 generates LTM configuration 1 and / or LTM configuration 2, ..., N as delta configurations for enhancing the serving DU configuration. In such a case, the DU 174 communicates 336 with the UE 102 based on LTM configuration 1 and at least a portion of the serving DU configuration.

[0129] In some implementations, the UE 102 uses a UE MAC entity (e.g., MAC 204B) to communicate with a DU MAC entity (e.g., MAC 204B) of the DU 174 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). In some implementations, the UE 102 resets the UE MAC entity after or in response to receiving the first LTM command and before performing 332 a random access procedure or communicating 336 with the DU 174 via the first cell. In some implementations, the DU 174 resets the DU MAC entity after (e.g., in response to) sending the first LTM command, receiving an acknowledgment 331, or determining that the UE 102 is connected to the first cell.

[0130] In some implementations, when the UE 102 resets the UE MAC entity, the UE 102 performs at least one of the following actions on the UE MAC entity (i.e., a UE MAC reset or a complete UE MAC reset):

[0131] • Initialize Bj for the configured logical channel to zero;

[0132] • Stop one or more timers;

[0133] • if the UE 102 is configured to perform a random access procedure (e.g., event 332) with a configuration (e.g., configuration 1), then the timeAlignmentTimer is considered expired;

[0134] • Set the New Data Indicator (NDI) for the UL HARQ process to a value of 0;

[0135] • Set the NDI for HARQ process ID to a value of 0 to monitor PDCCH in sidelink resource allocation mode 1;

[0136] • Refresh Msg3 buffer;

[0137] • Flush the MSGA buffer;

[0138] • cancel (if any) the triggered scheduling request process;

[0139] • cancel (if any) the triggered buffer status reporting procedure;

[0140] • cancelling (if any) the triggered power headroom reporting procedure;

[0141] • cancel (if any) the triggered consistent LBT fault;

[0142] • cancelling (if any) the triggered BFR;

[0143] • cancel (if any) the triggered sidelink buffer status reporting procedure;

[0144] • cancel (if any) the triggered preemptive buffer status reporting process;

[0145] • Cancellation (if any) of the triggered Time Advance Reporting process;

[0146] • cancel (if any) the triggered recommended bit rate query process;

[0147] • cancel (if any) the triggered configured uplink grant confirmation;

[0148] • cancel (if any) the triggered configured sidelink authorization confirmation;

[0149] • cancel (if any) the triggered query of the desired protection symbol;

[0150] • cancel (if any) the triggered positioning measurement gap activation / deactivation request procedure;

[0151] • Flushing the soft buffers used for DL ​​HARQ processes;

[0152] • For each of the DL HARQ processes, the next received transmission for a TB is considered the first transmission;

[0153] • Release (if any) the temporary C-RNTI;

[0154] • Reset one or more counters (for example, BFI_COUNTER and / or LBT_COUNTER).

[0155] In some implementations, when the DU 174 resets the DU MAC entity, the DU 174 performs at least one of the following actions on the DU MAC entity (i.e., a DU MAC reset or a complete DU MAC reset):

[0156] • Stop one or more timers;

[0157] • if the UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), the timeAlignmentTimer started and / or maintained by the DU 174 for the UE 102 is considered expired;

[0158] • Set the NDI for the DL HARQ process to a value of 0;

[0159] • Flushing the soft buffers used for UL HARQ processes;

[0160] • For each of the UL HARQ processes, the next received transmission for a TB is considered the first transmission;

[0161] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER)

[0162] Depending on the implementation, the UE 102 may determine to partially or completely reset the UE MAC entity. In some implementations, when the UE 102 resets the UE MAC entity as described above, the UE 102 completely resets the UE MAC entity (i.e., a complete UE MAC reset). In a complete UE MAC reset, the UE 102 performs some or all of the actions described above. In other implementations, when the UE 102 resets the UE MAC entity as described above, the UE 102 partially resets the UE MAC entity (i.e., a partial UE MAC reset). In a partial UE MAC reset, the UE 102 performs a subset or portion of some or all of the actions in a complete UE MAC reset.

[0163] In some implementations, the partial UE MAC reset includes at least one of the following actions:

[0164] • if the 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 the UE 102 is considered expired;

[0165] • Refresh Msg3 buffer;

[0166] • Flush the MSGA buffer;

[0167] • Release (if any) the temporary C-RNTI;

[0168] • Reset one or more counters (for example, BFI_COUNTER and / or LBT_COUNTER).

[0169] In some implementations, the partial UE MAC reset further includes at least one of the following actions:

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

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

[0172] • cancelling (if any) the triggered power headroom reporting procedure;

[0173] • cancel (if any) the triggered consistent LBT fault;

[0174] • cancelling (if any) the triggered BFR;

[0175] • cancel (if any) the triggered sidelink buffer status reporting procedure;

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

[0177] • Cancellation (if any) of the triggered Time Advance Reporting process;

[0178] • cancel (if any) the triggered recommended bit rate query process;

[0179] • cancel (if any) the triggered configured uplink grant confirmation;

[0180] • cancel (if any) the triggered configured sidelink authorization confirmation;

[0181] • cancel (if any) the triggered query of the desired protection symbol;

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

[0183] In some implementations, the partial UE MAC reset further includes at least one of the following actions:

[0184] • Stop the first part of one or more timers and retain the remaining part of one or more timers;

[0185] • Set the New Data Indicator (NDI) for the UL HARQ process to a value of 0;

[0186] • Set the NDI for HARQ process ID to a value of 0 to monitor PDCCH in sidelink resource allocation mode 1;

[0187] • Flushing the soft buffers used for DL ​​HARQ processes;

[0188] • For each of the DL HARQ processes, the next received transmission for a TB is considered the first transmission;

[0189] Depending on the implementation, DU 174 may determine to partially or completely reset the DU MAC entity. In some implementations, when DU 174 resets the DU MAC entity as described above, DU 174 completely resets the DU MAC entity (i.e., a full DU MAC reset). In a full DU MAC reset, DU 174 performs some or all of the actions described above. In other implementations, when DU 174 resets the DU MAC entity as described above, DU 174 partially resets the DU MAC entity (i.e., a partial DU MAC reset). In a partial DU MAC reset, DU 174 performs a subset or portion of some or all of the actions of a full DU MAC reset.

[0190] In some implementations, the partial DU MAC reset includes at least one of the following actions in the partial MAC reset:

[0191] • if the UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), the timeAlignmentTimer started and / or maintained by the DU 174 for the UE 102 is considered expired;

[0192] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER)

[0193] In some implementations, when a partial DU MAC reset includes at least one of the following actions for the MAC entity (i.e., DU MAC reset):

[0194] • Stop the first part of one or more timers and retain the remaining part of one or more timers;

[0195] • Set the NDI for the DL HARQ process to a value of 0;

[0196] • Flushing the soft buffers used for UL HARQ processes;

[0197] • For each of the UL HARQ processes, the next received transmission for a TB is considered the first transmission;

[0198] • Reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER)

[0199] In other implementations, UE 102 refrains from resetting the UE MAC entity in response to receiving the first LTM command. Similarly, DU 174 refrains from resetting the DU MAC entity after (e.g., in response to) sending the first LTM command, receiving the acknowledgment 331, or determining that UE 102 is connected to the first cell. In other words, UE 102 uses the UE MAC entity (not reset) to communicate with DU 174 on the first cell. Similarly, DU 174 uses the DU MAC entity (not reset) to communicate with UE 102 on the first cell during or after the random access procedure 332 or after determining that UE 102 is connected to the first cell.

[0200] In some implementations, the UE 102 uses at least one UE RLC entity (e.g., RLC 206B) to communicate RLC PDUs with at least one DU RLC entity (e.g., RLC 206B) of the DU 174 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). In some implementations, the UE 102 reestablishes some or all of the at least one UE RLC entity after or in response to receiving the first LTM command and before performing 332 a random access procedure or communicating 336 with the DU 174 via the first cell. In some implementations, the DU 174 reestablishes some or all of the at least one DU RLC entity after (e.g., in response to) sending the first LTM command, receiving the acknowledgment 331, or determining that the UE 102 is connected to the first cell.

[0201] In some implementations, LTM configuration 1 may or may not include one or more RLC re-establishment indications (e.g., reestablishRLC fields) that configure UE 102 to re-establish some or all of at least one UE RLC entity. If LTM configuration 1 includes an RLC re-establishment indication that configures UE 102 to re-establish a first UE RLC entity among at least one UE RLC entity that UE 102 uses to communicate RLC PDUs with DU 174, UE 102 re-establishes the first UE RLC entity in response to the RLC re-establishment indication and the first LTM command. In some implementations, UE 102 may re-establish the first UE RLC entity before performing 332 a random access procedure or communicating 336 with DU 174 via the first cell. In other implementations, UE 102 may re-establish the first UE RLC entity simultaneously with or after performing 332 a random access procedure. Otherwise, if LTM configuration 1 does not include an RLC re-establishment indication, UE 102 refrains from re-establishing the first UE RLC entity in response to the first LTM command.

[0202] In some implementations, when the UE 102 re-establishes the first UE RLC entity, the UE 102 performs at least one of the following actions for the first UE RLC entity:

[0203] • discard RLC SDUs, RLC SDU segments and RLC PDUs (if any);

[0204] • Stop and reset the timer (if it is running);

[0205] • Reset state variables to their initial values.

[0206] In some implementations, the state variables and timers are defined in 3GPP specification 38.322.

[0207] Otherwise, if LTM configuration 1 does not include an RLC re-establishment indication for the first UE RLC entity, UE 102 refrains from re-establishing the first UE RLC entity upon or upon receiving the first LTM command. In other words, UE 102 refrains from performing actions for re-establishing the first UE RLC entity of UE 102 upon or upon receiving the first LTM command. In some implementations, if LTM configuration 1 or element 1 does not include an RLC re-establishment indication and includes an indication that configuration 1 is a complete configuration, UE 102 may re-establish the first UE RLC entity of UE 102 upon or upon receiving the first LTM command. Otherwise, if LTM configuration 1 or element 1 does not include an RLC re-establishment indication and an indication that configuration 1 is a complete configuration, UE 102 refrains from re-establishing the first UE RLC entity upon or upon receiving the first LTM command.

[0208] Similarly, DU 174 reestablishes some or all of the at least one DU RLC entity (e.g., NR RLC 206B) used by DU 174 to communicate with at least one UE RLC entity of UE 102 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331) in response to the RLC reestablishment indication. In some implementations, DU 174 reestablishes a first DU RLC entity in the at least one DU RLC entity after sending a first LTM command, receiving an acknowledgment of the first LTM command from UE 102, or determining that UE 102 is connected to the first cell. In some implementations, the acknowledgment is a HARQ ACK. In other implementations, the acknowledgment is a MAC CE. In yet other implementations, the acknowledgment is a PUCCH transmission. In some implementations, when base station 104 reestablishes the first DU RLC entity, DU 174 performs at least one of the following actions for the first DU RLC entity:

[0209] • discard RLC SDUs, RLC SDU segments and RLC PDUs (if any);

[0210] • Stop and reset the timer (if it is running);

[0211] • Reset state variables to their initial values.

[0212] In some implementations, the state variables and timers are defined in 3GPP specification 38.322.

[0213] In other implementations, UE 102 refrains from reestablishing some or all of the at least one UE RLC entities in response to receiving the first LTM command. Similarly, DU 174 refrains from reestablishing some or more of the at least one DU RLC entities after (e.g., in response to) sending the first LTM command, receiving the acknowledgment 331, or determining that UE 102 is connected to the first cell. In other words, UE 102 uses some or all of the at least one UE RLC entity (not reestablished) to communicate with DU 174 on the first cell. For example, some or all of the at least one UE RLC entity includes the first UE RLC entity and / or the second UE RLC entity. Similarly, DU 174 uses some or all of the at least one DU RLC entity (not reestablished) to communicate with UE 102 on the first cell during or after the random access procedure 332 or after determining that UE 102 is connected to the first cell. For example, some or all of the at least one DU RLC entity includes the first DU RLC entity and / or the second DU RLC entity.

[0214] In some implementations, the UE 102 communicates UL PDCP PDUs and / or DL ​​PDCP PDUs with at least one CU PDCP entity (e.g., PDCP 210) of the CU 172 using at least one UE PDCP entity (e.g., PDCP 210) at event 302. In some implementations, the UE 102 performs a PDCP recovery procedure for some or all of the at least one UE PDCP entity after or in response to receiving the first LTM command. For example, the UE 102 performs a PDCP recovery procedure for a first UE PDCP entity among the at least one UE PDCP entity after or in response to receiving the first LTM command. During the PDCP recovery procedure, the UE 102 may or may not re-establish the first UE PDCP entity. After or in response to performing the PDCP recovery procedure, the UE 102 may resend at least a portion of the UL PDCP PDU to the CU 172 via the DU 174 and the first cell at event 336. Similarly, CU 172 performs a PDCP recovery procedure for some or all of the at least one CU PDCP entity after or in response to sending the first LTM command. For example, CU 172 performs a PDCP recovery procedure for a first CU PDCP entity among the at least one CU PDCP entity after or in response to sending the first LTM command. In some implementations, CU 172 performs the PDCP recovery procedure for the first CU PDCP entity in response to receiving the DU-to-CU message 329 or 334. In other implementations, CU 172 performs the PDCP recovery procedure for the first CU PDCP entity in response to receiving the DL data delivery status message. During the PDCP recovery procedure, CU 172 may or may not re-establish the first CU PDCP entity. After or in response to performing the PDCP recovery procedure, CU 172 may resend at least a portion of the DL PDCP PDU to UE 102 via DU 174 and the first cell at event 336.

[0215] In other implementations, the UE 102 avoids re-establishing some or all of the at least one UE PDCP entities in response to receiving the first LTM command. For example, some or all of the at least one UE PDCP entities include the first UE PDCP entity and / or the second UE PDCP entity. Similarly, after receiving (e.g., in response to) the DU to CU message 329 or 340 or after receiving (e.g., in response to) the DL data delivery status message, the CU 172 avoids re-establishing some or more of the at least one CU PDCP entities. In other words, the UE 102 uses some or all of the at least one UE PDCP entity (not re-established) to communicate with the CU 172 via the DU 174 and the first cell. For example, some or all of the at least one UE PDCP entity include the first UE PDCP entity and / or the second UE PDCP entity. Similarly, the CU 172 uses some or all of the at least one CU PDCP entity (not re-established) to communicate with the UE 102 via the DU 174 and the first cell. For example, some or all of the at least one CU PDCP entity include a first CU PDCP entity and / or a second CU PDCP entity.

[0216] In some implementations, after determining that the UE 102 is connected to the first cell, the CU 172 may send 338 a CU-to-DU message (e.g., a UE Context Modification Request message) to the DU 174 to instruct the DU 174 to stop communicating with the UE 102 and / or release or suspend the resources of the cell 124A configured for the UE 102. In response, the DU 174 may stop communicating with the UE 102 on the cell 124A and / or release or suspend the resources of the cell 124A configured for the UE 102 and send 340 a DU-to-CU message (e.g., a UE Context Modification Response message) to the CU 172. Events 338 (optional) and 340 (optional) may occur at Figure 3 It is collectively referred to as the resource release process 396.

[0217] After or while communicating with DU 174 on the first cell, events 344, 346, 348, 350, 351, 352, 354, and / or 356, similar to events 324, 326, 328, 330, 331, 332, 334, and / or 336, respectively, may occur. UE 102 sends 344 at least one measurement report to DU 174. The at least one measurement report includes at least one measurement result for a 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 that the first cell is unsuitable for communication with UE 102. After receiving the at least one measurement report (e.g., in response thereto), DU 174 determines to activate LTM configuration 2 and generates a second LTM command to activate LTM configuration 2 (i.e., the second LTM command instructs UE 102 to apply LTM configuration 2). The DU 174 then sends 350 a second LTM command to the UE 102 on the first cell.

[0218] When or in response to determining to activate LTM configuration 2 or to send the second LTM command, DU 174 may send 349 a DU-to-CU message to CU 172 indicating that LTM is being executed. In some implementations, DU 174 includes cell ID 2 or ID 2 (i.e., LTM ID) in DU-to-CU message 349 to indicate that DU 174 will activate LTM configuration 2. The DU may send DU-to-CU message 349 to CU 172 before or after sending LTM command 350.

[0219] The descriptions for events 324, 326, 328, 330, 331, 332, 334, and / or 336 may be applied to events 344, 346, 348, 350, 351, 352, 354, and / or 356 with simple changes. For example, “cell 124A,” “first LTM command,” “first cell,” “ID 1,” and / or “LTM configuration 1” may be replaced with “first cell,” “second LTM command,” “second cell,” “ID 2,” and / or “LTM configuration 2,” respectively.

[0220] Events 344, 346, 348, 350, 351, 352, and 354 Figure 3 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, 356 are Figure 3 This is collectively referred to as the LTM configuration and / or activation process 380.

[0221] Next reference Figure 4In 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 the first cell (e.g., cell 124C). Scenario 400 is similar to scenario 300. Therefore, the description of scenario 300 is generally applicable to scenario 400. The differences between scenarios 300 and 400 are described below.

[0222] Initially, UE 102 communicates 402 with S-DU 174A on cell 124A using a serving DU configuration, and communicates with CU 172 via S-DU 174A. During communication 402, UE 102 sends 404, 406 at least one measurement report (e.g., an L3 measurement report) to CU 172 via S-DU 174A. Based on the at least one measurement report, CU 172 determines cells 1, ..., N to be prepared for LTM for UE 102 (operated by T-DU 174B), 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 the determination, CU 172 performs 490 an LTM preparation procedure with T-DU 174B to (request T-DU 174B) prepare cells 1, ..., N for LTM for UE 102. In the LTM preparation process 490, the CU 172 sends a CU-to-DU message including cell IDs 1, ..., N to the T-DU 174B, requesting that the T-DU 174B prepare cells 1, ..., N for LTM for the UE 102. In response, the T-DU 174B sends a DU-to-DU message including LTM configurations 1, ..., N to the CU 172 in response to the CU-to-DU message. The LTM configurations 1, ..., N respectively configure cells 1, ..., N for LTM. Specifically, the LTM configurations 1, ..., N respectively include configuration parameters for communication on cells 1, ..., N. In some implementations, the CU-to-DU message and the DU-to-CU message in the process 490 are UE Context Setup Request and UE Context Setup Response messages, respectively. Similar to the LTM configuration delivery process 394 , the CU 172 then sends LTM configurations 1, . . . , N in an RRC reconfiguration message in an LTM configuration delivery process 494 .

[0223] After performing LTM preparation procedure 490, CU 172 may perform additional LTM preparation procedures with T-DU 174B to prepare cells N+1, ..., N+M for LTM for UE 102. M is a positive integer greater than zero. Similar to events 404 and 406, CU 172 may determine to do so based on one or more measurement reports received from UE 102 via S-DU 174A. During the additional LTM preparation procedure, CU 172 sends a CU-to-DU message including cell IDs N+1, ..., N+M to T-DU 174B 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-to-DU message, T-DU 174B sends a DU-to-DU message including LTM configurations N+1, ..., N+M to CU 172. LTM configurations N+1, ..., N+M respectively configure cells N+1, ..., N+M for LTM. Specifically, LTM configurations N+1, ..., N+M include configuration parameters for communication on cells N+1, ..., N+M, respectively. Similar to LTM configuration delivery procedures 394 or 494, CU 172 then sends LTM configurations N+1, ..., N+M in an RRC reconfiguration message in an additional LTM configuration delivery procedure.

[0224] In some implementations, the LTM preparation procedure 490 is a UE context establishment procedure, and the additional LTM preparation procedure is a UE context modification procedure.

[0225] In some implementations, the CU 172 and the S-DU 174A may perform process 380 with the UE 102, as described for Figure 3 In process 380, CU 172 and S-DU 174A perform processes 390 and / or 392 to prepare the cell of S-DU 174A for LTM for UE 102. Note that in process 380 or for Figure 3 The value N described can be compared with the Figure 4The value N described may be the same or different. In process 390, CU 172 may receive a first DU-to-CU message including a reference LTM configuration from S-DU 174A in event 310. In this case, CU 172 includes the reference LTM configuration (received from S-DU 174A) in the CU-to-DU message in the LTM preparation process 490. T-DU 174B generates LTM configurations 1, ..., N based on the reference LTM configuration received from CU 172. In such a case, T-DU 174B does not include the reference LTM configuration in the DU-to-CU message in process 490. In the case of an additional LTM preparation process, T-DU 174B does not include the reference LTM configuration in the DU-to-CU message in the additional LTM preparation process. CU 172 may not include the reference LTM configuration in the CU-to-DU message in the additional LTM preparation process with T-DU 174B. In case of the additional LTM preparation process, the T-DU 174B generates LTM configurations N+1, . . . , N+M based on the reference LTM configuration received from the CU 172 .

[0226] In some implementations, CU 172 does not provide a reference LTM configuration to T-DU 174B during LTM preparation process 490. In such a case, T-DU 174B generates a reference LTM configuration and generates LTM configurations 1, ..., N based on the reference LTM configuration. In such a case, T-DU 174B includes the reference LTM configuration in a DU-to-CU message in process 490. CU 172 sends the reference LTM configuration in an RRC reconfiguration message in process 490. In the case of an additional LTM preparation process, T-DU 174B generates LTM configurations N+1, ..., N+M based on the reference LTM configuration. In this case, T-DU 174B may not include the reference LTM configuration in a DU-to-CU message in the additional LTM preparation process. In some implementations, the reference LTM configuration generated by T-DU 174B is different from the reference LTM configuration generated by S-DU 174A. In other implementations, the reference LTM configuration generated by the T-DU 174B is the same as the reference LTM configuration generated by the S-DU 174A.

[0227] In some implementations, CU 172 assigns IDs 1, ..., N that respectively identify LTM configurations 1, ..., N (received from T-DU 174B) and performs process 492 with T-DU 174B to provide IDs 1, ..., N and / or cell IDs 1, ..., N to T-DU 174B, similar to process 392. Thus, T-DU 174B associates IDs 1, ..., N with LTM configurations 1, ..., N and / or cell IDs 1, ..., N, respectively. In other implementations, T-DU 174B assigns IDs 1, ..., N that respectively identify LTM configurations 1, ..., N (generated by T-DU 174B) and includes IDs 1, ..., N in the DU-to-CU message of process 490, similar to event 310. In some implementations, CU 172 assigns IDs N+1, ..., N+M that respectively identify LTM configurations N+1, ..., N+M, and performs a process (similar to process 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 process 392. Thus, T-DU 174B associates IDs N+1, ..., N+M with LTM configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M, respectively. In other implementations, T-DU 174B assigns IDs N+1, ..., N+M that respectively identify LTM configurations N+1, ..., N+M, and includes IDs 1, ..., N in a DU-to-CU message that appends an LTM preparation process, similar to event 310.

[0228] In some implementations, the CU 172 sends 412 a CU-to-DU message including IDs 1, ..., N to the S-DU 174A and receives 414 a DU-to-CU message from the S-DU 174A in response. The CU-to-DU message 412 and the DU-to-CU message 414 are transmitted in parallel. Figure 4, N and / or cell IDs 1, ..., N in the CU-DU message 412. In some implementations, the CU 172 includes the LTM configurations 1, ..., N and / or cell IDs 1, ..., N in the CU-DU message 412. In some alternative implementations, the CU 172 may perform multiple LTM ID transfer procedures to send the IDs 1, ..., N, cell IDs 1, ..., N, and / or LTM configurations 1, ..., N to the S-DU 174A. In each of the procedures, the CU 172 includes specific portions of the IDs 1, ..., N, cell IDs 1, ..., N, and / or LTM configurations 1, ..., N in a CU-to-DU message similar to message 412. Thus, the S-DU 174A associates the IDs 1, ..., N with the LTM configurations 1, ..., N and / or cell IDs 1, ..., N, respectively.

[0229] In some implementations, the CU 172 sends a CU-to-DU message including IDs N+1, ..., N+M to the S-DU 174A and, in response, receives a DU-to-CU message from the S-DU 174A, similar to the CU-to-DU message 412 and the DU-to-CU message 414, respectively. In some implementations, the CU 172 includes LTM configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M in the CU-to-DU message. In some alternative implementations, the CU 172 may perform multiple LTM ID transfer procedures to send IDs N+1, ..., N+M, cell IDs N+1, ..., N+M, and / or LTM configurations N+1, ..., N+M to the S-DU 174A. In each of the processes, the CU 172 includes specific portions of the IDs N+1, ..., N+M, cell IDs N+1, ..., N+M, and / or LTM configurations 1, ..., N in a CU-DU message similar to message 412. Thus, the S-DU 174A associates the IDs N+1, ..., N+M with the LTM configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M, respectively.

[0230] Later, similar to event 324, UE 102 may send 424 at least one measurement report to S-DU 174A. The at least one measurement report (e.g., an L1 measurement report) includes an event ID, a first measurement result for cell 1 of T-DU 174B, and / or includes a second measurement result for cell 124A. In some implementations, the first measurement result may be or include RSRP, RSRQ, and / or SINR obtained by UE 102 from a reference signal transmitted on cell 1. Similarly, the second measurement result may be or include RSRP, RSRQ, and / or SINR obtained by UE 102 from a reference signal transmitted on cell 124A. In some implementations, the event ID, RSRP, RSRQ, and / or SINR are L1 event ID, L1-RSRP, L1-RSRQ, and / or L1-SINR, respectively. Based on the first measurement result and / or the second measurement result, S-DU 174A may send 430 a first LTM command (i.e., LTM command 1) including ID 1 to UE 102 to instruct UE 102 to perform a cell change from cell 124A to cell 1 of T-DU 174B. When UE 102 receives the first LTM command, UE 102 identifies the LTM configuration identified by ID 1 (e.g., LTM configuration 1) and performs a cell change from cell 124A to cell 1 according to LTM configuration 1. After receiving the first LTM command (e.g., in response thereto), UE 102 may or may not perform 432 a random access procedure with T-DU 174B, similar to event 332. After receiving the first LTM command or completing the random access procedure 432 (e.g., in response thereto), UE 102 may communicate 436 with T-DU 174B on the first cell using LTM configuration 1 and / or the reference LTM configuration, and communicate with CU 172 via T-DU 174B, similar to event 336.

[0231] The resource release process 496 may be similar to the process 396. Alternatively, in the resource release process 496, the CU 172 may send a CU-to-DU message (e.g., a UE Context Release Command message) to the S-DU 174A to release the UE context of the UE 102. In response, the S-DU 174A releases the UE context of the UE 102 and sends 440 a DU-to-CU message (e.g., a UE Context Release Complete message) to the CU 172.

[0232] Events 380, 404, 406, 490, 492, 494, 494, 424, 426, 428, 429, 430, 431, 432, 434, 436, 496, 498, 456 Figure 4 is collectively referred to as the LTM configuration and / or activation process 480.

[0233] Next reference Figure 5A In scenario 500A, base station 106 operates as a MN and base station 104 operates as a SN. SN 104 includes CU 172 and DU 174. Scenario 500A is similar to scenario 300, except that scenario 500A is a DC scenario and scenario 300 is a single connection (SC) scenario. MN 106 may include a CU similar to Figure 3 CU and DU of base station 104.

[0234] Initially, UE 102 communicates with MN 106 and SN 104 in DC. At event 502, UE 102 communicates with DU 174 on cell 124A using the serving DU configuration and communicates with CU 172 via DU 174 using the serving CU configuration, similar to event 302. In some alternative implementations, UE 102 does not communicate with CU 172 via DU 174 in event 302. In some implementations, UE 102 may communicate 502 UL PDUs and / or DL ​​PDUs with MN 106 and / or SN 104 in DC via a radio bearer, which may include SRBs and / or DRBs. MN 106 and / or SN 104 may configure the radio bearer to UE 102. UE 102 communicates 502 UL PDUs and / or DL ​​PDUs with SN 104 in DC on an SCG (i.e., SCG radio resources) that SN 104 configures for communication with UE 102. UE 102 communicates UL PDUs and / or DL ​​PDUs with MN 106 in DC on an MCG (i.e., MCG radio resources) according to an MN configuration (i.e., MCG configuration). In some implementations, the serving DU configuration is an SN configuration (i.e., SCG configuration). In the MN configuration, MN 106 configures an MCG that includes at least one serving cell operated by MN 106 (e.g., cell 126 and / or other cells). In the serving DU configuration, SN 106A configures an SCG that includes at least one serving cell operated by SN 104 (e.g., cell 124A and / or other cells). In some implementations, the MN configuration includes multiple configuration parameters and UE 102 receives the configuration parameters in one or more RRC messages from MN 106. If targeted Figure 3As described above, the service DU configuration includes a plurality of configuration parameters. In some implementations, UE 102 receives these configuration parameters in one or more RRC messages from SN 104, for example, via MN 106 and / or over an SRB (e.g., SRB3) configured by MN 106 or SN 104 to exchange RRC messages between UE 102 and SN 104.

[0235] When UE 102 communicates with MN 106 and SN 104 in DC, MN 106 may perform 580 an LTM configuration and / or activation procedure with UE 102 similar to procedures 380 and / or 480. In some implementations, when communicating with MN 106 and SN 104 in DC, UE 102 may send at least one measurement report to CU 172 via DU 174 and cell 124A in events 504 and 506, similar to events 304 and 306, respectively. In other implementations, when communicating with MN 106 and SN 104 in DC, UE 102 may send 505 at least one measurement report to MN 106 via cell 126. MN 106, in turn, sends 507 the at least one measurement report to CU 172. In some implementations, MN 106 generates at least one SN message including the at least one measurement report and sends the at least one SN message to CU 172 in event 507. In one implementation, the at least one SN message includes an RRC Transfer message and / or an SN Modification Request message.

[0236] After receiving at least one measurement report (e.g., in response thereto) or while SN 104 is communicating with UE 102, SN 104 determines to prepare a first cell for UE 102, such as for Figure 3Events 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. After receiving the first LTM command 530, sending the confirmation 531, or determining that the UE 102 is successfully connected to the first cell 532 or 536, similar to event 336, the UE 102 operating with the MN 106 and the SN 104 in DC communicates 536 with the DU 174 on the first cell according to LTM configuration 1, and communicates 536 with the CU 172 via the DU 174. Later, DU 174 and / or CU 172 may perform an LTM execution process 598 with UE 102, similar to process 398 or 498, to instruct UE 102 to perform a cell change from the first cell to the second cell. As a result of process 598, similar to event 356, UE 102 operating in DC with MN 106 and SN 104 communicates 556 with DU 174 on the second cell according to LTM configuration 2, and communicates 556 with CU 172 via DU 174.

[0237] Events 504, 506, 505, 507, 590, 592, 594, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, 556 Figure 5A This is collectively referred to as the LTM configuration and / or activation process 581.

[0238] Next reference Figure 5BScenario 500B is generally similar to scenario 500A, except that SN 104 sends 517, 519 RRC reconfiguration messages to UE 102 via MN 106, and receives 521, 523 RRC reconfiguration complete messages from UE 102 via MN 106. RRC reconfiguration messages 517, 519 are similar to RRC reconfiguration messages 316, 318. RRC reconfiguration complete messages 521, 523 are similar to RRC reconfiguration messages 320, 322. In some implementations, SN 104 generates a first SN message (e.g., an SN Modification Required message, an SN Modification Required message, or an RRC Transfer message) including the RRC reconfiguration message and sends the first SN message to MN 106 in event 517. MN 106 generates an MN RRC message including the RRC reconfiguration message and sends 519 the MN RRC message to UE 102. In response, UE 102 generates an MN RRC Response message including an RRC Reconfiguration Complete message and sends 521 the 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 Transfer message) including the RRC Reconfiguration Complete message and sends the second SN message to SN 104 at event 523. In some implementations, the MN RRC message and the MN RRC Response message may be an RRC Reconfiguration message and an RRC Reconfiguration Complete message, respectively.

[0239] Events 504, 506, 505, 507, 590, 592, 594, 517, 519, 521, 523, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, 556 Figure 5B This is collectively referred to as the LTM configuration and / or activation process 582.

[0240] Next reference Figure 6AIn scenario 600A, similar to scenarios 300-500B, base station 106 operates as a MN, and base station 104 operates as a SN. Similar to base station 104 in scenario 400, SN 104 includes CU 172, S-DU 174A, and T-DU 174B. When UE 102 communicates with MN 106 and SN 104 in DC, MN 106 may perform 680 an LTM configuration and / or activation procedure similar to procedures 380 and / or 480 with UE 102. When UE 102 communicates with M-DU 174A and S-DU 174B in DC, CU 172 may perform 681 an LTM configuration and / or activation procedure similar to procedures 581 and / or 582 with UE 102 via M-DU 174A or S-DU 174B.

[0241] Next reference Figure 6B , scenario 600B is similar to scenarios 300 - 500B and 600A, except that SN 104 sends 617 , 619 an RRC reconfiguration message to UE 102 via MN 106 , and receives 621 , 623 an RRC reconfiguration complete message from UE 102 via MN 106 .

[0242] Next reference Figure 7A In scenario 700A, the base station 104 operates as both a MN and a SN, similar to scenarios 300-600B. The base station 104 includes a CU 172, a primary DU (M-DU) 174A, and a secondary DU (S-DU) 174B. Figure 3 Base station 104 or Figures 5A to 6B MN 106 in, CU 172 operates with M-DU 174A as MN and similarly Figures 5A to 6B In the SN 104, the CU 172 operates with the S-DU 174B as the SN.

[0243] In scenario 700A, UE 102 initially communicates 702 with M-DU 174A and S-DU 174B in DC and communicates 702 with CU 172 via M-DU 174A and S-DU 174B. At event 702, similar to event 302, UE 102 communicates with S-DU 174B on cell 124A using the serving DU configuration and communicates with CU 172 via S-DU 174B using the serving CU configuration. Events 704 and 706 are similar to events 304 and 306. In some implementations, similar to event 304, UE 102 may send 705 at least one measurement report to M-DU 174A. Similar to event 306, M-DU 174A then sends 707 at least one DU-to-CU message to CU 172 including the at least one measurement report. When UE 102 communicates with M-DU 174A and S-DU 174B under DC, CU 172 may perform 780 an LTM configuration and / or activation procedure similar to process 380 with UE 102 via M-DU 174A.

[0244] Events 704, 706, 705, 707, 790, 792, 794, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, 756 Figure 7A are collectively referred to as the LTM configuration and / or activation process 781.

[0245] Next reference Figure 7B , scenario 700B is similar to scenarios 300-600B and 700A, except that CU 172 sends 717, 719 an RRC reconfiguration message to UE 102 via M-DU 174A and receives 721, 723 an RRC reconfiguration complete message from UE 102 via M-DU 174A.

[0246] Events 704, 706, 705, 707, 790, 792, 794, 717, 719, 721, 723, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, 756 Figure 7B is collectively referred to as the LTM DU configuration and / or activation process 782.

[0247] Next reference Figure 8AIn scenario 800A, similar to scenarios 300-700B, base station 104 operates as both a mobile node and a network node. Base station 104 includes a control unit (CU) 172, a master DU (M-DU) 174A, a secondary DU (S-DU) 174B, and a target secondary DU (T-DU) 174C. CU 172 operates with M-DU 174A as a mobile node and with S-DU 174B as a network node. When UE 102 communicates with M-DU 174A and S-DU 174B in DC mode, CU 172 can perform 880 an LTM configuration and / or activation procedure similar to procedure 380 with UE 102 via M-DU 174A. When UE 102 communicates with M-DU 174A and S-DU 174B under DC, CU 172 may perform 881 an LTM configuration and / or activation procedure similar to procedure 581 or 582 with UE 102 via S-DU 174A.

[0248] Next reference Figure 8B , scenario 800B is similar to scenarios 300-700B and 800A, except that CU 172 sends 817, 819 an RRC reconfiguration message to UE 102 via M-DU 174A and receives 821, 823 an RRC reconfiguration complete message from UE 102 via M-DU 174A.

[0249] Next, refer to Figures 9 to 15 Several example methods that can be implemented in a RAN, such as a DU or CU, to support configuration for LTM are discussed. Figures 3 to 8B The examples and implementations described can be applied to Figures 9 to 15 .

[0250] Figure 9 An example method 900 is shown that may be implemented by a RAN (e.g., base station 104 or 106, DU 174 of base station 104 or 106, or DU 174A, DU 174B, and / or DU 174C of base station 104) for communicating with a UE (e.g., UE 102).

[0251] Method 900 begins at block 902, where the RAN communicates with a UE via at least one serving cell using a first serving DU configuration (e.g., events 302, 402, 502, 602, 702, 802). At block 904, the RAN sends a first reference LTM configuration, LTM configuration 1, ..., N, and LTM IDs 1, ..., N to the UE, where N is a positive integer and LTM configurations 1, ..., N configure cells 1, ..., N, respectively (e.g., 316, 318, 394, 380, 494, 480, 580, 594, 581, 517, 519, 582, 680, 694, 681, 617, 619, 682, 780, 794, 781, 717, 719, 782, 880, 894, 881, 817, 819, 882).

[0252] At block 906, the RAN may send a second serving DU configuration to the UE. In some implementations, the RAN sends an RRC reconfiguration message including the second serving DU configuration to the UE. In the event that the RAN includes a first DU operating at least one serving cell, the first DU sends the second DU configuration to the UE via the CU. For example, the first DU sends a DU-to-CU message including the second serving DU configuration to the CU, which in turn sends an RRC reconfiguration message including the second serving DU configuration to the UE via the first DU, the second DU, or the MN. At block 908, the RAN may communicate with the UE via at least one serving cell based on the second serving DU configuration. In some implementations, upon receiving the second serving DU configuration, the UE may communicate with the RAN via at least one serving cell based on the second serving DU configuration. In some implementations, the second serving DU configuration augments the first serving DU configuration. In such cases, the RAN communicates with the UE based on the second serving DU configuration and configuration parameters of the first serving DU configuration that are not augmented by the second serving DU configuration.

[0253] In some implementations, blocks 904 and 906 occur via at least one serving cell, CU, or MN.

[0254] At block 910, the RAN sends a first LTM command (e.g., 330, 398, 380, 430, 480, 580, 530, 581, 582, 680, 630, 681, 682, 780, 730, 781, 782, 880, 830, 881, 882) to the UE via one of the at least one serving cell, commanding the UE to perform a serving cell change to Cell 1. In some implementations, at block 910, the RAN determines to command the UE to perform a serving cell change to Cell 1 and sends the first LTM command in response to the determination. At block 912, the RAN detects that a UE accesses cell 1 (e.g., events 332, 380, 398, 432, 498, 480, 532, 598, 580, 581, 582, 632, 698, 680, 681, 682, 732, 798, 780, 781, 782, 832, 898, 880, 881, 882), for example, according to LTM configuration 1. The DU operating cell 1 may send a DU-to-CU message to the CU to indicate that the UE accesses cell 1 (e.g., events 334, 380, 434, 480, 534, 580, 581, 582, 634, 680, 681, 682, 734, 780, 781, 782, 834, 880, 881, 882). At block 914, the RAN communicates with the UE via cell 1 using the first reference LTM configuration and LTM configuration 1 (e.g., events 336, 380, 436, 480, 536, 580, 581, 582, 636, 680, 681, 682, 736, 780, 781, 782, 836, 880, 881, 882). In some implementations, after (i.e., in response to) detecting that the UE has accessed cell 1, the RAN communicates with the UE via cell 1 using the first reference LTM configuration and LTM configuration 1. In some implementations, the RAN refrains from applying the first serving DU configuration and / or the second serving DU configuration to communicate with the UE via cell 1 at block 914. In some implementations, the RAN applies the first plurality of configuration parameters in the first reference LTM configuration and the second plurality of configuration parameters in LTM configuration 1 to communicate with the UE, and retains the first reference LTM configuration and LTM configuration 1.

[0255] In some implementations, the RAN (e.g., the DU operating cell 1) sends a third service DU configuration including a third plurality of configuration parameters to the UE, for example, via cell 1, the CU, or the MN. In some implementations, the RAN sends an RRC reconfiguration message including the third service DU configuration to the UE. For example, the DU operating cell 1 sends the third DU configuration to the UE via the CU. Specifically, the DU sends a DU-to-CU message including the third service DU configuration to the CU, which then sends an RRC reconfiguration message including the third service DU configuration to the UE via the DU, another DU, or the MN. In some implementations, upon receiving the third service DU configuration, the UE may communicate with the RAN via cell 1 based on the third service DU configuration. In some implementations, the third configuration parameters augment the first plurality of configuration parameters and / or the second plurality of configuration parameters. In such cases, the RAN communicates with the UE based on the third service DU configuration and the first plurality of configuration parameters and / or the second plurality of configuration parameters that are not augmented by the second service DU configuration.

[0256] At block 916, the RAN sends a second LTM command (e.g., 350, 398, 380, 498, 480, 598, 581, 582, 680, 698, 681, 682, 780, 798, 781, 782, 880, 898, 881, 882) commanding the UE to perform a serving cell change to cell 2. In some implementations, at block 916, the RAN determines that the UE is commanded to perform a serving cell change to cell 2 and, in response to the determination, sends the second LTM command via cell 1 or another serving cell. At block 918, the RAN detects that the UE accesses cell 2 according to LTM configuration 2. In some implementations, the DU operating cell 2 may send a DU-to-CU message to the CU to instruct the UE to access cell 2 (e.g., events 354, 380, 398, 498, 480, 598, 580, 581, 582, 698, 680, 681, 682, 798, 780, 781, 782, 898, 880, 881, 882). At block 920, the RAN communicates with the RAN via cell 2 using the first reference LTM configuration and LTM configuration 2 (e.g., events 356, 380, 456, 480, 556, 580, 581, 582, 656, 680, 681, 682, 756, 780, 781, 782, 856, 880, 881, 882). In some implementations, after (i.e., in response to) detecting that the UE accesses cell 2, the RAN communicates with the UE via cell 2 using the first reference LTM configuration and LTM configuration 2. In some implementations, the RAN refrains from using LTM configuration 1 and the third serving DU configuration (if received) to communicate with the UE via cell 2 at block 920.

[0257] In some implementations, the RAN sends a third LTM command (e.g., 330, 350, 398, 380, 430, 498, 480, 580, 530, 550, 598, 581, 582, 680, 630, 650, 698, 681, 682, 780, 730, 750, 798, 781, 782, 880, 830, 850, 898, 881, 882) to the UE via cell 2. In some implementations, the RAN determines to command the UE to perform a serving cell change to cell 2 and sends the third LTM command in response to the determination. The RAN detects that the UE accesses cell 1 according to LTM configuration 1 (e.g., events 332, 380, 398, 432, 498, 480, 532, 598, 580, 581, 582, 632, 698, 680, 681, 682, 732, 798, 780, 781, 782, 832, 898, 880, 881, 882). In some implementations, the DU operating cell 1 may send a DU-to-CU message to the CU to instruct the UE to access cell 1 (e.g., events 334, 380, 398, 434, 480, 534, 580, 581, 582, 634, 680, 681, 682, 734, 780, 781, 782, 834, 880, 881, 882). After detecting that the UE accesses cell 1 (e.g., in response thereto), the RAN communicates with the UE via cell 1 using the first reference LTM configuration and LTM configuration 1 (e.g., events 336, 380, 436, 480, 536, 580, 581, 582, 636, 680, 681, 682, 736, 780, 781, 782, 836, 880, 881, 882). In some implementations, the RAN avoids applying the third serving DU configuration (if received) and LTM configuration 2 to communicate with the UE via cell 1.

[0258] In some implementations, the RAN node includes cell-specific configuration parameters for cells 1, ..., N in LTM configurations 1, ..., N, respectively. In some implementations, each of LTM configurations 1, ..., N includes a serving cell configuration for the corresponding cell (e.g., a special cell configuration such as SpCellConfig IE). When the UE receives the first LTM command, the UE determines cell 1 to access based on LTM configuration 1 upon receiving the first LTM command.

[0259] In some implementations, the RAN node includes DU-specific configuration parameters in the first reference LTM configuration. The DU-specific configuration parameters are common across cells 1, ..., N. In some alternative implementations of block 912, the RAN node detects that the UE accesses cell 1 in accordance with the first reference LTM configuration. In some alternative implementations of block 912, the RAN node detects that the UE accesses cell 1 in accordance with the first reference LTM configuration and LTM configuration 1. In some alternative implementations of block 918, the RAN node detects that the UE accesses cell 2 in accordance with the first reference LTM configuration. In some alternative implementations of block 918, the RAN node detects that the UE accesses cell 2 in accordance with the first reference LTM configuration.

[0260] Figure 10A An example method 1000A is shown, which may be implemented by a RAN (eg, base station 104 or 106, DU 174 of base station 104 or 106, or DU 174A, DU 174B, and / or DU 174C of base station 104) for communicating with a UE (eg, UE 102).

[0261] Method 1000A begins at blocks 902, 904, and 906 through 920 (optional). Flow proceeds to blocks 1002 and / or 1006. At block 1002, the RAN sends a second reference LTM configuration to the UE. At block 1004, the RAN replaces the first reference LTM configuration with the second reference LTM configuration. At block 1006, the RAN determines to update LTM configuration M among LTM configurations 1, ..., N, where 0 < M ≤ N. At block 1008, the RAN sends a new (subsequent) LTM configuration and LTM ID M to the UE to replace LTM configuration M. At block 1010, the RAN replaces LTM configuration M with the subsequent LTM configuration.

[0262] In some implementations, the RAN sends the second reference LTM configuration to the UE, similar to sending the first reference LTM configuration to the UE. In some implementations, the RAN sends the subsequent LTM configuration and LTM ID M to the UE, similar to sending LTM configurations 1, ..., N and LTM IDs 1, ..., N to the UE.

[0263] Figure 10B is a flow chart of an example method 1000B that is similar to method 1000A, except that method 1000B includes block 1005 instead of block 1004. At block 1005, the RAN modifies the first reference LTM configuration with the second reference LTM configuration.

[0264] Figure 10Cis a flow chart of an example method 1000C that is similar to methods 1000A and 1000B, except that method 1000C includes blocks 1012 , 1003 , 1014 , and 1016 .

[0265] At block 1012, the RAN includes the second reference LTM configuration in the message. At block 1003, the RAN determines whether the second reference LTM configuration is to replace the first LTM reference configuration. If the RAN determines that the second reference LTM configuration is to replace the first LTM configuration, the flow proceeds to block 1014. At block 1014, the RAN includes an indication that the second reference LTM configuration replaces the first reference LTM configuration. At block 1016, the RAN sends the message to the UE. Otherwise, if the RAN determines that the second reference LTM configuration is not to replace the first reference LTM configuration (i.e., the second reference LTM configuration is to modify the first reference LTM configuration), the flow proceeds to block 1016.

[0266] Figure 11 An example method 1100 is shown, which may be implemented by a RAN (eg, base station 104 or 106, DU 174 of base station 104 or 106, or DU 174A, DU 174B, and / or DU 174C of base station 104) for communicating with a UE (eg, UE 102).

[0267] Method 1100 begins at blocks 902, 904, 906, and 908. At block 1102, the RAN determines whether a second service DU configuration affects a first reference LTM configuration or LTM configurations 1, ..., N (e.g., the second service DU configuration causes configuration parameters in the first reference configuration or LTM configurations 1, ..., N to be invalid). If the RAN determines that the second service DU configuration affects the first reference configuration, the flow proceeds to blocks 1002 and 1004 or 1005. Otherwise, if the RAN determines that the second service DU configuration affects LTM configurations 1, ..., N, the flow proceeds to block 1104. At block 1104, the RAN sends new (subsequent) LTM configurations 1, ..., N and LTM IDs 1, ..., N to the UE. At block 1106, the RAN replaces LTM configurations 1, ..., N with subsequent LTM configurations 1, ..., N, e.g., based on LTM IDs 1, ..., N, respectively. If the RAN determines that the second serving DU configuration does not affect the first reference configuration and LTM configurations 1, ..., N, the flow proceeds to block 1108 where it ends.

[0268] Figure 12 An example method 1200 is shown that may be implemented by a UE (eg, UE 102) for performing a fast serving cell change with a RAN (eg, DU 174, CU 172, base station 104 or 106, or RAN 105).

[0269] Method 1200 begins at block 1202, where a UE communicates with a RAN via at least one serving cell using a first serving DU configuration (e.g., events 302, 402, 502, 602, 702, 802). At block 1204, the UE receives a first reference LTM configuration, LTM configurations 1, ..., N, and LTM IDs 1, ..., N from the RAN via at least one serving cell, where N is a positive integer and LTM configurations 1, ..., N configure cells 1, ..., N, respectively (e.g., 316, 318, 394, 380, 494, 480, 580, 594, 581, 582, 680, 694, 681, 682, 780, 794, 781, 782, 880, 894, 881, 882). At block 1206, the UE receives a second serving DU configuration from the RAN. At block 1208, the UE communicates with the RAN via at least one serving cell using the second serving DU configuration. At block 1210, the UE receives a first LTM command from the RAN via one of the at least one serving cells, instructing the UE to perform a serving cell change to Cell 1. At block 1211, the UE identifies LTM configuration 1 based on the first LTM command. At block 1212, in response to the first LTM command, the UE accesses Cell 1 according to LTM configuration 1. At block 1214, the UE communicates with the RAN via Cell 1 according to the first reference LTM configuration and LTM configuration 1. At block 1216, the UE receives a second LTM command from the RAN instructing the UE to perform a serving cell change to Cell 1. In some implementations, the UE receives the second LTM command via Cell 1 or another serving cell. At block 1217, the UE identifies LTM configuration 2 based on the second LTM command. At block 1218, in response to the second LTM command, the UE accesses Cell 2 according to LTM configuration 2. At block 1220 , the UE communicates with the RAN via cell 2 using the first reference LTM configuration and LTM configuration 2 .

[0270] Blocks 1202, 1204, 1206, 1208, 1210, 1212, 1214, 1216, 1218, and 1220 correspond to blocks 902, 904, 906, 908, 910, 912, 914, 916, 918, and 920, respectively. Figure 9 The examples and implementations described can be applied to Figure 12 .

[0271] Figure 13A An example method 1300A is shown that may be implemented by a UE (eg, UE 102) for performing a fast serving cell change with a RAN (eg, DU 174, CU 172, base station 104 or 106, or RAN 105).

[0272] Method 1300A begins at blocks 1202, 1204, and 1206 through 1224 (optional). At block 1302, the UE receives a second reference LTM configuration from the RAN. Flow proceeds from block 1302 to blocks 1304 or 1305. At block 1304, the UE replaces the first reference LTM configuration with the second reference LTM configuration. At block 1305, the UE modifies the first reference LTM configuration with the second reference LTM configuration. Flow proceeds from blocks 1304 and 1305 to block 1306. At block 1306, the UE receives a subsequent LTM configuration (i.e., a non-reference LTM configuration) and LTM ID M from the RAN. At block 1308, the UE determines whether LTM ID M is one of LTM IDs 1, ..., N. If the UE determines that LTM ID M is one of LTM IDs 1, ..., N, flow proceeds to block 1310. At block 1310, the UE identifies LTM configuration M based on LTM ID M. At block 1312, the UE replaces LTM configuration M with a (non-reference) LTM configuration. Otherwise, if the UE determines that LTM ID M is not one of LTM IDs 1, ..., N, the flow proceeds to block 1314. At block 1314, the UE stores LTM configuration M and LTM ID M.

[0273] In some implementations, the UE receives a second reference LTM configuration from the RAN, similar to receiving the first reference LTM configuration from the RAN. In some implementations, the UE receives a subsequent LTM configuration and LTM ID M from the RAN, similar to receiving LTM configurations 1, ..., N and LTM IDs 1, ..., N from the RAN.

[0274] against Figures 10A to 10C The examples and implementations described can be applied to Figure 12 .

[0275] Figure 13B 1300B is a flow chart of an example method 1300B that is similar to method 1300A, except that method 1300B includes block 1303. At block 1303, the UE determines whether it has received an indication that the second reference LTM configuration has replaced the first LTM configuration. If the UE has received the indication, the process proceeds to block 1304. Otherwise, if the UE has not received the indication, the process proceeds to block 1305.

[0276] Figure 14 An example method 1400 is shown that may be implemented by a UE (eg, UE 102) for performing a fast serving cell change with a RAN (eg, DU 174, CU 172, base station 104 or 106, or RAN 105).

[0277] Method 1400 begins at block 1402, where a UE communicates with a RAN via at least one serving cell using a serving DU configuration (e.g., events 302, 402, 502, 602, 702, 802). At block 1404, the UE receives a reference LTM configuration, a first LTM configuration, and a first LTM ID from the RAN via at least one serving cell, where the first LTM configuration configures the first cell (e.g., 316, 318, 394, 380, 494, 480, 580, 594, 581, 517, 519, 582, 680, 694, 681, 617, 619, 682, 780, 794, 781, 717, 719, 782, 880, 894, 881, 817, 819, 882). At block 1406, the UE receives a first LTM command from the RAN via one of the at least one serving cells, wherein the LTM command instructs the UE to perform a serving cell change to the first cell (e.g., 330, 398, 380, 430, 480, 580, 530, 581, 582, 680, 630, 681, 682, 780, 730, 781, 782, 880, 830, 881, 882). At block 1408, the UE determines whether the reference LTM configuration is a full configuration or an incremental configuration. If the UE determines that the reference LTM configuration is a full configuration, the flow proceeds to block 1410. At block 1410, after receiving the first LTM command (e.g., in response thereto), the UE refrains from applying the serving DU configuration to communicate with the RAN. At block 1412, upon receiving the first LTM command (e.g., in response thereto), the UE applies the first LTM configuration and at least a portion of the reference LTM configuration to communicate with the RAN via the first cell (e.g., events 336, 380, 436, 480, 536, 580, 581, 582, 636, 680, 681, 682, 736, 780, 781, 782, 836, 880, 881, 882). Otherwise, if the UE determines that the reference LTM configuration is an incremental configuration, the flow proceeds to block 1414. At box 1414, after receiving the first LTM command (e.g., in response thereto), the UE applies at least a portion of the service DU configuration, at least a portion of the reference LTM configuration, and the first LTM configuration to communicate with the RAN (e.g., events 336, 380, 436, 480, 536, 580, 581, 582, 636, 680, 681, 682, 736, 780, 781, 782, 836, 880, 881, 882).

[0278] Figure 15An example method 1500 is shown that can be implemented by a UE (eg, UE 102) for performing a fast serving cell change with a RAN (eg, DU 174, CU 172, base station 104 or 106, or RAN 105).

[0279] Method 1500 begins at block 1502, where a UE communicates with a RAN via at least one serving cell using a serving DU configuration (e.g., events 302, 402, 502, 602, 702, 802). At block 1504, the UE receives a first LTM configuration and a first LTM ID from the RAN via at least one serving cell using the serving DU configuration, where the first LTM configuration configures a first cell (e.g., 316, 318, 394, 380, 494, 480, 580, 594, 581, 517, 519, 582, 680, 694, 681, 617, 619, 682, 780, 794, 781, 717, 719, 782, 880, 894, 881, 817, 819, 882). At block 1506, the UE receives a first LTM command from the RAN via at least one serving cell, wherein the first LTM command instructs the UE to perform a serving cell change to the first cell (e.g., 330, 398, 380, 430, 480, 580, 530, 581, 582, 680, 630, 681, 682, 780, 730, 781, 782, 880, 830, 881, 882). At block 1508, the UE determines whether the UE has (is configured with) a reference LTM configuration. If the UE has the reference LTM configuration, the flow proceeds to block 1510. At block 1510, the UE refrains from applying the serving DU configuration to communicate with the RAN. At block 1512, after receiving the first LTM command (e.g., in response thereto), the UE communicates with the RAN via the first cell using the first LTM configuration and at least a portion of the reference LTM configuration (e.g., events 336, 380, 436, 480, 536, 580, 581, 582, 636, 680, 681, 682, 736, 780, 781, 782, 836, 880, 881, 882). Otherwise, if the UE determines that the UE does not have the reference LTM configuration, the flow proceeds to block 1514. At box 1514, after receiving the first LTM command (e.g., in response thereto), the UE communicates with the RAN via the first cell using at least a portion of the first LTM configuration and the serving DU configuration (e.g., events 336, 380, 436, 480, 536, 580, 581, 582, 636, 680, 681, 682, 736, 780, 781, 782, 836, 880, 881, 882).

[0280] against Figure 9 The description can be applied to Figure 14 and Figure 15 .

[0281] The following description can be applied to the above description.

[0282] In general, the description of one of the above figures may apply to another of the above figures. The examples, implementations, and methods described above may be combined if not in conflict. Events or blocks described above may be optional or omitted. For example, events or blocks with dashed lines in the figures may be optional. In some implementations, "message" is used and "information element (IE)" may be substituted for "message," and vice versa. In some implementations, "IE" is used and "field" may be substituted for "IE," and vice versa. In some implementations, "configuration" may be substituted for "configurations" or "configuration parameters," and vice versa. In some implementations, "LTM command" may be substituted for "serving cell change command," "layer 1 / layer 2 handover command," "lower layer handover command," or "lower layer serving cell change command." In some implementations, "some" means "one or more." In some implementations, "at least one" means "one or more." In some implementations, "DU configuration" may be substituted for "cell group configuration."

[0283] The user device (e.g., UE 102) in which the technology of the present disclosure may be implemented may 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 another personal media device, wearable device such as a smart watch, wireless hotspot, femtocell or broadband router. Further, in some cases, the user device may be embedded in an electronic system such as a head unit of a vehicle or an advanced driver assistance system (ADAS). Further, the user device may 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, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0284] Certain embodiments are described in this disclosure as including 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 that is capable of performing certain operations and can be configured or arranged in a certain manner. A hardware module may include dedicated circuitry or logic that is permanently configured to perform certain operations (e.g., as a dedicated processor, such as a field programmable gate array (FPGA) or application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.). A hardware module may also include programmable logic or circuitry that is temporarily configured by software to perform certain operations (e.g., as contained within a general-purpose processor or other programmable processor). The decision to implement a hardware module in a dedicated and permanently configured circuitry or in a temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[0285] When implemented in software, the techniques may be provided as part of the operating system, as a library used by multiple applications, as a specific software application, etc. The software may be executed by one or more general-purpose processors or one or more special-purpose processors.

[0286] Upon reading this disclosure, those skilled in the art will appreciate additional and alternative structural and functional designs for handling mobility between base stations using the principles disclosed herein. Thus, while specific embodiments and applications have been shown and described, it should be understood that the disclosed embodiments are not limited to the precise configurations and components disclosed herein. Various modifications, changes, 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 configuration method implemented in a user equipment (UE), the method comprising: receiving a first reference lower layer triggered mobility LTM configuration from a radio access network RAN ​​node; receiving a second reference LTM configuration from the RAN node; as well as The first reference LTM configuration is replaced with the second reference LTM configuration.

2. The method of claim 1, further comprising: A non-reference LTM configuration is received from the RAN node.

3. The method of claim 2, further comprising: receiving a subsequent non-reference LTM configuration and an LTM configuration identifier ID from the RAN node; In response to determining that the non-reference LTM configuration at the UE corresponds to the LTM configuration ID, the non-reference LTM configuration is replaced with the subsequent non-reference LTM configuration.

4. The method of claim 2, further comprising: receiving a subsequent non-reference LTM configuration and an LTM configuration identifier ID from the RAN node; In response to determining that the non-reference LTM configuration at the UE does not correspond to the LTM configuration ID, the subsequent non-reference LTM configuration and the LTM configuration ID are stored.

5. The method of any one of claims 2 to 4, further comprising, before receiving the subsequent non-reference LTM configuration: A radio resource control (RRC) reconfiguration message including the non-reference LTM configuration is received.

6. The method of claim 5, wherein: The RRC reconfiguration includes the first reference LTM configuration and the non-reference LTM configuration.

7. The method according to any one of claims 2 to 6, further comprising: Upon receiving the RRC reconfiguration message, avoiding immediately applying the non-reference LTM configuration.

8. The method according to any one of claims 2 to 7, wherein The non-reference LTM configuration is an incremental configuration that enhances the first reference configuration.

9. A configuration method implemented in a Radio Access Network (RAN) node, the method comprising: Sending a first reference lower layer triggered mobility LTM configuration to a user equipment UE; Sending a second reference LTM configuration to the UE; as well as The first reference LTM configuration is replaced with the second reference LTM configuration at the RAN node.

10. The method of claim 9, further comprising: generating a non-reference LTM configuration based on the reference LTM configuration; as well as The non-reference LTM configuration is sent to the UE.

11. The method of claim 10, wherein: The first reference LTM configuration is equal to the service distributed unit DU configuration.

12. The method of claim 10, wherein: A portion of the first reference LTM configuration is equal to a portion of the serving distributed unit DU configuration.

13. The method according to any one of claims 10 to 12, wherein The first reference LTM configuration and the non-reference LTM configuration are sent in the same message.

14. The method of any one of claims 10 to 13, further comprising: sending a subsequent non-reference LTM configuration and an LTM configuration ID corresponding to the non-reference LTM configuration and the non-reference LTM configuration to the UE; as well as The non-reference LTM configuration is replaced with the subsequent non-reference LTM configuration.

15. An apparatus comprising a transceiver and processing hardware, the apparatus being configured to implement the method of any preceding claim.

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