Managing lower layer triggered mobility configuration at user equipment

Abstract

A user equipment (UE) may implement a method for managing a lower layer triggered mobility protocol procedure. The method includes, at the UE, communicating with a distributed radio access network (RAN) node according to a serving distributed unit (DU) configuration and a centralized unit (CU) service configuration; receiving, at the UE, a reference lower layer triggered mobility (LTM) DU configuration and a reference LTM CU configuration from the distributed RAN node; and at the UE, communicating with the distributed RAN node using at least a portion of the reference LTM DU configuration and at least a portion of the reference LTM CU configuration.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of the filing date of Provisional U.S. Patent Application No. 63 / 446,329, entitled “MANAGING LOWER LAYER TRIGGEREDMOBILITY CONFIGURATIONS AT A UE,” filed on February 16, 2023. The entire contents of that provisional application are hereby expressly incorporated herein by reference. Technical Field

[0003] The present disclosure relates to wireless communications, and more particularly to managing mobility (ie, serving cell change) using control signaling at protocol layers lower than the Radio Resource Control (RRC) protocol layer. Background Art

[0004] This background description is provided for the purpose of generally presenting the context of the present disclosure. The work of the presently named inventors, to the extent that it is described in this background section, and aspects of the specification that might not have been considered prior art at the time of filing are neither explicitly nor implicitly admitted to be prior art with respect 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 Technical Specification (TS) 36.323) and New Radio (NR) (see 3GPP 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, in some examples, the UE and the base station use SRBs to exchange RRC messages and non-access stratum (NAS) messages, and DRBs can be used to transmit data on the user plane.

[0006] Depending on the scenario, the UE uses several types of SRBs and DRBs. When operating under dual connectivity (DC), the cells associated with the base station operating the master node (MN) define a master cell group (MCG), while the cells associated with the base station operating as the secondary node (SN) define a secondary cell group (SCG). 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 lower priority than SRB1 resources. More generally, SRB1 and SRB2 resources allow the UE and MN to exchange RRC messages related to the MN and embed RRC messages related to the SN. SRB1 and SRB2 resources can be referred to as MCG SRBs. SRB3 resources allow the UE and SN to exchange RRC messages related to the SN and can be referred to as SCG SRBs. Split SRBs allow the UE to exchange RRC messages directly with the MN via 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 SCG may be referred to as a split DRB.

[0007] In some scenarios, the UE simultaneously utilizes resources of multiple radio access network (RAN) nodes (e.g., base stations, or components of distributed base stations) interconnected by backhaul. When such network nodes support different radio access technologies (RATs), this type of connection is called multi-radio dual connectivity (MR-DC). When the UE operates under MR-DC, one base station operates as a master node (MN) covering a primary cell (PCell), while 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 determines to hand over the UE to a second base station and initiates a handover process.

[0008] When a UE moves from the coverage area of ​​one cell in the RAN to another, the RAN should configure the UE to perform a serving cell change. To perform a serving cell change, the RAN configures the UE to send Layer 3 (L3) measurements. Based on the L3 measurements received from the UE, the RAN sends an RRC reconfiguration message that configures a synchronous reconfiguration (e.g., the RRC reconfiguration message includes a ReconfigurationWithSync IE) for a serving cell (e.g., PCell or PSCell) change. In the case where the UE operates in carrier aggregation (CA) of at least one secondary cell (SCell) with a PCell or PSCell, the RAN releases the 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. Therefore, it is desirable to develop new mobility techniques to reduce the latency and overhead of fast serving cell changes. However, it is unclear how to manage the configuration of lower-layer triggered mobility at the UE. Summary of the Invention

[0009] An example embodiment of the technology of the present disclosure is a method implemented in a user equipment (UE), the method comprising: at the UE, communicating with a distributed radio access network (RAN) node based on a serving distributed unit (DU) configuration and a serving centralized unit (CU) configuration; receiving, at the UE, a reference lower layer triggered mobility (LTM) DU configuration and a reference LTM CU configuration from the distributed RAN node; and, at the UE, communicating with the distributed RAN node using at least a portion of the reference LTM DU configuration and at least a portion of the reference LTM CU configuration.

[0010] Another example embodiment of the techniques is a method implemented in a user equipment (UE), the method comprising: at the UE, communicating with a distributed radio access network (RAN) node according to a serving distributed unit (DU) configuration and a serving centralized unit (CU) configuration; receiving, at the UE, a reference lower layer triggered mobility (LTM) configuration from the distributed RAN node; and at the UE, releasing the reference LTM configuration in response to transitioning to an inactive state or an idle state.

[0011] Another example embodiment of the techniques is a device operating as a user equipment (UE) comprising processing hardware and configured to implement the above-described method. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1Ais 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);

[0013] 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;

[0014] Figure 2A is a block diagram of the example protocol stack, Figure 1A The UE communicates with the base station according to the protocol stack;

[0015] Figure 2B is a block diagram of the example protocol stack, Figure 1A The UE communicates with the CU and DU according to this protocol stack;

[0016] 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;

[0017] Figure 4 is similar to Figure 3 but wherein the base station includes a source DU (S-DU) and a target DU (T-DU);

[0018] Figure 5A is similar to Figure 3 Message passing diagram of an example scenario in which the UE communicates with the MN and SN under DC;

[0019] Figure 5B is similar to Figure 5A but a message passing diagram for an example scenario in which the CU provides a reference lower layer triggered mobility configuration to the UE via the MN;

[0020] Figure 6A is similar to Figure 3 Message passing diagram for an example scenario where the CU communicates with the S-DU and T-DU in the SN;

[0021] Figure 6B is similar to Figure 6A but a message passing diagram for an example scenario in which the CU provides a reference lower layer triggered mobility configuration to the UE via the MN;

[0022] Figure 7A is similar to Figure 3 Example scenario but message passing diagram of an example scenario where the CU communicates with the M-DU and S-DU;

[0023] Figure 7B is similar to Figure 7A 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;

[0024] Figure 8A is similar to Figure 3 Message passing diagram of an example scenario where the CU communicates with the M-DU, S-DU and T-DU;

[0025] 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;

[0026] Figure 9 is a flow chart depicting an example method implemented in a UE, wherein the UE receives a reference LTM DU configuration and a reference LTM CU configuration and / or an LTM CU configuration for communicating with a RAN;

[0027] Figure 10A is a flow chart depicting an example method implemented in a UE, wherein the UE determines whether to update a reference LTM configuration using a second LTM configuration based on whether the second reference LTM configuration includes a second reference DU or CU configuration;

[0028] Figure 10B is a flowchart depicting an example method similar to Figure 10A the example method of claim 1 , but wherein if the second reference LTM configuration does not include the second reference LTM DU or CU configuration, the UE additionally releases the first reference LTM DU or CU configuration;

[0029] Figure 10C is a flowchart depicting an example method similar to Figure 10A The example method of , but wherein if the second reference LTM configuration does not include the second reference LTM DU configuration, the UE additionally releases the first reference DU configuration;

[0030] Figure 10D is a flowchart depicting an example method similar to Figure 10A The example method of , but wherein if the second reference LTM configuration does not include the second reference LTM CU configuration, the UE additionally releases the first reference CU configuration;

[0031] Figure 11 is a flow chart depicting an example method implemented in a UE, wherein the UE determines whether to replace or modify a first reference LTM CU configuration and / or a first reference DU configuration based on whether the UE receives an indication to replace the first reference LTM CU or DU configuration;

[0032] Figure 12 is a flow chart depicting an example method implemented in a UE, wherein the UE determines whether to communicate with a RAN using a serving CU configuration or an LTM CU configuration based on whether the UE receives at least one LTM CU configuration;

[0033] Figure 13A is a flow chart depicting an example method implemented in a UE, wherein the UE determines whether to retain or release a reference LTM configuration based on whether an LTM configuration remains in the UE after releasing at least one LTM configuration;

[0034] Figure 13B is a flow chart depicting an example method, which is similar to the method of FIG. 103 , but in which the UE makes a determination based on whether the message includes an indication to release the reference LTM configuration;

[0035] Figure 14A is a flow chart depicting an example method implemented in a UE, wherein the UE transitions to an idle state or an inactive state and in response releases a reference LTM configuration; and

[0036] Figure 14B is a flowchart depicting an example method similar to Figure 14A The method of claim 1 , but wherein the UE releases the reference LTM configuration in response to transitioning to the idle state and retains the reference LTM configuration in response to transitioning to the inactive state. 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 (such as EUTRA or NR) or different RATs. 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. UE 102 may, for example, communicate with base station 104 and an additional base station (T-BS) in DC before the handover. Figure 1A After the handover is completed, UE 102 may continue to operate with base station 106 and the additional base station in DC or operate with base station 106 in single connectivity (SC). 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 1A160 . The base station 104 can be an eNB supporting the S1 interface for communicating with the EPC 111, an ng-eNB supporting the NG interface for communicating with the 5GC 160, or a gNB supporting the NR radio interface and the NG interface for communicating with the 5GC 160. In order to exchange messages directly with each other during the scenarios discussed below, the base stations 104 and 106 can support the X2 or Xn interface. Among other components, the EPC 111 can also include a serving gateway (SGW) 112, a mobility management entity (MME) 114, and a packet data network gateway (PGW) 116. The SGW 112 is typically configured to transmit user plane packets associated with audio calls, video calls, internet traffic, 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 (e.g., 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 under 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 is in a DC relationship 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 applied to other suitable radio access 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 executed by the one or more general-purpose processors. Additionally or alternatively, the processing hardware 130 may include a dedicated processing unit. The processing hardware 130 may include a PHY controller 132, which is configured to transmit 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 132 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 134, 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 136 to implement procedures and message delivery at the RRC sublayer of the protocol communication stack. For example, the RRC controller 132 may be configured to support RRC message delivery associated with a handover process and / or support necessary operations when the base station 104 operates as an MN relative to the SN or as an SN relative to the MN. The base station 106 may include processing hardware 140 similar to the processing hardware 130. Specifically, components 142, 144, and 146 may be similar to components 132, 134, and 136, respectively.

[0045] UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors (such as CPUs), non-transitory computer-readable memory storing machine-readable instructions executable on one or more general-purpose processors, and / or dedicated processing units. The PHY controller 152 is also configured to receive data and control signals on physical DL channels and / or DL ​​reference signals with the 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 152 is also configured to send data and control signals on physical UL channels and / or UL reference signals with the 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, the processing hardware 150 includes a MAC controller 154, which is configured to perform MAC functions with the base station 104 or 106. For example, MAC functions include random access procedures, managing UL timing advance for one or more user devices, and communicating UL / DL MAC PDUs with base station 104 or 106. Processing hardware 150 may also include RRC controller 156 to implement procedures and messaging at the RRC sublayer of the protocol communication stack.

[0046] In operation, UE 102 may use radio bearers (e.g., DRBs or SRBs) in 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.

[0047] 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 142, which is 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.

[0048] Figure 2A An example protocol stack 200 is shown in simplified form, according to which a UE 102 may communicate with an eNB / ng-eNB or gNB (e.g., one or more of base stations 104, 106).

[0049] 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 NR PHY 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 may 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 the SDAP sublayer 212 layered on top of the NR PDCP sublayer 210.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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) can be applied to events labeled with similar reference numbers in other figures.

[0054] 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 (e.g., using a serving CU configuration). In some implementations, UE 102 uses a serving DU configuration to communicate with CU 172 on cell 124A and other cells (e.g., using a serving CU configuration) under carrier aggregation (CA). Figure 1A174 on cell 124D (not shown). DU 174 operates other cells. In other implementations, UE 102 communicates with DU 174 only on cell 124A. In some implementations, UE 102 communicates with DU 174 on cell 124A and / or other cells via one or more TRPs. In some implementations, cell 124A is 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 is an SCell, and one of the other cells is a PCell. In such cases, the remaining cells include SCells and / or additional cells associated with the PCell or SCell. In the following description, depending on the implementation, base station 104 is DU 174, CU 172, or DU 174 and CU 172.

[0055] In some implementations, at event 302, UE 102 sends 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 a radio bearer, which includes SRBs and / or DRBs. In further implementations, base station 104 configures the radio bearer for UE 102. In some implementations, the UL control signals include UL control information, channel state information, hybrid automatic repeat request (HARQ) acknowledgement (ACK), HARQ negative ACK, scheduling request, and / or sounding reference signal. Similarly, in further implementations, UE 102 receives 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). In some implementations, the base station 104 sends the DCI on a physical downlink control channel (PDCCH) monitored by the UE 102 on cell 124A and / or other cells via one or more TRPs.

[0056] In some implementations, the serving DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some implementations, DU 174 sends the 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 a CellGroupConfig IE (e.g., as defined in 3GPP TS 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 a MeasConfig IE and / or a RadioBearerConfig IE (e.g., as defined in 3GPP TS 38.331), or includes configuration parameters in the MeasConfig IE and / or the RadioBearerConfig IE. In some implementations, the serving DU configuration includes a CSI-MeasConfig IE or configuration parameters for channel state information (CSI) measurement and reporting. In other implementations, the serving CU configuration includes a 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.

[0057] 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, the serving DU configuration or the 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. In some implementations, the L1 measurement configuration (e.g., a CSI-MeasConfig IE) includes an L1 measurement resource configuration and / or an L1 measurement report configuration. In further implementations, the L1 measurement resource configuration configures reference signal (e.g., CSI-RS) resources for UE 102 to measure and obtain 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 some implementations, DU 174 does not send an L1 measurement report to CU 172.

[0058] In some implementations, the L1 measurement configuration is a new RRC IE for Lower Layer Triggered Mobility (LTM) (e.g., defined in 3GPP TS 38.331 v18.0.0 and / or later). In some implementations, the L1 measurement resource configuration is a new RRC IE for LTM (e.g., defined in 3GPP TS 38.331 v18.0.0 and / or later). In some implementations, the L1 measurement report configuration is a new RRC IE for LTM (e.g., defined in 3GPP TS 38.331 v18.0.0 and / or later). In some implementations, each of the L1 measurement report configurations includes 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.

[0059] In some implementations, (each of) the L1 measurement reports includes 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 and / or at least one L1 signal-to-interference-plus-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 still other implementations, the UE 102 sends a portion of the L1 measurement report to the DU 174 on the PUCCH and sends the remainder of the L1 measurement report to the DU on the physical UL shared channel (PUSCH). That is, for each portion of the L1 measurement report, the UE 102 sends a PUCCH transmission including the L1 measurement report to the DU 174, and for each of the remaining portions of the L1 measurement report, the UE 102 sends a PUSCH transmission including the L1 measurement report to the DU 174. In some implementations, each of the components in the L1 measurement report is a portion of channel state information (CSI) (i.e., a CSI component) or CSI. In some implementations, the UE 102 includes other CSI components in (each of) the aforementioned PUCCH transmission and / or PUSCH transmission. In some implementations, the other CSI components include 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.

[0060] In some implementations, each of the L3 measurement reports includes 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 some implementations, 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 is an RRC message (e.g., a MeasurementReport message). In some implementations, each of the L3 measurement configurations includes a specific measurement identifier (e.g., measId), and each of the L3 measurement reports includes a specific measurement identifier in a specific L3 measurement configuration. In some implementations, 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 determines that the L3 measurement report is associated with the L3 measurement configuration identified by the measurement identifier.

[0061] 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, at event 304, the UE 102 generates one or more MAC PDUs to the DU 174, each MAC PDU including one or more of the MAC CEs.

[0062] In some implementations, the UE 102 performs measurements on one or more reference signals according to at least one measurement configuration. Depending on the implementation, the one or more reference signals 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 cell 124B). Figure 1A One or more reference signals are sent on a cell (not shown in the figure).

[0063] After (e.g., in response to) receiving one or more of the at least one measurement report from UE 102, 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, better than the strength and / or quality of cell 124A, and / or 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, better than the signal strength and / or quality of cell 124A, and / or better than the signal strength and / or quality of cell 124A by a first predetermined threshold, then DU 174 determines to prepare the first cell for UE 102. Alternatively, base station 104 determines to prepare the first cell for UE 102 regardless of whether a measurement report is received from UE 102.

[0064] 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 DU configuration (hereinafter referred to as LTM DU 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 DU configuration 1 to the CU 172 in response to the first CU-to-DU message. In some implementations, DU 174 includes cell ID 1 and LTM DU configuration 1 together in the IE of the first DU-to-CU message to indicate that LTM DU configuration 1 is associated with the first cell (i.e., cell ID 1). If DU 174 determines to prepare the first cell, DU 174 initiates sending the first DU-to-CU message to CU 172 rather than responding to a CU-to-DU message received from CU 172.

[0065] In some implementations, DU 174 includes the cell ID of the first cell associated with LTM DU configuration 1 in the first DU-to-CU message to indicate that LTM DU configuration 1 is configured for or associated with the first cell. CU 172 identifies that LTM DU configuration 1 is configured for or associated with the first cell. In some scenarios and implementations, CU 172 includes 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 DU configurations (e.g., LTM DU 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 DU configuration in the first DU-to-CU message to indicate which LTM DU configuration is associated with which cell (ID). Cells 1 and / or 2, ..., N are candidate cells.

[0066] In some implementations, CU 172 does not include a (reference) LTM DU configuration in the first CU-to-DU message. In such cases, DU 174 generates a reference LTM DU configuration, generates LTM DU configurations 1 and / or 2, ..., N (i.e., non-reference LTM DU configurations) based on the reference LTM DU configuration, and includes the reference LTM DU configuration in the first DU-to-CU message. In other implementations, CU 172 includes a reference LTM DU configuration in the first CU-to-DU message. In such cases, DU 174 generates LTM DU configurations 1 and / or 2, ..., N that are incremental configurations to enhance the reference LTM DU configuration. In still other implementations, CU 172 includes a reference LTM DU configuration (e.g., the first reference LTM DU configuration) in the first CU-DU message. In such a case, DU 174 generates a reference LTM DU configuration (e.g., a second reference LTM DU configuration) that replaces the first reference LTM DU configuration, generates LTM DU configurations 1 and / or 2, ..., N based on the second reference LTM DU configuration, and includes the second reference LTM DU configuration in the first DU to CU message.

[0067] In some implementations, the reference LTM DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some implementations, the reference LTM DU configuration is a CellGroupConfig IE (e.g., as defined in 3GPP specification 38.331). In other implementations, the reference LTM DU configuration includes configuration parameters in a CellGroupConfig IE. In some implementations, the reference LTM DU configuration includes a CSI-MeasConfig IE or configuration parameters for channel state information (CSI) measurement and / or reporting.

[0068] In some implementations, the reference LTM DU configuration is different from the serving DU configuration. In some implementations, a portion of the reference LTM DU configuration is identical to a portion of the serving DU configuration, and the remainder of the reference LTM DU configuration is different from the remainder of the serving DU configuration. In other implementations, the reference LTM DU configuration is identical to the serving DU configuration.

[0069] After receiving the first DU-to-CU message, CU 172 generates an RRC reconfiguration message (e.g., an RRCReconfiguration message) that includes LTM DU configuration 1 and sends 316 a second CU-to-DU message including the RRC reconfiguration message to DU 174. In some implementations, CU 172 includes the reference LTM DU configuration in RRC reconfiguration message 316. In other implementations, CU 172 does not include the reference LTM DU configuration in RRC reconfiguration message 316. In some implementations, if CU 172 sends the reference LTM DU configuration to UE 102 during event 302, CU 172 does not include the reference LTM DU configuration in RRC reconfiguration message 316. In other implementations, if CU 172 receives the reference LTM DU configuration from DU 174, CU 172 includes the LTM DU configuration in RRC reconfiguration message 316. Otherwise, if CU 172 does not receive the reference LTM DU configuration from DU 174 , CU 172 does not include the reference LTM DU configuration in RRC reconfiguration message 316 .

[0070] In some implementations, CU 172 includes LTM DU Configuration 1 and / or LTM CU Configuration 1 in a first container (e.g., a field / IE) and includes the first container (e.g., LTM Configuration 1) 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 DU Configuration 1 and / or LTM CU 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 DU Configuration 1). If the configuration is included in the first container, UE 102 avoids immediately applying the configuration. Otherwise, in further implementations, if the configuration is not included in the first container, UE 102 immediately applies the configuration. In some implementations, the first container is a first add or modify list (e.g., the ltm-ConfigToAddModList field, the LTM-ConfigToAddModList IE, the ltm-CandidateConfigToAddModList field, or the LTM-CandidateConfigToAddModList IE). CU 172 includes LTM DU configuration 1 and / or LTM CU configuration 1 in the first element (hereinafter referred to as element 1) of the first add or modify list. For example, element 1 is an add or modify IE (the ltm-ConfigToAddMod field, the LTM-ConfigToAddMod IE, the ltm-CandidateConfigToAddMod field, or the LTM-CandidateConfigToAddMod IE). In some implementations, when UE 102 receives the first add or modify list, UE 102 stores the first add or modify list (e.g., in a variable in random access memory (RAM)). In other alternative implementations, DU 174 generates the first container and includes the first container in the first DU-to-CU message. In yet other alternative implementations, the DU 174 generates element 1 and includes element 1 in the first DU-to-CU message.

[0071] In some implementations, the CU 172 includes LTM CU configuration 1 associated with LTM DU configuration 1 in the RRC reconfiguration message 316, the first container, or element 1. In some implementations, the CU 172 includes LTM CU configurations 2, ..., N associated with LTM DU configurations 2, ..., N, respectively, in the RRC reconfiguration message 316 or the second container. In other implementations, the CU 172 includes LTM CU configurations 2, ..., N associated with LTM DU configurations 2, ..., N, respectively, in elements 2, ..., N. Alternatively, the CU 172 does not include LTM CU configurations for some or all of LTM DU configuration 1 and / or LTM DU configurations 2, ..., N in the RRC reconfiguration message 316.

[0072] 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 message 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 performs an RRC connection reestablishment procedure in response to the invalid MAC-I. Otherwise, in further implementations, if UE 102 verifies that the MAC-I is valid, UE 102 processes 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).

[0073] Events 308 (optional) and 310 Figure 3are 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.

[0074] 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 some cases where the UE Context Modification Required message is included, CU 172 sends 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 sends 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.

[0075] In some implementations, CU 172 includes the reference LTM CU configuration in the RRC reconfiguration message 316 or the first container. In some implementations, CU 172 generates LTM CU configuration 1 (i.e., the non-reference LTM CU configuration) as an incremental configuration to enhance the reference LTM CU configuration. Similarly, in further implementations, CU 172 generates some or all of LTM CU configurations 2, ..., N as incremental configurations to enhance the reference LTM CU configuration. Alternatively, in the RRC reconfiguration message 316 or the first container, CU 172 includes the reference LTM CU configuration but not the non-reference LTM CU configuration. In some implementations, CU 172 includes the reference LTM CU configuration and / or the reference LTM DU configuration in an additional container (e.g., the reference LTM configuration) and includes the additional container in the RRC reconfiguration message 316.

[0076] In some implementations, the reference LTM CU configuration is different from the serving CU configuration. In some implementations, a portion of the reference LTM CU configuration is identical to a portion of the serving CU configuration, and the remainder of the reference LTM CU configuration is different from the remainder of the serving CU configuration. In yet other implementations, the reference LTM CU configuration is identical to the serving LTM CU configuration.

[0077] CU assigns ID to LTM DU configuration 1

[0078] In some implementations, CU 172 includes a first LTM ID (hereinafter referred to as ID 1) identifying LTM DU 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] In some implementations where CU 172 assigns or generates ID 1, CU 172 sends ID 1 to DU 174, and DU 174 associates ID 1 with LTM DU 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 DU configuration 1. In other implementations, after receiving the first DU-to-CU message, CU 172 sends 312 a third CU-to-DU message to DU 174 that includes ID 1, instead of including ID 1 in the first CU-to-DU message. In some implementations, in the third CU-to-DU message, CU 172 includes LTM DU configuration 1 and ID 1. CU 172 further indicates the association between ID 1 and LTM DU configuration 1. Thus, DU 174 directly associates ID 1 with LTM DU configuration 1. In other implementations, in the third CU-to-DU message, CU 172 includes cell ID 1 and ID 1 (i.e., the first LTM ID) and indicates an association between cell ID 1 and ID 1. Thus, in some such implementations, DU 174 associates ID 1 with LTM DU configuration 1 based on the association between cell ID 1 and ID 1 and the association between cell ID 1 and LTM DU configuration 1. In still other implementations, in the third CU-to-DU message, CU 172 includes LTM DU configuration 1, cell ID 1, and ID 1 and indicates an association between ID 1, LTM DU configuration 1, and cell ID 1. In some implementations, DU 174 sends 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 Figure 3 392. In other implementations, CU 172 includes ID 1, cell ID 1, and / or LTM DU configuration 1 in the second CU-to-DU message, as described above. Therefore, CU 172 may omit the third CU-to-DU message.

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

[0081] DU is assigned an ID for LTM DU configuration 1

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

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

[0084] In some implementations, neither the CU 172 nor the DU 174 assigns an ID for identifying a reference LTM DU configuration. In some implementations, neither the CU 172 nor the DU 174 assigns an ID for identifying a reference LTM CU configuration.

[0085] In some implementations, LTM DU Configuration 1 includes multiple configuration parameters for UE 102 to communicate with DU 174 on the first cell. In some implementations, 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 DU Configuration 1 is a CellGroupConfig IE (e.g., defined in 3GPP TS 38.331). In other implementations, LTM DU Configuration 1 includes configuration parameters in the CellGroupConfig IE.

[0086] In some implementations, LTM CU Configuration 1 includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, LTM CU Configuration 1 includes MeasConfig IE and / or RadioBearerConfig IE (e.g., as defined in 3GPP TS 38.331), or includes configuration parameters in MeasConfig IE and / or RadioBearerConfig IE. In some implementations, LTM DU Configuration 1 includes CSI-MeasConfig IE or configuration parameters for channel state information (CSI) measurement and reporting. In other implementations, LTMCU Configuration 1 includes CSI-MeasConfig IE or configuration parameters for channel state information (CSI) measurement and reporting.

[0087] In some implementations, DU 174 includes the random access configuration in LTM DU configuration 1. In other implementations, DU 174 does not include the random access configuration in LTM DU configuration 1. In some implementations, if cell 124A and the first cell are not synchronized, DU 174 determines to include the random access configuration in LTM DU configuration 1. Otherwise, if cell 124A and the first cell are synchronized, DU 174 determines not to include the random access configuration in LTM DU configuration 1. In other implementations, if DU 174 determines that UE 102 has not yet synchronized with the first cell in the UL, DU 174 determines to include the random access configuration in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 has already synchronized with the first cell in the UL, DU 174 determines not to include the random access configuration in LTM DU configuration 1. If LTM DU configuration 1 includes a random access configuration, UE 102 performs a random access procedure according to the random access configuration at event 332, as described below. Otherwise, if LTM DU configuration 1 does not include a random access configuration, UE 102 skips or avoids performing the random access procedure of event 332 in response to LTM DU configuration 1 not including a random access configuration.

[0088] In some implementations, DU 174 includes random access configuration parameters in LTM DU configuration 1 and / or reference LTM DU configuration regardless of whether cell 124A and the first cell are synchronized. UE 102 performs a random access procedure in event 332 according to the random access configuration parameters, as described below.

[0089] In some implementations, if cell 124A is synchronized with the first cell, DU 174 determines to include a first indication in LTM DU configuration 1, which configures UE 102 not to perform a random access procedure on the first cell. Otherwise, if cell 124A is not synchronized with the first cell, DU 174 determines not to include the first indication in LTM DU configuration 1. In other implementations, if DU 174 determines that UE 102 is already synchronized with the first cell in the UL, DU 174 determines to include the first indication in LTM DU configuration 1. Otherwise, if DU 174 determines that UE 102 is not yet synchronized with the first cell in the UL, DU 174 determines not to include the first indication in LTM DU configuration 1. If LTM DU configuration 1 includes the first indication, UE 102 skips or avoids performing the random access procedure of event 332 based on or in response to the first indication. Otherwise, if LTMDU configuration 1 does not include the first indication, then in response to LTMDU configuration 1 not including the first indication, UE 102 performs a random access procedure according to the random access configuration at event 332, as described below.

[0090] In some implementations, the DU 174 includes a reconfiguration with a synchronization configuration (e.g., a ReconfigurationWithSync IE) in the LTM DU Configuration 1 or the special cell configuration. In other implementations, the DU 174 does not include a reconfiguration with a synchronization configuration (e.g., a ReconfigurationWithSync IE) in the LTM DU 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 a synchronization configuration in the LTM DU Configuration 1. Otherwise, if the cell 124A and the first cell are synchronized, the DU 174 determines not to include the reconfiguration with a synchronization configuration in the LTM DU 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 a synchronization configuration in the LTM DU Configuration 1. Otherwise, if DU 174 determines that UE 102 is already synchronized with the first cell in the UL, DU 174 determines not to include a reconfiguration with a synchronization configuration in LTM DU Configuration 1. In some implementations, if LTM DU Configuration 1 includes a reconfiguration with a synchronization configuration, UE 102 performs a random access procedure at event 332 in response to or in accordance with the reconfiguration with the synchronization configuration, as described below. Otherwise, if LTM DU Configuration 1 does not include a reconfiguration with a 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 DU Configuration 1. In some implementations, cell ID 1 is a PCI. In another implementation, cell ID 1 is a CGI. In some implementations, cell ID 1 included in LTM DU Configuration 1 is a PCI, while cell ID 1 included in the first CU-to-DU message is a CGI. In some further implementations, LTM DU configuration 1 includes cell index 1 that indexes cell ID 1 or the first cell (e.g., cell index 1 is not a cell ID). The cell index occupies fewer bits than the cell ID. In some implementations, CU 172 sets cell index 1 to a value and includes cell index 1 in the first CU-to-DU message at event 308.

[0091] In some implementations, after receiving one or more of the at least one measurement report for event 304 (e.g., in response thereto), base station 104 (i.e., CU 172 or DU 174) determines to prepare additional cells of base station 104 for LTM (i.e., cells 2, ..., N) for UE 102. In some implementations, base station 104 determines to prepare additional cells for LTM for UE 102 because at least one measurement report indicates that base station 104 can use additional cells to communicate with UE 102. In some implementations, the additional cells include cell 124C and / or cells other than cells 124A, 124B, and 124C. In some implementations, CU 172 determines to prepare a particular cell of the additional cells for LTM for 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 some implementations, the corresponding predetermined threshold for the additional cell is different from the first predetermined threshold. In further implementations, the corresponding predetermined threshold for the additional cell is the same as the first predetermined threshold. In some implementations, the corresponding predetermined threshold for the additional cell is the same as the first predetermined threshold. Alternatively, base station 104 determines to prepare the additional cell for UE 102 regardless of whether a measurement report is received from UE 102.

[0092] If CU 172 determines to prepare an additional cell, CU 172 initiates at least one additional LTM preparation process and performs at least one additional 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. If DU 174 determines to prepare an additional cell, DU 174 initiates at least one additional LTM preparation process and performs at least one additional 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.

[0093] 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. In some implementations, the CU 172 includes the cell IDs 2, ..., N in CU-to-DU messages 2, ..., N, respectively, similar to the first CU-to-DU message, in the LTM preparation processes 2, ..., N. In the LTM preparation processes 2, ..., N, the DU 174 generates LTM DU configurations 2, ..., N that configure cells 2, ..., N, and includes the LTM DU configurations 2, ..., N in DU-to-CU messages 2, ..., N, respectively, as described for LTM DU configuration 1. When the DU 174 receives 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, 16, etc. In another example, the maximum number of "N" is 4, 8, 16, 32, etc. The examples and implementations of LTM DU configuration 1 are applicable to LTM DU configurations 2, ..., N.

[0094] 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 DU configurations 1, 2, ..., N for cells 1, 2, ..., N, respectively, in the first DU-to-CU message. In some implementations, in the first DU-to-CU message, the DU 174 includes cell IDs 1, 2, ..., N associated with the LTM DU configurations 1, 2, ..., N, respectively, to indicate that the LTM DU 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.

[0095] In some implementations, after receiving LTM DU configurations 2, ..., N from DU 174, CU 172 includes LTM DU configurations 2, ..., N in a first container. In some implementations, CU 172 includes LTM DU configurations 2, ..., N in elements 2, ..., N, respectively, and includes elements 2, ..., N in the first container. In some implementations, CU 172 includes LTM IDs (i.e., IDs 2, ..., N) used to identify LTM DU 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 includes IDs 2, ..., N and LTM DU configurations 2, ..., N in elements 2, ..., N in a first addition or modification list.

[0096] In some implementations, the CU 172 assigns IDs 2, ..., N for LTM DU 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 the LTM preparation processes 2, ..., N, respectively, from the DU 174.

[0097] In some implementations, CU 172 performs an LTM ID assignment process similar to process 392 with DU 174 for each of LTM DU configurations 2, ..., N. In other implementations, CU 172 includes IDs 2, ..., N and LTM DU configurations 2, ..., N in a third CU-to-DU message and indicates an association between IDs 2, ..., N and LTM DU configurations 2, ..., N, respectively. Thus, in some implementations, DU 174 associates LTM DU configurations 2, ..., N with IDs 2, ..., N, respectively. In still other implementations, CU 172 includes cell IDs 2, ..., N and IDs 2, ..., N in a third CU-to-DU message and indicates an association between cell IDs 2, ..., N and IDs 2, ..., N, respectively. Therefore, in further implementations, DU 174 associates LTM DU 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 DU configurations 2, ..., N, respectively. In other implementations, CU 172 includes IDs 2, ..., N, cell IDs 2, ..., N, and / or LTM DU configurations 2, ..., N in the second CU-to-DU message, as described above. Therefore, CU 172 may omit the third CU-to-DU message. In still other implementations, CU 172 includes IDs 2, ..., N in the first CU-to-DU message and indicates that IDs 2, ..., N are associated with cell IDs 2, ..., N, respectively. In some implementations, DU 174 includes IDs 2, ..., N in LTM DU configurations 2, ..., N. Therefore, CU 172 does not include IDs 2, ..., N in the RRC reconfiguration message, the first container, and / or elements 2, ..., N.

[0098] 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. In some implementations, CU 172 includes IDs 2, ..., N in an RRC reconfiguration message. In other implementations, DU 174 includes IDs 2, ..., N in LTM DU configurations 2, ..., N. Thus, CU 172 does not include an ID (e.g., an LTM ID) identifying each of LTM DU configurations 2, ..., N in the RRC reconfiguration message, the first container, and / or element 1.

[0099] In some alternative implementations, instead of using the first container, CU 172 generates a second container including LTM DU 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 is 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 is an addition or modification IE (e.g., a ltm-ConfigToAddMod field, a LTM-ConfigToAddMod IE, a ltm-CandidateConfigToAddMod field, or a LTM-CandidateConfigToAddMod IE). In some implementations, when the UE 102 receives the second addition or modification list, the UE 102 stores the second addition or modification list with the first addition or modification list (e.g., in a variable in random access memory (RAM)).

[0100] In some implementations, DU 174 includes cell IDs 2, ..., N in LTM DU configurations 2, ..., N, respectively, to identify cells 2, ..., N. In some implementations, each of the cell IDs 2, ..., N is a PCI. In some further implementations, LTM DU configurations 2, ..., N include cell indexes 2, ..., N that index cell IDs 2, ..., N or cells 2, ..., N, respectively. In some cases where CU 172 prepares cells 2, ..., N for LTM in process 390, CU 172 sets cell indexes 2, ..., N to different values ​​and includes the cell indexes 2, ..., N in the first CU-to-CU-to-DU message at event 308. In some cases where CU 172 prepares cells 2, ..., N in an additional LTM preparation process, CU 172 sets cell indexes 2, ..., N to different values ​​and includes the cell indexes 2, ..., N in the CU-to-DU message of the additional LTM preparation process. CU 172 sets the cell index 1, ..., N to different values. In some implementations, the cell IDs 1, ..., N in the LTM DU configurations 1, ..., N are different from the cell IDs 1, ..., N in the CU-to-DU messages described above.

[0101] In some implementations, each of the LTM DU configurations 1, ..., N includes physical configuration parameters, MAC configuration parameters, RLC configuration parameters, and / or L1 measurement configuration. In some implementations, each of the LTM DU configurations 1, ..., N is a CellGroupConfig IE (e.g., as defined in 3GPP TS 38.331). In other implementations, each of the LTM DU configurations 1, ..., N includes configuration parameters included in a CellGroupConfig IE (e.g., as defined in 3GPP TS 38.331). In some further implementations, the plurality of configuration parameters in each of the LTM DU 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, the LTM DU configurations 1, ..., N are CellGroupConfig IEs (e.g., as defined in 3GPP TS 38.331). In other implementations, LTM DU configurations 1, ..., N include configuration parameters in the CellGroupConfig IE.

[0102] In some implementations, CU 172 includes one or more additional LTM CU configurations in at least one of elements 2, ..., N, the first container, or the second container. Each of the additional LTM CU configurations is associated with a specific LTM DU configuration in LTM DU configurations 2, ..., N. Examples and implementations of the additional LTM CU configurations are similar to those of LTM CU configuration 1.

[0103] In some implementations, CU 172 determines to release LTM DU configuration M (or element M) from LTM DU configurations 1, ..., N (or element M from elements 1, ..., M), where 1 ≤ M ≤ N. In response to this determination, CU 172 sends an RRC reconfiguration message to UE 102 via DU 174 to instruct UE 102 to release LTM DU configuration M or element M. In some implementations, CU 172 generates a release list including ID (i.e., LTM ID) M for releasing LTM DU configuration M or element M, and includes the release list in the RRC reconfiguration message. In response to the RRC reconfiguration message, UE 102 releases LTM DU configuration M or element M and sends an RRC reconfiguration complete message to CU 172 via DU 174. In response to this determination, CU 172 sends a CU-to-DU message to DU 174 to instruct DU 174 to release LTM DU configuration M. In some implementations, to instruct DU 174 to release LTM DU configuration M, CU 172 includes the 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 DU 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 UE Context Modification Request and UE Context Modification Response messages, respectively.

[0104] In other implementations, DU 174 determines to release LTM DU configuration K. In response to this determination, DU 174 sends a DU-to-CU message to CU 172 to release LTM DU configuration K. In some implementations, to indicate the release of LTM DU configuration K, DU 174 includes 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. Further, 1 ≤ K ≤ N. After receiving the DU-to-CU message (e.g., in response thereto), CU 172 generates a release list including ID (i.e., LTM ID) K to release LTM DU configuration K or element K, and sends an RRC reconfiguration message including the release list to UE 102 via DU 174. In response, UE 102 releases LTM DU configuration K or element K and sends an RRC reconfiguration complete message to UE 102 via DU 174. In some implementations, CU 172 sends a CU-to-DU message to DU 174 in response to 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.

[0105] 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 sends 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, similar to event 304, UE 102 sends 324 at least one MAC CE including the at least one measurement report to DU 174. In some implementations, the UE 102 does not send the L1 measurement report to the DU 174 in the format of an RRC message.

[0106] 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 sends one or more RRC messages (e.g., RRCReconfiguration messages) including the at least one measurement configuration to UE 102 via DU 174 during event 302 and / or 316 and / or after event 306 or 316. Depending on the implementation, 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. In some implementations, the one or more reference signals include one or more SSBs and / or one or more CSI-RSs. UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurements and includes the at least one L1 measurement result and / or at least one L3 measurement result in the at least one measurement report at event 324. DU 174 transmits one or more reference signals on cell 124A, cell 1, and / or cell 2, ..., N. Depending on the implementation, the one or more reference signals are CSI-RS or SSB.

[0107] 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 is a CSI-MeasConfig IE (e.g., defined in 3GPP TS 38.331 v18.0.0 and / or later). In some implementations, the L1 measurement configuration includes a measurement reporting configuration. UE 102 sends an L1 measurement report to DU 174 on a PUCCH or MAC CE based on the measurement reporting configuration. DU 174 receives the L1 measurement report on a PUCCH or MAC CE based on the measurement reporting configuration. In some implementations, the measurement reporting configuration is a CSI-ReportConfig IE. In other implementations, each of the measurement reporting configurations is a new RRC IE. In some implementations, (each of) the measurement reporting configurations configures periodic reporting and / or event-triggered reporting of L1 measurement results.

[0108] In yet other implementations, the at least one measurement configuration includes a new type of measurement configuration (e.g., an LTM measurement configuration). In some implementations, the new type of measurement configuration is newly defined (e.g., in 3GPP TS v18.0.0 and / or later). In some implementations, the new type of 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 some implementations, the reference signal resource configuration is a CSI-ResourceConfig IE. In another implementation, as described above, the new type of 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 the PUCCH or MAC CE based on the measurement report configuration. In some such cases, the measurement report is an L1 measurement report or a new type of measurement report (e.g., an LTM measurement report). In some implementations, the new measurement configuration includes newly defined configuration parameters (eg, in 3GPP TS v18.0.0 and / or later).

[0109] After receiving at least one measurement report at event 324 (e.g., in response thereto), DU 174 generates a first LTM command to activate LTM DU configuration 1 (i.e., the first LTM command instructs UE 102 to apply LTM DU configuration 1 or perform a serving cell change for cell 1). DU 174 then sends 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 includes ID 1 in the first LTM command to indicate LTM DU configuration 1, and UE 102 determines (e.g., identifies) LTM DU configuration 1 or element 1 based on ID 1. In other implementations, DU 174 includes cell index 1, which indexes cell ID 1, in the first LTM command. UE 102 determines (eg, identifies) LTM DU configuration 1 or element 1 based on cell index 1. After determining LTM DU configuration 1 or element 1, UE 102 then applies LTM DU configuration 1 and / or LTM CU configuration 1 in response to receiving the first LTM command.

[0110] In yet other implementations, the DU 174 includes a bitmap in the first LTM command to activate LTM DU configuration 1 instead of ID 1 or cell index 1. The number of bits in the bitmap is greater than or equal to "N". In some implementations, bits 1, ..., N correspond to cell indexes 1, ..., N, IDs 1, ..., N, LTM DU configurations 1, ..., N, or elements 1, ..., N, respectively, and the DU 174 sets the corresponding bit (e.g., bit 1) in the bitmap to a first value to indicate cell index 1, ID 1, LTM DU configuration 1, or element 1. Thus, in some such implementations, the UE 102 determines cell index 1, ID 1, LTM DU configuration 1, or element 1 based on bit 1 in the bitmap being set to the first value. In further implementations, bits 0, ..., N-1 correspond to cell indices 1, ..., N, IDs 1, ..., N, LTM DU configurations 1, ..., N, or elements 1, ..., N, respectively, and the DU 174 sets the corresponding bit (e.g., bit 0) in the bitmap to a first value to indicate cell index 1, ID 1, LTM DU configuration 1, or element 1. Thus, in some such implementations, the UE 102 determines cell index 1, ID 1, LTM configuration 1, or element 1 based on bit 0 in the bitmap being set to the first value. In such implementations, the DU 174 sets the remaining bits in the bitmap to a second value to indicate that the remaining LTM DU 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. In general, depending on the implementation, if the DU 174 determines to activate LTM DU configuration L or change the serving cell to cell L, the DU 174 sets the corresponding bit in the bitmap (e.g., bit L or bit L-1) to a first value and sets the remaining bits to a second value, where 1 ≤ L ≤ N. In some implementations, the DU 174 sets at most one bit in the bitmap to the first value.

[0111] In some implementations, the at least one measurement report (e.g., an L1 measurement report or a new 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. In some implementations, the reference signal is a CSI-RS or an SSB. DU 174 determines to activate LTM DU Configuration 1 or transmit a first LTM command based on the at least one measurement result. In some implementations, DU 174 determines to activate LTM DU Configuration 1 because, when, or if at least one measurement result is above a second predetermined threshold. In some implementations, the at least one measurement result includes an L1-RSRP value, an L1-RSRQ value, and / or an L1-SINR value. In other implementations, the at least one measurement result includes an RSRP value, an RSRQ value, and / or an SINR value of a new type measurement report. In some implementations, the second predetermined threshold is different from the first predetermined threshold. In some implementations, the second predetermined threshold is greater than the first predetermined threshold. In this case, the at least one measurement 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 such a 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 DU Configuration 1.

[0112] In some implementations, at least one measurement report (e.g., an L3 measurement report) of events 324 and 326 includes at least one measurement result for the first cell. CU 172 determines to activate LTM DU 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 some implementations, the second predetermined threshold is greater than the first predetermined threshold. In such implementations, 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 further implementations, the second predetermined threshold is equal to the first predetermined threshold. In such implementations, 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, further indicating that the first cell is suitable for communication with UE 102. Therefore, in response to the signal strength or quality of the first cell being above the second predetermined threshold, CU 172 determines to activate LTM DU configuration 1. In response to this determination, CU 172 sends 328 a fourth CU-to-DU message to DU 174 to activate LTM DU configuration 1 or trigger a change in UE 102's serving cell to cell 1. In some implementations, CU 172 includes ID 1 in the fourth CU-to-DU message. In other implementations, CU 172 includes cell index 1 in the fourth CU-to-DU message. 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, in some such implementations, DU 174 determines to activate LTM DU configuration 1 based on cell index 1. In other implementations, CU 172 includes cell ID 1 in the fourth CU-to-DU message. Thus, DU 174 determines to activate LTM DU configuration 1 based on cell ID 1. In yet other implementations, CU 172 includes ID 1 in the fourth CU-to-DU message. Thus, in some such implementations, DU 174 determines to activate LTM DU Configuration 1 based on ID 1. In some implementations, the fourth CU-to-DU message and the fourth DU-to-CU message are 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 are new interface messages (e.g., F1 Application Protocol (F1AP) messages (e.g., defined in 3GPP TS 38.473 v18.0.0 and / or later versions)).

[0113] In some implementations, upon determining to activate LTM DU configuration 1 or sending 330 the first LTM command, or in response to determining to activate LTM DU configuration 1 or sending the first LTM command, DU 174 sends 329 a DU-to-CU message to CU 172 indicating that LTM is being executed. In some implementations, DU 174 includes cell ID 1 or ID 1 (i.e., LTM ID) in DU-to-CU message 329 to indicate that DU 174 is activating LTM DU configuration 1 or triggering a fast serving cell change. Depending on the implementation, the DU sends DU-to-CU message 329 to CU 172 before or after sending LTM command 330.

[0114] In some implementations, the first LTM command is a MAC CE included in the MAC PDU that UE 102 receives from DU 174 at event 330. In some implementations, the MAC CE is a new MAC CE (e.g., defined in 3GPP TS 38.321 v18.0.0 and / or later). In some implementations, DU 174 includes a subheader that identifies the new MAC CE in the MAC PDU, and UE 102 identifies the new MAC CE in the MAC PDU based on the subheader. In some implementations, the subheader includes a logical channel ID or an extended logical channel ID (e.g., defined in 3GPP TS) to identify the new MAC CE. For example, the logical channel ID or the extended logical channel ID is newly defined (e.g., in 3GPP TS 38.321 v18.0.0 and / or later). In other implementations, the first LTM command is 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 sends the DCI and the scrambled CRC on the PDCCH at event 330. In some implementations, the format of the DCI is an existing DCI format (e.g., as defined in 3GPP TS (e.g., 38.212)). In further implementations, the format of the DCI is a new DCI format (e.g., as defined in 3GPP TS (e.g., 38.212 v18.0.0 and / or later)).

[0115] 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.

[0116] In some implementations, after receiving the first LTM command, UE 102 sends 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 an existing MAC CE (e.g., as defined in 3GPP TS 38.321 v17.2.0 and / or later). In another example, the MAC CE is a new MAC CE (e.g., as defined in 3GPP TS 38.321 v18.0.0 and / or later). In still other implementations, the acknowledgment is a PUCCH transmission.

[0117] In some implementations, the CU 172 sends 316 an RRC reconfiguration message in response to the L3 measurement report 306 for the first cell. In some implementations, to configure the UE 102 to send the L3 measurement report 306, the CU 172 sends a first RRC reconfiguration message including an L3 measurement configuration (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. In some implementations, to configure the UE 102 to send the L1 or new-type measurement report 324, the CU 172 sends a second RRC reconfiguration message including an L1 or new-type measurement configuration to the UE 102. In some implementations, the first RRC reconfiguration message and the second RRC reconfiguration message are 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.

[0118] After receiving the first LTM command (e.g., in response thereto), UE 102 identifies LTM DU configuration 1 based on ID 1 and applies LTM DU configuration 1. In some implementations, UE 102 performs 332 a random access procedure on the first cell with DU 174 in response to applying LTM DU 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. In some implementations, UE 102 determines whether to perform a random access procedure based on LTM DU configuration 1. In some implementations, if LTM DU configuration 1 configures UE 102 to perform a random access procedure, UE 102 performs a random access procedure in event 332. For example, LTM DU 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 DU 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 DU configuration 1 does not include a reconfiguration with synchronization configuration, LTM DU configuration 1 configures UE 102 to not 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.

[0119] When UE 102 performs a random access procedure 332, UE 102 communicates 336 with DU 174 on the first cell using LTM DU configuration 1 and a reference LTM DU 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 DU configuration 1 at event 332 and / or event 336. In some scenarios or implementations, UE 102 communicates an UL PDU, a DLPDU, and / or a physical layer signal (e.g., a PUCCH transmission and a PDCCH transmission) to 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 a 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 DU configuration 1 includes a second C-RNTI, the UE identity is the second C-RNTI of UE 102. Otherwise, if LTM DU 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 DU configuration 1 includes a dedicated random access preamble.

[0120] 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 .

[0121] In the event that the UE 102 skips the random access procedure, the UE 102, after receiving the first LTM command (e.g., in response thereto), communicates 336 directly with the DU 174 on the first cell according to LTM DU configuration 1 and communicates with the CU 172 via the DU 174. For example, the UE 102 communicates UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) directly to the base station 104 at event 336. In some implementations, the DU 174 includes configuration parameters in the LTM DU configuration 1 that configure resources for the UE 102 to transmit at least one PUCCH or PUSCH transmission, and the UE 102 transmits at least one PUCCH or PUSCH transmission on the resources using the configuration parameters to indicate that the UE 102 is connected to the first cell. In other implementations, DU 174 transmits at least one DCI to UE 102 on a PDCCH on the first cell, commanding UE 102 to transmit at least one PUCCH or PUSCH transmission after transmitting the first LTM command. The at least one DCI configures resources for UE 102 to transmit the at least one PUCCH or PUSCH transmission, and UE 102 transmits the 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 DU Configuration 1 or the at least one DCI.

[0122] In the event that UE 102 receives the reference LTM DU configuration as described above, UE 102 communicates 336 with DU 174 on the first cell in accordance with LTM DU configuration 1 and at least a portion of the reference LTM DU configuration. In other words, UE 102 communicates 336 with DU 174 in accordance with the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration. Similarly, DU 174 communicates 336 with UE 102 on the first cell in accordance with LTM DU configuration 1 and at least a portion of the reference LTM DU configuration. In other words, DU 174 communicates 336 with UE 102 in accordance with the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration.

[0123] In the event that UE 102 receives neither LTM CU configuration 1 nor the reference LTM CU configuration, UE 102 communicates 336 with CU 172 via DU 174 using the serving CU configuration. Accordingly, if CU 172 sends neither LTM CU configuration 1 nor the reference CU configuration to UE 102, CU 172 communicates 336 with UE 102 via DU 174 using the serving CU configuration. In the event that UE 102 receives both LTM CU configuration 1 and the reference LTM CU configuration from CU 172, UE 102 communicates 336 with CU 172 via DU 174 using LTM CU configuration 1 and at least a portion of the reference LTM CU configuration that is not enhanced by LTM CU configuration 1. In such an event, CU 172 communicates 336 with UE 102 via DU 174 using LTM CU configuration 1 and at least a portion of the reference LTM CU configuration that is not enhanced by LTM CU configuration 1.

[0124] In the event that the UE 102 receives LTM CU configuration 1 from the CU 172 but does not receive the reference LTM CU configuration, the UE 102 communicates 336 with the CU 172 via the DU 174 using LTM CU configuration 1. In such an event, the CU 172 communicates 336 with the UE 102 via the DU 174 using LTM CU configuration 1. If LTM CU configuration 1 is a complete configuration, the UE 102 and the CU 172 communicate 336 with each other via the DU 174 using LTM CU configuration 1 instead of the serving CU configuration. In some implementations, if the UE 102 does not receive the reference LTM CU configuration from the base station 104, the UE 102 determines that LTM CU configuration 1 is a complete configuration. Accordingly, if the CU 172 determines to configure or configure LTM CU configuration 1 as a complete configuration, the CU 172 does not send the reference LTM CU configuration to the UE 102. In other implementations, the CU 172 includes a first indication (e.g., a field or IE) in the LTM CU configuration 1, the first container, the element 1, or the RRC reconfiguration message 316 to indicate that the LTM CU configuration 1 is a complete configuration. If the LTM CU configuration 1 is a delta configuration for enhancing the serving CU configuration, the UE 102 and the CU 172 communicate 336 with each other via the DU 174 using the LTM CU configuration 1 and at least a portion of the serving CU configuration that is not enhanced by the LTM CU configuration 1. In some implementations, if the UE 102 does not receive a reference LTM CU configuration from the base station 104, the UE 102 determines that the LTM CU configuration 1 is a delta configuration for enhancing the serving CU configuration. Accordingly, if the CU 172 determines to configure or configure the LTM CU configuration 1 as a delta configuration for enhancing the serving CU configuration, the CU 172 does not send the reference LTM CU configuration to the UE 102. In some implementations, the CU 172 indicates that the LTM CU configuration 1 is an incremental configuration for enhancing the serving CU configuration by not including a first indication in the LTM CU configuration 1, the first container, the element 1, and / or the RRC reconfiguration message 316. Alternatively, the CU 172 includes a second indication (e.g., a field or IE) in the LTM CU configuration 1, the first container, the element 1, or the RRC reconfiguration message 316 to indicate that the LTM CU configuration 1 is an incremental configuration for enhancing the serving CU configuration. In some implementations, the CU 172 indicates that the LTM CU configuration 1 is a complete configuration by not including the second indication in the LTM CU configuration 1, the first container, the element 1, and / or the RRC reconfiguration message 316.

[0125] In the event that UE 102 receives the reference LTM CU configuration from CU 172 but does not receive LTM CU configuration 1, UE 102 communicates 336 with CU 172 via DU 174 using the reference LTM CU configuration. In such an event, CU 172 communicates 336 with UE 102 via DU 174 using the reference LTM CU configuration. If the reference LTM CU configuration is a complete configuration, UE 102 and CU 172 communicate 336 with each other via DU 174 using the reference LTM CU configuration instead of the serving CU configuration. In some implementations, UE 102 and CU 172 determine that reference LTM CU configuration 1 is a complete configuration (e.g., as defined in 3GPP TS 38.331). In other implementations, CU 172 includes a first indication (e.g., a field or IE) in the reference LTM CU configuration, the first container, or the RRC reconfiguration message 316 to indicate that the reference LTM CU configuration is a complete configuration. If the reference LTM CU configuration is a delta configuration for enhancing the serving CU configuration, the UE 102 and the CU 172 communicate 336 with each other via the DU 174 using the reference LTM CU configuration and at least a portion of the serving CU configuration that is not enhanced by the reference LTM CU configuration. In some implementations, the CU 172 indicates that the reference LTM CU configuration is a delta configuration for enhancing the serving CU configuration by not including a first indication in the reference LTM CU configuration, the first container, element 1, and / or the RRC reconfiguration message 316. Alternatively, the CU 172 includes a second indication (e.g., a field or IE) in the reference LTM CU configuration, the first container, element 1, or the RRC reconfiguration message 316 to indicate that the reference LTM CU configuration is a delta configuration for enhancing the serving CU configuration. In some implementations, the CU 172 indicates that the reference LTM CU configuration is a complete configuration by not including the second indication in the reference LTM CU configuration, the first container, element 1, and / or the RRC reconfiguration message 316.

[0126] In the event that UE 102 receives neither the reference LTM CU configuration nor LTM CU configuration 1 from CU 172, UE 102 communicates 336 with CU 172 via DU 174 using the serving LTM CU configuration. In such an event, CU 172 communicates 336 with UE 102 via DU 174 using the serving LTM CU configuration.

[0127] 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 DU configuration 1. In some implementations in which the UE 102 performs the random access procedure 332, the UE 102 includes the RRC message in message 3 or message A. Alternatively, the UE 102 sends the RRC message after completing the random access procedure. In the event that the UE 102 skips the random access procedure 332, the UE 102 includes the RRC message 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 sends 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.

[0128] In other implementations, UE 102 refrains from sending an RRC message to base station 104 in response to applying LTM DU Configuration 1 or receiving a first LTM command. In some such cases, UE 102 includes or sends data in Message 3, Message A, or a PUSCH transmission as described above. In some implementations, UE 102 generates a MAC PDU and / or RLC PDU including the data and sends or includes the MAC PDU and / or RLC PDU in a PUSCH transmission. For example, depending on the implementation, the data is 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 that does not include an RRC Reconfiguration Complete message. The NAS PDU includes a Mobility Management (MM) message or a Session Management (SM) message. Depending on the implementation, the MM message is a 5G MM message or a 6G MM message, and the SM message is a 5G SM message or a 6G SM message. When the DU 174 receives the data, the DU 174 transmits the data to the CU 172 .

[0129] In some implementations, when DU 174 determines that UE 102 is successfully connected to the first cell at event 332 or 336, DU 174 sends 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 includes the cell ID 1 of the first cell in the DU-to-CU message at event 334. In some implementations, the cell ID is a PCI or CGI. Thus, CU 172 determines that UE 102 is connected to the first cell upon receiving the DU-to-CU message at event 334. In some implementations, when DU 174 determines that UE 102 is successfully connected to the first cell at event 332 or 336, DU 174 sends a DL data delivery status message or frame to CU 172 (e.g., the UP of CU 172). In some implementations, when or after the CU 172 receives the DU-to-CU message 329, the CU 172 stops or suspends sending DL data for the UE 102 to the DU 174 until it receives the DU-to-CU message 334. In some such implementations, the CU 172 stops or suspends sending because the DU 174 did not buffer DL data for the UE 102 during the LTM execution in events 330 and / or 332. After receiving the DU-to-CU message 334, the CU 172 continues or resumes sending DL data for the UE 102 to the DU 174. In other implementations, when the CU 172 receives the DU-to-CU message 329, the CU 172 continues sending DL data for the UE 102 to the DU 174. In some such implementations, the CU 172 continues sending because the DU 174 buffered DL data for the UE 102 during the LTM execution in events 330 and / or 332. When or after DU 174 detects that UE 102 accesses cell 1 , DU 174 sends DL data to UE 102 via cell 1 .

[0130] 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 stops communicating with UE 102 on cell 124A and / or releases resources of cell 124A configured for UE 102.

[0131] In some implementations, DU 174 generates some or all of LTM DU configuration 1 and / or LTM DU configurations 2, ..., N as complete configurations to replace the serving DU configuration. If LTM DU configuration 1 is a complete configuration, UE 102 and DU 174 communicate 336 with each other based on LTM DU configuration 1 rather than the serving DU configuration. In some implementations, DU 174 includes an indication in LTM DU configuration 1 that LTM DU configuration 1 is a complete configuration. In some implementations, in each of LTM DU configurations 2, ..., N, DU 174 includes an indication that the corresponding DU configuration is a complete configuration. In some implementations, each of the indications in LTM DU configurations 1, ..., N is a field or IE (i.e., the same field or IE). In other implementations, CU 172 includes a single indication that LTM DU configurations 1 and / or 2, ..., N are complete configurations in the RRC reconfiguration message at events 316 and 318. In some cases, for the second container, CU 172 includes a single indication that LTM DU configurations 2, ..., N are complete configurations in the additional RRC reconfiguration message. In yet other implementations, CU 172 includes a single indication that LTM DU configurations 1 and / or 2, ..., N are complete configurations in the first container. In yet other implementations, for each of LTM DU configurations 2, ..., N, CU 172 includes a specific indication that the corresponding LTM DU configuration is a complete configuration in the first container. In some cases, for the second container, CU 172 includes a single indication that LTM DU configurations 2, ..., N are complete configurations in the second container. In yet other implementations, CU 172 includes an indication that LTM DU configuration 1 is a complete configuration in element 1. In some implementations, in each of elements 2, ..., N, CU 172 includes an indication that the corresponding LTM DU configuration is a complete configuration. In some implementations, the UE 102 determines that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are full configurations based on the above indications. In some implementations, each of the above indications is different from the fullConfig field (e.g., as defined in the current 3GPP TS). In some implementations, each of the above indications is a fullConfig field (e.g., as defined in the current 3GPP TS). In the event that LTM DU configuration 1 is a full configuration, if received from the base station 104 (e.g., in the RRC reconfiguration message 318), the UE 102 does not apply the reference LTM DU configuration in event 336. In some such cases, the DU 174 does not include the reference LTM DU configuration in the first DU to CU message 310.

[0132] In other implementations, DU 174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as incremental configurations that enhance at least a portion of a reference LTM DU configuration. In other words, DU 174 generates LTM DU configurations 1, ..., N based on a reference LTM DU configuration. For example, if LTM DU configuration 1 is an incremental configuration, UE 102 and DU 174 utilize LTM DU configuration 1 to enhance at least a portion of the reference LTM DU configuration. Thus, UE 102 and DU 174 communicate 336 with each other based on LTM DU configuration 1 and the unenhanced portion of the reference LTM DU configuration. In some implementations, LTM DU configurations 1 and / or 2, ..., N, the first container, the second container, or the elements 1, ..., N do not include an indication that LTM DU configurations 1 and / or 2, ..., N are complete configurations, indicating that LTM DU configurations 1 and / or 2, ..., N are incremental configurations. In some implementations, the UE 102 determines that each of the LTM DU configurations 1 and / or 2, ..., N is an incremental configuration based on the indication not being included in the LTM DU configurations 1 and / or 2, ..., N, the first container, the second container, or the elements 1 and / or 2, ..., N.

[0133] In some implementations, if the UE 102 does not receive a reference LTM DU configuration for LTM DU configuration 1 and / or LTM DU configuration 2, ..., N, the UE 102 determines that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are complete configurations. Correspondingly, if the DU 174 does not obtain a reference LTM DU configuration for the UE 102 (i.e., the DU 174 does not generate a reference LTM DU configuration for the UE 102 and / or does not receive a reference LTM DU configuration for the UE 102 from the CU 172), the DU 174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as complete configurations.

[0134] In other implementations, if the UE 102 does not receive a reference LTM DU configuration for LTM DU configuration 1 and / or LTM DU configuration 2, ..., N, the UE 102 determines that LTM DU configuration 1 and / or LTM DU configuration 2, ..., N are incremental configurations for enhancing the serving DU configuration. In such a case, the UE 102 communicates 336 with the DU 174 based on LTM DU configuration 1 and at least a portion of the serving DU configuration that is not enhanced by LTM DU configuration 1. Correspondingly, if the DU 174 does not obtain a reference LTM DU configuration for the UE 102 (i.e., the DU 174 does not generate a reference LTM DU configuration for the UE 102 and / or does not receive a reference LTM DU configuration for the UE 102 from the CU 172), the DU 174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as incremental configurations for enhancing the serving DU configuration. In such cases, the DU 174 communicates 336 with the UE 102 according to the LTM DU configuration 1 and at least a portion of the serving DU configuration.

[0135] 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.

[0136] In some implementations, when the UE 102 resets the UE MAC entity, the UE 102 performs at least one of the following actions with respect to the UE MAC entity (i.e., a UE MAC reset or a complete UE MAC reset): (i) initializes Bj of the configured logical channels to zero; (ii) stops one or more timers; (iii) if the UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), deems timeAlignmentTimer expired; (iv) sets UL (v) Set the New Data Indicator (NDI) of the HARQ process to a value of 0; (vi) Set the NDI of the HARQ process ID to a value of 0 for monitoring PDCCH in sidelink resource allocation mode 1; (vi) Flush the Msg3 buffer; (vii) Flush the MSGA buffer; (viii) Cancel (if any) the triggered scheduling request process; (ix) Cancel (if any) the triggered buffer status report process; (x) Cancel (if any) the triggered power headroom report process; (xi) Cancel (if any) the triggered consistent LBT failure; (xii) Cancel (if any) the triggered BFR; (xiii) Cancel (if any) ) triggered sidelink buffer status reporting procedure; (xiv) cancel (if any) the triggered preemptive buffer status reporting procedure; (xv) cancel (if any) the triggered timing advance reporting procedure; (xvi) cancel (if any) the triggered recommended bit rate query procedure; (xvii) cancel (if any) the triggered configured uplink grant confirmation; (xviii) cancel (if any) the triggered configured sidelink grant confirmation; (xix) cancel (if any) the triggered expected protection symbol query; (xx) cancel (if any) the triggered positioning measurement gap activation / deactivation request procedure; (xxi) flush the soft buffer for the DL HARQ process; (xxii) for each of the DL HARQ processes, treat the next received transmission of the TB as the initial transmission; (xxiii) release (if any) the temporary C-RNTI; and / or (xiv) reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0137] In some implementations, when DU 174 resets the DU MAC entity, DU 174 performs at least one of the following actions with respect to the DU MAC entity (i.e., a DU MAC reset or a full DU MAC reset): (i) stops one or more timers; (ii) if UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), deems a timeAlignmentTimer started and / or maintained by DU 174 for UE 102 to have expired; (iii) sets the NDI for the DL HARQ process to a value of 0; (iv) flushes the soft buffers for the UL HARQ processes; (v) for each of the UL HARQ processes, treats the next received transmission of the TB as the initial transmission; and / or (vi) resets one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0138] Depending on the implementation, UE 102 determines to partially or completely reset the UE MAC entity. In some implementations, when UE 102 resets the UE MAC entity as described above, UE 102 completely resets the UE MAC entity (i.e., a complete UE MAC reset). In a complete UE MAC reset, UE 102 performs some or all of the actions described above. In other implementations, when UE 102 resets the UE MAC entity as described above, UE 102 partially resets the UE MAC entity (i.e., a partial UE MAC reset). In a partial UE MAC reset, UE 102 performs a subset or portion of some or all of the actions in a complete UE MAC reset.

[0139] In some implementations, the partial UE MAC reset includes at least one of the following actions: (i) if UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), then the timeAlignmentTimer of UE 102 is deemed to have expired; (ii) flushing the Msg3 buffer; (iii) flushing the MSGA buffer; (iv) releasing (if any) the temporary C-RNTI; and / or (v) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0140] In some implementations, some UEs The MAC reset further includes at least one of the following actions: (i) canceling (if any) the triggered scheduling request process; (ii) canceling (if any) the triggered buffer status reporting process; (iii) canceling (if any) the triggered power headroom reporting process; (iv) canceling (if any) the triggered consistent LBT failure; (v) canceling (if any) the triggered BFR; (vi) canceling (if any) the triggered sidelink buffer status reporting process; (vii) canceling (if any) the triggered preemptive buffer status reporting process; (viii) canceling (if any) the triggered timing advance reporting process; (ix) canceling (if any) the triggered recommended bit rate query process; (x) canceling (if any) the triggered configured uplink grant confirmation; (xi) canceling (if any) the triggered configured sidelink grant confirmation; (xii) canceling (if any) the triggered expected protection symbol query; and / or (xiii) canceling (if any) the triggered positioning measurement gap activation / deactivation request process.

[0141] In some implementations, the partial UE MAC reset further includes at least one of the following actions: (i) stopping a first portion of one or more timers and retaining a remaining portion of one or more timers; (ii) setting a new data indicator (NDI) for the UL HARQ process to a value of 0; (iii) setting the NDI for the HARQ process ID to a value of 0 for monitoring the PDCCH in sidelink resource allocation mode 1; (iv) flushing the soft buffer for the DL HARQ process; and / or (v) for each of the DL HARQ processes, treating the next received transmission of the TB as the initial transmission.

[0142] Depending on the implementation, DU 174 determines 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 complete DU MAC reset). In a complete 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 complete DU MAC reset.

[0143] In some implementations, the partial DU MAC reset includes at least one of the following actions in the partial MAC reset: (i) if the UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), deeming the timeAlignmentTimer started and / or maintained by the DU 174 for the UE 102 to be expired and / or (ii) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0144] In some implementations, when a partial DU MAC reset includes at least one of the following actions for the MAC entity (i.e., a DU MAC reset): (i) stopping a first portion of one or more timers and retaining a remaining portion of one or more timers; (ii) setting the NDI for the DL HARQ process to a value of 0; (iii) flushing the soft buffer for the UL HARQ process; (iv) for each of the UL HARQ processes, treating the next received transmission of the TB as the initial transmission; and / or (v) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0145] 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.

[0146] In some implementations, the UE 102 communicates RLC PDUs (e.g., events 302, 304, 318, 320, 324, 330, and / or 331) using at least one UE RLC entity (e.g., RLC 206B) to at least one DU RLC entity (e.g., RLC 206B) of the DU 174. 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.

[0147] In some implementations, LTM DU configuration 1 may or may not include one or more RLC re-establishment indicators (e.g., a reestablishRLC field) that configure UE 102 to re-establish some or all of at least one UE RLC entity. If LTM DU configuration 1 includes an RLC re-establishment indicator 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 to DU 174, UE 102 re-establishes the first UE RLC entity in response to the RLC re-establishment indicator and the first LTM command. In some implementations, UE 102 re-establishes 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 re-establishes the first UE RLC entity while or after performing 332 a random access procedure. Otherwise, if LTM DU configuration 1 does not include an RLC re-establishment indicator, UE 102 refrains from re-establishing the first UE RLC entity in response to the first LTM command.

[0148] In some implementations, when UE 102 reestablishes the first UE RLC entity, UE 102 performs at least one of the following actions for the first UE RLC entity: (i) discarding RLC SDUs, RLC SDU segments, and RLC PDUs (if any); (ii) stopping timers and resetting timers (if running); and / or (iii) resetting state variables to initial values. In some implementations, the state variables and timers are predefined (e.g., in 3GPP TS 38.322).

[0149] Otherwise, if LTM DU configuration 1 does not include an RLC re-establishment indication for the first UE RLC entity, then upon or upon receiving the first LTM command, UE 102 refrains from re-establishing the first UE RLC entity. In other words, upon or upon receiving the first LTM command, UE 102 refrains from performing actions for re-establishing the first UE RLC entity of UE 102. In some implementations, if LTM DU configuration 1 or element 1 does not include an RLC re-establishment indication and includes an indication that configuration 1 is a complete configuration, then upon or upon receiving the first LTM command, UE 102 re-establishes the first UE RLC entity of UE 102. Otherwise, if LTM DU configuration 1 or element 1 does not include an RLC re-establishment indication and an indication that configuration 1 is a complete configuration, then upon or upon receiving the first LTM command, UE 102 refrains from re-establishing the first UE RLC entity.

[0150] 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 the first DU RLC entity in the at least one DU RLC entity after sending the 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 still other implementations, the acknowledgment is a PUCCH transmission. In some implementations, when the base station 104 reestablishes the first DU RLC entity, the DU 174 performs at least one of the following actions for the first DU RLC entity: (i) discarding the RLC SDU, RLC SDU segment, and RLC PDU (if any); (ii) stopping and resetting the timer (if running); and / or (iii) resetting the state variable to an initial value. In some implementations, the state variable and timer are predefined (e.g., in 3GPP TS 38.322).

[0151] 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.

[0152] In some implementations, UE 102 communicates UL PDCP PDUs and / or DL ​​PDCP PDUs to at least one CU PDCP entity (e.g., PDCP 210) of CU 172 using at least one UE PDCP entity (e.g., PDCP 210) at event 302. In some implementations, UE 102, after or in response to receiving the first LTM command, performs a PDCP recovery procedure for some or all of the at least one UE PDCP entity. For example, UE 102, after or in response to receiving the first LTM command, performs a PDCP recovery procedure for a first UE PDCP entity among the at least one UE PDCP entity. Depending on the implementation, during the PDCP recovery procedure, UE 102 may or may not re-establish the first UE PDCP entity. In some implementations, after or in response to performing the PDCP recovery procedure, UE 102 resends at least a portion of the UL PDCP PDU to CU 172 via DU 174 and the first cell at event 336. Similarly, CU 172 performs a PDCP recovery procedure for some or all of 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. Depending on the implementation, during the PDCP recovery procedure, CU 172 may or may not re-establish the first CU PDCP entity. In some implementations, after or in response to performing the PDCP recovery procedure, CU 172 resends at least a portion of the DL PDCP PDU to UE 102 via DU 174 and the first cell at event 336.

[0153] 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.

[0154] In some implementations, after determining that the UE 102 is connected to the first cell, the CU 172 sends 338 a CU-to-DU message (e.g., a UE Context Modification Request message) to the DU 174 to instruct the DU 174 to cease communicating with the UE 102 and / or release or suspend the resources of the cell 124A configured for the UE 102. In some implementations, in response, the DU 174 ceases communicating with the UE 102 on the cell 124A and / or releases or suspends the resources of the cell 124A configured for the UE 102 and sends 340 a DU-to-CU message (e.g., a UE Context Modification Response message) to the CU 172. Events 338 (optional) and 340 (optional) are described in detail below. Figure 3 It is collectively referred to as the resource release process 396.

[0155] Depending on the implementation, after or while communicating with DU 174 on the first cell, events 344, 346, 348, 350, 351, 352, 354, and / or 356, respectively, similar to events 324, 326, 328, 330, 331, 332, 334, and / or 336, 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 not suitable for communication with UE 102. After receiving the at least one measurement report (e.g., in response thereto), DU 174 determines to activate LTM DU configuration 2 and generates a second LTM command to activate LTM DU configuration 2 (i.e., the second LTM command instructs UE 102 to apply LTM DU configuration 2). The DU 174 then sends 350 a second LTM command to the UE 102 on the first cell.

[0156] In some implementations, upon or in response to determining to activate LTM DU Configuration 2 or to send the second LTM command, the DU 174 sends 349 a DU-to-CU message to the CU 172 indicating that LTM is being executed. In some implementations, the DU 174 includes cell ID 2 or ID 2 (i.e., LTM ID) in the DU-to-CU message 349 to indicate that the DU 174 will activate LTM DU Configuration 2. In some implementations, the DU sends the DU-to-CU message 349 to the CU 172 before or after sending the LTM command 350.

[0157] The description of 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,” “LTM DU configuration 1,” and / or “LTM CU configuration 1” may be replaced with “first cell,” “second LTM command,” “second cell,” “ID 2,” “LTM DU configuration 2,” and / or “LTM CU configuration 2,” respectively.

[0158] 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 3is collectively referred to as the LTM DU configuration and / or activation process 380.

[0159] Next reference Figure 4 In scenario 400, base station 104 includes CU 172, source DU (S-DU) 174A, and target DU (T-DU) 174B. S-DU 174A operates cell 124A and optionally additional cells, while T-DU 174B operates the first cell (e.g., cell 124C). Scenario 400 is similar to scenario 300. Therefore, the description of scenario 300 can generally be applied to scenario 400. The differences between scenarios 300 and 400 are described below.

[0160] 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 to prepare cells 1, ..., N 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 prepare and / or request T-DU 174B to prepare cells 1, ..., N for LTM for UE 102. In some implementations, N is a positive integer greater than 0 or 1. In LTM preparation process 490, similar to event 308, CU 172 sends a CU-to-DU message including cell IDs 1, ..., N to T-DU 174B to request that T-DU 174B prepare cells 1, ..., N for LTM for UE 102. In response, similar to event 310, T-DU 174B sends a DU-to-DU message including LTM DU configurations 1, ..., N to CU 172. LTM DU configurations 1, ..., N respectively configure cells 1, ..., N for LTM. Specifically, LTM DU 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 process 490 are UE Context Setup Request and UE Context Setup Response messages, respectively. Similar to the LTM DU configuration delivery process 394, the CU 172 then sends the LTM configurations 1, ..., N in an RRC reconfiguration message in the LTM configuration delivery process 494. In some implementations, the T-DU 174B includes the cell indices 1, ..., N in the LTM DU configurations 1, ..., N, respectively. In some implementations, the CU 172 sets the cell indices 1, ..., N to different values ​​and includes the cell indices 1, ..., N in the CU-to-DU message of process 490.

[0161] In some implementations, after performing the LTM preparation procedure 490, the CU 172 performs an additional LTM preparation procedure with the T-DU 174B to prepare cells N+1, ..., N+M for LTM for the UE 102, where M is a positive integer greater than zero. In further implementations, similar to events 404 and 406, the CU 172 determines to do so based on one or more measurement reports received from the UE 102 via the S-DU 174A. In the additional LTM preparation procedure, the CU 172 sends a CU-to-DU message including cell IDs N+1, ..., N+M to the T-DU 174B to request that the T-DU 174B prepare cells N+1, ..., N+M for LTM for the UE 102. The cell IDs N+1, ..., N+M identify the cell IDs N+1, ..., N+M, respectively. In response to the CU-to-DU message, T-DU 174B sends a DU-to-CU message to CU 172 that includes LTM DU configurations N+1, ..., N+M. LTM DU configurations N+1, ..., N+M respectively configure cells N+1, ..., N+M for LTM. Specifically, LTM DU configurations N+1, ..., N+M respectively include configuration parameters for communication on cells N+1, ..., N+M. Similar to LTM configuration delivery procedures 394 or 494, CU 172 then sends LTM DU configurations N+1, ..., N+M in an RRC reconfiguration message in an additional LTM configuration delivery procedure.

[0162] 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.

[0163] In some implementations, the CU 172 and the S-DU 174A 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. Depending on the implementation, the process 380 or the process 392 for LTM may be performed by CU 172 and / or S-DU 174A. Figure 3 The value N described is the same as the Figure 4The value N described may be the same or different. In some implementations, in process 390, CU 172 receives a first DU-to-CU message from S-DU 174A at event 310 that includes a reference LTM DU configuration. In other implementations, CU 172 and S-DU 174A do not perform process 380 with UE 102. In some such cases, CU 172 performs a reference LTM DU configuration query process with S-DU 174A to obtain a reference LTM DU configuration. In process 488, CU 172 sends 460 a CU-to-DU message to S-DU 174A to request or query the reference LTM DU configuration. In some implementations, CU 172 includes an indication in the CU-to-DU message to request or query the reference LTM DU configuration. In response to the indication or CU-to-DU message 460, S-DU 174A sends 462 a DU-to-DU message to CU 172 that includes the reference LTM DU configuration. In some implementations, the indication is a reference LTM DU configuration query indication. In other implementations, the indication is an LTM indication, and the CU 172 includes the query indication (e.g., a GNB-DU Configuration Query IE) in the CU-to-DU message. After receiving the reference LTM DU configuration (i.e., in process 390 or process 488), the CU 172 includes the reference LTM DU configuration (e.g., received from the S-DU 174A) in the CU-to-DU message in the LTM preparation process 490. The T-DU 174B generates LTM DU configurations 1, ..., N based on the reference LTM DU configuration received from the CU 172. In such a case, the T-DU 174B does not include the reference LTM DU configuration in the DU-to-CU message in process 490. In the case of an additional LTM preparation process, the T-DU 174B does not include the reference LTM DU configuration in the DU-to-CU message in the additional LTM preparation process. In some implementations, CU 172 and T-DU 174B do not include the reference LTM DU configuration in the CU-to-DU message during the additional LTM preparation process. In the case of the additional LTM preparation process, T-DU 174B generates LTM DU configurations N+1, ..., N+M based on the reference LTM DU configuration received from CU 172.

[0164] In some implementations, CU 172 does not provide a reference LTM DU configuration to T-DU 174B during LTM preparation process 490. In such cases, T-DU 174B generates a reference LTM DU configuration and generates LTM DU configurations 1, ..., N based on the reference LTM DU configuration. In such cases, T-DU 174B includes the reference LTM DU configuration in a DU-to-CU message during process 490. CU 172 sends the reference LTM DU configuration in an RRC reconfiguration message during process 490. In the case of an additional LTM preparation process, T-DU 174B generates LTM DU configurations N+1, ..., N+M based on the reference LTM DU configuration. In some such cases, T-DU 174B does not include the reference LTM DU configuration in a DU-to-CU message during the additional LTM preparation process. In some implementations, the reference LTM DU configuration generated by T-DU 174B is different from the reference LTM DU configuration generated by S-DU 174A. In other implementations, the reference LTM DU configuration generated by T-DU 174B is the same as the reference LTM DU configuration generated by S-DU 174A.

[0165] In some implementations, the CU 172 assigns IDs 1, ..., N that respectively identify the LTM DU configurations 1, ..., N (e.g., received from the T-DU 174B), and performs process 492 with the T-DU 174B to provide the IDs 1, ..., N and / or the cell IDs 1, ..., N to the T-DU 174B, similar to process 392. Thus, the T-DU 174B associates the IDs 1, ..., N with the LTM DU configurations 1, ..., N and / or the cell IDs 1, ..., N, respectively. In other implementations, the T-DU 174B assigns IDs 1, ..., N that respectively identify the LTM DU configurations 1, ..., N (e.g., generated by the T-DU 174B), and includes the IDs 1, ..., N in the DU-to-CU message of process 490, similar to event 310. In some implementations, the CU 172 assigns IDs N+1, ..., N+M that respectively identify LTM DU configurations N+1, ..., N+M, and, similar to process 392, performs a process (similar to process 492) with the T-DU 174B to provide the IDs N+1, ..., N+M and / or cell IDs N+1, ..., N+M to the T-DU 174B. Thus, the T-DU 174B associates the IDs N+1, ..., N+M with the LTM DU configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M, respectively. In other implementations, the T-DU 174B assigns IDs N+1, ..., N+M that respectively identify LTM DU configurations N+1, ..., N+M, and, similar to event 310, includes the IDs 1, ..., N in a DU-to-CU message that appends the LTM preparation process.

[0166] 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 a manner similar to the embodiment of the present invention. Figure 4, N and / or cell IDs 1, ..., N in the CU-DU message 412. In some implementations, the CU 172 includes the LTM DU configurations 1, ..., N and / or cell IDs 1, ..., N in the CU-DU message 412. In some implementations, the CU 172 includes the IDs 1, ..., N in the CU-DU message 412. In further implementations, the CU 172 includes the cell indexes 1, ..., N in the CU-DU message 412. In some alternative implementations, the CU 172 performs multiple LTM ID transfer procedures to send the IDs 1, ..., N, the cell IDs 1, ..., N, and / or the LTM DU configurations 1, ..., N to the S-DU 174A. In each of the procedures, the CU 172 includes specific portions of the IDs 1, ..., N, the cell IDs 1, ..., N, and / or the LTM DU 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 DU configurations 1, ..., N and / or the cell IDs 1, ..., N, respectively. In other alternative implementations, the CU 172 performs multiple LTM cell index transmission procedures to send the cell indexes 1, ..., N, the cell IDs 1, ..., N, and / or the LTM DU configurations 1, ..., N to the S-DU 174A. In these procedures, the CU 172 includes specific portions of the cell indexes 1, ..., N, the cell IDs 1, ..., N, and / or the LTM configurations 1, ..., N in a CU-to-DU message similar to message 412. Thus, the S-DU 174A associates cell indices 1, ..., N with LTM DU configurations 1, ..., N and / or cell IDs 1, ..., N, respectively.

[0167] 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, which is similar to the CU-to-DU message 412 and the DU-to-CU message 414, respectively. In some implementations, the CU 172 includes the LTM DU configurations N+1, ..., N+M and / or the cell IDs N+1, ..., N+M in the CU-DU message. In some alternative implementations, the CU 172 performs multiple LTM ID transfer procedures to send the IDs N+1, ..., N+M, the cell IDs N+1, ..., N+M, and / or the LTM DU 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 DU 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 DU configurations N+1, ..., N+M and / or cell IDs N+1, ..., N+M, respectively.

[0168] In some implementations, when the CU 172 and S-DU 174A perform process 380 with the UE 102, the values ​​of IDs 1, ..., N of process 380 differ from the values ​​of IDs 1, ..., N and IDs N+1, ..., N+M described for scenario 400. In some implementations, when the CU 172 and S-DU 174A perform process 380 with the UE 102, the values ​​of cell IDs 1, ..., N of process 380 differ from the values ​​of cell IDs 1, ..., N and cell IDs N+1, ..., N+M described for scenario 400. In some implementations, when the CU 172 and S-DU 174A perform process 380 with the UE 102, the values ​​of cell indexes 1, ..., N of process 380 differ from the values ​​of cell indexes 1, ..., N and cell indexes N+1, ..., N+M described for scenario 400.

[0169] In some implementations, UE 102 then sends 424 at least one measurement report to S-DU 174A, similar to event 324. The at least one measurement report (e.g., an L1 measurement report) includes the event ID, a first measurement result for cell 1 of T-DU 174B, and / or a second measurement result for cell 124A. In some implementations, the first measurement result is or includes RSRP, RSRQ, and / or SINR obtained by UE 102 from a reference signal transmitted on cell 1. Similarly, in some implementations, the second measurement result is or includes RSRP, RSRQ, and / or SINR obtained by UE 102 from a reference signal transmitted on cell 124A. In some implementations, the event ID, RSRP, RSRQ, and / or SINR are L1 event ID, L1-RSRP, L1-RSRQ, and / or L1-SINR, respectively. In some implementations, based on the first measurement result and / or the second measurement result, the S-DU 174A sends 430 a first LTM command (i.e., LTM command 1) including ID 1 to the UE 102, instructing the UE 102 to perform a serving cell change to cell 1 of the T-DU 174B. In some implementations, the first LTM command includes ID 1. In other implementations, the first LTM command includes cell index 1. When the UE 102 receives the first LTM command, the UE 102 performs a serving cell change from the serving cell to cell 1 according to LTM DU configuration 1. Depending on the implementation, similar to event 332, after receiving the first LTM command (e.g., in response thereto), the UE 102 performs or does not perform 432 a random access procedure with the T-DU 174B. In some implementations, after receiving the first LTM command or completing the random access procedure 432 (e.g., in response thereto), similar to event 336, the UE 102 communicates 436 with the T-DU 174B on the first cell using the LTM DU configuration 1 and / or the reference LTM DU configuration, and communicates with the CU 172 via the T-DU 174B. In some implementations, if a serving cell change occurs in the process 380, the serving cell is cell 1 or cell 2 of the S-DU 174A. Otherwise, if no serving cell change occurs in the process 380 or the process 380 is not performed, the serving cell is cell 124A. If the first LTM command includes ID 1, the UE 102 identifies the LTM DU configuration 1 and / or cell ID 1 (i.e., cell 1) based on ID 1, as described with respect to FIG. Figure 3 If the first LTM command includes cell index 1, UE 102 identifies LTM DU configuration 1, cell ID 1 (i.e., cell 1), and / or LTM ID 1 based on cell index 1, as described with respect to Figure 3After receiving the first LTM command or successfully accessing cell 1 (eg, in response thereto), UE 102 applies LTM DU configuration 1 to communicate with T-DU 174B.

[0170] In some implementations, upon determining to activate LTM DU configuration 1 or sending the first LTM command 430, or in response to determining to activate LTM DU configuration 1 or sending the first LTM command, the S-DU 174A sends 429 a DU-to-CU message to the CU 172 indicating that LTM is being performed. In some implementations, the S-DU 174A includes cell ID 1 or ID 1 (i.e., LTM ID) in the DU-to-CU message 429 to indicate that the S-DU 174A is activating LTM DU configuration 1 or triggering a fast serving cell change. In some implementations, the S-DU 174A sends the DU-to-CU message 429 to the CU 172 before or after sending the LTM command 430. In some implementations, upon or after receiving the DU-to-CU message 429, the CU 172 stops or suspends sending DL data for the UE 102 to the S-DU 174A until receiving the DU-to-CU message 434. After receiving the DU to CU message 434, CU 172 starts, continues, or resumes sending DL data for UE 102 to T-DU 174B. When or after T-DU 174B detects that UE 102 accesses cell 1, T-DU 174B sends DL data to UE 102 via cell 1.

[0171] The resource release process 496 can be similar to the process 396. Alternatively, in some implementations, in the resource release process 496, the CU 172 sends 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.

[0172] 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.

[0173] Next reference Figure 5AIn 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.

[0174] Initially, UE 102 communicates with MN 106 and SN 104 in DC. At event 502, similar to event 302, UE 102 communicates with DU 174 on cell 124A using a serving DU configuration, and communicates with CU 172 via DU 174 using a serving CU configuration. In some alternative implementations, UE 102 does not communicate with CU 172 via DU 174 in event 302. In some implementations, UE 102 communicates 502 ULPDUs and / or DL ​​PDUs to MN 106 and / or SN 104 in DC via a radio bearer that includes an SRB and / or a DRB, depending on the implementation. In some implementations, MN 106 and / or SN 104 configure the radio bearer for UE 102. UE 102 communicates 502 UL PDUs and / or DL ​​PDUs to SN 104 in DC on an SCG (i.e., SCG radio resources) that SN 104 configures for communication with UE 102. UE 102 communicates 502 UL PDUs and / or DL ​​PDUs to 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 3 As described above, the service DU configuration includes a plurality of configuration parameters. In some implementations, UE 102 receives the configuration parameters in one or more RRC messages from SN 104 (e.g., 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).

[0175] In some implementations, when UE 102 is communicating with MN 106 and SN 104 in DC, similar to processes 380 and / or 480, MN 106 performs 580 an LTM DU configuration and / or activation process with UE 102. In some implementations, when communicating with MN 106 and SN 104 in DC, UE 102 sends 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 sends 505 at least one measurement report to MN 106 via cell 126. MN 106, in turn, sends 507 at least one measurement report to CU 172. In some implementations, the MN 106 generates at least one SN message including at least one measurement report and sends the at least one SN message to the CU 172 in event 507. In some implementations, the at least one SN message includes an RRC Transfer message and / or an SN Modification Request message.

[0176] 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 3 Events 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are similar to events 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, and 356, respectively. After receiving the first LTM command 530, sending 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 DU configuration 1, and communicates 536 with the CU 172 via the DU 174. In some implementations, later, similar to process 398 or 498, DU 174 and / or CU 172 performs an LTM execution process 598 with UE 102 to instruct UE 102 to perform a cell change from the first cell to the second cell. Due to 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 DU configuration 2, and communicates 556 with CU 172 via DU 174.

[0177] Events 504, 506, 505, 507, 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, 556 Figure 5A is collectively referred to as the LTM DU configuration and / or activation process 581.

[0178] Next reference Figure 5B Scenario 500B is generally similar to scenario 500A, except that SN 104 sends 517, 519 an RRC reconfiguration message to UE 102 via MN 106, and receives 521, 523 an RRC reconfiguration complete message 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 are an RRC Reconfiguration message and an RRC Reconfiguration Complete message, respectively.

[0179] 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 is collectively referred to as the LTM DU configuration and / or activation process 582.

[0180] Next reference Figure 6A In scenario 600A, similar to scenarios 300 to 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. In some implementations, when UE 102 communicates with MN 106 and SN 104 in DC, similar to processes 380 and / or 480, MN 106 performs 680 an LTM DU configuration and / or activation procedure with UE 102. In some implementations, when UE 102 communicates with M-DU 174A and S-DU 174B in DC, similar to processes 581 and / or 582, CU 172 performs 681 an LTM DU configuration and / or activation procedure with UE 102 via M-DU 174A or S-DU 174B.

[0181] Next reference Figure 6B , scenario 600B is similar to scenarios 300 to 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 .

[0182] Next reference Figure 7A In scenario 700A, similar to scenarios 300 to 600B, base station 104 operates as both a MN and a SN. Base station 104 includes CU 172, primary DU (M-DU) 174A, and 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.

[0183] 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 sends 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. In some implementations, when the UE 102 communicates with the M-DU 174A and the S-DU 174B under DC, similar to process 380 , the CU 172 performs 780 an LTM DU configuration and / or activation process with the UE 102 via the M-DU 174A.

[0184] 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.

[0185] Next reference Figure 7B , scenario 700B is similar to scenarios 300 through 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.

[0186] 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.

[0187] Next reference Figure 8AIn scenario 800A, similar to scenarios 300 to 700B, base station 104 operates as both a mobile node and a network node. Base station 104 includes a control unit (CU) 172, a primary 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. In some implementations, when UE 102 communicates with M-DU 174A and S-DU 174B in DC mode, similar to process 380, CU 172 performs 880 an LTM DU configuration and / or activation procedure with UE 102 via M-DU 174A. In some implementations, when UE 102 communicates with M-DU 174A and S-DU 174B under DC, similar to process 581 or 582, CU 172 performs 881 LTM DU configuration and / or activation process with UE 102 via S-DU 174A.

[0188] Next reference Figure 8B , scenario 800B is similar to scenarios 300 through 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.

[0189] Next, refer to Figures 9 to 14B Several example methods that may be implemented in a RAN node, 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 14B .

[0190] Figure 9 An example method 900 is shown that a UE (eg, UE 102) may implement to perform fast serving cell configuration with a RAN (eg, DU 174, CU 172, base station 104 or 106, or RAN 105).

[0191] Methodology 900 begins at block 902, where the UE communicates with the RAN via at least one serving cell using a first serving DU configuration and a first serving CU configuration (e.g., events 302, 380, 402, 480, 502, 580, 602, 680, 702, 780, 802, 880). At block 904, the UE receives a reference LTM CU configuration and / or LTM CU configurations 1, ..., N, a first reference LTM DU configuration, LTM DU 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 DU configurations 1, ..., N configure cells 1, ..., N, respectively (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 517, 519, 581, 582, 680, 694, 617, 619, 681, 682, 780, 794, 717, 719, 781, 782, 880, 894, 817, 819, 881, 882). At block 906, the UE receives a second serving DU configuration and / or a second serving CU configuration from the RAN. For example, the UE receives at least one message (eg, an RRC reconfiguration message) including the second serving DU configuration and / or the second serving CU configuration from the RAN.

[0192] At block 908, the UE communicates with the RAN via at least one serving cell according to the second serving DU configuration and / or the second serving CU configuration. At block 910, the UE receives a first LTM command from the RAN via one of the at least one serving cell, the first LTM command instructing the UE to perform a serving cell change to cell 1 (e.g., events 330, 380, 430, 480, 580, 530, 581, 582, 680, 630, 681, 682, 780, 730, 781, 782, 880, 830, 881, 882). At block 912, the UE accesses cell 1 in response to the first LTM command (e.g., events 332, 380, 432, 480, 580, 532, 581, 582, 680, 632, 681, 682, 780, 732, 781, 782, 880, 832, 881, 882). At block 914, the UE communicates with the RAN via cell 1 using the first reference LTM CU configuration and / or LTM CU configuration 1, the first reference LTM DU configuration, and LTM DU configuration 1 (e.g., events 336, 380, 436, 480, 580, 536, 581, 582, 680, 636, 681, 682, 780, 736, 781, 782, 880, 836, 881, 882). At block 916, the UE receives a second LTM command from the RAN instructing the UE to perform a serving cell change to cell 2 (e.g., events 350, 398, 380, 450, 498, 480, 580, 598, 581, 582, 680, 698, 681, 682, 780, 798, 781, 782, 880, 898, 881, 882). At block 918, the UE accesses cell 2 in response to the first LTM command (e.g., events 352, 398, 380, 452, 498, 480, 580, 598, 581, 582, 680, 698, 681, 682, 780, 798, 781, 782, 880, 898, 881, 882). At box 920, the UE communicates with the RAN via cell 2 using the first reference LTM CU configuration and / or LTM CU configuration 1, the first reference LTM DU configuration and LTM DU configuration 2 (e.g., events 356, 380, 456, 480, 580, 556, 581, 582, 680, 656, 681, 682, 780, 756, 781, 782, 880, 856, 881, 882).

[0193] Figure 10AAn example method 1000A is shown that a UE (eg, UE 102) may implement to manage LTM reference configurations with a RAN (eg, DU 174, CU 172, base station 104 or 106, or RAN 105).

[0194] Method 1000A begins at block 1002, where the UE performs blocks 902, 904, and 906 through 920 (optional). At block 1004, the UE receives a second reference LTM configuration from the RAN. At block 1006, the UE determines whether the second reference LTM configuration includes a second reference LTM CU configuration. If the UE determines at block 1006 that the second reference LTM configuration includes a second reference LTM CU configuration, the process proceeds to block 1008. At block 1008, the UE updates the first reference LTM CU configuration with the second LTM CU configuration. Otherwise, if the UE determines at block 1006 that the second reference LTM configuration does not include a second reference LTM CU configuration, the process proceeds to block 1010. The process proceeds from blocks 1006 and 1008 to block 1010. At block 1010, the UE determines whether the second reference LTM configuration includes a second reference LTM DU configuration. If the UE determines at block 1010 that the second reference LTM configuration includes the second reference LTM DU configuration, the process proceeds to block 1012. At block 1012, the UE updates the first reference LTM DU configuration with the second LTM DU configuration. Otherwise, if the UE determines at block 1010 that the second reference LTM configuration does not include the second reference LTM DU configuration, the process proceeds to block 1014. At block 1014, the process proceeds to the end.

[0195] In some implementations, the UE uses a method similar to that for Figures 3 to 8B The second reference LTM configuration is received in the manner of receiving the reference LTM CU configuration and / or the reference LTM DU configuration.

[0196] Figure 10B 1000B is a flow chart of an example method 1000B that is similar to method 1000A, except that method 1000B includes blocks 1009 and 1013 instead of block 1014. If the UE determines at block 1006 that the second reference LTM configuration does not include a second reference LTM CU configuration, the flow proceeds to block 1009. At block 1009, the UE releases the first reference LTM CU configuration. If the UE determines at block 1010 that the second reference LTM configuration does not include a second reference LTM DU configuration, the flow proceeds to block 1013. At block 1013, the UE releases the first reference LTM DU configuration.

[0197] Figure 10Cis a flow chart of an example method 1000C that is similar to methods 1000A and 1000B, except that method 1000C includes block 1013 instead of block 1014 .

[0198] Figure 10D is a flow chart of an example method 1000D that is similar to methods 1000A, 1000B, and 1000C, except that method 1000D includes block 1014 instead of block 1013 .

[0199] Figure 11 An example method 1100 is shown that a UE (eg, UE 102) may implement to manage LTM reference configurations with a RAN (eg, DU 174, CU 172, base station 104 or 106, or RAN 105).

[0200] Method 1100 begins at block 1102, where the UE performs blocks 902, 904, and (optionally) 906 through 920. At block 1102, the UE receives a second reference LTM CU configuration and / or a second reference LTM DU configuration from the RAN. At block 1104, the UE determines whether the UE has received an indication to replace the first reference LTM CU configuration and / or the first reference LTM DU configuration. If the UE determines at block 1104 that the UE has received an indication to replace the first reference LTM CU configuration and / or the first reference LTM DU configuration, the process proceeds to block 1106. At block 1106, the UE replaces the first reference LTM CU configuration and / or the first reference LTM DU configuration with the second reference LTM CU configuration and / or the second reference LTM DU configuration, respectively. In some implementations, the UE receives a message (e.g., an RRC reconfiguration message) from the RAN that includes the indication, the second reference LTM CU configuration, and / or the second reference LTM DU configuration.

[0201] Otherwise, if the UE determines at block 1104 that the UE has not received an indication to replace the first reference LTM CU configuration and / or the first reference LTC DU configuration, the flow proceeds to block 1108. At block 1108, the UE modifies the first reference LTM CU configuration and / or the first reference DU configuration with the second reference LTM CU configuration and / or the second reference LTM DU configuration, respectively.

[0202] In some implementations, the UE uses a method similar to that for Figures 3 to 8B The manner of receiving the reference LTM CU configuration and / or the reference LTM DU configuration is to receive the second reference LTM configuration and / or the second reference LTM DU configuration.

[0203] Figure 12An example method 1200 is shown that a UE (eg, UE 102) may implement to perform fast serving cell configuration with a RAN (eg, DU 174, CU 172, base station 104 or 106, or RAN 105).

[0204] 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 and a first serving CU configuration (e.g., events 302, 380, 402, 480, 502, 580, 602, 680, 702, 780, 802, 880). At block 1204, the UE receives an LTM DU configuration configuring the first cell from the RAN (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 517, 519, 581, 582, 680, 694, 617, 619, 681, 682, 780, 794, 717, 719, 781, 782, 880, 894, 817, 819, 881, 882). At block 1206, the UE receives an LTM command from the RAN instructing the UE to perform a serving cell change to the first cell (e.g., events 330, 380, 430, 480, 580, 530, 581, 582, 680, 630, 681, 682, 780, 730, 781, 782, 880, 830, 881, 882). At block 1208, the UE accesses the first cell in response to the LTM command (e.g., events 332, 380, 432, 480, 580, 532, 581, 582, 680, 632, 681, 682, 780, 732, 781, 782, 880, 832, 881, 882). At block 1210, the UE communicates with the RAN via the first cell using an LTM DU configuration (e.g., events 336, 380, 436, 480, 580, 536, 581, 582, 680, 636, 681, 682, 780, 736, 781, 782, 880, 836, 881, 882). At block 1212, the UE determines whether at least one LTM CU configuration has been received. If the UE determines at block 1212 that at least one LTM CU configuration has been received, the flow proceeds to block 1214. At block 1214, the UE communicates with the RAN via the first cell using the at least one LTM CU configuration after (e.g., in response to) receiving the LTM command (e.g., events 336, 380, 436, 480, 580, 536, 581, 582, 680, 636, 681, 682, 780, 736, 781, 782, 880, 836, 881, 882). Otherwise, if the UE determines at block 1212 that at least one LTM CU configuration has not been received, the flow proceeds to block 1216. At block 1216, after (e.g., in response to) receiving the LTM command, the UE communicates with the RAN via the first cell using the serving CU configuration.

[0205] Figure 13AAn example method 1300A is shown that a UE (e.g., UE 102) may implement for managing LTM reference configurations and non-reference LTM configurations with a RAN (e.g., DU 174, CU 172, base station 104 or 106, or RAN 105).

[0206] Method 1300A begins at block 1302, where a UE receives a reference LTM configuration and LTM configurations 1, ..., N from a RAN, where N is a positive integer and LTM DU configurations 1, ..., N are for LTM configuration cells 1, ..., N (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 517, 519, 581, 582, 680, 694, 617, 619, 681, 682, 780, 794, 717, 719, 781, 782, 880, 894, 817, 819, 881, 882). At block 1304, the UE receives a message from the RAN indicating the release of at least one of LTM configurations 1, ..., N. For example, the message is an RRC reconfiguration message. At block 1306, the UE releases at least one of the LTM configurations 1, ..., N in response to the message. At block 1308, the UE determines whether an LTM configuration (i.e., a non-reference LTM configuration) remains in the UE (i.e., the UE determines whether any non-reference LTM configuration has not been released). If the UE determines at block 1308 that an LTM configuration remains in the UE, the process proceeds to block 1310. At block 1310, the UE retains the reference LTM configuration. Otherwise, if the UE determines at block 1308 that no LTM configuration remains in the UE, the process proceeds to block 1312. At block 1312, the UE releases the reference LTM configuration.

[0207] In some implementations, the reference LTM configuration includes a reference LTM CU configuration and / or a reference LTM DU configuration. In some implementations, each of LTM configurations 1, ..., N includes a (non-reference) LTM CU configuration and a (non-reference) LTM DU configuration.

[0208] Figure 13B1300B is a flow chart of an example method 1300B that is similar to method 1300A, except that method 1300B includes blocks 1305, 1307, and 1309 instead of blocks 1304 and 1306. At block 1305, the UE receives a message from the RAN indicating the release of LTM configurations 1, ..., N. At block 1307, the UE releases LTM configurations 1, ..., N in response to the message. At block 1309, the UE determines whether the message includes an indication to release the reference LTM configuration. If the UE determines at block 1309 that the message does not include an indication to release the reference LTM configuration, the flow proceeds to block 1310. Otherwise, if the UE determines at block 1309 that the message includes an indication to release the reference LTM configuration, the flow proceeds to block 1312.

[0209] Figure 14A An example method 1400A is shown that a UE (e.g., UE 102) may implement for managing LTM configurations (e.g., LTM reference configurations and / or non-reference LTM configurations) with a RAN (e.g., DU 174, CU 172, base station 104 or 106, or RAN 105).

[0210] Method 1400A begins at block 1402, where the UE communicates with the RAN using a serving DU configuration and a serving CU configuration (e.g., events 302, 380, 402, 480, 502, 580, 602, 680, 702, 780, 802, 880). At block 1404, the UE receives a reference LTM configuration and / or LTM configurations 1, ..., N from the RAN, where N is a positive integer and LTM configurations 1, ..., N are for LTM configuration cells 1, ..., N (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 517, 519, 581, 582, 680, 694, 617, 619, 681, 682, 780, 794, 717, 719, 781, 782, 880, 894, 817, 819, 881, 882). At block 1405, the UE receives a message from the RAN configuring the UE to transition to an idle state or an inactive state. For example, the message is an RRC release message. In some implementations, the message includes a suspension configuration (e.g., SuspendConfig IE) that configures the UE to transition to an inactive state (e.g., RRC_INACTIVE state). In other implementations, the message does not include a suspension configuration that configures the UE to transition to an idle state (e.g., RRC_IDLE state).

[0211] At block 1406, the UE transitions to an idle state or an inactive state in response to the message. At block 1408, the UE releases the reference LTM configuration and / or LTM configurations 1, ..., N in response to transitioning to the idle or inactive state. The process proceeds from block 1408 to block 1410 or block 1414. At block 1410, the UE releases the serving CU configuration in response to transitioning to the idle state. At block 1412, the UE releases the serving DU configuration in response to transitioning to the idle state. At block 1414, the UE retains the serving CU configuration or at least a portion of the serving CU configuration in response to transitioning to the inactive state. At block 1416, the UE retains the serving DU configuration or at least a portion of the serving DU configuration in response to transitioning to the inactive state.

[0212] In some implementations, the reference LTM configuration includes a reference LTM CU configuration and / or a reference LTM DU configuration. In some implementations, each of LTM configurations 1, ..., N includes a (non-reference) LTM CU configuration and a (non-reference) LTM DU configuration.

[0213] Figure 14B 14 is a flow chart of an example method 1400B that is similar to method 1400A, except that method 1400B includes blocks 1407 and 1411 instead of block 1408. The flow proceeds from block 1406 to block 1407 or block 1411. At block 1407, the UE releases the reference LTM configuration and / or LTM configurations 1, ..., N in response to transitioning to the idle state. At block 1411, the UE retains the reference LTM configuration and / or LTM configurations 1, ..., N in response to transitioning to the inactive state.

[0214] In some implementations, a UE in an inactive state initiates a state transition procedure (e.g., an RRC Connection Resume procedure) with the RAN to transition from the inactive state to the connected state. During the state transition procedure, the UE sends an RRC Resume Request message to the RAN and receives an RRC Resume message in response. In response to the RRC Resume message, the UE transitions from the inactive state to the connected state and sends an RRC Resume Complete message to the RAN. Therefore, in some such implementations, the RAN sends an LTM command to the UE in the connected state, instructing the UE to perform a serving cell change to a cell configured with one of the retained LTM configurations 1, ..., N. Alternatively, the RAN indicates the release of the reference LTM configuration and / or LTM configurations 1, ..., N in the RRC Resume message. The UE releases the reference LTM configuration and / or LTM configurations 1, ..., N in response to the RRC Resume message. In a further alternative embodiment, after the UE transitions to the connected state, the RAN sends an RRC Reconfiguration message to the UE, indicating the release of the reference LTM configuration and / or LTM configurations 1, ..., N. The UE releases the reference LTM configuration and / or LTM configurations 1, ..., N in response to the RRC reconfiguration message.

[0215] In other implementations, if the UE performs the state transition procedure on a cell different from the cell in which the UE receives the message causing the UE to transition to the inactive state, the UE releases the reference LTM configuration and / or LTM configurations 1, ..., N in response to initiating or performing the state transition procedure. Otherwise, if the UE performs the state transition procedure on the same cell as the cell in which the UE receives the message causing the UE to transition to the inactive state, the UE retains the reference LTM configuration and / or LTM configurations 1, ..., N.

[0216] In yet other implementations, the UE releases the reference LTM configuration and / or LTM configurations 1, ..., N in response to initiating or performing the state transition procedure. In some implementations, the UE does this to simplify the implementation of the UE because the UE does not check whether the cell in which the UE performs the state transition procedure is the same cell in which the UE receives the message to transition the UE to the inactive state.

[0217] The following description can be applied to the above description.

[0218] 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 unless otherwise specified. 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, the term "message" may be used and may be replaced with "information element (IE)" or vice versa. In some implementations, the term "IE" may be used and may be replaced with "field" or vice versa. In some implementations, the term "configuration" may be replaced with "configurations" or "configuration parameters" or vice versa. In some implementations, the term "LTM command" may be replaced with a "serving cell change command," a "layer 1 / layer 2 handover command," a "lower layer handover command," or a "lower layer serving cell change command." In some implementations, "some" may mean "one or more." In some implementations, the term "at least one" may mean "one or more." In some implementations, the term "DU configuration" may be replaced with a "cell group configuration." In some implementations, "cell index" may be replaced with "serving cell index," "LTM cell index," "special cell (SpCell) index," "PCell index," or "PSCell index."

[0219] 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.

[0220] 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 can 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 can also include programmable logic or circuitry (e.g., as contained within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. 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) can be driven by cost and time considerations.

[0221] 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.

[0222] 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 method implemented in a user equipment (UE), the method comprising: At the UE, communicating with a distributed radio access network RAN ​​node according to a serving distributed unit DU configuration and a serving centralized unit CU configuration; receiving, at the UE, a reference lower layer triggered mobility LTM DU configuration and a reference LTMCU configuration from the distributed RAN node; as well as At the UE, communicating with the distributed RAN node using at least a portion of the reference LTM DU configuration and at least a portion of the reference LTM CU configuration.

2. The method of claim 1, further comprising: After receiving the reference LTM DU configuration and the reference LTM CU configuration, an LTM command is received at the UE from the distributed RAN node to perform a serving cell change from a first cell to a second cell.

3. The method of claim 2, wherein: Communicating with the distributed RAN node using at least a portion of the reference LTM DU configuration and at least a portion of the reference LTM CU configuration is performed via the second cell.

4. The method according to any one of the preceding claims, further comprising: A non-reference LTM DU configuration based on the reference LTM DU configuration and a non-reference LTM CU configuration based on the reference LTM CU configuration are received at the UE from the distributed RAN node.

5. The method of claim 4, wherein communicating with the distributed RAN node using at least a portion of the reference LTM DU configuration and at least a portion of the reference LTM CU configuration comprises: Communicating with a DU of the distributed RAN node using the non-reference LTM DU configuration based on the reference LTM DU configuration.

6. The method of claim 4 or 5, wherein communicating with the distributed RAN node using at least a portion of the reference LTM DU configuration and at least a portion of the reference LTM CU configuration comprises: Communicating with a CU of the distributed RAN node using the non-reference LTM CU configuration based on the reference LTM CU configuration.

7. A method as claimed in any one of the preceding claims, wherein: Receiving the reference LTM DU configuration and the reference LTM CU configuration includes receiving a single message including the reference LTM DU configuration and the reference LTM CU configuration.

8. A method implemented in a user equipment (UE), the method comprising: At the UE, communicating with a distributed radio access network RAN ​​node according to a serving distributed unit DU configuration and a serving centralized unit CU configuration; receiving, at the UE, a reference lower layer triggered mobility LTM configuration from the distributed RAN node; as well as At the UE, the reference LTM configuration is released in response to transitioning to an inactive state or an idle state.

9. The method of claim 8, further comprising: At least a portion of the serving CU configuration is retained in response to transitioning to the inactive state.

10. The method of claim 8 or 9, further comprising: At least a portion of the serving DU configuration is retained in response to transitioning to the inactive state.

11. The method according to any one of claims 8 to 10, further comprising: The serving CU configuration is released in response to transitioning to the idle state.

12. The method of any one of claims 8 to 11, further comprising: The serving DU configuration is released in response to transitioning to the idle state.

13. The method of any one of claims 8 to 12, further comprising: A non-reference LTM configuration is received at the UE.

14. The method of claim 13, further comprising: The non-reference LTM configuration is released at the UE in response to transitioning to the inactive state or the idle state.

15. A device operating as a User Equipment (UE), the device comprising processing hardware and configured to implement the method according to any one of the preceding claims.

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