Managing configurations for a user equipment in lower-layer triggered mobility

Abstract

Methods of wireless communication at a network entity is provided. In one aspect, the network entity performs (707) a procedure to prepare a configuration of a radio resource for a UE. Based on a determination (709) that the procedure is for LTM, the network entity refrains (715) from starting a timer based on performing the procedure. In another aspect, the network entity performs (707) a procedure to prepare a configuration of a radio resource for a UE. The network entity starts (711A) a timer based on performing the procedure. The network entity detects (917) that the timer expires, and, based on a determination (709) that the procedure is for LTM, refrains (921) from performing a release or cancellation procedure for the configuration based on expiry of the timer.

Description

PATENT APPLICATION Attorney Docket No.: G11438010070WO MANAGING CONFIGURATIONS FOR A USER EQUIPMENT IN LOWER-LAYER TRIGGERED MOBILITYCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No.63 / 746,675, filed on January 17, 2025, the content of which is incorporated herein by reference.FIELD OF THE DISCLOSURE

[0002] This disclosure relates to wireless communications and, more particularly, to managing configurations for cell switch in lower layer triggered mobility (LTM).BACKGROUND

[0003] The Third Generation Partnership Project (3GPP) specifies a radio interface referred to as fifth generation (5G) new radio (NR) (5G NR). An architecture for a 5G NR wireless communication system includes a 5G core (5GC) network, a 5G radio access network (5G-RAN), a user equipment (5G UE), etc. The 5G NR architecture seeks to provide increased data rates, decreased latency, and / or increased capacity compared to prior generation cellular communication systems.

[0004] Wireless communication systems, in general, provide various telecommunication services (e.g., telephony, video, data, messaging, etc.) based on multiple-access technologies, such as orthogonal frequency division multiple access (OFDMA) technologies, that support communication with multiple UEs. Improvements in mobile broadband continue the progression of such wireless communication technologies. For example, a user equipment (UE) may establish concurrent connections with two base stations to operate in dual connectivity (DC). Each base station may be an evolved node B (eNB) or a next generation node B (gNB).PATENT APPLICATION Attorney Docket No.: G11438010070WO SUMMARY

[0005] A UE may establish concurrent connections with two network nodes (e.g., base stations) to operate in DC. One of the two nodes is a master node (MN), associated with a master cell group (MCG), and the other of the two nodes is a secondary node (SN), associated with a secondary cell group (SCG). When the two network nodes support different radio access technologies (RATs), this type of connectivity is referred to as multiradio DC (MR-DC). When the UE moves from the coverage area of one cell to the coverage area of another cell, a mobility7procedure is needed. The mobility procedure may be triggered by lower layers (e.g., layer 1 (LI) / layer (L2)), known as lower layer triggered mobility (LTM).

[0006] When a base station communicates with the UE via a serving cell, the base station receives one or more layer 3 (L3) measurement results from the UE. Based on the L3 measurement results, the base station configures a LTM candidate cell. The base station then commands the UE to perform LTM cell switch based on LI or L3 measurement results. If the base station is a disaggregated base station, the base station may include a central unit (CU) and one or more distributed units (DUs). Because the signaling between network nodes and the UE for configuring LTM cell switch may be different from existing mobility procedures with immediate handover, there is a need for the network nodes to properly and efficiently configure, retain, and release radio resources in node addition or modification procedures.

[0007] Aspects of the present disclosure address the above-mentioned technical problems. As described in detail, implementations of this disclosure allow a network node to determine w hether to start a timer to protect the validity of radio resource configurations, depending on w hether the procedure is a LTM cell switch. Implementations of this disclosure also allow the network node to control whether to release a SN when the timer expires. With the features described in this disclosure, implementations of this disclosure improve the quality and efficiency of wireless communications by allowing robust LTM operations.

[0008] According to some aspects, a network entity performs a procedure to prepare a configuration of a radio resource for a UE. Based on a determination that the procedure is for LTM, the netw ork entity refrains from starting a timer based on performing the procedure.

[0009] According to some aspects, a network entity performs a procedure to prepare a configuration of a radio resource for a UE. The network entity starts a timer based onPATENT APPLICATION Attorney Docket No.: G11438010070WO performing the procedure. The network entity detects that the timer expires, and, based on a determination that the procedure is for LTM, refrains from performing a release or cancellation procedure for the configuration based on expiry' of the timer.

[0010] Aspects of the present disclosure may be implemented as, e.g., a wireless communication method, a wireless communication apparatus, a computer program product, or non-transitory computer-readable medium storing instructions executable by a processor.PATENT APPLICATION Attorney Docket No.: G11438010070WO BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 A is a block diagram of an example system in which a radio access network (RAN) and a user device can implement the techniques for managing LTM procedures related to a SN, according to some implementations.

[0012] Fig. IB is another block diagram of an example system in which a RAN and a user device can implement the techniques of this disclosure for managing LTM procedures related to an MN or an SN, according to some implementations.

[0013] Fig. 1C is a block diagram of an example base station including a CU and a DU that can operate in the system of Fig. 1A or Fig. IB, according to some implementations.

[0014] Fig. 2A is a block diagram of an example protocol stack according to which a UE communicates with base stations, according to some implementations.

[0015] Fig. 2B is a block diagram of an example protocol stack according to which a UE communicates with a CU and a DU, according to some implementations.

[0016] Fig. 3 is a signaling diagram for an intra-DU LTM, according to some implementations.

[0017] Fig. 4 is a signaling diagram for an inter-DU LTM, according to some implementations.

[0018] Fig. 5 is a signaling diagram of an example illustrating an inter-CU LTM between a UE and a base station (BS), according to some implementations.

[0019] Fig. 6 is signaling diagram of an example illustrating communications between a UE, a master node (MN) and a serving secondary node (S-SN) of a multi-radio dualconnectivity (MR-DC) configuration, and a candidate secondary node (C-SN) for inter-CU LTM cell switch, according to some implementations.

[0020] Figs. 7A and 7B are flowcharts each illustrating an example method of managing UE configurations for LTM cell switch, according to some implementations.

[0021] Figs. 8A and 8B are flowcharts each illustrating an example method of managing UE configurations for LTM cell switch according to some implementations.

[0022] Figs. 9-13 are flowcharts each illustrating an example method of managing UE configurations for LTM cell switch, according to some implementations.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0023] Fig. 14 is a diagram illustrating a hardware implementation for one or more example network entities, according to some implementations.DETAILED DESCRIPTION

[0024] The UE in some scenarios can concurrently utilize resources of multiple radio access network (RAN) nodes, interconnected by a backhaul. When a UE operates in MR-DC, one base station operates as a MN that covers a primary cell (PCell), and the other base station operates as a SN that covers 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 resources of one base station at a time. One base station and / or the UE determines that the UE should establish a radio connection with another base station. For example, one base station can determine to hand the UE over to the second base station, and initiate a handover procedure.

[0025] When the UE moves from coverage area of one cell to another cell in a RAN, at some point a serving cell change has to be performed for the UE. To perform the serving cell change, the RAN configures the UE to transmit L3 measurement results. Based on L3 measurement results received from the UE, the RAN transmits a RRC reconfiguration message configuring Reconfiguration with Synchronization (e.g., the RRC reconfiguration message includes a ReconflguratlonWithSync IE) for change of the serving cell (e.g.. PCell or PSCell). In cases where the UE operates in carrier aggregation (CA) of at least one secondary cell (SCell) with the PCell or PSCell, the RAN has to release the at least one SCell due to the change of the PCell or PSCell. The serving cell change involves complete L2 (and LI) resets, leading to longer latency, larger overhead and longer interruption time. Thus, 3 GPP has introduced.

[0026] While a base station of the RAN communicates with the UE via a serving cell, the base station receives one or more layer 3 (e.g., RRC) measurement results from the UE. The base station includes a CU and one or more DUs. One of the DU(s) operating the serving cell is a serving DU. Based on the L3 measurement result(s), the base station determines to configure a LTM candidate cell for LTM cell switch. To configure the LTM candidate cell for the UE, the base station transmits a LTM candidate configuration configuring the LTM candidate cell to the UE via RRC signaling. Later on, the base station receives one or more measurement results from the UE. Based on the one or more measurement result(s), the basePATENT APPLICATION Attorney Docket No.: G11438010070WO station determines that the LTM candidate cell qualifies to be a serving cell for the UE. Therefore, the base station transmits a LTM cell switch command to the UE to command the UE to perform the LTM cell switch to the LTM candidate cell. The UE performs a cell change from the serving cell to the LTM candidate cell in response to the LTM cell switch command. If the LTM candidate cell is operated by the serving DU, the LTM cell switch is an intra-CU intra-DU LTM cell switch. If the LTM candidate cell is operated by a candidate DU in the DU(s), the LTM cell switch is an intra-CU inter-DU LTM cell switch. 3GPP has enabled the intra-CU intra-DU LTM cell switch and intra-CU inter-DU LTN cell switch in Release 18 specifications. Although 3GPP has started to specify inter-CU LTM cell switch, there are still remaining issues for the inter-CU LTM involving MR-DC or non-MR-DC scenarios.

[0027] In inter-CU LTM and other LTM scenarios, because the signaling between network nodes and the UE for configuring LTM cell switch may be different from existing mobility procedures with immediate handover, there is a need for the network nodes to property and efficiently configure, retain, and release radio resources in node addition or modification procedures. Aspects of the present disclosure address the above-mentioned technical problems. As described in detail, implementations of this disclosure allow a network node to determine whether to start a timer to protect the validity of radio resource configurations, depending on whether the procedure is a LTM cell switch. Implementations of this disclosure also allow the network node to control whether to release a SN when the timer expires. With the features described in this disclosure, implementations of this disclosure improve the quality and efficiency of wireless communications by allowing robust LTM operations.

[0028] Fig. 1A depicts an example wireless communication system 100 in which communication devices can implement these techniques. The wireless communication system 100 includes a UE 102, a base station (BS) 104A, a base station 106A and a core network (CN) 110. The UE 102 initially connects to the base station 104A. In some scenarios, the base station 104A can perform an SN addition to configure the UE 102 to operate in dual connectivity (DC) with the base station 104A and the base station 106A. The base stations 104A and 106A operate as an MN and an SN for the UE 102, respectively.

[0029] In various configurations of the wireless communication system 100. the base station 104A can be implemented as a master eNB (MeNB) or a master gNB (MgNB), andPATENT APPLICATION Attorney Docket No.: G11438010070WO the base station 106A can be implemented as a secondary gNB (SgNB). The UE 102 can communicate with the base station 104A and the base station 106A via the same RAT such as EUTRA or NR, or different RATs. When the base station 104A is an MeNB and the base station 106A is a SgNB, the UE 102 can be in EUTRA-NR DC (EN-DC) with the MeNB and the SgNB.

[0030] In some cases, an MeNB or an SeNB is implemented as an ng-eNB rather than an eNB. When the base station 104A is a Master ng-eNB (Mng-eNB) and the base station 106A is a 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 104A is an MgNB and the base station 106A is an SgNB, the UE 102 may be in NR-NR DC (NR-DC) with the MgNB and the SgNB. When the base station 104A is an MgNB and the base station 106A is a Secondary ng-eNB (Sng-eNB), the UE 102 may be in NR-EUTRA DC (NE-DC) with the MgNB and the Sng-eNB.

[0031] In the scenarios where the UE 102 hands over from the base station 104A to the base station 106A, the base stations 104A and 106A operate as the source base station (S-BS) and a target base station (T-BS). respectively. The UE 102 can operate in DC with the base station 104A and an additional base station (not shown in Fig. 1 A) for example prior to the handover. The UE 102 can continue to operate in DC with the base station 106A and the additional base station or operate in single connectivity (SC) with the base station 106A, after completing the handover. The base stations 104A and 106A in this case operate as a source MN (S-MN) and a target MN (T-MN), respectively.

[0032] A core network (CN) 110 can be an evolved packet core (EPC) 111 or a fifthgeneration core (5GC) 160, both of which are depicted in Fig. 1A. The base station 104A can be an eNB supporting an S 1 interface for communicating with the EPC 111 , an ng-eNB supporting an NG interface for communicating with the 5GC 160, or a gNB that supports an NR radio interface as well as an NG interface for communicating with the 5GC 160. To directly exchange messages with each other during the scenarios discussed below, the base stations 104A and 106A can support an X2 or Xn interface. Among other components, the EPC 111 can include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. The SGW 112 is generally configured to transfer user-plane packets related to audio calls, video calls. Internet traffic, etc., and the MME 1 14 is configured to manage authentication, registration, paging, and otherPATENT APPLICATION Attorney Docket No.: G11438010070WO 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. The 5GC 160 includes a User Plane Function (UPF) 162 and an Access and Mobility Management (AMF) 164, and / or Session Management Function (SMF) 166. The UPF 162 is generally configured to transfer user-plane packets related to audio calls, video calls, Internet traffic, etc., the AMF 164 is configured to manage authentication, registration, paging, and other related functions, and the SMF 166 is configured to manage PDU sessions.

[0033] As illustrated in Fig. 1A, the base station 104A supports cell 124 A, and the base station 106A supports a cell 126 A. The cells 124A and 126 A can partially overlap, so that the UE 102 can communicate in DC with the base station 104A and the base station 106 A, where one of the base stations 104A and 106A is an MN and the other is an SN. The base station 104A can support additional cell(s) such as cells 124B and 124C, and the base station 106A can support additional cell(s) (not shown in Fig. 1A). The cells 124A, 124B and 124C can partially overlap, so that the UE 102 can communicate in carrier aggregation (CA) with the base station 104A. The base station 104A can operate the cells 124A, 124B and 124C via one or more transmit and receive points (TRPs). More particularly, when the UE 102 is in DC with the base station 104A and the base station 106 A. one of the base stations 104A and 106A operates as an MeNB, an Mng-eNB or an MgNB. and the other operates as an SgNB or an Sng-eNB.

[0034] In general, the wireless communication network 100 can include any suitable number of base stations supporting NR cells and / or EUTRA cells. More particularly, the EPC 111 or the 5GC 1 0 can be connected to any suitable number of base stations supporting NR cells and / or EUTRA cells. An example configuration in which the CN 110 is connected to additional base stations is discussed below with reference to Fig. IB. Although the examples below refer specifically to specific CN types (EPC, 5GC) and RAT types (5GNR and EUTRA), in general the techniques of this disclosure also can apply 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.

[0035] With continued reference to Fig. 1A, the base station 104A is equipped with processing hardware 130 that can include one or more general-purpose processors (e.g., CPUs) and a non-transitory computer-readable memory storing instructions that the one orPATENT APPLICATION Attorney Docket No.: G11438010070WO more general-purpose processors execute. Additionally or alternatively, the processing hardware 130 can include special-purpose processing units. The processing hardware 130 can include a PHY controller 132 configured to transmit data and control signal on physical downlink (DL) channels and DL reference signals with one or more user devices (e.g. UE 102) via one or more cells (e.g., the cell(s) 124A, 124B and / or 124C) and / or one or more TRPs. The PHY controller 132 is also configured to receive data and control signal on physical uplink (UL) channels and / or UL reference signals with the one or more user devices via one or more cells (e.g., the cell(s) 124A, 124B and / or 124C) and / or one or more TRPs. The processing hardware 130 in an example implementation includes a MAC controller 134 configured to perform MAC functions with one or more user devices. The MAC functions include a random access (RA) procedure, managing UL timing advance (TA) for the one or more user devices, and / or communicating UL / DL MAC PDUs with the one or more user devices. The MAC functions include lower triggered mobility (LTM) related functions as described below. The processing hardware 130 can further include an RRC controller 136 to implement procedures and messaging at the RRC sublayer of the protocol communication stack. For example, the RRC controller 132 may be configured to support RRC messaging associated with handover procedures, and / or to support the necessary operations when the base station 104A operates as an MN relative to an SN or as an SN relative to an MN. The base station 106A can include processing hardware 140 that is similar to processing hardware 130. In particular, components 142, 144, and 146 can be similar to the components 132, 134, and 136, respectively.

[0036] The UE 102 is equipped with processing hardware 150 that can 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 special-purpose processing units. The PHY controller 152 is also configured to receive data and control signal on physical DL channels and / or DL reference signals with the base station 104A or 106A via one or more cells (e.g., the cell(s) 124A, 124B, 124C and / or 126A) and / or one or more TRPs. The PHY controller 152 is also configured to transmit data and control signal on physical UL channels and / or UL reference signals with the base station 104A or 106A via one or more cells (e.g., the cell(s) 124 A, 124B, 124C and / or 126A) and / or one or more TRPs. The processing hardware 150 in an example implementation includes a MAC controller 154 configured to perform MAC functions with base station 104 A or 106A. For example, the MAC functions includes aPATENT APPLICATION Attorney Docket No.: G11438010070WO random access procedure, managing UL timing advance for the one or more user devices, and communicating UL / DL MAC PDUs with the base station 104A or 106 A. In another example, the MAC functions includes LTM related functions as described below. The processing hardware 150 can further include an RRC controller 156 to implement procedures and messaging at the RRC sublayer of the protocol communication stack.

[0037] In operation, the UE 102 in DC can use a radio bearer (e.g., a DRB or an SRB) that at different times terminates at the MN 104B or the SN 106A. The UE 102 can apply one or more security keys when communicating on the radio bearer, in the uplink (UL) (from the UE 102 to a base station) and / or downlink (from a base station to the UE 102) direction.

[0038] Fig. 1C depicts an example distributed implementation of a base station such as the base station 104A or 106 A. The base station in this implementation can include a centralized unit (CU) 172 and one or more distributed units (DUs) 174. The CU 172 is equipped with processing hardware that can 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 special-purpose processing units. In one example, the CU 172 is equipped with the processing hardware 130. In another example, the CU 172 is equipped with the processing hardware 140. The processing hardware 140 in an example implementation includes an SN RRC controller 142 configured to manage or control one or more RRC configurations and / or RRC procedures when the base station 106A operates as an SN. The DU 174A is also equipped with processing hardware that can 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 special-purpose processing units. In some examples, the processing hardware in an example implementation includes a medium access control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., a random access procedure) and a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station 106A operates as an MN or an SN. The process hardware may include further a physical layer controller configured to manage or control one or more physical layer operations or procedures.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0039] Fig. 2A illustrates, in a simplified manner, an example protocol stack 200 according to which the UE 102 can communicate with an eNB / ng-eNB and / or a gNB (e.g., one or more of the base stations 104A, 106A).

[0040] In the example stack 200, a physical layer (PHY) 202 A of EUTRA 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 an EUTRA PDCP sublayer 208 and, in some cases, to an 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 in turn can provide data transfer services to Service Data Adaptation Protocol (SDAP) 212 or a radio resource control (RRC) sublayer (not shown in Fig. 2A). The UE 102, in some implementations, supports both the EUTRA and the NR stack as show n in Fig. 2A, to support handover between EUTRA and NR base stations and / or to support DC over EUTRA and NR interfaces. Further, as illustrated in Fig. 2A, the UE 102 can support layering of NR PDCP 210 over EUTRA RLC 206A, and SDAP sublayer 212 over the NR PDCP sublayer 210.

[0041] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets (e.g., from an Internet Protocol (IP) layer, layered directly or indirectly over the PDCP layer 208 or 210) that can be referred to as service data units (SDUs), and output packets (e.g.. to the RLC layer 206A or 206B) that can be referred to as protocol data units (PDUs). Except where the difference between SDUs and PDUs is relevant, this disclosure for simplicity refers to both SDUs and PDUs as “packets.”

[0042] On a control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 can provide signaling radio bearers (SRBs) or RRC sublayer (not shown in Fig. 2A) to exchange RRC messages or non-access-stratum (NAS) messages, for example. On a user plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 can provide Data Radio Bearers (DRBs) to support data exchange. Data exchanged on the NR PDCP sublayer 210 can be SDAP PDUs, Internet Protocol (IP) packets or Ethernet packets.

[0043] Fig. 2B illustrates, in a simplified manner, an example protocol stack 250, 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 by the radio protocol stack 250 in Fig. 2B.PATENT APPLICATION Attorney Docket No.: G11438010070WO The CU at any of the base stations 104 A or 10 A can hold all the control and upper layer functionalities (e.g., RRC 214, SDAP 212, NR PDCP 210), while the lower layer operations (e.g., NR RLC 206B, NR MAC 204B, and NR PHY 202B) are delegated to the DU. To support connection to a 5GC, NR PDCP 210 provides SRBs to RRC 214, and NR PDCP 210 provides DRBs to SDAP 212 and SRBs to RRC 214.

[0044] Next, several example scenarios in which the base station operating in the system of Fig. 1 A transmits a configuration to the UE 102 and later activates a configuration for communication between the UE 102 and base station. Generally speaking, events in Figs. 3-10B that are similar are labeled with similar reference numbers (e.g., event 302 is similar to event 402 of Fig. 4, event 502 of Figs. 5A-5C. event 602 of Figs. 6A and 6B. and event 702 of Figs. 7-10B, event 390 is similar to event 490 of Fig. 4, event 590 of Fig. 5, and event 690 of Fig. 6), with differences discussed below where appropriate. With the exception of the differences shown in the figures and discussed below, any of the alternative implementations discussed with respect to a particular event (e.g., for messaging and processing) may apply to events labeled with similar reference numbers in other figures.

[0045] Referring first to Fig. 3, in a scenario 300. the base station 104A includes a CU 172 and DU 174 and the DU 174 operates the cell 124A. The UE 102 initially communicates 302 with the DU 174 on a serving cell (e.g., the cell 124A), using a serving DU configuration, and communicates with the CU 172 via the DU 174, using a serving CU configuration. The serving DU configuration includes configuration parameters provided by the DU 174, and the serving CU configuration includes configuration parameters provided by the CU 172. The DU 174 is a serving or a source DU (S-DU) for the UE 102. In other words. the DU 174 is a serving DU (S-DU) that is communicating with the UE 102. In some implementations, the UE 102 in carrier aggregation (CA) communicates with the DU 174 on the cell 124A and other cell(s) (e.g., cell 124D not shown in Fig. 1 A) using the serving DU configuration. The DU 174 operates the other cell(s). The cell 124A and / or the other cell(s) are serving cell(s) for the UE 102. In other implementations, the UE 102 in communicates with the DU 174 on the cell 124A only. In some implementations, the UE 102 communicates with the DU 174 on the cell 124A and / or other cell(s) (i.e.. serving cell(s)) via one or multiple TRPs. In the following description, events 394, 324, 350, 352, 354, and 326 occur on the serving cell(s). In some implementations, the cell 124A can be a PCell. In such cases, the other cell(s) include SCell(s) and / or additional cell(s) associated with the PCell or a SCell. In other implementations, the cell 124A can be a SCell, and one of the other cell(s) is a PCell. In suchPATENT APPLICATION Attorney Docket No.: G11438010070WO cases, the rest includes SCell(s) and / or additional cell(s) associated with the PCell or a SCell. In the following description, the base station 104A can be the DU 174, the CU 172 or the DU 174 and CU 172.

[0046] In the event 302, the UE 102 can transmit UL PDUs and / or UL control signals to the base station 104A on the cell 124A and / or other cell(s) via one or multiple TRPs. In some implementations, the UE 102 communicates UL PDUs and / or DL PDUs with the base station 104A via radio bearers which can include SRBs and / or DRB(s). The base station 104 A can configure the radio bearers to the UE 102. In some implementations, UL control signals include UL control information, channel state information, hybrid automatic repeat request (HARQ) acknowledgements (ACKs), HARQ negative ACKs, scheduling request(s) and / or sounding reference signal(s). Similarly, the UE 102 can receive DL PDUs and / or DL control signals from the base station 104A on the cell 124A and / or other cell(s) via one or multiple TRPs. In some implementations, the DL control signals include downlink control information (DCIs) and reference signals (e.g., synchronization signal block, channel state information reference signal(s) (CSI-RS(s)), and / or tracking reference signal(s)). The base station 104A can transmit the DCIs on physical downlink control channel(s) (PDCCH(s)) monitored by the UE 102, on the cell 124A and / or other cell(s) via one or multiple TRPs.

[0047] In some implementations, the serving DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some implementations, the serving DU configuration includes at least one first non-LTM TCI state configuration for the serving cell(s). In some implementations, the DU 174 can transmit these configuration parameters and / or the first non-LTM TCI state configuration(s) to the CU 172. The CU 172 generates one or more messages (e.g., RRC reconfiguration message(s)) including the configuration parameters and / or the first non-LTM TCI state configuration(s) and transmits the one or more messages to the UE 102 via the DU 174. In other implementations, the DU 174 transmits the configuration parameters and / or the first non-LTM TCI state configuration(s) to the UE 102 directly. In some implementations, the serving DU configuration is CellGroupConfig IE defined in 3GPP specification 38.331. In other implementations, the serving DU configuration includes configuration parameters in the CellGroupConfig IE. In some implementations, the serving CU configuration includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, the serving CU configuration includes a MeasConfig IE and / or a RadioBearerConftg IE defined in 3GPP specification 38.331 orPATENT APPLICATION Attorney Docket No.: G11438010070WO includes configuration parameters in the MeasConfig IE and / or RadioBearerConfig IE. The radio configuration parameters or the RadioBearerConfig IE configures one or more DRBs. 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 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 104A and the remaining portion of these configuration parameters from the base station 104A.

[0048] In some implementations, the DU 174 and the UE 102 communicate with each other using first non-LTM TCI state configuration(s), e.g., in the events 302, 318, 320, 324, 350, 354. and / or 326. In some implementations, the DU 174 transmits at least one first non-LTM TCI States Activation / Deactivation command (e.g., MAC control element (CE)) to the UE 102 to activate the first non-LTM TCI state configuration(s). The UE 102 activates the first non-LTM TCI state configuration(s) in response to the first non-LTM TCI States Activation / Deactivation command(s). In some implementations, the DU 174 includes a serving cell ID (e.g., a serving cell index) in each of the first non-LTM TCI States Activation / Deactivation command(s) to identify the first non-LTM TCI state configuration(s). Each of the serving cell ID(s) indicates a respective serving cell of the serving cell(s). In some implementations, the serving DU configuration includes the serving cell ID(s) and configures association(s) between the serving cell ID(s) and the first non-LTM TCI state configuration(s).

[0049] While communicating with the base station 104A, the UE 102 transmits 304 at least one measurement report to the DU 174. In some implementations, the measurement report(s) includes measurement results for a serving cell (e.g., the cell 124A) of the UE 102 and / or at least one non-serving cell. For each of the measurement report(s), the DU 174 transmits 306 a DU-to-CU message including the measurement report to the CU 172. In some implementations, the DU-to-CU message(s) of the event 306 is / are Fl application protocol (Fl AP) message(s) (e.g., UL RRC Message Transfer message(s)). The at least one serving cell includes the cell 124 A and / or other cell(s), and the at least one non-serving cell includes the cell 124B and / or additional cell(s). In some implementations, the serving CUPATENT APPLICATION Attorney Docket No.: G11438010070WO configuration includes at least one measurement configuration. Tn accordance with the measurement configured on(s), the UE 102 performs measurements and transmits 304 the measurement report(s) to the DU 174. In some implementations, the measurement configuration(s) includes Layer 3 (L3) measurement configuration(s) (e.g., MeasConfig IE(s)) and the measurement report(s) include L3 measurement report(s).

[0050] After (e.g., in response to) receiving one or some of the measurement report(s) from the UE 102, the CU 172 determines to prepare a first cell (e.g., cell 1 such as the cell 124B) as a LTM candidate cell for the UE 102. In some implementations, the base station 104A determines to prepare the first cell for the UE 102 because the measurement report(s) indicates that the first cell could be used by the base station 104 A to communicate with the UE 102. In some implementations, the base station 104A determines to prepare the first cell for the UE 102 because the measurement report(s) indicates that the first cell qualifies to be a LTM candidate cell that could be used for communication with the UE 102. In some implementations, if the L3 measurement report(s) indicates that signal strength and / or quality of the first cell is above a first predetermined threshold, is better than strength and / or quality of the serving cell (e.g., cell 124A), and / or is better than strength and / or quality of the serving cell by a first predetermined threshold, the CU 172 determines to prepare the first cell for the UE 102. Alternatively, the CU 172 determines to prepare the first cell for the UE 102 regardless of whether a measure report is received from the UE 102 or not.

[0051] In response to determining to prepare the first cell for LTM, the CU 172 transmits 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 identity (ID) 1 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 1 is cell global identity (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 some implementations, the CU 172 includes a LTM indicator in the first CU-to-DU message to indicate the DU 174 to prepare the first cell for LTM. In some implementations, the CU 172 includes the LTM indicator in a LTM Information Setup IE and includes the LTM Information Setup IE in the first CU-to-DU message. In yet other implementations, the CU 172 includes the LTM indicator in a LTM Information Modify IE and includes the LTM Information Modify IE in the first CU-to-DU message.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0052] Tn response to the first CU-to-DU message, the DU 174 generates a first LTM DU configuration (referred to herein after as LTM DU configuration 1) for the UE 102, which configures the first cell for LTM. In some implementations, the CU 172 includes a first LTM configuration ID (i.e., referred to herein after as LTM ID 1) in the first CU-to-DU message and the DU 174 associates the LTM ID 1 and / or the cell ID 1 with the LTM DU configuration 1. The DU 174 then transmits 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.

[0053] The events 308 and 310 are collectively referred to in Fig. 3 as a LTM preparation procedure 390.

[0054] In some implementations, the DU 174 includes, in the first DU-to-CU message, the cell ID 1 of the first cell associated with the LTM DU configuration 1 to indicate that the LTM DU configuration 1 is configured for or associated with the first cell. In cases where the CU 172 performs multiple LTM preparation procedures (e g., the procedure 390 and the LTM preparation procedure 2, ... , N described below) with the DU 174 to prepare multiple LTM candidate cells, the CU 172 can determine that the LTM DU configuration 1 is configured for or associated with the first cell, based on the cell ID 1 in the first DU-to-CU message.

[0055] In some implementations, the CU 172 does not include a LTM reference DU configuration in the first CU-to-DU message. In such cases, the DU 174 generates a LTM reference DU configuration and includes the LTM reference DU configuration in the first DU-to-CU message. In some implementations, the DU 174 generates the LTM DU configuration 1 as a delta configuration to augment the LTM reference DU configuration. In other implementations, the DU 174 generates the LTM DU configuration 1 as a complete configuration, i.e., not on top of the LTM reference DU configuration.

[0056] In some implementations, the CU 172 includes a LTM reference DU configuration request in the first CU-to-DU message, and the DU 174 generates the LTM reference DU configuration and includes the LTM reference DU configuration in the first DU-to-CU message in response to the request. In some implementations, the CU 172 determines whether the UE 102 supports a LTM reference configuration. If the CU 172 determines that the UE 102 supports a LTM reference configuration, the CU 172 includes the LTM reference DU configuration request in the first CU-to-DU message. The DU 174 includes the LTM reference DU configuration in the first DU-to-CU message in response to the LTM referencePATENT APPLICATION Attorney Docket No.: G11438010070WO DU configuration request. Otherwise, if the CU 172 determines that the UE 102 does not support a LTM reference configuration, the CU 172 does not include the LTM reference DU configuration request in the first CU-to-DU message. In this case, the DU 174 may generate the LTM DU configuration 1 as a complete configuration and may not include a / the LTM reference DU configuration in the first DU-to-CU message. In other implementations, the CU 172 transmits an additional CU-to-DU message including the LTM reference DU configuration request to the DU 174 instead of the first CU-to-DU message. In response, the DU 174 includes an additional DU-to-CU message including the LTM reference DU configuration to the CU 172. In yet other implementations, the DU 174 determines whether the UE 102 supports a LTM reference configuration. If the DU 174 determines that the UE 102 supports a LTM reference configuration, the DU 174 includes the LTM reference DU configuration in the first DU-to-CU message. Otherwise, if the DU 174 determines that the UE 102 does not support a LTM reference configuration, the DU 174 does not include a / the LTM reference DU configuration in the first DU-to-CU message.

[0057] In some implementations, the CU 172 includes a LTM reference DU configuration in the first CU-to-DU message. In some implementations, the CU 172 receives the LTM reference DU configuration from an additional DU during a LTM preparation procedure as described above and for Fig. 4. In other implementations, the CU 172 is preconfigured with the LTM reference DU configuration. In some implementations, the DU 174 generates the LTM DU configuration 1 as a delta configuration to augment the LTM reference DU configuration. In other implementations, the DU 174 ignores the LTM reference DU configuration and generates the LTM DU configuration 1 as a complete configuration, i.e., not on top of the LTM reference DU configuration.

[0058] If the DU 174 generates the LTM DU configuration 1 as a complete configuration, the DU 174 may include a complete configuration indication in the first DU-to-CU message to indicate that the LTM DU configuration 1 is a complete configuration. In some implementations, if the first CU-to-DU message does not include a / the LTM reference DU configuration, the CU 172 may determine that the LTM DU configuration 1 as a complete configuration. Otherwise, if the first CU-to-DU message includes a / the LTM reference DU configuration, the CU 172 may determine that the LTM DU configuration 1 is a delta configuration.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0059] Tn some implementations, the LTM reference DU configuration is different from the serving DU configuration. In some implementations, a portion of the LTM reference DU configuration is the same as a portion of the serving DU configuration and the rest of the LTM reference DU configuration is different from the rest of the serving DU configuration. In yet other implementations, the LTM reference DU configuration is the same as the serving DU configuration. In some implementations, the LTM reference DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some implementations, the LTM reference DU configuration is the CellGroupConflg IE defined in 3GPP specification 38.331. In other implementations, the LTM reference DU configuration includes configuration parameters in the CellGroupConflg IE. In some implementations, the LTM reference DU configuration includes a CSI-MeasConfig IE or configuration parameters for channel state information (CSI) measurement and / or reporting.

[0060] In some implementations, the LTM reference DU configuration is different from the serving DU configuration. In some implementations, a portion of the LTM reference DU configuration is the same as a portion of the serving DU configuration and the rest of the LTM reference DU configuration is different from the rest of the serving DU configuration. In other implementations, the LTM reference DU configuration is the same as the serving DU configuration.

[0061] To prepare the first cell as a LTM candidate cell for the UE 102, the CU 172 may¬ transmit 312 a second CU-to-DU message to the DU 174, including a CSI resource configuration (e.g., CSI resource configuration 1) and / or a LTM SSB configuration (i.e., LTM SSB configuration 1) to request the DU 174 to generate one or more CSI report configurations (e.g., (LTM) CSI report configuration(s) 1). The CSI resource configuration (e.g.. (LTM) CSI resource configuration(s) 1) include configuration parameters configuring at least one reference signal (RS) transmitted on the first cell. The RS(s) include SSB(s) and / or CSI-RS(s). The LTM SSB configuration include SSB configuration parameters configuring a SSB frequency, a subcarrier spacing, a SSB periodicity, SSB positions (e.g., SSB Positions In Burst IE) and / or SSB power for SSB(s) transmitted on the first cell.

[0062] After (e.g., in response to) receiving the CSI resource configuration, the DU 174 generates one or more CSI report configurations based on the CSI resource configuration and includes the CSI report configuration(s) in a serving DU configuration (referred to as aPATENT APPLICATION Attorney Docket No.: G11438010070WO second serving DU configuration to distinguish from the serving DU configuration in event 302). In some implementations, the CSI report configuration(s) configures the UE 102 to transmit CSI reports based on measurements of the RS(s). The DU 174 transmits 314 a second DU-to-CU message including the second serving DU configuration to the CU 172. In some implementations, the CSI resource configuration comprises (e.g., is or includes) one or more LTM-CSI-ResourceConfig-rl8 IES. In other implementations, the CSI resource configuration comprises an Itm-CSI-ResourceConfigToAddModList field / IE. In some implementations, the second serving DU configuration is a CellGroupConftg IE.

[0063] In some implementations, the CU 172 includes the cell ID 1 and / or the LTM ID 1 in the second CU-to-DU message. In one implementation, the CU 172 does so to indicate that the CSI resource configuration is / are associated with the first cell. In another implementation, the CU 172 does so for the DU 174 to associate the LTM ID 1 with the first cell, the cell ID 1, the LTM DU configuration 1, and / or the CSI report configuration(s). Based on the above implementation(s). the DU 174 can associate the LTM ID 1 and / or the cell ID 1 with configurations (e.g., LTM DU configuration 1, the CSI resource configuration, and / or the CSI report configuration(s)) related to the first cell. In such implementations, the CU 172 may or may not include the LTM ID 1 in the first CU-to-DU message.

[0064] In some alternative implementations, the CU 172 includes the CSI resource configuration in the first CU-to-DU message and the DU 174 includes the CSI report configuration(s) in the first DU-to-CU message.

[0065] In some implementations, the DU 174 transmits the LTM SSB configuration or the SSB configuration parameters to the CU 172, e.g., in the first DU-to-CU message, the second DU-to-CU message or an additional DU-to-CU message. In some implementations, the DU 174 transmits the additional DU-to-CU message in response to receiving an additional CU-to-DU message from the CU 172. In other implementations, the DU 174 transmits the fourth DU-to-CU message (e.g., a UE Context Modification Required message) in response to receiving the first CU-to-DU message or the second CU-to-DU message.

[0066] The events 312 and 314 are collectively referred to in Fig. 3 as a LTM CSI report configuration and / or LTM ID configuration procedure 392.

[0067] After receiving the first DU-to-CU message, the CU 172 generates a first LTM candidate configuration (i.e., LTM candidate configuration 1) including the LTM DU configuration 1 and generates a first RRC reconfiguration message including the LTMPATENT APPLICATION Attorney Docket No.: G11438010070WO candidate configuration 1 and the LTM ID 1. In some implementations, the CU 172 includes LTM CU configuration 1 in the LTM candidate configuration 1. In other implementations, the CU 172 does not include a LTM CU configuration in the LTM candidate configuration 1. The CU 172 transmits 316 a third CU-to-DU message including the first RRC reconfiguration message to the DU 174. In turn, the DU 174 transmits 318 the first RRC reconfiguration message to the UE 102. In response, the UE 102 transmits 320 a first RRC reconfiguration complete message to the DU 174. The DU 174 then transmits 322 a third DU-to-CU message including the first RRC reconfiguration complete message to the CU 172.

[0068] If the first DU-to-CU message includes the LTM reference DU configuration, the CU 172 generates a LTM reference configuration including the LTM reference DU configuration. In such cases, the CU 172 may include the LTM reference configuration in the first RRC reconfiguration message. In some implementations, the CU 172 includes a LTM reference CU configuration in the LTM reference configuration. In such cases, the CU 172 may generate the LTM CU configuration 1 as a delta configuration based on the LTM reference CU configuration. In other implementations, the CU 172 does not include a LTM reference CU configuration in the LTM reference configuration. In such cases, the CU 172 may generate the LTM CU configuration 1 as a complete configuration. Alternatively, the CU 172 transmits a second RRC reconfiguration message including the LTM reference configuration to the UE 102 via the DU 174, similar to the events 316 and 318. In response, the UE 102 transmits a second RRC reconfiguration complete message to the CU 172 via the DU 174, similar to the events 320 and 322. In some implementations, if the CU 172 does not receive a LTM reference DU configuration, the CU 172 may generate a LTM reference configuration including only the LTM reference CU configuration. In other implementations, if the CU 172 does not receive a LTM reference DU configuration, the CU 172 may not generate a LTM reference configuration.

[0069] In some implementations, if the first DU-to-CU message includes the complete configuration indication, the CU 172 may determine that the LTM DU configuration 1 as a complete configuration. Otherwise, if the first DU-to-CU message does not include the complete configuration indication, the CU 172 may determine that the LTM DU configuration 1 is a delta configuration. In some implementations, if the LTM DU configuration 1 is a complete configuration, the CU 172 generates the LTM candidate configuration 1 as a complete configuration. Otherwise, if the LTM DU configuration 1 is aPATENT APPLICATION Attorney Docket No.: G11438010070WO delta configuration, the CU 172 generates the LTM candidate configuration 1 as a delta configuration. If the LTM candidate configuration 1 is a complete configuration, the CU 172 includes, in the first RRC reconfiguration message, a complete configuration indication to indicate that the LTM candidate configuration 1 is a complete configuration. If the LTM candidate configuration 1 is a delta configuration, the CU 172 excludes the complete configuration indication from the first RRC reconfiguration message to indicate that the LTM candidate configuration 1 is a delta configuration.

[0070] In the case that the CU 172 performs the procedure 392, the CU 172 may include the second serving DU configuration in the first RRC reconfiguration message. Alternatively, the CU 172 transmits a third RRC reconfiguration message including the second serving DU configuration to the UE 102 via the DU 174, similar to the events 316 and 318. In response, the UE 102 transmits a third RRC reconfiguration complete message to the CU 172 via the DU 174, similar to the events 320 and 322.

[0071] In some implementations, the CU 172 includes the CSI resource configuration in the first RRC reconfiguration message, the second RRC reconfiguration message, or the third RRC reconfiguration message. In other implementations, the CU 172 transmits a fourth RRC reconfiguration message including the CSI resource configuration to the UE 102 via the DU 174, similar to the events 316 and 318. In response, the UE 102 transmits a fourth RRC reconfiguration complete message to the UE 102 via the DU 174, similar to the events 320 and 322.

[0072] In some implementations, the DU 174 transmits a DU-to-CU message to the CU 172, including early synchronization information for the UE 102. The DU-to-CU message may be the first DU-to-CU message, the second DU-to-CU message or a fourth DU-to-CU message. In some implementations, the DU 174 transmits the fourth DU-to-CU message in response to receiving a fourth CU-to-DU message from the CU 172. In other implementations, the DU 174 transmits the fourth DU-to-CU message (e.g., a UE Context Modification Required message) in response to receiving the first CU-to-DU message or the second CU-to-DU message. In one implementation, the DU 174 does so, if the DU 174 determines that the UE 102 supports (i.e., is capable of) early UL synchronization with a LTM candidate cell (e.g., early TA acquisition with a LTM candidate cell, early RA on a LTM candidate cell, or UE measured TA). Otherwise, if the DU 174 determines that the UE 102 does not support the early UL synchronization with a LTM candidate cell, the DU 174PATENT APPLICATION Attorney Docket No.: G11438010070WO does not transmit the early synchronization information to the CU 172. In other implementations, the CU 172 transmits a CU-to-DU message including an early synchronization information request (e.g., an IE) to the DU 174, and the DU 174 includes the early synchronization information in the DU-to-CU message in response to the early synchronization information request. The CU-to-DU message may be the first CU-to-DU message, the second CU-to-DU message or the fourth CU-to-DU message. In one implementation, the CU 172 does so if the CU 172 determines that the UE 102 supports the early UL synchronization with aLTM candidate cell. Otherwise, if the CU 172 determines that the UE 102 does not support the early UL synchronization with a LTM candidate cell, the CU 172 does not request the DU 174 to provide the early synchronization information for the UE 102. If the CU 172 receives the early synchronization information, the CU 172 includes the early synchronization information in the first, second, third or fourth RRC reconfiguration message. Alternatively, the CU 172 transmits a fifth RRC reconfiguration message including the early synchronization information to the UE 102 via the DU 174, similar to the events 316 and 318. In response, the UE 102 transmits a fifth RRC reconfiguration complete message to the CU 172 via the DU 174, similar to the events 320 and 322.

[0073] In some implementations, the early synchronization information includes a random access channel (RACH) configuration (i.e., RACH configuration 1) and / or one or more TCI state configurations (i.e., TCI state configuration(s) 1). In some implementations, the early synchronization request may include a request for a RACH configuration. If the early synchronization request includes the request for a RACH configuration, the DU 174 includes the RACH configuration in the early synchronization information or in the DU-to-CU message (e.g., be the first, second or fourth DU-to-CU message). Otherwise, if the early synchronization request does not include the request for a RACH configuration, the DU 174 neither includes the RACH configuration in the early synchronization information or in the DU-to-CU message.

[0074] In some implementations, the CU 172 includes, in the first, second, third, fourth and / or fifth RRC reconfiguration messages, one or more other LTM related configurations for the first cell. For example, the other LTM related configuration(s) include a PCI of the first cell and / or the LTM SSB configuration.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0075] The events 316, 318, 320, 322 are collectively referred to in Fig. 3 as a LTM configuration delivery procedure 394. The second, third, fourth and / or fifth RRC reconfiguration message(s)) and the second, third, fourth and / or fifth RRC reconfiguration complete message(s), the related CU-to-DU message(s) and / or the related DU-to-CU message(s) are also considered as part of the LTM configuration delivery procedure 394. In some implementations, the RRC reconfiguration message and the RRC reconfiguration complete message described above are an RRCReconfiguration message and an RRCReconflgurationComplete message, respectively.

[0076] 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. In some implementations, the second CU-to-DU message is a UE Context Modification Request message, and the second DU-to-CU message is a UE Context Modification Response message or a UE Context Modification Required message. In the case of the UE Context Modification Required message, the CU 172 can transmit a UE Context Modification Confirm message to the DU 174 in response to UE Context Modification Required message. In some implementations, the third CU-to-DU message is a DL RRC Message Transfer message. In other implementations, the third CU-to-DU message is a UE Context Modification Request message. In some implementations, the third DU-to-CU message is a UL RRC Message Transfer message. In other implementations, the third DU-to-CU message is a UE Context Modification Response message.

[0077] In some implementations, the LTM reference CU configuration is different from the serving CU configuration. In some implementations, a portion of the LTM reference CU configuration is the same as a portion of the serving CU configuration and the rest of the LTM reference CU configuration is different from the rest of the serving CU configuration. In yet other implementations, the LTM reference CU configuration is the same as the serving CU configuration.

[0078] In some implementations, the LTM reference CU configuration includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, the LTM CU configuration 1 includes a MeasConfig IE and / or a RadioBearerConfig IE defined in 3GPP specification 38.331 or includes configuration parameters in the MeasConfig IE and / or RadioBearerConfig IE.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0079] Tn some implementations, the LTM CU configuration 1 and / or the LTM reference CU configuration include PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, the LTM CU configuration 1 or the LTM reference CU configuration includes aMeasConflg IE and / or a RadioBearerConflg IE defined in 3GPP specification 38.331 or includes configuration parameters in the MeasConfig IE and / or RadioBearerConflg IE.

[0080] In some implementations, the LTM DU configuration 1 includes a plurality of configuration parameters for the UE 102 to communicate with the DU 174 on the first cell. In some implementations, the plurality of configuration parameters include physical layer configuration parameters (e.g.. PhysicalCellGroupConflg E), MAC layer configuration parameters (e.g.,MAC-CellGroupConflg IE) and / or RLC configuration parameters (e.g., RLC-BearerConfig IE(s)). In some further implementations, the plurality of configuration parameters include a special cell configuration (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConflg IE(s)). In some implementations, the LTM DU configuration 1 is CellGroupConflg IE defined in 3GPP specification 38.331. In other implementations, the LTM DU configuration 1 includes configuration parameters in the CellGroupConflg IE.

[0081] In some implementations, the LTM DU configuration 1 includes a first LI measurement configuration (e.g., a CSI-MeasConflg IE) and / or at least one first transmission configuration indicator (TCI) state configuration. In other implementations, the LTM CU configuration 1 includes the first TCI state configuration(s). In some implementations, the first LI measurement configuration includes at least one first RS resource configuration and / or at least one first report configuration. In some implementations, the first RS resource configuration(s) configures one or more RSs or one or more RS resources associated with the cell 1. The RS(s) includes SSB(s) and / or CSI-RS(s). The RS resource(s) includes SSB resource(s) and / or CSI-RS resource(s). In some implementations, each of the first RS resource configuration(s) includes a RS resource configuration ID. In some implementations, the first RS resource configuration(s) is / are (similar to) CSI-ResourceConfig IE(s). In some implementations, the first report configuration(s) configures one or more UL resources (e.g.. PUCCH resources or PUSCH resources) on the first cell for the UE 102 to transmit measurement results (e.g., CSI reports or LTM CSI reports). In some implementations, each of the first report configuration(s) includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the first RS resourcePATENT APPLICATION Attorney Docket No.: G11438010070WO configuration(s). In some implementations, each of the first TCI state configuration(s) configures a TCI state that associates one or two DL RSs with a corresponding quasicolocation (QCL) type. The DL RS(s) are associated with the cell 1.

[0082] After receiving the LTM-related configurations and the second serving DU configuration or after receiving the RRC reconfiguration message(s) described above, the UE 102 performs measurements on at least one first RS, generates at least one first LI measurement result based on the measurements, and transmits 324 at least one first LI measurement report including the first LI measurement result(s) to the DU 174. The first RS(s) may comprise SSB(s) and / or CSI-RS(s). In some implementations, the first RS(s) and / or transmission pattem(s) of the first RS(s) are configured in the CSI report configuration(s), the LTM SSB configuration, and / or the CSI resource configuration. The UE 102 performs the measurements on the first RS(s) in accordance with the CSI report configuration(s), the LTM SSB configuration, and / or the CSI resource configuration.

[0083] After receiving the LTM-related configurations and the second serving DU configuration or after receiving the RRC reconfiguration message(s) described above, the UE 102 performs measurements on at least one second RS, generates at least one second LI measurement result based on the measurements, and transmits at least one second LI measurement report including the first LI measurement result(s) to the DU 174. The second RS(s) may comprise SSB(s) and / or CSI-RS(s). In some implementations, the second RS(s) and / or transmission pattem(s) of the second RS(s) are configured in one or more second CSI report configurations and / or one or more second CSI resource configuration that are included in the serving DU configuration 302 and / or the second serving DU configuration. The UE 102 performs the measurements on the second RS(s) in accordance with the second CSI report configuration(s) and / or the second CSI resource configuration(s). The second CSI report configuration(s) may include non -LTM CSI report configuration(s) and / or LTM CSI report configuration(s). The second CSI resource configuration(s) may include non-LTM CSI resource configuration(s) and / or LTM CSI resource configuration(s).

[0084] After transmitting the RACH configuration to the UE 102 via the CU 172, the DU 174 may transmit 350 a PDCCH order to the UE 102 to command the UE 102 to transmit a RA preamble on the first cell. In response to the PDCCH order, the UE 102 transmits a RA preamble on the first cell. The DU 174 includes PDCCH order information in the PDCCH order. The PDCCH order information includes a RA preamble index, an UL or aPATENT APPLICATION Attorney Docket No.: G11438010070WO supplemental UL indicator, a SSB index and / or a physical RACH mask index. In some implementations, the DU 174 includes the LTM ID 1 in the PDCCH order to indicate the first cell. The UE 102 identifies the first cell based on the LTM ID 1 in the PDCCH order and transmits 352 the RA preamble on the first cell to the DU 174, using the PDCCH order information. Correspondingly, the DU 174 receives 352 the RA preamble in accordance with the PDCCH order information. In some implementations, the DU 174 may determine the SSB index, based on LI measurement report(s) 324, and / or the CSI resource configuration, the CSI report configuration and / or the LTM SSB configuration. In some implementations, the LI measurement report(s) may include the SSB index. In other implementations, the LI measurement report(s) include a SS / PBCH Block Resource Indicator (SSBRI) corresponding to the SSB index. Thus, the DU 174 determines the SSB index based on the SSBRI.

[0085] In some implementations, the DU 174 determines whether to transmit the PDCCH order based on the LI measurement result(s) 324. In some implementations, if the LI measurement result(s) indicate that the first cell qualifies for the UE 102 to perform RA for early UL synchronization, the DU 174 transmits the PDCCH order. Otherwise, if the LI measurement result(s) indicate that the first cell does not qualify for the UE 102 to perform RA for early UL synchronization, the DU 174 refrains from transmitting the PDCCH order. In other implementations, if the LI measurement result(s) indicate that the first cell qualifies for the UE 102 to access, the DU 174 transmits the PDCCH order. Otherwise, if the LI measurement result(s) indicate that the first cell does not qualify for the UE 102 to access, the DU 174 refrains from transmitting the PDCCH order. In yet other implementations, the DU 174 transmits the PDCCH order after receiving 320 the RRC reconfiguration complete message, regardless of the LI measurement result(s) 324.

[0086] After transmitting 324 the LI measurement report(s) or 352 the RA preamble, the UE 102 may transmit 354 additional LI measurement report(s) to the DU 174, similar to the event 324. The DU 174 determines to command the UE 102 to perform a LTM cell switch to the first cell based on the additional LI measurement report(s) and / or the LI measurement report(s) 324. In response to the determination, the DU 174 generates a LTM Cell Switch Command (e.g., a MAC CE) including the LTM ID 1 and transmits 326 the LTM Cell Switch Command to the UE 102. In response to the determination, the DU 174 may transmit 328 a DU-CU Cell Switch Notification message to the CU 172. In response to the LTM Cell Switch Command, the UE 102 performs a LTM cell switch to the first cell. In the LTM cell switch, the UE 102 accesses 332 the first cell and transmits 336 a RRC reconfiguration completePATENT APPLICATION Attorney Docket No.: G11438010070WO message to the DU 174 via the first cell. The DU 174 transmits 338 a DU-to-CU message (e.g., UL RRC Message Transfer message) including the RRC reconfiguration complete message to the CU 172. When the UE 102 receives the LTM Cell Switch Command, the UE 102 identifies the LTM candidate configuration 1 from the LTM ID 1 and accesses 332 the first cell using the LTM candidate configuration 1. Depending on implementations, the UE 102 may stop communicating on the serving cell(s) in response to the LTM Cell Switch Command. In turn, the DU 174 transmits a fifth DU-to-CU message including the RRC reconfiguration complete message to the CU 172. When the DU 174 detects the UE 102 accesses the first cell in the event 332, the DU 174 may transmit 334 an Access Success message to the CU 172 to indicate that the UE 102 has accessed the first cell.

[0087] In some alternative implementations, the UE 102 may transmit at least one L3 measurement result to the CU 172 via the DU 174 after event 320. Based on the at least one L3 measurement result, the CU 172 may send a CU-to-DU message to the DU 174, requesting or indicating to the DU 174 to trigger the LTM Cell Switch to the first cell for the UE 102. In some implementations, the CU-to-DU message includes a field or IE for the requesting or indicating. In response to the CU-to-DU message or the field or IE, the DU 174 transmits 350 the PDCCH order and / or 326 the LTM Cell Switch Command to the UE 102. In some implementations, the CU-to-DU message includes the at least one L3 measurement result. In some implementations, the DU 174 determine to send 350 the PDCCH order and / or 326 the LTM Cell Switch Command based on the at least one L3 measurement result. In some implementations, the CU-to-DU message is an existing message defined in 3GPP specification 38.473. For example, the CU-to-DU message is a UE Context Modification Request message or a CU-DU Cell Switch Notification message. In yet other implementations, the CU-to-DU message is a new CU-to-DU message that is newly defined in 3GPP specification 38.473 vl 8.4.0 or a later release / version.

[0088] In some implementations, the DU 174 includes, in the LTM Cell Switch Command, a TA value for UL synchronization with the first cell. In one implementation, the DU 174 derives the TA value based on the RA preamble (e.g., reception timing of the RA preamble). In another implementation, the DU 174 derives the TA value from an UL transmission on the serving cell (e.g., the cell 124A) from the UE 102. The UE 102 applies the TA value to synchronize with the first cell in UL transmission. After applying the TA value, the UE 102 transmits the first UL transmission on the first cell based on the LTM candidate configuration 1 without performing a RA procedure on the first cell. In some implementations, the UE 102PATENT APPLICATION Attorney Docket No.: G11438010070WO transmits the first UL transmission on the first cell using a UL grant. In such cases, the first UL transmission is a PUSCH transmission. In some implementations, the PUSCH transmission includes the RRC reconfiguration complete message 336. In some implementations, the UL grant is a configured grant and the LTM candidate configuration 1 or the LTM DU configuration 1 includes the configured grant configuration configuring the configured grant. In other implementations, the UL grant is a dynamic grant that the UE 102 receives on a PDCCH on the first cell. After transmitting the first UL transmission, the UE 102 receives a PDCCH transmission addresses to a C-RNTI of the UE 102 and determines that the LTM cell switch is completed successfully in response to receiving the PDCCH transmission.

[0089] The PDCCH transmission may include a UL grant or a DL assignment. In the case of the UL grant, the UE 102 transmits a PUSCH transmission to the DU 174 on the first cell using the UL grant. In the case of the DL assignment, the DU 174 transmits a PDSCH transmission to the UE 102 on the first cell in accordance with the DL assignment. The DU 174 may transmit 334 the Access Success message to the CU 172 after receiving (e.g., in response to) the first UL transmission, transmitting the PDCCH transmission, receiving the PUSH transmission or transmitting the PDSCH transmission.

[0090] In other implementations, the DU 174 does not include a TA value in the LTM Cell Switch Command. If the LTM Cell Switch Command does not include a / the TA value, the UE 102 performs 332 a RA procedure on the first cell in accordance with the RA configuration parameters. In some implementations, the RA configuration parameters are included in the LTM candidate configuration 1 or the LTM DU configuration 1. In some implementations, the RA configuration parameters configure PRACH resources, an association between SSB and PRACH resources, and / or one or more PRACH occasions. If the UE 102 successfully completes the RA procedure, the UE 102 determines the LTM cell switch to the first cell is completed successfully. Depending on implementations and / or the RA configuration parameters, the RA procedure can be a four-step RA procedure or a two-step RA procedure. During the four-step RA procedure, the UE 102 transmits a Message 3 on the first cell and the DU 174 transmits a Message 4 on the first cell to the UE 102 in response. During the two-step RA procedure, the UE 102 transmits a Message A on the first cell and the DU 174 transmits a Message B to the UE 102 on the first cell in response. The UE 102 may include the RRC reconfiguration complete message 336 in the Message 3 or Message A. Alternatively, the UE 102 transmits the RRC reconfiguration complete messagePATENT APPLICATION Attorney Docket No.: G11438010070WO 336 after completing the RA procedure. The DU 174 may transmit 334 the Access Success message to the CU 172, after receiving the Message 3, Message A or the RRC reconfiguration complete message 336 or transmitting the Message 4 or Message B.

[0091] After successfully completing the LTM cell switch to the first cell as described above, the UE 102 communicates 340 with the DU 174 and the CU 172 via the first cell, using the LTM candidate configuration 1. In the case of the LTM reference configuration, the UE 102 applies the LTM reference configuration first and then apply the LTM candidate configuration 1 to augment the LTM reference configuration.

[0092] In some implementations, each of the TCI state configuration(s) include a TCI state ID. In some implementations, the DU 174 includes, in the LTM Cell Switch Command, a first TCI state ID indicating a first one of the TCI state configuration(s). The UE 102 identifies the first one of the TC state configuration(s) based on the first TCI state ID and applies the first TCI state configuration to communicate UL transmissions and / or DL transmissions with the DU 174 in the events 332, 336 and / or 340. The DU 174 applies the first TCI state configuration to communicate UL transmissions and / or DL transmissions with the UE 102 in the events 332, 336 and / or 340

[0093] In some implementations, the CU 172 may prepare additional cell(s) (i.e., cell(s) 2, ... , N) as LTM candidate cell(s) for the UE 102 with the DU 174. before or after transmitting the LTM Cell Switch Command or during, before or after the procedure 390 or 392, as described above. N is an integer and larger than 1. For example, the CU 172 performs additional LTM preparation procedure(s) 2, ... , N with the DU 174 to prepare the cell(s) 2, ... N respectively. Each of the LTM preparation procedure(s) 2. ... , N is similar to the procedure 390. In the LTM preparation procedure(s) 2, ... , N, the CU 172 receives LTM DU configuration(s) 2, ... , N configuring the cell(s) 2, ... , N for LTM, respectively. The CU 172 generates LTM candidate configuration(s) 2, ..., N including the LTM DU configured on(s) 2, ...N. respectively. The CU 172 assigns LTM ID(s) 2. .... N to identify the LTM DU configuration(s) 2, ... , N and the LTM candidate configuration(s) 2, ... , N, respectively. The CU 172 may obtain CSI resource configuration 2, ... , N and perform CSI report configuration and / or LTM ID configuration procedure(s) 2, ... , N w ith the DU 174 to obtain the CSI report configuration(s) 2, ... , N, respectively, as described for the CSI resource configuration 1 and the CSI report configuration(s) 1. The CU 172 may obtain RACH configuration 2, ... , N for the cell(s) 2, ... , N respectively, as described for the RACHPATENT APPLICATION Attorney Docket No.: G11438010070WO configuration 1. The CU 172 may obtain TCI state configuration(s) 2, ... , N for the cell(s) 2, , N respectively, as described for the TCI state configuration(s) 1. Each of the CSI report configuration and / or LTM ID configuration procedure(s) 2, ... , N is similar to the procedure 392. The CU 172 may obtain LTM SSB configuration 2, ... , N for the cell(s) 2, ... , N, respectively, as described for the LTM SSB configuration 1. In some implementations, the CU 172 may perform LTM configuration delivery procedure 2, ... , N with the UE 102 to transmit a list of the {LTM ID 2, the LTM candidate configuration 2, the CSI resource configuration 2 (if obtained), the TCI state configuration 2 (if obtained), the RACH configuration 2 (if obtained), the LTM SSB configuration 2 (if obtained)}, ... , {the LTM ID N, the LTM candidate configuration N, the CSI resource configuration N, the TCI state configured on(s) N (if obtained), the RACH configuration N (if obtained), the LTM SSB configuration N (if obtained)} to the UE 102, respectively. Each of the LTM configuration delivery procedure 2, ... , N is similar to the procedure 394. In other implementations, the CU 172 includes the list in the first RRC reconfiguration message.

[0094] In some implementations, after receiving 334 the Access Success message or 338 the DU-to-CU message, the CU 172 may transmit 342 a CU-to-DU message to the DU 174. In one implementation, the CU 172 transmits 342 the CU-to-DU message to release radio resources and / or configurations of the serving cell(s) configured for the UE 102. In another implementation, the CU 172 transmits 342 the CU-to-DU message to release some of the LTM candidate cell(s) 2, ... , N. In this case, the CU 172. In response to the CU-to-DU message 342, the DU 174 transmits 344 a DU-to-CU message to the CU 172. In some implementations, the CU-to-DU message 342 and the DU-to-CU message 344 are a UE Context Modification Request message and a UE Context Modification Response message, respectively.

[0095] In some implementations, a LTM ID in a PDCCH order, a LTM Cell Switch Command and a RRC reconfiguration message is represented in different formats. For example, the PDCCH order or the LTM Cell Switch Command includes a first field to include the LTM ID 1 and the first RRC reconfiguration message includes a second field to include the LTM ID 1. In some implementations, the first field and the second field have different formats or coding schemes. For example, the first field uses a binary format (i.e., 3 bits) with a value range of 0, ... , 7 and the second field uses an integer format with a value range of 1, ... , 8. In this example, the first field with binary value 000b is equivalent to the second field with integer value 1, the first field with binary value 001b is equivalent to thePATENT APPLICATION Attorney Docket No.: G11438010070WO second field with integer value 2, ... , the first field with binary value 111 b is equivalent to the second field with integer value 8.

[0096] The events 304, 306, 390, 392, 394, and 324 are collectively referred to in Fig. 3 as an intra-CU intra-DU LTM configuration procedure 396. The events 304, 306, 390, 392, 394, 324, 350. 352, 354, 326, 328, 332, 334, 336, 338, and 340 are collectively referred to in Fig.3 as an intra-CU intra-DU LTM procedure 380.

[0097] Referring next to Fig. 4, in a scenario 400, the base station 104A includes a CU 172, a S-DU 174A and a candidate DU (C-DU) 174B. The S-DU 174A operates the cell 124A and optionally additional cell(s), while the C-DU 174B operates a first cell (e.g., cell 124C). The scenario 400 is an intra-CU inter-DU scenario, similar to the scenario 300. Thus, the descriptions for the scenario 300 can generally apply to the scenario 400. Some descriptions for the DU 174 in Fig. 3 may apply to the S-DU 174A in Fig. 4, and some descriptions for the DU 174 in Fig. 3 may apply to the C-DU 174B. The differences between the scenarios 300 and 400 are described below.

[0098] Initially, the UE 102 communicates 402 with the S-DU 174A on one or more serving cells (e.g., the cell 124A and / or other cell(s)) using a serving DU configuration and communicates with the CU 172 via the S-DU 174A using a serving CU configuration. In some implementations, the CU 172 and S-DU 174A might perform the LTM configuration procedure 396 or the LTM procedure 380 with the UE 102, as described for Fig. 3. In the case of the procedure 380, the UE 102 may perform a LTM cell switch to the first cell (e.g. cell 124B) as described for Fig. 3. Upon successfully completing the LTM cell switch, the first cell becomes a serving cell and cell 124A and / or the other cell(s) is / are no longer serving cell(s) for the UE 102. In the case of the procedure 396, the UE 102 does not perform a LTM cell switch. During the communication 402, the UE 102 transmits 404, 406 at least one measurement report (e.g., L3 measurement report(s)) to the CU 172 via the S-DU 174A. Based on the measurement report(s), the CU 172 determines to prepare cell 1 (e.g.. cell 124C operated by the C-DU 174B) for LTM for the UE 102. The cell 1 is identified by a cell ID (i.e., cell ID 1). In response to the determination, the CU 172 performs 490 a LTM preparation procedure with the C-DU 174B to (request the C-DU 174B to) prepare the cell 1 as a LTM candidate cell for the UE 102. In the LTM preparation procedure 490, the CU 172 transmits a first CU-to-DU message including a cell ID 1 of the cell 1 to the C-DU 174B to request the C-DU 174B to prepare the cell 1 as a LTM candidate cell for the UE 102, similarPATENT APPLICATION Attorney Docket No.: G11438010070WO to the event 308. In response, the C-DU 174B transmits a first DU-to-CU message including a LTM DU configuration (e.g., LTM DU configuration 1) to the CU 172, similar to the event 310. The CU 172 may or may not request a LTM reference DU configuration in the first CU-to-DU message, as described for Fig. 3. The C-DU 174B may or may not include a LTM reference DU configuration in the first DU-to-CU message, as described for Fig. 3.

[0099] In some implementations, if the CU 172 receives a LTM reference DU configuration from the S-DU 174A as described for Fig. 3, the CU 172 may include the LTM reference DU configuration in the first CU-to-DU message and the C-DU 174B may generate the LTM DU configuration as a delta configuration based on the LTM reference DU configuration. In such cases, the C-DU 174B does not transmit a LTM reference DU configuration for the UE 102 to the CU 172. In other implementations, the CU 172 receives a LTM reference DU configuration from the C-DU 174B, e.g., in the first DU-to-CU message or an additional DU-to-CU message as described for Fig. 3. In such cases, the CU 172 may generate a LTM reference configuration including the LTM reference DU configuration. The CU 172 may or may not include a LTM reference CU configuration in the LTM reference configuration.

[0100] To prepare the cell 1 for LTM, the CU 172 may perform 492 a LTM CSI report configuration and / or LTM ID configuration procedure with the S-DU 174A. In the procedure 492, the CU 172 transmits a second CU-to-DU message including a CSI resource configuration (e.g.. CSI resource configuration 1) and / or a LTM SSB configuration (i. e. , LTM SSB configuration 1) to the S-DU 174A, similar to the event 312. In response, the S-DU 174A transmits a second DU-to-CU message including one or more CSI report configurations (e.g., CSI report configuration(s) 1) to the CU 172. In some implementations, the CU 172 generates a LTM candidate configuration (e.g., LTM candidate configuration 1) including the LTM DU configuration and assigns a LTM ID (e.g., LTM ID 1) for identifying the LTM DU configuration and / or the LTM candidate configuration as described for Fig. 3. In some implementations, the CU 172 includes {the LTM ID 1, the cell ID 1} as a tuple in the second CU-to-DU message.

[0101] To prepare the cell 1 as a LTM candidate cell for the UE 102, the CU 172 may receive early synchronization information for the cell 1 in a DU-to-CU message (e.g., the first DU-to-CU message or an additional DU-to-CU message) from the C-DU 174B. In some implementations, the C-DU 174B transmits the additional DU-to-CU message in response toPATENT APPLICATION Attorney Docket No.: G11438010070WO receiving an additional CU-to-DU message from the CU 172. Tn other implementations, the C-DU 174B transmits the additional DU-to-CU message (e.g., a UE Context Modification Required message) in response to receiving the first CU-to-DU message. The early synchronization information includes aRACH configuration (e.g., RACH configuration 1) and / or at least one TCI state configuration (e.g., TCI state configuration(s) 1), as described for Fig. 3. In some implementations, the C-DU 174B includes, in the early synchronization information or in the DU-to-CU message, the PDCCH order information (PDCCH order information 1) for early UL synchronization with the first cell.

[0102] In some implementations, the CU 172 may receive the LTM SSB configuration or SSB configuration parameters in the LTM SSB configuration from the C-DU 174B, e.g.. in the first DU-to-CU message or an additional DU-to-CU message. In some implementations, the CU 172 may receive a PCI of the cell 1 from the C-DU 174B in the first DU-to-CU message or the additional DU-to-CU message. In some implementations, the C-DU 174B transmits the additional DU-to-CU message in response to receiving an additional CU-to-DU message from the CU 172. In other implementations, the C-DU 174B transmits the additional DU-to-CU message (e.g., a UE Context Modification Required message) in response to receiving the first CU-to-DU message.

[0103] As described for Fig. 3, the CU 172 performs 494 LTM configuration delivery procedure with the UE 102 to transmit the LTM ID 1 and the LTM candidate configuration to the UE 102. In some implementations, the CU 172 transmits {LTM ID. the LTM candidate configuration] as a tuple in a first RRC reconfiguration message in the procedure 494.Depending on the implementations, the CU 172 may include the LTM reference configuration, the CSI report configuration(s), the CSI resource configuration, the RACH configuration, the TCI state configuration(s), the LTM SSB configuration and / or the PCI of the cell 1 to the UE 102 in the first RRC reconfiguration message and / or other RRC reconfiguration message(s) transmitted to the UE 102, as described for Fig. 3. The CU 172 includes the LTM ID in the first RRC reconfiguration or the other RRC reconfiguration message(s) to indicate the CSI resource configuration, the RACH configuration, the TCI state configuration(s), the LTM SSB configuration and / or the PCI of the cell 1 are associated with the cell 1. For example, the CU 172 includes the CSI resource configuration, the RACH configuration, the TCI state configuration(s), the LTM SSB configuration and / or the PCI of the cell 1 in the tuple. In another example, the CU 172 includes {LTM ID, the CSI resource configuration, the RACH configuration, the TCI state configuration(s), the LTM SSBPATENT APPLICATION Attorney Docket No.: G11438010070WO configuration and / or the PCI of the cell 1 } as a tuple in the other RRC reconfiguration message(s). In response to each of the other RRC reconfiguration message(s), the UE 102 transmits a RRC reconfiguration complete message to the CU 172 via the S-DU 174A.

[0104] In some implementations, the PDCCH order information includes a frequency domain resource assignment, a RA preamble index, an UL or a supplemental UL indicator, a SSB index and / or a physical RACH mask index. The CU 172 may transmit a CU-to-DU message (e g., the second CU-to-DU message or an additional CU-to-DU message) including the PDCCH order information to the S-DU 174A. In some implementations, the CU 172 includes the LTM ID 1 or the cell ID 1 in the CU-to-DU message to indicate that the PDCCH order information is associated with the LTM ID 1 or the cell ID 1. For example, the CU 172 includes {the cell ID 1, the PDCCH order information} as a tuple in the CU-to-DU message. In the case of the additional CU-to-DU message, the S-DU 174A may transmit an additional DU-to-CU message to the CU 172 in response. The S-DU 174A transmits 450 a PDCCH order to the UE 102, based on the PDCCH order information. For example, The S-DU 174A transmits 450 a PDCCH order to the UE 102, including the PDCCH order information. In some implementations, the S-DU 174A may determine a SSB index included in the PDCCH order, based on LI measurement report(s) 424, and / or the CSI resource configuration, the CSI report configuration and / or the LTM SSB configuration. In some implementations, the S-DU 174A includes the LTM ID 1 in the PDCCH order to indicate the cell 1. In the case of the additional CU-to-DU message, the S-DU 174A may transmit an additional DU-to-CU message to the CU 172 in response. The UE 102 transmits 452 a RA preamble to the C-DU 174B on the cell 1, using the RACH configuration and / or the PDCCH order information. The C-DU 174B derives a TA value based on the RA preamble. The C-DU 174B transmits 456 a DU-CU TA Information Transfer message including the TA value to the CU 172. The CU 172 in turn transmits 458 a CU-DU TA Information Transfer message including the TA value to the S-DU 174A. In some implementations, the C-DU 174B includes the cell ID 1, the RA preamble index, a RA radio network temporary identifier (RA-RNTI) and / or a DU ID of the S-DU 174A in the message 456. In such cases, the CU 172 includes the cell ID 1, the RA preamble index, the RA-RNTI, and / or the DU ID of the S-DU 174A in the message 458. In response to determining to command the UE 102 to perform a LTM cell switch to the cell 1 , the S-DU 174A transmits 456 the LTM Cell Switch Command including the LTM ID 1 to the UE 102. If the S-DU 174A receives a TA value as described above, the S-DU 174A may include the TA value in the LTM Cell Switch Command. The S-DU 174A may include a firstPATENT APPLICATION Attorney Docket No.: G11438010070WO TCI state ID in the LTM Cell Switch Command. The first TCI state ID indicates a first one of the TCI state configuration(s).

[0105] In some implementations, the C-DU 174B determines the RA-RNTI based on a PRACH occasion in which the C-DU 174B receives the RA preamble 452. In some implementations, the C-DU 174B calculates the RA-RNTI as:RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f id + 14 * 80 * 8 * ul_carrier_id where s_id is the index of the first OFDM symbol of the PRACH occasion (0 < s_id < 14), t_id is the index of the first slot of the PRACH occasion in a system frame (0 < t_id < 80), where the subcarrier spacing to determine t_id is based on the value of p specified in clause 5.3.2 in 3GPP TS 38.211 for p = {0, 1 , 2, 3], and for p = {5, 6}, t_id is the index of the 120 kHz slot in a system frame that contains the PRACH occasion (0 < t_id < 80), f id is the index of the PRACH occasion in the frequency domain (0 < f id < 8), and ul_carrier_id is the UL carrier used for the RA Preamble transmission (0 for NUL carrier, and 1 for SUL carrier).

[0106] In response to determining to command the UE 102 to perform a LTM cell switch or transmiting 456 the LTM Cell Switch Command, the S-DU 174A transmits 428 aDU-CU Cell Switch Notification message to the CU 172 to indicate that the UE 102 performs a LTM cell switch to the cell 1. In response, the CU 172 transmits 430 a CU-DU Cell Switch Notification message to the C-DU 174B to indicate that the UE 102 performs a LTM cell switch to the cell 1. In some implementations, the S-DU 174A includes the first TCI state ID in the DU-CU Cell Switch Notification message and the CU 172 in turn includes the first TCI state ID in the CU-DU Cell Switch Notification message. The UE 102 and the C-DU 174B identify the first one of the TC state configuration(s) based on the first TCI state ID and apply the first TCI state configuration to communicate UL transmissions and / or DL transmissions in the events 432, 436 and / or 440.

[0107] In some implementations, each of the TCI state configuration(s) includes or is associated with a TCI state ID. In some implementations, the CU 172 may transmit a CU-to-DU message (e.g., the second CU-to-DU message or an additional CU-to-DU message) including the TCI state configuration(s) and / or the associated TCI state ID(s) to the S-DU 174A. In some implementations, the CU 172 includes the LTM ID 1 or the cell ID 1 in the CU-to-DU message to indicate that the TCI state configuration(s) is associated with the LTM ID 1 or the cell ID 1. For example, the CU 172 includes {the cell ID 1, the TCI state configuration(s)} as a tuple in the CU-to-DU message. In the case of the additional CU-to-PATENT APPLICATION Attorney Docket No.: G11438010070WO DU message, the S-DU 174A may transmit an additional DU-to-CU message to the CU 172 in response. In some implementations, the S-DU 174A includes, in the LTM Cell Switch Command 426, a first TCI state ID indicating a first one of the TCI state configuration(s). In some implementations, the S-DU 174A determines the first TCI state configuration or the fist TCI state ID. The UE 102 identifies the one of the TCI state configuration(s) based on the first TCI state ID and applies the first TCI state configuration in UL transmissions and / or DL receptions in the events 432, 436 and / or 440.

[0108] In some implementations, the CU 172 may prepare additional cell(s) (i.e., cell(s) 2, ... , N) as LTM candidate cell(s) for the UE 102 with the C-DU 174B, before or after transmitting the LTM Cell Switch Command or during, before or after the procedure 490 or 492, as described for Fig. 3.

[0109] In some implementations, the first CU-to-DU message and the first DU-to-CU message are a UE Context Setup Request message and a UE Context Setup Response message. In some implementations, the first CU-to-DU message and the first DU-to-CU message are a UE Context Modification Request message and a UE Context Modification Response message. In some implementations, the LTM preparation procedure 490 is a UE Context Setup procedure and the additional LTM preparation procedure is a UE Context Modification procedure. In other implementations, the LTM procedure 490 and the addition LTM preparation procedures are UE Context Setup procedures. In yet other implementations, the LTM procedure 490 and the addition LTM preparation procedures are UE Context Modification procedures.

[0110] The events 404, 406. 490, 492, 494. 494, and 424 are collectively referred to in Fig.4 as an intra-CU inter-DU LTM configuration procedure 496. The events 404, 406, 490, 492, 494, 494, 424, 450, 452, 454456, 458, 426, 428, 430, 432, 434, 436, 438, 440, 442, and 444 are collectively referred to in Fig. 4 as an intra-CU inter-DU LTM procedure 480.

[0111] Referring next to Fig. 5, in a scenario 500, the base station 104A operates as a serving or source base station (S-BS), and the base station 106A operates as a candidate base station (C-BS). The C-BS 106A includes a CU 172 and a DU 174. The scenario 500 is similar to the scenarios 300 and 400, except that the scenario 500 is an inter-CU scenario (i.e., inter-base station scenario) while the scenarios 300 and 400 are intra-CU (i.e., intra-base station) scenarios. The S-BS 104A can include a CU and a DU (not shown in Fig. 5), similar to the base station 104A of Figs. 3 and 4. Initially, the UE 102 communicates 502 with the S-PATENT APPLICATION Attorney Docket No.: G11438010070WO BS 104A via serving cell(s) using a serving configuration (a first serving configuration). In some implementations, the S-BS 104A includes a S-DU and a CU and the serving configuration may include a serving CU configuration and a serving DU configuration, as described for Figs. 3 and 4. While the communicating 502 with the UE 102, the S-BS 104A might perform 580 intra-CU LTM procedure(s) with the UE 102, similar to the procedures 380 and / or 480. Alternatively, while the communicating 502 with the UE 102, the S-BS 104A might perform 596 intra-CU LTM configuration procedure(s) with the UE 102, similar to the procedures 396 and / or 496.

[0112] While communicating with the S-BS 104A, the UE 102 transmits 504 at least one measurement report to the S-BS 104A. The measurement report(s) include measurement results for a serving cell of the UE 102 and / or at least one non-serving cell (e.g., cell 126A). The S-BS 104A determines to prepare a first cell (e.g., the cell 126A) as a LTM candidate cell for the UE 102, based on the measurement report(s). For example, the measurement report(s) include a PCI of the first cell and measurement result(s) of the cell 126A. The S-BS 104 A identifies that the first cell is operated by the base station 106 A based on the PCI, and determines that the first cell qualifies for LTM preparation based on the measurement result(s).

[0113] After (e.g., in response to) determining to prepare the first cell as a LTM candidate cell for the UE 102, the S-BS 104A (e g., the CU of the S-BS 104A) generates ^.Handover Request message including a first cell ID (i.e.. cell ID 1) of the first cell (i.e., cell 1). The S-BS 104A transmits 505 the Handover Request message to the CU 172. In some implementations, the Handover Request message includes a LTM indicator indicating the Handover Request message concerns LTM for the first cell ID. After (e.g., in response to) receiving ths Handover Request message, the CU 172 performs a LTM preparation procedure 590 with the DU 174 to prepare the first cell as a LTM candidate cell for the UE 102, similar to the procedure 390 or 490. In the procedure 590, the CU 172 transmits a first CU-to-DU message including the first cell ID to the DU 174 to request preparing the first cell, similar to the event 308. In response, the CU 172 may receive a first DU-to-CU message including a LTM DU configuration 1 from the DU 174, similar to the event 310. The CU 172 generates a first LTM candidate configuration (LTM candidate configuration 1). In response to the Handover Request message, the CU 172 transmits 507 a Handover Request Acknowledge message including the first LTM candidate configuration to the S-BS 104 A. In some implementations, the CU 172 includes the first cell ID in ths Handover Request AcknowledgePATENT APPLICATION Attorney Docket No.: G11438010070WO message to indicate that the first LTM candidate configuration is provided for or associated with the first cell (ID).

[0114] The events 505, 590, 507 are collectively referred to in Fig. 5 as an inter-CU LTM preparation procedure (or called inter-MN LTM preparation procedure) 598.

[0115] In some implementations, the Handover Request message includes a DU ID of the S-DU of the S-BS 104 A. In such cases, the CU 172 includes the DU ID in the first CU-to-DU message. In some implementations, the Handover Request message includes a BS ID of the S-BS 104 A. When receiving the BS ID, the CU 172 may include the BS ID in the first CU-to-DU message. For example, the BS ID is a gNB ID.

[0116] The CU 172 may or may not request a LTM reference DU configuration in the procedure 590, as described for Figs. 3 and 4. The DU 174 may or may not transmit a LTM reference DU configuration to the CU 172 in the procedure 590, as described for Figs. 3 and 4. In some implementations, the S-BS 104A (e.g.. the CU of the S-BS 104A) may obtain a LTM reference configuration, as described for Figs. 3 and 4. In other implementations, the S-BS 104A may receive a LTM reference configuration from another BS (not shown in Fig. 5) in another inter-CU LTM preparation procedure as described above and below. If the S-BS 104A obtains a LTM reference configuration, the S-BS 104A may include the LTM reference configuration (S-BS generated LTM reference configuration) in the Handover Request message. In some implementations, the S-BS 104A includes the LTM reference configuration in the inter-node RRC message HandoverPreparationlnformation or as an Xn Application Protocol (XnAP) IE or field and includes the inter-node RRC message or the XnAP IE in the Handover Request, message. Alternatively, the S-BS 104A determines to request or cause the C-BS 106 A to provide a complete LTM candidate configuration so that the S-BS 104 A does not include the LTM reference configuration in the Handover Request message. If the S-BS 104A does not obtain a LTM reference configuration, the S-BS 104A does not include a LTM reference configuration in the Handover Request message. If the Handover Request message includes a LTM reference configuration, the CU 172 may include the LTM reference configuration in the first CU-to-DU message. The DU 174 may extract a LTM reference DU configuration from the LTM reference configuration. Alternatively, the CU 172 extracts a LTM reference DU configuration from the LTM reference configuration and includes the LTM reference DU configuration in the first CU-to-DU message. The DU 174 may generate a LTM DU configuration as a delta configuration based on the LTM referencePATENT APPLICATION Attorney Docket No.: G11438010070WO DU configuration, as described for Fig. 3. Alternatively, the DU 174 may ignore the UTM reference (DU) configuration and generate a LTM DU configuration as a complete configuration, as described for Fig. 3.

[0117] Otherwise, if the Handover Request message does not include a LTM reference configuration, the CU 172 may or may not receive a LTM reference DU configuration from the DU 174 as described for Fig. 3. If the CU 172 receives a LTM reference DU configuration (e.g., in the first DU-to-CU message), the CU 172 generates a LTM reference configuration (C-BS generated LTM reference configuration) including the LTM reference DU configuration. The CU 172 may include a LTM reference CU configuration (candidate CU (C-CU) generated LTM reference CU configuration). Otherwise, if the CU 172 does not receive a LTM reference DU configuration from the DU 174 as described for Fig. 3, the CU 172 does not generate a LTM reference configuration. Alternatively, the CU 172 generates a LTM reference configuration (C-BS generated LTM reference configuration) only including a C-CU generated LTM reference CU configuration. In cases where the CU 172 generates a LTM reference configuration (C-BS generated LTM reference configuration), the CU 172 includes the C-BS generated LTM reference configuration in the Handover Request Acknowledge message.

[0118] In some implementations, if the LTM DU configuration 1 is a complete configuration, the CU 172 generates the LTM candidate configuration 1 as a complete configuration. The CU 172 may include a complete configuration indication (e.g., a BS-to-BS interface protocol field / IE) in the Handover Request Acknowledge message to indicate that the LTM candidate configuration 1 is a complete configuration. In some implementations, the BS-to-BS interface protocol is an Xn application protocol defined in 3GPP specification 38.423. In some implementations, the complete configuration indication is anew field / IE (e.g.. LTM specific) to avoid an impact to non-LTM configurations. In other implementations, the complete configuration indication is an existing field / IE defined in 3GPP specification 38.423. Otherwise, if the LTM DU configuration 1 is a delta configuration, the CU 172 generates the LTM candidate configuration 1 as a delta configuration. The CU 172 may exclude the complete configuration indication from the Handover Request Acknowledge message to indicate that the LTM candidate configuration 1 is a delta configuration. Alternatively, the CU 172 may include a delta configuration indication (e.g., a BS-to-BS interface protocol field / IE) in the Handover Request Acknowledge message to indicate that the LTM candidate configuration 1 is a deltaPATENT APPLICATION Attorney Docket No.: G11438010070WO configuration. In some implementations, the BS-to-BS interface protocol is an Xn application protocol defined in 3GPP specification 38.423. In some implementations, the delta configuration indication is a new field / IE (e.g., LTM specific) to avoid an impact to non-LTM configurations. In other implementations, the delta configuration indication is an existing field / IE defined in 3GPP specification 38.423. In some implementations, the BS-to-BS interface protocol field / IE have two values (i.e., a first value and a second value). The BS-to-BS interface protocol field / IE set to the first value is the complete configuration indication and the BS-to-BS interface protocol field / IE set to the second value is the delta configuration indication.

[0119] In some implementations, the S-BS 104A is preconfigured with a CSI resource configuration (e.g., (LTM) CSI resource configuration 1) and / or a LTM SSB configuration (LTM SSB configuration 1) for the first cell. In other implementations, the S-BS 104A receives the CSI resource configuration and / or the LTM SSB configuration from an Operations, Administration and Maintenance (0AM) node. In yet other implementations, the S-BS 104A receives the CSI resource configuration and / or the LTM SSB configuration from the CU 172. For example, the CU 172 includes the CSI resource configuration and / or the LTM SSB configuration in the Handover Request Acknowledge message. In some implementations, the CU 172 includes a PCI (PCI 1) of the first cell in the Handover Request Acknowledge message. To prepare the first cell as a candidate LTM cell for the UE 102, the CU of the S-BS 104A performs a LTM CSI report configuration and / or LTM ID configuration procedure (not shown in Fig. 5) with a S-DU of the S-BS 104A, similar to the procedure 392. In the LTM CSI report configuration and / or LTM ID configuration procedure, the CU of the S-BS 104A transmits the CSI resource configuration and / or the LTM SSB configuration to the S-DU of the S-BS 104A. In response, the CU of the S-BS 104A receives one or more CSI report configurations for the UE 102 from the S-DU of the S-BS 104A. In some implementations, the CU of the S-BS 104A receives the CSI report configuration(s) in a second serving DU configuration from the S-DU.

[0120] To prepare the first cell as a LTM candidate cell for the UE 102, the CU 172 may receive early synchronization information (early synchronization information 1) for the first cell from the DU 174 in a DU-to-CU message (e.g., the first DU-to-CU message or an additional DU-to-CU message). In some implementations, the DU 174 transmits the additional DU-to-CU message in response to receiving an additional CU-to-DU message from the CU 172. In other implementations, the DU 174 transmits the additional DU-to-CUPATENT APPLICATION Attorney Docket No.: G11438010070WO message (e.g., a UE Context Modification Required message) in response to receiving the first CU-to-DU message. The CU 172 includes the early synchronization information in the Handover Request Acknowledge message. The early synchronization information includes a RACH configuration (RACH configuration 1) and / or at least one TCI state configuration (TCI state configuration(s) 1). In some implementations, the DU 174 includes, in the early synchronization information or in the DU-to-CU message, PDCCH order information for early UL synchronization with the first cell. The CU 172 includes the PDCCH order information in the Handover Request Acknowledge message.

[0121] In some implementations, the CU 172 assigns a LTM ID (e.g., LTM ID 1) for identifying the first LTM candidate configuration and includes the LTM ID in the Handover Request Acknowledge message. In other implementations, the S-BS 104 A assigns a LTM ID (e.g., LTM ID 1) for identifying the first LTM candidate configuration.

[0122] After (e.g., in response to) receiving the Handover Request Acknowledge message, the S-BS 104A (e.g., the CU of the S-BS 104A) transmits 518 a first RRC reconfiguration message to the UE 102, including {the LTM ID 1 , the LTM candidate configuration 1 } as a tuple, similar to the event 318. If the Handover Request Acknowledge message includes the LTM reference configuration, the S-BS 104A may include the LTM reference configuration in the first RRC reconfiguration message. The S-BS 104A may include the CSI resource configuration 1, the TCI state configuration(s) 1, the RACH configuration 1, and / or the LTM SSB configuration 1 in the tuple, if received in the Handover Request Acknowledge message. Alternatively, the S-BS 104A transmits one or more additional RRC reconfiguration messages to the UE 102, including the CSI resource configuration 1, the TCI state configuration(s) 1, the RACH configuration 1, the LTM SSB configuration 1, and / or the PCI of the first cell. In each of the additional RRC reconfiguration message(s), the S-BS 104A includes the LTM ID 1 to indicate that the CSI resource configuration 1, the TCI state configuration(s) 1, the RACH configuration 1, the LTM SSB configuration 1, and / or the PCI of the first cell are associated with the first cell or configured for the first cell. The UE 102 transmits 520 a first RRC reconfiguration complete message to the S-BS 104A in response to the first RRC reconfiguration message. The UE 102 transmits an additional RRC reconfiguration complete message to the S-BS 104A in response to each of the additional RRC reconfiguration complete message. The RRC reconfiguration message(s) (i.e., the first RRC reconfiguration message and / or the additional RRC reconfiguration message(s)) and the RRC reconfiguration complete message(s) (i.e., the first RRC reconfiguration completePATENT APPLICATION Attorney Docket No.: G11438010070WO message and / or the additional RRC reconfiguration complete message(s)) form a LTM configuration delivery procedure. The S-BS 104A may include the second serving DU configuration in the first RRC reconfiguration message or one or the additional RRC reconfiguration message(s).

[0123] In some implementations, if the Handover Request Acknowledge message includes the complete configuration indication to indicate that the LTM candidate configuration 1 is a complete configuration, the S-BS 104A includes, in the first RRC reconfiguration message, a complete configuration indication (e.g., a RRC field / IE) to indicate that the LTM candidate configuration l is a complete configuration. Otherwise, if the Handover Request Acknowledge message does not include the complete configuration indication or includes the delta configuration indication to indicate that the LTM candidate configuration 1 is a delta configuration, the S-BS 104A excludes or does not include, in the first RRC reconfiguration message, the complete configuration indication (e.g., a RRC field / IE) to indicate that the LTM candidate configuration 1 is a delta configuration.

[0124] If the Handover Request Acknowledge message includes the PDCCH order information (PDCCH order information 1), the S-BS 104A transmits 550 a PDCCH order, based on the PDCCH order information. If the S-BS 104A is a distributed base station, the CU of the S-BS 104A may transmit the PDCCH order information to the S-DU of the S-BS 104A. For example, the S-BS 104A or the S-DU of the S-BS 104A transmits 550 a PDCCH order to the UE 102, including the PDCCH order information. In some implementations, the S-BS 104A or the S-DU of the S-BS 104A may determine a SSB index included in the PDCCH order, based on LI or L3 measurement report(s) 524, and / or the CSI resource configuration, the CSI report configuration and / or the LTM SSB configuration. In some implementations, the S-DU or the S-BS 104A includes the LTM ID 1 in the PDCCH order to indicate the first cell. The UE 102 transmits 552 a RA preamble to the DU 174 on the first cell, using the RACH configuration and / or the PDCCH order information. The S-DU or the S-BS 104A derives a TA value based on the RA preamble. The DU 174 transmits 556 nDU-CU TA Information Transfer message including the TA value to the CU 172. The CU 172 transmits 558 a CU-CU TA Information Transfer message including the TA value to the S-SB 104A (e.g., the CU of the S-BS 104A). In some implementations, the DU 174 includes the cell ID 1, the RA preamble index, a RA-RNTI, the DU ID of the S-DU of the S-BS 104 A, and / or the BS ID of the S-BS 104A in the message 556. In some implementations, the DU 174 does not include the BS ID in the message 556. In some implementations, the CU 172PATENT APPLICATION Attorney Docket No.: G11438010070WO includes the cell ID 1 , the RA preamble index, the RA-RNTT, the DU ID of the S-DU, and / or the BS ID of the S-BS 104A in the message 558. In some implementations, the CU 172 does not include the BS ID in the message 558. The CU of the S-BS 104A transmits a CU-DU TA Information Transfer message including the TA value, the cell ID 1, the RA preamble index, the RA-RNTI, and / or the DU ID of the S-DU, and / or the BS ID of the S-BS 104A to the S-DU of the S-BS 104 A. In some implementations, the CU of the S-BS 104A does not include the BS ID in the CU-DU TA Information Transfer message.

[0125] The events 524, 550, 552, 556, and 558 are collectively referred to in Fig. 5 as an early TA acquisition procedure 582.

[0126] In some implementations, the CU 172 determines an address (e.g., an IP address) of the S-BS 104A or the CU of the S-BS 104A, based on the BS ID of the S-BS 104A. In other implementations, the CU 172 determines an address (e.g.. an IP address) of the S-BS 104A or the CU of the S-BS 104A, based on the DU ID of the S-DU of the S-BS 104A. With these implementations, the CU 172 sends the CU-CU TA Information Transfer message to the S-BS 104A or the CU of the S-BS 104A in accordance with the address.

[0127] In response to determining to command the UE 102 to perform a LTM cell switch to the first cell, e.g., based on the measurement report(s) 524 and / or 554, the S-DU or the S-BS 104A transmits 526 the LTM Cell Switch Command including the LTM ID 1 to the UE 102. The S-DU may transmit 528 a Cell Switch Notification message to the CU, indicating that the LTM cell switch to the first cell is triggered for the UE 102. In response to the LTM Cell Switch Command, the UE 102 may stop communication on the serving cell(s). In response to the LTM Cell Switch Command, the UE 102 accesses 532 the first cell and transmits 536 a RRC reconfiguration complete message to DU 174. The DU 174 in turn transmits 538 a DU-to-CU message including the RRC reconfiguration complete message to the CU 172. After receiving 538 the DU-to-CU message or the RRC reconfiguration complete message, the C-BS 106A communicates 540 with the UE 102 in accordance with the first LTM candidate configuration and / or the LTM reference configuration. In some implementations, the UE 102 includes the LTM ID 1 in the RRC reconfiguration complete message 536 to indicate that the UE 102 applies the first LTM candidate configuration. In accordance ith the LTM ID 1, the CU 172 identifies the first LTM candidate configuration and / or the LTM reference configuration. In other implementations, the CU 172 identifies the first LTM candidate configuration and / or the LTM reference configuration based on the firstPATENT APPLICATION Attorney Docket No.: G11438010070WO cell ID included in the Access Success message 534. In such implementations, the CU 172 maintains or stores association information between the first cell ID, and the first LTM candidate configuration and / or the LTM reference configuration. When the CU 172 receives the first cell ID in the Access Success message, the CU 172 identifies the first LTM candidate configuration and / or the LTM reference configuration in accordance with the first cell ID and the association information.

[0128] In some implementations, after (e.g., in response to) event 532, 534, 538 and / or 541, the CU 172 performs a Path Switch procedure with the CN 110 (not shown in Fig. 5). In the Path Switch procedure, the CU 172 sends a Path Switch Request message to the CN 110 (e.g., AMF). The Path Switch Request message is to establish a UE associated signaling connection for the UE 102 between the CU 172 and the AMF and request a switch of a downlink termination point of a UP transport bearer (e.g., NG-U transport bearer) from an old termination point (e.g., the S-BS 104A or the S-CU of the S-BS 104A) towards a new7termination point (e.g.. the CU 172). In response to the Path Switch Request message, the CN 110 (e.g., AMF) establishes a UE associated signaling connection for the UE 102 with the CU 172 and switches the downlink termination point of the UP transport bearer from the old termination point tow ards the new termination point. In response to the Path Switch Request message, the CN 110 (e.g., AMF) transmits a Path Switch Request Acknowledge message to the CU 172. After the Path Switch procedure, the CN 110 (e.g., UPF) communicates UP data with the UE 102 via the S-BS 106A and the UP transport bearer.

[0129] In some implementations, if the S-DU or the S-BS 104A receives a TA value as described above, the S-DU or the S-BS 104A may include the TA value in the LTM Cell Switch Command. In some implementations, the S-DU or the S-BS 104A includes a first TCI state ID in the LTM Cell Switch Command. The first TCI state ID indicates a first one of the TCI state configuration(s).

[0130] In response to determining to command the UE 102 to perform the LTM cell switch or transmitting 526 the LTM Cell Switch Command, the S-DU of the S-BS 104A transmits a DU-CU Cell Switch Notification message to the CU of the S-BS 104A to indicate that the UE 102 performs or is performing a LTM cell switch to the first cell. In response to receiving the DU-CU Cell Switch Notification message, the CU of the S-BS 104A transmits 527 a CU-CU Cell Switch Notification message to the CU 172 to indicate that the UE 102 performs a LTM cell switch to the first cell. In response, the CU 172 transmits 530 a CU-DU Cell SwitchPATENT APPLICATION Attorney Docket No.: G11438010070WO Notification message to the DU 174 to indicate that the UE 102 performs a LTM cell switch to the first cell. In some implementations, the S-BS 104A includes the first TCI state ID in the CU-CU Cell Switch Notification message and the CU 172 then includes the first TCI state ID in the CU-DU Cell Switch Notification message. The UE 102 and the DU 174 identify the first one of the TC state configuration(s) based on the first TCI state ID and apply the first TCI state configuration to communicate UL transmissions and / or DL transmissions in the events 532, 536 and / or 540.

[0131] In some implementations, after (e.g., in response to) determining to command the UE 102 to perform the LTM cell switch, transmitting 526 the LTM Cell Switch Command, or receiving 527 the DU-CU Cell Switch Notification message, the S-BS 104A (e.g., the CU of the S-BS 104A) transmits 531 one or more Early Status Transfer messages to the CU 172, each including a DL COUNT value or a DISCARD DL COUNT value for a DRB over which the UE 102 and the S-BS 104A communicate 502 data with each other. In some implementations, after receiving 534 the Access Success message or receiving 538 the DU-to-CU message or the RRC reconfiguration complete message, the CU 172 transmits 539 a LTM Success message to the S-BS 104A (e.g., the CU of the S-BS 104A) to indicate that the LTM cell switch is completed successfully. In some implementations, the LTM Success message is a Handover Success message. In some implementations, the CU 172 includes the first cell ID in the LTM Success message. In other implementations, the CU 172 does not transmit a BS-to-BS message to the S-BS 104A (e.g., the CU of the S-BS 104A) to indicate that the LTM cell switch is completed successfully.

[0132] In some implementations, after (e.g., in response to) determining to command the UE 102 to perform the LTM cell switch, transmitting 526 the LTM Cell Switch Command, receiving 527 the DU-CU Cell Switch Notification message, or receiving 539 the LTM Success message, the S-BS 104A (e.g., the CU of the S-BS 104A) transmits 541 aSN Status Transfer message to the CU 172, including a DL COUNT value and / or a UL COUNT value for a / the DRB over which the UE 102 and the S-BS 104A communicate 502 data with each other.

[0133] In some implementations, after (e.g., in response to) receiving 534 the Access Success message, receiving 538 the DU-to-CU message or the RRC reconfiguration complete message or receiving 541 the SN Status Transfer message, the CU 172 transmits 543 a UEPATENT APPLICATION Attorney Docket No.: G11438010070WO C ontext Release message to the S-BS 104A. Tn response to the UE Context Release message, the S-BS 104A releases a UE context of the UE 102.

[0134] In some implementations, the S-BS 104A (e.g., the CU of the S-BS 104A) may prepare additional cell(s) (i.e., cell(s) 2, ... , N) as LTM candidate cell(s) for the UE 102 with the CU 172, before or after transmitting the LTM Cell Switch Command or during, before or after the procedure 598, as described above. The cell(s) 2, ..., N are identified by cell ID(s) 2, ... , N, respectively, and operated by the DU 174 and / or other DU(s) of the C-BS 106 A. N is an integer and larger than 1. For example, the S-BS 104A performs additional inter-CU LTM preparation procedure(s) 2, ... , N with the CU 172 to prepare the cell(s) 2, ...N respectively. Each of the inter-CU LTM preparation procedure(s) 2, ... , N is similar to the procedure 598. In the inter-CU LTM preparation procedure(s) 2, ... , N, the S-BS 104A receives LTM candidate configuration(s) 2, ... , N configuring the cell(s) 2, ... , N for LTM, respectively. As described above, the S-BS 104A orthe C-BS 106A assigns LTM ID(s) 2, ... , N to identify the LTM candidate configuration(s) 2. ... , N, respectively. The S-BS 104A may obtain CSI resource configuration 2, ... , N for the cell(s) 2, ... , N respectively, as described for the CSI resource configuration 1. The S-BS 104A may obtain CSI report configuration(s) 2, ... , N or the cell(s) 2, ... , N, respectively, as described for the CSI report configuration(s) 1. The S-BS 104A may obtain RACH configuration 2, ... , N for the cell(s) 2, ... , N respectively, as described for the RACH configuration 1. The S-BS 104A may obtain TCI state configuration(s) 2, ... , N for the cell(s) 2, ... , N respectively, as described for the TCI state configuration(s) 1. The S-BS 104A may obtain LTM SSB configuration 2, ..., N for the cell(s) 2, ... , N, respectively, as described for LTM SSB configuration 1. The S-BS 104A may obtain PCI(s) 2. ... , N for the cell(s) 2, ... , N respectively, as described for the PCI 1. In some implementations, the S-BS 104A may perform LTM configuration deliver}' procedure 2, ... , N with the UE 102 to transmit a list of the {LTM ID 2, the LTM candidate configuration 2, the CSI resource configuration 2 (if obtained), the TCI state configuration 2 (if obtained), the RACH configuration 2 (if obtained), the LTM SSB configuration 2 (if obtained), the PCI 2 (if obtained)}, ... , {the LTM ID N, the LTM candidate configuration N, the CSI resource configuration N, the TCI state configured on(s) N (if obtained), the RACH configuration N (if obtained), the LTM SSB configuration N (if obtained), the PCI N (if obtained)} to the UE 102, respectively. Each of the LTM configuration delivery procedure 2, ... , N is similar to the procedures 394. 494 and / or 594. In other implementations, the S-BS 104A includes the list in the first RRC reconfiguration message.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0135] Tn other implementations, the S-BS 104A performs the procedure 598 with the CU 172 to prepare one or more of the cell(s) 1 , ... , N as LTM candidate cell(s) for the UE 102. In such implementations, the S-BS 104A includes the cell ID(s) 1, ... , N in the Handover Request message 505 for LTM, as described for the cell ID 1. In some implementations, upon receiving the Handover Request message, the CU 172 determines or selects the cell(s) 1 , ... , M from the cell(s) 1, ... , N as LTM candidate cell(s). M is a positive integer and M < N. In other implementations, CU 172 prepares the cell(s) 1, ... , N for LTM as requested in the Handover Request message. The CU 172 performs LTM preparation procedure(s) 2, ... , M with the DU 172 to prepare the cell(s) 2, ... , M as LTM candidate cell(s) for the UE 102, respectively. The LTM preparation procedure(s) 2, ... , M are similar to the procedure 590 that the CU 172 performs with the DU 174 to prepare the cell 1. The CU 172 obtains the LTM candidate configuration(s) 2, .... M for the cell(s) 2, .... M as a result of the LTM preparation procedure(s) 2, ... , M respectively, similar to obtaining the LTM candidate configuration 1. The C-BS 106A may generate the LTM candidate configuration(s) 2, ..., M as complete configuration(s) or generate delta configuration(s) based on the LTM reference configuration, as described for the LTM candidate configuration 1. The CU 172 includes the LTM candidate configuration(s) 2, .... M in the Handover Request Acknowledge message. In some implementations, the CU 172 or the S-BS 104A assigns LTM ID(s) 2, ..., M to identify the LTM preparation procedure(s) 2, ... , M respectively, as described for the LTM ID 1. In the case the CU 172 assigns the LTM ID(s) 1, ... , M, the CU 172 includes the LTM ID(s) 1, ... , M with the LTM candidate configuration(s) 1. ... , M, respectively, in the Handover Request Acknowledge message, as described for the LTM ID 1 and the LTM candidate configuration 1.

[0136] In some implementations, the CU 172 obtains early synchronization information 2, ... , M for the cell(s) 2, ... , M, respectively, as described for the early synchronization information 1. The CU 172 includes the early synchronization information 2, ... , M in the Handover Request Acknowledge message. In some implementations, the CU 172 or the S-BS 104A obtains CSI resource configuration(s) 2. ... , M for the cell(s) 2, ... , M, respectively, as described for the CSI resource configuration 1. In the case that the CU 172 obtains the CSI resource configuration(s) 2, ..., M, the CU 172 includes the CSI resource configuration(s) 2, ... , M in the Handover Request Acknowledge message.

[0137] In some implementations, the CU 172 or the S-BS 104A obtains LTM SSB configuration(s) 2, ... , M for the cell(s) 2, ... , M, respectively, as described for the LTM SSBPATENT APPLICATION Attorney Docket No.: G11438010070WO configuration 1. In the case that the CU 172 obtains the LTM SSB configuration(s) 2, ... , M, the CU 172 includes the LTM SSB configuration(s) 2, .... M in the Handover Request Acknowledge message. In some implementations, the CU 172 or the S-BS 104A obtains PCI(s) 2, ... , M for the cell(s) 2, ... , M, respectively, as described for the PCI 1. In the case that the CU 172 obtains the PCI(s) 2, ..., M, the CU 172 includes the PCI(s) 2, ... , M in the Handover Request Acknowledge message.

[0138] In some implementations, the CU 172 includes a list of {the cell ID 1, the LTM ID 1 (if obtained or optional), the LTM candidate configuration 1, the CSI resource configuration 1 (if obtained or optional), the TCI state configuration 1 (if obtained or optional), the early synchronization information 1 (if obtained or optional), the LTM SSB configuration 1 (if obtained or optional), PCI 1 (if obtained or optional)}, , {the cell ID M, the LTM ID M (if obtained or optional), the LTM candidate configuration M, the CSI resource configuration M (if obtained or optional), the TCI state configuration M (if obtained or optional), the early synchronization information M (if obtained or optional), the LTM SSB configuration M (if obtained or optional), the PCI M (if obtained or optional)} in the Handover Request Acknowledge message.

[0139] In some implementations, the CU 172 obtains PDCCH order information 2, ... , M for the cell(s) 2, ... , M, respectively, as described for the PDCCH order information 1. In one implementation, the CU 172 includes the PDCCH order information 2, ... , M in the Handover Request Acknowledge message. In another implementation, the CU 172 includes the PDCCH order information 2, ... , M in the early synchronization information 2, ... , M, respectively. The S-BS 104A may obtain RACH configuration 2, TCI state configuration(s) 2 and / or the PDCCH order information 2, ... ., RACH configuration M, TCI state configuration(s) M and / or the PDCCH order information M from the early sy nchronization information 2, ... , M, respectively, or from the Handover Request Acknowledge message.

[0140] In some implementations, the S-BS 104A may perform LTM configuration delivery procedure 2, ... , M with the UE 102 to transmit a list of the {LTM ID 2, the LTM candidate configuration 2, the CSI resource configuration 2 (if obtained), the TCI state configuration 2 (if obtained), the RACH configuration 2 (if obtained), the LTM SSB configuration 2 (if obtained), the PCI 2 (if obtained)}, ... , {the LTM ID M, the LTM candidate configuration M, the CSI resource configuration M. the TCI state configuration(s) M (if obtained), the RACH configuration M (if obtained), the LTM SSB configuration M (if obtained), the PCI M (ifPATENT APPLICATION Attorney Docket No.: G11438010070WO obtained)} to the UE 102, respectively. Each of the LTM configuration delivery procedure 2, , M is similar to the procedures 394, 494 and / or 594. In other implementations, the S-BS 104A includes the list in the first RRC reconfiguration message.

[0141] In some implementations, the S-BS 104A may include measurement result(s) 1, ... , N for the cell(s) 1, ... , N respectively, in the Handover Request message. The S-BS 104A receives the measurement result(s) from the UE 102. The C-BS 106A may select or determine the cell(s) 1 , ... M, based on the measurement result(s) 1, ... , N. In other implementations, the C-BS 106A may select or determine the cell(s) 1, ...M, based on one or more other factors (e.g., capacity or load of the cell(s) 1, ... , N and / or a maximum number of LTM candidate cell(s)). In one implementation, the maximum number is included in the Handover Request message. In another implementation, the maximum number is a predetermined number.

[0142] Referring next to Fig. 6, in a scenario 600, the base station 104B operates as an MN, the base station 106A operates as a candidate SN (C-SN) and the base station 104A operates as a serving or source SN (S-SN). The MN 104B includes a CU 172 and a DU 174. The C-SN 106A and the S-SN 104A might include a CU and a DU (not shown in Fig. 6) similar to the C-BS 106A in the Fig. 5. The scenario 600 is similar to the scenario 500, except that the scenario 600A is a DC scenario and the scenario 500 is a single connectivity scenario.

[0143] Initially, the UE 102 in DC communicates 602 with the MN 104B and with S-SN 104A. In some implementations, the UE 102 communicates with the DU of the S-SN 104A on cell 124A using a serving DU configuration and communicates with the CU of the S-SN 104 A via the DU of the S-SN 104A using a serving CU configuration, similar to the event 302. In some implementations, the UE 102 in DC can communicate 602 UL PDUs and / or DL PDUs with the MN 104B and / or S-SN 104A via radio bearers which can include SRBs and / or DRB(s). The MN 104B and / or the S-SN 104A can configure the radio bearers to the UE 102. The UE 102 in DC communicates 602 UL PDUs and / or DL PDUs with the S-SN 104A on an SCG (i.e., SCG radio resources) that the S-SN 104A configures for communication with the UE 102. The UE 102 in DC communicates UL PDUs and / or DL PDUs with the MN 104B on an MCG (i.e., MCG radio resources) in accordance with a (serving) MN configuration (i.e., first serving MCG configuration). In some implementations, the serving DU configuration is a first SN configuration (i.e., first servingPATENT APPLICATION Attorney Docket No.: G11438010070WO SCG configuration). In the MN configuration, the MN 104B configures the MCG which includes at least one serving cell (e.g., the cell 124B and / or other cell(s)) operated by the MN 104B. In the serving DU configuration, the S-SN 104A configures the SCG which includes at least one serving cell (e.g., the cell 124A and / or other cell(s)) operated by the S-SN 104A. In some implementations, the MN configuration includes multiple configuration parameters and the UE 102 receives the configuration parameters in one or more RRC messages from the MN 104B. As described for Fig. 3, the serving DU configuration includes multiple configuration parameters. In some implementations, the UE 102 receives these configuration parameters in one or more RRC messages from the S-SN 104A, e.g, via the MN 104B and / or on an SRB (e.g., SRB3) that the MN 104B or S-SN 104A configures to exchange RRC messages between the UE 102 and the S-SN 104 A.

[0144] While communicating with the UE 102 in DC with the MN 104B and S-SN 104A, the S-SN 104A can perform 696 an intra-CU LTM configuration with the UE 102, similar to the procedures 396 and / or 496. While communicating with the UE 102 in DC with the MN 104B and S-SN 104A, the S-SN 104A can perform 680 an intra-CU LTM procedure with the UE 102, similar to the procedures 380 and / or 480. In the procedure 696 or 680, the CU of the S-SN 104A may transmit one or more RRC reconfiguration messages, each including one or more LTM candidate configurations, to the UE 102 via the SRB3, similar to the procedure 394 or 494. Alternatively, the CU of the S-SN 104A may transmit one or more RRC reconfiguration messages, each including one or more LTM candidate configurations, to the UE 102 via the MN 104B. In response to each of the RRC reconfiguration message(s), the UE 102 transmits a RRC reconfiguration complete message to the S-SN 104A via the MN 104B.

[0145] While communicating in DC with the MN 104B and S-SN 104 A, the UE 102 can transmit 604-1 at least one measurement report to the S-SN 104A directly, e.g. via the SRB3, similar to the events 304 / 306, the events 404 / 406 and the event 504. Alternatively, the UE 102 can transmit 604-2 the measurement report(s) to the MN 104B. The measurement report(s) include one or more measurement results of the first cell. In some implementations, the MN 104B generates at least one SN message including the measurement report(s) and transmits the SN message(s) to the CU 172. In one implementation, the SN message(s) include RRC Transfer message(s) and / or SN Modification Request message(s). The S-SN 104A (e.g., the CU of the S-SN 104A) generates a measurement configuration to configure the UE 102 to transmit the measurement report(s) and transmits the measurementPATENT APPLICATION Attorney Docket No.: G11438010070WO configuration to the UE 102 directly (e g., via the S-DU of the S-SN 104A) or via the MN 104B. Alternatively, the MN 104B generates a measurement configuration to configure the UE 102 to transmit the measurement report(s) and transmits the measurement configuration to the UE 102 directly (e.g., via the S-DU of the MN 104B)

[0146] In some implementations, based on the measurement report(s) received from the UE 102, the S-SN 104A (e.g., the CU of the S-SN 104A) determines to request the C-SN 106A preparing a first cell (e.g., the cell 126A) as a LTM candidate cell for the UE 102. In response to the determination, the S-SN 104A generates a SN Required message (a first SN Required message) including a first cell ID (i.e.. cell ID 1) of the first cell. In some implementations, the S-SN 104A includes a LTM indicator in the SN Required message, indicating the SN Required message is sent for LTM. In some implementations, the S-SN 104 A includes a C-SN ID (as a target SN ID) indicating the C-SN 106A in the SN Required message. In some implementations, the S-SN 104A includes the one or more measurement results of the first cell in the SN Required message. The S-SN 104A transmits 603 the SN Required message to the MN 104B. In some implementation, the one or more measurement results include the cell ID 1 and its corresponding measurement quantity results (e.g., a candidateCelllnfoListSN field / IE or MeasResultList2NR IE). After (e.g., in response to) receiving the SN Required message, the MN 104B transmits 605 a SN Request message (a first SN Request message) including the one or more measurement results of the first cell to the C-SN 106 A to request preparing the first cell as a LTM candidate cell for the UE 102. In other implementations, the MN 104B transmits 605 the SN Request message based on the measurement report(s) that the MN 104B received 604-2 from the UE 102.

[0147] In response to the SN Request message 603, the C-SN 106A performs a LTM preparation procedure 690 to prepare the first cell as a LTM candidate cell for the UE 102, similar to the procedure 390. 490 or 590. In the procedure 690, if the C-SN 106A includes a CU and a DU, the CU of the C-SN 106A transmits a first CU-to-DU message including the first cell ID to the DU of the C-SN 106A to request preparing the first cell, similar to the event 308. In response, the CU of the C-SN 106A may receive a first DU-to-CU message including a LTM DU configuration 1 from the DU of the C-SN 106 A, similar to the event 310. The CU of the C-SN 106A generates a first SCG LTM candidate configuration (SCG LTM candidate configuration 1). In response to the SN Request message, the (CU of the) C-SN 106A transmits 607 a SN Request Acknowledge message (a first SN Request Acknowledge message) including the first SCG LTM candidate configuration and the cell IDPATENT APPLICATION Attorney Docket No.: G11438010070WO 1 to the MN 104B. Tn some implementations, the C-SN 106 A includes a SCG LTM reference configuration in the SN Request Acknowledge message. The C-SN 106A may do so if the SN Request message includes a reference configuration request indicator. The reference configuration request indicator requests or indicates to the C-SN 106A to provide a SCG LTM reference configuration. If the C-SN 106A supports the reference configuration request indicator, the C-SN 106A includes the SCG LTM reference configuration in the SN Request Acknowledge message. In this case, the C-SN 106A generates the first SCG LTM candidate configuration augmenting the SCG LTM reference configuration. The C-SN 106A may include an indicator in the SN Request Acknowledge message, indicating that the first SCG LTM candidate configuration is a delta configuration. Otherwise, if the C-SN 106A does not support the reference configuration request indicator, the C-SN 106A does not include the SCG LTM reference configuration in the SN Request Acknowledge message. In this case, the C-SN 106A generates the first SCG LTM candidate configuration as a complete configuration and may include an indicator in the SN Request Acknowledge message to indicate that the first SCG LTM candidate configuration is a complete configuration. In some implementations, the MN 104B transmits 609 a SN Confirm message to the S-SN 104A in response to the SN Required message.

[0148] In some implementations, the C-SN 106A includes one or more LTM CSI resource configuration(s) (the LTM CSI resource configuration 1) for the first cell in the SN Request Acknowledge message. In some implementations, the CU of the C-SN 106A is preconfigured with the LTM CSI resource configuration(s). In other implementations, the CU receives the LTM CSI resource configuration(s) from the DU of the C-SN 106 A, where the DU operates the first cell. In yet other implementations, the CU receives the LTM CSI resource configuration(s) from an 0AM node.

[0149] In some implementations, the SN Request message includes a SCG LTM reference configuration. If the C-SN 106 A supports to use a SCG LTM reference configuration, the C-SN 106A generates the first SCG LTM candidate configuration augmenting the SCG LTM reference configuration. The C-SN 106A may include a delta configuration indication in the SN Request Acknowledge message, indicating that the first SCG LTM candidate configuration is a delta configuration. Alternatively, the C-SN 106A excludes a complete configuration indication in the SN Request Acknowledge message, indicating that the first SCG LTM candidate configuration is a delta configuration. In this case, the C-SN 106A does not include a SCG LTM reference configuration in the SN Request Acknowledge message.PATENT APPLICATION Attorney Docket No.: G11438010070WO Otherwise, if the C-SN 106A does not support to use a SCG LTM reference configuration, the C-SN 106 A generates the first SCG LTM candidate configuration as a complete configuration. In this case, may include a complete configuration indication in the SN Request Acknowledge message, indicating that the first SCG LTM candidate configuration is a complete configuration.

[0150] In some implementation, the C-SN 106A includes the first SCG LTM candidate configuration, the cell ID 1, and / or the SCG LTM reference configuration in a CG-Config IE or a CG-Configlnfo IE and includes the CG-Config IE or CG-Configlnfo IE in the SN Request Acknowledge message. In some implementations, the CU 172 includes the cell ID 1 in the SN Request Acknowledge message to indicate that the first SCG LTM candidate configuration is provided for or associated with the first cell (i.e., the cell ID 1).

[0151] In some implementations, after (e.g., in response to) receiving 607 the SN Request Acknowledge message, the CU 172 transmits 660, to the DU 174 of the MN 104B, a CU-to-DU message (e.g., a UE Context Modification Request message). In some implementations, the CU 172 includes a LTM indicator indicating ‘LTM-preparation’, the cell ID 1 indicating the prepared first PSCell, the CG-Config IE, the CG-Configlnfo IE, the first SCG LTM candidate configuration, and / or the SCG LTM reference configuration in the CU-to-DU message. In some implementations, the LTM indicator is a LTM Trigger lE / field. In some implementations, the LTM Trigger lE / filed is set to the value ‘LTM-preparation'. The CU 172 may include the LTM indicator in an Inter -SN LTM MCG Information IE ox Inter -CU SCG LTM MCG Information IE included in the CU-to-DU message. Based on the information provided in the CU-to-DU message, the DU 174 of the MN 104B may generate a LTM MCG configuration for the UE 102 and the first cell. The DU 172 then transmits 662 a DU-to-CU message (e.g., UE Context Modification Response message) including the LTM MCG configuration to the CU 172. In some implementations, the DU 174 includes the cell ID 1 (e g., in a Requested Target Cell ID field / IE) in the DU-to-CU message, indicating the LTM MCG configuration is associated with the first cell. In some implementations, the DU 174 includes the LTM MCG configuration in an existing field / IE included in the DU-to-CU message. The existing field / IE may be a CellGroupConfig IE or a DU to CU RRC Information IE defined in 3GPP specification 38.473 V19.0.0 or later version. In other implementations, the DU 174 includes the LTM MCG configuration in anew container field / IE specifically for this purpose. The DU 174 refrains from applying the LTM MCG configuration to communicate with the UE 102, until the DU 174 receives a further indicationPATENT APPLICATION Attorney Docket No.: G11438010070WO message (e.g., event 665 as described below) from the CU 172. The further indication message indicates the DU 174 to apply the LTM MCG configuration. In some alternative implementations, the DU 174 determines not to generate a LTM MCG configuration based on the information included in the CU-to-DU message. In such cases, the DU 174 transmits 662 a DU-to-CU message excluding (i.e., not including) a LTM MCG configuration to the CU 172 in response to the CU-to-DU message.

[0152] In some implementations, the DU 174 of the MN 104B generates a MCG LTM reference configuration based on the information in the CU-to-DU message 660 and includes the MCG LTM reference configuration in the DU-to-CU message 662. In some implementations, the CU 172 includes a reference configuration request indicator in the CU-to-DU message 660 to request a MCG LTM reference configuration. If the DU 174 supports the reference configuration request indicator, the DU 174 includes the MCG LTM reference configuration in the DU-to-CU message 662. Otherwise, if the DU 174 does not support the reference configuration request indicator, the DU 174 refrains from including a / the MCG LTM reference configuration in the DU-to-CU message 662.

[0153] In some implementations, the MN 104B transmits 663 an SN Request message (e.g., SN Modification Request message) to the S-SN 104A, including 1) the LTM CSI resource configuration(s), 2) the first SCG LTM candidate configuration, 3) the SCG LTM reference configuration, 4) a configuration ID (e.g., LTM ID 1), and / or 5) the cell ID 1. In response, the S-SN 104A transmits 664 a SN Request Acknowledge message (e.g.. SN Modification Request Acknowledge message) to the MN 104B. In some implementations, the MN 104B assigns the configuration ID for the first cell (i.e., the configuration ID is associated with the cell ID 1). The MN 104B configures the configuration ID to identify the LTM candidate configuration as described for event 616. In other implementations, the S-SN 104A assigns the configuration ID for the first cell (i.e.. the configuration ID is associated with the cell ID 1) and includes the configuration ID in the SN Required message. The S-SN 104 A configures the configuration ID to identify the LTM candidate configuration as described for event 616. The MN 104B associates the configuration ID (received from the S-SN 104A) with the LTM candidate configuration. In some alternative implementations, the S-SN 104A is preconfigured with the LTM CSI resource configuration(s). In other alternative implementations, the S-SN 104A receives the LTM CSI resource configuration(s) from the 0AM node.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0154] Tn some implementations, the S-SN 104A (e.g., a DU of the S-SN 104A) generates a second SN configuration for the UE 102 based on the LTM CSI resource configuration(s) and includes the second SN configuration in the SN Request Acknowledge message. In some implementations, the S-SN 104A generates the second SN configuration as a delta configuration on top of the first SN configuration. In some implementations, the S-SN 104A generates one or more LTM CSI report configuration(s) for the UE 102 based on the LTM CSI resource configuration(s) and includes the LTM CSI report configuration(s) in the second SN configuration.

[0155] In some implementations, the SN Request message 663 includes 6) a LTM SSB configuration (e.g.. a SSB Positions in Burst IE) for the first cell. In some implementations, the MN 104B receives the LTM SSB configuration in the SN Request Acknowledge message 607 from the C-SN 106 A. In some alternative implementations, the SN Request message 663 does not include a LTM SSB configuration for the first cell. In this case, the S-SN 104A obtains a SSB configuration (similar to the LTM SSB configuration) for the first cell from the 0AM node. In yet other implementations, the S-SN 104A obtains the SSB configuration from the C-SN 106 in an Xn Setup procedure (i.e., the Xn Setup Request message and Xn Setup Response message) with the C-SN 106 A. In yet other implementations, the S-SN 104A obtains the SSB configuration from the C-SN 106 in an NG-RAN node Configuration Update procedure (i.e.. the NG-RAN node Configuration Update message and the NG-RAN node Configuration Update Acknowledge message) with the C-SN 106A. In some implementations, the S-SN 104A uses LTM SSB configuration or the SSB configuration to determine a TA value received for the UE 102 in the early TA acquisition procedure 682. In some implementations, the S-SN 104A uses the LTM SSB configuration to generate the LTM CSI report configuration(s).

[0156] In some implementations, the SN Request message 663 and SN Request Acknowledge message 664 are an LTM Configuration Update message and an LTM Configuration Update Acknowledge message, respectively.

[0157] In some alternative implementations, the MN 104B includes some or all of the above configurations 1) - 6) in the SN Confirm message instead of the SN Request message 663. If the MN 104B includes the LTM CSI resource configuration(s) in the SN Confirm message, the S-SN 104A may transmit a SN message including the second SN configuration to the MN 104B. Tn some implementations, the SN message is a SN Modification RequiredPATENT APPLICATION Attorney Docket No.: G11438010070WO message. Tn response to the SN Modification Required message, the MN 104B may transmit a SN Modification Confirm message to the S-SN 104 A. In other implementations, the SN message is a RRC Transfer message.

[0158] In some implementations, the CU 172 generates a LTM candidate configuration (i.e., LTM candidate configuration 1) including the first SCG LTM candidate configuration and / or the LTM MCG configuration (if received from the DU 174 of the MN 104B in event 662) to configure the first cell for LTM. In some implementations, the LTM candidate configuration is a message (e.g., a RRC reconfiguration message). If the CU 172 receives the SCG LTM reference configuration and / or the MCG LTM reference configuration as described above, the CU 172 generates an LTM reference configuration (i.e.. a container) including the SCG LTM reference configuration and / or the MCG LTM reference configuration. In some implementations, the LTM reference configuration is a message (e.g., a RRC reconfiguration message). The CU 172 generates at least one RRC reconfiguration message(s) for the UE 102, including the second SN configuration, a tuple of the LTM candidate configuration and a configuration ID, and / or the LTM reference configuration. The CU 172 transmits 61 the RRC reconfiguration message(s) to the UE 102 via the DU 174. In response to each of the RRC reconfiguration message(s), the UE 102 transmits 620 an RRC reconfiguration complete message to the CU 172 via the DU 174. After receiving 620 the RRC reconfiguration complete message, the CU 172 may transmit 621 a SN Complete message (e.g., SN Reconfiguration Complete message) to the S-SN 104A, indicating that the UE 102 receives the second SN configuration. The UE 102 may include a SN configuration complete indication in the RRC reconfiguration complete message 620 and the MN 104B may include the SN configuration complete indication in the SN Complete message. In some implementations, the second SN configuration and the SN configuration complete indication are a RRC reconfiguration message and a RRC reconfiguration complete message, respectively. In some implementations, the SN Confirm message and the SN Complete message can be combined as a single SN message which can be a SN Confirm message or a SN Complete message as described above.

[0159] In some implementations, the MN 104B assigns the configuration ID (e.g.. LTM ID 1) for identifying the LTM candidate configuration including the first SCG LTM candidate configuration and / or the LTM MCG configuration. In other implementations, the MN 104B receives the configuration ID from the S-SN 104A as described above and associates the configuration ID with the LTM candidate configuration.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0160] The events 603, 604-1, 604-2, 605, 690, 607, 660, 662,609, 663, 664, 616, 620, and 621 are collectively referred to in Fig. 6 as an inter-SN LTM preparation procedure 681A.

[0161] In some implementations, the SN Required message and the SN Confirm message are aSN Change Required message and aSN Change Confirm message, respectively. In other implementations, the SN Required message and the SN Confirm message are a SN Modification Required message and a SN Modification Confirm message, respectively. In some implementations, the SN Request message and the SN Request Acknowledge message are a SN Addition Request message and a SN Addition Request Acknowledge message, respectively. In other implementations, the SN Request message and the SN Request Acknowledge message are a SN Modification Request message and a SN Modification Request Acknowledge message, respectively.

[0162] In some implementations, if the C-SN 106A is a distributed base station, the CU of the C-SN 106 A might request a SCG LTM reference DU configuration from the DU of the C-SN 106A in the procedure 690, as described for Figs. 3, 4 and 5. For example, the CU includes a reference configuration request indicator in the first CU-to-DU message for this request. If the DU supports the request (e.g., the reference configuration request indicator), the DU might transmit a SCG LTM reference DU configuration to the CU in the first DU-to-CU message of the procedure 690, as described for Figs. 3, 4 and 5. The CU then generates the SCG LTM reference configuration including the SCG LTM reference DU configuration.

[0163] In some implementations, the S-SN 104A (e.g., the CU of the S-SN 104 A) may obtain a SCG LTM reference configuration, as described for Figs. 3 and 4. In other implementations, the S-SN 104A may receive a SCG LTM reference configuration from the MN 106B (not shown in Fig. 6) in another inter-SN LTM preparation procedure as described above and below. If the S-SN 104A obtains a SCG LTM reference configuration, the S-SN 104 A may include the SCG LTM reference configuration (S-SN generated LTM reference configuration) in the SN Required message. In turn, the MN 104B includes the SCG LTM reference configuration in the SN Request message. Alternatively, the S-SN 104A determines to request or cause the C-SN 106A to provide a complete SCG LTM candidate configuration so that the S-SN 104A does not transmit the SCG LTM reference configuration to the C-SN 106 A. If the S-SN 104A does not obtain a SCG LTM reference configuration, the S-SN 104A does not include a SCG LTM reference configuration in the SN Required message. If the SN Required message includes a SCG LTM reference configuration, the MN 104B includes thePATENT APPLICATION Attorney Docket No.: G11438010070WO SCG LTM reference configuration in the SN Request message. Otherwise, if the SN Required message does not include a SCG LTM reference configuration, the MN 104B may not include the SCG LTM reference configuration in the SN Request message.

[0164] If the SN Request message 605 includes a SCG LTM reference configuration as described above, the CU of the C-SN 106A may include the SCG LTM reference configuration in the first CU-to-DU message. Alternatively, the CU 172 may retrieve a SCG LTM reference DU configuration from the SCG LTM reference configuration and includes the SCG LTM reference DU configuration in the first CU-to-DU message. Otherwise, if the SN Request message does not include a SCG LTM reference configuration, the CU of the C-SN 106A may or may not receive a SCG LTM reference DU configuration from the DU of the C-SN 106A as described for Fig. 3. If the CU receives a SCG LTM reference DU configuration (e.g., in the first DU-to-CU message), the CU generates a SCG LTM reference configuration (C-SN generated LTM reference configuration) including the SCG LTM reference DU configuration. The CU of the C-SN 106A may include a SCG LTM reference CU configuration (candidate CU (C-CU) generated LTM reference CU configuration).Otherwise, if the CU of the C-SN 106A does not receive a SCG LTM reference DU configuration from the DU of the C-SN 106A as described for Fig. 3, the CU does not generate a SCG LTM reference configuration. Alternatively, the CU generates a SCG LTM reference configuration (C-SN generated SCG LTM reference configuration) only including a C-CU generated SCG LTM reference CU configuration. In cases where the CU generates a LTM reference configuration (C-SN generated LTM reference configuration), the CU includes the C-SN generated LTM reference configuration in the SN Request Acknowledge message 607.

[0165] In some implementations, if the LTM DU configuration 1 is a complete configuration, the CU of the C-SN 106A generates the first SCG LTM candidate configuration as a complete configuration. The CU may include a complete configuration indication (e.g., a BS-to-BS interface protocol field / IE) in the SN Request Acknowledge message to indicate that the first SCG LTM candidate configuration is a complete configuration. In some implementations, the BS-to-BS interface protocol is an Xn application protocol defined in 3GPP specification 38.423. In some implementations, the complete configuration indication is a new field / IE (e.g., LTM specific) to avoid an impact to non-LTM configurations. In other implementations, the complete configuration indication is an existing field / IE defined in 3GPP specification 38.423. Otherwise, if the LTM DUPATENT APPLICATION Attorney Docket No.: G11438010070WO configuration 1 is a delta configuration, the CU generates the first SCG LTM candidate configuration as a delta configuration. The CU may exclude the complete configuration indication from the SN Request Acknowledge message to indicate that the first SCG LTM candidate configuration is a delta configuration. Alternatively, the CU may include a delta configuration indication (e.g., a BS-to-BS interface protocol field / IE) in the SN Request Acknowledge message to indicate that the first SCG LTM candidate configuration is a delta configuration. In some implementations, the BS-to-BS interface protocol is an Xn application protocol defined in 3GPP specification 38.423. In some implementations, the delta configuration indication is a new field / IE (e.g., LTM specific) to avoid an impact to non-LTM configurations. In other implementations, the delta configuration indication is an existing field / IE defined in 3GPP specification 38.423. In some implementations, the BS-to-BS interface protocol field / IE have two values (i.e., a first value and a second value). The BS-to-BS interface protocol field / IE set to the first value is the complete configuration indication and the BS-to-BS interface protocol field / IE set to the second value is the delta configuration indication.

[0166] To prepare the first cell as a candidate LTM cell for the UE 102, the CU of the S-SN 104A performs a LTM CSI report configuration and / or LTM ID configuration procedure (not shown in Fig. 6) with an S-DU of the S-SN 104A, similar to the procedure 392 or 492. In the LTM CSI report configuration and / or LTM ID configuration procedure, the CU of the S-SN 104A transmits the LTM CSI resource configuration(s) and / or the LTM SSB configuration to the S-DU of the S-SN 104A. In response, the CU of the S-SN 104A receives the LTM CSI report configuration(s) for the UE 102 from the S-DU of the S-SN 104A.

[0167] In some implementations, the CU of the C-SN 106A receives early synchronization information for the first cell and / or PDCCH order information from the DU of the C-SN 106 A, as described for Fig. 5. In some implementations, the early synchronization information includes a RACH configuration (e.g., RACH configuration 1) and / or at least one TCI state configurations (e.g., TCI state configuration(s) 1). The CU of the C-SN 106A includes the early synchronization information and / or the PDCCH order information in the SN Request Acknowledge message. The MN 104B includes the early synchronization information and / or the PDCCH order information in the SN Confirm message or in the SN Request to S-SN 104 A.PATENT APPLICATION Attorney Docket No.: G11438010070WO [01681 Tf the SN Request message or the SN Confirm message includes the PDCCH order information (PDCCH order information 1), the S-SN 104A may perform an early TA acquisition procedure 682 with the UE 102, the MN 104B, and the C-SN 106A. In the procedure 682. the S-SN 104A transmits a PDCCH order to the UE 102, based on the PDCCH order information. If the S-SN 104A is a distributed base station, the CU of the S-SN 104 A transmits the PDCCH order information to the S-DU of the S-SN 104A and the S-DU transmits the PDCCH order to the UE 102. In some implementations, the S-SN 104A or the S-DU may determine to transmit the PDCCH order, based on (e.g., in response to) the measurement report(s). In some implementations, the S-SN 104A or the S-DU may determine a SSB index included in the PDCCH order, based on LI measurement report(s), and / or the CSI resource configuration, the CSI report configuration and / or the LTM SSB configuration. In some implementations, the S-DU or the S-SN 104A includes the LTM ID 1 in the PDCCH order to indicate the first cell. The UE 102 transmits a RA preamble to the DU of the C-SN 106A on the first cell, using the RACH configuration and / or the PDCCH order information. The S-DU or the S-SN 104A derives a TA value based on the RA preamble. The DU of the C-SN 106A transmit DU-CU TA Information Transfer message including the TA value to the CU of the C-SN 106 A. The CU of the C-SN 106A transmits a CU-CU TA Information Transfer message (e.g., TA Information Transfer) including the TA value, the first cell ID, and the associated TA information for the UE 102 to the MN 104B (e.g., the CU 172 of the MN 104B). The MN 104B transmits a CU-CU TA Information Transfer message including the TA value, the first cell ID, and the associated TA information for the UE 102 to the S-SN 104 A. In some implementations, the DU of the C-SN 106A includes the cell ID 1, the RA preamble index, a RA-RNTI, and / or the DU ID of the S-DU of the S-SN 104A in the DU-CU TA Information Transfer message. In some implementations, the CU of the C-SN 106A includes the cell ID 1, the RA preamble index, the RA-RNTI, and / or the DU ID of the S-DU in the CU-CU TA Information Transfer message to the MN 104B. The MN 104B then includes the cell ID 1, the RA preamble index, the RA-RNTI, and / or the DU ID of the S-DU in the CU-CU TA Information Transfer message.

[0169] In response to determining to command the UE 102 to perform a LTM cell switch to the first cell, e.g., based on the LI or L3 measurement report(s) 654 or other LI or L3 measurement report(s) received before the event 654, the S-DU or the S-SN 104A transmits 626 a LTM Cell Switch Command including the configuration ID to the UE 102. In response to the LTM Cell Switch Command, the UE 102 may stop communication on the servingPATENT APPLICATION Attorney Docket No.: G11438010070WO cell(s). The S-SN 104A also transmits 627 to the MN 104B a CU-to-CU Cell Switch Notification message (e.g., Cell Switch Notification) including the first cell ID and / or the first TCI State ID. The MN 104B then transmits 628 to the C-SN 106A a CU-to-CU Cell Switch Notification message including the first cell ID and / or the first TCI State ID. The UE 102 and the DU of the C-SN 106A identify the first one of the TC state configuration(s) based on the first TCI state ID and apply the first TCI state configuration to communicate UL transmissions and / or DE transmissions in events 632, 636 and / or 640.

[0170] In response to the LTM Cell Switch Command, the UE 102 accesses 632 the first cell and transmits 636 the RRC reconfiguration complete message to the CU 172 via the DU 174. In some implementations, the RRC reconfiguration complete message includes the configuration ID and / or a SN configuration complete indication. For example, the SN configuration indication is an RRCReconfigurationC omplete message. After receiving 636 the RRC reconfiguration complete message, the CU 172 transmits 638 a SN Complete message (e.g., SN Reconfiguration Complete message). In some implementations, the CU 172 includes the SN configuration complete message in the SN Complete message. The C-SN 106A might transmit 639 a LTM Success message including the first cell ID or the configuration ID to the CU 172.

[0171] After (e.g., in response to) the event 627, 637, or 639, the CU 172 may transmit 665 a CU-to-DU message (e.g., UE Context Modification Request message) including the cell ID 1 and / or the configuration ID to the DU 174. In some implementations, the CU-to-DU message includes a LTM-executed indicator. The LTM-executed indicator, the cell ID 1, and / or the configuration ID indicates that a LTM cell switch to the first cell has been executed. In some implementations, the LTM-executed indicator is an LTM Trigger lE / field (e.g., under an Inter -SN LTM MCG Information IE or Inter -CU SCG LTM MCG Information IE) and the LTM Trigger lE / filed is set to "LTM-executed’. In response to or based on the LTM-executed indicator, the cell ID 1, and / or the configuration ID, the DU 174 identifies the LTM MCG configuration and applies 656 the LTM MCG configuration to communicate with the UE 102 in event 640. In other implementations, instead of including the LTM executed indicator, the CU 172 includes, in the CU-to-DU message, a newly defined container (e.g.. F1AP IE, Inter-SN LTM MCG Information IE or Inter -CU SCG LTM MCG Information IE) to indicate that the LTM cell switch to the first cell has been executed. The newly defined container may include the cell ID 1 and / or the configuration ID. Based on the newly defined container, the cell ID 1 and / or the configuration ID, the DU 174 identifies the LTM MCGPATENT APPLICATION Attorney Docket No.: G11438010070WO configuration and applies 656 the LTM MCG configuration in communication with the UE 102 in event 640. The DU 174, in response to the CU-to-DU message 665, might transmit 666 a DU-to-CU message (e.g., UE Context Modification Response message) to the CU 172 of the MN 104B. After (e.g.. in response to) the event 637, 639 or 665, the CU 172 might transmit 644 to the S-SN 104A a SN Request message (e.g., SN Modification Request message or a SN Release Request message) to inform the S-SN 104A to stop transmitting to the UE 102.

[0172] After event 632 or 638, the C-SN 106A communicates 640 with the UE 102 operating in DC with the MN 104B and the C-SN 106A. If the MN 104B transmits the LTM MCG configuration and / or the MCG LTM reference configuration, the MN 104B communicates 640 with the UE 102 on the same serving cell in accordance with the LTM MCG configuration and / or the MCG LTM reference configuration. The C-SN 106A communicates with the UE 102 on the first cell in accordance with the first SCG LTM candidate configuration and / or the SCG LTM reference configuration.

[0173] In some implementations, after (e.g., in response to) event 632, 638, or receiving the SN Status Transfer message as described below or an Access Success message indicating the UE 102 successfully accesses the first cell, the (CU of the) C-SN 106A performs a PDU Session path update procedure with the CN 110 (not show n in Fig. 6. The CU receives the Access Success message from the DU of the C-SN 106 A, similar to event 334 or 434. In the PDU Session path update procedure, the (CU of the) C-SN 106A sends a PDU Session Resource Modify Indication message to the CN 110 (e.g., AMF). The PDU Session Resource Modify' Indication message is to request a switch of a downlink termination point of a UP transport bearer (e.g., NG-U transport bearer) from an old termination point (e.g., the S-SN 104A or the S-CU of the S-SN 104A) towards a new termination point (e.g., the C-SN 106A or the CU of the C-SN 106A). In response to the PDU Session Resource Modify Indication message, the CN 110 (e.g., AMF) switches the downlink termination point of the UP transport bearer from the old termination point towards the new termination point. In response to the PDU Session Resource Modify Indication message, the CN 110 (e.g., AMF) transmits a PDU Session Resource Modify Confirm message to the CU 172. After the PDU Session path update procedure, the CN 110 (e.g., UPF) communicates UP data with the UE 102 via the S-BS 106 A and the UP transport bearer.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0174] Tn some implementations, if the S-DU or the S-SN 104A receives a TA value as described above, the S-DU or the S-SN 104A may include the TA value in the LTM Cell Switch Command. In some implementations, the S-DU or the S-SN 104A includes a first TCI state ID in the LTM Cell Switch Command. The first TCI state ID indicates a first one of the TCI state configuration(s).

[0175] In some implementations, after (e.g., in response to) determining to command the UE 102 to perform the LTM cell switch or transmitting 626 the LTM Cell Switch Command, the S-SN 104A transmits one or more Early Status Transfer messages to the MN 104B, each including a DL COUNT value or a DISCARD DL COUNT value for a DRB over which the UE 102 and the S-SN 104A communicate 602 data with each other. The MN 104B transmits one or more Early Status Transfer messages to C-SN 106 A, each including the DL COUNT value or the DISCARD DL COUNT value for the DRB over which the UE 102 and the S-SN 104A communicate 602 data with each other.

[0176] In some implementations, after (e.g., in response to) determining to command the UE 102 to perform the LTM cell switch, transmitting 626 the LTM Cell Switch Command, receiving the DU-CU Cell Switch Notification message from the S-DU, or receiving 644 the SN Request message, the S-SN 104A (e.g., the CU of the S-SN 104A) transmits a SN Status Transfer message to the MN 104B, including a DL COUNT value and / or a UL COUNT value for a / the DRB over which the UE 102 and the S-SN 104A communicate 602 data with each other. After (e.g., in response to) receiving the SN Status Transfer message from the S-SN 104A, the MN 104B transmits a SN Status Transfer message to the CU 172, including the DL COUNT value and / or the UL COUNT value.

[0177] In some implementations, before or after transmitting the LTM Cell Switch Command as described above, the S-SN 104A, the MN 104B, and / or one or more C-SNs (including the C-SN 106 A) perform additional inter-SN LTM preparation procedure(s) 2, ... , N to prepare cell(s) 2, ...N for LTM, respectively. The cell(s) 2, ... , N are identified by cell ID(s) 2, ... , N respectively. N is an integer larger than 1. Each of the inter-SN LTM preparation procedure(s) 2, ... , N is similar to the procedure 681 A. In the procedure(s) 2, .., N, the MN 104B may obtain tuple(s) {LTM ID 2, the LTM candidate configuration 2, the LTM CSI resource configuration 2 (if obtained), the TCI state configuration 2 (if obtained), the RACH configuration 2 (if obtained), the LTM SSB configuration 2 (if obtained)}, ... , {the LTM ID N, the LTM candidate configuration N, the LTM CSI resource configuration N,PATENT APPLICATION Attorney Docket No.: G11438010070WO the TCI state configuration(s) N (if obtained), the RACH configuration N (if obtained), the LTM SSB configuration N (if obtained)} for the cell(s) 2, ... , N respectively. In some implementations, the MN 104B transmits the tuple(s) to the UE 102 in LTM configuration delivery procedure(s) 2, ... , N. each is similar to events 616 and 620. In other implementations, the MN 104B includes the tuple(s) in the RRC reconfiguration message(s) 616.

[0178] In some implementations, the S-SN 104A may include the cell ID(s) 2, ... , N in the SN Required message 603. In some implementations, the MN 104B may include the cell ID(s) 2, ... , N in the SN Request message 605. In some implementations, the S-SN 104A includes one or more measurement results of the cell(s) 2. .... N in the SN Required message as described for the first cell. In some implementations, the MN 104B includes the one or more measurement results of the cell(s) 2, ... , N in the SN Request message as described for the first cell. In some implementations, the C-SN 106A may determine to prepare the first cell for LTM and not to prepare the cell(s) 2, ... , N for LTM. In some implementations, the C-SN 106A makes the determination based on capacity of the C-SN 106A and / or the measurement results of the first cell and the cell(s) 2, ... , N.

[0179] Next, several example methods, which can be implemented in a RAN node (e.g., a base station, a MN, a SN, a DU or a CU as described above), for LTM, are discussed next with reference to Figs. 7A-13. Descriptions and example implementations described for Figs.3-6 can apply to Figs. 7A-13. Similar steps are similarly labeled (e.g., 302, 402, 502, 602, etc.) and individual descriptions are therefore omitted.

[0180] Fig. 7A illustrates an example method 700 A, which can be implemented by a first RAN node (e.g., the S-BS 104A or the C-BS 106A in Fig. 5, the MN 104B, the S-SN 104A or the C-SN 106A in Fig. 6, or the CU 172 of the BS 104A, C-BS 106A, the MN 104B, the S-SN 104A or the C-SN 106A in Figs. 3-6). The method 700A begins at block 707, where the first RAN node performs a procedure to prepare configuration of radio resource for a UE (e.g., UE 102). At block 709, the first RAN node determines whether the procedure is for an LTM cell switch. In some implementations, the LTM cell switch is an intra-CU MCG LTM procedure, an inter-CU MCG LTM procedure, an inter-CU SCG LTM procedure, an intra-CU SCG LTM procedure, a combination of these procedures including a MCG LTM and a SCG LTM. or a (inter- or intra-) MCG LTM with a (simultaneous) SCG addition or change. In some implementations, the procedure for an LTM cell switch concerns a PCell or a PSCellPATENT APPLICATION Attorney Docket No.: G11438010070WO switch to take place at the first RAN node. In other implementations, the procedure for an LTM cell switch concerns a PCell switch to take place at a second RAN node (e.g., the MN 104B while the first RAN node is the S-SN 104A. the C-SN 106A, or a new added SN if the MN 104B initially operates in single connectivity with the UE alone). If the procedure is for the LTM cell switch (i.e., the ‘Yes’ branch), the flow proceeds from block 709 to block 715 where the first RAN node refrains from starting a timer in response to performing the procedure. If the procedure is not for the LTM cell switch (i.e., the ‘No’ branch) (e.g., the procedure is for immediate mobility such as immediate handover or immediate SN change), the flow proceeds from block 709 to block 711 A where the first RAN node starts the timer in response to performing the procedure and the timer protects validity of the configuration. The flow may further proceed from block 711 A to block 732 where the first RAN node detects that the UE accesses on the radio resources and then proceed from block 732 to block 713 A where the first RAN node stops the timer in response to block 732. Alternatively, the flow may proceed from block 711 A to block 738 where the first RAN node receives a message from the UE or a second RAN node and then proceed from block 738 to block 713A where the first RAN node stops the timer in response to block 738. Alternatively, the flow may proceed from block 711 A to block 734 where the first RAN node receives an Access Success message from a DU and then proceed from block 734 to block 713A where the first RAN node stops the timer in response to block 734. In cases that the timer expires before any of the blocks 732, 738, or 734, the corresponding actions for the first RAN node and / or the second RAN node are described in later example methods (e.g., method 900, 1000, 1100, or 1300).

[0181] In some implementations, instead of the determination of whether the procedure is for an LTM cell switch at block 709, the first RAN node determines whether the procedure is for a conditional mobility (e.g., conditional handover (CHO), conditional PSCell addition or change (CP AC), or CHO with SCG addition or change) at block 709. If the procedure is for conditional mobility7, the flow proceeds from block 709 to block 715. Otherwise, if the procedure is not for conditional mobility, the flow proceeds from block 709 to block 711 A and may proceed to block 732, 738, or 734, and then to block 713 A.

[0182] In other implementations, in addition to the determination of whether the procedure is for an LTM cell switch at block 709, the first RAN node also determines whether the procedure is for a conditional mobility7at block 709. If the procedure is for conditional mobility7, the flow proceeds from block 709 to block 715. Otherwise, if the procedure is notPATENT APPLICATION Attorney Docket No.: G11438010070WO for conditional mobility, the flow proceeds from block 709 to block 711 A and may proceed to block 732, 738, or 734, and then to block 713A.

[0183] Fig. 7B illustrates an example method 700B similar to the method 700 A, except that the method 700B has blocks 71 IB, 713B, 746, and 748 instead of blocks 711 A, 713A, and 715. The method 700B can be implemented by a first RAN node (e.g., the S-BS 104A or the C-BS 106A in Fig. 5, the MN 104B. the S-SN 104A or the C-SN 106A in Fig. 6. or the CU 172 of the BS 104A, C-BS 106A, the MN 104B, the S-SN 104A or the C-SN 106A in Figs. 3-6). The method 700B begins at block 707, where the first RAN node performs a procedure to prepare configuration of radio resource for a UE (e.g., UE 102). At block 709, the first RAN node determines whether the procedure is for an LTM cell switch. The example implementations for the LTM cell switch described for the method 700A can also be applied to the method 700B and the following methods (i.e., method 800 A, 800B, 900, 1000, 1100, 1200, or 1300) unless there is a further clarification.

[0184] If the procedure is not for the LTM cell switch (i.e., the ‘No’ branch) (e.g., the procedure is for immediate mobility such as immediate handover or immediate SN change), the flow proceeds from block 709 to block 71 IB where the first RAN node starts a first timer with a first timer value in response to performing the procedure and the timer protects validity’ of the configuration. The flow may further proceed from block 71 IB to block 732 and then proceed from block 732 to block 713B where the first RAN node stops the first timer in response to block 732. Alternatively, the flow may proceed from block 71 IB to block 738 and then proceed from block 738 to block 713B where the first RAN node stops the first timer in response to block 738. Alternatively, the flow may proceed from block 71 IB to block 734 and then proceed from block 734 to block 713B where the first RAN node stops the first timer in response to block 734. In cases that the first timer expires before any of the blocks 732, 738, or 734, the corresponding actions for the first RAN node and / or the second RAN node are described in later example methods (e.g., method 900, 1000, 1100, or 1300).

[0185] If the procedure is for the LTM cell switch (i.e., the ‘Yes’ branch), the flow proceeds from block 709 to block 746 where the first RAN node starts a second timer with a second timer value in response to performing the procedure and the timer protects validity7of the configurations, where the second timer value is larger than the first timer value. The flow may further proceed from block 746 to block 732 and then proceed from block 732 to block 748 where the first RAN node stops the second timer in response to block 732. Alternatively,PATENT APPLICATION Attorney Docket No.: G11438010070WO the flow may proceed from block 746 to block 738 and then proceed from block 738 to block 748 where the first RAN node stops the second timer in response to block 738. Alternatively, the flow may proceed from block 746 to block 734 and then proceed from block 734 to block 748 where the first RAN node stops the second timer in response to block 734. In cases that the second timer expires before any of the blocks 732, 738, or 734, the corresponding actions for the first RAN node and / or the second RAN node are described in later example methods (e.g., method 900, 1000, or 1100).

[0186] In some implementations, the first timer and the second timer are the same timer (i.e., refer to the same timer instance). In other implementations, the first timer and the second timer are different timers (i.e., refer to different timer instances).

[0187] In some implementations, instead of the determination of whether the procedure is for an LTM cell switch at block 709, the first RAN node determines whether the procedure is for a conditional mobility at block 709. If the procedure is for conditional mobility, the flow proceeds from block 709 to block 746 and may proceed to block 732, 738, or 734 and then to block 748. Otherwise, if the procedure is not for conditional mobility, the flow proceeds from block 709 to block 71 IB and may proceed to block 732, 738, or 734, and then to block 713B.

[0188] In other implementations, in addition to the determination of whether the procedure is for an LTM cell switch at block 709, the first RAN node also determines whether the procedure is for a conditional mobility at block 709. If the procedure is for conditional mobility, the flow proceeds from block 709 to block 746 and may proceed to block 732, 738, or 734 and then to block 748. Otherwise, if the procedure is not for conditional mobility, the flow proceeds from block 709 to block 71 IB and may proceed to block 732, 738, or 734, and then to block 713B.

[0189] Fig. 8 A illustrates an example method 800A similar to methods 700A or 700B, which can be implemented by an RAN node (e.g., the S-SN 104A or the C-SN 106A, or the CU 172 of the S-SN 104A or the C-SN 106A in Fig. 6). The method 800A begins at block 805, where the RAN node receives an SN Request message (e.g., S-Node Addition Request message or S-Node Modification Request message) for preparing radio resources for a UE (e.g., the UE 102) from an MN (e.g., the MN 104B in Fig. 6). At block 807, the RAN node transmits a SN Request Acknowledge message (e.g., S-Node Addition Request Acknowledge message or S-Node Modification Request Acknowledge message) for preparing radio resources for a UE to the MN. At block 809, the RAN node determines whether thePATENT APPLICATION Attorney Docket No.: G11438010070WO procedure is for an LTM cell switch. If the procedure is for the LTM cell switch (i.e., the ‘Yes’ branch), the flow proceeds from block 809 to block 815 where the RAN node refrains from starting a timer TXnncoveraii in response to receiving the SN Request message or transmitting the SN Request Acknowledge message. If the procedure is not for the LTM cell switch (i.e., the ‘No’ branch) (e.g., immediate SN change), the flow proceeds from block 809 to block 811 A where the RAN node starts the timer TXnncoveraii in response to receiving the SN Request message or transmitting the SN Request Acknowledge message. The timer TXnocoveraii protects validity of the configuration. The flow may further proceed from block 811 A to block 732 where the RAN node detects that the UE accesses on the radio resources and then proceed from block 732 to block 813A where the RAN node stops the timer TXnncoveraii in response to block 732. Alternatively, the flow may proceed from block 811A to block 838 where the RAN node receives a SN message (e.g., S-Node Reconfiguration Complete message) from the MN and then proceed from block 838 to block 813A where the RAN node stops the timer TXnncoveraii in response to block 838. Alternatively, the flow may proceed from block 811 A to block 734 where the RAN node receives an Access Success message from a DU and then proceed from block 734 to block 813 A where the RAN node stops the timer TXnncoveraii in response to block 734.

[0190] In some implementations, the timer TXnncoveraii, as described in 3GPP specification 38.423. specifies the maximum time in the S-NG-RAN node for either the S-NG-RAN node initiated S-NG-RAN node Modification procedure or the protection of the NG-RAN actions necessary' to configure UE resources at S-NG-RAN node Addition or M-NG-RAN node initiated S-NG-RAN node Modification. The timer TXnncoveraii can be used to protect the validity of the SN / SCG configuration generated by the SN.

[0191] In some implementations, instead of the determination of whether the procedure is for an LTM cell switch at block 809, the RAN node determines whether the procedure is for a conditional mobility at block 809. If the procedure is for conditional mobility7, the flow proceeds from block 809 to block 815. Otherwise, if the procedure is not for conditional mobility, the flow proceeds from block 809 to block 811 A and may proceed to block 732, 838, or 734, and then to block 813A.

[0192] In other implementations, in addition to the determination of whether the procedure is for an LTM cell switch at block 809, the first RAN node also determines whether the procedure is for a conditional mobility at block 809. If the procedure is for conditionalPATENT APPLICATION Attorney Docket No.: G11438010070WO mobility, the flow proceeds from block 809 to block 815. Otherwise, if the procedure is not for conditional mobility, the flow proceeds from block 809 to block 811 A and may proceed to block 732, 838, or 734, and then to block 813A.

[0193] Fig. 8B illustrates an example method 800B similar to the method 800A except that the method 800B has blocks 81 IB, 813B, 846, and 848 instead of blocks 811A, 813 A, and 815. The method 800B can be implemented by an RAN node (e.g., the S-SN 104A or the C-SN 106A, or the CU 172 of the S-SN 104A or the C-SN 106A in Fig. 6). The method 800B proceeds from block 805 to 807 and then to 809. At block 809, the RAN node determines whether the procedure is for an LTM cell switch. If the procedure is for the LTM cell switch (i.e., the "Yes’ branch), the flow proceeds from block 809 to block 846 where the RAN node starts a second timer with a second timer value in response to receiving the SN Request message or transmitting the SN Request Acknowledge message, where the second timer value is larger than a first timer value at block 81 IB. The flow' may proceed from block 846 to block 732 or 838 or 734 and then to block 848 where the RAN node stops the second timer in response to block 732, 838, or 734 (similar to method 700B). If the procedure is not for the LTM cell switch (i.e., the ‘No’ branch) (e.g., immediate SN change), the flow proceeds from block 809 to block 81 IB where the RAN node starts a first timer with the first timer value in response to in response to receiving the SN Request message or transmitting the SN Request Acknowledge message. The first timer and the second timer protect validity of the configuration. The flow may further proceed from block 81 IB to block 732, 838, or 734 and then proceed to block 813B where the RAN node stops the first timer in response to block 732, 838, or 734.

[0194] In some implementations, the first timer and the second timer are the same timer (i.e., refer to the same timer instance). In other implementations, the first timer and the second timer are different timers (i.e., refer to different timer instances).

[0195] In some implementations, instead of the determination of whether the procedure is for an LTM cell switch at block 809, the first RAN node determines whether the procedure is for a conditional mobility at block 809. If the procedure is for conditional mobility, the flow proceeds from block 809 to block 846 and may proceed to block 732, 838, or 734 and then to block 848. Otherwise, if the procedure is not for conditional mobility, the flow proceeds from block 809 to block 81 IB and may proceed to block 732, 838, or 734, and then to block 813B.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0196] Tn other implementations, in addition to the determination of whether the procedure is for an LTM cell switch at block 809, the first RAN node also determines whether the procedure is for a conditional mobility at block 809. If the procedure is for conditional mobility, the flow proceeds from block 809 to block 846 and may proceed to block 732, 838, or 734 and then to block 848. Otherwise, if the procedure is not for conditional mobility, the flow proceeds from block 809 to block 81 IB and may proceed to block 732, 838, or 734, and then to block 813B.

[0197] Examples and implementations described with reference to Figs. 7A and 7B can apply to Figs. 8A and 8B.

[0198] Fig. 9 illustrates an example method 900 related to the above described methods, which can be implemented by a first RAN node (e.g., the S-BS 104A or the C-BS 106A in Fig. 5, the MN 104B, the S-SN 104A or the C-SN 106A in Fig. 6, or the CU 172 of the BS 104 A, C-BS 106A, the MN 104B, the S-SN 104 A or the C-SN 106A in Figs. 3-6). The method 900 begins at block 707 and 711 A, where the first RAN node performs a procedure to prepare configuration of radio resource for a UE (e g., UE 102) and starts a timer in response to performing the procedure, the timer protects validity of the configurations. At block 917, the first RAN node detects the timer expires. At block 709, the first RAN node determines whether the procedure is for an LTM cell switch. If the procedure is for an LTM cell switch (i.e., the “YES'’ branch), the flow proceeds to block 921, where the first RAN node refrains from performing a release or cancellation procedure for releasing the configurations in response to the expiry of the timer. If the procedure is not for an LTM cell switch (i.e., the “NO” branch) (e.g., the procedure is for immediate mobility such as immediate handover or immediate SN change), the flow proceeds to block 919, where the first RAN node performs a release or cancellation procedure for releasing the configurations in response to the expiry of the timer.

[0199] In some implementations, the method 900 can also be applied to the expiry of the first timer described for the method 700B or 800B (i.e., the first RAN node may still perform a release or cancellation procedure for releasing the configurations in response to expiry of the first timer). In some implementations, in case that the second timer described for the method 700B or 800B expires while any of the blocks 732, 738, 734, or 838 has not happened, the first RAN node may still perform a release or cancellation procedure for releasing the configurations in response to expiry of the second timer. In otherPATENT APPLICATION Attorney Docket No.: G11438010070WO implementations, in case that the second timer described for the method 700B or 800B expires while any of the blocks 732, 738, 734, or 838 has not happened, the first RAN node may refrain from performing a release or cancellation procedure for releasing the configurations in response to expiry of the second timer.

[0200] In some implementations, the release procedure is an S-NG-RAN node initiated S-NG-RAN node Release procedure with an MN and the cancellation procedure is an S-NG-RAN node initiated S-NG-RAN node Modification with an MN for a UE as described in 3GPP specification 38.423. In other implementations, the release or cancellation procedure is a Handover Cancel or Conditional Handover Cancel procedure with a target or candidate RAN node for a UE as described in 3GPP specification 38.423. In yet another implementation, the release or cancellation procedure is a UE Context Release (gNB-CU initiated) procedure or a UE Context Modification (gNB-CU initiated) procedure with a DU for a UE.

[0201] Examples and implementations described with reference to Figs. 7A-8B can apply to Fig. 9.

[0202] Fig. 10 illustrates an example method 1000 similar to the method 900, 800 A, and 800B, which can be implemented by a RAN node (e.g., the S-SN 104A or the C-SN 106A in Fig. 6, or the CU 172 of the S-SN 104A or the C-SN 106A in Fig. 6). The method 1000 begins at block 805, 807, and 811A, where the RAN node receives an SN Request message for preparing radio resources for a UE from an MN, transmits an SN Request Acknowledge message for preparing radio resources for a UE to the MN, and starts a timer TXnDCoveraii in response to receiving the SN Request message or transmitting the SN Request Acknowledge message. At block 1017, the RAN node detects the timer TXnDCoveraii expires. At block 809, the RAN node determines whether the SN Request is for an LTM cell switch. If the procedure is for an LTM cell switch (i.e., the “YES'’ branch), the flow proceeds to block 1021, where the RAN node refrains from triggering an SN release procedure with the MN in response to the expiry of the timer TXnDCoveraii. If the procedure is not for an LTM cell switch (i.e., the “NO” branch) (e.g., the procedure is for immediate mobility such as immediate handover or immediate SN change), the flow proceeds to block 1019, where the RAN node performs a SN release procedure with the MN in response to the expiry of the timer TXnDCoveraii.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0203] Tn some implementations, the SN release procedure is an S-NG-RAN node initiated S-NG-RAN node Release procedure with the MN and the cancellation procedure is an S-NG-RAN node initiated S-NG-RAN node Modification with the MN as described in 3GPP specification 38.423.

[0204] Examples and implementations described with reference to Figs. 7A-9 can apply to Fig. 10.

[0205] Fig. 11 illustrates an example method 1100. which can be implemented by a RAN node (e.g., the S-SN 104A or the C-SN 106A in Fig. 6, or the CU 172 of the S-SN 104A or the C-SN 106A in Fig. 6). The method 1100 begins at block 1105, where the RAN node receives an SN Request message for LTM for a UE (e.g., UE 102) from an MN (e.g., MN 104B in Fig. 6). At block 1190, the RAN node may perform a LTM preparation procedure (i.e., a procedure to prepare configurations of radio resources for a UE for an LTM cell switch). At block 1107, the RAN node transmits an SN Request Acknowledge message for LTM for the UE to the MN. At block 1115, the RAN node refrains from starting a first timer TXnncoveraii for LTM when transmitting the SN Request Acknowledge message. At block 1113, the RAN node may start a second timer (other than the TXnocoveraii) for LTM when transmitting the SN Request Acknowledge message, where a timer value of the second timer is larger than a timer value of the first timer. At block 1117, the RAN node may detect the second timer expires. At block 1119, the RAN node may trigger an SN release procedure with the MN for the UE in response to expiry of the second timer.

[0206] In some implementations, the first timer and the second timer are the same timer (i.e., refer to the same timer instance). In other implementations, the first timer and the second timer are different timers (i.e., refer to different timer instances).

[0207] In some implementations, the SN Request message and the SN Request Acknowledge message is an S-Node Addition Request and an S-Node Addition Request Acknowledge message, respectively. In other implementations, the SN Request message and the SN Request Acknowledge message is an S-Node Modification Request and an S-Node Modification Request Acknowledge message, respectively.

[0208] Examples and implementations described with reference to Figs. 7A-10 can apply to Fig. 11.

[0209] Fig. 12 is a flowchart illustrating an example method 1200 of managing UE configurations for LTM cell switch, according to some implementations. The method 1200PATENT APPLICATION Attorney Docket No.: G11438010070WO may be performed by a RAN node (e g., the S-BS 104A or the C-BS 106A in Fig. 5, the MN 104B, the S-SN 104A or the C-SN 106A in Fig. 6, or the CU 172 of the BS 104A, C-BS 106A, the MN 104B, the S-SN 104A or the C-SN 106A in Figs. 3-6).

[0210] According to the method 1200, the RAN node performs 1207 a procedure to prepare a configuration of a radio resource for a UE. In some implementations, performance of the procedure includes receiving a SN Request message for preparing the configuration and transmitting a SN Request Acknowledge message for preparing the configuration.

[0211] In response to determining that the procedure is for LTM, the RAN node refrains 1215 from starting a timer based on performing the procedure. In some implementations, the procedure is for LTM cell switch. In some implementations, the timer is a TXnDCoveraii timer.

[0212] Examples and implementations described with reference to Figs. 7A-11 can apply to Fig. 12.

[0213] Fig. 13 is a flowchart illustrating an example method 1300 of managing UE configurations for LTM cell switch, according to some implementations. The method 1300 may be performed by a RAN node (e.g.. the S-BS 104A or the C-BS 106A in Fig. 5. the MN 104B, the S-SN 104A or the C-SN 106A in Fig. 6, or the CU 172 of the BS 104A, C-BS 106A, the MN 104B, the S-SN 104A or the C-SN 106A in Figs. 3-6).

[0214] According to the method 1300, the RAN node performs 1307 a procedure to prepare a configuration of a radio resource for a UE. In some implementations, performance of the procedure includes receiving a SN Request message for preparing the configuration and transmitting a SN Request Acknowledge message for preparing the configuration.

[0215] The RAN node starts 1311 a timer based on performing the procedure. In some implementations, the RAN node starts the timer in response to receiving the SN Request message. In some implementations, the RA node starts the timer in response to transmitting the SN Request Acknowledge message. In some implementations, the timer is a TXnDCoveraii timer.

[0216] The RAN node detects 1317 that the timer expires.

[0217] In response to determining that the procedure is for LTM, the RAN node refrains 1321 from performing a release or cancellation procedure for the configuration based on expiry of the timer. In some implementations, the release or cancellation procedure includes a secondary node, SN, Release procedure, a SN Modification procedure, a Handover CancelPATENT APPLICATION Attorney Docket No.: G11438010070WO procedure, a Conditional Handover Cancel procedure, a UE Context Release procedure, or a UE Context Modification procedure.

[0218] Examples and implementations described with reference to Figs. 7A-12 can apply to Fig. 13.

[0219] The following describes changes to 3GPP specification 38.423 to incorporate the methods above into the 3 GPP specification.

[0220] The changes may be made to § 8.3.1.2 “Successful Operation” include:

[0221] Interactions with the S-NG-RAN node Reconfiguration Completion procedure:

[0222] If the S-NG-RAN node admits at least one PDU session resource, the S-NG-RAN node shall start the timer TXnDCoveraii when sending the S-NODE ADDITION REQUEST ACKNOWLEDGE message to the M-NG-RAN node except for a request for conditional configuration or LTM configuration. The reception of the S-NODE RECONFIGURATION COMPLETE message shall stop the timer TXnDCoveraii if TXnDCoveraii is running.

[0223] The changes may be made to § 8.3.3.2 “Successful Operation” include:

[0224] Interactions with the S-NG-RAN node Reconfiguration Completion procedure:

[0225] If the S-NG-RAN node admits a modification of the UE context requiring the M-NG-RAN node to report about the success of the RRC connection reconfiguration procedure, the S-NG-RAN node shall start the timer TXnDCoveraii when sending the S-NODE MODIFICATION REQUEST ACKNOWLEDGE message to the M-NG-RAN node except for a request for conditional configuration or LTM configuration. The reception of the S-NG-RAN node RECONFIGURATION COMPLETE message shall stop the timer TXnDCoveraii if TXnDCoveraii is running.

[0226] FIG. 14 is a diagram 1400 illustrating an example of a hardware implementation for one or more network entities 104. The one or more network entities 104 may be a base station, a component of a base station, or may implement base station functionality’. The one or more network entities 104 may include, or may correspond to, at least one of the RU 176, the DU 174, or the CU 172. The CU 172 may include a CU processor 1446, which may have on-chip memory 1446'. In some aspects, the CU 172 may further include an additional module of memory 1456 and / or a communications interface 1448, both of which may be coupled to the CU processor 1446. The CU 172 can communicate with the DU 174 through aPATENT APPLICATION Attorney Docket No.: G11438010070WO midhaul link 1462, such as an Fl interface between the communications interface 1448 of the CU 172 and a communications interface 1428 of the DU 174.

[0227] The DU 174 may include a DU processor 1426, which may have on-chip memory 1426'. In some aspects, the DU 174 may further include an additional module of memory 1436 and / or the communications interface 1428, both of which may be coupled to the DU processor 1426. The DU 174 can communicate with the RU 176 through a fronthaul link 1460 between the communications interface 1428 of the DU 174 and a communications interface 1408 of the RU 176.

[0228] The RU 176 may include an RU processor 1406, which may have on-chip memory 1406'. In some aspects, the RU 176 may further include an additional module of memory 1416, the communications interface 1408, and one or more transceivers 1430, all of which may be coupled to the RU processor 1406. The RU 176 may further include antennas 1440, which may be coupled to the one or more transceivers 1430, such that the RU 176 can communicate through the one or more transceivers 1430 via the antennas 1440 with the UE 102.

[0229] The on-chip memory 1406', 1426', 1446' and the additional modules of memory71416, 1436, 1456 may each be considered a computer-readable medium I memory. Each computer-readable medium / memory may be non-transitory. Each of the processors 1406, 1426, 1446 is responsible for general processing, including execution of software stored on the computer-readable medium / memory. The software, when executed by the corresponding processor(s) 1406, 1426, 1446 causes the processor(s) 1406, 1426, 1446 to perform the various functions described herein. The computer-readable medium / memory¬ may also be used for storing data that is manipulated by the processor(s) 1406, 1426, 1446 when executing the software.

[0230] In examples, LTM controllers 150b and 150c may sit in the CU 172 and the DU 174, respectively. The LTM controllers 150b and 150c are configured to control CU 172 and DU 174 to perform LTM operations, such as those described above with reference to Figs. 6-13.

[0231] The LTM controllers 150b and 150c may be within one or more processors of the one or more network entities 104. The LTM controllers 150b and 150c may be one or more hardware components specifically configured to carry out the stated processes / algorithm, implemented by one or more processors 1406, 1426, 1446 configured to perform the statedPATENT APPLICATION Attorney Docket No.: G11438010070WO processes / algorithm, stored within a computer-readable medium for implementation by the one or more processors 1406, 1426, 1446, or a combination thereof.

[0232] Generally speaking, description for one of the above figures can apply to another of the above figures. Examples, implementations and methods described above can be combined, if there is no conflict. An event or block described above can be optional or omitted. For example, an event or block with dashed lines in the figures can be optional. The description described from the perspective of the receiving node also applies to the sending node. For example, a description that a receiving node (e.g., DU) receives a message from a sending node (e.g., CU) may be replaced by the sending node sending a message to the receiving node. Similarly, a description that a receiving node (e.g., CU) receives a message from a sending node (e.g., DU) may be replaced by the sending node sending a message to the receiving node.

[0233] In some implementations, '‘message” is used and can be replaced by “information element (IE)”, and vice versa. In some implementations, “IE” is used and can be replaced by “field”, and vice versa. In some implementations, “configuration” can be replaced by “configurations” or “configuration parameters”, and vice versa. In some implementations, the “LTM command” can be replaced by “serving cell change command”, “Layer 1 / Layer 2 LTM cell switch command”, “lower layer switching command” or “lower layer serving cell change command”. In some implementations, “some” means “one or more”. In some implementations, “at least one” means “one or more”. In some implementations, the “DU configuration” can be replaced by “cell group configuration”. In some implementations, the “cell index” can be replaced with “serving cell index”, “LTM cell index”, “special cell (SpCell) index’’, “PCell index” or “PSCell index”. In some implementations, the “serving” can be replaced by “source”. In some implementations, the “measurement report” can be replaced by “measurement result(s)” or “CSI report”. In some implementations, the “early TA acquisition” can be replaced by “early UL timing synchronization” or “early UL synchronization”. In some implementations, the “early TA acquisition on a / the candidate cell” can be replaced by “early UL timing synchronization with a / the candidate cell” or “early UL synchronization with a / the candidate cell”. In some implementations, “include” can be replaced by “comprise”. In some implementations, “exclude” can be replaced by '‘refrain from including”. In some implementations, "Handover Request” and "Handover Request Acknowledge” described above are for illustration of the invention and can be replaced by messages with general names. For example, "Handover Request” and "Handover RequestPATENT APPLICATION Attorney Docket No.: G11438010070WO Acknowledge” can be replaced by a first CU-to-CU message and a second CU-to-CU message, respectively. In another example, "Handover Request” and "‘Handover Request Acknowledge” can be replaced by a first interface message and a second interface message, respectively. In yet another example, "Handover Request” and "Handover Request Acknowledge” can be replaced by a first BS-to-BS message and a second BS-to-BS message, respectively. In some implementations, “SN Request”, “SN Confirm”, “SN Request” and “SN Request Acknowledge” described above are for illustration of the invention and can be replaced by messages with general names. For example, the "SN Required message” can be replaced by a SN-to-MN message. In another example, the “SN Confirm message” can be replaced by a MN-to-SN message.

[0234] A user device in which the techniques of this disclosure can be implemented (e.g. , the UE 102) can be any suitable device capable of wireless communications such as a smartphone, a tablet computer, a laptop computer, a mobile gaming console, a point-of-sale (POS) terminal, a health monitoring device, a drone, a camera, a media-streaming dongle or another personal media device, a wearable device such as a smartwatch, a wireless hotspot, a femtocell, or a broadband router. Further, the user device in some cases may be embedded in an electronic system such as the head unit of a vehicle or an advanced driver assistance system (ADAS). Still further, the user device can operate as an internet-of-things (loT) device or a mobile-internet device (MID). Depending on the type, the user device can include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0235] Certain embodiments are described in this disclosure as including logic or a number of components or modules. Modules may can be software modules (e.g., code, or machine-readable instructions stored on non-transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. A hardware module can comprise dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g., as encompassed 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 dedicated and permanently configured circuitry’, or in temporarilyPATENT APPLICATION Attorney Docket No.: G11438010070WO configured circuitry (e.g, configured by software) may be driven by cost and time considerations.

[0236] When implemented in software, the techniques can be provided as part of the operating system, a library' used by multiple applications, a particular software application, etc. The software can be executed by one or more general-purpose processors or one or more special-purpose processors.

[0237] The description herein is provided to enable a person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not limited to the aspects described herein, but are to be interpreted in view of the full scope of the present disclosure consistent with the language of the claims.

[0238] Reference to an element in the singular does not mean "‘one and only one” unless specifically stated, but rather “one or more.’’ Terms such as “if,” “when,” and “while” do not imply an immediate temporal relationship or reaction. That is, these phrases, e.g., “when,” do not imply an immediate action in response to or during the occurrence of an action, but simply imply that if a condition is met then an action will occur, but without requiring a specific or immediate time constraint for the action to occur. The terms “may”, “might”, and “can”, as used in this disclosure, often carry certain connotations. For example, “may” refers to a permissible feature that may or may not occur, “might” refers to a feature that probably occurs, and “can” refers to a capability' (e.g., capable of). The phrase “For example” often carries a similar connotation to “may” and, therefore, “may” is sometimes excluded from sentences that include “for example” or other similar phrases.

[0239] Unless specifically stated otherwise, the term "some” refers to one or more.Combinations such as “at least one of A, B, or C” or “one or more of A, B, or C” include any combination of A, B, and / or C, such as A and B, A and C, B and C, or A and B and C, and may include multiples of A, multiples of B, and / or multiples of C, or may include A only, B only, or C only. Sets should be interpreted as a set of elements where the elements number one or more. Terms or articles such as “a”, “an”, and / or “the” may refer to one of an item, feature, element, etc., that the term or article precedes, or may refer to more than one of said item, feature, element, etc. that the term or article precedes. For example, the recitation “a widget” does not preclude reference to multiples of said widget, as “multiple widgets”PATENT APPLICATION Attorney Docket No.: G11438010070WO necessarily includes "‘a widget’’. Hence, the recitation “a widget” may be interpreted as ‘'at least one widget” or, similarly, interpreted as “one or more widgets”.

[0240] Unless otherwise specifically indicated, ordinal terms such as “first” and “second” do not necessarily imply an order in time, sequence, numerical value, etc., but are used to distinguish between different instances of a term or phrase that follows each ordinal term.

[0241] Reference numbers, as used in the specification and figures, are sometimes cross-referenced among drawings to denote same or similar features. A feature that is exactly the same in multiple drawings may be labeled with the same reference number in the multiple drawings. A feature that is similar among the multiple drawings, but not exactly the same, may be labeled with reference numbers that have different leading numbers but have one or more of the same trailing numbers (e.g., 206, 306. 406, etc., may refer to similar features in the drawings). Hence, like numbers may refer to like actions.

[0242] Structural and functional equivalents to elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are encompassed by the claims. The words “module,” “mechanism,” “element,” “device,” and the like may not be a substitute for the word “means.” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.” As used herein, the phrase “based on” shall not be construed as a reference to a closed set of information, one or more conditions, one or more factors, or the like. In other words, the phrase “based on A”, where “A” may be information, a condition, a factor, or the like, shall be construed as “based at least on A” unless specifically recited differently.

[0243] Upon reading this disclosure, those of skill in the art will appreciate still additional and alternative structural and functional designs for handling mobility between base stations through the principles disclosed herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those of ordinary skill in the art, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.

[0244] The following examples are illustrative only and may be combined with other examples or teachings described herein, without limitation.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0245] Example 1 is a method of wireless communication at a network entity, including: performing a procedure to prepare a configuration of a radio resource for a user equipment, UE; and based on a determination that the procedure is for lower-layer triggered mobility', LTM, refraining from starting a timer based on performing the procedure.

[0246] Example 2 may be combined with the method of Example 1, wherein the timer is a first timer, the method further including: starting a second timer based on performing the procedure, wherein the second timer is configured to protect validity of the configuration for LTM.

[0247] Example 3 may be combined with the method of Example 2, further including: stopping the second timer upon at least one of: detection that the UE accesses the radio resource, reception of a message from the UE or another network entity, or reception of an Access Success message.

[0248] Example 4 may be combined with the method of Example 3, further including: detecting that the second timer expires: and triggering a secondary node, SN, release procedure with a master node, MN, based on expiry of the second timer.

[0249] Example 5 may be combined with the method of any of Examples 2-4, wherein the second timer is different from the first timer.

[0250] Example 6 may be combined with the method of Example 5, wherein the second timer has a value greater than a value of the first timer.

[0251] Example 7 may be combined with the method of Example 1, further including: based on another determination that the procedure is for immediate mobility, starting the timer based on performing the procedure, wherein the timer is configured to protect validity of the configuration for immediate mobility.

[0252] Example 8 may be combined with the method of Example 7, further including: stopping the timer upon at least one of: detection that the UE accesses the radio resource, reception of a message from the UE or another network entity, or reception of an Access Success message.

[0253] Example 9 is a method of wireless communication at a network entity', including: performing a procedure to prepare a configuration of a radio resource for a user equipment, UE; starting a timer based on performing the procedure; detecting that the timer expires; and based on a determination that the procedure is for lower layer triggered mobility, LTM,PATENT APPLICATION Attorney Docket No.: G11438010070WO refraining from performing a release or cancellation procedure for the configuration based on expity of the timer.

[0254] Example 10 may be combined with the method of Example 8, wherein the release or cancellation procedure includes at least one of: a secondary node, SN, Release procedure, a SN Modification procedure, a Handover Cancel procedure, a Conditional Handover Cancel procedure, a UE Context Release procedure, or a UE Context Modification procedure.

[0255] Example 11 may be combined with the method of Example 8 or 9, further including: based on another determination that the procedure is for immediate mobility, performing the release or cancellation procedure for the configuration based on the expiry of the timer.

[0256] Example 12 may be combined with the method of any of the preceding any of Examples, wherein the network entity is a secondary node, SN.

[0257] Example 13 may be combined with the method of Example 11, wherein performing the procedure includes: receiving, from a master node, MN. a SN Request message for preparing the configuration; and transmitting, to the MN, a SN Request Acknowledge message for preparing the configuration.

[0258] Example 14 may be combined with the method of Example 12, wherein the SN Request message includes at least one of: a SN Additional Request message, or a SN Modification Request message, and wherein the SN Request Acknowledge message includes at least one of: a SN Additional Request Acknowledge message, or a SN Modification Request Acknowledge message.

[0259] Example 15 may be combined with the method of Example 12 or 13. wherein determining that the procedure is for LTM includes determining that the SN Request message is for LTM.

[0260] Example 16 may be combined with the method of Example 14, wherein performing the procedure further includes performing a LTM preparation procedure.

[0261] Example 17 may be combined with the method of any of Examples 11-15, wherein the SN includes a central unit, CU, and a distributed unit, DU.

[0262] Example 18 may be combined with the method of Example 1 or 9, wherein the timer is a TXnDCoveraii timer.PATENT APPLICATION Attorney Docket No.: G11438010070WO

[0263] Example 19 may be combined with the method of any of the preceding any of Examples, wherein the LTM includes a LTM cell switch.

[0264] Example 20 may be combined with the method of Example 18, wherein the LTM cell switch includes at least one of: an intra-CU master cell group, MCG, LTM procedure, an inter-CU MCG LTM procedure, an intra-CU secondary cell group, SCG, LTM procedure, or an inter-CU SCG LTM procedure.

[0265] Example 21 may be combined with the method of Example 19 or 20. wherein the LTM cell switch includes a primary cell, PCelL switch or a primary secondary cell, PSCell, switch for the UE.

[0266] Example 22 is an apparatus for wireless communication including a memory, a transceiver, and a processor coupled to the memory and the transceiver, the apparatus being configured to implement a method as in any of Examples 1-21.

[0267] Example 23 is a non-transitory computer-readable medium storing computer executable code, the code when executed by a processor causes the processor to implement a method as in any of Examples 1-21.

[0268] Example 24 is a computer program product for implementing a method as in any of Examples 1-21.

Claims

PATENT APPLICATION Attorney Docket No.: G11438010070WO CLAIMSWhat is claimed is:

1. A method of wireless communication at a network entity (104A, 104B, 106A), comprising:performing (707) a procedure to prepare a configuration of a radio resource for a user equipment, UE, (102); andbased on a determination (709, 809) that the procedure is for lower-layer triggered mobility, LTM, refraining (715, 815) from starting a timer based on performing the procedure.

2. The method of claim 1 , wherein the timer is a first timer, the method further comprising:starting (746, 846, 1113) a second timer based on performing the procedure, wherein the second timer is configured to protect validity of the configuration for LTM.

3. The method of claim 2, further comprising: stopping (748, 848) the second timer upon at least one of:detection (732) that the UE accesses the radio resource,reception (838) of a message from the UE or another network entity, orreception (734) of an Access Success message.

4. The method of claim 3, further comprising:detecting (1117) that the second timer expires; andtriggering ( 1119) a secondary node, SN, (104 A, 106A) release procedure with a master node, MN, (104B) based on expity of the second timer.

5. The method of any of claims 2-4, wherein the second timer is different from the first timer.

6. The method of claim 5, wherein the second timer has a value greater than a value of the first timer.

7. The method of claim 1, further comprising:based on another determination (709, 809) that the procedure is for immediate mobility, starting (711A, 711B, 811A, 811B) the timer based on performing the procedure, wherein the timer is configured to protect validity of the configuration for immediate mobility’.PATENT APPLICATION Attorney Docket No.: G11438010070WO 8. The method of claim 7, further comprising: stopping (713A, 713B, 813A, 813B) the timer upon at least one of:detection (732) that the UE accesses the radio resource,reception (838) of a message from the UE or another network entity, orreception (734) of an Access Success message.

9. A method of wireless communication at a network entity (104A, 104B, 106A), comprising:performing (707. 807) a procedure to prepare a configuration of a radio resource for a user equipment, UE, (102);starting (711 A, 811 A) a timer based on performing the procedure;detecting (917) that the timer expires; andbased on a determination (709, 809) that the procedure is for lower layer triggered mobility, LTM, refraining (921. 1021) from performing a release or cancellation procedure for the configuration based on expiry of the timer.

10. The method of claim 8, wherein the release or cancellation procedure comprises at least one of:a secondary node, SN, Release procedure,a SN Modification procedure,a Handover Cancel procedure,a Conditional Handover Cancel procedure,a UE Context Release procedure, ora UE Context Modification procedure.

11. The method of claim 8 or 9, further comprising:based on another determination (709, 809) that the procedure is for immediate mobility, performing (919, 1019) the release or cancellation procedure for the configuration based on the expiry of the timer.

12. The method of any of the preceding claims, wherein the network entity is a secondary node, SN, (104A, 106 A).

13. The method of claim 11, wherein performing the procedure comprises:receiving (805, 1105), from a master node, MN, (104B), a SN Request message for preparing the configuration; andPATENT APPLICATION Attorney Docket No.: G11438010070WO transmitting (805, 807, 1107), to the MN (104B), a SN Request Acknowledge message for preparing the configuration.

14. The method of claim 12. wherein the SN Request message comprises at least one of: a SN Additional Request message, or a SN Modification Request message, and wherein the SN Request Acknowledge message comprises at least one of: a SN Additional Request Acknowledge message, or a SN Modification Request Acknowledge message.

15. The method of claim 12 or 13, wherein determining that the procedure is for LTM comprises determining that the SN Request message is for LTM.

16. The method of claim 14. wherein performing the procedure further comprises performing (1190) a LTM preparation procedure.

17. The method of any of claims 11-15, wherein the SN comprises a central unit, CU, and a distributed unit, DU.

18. The method of claim 1 or 9, wherein the timer is a TXnDCovcraii timer.

19. The method of claim 18. wherein the LTM comprises at least one of:an intra-CU master cell group, MCG, LTM procedure,an inter-CU MCG LTM procedure,an intra-CU secondary cell group, SCG, LTM procedure, oran inter-CU SCG LTM procedure.

20. An apparatus for wireless communication comprising a memory, a transceiver, and a processor coupled to the memory and the transceiver, the apparatus being configured to implement a method as in any of claims 1-19.

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