Uplink timing synchronization management

Abstract

The user equipment (UE) responds to obtaining a timing advance for the target cell from the radio access network (RAN) within the serving cell (1159) by starting or restarting the timing alignment timer for the target cell (1147, 1153), receiving a command to initiate a lower-layer triggered mobility (LTM) cell change for the target cell (113), and in response to the command, resetting the media access control (MAC) entity (1141), and maintaining the execution of the timing alignment timer when restarting the MAC entity (1170).

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority to and the benefit of the filing date of provisional U.S. Patent Application No. 63 / 525,653, titled "Managing Uplink Timing Synchronization," filed on July 7, 2023. The entire content of those provisional applications is hereby expressly incorporated by reference into this specification.

[0002] This disclosure relates to wireless communication, and more particularly to managing uplink synchronization between a user equipment (UE) and a radio access network (RAN).

Background Art

[0003] This description of the background art is provided to generally illustrate the background of the present disclosure. Within the scope described in this background art section, the achievements of the inventors named in this specification, as well as aspects of this specification that may not meet the requirements of prior art at the time of filing, are not to be recognized as prior art to the present disclosure, either expressly or implicitly.

[0004] In telecommunications systems, the Packet Data Convergence Protocol (PDCP) sublayer of the radio protocol stack provides services such as the transfer, encryption, and integrity protection of user plane data. For example, the PDCP layer defined for the Evolved Universal Terrestrial Radio Access (EUTRA) radio interface (see 3GPP® specification TS36.323) and New Radio (NR) (see 3GPP specification TS38.323) provides the ordering of protocol data units (PDUs) in the uplink direction (from user devices, also known as user equipment (UEs), to base stations) and the downlink direction (from base stations to UEs). Furthermore, the PDCP sublayer provides signaling radio bearers (SRBs) and data radio bearers (DRBs) to the radio resource control (RRC) sublayer. Generally speaking, UEs and base stations can use SRBs to exchange RRC messages and non-access layer (NAS) messages, and use DRBs to transport data on the user plane.

[0005] A UE can use several types of SRBs and DRBs. When operating in DC (dual connectivity), the cell associated with the base station operating as the master node (MN) defines the master cell group (MCG), and the cell associated with the base station operating as the secondary node (SN) defines the secondary cell group (SCG). The so-called SRB1 resource carries RRC messages, including NAS messages in some cases, over a dedicated control channel (DCCH), while the SRB2 resource supports RRC messages, including logged measurement information or NAS messages, also over the DCCH, but with a lower priority than the SRB1 resource. More generally, SRB1 and SRB2 resources allow the UE and MN to exchange RRC messages related to the MN and embed RRC messages related to the SN, and are sometimes called MCG SRBs. The SRB3 resource allows the UE and SN to exchange RRC messages related to the SN, and can be called an SCG SRB. The divided SRBs allow the UE to directly exchange RRC messages with the MN through the lower-layer resources of the MN and SN. Furthermore, a DRB that uses only MN lower-layer resources can be called an MCG DRB, a DRB that uses only SN lower-layer resources can be called an SCG DRB, and a DRB that uses both MCG and SCG lower-layer resources can be called a partitioned DRB.

[0006] In some scenarios, a UE can simultaneously utilize the resources of multiple radio access network (RAN) nodes interconnected in a backhaul (e.g., components of a base station or distributed base station). When these network nodes support different radio access technologies (RATs), this connection type is called multi-radio dual connectivity (MR-DC). When a UE operates in MR-DC, one base station acts as the master node (MN) covering a primary cell (PCell), and the other base station acts as the secondary node (SN) covering a primary secondary cell (PSCell). The UE communicates with the MN (via PCell) and with the SN (via PSCell). In other scenarios, the UE utilizes the resources of one base station at a time. One base station and / or a UE decide that the UE needs to establish radio connectivity with another base station. For example, one base station may decide to hand over the UE to a second base station and initiate the handover procedure.

[0007] When a UE moves from the coverage area of ​​one cell to the coverage area of ​​another cell within the RAN, at some point the UE and RAN need to perform a serving cell change. For this purpose, the RAN configures the UE to send Layer 3 (L3) measurements. Using the L3 measurements from the UE, the RAN sends an RRC reconfiguration message (e.g., the RRC reconfiguration message includes ReconfigurationWithSync IE) that configures reconfiguration with synchronization for serving cell changes (e.g., PCell or PSCell). When a UE operates in a carrier aggregation (CA) of a PCell or PSCell and at least one secondary cell (SCell), the RAN needs to release at least one SCell due to the PCell or PSCell change. Serving cell changes involve a complete L2 (and L1) reset, resulting in high latency, high overhead, and long downtime. For these reasons, the Third Generation Partnership Project (3GPP) proposed developing new mobility technologies for serving cell changes. These technologies aim to reduce latency and overhead and are referred to as LTM (low-layer triggered mobility), or faster serving cell switching.

[0008] When a UE switches from a serving cell to a target cell within a RAN, the UE must perform a random access procedure to synchronize with the target cell in the uplink, i.e., in the direction from the UE to the RAN. The UE can only begin data communication with the RAN via the target cell after the UE has successfully completed the random access procedure. As a result, data communication is interrupted during the serving cell switchover. If the UE can obtain a timing advance value (TA) for synchronization with the target cell before switching to the target cell, the UE can avoid this interruption. However, it is not yet clear how the UE and RAN manage uplink synchronization on the target cell before and after connecting to it. [Overview of the project]

[0009] An exemplary embodiment of the technology of this disclosure is a method implemented in a user device (UE). The method includes: starting or restarting a timing alignment timer of a target cell in response to obtaining a timing advance of the target cell from a radio access network (RAN) in a serving cell; receiving a command to initiate a lower-layer triggered mobility (LTM) cell change in the target cell; resetting a media access control (MAC) entity in response to the command; and maintaining the execution of the timing alignment timer while resetting the MAC entity.

[0010] Another exemplary embodiment of these technologies is a method implemented in a radio access network (RAN). The method includes providing a user device (UE) in a serving cell with a timing advance for a target cell; sending a command to the UE to initiate a lower-layer triggered mobility (LTM) cell change in the target cell; in response to sending the command, starting a timing alignment timer associated with the target cell; resetting a media access control (MAC) entity; and maintaining the execution of the timing alignment timer while resetting the MAC entity.

[0011] Another embodiment of these technologies is a device comprising processing hardware and configured to implement one of the above methods. [Brief explanation of the drawing]

[0012] [Figure 1A] This is a block diagram of an exemplary system in which a wireless access network (RAN) and user devices implement the technology of this disclosure to manage uplink timing synchronization. [Figure 1B] This is a block diagram of an exemplary base station, including the CU (centralized unit) and DU (distributed unit) operating in the system shown in Figure 1A. [Figure 2A] Figure 1A is a block diagram of an exemplary protocol stack for the UE to communicate with the base station. [Figure 2B] Figure 1A is a block diagram of an exemplary protocol stack for the UE to communicate with the CU and DU. [Figure 3] This illustrates an exemplary scenario in which a UE performs a low-layer triggered mobility (LTM) cell change from one cell in a DU to another cell in the DU. [Figure 4]This example scenario is generally similar to the one in Figure 3, except that the UE performs inter-DU LTM cell changes. [Figure 5A] This example scenario is generally similar to the one in Figure 3, except that the UE operates in dual connectivity (DC) with the base station. [Figure 5B] This exemplary scenario is generally similar to the scenario in Figure 5A, except that the secondary node (SN) sends an RRC reconfiguration message to the UE via the master node (MN). [Figure 6A] This example scenario is generally similar to the scenarios in Figures 3 to 5B, except that the UE communicates with the MN, SN, and DC to perform inter-DU cell changes. [Figure 6B] This exemplary scenario is generally similar to the scenarios in Figures 3-5B and 6A, except that the UE communicates via the DC and the SN sends an RRC reconfiguration message to the UE via the MN. [Figure 7A] This illustrates an exemplary scenario in which the UE communicates with M-DU and S-DU implemented within the same distributed base station at the DC, and receives the LTM configuration via the S-DU. [Figure 7B] This is an exemplary scenario similar to the one in Figure 7A, except that the UE receives the LTM configuration via the M-DU. [Figure 8A] This illustrates an exemplary scenario in which the UE communicates with the M-DU and S-DU implemented within the same distributed base station at the DC, and receives the LTM configuration via the S-DU to communicate with the T-DU. [Figure 8B] This illustrates an exemplary scenario similar to the one in Figure 8A, except that the UE receives the LTM configuration via the M-DU to communicate with the T-DU. [Figure 9A] This is a flowchart illustrating an exemplary method in the UE for managing uplink synchronization with the target cell using timing advances received via LTM commands. [Figure 9B]It is a flowchart of an exemplary method generally similar to the method of FIG. 9A, except that after the UE accesses the target cell, it starts or restarts a time alignment timer for uplink synchronization with the serving cell. [Figure 9C] It is a flowchart of an exemplary method generally similar to the method of FIG. 9A, except that it determines whether the UE needs to execute a random access procedure in the target cell according to whether the LTM command contains a TA value. [Figure 10A] It is a flowchart of an exemplary method in the RAN for managing uplink synchronization with the UE by using the timing advance transmitted in the LTM command. [Figure 10B] It is a flowchart of an exemplary method generally similar to the method of FIG. 10A, except that after the UE accesses the target cell, the RAN starts or restarts a time alignment timer for uplink synchronization with the serving cell. [Figure 10C] It is a flowchart of an exemplary method generally similar to the method of FIG. 10A, except that it determines whether the RAN needs to execute a random access procedure by the UE according to whether the LTM command contains a TA value. [Figure 11A] It is a flowchart of an exemplary method generally similar to the method of FIG. 9A, except that the UE receives a random access response containing a TA value from the RAN. [Figure 11B] It is a flowchart of an exemplary method generally similar to the method of FIG. 11A, except that the UE determines whether to instruct the LTM command to apply a TA value to the UE. [Figure 12A] It is a flowchart of an exemplary method in the RAN for managing uplink synchronization with the UE, including transmitting a command to the UE to transmit a random access preamble in the target cell. [Figure 12B]A flowchart of an exemplary method in a RAN for managing uplink synchronization with a UE, including determining whether it is necessary to execute a random access procedure with the UE depending on whether the LTM command instructs the UE to apply a TA value. [Figure 13] A flowchart of an exemplary method in a UE that is generally similar to the method of FIG. 11A, but the UE also detects an expiration of a time alignment timer associated with a target cell, even though a time alignment timer associated with a serving cell is running. [Figure 14A] A flowchart of an exemplary method in a UE that is generally similar to the method of FIG. 11A, but the UE also detects an expiration of a time alignment timer associated with a serving cell, even though a time alignment timer associated with a target cell is running. [Figure 14B] A flowchart of an exemplary method in a UE that is generally similar to the method of FIG. 11A, but the UE also detects an expiration of a time alignment timer associated with a serving cell, even though a time alignment timer associated with a target cell is running. [Figure 15] A flowchart of an exemplary method in a RAN that is generally similar to the method of FIG. 12A, but the RAN also detects an expiration of a time alignment timer associated with a target cell, even though a time alignment timer associated with a serving cell is running. [Figure 16A] A flowchart of an exemplary method in a RAN that is generally similar to the method of FIG. 12A, but the RAN also detects an expiration of a time alignment timer associated with a serving cell, even though a time alignment timer associated with a target cell is running. [Figure 16B]The flowchart shows an exemplary method in RAN that is generally similar to the method in Figure 12A, but the RAN also detects the expiration of the time alignment timer associated with the serving cell, while the time alignment timer associated with the target cell is still running. [Figure 17A] This flowchart illustrates an exemplary method in a UE for managing uplink synchronization, including determining which time alignment timers need to be started or restarted depending on the cell from which a random access response is received. [Figure 17B] This flowchart illustrates an exemplary method in a UE for managing uplink synchronization, including determining which time alignment timers need to be started or restarted depending on the cell from which the random access preamble was sent. [Figure 17C] This flowchart illustrates an exemplary method in a UE for managing uplink synchronization, including determining which time alignment timers need to be started or restarted depending on whether a random access preamble was sent for early TA acquisition. [Figure 18A] This flowchart illustrates an exemplary method in RAN for managing uplink synchronization, including determining which time alignment timers need to be started or restarted depending on the cell from which a random access response is received. [Figure 18B] This flowchart illustrates an exemplary method in a RAN for managing uplink synchronization, including determining which time alignment timers need to be started or restarted depending on the cell from which the random access preamble was sent. [Figure 18C] This flowchart illustrates an exemplary method in RAN for managing uplink synchronization, including determining which time alignment timers need to be started or restarted depending on whether a random access preamble was sent for early TA acquisition. [Modes for carrying out the invention]

[0013] Figure 1A shows an exemplary wireless communication system 100 in which user equipment (UE) and radio access network (RAN) can implement uplink timing synchronization technology. The wireless communication system 100 includes UE 102, base station (BS) 104, base station 106, and core network (CN) 110. UE 102 initially connects to base station 104. In some scenarios, base station 104 can perform SN addition and configure UE 102 to operate in dual connection (DC) with base station 104 and base station 106. Base stations 104 and 106 act as MN and SN to UE 102, respectively.

[0014] In various configurations of the wireless communication system 100, base station 104 can be implemented as a master eNB (MeNB) or a master gNB (MgNB), and base station 106 can be implemented as a secondary gNB (SgNB). UE 102 can communicate with base stations 104 and 106 via the same RAT, such as EUTRA or NR, or via different RATs. When base station 104 is a MeNB and base station 106 is an SgNB, UE 102 can be in EUTRA-NR DC (EN-DC) with the MeNB and SgNB.

[0015] In some cases, MeNB or SeNB is implemented as ng-eNB rather than eNB. When base station 104 is a master ng-eNB (Mng-eNB) and base station 106 is a SgNB, UE102 can be in a next-generation (NG) EUTRA-NR DC (NGEN-DC) with the Mng-eNB and SgNB. When base station 104 is a MgNB and base station 106 is a SgNB, UE102 can be in an NR-NR DC (NR-DC) with the MgNB and SgNB. When base station 104 is a MgNB and base station 106 is a secondary ng-eNB (Sng-eNB), UE102 can be in an NR-EUTRA DC (NE-DC) with the MgNB and Sng-eNB.

[0016] In a scenario where UE102 hands over from base station 104 to base station 106, base stations 104 and 106 operate as source base station (S-BS) and target base station (T-BS), respectively. UE102 can, for example, operate in DC with base station 104 and additional base stations (not shown in Figure 1A) before the handover. After completing the handover, UE102 can continue operating in DC with base station 106 and additional base stations, or it can operate in standalone connection (SC) with base station 106. In this case, base stations 104 and 106 operate as source MN (S-MN) and target MN (T-MN), respectively.

[0017] The core network (CN) 110 can be an evolved packet core (EPC) 111 or a fifth-generation core (5GC) 160, both shown in Figure 1A. The base station 104 can be an eNB supporting an S1 interface for communication with the EPC 111, an ng-eNB supporting an NG interface for communication with the 5GC 160, or a gNB supporting an NR radio interface and an NG interface for communication with the 5GC 160. To directly exchange messages during the scenarios described below, base stations 104 and 106 can support X2 or Xn interfaces. Among other components, the EPC 111 may include a serving gateway (SGW) 112, a mobility management entity (MME) 114, and a packet data network gateway (PGW) 116. The SGW 112 is typically configured to forward user plane packets related to voice calls, video calls, internet traffic, etc., while the MME 114 is configured to manage authentication, registration, paging, and other related functions. The PGW116 provides connectivity from the UE to one or more external packet data networks, such as the Internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network. The 5GC160 includes User Plane Function (UPF)162, Access and Mobility Management (AMF)164, and / or Session Management Function (SMF)166. The UPF162 is generally configured to forward user plane packets related to voice calls, video calls, internet traffic, etc., the AMF164 is configured to manage authentication, registration, paging, and other related functions, and the SMF166 is configured to manage PDU sessions.

[0018] As shown in Figure 1A, base station 104 supports cell 124A, and base station 106 supports cell 126. Cells 124A and 126 partially overlap, thereby allowing UE 102 to communicate with base stations 104 and 106 via DC, with one of base stations 104 and 106 being MN and the other SN. Base station 104 can support additional cells such as cells 124B and 124C, and base station 106 can support additional cells (not shown in Figure 1A). Since cells 124A, 124B, and 124C can partially overlap, UE 102 can communicate with base station 104 via carrier aggregation (CA). Base station 104 can operate cells 124A, 124B, and 124C via one or more transmit / receive points (TRPs). More specifically, when UE102 operates in DC with base stations 104 and 106, one of base stations 104 and 106 operates as a MeNB, Mng-eNB, or MgNB, and the other operates as an SgNB or Sng-eNB.

[0019] Generally, the wireless communication network 100 may include any suitable number of base stations that support NR cells and / or EUTRA cells. More specifically, the EPC 111 or 5GC 160 may be connected to any suitable number of base stations that support NR cells and / or EUTRA cells. In the following embodiments, specific CN types (EPC, 5GC) and RAT types (5G NR or EUTRA) are specifically referred to, but generally, the techniques of the present disclosure can also be applied to other suitable radio access and / or core network technologies such as sixth-generation (6G) radio access and / or 6G core networks or 5G NR-6G DC.

[0020] Continuing to refer to Figure 1A, the base station 104 comprises processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and non-temporary computer-readable memory for storing instructions executed by the one or more general-purpose processors. Additionally or alternatively, the processing hardware 130 may include a special-purpose processing unit.

[0021] The processing hardware 130 may implement an LTM controller 132 to support LTM procedures and a TA acquisition controller 134 to support early TA acquisition at the UE. The LTM controller 132 and the TA acquisition controller 134 may be implemented, for example, as sets of instructions executable by one or more processors. The processing hardware 130 may also implement additional components such as a PHY controller (not shown) configured to transmit data and to control signals on the physical downlink (DL) channel and DL reference signals on one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs on one or more user devices (e.g., UE 102). The PHY controller may be configured to receive data and to control signals on the physical uplink (UL) channel and / or UL reference signals on one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs on one or more user devices. The processing hardware 130 may also implement a MAC controller (not shown) configured to perform MAC functions on one or more user devices. The MAC functions include random access (RA) procedures that manage the UL timing advance of one or more user devices and / or communicate UL / DL MAC PDUs with one or more user devices. The MAC functions include lower triggered mobility (LTM) related functions as described below. The processing hardware 130 may further include an RRC controller (not shown) to perform procedures and messaging in the RRC sublayer of the protocol communication stack. For example, the RRC controller may be configured to support RRC messaging associated with handover procedures and / or to support operations required when base station 104 operates as an MN to an SN or as an SN to an MN.The base station 106 may include processing hardware 140 similar to processing hardware 130. In particular, components 142, 144, and 146 may be similar to components 132 and 134, respectively.

[0022] The UE102 includes processing hardware 150, which may include one or more general-purpose processors such as a CPU, non-temporary computer-readable memory for storing machine-readable instructions executable by one or more general-purpose processors, and / or a special-purpose processing unit. The processing hardware 150 may implement an LTM controller 152 to support LTM procedures and a TA acquisition controller 154 to support early TA acquisition in the serving cell and / or target cell. The LTM controller 152 and the TA acquisition controller 154 may be implemented, for example, as separate sets of instructions executable by one or more processors.

[0023] The processing hardware 150 may also implement additional components, such as a PHY controller (not shown) configured to receive data and to control signals on the physical DL channel and / or DL ​​reference signals at base station 104 or 106 via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. The PHY controller may be configured to transmit data and to control signals on the physical UL channel and / or UL reference signals at base station 104 or 106 via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. In an exemplary embodiment, the processing hardware 150 includes a MAC controller (not shown) configured to perform MAC functions at base station 104 or 106. For example, MAC functions include random access procedures for managing UL timing advances for one or more user devices and communicating UL / DL MAC PDUs with base station 104 or 106. In other examples, the MAC functionality includes the LTM-related functions described below. The processing hardware 150 may further include an RRC controller (not shown) to implement procedures and messaging in the RRC sublayer of the protocol communication stack.

[0024] During operation, UE102 in the DC can use radio bearers (e.g., DRB or SRB) that terminate at MN104 or SN106 at different times. UE102 can apply one or more security keys when communicating with the radio bearers in the uplink (UL) direction (from UE102 to the base station) and / or downlink direction (from the base station to UE102).

[0025] Figure 1B shows an exemplary distributed embodiment of a base station, such as base station 104 or 106. The base station in this embodiment includes an aggregation unit (CU) 172 and one or more distributed units (DU) 174. In some embodiments, the CU 172 includes processing hardware, and / or a dedicated processing unit, which includes one or more general-purpose processors, such as a CPU, and non-temporary computer-readable memory for storing machine-readable instructions executable on one or more general-purpose processors. In some embodiments, the CU 172 includes processing hardware 130. In further embodiments, the CU 172 includes processing hardware 140. In exemplary embodiments, the processing hardware 140 includes an SN RRC controller 142 configured to manage or control one or more RRC configurations and / or RRC procedures when base station 106 operates as an SN. In some embodiments, the DU 174 also includes processing hardware, and / or a dedicated processing unit, which includes one or more general-purpose processors, such as a CPU, and non-temporary computer-readable memory for storing machine-readable instructions executable on one or more general-purpose processors. In some embodiments, the processing hardware includes a media access control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., random access procedures), and a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station 106 operates as an MN or SN. In some embodiments, the process hardware includes a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0026] Figure 2A illustrates a simplified protocol stack 200 of the embodiment, in which UE102 communicates with an eNB / ng-eNB or gNB (e.g., one or more of base stations 104, 106) according to the protocol stack 200.

[0027] In an exemplary stack 200, the EUTRA physical layer (PHY) 202A provides a transport channel to the EUTRA MAC sublayer 204A, which then provides a logical channel to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A then provides an RLC channel to the EUTRA PDCP sublayer 208, and possibly to the NR PDCP sublayer 210. Similarly, the NR PHY 202B provides a transport channel to the NR MAC sublayer 204B, which then provides a logical channel to the NR RLC sublayer 206B. The NR RLC sublayer 206B then provides data transfer services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 then provides data transfer services to the Service Data Adaptive Protocol (SDAP) 212 or the Radio Resource Control (RRC) sublayer (not shown in Figure 2A). In some embodiments, the UE102 supports both EUTRA and NR stacks, as shown in Figure 2A, supports handover between EUTRA base stations and NR base stations, and / or supports DC via EUTRA and NR interfaces. Furthermore, as shown in Figure 2A, the UE102 supports layering of NR PDCP210 on EUTRA RLC206A and SDAP sublayer212 on NR PDCP sublayer210.

[0028] EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 receive packets referred to as Service Data Units (SDUs) (e.g., from the Internet Protocol (IP) layer, which is layered directly or indirectly on top of PDCP layer 208 or 210) and transmit packets referred to as Protocol Data Units (PDUs) (e.g., to RLC layer 206A or 206B). For simplification, this disclosure refers to both SDUs and PDUs as “packets” unless the difference between SDUs and PDUs is relevant.

[0029] In some embodiments, on the control plane, the EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 provide a signaling radio bearer (SRB) or RRC sublayer (not shown in Figure 2A) for exchanging, for example, RRC messages or non-access layer (NAS) messages. In some embodiments, on the user plane, the EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 provide a data radio bearer (DRB) to support data exchange. In further embodiments, the data exchanged in the NR PDCP sublayer 210 is SDAP PDU, Internet Protocol (IP) packets, or Ethernet packets.

[0030] Figure 2B shows a simplified exemplary protocol stack 250 in which UE102 communicates with DU (e.g., DU174) and CU (e.g., CU172). The radio protocol stack 200 is functionally divided as shown by the radio protocol stack 250 in Figure 2B. In some embodiments, the CU, located in either base station 104 or 106, holds all control and higher-layer functions (e.g., RRC214, SDAP212, NR PDCP210), while lower-layer operations (e.g., NR RLC206B, NR MAC204B, and NR PHY202B) are delegated to the DU. To support connectivity to 5GC, NR PDCP210 provides an SRB to RRC214, and NR PDCP210 provides a DRB to SDAP212 and an SRB to RRC214.

[0031] Next, in some exemplary scenarios, a base station operating in the system of Figure 1A sends a configuration to UE102, and then activates the configuration for communication between UE102 and the base station. Generally speaking, similar events in Figures 3-8B are labeled with similar reference numbers (for example, event 394 is similar to event 494 in Figure 4, event 594 in Figure 5A, event 694 in Figure 6A, event 794 in Figure 7A, and event 894 in Figure 8A), and differences are described below. Except for the differences shown in the figures and described below, any of the alternative embodiments described with respect to a particular event (e.g., messaging and processing) may apply to events with similar reference numbers in other figures.

[0032] Referring first to Figure 3, in Scenario 300, base station 104 includes CU172 and DU174, where DU174 operates cell 124A. UE102 initially communicates with DU174 on cell 124A using a serving DU configuration (302), and then communicates with CU172 via DU174 using, for example, a serving CU configuration. In other words, DU174 is the serving DU communicating with UE102. In some embodiments, UE102 in carrier aggregation (CA) communicates with DU174 on cell 124A and other cells (or more) (e.g., cell 124D, not shown in Figure 1A) using a serving DU configuration. DU174 operates other cells (or more). In other embodiments, UE102 communicates with DU174 only on cell 124A. In some embodiments, UE102 communicates with DU174 on cell 124A and / or other cells(s) via one or more transmit / receive points (TRPs). In some embodiments, cell 124A is a PCell. In such embodiments, the other cells(s) include SCell(s) and / or additional cells(s) associated with the PCell or SCell. In other embodiments, cell 124A is a SCell, and one of the other cells(s) is a PCell. In such embodiments, the DU174 includes SCell(s) and / or additional cells(s) associated with the PCell or SCell. In the following description, base station 104 is DU174, CU172, or DU174 and CU172.

[0033] In some embodiments, UE102 transmits the UL PDU and / or UL control signals to base station 104 on cell 124A and / or other cells(s) via one or more TRPs (302). In some embodiments, UE102 communicates the UL PDU and / or DL ​​PDU with base station 104 via a radio bearer including an SRB and / or DRB(s). In some embodiments, base station 104 constitutes the radio bearer for UE102. In some embodiments, the UL control signals include UL control information, channel status information, a HARQ (hybrid automatic repeat request) acknowledgment (ACK), a HARQ negative acknowledgment (negative ACK), a scheduling request(s), and / or a sounding reference signal(s). In further embodiments, UE102 receives the DL PDU and / or DL ​​control signals from base station 104 on cell 124A and / or other cells(s) via one or more TRPs. In some embodiments, the DL control signal includes DL control information (DCI) and reference signals (e.g., synchronization signal blocks, channel state information reference signals (CSI-RS(multiple)), and / or tracking reference signals(multiple)). In some embodiments, base station 104 transmits the DCI on a physical downlink control channel(s) (PDCCH(multiple)) monitored by UE 102 via one or more TRPs on cell 124A and / or other cells(multiple).

[0034] In some embodiments, the serving DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some embodiments, DU174 transmits these configuration parameters to CU172. CU172 generates one or more messages (e.g., RRC reconfiguration messages) containing the configuration parameters and transmits one or more messages to UE102 via DU174. In further embodiments, DU174 transmits the configuration parameters directly to UE102. In some embodiments, the serving DU configuration is a CellGroupConfig IE (e.g., as defined in 3GPP TS38.331). In further embodiments, the serving DU configuration includes configuration parameters in the CellGroupConfig IE. In even further embodiments, the serving CU configuration includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some embodiments, the serving CU configuration includes a MeasConfig IE and / or a RadioBearerConfig IE (e.g., as defined in 3GPP TS38.331), or the MeasConfig IE and / or RadioBearerConfig IE include configuration parameters. In some embodiments, the serving DU configuration includes a CSI-MeasConfig IE or configuration parameters for measuring and reporting channel status information (CSI). In further embodiments, the serving CU configuration includes a CSI-MeasConfig IE or configuration parameters for measuring and reporting CSI. In some embodiments, UE102 receives the serving CU configuration, or configuration parameters in the serving CU configuration, from CU172 via DU174. In further embodiments, UE102 receives a portion of the serving CU configuration and / or a portion of the serving DU configuration, along with the remaining portion of these configuration parameters, from base station 104, a base station other than base station 104.

[0035] While communicating with base station 104, UE 102 sends at least one measurement report to DU 174 (304). In some embodiments, the at least one measurement report includes a Layer 1 (L1) measurement report and / or a Layer 3 (L3) measurement report for at least one serving cell and / or at least one non-serving cell of UE 102. For each L3 measurement report, DU 174 sends a DU-to-CU message containing the L3 measurement report to CU 172 (306). In some embodiments, the DU-to-CU message for event 306 is an F1 Application Protocol (F1AP) message (e.g., a UL RRC message forwarding message). In some embodiments, DU 174 does not send or refrains from sending an L1 measurement report to CU 172. The at least one serving cell includes cell 124A and / or other cells, and the at least one non-serving cell includes cell 124B and / or cell 124C. In some embodiments, a serving DU configuration or serving CU configuration includes at least one measurement configuration. In some embodiments, UE102 receives one or more RRC messages (e.g., RRCReconfiguration messages) from CU172 via DU174 that include at least one measurement configuration in event 302. According to at least one measurement configuration, UE102 performs a measurement and sends at least one measurement report to DU174 (304). In some embodiments, at least one measurement configuration includes an L3 measurement configuration (e.g., MeasConfig IE) and / or an L1 measurement configuration. In some embodiments, an L1 measurement configuration (e.g., CSI-MeasConfig IE) includes an L1 measurement resource configuration and / or an L1 measurement report configuration. In some embodiments, the L1 measurement resource configuration configures the reference signal and / or reference signal resources of UE102 to measure and obtain L1 measurement results. In some embodiments, the reference signal includes CSI-RS and / or synchronization signal (SS) / physical broadcast channel (PBCH) resource block (SSB).For example, an L1 measurement resource configuration is CSI-ResourceConfig IE. In some embodiments, an L1 measurement report configuration configures UE102 to send L1 measurement results / reports. For example, an L1 measurement report configuration(s) is CSI-ReportConfig IE(s). For example, UE102 sends L3 measurement reports(s) to CU172 via DU174 according to an L3 measurement configuration(s). UE102 sends L1 measurement reports(s) to DU174 according to an L1 measurement configuration(s) or L1 measurement report configuration(s). In some embodiments, DU174 does not send L1 measurement reports(s) to CU172.

[0036] In some embodiments, the L1 measurement configuration(s) are RRC IE(s) (e.g., defined in 3GPP TS38.331) specifically defined for LTM (lower-layer triggered mobility). In some embodiments, the L1 measurement resource configuration(s) are RRC IE(s) (e.g., defined in 3GPP TS38.331) specifically defined for LTM. In some embodiments, the L1 measurement report configuration(s) are RRC IE(s) (e.g., defined in 3GPP TS38.331) specifically defined for LTM. In some embodiments, each of the L1 measurement report configuration(s) includes a trigger event configuration that constitutes a trigger event to trigger UE102 to send an L1 measurement report. When UE102 detects a trigger event, UE102 sends an L1 measurement report to DU174.

[0037] In some embodiments, each of the L1 measurement reports includes at least one L1 measurement result. In some embodiments, the at least one L1 measurement result includes at least one L1-RSRP (L1 reference signal received power) value and / or at least one L1-SINR (L1 Signal-to-Interference-Noise Ratio) value. In some embodiments, for each of the L1 measurement reports, UE102 sends a PUCCH transmission containing the L1 measurement report to DU174. That is, UE102 sends each of the L1 measurement reports on PUCCH to DU174. In further embodiments, for each of the L1 measurement reports, UE102 sends a PUSCH transmission containing the L1 measurement report to DU174. That is, UE102 sends each of the L1 measurement reports on PUSCH to DU174. In further embodiments, UE102 transmits a portion of an L1 measurement report(s) on a PUCCH(s) and the rest of an L1 measurement report(s) on a physical UL shared channel(s) (e.g., PUSCH(s)) to DU174. That is, for each portion of an L1 measurement report(s), UE102 transmits a PUCCH transmission containing the L1 measurement report to DU174, and for each rest of an L1 measurement report(s), UE102 transmits a PUSCH transmission containing the L1 measurement report to DU174. In some embodiments, each of the L1 measurement reports(s) is a portion (i.e., a CSI component) or an entire CSI. In some embodiments, UE102 includes other CSI components(s) in each of the above PUCCH transmissions(s) and / or PUSCH transmissions(s). In some embodiments, other CSI components may include a channel quality indicator (CQI), a precoding matrix indicator (PMI), a CSI-RS resource indicator (CRI), an SSB resource indicator (SSBRI), a layer indicator (LI), and / or a rank indicator (RI).In some embodiments, the UE102 does not send L1 measurement reports(s) to the DU174 in RRC message(s) format.

[0038] In some embodiments, each L3 measurement report(s) includes at least one L3 measurement result. In further embodiments, at least one L3 measurement result includes at least one RSRP (e.g., value) and / or at least one SINR (e.g., value). In some embodiments, UE102 transmits each L3 measurement report(s) on PUSCH to CU172 via DU174. In some embodiments, each L3 measurement report(s) includes an RRC message (e.g., MeasurementReport message). In further embodiments, each L3 measurement configuration(s) includes a specific measurement identity (e.g., measId), and each L3 measurement report(s) includes a specific measurement identity for a particular L3 measurement configuration. In some embodiments, when CU172 receives an L3 measurement report from UE102 via DU174, including the measurement identity and L3 measurement result, CU172 determines that the L3 measurement report is associated with the L3 measurement configuration identified by the measurement identity.

[0039] In some embodiments, for at least one measurement report (e.g., L1 measurement report(or more)), UE102 transmits (304) the measurement report to DU174 via a MAC control element (CE) containing the measurement report. To transmit (304) to DU174, UE102 generates one or more MAC PDUs, each MAC PDU containing one or more MAC CE(or more).

[0040] In some embodiments, UE102 performs measurements on one or more reference signals according to at least one measurement configuration. In some embodiments, one or more reference signals include one or more synchronization signals (SS) / physical broadcast channel (PBCH) resource blocks (SSB) and / or one or more CSI-RS. From the measurements, UE102 obtains at least one L1 measurement result and / or at least one L3 measurement result. DU174 transmits one or more reference signals on cell 124A and other cells(s) (e.g., cell 124B, cell 124C and / or other cells(s) not shown in Figure 1A).

[0041] After receiving one or more of at least one measurement reports from UE102 (e.g., in response to receiving them), base station 104 (i.e., CU172 or DU174) decides to prepare a first cell (e.g., cell 124B) for LTM to UE102. In some embodiments, base station 104 decides to prepare a first cell for UE102 because at least one measurement report indicates that the first cell will use base station 104 to communicate with UE102. In some embodiments, base station 104 decides to prepare a first cell for UE102 because at least one measurement report indicates that the first cell is qualified as a candidate cell for communication with UE102. In some embodiments, if an L3 measurement report indicates that the signal strength and / or quality of the first cell exceeds a first predetermined threshold, improves the strength and / or quality of cell 124A, and / or improves the strength and / or quality of cell 124A by a first predetermined threshold, CU172 decides to prepare the first cell for UE102. In further embodiments, if an L1 measurement report indicates that the signal strength and / or quality of the first cell exceeds a first predetermined threshold, improves the strength and / or quality of cell 124A, and / or improves the strength and / or quality of cell 124A by a first predetermined threshold, DU174 decides to prepare the first cell for UE102. Alternatively, base station 104 decides to prepare the first cell for UE102 regardless of whether a measurement report is received from UE102.

[0042] If CU172 decides to prepare a first cell for LTM, CU172 sends a first CU-to-DU message to DU174 for preparing the first cell for UE102 (308). In some embodiments, CU172 includes a cell identity (ID) 1 of the first cell in the first CU-to-DU message to request DU174 to prepare the first cell for LTM in UE102. For example, cell ID 1 is the cell global identity (CGI). In other examples, cell ID is part of the CGI. In yet another example, cell ID is the physical cell ID (PCI). In response to the first CU-to-DU message, DU174 generates a first LTM DU configuration of UE102 (for example, hereafter referred to as LTM DU configuration 1) which constitutes the first cell for LTM. Next, DU174 sends a first DU-to-CU message to CU172 in response to the first CU-to-DU message, which includes the LTM DU configuration 1 (310). In some embodiments, DU174 includes cell ID 1 along with the LTM DU configuration 1 in the IE of the first DU-to-CU message to indicate that the LTM DU configuration 1 is associated with a first cell (i.e., cell ID 1). If DU174 decides to prepare the first cell, DU174 initiates sending a first DU-to-CU message to CU172 instead of responding to the CU-to-DU message received from CU172.

[0043] In some embodiments, DU174 includes the cell ID of the first cell associated with LTM DU configuration 1 in the first DU-to-CU message to indicate that LTM DU configuration 1 is configured for or associated with the first cell. CU172 identifies that LTM DU configuration 1 is configured for or associated with the first cell. In some embodiments, CU172 includes additional cell IDs (e.g., cell IDs (multiple) 2, ..., N) in the first CU-to-DU message to prepare additional cells (multiple) (e.g., cell(multiple) 2, ..., N) for LTM in UE102, and DU174 includes additional LTM DU configurations (multiple) (e.g., LTM DU configurations (multiple) 2, ..., N) for the additional cells (multiple) as described below. In such cases, DU174 includes instructions in the first DU-to-CU message indicating which LTM DU configuration is associated with which cell(ID). Cell(s) 1 and / or 2, ..., N are candidate cells(s).

[0044] In some embodiments, CU172 does not include an LTM DU configuration (e.g., a reference configuration) in the first CU-to-DU message. In such cases, DU174 generates a reference LTM DU configuration, generates LTM DU configurations 1 and / or 2, ..., N (i.e., non-reference LTM DU configurations) based on the reference LTM DU configuration, and includes the reference LTM DU configuration in the first DU-to-CU message. In further embodiments, CU172 includes a reference LTM DU configuration in the first CU-to-DU message. In such cases, DU174 generates LTM DU configurations 1 and / or 2, ..., N, which are delta configurations to extend the reference LTM DU configuration. In yet another embodiment, CU172 includes a reference LTM DU configuration (e.g., a first reference LTM DU configuration) in the first CU-to-DU message. In such a case, DU174 generates a reference LTM DU configuration (e.g., a second reference LTM DU configuration) that replaces the first reference LTM DU configuration, generates LTM DU configurations 1 and / or 2, ..., N based on the second reference LTM DU configuration, and includes the second reference LTM DU configuration in the first DU-to-CU message.

[0045] In some embodiments, the reference LTM DU configuration includes physical layer configuration parameters, MAC configuration parameters, and / or RLC configuration parameters. In some embodiments, the reference LTM DU configuration is a CellGroupConfig IE (as defined, for example, in 3GPP TS38.331). In further embodiments, the reference LTM DU configuration includes configuration parameters in the CellGroupConfig IE. In even further embodiments, the reference LTM DU configuration includes a CSI-MeasConfig IE or configuration parameters for CSI measurement and / or reporting.

[0046] In some embodiments, the reference LTM DU configuration differs from the serving DU configuration. In further embodiments, a portion of the reference LTM DU configuration is the same as a portion of the serving DU configuration, and the remaining portion of the reference LTM DU configuration differs from the remaining portion of the serving DU configuration. In yet another embodiment, the reference LTM DU configuration is the same as the serving DU configuration.

[0047] After receiving the first DU-to-CU message, CU172 generates an RRC reconfiguration message (e.g., an RRCReconfiguration message) containing LTM DU configuration 1 and sends a second CU-to-DU message to DU174 along with the RRC reconfiguration message (316). In some embodiments, CU172 sends a reference LTM DU configuration in the RRC reconfiguration message (316). In further embodiments, CU172 sends the RRC reconfiguration message without a reference LTM DU configuration (316). In some embodiments, if CU172 sends a reference LTM DU configuration to UE102 (302), CU172 sends the RRC reconfiguration message without a reference LTM DU configuration (316). In further embodiments, if CU172 receives a reference LTM DU configuration from DU174, CU172 sends the LTM DU configuration in the RRC reconfiguration message (316). Otherwise, if CU172 does not receive a reference LTM DU configuration from DU174, CU172 sends an RRC reconfiguration message without a reference LTM DU configuration (316).

[0048] In some embodiments, CU172 transmits LTM DU Configuration 1 and / or LTM CU Configuration 1 in a first container (e.g., field / IE) (316 and 318), and includes the first container (e.g., LTM Configuration 1) in the RRC reconfiguration message. In such cases, CU172 generates the first container. The first container instructs UE102 not to immediately apply LTM DU Configuration 1 and / or LTM CU Configuration 1. In some embodiments, UE102 receives an RRC reconfiguration message containing the configuration (e.g., LTM DU Configuration 1) (318). If the configuration is included in the first container, UE102 refrains from immediately applying the configuration. Otherwise, if the configuration is not included in the first container, UE102 applies the configuration immediately. In some embodiments, the first container contains or is a first modification list (e.g., an ltm-ConfigToAddModList field, an ltm-CandidateToAddModList field, or an ltm-CandidateConfigToAddModList field). CU172 includes LTM DU Configuration 1 and / or LTM CU Configuration 1 in a first element of the first modification list (e.g., hereinafter referred to as element 1). In some embodiments, CU172 generates an RRC message (e.g., an RRCRecconfiguration message) containing LTM DU Configuration 1 and / or LTM CU Configuration 1, and includes the RRC message in element 1. In some embodiments, element 1 is an modification IE (e.g., an LTM-ConfigToAddMod IE, an LTM-Candidate IE, an LTM-CandidateToAddMod IE, or an LTM-CandidateConfigToAddMod IE). In some embodiments, when UE102 receives a first add-or-modify list, UE102 stores the first add-or-modify list in a variable, for example, in its random access memory (RAM). In further embodiments, DU174 generates a first container and includes the first container in a first DU-to-CU message.In further embodiments, DU174 generates element 1 and includes element 1 in the first DU-to-CU message.

[0049] In some embodiments, CU172 transmits LTM CU configuration 1 in an RRC reconfiguration message and a first container or element 1 (316), and LTM CU configuration 1 is associated with LTM DU configuration 1. In some embodiments, in order to associate LTM CU configuration 1 with LTM DU configuration 1, CU172 includes LTM CU configuration 1 together with LTM DU configuration in element 1. In some embodiments, CU172 transmits LTM CU configuration(s) 2, ..., N in an RRC reconfiguration message or a second container (316), and LTM CU configuration(s) 2, ..., N are each associated with LTM DU configuration(s) 2, ..., N. In further embodiments, in order to associate LTM CU configurations 2, ..., N with LTM DU configurations 2, ..., N, CU172 includes LTM CU configurations 2, ..., N and LTM DU configurations 2, ..., N, respectively, in element(multiple) 2, ..., N. In further embodiments, CU172 includes LTM CU configurations 2, ..., N associated with LTM DU configurations 2, ..., N, respectively, in element(multiple) 2, ..., N. In further embodiments, CU172 transmits an RRC reconfiguration message without some or all of the LTM CU configurations 1 and / or LTM DU configurations 2, ..., N (316).

[0050] After receiving the RRC Reconfiguration message (316), DU174 sends the RRC Reconfiguration message to UE102 (318). In response, UE102 sends an RRC Reconfiguration Complete message (e.g., an RRCReconfigurationComplete message) to DU174 (320), and DU174 then sends a second DU-to-CU message containing the RRC Reconfiguration Complete message to CU172 (322). In some embodiments, CU172 performs security protection (e.g., integrity protection and / or encryption) on the RRC Reconfiguration message. For example, CU172 generates an integrity message authentication code (MAC-I) for the RRC Reconfiguration message, encrypts the RRC Reconfiguration message and MAC-I to obtain an encrypted RRC Reconfiguration message and encrypted MAC-I, and sends a PDCP PDU containing the encrypted RRC Reconfiguration message and encrypted MAC-I to UE102 via DU174 (316 and 318). When UE102 receives a PDCP PDU from CU172 via DU174 (316 and 318), UE102 decrypts the encrypted RRC reconfiguration and encrypted MAC-I to obtain the RRC reconfiguration message and MAC-I, and verifies whether the MAC-I is valid. If UE102 verifies that the MAC-I is invalid, UE102 discards or ignores the RRC reconfiguration message. In some embodiments, UE102 performs an RRC connection re-establishment procedure in response to an invalid MAC-I. In some embodiments, if UE102 verifies that the MAC-I is valid, UE102 processes the RRC reconfiguration. UE102 refrains from applying (i.e., executing) LTM DU configuration 1 until it receives an LTM command to activate LTM DU configuration 1 (330 and 350).

[0051] Events 308 (optional) and 310 are collectively referred to as LTM preparation procedure 390 in Figure 3. Events 316, 318, 320, and 322 are collectively referred to as LTM configuration and distribution procedure 394 in Figure 3.

[0052] In some embodiments, the first CU-to-DU message is a UE context modification request message, and the first DU-to-CU message is a UE context modification response message or a UE context modification request message. In some embodiments, CU172 sends a UE context modification acknowledgment message to DU174 in response to the UE context modification request message. In some embodiments, the second CU-to-DU message is a DL RRC message forwarding message. In further embodiments, the second CU-to-DU message is a UE context modification request message, and DU174 sends a second DU-to-CU message (e.g., a UE context modification response message) to CU172 in response to the second CU-to-DU message.

[0053] In some embodiments, CU172 includes a reference LTM CU configuration in the RRC reconfiguration message or a first container (316). In some embodiments, CU172 generates LTM CU configuration 1 (i.e., a non-reference LTM CU configuration) as a delta configuration to extend the reference LTM CU configuration. In some embodiments, CU172 generates some or all of LTM CU configurations 2, ..., N as delta configurations to extend the reference LTM CU configuration. In some embodiments, CU172 transmits the reference LTM CU configuration excluding the non-reference LTM CU configuration in the RRC reconfiguration message or a first container (316). In further embodiments, CU172 transmits the reference LTM CU configuration and / or the reference LTM DU configuration in an additional container (e.g., a reference LTM configuration) within the RRC configuration message (316).

[0054] In some embodiments, the reference LTM CU configuration differs from the serving CU configuration. In some embodiments, a portion of the reference LTM CU configuration is the same as a portion of the serving CU configuration, and the remaining portion of the reference LTM CU configuration differs from the remaining portion of the serving CU configuration. In further embodiments, the reference LTM CU configuration is the same as the serving LTM CU configuration.

[0055] In some embodiments, CU172 includes a first LTM ID (hereinafter referred to as ID1) for identifying LTM DU configuration 1 or element 1 in the RRC reconfiguration message. In some embodiments, CU172 includes ID1 in the first container or element 1. In some embodiments, CU172 assigns ID1.

[0056] In some embodiments, CU172 sends ID1 to DU174, and DU174 associates ID1 with LTM DU configuration 1 and / or cell ID1. In some embodiments, CU172 includes ID1 in a first CU-to-DU message. In some embodiments, after receiving a first DU-to-CU message, CU172 sends a third CU-to-DU message containing ID1 to DU174 instead of including ID1 in the first CU-to-DU message (312). In some embodiments, in the third CU-to-DU message, CU172 includes LTM DU configuration 1 and ID1, instructing the association between ID1 and LTM DU configuration 1. Thus, DU174 directly associates ID1 with LTM DU configuration 1. In further embodiments, in a third CU-to-DU message, CU172 includes cell ID1 and ID1 (i.e., the first LTM ID), instructing an association between cell ID1 and ID1. Thus, DU174 associates ID1 with LTM DU configuration 1 based on the association between cell ID1 and ID1 and the association between cell ID1 and LTM DU configuration 1. In further embodiments, in a third CU-to-DU message, CU172 includes LTM DU configuration 1, cell ID1, and / or ID1, instructing an association between ID1, LTM DU configuration 1, and / or cell ID1. In some embodiments, DU174 sends a third DU-to-CU message to CU172 in response to the third CU-to-DU message (314). In some embodiments, the third CU-to-DU message and the third DU-to-CU message are a UE context modification request message and a UE context modification response message. Events 312 (optional) and 314 (optional) are collectively referred to as LTM ID assignment procedure 392 in Figure 3. In some embodiments, CU172 includes ID1, cell ID1, and / or LTM DU configuration 1 in the second CU-to-DU message, as described above. Therefore, the third CU-to-DU message is omitted.

[0057] In some embodiments, CU172 includes ID1 in the first CU-to-DU message, and DU174 includes ID1 in LTM DU configuration 1, the first container, or element 1. Alternatively, DU174 does not include ID1 in LTM DU configuration 1, the first container, and / or element 1.

[0058] In some embodiments, CU172 includes a reference LTM DU configuration in a first container. For example, CU172 includes a reference LTM DU configuration in a field of the first container that is different from the field of the first container that includes LTM DU configuration 1. In some embodiments, CU172 includes the reference LTM DU configuration in an RRC reconfiguration message outside the first container (316). For example, CU172 generates a third container (e.g., field / IE) that includes the first container and the reference LTM DU configuration, and includes the third container in an RRC reconfiguration message (316). In further embodiments, DU174 includes a reference LTM DU configuration in a first container. For example, DU174 includes a reference LTM DU configuration in a field of the first container that is different from the field of the first container that includes LTM DU configuration 1. In further embodiments, DU174 generates a fourth container (e.g., field / IE) containing the first container and the reference LTM DU configuration, and includes the fourth container in the first DU-to-CU message (310). In such cases, CU172 includes the fourth container in the RRC reconfiguration message (316). Alternatively, CU172 retrieves the reference LTM DU configuration and LTM DU configuration 1 from the fourth container and includes the reference LTM DU configuration and LTM DU configuration 1 as described above.

[0059] In some embodiments, neither CU172 nor DU174 are assigned an ID to identify the reference LTM DU configuration. In some embodiments, neither CU172 nor DU174 are assigned an ID to identify the reference LTM CU configuration.

[0060] In some embodiments, LTM DU configuration 1 includes several configuration parameters for UE102 to communicate with DU174 on a first cell. In some embodiments, the several configuration parameters include physical layer configuration parameters (e.g., PhysicalCellGroupConfig IE), MAC layer configuration parameters (e.g., MAC-CellGroupConfig IE), and / or RLC configuration parameters (e.g., RLC-BearerConfig IE(or more)). In further embodiments, the several configuration parameters include special cell configurations (e.g., SpCellConfig IE), and / or one or more SCell configurations (e.g., SCellConfig IE(or more)). In some embodiments, LTM DU configuration 1 is a CellGroupConfig IE (e.g., as defined in 3GPP TS38.331). In other embodiments, LTM DU configuration 1 includes configuration parameters in the CellGroupConfig IE.

[0061] In some embodiments, LTM CU configuration 1 includes PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some embodiments, LTM CU configuration 1 includes MeasConfig IE and / or RadioBearerConfig IE (e.g., as defined in 3GPP TS38.331), or includes configuration parameters in MeasConfig IE and / or RadioBearerConfig IE. In some embodiments, LTM DU configuration 1 includes L1 measurement configuration 1 (e.g., CSI-MeasConfig IE) and / or at least one configuration indicator (TCI) state configuration. In further embodiments, LTM CU configuration 1 includes L1 measurement configuration and / or TCI state configuration(s) 1. In some embodiments, the L1 measurement configuration includes at least one reference signal (RS) resource configuration 1 and / or at least one report configuration 1. In some embodiments, RS resource configuration(s) 1 constitute one or more RSs or one or more RS resources associated with cell 1. An RS(s) may include an SSB(s) and / or a CSI-RS(s). An RS resource(s) may include an SSB resource(s) and / or a CSI-RS(s). In some embodiments, each RS resource configuration(s)1 includes an RS resource configuration ID. In some embodiments, an RS resource configuration(s)1 is (or similar to) a CSI-ResourceConfig IE(s). In some embodiments, a report configuration(s)1 configures one or more UL resources (e.g., a PUCCH resource or a PUSCH resource) on cell 1 so that UE102 can send measurement results. In some embodiments, each report configuration(s)1 includes one or more RS resource configuration IDs that identify one or more RS resource configurations included in an RS resource configuration(s)1. In some embodiments, each TCI state configuration(s)1 configures a TCI state that associates one or more DL RSs with the corresponding pseudo-collocation (QCL) type. DL RS(s) are associated with cell 1.

[0062] In some embodiments, DU174 includes an L1 measurement configuration 1 and / or TCI state configuration(s) 1 in the serving DU configuration 1 (e.g., a non-LTM DU configuration). In some embodiments, DU174 includes the serving DU configuration in a first DU-to-CU message. In other embodiments, DU174 sends an additional DU-to-CU message to CU172 that includes the serving DU configuration. In some embodiments, the additional DU-to-CU message is a UE context correction request message. In some embodiments, CU172 sends the serving DU configuration 1 in an RRC reconfiguration message (316 and 318). In other embodiments, CU172 sends another RRC reconfiguration message to UE102 via DU174 that includes the serving DU configuration.

[0063] In some embodiments, DU174 includes a random access configuration in LTM DU configuration 1. In other embodiments, DU174 does not include a random access configuration in LTM DU configuration 1. In some embodiments, if cell 124A and the first cell are not synchronized, DU174 decides to include a random access configuration in LTM DU configuration 1. Otherwise, if cell 124A and the first cell are synchronized, DU174 decides not to include a random access configuration in LTM DU configuration 1. In some embodiments, if DU174 determines that UE102 is not synchronized with the first cell in UL, DU174 decides to include a random access configuration in LTM DU configuration 1. Otherwise, if DU174 determines that UE102 is synchronized with the first cell in UL, DU174 decides not to include a random access configuration in LTM DU configuration 1. If LTM DU configuration 1 includes a random access configuration, UE102 executes the random access procedure according to the random access configuration, as described below (332). Otherwise, if LTM DU configuration 1 does not include a random access configuration, or if LTM instructs UE102 to skip the random access procedure, UE102 skips or refrains from executing the random access procedure in response to LTM DU configuration 1 excluding the random access configuration (332).

[0064] In some embodiments, DU174 includes random access configuration parameters in LTM DU configuration 1 and / or reference LTM DU configuration, regardless of whether cell 124A and the first cell are synchronized. UE102 performs random access procedures according to the random access configuration parameters, as described below (332). In some embodiments, the random access configuration parameters constitute a physical random access channel (PRACH) resource, an association between the SSB resource and the PRACH resource, and / or one or more PRACH occasions.

[0065] In some embodiments, if cell 124A and the first cell are synchronized, DU174 decides to include a first instruction in LTM DU configuration 1 that configures UE102 not to perform a random access procedure in the first cell. Otherwise, if cell 124A and the first cell are not synchronized, DU174 decides not to include the first instruction in LTM DU configuration 1. In further embodiments, if DU174 determines that UE102 is synchronized with the first cell in UL, DU174 decides to include the first instruction in LTM DU configuration 1. Otherwise, if DU174 determines that UE102 is not synchronized with the first cell in UL, DU174 decides not to include the first instruction in LTM DU configuration 1. If LTM DU configuration 1 includes the first instruction, UE102 skips or refrains from performing a random access procedure in accordance with or in response to the first instruction (332). Otherwise, if LTM DU configuration 1 does not include the first instruction, UE 102 performs a random access procedure according to the random access configuration in response to LTM DU configuration 1 excluding the first instruction, as described below (332).

[0066] In some embodiments, DU174 includes a reconfiguration with a synchronization configuration (e.g., ReconfigurationWithSync IE) in LTM DU configuration 1 or a special cell configuration. In further embodiments, DU174 does not include a reconfiguration with a synchronization configuration (e.g., ReconfigurationWithSync IE) in LTM DU configuration 1 or a special cell configuration. In some embodiments, if cell 124A and the first cell are not synchronized, DU174 decides to include a reconfiguration with a synchronization configuration in LTM DU configuration 1. Otherwise, if cell 124A and the first cell are synchronized, DU174 decides not to include a reconfiguration with a synchronization configuration in LTM DU configuration 1. In further embodiments, if DU174 determines that UE102 is not synchronized with the first cell in UL, DU174 decides to include a reconfiguration with a synchronization configuration in LTM DU configuration 1. Otherwise, if DU174 determines that UE102 is synchronized with the first cell in UL, DU174 determines that LTM DU configuration 1 does not include a reconfiguration with a synchronous configuration. In some embodiments, if LTM DU configuration 1 includes a reconfiguration with a synchronous configuration, UE102 performs a random access procedure as described below in response to or in accordance with the reconfiguration with a synchronous configuration (332). Otherwise, if LTM DU configuration 1 does not include a reconfiguration with a synchronous configuration, UE102 skips or refrains from performing a random access procedure (332). In some embodiments, DU174 includes the cell ID (i.e., cell ID1) of cell 1 (i.e., the first cell) in LTM DU configuration 1. In some embodiments, cell ID1 is PCI. In further embodiments, cell ID1 is CGI. In some embodiments, cell ID1 included in LTM DU configuration 1 is PCI, and cell ID1 included in the first CU-to-DU message is CGI. In further embodiments, the LTM DU configuration 1 includes cell ID 1 or cell index 1 which indexes to a first cell. Cell index 1 is not the cell ID. The cell index requires fewer bits than the cell ID.In some embodiments, CU172 sets cell index 1 to a value and includes cell index 1 in the first CU-to-DU message (308).

[0067] In some embodiments, after receiving one or more of at least one measurement reports (304) (for example, in response to receiving them), base station 104 (i.e., CU172 or DU174) decides to prepare additional cells (i.e., cells 2, ..., N) of base station 104 for LTM to UE 102. In some embodiments, base station 104 decides to prepare additional cells (i.e., cells 2, ..., N) for LTM to UE 102 because at least one measurement report indicates that additional cells (i.e., cells 2, ..., N) may be used by base station 104 to communicate with UE 102. In some embodiments, additional cells (i.e.) include cell 124C, and / or cells (i.e.) other than cells 124A, 124B, and 124C. In some embodiments, if the L3 measurement report indicates that the signal strength and / or quality of a particular cell of an additional cell(s) exceeds a predetermined threshold and / or is better than that of cell 124A, the CU172 decides to prepare the particular cell for LTM in the UE102. In some embodiments, if the L1 measurement report indicates that the signal strength and / or quality of a particular cell of an additional cell(s) exceeds a first predetermined threshold and / or is better than that of cell 124A, the DU174 decides to prepare the particular cell for LTM in the UE102. In some embodiments, the predetermined threshold(s) of each additional cell are different from the first predetermined threshold. In some embodiments, the predetermined threshold(s) of each additional cell(s) are the same as the first predetermined threshold. In further embodiments, the predetermined thresholds of each additional cell are the same or different. Alternatively, base station 104 may decide to prepare an additional cell(s) for UE102, regardless of whether a measurement report is received from UE102.

[0068] In some embodiments, CU172 decides to prepare additional cells, and CU172 initiates and executes at least one additional LTM preparation procedure with DU174 to prepare additional cells for the LTM, each LTM preparation procedure being similar to procedure 390.

[0069] In some embodiments, CU172 and DU174 perform LTM preparation steps 2, ..., N, respectively, to prepare cell(s) 2, ..., N, similar to step 390. In some embodiments, CU172 includes cell(s) 2, ..., N in CU-to-DU messages 2, ..., N, similar to the first CU-to-DU message. In LTM preparation steps 2, ..., N, DU174 generates LTM DU configurations 2, ..., N that constitute cell(s) 2, ..., N, as described for LTM DU configuration 1, and includes LTM DU configurations 2, ..., N in DU-to-CU messages 2, ..., N, respectively. When DU174 receives CU-to-DU messages 2, ..., N, DU-to-CU messages 2, ..., N respond to CU-to-DU messages 2, ..., N, respectively. "N" is an integer greater than 1. For example, "N" can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16. In other examples, the maximum number for "N" is 4, 8, 16, or 32. In some embodiments, LTM DU configuration 1 applies to LTM DU configurations 2, ..., N.

[0070] In further embodiments, CU172 and DU174 perform a single LTM preparation procedure (i.e., LTM preparation procedure 390) to prepare cell(s) 1, 2, ..., N. In some embodiments, in the first DU-to-CU message, DU174 includes LTM DU configuration(s) 1, 2, ..., N for each of cell(s) 1, 2, ..., N. In some embodiments, in the first DU-to-CU message, DU174 includes cell(s) 1, 2, ..., N along with LTM DU configuration(s). In some embodiments, CU172 decides to perform the LTM preparation procedure (390), and CU172 includes cell(s) 1, 2, ..., N in the first CU-to-DU message to request DU174 to prepare cell(s) 1, 2, ..., N for LTM.

[0071] In some embodiments, after receiving LTM DU configuration(s) 2, ..., N from DU174, CU172 includes LTM DU configuration(s) 2, ..., N in a first container. In some embodiments, CU172 includes LTM DU configuration(s) 2, ..., N in element(s) 2, ..., N, and includes element(s) 2, ..., N in a first container. In some embodiments, CU172 includes LTM ID(s) (i.e., ID(s) 2, ..., N) for each LTM DU configuration(s) 2, ..., N in the RRC reconfiguration message to identify them. In some embodiments, CU172 includes ID(s) 2, ..., N in a first container. In some embodiments, CU172 includes ID(s)2, ..., N and LTM DU configuration(s)2, ..., N in the first modification list of elements(s).

[0072] In some embodiments, CU172 assigns IDs 2, ..., N to LTM DU configurations 2, ..., N, respectively. In further embodiments, CU172 receives IDs 2, ..., N from DU174 in the first DU-to-CU message of step 390. In yet another embodiment, CU172 receives IDs 2, ..., N from DU174 in DU-to-CU messages 2, ..., N of LTM preparation steps 2, ..., N, respectively.

[0073] In some embodiments, CU172 performs the LTM ID assignment procedure with DU174 for each LTM DU configuration 2, ..., N, similar to procedure 392. In further embodiments, CU172 includes and instructs a third CU-to-DU message that associates IDs 2, ..., N with LTM DU configurations 2, ..., N. In some embodiments, DU174 associates LTM DU configurations 2, ..., N with IDs 2, ..., N, respectively. In yet another embodiment, CU172 includes and instructs a third CU-to-DU message that associates cell IDs 2, ..., N with IDs 2, ..., N. In some embodiments, DU174 associates LTM DU configurations 2, ..., N with IDs 2, ..., N, respectively, based on the associations between cell IDs 2, ..., N and IDs 2, ..., N, and between cell IDs 2, ..., N and LTM DU configurations 2, ..., N. In other embodiments, CU172 includes IDs 2, ..., N, cell IDs 2, ..., N and / or LTM DU configurations 2, ..., N in a second CU-to-DU message, as described above. Thus, a third CU-to-DU message is omitted. In yet another embodiment, CU172 includes IDs 2, ..., N in a first CU-to-DU message, indicating that IDs 2, ..., N are associated with cell IDs 2, ..., N, respectively. In some embodiments, DU174 includes IDs 2, ..., N in the LTM DU configuration(s) 2, ..., N. Therefore, CU172 does not include IDs 2, ..., N in the RRC reconfiguration message, the first container and / or element(s) 2, ..., N.

[0074] In further embodiments, DU174 assigns IDs 2, ..., N. In some embodiments, DU174 includes IDs 2, ..., N in the first DU-to-CU message of procedure 390. In further embodiments, DU174 includes IDs 2, ..., N in the DU-to-CU messages of LTM preparation procedures 2, ..., N. In some embodiments, CU172 includes IDs 2, ..., N in the RRC reconfiguration message. In other embodiments, DU174 includes IDs 2, ..., N in the LTM DU configurations 2, ..., N. Thus, CU172 does not include an ID (e.g., LTM ID) identifying each LTM DU configuration 2, ..., N in the RRC reconfiguration message, the first container, and / or element 1.

[0075] In some embodiments, instead of using the first container, CU172 generates a second container containing LTM DU configuration(s) 2, ..., N or element(s) 2, ..., N. In some embodiments, CU172 sends an additional RRC reconfiguration message containing the second container to UE102 via DU174, similar to events 316 and 318. In response, UE102 sends an additional RRC reconfiguration complete message to CU172 via DU174, similar to events 320 and 322. In some embodiments, the second container is a second add or modify list (e.g., an ltm-ConfigToAddModList field, LTM-ConfigToAddModList IE, ltm-CandidateConfigToAddModList field, or LTM-CandidateConfigToAddModList IE), where each element 2, ..., N is an add or modify IE (e.g., an ltm-ConfigToAddMod field, LTM-ConfigToAddMod IE, ltm-CandidateConfigToAddMod field, or LTM-CandidateConfigToAddMod IE). In some embodiments, UE102 receives the second add or modify list and stores the second add or modify list together with the first add or modify list (e.g., in a variable in its random access memory (RAM)).

[0076] In some embodiments, DU174 includes cell IDs 2, ..., N in the LTM DU configuration 2, ..., N to identify cell(s) 2, ..., N. In some embodiments, each cell ID 2, ..., N is PCI. In further embodiments, the LTM DU configuration 2, ..., N includes cell index(s) 2, ..., N, each indexing cell ID(s) 2, ..., N or cell(s) 2, ..., N. In some embodiments, CU172 prepares cell(s) 2, ..., N for the LTM in step 390, CU172 sets cell index(s) 2, ..., N to different values, and includes cell index(s) 2, ..., N in the first CU-to-CU-to-DU message in 308. In some embodiments, CU172 prepares cells 2, ..., N in additional LTM preparation steps, sets cell indexes 2, ..., N to different values, and includes cell indexes 2, ..., N in the CU-to-DU messages of the additional LTM preparation steps. CU172 sets cell indexes 1, ..., N to different values. In some embodiments, cell IDs 1, ..., N in LTM DU configurations 1, ..., N are different from cell IDs 1, ..., N in the aforementioned CU-to-DU messages.

[0077] In some embodiments, each LTM DU configuration(s) 1, ..., N includes physical configuration parameters, MAC configuration parameters, RLC configuration parameters, and / or L1 measurement configuration(s). In some embodiments, each LTM DU configuration(s) 1, ..., N is a CellGroupConfig IE (e.g., as defined in 3GPP TS38.331). In further embodiments, each LTM DU configuration(s) 1, ..., N includes configuration parameters contained within the CellGroupConfig IE (e.g., as defined in 3GPP TS38.331). In even further embodiments, multiple configuration parameters within each LTM DU configuration(s) include specific special cell configurations (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE(s)). In some embodiments, LTM DU configurations 1, ..., N are CellGroupConfig IEs (multiple) (as defined, for example, in 3GPP TS38.331). In further embodiments, LTM DU configurations 1, ..., N include configuration parameters in the CellGroupConfig IE.

[0078] In some embodiments, CU172 includes one or more additional LTM CU configurations in at least one of elements 2, ..., N, a first container, or a second container. Each of the additional LTM CU configurations is associated with a particular LTM DU configuration of LTM DU configurations 2, ..., N. In some embodiments, the additional LTM CU configurations are similar to LTM CU configuration 1.

[0079] In some embodiments, CU172 decides to release an LTM DU configuration M (or an element M of an element 1, ..., M) of an LTM DU configuration 1, ..., N, where 1 ≤ M ≤ N. In response to the decision, CU172 sends an RRC reconfiguration message to UE102 via DU174 instructing UE102 to release the LTM DU configuration M or element M. In some embodiments, CU172 generates a release list containing IDs (i.e., LTM IDs) M for releasing the LTM DU configuration M or element M, and includes that release list in the RRC reconfiguration message. In response to the RRC reconfiguration message, UE102 releases the LTM DU configuration M or element M and sends an RRC reconfiguration complete message to CU172 via DU174. In response to the decision, CU172 sends a CU-to-DU message to DU174 instructing DU174 to release the LTM DU configuration M. In some embodiments, to instruct DU174 to release the LTM DU configuration M, CU172 includes a cell ID M or ID (i.e., LTM ID) M in a release instruction (e.g., a field or IE) within the CU-to-DU message. In response, DU174 releases the LTM DU configuration M and sends a DU-to-CU message to CU172. In some embodiments, the CU-to-DU message and the DU-to-CU message are a UE context modification request message and a UE context modification response message, respectively.

[0080] In other embodiments, DU174 decides to release LTM DU configuration K. In response to this decision, DU174 sends a DU-to-CU message to CU172 to release LTM DU configuration K. In some embodiments, to indicate that LTM DU configuration K is to be released, DU174 includes a release instruction (e.g., a field or IE) in the DU-to-CU message containing cell ID K or ID (i.e., LTM ID) K (e.g., 1 ≤ K ≤ N). After receiving the DU-to-CU message (e.g., in response thereto), CU172 generates a release list containing ID (i.e., LTM ID) K to release LTM DU configuration K or element K and sends an RRC reconfiguration message containing the release list to UE102 via DU174. In response, UE102 releases LTM DU configuration K or element K and sends an RRC reconfiguration complete message to UE102 via DU174. In some embodiments, CU172 sends a CU-to-DU message to DU174 in response to a DU-to-CU message. In some embodiments, the DU-to-CU message and the CU-to-DU message are a UE context correction request message and a UE context correction confirmation message, respectively.

[0081] In some embodiments, after UE102 receives an RRC reconstruction (318) or sends an RRC reconstruction complete message (320), UE102 sends at least one measurement report to DU174 (324), similar to event 304. In some embodiments, DU174 sends a DU-to-CU message containing at least one measurement report to CU172 (326), similar to event 306. In other embodiments, DU174 does not send at least one measurement report to CU172. In some embodiments, the at least one measurement report includes an L1 measurement report or L3 measurement report in 324, as described for event 304. In some embodiments, UE102 sends at least one measurement report on PUCCH(pl) and / or PUSCH(pl) to DU174 (324), similar to event 304. In further embodiments, UE102 sends at least one MAC CE containing at least one measurement report to DU174, similar to event 304 (324). In some embodiments, UE102 does not send L1 measurement reports(or more) to DU174 in RRC message(or more) format.

[0082] In some embodiments, UE102 transmits at least one measurement report to DU174 according to at least one measurement configuration (324). The at least one measurement configuration configures UE102 to perform a measurement and report the measurement results. CU172 transmits at least one measurement configuration to UE102 via DU174. In some embodiments, CU172 transmits one or more RRC messages (e.g., RRCReconfiguration messages) containing at least one measurement configuration to UE102 via DU174 (302 and / or 316 and / or 306 or 316). In some embodiments, one or more RRC messages include an RRC reconfiguration message in 316. According to at least one measurement configuration, UE102 performs a measurement on one or more reference signals. In some embodiments, one or more reference signals include one or more SSBs and / or one or more CSI-RSs. In some embodiments, UE102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurement (324) and includes at least one L1 measurement result and / or at least one L3 measurement result in at least one measurement report. DU174 transmits one or more reference signals on cell 124A, cell 1 and / or cell(s) 2, ..., N. In some embodiments, one or more reference signals are CSI-RS(s) or SSB(s).

[0083] In some embodiments, at least one measurement configuration includes L3 measurement configurations (multiple) (e.g., MeasConfig IE(multiple)) in 304. In further embodiments, at least one measurement configuration includes, or is, an L1 measurement configuration(multiple) as described above. In further embodiments, the L1 measurement configuration(multiple) is a CSI-MeasConfig IE(multiple) (e.g., as defined in 3GPP TS38.331). In further embodiments, the L1 measurement configuration(multiple) includes RS resource configuration(multiple) and / or report configuration(multiple). UE102 sends L1 measurement reports(multiple) regarding UL resources (e.g., physical uplink control channel (PUCCH) resources or physical unlink shared channel (PUSCH) resources) to DU174 (324) according to the report configuration(multiple). DU174 receives L1 measurement reports(multiple) regarding UL resources according to the report configuration(multiple). In some embodiments, the report configuration(s) are similar to the CSI-ReportConfig IE(s). In other embodiments, each report configuration is a specially defined RRC IE(s). In some embodiments, each report configuration constitutes periodic reporting and / or event-triggered reporting of L1 measurement results(s).

[0084] In some embodiments, the L1 measurement report is a CSI report. In other embodiments, the L1 measurement report is a MAC CE. In some embodiments, each measurement report includes one or more RS resource indicators and / or one or more quantized measurements. UE102 performs measurements on RS(multiple) or RS resources(multiple) according to the RS resource configuration(s) and / or report configuration(s), and obtains quantized measurements from these measurements. In some embodiments, the RS resource indicator(s) indicate the RS(multiple) or RS resources(s) on which UE102 performs measurements or from which quantized measurements are obtained. In some embodiments, the RS resource indicator(s) include one or more SSB resource indicators (SSBRI(multiple)) and / or one or more CSI-RS resource indicators (CRI(multiple)). In some embodiments, the quantized measurements include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0085] In further embodiments, at least one measurement configuration includes a measurement configuration of a specifically defined type (e.g., an LTM measurement configuration as defined in 3GPP TS). In some embodiments, the specifically defined measurement configuration includes a reference signal resource configuration(s) that constitutes the resources to which DU174 transmits reference signals. For example, the reference signal resource configuration(s) includes CSI-RS(s) and / or SSB(s). In one embodiment, the reference signal resource configuration(s) is a CSI-ResourceConfig IE(s). In some embodiments, the specifically defined measurement configuration includes a measurement report configuration as described above. UE102 sends a measurement report(s) regarding PUCCH(s) or MAC CE(s) to DU174 according to the measurement report configuration(s). DU174 receives a measurement report(s) regarding PUCCH(s) or MAC CE(s) according to the measurement report configuration(s). In some embodiments, the measurement report(s) may be L1 measurement reports(s) or specifically defined measurement reports(s) (e.g., LTM measurement reports(s)). In some embodiments, the specifically defined measurement configuration includes specifically defined configuration parameters (e.g., those specified in the 3GPP TS).

[0086] In response to receiving at least one measurement report (324), DU174 generates a first LTM command to activate LTM DU configuration 1 (i.e., the first LTM command sends to UE102 a command to apply LTM DU configuration 1, or a command to perform a serving cell change to cell 1). DU174 then sends the first LTM command to UE102 (330). In some embodiments, DU174 sends the first LTM command to UE102 at cell 124A. In further embodiments, DU174 sends the first LTM command to UE102 at cell 124D. In some embodiments, DU174 includes an ID 1 in the first LTM command to indicate LTM DU configuration 1 or element 1, and UE102 determines LTM DU configuration 1 or element 1 according to the ID 1.

[0087] In some embodiments, DU174 includes a cell index 1 that indexes cell ID 1 in the first LTM command. UE102 determines LTM DU configuration 1 or element 1 based on cell index 1. Before receiving the first LTM command, UE102 retrieves cell index 1 from LTM DU configuration 1 or element 1 and establishes association 1 between cell index 1 and LTM DU configuration 1 or element 1. In other words, UE102 decodes LTM DU configuration 1 or element 1 to retrieve cell index 1 before receiving the first LTM command. Thus, UE102 determines LTM DU configuration 1 or element 1 according to cell index 1 and association 1. Before receiving the first LTM command, UE102 retrieves cell indices 2, ..., N from the LTM DU configuration(s) or elements 2, ..., N and establishes the respective associations 2, ..., N between the cell indices 2, ..., N and the LTM DU configuration(s) or elements 2, ..., N. In other words, before receiving the first LTM command, UE102 decodes the LTM DU configuration(s) or elements 2, ..., N to obtain the cell indices 2, ..., N.

[0088] In further embodiments, DU174 includes cell ID1 in the first LTM command, where cell ID1 identifies cell 1. In some embodiments, cell ID1 in the first LTM command is the same as cell ID1 in the first CU-to-DU message. In some embodiments, DU174 determines cell ID1 in the first LTM command (e.g., PCI) from cell ID1 received in the first CU-to-DU message (e.g., CGI). UE102 determines (e.g., identifies) LTM DU configuration 1 or element 1 based on cell ID1. Before receiving the first LTM command, UE102 retrieves cell ID1 from LTM DU configuration 1 or element 1 and establishes association 1 between cell ID1 and LTM DU configuration 1 or element 1. In other words, UE102 decodes LTM DU configuration 1 or element 1 to retrieve cell ID1 before receiving the first LTM command. Therefore, UE102 identifies LTM DU configuration 1 or element 1 according to cell ID 1 (e.g., from the first LTM command) and association 1. Before receiving the first LTM command, UE102 obtains cell ID 2, ..., N from LTM DU configuration(s) or element(s) 2, ..., N and establishes association(s) 2, ..., N between cell ID(s) 2, ..., N and LTM DU configuration(s) or element(s) 2, ..., N. In other words, before receiving the first LTM command, UE102 decodes LTM DU configuration(s) or element(s) 2, ..., N to obtain cell ID(s) 2, ..., N. In some embodiments, DU174 has a mapping table to store the mappings between PCI(s) 1, ..., N and CGI(s) 1, ..., N for each cell(s).

[0089] In further embodiments, DU174 includes a bitmap in the first LTM command for activating LTM DU configuration 1 instead of ID 1 or cell index 1. The number of bits in the bitmap is N or greater. In some embodiments, bits 1, ..., N correspond to cell index 1, ..., N, ID 1, ..., N, LTM DU configuration 1, ..., N, or element 1, ..., N, respectively, and DU174 sets the corresponding bit in the bitmap (e.g., bit 1) to a first value to indicate cell index 1, ID 1, LTM DU configuration 1, or element 1. In some embodiments, UE102 determines cell index 1, ID 1, LTM DU configuration 1, or element 1 according to bit 1 set to a first value in the bitmap. In some embodiments, bits 0, ..., N-1 correspond to cell index(s) 1, ..., N, ID(s) 1, ..., N, LTM DU configuration(s) 1, ..., N, or element(s) 1, ..., N, respectively, and DU174 sets the corresponding bit in the bitmap (e.g., bit 0) to a first value to indicate cell index 1, ID1, LTM DU configuration(s) 1, or element(s). In some embodiments, UE102 determines cell index 1, ID1, LTM DU configuration(s) 1, ..., N, or element(s) 1 according to bit 0 set to the first value in the bitmap. In some embodiments, DU174 sets the remaining bits in the bitmap to a second value to indicate that the rest of LTM DU configuration(s) 1, ..., N are not activated. In some embodiments, the first value is 1 and the second value is zero. In further embodiments, the first value is zero and the second value is 1. In some embodiments, when DU174 decides to activate LTM DU configuration L or change the serving cell to cell L of UE102, DU174 sets the corresponding bit in the bitmap (e.g., bit L or bit L-1) to a first value and the remaining bits to a second value (1 ≤ L ≤ N). In some embodiments, DU174 sets up to 1 bit in the bitmap to a first value.

[0090] After determining or identifying LTM DU configuration 1 or element 1, UE102 applies LTM DU configuration 1 and / or LTM CU configuration after receiving a first LTM command (for example, in response to receiving it).

[0091] In some embodiments, at least one measurement report 324 (e.g., an L1 measurement report or a specifically defined measurement report) includes at least one measurement result from a first cell, a TRP(or more) from the first cell, or a reference signal(or more) transmitted from the first cell. In some embodiments, the reference signal(or more) is CSI-RS(or more) or SSB(or more). Based on at least one measurement result, DU174 decides to activate LTM DU configuration 1 or to transmit a first LTM command. In some embodiments, DU174 decides to activate LTM DU configuration 1 if at least one measurement result exceeds a second predetermined threshold. In some embodiments, at least one measurement result includes L1-RSRP(or more), L1-RSRQ(or more), and / or L1-SINR(or more). In other embodiments, at least one measurement result includes RSRP values, RSRQ values, and / or SINR values ​​from a specifically defined measurement report(s). In some embodiments, a second predetermined threshold is different from a first predetermined threshold. In some embodiments, the second predetermined threshold is greater than the first predetermined threshold. In this case, at least one measurement result indicates that the first cell is suitable for communication with UE102. In some embodiments, the second predetermined threshold is equal to the first predetermined threshold. In this case, at least one measurement result indicates that the first cell is successively above the second predetermined threshold or the first predetermined threshold. This indicates that the first cell is suitable for communication with UE102. Therefore, DU174 decides to activate LTM DU configuration 1 when the signal strength or quality of the first cell exceeds the second predetermined threshold of UE102.

[0092] In some embodiments, at least one measurement report (e.g., L3 measurement report(s)) includes at least one measurement result at 324 and 326 of the first cell. CU172 decides to activate LTM DU configuration 1 or send a first LTM command because at least one measurement result indicates that the signal strength or quality of the first cell exceeds a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In further embodiments, the second predetermined threshold is greater than the first predetermined threshold. In such embodiments, at least one measurement report indicates that the signal strength or quality of the first cell is suitable for communication with UE102 (326). In yet another embodiment, the second predetermined threshold is equal to the first predetermined threshold. In such embodiments, at least one measurement report indicates that the signal strength or quality of the first cell is successively above the second predetermined threshold or the first predetermined threshold (326). This also indicates that the first cell is suitable for communication with UE102. Thus, CU172 decides to activate LTM DU configuration 1 in response that the signal strength or quality of the first cell exceeds a second predetermined threshold. In response to this decision, CU172 sends a fourth CU-to-DU message to DU174 to activate LTM DU configuration 1 or to trigger a change in the serving cell of UE102 to cell 1 (328). In some embodiments, CU172 includes ID 1 in the fourth CU-to-DU message. In further embodiments, CU172 includes cell index 1 in the fourth CU-to-DU message. In response to the fourth CU-to-DU message, DU174 sends a first LTM command to UE102 (330) and optionally sends a fourth DU-to-CU message to CU172. In some embodiments, CU172 includes cell index 1 in the fourth CU-to-DU message. In some embodiments, DU174 decides to activate LTM DU configuration 1 according to cell index 1. In further embodiments, CU172 includes cell ID 1 in the fourth CU-to-DU message.Therefore, DU174 decides to activate LTM DU configuration 1 according to cell ID 1. In further embodiments, CU172 includes ID 1 in the fourth CU-to-DU message. In some embodiments, DU174 decides to activate LTM DU configuration 1 according to ID 1. In further embodiments, the fourth CU-to-DU message and the fourth DU-to-CU message are a UE context correction request message and a UE context correction response message, respectively. In further embodiments, the fourth CU-to-DU message and / or the fourth DU-to-CU message are a specifically defined interface message (e.g., an F1AP message as defined in 3GPP TS38.473).

[0093] In some embodiments, when DU174 decides to activate LTM DU configuration 1 or to send a first LTM command (330), DU174 sends a DU-to-CU message to CU172 to perform LTM (329). In further embodiments, DU174 includes cell ID1 or ID1 (i.e., LTM ID) in the DU-to-CU message at 329 to instruct DU174 to activate LTM DU configuration 1 or to trigger a fast serving cell change (i.e., an LTM serving cell change). In yet another embodiment, DU sends a DU-to-CU message to CU172 (329) before or after sending an LTM command (330).

[0094] In some embodiments, UE102 receives a first LTM command from DU174 by MAC CE contained in the MAC PDU (330). In some embodiments, MAC CE is a specifically defined MAC CE (e.g., defined in 3GPP TS38.321). In some embodiments, DU174 includes a subheader that identifies the specifically defined MAC CE in the MAC PDU, and UE102 identifies the specifically defined MAC CE in the MAC PDU according to the subheader. In some embodiments, the subheader includes a logical channel ID or extended logical channel ID to identify the specifically defined MAC CE. For example, the logical channel ID or extended logical channel ID is a specifically defined ID (e.g., defined in 3GPP TS38.321). In further embodiments, the first LTM command is a DCI that UE102 receives from DU174 at PDCCH (330). DU174 generates the CRC for DCI, scrambles the CRC with the first C-RNTI of UE102, and transmits the DCI and the scrambled CRC with PDCCH (330). In some embodiments, a DCI format exists (e.g., specified in 3GPP TS38.212). In further embodiments, the DCI format is a specifically defined DCI format (e.g., specified in 3GPP TS38.212).

[0095] In some embodiments, DU174 does not perform security protection (e.g., integrity protection and / or encryption) on the first LTM command. This speeds up the processing of the first LTM command by UE102 because UE102 does not perform security checks (e.g., decryption and / or integrity checks) on the first LTM command.

[0096] In some embodiments, after receiving the first LTM command, UE102 sends an acknowledgment to DU174 on cell 124A or cell 124D to indicate that UE102 has received the first LTM command (331). In some embodiments, the acknowledgment is a HARQ ACK. In some embodiments, the acknowledgment is a MAC CE. For example, the MAC CE is an existing MAC CE (e.g., specified in 3GPP specification 38.321). As a further example, the MAC CE is a specifically defined MAC CE (e.g., specified in 3GPP specification 38.321). In yet another embodiment, the acknowledgment is a PUCCH transmission.

[0097] In some embodiments, CU172 sends an RRC reconfiguration message (316) in response to receiving an L3 measurement report for a first cell (306). In further embodiments, CU172 sends a first RRC reconfiguration message to UE102 containing an L3 measurement configuration (e.g., MeasConfig IE) in order to configure UE102 to send an L3 measurement report (304). In some embodiments, DU174 sends a first LTM command (330) in response to an L1 measurement report for a first cell (324). In some embodiments, CU172 sends a second RRC reconfiguration message to UE102 containing an L1 or a specifically defined measurement configuration in order to configure UE102 to send an L1 or a specifically defined measurement report (324). In some embodiments, the first and second RRC reconfiguration messages are the same message (i.e., the same instance). In further embodiments, the first and second RRC reconfiguration messages are different messages. In further embodiments, CU172 transmits a second RRC reconfiguration message (316). In further embodiments, the second RRC reconfiguration message is a different message (i.e., not the same instance).

[0098] After receiving the first LTM command (for example, in response to receiving it), UE102 accesses the first cell (332). UE102 identifies the LTM DU configuration 1 according to the ID1, cell ID1, or cell index1 received in the first LTM command and applies the LTM DU configuration 1 to communicate with DU174 in the first cell. In some embodiments, UE102 disconnects from cell 124A after receiving the first LTM command (for example, in response to receiving it) or after sending an acknowledgment (331). In some embodiments, UE102 stops communication with cell 124A after receiving the first LTM command (330) (for example, in response to receiving it) or after sending an acknowledgment (331) (for example, in response to sending it). In some embodiments, UE102 accesses the first cell by performing a random access procedure on DU174 and the first cell in response to receiving a first LTM command. In other embodiments, UE102 skips the random access procedure and, after receiving the first LTM command (for example, in response to receiving it), sends a first transmission on the first cell (for example, a PUSCH transmission or a PUCCH transmission) to DU174.

[0099] In some embodiments, DU174 configures UE102's access to a first cell in LTM DU configuration 1, including whether UE102 performs a random access procedure. Upon receiving a first LTM command (e.g., a first LTM command), UE102 determines whether it should perform a random access procedure in the first cell according to LTM DU configuration 1. If LTM DU configuration 1 configures UE102 to perform a random access procedure, UE102 performs a random access procedure in the first cell to connect to the first cell (332). For example, LTM DU configuration 1 includes a reconfiguration with a synchronous configuration (e.g., ReconfigurationWithSync IE) to configure UE102 to perform a random access procedure when UE102 receives an LTM command for the first cell. In some embodiments, in LTM DU configuration 1, DU174 configures UE102 to skip the random access procedure for LTM serving cell changes to the first cell. In such cases, after receiving the first LTM command, UE102 skips the random access procedure and sends the first transmission (e.g., a PUSCH transmission or a PUCCH transmission) in the first cell to DU174 (332). In some embodiments, DU174 configures UE102 to skip the random access procedure for LTM serving cell changes to the first cell by excluding reconfiguration with a synchronous configuration in LTM DU configuration 1.

[0100] In further embodiments, LTM DU configuration 1 includes reconfiguration with synchronous or random access configuration. In such cases, DU 174 configures UE 102 to perform a random access procedure on a first cell in an LTM command. In some embodiments, UE 102 performs a random access procedure on the first cell in accordance with the first LTM command (332). In further embodiments, DU 174 includes an instruction (e.g., a field) in the first LTM command that instructs to skip the random access procedure. In response to this instruction or a first LTM command containing this instruction, UE 102 skips the random access procedure and directly sends a first transmission (e.g., a PUSCH transmission or a PUCCH transmission) on the first cell to access the first cell. In further embodiments, DU 174 omits the instruction in the first LTM command to configure UE 102 to perform a random access procedure. In response to the first LTM command excluding the instruction, UE102 performs a random access procedure on the first cell to access the first cell. In a further embodiment, DU174 includes a timing advance value instructing the first LTM command to skip the random access procedure. In response to receiving the timing advance value, or a first LTM command containing the timing advance value, UE102 skips the random access procedure and uses the timing advance value to send a first transmission on the first cell to access the first cell. In a further embodiment, DU174 omits the timing advance value in the first LTM command to configure UE102 to perform a random access procedure. In response to the first LTM command omitting the timing advance command, UE102 performs a random access procedure on the first cell to access the first cell.

[0101] In some embodiments, the random access procedure is a four-step random access procedure. In some embodiments, the random access procedure is a two-step random access procedure. In further embodiments, the random access procedure is a non-conflict random access procedure. In yet another embodiment, the random access procedure is a conflict-based random access procedure. If the random access procedure is a four-step random access procedure, UE102 sends message 3, which contains the UE identity, to DU174 via the first cell. DU174 responds to message 3 by sending a contention resolution message (e.g., message 4) to UE102. If the random access procedure is a two-step random access procedure, UE102 sends message A, which contains the UE identity, to DU174 via the first cell. DU174 responds to message A by sending a contention resolution message (e.g., message B) to UE102. In some embodiments, when UE102 receives a conflict resolution message from DU174 in the first cell, UE102 determines that UE102 has successfully completed the random access procedure (i.e., UE102 has successfully accessed the first cell). In some embodiments, LTM DU configuration 1 includes a second C-RNTI, and the UE identity is the second C-RNTI of UE102. In some embodiments, the conflict resolution message is a PDCCH transmission addressed to the second C-RNTI. In further embodiments, LTM DU configuration 1 does not include a C-RNTI, and the UE identity is the first C-RNTI. In further embodiments, the conflict resolution message is a PDCCH transmission addressed to the first C-RNTI.

[0102] If LTM DU configuration 1 includes a dedicated random access preamble, the random access procedure is a non-conflicting random access procedure. In such a case, UE102 sends the dedicated random access preamble to DU174 via the first cell. When UE102 receives a random access response from DU174 on the first cell that includes the ID of the dedicated random access preamble, UE102 successfully completes the random access procedure (i.e., UE102 successfully accesses the first cell).

[0103] If DU174 configures UE102 to perform a random access procedure on the first cell as described above, DU174 detects that UE102 has access to the first cell when DU174 receives message 3, message A, or a dedicated preamble in the random access procedure. In some embodiments, DU174 configures UE102 to skip the random access procedure, and DU174 receives a first transmission indicating that UE102 has access to the first cell.

[0104] In some embodiments, UE102 sends a first transmission (e.g., a PUSCH transmission) in the first cell using a UL grant. In some embodiments, the first LTM command includes a UL grant. In further embodiments, when UE102 performs an LTM serving cell change to the first cell in response to the first LTM command, UE102 receives a first DCI including a UL grant at a PDCCH on the first cell. In some embodiments, when UE102 switches to the first cell in response to the first LTM command, UE102 attempts to receive a first DCI or UL grant by monitoring one or more PDCCHs on the first cell according to LTM DU configuration 1. While monitoring one or more PDCCHs on the first cell, UE102 receives the first DCI and the CRC of the first DCI at the PDCCHs. If LTM DU configuration 1 includes a second C-RNT, UE102 uses the CRC and the second C-RNTI to determine that the first DCI has been sent to UE102. If LTM DU configuration 1 does not include a second C-RNT, UE102 uses the CRC and the first C-RNTI to determine that the first DCI has been sent to UE102.

[0105] In some embodiments, CU172 transmits at least one first TCI state configuration to UE102 via DU174. In some embodiments, each first TCI state configuration constitutes a TCI state such that UE102 transmits and / or receives data and / or control signals in a first cell. In some embodiments, each TCI state associates one or two DL RSs with a corresponding QCL type, and each DL RS is associated with a specific cell in cell(s) 1, ..., N. In some embodiments, CU172 receives a DU-to-CU message from DU174 containing the first TCI state configuration and transmits an RRC message containing the first TCI state configuration to UE102 via DU174. In further embodiments, DU174 includes a first TCI state configuration(s) in a serving DU configuration (e.g., CellGroupConfig IE) and includes the serving DU configuration in a DU-to-CU message. In some embodiments, DU174 includes an LTM DU configuration 1 in 312 in a first interface protocol IE / field and includes the serving DU configuration in a second interface protocol IE / field within the DU-to-CU message.

[0106] In some embodiments, the first interface protocol IE / field is defined as part of the format of the DU-to-CU message. CU172 includes the serving DU configuration in the RRC message. In some embodiments, CU172 refrains from including the serving DU configuration in the container (e.g., the first container) for the LTM. In other embodiments, CU172 includes the first TCI state configuration(s) in the element for the LTM, the additional or modified list for the LTM, or the container, which are analogous to element 1, the first additional or modified list, or the first container, respectively. In some embodiments, the RRC message is the RRC reconfiguration message 316, 318, or other RRC reconfiguration message (not shown in Figure 3). In some embodiments, the DU-to-CU message is message 312, message 314, the UE context modification response message, or the UE context modification request message. In some embodiments, DU174 also includes the first TCI state configuration(s) in the LTM DU configuration 1. In further embodiments, DU174 refrains from including a first TCI state configuration(s) in the LTM DU configuration(s).

[0107] In some embodiments, the first interface protocol IE / field is the first F1AP IE / field, and the second interface protocol IE / field is the second F1AP IE / field. In some embodiments, the first F1AP IE / field and one of the second F1AP IE / fields are F1AP CellGroupConfig IE / fields, while the other is not an F1AP CellGroupConfig IE / field. In some embodiments, DU174 includes the first F1AP IE / field at 312 in the RRC information IE from DU to CU, and the second F1AP IE / field in the RRC information IE from DU to CU in the DU-to-CU message. In further embodiments, neither the first nor the second F1AP IE / field is an F1AP CellGroupConfig IE / field. In further embodiments, the second F1AP IE / field is an RRC information IE from DU to CU, and the first F1AP IE / field is an IE specifically defined to include the LTM DU configuration.

[0108] In some embodiments, after receiving a first LTM command (for example, in response to receiving it) or while accessing a first cell (332), UE102 monitors one or more PDCCHs on the first cell using some or all of the first TCI state configurations. In some embodiments, each first TCI state configuration includes a TCI state ID that identifies the corresponding TCI state configuration. For example, a first TCI state configuration includes TCI state configurations 1, ..., L, where L is a positive integer greater than zero. TCI state configurations 1, ..., L include TCI state IDs 1, ..., L that identify each TCI state configuration. DU174 includes TCI state ID 1 in the first LTM command to instruct UE102 to apply TCI state configuration 1 to communicate with the first cell. After receiving a first LTM command (for example, in response to receiving it), UE102 accesses and / or communicates with a first cell using TCI state configuration 1 according to TCI state ID 1. For example, UE102 uses TCI state configuration 1 to monitor one or more PDCCHs and / or send a first transmission. In some embodiments, DU174 detects that UE102 is accessing a first cell based on TCI state configuration 1 and communicates with UE102 in the first cell. For example, DU174 receives a first transmission from UE102 in the first cell based on TCI state configuration 1.

[0109] In some embodiments, DU174 includes TCI state ID 2 in the first LTM command to instruct UE102 to apply TCI state configuration 2 to communicate in the first cell, in addition to TCI state ID 1. After receiving the first LTM command (for example, in response to receiving it), UE102 accesses and / or communicates in the first cell using TCI state configurations 1 and 2 according to TCI state ID 1 and TCI state ID 2. For example, UE102 monitors one or more PDCCHs on the first cell using TCI state configuration 1 and sends a first transmission on the first cell using TCI state configuration 2. In other examples, UE102 monitors one or more PDCCHs on the first cell using TCI state configuration 1 and TCI state configuration 2 and sends a first transmission on the first cell using one of TCI state configuration 1 and TCI state configuration 2. In some embodiments, DU174 detects that UE102 is accessing a first cell based on TCI state configuration 1 and / or TCI state configuration 2, and communicates with UE102 on the first cell. For example, DU174 receives a first transmission from UE102 on the first cell based on TCI state configuration 1 and TCI state configuration 2.

[0110] In further embodiments, DU174 does not include a TCI state ID in the first LTM command. In such cases, UE102 communicates with the first DU on the first cell using at least one first TCI state after receiving the first LTM command (for example, in response to receiving it). In some embodiments, DU174 detects that UE102 is accessing the first cell based on the first TCI state configuration(s) and communicates with UE102 on the first cell.

[0111] In some embodiments, before sending the first LTM command, DU174 sends one or more activation commands to activate some or all of the first TCI state configuration(s). In some embodiments, each activation command is a MAC CE. In further embodiments, each activation command is a DCI. In some embodiments, DU174 includes TCI state ID1 and / or TCI state ID2 in the activation command(s) to activate TCI state configuration 1 and / or TCI state configuration 2, respectively. Thus, upon receiving the activation command(s), UE102 determines or identifies that TCI state configuration 1 and / or TCI state configuration 2 will be activated. In other embodiments, DU174 includes all TCI state ID(s) of the first TCI state configuration(s) in the activation command(s). Thus, upon receiving the activation command(s), UE102 determines or identifies that the first TCI state configuration(s) will be activated. In some embodiments, DU174 refrains from including TCI state IDs of TCI state configurations that DU174 has not activated in UE102 in the first LTM command. In some embodiments, DU174 includes cell ID1 or cell index1 in the activation command(s). Based on cell ID1 or cell index1 in the activation command(s) and one or more TCI state IDs, UE102 determines that the activation command(s) activate one or more TCI state configurations in the first TCI state configuration(s), where each TCI state ID(s) identifies a specific TCI state configuration(s) in the TCI state configuration(s).

[0112] In some embodiments, UE102 communicates with DU174 on cell 124A using one or more TCI state configurations (e.g., events 302, 304, 318, 320, 324, 330). In some embodiments, each TCI state configuration(s) configures a TCI state so that UE102 transmits and / or receives data and / or control signals on cell 124A. In some embodiments, UE102 stops using the TCI configuration(s) upon receiving a first LTM command.

[0113] After successfully accessing the first cell, UE102 communicates with DU174 on the first cell using LTM DU configuration 1 and / or a reference LTM DU configuration (336), and communicates with CU172 via DU174. In such a case, DU174 communicates with UE102 on the first cell using LTM DU configuration 1 (336). In some embodiments, UE102 communicates with DU174 on the first cell using PUSCH, PDSCH, PUCCH, PDCCH, and / or Sounding Reference Signal (SRS) transmissions (336). In some embodiments, UE102 uses some or all of the first TCI state configuration(s) to perform communication with DU174 (336). Similarly, DU174 uses some or all of the first TCI state configuration(s) to perform communication with UE102 (336). In some embodiments, DU174 includes one or more additional TCI state configurations in LTM DU configuration 1. In some embodiments, DU174 sends one or more activation commands to UE102 via the first cell to activate the additional TCI state configuration(s) (336). Upon receiving the activation command(s), UE102 decides to activate the additional TCI state configuration(s). In some embodiments, each activation command(s) is a MAC CE. In further embodiments, each activation command(s) is a DCI. After receiving the activation command(s), UE102 uses the additional TCI state configuration(s) to communicate with DU174 in the first cell. Similarly, after sending the activation command(s), DU174 uses the additional TCI state configuration(s) to communicate with UE102 in the first cell.

[0114] When UE102 receives a reference LTM DU configuration as described above, UE102 communicates with DU174 in the first cell according to LTM DU configuration 1 and at least a portion of the reference LTM DU configuration (336). In other words, UE102 communicates with DU174 according to the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration (336). Similarly, DU174 communicates with UE102 in the first cell according to LTM DU configuration 1 and at least a portion of the reference LTM DU configuration (336). In other words, DU174 communicates with UE102 according to the configuration parameters in LTM DU configuration 1 and the reference LTM DU configuration (336).

[0115] If UE102 does not receive either LTM CU configuration 1 or the reference LTM CU configuration, UE102 communicates with CU172 via DU174 using the serving CU configuration (336). Accordingly, if CU172 does not send either LTM CU configuration 1 or the reference CU configuration to UE102, CU172 communicates with UE102 via DU174 using the serving CU configuration (336). If UE102 receives both LTM CU configuration 1 and the reference LTM CU configuration from CU172, UE102 communicates with CU172 via DU174 using LTM CU configuration 1 and the reference LTM CU configuration not extended by LTM CU configuration 1 (e.g., at least a portion thereof) (336). In this case, CU172 communicates with UE102 via DU174 using LTM CU configuration 1 and a reference LTM CU configuration (e.g., at least a portion thereof) that is not extended by LTM CU configuration 1 (336).

[0116] If UE102 receives LTM CU configuration 1 from CU172 but does not receive a reference LTM CU configuration, UE102 communicates with CU172 via DU174 using LTM CU configuration 1 (336). In this case, CU172 communicates with UE102 via DU174 using LTM CU configuration 1 (336). If LTM CU configuration 1 is a full configuration, UE102 and CU172 communicate with each other via DU174 using LTM CU configuration 1 instead of a serving CU configuration (336). In some embodiments, if UE102 does not receive a reference LTM CU configuration from base station 104, UE102 determines that LTM CU configuration 1 is a full configuration. Accordingly, if CU172 decides to configure LTM CU configuration 1 as a full configuration, CU172 does not send a reference LTM CU configuration to UE102. In some embodiments, CU172 includes a first instruction (e.g., a field or IE) in 336 to indicate that LTM CU configuration 1 is a full configuration within LTM CU configuration 1, a first container, element 1, or an RRC reconfiguration message. If LTM CU configuration 1 is a delta configuration for extending the serving CU configuration, UE102 and CU172 communicate with each other via DU174 using LTM CU configuration 1 and at least a portion of the serving CU configuration not extended by LTM CU configuration 1 (336). In some embodiments, if UE102 does not receive a reference LTM CU configuration from base station 104, UE102 determines that LTM CU configuration 1 is a delta configuration for extending the serving CU configuration. Accordingly, if CU172 decides to configure LTM CU configuration 1 as a delta configuration for extending the serving CU configuration, CU172 does not send a reference LTM CU configuration to UE102. In some embodiments, CU172 indicates that LTM CU configuration 1 is a delta configuration for extending the serving CU configuration by excluding LTM CU configuration 1, first container, element 1, and / or first instruction in the RRC reconfiguration message (316).Alternatively, CU172 may include a second instruction (e.g., a field or IE) in 316 to indicate that LTM CU configuration 1 is a delta configuration for extending the serving CU configuration within LTM CU configuration 1, the first container, element 1, or the RRC reconfiguration message. In some embodiments, CU172 indicates that LTM CU configuration 1 is a full configuration by omitting the second instruction in LTM CU configuration 1, the first container, element 1, and / or the RRC reconfiguration message (316).

[0117] If UE102 receives a reference LTM CU configuration from CU172 but does not receive LTM CU configuration 1, UE102 communicates with CU172 via DU174 using the reference LTM CU configuration (336). In this case, CU172 communicates with UE102 via DU174 using the reference LTM CU configuration (336). If the reference LTM CU configuration is a full configuration, UE102 and CU172 communicate with each other via DU174 using the reference LTM CU configuration instead of the serving CU configuration (336). In some embodiments, UE102 and CU172 determine that reference LTM CU configuration 1 is a full configuration (for example, as specified in 3GPP TS38.331). In some embodiments, CU172 includes a first instruction (e.g., a field or IE) in 316 to indicate that the reference LTM CU configuration is a full configuration within the reference LTM CU configuration, the first container, or the RRC reconfiguration message. If the reference LTM CU configuration is a delta configuration for extending the serving CU configuration, UE102 and CU172 communicate with each other via DU174 using the reference LTM CU configuration and at least a portion of the serving CU configuration not extended by the reference LTM CU configuration (336). In some embodiments, CU172 indicates that the reference LTM CU configuration is a delta configuration for extending the serving CU configuration by omitting the first instruction in the reference LTM CU configuration, the first container, element 1, and / or the RRC reconfiguration message (316). Alternatively, CU172 may include a second instruction (e.g., a field or IE) in 316 to indicate that the reference LTM CU configuration is a delta configuration for extending the serving CU configuration within the reference LTM CU configuration, the first container, element 1, or the RRC reconfiguration message. In some embodiments, CU172 indicates that the reference LTM CU configuration is a full configuration by omitting the second instruction in the reference LTM CU configuration, the first container, element 1, and / or the RRC reconfiguration message (316).

[0118] If UE102 does not receive either the reference LTM CU configuration or LTM CU configuration 1 from CU172, UE102 communicates with CU172 via DU174 using the serving LTM CU configuration (336). In this case, CU172 communicates with UE102 via DU174 using the serving LTM CU configuration (336).

[0119] In some embodiments, UE102 sends an RRC message (e.g., an RRC reconfiguration complete message) to CU172 via DU174 and the first cell to instruct UE102 to apply LTM DU configuration 1. In some embodiments, UE102 performs a random access procedure (332) and UE102 includes the RRC message in message 3 or message A. Alternatively, UE102 sends the RRC message after completing the random access procedure. In some embodiments, UE102 skips the random access procedure (332) and UE102 includes the RRC message in one of at least one PUSCH transmissions. In some embodiments, UE102 maintains communication with base station 104 on cell 124A (i.e., UE102 does not disconnect from cell 124A) and UE102 sends the RRC message to base station 104 via cell 124A. When DU174 receives an RRC message, it sends an RRC message to CU172.

[0120] In further embodiments, UE102 refrains from sending an RRC message to base station 104 in response to applying LTM DU configuration 1 or receiving a first LTM command. In some embodiments, UE102 includes or sends data in message 3, message A, or PUSCH transmission as described above. In further embodiments, UE102 generates a MAC PDU and / or RLC PDU containing data and sends or includes the MAC PDU and / or RLC PDU in a PUSCH transmission. In some embodiments, the data is a PDCP PDU, SDAP PDU, LTE Positioning Protocol (LPP) PDU, RRC PDU, and / or NAS PDU. The RRC PDU includes a UL-DCCH-Message excluding an RRC reconfiguration complete message. The NAS PDU includes a Mobility Management (MM) message or a Session Management (SM) message. In some embodiments, the MM message is a 5G MM message or a 6G MM message, and the SM message is a 5G SM message or a 6G SM message. When DU174 receives data, it sends this data to CU172.

[0121] In some embodiments, when DU174 determines (332 or 336) that UE102 has successfully connected to the first cell, DU174 sends a DU-to-CU message (e.g., an access success message) to CU172 (e.g., CP of CU172) (334). In further embodiments, DU174 includes cell ID 1 at 334 of the first cell in the DU-to-CU message. In some embodiments, the cell ID is PCI or CGI. Thus, when CU172 receives the DU-to-CU message, it determines that UE102 has connected to the first cell (334). When DU174 determines (332 or 336) that UE102 has successfully connected to the first cell, DU174 sends a DL data delivery status message or frame to CU172 (e.g., UP of CU172). In some embodiments, when CU172 receives a DU-to-CU message (329), or after receiving it, CU172 stops or suspends sending DL data of UE102 to DU174 until it receives another DU-to-CU message (334). In some embodiments, because DU174 does not buffer DL data of UE102 during LTM execution, CU172 stops or suspends sending (330 and / or 332). After receiving a DU-to-CU message (334), CU172 continues or resumes sending DL data of UE102 to DU174. In further embodiments, CU172 receives a DU-to-CU message (329), and CU172 continues sending DL data of UE102 to DU174. In further embodiments, DU174 buffers DL data for UE102 during LTM execution, so CU172 continues to transmit (330 and / or 332). When DU174 detects, or after, that UE102 is accessing cell 1, DU174 transmits DL data to UE102 via cell 1.

[0122] In some embodiments, when UE102 decides to connect to a first cell, sends a first LTM command (330) or receives an acknowledgment (331), DU174 stops communicating with UE102 on cell 124A and / or releases the resources of cell 124A configured for UE102.

[0123] In some embodiments, DU174 generates some or all of LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as full configurations to replace the serving DU configuration. When LTM DU configuration 1 is a full configuration, UE102 and DU174 communicate with each other according to LTM DU configuration 1 instead of the serving DU configuration (336). In some embodiments, DU174 includes an instruction indicating that LTM DU configuration 1 is a full configuration. In some embodiments, in each LTM DU configuration 2, ..., N, DU174 includes an instruction indicating that the corresponding DU configuration is a full configuration. In further embodiments, each instruction in LTM DU configuration 1, ..., N is a field or IE (i.e., the same field or IE). In further embodiments, CU172 includes a single instruction in the RRC reconfiguration messages in 316 and 318 indicating that LTM DU configuration(s) 1 and / or 2, ..., N is fully configured. In further embodiments, CU172 includes a single instruction in an additional RRC reconfiguration message in a second container indicating that LTM DU configuration(s) 2, ..., N is fully configured. In even further embodiments, CU172 includes a single instruction in the first container indicating that LTM DU configuration(s) 1 and / or 2, ..., N is fully configured. In even further embodiments, for each of LTM DU configuration(s) 2, ..., N, CU172 includes a specific instruction in the first container indicating that the corresponding LTM DU configuration is fully configured. In some embodiments, with respect to the second container, CU172 includes a single instruction indicating that the LTM DU configuration(s) 2, ..., N is a full configuration(s). In further embodiments, CU172 includes an instruction for element 1 indicating that LTM DU configuration 1 is a full configuration. In some embodiments, for each of elements 2, ..., N, CU172 includes an instruction indicating that the corresponding LTM DU configuration is a full configuration.In some embodiments, UE102 determines, based on the above directives, that LTM DU configuration 1 and / or LTM DU configurations 2, ..., N are full configurations. In some embodiments, each of the above directives is different from the fullConfig field (e.g., as defined in the current 3GPP TS). In some embodiments, each of the above directives is the fullConfig field (e.g., as defined in the 3GPP TS). If LTM DU configuration 1 is a full configuration, UE102 does not apply the reference LTM DU configuration when received from base station 104 (e.g., when UE102 receives an RRC reconfiguration message (318) (336). In some embodiments, DU174 does not include the reference LTM DU configuration in the first DU-to-CU message at 310.

[0124] In some embodiments, DU174 generates LTM DU configuration 1 and / or LTM DU configuration 2, ..., N as delta configurations that extend a reference LTM DU configuration (e.g., a portion thereof). In other words, DU174 generates LTM DU configurations 1, ..., N based on a reference LTM DU configuration. For example, if LTM DU configuration 1 is a delta configuration, UE102 and DU174 extend the reference LTM DU configuration (e.g., a portion thereof) by LTM DU configuration 1. Thus, UE102 and DU174 communicate with each other according to LTM DU configuration 1 (336) and do not extend a portion of the reference LTM DU configuration. In some embodiments, an LTM DU configuration(s) 1, and / or 2, ..., N, a first container, a second container or element(s) 1, ..., N excludes instructions(s) indicating that an LTM DU configuration(s) 1, and / or 2, ..., N is a full configuration(s) in order to indicate that an LTM DU configuration(s) 1, and / or 2, ..., N is a delta configuration(s). In some embodiments, UE102 determines that each LTM DU configuration(s) 1, and / or 2, ..., N is a delta configuration based on the instructions excluded within the LTM DU configuration(s) 1, and / or 2, ..., N, a first container, a second container or element(s) 1, and / or 2, ..., N.

[0125] In some embodiments, if UE102 does not receive a reference LTM DU configuration for LTM DU configuration 1 and / or LTM DU configuration(s) 2, ..., N, UE102 determines that LTM DU configuration 1 and / or LTM DU configuration(s) 2, ..., N are full configuration(s). Accordingly, if DU174 does not obtain a reference LTM DU configuration for UE102 (i.e., DU174 does not generate a reference LTM DU configuration for UE102 and / or does not receive a reference LTM DU configuration for UE102 from CU172), DU174 generates LTM DU configuration 1 and / or LTM DU configuration(s) 2, ..., N as full configuration(s).

[0126] In a further embodiment, if UE102 does not receive a reference LTM DU configuration for LTM DU configuration 1 and / or LTM DU configuration(s) 2, ..., N, UE102 determines that LTM DU configuration 1 and / or LTM DU configuration(s) 2, ..., N are delta configuration(s) to extend the serving DU configuration. In such a case, UE102 communicates with DU174 according to LTM DU configuration 1 and at least a portion of the serving DU configuration not extended by LTM DU configuration 1 (336). Accordingly, if DU174 does not obtain a reference LTM DU configuration for UE102 (i.e., DU174 does not generate a reference LTM DU configuration for UE102 and / or does not receive a reference LTM DU configuration for UE102 from CU172), DU174 generates LTM DU configuration 1 and / or LTM DU configurations 2, ..., N as delta configurations to extend the serving DU configuration. In such a case, DU174 communicates with UE102 according to LTM DU configuration 1 and at least a portion of the serving DU configuration (336).

[0127] In some embodiments, UE102 uses the UE MAC entity (e.g., MAC204B) to communicate with the DU MAC entity (e.g., MAC204B) of DU174 (e.g., events 302, 304, 318, 320, 324, 330 and / or 331). In some embodiments, UE102 resets the UE MAC entity after receiving or in response to receiving a first LTM command and before performing a random access procedure (332) or before communicating with DU174 via the first cell (336). In some embodiments, DU174 resets the DU MAC entity after sending a first LTM command (e.g., in response to sending it), after receiving an acknowledgment (331) (e.g., in response to receiving it), or after deciding that UE102 will connect to the first cell (e.g., in response to deciding it).

[0128] In some embodiments, when UE102 resets a UE MAC entity, UE102 performs the following actions on the UE MAC entity (i.e., UE MAC reset or full UE MAC reset): (i) initialize the Bj of the configured logical channel(s) to zero, stop one or more timers, and consider the timeAlignmentTimer(s) to expire if UE102 is configured to perform a random access procedure in a configuration (e.g., configuration 1) (e.g., event 332), and UL (ii) Actions to set a new data indicator (multiple) (e.g., NDI(multiple)) of the HARQ process(s) to value 0, set the NDI(multiple) of the HARQ process ID(s) to value 0 to monitor PDCCH in sidelink resource allocation mode 1, flush the Msg3 buffer, and flush the MSGA buffer; (ii) Actions to cancel any of the following triggered procedures, namely scheduling requests, buffer status reports, power headroom reports, consistent LBT failures, BFRs, sidelink buffer status reports, preemptive buffer status reports, timing advance reports, recommended bitrate queries, configured uplink grant confirmations, configured sidelink grant confirmations, desired guard symbol queries, or positioning gap activation / deactivation requests; (iii) Actions to flush the soft buffer of the DL HARQ process(s); (iv) DL For each HARQ process(s), perform at least one of the following actions: (v) treat the transmission received after the TB as the very first transmission; (v) release any temporary C-RNTIs; and (vi) reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0129] In some embodiments, when DU174 resets a DU MAC entity, DU174 performs at least one of the following actions on the DU MAC entity (i.e., a DU MAC reset or a full DU MAC reset): (i) stopping one or more timers; (ii) if UE102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), deeming a timeAlignmentTimer(or) that DU174 starts and / or maintains for UE102 to expire; (iii) setting the NDI(or) of a DL HARQ process(or) to the value 0; (iv) flushing the soft buffer of a UL HARQ process(or); (v) for each UL HARQ process(or), deeming the transmission received after TB as the first transmission; and (vi) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0130] In some embodiments, UE102 decides to partially or completely reset the UE MAC entity. In some embodiments, when UE102 resets the UE MAC entity as described above, UE102 completely resets the UE MAC entity (i.e., a full UE MAC reset). In a full UE MAC reset, UE102 performs some or all of the actions described above. In further embodiments, when UE102 resets the UE MAC entity as described above, UE102 partially resets the UE MAC entity (i.e., a partial UE MAC reset). In a partial UE MAC reset, UE102 performs some or all of the actions in a full UE MAC reset.

[0131] In some embodiments, a partial UE MAC reset includes at least one of the following actions: (i) if UE102 is configured to perform a random access procedure in configuration (e.g., configuration 1) (e.g., event 332), the action of deeming the timeAlignmentTimer(s) of UE102 expired; (ii) the action of flushing the Msg3 buffer; (iii) the action of flushing the MSGA buffer; (iv) the action of releasing any temporary C-RNTIs; and (v) the action of resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0132] In some embodiments, a partial UE MAC reset further includes canceling at least one of the following triggered procedures: (i) scheduling requests, buffer status reports, power headroom reports, consistent LBT failures, BFRs, sidelink buffer status reports, preemptive buffer status reports, timing advance reports, recommended bitrate queries, configured uplink grant confirmations, configured sidelink grant confirmations, desired guard symbol queries, and positioning gap activation / deactivation requests.

[0133] In some embodiments, a partial UE MAC reset further includes at least one of the following actions: (i) stopping a first portion of one or more timers and retaining the remaining portions of one or more timers; (ii) setting a new data indicator (NDI(multiple)) of a UL HARQ process(multiple) to the value 0; (iii) setting the NDI(multiple) of a HARQ process ID(multiple) to the value 0 in order to monitor PDCCH in sidelink resource allocation mode 1; (iv) flushing the soft buffer of a DL HARQ process(multiple); and (v) for each DL HARQ process(multiple), treating the transmission received after TB as the first transmission.

[0134] In some embodiments, DU174 decides to partially or completely reset the DU MAC entity. In further embodiments, when DU174 resets the DU MAC entity as described above, DU174 completely resets the DU MAC entity (i.e., a full DU MAC reset). In a full DU MAC reset, DU174 performs some or all of the actions described above. In yet another embodiment, when DU174 resets the DU MAC entity as described above, DU174 partially resets the DU MAC entity (i.e., a partial DU MAC reset). In a partial DU MAC reset, DU174 performs some or all of the actions in a full DU MAC reset.

[0135] In some embodiments, a partial DU MAC reset includes at least one of the following actions: (i) if UE102 is configured to perform a random access procedure in configuration (e.g., configuration 1) (e.g., event 332), the action of deeming a timeAlignmentTimer(s) that DU174 starts and / or maintains for UE102 to be expired; and (ii) the action of resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0136] In some embodiments, a partial DU MAC reset includes at least one of the following actions of a MAC entity (i.e., a DU MAC reset): (i) stopping a first portion of one or more timers and retaining the remaining portions of one or more timers; (ii) setting the NDI(Non-Digit Indicators) of a DL HARQ process(s) to the value 0; (iii) flushing the soft buffer of a UL HARQ process(s); (iv) treating the transmission received after a TB as the first transmission for each UL HARQ process(s); and (v) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0137] In a further embodiment, UE102 refrains from resetting the UE MAC entity in response to receiving a first LTM command. Similarly, DU174 refrains from resetting the DU MAC entity after sending a first LTM command (e.g., in response to sending it), after receiving an acknowledgment (331) (e.g., in response to receiving it), or after UE102 has decided to connect to a first cell (e.g., in response to deciding to do so). In other words, UE102 communicates with DU174 on the first cell using the UE MAC entity (which has not been reset). Similarly, DU174 communicates with UE102 on the first cell using the DU MAC entity (which has not been reset) during or after a random access procedure, or after UE102 has decided to connect to a first cell (332).

[0138] In some embodiments, UE102 uses at least one UE RLC entity (e.g., RLC206B) to communicate with at least one DU RLC entity (e.g., RLC206B) of DU174 and the RLC PDU (e.g., events 302, 304, 318, 320, 324, 330 and / or 331). In some embodiments, UE102 re-establishes some or all of the at least one UE RLC entities after receiving a first LTM command (332), or in response to receiving it, and before performing a random access procedure, or before communicating with DU174 via the first cell (336). In some embodiments, DU174 re-establishes some or all of at least one DU RLC entities after sending a first LTM command (e.g., in response to sending it), after receiving an acknowledgment (331) (e.g., in response to receiving it), or after UE102 decides to connect to a first cell (e.g., in response to deciding to do so).

[0139] In some embodiments, LTM DU configuration 1 optionally includes one or more RLC reestablishment instructions (e.g., reestablishRLC field(s)) that configure UE102 to reestablish some or all of at least one UE RLC entity. In some embodiments, LTM DU configuration 1 includes an RLC reestablishment instruction that configures UE102 to reestablish a first UE RLC entity of at least one UE RLC entity that UE102 uses to communicate an RLC PDU(s) with DU174, and UE102 reestablishes the first UE RLC entity in response to the RLC reestablishment instruction and the first LTM command. In some embodiments, UE102 reestablishes the first UE RLC entity (332) before performing a random access procedure or before communicating with DU174 via the first cell (336). In further embodiments, UE102 reestablishes the first UE RLC entity during or after performing a random access procedure (332). Otherwise, if LTM DU configuration 1 does not include an RLC re-establishment instruction, UE102 refrains from re-establishing the first UE RLC entity in response to the first LTM command.

[0140] In some embodiments, when UE102 re-establishes the first UE RLC entity, UE102 performs at least one of the following actions on the first UE RLC entity: (i) discard any RLC SDUs, RLC SDU segments, and RLC PDUs; (ii) stop and reset any running timers; and (iii) reset state variables to their initial values. In some embodiments, state variables and timers are defined, for example, in 3GPP TS38.322.

[0141] Otherwise, if LTM DU configuration 1 does not include an RLC re-establishment instruction for the first UE RLC entity, UE 102 refrains from re-establishing the first UE RLC entity when it receives or becomes aware of the first LTM command. In other words, when UE 102 receives or becomes aware of the first LTM command, it refrains from taking any action to re-establish the first UE RLC entity of UE 102. In some embodiments, if LTM DU configuration 1 or element 1 does not include an RLC re-establishment instruction but includes an instruction indicating that configuration 1 is a full configuration, UE 102 re-establishes the first UE RLC entity of UE 102 when it receives or becomes aware of the first LTM command. Otherwise, if LTM DU configuration 1 or element 1 does not include an RLC re-establishment instruction and an instruction indicating that configuration 1 is a full configuration, UE 102 refrains from re-establishing the first UE RLC entity when it receives or becomes aware of the first LTM command.

[0142] Similarly, DU174 re-establishes some or all of at least one DU RLC entity (e.g., NR RLC206B) that DU174 uses to communicate with at least one UE RLC entity of UE102 in response to an RLC re-establishment instruction (e.g., events 302, 304, 318, 320, 324, 330 and / or 331). In some embodiments, DU174 re-establishes the first DU RLC entity of at least one DU RLC entity after sending a first LTM command, after receiving an acknowledgment of the first LTM command from UE102, or after UE102 has decided to connect to a first cell. In some embodiments, the acknowledgment is a HARQ ACK. In further embodiments, the acknowledgment is a MAC CE. In yet another embodiment, the acknowledgment is a PUCCH transmission. In some embodiments, when base station 104 re-establishes the first DU RLC entity, DU 174 performs at least one of the following actions on the first DU RLC entity: (i) discarding any existing RLC SDU(s), RLC SDU(s), and RLC PDU(s); (ii) stopping and resetting any running timer(s); and (iii) resetting state variables to their initial values. In some embodiments, state variables and / or timers (for example, as defined in 3GPP TS38.322).

[0143] In other embodiments, UE102 refrains from re-establishing some or all of at least one UE RLC entity in response to receiving a first LTM command. Similarly, DU174 refrains from re-establishing some or more of at least one DU RLC entity after sending a first LTM command (e.g., in response to sending it), after receiving an acknowledgment (331) (e.g., in response to receiving it), or after UE102 decides to connect to a first cell (e.g., in response to deciding to do so). In other words, UE102 communicates with DU174 on the first cell using some or all of at least one UE RLC entity (that has not been re-established). For example, some or all of the at least one UE RLC entity includes a first UE RLC entity and / or a second UE RLC entity. Similarly, DU174 communicates with UE102 using some or all of at least one DU RLC entity (not re-established) on the first cell during or after the random access procedure, or after UE102 has decided to connect to the first cell (332). For example, some or all of the at least one DU RLC entity includes the first DU RLC entity and / or the second DU RLC entity.

[0144] In some embodiments, UE102 uses at least one UE PDCP entity (e.g., PDCP210) to communicate (302) UL PDCP PDUs and / or DL ​​PDCP PDUs with at least one CU PDCP entity (e.g., PDCP210) of CU172. In some embodiments, UE102 performs some or all of the PDCP recovery procedures of at least one UE PDCP entity after receiving or in response to receiving a first LTM command. For example, UE102 performs the PDCP recovery procedure of the first UE PDCP entity of at least one UE PDCP entity after receiving or in response to receiving a first LTM command. In the PDCP recovery procedure, UE102 optionally re-establishes the first UE PDCP entity. In some embodiments, after or in response to performing a PDCP recovery procedure, UE102 retransmits at least a portion of the UL PDCP PDU to CU172 via DU174 and the first cell (336). Similarly, CU172 performs a PDCP recovery procedure on some or all of at least one CU PDCP entity after or in response to sending a first LTM command. For example, CU172 performs a PDCP recovery procedure on the first CU PDCP entity of at least one CU PDCP entity after or in response to sending a first LTM command. In some embodiments, CU172 performs a PDCP recovery procedure on the first CU PDCP entity in response to receiving a DU-to-CU message (329 or 334). In further embodiments, CU172 performs a PDCP recovery procedure on the first CU PDCP entity in response to receiving a DL data delivery status message. In the PDCP recovery procedure, CU172 optionally re-establishes the first CU PDCP entity.In some embodiments, after or in response to performing a PDCP recovery procedure, CU172 retransmits at least a portion of the DL PDCP PDU to UE102 via DU174 and the first cell (336).

[0145] In a further embodiment, UE102 refrains from re-establishing some or all of at least one UE PDCP entity in response to receiving a first LTM command. For example, some or all of the at least one UE PDCP entity includes a first UE PDCP entity and / or a second UE PDCP entity. Similarly, CU172 refrains from re-establishing some or more of at least one CU PDCP entity after receiving a DU-to-CU message (329 or 340) (e.g., in response to receiving it) or after receiving a DL data delivery status message (e.g., in response to receiving it). In other words, UE102 communicates with CU172 via DU174 and the first cell using some or all of at least one UE PDCP entity (that has not been re-established). For example, some or all of the at least one UE PDCP entity includes a first UE PDCP entity and / or a second UE PDCP entity. Similarly, CU172 communicates with UE102 using some or all of at least one CU PDCP entity (not re-established) via DU174 and the first cell. For example, some or all of the at least one CU PDCP entity includes a first CU PDCP entity and / or a second CU PDCP entity.

[0146] In some embodiments, after UE102 decides to connect to the first cell, CU172 sends a CU-to-DU message (e.g., a UE context correction request message) to DU174 to instruct DU174 to stop communicating with UE102 and / or to release or suspend the resources configured for UE102 in cell 124A (338). In some embodiments, DU174 stops communicating with UE102 on cell 124A and / or releases or suspends the resources configured for UE102 in cell 124A and sends a DU-to-CU message (e.g., a UE context correction request message) to CU172 (340). Events 338 (optional) and 340 (optional) are collectively referred to as resource release procedure 396 in Figure 3.

[0147] In some embodiments, events 344, 346, 348, 350, 351, 352, 354, and / or 356 occur after or during communication with DU174 in the first cell, similar to events 324, 326, 328, 330, 331, 332, 334, and / or 336, respectively. UE102 sends at least one measurement report to DU174 (344). The at least one measurement report includes at least one measurement result for the second cell (i.e., cell 2). The at least one measurement result indicates that the second cell is suitable for communication with UE102 and / or that the first cell is not suitable for communication with UE102. After receiving at least one measurement report (for example, in response to receiving it), DU174 decides to activate LTM DU configuration 2 and generates a second LTM command to activate LTM DU configuration 2 (i.e., the second LTM command sends a command to UE102 to apply LTM DU configuration 2). DU174 then sends the second LTM command to UE102 on the first cell (350).

[0148] In some embodiments, in response to deciding to activate LTM DU configuration 2 or to send a second LTM command, DU174 sends a DU-to-CU message to CU172 instructing LTM execution (349). In some embodiments, DU174 includes a cell ID2 or ID2 (i.e., LTM ID) in the DU-to-CU message in 349 to instruct DU174 to activate LTM DU configuration 2. In some embodiments, DU sends a DU-to-CU message to CU172 before or after sending an LTM command (350) (349).

[0149] At least part of the descriptions of events 324, 326, 328, 330, 331, 332, 334 and / or 336 can generally be applied to events 344, 346, 348, 350, 351, 352, 354 and / or 356. For example, "Cell 124A", "First LTM Command", "First Cell", "ID1", "LTM DU Configuration 1" and / or "LTM CU Configuration 1" are replaced with "First Cell", "Second LTM Command" and "Second Cell", "ID2", "LTM DU Configuration 2" and / or "LTM CU Configuration 2", respectively.

[0150] Events 344, 346, 348, 350, 351, 352, and 354 are collectively referred to as LTM execution procedure 398 in Figure 3. Events 304, 306, 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, and 356 are collectively referred to as LTM DU configuration and / or activation procedure 380 in Figure 3.

[0151] Referring to Figure 4, in Scenario 400, base station 104 includes CU 172, source DU (S-DU) 174A, and target DU (T-DU) 174B. S-DU 174A operates cell 124A and optionally additional cells, and T-DU 174B operates the first cell (e.g., cell 124C). Scenario 400 is similar to Scenario 300. In some embodiments, the description of Scenario 300 generally applies to Scenario 400. The differences between Scenario 300 and 400 are described below.

[0152] First, UE102 communicates with S-DU174A on cell 124A using a serving DU configuration (402), and communicates with CU172 via S-DU174A. S-DU174A is a serving DU similar to DU174 in Figure 3A. During communication 402, UE102 sends at least one measurement report (e.g., L3 measurement report(s)) to CU172 via S-DU174A (404 and 406). Based on at least one measurement report, CU172 decides to prepare cells(s) 1, ..., N (e.g., operated by T-DU174B) for UE102's LTM, where N is a positive integer greater than 0 or 1. Cells(s) 1, ..., N are identified by cell(s) 1, ..., N, respectively. In response to the decision, CU172, together with T-DU174B, executes an LTM preparation procedure to prepare (for example, request T-DU174B to prepare) cell(s) 1, ..., N for the LTM of UE102 (490). In some embodiments, N is zero or a positive integer greater than 1. In the LTM preparation procedure, CU172 sends a CU-to-DU message containing cell(s) 1, ..., N to T-DU174B, similar to event 308, requesting T-DU174B to prepare cell(s) 1, ..., N for the LTM of UE102 (490). In response, T-DU174B sends a DU-to-DU message containing LTM DU configuration(s) 1, ..., N to CU172, similar to event 310. LTM DU configurations 1, ..., N each constitute cell 1, ..., N for the LTM. Specifically, LTM DU configurations 1, ..., N each contain configuration parameters for communication in cell 1, ..., N. In some embodiments, the CU-to-DU message and DU-to-CU message in step 490 are the UE context setup request message and the UE context setup response message, respectively. Next, CU 172 is similar to LTM configuration delivery procedure 394, in which LTM configuration delivery procedure 494 sends LTM DU configurations 1, ..., N in an RRC reconfiguration message.In some embodiments, T-DU174B includes cell index(s) 1, ..., N in LTM DU configuration(s), respectively. In some embodiments, CU172 sets cell index(s) 1, ..., N to different values, and 490 includes cell index(s) 1, ..., N in the CU-to-DU message.

[0153] In some embodiments, after performing the 490 LTM preparation procedure, CU172 performs additional similar LTM preparation procedures with T-DU174B to prepare cell(s) N+1, ..., N+M for the LTM of UE102, where M is a positive integer greater than zero. In some embodiments, CU172 determines one or more measurement reports received from UE102 via S-DU174A, as well as events 404, 406. In the additional LTM preparation procedure, CU172 sends a CU-to-DU message containing cell(s) N+1, ..., N+M to T-DU174B requesting T-DU174B to prepare cell(s) N+1, ..., N+M for the LTM of UE102, where cell(s) N+1, ..., N+M each identify cell(s). In response to the CU-to-DU message, T-DU174B sends a DU-to-DU message to CU172 containing LTM DU configurations N+1, ..., N+M. The LTM DU configurations N+1, ..., N+M each configure cell N+1, ..., N+M for the LTM. In detail, the LTM DU configurations N+1, ..., N+M each contain configuration parameters for communication in cell N+1, ..., N+M. CU172 then sends the LTM DU configurations N+1, ..., N+M in an RRC reconfiguration message in an additional similar LTM configuration delivery procedure (394 or 494).

[0154] In some embodiments, LTM preparation procedure 490 is a UE context setup procedure, and additional LTM preparation procedures are UE context modification procedures.

[0155] In some embodiments, CU172 and S-DU174A perform steps 380 and 390, as described in Figure 3. In step 380, CU172 and S-DU174A perform steps 390 and / or 392 to prepare the cell(s) of S-DU174A for the LTM of UE102. In some embodiments, the value N in step 380 in Figure 3 is the same as or different from the value N described in Figure 4. In some embodiments, in step 390, CU172 receives a first DU-to-CU message from S-DU174A containing a reference LTM DU configuration (310). In further embodiments, CU172 and S-DU174A do not perform steps 380 and 390. In some embodiments, CU172 executes the reference LTM DU configuration query procedure 488 with S-DU174A to obtain the reference LTM DU configuration. In procedure 488, CU172 sends a CU-to-DU message to S-DU174A to request or query the reference LTM DU configuration (460). In some embodiments, CU172 includes an instruction in the CU-to-DU message to request or query the reference LTM DU configuration. In response to the instruction or CU-to-DU message 460, S-DU174A sends a DU-to-CU message containing the reference LTM DU configuration to CU172 (462). In some embodiments, the instruction is a reference LTM DU configuration query instruction. In further embodiments, the instruction is an LTM instruction, and CU172 includes a query instruction (e.g., a GNB-DU configuration query IE) in the CU-to-DU message. After receiving a reference LTM DU configuration (i.e., in either step 390 or step 488), CU172 includes the reference LTM DU configuration (e.g., received from S-DU174A) in the CU-to-DU message in the LTM preparation step 490. T-DU174B generates LTM DU configurations 1, ..., N based on the reference LTM DU configuration received from CU172. In such cases, T-DU174B does not include the reference LTM DU configuration in the DU-to-CU message in step 490.For additional LTM preparation steps, T-DU174B does not include a reference LTM DU configuration in the DU-to-CU message in the additional LTM preparation step. In some embodiments, CU172 does not include a reference LTM DU configuration in the CU-to-DU message in the additional LTM preparation step with T-DU174B. For additional LTM preparation steps, T-DU174B generates LTM DU configurations N+1, ..., N+M based on the reference LTM DU configuration received from CU172.

[0156] In some embodiments, CU172 does not provide T-DU174B with a reference LTM DU configuration in LTM preparation procedure 490. In such cases, T-DU174B generates a reference LTM DU configuration and generates LTM DU configurations 1, ..., N based on the reference LTM DU configuration. In such cases, T-DU174B includes the reference LTM DU configuration in the DU-to-CU message in procedure 490. CU172 sends the reference LTM DU configuration in the RRC reconfiguration message in procedure 490. For additional LTM preparation procedures, T-DU174B generates LTM DU configurations N+1, ..., N+M based on the reference LTM DU configuration. In some embodiments, T-DU174B does not include the reference LTM DU configuration in the DU-to-CU message in additional LTM preparation procedures. In some embodiments, the reference LTM DU configuration generated by T-DU174B is different from the reference LTM DU configuration generated by S-DU174A. In further embodiments, the reference LTM DU configuration generated by T-DU174B is the same as the reference LTM DU configuration generated by S-DU174A.

[0157] In some embodiments, CU172 includes LTM DU configuration(s) 1, ..., N in the CU-to-DU message of step 490, and T-DU174B generates LTM DU configuration(s) 1, ..., N and / or N+1, ..., N+M, taking into account or based on the configuration(s) within the LTM DU configuration(s) of step 380.

[0158] In some embodiments, the LTM DU configuration X in step 380 includes at least one reference signal (RS) resource configuration X such that 1 ≤ X ≤ N. Each RS resource configuration X constitutes one or more RSs or one or more RS resources associated with cell X of S-DU174A. An RS may include an SSB and / or a CSI-RS. An RS resource may include an SSB resource and / or a CSI-RS resource. In some embodiments, each RS resource configuration X includes an RS resource configuration ID. In some embodiments, an RS resource configuration X is a CSI-ResourceConfig IE (or similar). In some embodiments, the LTM DU configuration X includes a CSI-MeasConfig IE, and the CSI-MeasConfig IE includes a CSI-ResourceConfig IE. T-DU174B generates at least one report configuration 1 in cell 1 of T-DU174B for reporting measurement results of RS(s) or RS resources(s), and includes report configuration(s) 1 in LTM DU configuration 1. In some embodiments, report configuration(s) 1 is a CSI-ReportConfig IE(s) (e.g., similar). In some embodiments, T-DU174B generates at least one RS resource configuration 1 considering or based on RS resource configuration(s) X, and includes RS resource configuration(s) 1 in LTM DU configuration 1. In some embodiments, T-DU174B includes RS resource configuration(s) X in RS resource configuration(s) 1. In other embodiments, T-DU174B includes each RS resource configuration(s) X in RS resource configuration(s) 1, except for the RS resource configuration ID(s) within RS resource configuration(s) X. T-DU174B assigns an RS resource configuration ID to a value for each RS resource configuration (multiple configurations are possible) (for example, including RS resource configuration (multiple configurations) X), and includes the RS resource configuration ID in the corresponding RS resource configuration.

[0159] In some embodiments, report configuration(s) 1 configures one or more UL resources (e.g., a PUCCH resource or a PUSCH resource) on cell 1 so that UE 102 can transmit measurement results. In some embodiments, each report configuration(s) 1 includes one or more RS resource configuration IDs that identify one or more RS resource configurations included in RS resource configuration(s) 1. After UE 102 performs an LTM serving cell change from cell 124A to cell 1, UE 102 communicates with S-DU 174B (i.e., T-DU 17B becomes UE 102's S-DU) according to report configuration(s) 1 and transmits measurement results regarding the UL resources(s) to S-DU 174B via cell 1. Correspondingly, S-DU 174B receives measurement results regarding the UL resources(s) from UE 102 via cell 1 according to report configuration(s) 1. In some embodiments, each measurement result includes one or more RS resource indicators and / or one or more quantized measurements. UE102 performs measurements on RS(multiple) or RS resources(multiple) according to RS resource configuration(s)1 and / or report configuration(s)1, and obtains quantized measurements from these measurements. In some embodiments, RS resource indicator(s) indicate the RS(multiple) or RS resources(multiple) on which UE102 performs measurements or from which quantized measurements are obtained. In some embodiments, the RS resource indicator(s) include one or more SSB resource indicators (e.g., SSBRI(multiple)) and / or one or more CSI-RS resource indicators (CRI(multiple)). In some embodiments, the quantized measurements include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0160] In some embodiments, T-DU174B also includes additional RS resource configurations (multiple) in LTM DU configuration 1. Each additional RS resource configuration (multiple) constitutes one or more additional RSs or one or more additional RS resources associated with cell 1. Additional RS(multiple) include SSB(multiple) and / or CSI-RS(multiple). Additional RS resources (multiple) include SSB resources(multiple) and / or CSI-RS resources(multiple). In some embodiments, each additional RS resource configuration (multiple) includes an RS resource configuration ID. In some embodiments, an additional RS resource configuration (multiple) is a CSI-ResourceConfig IE(multiple) (e.g., similar). In some embodiments, T-DU174B includes CSI-ResourceConfig IE(multiple) in CSI-MeasConfig IE. The T-DU174B generates at least one additional report configuration in cell 1 of the T-DU174B for reporting measurement results of RS(s) or RS resources(s), and includes the additional report configuration(s) in LTM DU configuration 1. In some embodiments, the additional report configuration(s) are CSI-ReportConfig IE(s) (e.g., similar).

[0161] In some embodiments, an additional report configuration(s) configures one or more UL resources (e.g., a PUCCH resource or a PUSCH resource) on cell 1 so that UE102 transmits measurement results. In some embodiments, each additional report configuration(s) includes one or more RS resource configuration IDs that identify one or more RS resource configurations included in an additional RS resource configuration(s). After UE102 performs an LTM serving cell change from cell 124A to cell 1, UE102 communicates with S-DU174B (436) according to the additional report configuration(s) and transmits measurement results regarding the UL resources(s) to S-DU174B via cell 1. Correspondingly, S-DU174B receives measurement results regarding the UL resources(s) from UE102 via cell 1 according to the additional report configuration(s). In some embodiments, each measurement result includes one or more RS resource indicators and / or one or more quantized measurements. UE102 performs measurements on additional RS(s) or additional RS resources(s) according to additional RS resource configurations and / or additional reporting configurations(s), and obtains quantized measurements from these measurements. In some embodiments, RS resource indicators(s) indicate the additional RS(s) or RS resources(s) on which UE102 performs measurements or from which quantized measurements are obtained. In some embodiments, the RS resource indicators(s) include one or more SSB resource indicators (SSBRI(s)) and / or one or more CSI-RS resource indicators (CRI(s)). In some embodiments, the quantized measurements include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0162] In some embodiments, T-DU174B similarly generates RS resource configurations 2, ..., N, and / or N+1, ..., N+M, and / or report configurations 2, ..., N, and / or N+1, ..., N+M, taking into account or based on RS resource configuration(s) X, and as described above, includes RS resource configurations 2, ..., N, and / or N+1, ..., N+M, and / or report configurations 2, ..., N, and / or N+1, ..., N+M, respectively, in LTM DU configurations 2, ..., N, and / or N+1, ..., N+M.

[0163] In other embodiments, the LTM DU configuration X of step 380 includes at least one TCI state configuration X such that 1 ≤ X ≤ N. Each TCI state configuration(s) X constitutes a TCI state that associates one or two DL RSs with the corresponding QCL type. In some embodiments, the DL RS(s) are associated with a cell X operated by S-DU174A. In some embodiments, each TCI state configuration(s) X includes a TCI state ID. In some embodiments, each TCI state configuration(s) X is a TCI-State IE. In some embodiments, the TCI state configuration(s) X includes / / a ul-TCI-ToAddModList-r17 field, one or more TCI-UL-State-r17 IEs, a dl-OrJointTCI-StateToAddModList-r17 field, one or more TCI-State IEs, a TCI-ActivatedConfig IE and / or a tci-StatesToAddModList field. In some embodiments, the LTM DU configuration X includes a PDSCH-Config IE, and the PDSCH-Config IE includes a TCI state configuration(s) X. In some embodiments, T-DU174B generates at least one TCI state configuration 1 considering or based on a TCI state configuration(s) X, and includes a TCI state configuration(s) 1 in the LTM DU configuration 1. In some embodiments, a TCI state configuration(s) 1 includes a TCI state configuration(s) X. In other embodiments, T-DU174B includes each TCI state configuration(s) X in a TCI state configuration(s) X, except for the TCI state ID(s) within the TCI state configuration(s) X. T-DU174B assigns a TCI state ID to a value for each TCI state configuration(s) 1 (e.g., including a TCI state configuration(s) X), and includes the TCI state ID in the corresponding TCI state configuration. In some embodiments, the UE102 and S-DU174B communicate with each other (436), and the S-DU174B sends an LTM command to the UE102 to send a command to perform a fast serving cell change to cell X.S-DU174B includes the TCI state ID in the LTM command to send an instruction to UE102 to apply the TCI state configuration identified by the TCI state ID in order to communicate in cell X, where the TCI state configuration is one of TCI state configuration(s)X, or includes one of TCI state configuration(s)X.

[0164] In further embodiments, T-DU174B similarly generates TCI state configurations 2, ..., N, taking into account or based on RS resource configuration(s) X, and includes TCI state configurations 2, ..., N, and / or N+1, ..., N+M in LTM DU configurations 2, ..., N, and / or N+1, ..., N+M, respectively, as described above.

[0165] In some embodiments, if CU172 performs step 380 after performing step 490, CU172 includes LTM DU configuration(s) 1, ..., N of step 490 in the CU-to-DU message of step 380, and S-DU174A generates LTM DU configuration(s) 1, ..., N of step 380 in the same manner as described above, taking into account or based on the configurations within LTM DU configuration(s) of step 490.

[0166] In some embodiments, CU172 assigns IDs 1, ..., N to identify each LTM DU configuration 1, ..., N (for example, received from T-DU174B), and performs step 492 with T-DU174B to provide IDs 1, ..., N and / or cell IDs 1, ..., N to T-DU174B, similar to step 392. Thus, T-DU174B associates IDs 1, ..., N with each LTM DU configuration 1, ..., N and / or cell IDs 1, ..., N. In other embodiments, T-DU174B assigns IDs 1, ..., N to identify each LTM DU configuration 1, ..., N (generated by T-DU174B), similar to event 310, and includes IDs 1, ..., N in the DU-to-CU message of step 490. In some embodiments, CU172 assigns IDs N+1, ..., N+M to identify each LTM DU configuration N+1, ..., N+M, similar to step 392, and performs a procedure (e.g., similar to step 492) with T-DU174B to provide IDs N+1, ..., N+M and / or cell IDs N+1, ..., N+M to T-DU174B, similar to step 392. Therefore, T-DU174B associates ID(s) N+1, ..., N+M with LTM DU configuration(s) N+1, ..., N+M and / or cell ID(s) N+1, ..., N+M, respectively. In other embodiments, T-DU174B assigns ID(s) N+1, ..., N+M to identify LTM DU configuration(s) N+1, ..., N+M, respectively, as in event 310, and includes ID(s) 1, ..., N in the DU-to-CU message of the additional LTM preparation procedure.

[0167] In some embodiments, CU172 sends a CU-to-DU message containing ID(s) 1, ..., N to S-DU174A (412) and receives a DU-to-CU message from S-DU174A in response (414). The CU-to-DU message 412 and the DU-to-CU message 414 are collectively referred to as the LTM ID transfer procedure 493 or the LTM cell index transfer procedure 493 in Figure 4. In some embodiments, messages 412 and 414 are the UE context correction request message and the UE context correction response message, respectively. In some embodiments, CU172 includes LTM DU configuration(s) 1, ..., N and / or cell ID(s) 1, ..., N in the CU-to-DU message in 412. In some embodiments, CU172 includes ID(s) 1, ..., N in the CU-to-DU message in 412. In some embodiments, CU172 includes cell index(s) 1, ..., N in the CU-to-DU message 412. In further embodiments, CU172 performs multiple LTM ID transfer procedures to send ID(s) 1, ..., N, cell ID(s) 1, ..., N and / or LTM DU configuration(s) 1, ..., N to S-DU174A. In each procedure, CU172 includes a specific portion of ID(s) 1, ..., N, cell ID(s) 1, ..., N and / or LTM DU configuration(s) 1, ..., N in a CU-to-DU message similar to message 412. Thus, S-DU174A associates ID(s) 1, ..., N with LTM DU configuration(s) 1, ..., N and / or cell ID(s) 1, ..., N, respectively. In further embodiments, CU172 performs multiple LTM cell index transfer procedures to send cell index(s) 1, ..., N, cell ID(s) 1, ..., N and / or LTM DU configuration(s) 1, ..., N to S-DU174A.In each step, CU172 includes a specific portion of cell index(s) 1, ..., N, cell ID(s) 1, ..., N and / or LTM DU configuration(s) 1, ..., N in a CU-to-DU message similar to message 412. Thus, S-DU174A associates cell index(s) 1, ..., N with LTM DU configuration(s) 1, ..., N and / or cell ID(s) 1, ..., N, respectively.

[0168] In some embodiments, S-DU174A generates a first serving DU configuration based on LTM DU configurations 1, 2, ..., and / or N, and 414 includes the first serving DU configuration in a DU-to-CU message. In some embodiments, the first serving DU configuration includes configurations that update (e.g., extend, modify, or replace) the serving DU configuration in 402. In other embodiments, the first serving DU configuration includes configurations that are not included in the serving DU configuration in 402. CU172 sends an RRC reconfiguration message containing the first serving DU configuration to UE102. Upon receiving the RRC reconfiguration message, UE102 applies the first serving DU configuration to communicate with the serving DU. For example, the RRC reconfiguration message is the RRC reconfiguration message in step 494, or similar. In some embodiments, UE102 communicates with S-DU174A using a configuration included in the serving DU configuration that has not been updated by the first serving DU configuration (402). The following is an exemplary embodiment for generating the first serving DU configuration based on LTM DU configurations 1, ..., N.

[0169] In some embodiments, the LTM DU configuration Y in step 490 includes at least one RS resource configuration Y such that 1 ≤ Y ≤ N. Each RS resource configuration Y constitutes one or more RSs or one or more RS resources associated with cell Y of T-DU174B. An RS may include an SSB and / or a CSI-RS. An RS resource may include an SSB resource and / or a CSI-RS. In some embodiments, each RS resource configuration Y includes an RS resource configuration ID. In some embodiments, an RS resource configuration Y is a CSI-ResourceConfig IE (or similar). In some embodiments, the LTM DU configuration Y includes a CSI-MeasConfig IE, and the CSI-MeasConfig IE includes a CSI-ResourceConfig IE. S-DU174A generates at least one serving report configuration for reporting measurement results of RS(s) or RS resources(s) on cell 124A, and includes the serving report configuration(s) in the first serving DU configuration. In some embodiments, the serving report configuration(s) is a CSI-ReportConfig IE(s) (e.g., similar). In some embodiments, S-DU174A generates at least one serving RS resource configuration(s) considering or based on RS resource configuration(s) Y, and includes the serving RS resource configuration(s) in the first serving DU configuration. In some embodiments, S-DU174A includes RS resource configuration(s) Y in the serving RS resource configuration(s). In other embodiments, S-DU174A includes each RS resource configuration(s) Y in the serving RS resource configuration(s), except for the RS resource configuration ID(s) within the RS resource configuration(s) Y. S-DU174A assigns an RS resource configuration ID to a value for each serving RS resource configuration (multiple configurations are possible) (for example, including RS resource configuration (multiple configurations) Y), and includes the RS resource configuration ID in the corresponding serving RS resource configuration.

[0170] In some embodiments, a serving report configuration(s) configures one or more UL resources (e.g., a PUCCH resource or a PUSCH resource) on cell 124A so that UE102 can transmit measurement results. In some embodiments, each serving report configuration(s) includes one or more RS resource configuration IDs that identify one or more RS resource configurations included in a serving RS resource configuration(s). While UE102 is communicating with S-DU174A, UE102 transmits measurement results regarding the UL resources(s) to S-DU174A via cell 124A according to a serving report configuration(s) (e.g., event 424). Correspondingly, S-DU174A receives measurement results regarding the UL resources(s) from UE102 via cell 124A according to a serving report configuration(s). In some embodiments, each measurement result includes one or more RS resource indicators and / or one or more quantized measurements. UE102 performs measurements on RS(multiple) or RS resources(multiple) according to the serving RS resource configuration(s) and / or serving report configuration(s), and obtains quantized measurements from these measurements. In some embodiments, RS resource indicator(s) indicate the RS(multiple) or RS resources(s) on which UE102 performs measurements or obtains quantized measurements. In some embodiments, the RS resource indicator(s) include one or more SSB resource indicators (SSBRI(multiple)) and / or one or more CSI-RS resource indicators (CRI(multiple)). In some embodiments, the quantized measurements include one or more L1-RSRP values ​​and / or one or more L1-SINR values.

[0171] In other embodiments, the LTM DU configuration Y of step 490 includes at least one TCI state configuration Y such that 1 ≤ Y ≤ N. Each TCI state configuration Y constitutes a TCI state that associates one or two DL RSs with the corresponding QCL type. In some embodiments, the DL RS(s) are associated with a cell Y operated by T-DU174B. In some embodiments, each TCI state configuration Y includes a TCI state ID. In further embodiments, each TCI state configuration Y is a TCI-State IE. In even further embodiments, each TCI state configuration Y includes the ul-TCI-ToAddModList-r17 field, one or more TCI-UL-State-r17 IEs, the dl-OrJointTCI-StateToAddModList-r17 field, one or more TCI-State IEs, the TCI-ActivatedConfig IE, and / or the tci-StatesToAddModList field. In some embodiments, the LTM DU configuration Y includes a PDSCH-Config IE, and the PDSCH-Config IE includes a TCI state configuration(s) Y. In some embodiments, S-DU174A generates at least one serving TCI state configuration, taking into account or based on a TCI state configuration(s) Y, and includes a serving TCI state configuration(s) in the first serving DU configuration. In some embodiments, serving TCI state configuration(s) 1 includes a TCI state configuration(s) Y. In further embodiments, S-DU174A includes each TCI state configuration(s) Y in the serving TCI state configuration(s), except for the TCI state ID(s) within the TCI state configuration(s) Y. S-DU174A assigns a TCI state ID to a value for each serving TCI state configuration(s) (including TCI state configuration(s) Y), and includes the TCI state ID in the corresponding serving TCI state configuration. In some embodiments, the S-DU174A communicates with the UE102 (436), and the S-DU174A sends an LTM command to the UE102 to send a command to perform a fast serving cell change to cell Y.S-DU174A includes the TCI state ID in the LTM command to send an instruction to UE102 to apply the TCI state configuration identified by the TCI state ID in order to communicate in cell Y, where the TCI state configuration is one of TCI state configuration(s) Y, or includes one of TCI state configuration(s) Y.

[0172] In some embodiments, CU172 sends a CU-to-DU message containing ID(s) N+1, ..., N+M to S-DU174A, similar to CU-to-DU message 412 and DU-to-CU message 414, respectively, and receives a DU-to-CU message from S-DU174A in response. In some embodiments, CU172 includes LTM DU configuration(s) N+1, ..., N+M and / or cell ID(s) N+1, ..., N+M in the CU-to-DU message. In further embodiments, CU172 performs multiple LTM ID transfer procedures to send ID(s) N+1, ..., N+M, cell ID(s) N+1, ..., N+M and / or LTM DU configuration(s) N+1, ..., N+M to S-DU174A. In each step, CU172 includes a specific portion of ID(s) N+1, ..., N+M, cell ID(s) N+1, ..., N+M and / or LTM DU configuration(s) 1, ..., N in a CU-to-DU message similar to message 412. Thus, S-DU174A associates ID(s) N+1, ..., N+M with LTM DU configuration(s) N+1, ..., N+M and / or cell ID(s) N+1, ..., N+M, respectively. In some embodiments, S-DU174A generates a second serving DU configuration based on LTM DU configuration(s) N+1, N+2, ..., and / or N+M, and includes the second serving DU configuration in a DU-to-CU message. In some embodiments, the second serving DU configuration includes configurations that update (e.g., extend, modify, or replace) the first serving DU configuration in 402, and / or configurations that update configurations included in the serving DU configuration but not updated by the first serving DU configuration. In further embodiments, the second serving DU configuration includes configurations not included in the first serving DU configuration. CU172 sends an RRC reconfiguration message containing the second serving DU configuration to UE102 via S-DU174A. Upon receiving the RRC reconfiguration message, UE102 applies the second serving DU configuration to communicate with the serving DU.For example, the RRC reconfiguration message is the RRC reconfiguration message in procedure 494, or similar. In some embodiments, UE102 communicates with S-DU174A using a serving DU configuration and / or a configuration included in the first serving DU configuration that has not been updated by the second serving DU configuration (402). In some embodiments, S-DU174A generates one or more new L1 measurement configurations based on the L1 measurement configurations in LTM DU configurations N+1, N+2, ..., and / or N+M, and includes the new L1 measurement configurations in the second serving DU configuration. In some embodiments, S-DU174A generates one or more new TCI state configurations based on the TCI state configurations in LTM DU configurations N+1, N+2, ..., and / or N+M, and includes the new TCI state configurations in the second serving DU configuration.

[0173] In some embodiments, CU172 and S-DU174A perform a procedure with UE102 (380), and the values ​​of the procedure ID(s) 1, ..., N are different from the values ​​of ID(s) 1, ..., N and ID(s) N+1, ..., N+M described in Scenario 400. In some embodiments, CU172 and S-DU174A perform a procedure with UE102 (380), and the values ​​of the procedure cell ID(s) 1, ..., N are different from the values ​​of cell ID(s) 1, ..., N and cell ID(s) N+1, ..., N+M described in Scenario 400. In some embodiments, CU172 and S-DU174A perform a procedure with UE102 (380), where the values ​​of the cell index(s) 1, ..., N of the procedure are different from the values ​​of the cell index(s) 1, ..., N and N+1, ..., N+M described in Scenario 400.

[0174] In some embodiments, UE102 transmits at least one measurement report to S-DU174A, similar to event 324 (424). At least one measurement report (e.g., L1 measurement report(s)) includes an event ID, a first measurement result(s) for cell 1 of T-DU174B, and / or a second measurement result(s) for cell 124A. In some embodiments, the first measurement result(s) is or includes RSRP, RSRQ, and / or SINR obtained by UE102 from reference signals(s) transmitted in cell 1. In further embodiments, the second measurement result(s) is or includes RSRP, RSRQ, and / or SINR obtained by UE102 from reference signals(s) transmitted in cell 124A. In some embodiments, the event ID, RSRP, RSRQ, and / or SINR are L1-event ID, L1-RSRP, L1-RSRQ, and / or L1-SINR, respectively. In some embodiments, based on a first(or more) measurement result and / or a second(or more) measurement result, S-DU174A sends a first LTM command (i.e., LTM command 1) including ID 1 to UE102 to order T-DU174B to perform a serving cell change to cell 1 (430). In some embodiments, the first LTM command includes ID 1. In further embodiments, the first LTM command includes cell index 1. Upon receiving the first LTM command, UE102 performs a serving cell change from serving cell to cell 1 according to LTM DU configuration 1. In some embodiments, after receiving a first LTM command (e.g., in response thereto), UE102 performs a random access procedure with T-DU174B, as in event 332 (432). In some embodiments, after receiving a first LTM command (e.g., in response thereto), or after completing the random access procedure (432), UE102 communicates with T-DU174B on the first cell using LTM DU configuration 1 and / or reference LTM DU configuration (436), as in event 336, and communicates with CU172 via T-DU174B.In some embodiments, if a serving cell change occurs in step 380, the serving cell is cell 1 or cell 2 of S-DU174A. Otherwise, if no serving cell change occurs in step 380, or if step 380 is not performed, the serving cell is cell 124A. If the first LTM command includes ID 1, UE102 identifies LTM DU configuration 1 and / or cell ID 1 (i.e., cell 1) based on ID 1, as illustrated in Figure 3. If the first LTM command includes cell index 1, UE102 identifies LTM DU configuration 1, cell ID 1 (i.e., cell 1), and / or LTM ID 1 based on cell index 1, as illustrated in Figure 3. After receiving the first LTM command or successfully accessing cell 1 (e.g., in response thereto), UE102 applies LTM DU configuration 1 to communicate with T-DU174B.

[0175] In some embodiments, upon deciding to activate LTM DU configuration 1 or to send a first LTM command (430), or in response to such a decision, S-DU174A sends a DU-to-CU message to CU172 instructing LTM execution (429). In some embodiments, S-DU174A includes cell ID1 or ID1 (i.e., LTM ID) in the DU-to-CU message at 429 to instruct S-DU174A to activate LTM DU configuration 1 or to trigger a change in the LTM serving cell. In further embodiments, S-DU174A sends a DU-to-CU message to CU172 (429) before or after sending an LTM command (430). In some embodiments, when CU172 receives a DU-to-CU message (429), or after receiving it, CU172 stops or suspends sending DL data for UE102 to S-DU174A until it receives another DU-to-CU message (434). After receiving a DU-to-CU message (434), CU172 starts, continues, or resumes sending DL data for UE102 to T-DU174B. When T-DU174B detects that UE102 is accessing cell 1, or after detecting it, T-DU174B sends DL data to UE102 via cell 1.

[0176] In some embodiments, the resource release procedure 496 is the same as procedure 396. In some embodiments, in the resource release procedure 496, CU172 sends a CU-to-DU message (e.g., a UE context release command message) to S-DU174A to release the UE context of UE102. In response, S-DU174A releases the UE context of UE102 and sends a DU-to-CU message (e.g., a UE context release complete message) to CU-172 (440).

[0177] Events 380, 404, 406, 490, 492, 494, 494, 424, 426, 428, 429, 430, 431, 432, 434, 436, 496, 498, and 456 are collectively referred to as LTM Configuration and / or Activation Procedure 480 in Figure 4.

[0178] Next, referring to Figure 5A, in Scenario 500A, base station 106 operates as MN, while base station 104 operates as SN. SN104 includes CU172 and DU174. Scenario 500A is similar to Scenario 300, except that Scenario 500A is a DC scenario and Scenario 300 is a Single-Connected (SC) scenario. In some embodiments, MN106 includes CU and DU, similar to base station 104 in Figure 3.

[0179] Initially, UE102 in the DC communicates with MN106 and also with SN104. In event 502, UE102 communicates with DU174 on cell 124A using a serving DU configuration, and with CU172 via DU174 using a serving CU configuration, similar to event 302. In some embodiments, UE102 does not communicate with CU172 via DU174 (302). In some embodiments, UE102 in the DC communicates with MN106 and / or SN104 via a radio bearer including an SRB and / or DRB(plural) (502). In some embodiments, MN106 and / or SN104 constitute a radio bearer to UE102. In the DC, UE102 communicates the UL PDU and / or DL ​​PDU with SN104 in the SCG (i.e., SCG radio resource) which SN104 configures for communication with UE102 (502). In the DC, UE102 communicates the UL PDU and / or DL ​​PDU with MN106 in the MCG (i.e., MCG radio resource) according to the MN configuration (i.e., MCG configuration). In some embodiments, the serving DU configuration is the SN configuration (i.e., SCG configuration). In the MN configuration, MN106 configures the MCG which includes at least one serving cell (e.g., cell 126 and / or other cells) operated by MN106. In the serving DU configuration, SN106A configures the SCG which includes at least one serving cell (e.g., cell 124A and / or other cells) operated by SN104. In some embodiments, the MN configuration includes multiple configuration parameters, and the UE102 receives these configuration parameters from the MN106 in one or more RRC messages. As illustrated in Figure 3, the serving DU configuration includes multiple configuration parameters. In some embodiments, the UE102 receives these configuration parameters from the SN104 in one or more RRC messages, for example, via the MN106 and / or on an SRB (e.g., SRB3) configured so that the MN106 or SN104 exchanges RRC messages between the UE102 and the SN104.

[0180] In some embodiments, while UE102 is communicating with MN106 and SN104 over DC, MN106 performs the LTM DU configuration and / or activation procedure with UE102, as in steps 380 and / or 480 (580). In some embodiments, while UE102 is communicating with MN106 and SN104 over DC, UE102 sends at least one measurement report to CU172 via DU174 and cell 124A in events 504 and 506, as in events 304 and 306, respectively. In further embodiments, while UE102 is communicating with MN106 and SN104 over DC, UE102 sends at least one measurement report to MN106 via cell 126 (505). MN106 then sends at least one measurement report to CU172 (507). In some embodiments, the MN106 generates at least one SN message containing at least one measurement report and transmits at least one SN message to the CU172 (507). In one embodiment, at least one SN message contains RRC forwarding messages and / or SN correction request messages.

[0181] After receiving at least one measurement report (for example, in response to it), or while SN104 is communicating with UE102, SN104 decides to prepare a first cell for UE102, as described in Figure 3. Events 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are similar to events 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, and 356, respectively. After receiving the first LTM command (530), sending an acknowledgment (531), or determining that UE102 has successfully connected to the first cell (532 or 536), UE102, operating with MN106 and SN104 in the DC, communicates with DU174 in the first cell (536) and with CU172 via DU174 (536), in accordance with LTM DU configuration 1, as in event 336. In some embodiments, DU174 and / or CU172 then execute LTM execution procedure 598 with UE102 to send a command to UE102 to perform a cell change from the first cell to the second cell, as in procedure 398 or 498. As a result of step 598, MN106 and SN104 and UE102 operating in DC communicate with DU174 on the second cell according to LTM DU configuration 2 (556), and communicate with CU172 via DU174 (556), similar to event 356.

[0182] Events 504, 506, 505, 507, 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are collectively referred to as LTM DU configuration and / or activation procedure 581 in Figure 5A.

[0183] Referring now to Figure 5B, Scenario 500B is generally similar to Scenario 500A, except that SN104 sends RRC reconfiguration messages to UE102 via MN106 (517, 519) and receives RRC reconfiguration completion messages from UE102 via MN106 (521, 523). RRC reconfiguration messages 517, 519 are similar to RRC reconfiguration messages 316, 318. RRC reconfiguration completion messages 521, 523 are similar to RRC reconfiguration messages 320, 322. In some embodiments, SN104 generates a first SN message (e.g., an SN correction request message, an SN correction request message, or an RRC forwarding message) containing the RRC reconfiguration message and sends the first SN message to MN106 (517). MN106 generates an MN RRC message containing the RRC reconfiguration message and sends the MN RRC message to UE102 (519). In response, UE102 generates an MN RRC response message containing an RRC reconstruction complete message and transmits the MN RRC response message to MN106 (521). In some embodiments, MN106 generates a second SN message (e.g., an SN reconstruction complete message or an RRC forwarding message) containing an RRC reconstruction complete message and transmits the second SN message to SN104 (523). In some embodiments, the MN RRC message and the MN RRC response message are the RRC reconstruction message and the RRC reconstruction complete message, respectively.

[0184] Events 504, 506, 505, 507, 590, 592, 594, 517, 519, 521, 523, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are collectively referred to as LTM DU configuration and / or activation procedure 582 in Figure 5B.

[0185] Next, referring to Figure 6A, in scenario 600A, as in scenarios 300-500B, base station 106 operates as MN, while base station 104 operates as SN. SN104 includes CU172, S-DU174A, and T-DU174B, as in base station 104 in scenario 400. In some embodiments, while UE102 is communicating with MN106 and SN104 over DC, MN106 performs the LTM DU configuration and / or activation procedure with UE102, as in steps 380 and / or 480 (680). In some embodiments, while UE102 is communicating with M-DU174A and S-DU174B over DC, CU172 performs the LTM DU configuration and / or activation procedure with UE102 via M-DU174A or S-DU174B, as in step 581 or 582 (681).

[0186] Next, referring to Figure 6B, Scenario 600B is similar to scenarios 300-500B and 600A, except that SN104 sends an RRC reconstruction message to UE102 via MN106 (617, 619) and receives an RRC reconstruction complete message from UE102 via MN106 (621, 623).

[0187] Next, referring to Figure 7A, in Scenario 700A, base station 104 operates as MN and SN, similar to Scenarios 300-600B. Base station 104 includes CU172, Master DU (M-DU) 174A, and Secondary DU (S-DU) 174B. CU172 operates as MN with M-DU174A, similar to base station 104 in Figure 3 or MN106 in Figures 5A-6B, and CU172 operates as SN with S-DU174B, similar to SN104 in Figures 5A-6B.

[0188] In scenario 700A, UE102 first communicates with M-DU174A and S-DU174B at DC (702), and then communicates with CU172 via M-DU174A and S-DU174B (702). Similar to event 302, UE102 communicates with S-DU174B on cell 124A using a serving DU configuration (702), and then communicates with CU172 via S-DU174B using a serving CU configuration. Events 704 and 706 are similar to events 304 and 306. In some embodiments, UE102 sends at least one measurement report to M-DU174A, similar to event 304 (705). M-DU174A then sends at least one DU-to-CU message containing at least one measurement report to CU172, similar to event 306 (707). In some embodiments, while UE102 is communicating with M-DU174A and S-DU174B via DC, CU172 performs the LTM DU configuration and / or activation procedure with UE102 via M-DU174A, as in procedure 380 (780).

[0189] Events 704, 706, 705, 707, 790, 792, 794, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, and 756 are collectively referred to as LTM Configuration and / or Activation Procedure 781 in Figure 7A.

[0190] Next, referring to Figure 7B, Scenario 700B is similar to scenarios 300-600B and 700A, except that CU172 sends an RRC reconfiguration message to UE102 via M-DU174A (717, 719) and receives an RRC reconfiguration complete message from UE102 via M-DU174A (721, 723).

[0191] Events 704, 706, 705, 707, 790, 792, 794, 717, 719, 721, 723, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, and 756 are collectively referred to as LTM DU configuration and / or activation procedure 782 in Figure 7B.

[0192] Referring next to Figure 8A, in scenario 800A, base station 104 operates as MN and SN, similar to scenarios 300-700B. Base station 104 includes CU172, master DU (M-DU) 174A, secondary DU (S-DU) 174B, and target secondary DU (T-DU) 174C. CU172 operates as MN with M-DU174A and as SN with S-DU174B. In some embodiments, while UE102 is communicating with M-DU174A and S-DU174B at DC, CU172 performs the LTM DU configuration and / or activation procedure with UE102 via M-DU174A, similar to procedure 380 (880). In a further embodiment, while UE102 is communicating with M-DU174A and S-DU174B via DC, CU172 performs the LTM DU configuration and / or activation procedure with UE102 via S-DU174A, as in procedure 581 or 582 (881).

[0193] Next, referring to Figure 8B, Scenario 800B is similar to scenarios 300-700B and 800A, except that CU172 sends an RRC reconfiguration message to UE102 via M-DU174A (817, 819) and receives an RRC reconfiguration complete message from UE102 via M-DU174A (821, 823).

[0194] In some embodiments, a base station, a RAN node such as a DU or CU, or an UE implements LTM Early Timing Advance (TA) acquisition, as described below with reference to Figures 9A to 14. At least some of the descriptions in Figures 3 to 8B can be applied to Figures 9A to 14.

[0195] Figure 9A shows an exemplary method 900A that a UE (e.g., UE102 in Figures 3-8B) can implement to handle early TA acquisition with a RAN (e.g., RAN105 or base stations 104 and 106 in Figures 3-8B).

[0196] Method 900A begins in block 902, when the UE communicates with the RAN via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). In block 909, while the UE is communicating with the RAN via the serving cell, it starts a first time alignment timer for uplink synchronization with the serving cell. In block 918, the UE receives an LTM configuration from the RAN, which constitutes a first cell (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 581, 582, 680, 694, 617, 619, 780, 794, 880, 881, 894, 817, and 819). The first cell is the target or candidate cell for the LTM. In block 925, the UE receives a first command from the RAN via the serving cell, which sends a command to the UE to send a random access preamble in the first cell.

[0197] In block 927, the UE sends a first random access preamble to the RAN on the first cell in response to a first command. In block 930A, the UE receives an LTM command from the RAN via the serving cell, which sends a command to the UE to connect to the first cell, including a TA value (e.g., events 330, 350, 398, 380, 430, 450, 498, 480, 580, 530, 598, 581, 582, 680, 681, 630, 698, 780, 730, 798, 880, 881, 830, and 898). In block 941, the UE resets the MAC entity in response to receiving the LTM command. In some embodiments, the UE communicates with the RAN using the MAC entity, in block 902. In block 932, the UE accesses the first cell in response to receiving an LTM command (e.g., events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). In block 947, the UE starts a second time alignment timer for uplink synchronization with the first cell. In block 936, the UE communicates with the RAN on the first cell using the TA value and LTM configuration (for example, events 336, 356, 380, 436, 456, 480, 536, 556, 580, 581, 582, 636, 656, 680, 681, 736, 756, 780, 836, 856, 880, and 881).

[0198] In some embodiments, the UE receives a first command while the first time alignment timer is running. In other embodiments, the UE receives a first command while the first time alignment timer is not running. In some embodiments, the UE disconnects from the serving cell upon receiving an LTM command. In further embodiments, the UE disconnects from the serving cell upon successfully accessing the first cell. In some embodiments, upon successfully accessing the first cell, the UE determines the first cell to be the new serving cell.

[0199] In some embodiments, the UE starts a second time alignment timer after receiving (e.g., in response to) an LTM command. In some embodiments, the UE starts a second time alignment timer after resetting the MAC entity. In further embodiments, the UE starts a second time alignment timer before resetting the MAC entity. In such cases, the UE refrains from stopping the second time alignment timer and / or determining that the second time alignment timer has expired when it resets the MAC entity. In some embodiments, the UE stops the first time alignment timer and determines that the first time alignment timer has expired in response to resetting the MAC entity.

[0200] In some embodiments, in block 902, the UE starts a MAC timer associated with the MAC entity to communicate with the RAN via the serving cell. The UE stops the MAC timer in response to resetting the MAC entity. In some embodiments, the MAC timer includes a timer for operating DRX (discontinuous reception) with the RAN in the serving cell. In some embodiments, the MAC timer includes one or more timers for HARQ operation with the RAN in the serving cell.

[0201] In some embodiments, depending on the time when the RAN receives the first random access preamble, the RAN obtains the TA values ​​of the UE and the first cell. In some embodiments, after sending the first random access preamble, the UE continues to communicate with the RAN via the serving cell until it receives an LTM command.

[0202] In some embodiments, the LTM configuration includes an LTM DU configuration that constitutes the first cell of the LTM as described above. In some embodiments, the RAN includes the LTM DU configuration in an RRC message (e.g., an RRC reconfiguration message) and the LTM configuration includes an RRC message. In some embodiments, the RAN includes the LTM CU configuration in an RRC message. The LTM CU configuration and the LTM DU configuration include the configurations described above. In some embodiments, the LTM configuration is an LTM-Candidate IE or an LTM-CandidateToAddMod IE. In other embodiments, the LTM configuration is an LTM-Config IE.

[0203] In some embodiments, the first command includes configuration parameters such as a first random access preamble index, an indicator pointing to UL or SUL (supplementary UL), an SSB index, and / or a physical random access channel (PRACH) mask index. The first random access preamble index points to, identifies, or indexes the first random access preamble. Thus, the UE generates or selects the first random access preamble according to the first random access preamble index. In some embodiments, the PRACH mask index constitutes one or more PRACH occasions. The UE determines the PRACH occasion to send the first random access preamble based on the SSB index and / or the PRACH mask index. In some embodiments, an indicator set to 0 points to UL, and an indicator set to 1 points to SUL. The UE sends the first random access preamble with UL or SUL in the first cell according to the indicator. In some embodiments, the first command includes a DCI format identifier and / or a frequency-domain resource allocation field. In some embodiments, the DCI format identifier is set to zero for both the first and second formats. In some embodiments, all bits in the frequency-domain resource allocation field are set to zero.

[0204] In some embodiments, the LTM configuration includes random access configuration parameters. In some embodiments, the random access configuration parameters include a PRACH root sequence index and / or a PRACH subcarrier interval. In some embodiments, the UE uses the PRACH root sequence index and a first random access preamble index to generate or select a first random access preamble. In some embodiments, the LTM configuration includes a random access channel (RACH) configuration that includes random access configuration parameters. The UE uses 1) random access configuration parameters and 2) an indicator (e.g., indicating UL or SUL), an SSB index, and / or a PRACH mask index to send a first random access preamble in a first cell.

[0205] In some embodiments, the LTM configuration includes the cell ID of the first cell (e.g., PCI). In some embodiments, the first command includes a (new) field that indicates the first cell to which a random access preamble (e.g., the first random access preamble) is sent (or will be sent). In some embodiments, the new field includes the cell ID of the first cell. Based on the cell ID included in the first command, the UE determines that the first cell is the cell to which the UE sends the first random access preamble. The UE identifies the LTM configuration based on the cell ID. In other embodiments, the LTM configuration includes the cell index of the first cell, and this cell index is included in the new field. The cell index is not the cell ID, and the size of the cell index is smaller than the size of the cell ID. The UE identifies the LTM configuration based on the cell index. Based on the cell ID included in the LTM configuration, the UE determines that the first cell is the cell to which the UE sends the first random access preamble. In a further embodiment, the new field includes an LTM ID that identifies the LTM configuration, and the UE identifies the LTM configuration according to this LTM ID. The UE receives the LTM ID along with the LTM configuration as described above. Based on the cell ID included in the LTM configuration, the UE determines that the first cell is the cell to which the UE sends the first random access preamble.

[0206] In some embodiments, the UE receives other LTM configurations from the RAN, each of which constitutes a cell and includes a cell ID that identifies the cell, as illustrated in Figures 3 to 8B. In some embodiments, each of the other LTM configurations constitutes a cell and includes a cell index that points to the cell, as illustrated in Figures 3 to 8B. In some embodiments, each of the other LTM configurations constitutes a cell and is associated with an LTM ID, as illustrated in Figures 3 to 8B.

[0207] In some embodiments, the first command is in DCI or PDCCH order. The UE receives the first command in PDCCH order from the RAN via the serving cell. In other embodiments, the first command is a MAC CE. The UE receives a MAC PDU containing the first command from the RAN via the serving cell.

[0208] In some embodiments, the RAN sets the frequency domain resource allocation field to a dedicated value (e.g., non-zero) to indicate that the first command includes a new field that indicates a cell. The RAN sets all bits in the frequency domain resource allocation field to zero to indicate that the second command does not include a new field that indicates a cell. In other embodiments, the RAN sets the frequency domain resource allocation field to zero in both the first and second commands.

[0209] In some embodiments, the UE sends a first random access preamble on the first cell to the RAN using 1) random access configuration parameters included in the LTM configuration and / or 2) configuration parameters included in the first command.

[0210] In some embodiments, the UE receives the RACH configuration from the RAN in addition to the LTM configuration. In some embodiments, the UE receives RRC messages from the RAN that include both the RACH configuration and the LTM configuration (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 581, 582, 680, 694, 617, 619, 780, 794, 880, 881, 894, 817, and 819). The RACH configuration sets the random access configuration parameters for the first cell for early TA acquisition. In such cases, the UE sends a first random access preamble to the RAN on the first cell using 1) the random access configuration parameters included in the RACH configuration instead of the LTM configuration, and / or 2) the configuration parameters included in the first command.

[0211] In some embodiments, the RACH configuration includes the cell ID of the first cell (e.g., PCI). In some embodiments, the first command includes a (new) field that indicates the first cell to which a random access preamble (e.g., the first random access preamble) is sent (e.g., will be sent). In some embodiments, the new field includes the cell ID of the first cell. Based on the cell ID included in the first command, the UE determines that the first cell is the cell to which the UE sends the first random access preamble. The UE identifies the RACH configuration based on the cell ID. In other embodiments, the RACH configuration includes the cell index of the first cell, and this cell index is included in the new field. The cell index is not the cell ID, and the size of the cell index is smaller than the size of the cell ID. The UE identifies the RACH configuration based on the cell index. Based on the cell ID included in the RACH configuration, the UE determines that the first cell is the cell to which the UE sends the first random access preamble. In further embodiments, the new field includes an LTM ID that identifies the LTM configuration, and the RACH configuration and UE identify the RACH configuration according to this LTM ID. The UE receives the LTM ID along with the LTM configuration and RACH configuration as described above. Based on the cell ID included in the LTM configuration or RACH configuration, the UE determines that the first cell is the cell to which the UE sends the first random access preamble. In some embodiments, the UE receives other RACH configurations from the RAN. In some embodiments, each of the other RACH configurations includes random access configuration parameters for the cell for early TA acquisition. In further embodiments, each of the other RACH configurations includes a cell ID that identifies the cell. Also in further embodiments, each of the other RACH configurations includes a cell index that points to the cell. In some embodiments, each of the other RACH configurations is associated with an LTM ID as described above.

[0212] In some embodiments, the UE transmits multiple UE functions to the RAN via a serving cell in block 902. In further embodiments, the UE transmits multiple UE functions to the RAN via other serving cells. In some embodiments, the multiple UE functions include a first UE function that instructs support for LTM. In further embodiments, the multiple UE functions include a second UE function that instructs support for early TA acquisition. In some embodiments, the UE receives an early TA acquisition configuration from the RAN to enable or configure early TA acquisition. In response to receiving the early TA acquisition configuration, the UE enables early TA acquisition. When early TA acquisition is enabled, the UE attempts to receive a command (e.g., a first command) from the RAN via the serving cell that sends a command to the UE to transmit a random access preamble at the target cell or candidate cell. If the UE does not receive an early TA acquisition configuration, the UE refrains from attempting to receive a command (e.g., a first command) that sends a command to the UE to transmit a random access preamble at the target cell or candidate cell.

[0213] In some embodiments, the UE starts a first time alignment timer with a first timer value and a second time alignment timer with a second timer value. In some embodiments, the first and second timer values ​​are the same or different. In some embodiments, the UE receives a System Information Block (SIB) (e.g., SIB1) containing the first timer value from the RAN on a serving cell. In further embodiments, the UE receives an RRC message (e.g., an RRC setup message, an RRC restart message, or an RRC reconfiguration message) containing the first timer value from the RAN via the serving cell or other serving cells. In some embodiments, the LTM configuration includes a second timer value.

[0214] In some embodiments, while the UE is communicating with the RAN on the serving cell, it receives a TA command from the RAN on the serving cell, containing a new TA value. The UE adjusts its uplink transmission timing with the serving cell based on the new TA value and restarts a first time alignment timer in response to receiving the TA command. In some embodiments, the TA command is MAC CE. In some embodiments, while the UE is communicating with the RAN on the first cell in block 936, it receives a TA command from the RAN on the first cell, containing a new TA value. The UE adjusts its uplink transmission timing with the first cell based on the new TA value and restarts a second time alignment timer in response to receiving the TA command.

[0215] Figure 9B is an illustrative flowchart of Method 900B, similar to Method 900A except that Method 900B includes block 953 instead of block 947. In block 953, the UE starts or restarts the first time alignment timer for uplink synchronization with the first cell.

[0216] Figure 9C is an exemplary flowchart of Method 900C, similar to Methods 900A and 900B, except that Method 900C includes blocks 930C, 933, 957, 959, 947, and 953 instead of block 930A. In block 930C, the UE receives an LTM command from the RAN via a serving cell, and the LTM command sends a command to the UE to connect to a first cell. In block 933, the UE determines whether the LTM command includes a TA value. If the UE determines in block 933 that the LTM command includes a TA value, the flow proceeds to block 932. The flow then proceeds from block 932 to either block 947 or block 953. Otherwise, if the UE determines in block 933 that the LTM command does not include a TA value, the flow proceeds to block 957. In block 957, the UE performs a random access procedure on the RAN and the first cell (for example, events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). In block 959, the UE receives a random access response from RAN on the first cell in the random access procedure, which includes the TA value (e.g., events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). The flow proceeds from block 959 to block 947 or 953. In block 947, after receiving the random access response (e.g., in response to receiving it), the UE starts a second time alignment timer for uplink synchronization with the first cell. In block 953, after receiving the random access response (e.g., in response to receiving it), the UE starts or restarts the first time alignment timer for uplink synchronization with the first cell. The flow proceeds from blocks 947, 953, 947 and 953 to block 936.

[0217] In some embodiments, in block 947, the UE stops the first time alignment timer after (for example, in response to) a random access response. In other embodiments, in block 947, the UE maintains the execution of the first time alignment timer. In some embodiments, if the first time alignment timer expires while the second time alignment timer is running, the UE communicates with the RAN in the first cell and ignores the expiration of the first time alignment timer. In other words, in such cases, the UE does not take any action in response to the expiration of the first time alignment timer.

[0218] Figure 10A shows an exemplary method 1000A of a RAN (e.g., RAN 105 in Figures 3 to 8B, or base stations 104, 106, or DU 174, 174A, 174B, or 174C) managing the early TA acquisition of a UE (e.g., UE 102 in Figures 3 to 8B).

[0219] Method 1000A begins in block 1002, when the RAN communicates with the UE via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). In block 1009, while the RAN is communicating with the UE via the serving cell, it starts a first time alignment timer for uplink synchronization with the UE. In block 1018, RAN sends an LTM configuration to the UE, which constitutes a first cell (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 581, 582, 680, 694, 617, 619, 780, 794, 880, 881, 894, 817, and 819). In block 1025, RAN sends a first command to the UE via the serving cell, which in turn sends a command to the UE to send a first random access preamble in the first cell. In block 1027, RAN receives the first random access preamble in the first cell from the UE. In block 1030A, the RAN sends an LTM command to the UE via the serving cell, which sends a command to the UE to connect to the first cell, including a TA value (e.g., events 330, 350, 398, 380, 430, 450, 498, 480, 580, 530, 598, 581, 582, 680, 681, 630, 698, 780, 730, 798, 880, 881, 830, and 898). In block 1041, the RAN resets the MAC entity in response to sending the LTM command. In some embodiments, the RAN communicates with the UE using a MAC entity (i.e., a first MAC entity) in block 1002. In some embodiments, the RAN communicates with the UE using another MAC entity (i.e., a second MAC entity) in block 1002. In a further embodiment, the RAN resets the MAC entity in response to preparing a first cell for LTM, instead of sending an LTM command.In block 1032, RAN detects that the UE will access the first cell after sending an LTM command (e.g., events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). In block 1047, RAN starts a second time alignment timer on the first cell for uplink synchronization with the UE. In block 1036, the RAN communicates with the UE on the first cell using the TA value while maintaining the execution of the second time alignment timer (e.g., events 336, 356, 380, 436, 456, 480, 536, 556, 580, 581, 582, 636, 656, 680, 681, 736, 756, 780, 836, 856, 880, and 881).

[0220] In some embodiments, depending on the time when the RAN receives the first random access preamble, the RAN obtains (e.g., calculates or derives) a TA value for uplink synchronization with the UE on the first cell. In some embodiments, after receiving the first random access preamble, the RAN continues to communicate with the UE via the serving cell until it sends an LTM command.

[0221] In some embodiments, the RAN starts a second time alignment timer after receiving a first random access preamble (e.g., in response to receiving it) or after obtaining the TA value of the UE (e.g., in response to obtaining it). In further embodiments, the RAN starts a second time alignment timer after sending an LTM command. In some embodiments, the RAN starts a second time alignment timer after resetting a MAC entity. In further embodiments, the RAN starts a second time alignment timer before resetting a MAC entity. In such cases, the RAN refrains from stopping the second time alignment timer and / or determining that the second time alignment timer has expired when it resets a MAC entity. In some embodiments, the RAN stops the first time alignment timer and determines that the first time alignment timer has expired in response to resetting a MAC entity.

[0222] In some embodiments, in block 1002, the RAN starts a MAC timer associated with a MAC entity to communicate with the UE via the serving cell. The RAN stops the MAC timer in response to resetting the MAC entity. In some embodiments, the MAC timer includes a timer for operating DRX with the RAN in the serving cell. In some embodiments, the MAC timer includes one or more timers for HARQ operation with the UE in the serving cell.

[0223] In some embodiments, the RAN receives a first random access preamble from the UE on the first cell using 1) random access configuration parameters included in the LTM configuration and / or 2) configuration parameters included in the first command. In some embodiments, the RAN sends a RACH configuration to the UE in addition to the LTM configuration. For example, the RAN sends an RRC message to the UE containing both the RACH configuration and the LTM configuration (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 581, 582, 680, 694, 617, 619, 780, 794, 880, 881, 894, 817, and 819). The RACH configuration configures the random access configuration parameters of the first cell for early TA acquisition. In such a case, RAN receives a first random access preamble from the UE on the first cell using 1) random access configuration parameters included in the RACH configuration and / or 2) configuration parameters included in the first command.

[0224] In some embodiments, the RAN receives multiple UE functions from the UE via a serving cell in block 1002. In further embodiments, the RAN receives multiple UE functions from the UE via other serving cells. In yet another embodiment, the RAN receives multiple UE functions from a CN (e.g., CN110 or AMF164). In some embodiments, the multiple UE functions include a first UE function that instructs support for LTM. In response to receiving the first UE function, the RAN sends an LTM configuration to the UE. In some embodiments, the multiple UE functions include a second UE function that instructs support for early TA acquisition. In some embodiments, the RAN sends an early TA acquisition configuration to the UE to enable or configure early TA acquisition. When the UE enables early TA acquisition, the RAN sends a command (e.g., the first command) to the UE via a serving cell that sends a command to the UE to send a random access preamble on the target cell or candidate cell.

[0225] In some embodiments, while the RAN is communicating with the UE on the serving cell, it sends a TA command containing a new TA value to the UE on the serving cell in order to adjust the uplink transmission timing between the serving cell and the UE. In response to sending the TA command, the RAN restarts a first time alignment timer. In some embodiments, the TA command is MAC CE. In some embodiments, while the RAN is communicating with the UE on the first cell in block 1036, it sends a TA command containing a new TA value to the UE on the first cell in order to adjust the uplink transmission timing between the first cell and the UE. In response to sending the TA command, the RAN restarts a second time alignment timer.

[0226] In some embodiments, the RAN sends a first command while the first time alignment timer is running. In further embodiments, the RAN sends a first command while the first time alignment timer is not running.

[0227] Figure 10B is an exemplary flowchart of Method 1000B, similar to Method 1000A except that Method 1000B includes block 1053 instead of block 1047. In block 1053, the RAN starts or restarts the first time network alignment timer for uplink synchronization with the UE at the first cell in response to sending an LTM command.

[0228] Figure 10C is an exemplary flowchart of Method 1000C, similar to Methods 1000A and 1000B, except that Method 1000C includes blocks 1030C, 1033, 1057, 1059, 1047, 1053, and 1036 instead of block 1030A. In block 1013, RAN sends an LTM command to the UE via a serving cell, and the LTM command sends a command to the UE that connects to the first cell. In block 1033, RAN determines whether the LTM command includes a TA value. If RAN determines in block 1033 that the LTM command includes a TA value, the flow proceeds to block 1032. The flow then proceeds from block 1032 to either block 1047 or block 1053. Otherwise, if RAN determines in block 1033 that the LTM command does not include a TA value, the flow proceeds to block 1057. In block 1057, RAN performs a random access procedure with UE and the first cell (e.g., events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). The flow then proceeds from block 1059 to block 1047 or block 1053. In block 1059, the RAN sends a random access response containing the TA value to the UE on the first cell in the random access procedure (e.g., events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). In block 1053, after the RAN has sent the random access response (e.g., in response to sending it) or after it has received the TA value (e.g., in response to receiving it), it starts or restarts the first time alignment timer for uplink synchronization with the UE on the first cell.In block 1047, after the RAN sends a random access response (e.g., in response to sending it) or after obtaining a TA value (e.g., in response to obtaining it), it starts a second time alignment timer for uplink synchronization with the UE on the first cell. The flow proceeds from blocks 1047, 1053, 1047, and / or 1053 to block 1036.

[0229] At least some of the explanations in Figures 9A to 9C can be applied to Figures 10A to 10C.

[0230] Figure 11A shows an exemplary method 1100A for a UE (e.g., UE102 in Figures 3-8B) to process early TA acquisition with a RAN (e.g., RAN105 or base stations 104 and 106 in Figures 3-8B).

[0231] Method 1100A begins in block 1102, when the UE communicates with the RAN via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). In block 1109, while the UE is communicating with the RAN via the serving cell, it starts a first time alignment timer for uplink synchronization with the serving cell. In block 1118, the UE receives an LTM configuration from the RAN, which constitutes a first cell (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 581, 582, 680, 694, 617, 619, 780, 794, 880, 881, 894, 817, and 819). In block 1125, the UE receives a first command from the RAN via the serving cell, which sends a command to the UE to send a first random access preamble in the first cell. In block 1127, in response to the first command, the UE sends a first random access preamble to the RAN on the first cell. In block 1159, in response to the first random access preamble, the UE receives a random access response from the RAN, including a TA value, on the serving cell or on the first cell. In block 1147, the UE starts a second time alignment timer for uplink synchronization with the first cell in response to receiving a random access response. In some embodiments, the UE maintains the execution of the first time alignment timer in response to receiving a random access response. In further embodiments, the UE refrains from stopping the execution of the first time alignment timer in response to receiving a random access response. In block 1130, the UE receives an LTM command from the RAN via the serving cell after receiving a random access response message, and the LTM command sends a command to the UE to connect to the first cell. In block 1141, the UE resets the MAC entity in response to receiving the LTM command and maintains the execution of the second time alignment timer while resetting the MAC entity.In block 1116, the UE accesses the first cell in response to receiving an LTM command. In block 1136, the UE communicates with the RAN in the first cell using the TA value while maintaining the execution of the second time alignment timer.

[0232] Figure 11A is generally similar to Figure 9A, and the explanation for Figure 9A can also be applied to Figure 11A, although differences are explained below as needed. The LTM command in block 1130 does not include the TA value, while the LTM command in block 930A includes the TA value. The RAN does not send a random access response to the UE in response to the first random access preamble in Figure 9A. The UE starts a second time alignment timer in block 1147 in response to receiving the random access response, and the UE starts a second time alignment timer in block 947 in response to receiving the LTM command.

[0233] Figure 11B is a flowchart of an exemplary method 1100B, similar to method 1100A, except that method 1100B includes blocks 1171, 1157, 1159, 1147, and 1153. In block 1171, the UE decides whether to instruct the LTM command to apply the TA value. If the UE decides in block 1171 that the LTM command should apply the TA value, the flow proceeds to blocks 1170 and 1116. Otherwise, if the UE decides in block 1171 that the LTM command should not apply the TA value, the flow proceeds to block 1157. In block 1157, the UE performs a random access procedure on the RAN and the first cell (for example, events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). In block 1159, the UE receives a random access response from the RAN on the first cell containing the TA value in the random access procedure (e.g., events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). The flow proceeds from block 1159 to block 1147 or block 1153. In block 1147, the UE starts a second time alignment timer on the first cell for uplink synchronization with the RAN. In block 1153, the UE starts or restarts the first time alignment timer on the first cell for uplink synchronization with the RAN. The flow proceeds from blocks 1147, 1153, and / or 1116 to block 1136.

[0234] In some embodiments, in block 1147, the UE stops the first time alignment timer after (e.g., in response to) a random access response. In further embodiments, the UE maintains or refrains from stopping the execution of the first time alignment timer after (e.g., in response to) a random access response in block 1147. In some embodiments, if the first time alignment timer expires while the second time alignment timer is running, the UE communicates with the RAN in the first cell and ignores the expiration of the first time alignment timer. In other words, in such cases, the UE takes no action in response to the expiration of the first time alignment timer.

[0235] In some embodiments, the LTM command includes a first instruction in block 1130 that instructs the UE to apply the TA value received in the random access response. In further embodiments, the LTM command includes a second instruction in block 1130 that instructs the UE not to apply the TA value received in the random access response. In even further embodiments, the LTM command omits the first instruction that instructs the UE not to apply the TA value received in the random access response. In even further embodiments, the LTM command omits the second instruction that instructs the UE to apply the TA value received in the random access response.

[0236] Figure 11B is generally similar to Figure 9B, and the explanation for Figure 9B can also be applied to Figure 11B.

[0237] Figure 12A shows an exemplary method 1200A of a RAN (e.g., RAN 105 in Figures 3 to 8B, or base stations 104, 106, or DU 174, 174A, and 174B or 174C) managing the early TA acquisition of a UE (e.g., UE 102).

[0238] Method 1200A begins in block 1202, when the RAN communicates with the UE via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). In block 1209, while the RAN is communicating with the UE via the serving cell, it starts a first time alignment timer for uplink synchronization with the UE. In block 1218, RAN sends an LTM configuration to the UE, which constitutes a first cell (e.g., events 316, 318, 394, 380, 494, 480, 580, 594, 581, 582, 680, 694, 617, 619, 780, 794, 880, 881, 894, 817, and 819). In block 1225, RAN sends a first command to the UE via the serving cell, which in turn sends a command to the UE to send a first random access preamble on the first cell. In block 1227, after sending the first command, RAN receives the first random access preamble from the UE on the first cell. In block 1259, in response to receiving the first random access preamble, RAN sends a random access response to the UE on the serving cell or the first cell. In block 1247, the RAN starts a second time alignment timer on the first cell for uplink synchronization with the UE. In block 1230, the RAN sends an LTM command to the UE via the serving cell after sending a random access response, and the LTM command sends a command to the UE to connect to the first cell (e.g., events 330, 350, 398, 380, 430, 450, 498, 480, 580, 530, 598, 581, 582, 680, 681, 630, 698, 780, 730, 798, 880, 881, 830, and 898). In block 1241, the RAN resets the MAC entity in response to sending the LTM command. In block 1270, the RAN maintains the execution of the second time alignment timer when resetting the MAC entity.In block 1232, RAN detects that the UE accesses the first cell after sending an LTM command (for example, events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). In block 1236, the RAN communicates with the UE on the first cell using the TA value while maintaining the execution of the second time alignment timer (e.g., events 336, 356, 380, 436, 456, 480, 536, 556, 580, 581, 582, 636, 656, 680, 681, 736, 756, 780, 836, 856, 880, and 881).

[0239] Figure 12A is generally similar to Figure 10A, and the explanation for Figure 10A can be applied to Figure 12A as well, although differences are explained below as needed. The LTM command in block 1230 does not include the TA value, while the LTM command in block 1030A includes the TA value. The RAN does not send a random access response to the UE in response to the first random access preamble in Figure 10A. In block 1247, the RAN starts a second time alignment timer in response to sending a random access response, and in block 1047, the RAN starts a second time alignment timer in response to sending an LTM command. The explanation for Figure 11A can be applied to Figure 12A.

[0240] Figure 12B is an exemplary flowchart of Method 1200B, similar to Method 1200A, except that Method 1200B includes blocks 1271, 1257, 1259, 1247, and 1253. In block 1271, RAN determines whether the LTM command instructs to apply the TA value. If RAN determines in block 1271 that the LTM command instructs to apply the TA value, the flow proceeds to blocks 1270 and 1232. Otherwise, if RAN determines in block 1271 that the LTM command instructs not to apply the TA value, the flow proceeds to block 1257. In block 1257, RAN performs a random access procedure with UE and the first cell (for example, events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). In block 1259, the RAN sends a random access response containing the TA value to the UE on the first cell in the random access procedure (e.g., events 332, 352, 398, 380, 432, 452, 498, 480, 580, 532, 598, 581, 582, 680, 632, 698, 681, 780, 732, 798, 880, 881, 832, and 898). The flow proceeds from block 1259 to block 1247 or block 1253. In block 1247, the RAN starts a second time alignment timer for uplink synchronization with the UE on the first cell. In block 1253, the RAN starts or restarts the first time alignment timer for uplink synchronization with the UE on the first cell. The flow proceeds from blocks 1247, 1253, and / or 1232 to block 1236.

[0241] In some embodiments, in block 1247, the RAN stops the first time alignment timer after a random access response (e.g., in response thereto). In other embodiments, the RAN maintains or refrains from stopping the execution of the first time alignment timer after a random access response (e.g., in response thereto) in block 1247. In some embodiments, if the first time alignment timer expires while the second time alignment timer is running, the RAN communicates with the UE in the first cell and ignores the expiration of the first time alignment timer. In other words, in such cases, the RAN takes no action in response to the expiration of the first time alignment timer.

[0242] Figure 12B is generally similar to Figure 10B, and the explanation for Figure 10B can also be applied to Figure 12B. Similarly, the explanation for Figure 11B can also be applied to Figure 12B.

[0243] Figure 13 shows an exemplary method 1300 for a UE (e.g., UE102 in Figures 3-8B) to handle a time alignment timer for uplink synchronization with a RAN (e.g., RAN105 or base stations 104, 106 in Figures 3-8B).

[0244] Method 1300 begins in block 1301, in which the UE performs the actions described in blocks 1102, 1109, 1118, 1125, 1127, 1159, and 1147. In block 1372, the UE detects that the second time alignment is about to expire while the first time alignment timer is running. In block 1374, the UE responds to this detection by continuing to run the first time alignment timer.

[0245] Figure 14A shows an exemplary method 1400A for a UE (e.g., UE102 in Figures 3-8B) to handle a time alignment timer for uplink synchronization with a RAN (e.g., RAN105 or base stations 104, 106 in Figures 3-8B).

[0246] Method 1400A begins in block 1401, in which the UE performs the actions described in blocks 1102, 1109, 1118, 1125, 1127, 1159, and 1147. In block 1473, the UE detects that the first time alignment is about to expire while the second time alignment timer is running. In block 1475, the UE continues running the second time alignment timer in response to this detection.

[0247] Figure 14B is a flowchart of an exemplary method 1400B, similar to method 1400A, except that method 1400B includes block 1476 instead of block 1406. In block 1476, the UE stops a second time alignment timer in response to this detection.

[0248] The descriptions of Figures 9A-9C and 11A-11B can be applied to Figures 13, 14A, and 14B. Similarly, the descriptions of Figures 13, 14A, and 14B can be applied to Figures 9A-9C and 11A-11B.

[0249] Figure 15 shows an exemplary method 1500 for a RAN (e.g., RAN105 or base stations 104, 106 or DU174, 174A, 174B or 174C in Figures 3-8B) to handle a time alignment timer for uplink synchronization with a UE (e.g., UE102 in Figures 3-8B).

[0250] Method 1500 begins in block 1501, in which the RAN performs the actions described in blocks 1202, 1209, 1218, 1225, 1227, 1259, and 1247. In block 1572, the RAN detects that the second time alignment is about to expire while the first time alignment timer is running. In block 1574, the RAN responds to this detection by continuing to run the first time alignment timer.

[0251] Figure 16A shows an exemplary method 1600A for a RAN (e.g., RAN105 or base stations 104, 106 or DU174, 174A, 174B or 174C in Figures 3-8B) to handle a time alignment timer for uplink synchronization with a UE (e.g., UE102 in Figures 3-8B).

[0252] Method 1600A begins in block 1601, in which the RAN performs the actions described in blocks 1202, 1209, 1218, 1225, 1227, 1259, and 1247. In block 1673, the RAN detects that the first time alignment is about to expire while the second time alignment timer is running. In block 1675, the RAN continues running the second time alignment timer in response to this detection.

[0253] Figure 16B is a flowchart of an exemplary method 1600B, similar to method 1600A, except that method 1600B includes block 1677 instead of block 1675. In block 1677, the RAN stops the second time alignment timer in response to this detection.

[0254] The descriptions of Figures 10A to 10C and Figures 12A to 12B can be applied to Figures 15, 16A, and 16B. Similarly, the descriptions of Figures 15, 16A, and 16B can be applied to Figures 10A to 9C and Figures 12A to 12B.

[0255] Figure 17A shows an exemplary method 1700A for a UE (e.g., UE102 in Figures 3-8B) to handle a time alignment timer for uplink synchronization with a RAN (e.g., RAN105 or base stations 104, 106 in Figures 3-8B).

[0256] Method 1700A begins in block 1702, when the UE communicates with the RAN via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). In block 1709, the UE starts a first time alignment timer for uplink synchronization with the serving cell while communicating with the RAN via the serving cell. In block 1727, the UE sends a random access preamble to the RAN. In block 1759, the UE receives a random access response from the RAN containing the TA value in response to the random access preamble. In block 1791A, the UE decides whether to receive the random access response in the serving cell or in a candidate cell. If the UE determines in block 1791A that it has received a random access response at the serving cell, the flow proceeds to block 1753. In block 1753, the UE restarts a first time alignment timer in response to receiving the random access response. In some embodiments, the UE uses a TA value to adjust the uplink transmission timing with the serving cell. Otherwise, if the UE determines in block 1791A that it has received a random access response at a candidate cell, the flow proceeds to block 1747. In block 1747, the UE starts a second time alignment timer in response to receiving the random access response. In some embodiments, the UE uses a TA value to adjust the uplink transmission timing with the candidate cell.

[0257] In some embodiments, a certain / preceding candidate cell is a cell of the LTM (e.g., a target cell) (e.g., the first cell described above). In some embodiments, the UE maintains or refrains from stopping the first time alignment timer when starting a second time alignment timer or in response to receiving a random access response in a candidate cell.

[0258] Figure 17B is a flowchart of an exemplary method 1700B, similar to method 1700A except that method 1700B includes block 1791B instead of block 1791A.

[0259] In block 1791B, the UE decides whether to send the random access preamble in the serving cell or in the candidate cell. If the UE decides to send the random access preamble in the serving cell in block 1791B, the flow proceeds to block 1753. Otherwise, if the UE decides to send the random access preamble in the candidate cell in block 1791B, the flow proceeds to block 1747.

[0260] Figure 17C is a flowchart of an exemplary method 1700C, similar to method 1700A except that method 1700C includes block 1791C instead of block 1791A.

[0261] In block 1791C, the UE decides whether to send an early TA acquisition for the random access preamble. If the UE decides in block 1791C to send a random access preamble that will not be used for early TA acquisition, the flow proceeds to block 1753. Otherwise, if the UE decides in block 1791C to send a random access preamble for early TA acquisition, the flow proceeds to block 1747.

[0262] The descriptions of Figures 9A-9C, 11A-11B, 13, 14A, and 14B can be applied to Figures 17A-17C. Similarly, the descriptions of Figures 17A-17C can be applied to Figures 9A-9C, 11A-11B, 13, 14A, and 14B.

[0263] Figure 18A shows an exemplary method 1800A of a RAN (e.g., RAN 105 in Figures 3-8B, or base stations 104, 106, or DU 174, 174A, 174B, or 174C) managing the early TA acquisition of a UE (e.g., UE 102).

[0264] Method 1800A begins in block 1802, when the RAN communicates with the UE via the serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). In block 1809, while the RAN is communicating with the UE via the serving cell, it starts a first time alignment timer for uplink synchronization between the UE and the serving cell. In block 1827, the RAN receives a random access preamble from the UE. In block 1859, in response to the random access preamble, the RAN sends a random access response containing the TA value to the UE. In block 1891A, the RAN decides whether to send the random access response in the serving cell or in a candidate cell. If RAN decides to send a random access response in the serving cell in block 1891A, the flow proceeds to block 1853. In block 1853, RAN restarts the first time alignment timer in response to sending the random access response. Otherwise, if RAN decides to send a random access response in the candidate cell in block 1891A, the flow proceeds to block 1847. In block 1847, RAN starts the second time alignment timer in response to sending the random access response.

[0265] In some embodiments, a certain / preceding candidate cell is a cell of the LTM (e.g., a target cell) (e.g., the first cell described above). In some embodiments, the RAN maintains or refrains from stopping the first time alignment timer when starting the second time alignment timer or in response to sending a random access response on the candidate cell.

[0266] Figure 18B is a flowchart of an exemplary method 1800B, similar to method 1700A except that method 1800B includes block 1891B instead of block 1891A.

[0267] In block 1891B, RAN decides whether to receive the random access preamble in the serving cell or in a candidate cell. If RAN decides in block 1891B to receive the random access preamble in the serving cell, the flow proceeds to block 1853. Otherwise, if RAN decides in block 1891B to receive the random access preamble in a candidate cell, the flow proceeds to block 1847.

[0268] Figure 18C is a flowchart of an exemplary method 1800C, similar to method 1800A, except that method 1800C includes block 1891C instead of block 1891A.

[0269] In block 1891C, RAN determines whether it receives an early TA acquisition for a random access preamble. If RAN receives a random access preamble in block 1891C and determines that it is not for early TA acquisition, the flow proceeds to block 1753. Otherwise, if RAN determines that it receives a random access preamble in block 1891C for early TA acquisition, the flow proceeds to block 1847.

[0270] The descriptions of Figures 10A-10C, 12A-12B, 15, 16A, and 16B can be applied to Figures 18A-18C. Similarly, the descriptions of Figures 18A-18C can be applied to Figures 10A-10C, 12A-12B, 15, 16A, and 16B.

[0271] In some embodiments, the following description applies to the description above.

[0272] Generally speaking, the description for one of the above figures also applies to the above figures. The above examples, embodiments, and methods can be combined as long as there is no contradiction. The above events or blocks are optional or omitted. For example, the events or blocks with dashed lines in the figure are optional. In some embodiments, "message" is used and replaced with "information element (IE)", and vice versa. In some embodiments, "IE" is used, but "IE" is replaced with "field", and vice versa. In some embodiments, "configuration (singular)" is replaced with "configurations (plural)" or "configuration parameters", and vice versa. In some embodiments, "LTM command" is replaced with "serving cell change command", "layer 1 / layer 2 switching command", "lower layer switching command", or "lower layer serving cell change command". In some embodiments, "some" means "one or more". In some embodiments, "at least one" means "one or more". In some embodiments, "DU configuration" is replaced with "cell group configuration". In some embodiments, "cell index" is replaced with "serving cell index", "LTM cell index", "special cell (SpCell) index", "PCell index", or "PSCell index". In some embodiments, "serving" is replaced with "source". In some embodiments, "measurement report" is replaced with "measurement results (plural)". In some embodiments, "early TA acquisition" is replaced with "early timing synchronization", "early timing synchronization with the target cell", "early TA value acquisition", or "early TA value acquisition of the target cell". In some embodiments, "early TA acquisition configuration" is replaced with "early TA acquisition instruction" or "instruction to enable early TA acquisition".

[0273] A user device (e.g., UE102) that can implement the technology of this disclosure may be any suitable wireless communication device, such as a smartphone, tablet computer, laptop computer, mobile game console, point-of-sale (POS) terminal, health management device, drone, camera, media streaming dongle or other personal media device, wearable device such as a smartwatch, wireless hotspot, femtocell, or broadband router. Furthermore, the user device may optionally be embedded in an electronic system such as a vehicle head unit or advanced driver-assistance system (ADAS). In addition, the user device may operate as an Internet of Things (IoT) device or a mobile internet device (MID). Depending on the type, the user device may include one or more general-purpose processors, computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0274] Certain embodiments are described in this disclosure as including logic or some components or modules. A module can be a software module (e.g., code or machine-readable instructions stored in a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit that can perform certain operations and can be configured or arranged in a certain manner. A hardware module can include dedicated circuitry or logic that is permanently configured (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)) to perform a particular operation. A hardware module can also include programmable logic or circuitry (e.g., included 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 with dedicated permanently configured circuitry or with temporarily configured circuitry (e.g., configured by software) can be made considering cost and time.

[0275] When implemented in software, techniques can be provided as part of an operating system, libraries used by multiple applications, a particular software application, etc. The software can be executable by one or more general-purpose processors or one or more special-purpose processors.

[0276] As used herein, “comprises,” “comprising,” “includes,” “including,” “has,” “having,” or any other variation thereof are intended to encompass non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of elements is not necessarily limited to these elements alone, and may include other elements not expressly enumerated or inherent in such process, method, article, or apparatus. Furthermore, unless expressly stated otherwise, “or” refers to an inclusive or not an exclusive or. For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist); A is false (does not exist) and B is true (or exists); and both A and B are true (or exist).

Claims

1. A method implemented in user equipment (UE), In response to obtaining the timing advance of the target cell from the wireless access network (RAN) within the serving cell, the timing alignment timer of the target cell is started or restarted. The system receives a command to initiate an LTM (lower-layer triggered mobility) cell change for the target cell, In response to the aforementioned command, reset the Media Access Control (MAC) entity, A method comprising: resetting the MAC entity, and maintaining the execution of the timing alignment timer.

2. The method according to claim 1, further comprising accessing the target cell and communicating with the cell using the timing advance while the timing alignment timer is running.

3. The method according to claim 1 or 2, wherein maintaining the timing alignment timer is in response to determining that the LTM command includes the timing advance.

4. The acquisition of the aforementioned timing advance is The target cell receives a command to send a random access preamble, The method according to claim 1, comprising receiving the timing advance in a random access response message.

5. The method according to any one of claims 1 to 4, further comprising receiving the LTM configuration of the target cell before receiving the command to initiate the LTM cell modification.

6. Starting or restarting the timing alignment timer of the target cell includes restarting the timing alignment timer, The above method further, The method according to any one of claims 1 to 5, comprising starting the timing alignment timer of the serving cell before restarting the timing alignment timer of the target cell.

7. The method further includes starting the first timing alignment timer of the serving cell before restarting the timing alignment timer of the target cell. The method according to any one of claims 1 to 5, wherein starting or restarting the timing alignment timer of the target cell includes starting a second timing alignment timer.

8. The above method further, While the first timing alignment timer is running, the expiration of the second timing alignment timer is detected, The method according to claim 7, comprising maintaining the execution of the first timing alignment in response to the detection.

9. The above method further, While the second timing alignment timer is running, the expiration of the first timing alignment timer is detected, The method according to claim 7, comprising maintaining the execution of the second timing alignment in response to the detection.

10. The method further includes starting the first timing alignment timer of the serving cell before restarting the timing alignment timer of the target cell. The method according to claim 1, wherein starting or restarting the timing alignment timer of the target cell includes starting a second timing alignment timer in response to receiving a response to a random access preamble in the candidate cell.

11. The method further includes starting the first timing alignment timer of the serving cell before restarting the timing alignment timer of the target cell. The method according to claim 1, wherein starting or restarting the timing alignment timer of the target cell includes starting a second timing alignment timer in response to transmitting a random access preamble at the candidate cell.

12. The method further includes starting the first timing alignment timer of the serving cell before restarting the timing alignment timer of the target cell. The method according to claim 1, wherein starting or restarting the timing alignment timer of the target cell includes starting a second timing alignment timer in response to sending a random access preamble for early timing alignment acquisition.

13. A method implemented in a wireless access network (RAN), To provide user equipment (UE) within a serving cell with timing advances for the target cell, Sending a command to the UE to initiate LTM (lower-layer triggered mobility) cell modification to the target cell, In response to the transmission of the command, the timing alignment timer associated with the target cell is started, Resetting the Media Access Control (MAC) entity, A method comprising: resetting the MAC entity, and maintaining the execution of the timing alignment timer.

14. The method according to claim 14, wherein the restart of the MAC entity is in response to the determination that the command includes the timing advance value.

15. A device comprising processing hardware and configured to implement the method according to any one of claims 1 to 14.