EP4725247A1 - Managing uplink timing synchronization - Google Patents

Managing uplink timing synchronization

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Publication number
EP4725247A1
EP4725247A1 EP24748504.8A EP24748504A EP4725247A1 EP 4725247 A1 EP4725247 A1 EP 4725247A1 EP 24748504 A EP24748504 A EP 24748504A EP 4725247 A1 EP4725247 A1 EP 4725247A1
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EP
European Patent Office
Prior art keywords
configuration
ltm
cell
implementations
message
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EP24748504.8A
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German (de)
French (fr)
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Chih-Hsiang Wu
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Google LLC
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Google LLC
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
    • H04W56/0045—Synchronisation arrangements compensating for timing error of reception due to propagation delay compensating for timing error by altering transmission time

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

A user equipment (UE) starts or restarting (1147, 1153) a timing alignment timer for a target cell in response to obtaining (1159), from a radio access network (RAN) in a serving cell, a timing advance for the target cell; receives (113) a command to initiate a lower-layer triggered mobility (LTM) cell change to the target cell; resets (1141) a medium access control (MAC) entity in response to the command; and keeps the timing alignment timer running upon the restarting the MAC entity (1170).

Description

MANAGING UPLINK TIMING SYNCHRONIZATION CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of the filing date of provisional U.S. Patent Application No 63/525,653, entitled “Managing Uplink Timing Synchronization,” filed on July 7, 2023. The entire contents of the provisional application are hereby expressly incorporated herein by reference.
FIELD OF THE DISCLOSURE
[0002] This disclosure relates to wireless communications and, more particularly, to managing uplink synchronization between a user equipment (UE) and a radio access network (RAN).
BACKGROUND
[0003] This background description is provided for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
[0004] In telecommunication systems, the Packet Data Convergence Protocol (PDCP) sublayer of the radio protocol stack provides services such as transfer of user-plane data, ciphering, integrity protection, etc. For example, the PDCP layer defined for the Evolved Universal Terrestrial Radio Access (EUTRA) radio interface (see 3GPP specification TS 36.323) and New Radio (NR) (see 3GPP specification TS 38.323) provides sequencing of protocol data units (PDUs) in the uplink direction (from a user device, also known as a user equipment (UE), to a base station) as well as in the downlink direction (from the base station to the UE). Further, the PDCP sublayer provides signaling radio bearers (SRBs) and data radio bearers (DRBs) to the Radio Resource Control (RRC) sublayer. Generally speaking, the UE and a base station can use SRBs to exchange RRC messages as well as non-access stratum (NAS) messages, and can use DRBs to transport data on a user plane.
[0005] UEs can use several types of SRBs and DRBs. When operating in dual connectivity (DC), the cells associated with the base station operating the master node (MN) define a master cell group (MCG), and the cells associated with the base station operating as the secondary node (SN) define the secondary cell group (SCG). So-called SRB1 resources carry RRC messages, which in some cases include NAS messages over the dedicated control channel (DCCH), and SRB2 resources support RRC messages that include logged measurement information or NAS messages, also over the DCCH but with lower priority than SRB1 resources. More generally, SRB1 and SRB2 resources allow the UE and the MN to exchange RRC messages related to the MN and embed RRC messages related to the SN, and also can be referred to as MCG SRBs. SRB3 resources allow the UE and the SN to exchange RRC messages related to the SN, and can be referred to as SCG SRBs. Split SRBs allow the UE to exchange RRC messages directly with the MN via lower layer resources of the MN and the SN. Further, DRBs using the lower-layer resources of only the MN can be referred as MCG DRBs, DRBs using the lower-layer resources of only the SN can be referred as SCG DRBs, and DRBs using the lower-layer resources of both the MCG and the SCG can be referred to as split DRBs.
[0006] The UE in some scenarios can concurrently utilize resources of multiple radio access network (RAN) nodes (e.g., base stations or components of a distributed base station), interconnected by a backhaul. When these network nodes support different radio access technologies (RATs), this type of connectivity is referred to as Multi-Radio Dual Connectivity (MR-DC). When a UE operates in MR-DC, one base station operates as a master node (MN) that covers a primary cell (PCell), and the other base station operates as a secondary node (SN) that covers a primary secondary cell (PSCell). The UE communicates with the MN (via the PCell) and the SN (via the PSCell). In other scenarios, the UE utilizes resources of one base station at a time. One base station and/or the UE determines that the UE should establish a radio connection with another base station. For example, one base station can determine to hand the UE over to the second base station, and initiate a handover procedure.
[0007] When the UE moves from the coverage area of one cell to the coverage area of another cell in a RAN, the UE and the RAN at some point must perform a serving cell change. To this end, the RAN configures the UE to transmit Layer 3 (L3) measurement results. Using the L3 measurement results from the UE, the RAN transmits an RRC reconfiguration message configuring Reconfiguration with Synchronization (e.g., the RRC reconfiguration message includes a ReconfigurationWithSync IE) for a change of the serving cell (e.g., PCell or PSCell). When the UE operates in carrier aggregation (CA) of at least one secondary cell (SCell) with the PCell or PSCell, the RAN has to release the at least one SCell due to the change of the PCell or PSCell. The serving cell change involves complete L2 (and LI) resets, leading to longer latency, larger overhead, and longer interruption time. For these reasons, the 3rd Generation Partnership Project (3GPP) proposed to develop new mobility techniques for serving cell changes. These techniques aim to reduce latency and overhead and are called low-layer triggered mobility (LTM), or faster serving cell switching.
[0008] When a UE switches from a serving cell to a target cell in a RAN, the UE has to perform a random access procedure in order to synchronize with the target cell in the uplink, i.e., in the direction from the UE to the RAN. The UE can start communicating data with the RAN via the target cell only after the UE successfully completes the random access procedure. As a result, an interruption in data communication occurs during the serving cell switch. If the UE could obtain a timing advance value (TA) for synchronization with the target cell before switching to the target cell, the UE could avoid this interruption. However, it is still not clear how the UE and the RAN manage uplink synchronization on the target cell with each other before and after connecting to the target cell.
SUMMARY
[0009] An example embodiment of the techniques of this disclosure is a method implemented in a user equipment (UE). The method comprises starting or restarting a timing alignment timer for a target cell in response to obtaining, from a radio access network (RAN) in a serving cell, a timing advance for the target cell; receiving a command to initiate a lower- layer triggered mobility (LTM) cell change to the target cell; resetting a medium access control (MAC) entity in response to the command; and keeping the timing alignment timer running upon the resetting the MAC entity.
[0010] Another example embodiment of these techniques is a method implemented in a radio access network (RAN). The method comprises providing, to a user equipment (UE) in a serving cell, a timing advance for a target cell; transmitting, to the UE, a command to initiate a lower-layer triggered mobility (LTM) cell change to the target cell; starting a timing alignment timer associated for the target cell, in response to the transmitting of the command; resetting a medium access control (MAC) entity; and keeping the timing alignment timer running upon the resetting the MAC entity.
[0011] Yet another example embodiment of these techniques is a device comprising processing hardware and configured to implement one of the methods above. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Fig. 1A is a block diagram of an example system in which a radio access network (RAN) and a user device implements the techniques of this disclosure for managing uplink timing synchronization;
[0013] Fig. IB is a block diagram of an example base station including a centralized unit (CU) and a distributed unit (DU) that operates in the system of Fig. 1 A;
[0014] Fig. 2A is a block diagram of an example protocol stack according to which the UE of Fig. 1A communicates with base stations;
[0015] Fig. 2B is a block diagram of an example protocol stack according to which the UE of Fig. 1A communicates with a CU and a DU;
[0016] Fig. 3 illustrates an example scenario in which a UE performs a low-layer triggered mobility (LTM) cell change from one cell of a DU to another cell of the DU;
[0017] Fig. 4 illustrates an example scenario generally similar to that of Fig. 3, except the UE performs an inter-DU LTM cell change;
[0018] Fig. 5A illustrates an example scenario generally similar to that of Fig. 3, except the UE operates in dual connectivity (DC) with the base stations;
[0019] Fig. 5B illustrates an example scenario generally similar to that of Fig. 5A, except the Secondary Node (SN) transmits the RRC reconfiguration message to the UE via the Master Node (MN);
[0020] Fig. 6A illustrates an example scenario generally similar to that of Figs. 3-5B, except the UE communicates in DC to an MN and an SN to perform an inter-DU cell change;
[0021] Fig. 6B illustrates an example scenario generally similar to that of Figs. 3-5B and Fig. 6A, except the UE communicates in DC, and the SN transmits the RRC reconfiguration message to the UE via the MN;
[0022] Fig. 7A illustrates an example scenario in which a UE communicates in DC with an M-DU and an S-DU implemented in a same distributed base station, and receives an LTM configuration via the S-DU;
[0023] Fig. 7B illustrates an example scenario similar to that of Fig. 7A, except the UE receives the LTM configuration via the M-DU; [0024] Fig. 8A illustrates an example scenario in which a UE communicates in DC with an M-DU and an S-DU implemented in a same distributed base station, and receives an LTM configuration via the S-DU to communicate with a T-DU;
[0025] Fig. 8B illustrates an example scenario similar to that of Fig. 8A, except the UE receives the LTM configuration via the M-DU to communicate with a T-DU;
[0026] Fig. 9A is a flow diagram of an example method in a UE for managing uplink synchronization with a target cell using a timing advance received in an LTM command;
[0027] Fig. 9B is a flow diagram of an example method generally similar to that of Fig. 9A, except the UE starts or restarts the time alignment timer for uplink synchronization with the serving cell, after accessing the target cell;
[0028] Fig. 9C is a flow diagram of an example method generally similar to that of Fig. 9A, except that the UE determines whether it should perform a random access procedure in the target cell depending on whether the LTM command includes a TA value;
[0029] Fig. 10A is a flow diagram of an example method in a RAN for managing uplink synchronization with a UE using a timing advance transmitted in an LTM command;
[0030] Fig. 10B a flow diagram of an example method generally similar to that of Fig. 10A, except the RAN starts or restarts the time alignment timer for uplink synchronization with the serving cell, after the UE accesses the target cell;
[0031] Fig. 10C is a flow diagram of an example method generally similar to that of Fig. 10A, except that the RAN determines whether it should perform a random access procedure with the UE depending on whether the LTM command includes a TA value;
[0032] Fig. 11 A is a flow diagram of an example method generally similar to that of Fig. 9A, except the UE receives a random access response including a TA value from a RAN;
[0033] Fig. 1 IB is a flow diagram of an example method generally similar to that of Fig.
11 A, except the UE determines whether the LTM command instructs the UE to apply the TA value;
[0034] Fig. 12A is a flow diagram of an example method in a RAN for managing uplink synchronization with a UE, including sending a command to the UE for transmitting a random access preamble in a target cell; [0035] Fig. 12B is a flow diagram of an example method in a RAN for managing uplink synchronization with a UE, including determining whether to perform a random access procedure with a UE depending on whether the LTM command instructs the UE to apply a TA value;
[0036] Fig. 13 is a flow diagram of an example method in a UE generally similar to that of Fig. 11 A, but with the UE also detecting the expiration of the time alignment timer associated with the target cell, while the time alignment timer associated with the serving cell is still running;
[0037] Figs. 14A and 14B are a flow diagram of an example method in a UE generally similar to that of Fig, 11 A, but with the UE also detecting 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;
[0038] Fig. 15 is a flow diagram of an example method in a RAN generally similar to that of Fig. 12A, but with the RAN also detecting the expiration of the time alignment timer associated with the target cell, while the time alignment timer associated with the serving cell is still running;
[0039] Figs. 16A and 16B are a flow diagram of an example method in a RAN generally similar to that of Fig. 12A, but with the RAN also detecting 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;
[0040] Fig. 17A is a flow diagram of an example method in a UE for managing uplink synchronization, including determining which time alignment timer to start or restart depending on the cell in which the random access response was received;
[0041] Fig. 17B is a flow diagram of an example method in a UE for managing uplink synchronization, including determining which time alignment timer to start or restart depending on the cell in which the random access preamble was transmitted;
[0042] Fig. 17C is a flow diagram of an example method in a UE for managing uplink synchronization, including determining which time alignment timer to start or restart depending on whether the random access preamble was transmitted was transmitted for early TA acquisition; [0043] Fig. 17A is a flow diagram of an example method in a UE for managing uplink synchronization, including determining which time alignment timer to start or restart depending on the cell in which the random access response was received;
[0044] Fig. 17B is a flow diagram of an example method in a UE for managing uplink synchronization, including determining which time alignment timer to start or restart depending on the cell in which the random access preamble was transmitted;
[0045] Fig. 17C is a flow diagram of an example method in a UE for managing uplink synchronization, including determining which time alignment timer to start or restart depending on whether the random access preamble was transmitted was transmitted for early TA acquisition;
[0046] Fig. 18A is a flow diagram of an example method in a RAN for managing uplink synchronization, including determining which time alignment timer to start or restart depending on the cell in which the random access response was received;
[0047] Fig. 18B is a flow diagram of an example method in a RAN for managing uplink synchronization, including determining which time alignment timer to start or restart depending on the cell in which the random access preamble was transmitted; and
[0048] Fig. 18C is a flow diagram of an example method in a RAN for managing uplink synchronization, including determining which time alignment timer to start or restart depending on whether the random access preamble was transmitted was transmitted for early TA acquisition.
DETAILED DESCRIPTION OF THE DRAWINGS
[0049] Fig. 1A depicts an example wireless communication system 100 in which a user equipment (UE) and a radio access network (RAN) can implement uplink timing synchronization techniques. The wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106 and a core network (CN) 110. The UE 102 initially connects to the base station 104. In some scenarios, the base station 104 can perform an SN addition to configure the UE 102 to operate in dual connectivity (DC) with the base station 104 and the base station 106. The base stations 104 and 106 operate as an MN and an SN for the UE 102, respectively.
[0050] In various configurations of the wireless communication system 100, the base station 104 can be implemented as a master eNB (MeNB) or a master gNB (MgNB), and the base station 106 can be implemented as a secondary gNB (SgNB). The UE 102 can communicate with the base station 104 and the base station 106 via the same RAT such as EUTRA or NR, or different RATs. When the base station 104 is an MeNB and the base station 106 is a SgNB, the UE 102 can be in EUTRA-NR DC (EN-DC) with the MeNB and the SgNB.
[0051] In some cases, an MeNB or an SeNB is implemented as an ng-eNB rather than an eNB. When the base station 104 is a Master ng-eNB (Mng-eNB) and the base station 106 is a SgNB, the UE 102 can be in next generation (NG) EUTRA-NR DC (NGEN-DC) with the Mng-eNB and the SgNB. When the base station 104 is an MgNB and the base station 106 is an SgNB, the UE 102 may be in NR-NR DC (NR-DC) with the MgNB and the SgNB. When the base station 104 is an MgNB and the base station 106 is a Secondary ng-eNB (Sng-eNB), the UE 102 may be in NR-EUTRA DC (NE-DC) with the MgNB and the Sng-eNB.
[0052] In the scenarios where the UE 102 hands over from the base station 104 to the base station 106, the base stations 104 and 106 operate as the source base station (S-BS) and a target base station (T-BS), respectively. The UE 102 can operate in DC with the base station 104 and an additional base station (not shown in Fig. 1A) prior to the handover, for example. The UE 102 can continue to operate in DC with the base station 106 and the additional base station, or operate in single connectivity (SC) with the base station 106, after completing the handover. The base stations 104 and 106 in this case operate as a source MN (S-MN) and a target MN (T-MN), respectively.
[0053] A core network (CN) 110 can be an evolved packet core (EPC) 111 or a fifthgeneration core (5GC) 160, both of which are depicted in Fig. 1A. The base station 104 can be an eNB supporting an SI interface for communicating with the EPC 111, an ng-eNB supporting an NG interface for communicating with the 5GC 160, or a gNB that supports an NR radio interface as well as an NG interface for communicating with the 5GC 160. To directly exchange messages with each other during the scenarios discussed below, the base stations 104 and 106 can support an X2 or Xn interface. Among other components, the EPC 111 can include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. The SGW 112 is generally configured to transfer user-plane packets related to audio calls, video calls, Internet traffic, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The PGW 116 provides connectivity from the UE to one or more external packet data networks, e.g., an Internet network and/or an Internet Protocol (IP) Multimedia Subsystem (IMS) network. The 5GC 160 includes a User Plane Function (UPF) 162 and an Access and Mobility Management (AMF) 164, and/or Session Management Function (SMF) 166. The UPF 162 is generally configured to transfer user-plane packets related to audio calls, video calls, Internet traffic, etc., the AMF 164 is configured to manage authentication, registration, paging, and other related functions, and the SMF 166 is configured to manage PDU sessions.
[0054] As illustrated in Fig. 1A, the base station 104 supports a cell 124A, and the base station 106 supports a cell 126. The cells 124A and 126 can partially overlap, so that the UE 102 can communicate in DC with the base station 104 and the base station 106, where one of the base stations 104 and 106 is an MN and the other is an SN. The base station 104 can support additional cell(s) such as cells 124B and 124C, and the base station 106 can support additional cell(s) (not shown in Fig. 1A). The cells 124A, 124B and 124C can partially overlap, so that the UE 102 can communicate in carrier aggregation (CA) with the base station 104. The base station 104 can operate the cells 124A, 124B and 124C via one or more transmit and receive points (TRPs). More particularly, when the UE 102 is in DC with the base station 104 and the base station 106, one of the base stations 104 and 106 operates as an MeNB, an Mng-eNB or an MgNB, and the other operates as an SgNB or an Sng-eNB.
[0055] In general, the wireless communication network 100 can include any suitable number of base stations supporting NR cells and/or EUTRA cells. More particularly, the EPC 111 or the 5GC 160 can be connected to any suitable number of base stations supporting NR cells and/or EUTRA cells. Although the examples below refer specifically to specific CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general the techniques of this disclosure also can apply to other suitable radio access and/or core network technologies such as sixth generation (6G) radio access and/or 6G core network or 5G NR-6G DC.
[0056] With continued reference to Fig. 1A, the base station 104 is equipped with processing hardware 130 that can include one or more general-purpose processors (e.g., CPUs) and a non-transitory computer-readable memory storing instructions that the one or more general-purpose processors execute. Additionally or alternatively, the processing hardware 130 can include special-purpose processing units.
[0057] The processing hardware 130 can implement an LTM controller 132 to support LTM procedures and a TA acquisition controller 134 to support early TA acquisition at UEs. The LTM controller 132 and the TA acquisition controller 134 can be implemented as respective sets of instructions executable by one or more processors, for example. The processing hardware 130 can also implement additional components such as a PHY controller (not shown) configured to transmit data and control signal on physical downlink (DL) channels and DL reference signals with one or more user devices (e.g. UE 102) via one or more cells (e.g., the cell(s) 124A, 124B and/or 124C) and/or one or more TRPs. The PHY controller can be configured to receive data and control signal on physical uplink (UL) channels and/or UL reference signals with the one or more user devices via one or more cells (e.g., the cell(s) 124A, 124B and/or 124C) and/or one or more TRPs. The processing hardware 130 can also implement a MAC controller (not shown) configured to perform MAC functions with one or more user devices. The MAC functions include a random access (RA) procedure, managing UL timing advance for the one or more user devices, and/or communicating UL/DL MAC PDUs with the one or more user devices. The MAC functions include lower triggered mobility (LTM) related functions as described below. The processing hardware 130 can further include an RRC controller (not shown) to implement procedures and messaging at the RRC sublayer of the protocol communication stack. Lor example, the RRC controller may be configured to support RRC messaging associated with handover procedures, and/or to support the necessary operations when the base station 104 operates as an MN relative to an SN or as an SN relative to an MN. The base station 106 can include processing hardware 140 that is similar to processing hardware 130. In particular, components 142, 144, and 146 can be similar to the components 132 and 134, , respectively.
[0058] The UE 102 is equipped with processing hardware 150 that can include one or more general-purpose processors such as CPUs and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and/or special-purpose processing units. The processing hardware 150 can 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 a target cell. The LTM controller 152 and the TA acquisition controller 154 can be implemented as respective sets of instructions executable by one or more processors, for example.
[0059] The processing hardware 150 can also implement additional components such as a PHY controller (not shown) configured to receive data and control signal on physical DL channels and/or DL reference signals with the base station 104 or 106 via one or more cells (e.g., the cell(s) 124A, 124B, 124C and/or 126) and/or one or more TRPs. The PHY controller can be configured to transmit data and control signal on physical UL channels and/or UL reference signals with the base station 104 or 106 via one or more cells (e.g., the cell(s) 124A, 124B, 124C and/or 126) and/or one or more TRPs. The processing hardware 150 in an example implementation includes a MAC controller (not shown) configured to perform MAC functions with base station 104 or 106. For example, the MAC functions includes a random access procedure, managing UL timing advance for the one or more user devices, and communicating UL/DL MAC PDUs with the base station 104 or 106. In another example, the MAC functions includes LTM related functions as described below. The processing hardware 150 can further include an RRC controller (not shown) to implement procedures and messaging at the RRC sublayer of the protocol communication stack.
[0060] In operation, the UE 102 in DC can use a radio bearer (e.g., a DRB or an SRB) that at different times terminates at the MN 104 or the SN 106. The UE 102 can apply one or more security keys when communicating on the radio bearer, in the uplink (UL) (from the UE 102 to a base station) and/or downlink (from a base station to the UE 102) direction.
[0061] Fig. IB depicts an example distributed implementation of a base station such as the base station 104 or 106. The base station in this implementation includes a centralized unit (CU) 172 and one or more distributed units (DUs) 174. In some implementations, the CU 172 is equipped with processing hardware that includes one or more general-purpose processors, such as CPUs, and non-transitory computer-readable memory storing machine- readable instructions executable on the one or more general-purpose processors, and/or special-purpose processing units. In some implementations, the CU 172 is equipped with the processing hardware 130. In yet further implementations, the CU 172 is equipped with the processing hardware 140. The processing hardware 140 in an example implementation includes an SN RRC controller 142 configured to manage or control one or more RRC configurations and/or RRC procedures when the base station 106 operates as an SN. In some implementations, the DU 174 is also equipped with processing hardware that includes one or more general-purpose processors, such as CPUs, and non-transitory computer-readable memory storing machine -readable instructions executable on the one or more general- purpose processors, and/or special-purpose processing units. In some implementations, the processing hardware includes a medium access control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., a random access procedure) and a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station 106 operates as an MN or an SN. In some implementations, the process hardware includes a physical layer controller configured to manage or control one or more physical layer operations or procedures.
[0062] Fig. 2A illustrates, in a simplified manner, an example protocol stack 200 according to which the UE 102 communicates with an eNB/ng-eNB or a gNB (e.g., one or more of the base stations 104, 106).
[0063] In the example stack 200, a physical layer (PHY) 202A of EUTRA provides transport channels to the EUTRA MAC sublayer 204A, which in turn provides logical channels to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A in turn provides RLC channels to an EUTRA PDCP sublayer 208 and, in some cases, to an NR PDCP sublayer 210. Similarly, the NR PHY 202B provides transport channels to the NR MAC sublayer 204B, which in turn provides logical channels to the NR RLC sublayer 206B. The NR RLC sublayer 206B in turn provides data transfer services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 in turn provides data transfer services to Service Data Adaptation Protocol (SDAP) 212 or a radio resource control (RRC) sublayer (not shown in Fig. 2A). The UE 102, in some implementations, supports both the EUTRA and the NR stack as shown in Fig. 2A, to support handover between EUTRA and NR base stations and/or to support DC over EUTRA and NR interfaces. Further, as illustrated in Fig. 2A, the UE 102 supports layering of NR PDCP 210 over EUTRA RLC 206 A, and SDAP sublayer 212 over the NR PDCP sublayer 210.
[0064] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets (e.g., from an Internet Protocol (IP) layer, layered directly or indirectly over the PDCP layer 208 or 210) referred to as service data units (SDUs), and transmit packets (e.g., to the RLC layer 206 A or 206B) referred to as protocol data units (PDUs). Except where the difference between SDUs and PDUs is relevant, this disclosure for simplicity refers to both SDUs and PDUs as “packets.”
[0065] In some implementations, on a control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 provides signaling radio bearers (SRBs) or RRC sublayer (not shown in Fig. 2A) to exchange RRC messages or non-access-stratum (NAS) messages, for example. In some implementations, on a user plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 provides Data Radio Bearers (DRBs) to support data exchange. In further implementations, data exchanged on the NR PDCP sublayer 210 are SDAP PDUs, Internet Protocol (IP) packets or Ethernet packets.
[0066] Fig. 2B illustrates, in a simplified manner, an example protocol stack 250, which the UE 102 communicates with a DU (e.g., DU 174) and a CU (e.g., CU 172). The radio protocol stack 200 is functionally split as shown by the radio protocol stack 250 in Fig. 2B. In some implementations, the CU at any of the base stations 104 or 106 hold all the control and upper layer functionalities (e.g., RRC 214, SDAP 212, NR PDCP 210), while the lower layer operations (e.g., NR RLC 206B, NR MAC 204B, and NR PHY 202B) are delegated to the DU. To support connection to a 5GC, NR PDCP 210 provides SRBs to RRC 214, and NR PDCP 210 provides DRBs to SDAP 212 and SRBs to RRC 214.
[0067] Next, several example scenarios in which the base station operating in the system of Fig. 1A transmits a configuration to the UE 102 and later activates a configuration for communication between the UE 102 and base station. Generally speaking, events in Figs. 3- 8B that are similar are labeled with similar reference numbers (e.g., event 394 is similar to event 494 of Figs 4, event 594 of Fig. 5A, event 694 of Fig. 6A, event 794 of Fig. 7A, and event 894 of Fig. 8A), with differences discussed below where appropriate. With the exception of the differences shown in the figures and discussed below, any of the alternative implementations discussed with respect to a particular event (e.g., for messaging and processing) may apply to events labeled with similar reference numbers in other figures.
[0068] Referring first to Fig. 3, in a scenario 300, the base station 104 includes a CU 172 and a DU 174 and the DU 174 operates the cell 124A. The UE 102 initially communicates 302 with the DU 174 on the cell 124A using a serving DU configuration, and communicates with the CU 172 via the DU 174, e.g., using a serving CU configuration. In other words, the DU 174 is a serving DU that is communicating with the UE 102. In some implementations, the UE 102 in carrier aggregation (CA) communicates with the DU 174 on the cell 124A and other cell(s) (e.g., cell 124D not shown in Fig. 1A) using the serving DU configuration. The DU 174 operates the other cell(s). In other implementations, the UE 102 communicates with the DU 174 on the cell 124A only. In some implementations, the UE 102 communicates with the DU 174 on the cell 124A and/or other cell(s) via one or multiple transmission reception points (TRPs). In some implementations, the cell 124A is a PCell. In such cases, the other cell(s) include SCell(s) and/or additional cell(s) associated with the PCell or a SCell. In other implementations, the cell 124A is a SCell, and one of the other cell(s) is a PCell. In such cases, the rest includes SCell(s) and/or additional cell(s) associated with the PCell or a SCell. In the following description, the base station 104 is the DU 174, the CU 172 or the DU 174 and CU 172.
[0069] In some implementations the UE 102 transmits 302 the UL PDUs and/or the UL control signals to the base station 104 on the cell 124A and/or other cell(s) via one or multiple TRPs. In some implementations, the UE 102 communicates UL PDUs and/or DL PDUs with the base station 104 via radio bearers which includes SRBs and/or DRB(s). In some implementations, the base station 104 configures the radio bearers for the UE 102. In some implementations, UL control signals include UL control information, channel state information, hybrid automatic repeat request (HARQ) acknowledgements (ACKs), HARQ negative ACKs, scheduling request(s) and/or sounding reference signal(s). In further implementations, the UE 102 receives DL PDUs and/or DL control signals from the base station 104 on the cell 124A and/or other cell(s) via one or multiple TRPs. In some implementations, the DL control signals include DL control information (DCIs) and reference signals (e.g., synchronization signal block, channel state information reference signal(s) (CSI- RS(s)), and/or tracking reference signal(s)). In some implementations, the base station 104 transmits the DCIs on physical downlink control channel(s) (PDCCH(s)) monitored by the UE 102, on the cell 124A and/or other cell(s) via one or multiple TRPs.
[0070] In some implementations, the serving DU configuration includes physical layer configuration parameters, MAC configuration parameters, and/or RLC configuration parameters. In some implementations, the DU 174 transmits these configuration parameters to the CU 172. The CU 172 generates one or more messages (e.g., RRC reconfiguration message(s)) including the configuration parameters and transmits the one or more messages to the UE 102 via the DU 174. In further implementations, the DU 174 transmits the configuration parameters to the UE 102 directly. In some implementations, the serving DU configuration is CellGroupConfig IE (e.g., as defined in 3GPP TS 38.331). In further implementations, the serving DU configuration includes configuration parameters in the CellGroupConfig IE. In yet further implementations, the serving CU configuration includes PDCP configuration parameters, measurement configuration parameters, and/or radio bearer configuration parameters. In some implementations, the serving CU configuration includes a MeasConfig IE and/or a RadioBearerConfig IE (e.g., as defined in 3GPP TS 38.331) or includes configuration parameters in the MeasConfig IE and/or RadioBearerConfig IE. In some implementations, the serving DU configuration includes a CSl-MeasConfig IE or configuration parameters for channel state information (CSI) measurement and reporting. In further implementations, the serving CU configuration includes a CSl-MeasConfig IE or configuration parameters for CSI measurement and reporting. In some implementations, the UE 102 receives the serving CU configuration or the configuration parameters in the serving CU configuration from the CU 172 via the DU 174. In further implementations, the UE 102 receives a portion of the serving CU configuration and/or a portion of the serving DU configuration from a base station other than the base station 104 and the remaining portion of these configuration parameters from the base station 104.
[0071] While communicating with the base station 104, the UE 102 transmits 304 at least one measurement report to the DU 174. In some implementations, the at least one measurement report includes a Layer 1 (LI) measurement reports and/or a Layer 3 (L3) measurement reports for at least one serving cell of the UE 102 and/or at least one nonserving cell. For each of the L3 measurement reports, the DU 174 transmits 306 a DU-to-CU message including the L3 measurement report to the CU 172. In some implementations, the DU-to-CU message of the event 306 is an Fl application protocol (F1AP) message (e.g., UL RRC Message Transfer message). In some implementations, the DU 174 does not transmit or refrains from transmitting the LI measurement report to the CU 172. The at least one serving cell includes the cell 124A and/or other cell(s), and the at least one non-serving cell includes the cell 124B and/or cell 124C. In some implementations, the serving DU configuration or the serving CU configuration includes at least one measurement configuration. In some implementations, the UE 102 receives one or more RRC messages (e.g., RRCReconfiguration messages) including the at least one measurement configuration from the CU 172 via the DU 174 in the event 302. In accordance with the at least one measurement configuration, the UE 102 performs measurements and transmits 304 the at least one measurement report to the DU 174. In some implementations, the at least one measurement configuration includes an L3 measurement configuration (e.g., MeasConfig IE) and/or LI measurement configuration. In some implementations, the LI measurement configuration (e.g., CSl-MeasConfig IE)includes an LI measurement resource configuration and/or an LI measurement reporting configuration. In some implementations, the LI measurement resource configuration configures reference signals and/or resources of the reference signals for the UE 102 to measure and obtain LI measurement results. In some implementations, the reference signals includes CSLRSs and/or Synchronization Signal (SS)/Physical Broadcast Channel (PBCH) Resource Blocks (SSBs). For example, the LI measurement resource configurations are CSI- ResourceConfig IES. In some implementations, the LI measurement reporting configuration configures the UE 102 to transmit LI measurement results/reports. For example, the LI measurement report configuration(s) is/are CSl-ReportConfig IE(s). For example, the UE 102 transmits the L3 measurement report(s) to the CU 172 via the DU 174 in accordance with the L3 measurement configuration(s). The UE 102 transmits the LI measurement report(s) to the DU 174 in accordance with the LI measurement configuration(s) or LI measurement reporting configuration(s). In some implementations, the DU 174 does not transmit the LI measurement report(s) to the CU 172.
[0072] In some implementations, the LI measurement configuration(s) are specifically defined RRC IE(s) (e.g., as defined in the 3GPP TS 38.331) for a lower layer triggered mobility (LTM). In some implementations, the LI measurement resource configuration(s) are specifically defined RRC IE(s) (e.g., as defined in the 3GPP TS 38.331) for the LTM. In some implementations, the LI measurement reporting configuration(s) are specially defined as RRC IE(s) (e.g., as defined in the 3GPP TS 38.331) for the LTM. In some implementations, each of the LI measurement reporting configuration(s) includes a trigger event configuration configuring a trigger event to trigger the UE 102 to transmit an LI measurement report. If the UE 102 detects the trigger event, the UE 102 transmits an LI measurement report to the DU 174.
[0073] In some implementations, (each of) the LI measurement report(s) includes at least one LI measurement result. In some implementations, the at least one LI measurement result includes at least one LI reference signal received power (Ll-RSRP) value and/or at least one LI Signal-to-Interference-Noise Ratio (Ll-SINR) value. In some implementations, for each of the LI measurement report(s), the UE 102 transmits a PUCCH transmission including the LI measurement report to the DU 174. That is, the UE 102 transmits the each of the LI measurement report(s) on a PUCCH to the DU 174. In further implementations, for each of the LI measurement report(s), the UE 102 transmits a PUSCH transmission including the LI measurement report to the DU 174. That is, the UE 102 transmits the each of the LI measurement report(s) on a PUSCH to the DU 174. In yet further implementations, the UE 102 transmits a portion of the LI measurement report(s) on PUCCH(s) and the rest of the LI measurement report(s) on physical UL shared channel(s) (e.g., PUSCH(s)) to the DU 174. That is, for each of the portion of the LI measurement report(s), the UE 102 transmits a PUCCH transmission including the LI measurement report to the DU 174, and for each of the rest of the LI measurement report(s), the UE 102 transmits a PUSCH transmission including the LI measurement report to the DU 174. In some implementations, each of the LI measurement report(s) is a part of a CSI (i.e., a CSI component) or a CSI in its entirety. In some implementations, the UE 102 includes other CSI component(s) in (each of) the PUCCH transmission(s) and/or PUSCH transmission(s) described above. In some implementations, the other CSI component(s) includes a channel quality indicator (CQI), a Precoding Matrix Indicator (PMI), a CSLRS Resource Indicator (CRI), a SSB Resource Indicator (SSBRI), a Layer Indicator (LI), and/or a Rank Indicator (RI). In some implementations, the UE 102 does not transmit the LI measurement report(s) in the format of RRC message(s) to the DU 174.
[0074] In some implementations, each of the L3 measurement report(s) includes at least one L3 measurement result. In further implementations, the at least one L3 measurement result includes at least one RSRP (e.g., a value) and/or at least one SINR (e.g., a value). In some implementations, the UE 102 transmits each of the L3 measurement report(s) on a PUSCH to the CU 172 via the DU 174. In some implementations, each of the L3 measurement report(s) includes an RRC message (e.g., MeasurementReport message). In further implementations, each of the L3 measurement configuration(s) includes a particular measurement identity (e.g., measld) and each of the L3 measurement report(s) includes a particular measurement identity in a particular L3 measurement configuration. In some implementations, when the CU 172 receives an L3 measurement report including a measurement identity and an L3 measurement result from the UE 102 via the DU 174, the CU 172 determines that the L3 measurement report is associated to an L3 measurement configuration identified by the measurement identity.
[0075] In some implementations, for each of the at least one measurement report (e.g., LI measurement report(s)), the UE 102 transmits 304 to the DU 174 with a MAC control element (CE) which includes the measurement report. To transmit 304 to the DU 174, the UE 102 generates one or more MAC PDUs each including one or more of the MAC CE(s).
[0076] In some implementations, the UE 102 performs measurements on one or more reference signals in accordance with the at least one measurement configuration. In some implementations, the one or more reference signals includes one or more Synchronization Signal (SS)/ Physical Broadcast Channel (PBCH) Resource Blocks (SSBs) and/or one or more CSLRS s. The UE 102 obtains the at least one LI measurement result and/or at least one L3 measurement result from the measurements. The DU 174 transmits the one or more reference signals on the cell 124A and other cell(s) (e.g., the cell 124B, the cell 124C and/or cell(s) not shown in Fig. 1A).
[0077] After (e.g., in response to) receiving one or some of the at least one measurement report from the UE 102, the base station 104 (i.e., the CU 172 or DU 174) determines to prepare a first cell (e.g., the cell 124B) for LTM for the UE 102. In some implementations, the base station 104 determines to prepare the first cell for the UE 102 because the at least one measurement report indicates that the first cell uses the base station 104 to communicate with the UE 102. In some implementations, the base station 104 determines to prepare the first cell for the UE 102 because the at least one measurement report indicates that the first cell qualifies as a candidate cell for communication with the UE 102. In some implementations, if the L3 measurement report(s) indicates that signal strength and/or quality of the first cell is above a first predetermined threshold, is better in strength and/or quality of the cell 124A, and/or is better in strength and/or quality of the cell 124A by a first predetermined threshold, the CU 172 determines to prepare the first cell for the UE 102. In further implementations, if the LI measurement report(s) indicates that signal strength and/or quality of the first cell is above a first predetermined threshold, is better in signal strength and/or quality of the cell 124A, and/or is better in signal strength and/or quality of the cell 124A by a first predetermined threshold, the DU 174 determines to prepare the first cell for the UE 102. Alternatively, the base station 104 determines to prepare the first cell for the UE 102 regardless of whether a measure report is received from the UE 102 or not.
[0078] In the case that the CU 172 determines to prepare the first cell for LTM, the CU 172 transmits 308 a first CU-to-DU message to the DU 174 to prepare the first cell for the UE 102. In some implementations, the CU 172 includes a cell identity (ID) 1 of the first cell in the first CU-to-DU message to request the DU 174 to prepare the first cell for LTM for the UE 102. For example, the cell ID 1 is cell global identity (CGI). In another example, the cell ID is a portion of the CGI. In yet another example, the cell ID is a physical cell ID (PCI). In response to the first CU-to-DU message, the DU 174 generates a first LTM DU configuration (e.g., referred to herein after as LTM DU configuration 1) for the UE 102, which configures the first cell for LTM. The DU 174 then transmits 310 a first DU-to-CU message including the LTM DU configuration 1 to the CU 172 in response to the first CU-to-DU message. In some implementations, the DU 174 includes the cell ID 1 together with the LTM DU configuration 1 in an IE of the first DU-to-CU message to indicate that the LTM DU configuration 1 is associated with the first cell (i.e., the cell ID 1). In the case that the DU 174 determines to prepare the first cell, the DU 174 initiates transmission of the first DU-to-CU message to the CU 172 instead of in response to a CU-to-DU message received from the CU 172.
[0079] In some implementations, the DU 174 includes in the first DU-to-CU message, the cell ID of the first cell associated with the LTM DU configuration 1 to indicate that the LTM DU configuration 1 is configured for or associated with the first cell. The CU 172 identifies the LTM DU configuration 1 is configured for or associated with the first cell. In some implementations, the CU 172 includes additional cell ID(s) (e.g., cell ID(s) 2, ..., N) in the first CU-to-DU message to prepare additional cell(s) (e.g., cell(s) 2, ..., N) for LTM for the UE 102, and the DU 174 includes additional LTM DU configuration(s) (e.g., LTM DU configuration(s) 2, ..., N) for additional cell(s), as described below. In such cases the DU 174 includes, in the first DU-to-CU message, an indication of which LTM DU configuration is associated to which cell (ID). The cell(s) 1 and/or 2, ..., N are candidate cell(s).
[0080] In some implementations, the CU 172 does not include a LTM DU configuration (e.g., a reference configuration) in the first CU-to-DU message. In such cases, the DU 174 generates a reference LTM DU configuration, generates the LTM DU configuration(s) 1 and/or 2, ..., N (i.e., non-reference LTM DU configuration(s)) based on the reference LTM DU configuration, and includes the reference LTM DU configuration in the first DU-to-CU message. In further implementations, the CU 172 includes a reference LTM DU configuration in the first CU-to-DU message. In such cases, the DU 174 generates the LTM DU configuration(s) 1, and/or 2, ..., N which are delta configuration(s) to augment the reference LTM DU configuration. In yet further implementations, the CU 172 includes a reference LTM DU configuration (e.g., a first reference LTM DU configuration) in the first CU-to-DU message. In such cases, the DU 174 generates a reference LTM DU configuration (e.g., a second reference LTM DU configuration) replacing the first reference LTM DU configuration, generates the LTM DU configuration(s) 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.
[0081] In some implementations, the reference LTM DU configuration includes physical layer configuration parameters, MAC configuration parameters, and/or RLC configuration parameters. In some implementations, the reference LTM DU configuration is CellGroupConfig IE (e.g., as defined in 3GPP TS 38.331). In further implementations, the reference LTM DU configuration includes configuration parameters in the CellGroupConfig IE. In yet further implementations, the reference LTM DU configuration includes a CS1- MeasConfig IE or configuration parameters for CSI measurement and/or reporting.
[0082] In some implementations, the reference LTM DU configuration is different from the serving DU configuration. In further implementations, a portion of the reference LTM DU configuration is the same as a portion of the serving DU configuration and the rest of the reference LTM DU configuration is different from the rest of the serving DU configuration. In yet further implementations, the reference LTM DU configuration is the same as the serving DU configuration.
[0083] After receiving the first DU-to-CU message, the CU 172 generates an RRC reconfiguration message (e.g., an RRCReconfiguration message) including the LTM DU configuration 1 and transmits 316 to the DU 174 a second CU-to-DU message with the RRC reconfiguration message. In some implementations, the CU 172 transmits 316 the reference LTM DU configuration in the RRC reconfiguration message. In further implementations, the CU 172 transmits 316 without the reference LTM DU configuration in the RRC reconfiguration message. In some implementations, if the CU 172 transmits 302 the reference LTM DU configuration to the UE 102, the CU 172 transmits 316 without the reference LTM DU configuration in the RRC reconfiguration message. In further implementations, if the CU 172 receives the reference LTM DU configuration from the DU 174, the CU 172 transmits 316 the LTM DU configuration in the RRC reconfiguration message. Otherwise, if the CU 172 does not receive a reference LTM DU configuration from the DU 174, the CU 172 transmits 316 without the reference LTM DU configuration in the RRC reconfiguration message.
[0084] In some implementations, the CU 172 transmits 316 and 318 the LTM DU configuration 1 and/or the LTM CU configuration 1 in a first container (e.g., a field/IE) and includes the first container (e.g., LTM configuration 1) in the RRC reconfiguration message. In such cases, the CU 172 generates the first container. The first container indicates to the UE 102 not to apply the LTM DU configuration 1 and/or the LTM CU configuration 1 immediately. In some implementations, the UE 102 receives 318 an RRC reconfiguration message including a configuration (e.g., the LTM DU configuration 1). If the configuration is included in the first container, the UE 102 refrains from immediately applying the configuration. Otherwise, if the configuration is not included in the first container, the UE 102 applies the configuration immediately. In some implementations, the first container includes or is a first addition or modification list (e.g., Itm-ConfigToAddModList field, Itm- CandidateToAddModList field, or Itm-CandidateConfigToAddModList field) . The CU 172 includes the LTM DU configuration 1 and/or the LTM CU configuration 1 in a first element (e.g., referred to herein after as element 1) of the first addition or modification list. In some implementations, the CU 172 generates an RRC message (e.g., RRCRecconfiguration message) including the LTM DU configuration 1 and/or the LTM CU configuration 1, and includes the RRC message in the element 1. In some implementations, the element 1 is an addition or modification IE (e.g., LTM-ConfigToAddMod IE, LTM-Candidate IE, LTM- CandidateToAddMod l , or LTM-CandidaleConfigToAddMod \ ). In some implementations, when the UE 102 receives the first addition or modification list, the UE 102 stores the first addition or modification list, e.g., in a variable in its random access memory (RAM). In further implementations, the DU 174 generates the first container and includes the first container in the first DU-to-CU message. In yet further implementations, the DU 174 generates the element 1 and includes the element 1 in the first DU-to-CU message.
[0085] In some implementations, the CU 172 transmits 316 a LTM CU configuration 1 in the RRC reconfiguration message and the first container or the element 1, where the LTM CU configuration 1 is associated with the LTM DU configuration 1. In some implementations, to associate the LTM CU configuration 1 with the LTM DU configuration
1, the CU 172 includes the LTM CU configuration 1 with the LTM DU configuration in the element 1. In some implementations, the CU 172 transmits 316 the LTM CU configuration(s)
2, ..., N in the RRC reconfiguration message or the second container, where the LTM CU configuration(s) 2, ..., N is associated with the LTM DU configuration(s) 2, ..., N, respectively. In further implementations, to associate the LTM CU configuration(s) 2, ..., N with the LTM DU configuration(s) 2, ..., N , the CU 172 includes the LTM CU configuration(s) 2, ..., N and the LTM DU configuration(s) in the element(s) 2, ..., N, respectively. In yet further implementations, the CU 172 includes in the element(s) 2, ..., N, the LTM CU configuration(s) 2, ..., N associated with the LTM DU configuration(s) 2, ..., N, respectively. In yet further implementations, the CU 172 transmits 316 without the LTM CU configuration(s) for some or all of the LTM DU configuration 1 and/or LTM DU configuration(s) 2, ..., N in the RRC reconfiguration message.
[0086] After receiving 316 the RRC reconfiguration message, the DU 174 transmits 318 the RRC reconfiguration message to the UE 102. In response, the UE 102 transmits 320 a RRC reconfiguration complete message (e.g., an RRCReconfigurationComplete message) to the DU 174, which in turn transmits 322 with a second DU-to-CU message including the RRC reconfiguration complete message to the CU 172. In some implementations, the CU 172 performs security protection (e.g., integrity protection and/or encryption) on the RRC reconfiguration message. For example, the CU 172 generates a message authentication code for integrity (MAC-I) for the RRC reconfiguration message, encrypts the RRC reconfiguration message and the MAC-I to obtain an encrypted RRC reconfiguration message and an encrypted MAC-I, and transmits 316 and 318 a PDCP PDU including the encrypted RRC reconfiguration message and encrypted MAC-I to the UE 102 via the DU 174. When the UE 102 receives 316 and 318 the PDCP PDU from the CU 172 via the DU 174, the UE 102 decrypts the encrypted RRC reconfiguration and encrypted MAC-I to obtain the RRC reconfiguration message and MAC-I and verifies whether the MAC-I is valid. If the UE 102 verifies the MAC-I is invalid, the UE 102 discards or ignores the RRC reconfiguration message. In some implementations, the UE 102 performs a RRC connection reestablishment procedure in response to the invalid MAC-I. In some implementations, if the UE 102 verifies the MAC-I is valid, the UE 102 processes the RRC reconfiguration. The UE 102 refrains from applying (i.e., executing) the LTM DU configuration 1 until receiving 330 and 350 an LTM command activating the LTM DU configuration 1.
[0087] The events 308 (optional) and 310 are collectively referred to in Fig. 3 as a LTM preparation procedure 390. The events 316, 318, 320, 322 are collectively referred to in Fig. 3 as an LTM configuration delivery procedure 394.
[0088] In some implementations, the first CU-to-DU message is a UE Context Modification Request message, and the first DU-to-CU message is a UE Context Modification Response message or UE Context Modification Required message. In some implementations, the CU 172 transmits a UE Context Modification Confirm message to the DU 174 in response to UE Context Modification Required message. In some implementations, the second CU-to-DU message is a DE RRC Message Transfer message. In further implementations, the second CU-to-DU message is a UE Context Modification Request message and the DU 174 transmits a second DU-to-CU message (e.g., UE Context Modification Response message) to the CU 172 in response to the second CU-to-DU message. [0089] In some implementations, the CU 172 includes 316 a reference LTM CU configuration in the RRC reconfiguration message or the first container. In some implementations, the CU 172 generates the LTM CU configuration 1 (i.e., non-reference LTM CU configuration) as a delta configuration to augment the reference LTM CU configuration. In some implementations, the CU 172 generates some or all of the LTM CU configuration(s) 2, ..., N as delta configuration(s) to augment the reference LTM CU configuration. In some implementations, the CU 172 transmits 316 the reference LTM CU configuration excluding the non-reference LTM CU configuration in the RRC reconfiguration message or the first container . In further implementations, the CU 172 transmits 316 with the reference LTM CU configuration and/or with the reference LTM DU configuration in an additional container (e.g., the reference LTM configuration) in the RRC configuration message.
[0090] In some implementations, the reference LTM CU configuration is different from the serving CU configuration. In some implementations, a portion of the reference LTM CU configuration is the same as a portion of the serving CU configuration and the rest of the reference LTM CU configuration is different from the rest of the serving CU configuration. In further implementations, the reference LTM CU configuration is the same as the serving LTM CU configuration.
[0091] In some implementations, the CU 172 includes, in the RRC reconfiguration message, a first LTM ID (referred to herein after as ID 1) for identifying the LTM DU configuration 1 or the element 1. In some implementations, the CU 172 includes the ID 1 in the first container or element 1. In some implementations, the CU 172 assigns the ID 1.
[0092] In some implementations, the CU 172 transmits the ID 1 to the DU 174, and the DU 174 associates the ID 1 with the LTM DU configuration 1 and/or the cell ID 1. In some implementations, the CU 172 includes the ID 1 in the first CU-to-DU message. In some implementations, after receiving the first DU-to-CU message, the CU 172 transmits 312 a third CU-to-DU message including the ID 1 to the DU 174 instead of including the ID 1 in the first CU-to-DU message. In some implementations, in the third CU-to-DU message, the CU 172 includes the LTM DU configuration 1 and the ID 1 and indicate the association between the ID 1 and LTM DU configuration 1. Thus, the DU 174 directly associates the ID 1 with the LTM DU configuration 1. In further implementations, in the third CU-to-DU message, the CU 172 includes the cell ID 1 and the ID 1 (i.e., the first LTM ID) and indicates the association between the cell ID 1 and the ID 1. Thus, the DU 174 associates the ID 1 with the LTM DU configuration 1, based on the association between the cell ID 1 and the ID 1 and the association between the cell ID 1 and the LTM DU configuration 1. In yet further implementations, in the third CU-to-DU message, the CU 172 includes the LTM DU configuration 1, the cell ID 1 and/or the ID 1 and indicates the association between the ID 1, LTM DU configuration 1 and/or the cell ID 1. In some implementations, the DU 174 transmits 314 a third DU-to-CU message to the CU 172 in response to the third CU-to-DU message. In some implementations, the third CU-to-DU message and third DU-to-CU message are UE Context Modification Request messages and UE Context Modification Response messages. The events 312 (optional) and 314 (optional) are collectively referred to in Fig. 3 as a LTM ID assignment procedure 392. In some implementations, the CU 172 includes the ID 1, the cell ID 1 and/or the LTM DU configuration 1 in the second CU-to-DU message as described above. Thus, the third CU-to-DU message is omitted.
[0093] In some implementations, the CU 172 includes the ID 1 in the first CU-to-DU message and the DU 174 includes the ID 1 in the LTM DU configuration 1, the first container or the element 1. Alternatively, the DU 174 does not include the ID 1 in the LTM DU configuration 1, the first container and/or the element 1.
[0094] In some implementations, the CU 172 includes the reference LTM DU configuration in the first container. For example, the CU 172 includes the reference LTM DU configuration in a field of the first container, different from a field of the first container including the LTM DU configuration 1. In some implementations, the CU 172 includes 316 the reference LTM DU configuration in the RRC reconfiguration message outside the first container. For example, the CU 172 generates a third container (e.g., a field/IE) to include the first container and the reference LTM DU configuration and includes 316 the third container in the RRC reconfiguration message. In further implementations, the DU 174 includes the reference LTM DU configuration in the first container. For example, the DU 174 includes the reference LTM DU configuration in a field of the first container, different from a field of the first container including the LTM DU configuration 1. In yet further implementations, the DU 174 generates a fourth container (e.g., a field/IE) to include the first container and the reference LTM DU configuration and includes 310 the fourth container in the first DU-to-CU message. In such cases, the CU 172 includes 316 the fourth container in the RRC reconfiguration message. Alternatively, the CU 172 retrieves the reference LTM DU configuration and the LTM DU configuration 1 from the fourth container and includes the reference LTM DU configuration and the LTM DU configuration 1 as described above.
[0095] In some implementations, neither the CU 172 nor the DU 174 assign an ID to identify the reference LTM DU configuration. In some implementations, neither the CU 172 nor the DU 174 assign an ID to identify the reference LTM CU configuration.
[0096] In some implementations, the LTM DU configuration 1 includes a plurality of configuration parameters for the UE 102 to communicate with the DU 174 on the first cell. In some implementations, the plurality of configuration parameters includes 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(s)). In further implementations, the plurality of configuration parameters include a special cell configuration (e.g., SpCellConfig IE) and/or one or more SCell configurations (e.g., SCellConfig IE(s)). In some implementations, the LTM DU configuration 1 is CellGroupConfig IE (e.g., as defined in the 3GPP TS 38.331). In other implementations, the LTM DU configuration 1 includes configuration parameters in the CellGroupConfig IE.
[0097] In some implementations, the LTM CU configuration 1 includes PDCP configuration parameters, measurement configuration parameters, and/or radio bearer configuration parameters. In some implementations, the LTM CU configuration 1 includes a MeasConfig IE and/or a RadioBearerConfig IE (e.g., as defined in the 3GPP TS 38.331) or includes configuration parameters in the MeasConfig IE and/or RadioBearerConfig IE. In some implementations, the LTM DU configuration 1 includes an LI measurement configuration 1 (e.g., a CSl-MeasConfig IE) and/or at least one configuration indicator (TCI) state configuration. In further implementations, the LTM CU configuration 1 includes the LI measurement configuration and/or the TCI state configuration(s) 1. In some implementations, the LI measurement configuration includes at least one reference signal (RS) resource configuration 1 and/or at least one report configuration 1. In some implementations, the RS resource configuration(s) 1 configures one or more RSs or one or more RS resources associated with the cell 1. The RS(s) includes SSB(s) and/or CSLRS(s). The RS resource(s) includes SSB resource(s) and/or CSLRS resource(s). In some implementations, each of the RS resource configuration(s) 1 includes a RS resource configuration ID. In some implementations, the RS resource configuration(s) 1 is/are (similar to) CSl-ResourceConfig IE(s). In some implementations, the report configuration(s) 1 configures one or more UL resources (e.g., PUCCH resources or PUSCH resources) on the cell 1 for the UE 102 to transmit measurement results. In some implementations, each of the report configuration(s) 1 includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the RS resource configuration(s) 1. In some implementations, each of the TCI state configuration(s) 1 configures a TCI state that associates one or two DL RSs with a corresponding quasi-colocation (QCL) type. The DL RS(s) are associated with the cell 1.
[0098] In some implementations, the DU 174 includes the LI measurement configuration 1 and/or the TCI state configuration(s) 1 in a serving DU configuration 1 (e.g., non-LTM DU configuration). In some implementations, the DU 174 includes the serving DU configuration in the first DU-to-CU message. In other implementations, the DU 174 transmits an additional DU-to-CU message including the serving DU configuration to the CU 172. In some implementations, the additional DU-to-CU message is a UE Context Modification Required message. In some implementations, the CU 172 transmits 316 and 318 the serving DU configuration 1 in the RRC reconfiguration messages. In other implementations, the CU 172 transmits another RRC reconfiguration message including the serving DU configuration to the UE 102 via the DU 174.
[0099] In some implementations, the DU 174 includes a random access configuration in the LTM DU configuration 1. In other implementations, the DU 174 does not include a random access configuration in the LTM DU configuration 1. In some implementations, if the cell 124A and a first cell are not synchronized, the DU 174 determines to include the random access configuration in the LTM DU configuration 1. Otherwise, if the cell 124A and the first cell are synchronized, the DU 174 determines to not include the random access configuration in the LTM DU configuration 1. In some implementations, if the DU 174 determines that the UE 102 has not synchronized in the UL with the first cell, the DU 174 determines to include the random access configuration in the LTM DU configuration 1. Otherwise, if the DU 174 determines that the UE 102 has synchronized in the UL with the first cell, the DU 174 determines to not include the random access configuration in the LTM DU configuration 1. If the LTM DU configuration 1 includes the random access configuration, the UE 102 performs 332 the random access procedure in accordance with the random access configuration, as described below. Otherwise, if the LTM DU configuration 1 does not include the random access configuration or indicates the UE 102 to skip a random access procedure in LTM, the UE 102 skips or refrains 332 from performing the random access procedure in response to the LTM DU configuration 1 excluding the random access configuration.
[0100] In some implementations, the DU 174 includes random access configuration parameters in the LTM DU configuration 1 and/or the reference LTM DU configuration regardless of whether the cell 124A and first cell are synchronized or not. The UE 102 performs 332 the random access procedure in accordance with the random access configuration parameters, as described below. In some implementations, the random access configuration parameters configure physical random access channel (PRACH) resources, an association between SSB and PRACH resources, and/or one or more PRACH occasions.
[0101] In some implementations, if the cell 124A and first cell are synchronized, the DU 174 determines to include, in the LTM DU configuration 1, a first indication configuring the UE 102 not to perform a random access procedure on the first cell. Otherwise, if the cell 124A and the first cell are not synchronized, the DU 174 determines to not include the first indication in the LTM DU configuration 1. In further implementations, if the DU 174 determines that the UE 102 has synchronized in the UL with the first cell, the DU 174 determines to include the first indication in the LTM DU configuration 1. Otherwise, if the DU 174 determines that the UE 102 has not synchronized in UL with the first cell, the DU 174 determines to not include the first indication in the LTM DU configuration 1. If the LTM DU configuration 1 includes the first indication, the UE 102 skips or refrains 332 from performing the random access procedure in accordance with or in response to the first indication. Otherwise, if the LTM DU configuration 1 does not include the first indication, the UE 102 performs 332 the random access procedure in accordance with the random access configuration, in response to the LTM DU configuration 1 excluding the first indication, as described below.
[0102] In some implementations, the DU 174 includes a reconfiguration with sync configuration (e.g., ReconfigurationWithSync IE) in the LTM DU configuration 1 or special cell configuration. In further implementations, the DU 174 does not include a reconfiguration with sync configuration (e.g., ReconfigurationWithSync IE) in the LTM DU configuration 1 or special cell configuration. In some implementations, if the cell 124A and the first cell are not synchronized, the DU 174 determines to include the reconfiguration with sync configuration in the LTM DU configuration 1. Otherwise, if the cell 124A and the first cell 1 are synchronized, the DU 174 determines to not include the reconfiguration with sync configuration in the LTM DU configuration 1. In yet further implementations, if the DU 174 determines that the UE 102 has not synchronized in the UL with the first cell, the DU 174 determines to include the reconfiguration with sync configuration in the LTM DU configuration 1. Otherwise, if the DU 174 determines that the UE 102 has synchronized in the UL with the first cell, the DU 174 determines to not include the reconfiguration with sync configuration in the LTM DU configuration 1. In some implementations, if the LTM DU configuration 1 includes the reconfiguration with sync configuration, the UE 102 performs 332 the random access procedure as described below, in response to or in accordance with the reconfiguration with sync configuration. Otherwise, if the LTM DU configuration 1 does not include the reconfiguration with sync configuration, the UE 102 skips or refrains from performing 332 the random access procedure. In some implementations, the DU 174 includes a cell ID (i.e., cell ID 1) of cell 1 (i.e., the first cell) in the LTM DU configuration 1. In some implementation, the cell ID 1 is a PCI. In further implementations, the cell ID 1 is a CGI. In some implementations, the cell ID 1 included in the LTM DU configuration 1 is a PCI, while the cell ID 1 included in the first CU-to-DU message is a CGI. In yet further implementations, the LTM DU configuration 1 includes a cell index 1 indexing the cell ID 1 or the first cell. The cell index 1 is not a cell ID. The cell index takes fewer bits than the cell ID. In some implementations, the CU 172 sets the cell index 1 to a value and includes 308 the cell index 1 in the first CU-to-DU message.
[0103] In some implementations, after (e.g., in response to) receiving 304 one or some of the at least one measurement report, the base station 104 (i.e., the CU 172 or DU 174) determines to prepare additional cell(s) (i.e., cell(s) 2, ..., N) of the base station 104 for LTM for the UE 102. In some implementation, the base station 104 determines to prepare the additional cell(s) for LTM for the UE 102 because the at least one measurement report indicates that the additional cell(s) could be used by the base station 104 to communicate with the UE 102. In some implementations, the additional cell(s) includes the cell 124C and/or cell(s) other than the cells 124A, 124B and 124C. In some implementations, if the L3 measurement report(s) indicates that the signal strength and/or quality of a particular cell of the additional cell(s) is above a respective predetermined threshold and/or is better than the cell 124A, the CU 172 determines to prepare the particular cell for LTM for the UE 102. In some implementations, if the LI measurement report(s) indicates that the signal strength and/or quality of a particular cell of the additional cell(s) is above a first predetermined threshold and/or is better than the cell 124A, the DU 174 determines to prepare the particular cell for LTM for the UE 102. In some implementation, the respective predetermined threshold(s) for the additional cells is different from the first predetermined threshold. In some implementations, the respective predetermined threshold(s) for the additional cell(s) is the same as the first predetermined threshold. In further implementations, the respective predetermined thresholds for the additional cells is the same or different. Alternatively, the base station 104 determines to prepare the additional cell(s) for the UE 102 regardless of whether a measurement report is received from the UE 102 or not.
[0104] In some implementations, the CU 172 determines to prepare the additional cell(s), the CU 172 initiates and performs at least one additional LTM preparation procedure with the DU 174 to prepare the additional cell(s) for LTM, where each of the LTM preparation procedures are similar to the procedure 390. In some implementations, the DU 174 determines to prepare the additional cell(s), the DU 174 initiates and performs at least one additional LTM preparation procedure with the CU 172 to prepare the additional cell(s) for LTM, where each of the LTM preparation procedures are similar to the procedure 390.
[0105] In some implementations, the CU 172 and DU 174 perform LTM preparation procedure(s) 2, ..., N to prepare the cell(s) 2, ..., N, respectively, similar to the procedure 390. In some implementations, CU 172 includes the cell ID(s) 2, ..., N in CU-to-DU message(s) 2, ..., N in the LTM preparation procedure(s) 2, ..., N, respectively, similar to the first CU-to-DU message. In the LTM preparation procedure(s) 2, ..., N, the DU 174 generates LTM DU configuration(s) 2, ..., N configuring the cell(s) 2, ..., N and includes the LTM DU configuration(s) 2, ..., N in DU-to-CU message(s) 2, .., N, respectively, as described for the LTM DU configuration 1. In the case that the DU 174 receives the CU-to- DU message(s) 2, ..., N, the DU-to-CU message(s) 2, ..., N responds to the CU-to-DU message(s) 2, ..., N, respectively . “N” is an integer and larger than one. Lor example, “N” is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 14, 15 or 16. In another example, the maximum number of “N” is 4, 8, 16 or 32. In some implementations, the LTM DU configuration 1 applies to the LTM DU configuration(s) 2, ..., N.
[0106] In further implementations, the CU 172 and DU 174 performs a single LTM preparation procedure (i.e., the LTM preparation procedure 390) to prepare the cell(s) 1, 2, ..., N. In some implementations, in the first DU-to-CU message the DU 174 includes the LTM DU configuration(s) 1, 2, ..., N for the cell(s) 1, 2, ..., N, respectively. In some implementations, in the first DU-to-CU message, the DU 174 includes the cell ID(s) 1, 2, ..., N with the LTM DU configuration(s) 1, 2, ..., N, respectively. In some implementations, the CU 172 determines to perform 390 the LTM preparation procedure, the CU 172 includes the cell ID(s) 1, 2, ..., N in the first CU-to-DU message to request the DU 174 to prepare the cell(s) 1, 2, ..., N, respectively, for LTM.
[0107] In some implementations, after receiving the LTM DU configuration(s) 2, ..., N from the DU 174, the CU 172 includes the LTM DU configuration(s) 2, ..., N in the first container. In some implementations, the CU 172 includes the LTM DU configuration(s) 2, ... , N in element(s) 2, ... , N, and includes the element(s) 2, ... , N in the first container. In some implementations, the CU 172 includes, in the RRC reconfiguration message, LTM ID(s) (i.e., ID(s) 2, ..., N) for identifying the LTM DU configuration(s) 2, ..., N, respectively. In some implementations, the CU 172 includes the ID(s) 2, ..., N in the first container. In some implementations, the CU 172 includes the ID(s) 2, ..., N and LTM DU configuration(s) 2, ..., N in the element(s) 2, ..., N in the first addition or modification list.
[0108] In some implementations, the CU 172 assigns the ID(s) 2, ..., N for the LTM DU configuration(s) 2, ..., N, respectively. In further implementations, the CU 172 receives the ID(s) 2, ..., N from the DU 174 in the first DU-to-CU message of the procedure 390. In yet further implementations, the CU 172 receives from the DU 174 the ID(s) 2, ..., N in the DU- to-CU message(s) 2, ..., N of the LTM preparation procedure(s) 2, ..., N, respectively.
[0109] In some implementations, the CU 172 performs a LTM ID assignment procedure with the DU 174 for each of the LTM DU configuration(s) 2, ..., N, similar to the procedure 392. In further implementations, the CU 172 includes and indicates the association of the ID(s) 2, ..., N and the LTM DU configuration(s) 2, ..., N in the third CU-to-DU message. In some implementations, the DU 174 associates the LTM DU configuration(s) 2, ..., N with the ID(s) 2, ..., N, respectively. In yet further implementations, the CU 172 includes and indicates the association of the cell ID(s) 2, ..., N and the ID(s) 2, ..., N in the third CU-to- DU message, respectively. In some implementations, the DU 174 associates the LTM DU configuration(s) 2, ..., N with the ID(s) 2, ..., N, respectively, based on the association between the cell ID(s) 2, ..., N and the ID(s) 2, ..., N and the association between the cell ID(s) 2, ..., N and the LTM DU configuration(s) 2, ..., N, respectively. In other implementations, the CU 172 includes the ID(s) 2, ..., N, the cell ID(s) 2, ..., N and/or the LTM DU configuration(s) 2, ..., N in the second CU-to-DU message as described above. Thus, the third CU-to-DU message is omitted. In yet further implementations, the CU 172 includes the ID(s) 2, ..., N in the first CU-to-DU message and indicate the ID(s) 2, ..., N is/are respectively associated with the cell ID(s) 2, ..., N. In some implementations, the DU 174 includes the ID(s) 2, ..., N in the LTM DU configuration(s) 2, ..., N. Thus, the CU 172 does not include the ID(s) 2, ..., N in the RRC reconfiguration message, first container and/or element(s) 2, ..., N.
[0110] In further implementations, the DU 174 assigns the ID(s) 2, ..., N. In some implementations, the DU 174 includes the ID(s) 2, ..., N in the first DU-to-CU message of the procedure 390. In yet further implementations, the DU 174 includes the ID(s) 2, ..., N in the DU-to-CU message(s) 2, ..., N of the LTM preparation procedure(s) 2, .. ,,N. In some implementations, the CU 172 includes the ID(s) 2, ..., N in the RRC reconfiguration message. In other implementations, the DU 174 includes the ID(s) 2, ..., N in the LTM DU configuration(s) 2, ..., N. Thus, the CU 172 does not include an ID (e.g., LTM ID) identifying each of the LTM DU configuration(s) 2, ..., N in the RRC reconfiguration message, first container and/or element 1.
[0111] In some implementations, the CU 172 generates a second container including the LTM DU configuration(s) 2, ..., N or element(s) 2, ..., N instead of using the first container. In some implementations, CU 172 transmits an additional RRC reconfiguration message including the second container to the UE 102 via the DU 174, similar to the events 316 and 318. In response, the UE 102 transmits an additional RRC reconfiguration complete message to the CU 172 via the DU 174, similar to the events 320 and 322. In some implementations, the second container is a second addition or modification list (e.g., Itm-ConfigToAddModList field, LTM-ConfigToAddModList IE, Itm-CandidateConfigToAddModList field, or LTM- CandidateConfigToAddModList IE), and each of the element 2, ..., N are an addition or modification IE (e.g., Itm-ConfigToAddMod field, LTM-ConfigToAddMod l , Itm- CandidateConfigToAddMod field, or LTM-CandidateConfigToAddMod IE). In some implementations, the UE 102 receives the second addition or modification list and stores the second addition or modification list together with the first addition or modification list (e.g., in a variable in its random access memory (RAM)).
[0112] In some implementations, the DU 174 includes cell ID(s) 2, ..., N in the LTM DU configuration(s) 2, ..., N to identify the cell(s) 2, ..., N, respectively. In some implementations, each of the cell ID(s) 2, ..., N is a PCI. In further implementations, the LTM DU configuration(s) 2, .. N includes cell index(es) 2 , .. N indexing the cell ID(s) 2, .. N or the cell(s) 2, .. N, respectively. In some implementations, the CU 172 prepares the cell(s) 2, .. N for LTM in the procedure 390, the CU 172 sets the cell index(es) 2, ..., N to different value(s) and includes 308 the cell index(es) 2, ..., N in the first CU-to CU-to-DU message. In some implementations, the CU 172 prepares the cell(s) 2, ..., N in the additional LTM preparation procedure(s), the CU 172 sets the cell index(es) 2, ..., N to different values and includes the cell index(es) 2, ..., N in CU-to-DU message(s) of the additional LTM preparation procedure(s). The CU 172 sets the cell index(es) 1, ..., N to different values. In some implementations, the cell ID(s) 1, ..., N in the LTM DU configuration(s) 1, ..., N are different from the cell ID(s) 1, ..., N in the CU-to-DU message(s) described above.
[0113] In some implementations, each of the LTM DU configuration(s) 1, ..., N includes physical configuration parameters, MAC configuration parameters, RLC configuration parameters and/or LI measurement configuration(s). In some implementations, each of the LTM DU configuration(s) 1, ..., N is a CellGroupConfig IE (e.g., as defined in the 3GPP TS 38.331). In further implementations, each of the LTM DU configuration(s) 1, ..., N include configuration parameters included in a CellGroupConfig IE (e.g., as defined in the 3GPP TS 38.331). In yet further implementations, the plurality of configuration parameters in each of the LTM DU configuration(s) include a particular special cell configuration (e.g., SpCellConfig IE) and/or one or more SCell configurations (e.g., SCellConfig IE(s)). In some implementations, the LTM DU configuration(s) 1, ..., N are CellGroupConfig IE(s) (e.g., as defined in the 3GPP TS 38.331). In further implementations, the LTM DU configuration(s) 1, ..., N include configuration parameters in the CellGroupConfig IE.
[0114] In some implementations, the CU 172 includes one or more additional LTM CU configurations in at least one of the element(s) 2, ..., N, the first container or the second container. Each of the additional LTM CU configurations are associated with a particular LTM DU configuration of the LTM DU configuration(s) 2, ..., N. In some implementations, the additional LTM CU configurations are similar to the LTM CU configuration 1.
[0115] In some implementations, the CU 172 determines to release the LTM DU configuration M of the LTM DU configuration(s) 1, ..., N (or the element M of the element(s) 1, ..., M). 1 < M < N. In response to the determination, the CU 172 transmits a RRC reconfiguration message to the UE 102 via the DU 174 to indicate the UE 102 to release the LTM DU configuration M or element M. In some implementations, the CU 172 generates a release list including the ID (i.e., LTM ID) M for releasing the LTM DU configuration M or element M and includes the release list in the RRC reconfiguration message. In response to the RRC reconfiguration message, the UE 102 releases the LTM DU configuration M or element M and transmits a RRC reconfiguration complete message to the CU 172 via the DU 174. In response to the determination, the CU 172 transmits a CU-to-DU message to the DU 174 to indicate the DU 174 to release the LTM DU configuration M. In some implementations, to indicate the DU 174 to release the LTM DU configuration M, the CU 172 includes the cell ID M or the ID (i.e., LTM ID) M in a release indication (e.g., a field or IE) in the CU-to-DU message. In response, the DU 174 releases the LTM DU configuration M and transmits a DU-to-CU message to the CU 172. In some implementations, the CU-to-DU message and DU-to-CU message are a UE Context Modification Request message and a UE Context Modification Response message, respectively.
[0116] In other implementations, the DU 174 determines to release the LTM DU configuration K. In response to the determination, the DU 174 transmits a DU-to-CU message to the CU 172 to release the LTM DU configuration K. In some implementations, to indicate the LTM DU configuration K is released, the DU 174 includes the cell ID K or the ID (i.e., LTM ID) K in a release indication (e.g., a field or IE) in the DU-to-CU message (e.g., 1 < K < N). After (e.g., in response to) receiving the DU-to-CU message, the CU 172 generates a release list including the ID (i.e., LTM ID) K to release the LTM DU configuration K or element K and transmits a RRC reconfiguration message including the release list to the UE 102 via the DU 174. In response, the UE 102 releases the LTM DU configuration K or element K and transmits a RRC reconfiguration complete message to the UE 102 via the DU 174. In some implementations, the CU 172 transmits a CU-to-DU message to the DU 174 in response to the DU-to-CU message. In some implementations, the DU-to-CU message and CU-to-DU message are a UE Context Modification Required message and a UE Context Modification Confirm message, respectively.
[0117] In some implementations, after the UE 102 receives 318 the RRC reconfiguration or transmits 320 the RRC reconfiguration complete message, the UE 102 transmits 324 at least one measurement report to the DU 174, similar to the event 304. In some implementations, the DU 174 transmits 326 a DU-to-CU message including the at least one measurement report to the CU 172, similar to the event 306. In other implementations, the DU 174 does not transmit the at least one measurement report to the CU 172. In some implementations, the at least one measurement report includes 324 LI measurement report(s) or L3 measurement repot(s), as described for the event 304. In some implementations, the UE 102 transmits 324 the at least one measurement report on PUCCH(s) and/or PUSCH(s) to the DU 174, similar to the event 304. In further implementations, the UE 102 transmits 324 at least one MAC CE including the at least one measurement report to the DU 174, similar to the event 304. In some implementations, the UE 102 does not transmit the LI measurement report(s) in the format of an RRC message(s) to the DU 174.
[0118] In some implementations, the UE 102 transmits 324 the at least one measurement report to the DU 174 in accordance with at least one measurement configuration. The at least one measurement configuration configures the UE 102 to perform measurements and report measurement results. The CU 172 transmits the at least one measurement configuration to the UE 102 via the DU 174. In some implementations, the CU 172 transmits 302 and/or 316 and/or 306 or 316 one or more RRC messages (e.g., RRCReconfiguration message(s)) including the at least one measurement configuration to the UE 102 via the DU 174. In some implementations, the one or more RRC messages includes 316 the RRC reconfiguration message. In accordance with the at least one measurement configuration, the UE 102 performs measurements on one or more reference signals. In some implementations, the one or more reference signals includes one or more SSBs and/or one or more CSLRSs. In some implementations, the UE 102 obtains 324 the at least one LI measurement result and/or at least one L3 measurement result from the measurements and includes the at least one LI measurement result and/or at least one L3 measurement result in the at least one measurement report. The DU 174 transmits the one or more reference signals on the cell 124A, the cell 1 and/or the cell(s) 2, ..., N. In some implementations, the one or more reference signals are a CSLRS(s) or SSB(s).
[0119] In some implementations, the at least one measurement configuration includes 304 L3 measurement configuration(s) (e.g., MeasConfig IE(s)). In further implementations, the at least one measurement configuration includes or is LI measurement configuration(s), as described above. In yet further implementations, the LI measurement configuration(s) is a CSI-MeasConfig IE(s) (e.g., as defined in 3GPP TS 38.331). In yet further implementations, the LI measurement configuration(s) includes RS resource configuration(s) and/or report configuration(s). The UE 102 transmits 324 the LI measurement report(s) on UL resources (e.g., the physical uplink control channel (PUCCH) resources or the physical unlink shared channel (PUSCH) resources) to the DU 174 in accordance with the report configuration(s). The DU 174 receives the LI measurement report(s) on the UL resources in accordance with the report configuration(s). In some implementations, the report configuration(s) are similar to the CSl-ReportConfig IE(s). In other implementations, each report configuration is a specifically defined RRC IE. In some implementations, each report configuration configures periodically reporting and/or event-triggered reporting of the LI measurement result(s).
[0120] In some implementations, the LI measurement report is a CSI report. In other implementations, the LI measurement report is a MAC CE. In some implementations, each of the measurement reports includes one or more RS resource indicators and/or one or more quantized measurement values. The UE 102 performs measurements on the RS(s) or the RS resource(s) in accordance with the RS resource configuration(s) and/or the report configuration(s) and obtains the quantized measurement values from the measurements. In some implementations, the RS resource indicator(s) indicates the RS(s) or a RS resource(s) where the UE 102 performs measurements or obtains the quantized measurement values. In some implementations, the RS resource indicator(s) includes one or more SSB resource indicators (SSBRI(s)) and/or one or more CSI- RS resource indicators (CRI(s)). In some implementations, the quantized measurement values includes one or more Ll-RSRP values and/or one or more Ll-SINR values.
[0121] In further implementations, the at least one measurement configuration includes a specifically defined type of measurement configuration (e.g., an LTM measurement configuration as defined in the 3GPP TS). In some implementations, the specifically defined measurement configuration includes reference signal resource configuration(s) configuring resources where the DU 174 transmits reference signals. For example, the reference signal resource configuration(s) include CSLRS(s) and/or SSB(s). In one implementation, the reference signal resource configuration(s) is/are CSl-ResourceConfig IE(s). In some implementations, the specifically defined measurement configuration includes measurement report configurations, as described above. The UE 102 transmits the measurement report(s) on PUCCH(s) or MAC CE(s) to the DU 174 in accordance with the measurement report configuration(s). The DU 174 receives the measurement report(s) on PUCCH(s) or MAC CE(s) in accordance with the measurement report configuration(s). In some implementations, the measurement report(s) is a LI measurement report(s) or a specifically defined measurement report(s) (e.g., LTM measurement report(s)). In some implementations, the specifically defined measurement configuration includes a specifically defined configuration parameters (e.g., as defined in the 3GPP TS ). [0122] In response to receiving 324 the at least one measurement report, the DU 174 generates a first LTM command to activate the LTM DU configuration 1 (i.e., the first LTM command commands the UE 102 to apply the LTM DU configuration 1 or to perform a serving cell change to the cell 1). The DU 174 then transmits 330, the first LTM command to the UE 102. In some implementations, the DU 174 transmits the first LTM command on the cell 124A to the UE 102. In further implementations, the DU 174 transmits the first LTM command on the cell 124D to the UE 102. In some implementations, the DU 174 includes the ID 1 in the first LTM command to indicate the LTM DU configuration 1 or element 1, and the UE 102 determines the LTM DU configuration 1 or element 1 in accordance with the ID 1.
[0123] In some implementations, the DU 174 includes the cell index 1 indexing the cell ID 1 in the first LTM command. The UE 102 determines the LTM DU configuration 1 or element 1, based on the cell index 1. Before receiving the first LTM command, the UE 102 retrieves the cell index 1 from the LTM DU configuration 1 or element 1, and establishes an association 1 between the cell index 1 and the LTM DU configuration 1 or element 1. In other words, the UE 102 decodes the LTM DU configuration 1 or element 1 to obtain the cell index 1, before receiving the first LTM command. Thus, the UE 102 determines the LTM DU configuration 1 or element 1 in accordance with the cell index 1 and the association 1. Before receiving the first LTM command, the UE 102 retrieves the cell index(es) 2, ..., N from the LTM DU configuration(s) or element(s) 2, ..., N and establishes association(s) 2, ..., N between the cell index(es) 2, ..., N and the LTM DU configuration(s) or element(s) 2, ..., N, respectively. In other words, the UE 102 decodes the LTM DU configuration(s) or element(s) 2, ..., N to obtain the cell index(es) 2, ..., N, before receiving the first LTM command.
[0124] In further implementations, the DU 174 includes cell ID 1 in the first LTM command, where the cell ID 1 identifies the cell 1. In some implementations, the cell ID 1 within the first LTM command is the same as the cell ID 1 within the first CU-to-DU message. In some implementations, the DU 174 determines the cell ID 1 (e.g., PCI) within the first LTM command from the cell ID 1 (e.g., CGI) received in the first CU-to-DU message. The UE 102 determines (e.g., identifies) the LTM DU configuration 1 or element 1, based on the cell ID 1. Before receiving the first LTM command, the UE 102 retrieves the cell ID 1 from the LTM DU configuration 1 or element 1 and establishes an association 1 between the cell ID 1 and the LTM DU configuration 1 or element 1. In other words, the UE 102 decodes the LTM DU configuration 1 or element 1 to obtain the cell ID 1, before receiving the first LTM command. Thus, the UE 102 identifies the LTM DU configuration 1 or element 1 in accordance with the cell ID 1 (e.g., from the first LTM command) and the association 1. Before receiving the first LTM command, the UE 102 retrieves the cell ID(s) 2, ..., N from the LTM DU configuration(s) or element(s) 2, ..., N and establishes association(s) 2, ... , N between the cell ID(s) 2, ... , N and the LTM DU configuration(s) or element(s) 2, ..., N, respectively. In other words, the UE 102 decodes the LTM DU configuration(s) or element(s) 2, ..., N to obtain the cell ID(s) 2, ..., N, before receiving the first LTM command. In some implementations, the DU 174 has a mapping table to store mappings between the PCI(s) 1, ..., N and the CGI(s) 1, ..., N for the cell(s) 1, ..., N, respectively.
[0125] In further implementations, the DU 174 includes a bit map in the first LTM command to activate the LTM DU configuration 1, instead of the ID 1 or cell index 1. The number of bits in the bit map is larger than or equal to “N”. In some implementations, bit 1, ..., N corresponds to the cell index(es) 1, ..., N, the ID(s) 1, ..., N, the LTM DU configuration(s) 1, ..., N or the element(s) 1, ..., N, respectively, and the DU 174 sets a corresponding bit (e.g., bit 1) in the bit map to a first value to indicate the cell index 1, the ID 1, the LTM DU configuration 1 or the element 1. In some implementations, the UE 102 determines the cell index 1, the ID 1, LTM DU configuration 1, or element 1 in accordance with the bit 1 set to the first value in the bit map. In some implementations, bit 0, ..., N-l corresponds to the cell index(es) 1, ..., N, the ID(s) 1, ..., N, the LTM DU configuration(s) 1, ..., N or the element (s) 1, ..., N, respectively, and the DU 174 sets a corresponding bit (e.g., bit 0) in the bit map to a first value to indicate the cell index 1, the ID 1, the LTM DU configuration 1, or the element 1. In some implementations, the UE 102 determines the cell index 1, the ID 1, LTM DU configuration 1, or element 1 in accordance with the bit 0 set to the first value in the bit map. In some implementations, the DU 174 sets the remaining bits in the bit map to a second value to indicate that the rest of the LTM DU configuration(s) 1, ..., N is/are not activated. In some implementations, the first value is one and the second value is zero. In further implementations, the first value is zero and the second value is one. In some implementations, if the DU 174 determines to activate the LTM DU configuration L or change a serving cell to the cell L for the UE 102, the DU 174 sets the corresponding bit (e.g., bit L or bit L-7) in the bit map to the first value and sets the remaining bits to the second value, where 1 < L < N. In some implementations, the DU 174 sets at most one bit in the bit map to the first value.
[0126] After determining or identifying the LTM DU configuration 1 or element 1, the UE 102 applies the LTM DU configuration 1 and/or LTM CU configuration after (e.g., in response to) receiving the first LTM command.
[0127] In some implementations, the at least one measurement report 324 (e.g., LI measurement report or a specifically defined measurement report) includes at least one measurement result for the first cell, TRP(s) of the first cell or reference signal(s) transmitted on the first cell. In some implementations, the reference signal(s) is CSLRS(s) or SSB(s). The DU 174 determines to activate the LTM DU configuration 1 or transmit the first LTM command, based on the at least one measurement result. In some implementations, the DU 174 determines to activate the LTM DU configuration 1 when the at least one measurement result is above a second predetermined threshold. In some implementations, the at least one measurement result includes Ll-RSRP value(s), Ll-RSRQ value(s) and/or Ll-SINR value(s). In other implementations, the at least one measurement result includes RSRP value(s), RSRQ value(s) and/or SINR value(s) for the specifically defined measurement report(s). In some implementations, the second predetermined threshold is different from the first predetermined threshold. In some implementations, the second predetermined threshold is larger than the first predetermined threshold. In this case, the at least one measurement result indicates that the first cell is suitable for communication with the UE 102. In some implementations, the second predetermined threshold is equal to the first predetermined threshold. In this case, the at least one measurement result indicates that the first cell has been continuously above the second predetermined threshold or the first predetermined threshold. This indicates that the first cell is suitable for communication with the UE 102. Thus, the DU 174 determines to activate the LTM DU configuration 1 when the signal strength or quality of the first cell is above the second predetermined threshold for the UE 102.
[0128] In some implementations, the at least one measurement report (e.g., L3 measurement report(s)) includes 324 and 326 at least one measurement result for the first cell. The CU 172 determines to activate the LTM DU configuration 1 or transmit the first LTM command, because the at least one measurement result indicates that the signal strength or quality of the first cell is above a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In further implementations, the second predetermined threshold is larger than the first predetermined threshold. In such an implementation, the at least one measurement report indicates 326 that the signal strength or quality of the first cell is suitable for communication with the UE 102. In yet further implementations, the second predetermined threshold is equal to the first predetermined threshold. In such an implementation, the at least one measurement report indicates 326 that the signal strength or quality of the first cell has been continuously above the second predetermined threshold or the first predetermined threshold. This also indicates that the first cell is suitable for communication with the UE 102. Thus, the CU 172 determines to activate the LTM DU configuration 1 in response to the signal strength or quality of the first cell exceeding the second predetermined threshold. In response to the determination, the CU 172 transmits 328 a fourth CU-to-DU message to the DU 174 to activate the LTM DU configuration 1 or trigger a serving cell change to the cell 1 for the UE 102. In some implementations, the CU 172 includes the ID 1 in the fourth CU-to-DU message. In further implementations, the CU 172 includes the cell index 1 in the fourth CU- to-DU message. In response to the fourth CU-to-DU message, the DU 174 transmits 330 the first LTM command to the UE 102 and optionally transmits a fourth DU-to-CU message to the CU 172. In some implementations, the CU 172 includes the cell index 1 in the fourth CU-to-DU message. In some implementations, the DU 174 determines to activate the LTM DU configuration 1 in accordance with the cell index 1. In further implementations, the CU 172 includes the cell ID 1 in the fourth CU-to-DU message. Thus, the DU 174 determines to activate the LTM DU configuration 1 in accordance with the cell ID 1. In yet further implementations, the CU 172 includes the ID 1 in the fourth CU-to-DU message. In some implementations, the DU 174 determines to activate the LTM DU configuration 1 in accordance with the ID 1. In further implementations, the fourth CU-to-DU message and fourth DU-to-CU message are a UE Context Modification Request message and a UE Context Modification Response message, respectively. In yet further implementations, the fourth CU- to-DU message and/or fourth DU-to-CU message are specifically defined interface messages (e.g., E1AP messages as defined in 3GPP TS 38.473).
[0129] In some implementations, when determining to activate the LTM DU configuration 1 or transmit 330 the first LTM command, the DU 174 transmits 329 to the CU 172 a DU-to- CU message to execute LTM. In further implementations, the DU 174 includes 329 the cell ID 1 or the ID 1 (i.e., LTM ID) in the DU-to-CU message to indicate the DU 174 activate the LTM DU configuration 1 or trigger a fast-serving cell change (i.e., a LTM serving cell change). In yet further implementations, the DU transmits 329 the DU-to-CU message to the CU 172 before or after transmitting 330 the LTM command.
[0130] In some implementations, the UE 102 receives 330 from the DU 174 the first LTM command with a MAC CE included in a MAC PDU. In some implementations, the MAC CE is a specifically defined MAC CE (e.g., as defined in the 3GPP TS 38.321). In some implementations, the DU 174 includes a sub-header identifying the specifically defined MAC CE in the MAC PDU and the UE 102 identifies the specifically defined MAC CE in the MAC PDU in accordance with the sub-header. In some implementations, the sub-header 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 are specifically defined IDs (e.g., as defined in 3GPP TS 38.321). In further implementations, the first LTM command is a DCI that the UE 102 receives 330 on a PDCCH from the DU 174. The DU 174 generates a CRC for the DCI, scrambles the CRC with a first C-RNTI of the UE 102, and transmits 330 the DCI and scrambled CRC on the PDCCH. In some implementation, a format of the DCI exists (e.g., as defined in the 3GPP TS 38.212). In further implementations, the format of the DCI is a specifically defined DCI format (e.g., as defined in the 3GPP TS 38.212).
[0131] In some implementations, the DU 174 does not perform security protection (e.g., integrity protection and/or encryption) on the first LTM command. This speeds up processing the first LTM command in the UE 102 because the UE 102 does not perform a security check (e.g., decryption and/or integrity check) on the first LTM command.
[0132] In some implementations, after receiving the first LTM command, the UE 102 transmits 331 an acknowledgement to the DU 174 on the cell 124A or cell 124D to indicate that the UE 102 receives the first LTM command. In some implementations, the acknowledgement is a HARQ ACK. In some implementations, the acknowledgement is a MAC CE. For example, the MAC CE is an existing MAC CE (e.g., defined in the 3GPP specification 38.321). As a further example, the MAC CE is a specifically defined MAC CE (e.g., as defined in the 3GPP specification 38.321). In yet further implementations, the acknowledgement is a PUCCH transmission.
[0133] In some implementations, the CU 172 transmits 316 the RRC reconfiguration message in response to receiving 306 the L3 measurement report for the first cell. In further implementations, to configure the UE 102 to transmit 304 the L3 measurement report, the CU 172 transmits a first RRC reconfiguration message including the L3 measurement configuration (e.g., a MeasConfig IE) to the UE 102. In some implementations, the DU 174 transmits 330 the first LTM command when responding 324 to the LI measurement report for the first cell. In some implementations, to configure the UE 102 to transmit 324 the LI or specifically defined measurement report, the CU 172 transmits a second RRC reconfiguration message including the LI or a specifically defined measurement configuration to the UE 102. In some implementations, the first and second RRC reconfiguration messages are the same message (i.e., the same instance). In further implementations, the first and second RRC reconfiguration messages are different messages. In yet further implementations, the CU 172 transmits 316 the second RRC reconfiguration message. In further implementations, the second RRC reconfiguration message is a different message (i.e., not the same instance).
[0134] After (e.g., in response to) receiving the first LTM command, the UE 102 accesses 332 the first cell. The UE 102 identifies the LTM DU configuration 1 in accordance with the ID 1, the cell ID 1 or the cell index 1 received in the first LTM command and applies the LTM DU configuration 1 to communicate with the DU 174 on the first cell. In some implementations, the UE 102 disconnects from the cell 124A, after (e.g., in response to) receiving the first LTM command or after transmitting 331 the acknowledgement. In some implementations, the UE 102 stops communicating on the cell 124A after (e.g., in response to) receiving 330 the first LTM command or transmitting 331 the acknowledgement. In some implementations, the UE 102 accesses the first cell by performing a random access procedure on the first cell with the DU 174, in response to receiving the first LTM command. In other implementations, the UE 102 skips a random access procedure and transmits the first transmission (e.g., a PUSCH transmission or a PUCCH transmission) on the first cell to the DU 174, after (e.g., in response to) receiving the first LTM command.
[0135] In some implementations, the DU 174 configures the access of the UE 102 to the first cell, including whether or not the UE 102 performs a random access procedure, in the LTM DU configuration 1. When receiving the first LTM command (e.g., the first LTM command), the UE 102 determines whether to perform a random access procedure on the first cell in accordance with the LTM DU configuration 1. If the LTM DU configuration 1 configures the UE 102 to perform a random access procedure, the UE 102 performs 332 a random access procedure on the first cell in order to connect to the first cell. For example, the LTM DU configuration 1 includes a reconfiguration with sync configuration (e.g.,
ReconfigurationWithSync IE) to configure the UE 102 to perform a random access procedure when the UE 102 receives a LTM command for the first cell. In some implementations, in the LTM DU configuration 1, the DU 174 configures the UE 102 to skip the random access procedure for a LTM serving cell change to the first cell. In such cases, after receiving the first LTM command, the UE 102 skips the random access procedure and transmits 332 the first transmission (e.g., a PUSCH transmission or a PUCCH transmission) on the first cell to the DU 174. In some implementations, the DU 174 excludes a reconfiguration with sync configuration in the LTM DU configuration 1 to configure the UE 102 to skip a random access procedure for a LTM serving cell change to the first cell.
[0136] In further implementations, the LTM DU configuration 1 includes the reconfiguration with sync configuration or the random access configuration. In such cases, the DU 174 configures the UE 102 to perform a random access procedure on the first cell in a LTM command. In some implementations, the UE 102 performs 332 the random access procedure on the first cell in accordance with the first LTM command. In further implementations, the DU 174 includes in the first LTM command, an indication (e.g., a field) indicating skipping a random access procedure. In response to the indication or the first LTM command including the indication, the UE 102 skips a random access procedure and directly transmits the first transmission (e.g., a PUSCH transmission or a PUCCH transmission) on the first cell to access the first cell. In further implementations, the DU 174 excludes the indication in the first LTM command to configure the UE 102 to perform a random access procedure. In response to the first LTM command excluding the indication, the UE 102 performs a random access procedure on the first cell to access the first cell. In yet further implementations, the DU 174 includes a timing advance value in the first LTM command to indicate skipping a random access procedure. In response to receiving the timing advance value or the first LTM command including the timing advance value, the UE 102 skips a random access procedure and transmits the first transmission on the first cell to access the first cell, using the timing advance value. In yet further implementations, the DU 174 excludes, in the first LTM command, a timing advance value to configure the UE 102 to perform a random access procedure. In response to the first LTM command excluding a timing advance command, the UE 102 performs a random access procedure on the first cell to access the first cell.
[0137] In some implementations, the random access procedure is a four-step, random access procedure. In some implementations, the random access procedure is a two-step, random access procedure. In further implementations, the random access procedure is a contention-free, random access procedure. In yet further implementations, the random access procedure is a contention-based, random access procedure. In cases where the random access procedure is a four-step, random access procedure, the UE 102 transmits a Message 3 including a UE identity to the DU 174 via the first cell in the random access procedure. The DU 174 transmits a contention resolution message (e.g., a Message 4) to the UE 102 in response to the Message 3. In cases where the random access procedure is a two-step, random access procedure, the UE 102 transmits a Message A including the UE identity to the DU 174 via the first cell in the random access procedure. The DU 174 transmits a contention resolution message (e.g., Message B) to the UE 102 in response to the Message A. In some implementations, when the UE 102 receives the contention resolution message from the DU 174 on the first cell, the UE 102 determines that the UE 102 successfully completes the random access procedure (i.e., the UE 102 successfully accesses the first cell). In some implementations, the LTM DU configuration 1 includes a second C-RNTI and the UE identity is the second C-RNTI of the UE 102. In some implementations, the contention resolution message is a PDCCH transmission addressed to the second C-RNTI. In further implementations, the LTM DU configuration 1 does not include a C-RNTI and the UE identity is the first C-RNTI. In further implementations, the contention resolution message is a PDCCH transmission addressed to the first C-RNTI.
[0138] In cases where the LTM DU configuration 1 includes a dedicated random access preamble, the random access procedure is a contention-free, random access procedure. In such cases, the UE 102 transmits the dedicated random access preamble to the DU 174 via the first cell. When the UE 102 receives a random access response including an ID of the dedicated random access preamble from the DU 174 on the first cell, the UE 102 successfully completes the random access procedure (i.e., the UE 102 successfully accesses the first cell).
[0139] If the DU 174 configures the UE 102 to perform a random access procedure on the first cell as described above, the DU 174 detects that the UE 102 has access to the first cell when the DU 174 receives Message 3, Message A, or the dedicated preamble in the random access procedure. In some implementations, the DU 174 configures the UE 102 to skip a random access procedure and the DU 174 receives the first transmission indicating the UE 102 has access to the first cell.
[0140] In some implementations, the UE 102 transmits the first transmission (e.g., the
PUSCH transmission) on the first cell using a UL grant. In some implementations, the first LTM command includes the UL grant. In further implementations, when the UE 102 performs a LTM serving cell change to the first cell in response to the first LTM command, the UE 102 receives a first DO including the UL grant on a PDCCH on the first cell. In some implementations, the UE 102 attempts to receive the first DCI or the UL grant by monitoring one or more PDCCHs on the first cell in accordance with the LTM DU configuration 1, when the UE 102 switches to the first cell in response to the first LTM command. While monitoring one or more PDCCHs on the first cell, the UE 102 receives the first DCI and a CRC of the first DCI on the PDCCH. In the case that the LTM DU configuration 1 includes the second C-RNT, the UE 102 determines that the first DCI was sent for the UE 102, using the CRC and the second C-RNTI. In the case that the LTM DU configuration 1 does not include the second C-RNT, the UE 102 determines that the first DCI was sent for the UE 102, using the CRC and the first C-RNTI.
[0141] In some implementations, the CU 172 transmits at least one first TCI state configuration to the UE 102 via the DU 174. In some implementations, each of the first TCI state configuration(s) configures a TCI state for the UE 102 to transmit and/or receive data and/or a control signal on the first cell. In some implementations, each TCI state associates one or two DL RSs with a corresponding QCL type and the DL RS(s) associate with a particular cell of the cell(s) 1, ..., N. In some implementations, the CU 172 receives a DU- to-CU message including the first TCI state configuration(s) from the DU 174 and transmits a RRC message including the first TCI state configuration(s) to the UE 102 via the DU 174. In further implementations, the DU 174 includes the first TCI state configuration(s) in a serving DU configuration (e.g., CellGroupConfig IE) and includes the serving DU configuration in the DU-to-CU message. In some implementations, the DU 174 includes 312 the LTM DU configuration 1 in a first interface protocol lE/field, and includes the serving DU configuration in a second interface protocol lE/field in the DU-to-CU message.
[0142] In some implementations, the first interface protocol lE/field is defined as part of a format of the DU-to-CU message. The CU 172 includes the serving DU configuration in the RRC message. In some implementations, the CU 172 refrains from including the serving DU configuration in a container for LTM (e.g., the first container). In other implementations, the CU 172 includes the first TCI state configuration(s) in an element for LTM, an addition or modification list for LTM, or a container, similar to the element 1, the first addition or modification list, or the first container, respectively. In some implementations, the RRC message is the RRC reconfiguration message 316, 318 or another RRC reconfiguration message (not shown in Fig. 3). In some implementations, the DU-to-CU message is the message 312, the message 314, a UE Context Modification Response message, or a UE Context Modification Required message. In some implementations, the DU 174 also includes the first TCI state configuration(s) in the LTM DU configuration 1. In further implementations, the DU 174 refrains from including the first TCI state configuration(s) in the LTM DU configuration 1.
[0143] In some implementations, the first interface protocol lE/field is a first F1AP lE/field and the second interface protocol lE/field is a second F1AP lE/field. In some implementations, one of the first F1AP lE/field and the second F1AP lE/field is a F1AP CellGroupConfig lE/field and the other is not the F1AP CellGroupConfig lE/field. In some implementations, the DU 174 includes 312 the first F1AP lE/field in a DU to CU RRC Information IE and includes the second F1AP lE/field in the DU to CU RRC Information IE in the DU-to-CU message. In further implementations, neither the first F1AP lE/field nor the second F1AP IE is a F1AP CellGroupConfig lE/field. In yet further implementations, the second F1AP lE/field is the DU to CU RRC Information IE and the first F1AP lE/field is a specifically defined IE for including a LTM DU configuration.
[0144] In some implementations, after (e.g., in response to) receiving the first LTM command or while accessing 332 the first cell, the UE 102 monitors one or more PDCCHs on the first cell using some or all of the first TCI state configuration(s). In some implementations, each of the first TCI state configuration(s) includes a TCI state ID identifying the corresponding TCI state configuration. For example, the first TCI state configuration(s) includes TCI state configuration(s) 1, ..., L, where L is a positive integer larger than zero. The TCI state configuration(s) 1, ..., L include TCI state ID(s) 1, ..., L identifying the TCI state configuration(s) 1, ..., L, respectively. The DU 174 includes the TCI state ID 1 in the first LTM command to indicate to the UE 102 to apply the TCI state configuration 1 to communicate on the first cell. After (e.g., in response to) receiving the first LTM command, the UE 102 accesses and/or communicates on the first cell using the TCI state configuration 1 in accordance with the TCI state ID 1. For example, the UE 102 monitors one or more PDCCHs and/or transmits the first transmission, using the TCI state configuration 1. In some implementations, the DU 174 detects that the UE 102 accesses the first cell and communicates with the UE 102 on the first cell, based on the TCI state configuration 1. For example, the DU 174 receives the first transmission from the UE 102 on the first cell, based on the TCI state configuration 1. [0145] In some implementations, the DU 174 includes the TCI state ID 2 in the first LTM command to indicate to the UE 102 to apply the TCI state configuration 2 to communicate on the first cell, in addition to the TCI state ID 1. After (e.g., in response to) receiving the first LTM command, the UE 102 accesses and/or communicates on the first cell using the TCI state configurations 1 and 2 in accordance with the TCI state ID 1 and the TCI state ID 2. For example, the UE 102 monitors one or more PDCCHs on the first cell using the TCI state configuration 1 and transmits the first transmission on the first cell using the TCI state configuration 2. In another example, the UE 102 monitors one or more PDCCHs on the first cell using the TCI state configuration 1 and the TCI state configuration 2 and transmits the first transmission on the first cell using one of the TCI state configuration 1 and the TCI state configuration 2. In some implementations, the DU 174 detects that the UE 102 accesses the first cell and communicates with the UE 102 on the first cell, based on the TCI state configuration 1 and/or the TCI state configuration 2. For example, the DU 174 receives the first transmission from the UE 102 on the first cell, based on one of the TCI state configuration 1 and the TCI state configuration 2.
[0146] In further implementations, the DU 174 does not include a TCI state ID in the first LTM command. In such cases, the UE 102 communicates on the first cell with the first DU using the at least one first TCI state, after (e.g., in response to) receiving the first LTM command. In some implementations, the DU 174 detects that the UE 102 accesses the first cell and communicates with the UE 102 on the first cell, based on the first TCI state configuration(s).
[0147] In some implementations, before transmitting the first LTM command, the DU 174 transmits one or more activation commands to activate some or all of the first TCI state configuration(s). In some implementations, each of the activation commands are a MAC CE. In further implementations, each of the activation commands are a DCI. In some implementations, the DU 174 includes the TCI state ID 1 and/or TCI state ID 2 in the activation command(s) to activate the TCI state configuration 1 and/or the TCI state configuration 2, respectively. Accordingly, the UE 102 determines or identifies that the TCI state configuration 1 and/or the TCI state configuration 2 is/are activated upon receiving the activation command(s). In other implementations, the DU 174 includes all the TCI state ID(s) for the first TCI state configuration(s) in the activation command(s). Accordingly, the UE 102 determines or identifies that the first TCI state configuration(s) is/are activated upon receiving the activation command(s). In some implementations, the DU 174 refrains from including, in the first LTM command, a TCI state ID for a TCI state configuration that the DU 174 has not activated for the UE 102. In some implementations, the DU 174 includes the cell ID 1 or the cell index 1 in the activation command(s). Based on the cell ID 1 or cell index 1, and the one or more TCI state IDs in the activation command(s), the UE 102 determines that the activation command(s) activates the one or more TCI state configurations in the first TCI state configuration(s), where each of the TCI state ID(s) identifies a particular TCI state configuration of the TCI state configuration(s).
[0148] In some implementations, the UE 102 communicates (e.g., events 302, 304, 318, 320, 324, 330) with the DU 174 on the cell 124A, using one or more TCI state configurations. In some implementations, each of the TCI state configuration(s) configures a TCI state for the UE 102 to transmit and/or receive data and/or a control signal on the cell 124A. In some implementations, the UE 102 stops using the TCI configuration(s) upon receiving the first LTM command.
[0149] After successfully accessing the first cell, the UE 102 communicates 336 with the DU 174 on the first cell using the LTM DU configuration 1 and/or reference LTM DU configuration and communicates with the CU 172 via the DU 174. In such cases, the DU 174 communicates 336 with the UE 102 on the first cell using the LTM DU configuration 1. In some implementations, the UE 102 communicates 336 PUSCH transmissions, PDSCH transmissions, PUCCH transmissions, PDCCH transmissions, and/or sounding reference signal (SRS) transmissions with the DU 174 on the first cell. In some implementations, the UE 102 uses some or all of the first TCI state configuration(s) to perform 336 the communication with the DU 174. Similarly, the DU 174 uses some or all of the first TCI state configuration(s) to perform 336 the communication with the UE 102. In some implementations, the DU 174 includes one or more additional TCI state configurations in the LTM DU configuration 1. In some implementations, the DU 174 transmits 336 one or more activation commands to the UE 102 via the first cell to activate the additional TCI state configuration(s). The UE 102 determines that the additional TCI state configuration(s) is/are activated upon receiving the activation command(s). In some implementations, each of the activation command(s) is a MAC CE. In further implementations, each of the activation command(s) is a DCI. After receiving the activation command(s), the UE 102 uses the additional TCI state configuration(s) to communicate with the DU 174 on the first cell. Similarly, after transmitting the activation command(s), the DU 174 uses the additional TCI state configuration(s) to communicate with the UE 102 on the first cell. [0150] In the case that the UE 102 receives the reference LTM DU configuration as described above, the UE 102 communicates 336 with and the DU 174 on the first cell in accordance with the LTM DU configuration 1 and at least a portion of the reference LTM DU configuration. In other words, the UE 102 communicates 336 with the DU 174 in accordance with configuration parameters in the LTM DU configuration 1 and the reference LTM DU configuration. Similarly, the DU 174 communicates 336 with the UE 102 on the first cell in accordance with the LTM DU configuration 1 and at least a portion of the reference LTM DU configuration. In other words, the DU 174 communicates 336 with the UE 102 in accordance with configuration parameters in the LTM DU configuration 1 and the reference LTM DU configuration.
[0151] In the case that the UE 102 receives neither the LTM CU configuration 1 nor a reference LTM CU configuration, the UE 102 communicates 336 with the CU 172 via the DU 174 using the serving CU configuration. Correspondingly, if the CU 172 neither transmits the LTM CU configuration 1 nor a reference CU configuration to the UE 102, the CU 172 communicates 336 with the UE 102 via the DU 174 using the serving CU configuration. In the case that the UE 102 receives the LTM CU configuration 1 and the reference LTM CU configuration from the CU 172, the UE 102 communicates 336 with the CU 172 via the DU 174 using the LTM CU configuration 1 and (e.g., at least a portion of) the reference LTM CU configuration not augmented by the LTM CU configuration 1. In this case, the CU 172 communicates 336 with the UE 102 via the DU 174 using the LTM CU configuration 1 and (e.g., at least a portion of) the reference LTM CU configuration not augmented by the LTM CU configuration 1.
[0152] In the case that the UE 102 receives the LTM CU configuration 1 and does not receive the reference LTM CU configuration from the CU 172, the UE 102 communicates 336 with the CU 172 via the DU 174 using the LTM CU configuration 1. In this case, the CU 172 communicates 336 with the UE 102 via the DU 174 using the LTM CU configuration 1. If the LTM CU configuration 1 is a full configuration, the UE 102 and CU 172 communicates 336 with each other via the DU 174 using the LTM CU configuration 1 instead of the serving CU configuration. In some implementations, if the UE 102 does not receive a reference LTM CU configuration from the base station 104, the UE 102 determines that the LTM CU configuration 1 is a full configuration. Correspondingly, if the CU 172 determines to configure or configures the LTM CU configuration 1 as a full configuration, the CU 172 does not transmit a reference LTM CU configuration to the UE 102. In some implementations, the CU 172 includes 336 a first indication (e.g., a field or IE) in the LTM CU configuration 1, the first container, the element 1 or the RRC reconfiguration message to indicate that the LTM CU configuration 1 is a full configuration. If the LTM CU configuration 1 is a delta configuration to augment the serving CU configuration, the UE 102 and the CU 172 communicates 336 with each other via the DU 174 using the LTM CU configuration 1 and at least a portion of the serving CU configuration not augmented by the LTM CU configuration 1. In some implementations, if the UE 102 does not receive a reference LTM CU configuration from the base station 104, the UE 102 determines that the LTM CU configuration 1 is a delta configuration to augment the serving CU configuration. Correspondingly, if the CU 172 determines to configure or configures the LTM CU configuration 1 as a delta configuration to augment the serving CU configuration, the CU 172 does not transmit a reference LTM CU configuration to the UE 102. In some implementations, the CU 172 indicates that the LTM CU configuration 1 is a delta configuration to augment the serving CU configuration, by excluding 316 the first indication in the LTM CU configuration 1, the first container, the element 1, and/or the RRC reconfiguration message. Alternatively, the CU 172 includes 316 a second indication (e.g., a field or IE) in the LTM CU configuration 1, the first container, the element 1, or the RRC reconfiguration message to indicate that the LTM CU configuration 1 is a delta configuration to augment the serving CU configuration. In some implementations, the CU 172 indicates 316 that the LTM CU configuration 1 is a full configuration, by excluding the second indication in the LTM CU configuration 1, the first container, the element 1, and/or the RRC reconfiguration message.
[0153] In the case that the UE 102 receives the reference LTM CU configuration and does not receive the LTM CU configuration 1 from the CU 172, the UE 102 communicates 336 with the CU 172 via the DU 174 using the reference LTM CU configuration. In this case, the CU 172 communicates 336 with the UE 102 via the DU 174 using the reference LTM CU configuration. If the reference LTM CU configuration is a full configuration, the UE 102 and CU 172 communicates 336 with each other via the DU 174 using the reference LTM CU configuration instead of the serving CU configuration. In some implementations, the UE 102 and CU 172 determine that the reference LTM CU configuration 1 is a full configuration (e.g., as defined in the 3GPP TS 38.331). In some implementations, the CU 172 includes 316 a first indication (e.g., a field or IE) in the reference LTM CU configuration the first container or the RRC reconfiguration message to indicate that the reference LTM CU configuration is a full configuration. If the reference LTM CU configuration is a delta configuration to augment the serving CU configuration, the UE 102 and CU 172 communicates 336 with each other via the DU 174 using the reference LTM CU configuration and at least a portion of the serving CU configuration not augmented by the reference LTM CU configuration. In some implementations, the CU 172 indicates 316 that the reference LTM CU configuration is a delta configuration to augment to the serving CU configuration, by excluding the first indication in the reference LTM CU configuration, the first container, the element 1, and/or the RRC reconfiguration message. Alternatively, the CU 172 includes 316 a second indication (e.g., a field or IE) in the reference LTM CU configuration, the first container, the element 1, or the RRC reconfiguration message to indicate that the reference LTM CU configuration is a delta configuration to augment the serving CU configuration. In some implementations, the CU 172 indicates 316 that the reference LTM CU configuration is a full configuration, by excluding the second indication in the reference LTM CU configuration, the first container, the element 1, and/or the RRC reconfiguration message.
[0154] In the case that the UE 102 neither receives the reference LTM CU configuration nor the LTM CU configuration 1 from the CU 172, the UE 102 communicates 336 with the CU 172 via the DU 174 using the serving LTM CU configuration. In this case, the CU 172 communicates 336 with the UE 102 via the DU 174 using the serving LTM CU configuration.
[0155] In some implementations, the UE 102 transmits an RRC message (e.g., RRC reconfiguration complete message) to the CU 172 via the DU 174 and the first cell to indicate that the UE 102 applies the LTM DU configuration 1. In implementations, the UE 102 performs 332 the random access procedure, the UE 102 includes the RRC message in the Message 3 or Message A. Alternatively, the UE 102 transmits the RRC message after completing the random access procedure. In some implementations the UE 102 skip 332 the random access procedure, the UE 102 includes the RRC message in a PUSCH transmission of the at least one PUSCH transmission. In some implementations, the UE 102 maintains communication on the cell 124A with the base station 104 (i.e., the UE 102 does not disconnect from the cell 124A) and the UE 102 transmits the RRC message to the base station 104 via the cell 124A. When the DU 174 receives the RRC message, the DU 174 transmits the RRC message to the CU 172. [0156] In further implementations, the UE 102 refrains from transmitting the RRC message to the base station 104 in response to applying the LTM DU configuration 1 or receiving the first LTM command. In some implementations, the UE 102 includes or transmits data in the Message 3, Message A or PUSCH transmission as described above. In further implementations, the UE 102 generates a MAC PDU and/or a RLC PDU including the data and transmits or includes the MAC PDU and/or RLC PDU in the PUSCH transmission. In some implementations, the data is a PDCP PDU, a SDAP PDU, an LTE Positioning Protocol (LPP) PDU, a RRC PDU, and/or a 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 implementations, the MM message is a 5G MM message or a 6G MM message, and the SM message is a 5G SM message or a 6G SM message. When the DU 174 receives the data, the DU 174 transmits the data to the CU 172.
[0157] In some implementations, when the DU 174 determines 332 or 336 that the UE 102 successfully connects to the first cell, the DU 174 transmits 334 a DU-to-CU message (e.g., Access Success message) to the CU 172 (e.g., a CP of the CU 172). In further implementations, the DU 174 includes 334 the cell ID 1 of the first cell in the DU-to-CU message. In some implementations, the cell ID is a PCI or a CGI. Thus, the CU 172 determines 334 that the UE 102 connects to the first cell upon receiving the DU-to-CU message. When the DU 174 determines 332 or 336 that the UE 102 successfully connects to the first cell, the DU 174 transmits a DL Data Delivery Status message or frame to the CU 172 (e.g., a UP of the CU 172). In some implementations, when or after the CU 172 receives 329 the DU-to-CU message, the CU 172 stops or suspends transmitting DL data for the UE 102 to the DU 174 until receiving 334 the DU-to-CU message. In some implementations, the CU 172 stops or suspends transmitting 330 and/or 332 because the DU 174 does not buffer DL data for the UE 102 during the LTM execution . After receiving 334 the DU-to-CU message, the CU 172 continues or resumes transmitting DL data for the UE 102 to the DU 174. In further implementations, the CU 172 receives 329 the DU-to-CU message and the CU 172 continues transmitting DL data for the UE 102 to the DU 174. In yet further implementations, the CU 172 continues transmitting 330 and/or 332 because the DU 174 buffers DL data for the UE 102 during the LTM execution. When or after the DU 174 detects the UE 102 accesses the cell 1, the DU 174 transmits the DL data to the UE 102 via the cell 1. [0158] In some implementations, when determining that the UE 102 connects to the first cell, transmitting 330 the first LTM command, or receiving 331 the acknowledgement, the DU 174 stops communicating with the UE 102 on the cell 124A and/or releases resources of the cell 124 A configured for the UE 102.
[0159] In some implementations, the DU 174 generates some or all of the LTM DU configuration 1 and/or LTM DU configuration(s) 2, ..., N as full configuration(s) to replace the serving DU configuration. If the LTM DU configuration 1 is a full configuration, the UE 102 and DU 174 communicates 336 with each other in accordance with the LTM DU configuration 1 instead of the serving DU configuration. In some implementations, the DU 174 includes an indication indicating that the LTM DU configuration 1 is a full configuration in the LTM DU configuration 1. In some implementations, in each of the LTM DU configuration(s) 2, ..., N, the DU 174 includes an indication to indicate that the corresponding DU configuration is a full configuration. In further implementations, each of the indication(s) in the LTM DU configuration(s) 1, ..., N is a field or IE (i.e., the same field or IE). In further implementations, the CU 172 includes 316 and 318, in the RRC reconfiguration message a single indication indicating that the LTM DU configuration(s) 1 and/or 2, ..., N is/are full configuration(s). In further implementations with the second container, the CU 172 includes in the additional RRC reconfiguration message a single indication indicating that the LTM DU configuration(s) 2, ..., N is/are full configuration(s). In yet further implementations, the CU 172 includes, in the first container, a single indication indicating that the LTM DU configuration(s) 1 and/or 2, ..., N is/are full configuration(s). In yet further implementations, for each of the LTM DU configuration(s) 2, ..., N, the CU 172 includes, in the first container, a particular indication indicating the corresponding LTM DU configuration is a full configuration. In some implementations with the second container, the CU 172 includes, in the second container, a single indication indicating that the LTM DU configuration(s) 2, ..., N is/are full configuration(s). In yet further implementations, the CU 172 includes, in the element 1, an indication indicating that the LTM DU configuration 1 is a full configuration. In some implementations, in each of the element(s) 2, ..., N the CU 172 includes an indication indicating that the corresponding LTM DU configuration is a full configuration. In some implementations, the UE 102 determines that the LTM DU configuration 1 and/or LTM DU configuration(s) 2, ..., N is/are full configuration(s) based on the indication(s) above. In some implementations, each of the indication(s) above is different from fullConfig field (e.g., as defined in the current 3GPP TS). In some implementations, each of the indication(s) above is afullConfig field (e.g. as defined in the 3GPP TS). In the case that the LTM DU configuration 1 is a full configuration, the UE 102 does not apply 336 the reference LTM DU configuration if received from the base station 104 (e.g., the UE 102 receives 318 the RRC reconfiguration message). In some implementations, the DU 174 does not include 310 a reference LTM DU configuration in the first DU-to-CU message.
[0160] In some implementations, the DU 174 generates the LTM DU configuration 1 and/or LTM DU configuration(s) 2, ..., N as delta configuration(s) that augment (e.g., a portion of) the reference LTM DU configuration. In other words, the DU 174 generates the LTM DU configuration(s) 1, .. ,N based on the reference LTM DU configuration. Lor example, if the LTM DU configuration 1 is a delta configuration, the UE 102 and DU 174 augment (e.g., the portion of) the reference LTM DU configuration with the LTM DU configuration 1. Thus, the UE 102 and DU 174 communicate 336 with each other in accordance with the LTM DU configuration 1 and unaugment the portion of the reference LTM DU configuration. In some implementations, the LTM DU configuration(s) 1, and/or 2..., N, first container, second container or element(s) 1, ..., N exclude indication(s) indicating that the LTM DU configuration(s) 1, and/or 2..., N is/are full configuration(s) to indicate that the LTM DU configuration(s) 1 and/or 2, ..., N is/are delta configuration(s). In some implementations, the UE 102 determines that each of the LTM DU configuration(s) 1 and/or 2, ... , N is a delta configuration based on that the indication that excludes in the LTM DU configuration(s) 1 and/or 2, ...,N, first container, second container or element(s) 1 and/or 2, ..., N.
[0161] In some implementations, if the UE 102 does not receive a reference LTM DU configuration for the LTM DU configuration 1 and/or the LTM DU configuration(s) 2, ..., N, the UE 102 determines that the LTM DU configuration 1, and/or the LTM DU configuration(s) 2, ..., N are full configuration(s). Correspondingly, if the DU 174 does not obtain a reference LTM DU configuration for the UE 102 (i.e., the DU 174 does not generate a reference LTM DU configuration for the UE 102 and/or receive a reference LTM DU configuration for the UE 102 from the CU 172), the DU 174 generates the LTM DU configuration 1, and/or the LTM DU configuration(s) 2, ..., N as full configuration(s).
[0162] In further implementations, if the UE 102 does not receive a reference LTM DU configuration for the LTM DU configuration 1 and/or the LTM DU configuration(s) 2, ..., N, the UE 102 determines that the LTM DU configuration 1, and/or the LTM DU configuration(s) 2, N are delta configuration(s) to augment the serving DU configuration. In such cases, the UE 102 communicates 336 with the DU 174 in accordance with the LTM DU configuration 1 and at least a portion of the serving DU configuration not augmented by LTM DU configuration 1. Correspondingly, if the DU 174 does not obtain a reference LTM DU configuration for the UE 102 (i.e., the DU 174 does not generate a reference LTM DU configuration for the UE 102 and/or receive a reference LTM DU configuration for the UE 102 from the CU 172), the DU 174 generates the LTM DU configuration 1, and/or the LTM DU configuration(s) 2, ..., N as delta configuration(s) to augment the serving DU configuration. In such cases, the DU 174 communicates 336 with the UE 102 in accordance with the LTM DU configuration 1 and the at least a portion of the serving DU configuration.
[0163] In some implementations, the UE 102 uses a UE MAC entity (e.g., MAC 204B) to communicate with a DU MAC entity (e.g., MAC 204B) of the DU 174 (e.g., the events 302, 304, 318, 320, 324, 330 and/or 331). In some implementations, the UE 102 resets the UE MAC entity, after or in response to receiving the first LTM command and before performing 332 the random access procedure or communicating 336 with the DU 174 via the first cell. In some implementations, the DU 174 resets the DU MAC entity after (e.g., in response to) transmitting the first LTM command, receiving 331 the acknowledgement or determining that the UE 102 connects to the first cell.
[0164] In some implementations, when the UE 102 resets the UE MAC entity, the UE 102 performs at least one of the following actions for the UE MAC entity (i.e., a UE MAC reset or a full UE MAC reset): (i) initialize Bj for configured logical channel(s) to zero, stop one or more timers, consider timeAlignmentTimeris) as expired if the UE 102 is configured to perform the random access procedure (e.g., the event 332) in the configuration (e.g., the configuration 1), set new data indicator(s) (e.g., NDI(s)) for UL HARQ process(es) to value 0, set NDI(s) for HARQ process ID(s) to value 0 for monitoring PDCCH in Sidelink resource allocation mode 1, flush Msg3 buffer, and flush MSGA buffer, (ii) cancel, if any, one of the following triggered procedures: Scheduling Request, Buffer Status Reporting, Power Headroom Reporting, consistent LBT failure, BFR, Sidelink Buffer Status Reporting, Preemptive Buffer Status Reporting, Timing Advance Reporting, Recommended bit rate query, configured uplink grant confirmation, configured sidelink grant confirmation, Desired Guard Symbol query, or Positioning Measurement Gap Activation/Deactivation Request, (iii) flush soft buffers for DL HARQ process(es), (iv) for each of the DL HARQ process(es), consider the next received transmission for a TB as the very first transmission, (v) release, if any, Temporary C-RNTI, and (vi) reset one or more counters (e.g., BFI_COUNTERs and/or LBT_COUNTERs).
[0165] In some implementations, when the DU 174 resets the DU MAC entity, the DU 174 performs at least one of the following actions for the DU MAC entity (i.e., s DU MAC reset or a full DU MAC reset): (i) stop one or more timers, (ii) consider limeAlignmenlTimer( ). that the DU 174 starts and/or maintains for the UE 102, as expired, if the UE 102 is configured to perform the random access procedure (e.g., the event 332) in the configuration (e.g., the configuration 1), (iii) set NDI(s) for DL HARQ process(es) to value 0, (iv) flush soft buffers for UL HARQ process(es), (v) for each of the UL HARQ process(es), consider the next received transmission for a TB as the very first transmission, and (vi) reset one or more counters (e.g., BFI_COUNTERs and/or LBT_COUNTERs).
[0166] In some implementations, the UE 102 determines to partially or fully reset the UE MAC entity. In some implementations, when the UE 102 resets the UE MAC entity as described above, the UE 102 fully resets the UE MAC entity (i.e., a full UE MAC reset). In the full UE MAC reset, the UE 102 performs some or all of the actions described above. In further implementations, when the UE 102 resets the UE MAC entity as described above, the UE 102 partially resets the UE MAC entity (i.e., a partial UE MAC reset). In the partial UE MAC reset, the UE 102 performs a subset or portion of the some or all of the actions in the full UE MAC reset.
[0167] In some implementations, the partial UE MAC reset includes at least one of the following actions: (i) consider timeAlignmentTimeris) of the UE 102 as expired, if the UE 102 is configured to perform the random access procedure (e.g., the event 332) in the configuration (e.g., the configuration 1), (ii) flush Msg3 buffer, (iii) flush MSGA buffer, (iv) release, if any, Temporary C-RNTI, and (v) reset one or more counters (e.g., BFI_COUNTERs and/or LBT_COUNTERs).
[0168] In some implementations, the partial UE MAC reset further includes at least canceling one of the following triggered procedures: (i) Scheduling Request, Buffer Status Reporting, Power Headroom Reporting, consistent LBT failure, BFR, Sidelink Buffer Status Reporting, Pre-emptive Buffer Status Reporting, Timing Advance Reporting, Recommended bit rate query, configured uplink grant confirmation, configured sidelink grant confirmation, Desired Guard Symbol query, and Positioning Measurement Gap Activation/Deactivation Request.
[0169] In some implementations, the partial UE MAC reset further includes at least one of the following actions: (i) stop a first portion of the one or more timers and retain the rest of the one or more timers, (ii) set new data indicator(s) (NDI(s)) for UL HARQ process(es) to value 0, (iii) set NDI(s) for HARQ process ID(s) to value 0 for monitoring PDCCH in Sidelink resource allocation mode 1, (iv) flush soft buffers for DL HARQ process(es), and (v) for each of the DL HARQ process(es) consider the next received transmission for a TB as the very first transmission.
[0170] In some implementations, the DU 174 determines to partially or fully reset the DU MAC entity. In further implementations, when the DU 174 resets the DU MAC entity as described above, the DU 174 fully resets the DU MAC entity (i.e., a full DU MAC reset). In the full DU MAC reset, the DU 174 performs some or all of the actions described above. In yet further implementations, when the DU 174 resets the DU MAC entity as described above, the DU 174 partially resets the DU MAC entity (i.e., a partial DU MAC reset). In the partial DU MAC reset, the DU 174 performs a subset or portion of the some or all of the actions in the full DU MAC reset.
[0171] In some implementations, the partial DU MAC reset includes at least one of the following actions in the partial MAC reset: (i) consider timeAlignmentTimer(s), that the DU 174 starts and/or maintains for the UE 102, as expired, if the UE 102 is configured to perform the random access procedure (e.g., the event 332) in the configuration (e.g., the configuration 1), and (ii) reset one or more counters (e.g., BFI_COUNTERs and/or LBT_COUNTERs)
[0172] In some implementations, when the partial DU MAC reset includes at least one of the following actions for the MAC entity (i.e., DU MAC reset): (i) stop a first portion of the one or more timers and retain the rest of the one or more timers, (ii) set NDI(s) for DL HARQ process(es) to value 0, (iii) flush soft buffers for UL HARQ process(es), (iv) for each of the UL HARQ process(es) consider the next received transmission for a TB as the very first transmission, and (v) reset one or more counters (e.g., BFI_COUNTERs and/or LBT_COUNTERs).
[0173] In further implementations, the UE 102 refrains from resetting the UE MAC entity in response to receiving the first LTM command. Similarly, the DU 174 refrains from resetting the DU MAC entity after (e.g., in response to) transmitting the first LTM command, receiving 331 the acknowledgement or determining that the UE 102 connects to the first cell. In other words, the UE 102 communicates with the DU 174 on the first cell using the UE MAC entity (not reset). Similarly, the DU 174 communicates 332 with the UE 102 using the DU MAC entity (not reset) on the first cell during or after the random access procedure or after determining that the UE 102 connects to the first cell.
[0174] In some implementations, the UE 102 uses at least one UE RLC entity (e.g., RLC 206B) to communicate RLC PDUs with at least one DU RLC entity (e.g., RLC 206B) of the DU 174 (e.g., the events 302, 304, 318, 320, 324, 330 and/or 331). In some implementations, the UE 102 reestablishes some or all of the at least one UE RLC entity, after or in response to receiving 332 the first LTM command and before performing the random access procedure or communicating 336 with the DU 174 via the first cell. In some implementations, the DU 174 reestablishes some or all of the at least one DU RLC entity after (e.g., in response to) transmitting the first LTM command, receiving 331 the acknowledgement or determining that the UE 102 connects to the first cell.
[0175] In some implementations, the LTM DU configuration 1 optionally includes one or more RLC reestablishment indications (e.g., reestablishRLC field(s)) configuring the UE 102 to reestablish some or all of the at least one UE RLC entity. In some implementations, the LTM DU configuration 1 includes the RLC reestablishment indication configuring the UE 102 to reestablish a first UE RLC entity, of the at least one UE RLC entity, that the UE 102 uses to communicate RLC PDU(s) with the DU 174, the UE 102 reestablishes the first UE RLC entity in response to the RLC reestablishment indication and the first LTM command. In some implementations, the UE 102 reestablishes 332 the first UE RLC entity before performing the random access procedure or communicating 336 with the DU 174 via the first cell. In further implementations, the UE 102 reestablishes the first UE RLC entity while or after performing 332 the random access procedure. Otherwise, if the LTM DU configuration 1 does not include the RLC reestablishment indication, the UE 102 refrains from reestablishing the first UE RLC entity in response to the first LTM command.
[0176] In some implementations, when the UE 102 reestablishes the first UE RLC entity, the UE 102 performs at least one of the following actions for the first UE RLC entity: (i) discard RLC SDU(s), RLC SDU segment(s), and RLC PDU(s), if any, (ii) stop and reset any timer(s) that are running, and (iii) reset state variables to initial values. In some implementations, the state variables and timer(s) (e.g., as defined in 3GPP TS 38.322). [0177] Otherwise, if the LTM DU configuration 1 does not include the RLC reestablishment indication for the first UE RLC entity, the UE 102 refrains from reestablishing the first UE RLC entity upon or when receiving the first LTM command. In other words, the UE 102 refrains from preforming the actions for reestablishing the first UE RLC entity of the UE 102 upon or when receiving the first LTM command. In some implementations, if the LTM DU configuration 1 or element 1 does not include the RLC reestablishment indication and includes an indication indicating that the configuration 1 is a full configuration, the UE 102 reestablishes the first UE RLC entity of the UE 102 upon or when receiving the first LTM command. Otherwise, if the LTM DU configuration 1 or element 1 does not include the RLC reestablishment indication and the indication indicating that the configuration 1 is a full configuration, the UE 102 refrains from reestablishing the first UE RLC entity upon or when receiving the first LTM command.
[0178] Similarly, the DU 174 reestablishes some or all of at least one DU RLC entity (e.g., NR RLC 206B) that the DU 174 uses to communicate with the at least one UE RLC entity of the UE 102 (e.g., the events 302, 304, 318, 320, 324, 330 and/or 331) in response to the RLC reestablishment indication. In some implementations, the DU 174 reestablishes a first DU RLC entity of the at least one DU RLC entity after transmitting the first LTM command, receiving an acknowledgement for the first LTM command from the UE 102, or determining that the UE 102 connects to the first cell. In some implementations, the acknowledgement is a HARQ ACK. In further implementations, the acknowledgement is a MAC CE. In yet further implementations, the acknowledgement is a PUCCH transmission. In some implementations, when the base station 104 reestablishes the first DU RLC entity, the DU 174 performs at least one of the following actions for the first DU RLC entity: (i) discard any existing RLC SDU(s), RLC SDU segment(s), and RLC PDU(s), (ii) stop and reset timer(s) running, and (iii) reset state variables to initial values.
In some implementations, the state variables and timer(s) (e.g., as defined in 3GPP TS 38.322).
[0179] In other implementations, the UE 102 refrains from reestablishing some or all of the at least one UE RLC entity in response to receiving the first LTM command. Similarly, the DU 174 refrains from reestablishing some or more of the at least one DU RLC entity after (e.g., in response to) transmitting the first LTM command, receiving 331 the acknowledgement or determining that the UE 102 connects to the first cell. In other words, the UE 102 communicates with the DU 174 on the first cell using the some or all of the at least one UE RLC entity (not reestablished). For example, the some or all of the at least one UE RLC entity includes the first UE RLC entity and/or a second UE RLC entity. Similarly, the DU 174 communicates 332 with the UE 102 using the some or all of the at least one DU RLC entity (not reestablished) on the first cell during or after the random access procedure or after determining that the UE 102 connects to the first cell. For example, the some or all of the at least one DU RLC entity includes the first DU RLC entity and/or a second DU RLC entity.
[0180] In some implementations, the UE 102 uses at least one UE PDCP entity (e.g., PDCP 210) to communicate 302 UL PDCP PDUs and/or DL PDCP PDUs with at least one CU PDCP entity (e.g., PDCP 210) of the CU 172. In some implementations, the UE 102 performs a PDCP recovery procedure for some or all of the at least one UE PDCP entity, after or in response to receiving the first LTM command. For example, the UE 102 performs a PDCP recovery procedure for a first UE PDCP entity of the at least one UE PDCP entity, after or in response to receiving the first LTM command. In the PDCP recovery procedure, the UE 102 optionally reestablish the first UE PDCP entity. In some implementations, after or in response to performing the PDCP recovery procedure, the UE 102 retransmits 336 at least a portion of the UL PDCP PDUs to the CU 172 via the DU 174 and the first cell. Similarly, the CU 172 performs a PDCP recovery procedure for some or all of the at least one CU PDCP entity after or in response to transmitting the first LTM command. For example, the CU 172 performs a PDCP recovery procedure for a first CU PDCP entity of the at least one CU PDCP entity, after or in response to transmitting the first LTM command. In some implementations, the CU 172 performs 329 or 334 the PDCP recovery procedure for the first CU PDCP entity in response to receiving the DU-to-CU message. In further implementations, the CU 172 performs the PDCP recovery procedure for the first CU PDCP entity in response to receiving the DL Data Delivery Status message. In the PDCP recovery procedure, the CU 172 optionally reestablish the first CU PDCP entity. In some implementations, after or in response to performing the PDCP recovery procedure, the CU 172 retransmits 336 at least a portion of the DL PDCP PDUs to the UE 102 via the DU 174 and the first cell.
[0181] In further implementations, the UE 102 refrains from reestablishing some or all of the at least one UE PDCP entity in response to receiving the first LTM command. For example, the some or all of the at least one UE PDCP entity includes the first UE PDCP entity and/or a second UE PDCP entity. Similarly, the CU 172 refrains from reestablishing some or more of the at least one CU PDCP entity, after (e.g., in response to) receiving 329 or 340 the DU-to-CU message or after (e.g., in response to) receiving the DL Data Delivery Status message. In other words, the UE 102 communicates with the CU 172 via the DU 174 and the first cell using the some or all of the at least one UE PDCP entity (not reestablished). For example, the some or all of the at least one UE PDCP entity includes the first UE PDCP entity and/or a second UE PDCP entity. Similarly, the CU 172 communicates with the UE 102 using the some or all of the at least one CU PDCP entity (not reestablished) via the DU 174 and the first cell. For example, the some or all of the at least one CU PDCP entity includes the first CU PDCP entity and/or a second CU PDCP entity.
[0182] In some implementations, after determining that the UE 102 connects to the first cell, the CU 172 transmits 338 a CU-to-DU message (e.g., a UE Context Modification Request message) to the DU 174 to indicate to the DU 174 to stop communicating with the UE 102 and/or to release or suspend resources, of the cell 124A, configured for the UE 102. In some implementations, the DU 174 stops communicating on the cell 124A with the UE 102 and/or releases or suspends resources, of the cell 124A, configured for the UE 102, and transmit 340 a DU-to-CU message (e.g., a UE Context Modification Response message) to the CU-172. The events 338 (optional) and 340 (optional) are collectively referred to in Fig. 3 as a resource release procedure 396.
[0183] In some implementations, after or while communicating with the DU 174 on the first cell, events 344, 346, 348, 350, 351, 352, 354 and/or 356 occurs, similar to the events 324, 326, 328, 330, 331, 332, 334 and/or 336, respectively. The UE 102 transmits 344 at least one measurement report to the DU 174. The at least one measurement report includes at least one measurement result for a second cell (i.e., the cell 2). The at least one measurement result indicates that the second cell is suitable for communication with UE 102 and/or the first cell is not suitable for communication with the UE 102. After (e.g., in response to) receiving the at least one measurement report, the DU 174 determines to activate the LTM DU configuration 2 and generates a second LTM command to activate the LTM DU configuration 2 (i.e., the second LTM command commands for the UE 102 to apply the LTM DU configuration 2). The DU 174 then transmits 350 the second LTM command to the UE on the first cell to the UE 102. [0184] In some implementations, in response to determining to activate the LTM DU configuration 2 or transmit the second LTM command, the DU 174 transmits 349 to the CU 172 a DU-to-CU message indicating LTM execution. In some implementations, the DU 174 includes 349 the cell ID 2 or the ID 2 (i.e., LTM ID) in the DU-to-CU message to indicate that the DU 174 activate the LTM DU configuration 2. In some implementations, the DU transmits 349 the DU-to-CU message to the CU 172 before or after transmitting 350 the LTM command.
[0185] At least some of the discussion of the events 324, 326, 328, 330, 331, 332, 334 and/or 336 can generally apply to the events 344, 346, 348, 350, 351, 352, 354 and/or 356. For example, “ cell 124A”, “first LTM command”, “first cell”, “ID 1”, “LTM DU configuration 1” and/or “LTM CU configuration 1” are replaced with “first cell”, “second LTM command” and “second cell”, “ID 2”, “LTM DU configuration 2” and/or “LTM CU configuration 2”, respectively.
[0186] The events 344, 346, 348, 350, 351, 352, 354 are collectively referred to in Fig. 3 as an LTM execution procedure 398. The events 304, 306, 390, 392, 394, 324, 326, 328, 329, 330, 331, 332, 334, 336, 396, 398, 356 are collectively referred to in Fig. 3 as an LTM DU configuration and/or activation procedure 380.
[0187] Referring next to Fig. 4, in a scenario 400, the base station 104 includes a CU 172, a source DU (S-DU) 174A and a target DU (T-DU) 174B. The S-DU 174A operates the cell 124A and optionally additional cell(s), while the T-DU 174B operates a first cell (e.g., cell 124C). The scenario 400 is similar to the scenario 300. In some implementations, the discussion of the scenario 300 generally applies to the scenario 400. The differences between the scenarios 300 and 400 are described below.
[0188] Initially, the UE 102 communicates 402 with the S-DU 174A on cell 124A using a serving DU configuration and communicates with the CU 172 via the S-DU 174A. The S-DU 174A is a serving DU similar to the DU 174 in Fig. 3A. During the communication 402, the UE 102 transmits 404 and 406 at least one measurement report (e.g., L3 measurement report(s)) to the CU 172 via the S-DU 174A. Based on the at least one measurement report, the CU 172 determines to prepare cell(s) 1, ..., N (e.g., operated by the T-DU 174B) for LTM for the UE 102, where N is a positive integer larger than 0 or 1. The cell(s) 1, ..., N are identified by cell ID(s) 1, ..., N, respectively. In response to the determination, the CU 172 performs 490 an LTM preparation procedure with the T-DU 174B to (e.g., request the T-DU 174B to) prepare cell(s) 1, .. N for LTM for the UE 102. In some implementations, N is a positive integer larger than zero or 1. In the LTM preparation procedure, the CU 172 transmits 490 a CU-to-DU message including the cell ID(s) 1, ..., N to the T-DU 174B to request the T-DU 174B to prepare the cell(s) 1, ..., N for LTM for the UE 102, similar to the event 308. In response, the T-DU 174B transmits a DU-to-DU message including the LTM DU configuration(s) 1, ..., N to the CU 172, similar to the event 310. The LTM DU configuration(s) 1, ..., N configures the cell(s) 1, ..., N for LTM, respectively. Specifically, the LTM DU configuration(s) 1, ..., N include configuration parameters for communication on the cell(s) 1, ..., N, respectively. In some implementations, the CU-to-DU message and the DU-to-CU message in the procedure 490 is a UE Context Setup Request message and a UE Context Setup Response message, respectively. The CU 172 then transmits the LTM DU configuration(s) 1, ..., N in an RRC reconfiguration message in an LTM configuration delivery procedure 494, similar to the LTM configuration delivery procedure 394. In some implementations, the T-DU 174B includes cell index(es) 1, ..., N in the LTM DU configuration(s) 1, ..., N, respectively. In some implementations, the CU 172 sets the cell index(es) 1, ..., N to different values and includes 490 the cell index(es) 1, ..., N in the CU- to-DU message.
[0189] In some implementations, after performing 490 the LTM preparation procedure, the CU 172 performs an additional similar LTM preparation procedure(s) with the T-DU 174B to prepare cell(s) N+l, ..., N+M for LTM for the UE 102. M is a positive integer larger than zero. In some implementations, the CU 172 determines one or more measurement reports received from the UE 102 via the S-DU 174A, similar to the events 404, 406. In the additional LTM preparation procedure, the CU 172 transmits a CU-to-DU message including cell ID(s) N+l, ..., N+M to the T-DU 174B to request the T-DU 174B to prepare the cell(s) N+l, ..., N+M for LTM for the UE 102. The cell ID(s) N+l, ..., N+M identifies the cell ID(s) N+l, ..., N+M, respectively. In response to the CU-to-DU message, the T-DU 174B transmits a DU-to-DU message including the LTM DU configuration(s) N+l, ..., N+M to the CU 172. The LTM DU configuration(s) N+l, ..., N+M configures the cell(s) N+l, ..., N+M for LTM, respectively. In details, the LTM DU configuration(s) N+l, ..., N+M include configuration parameters for communication on the cell(s) N+l, ..., N+M, respectively. The CU 172 then transmits 394 or 494 the LTM DU configuration(s) N+l, ..., N+M in a RRC reconfiguration message in an additional similar LTM configuration delivery procedure. [0190] In some implementations, the LTM preparation procedure 490 is a UE Context Setup procedure, and the additional LTM preparation procedure is a UE Context Modification procedure.
[0191] In some implementations, the CU 172 and S-DU 174A performs 380 the procedure with the UE 102, as described for Fig. 3. In the procedure 380, the CU 172 and S-DU 174A performs 390 and/or 392 the procedure(s) to prepare cell(s) of the S-DU 174A for LTM for the UE 102. In some implementations, the value N in the procedure or described 380 for Fig. 3 is the same as or different from the value N described for Fig. 4. In some implementations, in the procedure 390, the CU 172 receives 310 the first DU-to-CU message including the reference LTM DU configuration from the S-DU 174A. In further implementations, the CU 172 and S-DU 174A do not perform 380 the procedure with the UE 102. In implementations, the CU 172 performs 488 a reference LTM DU configuration query procedure with the S-DU 174A to obtain a reference LTM DU configuration. In the procedure 488, the CU 172 transmits 460 a CU-to-DU message to the S-DU 174A to request or query a reference LTM DU configuration. In some implementations, the CU 172 includes an indication in the CU-to- DU message to request or query a reference LTM DU configuration. In response to the indication or CU-to-DU message 460, the S-DU 174A transmits 462 a DU-to-CU message including a reference LTM DU configuration to the CU 172. In some implementations, the indication is a reference LTM DU configuration query indication. In further implementations, the indication is an LTM indication, and the CU 172 includes a query indication (e.g., GNB- DU Configuration Query IE) in the CU-to-DU message. After receiving the reference LTM DU configuration (i.e., either in the procedure 390 or in the procedure 488), the CU 172 includes 490 the reference LTM DU configuration (e.g., received from the S-DU 174A) in the CU-to-DU message in the LTM preparation procedure. The T-DU 174B generates the LTM DU configuration(s) 1, ..., N based on the reference LTM DU configuration received from the CU 172. In such cases, the T-DU 174B does not include a reference LTM DU configuration in the DU-to-CU message in the procedure 490. In the case of the additional LTM preparation procedure, the T-DU 174B does not include a reference LTM DU configuration in the DU-to-CU message in the additional LTM preparation procedure. In some implementations, the CU 172 does not include the reference LTM DU configuration in CU-to-DU message in the additional LTM preparation procedure with the T-DU 174B. In the case of the additional LTM preparation procedure, the T-DU 174B generates the LTM DU configuration(s) N+l, ..., N+M based on the reference LTM DU configuration received from the CU 172.
[0192] In some implementations, the CU 172 does not provide a reference LTM DU configuration to the T-DU 174B in the LTM preparation procedure 490. In such cases, the T- DU 174B generates a reference LTM DU configuration and generates the LTM DU configuration(s) 1, ..., N based on the reference LTM DU configuration. In such cases, the T- DU 174B includes the reference LTM DU configuration in the DU-to-CU message in the procedure 490. The CU 172 transmits the reference LTM DU configuration in the RRC reconfiguration message in the procedure 490. In the case of the additional LTM preparation procedure, the T-DU 174B generates the LTM DU configuration(s) N+l, ..., N+M based on the reference LTM DU configuration. In some implementations, the T-DU 174B does not include the reference LTM DU configuration in the DU-to-CU message in the additional LTM preparation procedure. In some implementations, the reference LTM DU configuration the T-DU 174B generates is different from the reference LTM DU configuration the S-DU 174A generates. In further implementations, the reference LTM DU configuration the T-DU 174B generates is the same as the reference LTM DU configuration generated by the S-DU 174A.
[0193] In some implementations, the CU 172 includes the LTM DU configuration(s) 1, ..., N of the procedure 380 in the CU-to-DU message of the procedure 490, and the T-DU 174B generates the LTM DU configuration(s) 1, ..., N and/or N+l, ..., N+M, considering or based on configuration(s) in the LTM DU configuration(s) of the procedure 380.
[0194] In some implementations, the LTM DU configuration X of the procedure 380 includes at least one reference signal (RS) resource configuration X, where 1 < X < N. Each of the RS resource configuration(s) X configures one or more RSs or one or more RS resources associated with the cell X of the S-DU 174A. The RS(s) includes SSB(s) and/or CSLRS(s). The RS resource(s) includes SSB resource(s) and/or CSLRS resource(s). In some implementations, each of the RS resource configuration(s) X includes a RS resource configuration ID. In some implementations, the RS resource configuration(s) X is/are (e.g., similar to) CSl-ResourceConfig IE(s). In some implementations, the LTM DU configuration X includes a CSl-MeasConfig IE and the CSl-MeasConfig IE includes the CSl- ResourceConfig IE(s). The T-DU 174B generates at least one report configuration 1 for reporting, on the cell 1 of the T-DU 174B, measurement results of the RS(s) or RS resource(s) and includes the report configuration(s) 1 in the LTM DU configuration 1. In some implementations, the report configuration(s) 1 is/are (e.g., similar to) CSl-ReportConfig IE(s). In some implementations, the T-DU 174B generates at least one RS resource configuration 1, considering or based on the RS resource configuration(s) X and includes the RS resource configuration(s) 1 in the LTM DU configuration 1. In some implementations, the T-DU 174B includes the RS resource configuration(s) X in the RS resource configuration(s) 1. In other implementations, the T-DU 174B includes each of the RS resource configuration(s) X in the RS resource configuration(s) 1, except the RS resource configuration ID(s) in the RS resource configuration(s) X. The T-DU 174B assigns an RS resource configuration ID to a value for each of the RS resource configuration(s) 1 (e.g., including the RS resource configuration(s) X) and includes the RS resource configuration ID in the corresponding RS resource configuration.
[0195] In some implementations, the report configuration(s) 1 configures one or more UL resources (e.g., PUCCH resources or PUSCH resources) on the cell 1 for the UE 102 to transmit measurement results. In some implementations, each of the report configuration(s) 1 includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the RS resource configuration(s) 1. After the UE 102 performs a LTM serving cell change to the cell 1 from the cell 124A, the UE 102 communicates with the S-DU 174B (i.e., the T-DU 17B becomes a S-DU for the UE 102) and transmits measurement results on the UL resource(s) via the cell 1 to the S-DU 174B, in accordance with the report configuration(s) 1. Correspondingly, the S-DU 174B receives the measurement results on the UL resource (s) via the cell 1 from the UE 102, in accordance with the report configuration(s) 1. In some implementations, each of the measurement results includes one or more RS resource indicators and/or one or more quantized measurement values. The UE 102 performs measurements on the RS(s) or the RS resource(s) in accordance with the RS resource configuration(s) 1 and/or the report configuration(s) 1 and obtains the quantized measurement values from the measurements. In some implementations, the RS resource indicator(s) indicates the RS(s) or a RS resource(s) where the UE 102 performs measurements or obtains the quantized measurement values. In some implementations, the RS resource indicator(s) includes one or more SSB resource indicators (e.g., SSBRI(s)) and/or one or more CSLRS resource indicators (CRI(s)). In some implementations, the quantized measurement values includes one or more Ll-RSRP values and/or one or more Ll-SINR values. [0196] In some implementations, the T-DU 174B also includes additional RS resource configuration(s) in the LTM DU configuration 1. Each of the additional RS resource configuration(s) configures one or more additional RSs or one or more additional RS resources associated with the cell 1. The additional RS(s) includes SSB(s) and/or CSI-RS(s). The additional RS resource(s) includes SSB resource(s) and/or CSI-RS resource(s). In some implementations, each of the additional RS resource configuration(s) includes a RS resource configuration ID. In some implementations, the additional RS resource configuration(s) is/are (e.g., similar to) CSl-ResourceConfig IE(s). In some implementations, the T-DU 174B includes the CSI-ResourceConfig IE(s) in the CSI-MeasConfig IE. The T-DU 174B generates at least one additional report configuration for reporting, on the cell 1 of the T-DU 174B, measurement results of the RS(s) or RS resource(s) and includes the additional report configuration(s) in the LTM DU configuration 1. In some implementations, the additional report configuration(s) is/are (e.g., similar to) CSl-ReportConfig IE(s).
[0197] In some implementations, the additional report configuration(s) configures one or more UL resources (e.g., PUCCH resources or PUSCH resources) on the cell 1 for the UE 102 to transmit measurement results. In some implementations, each of the additional report configuration(s) includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the additional RS resource configuration(s). After the UE 102 performs an LTM serving cell change to the cell 1 from the cell 124A, the UE 102 communicates 436 with the S-DU 174B and transmits measurement results on the UL resource(s) via the cell 1 to the S-DU 174B, in accordance with the additional report configuration(s). Correspondingly, the S-DU 174B receives the measurement results on the UL resource (s) via the cell 1 from the UE 102, in accordance with the additional report configuration(s). In some implementations, each of the measurement results includes one or more RS resource indicators and/or one or more quantized measurement values. The UE 102 performs measurements on the additional RS(s) or the additional RS resource(s) in accordance with the additional RS resource configuration(s) and/or the additional report configuration(s) and obtains the quantized measurement values from the measurements. In some implementations, the RS resource indicator(s) indicates the additional RS(s) or a RS resource(s) where the UE 102 performs measurements or obtains the quantized measurement values. In some implementations, the RS resource indicator(s) includes one or more SSB resource indicators (SSBRI(s)) and/or one or more CSI-RS resource indicators (CRI(s)). In some implementations, the quantized measurement values includes one or more Ll-RSRP values and/or one or more Ll-SINR values.
[0198] In some implementations, the T-DU 174B similarly generates RS resource configuration(s) 2, ..., N, and/or N+l, ..., N+M and/or report configuration(s) 2, ..., N, and/or N+l, ..., N+M, considering or based on the RS resource configuration(s) X, and includes the RS resource configuration(s) 2, ..., N, and/or N+l, ..., N+M and/or the report configuration(s) 2, ..., N, and/or N+l, ..., N+M in the LTM DU configuration(s) 2, ..., N, and/or N+l, ..., N+M, respectively, as described above.
[0199] In other implementations, the LTM DU configuration X of the procedure 380 includes at least one TCI state configuration X, where 1 < X < N. Each of the TCI state configuration(s) X configures a TCI state that associates one or two DL RSs with a corresponding QCL type. In some implementations, the DL RS(s) are associated with the cell X operated by the S-DU 174A. In some implementations, each of the TCI state configuration(s) X includes a TCI state ID. In some implementations, each of the TCI state configuration(s) X is a TCl-State IE. In some implementations, the TCI state configuration(s) X includes/is/are a ul-TCl-ToAddModList-rl7 field, one or more TCl-UL-State-rl7 IES, a dl- OrJointTCl-StateToAddModList-rl7 field, one or more TCl-State IEs, TC ActivatedConfig IE and/or a tci-StatesToAddModList field. In some implementations, the LTM DU configuration X includes a PDSCH-Config IE and the PDSCH-Config IE includes the TCI state configuration(s) X. In some implementations, the T-DU 174B generates at least one TCI state configuration 1, considering or based on the TCI state configuration(s) X and includes the TCI state configuration(s) 1 in the LTM DU configuration 1. In some implementations, the TCI state configuration(s) 1 includes the TCI state configuration(s) X. In other implementations, the T-DU 174B includes each of the TCI state configuration(s) X in the TCI state configuration(s) 1, except the TCI state ID(s) in the TCI state configuration(s) X. The T-DU 174B assigns a TCI state ID to a value for each of the TCI state configuration(s) 1 (e.g., including the TCI state configuration(s) X) and includes the TCI state ID in the corresponding TCI state configuration. In some implementations, the UE 102 and the S-DU 174B communicate 436 with one another, the S-DU 174B transmits an LTM command to the UE 102 to command the UE 102 to perform a fast serving cell change to the cell X. The S-DU 174B includes a TCI state ID in the LTM command to indicate to the UE 102 to apply a TCI state configuration identified by the TCI state ID to communicate on the cell X, where the TCI state configuration is one of the TCI state configuration(s) X or includes configurations of one of the TCI state configuration(s) X.
[0200] In further implementations, the T-DU 174B similarly generates TCI state configuration(s) 2, .. N, considering or based on the RS resource configuration(s) X, and includes the TCI state configuration(s) 2, .. N, and/or N+l, .. N+M in the LTM DU configuration(s) 2, N, and/or N+l, ..., N+M, respectively, as described above.
[0201] In some implementations, in cases where the CU 172 performs the procedure 380 after performing the procedure 490, the CU 172 includes the LTM DU configuration(s) 1, ..., N of the procedure 490 in the CU-to-DU message of the procedure 380, and the S-DU 174A generates the LTM DU configuration(s) 1, ..., N of the procedure 380, considering or based on configurations in the LTM DU configuration(s) of the procedure 490, in a similar way as described above.
[0202] In some implementations, the CU 172 assigns ID(s) 1, ..., N identifying the LTM DU configuration(s) 1, ..., N (e.g., received from the T-DU 174B), respectively, and performs the procedure 492 with the T-DU 174B to provide the ID(s) 1, ..., N and/or cell ID(s) 1, ..., N to the T-DU 174B, similar to the procedure 392. Thus, the T-DU 174B associates the ID(s) 1, ..., N with the LTM DU configuration(s) 1, ..., N and/or the cell ID(s) 1, ..., N, respectively. In other implementations, the T-DU 174B assigns ID(s) 1, ..., N identifying the LTM DU configuration(s) 1, ..., N (generated by the T-DU 174B), respectively and includes the ID(s) 1, ..., N in the DU-to-CU message of the procedure 490, similar to the event 310. In some implementations, the CU 172 assigns ID(s) N+l, ..., N+M identifying the LTM DU configuration(s) N+l, ..., N+M, respectively, and performs a procedure (e.g., similar to the procedure 492) with the T-DU 174B to provide the ID(s) N+l, ..., N+M and/or cell ID(s) N+l, ..., N+M to the T-DU 174B, similar to the procedure 392. Thus, the T-DU 174B associates the ID(s) N+l, ..., N+M with the LTM DU configuration(s) N+l, ..., N+M and/or the cell ID(s) N+l, ..., N+M, respectively. In other implementations, the T-DU 174B assigns ID(s) N+l, ..., N+M identifying the LTM DU configuration(s) N+l, ..., N+M, respectively and includes the ID(s) 1, ..., N in the DU-to-CU message of the additional LTM preparation procedure, similar to the event 310.
[0203] In some implementations, the CU 172 transmits 412 a CU-to-DU message including the ID(s) 1, ..., N to the S-DU 174A and receives 414 a DU-to-CU message from the S-DU 174A in response. The CU-to-DU message 412 and DU-to-CU message 414 are collectively referred to in Fig. 4 as a LTM ID transfer procedure 493 or a LTM cell index transfer procedure 493. In some implementations, the message 412 and message 414 is a UE Context Modification Request message and a UE Context Modification Response message, respectively. In some implementations, the CU 172 includes 412 the LTM DU configuration(s) 1, ..., N and/or cell ID(s) 1, ..., N in the CU-to-DU message. In some implementation, the CU 172 includes 412 the ID(s) 1, ..., N in the CU-to-DU message. In some implementations, the CU 172 includes 412 the cell index(es) 1, ..., N in the CU-to-DU message. In further implementations, the CU 172 performs multiple LTM ID transfer procedures to transmit the ID(s) 1, ..., N, cell ID(s) 1, ..., N and/or LTM DU configuration(s) 1, ..., N to the S-DU 174A. In each of the procedures, the CU 172 includes a particular portion of the 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 the message 412. Thus, the S-DU 174A associates the ID(s) 1, ..., N with the LTM DU configuration(s) 1, ..., N and/or the cell ID(s) 1, ..., N, respectively. In yet further implementations, the CU 172 performs multiple LTM cell index transfer procedures to transmit the cell index(es) 1, ..., N, cell ID(s) 1, ..., N and/or LTM DU configuration(s) 1, ..., N to the S-DU 174A. In each of the procedures, the CU 172 includes a particular portion of the cell index(es) 1, ..., N, cell ID(s) 1, ..., N and/or LTM DU configuration(s) 1, ..., N in a CU-to-DU message similar to the message 412. Thus, the S-DU 174A associates the cell index(es) 1, ..., N with the LTM DU configuration(s) 1, ..., N and/or the cell ID(s) 1, ..., N, respectively.
[0204] In some implementations, the S-DU 174A generates a first serving DU configuration, based on the LTM DU configuration(s) 1, 2,... , and/or N, and includes 414 the first serving DU configuration in the DU-to-CU message. In some implementations, the first serving DU configuration includes 402 configurations updating (e.g., augmenting, modifying or replacing) the serving DU configuration. In other implementations, the first serving DU configuration includes 402 configurations that are not included in the serving DU configuration. The CU 172 transmits an RRC reconfiguration message including the first serving DU configuration to the UE 102. The UE 102 applies the first serving DU configuration to communicate with the serving DU upon receiving the RRC reconfiguration message. Lor example, the RRC reconfiguration message is or is similar to the RRC reconfiguration message in the procedure 494. In some implementations, the UE 102 communicates 402 with the S-DU 174A using configurations included in the serving DU configuration that are not updated by the first serving DU configuration. The following are example implementations of generating the first serving DU configuration based on the LTM DU configuration 1, N.
[0205] In some implementations, the LTM DU configuration Y of the procedure 490 includes at least one RS resource configuration Y, where 1 < Y < N. Each of the RS resource configuration(s) Y configures one or more RSs or one or more RS resources associated with the cell Y of the T-DU 174B. The RS(s) includes SSB(s) and/or CSLRS(s). The RS resource(s) includes SSB resource(s) and/or CSLRS resource(s). In some implementations, each of the RS resource configuration(s) Y includes a RS resource configuration ID. In some implementations, the RS resource configuration(s) Y is/are (e.g., similar to) CS1- ResourceConfig IE(s). In some implementations, the LTM DU configuration Y includes a CSl-MeasConfig IE and the CSl-MeasConfig IE includes the CSl-ResourceConfig IE(s). The S-DU 174A generates at least one serving report configuration for reporting, on the cell 124A, measurement results of the RS(s) or RS resource(s) and includes the serving report configuration(s) in the first serving DU configuration. In some implementations, the serving report configuration(s) is/are (e.g., similar to) CSl-ReportConfig IE(s). In some implementations, the S-DU 174A generates at least one serving RS resource configuration, considering or based on the RS resource configuration(s) Y and includes the serving RS resource configuration(s) in the first serving DU configuration. In some implementations, the S-DU 174A includes the RS resource configuration(s) Y in the serving RS resource configuration(s). In other implementations, the S-DU 174A includes each of the RS resource configuration(s) Y in the serving RS resource configuration(s), except the RS resource configuration ID(s) in the RS resource configuration(s) Y. The S-DU 174A assigns an RS resource configuration ID to a value for each of the serving RS resource configuration(s) (e.g., including the RS resource configuration(s) Y) and includes the RS resource configuration ID in the corresponding serving RS resource configuration.
[0206] In some implementations, the serving report configuration(s) configures one or more UL resources (e.g., PUCCH resources or PUSCH resources) on the cell 124A for the UE 102 to transmit measurement results. In some implementations, each of the serving report configuration(s) includes one or more RS resource configuration IDs identifying one or more RS resource configurations included in the serving RS resource configuration(s). While the UE 102 communicates with the S-DU 174A, the UE 102 transmits measurement results on the UL resource(s) via the cell 124A to the S-DU 174A, in accordance with the serving report configuration(s) (e.g., event 424). Correspondingly, the S-DU 174A receives the measurement results on the UL resource(s) via the cell 124A from the UE 102, in accordance with the serving report configuration(s). In some implementations, each of the measurement results includes one or more RS resource indicators and/or one or more quantized measurement values. The UE 102 performs measurements on the RS(s) or the RS resource(s) in accordance with the serving RS resource configuration(s) and/or the serving report configuration(s) and obtains the quantized measurement values from the measurements. In some implementations, the RS resource indicator(s) indicates the RS(s) or a RS resource(s) where the UE 102 perform measurements or obtains the quantized measurement values. In some implementations, the RS resource indicator(s) includes one or more SSB resource indicators (SSBRI(s)) and/or one or more CSI-RS resource indicators (CRI(s)). In some implementations, the quantized measurement values includes one or more Ll-RSRP values and/or one or more Ll-SINR values.
[0207] In other implementations, the LTM DU configuration Y of the procedure 490 includes at least one TCI state configuration Y, where 1 < Y < N. Each of the TCI state configuration(s) Y configures a TCI state that associates one or two DL RSs with a corresponding QCL type. In some implementations, the DL RS(s) are associated with the cell Y operated by the T-DU 174B. In some implementations, each of the TCI state configuration(s) Y includes a TCI state ID. In further implementations, each of the TCI state configuration(s) Y is a TCl-State IE. In yet further implementations, the TCI state configuration(s) Y includes/is/are an ul-TCl-ToAddModList-rl7 field, one or more TC1-UL- State-rl7 IES, a dl-OrJointTCl-StateToAddModList-rl7 field, one or more TCl-State IES, TC ActivatedConfig IE and/or a tci-StatesToAddModList field. In some implementations, the LTM DU configuration Y includes a PDSCH-Config IE and the PDSCH-Config IE includes the TCI state configuration(s) Y. In some implementations, the S-DU 174A generates at least one serving TCI state configuration, considering or based on the TCI state configuration(s) Y and includes the serving TCI state configuration(s) in the first serving DU configuration. In some implementations, the serving TCI state configuration(s) 1 includes the TCI state configuration(s) Y. In further implementations, the S-DU 174A includes each of the TCI state configuration(s) Y in the serving TCI state configuration(s), except the TCI state ID(s) in the TCI state configuration(s) Y. The S-DU 174A assigns a TCI state ID to a value for each of the serving TCI state configuration(s) (including the TCI state configuration(s) Y) and includes the TCI state ID in the corresponding serving TCI state configuration. In some implementations, the S-DU 174A communicates 436 with the UE 102 and the S-DU 174A transmits a LTM command to the UE 102 to command the UE 102 to perform a fast serving cell change to the cell Y. The S-DU 174A includes a TCI state ID in the LTM command to indicate to the UE 102 to apply a TCI state configuration identified by the TCI state ID to communicate on the cell Y, where the TCI state configuration is one of the TCI state configuration(s) Y or includes configurations of one of the TCI state configuration(s) Y.
[0208] In some implementations, the CU 172 transmits a CU-to-DU message including the ID(s) N+l, .. N+M to the S-DU 174A and receives a DU-to-CU message from the S-DU 174A in response, similar to the CU-to-DU message 412 and the DU-to-CU message 414, respectively. In some implementations, the CU 172 includes the LTM DU configuration(s) N+l, ..., N+M and/or cell ID(s) N+l, ..., N+M in the CU-to-DU message. In further implementations, the CU 172 performs multiple LTM ID transfer procedures to transmit the ID(s) N+l, ..., N+M, cell ID(s) N+l, ..., N+M and/or LTM DU configuration(s) N+l, ..., N+M to the S-DU 174A. In each of the procedures, the CU 172 includes a particular portion of the ID(s) N+l, ..., N+M, cell ID(s) N+l, ..., N+M and/or LTM DU configuration(s) 1, ..., N in a CU-to-DU message similar to the message 412. Thus, the S-DU 174A associates the ID(s) N+l, ..., N+M with the LTM DU configuration(s) N+l, ..., N+M and/or the cell ID(s) N+l, ..., N+M, respectively. In some implementations, the S-DU 174A generates a second serving DU configuration, based on the LTM DU configuration(s) N+l, N+2, ..., and/or N+M, and includes the second serving DU configuration in the DU-to-CU message. In some implementations, the second serving DU configuration includes 402 configurations updating (e.g., augmenting, modifying or replacing) the first serving DU configuration and/or updating configurations included in the serving DU configuration and not updated by the first serving DU configuration. In further implementations, the second serving DU configuration includes configurations that are not included in the first serving DU configuration. The CU 172 transmits an RRC reconfiguration message including the second serving DU configuration to the UE 102 via the S-DU 174A. The UE 102 applies the second serving DU configuration to communicate with the serving DU upon receiving the RRC reconfiguration message. Lor example, the RRC reconfiguration message is or is similar to the RRC reconfiguration message in the procedure 494. In some implementations, the UE 102 communicates 402 with the S-DU 174A using configurations included in the serving DU configuration and/or the first serving DU configuration that are not updated by the second serving DU configuration. In some implementations, the S-DU 174A generates one or more new LI measurement configurations, based on LI measurement configuration(s) in the LTM DU configuration(s) N+l, N+2,... , and/or N+M, and includes the new LI measurement configuration(s) in the second serving DU configuration. In some implementations, the S-DU 174A generates one or more new TCI state configuration, based on TCI state configuration(s) in the LTM DU configuration(s) N+l, N+2,... , and/or N+M, and includes the new TCI state configuration(s) in the second serving DU configuration.
[0209] In some implementations, the CU 172 and S-DU 174A perform 380 the procedure with the UE 102, the value(s) of the ID(s) 1, ..., N of the procedure are different from the value(s) of the ID(s) 1, ...., N, and the ID(s) N+l ,...., N+M described for the scenario 400. In some implementations, the CU 172 and S-DU 174A perform 380 the procedure with the UE 102, the value(s) of the cell ID(s) 1, ..., N of the procedure are different from the value(s) of the cell ID(s) 1, ...., N, and the cell ID(s) N+l ,...., N+M described for the scenario 400. In some implementations, the CU 172 and S-DU 174A perform 380 the procedure with the UE 102, the value(s) of the cell index(es) 1, ..., N of the procedure are different from the value(s) of the cell index(es) 1, ...., N, and the cell index(es) N+l ,...., N+M described for the scenario 400.
[0210] In some implementations, the UE 102 transmits 424 at least one measurement report to the S-DU 174A, similar to the event 324. The at least one measurement report (e.g., LI measurement report(s)) includes an event ID, first measurement result(s) for the cell 1 of the T-DU 174B, and/or includes second measurement result(s) for the cell 124A. In some implementations, the first measurement result(s) are or include RSRP, RSRQ, and/or SINR that the UE 102 obtains from reference signal(s) transmitted on the cell 1. In further implementations, the second measurement result(s) are or include RSRP, RSRQ, and/or SINR that the UE 102 obtains from reference signal(s) transmitted on the cell 124A. In some implementations, the event ID, RSRP, RSRQ and/or SINR are Ll-event ID, Ll-RSRP, Ll- RSRQ and/or Ll-SINR, respectively. In some implementations, based on the first measurement result(s) and/or second measurement result(s), the S-DU 174A transmits 430 a first LTM command (i.e., LTM command 1) including the ID 1 to the UE 102 to order the UE 102 to perform a serving cell change to the cell 1 of the T-DU 174B. In some implementations, the first LTM command includes the ID 1. In further implementations, the first LTM command includes the cell index 1. When the UE 102 receives the first LTM command, the UE 102 performs a serving cell change to the cell 1 from a serving cell in accordance with the LTM DU configuration 1. In some implementations, after (e.g., in response to) receiving the first LTM command, the UE 102 performs 432 a random access procedure with the T-DU 174B, similar to the event 332. In some implementations, after (e.g., in response to) receiving the first LTM command or completing 432 the random access procedure, the UE 102 communicates 436 with the T-DU 174B on the first cell using the LTM DU configuration 1 and/or reference LTM DU configuration and communicates with the CU 172 via the T-DU 174B, similar to the event 336. In some implementations, when a serving cell change occurs in the procedure 380, the serving cell is cell 1 or cell 2 of the S- DU 174A. Otherwise, if no serving cell change occurs in the procedure 380 or the procedure 380 is not performed, the serving cell is the cell 124A. If the first LTM command includes the ID 1, the UE 102 identifies the LTM DU configuration 1 and/or cell ID 1 (i.e., the cell 1), based the ID 1, as described for Eig. 3. If the first LTM command includes the cell index 1, the UE 102 identifies the LTM DU configuration 1, cell ID 1 (i.e., the cell 1), and/or LTM ID 1 based on the cell index 1 as described for Eig. 3. The UE 102 applies the LTM DU configuration 1 to communicate with the T-DU 174B, after (e.g., in response to) receiving the first LTM command or successfully accessing the cell 1.
[0211] In some implementations, when or in response to determining to activate the LTM DU configuration 1 or transmit 430 the first LTM command, the S-DU 174A transmits 429 to the CU 172 a DU-to-CU message indicating LTM execution. In some implementations, the S-DU 174A includes 429 the cell ID 1 or the ID 1 (i.e., LTM ID) in the DU-to-CU message to indicate that the S-DU 174A is to activate the LTM DU configuration 1 or trigger a LTM serving cell change. In further implementations, the S-DU 174A transmits 429 the DU-to- CU message to the CU 172 before or after transmitting 430 the LTM command. In some implementations, when or after the CU 172 receives 429 the DU-to-CU message, the CU 172 stops or suspends transmitting DL data for the UE 102 to the S-DU 174A until receiving 434 the DU-to-CU message. After receiving 434 the DU-to-CU message, the CU 172 starts, continues, or resumes transmitting DL data for the UE 102 to the T-DU 174B. When or after the T-DU 174B detects that UE 102 accesses the cell 1, the T-DU 174B transmits the DL data to the UE 102 via the cell 1.
[0212] In some implementations, the resource release procedure 496 is similar to the procedure 396. In some implementations, in the resource release procedure 496, the CU 172 transmits a CU-to-DU message (e.g., a UE Context Release Command message) to the S-DU 174A to release a UE context of the UE 102. In response, the S-DU 174A releases a UE context of the UE 102 and transmits 440 a DU-to-CU message (e.g., a UE Context Release Complete message) to the CU-172.
[0213] The events 380, 404, 406, 490, 492, 494, 494, 424, 426, 428, 429, 430, 431, 432, 434, 436, 496, 498, 456 are collectively referred to in Fig. 4 as a LTM configuration and/or activation procedure 480.
[0214] Referring next to Fig. 5A, in a scenario 500A, the base station 106 operates as an MN, and the base station 104 operates as an SN. The SN 104 includes a CU 172 and a DU 174. The scenario 500A is similar to the scenario 300, except that the scenario 500A is a DC scenario and the scenario 300 is a single connectivity (SC) scenario. In some implementations, the MN 106 includes a CU and a DU similar to the base station 104 of Fig. 3.
[0215] Initially, the UE 102 in DC communicates with the MN 106 and with SN 104. In the event 502, the UE 102 communicates with the DU 174 on cell 124A using a serving DU configuration and communicates with the CU 172 via the DU 174 using a serving CU configuration, similar to the event 302. In some implementations, the UE 102 does not communicate 302 with the CU 172 via the DU 174. In some implementations, the UE 102 in DC communicates 502 UL PDUs and/or DL PDUs with the MN 106 and/or SN 104 via radio bearers which include SRBs and/or DRB(s). In some implementations, the MN 106 and/or the SN 104 configures the radio bearers to the UE 102. The UE 102 in DC communicates 502 UL PDUs and/or DL PDUs with the SN 104 on an SCG (i.e., SCG radio resources) that the SN 104 configures for communication with the UE 102. The UE 102 in DC communicates UL PDUs and/or DL PDUs with the MN 106 on an MCG (i.e., MCG radio resources) in accordance with a MN configuration (i.e., MCG configuration). In some implementations, the serving DU configuration is a SN configuration (i.e., SCG configuration). In the MN configuration, the MN 106 configures the MCG which includes at least one serving cell (e.g., the cell 126 and/or other cell(s)) operated by the MN 106. In the serving DU configuration, the SN 106 A configures the SCG which includes at least one serving cell (e.g., the cell 124A and/or other cell(s)) operated by the SN 104. In some implementations, the MN configuration includes multiple configuration parameters, and the UE 102 receives the configuration parameters in one or more RRC messages from the MN 106. As described for Fig. 3, the serving DU configuration includes multiple configuration parameters. In some implementations, the UE 102 receives these configuration parameters in one or more RRC messages from the SN 104, e.g., via the MN 106 and/or on an SRB (e.g., SRB3) that the MN 106 or SN 104 configures to exchange RRC messages between the UE 102 and the SN 104.
[0216] In some implementations, while the UE 102 communicates in DC with the MN 106 and SN 104, the MN 106 performs 580 a LTM DU configuration and/or activation procedure with the UE 102, similar to the procedures 380 and/or 480. In some implementations, while communicating in DC with the MN 106 and SN 104, the UE 102 transmits the at least one measurement report to the CU 172 via the DU 174 and cell 124A in the events 504 and 506, similar to the events 304 and 306, respectively. In further implementations, while communicating in DC with the MN 106 and SN 104, the UE 102 transmits 505 at least one measurement report to the MN 106 via the cell 126. The MN 106 in turn transmits 507 the at least one measurement report to the CU 172. In some implementations, the MN 106 generates at least one SN message including the at least one measurement report and transmits 507 the at least one SN message to the CU 172. In one implementation, the at least one SN message includes an RRC Transfer message(s) and/or an SN Modification Request message(s).
[0217] After (e.g., in response to) receiving the at least one measurement report or while the SN 104 communicates with the UE 102, the SN 104 determines to prepare the first cell for the UE 102, as described for Fig. 3. The events 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, and 556 are similar to the 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, transmitting 531 the acknowledgement, or determining that the UE 102 successfully connects 532 or 536 to the first cell, the UE 102 operating in DC with the MN 106 and SN 104 communicates 536 with the DU 174 on the first cell in accordance with the LTM DU configuration 1 and communicates 536 with the CU 172 via the DU 174, similar to the event 336. In some implementations, the DU 174 and/or CU 172 later performs the LTM execution procedure 598 with the UE 102 to command the UE 102 to perform a cell change from the first cell to the second cell, similar to the procedure 398 or 498. As a result of the procedure 598, the UE 102 operating in DC with the MN 106 and SN 104 communicates 556 with the DU 174 on the second cell in accordance with the LTM DU configuration 2 and communicates 556 with the CU 172 via the DU 174, similar to the event 356. [0218] The events 504, 506, 505, 507, 590, 592, 594, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, 556 are collectively referred to in Fig. 5A as a LTM DU configuration and/or activation procedure 581.
[0219] Referring next to Fig. 5B, a scenario 500B is generally similar to the scenario 500A, except that the SN 104 transmits 517, 519 the RRC reconfiguration message to the UE 102 via the MN 106 and receives 521, 523 the RRC reconfiguration complete message from the UE 102 via the MN 106. The RRC reconfiguration message 517, 519 is similar to the RRC reconfiguration message 316, 318. The RRC reconfiguration complete message 521, 523 is similar to the RRC reconfiguration message 320, 322. In some implementations, the SN 104 generates a first SN message (e.g., SN Modification Required message, SN Modification Required message, or RRC Transfer message) including the RRC reconfiguration message and transmits 517 the first SN message to the MN 106. The MN 106 generates a MN RRC message including the RRC reconfiguration message and transmits 519 the MN RRC message to the UE 102. In response, the UE 102 generates a MN RRC response message including the RRC reconfiguration complete message and transmits 521 the MN RRC response message to the MN 106. In some implementations, the MN 106 generates a second SN message (e.g., the SN Reconfiguration Complete message or the RRC Transfer message) including the RRC reconfiguration complete message and transmits 523 the second SN message to the SN 104. In some implementations, the MN RRC message and MN RRC response message is an RRC reconfiguration message and an RRC reconfiguration complete message, respectively.
[0220] The events 504, 506, 505, 507, 590, 592, 594, 517, 519, 521, 523, 524, 526, 528, 529, 530, 531, 532, 534, 536, 596, 598, 556 are collectively referred to in Fig. 5B as an LTM DU configuration and/or activation procedure 582.
[0221] Referring next to Fig. 6A, in a scenario 600A, the base station 106 operates as an MN, and the base station 104 operates as an SN, similar to the scenarios 300-500B. The SN 104 includes a CU 172, an S-DU 174A and a T-DU 174B, similar to the base station 104 in the scenario 400. In some implementations, while the UE 102 communicates in DC with the MN 106 and SN 104, the MN 106 performs 680 an LTM DU configuration and/or activation procedure with the UE 102, similar to the procedures 380 and/or 480. In some implementations, while the UE 102 communicates in DC with the M-DU 174A and S-DU 174B, the CU 172 performs 681 an LTM DU configuration and/or activation procedure with the UE 102 via the M-DU 174A or S-DU 174B, similar to the procedure 581 or 582.
[0222] Referring next to Fig. 6B, scenario 600B is similar to the scenarios 300-500B and 600A, except that that the SN 104 transmits 617, 619 the RRC reconfiguration message to the UE 102 via the MN 106 and receives 621, 623 the RRC reconfiguration complete message from the UE 102 via the MN 106.
[0223] Referring next to Fig. 7A, in a scenario 700A, the base station 104 operates as an MN and as an SN, similar to the scenarios 300-600B. The base station 104 includes a CU 172, a master DU (M-DU) 174A and a secondary DU (S-DU) 174B. The CU 172 operates with the M-DU 174A as an MN, similar to the base station 104 in Fig. 3 or the MN 106 in Figs. 5A-6B, and the CU 172 operates with the S-DU 174B as an SN, similar to the SN 104 in Figs. 5A-6B.
[0224] In the scenario 700A, the UE 102 initially communicates 702 in DC with the M-DU 174A and S-DU 174B and communicates 702 with the CU 172 via the M-DU 174A and S- DU 174B. The UE 102 communicates 702 with the S-DU 174B on cell 124A using a serving DU configuration and communicates with the CU 172 via the S-DU 174B using a serving CU configuration, similar to the event 302. Events 704 and 706 are similar to the events 304 and 306. In some implementations, the UE 102 transmits 705 at least one measurement report to the M-DU 174A, similar to the event 304. The M-DU 174A in turn transmits 707 at least one DU-to-CU message including the at least one measurement report to the CU 172, similar to the event 306. In some implementations, while the UE 102 communicates in DC with the M- DU 174A and S-DU 174B, the CU 172 performs 780 an LTM DU configuration and/or activation procedure with the UE 102 via the M-DU 174A, similar to the procedure 380.
[0225] The events 704, 706, 705, 707, 790, 792, 794, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, 756 are collectively referred to in Fig. 7A as an LTM configuration and/or activation procedure 781.
[0226] Referring next to Fig. 7B, scenario 700B is similar to the scenarios 300-600B and 700A, except that the CU 172 transmits 717, 719 the RRC reconfiguration message to the UE 102 via the M-DU 174A and receives 721, 723 the RRC reconfiguration complete message from the UE 102 via the M-DU 174A. [0227] The events 704, 706, 705, 707, 790, 792, 794, 717, 719, 721, 723, 724, 726, 728, 729, 730, 731, 732, 734, 736, 796, 798, 756 are collectively referred to in Fig. 7B as an LTM DU configuration and/or activation procedure 782.
[0228] Referring next to Fig. 8A, in scenario 800A, the base station 104 operates as an MN and an SN, similar to the scenarios 300-700B. The base station 104 includes a CU 172, a master DU (M-DU) 174A, a secondary DU (S-DU) 174B and a target secondary DU (T-DU) 174C. The CU 172 operates with the M-DU 174A as an MN and operates with the S-DU 174B as an SN. In some implementations, while the UE 102 communicates in DC with the M-DU 174A and the S-DU 174B, the CU 172 performs 880 an LTM DU configuration and/or activation procedure with the UE 102 via the M-DU 174A, similar to the procedure 380. In further implementations, while the UE 102 communicates in DC with the M-DU 174 A and the S-DU 174B, the CU 172 performs 881 an LTM DU configuration and/or activation procedure with the UE 102 via the S-DU 174A, similar to the procedure 581 or 582.
[0229] Referring next to Fig. 8B, scenario 800B is similar to the scenarios 300-700B and 800A, except that that the CU 172 transmits 817, 819 the RRC reconfiguration message to the UE 102 via the M-DU 174A and receives 821, 823 the RRC reconfiguration complete message from the UE 102 via the M-DU 174A.
[0230] In some implementations, a RAN node such as a base station, a DU or a CU, or a UE implements early timing advance (TA) acquisitions for LTM, are discussed next with reference to Figs. 9A-14. At least some of the discussion of Figs. 3-8B can apply to Figs. 9A- 14.
[0231] Fig. 9A illustrates an example method 900A, for a UE (e.g., the UE 102 in Figs. 3- 8B) can implement to handle early TA acquisition with a RAN (e.g., the RAN 105, or the base station 104 and 106 in Figs. 3-8B).
[0232] The method 900A begins at block 902, where the UE communicates with a RAN via a serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). At block 909, the UE starts a first time alignment timer for uplink synchronization with the serving cell, while communicating with the RAN via the serving cell. At block 918, the UE receives an LTM configuration from the RAN, where the LTM configuration configures 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 a target cell or a candidate cell for LTM. At block 925, the UE receives a first command from the RAN via the serving cell, where the first command commands the UE to transmit a random access preamble on the first cell.
[0233] At block 927, the UE transmits a first random access preamble on the first cell to the RAN in response to the first command. At block 930A, the UE receives an LTM command from the RAN via the serving cell, where the LTM command commands the UE to connect to the first cell and includes the 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). At block 941, the UE resets a MAC entity in response to receiving the LTM command. In some implementations, the UE at block 902 communicates with the RAN using the MAC entity. At block 932, the UE accesses the first cell in response to receiving the 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). At block 947, the UE starts a second time alignment timer for uplink synchronization with the first cell. At block 936, the UE communicates with the RAN on the first cell using the TA value and the LTM configuration (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).
[0234] In some implementations, the UE receives the first command while the first time alignment timer is running. In other implementations, the UE receives the first command while the first time alignment timer is not running. In some implementations, the UE disconnects from the serving cell upon receiving the LTM command. In further implementations, the UE disconnects from the serving cell upon successfully accessing the first cell. In some implementations, when the UE successfully accesses the first cell, the UE determines the first cell as a new serving cell.
[0235] In some implementations, the UE starts the second time alignment timer after (e.g., in response to) receiving the LTM command. In some implementations, the UE starts the second time alignment timer after resetting the MAC entity. In further implementations, the UE starts the 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 expires, when resetting the MAC entity. In some implementations, the UE stops the first time alignment timer and determines that the first time alignment timer expired, in response to resetting the MAC entity. [0236] In some implementations, at block 902, the UE starts MAC timers associated with the MAC entity for communicating with the RAN via the serving cell. The UE stops the MAC timers in response to resetting the MAC entity. In some implementations, the MAC timers include timers for operating discontinuous reception (DRX) with the RAN on the serving cell. In some implementations, the MAC timers include one or more timers for HARQ operation with the RAN on the serving cell.
[0237] In some implementations, the RAN obtains a TA value for the UE and the first cell according to the time when the RAN receives the first random access preamble. In some implementations, after transmitting the first random access preamble, the UE continues communicating with the RAN via the serving cell until receiving the LTM command.
[0238] In some implementations, the LTM configuration includes an LTM DU configuration configuring a first cell for LTM as described above. In some implementations, the RAN includes the LTM DU configuration in an RRC message (e.g., an RRC reconfiguration message) and includes the RRC message in the LTM configuration. In some implementations, the RAN includes an LTM CU configuration in the RRC message. The LTM CU configuration and LTM DU configuration include configurations as described above. In some implementations, the LTM configuration is an LTM-Candidate IE or an LTM-CandidateToAddMod IE. In other implementations, the LTM configuration is an LTM- Config IE.
[0239] In some implementations, the first command includes configuration parameters such as a first random access preamble index, an indicator indicating a UL or a supplementary UL (SUL), an SSB index, and/or a physical random access channel (PRACH) mask index. The first random access preamble index indicates, identifies, or indexes the first random access preamble. Thus, the UE generates or selects the first random access preamble in accordance with the first random access preamble index. In some implementations, the PRACH mask index configures one or more PRACH occasions. The UE determines a PRACH occasion to transmit the first random access preamble based on the SSB index and/or the PRACH mask index. In some implementations, the indicator set to 0 indicates UL and the indicator set to 1 indicates SUL. The UE transmits the first random access preamble on UL or SUL of the first cell in accordance with the indicator. In some implementations, the first command includes an identifier for DCI formats and/or a frequency domain resource assignment field. In some implementations, the identifier for DCI formats is set to zero for the first format and the second format. In some implementations, all the bits in the frequency domain resource assignment field are set to zero.
[0240] In some implementations, the LTM configuration includes random access configuration parameters. In some implementations, the random access configuration parameters include a PRACH root sequence index and/or a subcarrier spacing of PRACH. In some implementations, the UE generates or selects the first random access preamble using the PRACH root sequence index and the first random access preamble index. In some implementations, the LTM configuration includes a random access channel (RACH) configuration that includes the random access configuration parameters. The UE transmits the first random access preamble on the first cell, using 1) the random access configuration parameters and 2) the indicator (e.g., indicating UL or SUL), the SSB index, and/or the PRACH mask index.
[0241] In some implementations, the LTM configuration includes a cell ID (e.g., PCI) of the first cell. In some implementations, the first command includes a (new) field indicating the first cell where a random access preamble (e.g., the first random access preamble) is (to be) transmitted. In some implementations, the new field includes the cell ID of the first cell. Based on the cell ID included in the first command, the UE determines the first cell is the cell where the UE is to transmit the first random access preamble. The UE identifies the LTM configuration based on the cell ID. In other implementations, the LTM configuration includes a cell index for the first cell and the new field includes the cell index. 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 the first cell is the cell where the UE is to transmit the first random access preamble. In further implementations, the new field includes an LTM ID identifying the LTM configuration and the UE identifies the LTM configuration in accordance with the LTM ID. The UE receives the LTM ID together with the LTM configuration as described above. Based on the cell ID included in the LTM configuration, the UE determines the first cell is the cell where the UE is to transmit the first random access preamble.
[0242] In some implementations, the UE receives other LTM configurations from the RAN and each of the other LTM configurations configures a cell and includes a cell ID identifying the cell, as described for Eigs. 3-8B. In some implementations, each of the other LTM configurations configures a cell and includes a cell index indicating the cell, as described for Figs. 3-8B. In some implementations, each of the other LTM configurations configures a cell and is associated with a LTM ID, as described for Figs. 3-8B.
[0243] In some implementations, the first command is a DO or a PDCCH order. The UE receives the first command on a PDCCH from the RAN via the serving cell. In other implementations, the first command is a MAC CE. The UE receives a MAC PDU including the first command from the RAN via the serving cell.
[0244] In some implementations, the RAN sets the frequency domain resource assignment field to a specific value (e.g., other than zero) to indicate that the first command includes the new field indicating a cell. The RAN sets all bits in the frequency domain resource assignment field to zero to indicate that the second command does not include the new field indicating a cell. In other implementations, the RAN sets the frequency domain resource assignment field in the first command and the second command to zero.
[0245] In some implementations, the UE transmits the first random access preamble to the RAN on the first cell, using 1) random access configuration parameters included in the LTM configuration and/or 2) the configuration parameters included in the first command.
[0246] In some implementations, the UE receives a RACH configuration from the RAN in addition to the LTM configuration. In some implementations, the UE receives an RRC message including the RACH configuration and the LTM configuration from the RAN (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 random access configuration parameters for the first cell for early TA acquisition. In such cases, the UE transmits the first random access preamble to the RAN on the first cell, using 1) 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.
[0247] In some implementations, the RACH configuration includes a cell ID (e.g., PCI) of the first cell. In some implementations, the first command includes a (new) field indicating the first cell where a random access preamble (e.g., the first random access preamble) is (e.g., to be) transmitted. In some implementations, the new field includes the cell ID of the first cell. Based on the cell ID included in the first command, the UE determines the first cell is the cell where the UE is to transmit the first random access preamble. The UE identifies the RACH configuration based on the cell ID. In other implementations, the RACH configuration includes a cell index for the first cell and the new field includes the cell index. 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 the first cell is the cell where the UE is to transmit the first random access preamble. In further implementations, the new field includes an LTM ID identifying the LTM configuration, and the RACH configuration and the UE identifies the RACH configuration in accordance with the LTM ID. The UE receives the LTM ID together with the LTM configuration and the RACH configuration as described above. Based on the cell ID included in the LTM configuration or the RACH configuration, the UE determines the first cell is the cell where the UE transmits the first random access preamble. In some implementations, the UE receives other RACH configurations from the RAN. In some implementations, each of the other RACH configurations includes random access configuration parameters for a cell for early TA acquisition. In further implementations, each of the other RACH configurations includes a cell ID identifying a cell. In yet further implementations, each of the other RACH configurations includes a cell index indicating a cell. In some implementations, each of the other RACH configurations are associated with an LTM ID, as described above.
[0248] In some implementations, the UE transmits a plurality of UE capabilities to the RAN via the serving cell at block 902. In further implementations, the UE transmits the plurality of UE capabilities to the RAN via another serving cell. In some implementations, the plurality of UE capabilities includes a first UE capability indicating support of LTM. In further implementations, the plurality of UE capabilities includes a second UE capability indicating support of early TA acquisition. In some implementations, the UE receives an early TA acquisition configuration from the RAN to enable or configure early TA acquisition. The UE enables the early TA acquisition in response to receiving the early TA acquisition configuration. When enabling the early TA acquisition, the UE attempts to receive from the RAN via the serving cell, a command (e.g., the first command) that commands the UE to transmit a random access preamble on a target cell or a candidate cell. If the UE does not receive the early TA acquisition configuration, the UE refrains from attempting to receive a command (e.g., the first command) commands the UE to transmit a random access preamble on a target cell or a candidate cell.
[0249] In some implementations, the UE starts the first time alignment timer with a first timer value and starts the second time alignment timer with a second timer value. In some implementations, the first timer value and the second timer value are the same or different. In some implementations, the UE receives a system information block (SIB) (e.g., SIB1) including the first timer value on the serving cell from the RAN. In further implementations, the UE receives an RRC message (e.g., an RRC setup message, an RRC resume message, or an RRC reconfiguration message) including the first timer value from the RAN via the serving cell or another serving cell. In some implementations, the LTM configuration includes the second timer value.
[0250] In some implementations, while communicating with the RAN on the serving cell, the UE receives a TA command including a new TA value from the RAN on the serving cell. The UE adjusts uplink transmission timing with the serving cell based on the new TA value and restarts the first time alignment timer in response to receiving the TA command. In some implementations, the TA command is a MAC CE. In some implementations, while communicating with the RAN on the first cell at block 936, the UE receives a TA command including a new TA value from the RAN on the first cell. The UE adjusts uplink transmission timing with the first cell based on the new TA value and restarts the second time alignment timer in response to receiving the TA command.
[0251] Fig. 9B is a flow diagram of an example method 900B similar to the method 900A, except that method 900B includes block 953 instead of block 947. At block 953, the UE starts or restarts the first time alignment timer for uplink synchronization with the first cell.
[0252] Fig. 9C is a flow diagram of an example method 900C similar to the methods 900A and 900B, except that method 900C includes blocks 930C, 933, 957, 959, 947, and 953 instead of block 930A. At block 930C, the UE receives an LTM command from the RAN via the serving cell, where the LTM command commands the UE to connect to the first cell. At block 933, the UE determines whether the LTM command includes a TA value. If the UE determines that the LTM command includes a TA value at block 933, the flow proceeds to block 932. The flow then proceeds to either block 947 or block 953 from block 932. Otherwise, if the UE determines that the LTM command does not include a TA value at block 933 and the flow proceeds to block 957. At block 957, the UE performs a random access procedure on the first cell with the RAN (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). At block 959, the UE receives a random access response including a TA value from the RAN 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 to block 947 or 953 from block 959. At block 947, the UE starts a second time alignment timer for uplink synchronization with the first cell after (e.g., in response to) receiving the random access response. At block 953, the UE starts or restarts the first time alignment timer for uplink synchronization with the first cell after (e.g., in response to) receiving the random access response. The flow proceeds to block 936 from blocks 947, 953, 947 and 953.
[0253] In some implementations, the UE at block 947 stops the first time alignment timer after (e.g., in response to) the random access response. In other implementations, the UE at block 947 maintains the first timer alignment timer running. In some implementations, when the first time alignment timer expires while the second timer alignment timer is running, the UE communicates with the RAN on the first cell and ignores expiry of the first time alignment timer. In other words, the UE in such cases takes no action in response to expiry of the first time alignment timer.
[0254] Fig. 10A illustrates an example method 1000A, for a RAN (e.g., the RAN 105, or the base station 104, 106 or DU 174, 174A, 174B or 174C in Figs. 3-8B) that manages early TA acquisition for a UE (e.g., the UE 102 in Figs. 3-8B).
[0255] The method 1000A begins at block 1002, where the RAN communicates with a UE via a serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). At block 1009, the RAN starts a first time alignment timer for uplink synchronization with the UE while communicating with the UE via the serving cell. At block 1018, the RAN transmits an LTM configuration to the UE, where the LTM configuration configures 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). At block 1025, the RAN transmits a first command to the UE via the serving cell, where the first command commands the UE to transmit a first random access preamble on the first cell. At block 1027, the RAN receives the first random access preamble on the first cell from the UE. At block 1030A, the RAN transmits an LTM command to the UE via the serving cell, where the LTM command commands the UE to connect to the first cell and includes 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). At block 1041, the RAN resets a MAC entity in response to transmitting the LTM command. In some implementations, the RAN at block 1002 communicates with the UE using the MAC entity (i.e., a first MAC entity). In some implementations, the RAN at block 1002 communicates with the UE using another MAC entity (i.e., a second MAC entity). In further implementations, the RAN resets the MAC entity in response to preparing the first cell for LTM instead of transmitting the LTM command. At block 1032, the RAN detects that the UE accesses the first cell after transmitting the 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). At block 1047, the RAN starts a second time alignment timer for uplink synchronization on the first cell with the UE. At block 1036, the RAN communicates with the UE on the first cell using the TA value, while maintaining the second time alignment timer running (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).
[0256] In some implementations, the RAN obtains (e.g., calculates or derives) a TA value for uplink synchronization with the UE on the first cell according to the time when the RAN receives the first random access preamble. In some implementations, after receiving the first random access preamble, the RAN continues communicating with the UE via the serving cell until transmitting the LTM command.
[0257] In some implementations, the RAN starts the second time alignment timer after (e.g., in response to) receiving the first random access preamble or obtaining the TA value for the UE. In further implementations, the RAN starts the second time alignment timer after transmitting the LTM command. In some implementations, the RAN starts the second time alignment timer after resetting the MAC entity. In further implementations, the RAN starts the second time alignment timer before resetting the MAC entity. In such cases, the RAN refrains from stopping the second time alignment timer and/or determining that the second time alignment timer expires, when resetting the MAC entity. In some implementations, the RAN stops the first time alignment timer and determines that the first time alignment timer expired, in response to resetting the MAC entity.
[0258] In some implementations, at block 1002, the RAN starts MAC timers associated with the MAC entity for communicating with the UE via the serving cell. The RAN stops the MAC timers in response to resetting the MAC entity. In some implementations, the MAC timers include timers for operating DRX with the RAN on the serving cell. In some implementations, the MAC timers include one or more timers for HARQ operation with the UE on the serving cell.
[0259] In some implementations, the RAN receives the 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 implementations, the RAN transmits an RACH configuration to the UE in addition to the LTM configuration. For example, the RAN transmits an RRC message including the RACH configuration and the LTM configuration to the UE (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 random access configuration parameters for the first cell for early TA acquisition. In such cases, the RAN receives the 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) the configuration parameters included in the first command.
[0260] In some implementations, the RAN receives a plurality of UE capabilities via the serving cell from the UE at block 1002. In further implementations, the RAN receives the plurality of UE capabilities from the UE via another serving cell. In yet further implementations, the RAN receives the plurality of UE capabilities from a CN (e.g., the CN 110 or AMF 164). In some implementations, the plurality of UE capabilities includes a first UE capability indicating support of LTM. The RAN transmits the LTM configuration to the UE in response to receiving the first UE capability. In some implementations, the plurality of UE capabilities includes a second UE capability indicating support of early TA acquisition.
In some implementations, the RAN transmits an early TA acquisition configuration to the UE to enable or configure early TA acquisition. When enabling the early TA acquisition for the UE, the RAN transmits to the UE via the serving cell, a command (e.g., the first command) that commands the UE to transmit a random access preamble on a target cell or a candidate cell.
[0261] In some implementations, while communicating with the UE on the serving cell, the RAN transmits a TA command including a new TA value to the UE on the serving cell to adjust uplink transmission timing of the UE with the serving cell. The RAN restarts the first time alignment timer in response to transmitting the TA command. In some implementations, the TA command is a MAC CE. In some implementations, while communicating with the UE on the first cell at block 1036, the RAN transmits a TA command including a new TA value to the UE on the first cell to adjust uplink transmission timing of the UE with the first cell. The RAN restarts the second time alignment timer in response to transmitting the TA command.
[0262] In some implementations, the RAN transmits the first command while the first time alignment timer is running. In further implementations, the RAN transmits the first command while the first time alignment timer is not running.
[0263] Fig. 10B is a flow diagram of an example method 1000B similar to the method 1000A, except that method 1000B includes block 1053 instead of block 1047. At block 1053, the RAN starts or restarts the first time network alignment timer for uplink synchronization on the first cell with the UE in response to transmitting the LTM command.
[0264] Fig. 10C is a flow diagram of an example method 1000C similar to the methods 1000A and 1000B, except that method 1000C includes blocks 1030C, 1033, 1057, 1059, 1047, 1053 and 1036 instead of block 1030A. At block 1013, the RAN transmits a LTM command to the UE via the serving cell, where the LTM command commands the UE to connect to the first cell. At block 1033, the RAN determines whether the LTM command includes a TA value. If the RAN determines that the LTM command includes a TA value at block 1033, the flow proceeds to block 1032. The flow then proceeds to either block 1047 or block 1053 from block 1032. Otherwise, if the RAN determines that the LTM command does not include a TA value at block 1033, the flow proceeds to block 1057. At block 1057, the RAN performs a random access procedure on the first cell with the UE (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 to block 1047 or block 1053 from block 1059. At block 1059, the RAN transmits a random access response including a 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). At block 1053, the RAN starts or restarts the first time alignment timer for uplink synchronization on the first cell with the UE after (e.g., in response to) transmitting the random access response or obtaining the TA value. At block 1047, the RAN starts a second time alignment timer for uplink synchronization on the first cell with the UE after (e.g., in response to) transmitting the random access response or obtaining the TA value. The flow proceeds to block 1036 from blocks 1047, 1053, 1047, and/or 1053.
[0265] At least some of the discussion of Figs 9A-9C can apply to Figs. 10A-10C. [0266] Fig. 11A illustrates an example method 1100A, for a UE (e.g., the UE 102 in Figs. 3-8B) that handles early TA acquisition with a RAN (e.g., the RAN 105, or the base station 104 and the base station 106 in Figs. 3-8B).
[0267] The method 1100A begins at block 1102, where the UE communicates with a RAN via a serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). At block 1109, the UE starts a first time alignment timer for uplink synchronization with the serving cell while communicating with the RAN via the serving cell. At block 1118, the UE receives an LTM configuration from the RAN, where the LTM configuration configures 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). At block 1125, the UE receives a first command from the RAN via the serving cell, where the first command commands the UE to transmit a first random access preamble on the first cell. At block 1127, the UE transmits the first random access preamble on the first cell to the RAN in response to the first command. At block 1159, the UE receives a random access response including a TA value from the RAN on the serving cell or the first cell, in response to the first random access preamble. At block 1147, the UE starts a second time alignment timer for uplink synchronization with the first cell in response to receiving the random access response. In some implementations, the UE maintains the first time alignment timer running in response to receiving the random access response. In further implementations, the UE refrains from stopping the first time alignment timer running in response to receiving the random access response. At block 1130, the UE receives an LTM command from the RAN via the serving cell after receiving the random access response message, where the LTM command commands the UE to connect the first cell. At block 1141, the UE resets a MAC entity in response to receiving the LTM command and maintains the second time alignment timer running when resetting the MAC entity. At block 1116, the UE accesses the first cell in response to receiving the LTM command. At block 1136, the UE communicates with the RAN on the first cell using the TA value while maintaining the second time alignment timer running.
[0268] Fig. 11 A is generally similar to Fig. 9A, and the discussion of Fig. 9A can apply to Fig. 11 A, with the differences discussed below where appropriate. The LTM command in block 1130 does not include a TA value and the LTM command in block 930A includes a TA value. The RAN does not transmit a random access response to the UE in response to the first random access preamble in Fig. 9A. The UE at block 1147 starts the second time alignment timer in response to receiving the random access response and the UE in block 947 starts the second time alignment timer in response to receiving the LTM command.
[0269] Fig. 1 IB is a flow diagram of an example method 1100B similar to the method 1100A, except that method 1100B includes blocks 1171, 1157, 1159, 1147, and 1153. At block 1171, the UE determines whether the LTM command indicates to apply the TA value. If the UE determines that the LTM command indicates to apply the TA value at block 1171, the flow proceeds to blocks 1170 and 1116. Otherwise, if the UE determines that the LTM command indicates not to apply the TA value at block 1171, the flow proceeds to block 1157. At block 1157, the UE performs a random access procedure on the first cell with the RAN (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). At block 1159, the UE receives a random access response including a TA value from the RAN 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 to block 1147 or block 1153 from block 1159. At block 1147, the UE starts a second time alignment timer for uplink synchronization on the first cell with the RAN. At block 1153, the UE starts or restarts the first time alignment timer for uplink synchronization on the first cell with the RAN. The flow proceeds to block 1136 from blocks 1147, 1153, and/or 1116.
[0270] In some implementations, the UE at block 1147 stops the first time alignment timer after (e.g., in response to) the random access response. In further implementations, the UE at block 1147 maintains or refrains from stopping the first timer alignment timer running after (e.g., in response to) the random access response. In some implementations, when the first time alignment timer expires while the second timer alignment timer is running, the UE communicates with the RAN on the first cell and ignores expiry of the first time alignment timer. In other words, the UE in such cases takes no action in response to expiry of the first time alignment timer.
[0271] In some implementations, the LTM command in block 1130 includes a first indication indicating the UE to apply the TA value received in the random access response. In further implementations, the LTM command in block 1130 includes a second indication indicating the UE not to apply the TA value received in the random access response. In yet further implementations, the LTM command excludes the first indication to indicate the UE not to apply the TA value received in the random access response. In yet further implementations, the LTM command excludes the second indication to indicate to the UE to apply the TA value received in the random access response.
[0272] Fig. 1 IB is generally similar to Fig. 9B, and the discussion of Fig. 9B can apply to Fig. 11B.
[0273] Fig. 12A illustrates an example method 1200A, for a RAN (e.g., the RAN 105, or the base station 104, 106 or DU 174, 174A, and 174B or 174C in Figs. 3-8B) that manages early TA acquisition for a UE (e.g., the UE 102).
[0274] The method 1200A begins at block 1202, where the RAN communicates with a UE via a serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). At block 1209, the RAN starts a first time alignment timer for uplink synchronization with the UE while communicating with the UE via the serving cell. At block 1218, the RAN transmits an ETM configuration to the UE, where the LTM configuration configures 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). At block 1225, the RAN transmits a first command to the UE via the serving cell, where the first command commands the UE to transmit a first random access preamble on the first cell. At block 1227, the RAN receives the first random access preamble on the first cell from the UE after transmitting the first command. At block 1259, the RAN transmits a random access response to the UE on the serving cell or the first cell, in response to receiving the first random access preamble. At block 1247, the RAN starts a second time alignment timer for uplink synchronization on the first cell with the UE. At block 1230, the RAN transmits an LTM command to the UE via the serving cell after transmitting the random access response, where the LTM command commands the UE to connect 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). At block 1241, the RAN resets a MAC entity in response to transmitting the LTM command. At block 1270, the RAN maintains the second time alignment timer running when resetting the MAC entity. At block 1232, the RAN detects that the UE accesses the first cell after transmitting the 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). At block 1236, the RAN communicates with the UE on the first cell using the TA value, while maintaining the second time alignment timer running (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).
[0275] Fig. 12A is generally similar to Fig. 10A, and the discussion of Fig. 10A can apply to Fig. 12A, with the differences discussed below where appropriate. The LTM command in block 1230 does not include a TA value and the LTM command in block 1030A includes a TA value. The RAN does not transmit a random access response to the UE in response to the first random access preamble in Fig. 10A. The RAN in block 1247 starts the second time alignment timer in response to transmitting the random access response and the RAN in block 1047 starts the second time alignment timer in response to transmitting the LTM command. The discussion of Fig. 11 A can apply to Fig. 12A.
[0276] Fig. 12B is a flow diagram of an example method 1200B similar to the method 1200A, except that method 1200B includes blocks 1271, 1257, 1259, 1247, and 1253. At block 1271, the RAN determines whether the LTM command indicates to apply the TA value. If the RAN determines that the LTM command indicates to apply the TA value at block 1271, the flow proceeds to blocks 1270 and 1232. Otherwise, if the RAN determines that the LTM command indicates not to apply the TA value at block 1271, the flow proceeds to block 1257. At block 1257, the RAN performs a random access procedure on the first cell with the UE (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). At block 1259, the RAN transmits a random access response including a 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 to block 1247 or block 1253 from block 1259. At block 1247, the RAN starts a second time alignment timer for uplink synchronization on the first cell with the UE. At block 1253, the RAN starts or restarts the first time alignment timer for uplink synchronization on the first cell with the UE. The flow proceeds to block 1236 from blocks 1247, 1253, and/or 1232.
[0277] In some implementations, the RAN at block 1247 stops the first time alignment timer after (e.g., in response to) the random access response. In other implementations, the RAN at block 1247 maintains or refrains from stopping the first timer alignment timer running after (e.g., in response to) the random access response. In some implementations, when the first time alignment timer expires while the second timer alignment timer is running, the RAN communicates with the UE on the first cell and ignores expiry of the first time alignment timer. In other words, the RAN in such cases takes no action in response to expiry of the first time alignment timer.
[0278] Fig. 12B is generally similar to Fig. 10B, and the discussion of Fig. 10B can apply to Fig. 12B. The discussion of Fig. 11B can also apply to Fig. 12B.
[0279] Fig. 13 illustrates an example method 1300, for a UE (e.g., the UE 102 in Figs. 3- 8B), that handles time alignment timers for uplink synchronization with a RAN (e.g., the RAN 105, or the base station 104, 106 in Figs. 3-8B).
[0280] The method 1300 begins at block 1301, where the UE performs actions described in blocks 1102, 1109, 1118, 1125, 1127, 1159, and 1147. At block 1372, the UE detects the second time alignment expires, while the first time alignment timer is running. At block 1374, the UE keeps the first time alignment timer running in response to the detection.
[0281] Fig. 14A illustrates an example method 1400A, for a UE (e.g., the UE 102 in Figs.
3-8B), that handles time alignment timers for uplink synchronization with a RAN (e.g., the RAN 105, or the base station 104, 106 in Figs. 3-8B).
[0282] The method 1400A begins at block 1401, where the UE performs actions described in blocks 1102, 1109, 1118, 1125, 1127, 1159, and 1147. At block 1473, the UE detects the first time alignment expires, while the second time alignment timer is running. At block
1475, the UE keeps the second time alignment timer running in response to the detection.
[0283] Fig. 14B is a flow diagram of an example method 1400B similar to the method 1400A, except that the method 1400B includes block 1476 instead of block 1406. At block
1476, the UE stops the second time alignment timer in response to the detection.
[0284] The discussion of Figs. 9A-9C and 11A-11B can apply to Figs. 13, 14A, and 14B. Likewise, the discussion of Figs. 13, 14A, and 14B can apply to Figs. 9A-9C and 11A-11B.
[0285] Fig. 15 illustrates an example method 1500, for a RAN (e.g., the RAN 105, or the base station 104, 106 or DU 174, 174A, 174B, or 174C in Figs. 3-8B) that handles time alignment timers for uplink synchronization with a UE (e.g., the UE 102 in Figs. 3-8B).
[0286] The method 1500 begins at block 1501, where the RAN performs actions described in blocks 1202, 1209, 1218, 1225, 1227, 1259, and 1247. At block 1572, the RAN detects the second time alignment expires, while the first time alignment timer is running. At block 1574, the RAN keeps the first time alignment timer running in response to the detection. [0287] Fig. 16A illustrates an example method 1600A, for a RAN (e.g., the RAN 105, or the base station 104, 106 or DU 174, 174A, 174B, or 174C in Figs. 3-8B) that handles time alignment timers for uplink synchronization with a UE (e.g., the UE 102 in Figs. 3-8B).
[0288] The method 1600A begins at block 1601, where the RAN performs actions described in blocks 1202, 1209, 1218, 1225, 1227, 1259, and 1247. At block 1673, the RAN detects the first time alignment expires, while the second time alignment timer is running. At block 1675, the RAN keeps the second time alignment timer running in response to the detection.
[0289] Fig. 16B is a flow diagram of an example method 1600B similar to the method 1600A, except that the method 16s00B includes block 1677 instead of block 1675. At block 1677, the RAN stops the second time alignment timer in response to the detection.
[0290] The discussion of Figs. 10A-10C and 12A-12B can apply to Figs. 15, 16A and 16B. Likewise, the description for Figs. 15, 16A and 16B can apply to Figs. 10A-9C and 12A-12B.
[0291] Fig. 17A illustrates an example method 1700A, for a UE (e.g., the UE 102 in Figs. 3-8B) that handles time alignment timers for uplink synchronization with a RAN (e.g., the RAN 105, or the base station 104, 106 in Figs. 3-8B).
[0292] The method 1700A begins at block 1702, where the UE communicates with a RAN via a serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). At 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. At block 1727, the UE transmits a random access preamble to the RAN. At block 1759, the UE receives a random access response including a TA value from the RAN in response to the random access preamble. At block 1791 A, the UE determines whether the UE receives the random access response on the serving cell or a candidate cell. If the UE determines that the UE receives the random access response on the serving cell at block 1791 A, flow proceeds to block 1753. At block 1753, the UE restarts the first time alignment timer in response to receiving the random access response. In some implementations, the UE adjusts uplink transmission timing with the serving cell using the TA value. Otherwise, if the UE determines that the UE receives the random access response on the candidate cell at block 1791 A, flow proceeds to block 1747. At block 1747, the UE starts a second time alignment timer in response to receiving the random access response. In some implementations, the UE adjusts the uplink transmission timing with the candidate cell using the TA value. [0293] In some implementation, a/the candidate cell is a (e.g., target) cell for LTM (e.g., the first cell described above). In some implementations, the UE maintains or refrains from stopping the first time alignment timer when starting the second time alignment timer or in response to receiving the random access response on the candidate cell.
[0294] Fig. 17B is a flow diagram of an example method 1700B similar to the method 1700A, except that the method 1700B includes block 1791B instead of block 1791A.
[0295] At block 1791B, the UE determines whether the UE transmits the random access preamble on the serving cell or a candidate cell. If the UE determines that the UE transmits the random access preamble on the serving cell at block 179 IB, the flow proceeds to block 1753. Otherwise, if the UE determines that the UE transmits the random access preamble on the candidate cell at block 179 IB, the flow proceeds to block 1747.
[0296] Fig. 17C is a flow diagram of an example method 1700C similar to the method 1700A, except that the method 1700C includes block 1791C instead of block 1791A.
[0297] At block 1791C, the UE determines whether the UE transmits the random access preamble early TA acquisition. If the UE determines that the UE transmits the random access preamble that is not used for early TA acquisition at block 1791C, the flow proceeds to block 1753. Otherwise, if the UE determines that the UE transmits the random access preamble for early TA acquisition at block 1791C, the flow proceeds to block 1747.
[0298] The discussion of Figs. 9A-9C, 11A-11B, 13, 14A and 14B can apply to Figs. 17A- 17C. Likewise, the discussion of Figs. 17A-17C can apply to Figs. 9A-9C, 11A-11B, 13, 14A, and 14B.
[0299] Fig. 18A illustrates an example method 1800A, for a RAN (e.g., the RAN 105, or the base station 104, 106 or DU 174, 174A, 174B, or 174C in Figs. 3-8B) that manages early TA acquisition for a UE (e.g., the UE 102).
[0300] The method 1800A begins at block 1802, where the RAN communicates with a UE via a serving cell (e.g., events 302, 402, 502, 602, 702, 802, 380, 480, 580, 680, 780, 880, 581, 582, 681, 780, 880, and 881). At block 1809, the RAN starts a first time alignment timer for uplink synchronization on the serving cell with the UE while communicating with the UE via the serving cell. At block 1827, the RAN receives a random access preamble from the UE. At block 1859, the RAN transmits a random access response including a TA value to the UE in response to the random access preamble. At block 1891 A, the RAN determines whether the RAN transmits the random access response on the serving cell or a candidate cell. If the RAN determines that the RAN transmits the random access response on the serving cell at block 1891A, the flow proceeds to block 1853. At block 1853, the RAN restarts the first time alignment timer in response to transmitting the random access response. Otherwise, if the RAN determines that the RAN transmits the random access response on the candidate cell at block 1891A, the flow proceeds to block 1847. At block 1847, the RAN starts a second time alignment timer in response to transmitting the random access response.
[0301] In some implementation, a/the candidate cell is a (e.g., a target) cell for LTM (e.g., the first cell described above). In some implementations, the RAN maintains or refrains from stopping the first time alignment timer when starting the second time alignment timer or in response to transmitting the random access response on the candidate cell.
[0302] Fig. 18B is a flow diagram of an example method 1800B similar to the method 1700A, except that the method 1800B includes block 1891B instead of block 1891A.
[0303] At block 1891B, the RAN determines whether the RAN receives the random access preamble on the serving cell or a candidate cell. If the RAN determines that the RAN receives the random access preamble on the serving cell at block 1891B, the flow proceeds to block 1853. Otherwise, if the RAN determines that the RAN receives the random access preamble on the candidate cell at block 1891B, the flow proceeds to block 1847.
[0304] Fig. 18C is a flow diagram of an example method 1800C similar to the method 1800A, except that the method 1800C includes block 1891C instead of block 1891 A.
[0305] At block 1891C, the RAN determines whether the RAN receives the random access preamble early TA acquisition. If the RAN determines that the RAN receives the random access preamble and is not for early TA acquisition at block 1891C, the flow proceeds to block 1753. Otherwise, if the RAN determines that the RAN receives the random access preamble for early TA acquisition at block 1891C, the flow proceeds to block 1847.
[0306] The discussion of Figs. 10A-10C, 12A-12B, 15, 16A, and 16B can apply to Figs. 18A-18C. Likewise, the discussion of Figs. 18A-18C can apply to Figs. 10A-10C, 12A-12B, 15, 16A, and 16B.
[0307] In some implementations, the following description applies to the description above. [0308] Generally speaking, description for one of the above figures apply to the above figures. Examples, implementations, and methods described above are combined, if there is no conflict. An event or block described above is optional or omitted. For example, an event or block with dashed lines in the figures is optional. In some implementations, “message” is used and is replaced by “information element (IE)”, and vice versa. In some implementations, “IE” is used and is replaced by “field”, and vice versa. In some implementations, “configuration” is replaced by “configurations” or “configuration parameters”, and vice versa. In some implementations, the “LTM command” is replaced by “serving cell change command”, “Layer 1/Layer 2 switching command”, “lower layer switching command”, or “lower layer serving cell change command”. In some implementations, “some” means “one or more”. In some implementations, “at least one” means “one or more”. In some implementations, the “DU configuration” is replaced by “cell group configuration”. In some implementations, the “cell index” is replaced with “serving cell index”, “LTM cell index”, “special cell (SpCell) index”, “PCell index”, or “PSCell index”. In some implementations, the “serving” is replaced by “source”. In some implementations, the “measurement report” is replaced by “measurement result(s)”. In some implementations, the “early TA acquisition” is replaced by “early timing synchronization”, “early timing synchronization with a target cell”, “early TA value acquisition”, or “early TA value acquisition for a target cell”. In some implementations, the “early TA acquisition configuration” is replaced by “early TA acquisition indication” or “early TA acquisition enabling indication”.
[0309] A user device in which the techniques of this disclosure can be implemented (e.g., the UE 102) can be any suitable device capable of wireless communications such as a smartphone, a tablet computer, a laptop computer, a mobile gaming console, a point-of-sale (POS) terminal, a health monitoring device, a drone, a camera, a media- streaming dongle or another personal media device, a wearable device such as a smartwatch, a wireless hotspot, a femtocell, or a broadband router. Further, the user device in some cases may be embedded in an electronic system such as the head unit of a vehicle or an advanced driver assistance system (ADAS). Still further, the user device can operate as an intemet-of-things (loT) device or a mobile-internet device (MID). Depending on the type, the user device can include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc. [0310] Certain embodiments are described in this disclosure as including logic or a number of components or modules. Modules may can be software modules (e.g., code, or machine- readable instructions stored on non-transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. A hardware module can comprise dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application- specific integrated circuit (ASIC), a digital signal processor (DSP), etc.) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g., as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.
[0311] When implemented in software, the techniques can be provided as part of the operating system, a library used by multiple applications, a particular software application, etc. The software can be executed by one or more general-purpose processors or one or more special-purpose processors.
[0312] As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Claims

What is claimed is:
1. A method implemented in a user equipment (UE), the method comprising: starting or restarting a timing alignment timer for a target cell in response to obtaining, from a radio access network (RAN) in a serving cell, a timing advance for the target cell; receiving a command to initiate a lower-layer triggered mobility (LTM) cell change to the target cell; resetting a medium access control (MAC) entity in response to the command; and keeping the timing alignment timer running upon the resetting the MAC entity.
2. The method of 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 of claim 1 or 2, wherein: the keeping the timing alignment timer is response to determining that the LTM command included the timing advance.
4. The method of claim 1, wherein the obtaining of the timing advance includes: receiving a command to transmit a random access preamble in the target cell, and receiving the timing advance in a random access response message.
5. The method of any of the preceding claims, further comprising: receiving, prior to the receiving the command to initiate the LTM cell change, an
LTM configuration for the target cell.
6. The method of any of the preceding claims, wherein: the starting or restarting the timing alignment timer for the target cell includes restarting the timing alignment timer; the method further comprising: starting, prior to the restarting the timing alignment timer for the target cell, the timing alignment timer for the serving cell.
7. The method of any of claims 1-5, further comprising: starting, prior to the restarting the timing alignment timer for the target cell, a first timing alignment timer for the serving cell; wherein the starting or restarting the timing alignment timer for the target cell includes starting a second timing alignment timer.
8. The method of claim 7, further comprising: detect expiration of the second timing alignment timer, while the first timing alignment timer is running; and in response to the detecting, keeping the first timing alignment running.
9. The method of claim 7, further comprising: detect expiration of the first timing alignment timer, while the second timing alignment timer is running; and in response to the detecting, keeping the second timing alignment running.
10. The method of claim 1, further comprising: starting, prior to the restarting the timing alignment timer for the target cell, a first timing alignment timer for the serving cell; wherein: the starting or restarting the timing alignment timer for the target cell includes starting a second timing alignment timer in response to receiving, in the candidate cell, a response to a random access preamble.
11. The method of claim 1 , further comprising: starting, prior to the restarting the timing alignment timer for the target cell, a first timing alignment timer for the serving cell; wherein: the starting or restarting the timing alignment timer for the target cell includes starting a second timing alignment timer in response to transmitting, in the candidate cell, a random access preamble.
12. The method of claim 1, further comprising: starting, prior to the restarting the timing alignment timer for the target cell, a first timing alignment timer for the serving cell; wherein: the starting or restarting the timing alignment timer for the target cell includes starting a second timing alignment timer in response to transmitting a random access preamble for early timing alignment acquisition.
13. A method implemented in a radio access network (RAN), the method comprising: providing, to a user equipment (UE) in a serving cell, a timing advance for a target cell; transmitting, to the UE, a command to initiate a lower-layer triggered mobility (LTM) cell change to the target cell; starting a timing alignment timer associated for the target cell, in response to the transmitting of the command; resetting a medium access control (MAC) entity; and keeping the timing alignment timer running upon the resetting the MAC entity.
14. The method of claim 14, wherein: the restarting of the MAC entity in response to determining that the command includes the timing advance value.
15. A device comprising processing hardware and configured to implement a method of any of the preceding claims.
EP24748504.8A 2023-07-07 2024-07-08 Managing uplink timing synchronization Pending EP4725247A1 (en)

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