Managing a serving cell change in a user equipment

Abstract

A user equipment (UE) communicates with a radio access network (RAN) according to a first configuration, and uses a medium access control (MAC) entity associated with a cell group. The UE receives, from the RAN, a second configuration for use subsequent to receiving an activation command; receives the activation command from the RAN; andjn response to the activation command, uses the second configuration to communicate with the RAN. The UE determines whether to reset the MAC entity in accordance with an indication from the RAN.

Description

MANAGING A SERVING CELL CHANGE IN A USER EQUIPMENTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of the filing date of provisional U.S. Patent Application No. 63 / 409,780 entitled “MANAGING A SERVING CELL CHANGE IN A USER EQUIPMENT,” filed on September 24, 2022. 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 enabling a fast serving cell change for a user equipment (UE) using a control signaling of a protocol layer lower than a radio resource control (RRC) protocol layer.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, in some scenarios, the UE and a base station use SRBs to exchange RRC messages as well as non-access stratum (NAS) messages. In further scenarios, the UE and base station use DRBs to transport data on a user plane.

[0005] Depending on the scenario, UEs 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 base1SUBSTITUTE SHEET RULE 26station operating as the secondary node (SN) define the secondary cell group (SCG). 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 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, concurrently utilizes resources of multiple radio access network (RAN) nodes (e.g., base stations or components of a distributed base station), interconnected by a backhaul. When such 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 determine that the UE should establish a radio connection with another base station. For example, one base station determines to hand the UE over to the second base station and initiates a handover procedure.

[0007] When the UE moves from coverage area of one cell to another cell in a RAN, at some point a serving cell change will be performed for the UE. To perform the serving cell change, the RAN configures the UE to transmit Layer 3 (L3) measurement results. Based on L3 measurement results received 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 change of the serving cell (e.g., PCell or PSCell). In cases where the UE operates in carrier aggregation (CA) of at least one secondary cell (SCell) with the PCell or PSCell, the RAN has to release the at least one SCell due to the change of the PCell or PSCell. The serving cell change involves complete L2 (and 2SUBSTITUTE SHEET RULE 26LI) resets, leading to longer latency, larger overhead, and longer interruption time. Thus, it is desirable to develop new mobility techniques to reduce latency and overhead for fast serving cell change. However, it is not clear how to develop and realize the fast serving cell change.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Fig. 1A is a block diagram of an example system in which a radio access network (RAN) and a user device can implement the techniques of this disclosure for managing conditional procedures related to a secondary node (SN);

[0009] Fig. IB is a block diagram of an example base station including a centralized unit (CU) and a distributed unit (DU) that can operate in the system of Fig. 1 A;

[0010] Fig. 2 is a block diagram of an example protocol stack according to which the UE of Fig. 1A communicates with base stations;

[0011] Fig. 3 is a messaging diagram of an example scenario where a base station configures a UE to perform a lower layer procedure for a cell change operation;

[0012] Fig. 4 is a messaging diagram of an example scenario where a base station configures a UE to perform a lower layer procedure for an inter-DU cell change operation;

[0013] Fig. 5A is a messaging diagram of an example scenario where an MN operates in DC with an SN to perform a lower layer procedure for a cell change operation;

[0014] Fig. 5B is a messaging diagram of an example scenario similar to that of Fig. 5A, but in which the MN configures the UE directly;

[0015] Fig. 6A is a messaging diagram of an example scenario similar to that of Fig. 5A, but in which the cell change operation is an inter-DU cell change operation;

[0016] Fig. 6B is a messaging diagram of an example scenario similar to that of Fig. 5B, but in which the cell change operation is an inter-DU cell change operation;

[0017] Fig. 7A is a messaging diagram of an example scenario similar to that of Fig. 5A, but in which the base station operates as the MN (e.g., an M-DU) and the SN (e.g., an S-DU) to perform the cell change operation;

[0018] Fig. 7B is a messaging diagram of an example scenario similar to that of Fig. 7A, but in which the MN configures the UE directly;

[0019] Fig. 8A is a messaging diagram of an example scenario similar to that of Fig. 7A, but in which the cell change operation is an inter-DU cell change operation;3SUBSTITUTE SHEET (RULE 26)

[0020] Fig. 8B is a messaging diagram of an example scenario similar to that of Fig. 7B, but in which the cell change operation is an inter-DU cell change operation;

[0021] Fig. 9A is a flow diagram depicting an example method, implemented in a UE, in which the UE receives an RRC message including a second configuration and including a MAC retention indication, and the UE refrains from resetting the MAC entity;

[0022] Fig. 9B is a flow diagram depicting an example method similar to that of Fig. 9A, but in which the RRC message excludes the MAC retention indication, and the UE resets the MAC entity;

[0023] Fig. 9C is a flow diagram depicting an example method similar to that of Fig. 9A, but in which the UE resets the MAC entity;

[0024] Fig. 9D is a flow diagram depicting an example method similar to that of Fig. 9B, but in which the UE refrains from resetting the MAC entity;

[0025] Fig. 9E is a flow diagram depicting an example method similar to that of Fig. 9A, but in which the RRC message includes a partial MAC reset indication, and the UE partially resets the MAC entity;

[0026] Fig. 9F is a flow diagram depicting an example method similar to that of Fig. 9E, but in which the RRC message excludes the partial MAC reset indication, and the UE fully resets the MAC entity;

[0027] Fig. 9G is a flow diagram depicting an example method similar to that of Fig. 9A, but in which the UE receives the second configuration and partially resets the MAC entity;

[0028] Fig. 10A is a flow diagram depicting an example method, implemented in a UE, in which the UE determines whether to perform the actions of Fig. 9A or 9B based on whether the RRC message or second configuration includes a MAC retention indication;

[0029] Fig. 10B is a flow diagram depicting an example method similar to that of Fig. 10A, but in which the UE determines whether to perform the actions of Fig. 9C or 9D based on whether the RRC message or second configuration includes a MAC reset indication;

[0030] Fig. 10C is a flow diagram depicting an example method similar to that of Fig. 10A, but in which the UE determines whether to perform the actions of Fig. 9A or 9C based on whether the RRC message or second configuration includes a MAC retention indication or a MAC reset indication;4SUBSTITUTE SHEET (RULE 26)

[0031] Fig. 10D is a flow diagram depicting an example method similar to that of Fig. 10A, but in which the UE determines whether to perform the actions of Fig. 9E or 9F based on whether the RRC message or second configuration includes a MAC partial reset indication;

[0032] Fig. 10E is a flow diagram depicting an example method similar to that of Fig. 10A, but in which the UE determines whether to perform the actions of Fig. 9G or perform a full reset based on whether the UE receives a configuration activation command;

[0033] Fig. 11 A is a flow diagram depicting an example method, implemented in a DU, in which the DU transmits a second configuration including a MAC retention indication to a CU;

[0034] Fig. 1 IB is a flow diagram depicting an example method similar to that of Fig.11 A, but in which the DU transmits a message including the second configuration and the MAC retention indication;

[0035] Fig. 11C is a flow diagram depicting an example method similar to that of Fig. 11 A, but in which the second configuration excludes the MAC retention indication;

[0036] Fig. 1 ID is a flow diagram depicting an example method similar to that of Fig.1 IB, but in which the message excludes the MAC retention indication;

[0037] Fig. 1 IE is a flow diagram depicting an example method similar to that of Fig. 11 A, but in which the second configuration includes a MAC reset indication;

[0038] Fig. 1 IF is a flow diagram depicting an example method similar to that of Fig. 1 IB, but in which the message includes a MAC reset indication;

[0039] Fig. 11G is a flow diagram depicting an example method similar to that of Fig. 11C, but in which the second configuration excludes a MAC reset indication;

[0040] Fig. 11H is a flow diagram depicting an example method similar to that of Fig.1 ID, but in which the message excludes a MAC reset indication;

[0041] Fig. 12 is a flow diagram depicting an example method, implemented in a DU, in which the DU determines whether to perform actions of Figs. 11A, 1 IB, 11G, or 11H or actions of Figs. 11C, 1 ID, 1 IE, or 1 IF based on whether the DU configures the UE to reset a MAC entity;5SUBSTITUTE SHEET (RULE 26)

[0042] Fig. 13A is a flow diagram depicting an example method, implemented in a CU, in which the CU receives a message including a first configuration and a MAC retention indication;

[0043] Fig. 13B is a flow diagram depicting an example method similar to that of Fig. 13A, but in which the message excludes the MAC retention indication;

[0044] Fig. 13C is a flow diagram depicting an example method similar to that of Fig. 13A, but in which the message includes a MAC reset indication;

[0045] Fig. 13D is a flow diagram depicting an example method similar to that of Fig.13C, but in which the message excludes the MAC reset indication;

[0046] Fig. 14A is a flow diagram depicting an example method, implemented in a CU, in which the CU determines whether to transmit the MAC retention indication to the UE based on whether the message includes a MAC retention indication;

[0047] Fig. 14B is a flow diagram depicting an example method similar to that of Fig. 14A, but in which the determination is regarding a MAC reset indication;

[0048] Fig. 14C is a flow diagram depicting an example method similar to that of Fig.14A, but in which the determination is regarding a MAC retention indication and / or a MAC reset indication;

[0049] Fig. 15A is a flow diagram depicting an example method, implemented in a DU, in which the DU determines whether to reset the MAC entity based on whether the serving cell change is triggered by the DU or a CU; and

[0050] Fig. 15B is a flow diagram depicting an example method similar to that of Fig.15 A, but in which the determination is based on whether the DU configures the UE to reset a MAC entity.DETAILED DESCRIPTION OF THE DRAWINGS

[0051] Fig. 1A depicts an example wireless communication system 100 in which communication devices can implement these techniques. The wireless communication system 100 includes a UE 102, a base station (BS) 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 dual6SUBSTITUTE SHEET (RULE 26)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.

[0052] 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.

[0053] 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.

[0054] 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) for example prior to the handover. 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.

[0055] 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) 114,7SUBSTITUTE SHEET (RULE 26)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.

[0056] As illustrated in Fig. 1A, the base station 104 supports 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.

[0057] 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.

[0058] 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 or8SUBSTITUTE SHEET (RULE 26)more general-purpose processors execute. Additionally or alternatively, the processing hardware 130 can include special-purpose processing units. The processing hardware 130 can include a PHY controller 132 configured to transmit data and control signal on physical downlink (DL) channels and DL reference signals with one or more user devices (e.g., UE 102) via one or more cells (e.g., the cell(s) 124A, 124B and / or 124C) and / or one or more TRPs. The PHY controller 132 is also configured to receive data and control signal on physical uplink (UL) channels and / or UL reference signals with the one or more user devices via one or more cells (e.g., the cell(s) 124A, 124B and / or 124C) and / or one or more TRPs. The processing hardware 130 in an example implementation includes a MAC controller 134 configured to perform MAC functions with one or more user devices. The MAC functions includes 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 processing hardware 130 can further include an RRC controller 136 to implement procedures and messaging at the RRC sublayer of the protocol communication stack. For example, the RRC controller 132 may be configured to support RRC messaging associated with handover procedures, and / or to support the necessary operations when the base station 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, 134, and 136, respectively.

[0059] The UE 102 is equipped with processing hardware 150 that can include one or more general-purpose processors such as CPUs and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or special-purpose processing units. The PHY controller 152 is also configured to receive data and control signal on physical DL channels and / or DL reference signals with the base station 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 152 is also 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 154 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 PDUs9SUBSTITUTE SHEET (RULE 26)with the base station 104 or 106. The processing hardware 150 can further include an RRC controller 156 to implement procedures and messaging at the RRC sublayer of the protocol communication stack.

[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 can include a centralized unit (CU) 172 and one or more distributed units (DUs) 174. The CU 172 is equipped with processing hardware that can include one or more general-purpose processors such as CPUs and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or special-purpose processing units. In one example, the CU 172 is equipped with the processing hardware 130. In another example, the CU 172 is equipped with the processing hardware 140. The processing hardware 140 in an example implementation includes an SN RRC controller 142 configured to manage or control one or more RRC configurations and / or RRC procedures when the base station 106 operates as an SN. The DU 174 is also equipped with processing hardware that can include one or more general-purpose processors such as CPUs and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or special-purpose processing units. In some examples, the processing hardware in an example implementation includes a medium access control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., a random access procedure) and a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station 106 operates as an MN or an SN. The process hardware may include further a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0062] Next, Fig. 2 illustrates in a simplified manner a radio protocol stack according to which the UE 102 can communicate with an eNB / ng-eNB or a gNB. Each of the base stations 104 or 106 can be the eNB / ng-eNB or the gNB.10SUBSTITUTE SHEET (RULE 26)

[0063] The physical layer (PHY) 202A of EUTRA provides transport channels to the EUTRA Medium Access Control (MAC) sublayer 204A, which in turn provides logical channels to the EUTRA Radio Link Control (RLC) sublayer 206A, and the EUTRA RLC sublayer in turn provides RLC channels to the EUTRA PDCP sublayer 208 and, in some cases, NR PDCP sublayer 210. Similarly, the PHY 202B of NR provides transport channels to the NR MAC sublayer 204B, which in turn provides logical channels to the NR RLC sublayer 206B, and the NR RLC sublayer 206B in turn provides RLC channels to the NR PDCP sublayer 210. The UE 102 in some implementations supports both the EUTRA and the NR stack, to support handover between EUTRA and NR base stations and / or DC over EUTRA and NR interfaces. Further, as illustrated in Fig. 2A, the UE 102 can support layering of NR PDCP 210 over EUTRA RLC 206A.

[0064] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets (e.g., from the Internet Protocol (IP) layer, layered directly or indirectly over the PDCP layer 208 or 210) that can be referred to as service data units (SDUs), and output packets (e.g., to the RLC layer 206A or 206B) that can be referred to as protocol data units (PDUs). Except where the difference between SDUs and PDUs is relevant, this disclosure for simplicity refers to both SDUs and PDUs as “packets.”

[0065] On a control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 provide SRBs to exchange Radio Resource Control (RRC) messages, for example. On a user plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 provide DRBs to support data exchange.

[0066] When the UE 102 operates in EUTRA / NR DC (EN-DC), with the base station 104 operating as a MeNB and the base station 106 operating as a SgNB, the network can provide the UE 102 with an MN-terminated bearer that uses EUTRA PDCP 208 or MN-terminated bearer that uses NR PDCP 210. The network in various scenarios also can provide the UE 102 with an SN-terminated bearer, which use only NR PDCP 210. The MN-terminated bearer can be an MCG bearer or a split bearer. The SN-terminated bearer can be a SCG bearer or a split bearer. The MN-terminated bearer can be an SRB (e.g., SRB 1 or SRB2) or a DRB. The SN-terminated bearer can an SRB (e.g., SRB) or a DRB.

[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 the configuration for communication between the UE 102 and base station. Generally speaking, events in Figs. 3-11SUBSTITUTE SHEET (RULE 26)7B that are similar are labeled with similar reference numbers e.g., event 316 is similar to event 416 of Figs 4A and 4B, event 516 of Fig. 5A, event 517 of Fig. 5B, event 616 of Fig. 6A, event 617 of Fig. 6B, event 716 of Fig. 7A, and event 717 of Fig. 7B), 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 base station 104 on cell 124A using a first configuration. 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 first 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 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 an SCell. In other implementations, the cell 124A is an SCell, and one of the other cell(s) is a PCell. In such cases, the other cell(s) include SCell(s) and / or additional cell(s) associated with the PCell or an SCell. In the following description, the base station 104 can be the DU 174, the CU 172, or the DU 174 and CU 172.

[0069] In some implementations, in the event 302, the UE 102 transmits UL PDUs and / or 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 include SRBs and / or DRB(s). In further 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). Similarly, 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 downlink control information (DCIs) and reference signals (e.g., synchronization signal block), channel state information reference12SUBSTITUTE SHEET (RULE 26)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 first configuration includes physical layer configuration parameters, MAC configuration parameters, RLC configuration parameters, PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, the first configuration includes a CellGroupConfig IE (e.g., defined in 3GPP specification 38.331) or configuration parameters in the CellGroupConfig IE. In some implementations, the first configuration includes a CS1- MeasConfig IE, a MeasConfig IE and / or a RadioBearerConfig IE (e.g., defined in 3GPP specification 38.331) or includes configuration parameters in the CSl-MeasConfig IE, MeasConfig IE and / or RadioBearerConfig IE. In some implementations, the UE 102 receives the configuration parameters from the base station 104. In other implementations, the UE 102 receives a portion of the configuration parameters from a base station other than the base station 104 and the remaining portion of the 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 Layer 1 (LI) measurement report(s) and / or Layer 3 (L3) measurement report(s) for at least one serving cell of the UE 102 and / or at least one nonserving cell. For each of the L3 measurement report(s), 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(s) of the event 306 are Fl application protocol (F1AP) message(s) (e.g., UL RRC Message Transfer message(s)). In some implementations, the UE 102 does not transmit or refrains from transmitting the LI measurement report(s) to the CU 172. The at least one serving cell includes the cell 124A and / or other cell(s), and the at least one nonserving cell includes the cell 124B and / or cell 124C. In some implementations, the first configuration includes at least one measurement configuration. In some implementations, the UE 102 receives one or more RRC messages (e.g., RRCReconfiguration message(s)), 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 L313SUBSTITUTE SHEET (RULE 26)measurement configuration(s) (e.g., MeasConfig IE(s)) and / or LI measurement configuration(s). For example, the LI measurement configuration(s) (e.g., CSl-MeasConfig IE(s)) include CSI resource configuration(s) (e.g., CSl-ResourceConfig IE(s)) and / or CSI reporting configuration(s) (e.g., CSl-ReportConfig IE(s)). 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). In some implementations, the at least one measurement configuration includes new-type measurement configuration(s) (e.g., new RRC IE(s) (e.g., as defined in 3GPP specification 38.331 vl8.0.0 and / or later version)) for the fast serving cell change. For example, the new-type measurement configuration(s) include CSI resource configuration(s) (e.g., CSl-ResourceConfig IE(s)) and / or new-type reporting configuration(s). In such implementations, the at least one measurement report includes new-type measurement report(s) associated with the new-type measurement configuration(s). The UE 102 transmits the new-type measurement report(s) to the DU 174 in accordance with the new-type measurement configuration(s). In some implementations, each of the new-type reporting configuration(s) includes a trigger event configuration configuring a trigger event to trigger the UE 102 to transmit a new-type measurement report. If the UE 102 detects the trigger event, the UE 102 transmits a new-type measurement report to the DU 174.

[0072] In some implementations, the LI measurement report(s) include 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 Ll-Signal to Interference Noise Ratio (Ll-SINR) value. For each of the LI measurement report(s), the UE 102 transmits a PUCCH transmission, including the LI measurement report, to the DU 174, in some implementations. That is, the UE 102 transmits each of the LI measurement report(s) on a PUCCH to the DU 174. In other 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 each of the LI measurement report(s) on a PUSCH to the DU 174. In yet other 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) (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 of14SUBSTITUTE SHEET (RULE 26)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 channel state information (CSI) (i.e., a CSI component) or CSI. In some implementations, the UE 102 includes other CSI component(s) in the PUCCH transmission(s) and / or PUSCH transmission(s) described above. In some implementations, the other CSI component(s) include components such as a channel quality indicator (CQI), a Precoding Matrix Indicator (PMI), a CSLRS Resource Indicator (CRI), a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) Resource Block Indicator (SSBRI), a Layer Indicator (LI), and / or a Rank Indicator (RI).

[0073] In some implementations, each of the L3 measurement report(s) includes at least one L3 measurement result. In some implementations, the at least one L3 measurement result includes at least one RSRP (value) and / or at least one SINR (value). In some implementations, the UE 102 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) is an RRC message (e.g., MeasurementReport message). In some implementations, each of the L3 measurement configuration(s) includes a particular measurement identity (e.g., measldp 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 with an L3 measurement configuration identified by the measurement identity.

[0074] In some alternative implementations, for each of the at least one measurement report (e.g., LI measurement report(s) and / or new-type measurement report(s)), the UE 102 transmits a MAC control element (CE) including the measurement report to the DU 174 in the event 304. To transmit the MAC CE(s), the UE 102 generates one or more MAC PDUs, each including one or more of the MAC CE(s), for the DU 174 in the event 304.

[0075] In some implementations, the UE 102 performs measurements on one or more reference signals in accordance with the at least one measurement configuration. In further implementations, the one or more reference signals include one or more Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) Resource Blocks (SSBs) and / or one or more CSLRS s. The UE 102 obtains the at least one LI measurement result and / or at least one L315SUBSTITUTE SHEET (RULE 26)measurement result from the measurements. The DU 174 transmits the one or more reference signals on the cells 124A and 124B, and, in some implementations, the cell 124C and / or other cell(s).

[0076] 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 the cell 124B for the UE 102. In some implementations, the base station 104 determines to prepare the cell 124B for the UE 102 because the at least one measurement report indicates that the cell 124B could be used by the base station 104 to communicate with the UE 102. In some implementations, the base station 104 determines to prepare the cell 124B for the UE 102 because the at least one measurement report indicates that the cell 124B qualifies to be used for communication with the UE 102. In some implementations, if the L3 measurement report(s) indicate that signal strength and / or quality of the cell 124B is above a first predetermined threshold and / or is better (e.g., higher) than the cell 124A, the CU 172 determines to prepare the cell 124B for the UE 102. In other implementations, if the LI measurement report(s) or new-type measurement report(s) indicate that signal strength and / or quality of the cell 124B is above a first predetermined threshold and / or is better (e.g., higher) than the cell 124A, the DU 174 determines to prepare the cell 124B for the UE 102. Alternatively, the base station 104 determines to prepare the cell 124B for the UE 102 regardless of whether a measure report is received from the UE 102 or not.

[0077] In some implementations, if the CU 172 determines to prepare the cell 124B, the CU 172 transmits 308 a first CU-to-DU message to the DU 174 to prepare the cell 124B for the UE 102. In some implementations, the CU 172 includes a cell identity (ID) of the cell 124B in the first CU-to-DU message. For example, the cell ID is cell global identity (CGI). In another example, the cell ID is a physical cell ID (PCI). In response, the DU 174 generates a second configuration (referred to herein as configuration 1) configuring the cell 124B and transmits 310 a first DU-to-CU message including the second configuration to the CU 172. In further implementations, if the DU 174 determines to prepare the cell 124B, the DU 174 initiates transmission of the first DU-to-CU message to the CU 172.

[0078] After receiving the first DU-to-CU message, the CU 172 generates an RRC reconfiguration message (e.g., an RRCReconfiguration message), including the configuration 1, and transmits 316 a second CU-to-DU message including the RRC reconfiguration message to the DU 174. In turn, the DU 174 transmits 318 the RRC reconfiguration message16SUBSTITUTE SHEET (RULE 26)to the UE 102. In response, the UE 102 transmits 320 an RRC reconfiguration complete message (e.g., an RRCReconfigurationComplete message) to the DU 174, which in turn transmits 322 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 a PDCP PDU including the encrypted RRC reconfiguration message and encrypted MAC-I to the UE 102 via the DU 174 in the events 316 and 318. When the UE 102 receives the PDCP PDU from the CU 172 via the DU 174 (i.e., events 316 and 318), the UE 102 decrypts the encrypted RRC reconfiguration and encrypted MAC-I to obtain the RRC reconfiguration message and MAC-I, and the UE 102 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 an RRC connection reestablishment procedure in response to the invalid MAC-I. Otherwise, in further 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 configuration 1 until receiving a configuration activation command activating the configuration 1 (e.g., event 330).

[0079] 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 cases for the UE Context Modification Required message, the CU 172 transmits a UE Context Modification Confirm message to the DU 174 in response to the UE Context Modification Required message. In some implementations, the second CU-to-DU message is a DE RRC Message Transfer message. In other 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.

[0080] The events 308 and 310 are collectively referred to in Fig. 3 as a serving cell preparation procedure 390.17SUBSTITUTE SHEET (RULE 26)

[0081] In some implementations, the CU 172 includes a field or an IE in the RRC reconfiguration message of the events 316 and 318 to indicate to the UE 102 not to apply the configuration 1 immediately. In some implementations, the field or IE is currently defined (e.g., in 3GPP specification 38.331 vl8.0.0 and / or later versions). In further implementations, the field or IE is newly defined (e.g., in a 3GPP 6G specification). In some implementations, the field or IE is an indicator. If the RRC reconfiguration message of the event 318 includes the indicator, the UE 102 refrains from immediately applying the configuration 1. Otherwise, if the RRC reconfiguration message of the event 318 does not include the indicator, the UE 102 applies the configuration 1 immediately. In other implementations, the field or IE is a container (e.g., the first container and / or second container described below). For example, the UE 102 receives an RRC reconfiguration message (e.g., the RRC reconfiguration message of the event 318) including a configuration (e.g., configuration 1). If the configuration is included in the container, the UE 102 refrains from immediately applying the configuration. Otherwise, if the configuration is not included in the container, the UE 102 applies the configuration immediately.

[0082] In some implementations, after receiving the configuration 1 in the event 310, the CU 172 generates a first container including the configuration 1, includes the first container in the RRC reconfiguration message, and transmits the RRC reconfiguration message to the UE 102 in the event 316. Alternatively, the DU 174 generates the first container and includes the first container in the first DU-to-CU message. In some implementations, the first container is a first addition or modification list (e.g., ConfigToAddModList IE, CellConfigToAddModList IE, MobilityToAddModList IE, MobilityConfigToAddModList IE, or CellGroupConfigToAddModList IE). The base station 104 includes the configuration 1 in a first element (referred to herein as element 1) of the first addition or modification list. For example, the element 1 is an addition or modification IE (e.g., ConfigToAddMod IE, CellConfigToAddMod IE, MobilityToAddMod IE, MobilityConfigToAddMod IE, or CellGroupConfigToAddMod IE). 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 a random access memory (RAM)).

[0083] In some implementations, the CU 172 includes, in the RRC reconfiguration message, a first ID (referred to herein as ID 1) for identifying the configuration 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 for the configuration 1. In other18SUBSTITUTE SHEET (RULE 26)implementations, the CU 172 receives the ID 1 from the DU 174 in the first DU-to-CU message, as described below.

[0084] In some implementations, the CU 172 transmits the ID 1 to the DU 174, so that the DU 174 associates the ID 1 with the configuration 1. In some implementations, the CU 172 includes the ID 1 in the first CU-to-DU message. In further implementations, the CU 172 transmits 312 a third CU-to-DU message including the ID 1 to the DU 174. In some such cases, the CU 172 includes the configuration 1 in the third CU-to-DU message to indicate the association between the ID 1 and configuration 1. In further 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. The events 312 and 314 are collectively referred to in Fig. 3 as an ID allocation procedure 392.

[0085] In some implementations, in cases where the CU 172 includes the ID 1 in the first CU-to-DU message, the DU 174 includes the ID 1 in the configuration 1. In such cases, the CU 172 does not include the ID 1 in the RRC reconfiguration message, first container and / or element 1.

[0086] In some alternative implementations, the DU 174 assigns the ID 1 for identifying the configuration 1. In some implementations, the DU 174 includes the ID 1 in the first DU- to-CU message. In further implementations, the CU 172 includes the ID 1 in the RRC reconfiguration message. In other implementations, the DU 174 includes the ID 1 in the configuration 1. Thus, the CU 172 does not include an ID identifying the configuration 1 in the RRC reconfiguration message, first container, and / or element 1.

[0087] In some implementations, the configuration 1 includes a plurality of configurations for the UE 102 to communicate with the DU 174 on the cell 124B. In some implementations, the plurality of configurations 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 some further implementations, the plurality of configurations includes a special cell configuration (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE(s)).

[0088] In some implementations, the DU 174 includes a random access configuration in the configuration 1. In other implementations, the DU 174 does not include a random access configuration in the configuration 1. In some implementations, if the cell 124A and cell19SUBSTITUTE SHEET (RULE 26)124B are not synchronized, the DU 174 determines to include the random access configuration in the configuration 1. Otherwise, if the cell 124A and cell 124B are synchronized, the DU 174 determines to not include the random access configuration in the configuration 1. In other implementations, if the DU 174 determines that the UE 102 has not synchronized in UL with the cell 124B, the DU 174 determines to include the random access configuration in the configuration 1. Otherwise, if the DU 174 determines that the UE 102 has synchronized in UL with the cell 124B, the DU 174 determines to not include the random access configuration in the configuration 1. If the configuration 1 includes the random access configuration, the UE 102 performs the random access procedure in the event 332 in accordance with the random access configuration, as described below. Otherwise, if the configuration 1 does not include the random access configuration, the UE 102 skips the random access procedure of the event 332 in response to the configuration 1 excluding the random access configuration.

[0089] In some implementations, the DU 174 includes a random access configuration in the configuration 1 regardless of whether the cells 124A and 124B are synchronized or not. In some implementations, if the cell 124A and cell 124B are synchronized, the DU 174 determines to include, in the configuration 1, a first indication configuring the UE 102 not to perform a random access procedure on the cell 124B. Otherwise, if the cell 124A and cell 124B are not synchronized, the DU 174 determines to not include the first indication in the configuration 1. In other implementations, if the DU 174 determines that the UE 102 has synchronized in UL with the cell 124B, the DU 174 determines to include the first indication in the configuration 1. Otherwise, if the DU 174 determines that the UE 102 has not synchronized in UL with the cell 124B, the DU 174 determines to not include the first indication in the configuration 1. If the configuration 1 includes the first indication, the UE 102 skips the random access procedure of the event 332 in accordance with or in response to the first indication. Otherwise, if the configuration 1 does not include the first indication, the UE 102 performs the random access procedure in accordance with the random access procedure in the event 332, in response to the configuration 1 excluding the first indication, as described below.

[0090] In some implementations, the DU 174 includes a reconfiguration with sync configuration (e.g., ReconfigurationWithSync IE) in the configuration 1 or special cell configuration. In other implementations, the DU 174 does not include a reconfiguration with sync configuration (e.g., ReconfigurationWithSync IE) in the configuration 1 or special cell20SUBSTITUTE SHEET (RULE 26)configuration. In some implementations, if the cell 124A and cell 124B are not synchronized, the base station 104 determines to include the reconfiguration with sync configuration in the configuration 1. Otherwise, if the cell 124A and cell 124B are synchronized, the DU 174 determines to not include the reconfiguration with sync configuration in the configuration 1. In other implementations, if the DU 174 determines that the UE 102 has not synchronized in UL with the cell 124B, the DU 174 determines to include the reconfiguration with sync configuration in the configuration 1. Otherwise, if the DU 174 determines that the UE 102 has synchronized in UL with the cell 124B, the DU 174 determines to not include the reconfiguration with sync configuration in the configuration 1. In some implementations, if the configuration 1 includes the reconfiguration with sync configuration, the UE 102 performs the random access procedure in the event 332, as described below, in response to or in accordance with the reconfiguration with sync configuration. Otherwise, if the configuration 1 does not include the reconfiguration with sync configuration, the UE 102 skips the random access procedure of the event 332. In some implementations, the DU 174 includes a cell ID (i.e., cell ID 1) of cell 1 (i.e., the cell 124B) in the configuration 1. In some implementations, the cell ID 1 is a PCI. In further implementations, the cell ID 1 is a CGI. In some further implementations, the configuration 1 includes a cell index 1 (e.g., a serving cell index) indexing the cell ID 1 or the cell 124B.

[0091] In some implementations, after (e.g., in response to) receiving one or some of the at least one measurement report of the event 304, the base station 104 (i.e., the CU 172 or DU 174) determines to prepare other cell(s) of the base station 104 for the UE 102. In some implementations, the base station 104 determines to prepare the other cell(s) because the at least one measurement report indicates that the other cell(s) could be used by the base station 104 to communicate with the UE 102. In some implementations, the other cell(s) include the cell 124C and / or cells other than the cells 124A, 124B, and 124C. In some implementations, if the L3 measurement report(s) indicate that signal strength and / or quality of a particular cell of the other cell(s) is above a respective predetermined threshold and / or is better (e.g., higher) than the cell 124A, the CU 172 determines to prepare the particular cell for the UE 102. In other implementations, if the LI measurement report(s) or new-type measurement report(s) indicate that signal strength and / or quality of a particular cell of the other cell(s) is above a first predetermined threshold and / or is better (e.g., higher) than the cell 124A, the DU 174 determines to prepare the particular cell for the UE 102. In some implementations, the respective predetermined threshold(s) for the other cells are different from the first21SUBSTITUTE SHEET (RULE 26)predetermined threshold. In further implementations, the respective predetermined threshold(s) for the other cell(s) are the same as the first predetermined threshold. In some implementations, the respective predetermined thresholds for the other cells are the same or different. Alternatively, the base station 104 determines to prepare the other cell(s) for the UE 102 regardless of whether a measure report is received from the UE 102 or not.

[0092] In some implementations, in response to the determination to prepare the other cell(s), the CU 172 and DU 174 perform at least one other serving cell preparation procedure to prepare the other cell(s), where each of the at least one other serving cell preparation procedure is similar to the procedure 390. In further implementations, the CU 172 includes cell ID(s) of the other cell(s) in at least one CU-to-DU message of the at least one serving cell preparation procedure, similar to the first CU-to-DU message. In some implementations, the CU 172 and DU 174 perform an additional serving cell preparation procedure to prepare each of the other cell(s), similar to the procedure 390. In some such cases, the CU 172 includes a cell ID of a particular cell of the other cell(s) in a CU-to-DU message of the serving cell preparation procedure, similar to the first CU-to-DU message. In the serving cell preparation procedure(s), the DU 174 generates configuration(s) 2, ..., N, each configuring a particular cell of the other cell(s), and transmits the configuration(s) 2, ..., N to the CU 172, as described for the configuration 1. “N” is an integer and larger than one. For example, “N” is 2, 4, 6, 8, 10, 12, 14 or 16. Examples and implementations of the configuration 1 can apply to the configuration(s) 2, ..., N.

[0093] In other implementations, the CU 172 determines to prepare the other cell(s) in the procedure 390. In some such cases, the CU 172 includes a cell ID for each of the other cell(s) in the first CU-to-DU message, and the DU 174 includes the configuration(s) 2, ..., N in the first DU-to-CU message. In yet other implementations, the DU 174 determines to prepare the other cell(s) in the procedure 390 and includes the configuration(s) 2, ..., N in the first DU-to-CU message.

[0094] In some implementations, after receiving the configuration(s) 2, ..., N from the DU 174, the CU 172 includes the configuration(s) 2, ..., N in the first container. In some implementations, the CU 172 includes the 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, ID(s) 2, ..., N for identifying the configuration(s) 2, ..., N, respectively. In some implementations, the CU 172 includes the22SUBSTITUTE SHEET (RULE 26)ID(s) 2, .. N in the first container. For example, the CU 172 includes the ID(s) 2, .. N and configuration(s) 2, .. N in the element(s) 2, .. N in the first addition or modification list.

[0095] In some implementations, the CU 172 assigns the ID(s) 2, ..., N for the configuration(s) , ..., N. In other 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 or in DU-to-CU message(s) of the at least one other serving cell preparation procedure or additional serving cell preparation procedure(s).

[0096] In some implementations, the CU 172 performs an ID allocation procedure with the DU 174 for each of the configuration(s) 2, ..., N, similar to the procedure 392. In such cases, the DU 174 includes the ID(s) 2, ..., N in the configuration(s) 2, ..., N. In such cases, the CU 172 does not include the ID(s) 2, ..., N in the RRC reconfiguration message, first container, and / or element(s) 2, ... , N.

[0097] In some alternative implementations, the DU 174 assigns the ID(s) 2, ..., N in the configuration(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 or in DU-to-CU message(s) of the at least one other serving cell preparation procedure or additional serving cell preparation procedure(s). The CU 172 includes the ID(s) 2, ..., M in the RRC reconfiguration message. In other implementations, the DU 174 includes the ID(s) 2, ..., N in the configuration(s) 2, ..., N. Thus, the CU 172 does not include an ID identifying each of configuration(s) 2, ..., N in the RRC reconfiguration message, first container and / or element 1.

[0098] In some alternative implementations, the CU 172 generates a second container including the configuration(s) 2, ..., N or element(s) 2, ..., N instead of using the first container. Alternatively, the DU 174 generates the second container and includes the second container in the first DU-to-CU message or a DU-to-CU message of the other serving cell preparation procedure. The CU 172 then 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., ConfigToAddModList IE, CellConfigToAddModList IE, MobilityToAddModList IE, MobilityConfigToAddModList IE, or CellGroupConfigToAddModList IE), and each of the element(s) 2, ..., N is an addition or modification IE (e.g., ConfigToAddMod IE,23SUBSTITUTE SHEET (RULE 26)ReconfigToAddMod IE, CellConfigToAddMod IE, MobilityToAddMod IE, MobilityConfigToAddMod IE, or CellGroupConfigToAddMod IE). In some implementations, when the UE 102 receives the second addition or modification list, the UE 102 stores the second addition or modification list together with the first addition or modification list (e.g., in a variable in the RAM).

[0099] In some implementations, the DU 174 includes cell ID(s) 2, ..., N in the configuration(s) 2, ..., N, respectively. The cell ID(s) 2, ..., N identify cell(s) 2, ..., N, respectively. In some implementations, each of the cell ID(s) 2, ..., N is a PCI. In some further implementations, the configuration(s) 2, ..., N include cell index(es) 2 , ..., N (e.g., service cell index(es)) indexing the cell ID(s) 2, ..., N or the cell(s) 2, ..., N, respectively.

[0100] In some implementations, each of the configuration(s) 1 and / or 2, ..., N is a CellGroupConfig IE. In such implementations, the following are example structures of the first or second addition or modification list (e.g., CellGroupConfigToAddModList IE), and CellGroupConfigToAddMod IE is an element of the first or second addition or modification list.

[0101] In some implementations, the CU 172 transmits, to the UE 102, a release list to release one or more configurations of the configuration(s) 1, ..., N via the DU 174. For example, the CU 172 transmits an RRC reconfiguration message including the release list to the UE 102 via the DU 174. In response, the UE 102 transmits an RRC reconfiguration complete message to the CU 172 via the DU 174. In some implementations, the base station 104 includes ID(s) of the one or more configurations in the release list to indicate the one or more of the configurations to be released. The UE 102 identifies the one or more of the configurations in accordance with the ID(s) and releases the one or more of the configurations in response to the release list.

[0102] In some implementations, the base station 104 transmits, to the UE 102, a third addition or modification list, which is empty or does not include a configuration, to release all of the configuration(s) 1, ..., N. In some implementations, the base station 104 transmits an RRC reconfiguration message, including the third addition or modification list, to the UE 102. In response, the UE 102 transmits an RRC reconfiguration complete message to the CU 172 via the DU 174. The UE 102 releases all of the configuration(s) 1, ..., N in response to the third addition or modification list.24SUBSTITUTE SHEET (RULE 26)

[0103] In some implementations, the CU 172 determines to release one configuration, more configurations, or all of the configuration(s) 1, ..., N, and transmits a CU-to-DU message to the DU 174 to indicate to the DU 174 to release the one, more, or all of the configuration(s) 1, ..., N. For example, the CU 172 includes one, more, or all of the ID(s) 1, ..., N in the CU-to-DU message to indicate to the DU 174 to release the one, more, or all of the configuration(s) 1, ..., N. Depending on the implementation, each of the cell ID(s) 1, ..., N is a CGI or PCI. In some implementations, in response, the DU 174 releases the one, more, or all of configuration(s) 1, ..., N and transmits a DU-to-CU message to the CU 172. In other implementations, the DU 174 determines to release one, more, or all of the configuration(s) 1, ..., N and transmits a DU-to-CU message including ID(s) of the one, more, or all of the configuration(s) 1, ..., N to the CU 172. After (e.g., in response to) receiving the DU-to-CU message, the CU 172 generates the release list or the third addition or modification list to release the one, more, or all of the configuration(s) 1, ..., N.

[0104] In yet other implementations, the DU 174 generates the release list or the third addition or modification list. In some such cases, the DU 174 transmits a DU-to-CU message, including the release list or the third addition or modification list, to the CU 172. In some implementations, the CU 172 transmits a CU-to-DU message to the DU 174 in response. In some implementations the DU 174 determines to release the one, more, or all of the configuration(s) 1, ... , N. In other implementations, the DU 174 receives, from the CU 172, a CU-to-DU message including the ID(s) of the one, more, or all of the configuration(s) 1, ..., N to indicate to release the one, more, or all of the configuration(s) 1, ..., N.

[0105] Example Implementation 1CellGroupConfigToAddModList ::= SEQUENCE (SIZE (1.. maxNrofConfigCells)) OF CellGroupConfigToAddMod CellGroupConfigToAddMod ::= SEQUENCE { configld Configld, cellGroupConfig OCTET STRING (CONTAINING CellGroupConfig) OPTIONAL,•••}CellGroupConfigToReleaseList ::= SEQUENCE (SIZE (1.. maxNrofConfigCells)) OF Configld maxNrofConfigCells ::= 8For example, the first addition or modification list is a first CellGroupConfigToAddModList IE, and the second addition or modification list is a second CellGroupConfigToAddModList IE. The element 1 is a CellGroupConfigToAddMod IE 1, and the element(s) 2, ..., N is / are CellGroupConfigToAddMod IE(s) 2, ..., N, respectively. The ID 1 and configuration 1 are a25SUBSTITUTE SHEET (RULE 26)Configld and a CellGroupConfig IE in the CellGroupConfigToAddMod IE 1, respectively. The ID(s) 2, .. N and configuration(s) 2, .. N are a Configld and a CellGroupConfig IE in the CellGroupConfigToAddMod IE(s) 2, N, respectively. In some implementations, the first CellGroupConfigToAddModList IE includes the CellGroupConfigToAddMod IE 1, and the second CellGroupConfigToAddModList IE includes the CellGroupConfigToAddMod IE(s) 2, ..., N. In further implementations, the first CellGroupConfigToAddModList IE includes the CellGroupConfigToAddMod IE(s) 1, ..., N.

[0106] In some implementations, the release list is a CellGroupConfigToReleaseList IE. In further implementations, the base station 104 includes one or more ConfiglD IES in the CellGroupConfigToReleaseList IE to release one or more CellGroupConfigToAddMod IEs of the CellGroupConfigToAddMod IE(s) 1, ..., N. The one or more CellGroupConfigToAddMod IEs are identified by the one or more ConfiglD IEs.

[0107] Example Implementation 2Example Implementation 2 is similar to Example Implementation 1, except that the CellGroupConfigToAddMod IE does not include a Configld.CellGroupConfigToAddModList ::= SEQUENCE (SIZE (0.. maxNrofConfigCells)) OF CellGroupConfigToAddModCellGroupConfigToAddMod ::= SEQUENCE {CellGroupConfig OCTET STRING (CONTAINING CellGroupConfig) OPTIONAL,} maxNrofConfigCells ::= 8In some implementations, the ID(s) 1, ..., N are implicitly indicated by the order of the CellGroupConfigToAddMod IE(s) 1, ..., N in the first or second CellGroupConfigToAddModList. For example, the CellGroupConfigToAddMod IE 1 is the first IE in the first CellGroupConfigToAddModList IE, which implicitly indicates that the ID 1 has value X. X can be zero or one. If the first CellGroupConfigToAddModList IE includes the CellGroupConfigToAddMod IE(s) 1, ..., N in sequence, the ID(s) 1, ..., N have values X, X+l, ...., X+(N-1). In some implementations, if the base station 104 transmits the second CellGroupConfigToAddModList IE to the UE 102, the UE 102 and base station 104 replace the first CellGroupConfigToAddModList IE with the second CellGroupConfigToAddModList IE. If the second CellGroupConfigToAddModList IE includes theCellGroupConfigToAddMod IE(s) 2, ..., N in sequence, the ID(s) 2, ..., N are values X, X+l,26SUBSTITUTE SHEET (RULE 26)...., X+N-2. If the second CellGroupConfigToAddModList IE includes the CellGroupConfigToAddMod IE(s) 1, ..., N in sequence, the ID(s) 1, ..., N are values X, X+l, ...., X+N- 1. In some alternative implementations, the ID(s) 1 , ... , N are the cell ID(s) 1 , ... , N.

[0108] In some implementations, the base station 104 transmits a CellGroupConfigToAddModList IE including zero CellGroupConfigToAddMod IE to release all of the CellGroupConfigToAddMod IE(s) 1, N.

[0109] In the Example Implementations 1 and 2, the “CellGroupConfigToAddModList”, “CellGroupConfigToAddMod” , "configld”, “Configld” “cellGroupConfig” , “CellGroupConfigToReleaseList” , and “maxNrofConfigCells” are exemplary only and should not be considered to restrict scope and application of the invention.

[0110] In other implementations, each of the configuration(s) 1 and / or 2, ..., N is an RRCReconfiguration message. In such implementations, the following (i.e., Example Implementations 3-6) are example structures of the first or second addition or modification list.

[0111] Example Implementation 3In Example Implementation 3, the first or second addition or modification list is a CondReconfigToAddModList-rl6 IE (e.g., as defined in 3GPP specification 38.331 from Release 16), and a CondReconfigToAddMod IE is an element of the list.CondReconfigToAddModList-rl6 ::= SEQUENCE (SIZE (1.. maxNrofCondCells-r!6)) OFCondReconfigT o AddMod-r 16CondReconfigToAddMod-rl6 ::= SEQUENCE { condReconfigld-r 16 CondReconfigld-r 16 , condExecutionCond-r 16 SEQUENCE (SIZE (1..2)) OF MeasldOPTIONAL, - Need M condRRCReconfig-r 16 OCTET STRING (CONTAINING RRCReconfiguration)OPTIONAL, — Cond condReconfigAdd[[ condExecutionCondSCG-rl7 OCTET STRING (CONTAININGCondReconfigExecCondSCG-rl7) OPTIONAL — Need M]]}CondReconfigExecCondSCG-rl7 ::= SEQUENCE (SIZE (1..2)) OF MeasldCondReconfigToRemoveList-rl6 ::= SEQUENCE (SIZE (1.. maxNrofCondCells-rl6)) OFCondReconfigld-r 16SUBSTITUTE SHEET (RULE 26)For example, the first addition or modification list is a first CondReconfigToAddModList-rl6 IE and a second CondReconfigToAddModList-rl6 IE. The element 1 is a CondReconfigToAddMod-rl6 IE 1, and the element(s) 2, N are CondReconfigToAddMod- rl6 IE(s) 2, N, respectively. The ID 1 and configuration 1 are a CondReconfigld and an RRCReconfiguration message in the CondReconfigToAddMod IE 1, respectively. The ID(s) 2, ..., N and configuration(s) 2, ..., N are a CondReconfigld and an RRCReconfiguration message in the CondReconfigToAddMod IE(s) 2, ..., N, respectively. In some implementations, the first CondReconfigToAddModList-rl6 IE includes the CondReconfigToAddMod-rl6 IE 1, and the second CondReconfigToAddModList-rl6 IE includes the CondReconfigToAddMod-rl6 IE(s) 2, ..., N. In further implementations, the first CondReconfigToAddModList-rl6 IE includes the CondReconfigToAddMod-rl6 IE(s) 1, ..., N.

[0112] In this example implementation, the base station 104 includes a condition configuration (i.e., condExecutionCond-rl6) in at least one of the CondReconfigToAddMod- rl6 IE(s). In some implementations, if the UE 102 supports a conditional procedure (e.g., conditional handover (CHO), conditional PSCell addition (CPA), or conditional PSCell change (CPC)), the UE 102 evaluates one or more conditions configured in the condExecutionCond-rl6 field for the conditional procedure. If the UE 102 detects that at least one or all of the one or more conditions in the condExecutionCond-rl6 field in a particular CondReconfigToAddMod-rl6 IE is met, the UE 102 immediately applies configurations in an RRCReconfiguration message in the CondReconfigToAddMod-rl6 IE (e.g., as described in 3GPP specification 38.331). In some implementations, the base station 104 does not include a condition configuration (i.e., condExecutionCond-rl6) in any one or some of the CondReconfigToAddMod-rl6 IE(s). Thus, the UE 102 is not configured to perform or does not perform any evaluation (i.e., detection or determination) of a condition for a conditional procedure (e.g., conditional handover) for the CondReconfigToAddMod-rl6 IE(s) not including a condition configuration (i.e., condExecutionCond-ri6).

[0113] In some implementations, the release list is a CondReconfigToRemoveEist-rl6 IE. In further implementations, the base station 104 includes one or more CondReconfiglD IES in the CondReconfigToRemoveEist-rl6 IE to release one or more CondReconfigToAddMod-rl6 IEs of the CondReconfigToAddMod-rl6 IE(s) 1, ..., N. The one or more CondReconfigToAddMod-rl6 IEs are identified by the one or more CondReconfiglD IEs.28SUBSTITUTE SHEET (RULE 26)

[0114] Example Implementation 4Example Implementation 4 is similar to Example Implementation 3, except that, in some implementations, a new indicator (e.g., fastServingCellChange-rl8 field) is optionally included in a CondReconfigT oAddMod-r 16 IE. In some implementations, the new indicator indicates that the CondReconfigT oAddMod-r 16 IE (i.e., an RRCReconfiguration message or condRRCReconfig-rl6 in the IE) is configured for fast serving cell change (i.e., see description for event 312). If the base station 104 does not include the new indicator in a CondReconfigT oAddMod-r 16 IE, the CondReconfigT oAddMod-r 16 IE is not configured for fast serving cell change.CondReconfigToAddModList-rl6 ::= SEQUENCE (SIZE (1.. maxNrofCondCells-rl6)) OFCondReconfigT o AddMod-r 16CondReconfigT oAddMod-r 16 := SEQUENCE { condReconfigld-r 16 CondReconfigld-r 16 , condExecutionCond-r 16 SEQUENCE (SIZE (1..2)) OF MeasldOPTIONAL, - Need M condRRCReconfig-r 16 OCTET STRING (CONTAINING RRCReconfiguration)OPTIONAL, — Cond condReconfigAdd[[ condExecutionCondSCG-rl7 OCTET STRING (CONTAININGCondReconfigExecCondSCG-rl7) OPTIONAL — Need M]],[[ fastServingCellChange-rl8 ENUMERATED {true} OPTIONAL, -Cond fastServingCellChange M]]}CondReconfigExecCondSCG-rl7 ::= SEQUENCE (SIZE (1..2)) OF MeasldCondReconfigToRemoveList-rl6 ::= SEQUENCE (SIZE (1.. maxNrofCondCells-rl6)) OFCondReconfigld-r 16

[0115] Example Implementation 5Some implementations of Example Implementations 3 and 4 may involve the UE 102 supporting conditional procedures (e.g., conditional handover (CHO), conditional PSCell addition (CPA), and / or conditional PSCell change (CPC)). If the UE 102 does not support the conditional procedures, the base station 104 does not configure or enable fast serving cell change for the UE 102. Thus, Example Implementation 5 decouples from the conditional procedures.ReconfigToAddModList ::= SEQUENCE (SIZE (1.. maxNrofConfigCells)) OF ReconfigToAddMod29SUBSTITUTE SHEET (RULE 26)ReconfigToAddMod ::= SEQUENCE { configld Configld, cellGroupConfig OCTET STRING (CONTAINING RRCReconfiguration)OPTIONAL,}ReconfigToReleaseList ::= SEQUENCE (SIZE (1.. maxNrofConfigCells)) OF Configld maxNrofConfigCells ::= 8In some implementations, the first addition or modification list is a first ReconfigToAddModList IE and the second addition or modification list is a second ReconfigToAddModList IE. The element 1 is a ReconfigToAddMod IE 1, and the element(s) 2, ..., N are ReconfigToAddMod IE(s) 2, ..., N, respectively. The ID 1 and configuration 1 are a Configld and an RRCReconfiguration IE in the ReconfigToAddMod IE 1. The ID(s) 2, ..., N and configuration(s) 2, ..., N are a Configld and an RRCReconfiguration IE in the ReconfigToAddMod IE(s) 2, ..., N, respectively. In some implementations, the first ReconfigToAddModList IE includes the ReconfigToAddMod IE 1 and the second ReconfigToAddModList IE includes the ReconfigToAddMod IE(s) 2, ..., N. In further implementations, the first ReconfigToAddModList IE includes the ReconfigToAddMod IE 1, ..., N.

[0116] In some implementations, the release list is a ReconfigToReleaseList IE. In further implementations, the base station 104 includes one or more ConfiglD IES in the ReconfigToReleaseList IE to release one or more ReconfigToAddMod IEs of the ReconfigToAddMod IE(s) 1, ..., N. The one or more ReconfigToAddMod IEs are identified by the one or more ConfiglD IEs.

[0117] Example Implementation 6ReconfigToAddModList ::= SEQUENCE (SIZE (0.. maxNrofConfigCells)) OF ReconfigToAddMod ReconfigToAddMod ::= SEQUENCE { cellGroupConfig OCTET STRING (CONTAINING RRCReconfiguration) OPTIONAL,} maxNrofConfigCells ::= 8Example Implementation 6 is similar to Example Implementation 5, except that the ReconfigToAddMod IE does not include a Configld. In some implementations, the ID(s) 1, ..., N are implicitly indicated by the order of the ReconfigToAddMod IE(s) 1, ..., N in the first or second ReconfigToAddModList. For example, the ReconfigToAddMod IE 1 is the first IE in the first ReconfigToAddModList IE, which implicitly indicates that the ID 1 has value30SUBSTITUTE SHEET (RULE 26)X. X can be zero or one. If the first ReconfigToAddModList IE includes the ReconfigToAddMod IE(s) 1, ..., N in sequence, the ID(s) 1, ..., N have values X, X+l, ...., X+(N-1). In some implementations, if the base station 104 transmits the second ReconfigToAddModList IE to the UE 102, the UE 102 and base station 104 replace the first ReconfigToAddModList IE with the second ReconfigToAddModList IE. If the second ReconfigToAddModList IE includes the ReconfigToAddMod IE(s) 2, ..., N in sequence, the ID(s) 2, ..., N are values X, X+l, ...., X+N-2. If the second ReconfigToAddModList IE includes the ReconfigToAddMod IE(s) 1, ..., N in sequence, the ID(s) 1, ..., N have values X, X+l, ...., X+N-l. In some alternative implementations, the ID(s) 1, ..., N are the cell ID(s) 1, ..., N.

[0118] In some implementations, the base station 104 transmits a ReconfigToAddModListIE including zero ReconfigToAddMod IE to release all of the ReconfigToAddMod IE(s) 1, ...,N.

[0119] In the Example Implementations 5 and 6, the “ReconfigToAddModList” , “ReconfigToAddMod” , “configld”, "Con igld” , “ CellGroupConfig” , “ReconfigToReleaseList” , and “maxNrofConfigCells” are exemplary and should not restrict scope and application of the invention.

[0120] Example Implementation 7Example Implementation 7 is a combination of the Example Implementations 1 and 5, as shown below. Depending on implementation, any of the configuration(s) 1, ..., N is a CellGroupConfig IE or an RCReconfiguration message. Examples and implementations described for the Example Implementations 1 and 5 can apply to Example Implementation 7.ReconfigToAddModList ::= SEQUENCE (SIZE (1.. maxNrofConfigCells)) OFReconfigToAddModReconfigToAddMod ::= SEQUENCE { configld Configld, CellGroupConfig CHOICE {CellGroupConfig 1 OCTET STRING (CONTAINING CellGroupConfig) OPTIONAL, cellGroupConfig2 OCTET STRING (CONTAINING RRCReconfiguration)OPTIONAL,}ReconfigToReleaseList ::= SEQUENCE (SIZE (1.. maxNrofConfigCells)) OF Configld maxNrofConfigCells ::= 831SUBSTITUTE SHEET (RULE 26)

[0121] After receiving the RRC reconfiguration message in the event 318 or transmitting the RRC reconfiguration complete message in the event 320, 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 of the event 324 includes LI measurement report(s), L3 measurement repot(s), and / or new-type measurement report(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 other 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, each of the at least one measurement report of the event 324 is not an RRC message.

[0122] 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. For example, the CU 172 transmits 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 after the event 306 or 316. Depending on the implementation, the one or more RRC messages do or do not include the RRC reconfiguration message of the event 316. 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 include one or more SSBs and / or one or more CSI-RSs. The UE 102 obtains 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 measurement report of the event 324. The DU 174 transmits the one or more reference signals on the cells 124A and 124B, and, in some implementations, the cell 124C and / or other cell(s). In some implementations, the measurement configuration(s) include L3 measurement configuration(s) (e.g., MeasConfig IE(s)), LI measurement configuration(s) (e.g., CSl-MeasConfig IE(s)), and / or new-type measurement configuration(s), as described for the event 304.32SUBSTITUTE SHEET (RULE 26)

[0123] In some implementations, the new-type measurement configuration(s) as described for the events 304 and 324 are similar to the L3 measurement configuration(s). For example, the new-type measurement configuration includes a portion of configuration parameters defined in a MeasConfig IE. In other implementations, the new-type measurement configuration(s) as described for the events 304 and 324 are similar to the LI measurement configuration(s). For example, the new-type measurement configuration includes a portion of configuration parameters (e.g., CSl-ResourceConfig IE(s) and / or CSl-ReportConfig IE(s)) defined in a CSl-MeasConfig IE.

[0124] After (e.g., in response to) receiving the at least one measurement report in the event 324, the DU 174 transmits 330 a first configuration activation command to the UE 102 to activate the configuration 1. For example, the base station 104 transmits the first configuration activation command on the cell 124A. In another example, the base station 104 transmits the first configuration activation command on the cell 124D. In some implementations, the DU 174 includes the ID 1 of in the first configuration activation command. The UE 102 determines and activates the configuration 1, in accordance with the first configuration activation command and ID 1. In other implementations, the DU 174 includes, in the first configuration activation command, the cell index 1 (e.g., a serving cell index) or cell ID 1 included in the configuration 1. The UE 102 determines and activates the configuration 1, in accordance with the first configuration activation command and the cell index 1 or cell ID 1.

[0125] In yet other implementations, the DU 174 includes a bit map in the first configuration activation command to activate the configuration 1, instead of the ID 1, cell 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 configuration(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 ID 1 or the configuration 1. In further implementations, bit 0, ..., N-l corresponds to the configuration(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 ID 1 or the configuration 1. Thus, the UE 102 can determine the particular ID or particular configuration in accordance with the bit 1 or bit 0 set to the first value in the bit map. In such implementations, the DU 174 sets the remaining bits in the bit map to a second value to indicate that the reset of the configuration(s) 1, ..., N is not activated. In some implementations, the first value is one and the second value is zero. In other implementations, the first value is zero and the second value is one. In some33SUBSTITUTE SHEET (RULE 26)implementations, if the DU 174 determines to activate another configuration (e.g., configuration K) in addition to the configuration 1, the DU 174 sets the corresponding bit (e.g., bit K or bit K-l) in the bit map to the first value, where 1<=K<=N.

[0126] In some implementations, the at least one measurement report (e.g., LI measurement report(s) or new-type measurement report(s)) of the event 324 includes at least one measurement result for the cell 124B. The DU 174 determines to activate the configuration 1 because the at least one measurement result indicates that signal strength or quality of the cell 124B is above a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In some implementations, the second predetermined threshold is larger than the first predetermined threshold. In such implementations, the at least one measurement report of the event 324 indicates that signal strength or quality of the cell 124B is suitable for communication with the UE 102. In further implementations, the second predetermined threshold is equal to the first predetermined threshold. In such implementations, the at least one measurement report of the event 324 indicates that signal strength or quality of the cell 124B has been continuously above the second predetermined threshold or the first predetermined threshold. This also indicates that the cell 124B is suitable for communication with the UE 102. Thus, the DU 174 determines to activate the configuration 1 (i.e., fast serving cell change to the cell 124B) in response to determining that signal strength or quality of the cell 124B is above the second predetermined threshold.

[0127] In some implementations, the at least one measurement report (e.g., L3 measurement report(s)) of the events 324 and 326 includes at least one measurement result for the cell 124B. The CU 172 determines to activate the configuration 1 because the at least one measurement result indicates that signal strength or quality of the cell 124B is above a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In some implementations, the second predetermined threshold is larger than the first predetermined threshold. In such implementations, the at least one measurement report of the event 326 indicates that signal strength or quality of the cell 124B is suitable for communication with the UE 102. In further implementations, the second predetermined threshold is equal to the first predetermined threshold. In implementations, the at least one measurement report of the event 326 indicates that signal strength or quality of the cell 124B has been continuously above the second predetermined threshold or the first predetermined threshold. This also indicates that the cell 124B is suitable for communication 34SUBSTITUTE SHEET (RULE 26)with the UE 102. Thus, the CU 172 determines to activate the configuration 1 (i.e., fast serving cell change to the cell 124B) in response to determining that signal strength or quality of the cell 124B is above the second predetermined threshold.

[0128] In response to the determination, the CU 172 transmits 328 a fourth CU-to-DU message to the DU 174 to activate the configuration 1. In response to the fourth CU-to-DU message, the DU 174 transmits 330 the first configuration activation 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 (e.g., a serving cell index) in the fourth CU-to-DU message. Thus, the DU 174 can determine to activate the configuration 1 in accordance with the (serving) cell index 1. In other implementations, the CU 172 includes the cell ID 1 in the fourth CU-to-DU message. Thus, the DU 174 can determine to activate the configuration 1 in accordance with the cell ID. In yet other implementations, the CU 172 includes the ID 1 in the fourth CU-to-DU message. Thus, the DU 174 can determine to activate the configuration 1 in accordance with the ID 1. In some 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 other implementations, the fourth CU-to-DU message is a new interface message (e.g., an Fl application protocol (F1AP) message (e.g., defined in 3GPP specification 38.473 vl8.0.0 and / or later versions)). In other implementations, the fourth DU-to-CU message is a new interface message (e.g., a new F1AP message (e.g., defined in 3GPP specification 38.473 v 18.0.0 and / or later versions)).

[0129] In some implementations, the first configuration activation command is a MAC CE included in a MAC PDU that the UE 102 receives from the DU 174 in the event 330. In some implementations, the MAC CE is a new MAC CE (e.g., defined in 3GPP specification 38.321 vl8.0.0 and / or later versions). In some implementations, the DU 174 includes a subheader identifying the MAC CE in the MAC PDU, and the UE 102 identifies the MAC CE in the MAC PDU in accordance with the subheader. Depending on the implementation, the subheader includes a logical channel ID or extended logical channel ID (e.g., defined in a 3GPP specification) to identify the MAC CE. For example, the logical channel ID or extended logical channel ID are newly defined (e.g., in 3GPP specification 38.321 vl8.0.0 and / or later versions). In other implementations, the first configuration activation command is a DCI that the UE 102 receives on a PDCCH in the event 330. The DU 174 generates a CRC for the DCI, scrambles the CRC with a first C-RNTI of the UE 102, and transmits the 35SUBSTITUTE SHEET (RULE 26)DO and scrambled CRC on the PDCCH in the event 330. In some implementations, a format of the DCI is an existing DCI format (e.g., defined in a 3GPP specification (e.g., 38.212)). In further implementations, the format of the DCI is a new DCI format (e.g., defined in a 3GPP specification (e.g., 38.212 vl8.0.0 or later versions)).

[0130] In some implementations, the DU 174 does not perform security protection (e.g., integrity protection and / or encryption) on the first configuration activation command. This speeds up processing the first configuration activation command in the UE 102 because the UE 102 does not spend time to perform a security check (e.g., decryption and / or integrity check) on the first configuration activation command.

[0131] In some implementations, after receiving the first configuration activation 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 configuration activation command. In some implementations, the acknowledgement is a HARQ ACK. In other implementations, the acknowledgement is a MAC CE. For example, the MAC CE is an existing MAC CE (e.g., defined in 3GPP specification 38.321 vl7.1.0). In another example, the MAC CE is a new MAC CE (e.g., defined in 3GPP specification 38.321 vl8.0.0 and / or later versions). In yet other implementations, the acknowledgement is a PUCCH transmission.

[0132] In some implementations, the CU 172 transmits 316 the RRC reconfiguration message in response to the L3 measurement report for the cell 124B that the CU 172 receives in the event 306. In further implementations, the CU 172 transmits a first RRC reconfiguration message, including a MeasConfig IE, to the UE 102 to configure the UE 102 to transmit the L3 measurement report. In some implementations, the DU 174 transmits 330 the first configuration activation command in response to the LI measurement report for the cell 124B that the DU 174 receives in the event 324. In further implementations, the CU 172 transmits a second RRC reconfiguration message, including a CSl-MeasConfig IE, to the UE 102 to configure the UE 102 to transmit the LI measurement report. In some implementations, the first and second RRC reconfiguration messages are the same message (i.e., the same instance). In other implementations, the first and second RRC reconfiguration messages are different messages. In some implementations, the second RRC reconfiguration message is the RRC reconfiguration message of the event 316. In other implementations, the second RRC reconfiguration message is different from the RRC reconfiguration message of the event 316.36SUBSTITUTE SHEET (RULE 26)

[0133] After (e.g., in response to) receiving the first configuration activation command, the UE 102 identifies the particular configuration (e.g., the configuration 1) in accordance with the particular ID (e.g., the ID 1) and immediately applies the configuration 1. In some implementations, the UE 102 performs 332 a random access procedure on the cell 124B with the DU 174 in response to applying the configuration 1. In some implementations, the UE 102 disconnects from the cell 124A after (e.g., in response to) receiving the first configuration activation command or transmitting the acknowledgement. In other words, the UE 102 stops communicating on the cell 124A (e.g., in response to) receiving 330 the first configuration activation command or transmitting 331 the acknowledgement. In such cases, the UE 102 performs 332 the random access procedure after disconnecting from the cell 124A. In some implementations, the UE 102 determines whether to perform the random access procedure in accordance with the configuration 1. In some implementations, if the configuration 1 configures the UE 102 to perform a random access procedure, the UE 102 performs the random access procedure in the event 332. For example, the configuration 1 includes a reconfiguration with sync configuration (e.g., ReconfigurationWithSync IE) to configure the UE 102 to perform a random access procedure. Otherwise, if the configuration 1 does not configure the UE 102 to perform a random access procedure or configures the UE 102 to skip a random access procedure, the UE 102 refrains from performing a random access procedure with the DU 174 upon receiving the first configuration activation command. In such cases, the UE 102 skips the event 316. For example, if the configuration 1 excludes a reconfiguration with sync configuration, the configuration 1 configures the UE 102 not to perform a random access procedure. In some implementations, the random access procedure is a four-step random access procedure. In other implementations, the random access procedure is a two-step random access procedure. In some implementations, the random access procedure is a contention-free random access procedure. In other implementations, the random access procedure is a contention-based random access procedure.

[0134] In cases where the UE 102 performs 332 the random access procedure, the UE 102 communicates 336 with the DU 174 on cell 124B using the configuration 1 and communicates with the CU 172 via the DU 174 after successfully completing the random access procedure. For example, the UE 102 communicates UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) with the base station 104 in the event 318. In such cases, the UE 102 successfully completes the random access procedure when the UE 102 receives a contention resolution from the DU 174. In37SUBSTITUTE SHEET (RULE 26)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 cell 124B in the random access procedure. 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 cell 124B in the random access procedure. In some implementations, if the configuration 1 includes a second C-RNTI, the UE identity is the second C-RNTI of the UE 102. Otherwise, if the configuration 1 does not include a C-RNTI, the UE identity is the first C-RNTI. In cases where the random access procedure is a contention free random access procedure, the UE 102 transmits the dedicated random access preamble to the DU 174 via the cell 124B. In such cases, the configuration 1 includes the dedicated random access preamble.

[0135] The DU 174 identifies or determines that the UE 102 connects to the cell 124B upon receiving the UE identity or the dedicated preamble from the UE 102 in the random access procedure.

[0136] 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 cell 124B to indicate that the UE 102 applies the configuration 1. In some implementations, the UE 102 includes the RRC message in the Message 3. In further implementations, the UE 102 includes the RRC message in the Message A. In yet further implementations, the UE 102 transmits the RRC message after completing the random access procedure. In other implementations, if 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), the UE 102 transmits the RRC message to the base station 104 via the cell 124A. In yet other implementations, the UE 102 refrains from transmitting the RRC message to the base station 104 in response to applying the configuration 1 or receiving the first configuration activation command.

[0137] In some cases where the UE 102 skips the random access procedure, the UE 102 directly communicates 336 with the base station 104 on cell 124B in accordance with the configuration 1 after (e.g., in response to) receiving the first configuration activation command. For example, the UE 102 communicates UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) with the base station 104 in the event 318. In some such cases, the UE 102 transmits 336 at least one PUCCH transmission on the cell 124B to the DU 174 in accordance with the configuration 1, after (e.g., in response to) receiving the first configuration activation command. In some38SUBSTITUTE SHEET (RULE 26)implementations, the DU 174 transmits at least one DCI on a PDCCH on the cell 124B to the UE 102 to command the UE 102 to transmit the at least one PUCCH or PUSCH transmission after transmitting the first configuration activation command. The DU 174 identifies or determines that the UE 102 connects to the cell 124B upon receiving the PUCCH or PUSCH transmission. In other implementations, the UE 102 transmits the at least one PUCCH or PUSCH transmission regardless of receiving a DCI on a PDCCH on the cell 124B. The DU 174 identifies or determines that the UE 102 connects to the cell 124B upon receiving the PUCCH or PUSCH transmission. 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 cell 124B to indicate that the UE 102 applies the configuration 1. The CU 172 identifies or determines that the UE 102 connects to the cell 124B upon receiving the RRC message. In other implementations, if 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), the UE 102 transmits the RRC message to the base station 104 via the cell 124A. In yet other implementations, the UE 102 refrains from transmitting the RRC message to the base station 104 in response to applying the configuration 1 or receiving the first configuration activation command.

[0138] In some implementations, when the DU 174 determines that the UE 102 successfully connects to the cell 124B in the event 332 or 336, the DU 174 transmits 334 a DU-to-CU message (e.g., Access Success message) to the CU 172. In some implementations, the DU 174 includes a cell ID of the cell 124B in the DU-to-CU message of the event 334. The cell ID can be a PCI or a CGI. Thus, the CU 172 determines that the UE 102 connects to the cell 124B upon receiving the DU-to-CU message of the event 334. In further implementations, when the DU 174 determines that the UE 102 successfully connect to the cell 124B in the event 332 or 336, the DU 174 transmits a DL Data Delivery Status message or frame to the CU 172.

[0139] In some implementations, when determining that the UE 102 connects to the cell 124B, transmitting 330 the first configuration activation command, or receiving 331 the acknowledgement, the DU 174 stops communicating with the UE 102 on the cell 124A. In some implementations, when determining that the UE 102 connects to the cell 124B, transmitting 330 the first configuration activation command, or receiving 331 the acknowledgement, the DU 174 releases resources of cell 124A configured for the UE 102.39SUBSTITUTE SHEET (RULE 26)

[0140] The events 304, 306, 390, 392, 316, 318, 320, 322, 324, 326, 328, 330, 331, 332, 334, 336, 394 are collectively referred to in Fig. 3 as a fast serving cell configuration procedure 380.

[0141] In some implementations, the DU 174 generates the configuration 1 and / or configuration(s) 2, N as full configuration(s) replacing the first configuration or a particular configuration in the first configuration. In some implementations, if the configuration 1 is a full configuration, the UE 102 and DU 174 communicate 336 with each other in accordance with the configuration 1 instead of the first configuration or particular configuration. In some implementations, the DU 174 includes an indication that the configuration 1 is a full configuration in the configuration 1. In other implementations, the RRC reconfiguration message of the events 316, 318 includes an indication that the configuration 1 is a full configuration. In yet other implementations, the first container includes an indication that the configuration 1 is a full configuration. In yet other implementations, the element 1 (e.g., ConfigToAddMod IE, CellGroupConfigToAddMod, MobilityToAddMod IE, Mobility ConfigToAddMod IE, or CellGroupConfigToAddMod IE) includes an indication that the configuration 1 is a full configuration. In some implementations, the UE 102 determines that configuration 1 is a full configuration based on the indication that the configuration 1 is a full configuration. In some implementations, the indication that the configuration 1 is different from fidlConfig field (e.g., defined in the current 3GPP specifications). In other implementations, the indication that the configuration 1 is fidlConfig field in an RRCReconfiguration message (e.g., defined in the current 3GPP specifications).

[0142] In other implementations, the DU 174 generates the configuration 1 and / or configuration(s) 2, ..., N as delta configuration(s) augmenting at least a portion of the first configuration. In other words, the DU 174 generates the configuration(s) 1, ..., N on top of the first configuration. For example, if the configuration 1 is a delta configuration, the UE 102 and DU 174 augment at least the portion of the first configuration with the configuration 1. Thus, the UE 102 and base station 104 communicate 336 with each other in accordance with the configuration 1 and unaugmented portion of the first configuration. In some implementations, the configuration 1 includes an indication that the configuration 1 is a delta configuration. In other implementations, the first container includes an indication that the configuration 1 is a delta configuration. In yet other implementations, the element 1 includes an indication that the configuration 1 is a delta configuration. In some implementations, the 40SUBSTITUTE SHEET (RULE 26)UE 102 determines that configuration 1 is a full configuration based on the indication that the configuration 1 is a delta configuration. In some alternative implementations, the configuration 1, first container, or element 1 excludes an indication that the configuration 1 is a full configuration to indicate that the configuration 1 is a delta configuration. In further implementations, the UE 102 determines that the configuration 1 is a delta configuration based on the exclusion of the indication in the configuration 1, first container, or element 1.

[0143] In some implementations, if the configuration 1 is a full configuration, the UE 102 releases the first configuration or the particular configuration in the first configuration after (e.g., in response to) receiving 330 the first configuration activation command, transmitting 331 the acknowledgement, successfully performing the 332 the random access procedure, or receiving the first DCI on a PDCCH addressed to the UE identity of the UE 102 on the cell 124B. In some implementations, if the configuration 1 is a full configuration, the DU 174 releases the first configuration or the particular configuration in the first configuration after (e.g., in response to) transmitting 330 the first configuration activation command, receiving 331 the acknowledgement, successfully performing the 332 the random access procedure, or receiving a particular transmission from the UE 102 on the cell 124B. In some implementations, the particular transmission is a PUCCH transmission. In further implementations, the transmission is a PUSCH transmission. In some implementations, after transmitting the first configuration activation command, the DU 174 generates a DCI and a CRC of the DCI, scrambles the CRC with the UE identity of the UE 102, and transmits the DCI and scrambled CRC on a PDCCH on the cell 124B. When the UE 102 receives the DCI and scrambled CRC and verifies that the scrambled CRC is valid using the UE identity, the UE 102 transmits the PUSCH transmission to the DU 174 on the cell 124B.

[0144] In some implementations, the first configuration or the particular configuration is a first CellGroupConfig IE (i.e., the first configuration includes configuration parameters defined in the first CellGroupConfig IE), and the configuration 1 is a second CellGroupConfig IE.

[0145] In some implementations, the UE 102 uses a UE MAC entity (e.g., MAC 204B) to communicate with the DU 174 (e.g., the events 302, 304, 318, 320, 324, 330, and / or 331). In some implementations, the base station 104 configures whether the UE 102 resets the UE MAC entity upon receiving the first configuration activation command. In some implementations, the base station 104 includes a MAC reset indication in the configuration 141SUBSTITUTE SHEET (RULE 26)or element 1 to configure the UE 102 to reset the UE MAC entity, and the base station 104 excludes the MAC reset indication in the configuration 1 or element 1 to configure the UE 102 not to reset the UE MAC entity. If the configuration 1 or element 1 includes the MAC reset indication, the UE 102 resets the UE MAC entity in response to the MAC reset indication upon receiving the first configuration activation command.

[0146] Otherwise, if the configuration 1 or element 1 does not include the MAC reset indication, the UE 102 refrains from resetting the UE MAC entity upon or when receiving the first configuration activation command. In some implementations, if the configuration 1 or element 1 does not include the MAC reset indication and includes an indication that the configuration is a full configuration, the UE 102 resets the UE MAC entity upon or when receiving 330 the first configuration activation command. Otherwise, if the configuration 1 or element 1 does not include the MAC reset indication and the indication that the configuration is a full configuration, the UE 102 refrains from resetting the UE MAC entity upon or when receiving 330 the first configuration activation command.

[0147] In some implementations, the base station 104 (e.g., the DU 174 or CU 172) uses a DU MAC entity (e.g., NR MAC 204B) to communicate with the UE 102 (e.g., the events 302, 304, 318, 320, 324, 330, and / or 331). If the base station 104 includes the MAC reset indication in the configuration 1 or element 1, the DU 174 resets the DU MAC entity in response to the MAC reset indication after transmitting 330 the first configuration activation command, receiving 331 the acknowledgement, or determining that the UE 102 connects to the cell 124B in the event 332 or 336.

[0148] Otherwise, if the configuration 1 or element 1 does not include the MAC reset indication, the DU 174 refrains from resetting the DU MAC entity after (e.g., in response to) transmitting 330 the first configuration activation command. Thus, the DU 174 continues to use the retained (i.e., un-reset) DU MAC entity to communicate with the UE 102 after transmitting 330 the first configuration activation command, receiving 331 the acknowledgement, or determining that the UE 102 connects to the cell 124B in the event 332 or 336.

[0149] In some implementations, the DU 174 includes the MAC reset indication in a MAC- CellGroupConfig IE in the configuration 1 (e.g., CellGroupConfig IE). In other implementations, the DU 174 includes the MAC reset indication in the CellGroupConfig IE42SUBSTITUTE SHEET (RULE 26)and outside the MAC-CellGroupConfig IE. In yet other implementations, the DU 174 includes the MAC reset indication in the element 1 and outside the configuration 1.

[0150] In some implementations, if the configuration 1 or element 1 does not include the MAC reset indication and includes an indication that the configuration 1 is a full configuration, the DU 174 resets the DU MAC entity after transmitting 330 the first configuration activation command, receiving 331 the acknowledgement, or determining that the UE 102 connects to the cell 124B in the event 332 or 336. Alternatively, the DU 174 releases the DU MAC entity and establishes a new DU MAC entity for communication with the UE 102 via the cell 124B instead of resetting the DU MAC entity. Otherwise, if the configuration 1 or element 1 does not include the MAC reset indication and the indication that the configuration 1 is a full configuration, the DU 174 refrains from resetting the DU MAC entity after transmitting (e.g., in response to) 330 the first configuration activation command.

[0151] In an alternative implementation, the base station 104 (e.g., the DU 174 or CU 172) includes a MAC retention indication in a configuration or element (e.g., the configuration 1 or element 1) to configure the UE 102 to not reset the UE MAC entity, and excludes the MAC retention indication in the configuration or element to configure the UE 102 to reset the UE MAC entity. If the configuration or element includes the MAC retention indication, the UE 102 refrains from resetting the UE MAC entity in response to the MAC retention indication upon receiving a configuration activation command (e.g., the first configuration activation command). Otherwise, if the configuration or element does not include the MAC retention indication, the UE 102 resets the UE MAC entity upon or when receiving the configuration activation command.

[0152] The DU 174 uses a DU MAC entity (e.g., NR MAC 204B) to communicate with the UE 102 (e.g., the events 302, 304, 318, 320, 324, 330, and / or 331). If the base station 104 includes the MAC retention indication in the configuration or element (e.g., the configuration 1 or element 1), the DU 174 refrains from resetting a DU MAC entity in response to the MAC retention indication after transmitting the configuration activation command (e.g., the first configuration activation command) to the UE 102. Thus, the DU 174 continues to use the retained (i.e., un-reset) DU MAC entity to communicate with the UE 102 after transmitting 330 the first configuration activation command, receiving 331 the43SUBSTITUTE SHEET (RULE 26)acknowledgement, or determining that the UE 102 connects to the cell 124B at event 332 or 336.

[0153] In some implementations, the DU 174 includes the MAC retention indication in a MAC-CellGroupConfig IE in the configuration 1 (e.g., CellGroupConfig IE). In other implementations, the DU 174 includes the MAC retention indication in the CellGroupConfig IE and outside the MAC-CellGroupConfig IE. In yet other implementations, the DU 174 includes the MAC retention indication in the element 1 and outside the configuration 1.

[0154] Otherwise, if the configuration 1 or element 1 does not include the MAC retention indication, the DU 174 resets the DU MAC entity after (e.g., in response to) transmitting 330 the first configuration activation command.

[0155] In some implementations, base station 104 do or do not include an indication that the configuration 1 is a full configuration. If the base station 104 includes, in the configuration 1 or element 1, the indication that the configuration 1 is a full configuration, the base station 104 refrains from including the MAC retention indication in the configuration 1 or element 1. Otherwise, if the base station 104 does not include, in the configuration 1 or element 1, the indication that the configuration 1 is a full configuration, the base station 104 includes the MAC retention indication in the configuration 1 or element 1.

[0156] In an alternative implementation, the base station 104 (e.g., the DU 174 or CU 172) includes a MAC partial reset indication in a configuration or element (e.g., the configuration 1 or element 1) to configure the UE 102 to partially reset the UE MAC entity, and excludes the MAC partial reset indication in the configuration or element to configure that the UE 102 fully resets the UE MAC entity. If the configuration or element includes the MAC partial reset indication, the UE 102 partially resets the UE MAC entity upon receiving a configuration activation command (e.g., the first configuration activation command). Otherwise, if the configuration or element does not include the MAC partial reset indication, the UE 102 fully resets the UE MAC entity after (e.g., in response to) receiving the configuration activation command. In some implementations, when the UE partially resets the UE MAC entity, the UE 102 retains (e.g., maintains or keeps) an operation state of the UE MAC entity or omits one or more actions that the UE 102 performs when the UE 102 fully resets the UE MAC entity.

[0157] If the base station 104 includes the MAC partial reset indication in the configuration or element (e.g., the configuration 1 or element 1), the DU 174 partially resets 44SUBSTITUTE SHEET (RULE 26)the DU MAC entity in response to the MAC partial reset indication after transmitting the configuration activation command (e.g., the first configuration activation command) to the UE 102.

[0158] In some implementations, the DU 174 includes the MAC partial reset indication in a MAC-CellGroupConfig IE in the configuration 1 (e.g., CellGroupConfig IE). In other implementations, the DU 174 includes the MAC partial reset indication in the CellGroupConfig IE and outside the MAC -CellGroupConfig IE. In yet other implementations, the DU 174 includes the MAC partial reset indication in the element 1 and outside the configuration 1.

[0159] Otherwise, if the configuration 1 or element 1 does not include the MAC partial reset indication, the DU 174 fully resets the DU MAC entity after (e.g., in response to) transmitting 330 the first configuration activation command. In some implementations, base station 104 does or does not include an indication that the configuration 1 is a full configuration. In some implementations, if the base station 104 includes, in the configuration 1 or element 1, the indication that the configuration 1 is a full configuration, the base station 104 refrains from including the MAC partial reset indication in the configuration 1 or element 1. Otherwise, in further implementations, if the base station 104 does not include, in the configuration 1 or element 1, the indication that the configuration 1 is a full configuration, the base station 104 includes the MAC partial reset indication in the configuration 1 or element 1. In some alternative implementations, the base station 104 includes the MAC partial reset indication in cases where the base station 104 includes, in the configuration 1 or element 1, the indication that the configuration 1 is a full configuration.

[0160] In some implementations, the base station 104 (e.g., the DU 174 or CU 172) does not include, in a configuration or element (e.g., the configuration 1 or element 1) or an RRC message (e.g., events 316, 318) including the configuration or element, an indication related to resetting the UE MAC entity. In such cases, the UE 102 partially resets the UE MAC entity after (e.g., in response to) receiving the first configuration activation command. In such cases, the DU 174 partially resets the DU MAC entity after transmitting the first configuration activation command, receiving 331 the acknowledgement, performing 336 the random access procedure with the UE 102, or determining that the UE 102 connects to the cell 124B.45SUBSTITUTE SHEET (RULE 26)

[0161] In some implementations, when the UE 102 determines to reset or resets the UE MAC entity as described above, the UE 102 resets the UE MAC entity before performing 332 the random access procedure or communicating 336 with the base station 104 via the cell 124B. 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., UE MAC reset or full UE MAC reset): (i) initialize Bj for configured logical channel(s) to zero; (ii) stop one or more timers; (iii) 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); (iv) set new data indicator(s) (NDI(s)) for UL HARQ process(es) to value 0; (v) set NDI(s) for HARQ process ID(s) to value 0 for monitoring PDCCH in Sidelink resource allocation mode 1; (vi) flush Msg3 buffer; (vii) flush MSGA buffer; (viii) cancel, if any, triggered Scheduling Request procedure; (ix) cancel, if any, triggered Buffer Status Reporting procedure; (x) cancel, if any, triggered Power Headroom Reporting procedure; (xi) cancel, if any, triggered consistent LBT failure; (xii) cancel, if any, triggered BFR; (xiii) cancel, if any, triggered Sidelink Buffer Status Reporting procedure; (xiv) cancel, if any, triggered Pre-emptive Buffer Status Reporting procedure; (xv) cancel, if any, triggered Timing Advance Reporting procedure; (xvi) cancel, if any, triggered Recommended bit rate query procedure; (xvii) cancel, if any, triggered configured uplink grant confirmation; (xviii) cancel, if any, triggered configured sidelink grant confirmation; (xix) cancel, if any, triggered Desired Guard Symbol query; (xx) cancel, if any, triggered Positioning Measurement Gap Activation / Deactivation Request procedure; (xxi) flush soft buffers for DL HARQ process(es); (xxii) for each of the DL HARQ process(es), consider the next received transmission for a TB as the very first transmission; (xxiii) release, if any, Temporary C- RNTI; (xiv) reset one or more counters (e.g., BFI_COUNTERs and / or LBT_COUNTERs); (xxv) etc.

[0162] 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., DU MAC reset or 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 next46SUBSTITUTE SHEET (RULE 26)received transmission for a TB as the very first transmission; (vi) reset one or more counters (e.g., BFI_COUNTERs and / or LBT_COUNTERs); (vii) etc.

[0163] Depending on the implementation, 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 other implementations, when the UE 102 resets the UE MAC entity as described above, the UE 102 partially resets the UE MAC entity (i.e., a partial UE MAC reset). In 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.

[0164] In some implementations, the partial UE MAC reset includes at least one of the following actions: (i) consider limeAlignmenlTimer( ) 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 / or (v) reset one or more counters (e.g., BFI_COUNTERs and / or LBT_COUNTERs).

[0165] In some implementations, the partial UE MAC reset further includes at least one of the following actions: (i) cancel, if any, triggered Scheduling Request procedure; (ii) cancel, if any, triggered Buffer Status Reporting procedure; (iii) cancel, if any, triggered Power Headroom Reporting procedure; (iv) cancel, if any, triggered consistent LBT failure; (v) cancel, if any, triggered BFR; (vi) cancel, if any, triggered Sidelink Buffer Status Reporting procedure; (vii) cancel, if any, triggered Pre-emptive Buffer Status Reporting procedure;(viii) cancel, if any, triggered Timing Advance Reporting procedure; (ix) cancel, if any, triggered Recommended bit rate query procedure; (x) cancel, if any, triggered configured uplink grant confirmation; (xi) cancel, if any, triggered configured sidelink grant confirmation; (xii) cancel, if any, triggered Desired Guard Symbol query; and / or (xiii) cancel, if any, triggered Positioning Measurement Gap Activation / Deactivation Request procedure.

[0166] 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 / or47SUBSTITUTE SHEET (RULE 26)(v) for each of the DL HARQ process(es), consider the next received transmission for a TB as the very first transmission.

[0167] Depending on the implementation, the DU 174 determines to partially or fully reset the DU MAC entity. In some 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 other 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.

[0168] 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 / or (ii) reset one or more counters (e.g., BFI_COUNTERs and / or LBT_COUNTERs).

[0169] In some implementations, 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 / or (v) reset one or more counters (e.g., BFI_COUNTERs and / or LBT_COUNTERs).

[0170] In some implementations, the configuration 1 do or do not include one or more RLC reestablishment indications (e.g., reestablishRLC field(s)) configuring the UE 102 to reestablish one or more RLC entities (e.g., RLC 206B) that the UE 102 uses to communicate with the DU 174 (e.g., the events 302, 304, 318, 320, 324, 330, and / or 331). If the configuration 1 includes the RLC reestablishment indication configuring the UE 102 to reestablish an RLC entity (e.g., RLC 206B) that the UE 102 uses to communicate RLC PDU(s) with the base station 104 (e.g., the events 302, 304, 318, 320, 324, 330, and / or 331), the UE 102 reestablishes the RLC entity in response to the RLC reestablishment indication. In some implementations, the UE 102 reestablishes the RLC entity before performing 332 the random access procedure or communicating 336 with the base station 104 via the cell 124B.48SUBSTITUTE SHEET (RULE 26)In other implementations, the UE 102 reestablishes the RLC entity while or after performing 332 the random access procedure. In some implementations, when the UE 102 reestablishes the RLC entity, the UE 102 performs at least one of the following actions for the RLC entity: (i) discard RLC SDU(s), RLC SDU segment(s), and RLC PDU(s), if any; (ii) stop and reset timer(s), if running; (iii) reset state variables to initial values. In some implementations, the state variables and timer(s) are currently defined (e.g., in 3GPP specification 38.322).

[0171] Otherwise, if the configuration 1 does not include the RLC reestablishment indication for the RLC entity, the UE 102 refrains from reestablishing the RLC entity upon or when receiving the first configuration activation command. In other words, the UE 102 refrains from preforming the actions for reestablishing the RLC entity of the UE 102 upon or when receiving the first configuration activation command. In some implementations, if the configuration 1 or element 1 does not include the RLC reestablishment indication and includes an indication that the configuration 1 is a full configuration, the UE 102 reestablishes the RLC entity of the UE 102 upon or when receiving the first configuration activation command. Otherwise, if the configuration 1 or element 1 does not include the RLC reestablishment indication, and the indication that the configuration 1 is a full configuration, the UE 102 refrains from reestablishing the RLC entity upon or when receiving the first configuration activation command.

[0172] Similarly, the DU 174 reestablishes an RLC entity (e.g., NR RLC 206B) that the DU 174 uses to communicate with the 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 the RLC entity after transmitting the first configuration activation command, receiving an acknowledgement for the first configuration activation command from the UE 102, or determining that the UE 102 connects to the cell 124B. In some implementations, the acknowledgement is a HARQ ACK. In other implementations, the acknowledgement is a MAC CE. In yet other implementations, the acknowledgement is a PUCCH transmission. In some implementations, when the base station 104 reestablishes the RLC entity, the DU 174 performs at least one of the following actions for the RLC entity: (i) discard RLC SDU(s), RLC SDU segment(s), and RLC PDU(s), if any; (ii) stop and reset timer(s), if running; and / or (iii) reset state variables to initial values. In some implementations, the state variables and timer(s) are currently defined (e.g., in 3GPP specification 38.322).49SUBSTITUTE SHEET (RULE 26)

[0173] In some implementations, the description for the configuration 1 above applies to the configuration(s) 2, ... , N as well.

[0174] In some implementations, after (e.g., in response to) determining that the UE 102 connects to the cell 124B, 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 response, 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 transmits 340 a DU-to-CU message (e.g., a UE Context Modification Response message) to the CU-172. The events 338 and 340 are collectively referred to in Fig. 3 as procedure 394 (e.g., UE Context Modification procedure).

[0175] 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, in some implementations, operates the cell 124B, while the T-DU 174B operates the cell 124C. The scenario 400 is similar to the scenario 300. Thus, the descriptions for the scenario 300 can generally apply to the scenario 400. In particular, the descriptions for cell 124B in the scenario 300 can apply to the cell 124C. Further, it will be understood that some descriptions with regard to the scenario 300 can apply to the scenario 400, but to one or both of the S-DU 174A or the T-DU 174B (e.g., events 408, 410, 432, 434, etc.).

[0176] In some implementations, after (e.g., in response to) determining that the UE 102 connects to the cell 124B, the CU 172 transmits 438 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. Alternatively, the CU 172 transmits 438 a CU-to-DU message (e.g., a UE Context Modification Request message) to the S-DU 174A to indicate to the S-DU 174A to stop communicating with the UE 102 and / or to release or suspend resources, of the cell 124A, configured for the UE 102. In response, in further implementations, the S-DU 174A 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 transmits 440 a DU-to-CU message (e.g., a UE Context Modification Response message) to the CU-172.50SUBSTITUTE SHEET (RULE 26)

[0177] 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. 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 and communicates with the CU 172 via the DU 174 using a first configuration, similar to the event 302. 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 configure the radio bearers for the UE 102.

[0178] The UE 102 in DC communicates 502 UL PDUs and / or DL PDUs with the SN 104 on an SCG 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 in accordance with an MN configuration (i.e., MCG configuration). In some implementations, the first configuration is an 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 first configuration, the SN 106A 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. In other implementations, the first configuration includes multiple configuration parameters, and the UE 102 receives the configuration parameters in one or more RRC messages from the SN 104 (e.g., via the MN 106) 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.

[0179] In some implementations, while communicating in DC with the MN 106 and SN 104, the MN 106 performs 580 a fast serving cell configuration procedure with the UE 102, similar to the procedure 380. 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 other 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 51SUBSTITUTE SHEET (RULE 26)172. In some implementations, the MN 106 generates at least one SN message including the at least one measurement report and transmits the at least one SN message to the CU 172 in the event 507. In some implementations, the at least one SN message includes RRC Transfer message(s) and / or SN Modification Request message(s).

[0180] After (e.g., in response to) receiving the at least one measurement report or while the base station 104 communicates with the UE 102, the base station 104 determines to prepare the cell 124B for the UE 102, as described for Fig. 3. The events 590, 592, 516, 518, 520, 522, 524, 526, 528, 530, 531, 532, 534, 536, and 594 are similar to the events 390, 392, 316, 318, 320, 322, 324, 326, 328, 330, 331, 332, 334, 336, and 394, respectively. After receiving the first configuration activation command, transmitting the acknowledgement, or determining that the UE 102 connects to the cell 124B, the UE 102 operating in DC with the MN 106 and SN 104 communicates 536 with the SN 104 on the cell 124B in accordance with the configuration 1, similar to the event 336.

[0181] 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. 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 the first SN message to the MN 106 in the event 517. In some implementations, the MN 106 generates a second SN message (e.g., SN Reconfiguration Complete message or RRC Transfer message), including the RRC reconfiguration complete message, and transmits the second SN message to the SN 104 in the event 523.

[0182] 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. Further, it will be understood that some descriptions with regard to the scenarios 300-500B can apply to the scenario 600A, but to one or both of the S-DU 174A or the T-DU 174B (e.g., events 608, 610, 632, 634, etc.).

[0183] Referring next to Fig. 6B, a scenario 600B similar to the scenarios 300-500B and 600A, except that that the SN 104 transmits 617, 619 the RRC reconfiguration message to the52SUBSTITUTE SHEET (RULE 26)UE 102 via the MN 106 and receives 621, 623 the RRC reconfiguration complete message from the UE 102 via the MN 106.

[0184] Referring next to Fig. 7A, in a scenario 700A, the base station 104 operates as an MN and 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 the 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.

[0185] In the scenario 700A, the UE 102 initially communicates 702 in DC with the M-DU 174A and S-DU 174B, and the UE 102 communicates 702 with the CU 172 via the M-DU 174A and S-DU 174B. In the event 702, the UE 102 communicates with the S-DU 174B on cell 124A and communicates with the CU 172 via the S-DU 174B, using a first configuration. 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.

[0186] Referring next to Fig. 7B, a scenario 700B 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.

[0187] Referring next to Fig. 8A, in a 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 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.Further, it will be understood that some descriptions with regard to the scenarios 300-700B can apply to the scenario 800A, but to one or both of the S-DU 174A or the T-DU 174B (e.g., events 808, 810, 832, 834, etc.).

[0188] Referring next to Fig. 8B, a scenario 800B 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.53SUBSTITUTE SHEET (RULE 26)

[0189] Next, several example methods, which can be implemented in the UE to support MAC protocol operation when activating a configuration, are discussed next with reference to Figs. 9A-10E. Examples and implementations described for Figs. 3-8B can apply to Figs. 9A-10E.

[0190] Fig. 9A illustrates a method 900A, which can be implemented by a UE (e.g., the UE 102), for configuring and activating a configuration with a RAN (e.g., the the base station 104 / 106 or the DU 174).

[0191] The method 900A begins at block 902, where the UE communicates with the RAN using a first configuration and a MAC entity (e.g., events 302, 380, 402, 480, 502, 580, 602, 680, 702, 780, 802, 880). At block 904A, the UE receives, from the RAN, an RRC message including a second configuration and including a MAC retention indication (e.g., events 316, 318, 416, 418, 516, 518, 517, 519, 616, 618, 617, 619, 716, 718, 717, 719, 816, 818, 817, 819). At block 906, the UE receives a configuration activation command from the RAN to activate the second configuration (e.g., events 330, 380, 430, 530, 580, 630, 680, 730, 780, 830, 880). At block 908A, the UE refrains from resetting the MAC entity in response to the MAC retention indication. In some implementations, at block 910, the UE performs a random access procedure with the RAN (e.g., events 332, 432, 532, 632, 732, 832). At block 912, the UE communicates with the RAN using the second configuration and MAC entity (e.g., events 336, 436, 536, 636, 736, 836). In other words, the UE continues to use the MAC entity to communicate with the RAN without resetting the MAC entity, after receiving the configuration activation command or performing the random access procedure.

[0192] Fig. 9B is a flow diagram of an example method 900B similar to the method 900A, except that method 900B includes blocks 904B and 908B instead of blocks 904A and 908A. At block 904B, the UE receives, from the RAN, an RRC message including a second configuration and excluding a MAC retention indication to configure the MAC entity to reset (e.g., events 316, 318, 416, 418, 516, 518, 517, 519, 616, 618, 617, 619, 716, 718, 717, 719, 816, 818, 817, 819). At block 908B, the UE resets the MAC entity in response to the RRC message excluding a MAC retention indication. Thus, the UE at block 912 communicates with the RAN using the second configuration and MAC entity after resetting the MAC

[0193] Fig. 9C is a flow diagram of an example method 900C similar to the method 900A, except that method 900C includes blocks 904C and 908C instead of blocks 904A and 908A. At block 904C, the UE receives, from the RAN, an RRC message including a second54SUBSTITUTE SHEET (RULE 26)configuration and including a MAC reset indication (e.g., events 316, 318, 416, 418, 516, 518, 517, 519, 616, 618, 617, 619, 716, 718, 717, 719, 816, 818, 817, 819). At block 908C, the UE resets the MAC entity in response to the MAC reset indication.

[0194] Fig. 9D is a flow diagram of an example method 900D similar to the method 900A, except that method 900D includes blocks 904D and 908D instead of blocks 904A and 908A. At block 904D, the UE receives, from the RAN, an RRC message including a second configuration and excluding a MAC reset indication to configure the MAC entity not to reset (e.g., events 316, 318, 416, 418, 516, 518, 517, 519, 616, 618, 617, 619, 716, 718, 717, 719, 816, 818, 817, 819). At block 908D, the UE refrains from resetting the MAC entity in response to the RRC message excluding a MAC reset indication.

[0195] Fig. 9E is a flow diagram of an example method 900E similar to the method 900A, except that method 900E includes blocks 904E and 908E instead of blocks 904A and 908A. At block 904E, the UE receives, from the RAN, an RRC message including a second configuration and a MAC partial reset indication to configure the MAC entity to partially reset (e.g., events 316, 318, 416, 418, 516, 518, 517, 519, 616, 618, 617, 619, 716, 718, 717, 719, 816, 818, 817, 819). At block 908E, the UE partially resets the MAC entity in response to the MAC partial reset indication.

[0196] Fig. 9F is a flow diagram of an example method 900F similar to the method 900A, except that method 900F includes blocks 904F and 908F instead of blocks 904A and 908A. At block 904F, the UE receives, from the RAN, an RRC message including a second configuration and excluding a MAC partial reset indication to configure the MAC entity to fully reset (e.g., events 316, 318, 416, 418, 516, 518, 517, 519, 616, 618, 617, 619, 716, 718,717, 719, 816, 818, 817, 819). At block 908F, the UE fully resets the MAC entity in response to the RRC message excluding a MAC partial reset indication.

[0197] Fig. 9G is a flow diagram of an example method 900G similar to the method 900A, except that method 900G includes blocks 904G and 908G instead of blocks 904A and 908A. At block 904G, the UE receives, from the RAN, an RRC message including a second configuration (e.g., events 316, 318, 416, 418, 516, 518, 517, 519, 616, 618, 617, 619, 716,718, 717, 719, 816, 818, 817, 819). At block 908G, the UE partially resets the MAC entity in response to configuration activation command.55SUBSTITUTE SHEET (RULE 26)

[0198] Fig. 10A illustrates a method 1000A, which can be implemented by a UE (e.g., the UE 102), for configuring and activating a configuration with a RAN (e.g., the base station 104 / 106 or the DU 174).

[0199] The method 1000A begins at block 1002, where the UE communicates with the RAN using a first configuration and a MAC entity (e.g., events 302, 402, 502, 602, 702, 802). At block 1004, the UE receives an RRC message including a second configuration from the RAN (e.g., events 316, 318, 416, 418, 516, 518, 517, 519, 616, 618, 617, 619, 716, 718, 717, 719, 816, 818, 817, 819). In some implementations, at block 1006, the UE receives a configuration activation command from the RAN to activate the second configuration (e.g., events 330, 380, 430, 530, 580, 630, 680, 730, 780, 830, 880). At block 1008A, the UE determines whether the RRC message or second configuration includes a MAC retention indication. If the UE determines that the RRC message or second configuration includes a MAC retention indication, the flow proceeds to blocks 1010A. At block 1010A, the UE performs the actions described above with regard to block 908A. Otherwise, if the RAN node determines that the RRC message or second configuration does not include a MAC retention indication, the flow proceeds to block 1012A. At block 1012A, the UE performs the actions described above with regard to block 908B. The flow proceeds to block 1014 from block 1010 as well as from block 1012A. In some implementations, at block 1014, the UE performs a random access procedure with the RAN. At block 1016, the UE communicates with the RAN using the second configuration and MAC entity.

[0200] Fig. 10B is a flow diagram of an example method 1000B similar to the method 1000A, except that method 1000B includes blocks 1008B, 1010B, and 1012B instead of blocks 1008A, 1010A, and 1012A. At block 1008B, the UE determines whether the RRC message or second configuration includes a MAC reset indication. If the UE determines that the RRC message or second configuration includes a MAC reset indication, the flow proceeds to blocks 1010B. At block 1010B, the UE performs the actions described above with regard to block 908C. Otherwise, if the UE determines that the RRC message or second configuration does not include a MAC reset indication, the flow proceeds to block 1012B. At block 1012B, the UE performs the actions described above with regard to block 908D.

[0201] Fig. 10C is a flow diagram of an example method 1000C similar to the methods 1000A and 1000B, except that method 1000C includes block 1008C instead of blocks 1008 A and 1008B. At block 1008C, the UE determines whether the RRC message or second56SUBSTITUTE SHEET (RULE 26)configuration includes a MAC retention indication or MAC reset indication. If the UE determines that the RRC message or second configuration includes a MAC retention indication, the flow proceeds to block 1010A. Otherwise, if the UE determines that the RRC message or second configuration includes a MAC reset indication, the flow proceeds to block 1010B.

[0202] Fig. 10D is a flow diagram of an example method WOOD similar to the method 1000A, except that method WOOD includes blocks 1008D, 1010D, and 1012D instead of blocks 1008A, 1010A, and 1012A. At block 1008D, the UE determines whether the RRC message or second configuration includes a MAC partial reset indication. If the UE determines that the RRC message or second configuration includes a MAC partial reset indication, the flow proceeds to blocks 1010D. At block 1010D, the UE performs the actions described above with regard to block 908E. Otherwise, if the UE determines that the RRC message or second configuration does not include a MAC partial reset indication, the flow proceeds to block 1012D. At block 1012D, the UE performs the actions described above with regard to block 908F.

[0203] Fig. 10E is a flow diagram of an example method 1000E similar to the method 1000A, except that method 1000E includes blocks 1007, 1008E, 1010E, and 1012E instead of blocks 1006, 1008A, 1010A, and 1012A. At block 1007, the UE applies the second configuration. At block 1008E, the UE determines whether the UE receives a configuration activation command from the RAN to activate the second configuration. If the UE determines that the UE receives a configuration activation from the RAN to activate the second configuration, the flow proceeds to block 1010E. At block 1010E, the UE performs the actions described above with regard to block 908G. Otherwise, if the UE does not receive a configuration activation command from the RAN to activate the second configuration, the flow proceeds to block 1012E. At block 1012E, the UE fully resets the MAC entity in response to the RRC message.

[0204] Next, several example methods, that can be implemented in in one or more RAN nodes such as base stations, DUs or CUs, or in a RAN to support MAC protocol operation involving a configuration activation, are discussed next with reference to Figs. 11A-15B. Examples and implementations described for Figs. 3-8B can apply to Figs. 11A-15B.57SUBSTITUTE SHEET (RULE 26)

[0205] Fig. 11A illustrates a method 1100A, which can be implemented by a DU (e.g., the DU 174), for configuring and activating a serving cell configuration for a UE (e.g., the UE 102).

[0206] In some implementations, the method 1100A begins at block 1102, where the DU communicates with a UE using a first configuration (e.g., events 302, 380, 502, 580, 702, 780). In further implementations, at block 1104, the DU receives, from a CU, a first CU-to- DU message to request configuration for the UE (e.g., events 308, 390, 380, 408, 490, 508, 590, 580, 608, 690, 680, 708, 790, 780, 808, 890, 880). At block 1106A, the DU transmits, to the CU, a first DU-to-CU message, including a second configuration, wherein the second configuration includes a MAC retention indication for configuring a MAC entity not to reset (e.g., events 310, 390, 380, 410, 490, 480, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). In some implementations, at block 1108, the DU transmits the second configuration to the UE (e.g., event 316, 318, 380, 516, 517, 519, 518, 580, 716, 718, 717, 719, 780). In further implementations, at block 1110, the DU transmits a configuration activation command to the UE to activate the second configuration (e.g., events 330, 380, 530, 580, 730, 780). At block 1112, the DU communicates with the UE in accordance with the second configuration and MAC retention indication (e.g., events 332, 336, 380, 432, 436, 480, 532, 536, 580, 632, 636, 680, 732, 736, 780, 832, 836, 880). The blocks 1106A, 1108, 1110, and 1112 are collectively referred to in Fig. 11A as block 1150A.

[0207] In cases where the DU is a target DU (e.g., the T-DU 174B in Fig. 4A, 4B, 6A, or 6B, or the T-DU 174C in Fig. 8A or 8B), blocks 1102, 1108, and 1110 are omitted. In some implementations, the DU at block 1102 communicates with the UE via a first cell (i.e., a serving cell) identified by a first cell ID. In some implementations, the first CU-to-DU message includes a second cell ID identifying a second cell (i.e., a target serving cell), and the DU generates the second configuration for the UE to communicate with the DU via the second cell. In some implementations, the second cell ID is an NR CGI. In some implementations, the second configuration includes a third cell ID (e.g., PCI) of the second cell.

[0208] In some implementations, in cases where the DU receives the first CU-to-DU message, the DU transmits the first DU-to-CU message to the CU in response to the first CU- to-DU message. In other implementations, the DU proactively transmits the first DU-to-CU message to the CU. In some implementations, the first CU-to-DU message is a UE Context58SUBSTITUTE SHEET (RULE 26)Modification Request message. In some implementations, the first DU-to-CU message is a UE Context Modification Response message or a UE Context Modification Required message. In other implementations, the first CU-to-DU message and first DU-to-CU message are UE Context Setup Request message and UE Context Setup Response message, respectively.

[0209] Fig. 1 IB is a flow diagram of an example method 1100B similar to the method 1100A, except that method 1100B includes blocks 1106B and 1109 instead of blocks 1106 A and 1108. At block 1106B, the DU transmits, to the CU, a first DU-to-CU message, including a second configuration and a MAC retention indication for configuring a MAC entity not to reset (e.g., events 310, 390, 380, 510, 590, 580, 710, 790, 780). In other words, the MAC retention indication is not included in the second configuration. In some implementations, at block 1109, the DU transmits the second configuration and MAC retention indication to the UE (e.g., event 316, 318, 380, 516, 518, 517, 519, 580, 716, 718, 717, 719, 780). The blocks 1106B, 1109, 1110, and 1112 are collectively referred to in Fig.1 IB as block 1150B. In cases where the DU is a target DU (e.g., the T-DU 174B in Fig. 4A, 4B, 6A, or 6B, or the T-DU 174C in Fig. 8A or 8B), block 1109 is omitted.

[0210] Fig. 11C is a flow diagram of an example method 1100C similar to the methods 1100A and / or 1100B, except that method 1100C includes blocks 1106C and 1111 instead of blocks 1106A and 1112. At block 1106C, the DU transmits, to the CU, a first DU-to-CU message, including a second configuration, wherein the second configuration excludes a MAC retention indication to reset a MAC entity (e.g., events 310, 390, 380, 410, 480, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). In some implementations, the DU generates the second configuration excluding the MAC retention indication. At block 1111, the DU communicates with the UE in accordance with the second configuration (e.g., events 332, 336, 380, 432, 426, 480, 532, 536, 580, 632, 636, 680, 732, 736, 780, 832, 836, 880). The blocks 1106C, 1108, 1110, and 1111 are collectively referred to in Fig. 11C as block 1150C.

[0211] Fig. 1 ID is a flow diagram of an example method 1100D similar to the methods 1100A-C, except that method 1100D includes block 1106D instead of block 1106C. At block 1106D, the DU transmits, to the CU, a first DU-to-CU message, including a second configuration and excluding a MAC retention indication to reset a MAC entity (e.g., events 310, 390, 380, 410, 490, 480, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). In59SUBSTITUTE SHEET (RULE 26)some implementations, the DU generates the first DU-to-CU message excluding the MAC retention indication. The blocks 1106D, 1108, 1110, and 1111 are collectively referred to in Fig. 11D as block 1150D.

[0212] Fig. 1 IE is a flow diagram of an example method 1100E similar to the methods 1100A-D, except that method 1100E includes blocks 1106E and 1113 instead of blocks 1106A and 1112. At block 1106E, the DU transmits, to the CU, a first DU-to-CU message, including a second configuration, wherein the second configuration includes a MAC reset indication to reset a MAC entity (e.g., events 310, 390, 380, 410, 480, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). In some implementations, the DU generates the second configuration including the MAC reset indication. At block 1113, the DU communicates with the UE in accordance with second configuration and MAC reset indication (e.g., events 332, 336, 380, 432, 426, 480, 532, 536, 580, 632, 636, 680, 732, 736, 780, 832, 836, 880). The blocks 1106E, 1108, 1110, and 1113 are collectively referred to in Fig. HE as block 1150E.

[0213] In some implementations, the MAC reset indication is a MAC partial reset indication indicating a partial MAC reset as described above. In other implementations the MAC reset indication indicates a full MAC reset as described above.

[0214] Fig. 1 IF is a flow diagram of an example method 1100F similar to the methods 1100A-E, except that method 1100F includes blocks 1106F and 1107 instead of blocks 1106E and 1108. At block 1106F, the DU transmits, to the CU, a first DU-to-CU message, including a second configuration and including a MAC reset indication to reset a MAC entity (e.g., events 310, 390, 380, 410, 490, 480, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). In some implementations, the DU generates the first DU-to-CU message including the MAC reset indication. In some implementations, at block 1107, the DU transmits the second configuration and MAC reset indication to the UE (e.g., event 316, 318, 380, 516, 518, 517, 519, 580, 716, 718, 717, 719, 780). The blocks 1106F, 1107, 1110, and 1113 are collectively referred to in Fig. 1 IF as block 1150F. In cases where the DU is a target DU (e.g., the T-DU 174B in Fig. 4A, 4B, 6A, or 6B, or the T-DU 174C in Fig. 8A or 8B), block 1107 is omitted.

[0215] In some implementations, the MAC reset indication is a MAC partial reset indication configuring a partial MAC reset as described above. In other implementations, the MAC reset indication configures a full MAC reset as described above.60SUBSTITUTE SHEET (RULE 26)

[0216] Fig. 11G is a flow diagram of an example method 1100G similar to the methods 1100A-F, except that method 1100G includes block 1106G instead of block 1106C. At block 1106G, the DU transmits, to the CU, a first DU-to-CU message, including a second configuration, wherein the second configuration excludes a MAC reset indication to configure a MAC entity not to reset (e.g., events 310, 390, 380, 510, 590, 580, 710, 790, 780). In some implementations, the DU generates the second configuration excluding the MAC reset indication. The blocks 1106G, 1108, 1110, and 1111 are collectively referred to in Fig. UG as block 1150G.

[0217] Fig. 11H is a flow diagram of an example method 1100H similar to the methods 1100A-G, except that method 1100H includes block 1106H instead of block 1106C. At block 1106H, the DU transmits, to the CU, a first DU-to-CU message, including a second configuration and excluding a MAC reset indication to configure a MAC entity not to reset (e.g., events 310, 390, 380, 510, 590, 580, 710, 790, 780). In some implementations, the DU generates the first DU-to-CU message excluding the MAC reset indication. The blocks 1106H, 1108, 1110, and 1111 are collectively referred to in Fig. 11H as block 1150H.

[0218] Fig. 12 illustrates a method 1200, which can be implemented by a DU (e.g., the DU 174), for configuring and activating a serving cell configuration for a UE (e.g., the UE 102).

[0219] The method 1200 begins at block 1202, where the DU communicates with a UE using a first configuration (e.g., events 302, 380, 502, 580, 702, 780). At block 1204, the DU receives, from a CU, a first CU-to-DU message to request configuration for the UE (e.g., events 308, 390, 380, 408, 490, 480, 508, 590, 580, 608, 690, 680, 708, 790, 780, 808, 890, 880). At block 1206, the DU determines whether to configure the UE to reset a MAC entity. If the DU determines not to configure the UE to reset a MAC entity, the flow proceeds to block 1210. At block 1210, the DU performs the actions described above with regard to blocks 1150A, 1150B, 1150G, or 1150H. Otherwise, if the DU determines to configure the UE to reset a MAC entity, the flow proceeds to block 1212. At block 1212, the DU performs the actions described above with regard to blocks 1150C, 1150D, 1150E, or 1150F.

[0220] In cases where the DU is a target DU (e.g., the T-DU 174B in Fig. 4A, 4B, 6A, or 6B, or the T-DU 174C in Fig. 8A or 8B), block 1202 is omitted.

[0221] Fig. 13A illustrates a method 1300A, which can be implemented by CU (e.g., the CU 172 for configuring a serving cell configuration for a UE (e.g., the UE 102).61SUBSTITUTE SHEET (RULE 26)

[0222] The method 1300A begins at block 1302, where the CU communicates with a UE (e.g., events 302, 380, 402, 502, 580, 602, 680, 702, 780, 802, 880). In some implementations, at block 1304, the CU transmits, to a first DU, a first CU-to-DU message to request configuration for the UE (e.g., events 308, 390, 380, 408, 490, 480, 508, 590, 580, 608, 690, 680, 708, 790, 780, 808, 890, 880). At block 1306A, the CU receives, from the first DU, a first DU-to-CU message, including a first configuration and including a MAC retention indication to configure a MAC entity not to reset (e.g., events 310, 390, 380, 410, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). At block 1309. the CU transmits the first configuration and MAC retention indication to the UE (e.g., event 316, 318, 380, 416, 418, 480, 516, 518, 517, 519, 580, 616, 618, 617, 619, 680, 716, 718, 717, 719, 780, 816, 818, 817, 819, 880).

[0223] In some implementations, the CU at block 1302 communicates with the UE via the first DU and / or a second DU. In some implementations, the CU at block 1309 transmits the first configuration and MAC retention indication to the UE via the first DU or second DU.

[0224] Fig. 13B is a flow diagram of an example method 1300B similar to the method 1300A, except that method 1300B includes blocks 1306B and 1308 instead of blocks 1306 A and 1309. At block 1306B, the CU receives, from the DU, a first DU-to-CU message, including a first configuration and excluding a MAC retention indication to configure a MAC entity to reset (e.g., events 310, 390, 380, 410, 490, 480, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). At block 1308, the CU transmits the first configuration to the UE (e.g., event 316, 318, 380, 416, 418, 480, 516, 518, 517, 519, 580, 616, 618, 617, 619, 680, 716, 718, 717, 719, 780, 816, 818, 817, 819, 880). In some implementations, the CU at block 1308 transmits the first configuration to the UE via the first DU or second DU.

[0225] Fig. 13C is a flow diagram of an example method 1300C similar to the method 1300A, except that method 1300C includes blocks 1306C and 1307 instead of blocks 1306 A and 1309. At block 1306C, the CU receives, from the DU, a first DU-to-CU message, including a first configuration and including a MAC reset indication to configure a MAC entity to reset (e.g., events 310, 390, 380, 410, 490, 480, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). At block 1307, the CU transmits the first configuration and MAC reset indication to the UE (e.g., event 316, 318, 380, 416, 418, 480, 516, 518, 517, 519, 580, 616, 618, 617 619, 680, 716, 718, 717, 719, 780, 816, 818, 817, 819, 880). In some62SUBSTITUTE SHEET (RULE 26)implementations, the CU at block 1307 transmits the first configuration and MAC reset indication to the UE via the first DU or second DU.

[0226] In some implementations, the MAC reset indication is a MAC partial reset indication configuring a partial MAC reset as described above. In other implementations, the MAC reset indication configures a full MAC reset as described above.

[0227] Fig. 13D is a flow diagram of an example method 1300D similar to the method 1300B, except that method I 300D includes block 1306D instead of block 1306B. At block 1306D, the CU receives, from the DU, a first DU-to-CU message, including a first configuration and excluding a MAC reset indication to configure a MAC entity not to reset (e.g., events 310, 390, 380, 410, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880).

[0228] Fig. 14A illustrates a method 1400A, which can be implemented by a CU (e.g., the CU 172) for configuring a serving cell configuration for a UE (e.g., the UE 102).

[0229] The method 1400A begins at block 1402, where the CU communicates with a UE (e.g., events 302, 380, 402, 480, 502, 580, 602, 680, 702, 780, 802, 880). In some implementations, at block 1404, the CU transmits, to a first DU, a first CU-to-DU message to request configuration for the UE (e.g., events 308, 390, 380, 408, 490, 480, 508, 590, 580, 608, 690, 680, 708, 790, 780, 808, 890, 880). At block 1406, the CU receives, from the first DU, a first DU-to-CU message including a first configuration (e.g., events 310, 390, 380, 410, 490, 480, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). At block 1408, the CU determines whether the first DU-to-CU message includes a MAC retention indication. If the CU determines that the first DU-to-CU message includes a MAC retention indication, the flow proceeds to block 1410. At block 1410, the CU performs the actions described above with regard to block 1309. Otherwise, if the CU determines that the first DU-to-CU message does not include a MAC retention indication, the flow proceeds to block 1412. At block 1412, the CU performs the actions described above with regard to block 1308.

[0230] Fig. 14B is a flow diagram of an example method 1400B similar to the method 1400A, except that method 1400B includes block 1407 instead of block 1408. At block 1407, the CU determines whether the first DU-to-CU message includes a MAC reset indication. If the CU determines that the first DU-to-CU message includes a MAC reset indication, the flow proceeds to block 1410. At block 1410, the CU performs the actions described above with regard to block 1307. Otherwise, if the CU determines that the first 63SUBSTITUTE SHEET (RULE 26)DU-to-CU message does not include a MAC reset indication, the flow proceeds to block 1412. At block 1412, the CU performs the actions described above with regard to block 1308.

[0231] Fig. 14C is a flow diagram of an example method 1400C similar to the methods 1400A and / or 1400B, except that method 1400C includes block 1409 instead of block 1408. At block 1409, the CU determines whether the first DU-to-CU message includes a MAC retention indication or a MAC reset indication. If the CU determines that the first DU-to-CU message includes a MAC retention indication, the flow proceeds to block 1410. At block 1410, the CU performs the actions described above with regard to block 1309. Otherwise, if the CU determines that the first DU-to-CU message includes a MAC reset indication, the flow proceeds to block 1412. At block 1412, the CU performs the actions described above with regard to block 1307.

[0232] Fig. 15A illustrates a method 1500A, which can be implemented by a DU (e.g., the DU 174), for configuring and activating a serving cell configuration for a UE (e.g., the UE 102).

[0233] The method 1500A begins at block 1502, where the DU communicates with a UE on a first serving cell using a MAC entity (e.g., events 302, 380, 502, 580, 702, 780). At block 1504, the DU performs a serving cell change, with the UE, from the first serving cell to a second serving cell (e.g., events 332, 336, 380, 432, 436, 480, 532, 536, 580, 632, 636, 680, 732, 736, 780, 832, 836, 880). At block 1506, the DU determines whether the serving cell change is triggered by the DU or a CU. If the DU determines that the serving cell change is triggered by the DU, the flow proceeds to block 1508. At block 1508, the DU refrains from resetting the MAC entity. At block 1510, the DU communicates with the UE on the second serving cell using the MAC entity (e.g., events 332, 336, 380, 432, 436, 480, 532, 536, 580, 632, 636, 680, 732, 736, 780, 832, 836, 880). Otherwise, if the DU determines that the serving cell change is triggered by a CU, the flow proceeds to block 1512. At block 1512, the DU resets the MAC entity. At block 1514, the DU communicates with the UE on the second serving cell using the reset MAC entity (e.g., events 332, 336, 380, 432, 436, 480, 532, 536, 580, 632, 636, 680, 732, 736, 780, 832, 836, 880).

[0234] Fig. 15B is a flow diagram of an example method 1500B similar to the method 1500A, except that method 1500B includes block 1507 instead of block 1506. At block 1507, the DU determines whether to configure the UE to reset a MAC entity. If the DU64SUBSTITUTE SHEET (RULE 26)determines to configure the UE not to reset a MAC entity, the flow proceeds to block 1508. Otherwise, if the CU determines to configure the UE to reset a MAC entity, the flow proceeds to block 1512.

[0235] The following description may be applied to the description above.

[0236] Generally speaking, description for one of the above figures can apply to another of the above figures. Examples, implementations and methods described above can be combined, if there is no conflict. An event or block described above can be optional or omitted. For example, an event or block with dashed lines in the figures can be optional. In some implementations, “message” is used and can be replaced by “information element (IE)”, and vice versa. In some implementations, “IE” is used and can be replaced by “field”, and vice versa. In some implementations, “configuration” can be replaced by “configurations” or “configuration parameters”, and vice versa. In some implementations, the “configuration activation command” can be replaced by “serving cell change command”, “Layer 1 / Layer 2 switching command”, “lower layer switching command” or “ lower layer serving cell change command”. The “fast serving cell configuration procedure” can be replaced by “fast serving cell change procedure”.

[0237] A user device in which the techniques of this disclosure can be implemented (e.g., the UE 102) can be any suitable device capable of wireless communications such as a smartphone, a tablet computer, a laptop computer, a mobile gaming console, a point-of-sale (POS) terminal, a health monitoring device, a drone, a camera, a media- streaming dongle or another personal media device, a wearable device such as a smartwatch, a wireless hotspot, a femtocell, or a broadband router. Further, the user device in some cases may be embedded in an electronic system such as the head unit of a vehicle or an advanced driver assistance system (ADAS). Still further, the user device can operate as an internet-of-things (loT) device or a mobile-internet device (MID). Depending on the type, the user device can include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0238] 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 comprise65SUBSTITUTE SHEET (RULE 26)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.

[0239] 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.

[0240] Upon reading this disclosure, those of skill in the art will appreciate still additional and alternative structural and functional designs for handling mobility between base stations through the principles disclosed herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those of ordinary skill in the art, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.66SUBSTITUTE SHEET (RULE 26)

Claims

What is claimed is:

1. A method implemented in a user equipment (UE), the method comprising: communicating with a radio access network (RAN) according to a first configuration, including using a medium access control (MAC) entity associated with a cell group; receiving, from the RAN, a second configuration for use subsequent to receiving an activation command; receiving the activation command from the RAN; and in response to the activation command: using the second configuration to communicate with the RAN, including determining whether to reset the MAC entity in accordance with a MAC retention indication from the RAN.

2. The method of claim 1, wherein the determining whether to reestablish the RLC entity includes is based on whether the second configuration includes an RLC reestablishment indication.

3. The method of claim 1 or 2, further comprising: reestablishing the RLC entity prior to performing a random access procedure in accordance with the second configuration.

4. The method of claim 1 or 2, further comprising: reestablishing the RLC entity subsequent to performing a random access procedure in accordance with the second configuration.

5. The method of claim 1 or 2, further comprising: reestablishing the RLC entity, including discarding one or more of: an RLC service data units (SDU)s, an RLC SDU segment, or an RLC protocol data unit (PDU).

6. The method of claim 1, 2, or 5, further comprising: resetting a timer associated with the RLC entity.

7. The method of claim 1, 2, or 5, further comprising: resetting a state variable associated with the RLC entity to an initial value.

8. The method of claim 2, further comprising: refraining from reestablishing the RLC entity in response to determining that the second configuration omits the RLC reestablishment indication.

9. The method of any of the preceding claims, wherein the determining whether to reestablish the RLC entity is further based on whether the UE is configured to reestablish the RLC entity.

10. The method of any of the preceding claims, wherein: the second configuration includes a fast serving cell configuration, and the activation command is based on a lower layer measurement report from the UE.

11. A user equipment (UE) comprising: a transceiver; and processing hardware configured to implement a method of any of the preceding claims.

12. A method implemented in a radio access network (RAN) node, the method comprising: communicating with a user equipment (UE) in accordance with a first configuration; generating a second configuration, including refraining from including a reestablishment indication for a radio link control (RLC) bearer in the second configuration, when the second configuration is to be activated at the UE via a command from the RAN; and transmitting, to the UE, the second configuration.

13. The method of claim 12, further comprising: transmitting, to the UE and subsequent to the transmitting of the second configuration, an activation command; and communicating with the UE in accordance with the second configuration and using the RLC bearer.

14. The method of any one of claims 12 or 13, wherein: the RAN node is a distributed unit (DU) of a distributed base station; the method further comprising: transmitting the second configuration to the CU; and receiving, from the CU, a radio resource control (RRC) message addressed to the UE, the RRC message including the second configuration.

15. A network node comprising processing hardware configured to implement a method according to any one of the preceding claims.

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