Managing fast serving cell changes in decomposed base stations

Abstract

A distributed base station includes a centralized unit (CU), a source distributed unit (DU), and a target DU. The CU receives, from the target DU, a configuration related to a target cell for a user equipment (UE) currently communicating with the CU via the source DU to make a serving cell change, the serving cell change to the target cell being initiated after a measurement report from the UE. The CU sends the configuration to the UE via the source DU.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit and priority of the filing date of U.S. Provisional Patent Application No. 63 / 409,705, filed on September 23, 2022, with the title "MANAGING A FAST SERVING CELL CHANGE IN A DISAGGREGATED BASE STATION". The entire content of the provisional application is hereby incorporated by reference in its entirety. Technical Field

[0003] This disclosure relates to wireless communication, and more particularly, to using control signaling at a protocol layer below the radio resource control (RRC) protocol layer to enable fast serving cell change for a user equipment (UE). Background Art

[0004] This background description is provided for the purpose of generally presenting the context of the disclosure. The work of the currently named inventors (to the extent it is described in this background art section) and aspects of the specification that may not have been prior art at the time of filing are neither expressly nor impliedly admitted to be prior art of the disclosure.

[0005] In a telecommunications system, the packet data convergence protocol (PDCP) sub - layer of the radio protocol stack provides services such as user - plane data transfer, encryption, integrity protection, etc. For example, the PDCP layer defined for the evolved universal terrestrial radio access (EUTRA) radio interface (see 3GPP specification TS 36.323) and new radio (NR) (see 3GPP specification TS 38.323) provides sorting of protocol data units (PDUs) in the uplink direction (from the user device (also referred to as user equipment (UE)) to the base station) and in the downlink direction (from the base station to the UE). In addition, the PDCP sub - layer provides signaling radio bearers (SRBs) and data radio bearers (DRBs) to the radio resource control (RRC) sub - layer. Generally, in some scenarios, the UE and the base station use SRBs to exchange RRC messages and non - access stratum (NAS) messages. In further scenarios, the UE and the base station use DRBs to transmit data on the user plane.

[0006] Depending on the scenario, the UE uses several types of SRBs and DRBs. When operating in dual connectivity (DC), the cell associated with the base station operating as the master node (MN) defines the master cell group (MCG), while the cell associated with the base station used as the secondary node (SN) defines the secondary cell group (SCG). SRB1 resources carry RRC messages that include NAS messages on a dedicated control channel (DCCH) in some cases, while SRB2 resources support RRC messages that include logged measurement information or NAS messages, also on the DCCH, but with a 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 directly exchange RRC messages with the MN via the lower-layer resources of the MN and the SN. Additionally, a DRB that uses only the lower-layer resources of the MN can be referred to as an MCG DRB, a DRB that uses only the lower-layer resources of the SN can be referred to as an SCG DRB, and a DRB that uses the lower-layer resources of both the MCG and the SCG can be referred to as a split DRB.

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

[0008] When a UE moves from the coverage area of one cell in the RAN to another cell, at some point in time, a serving cell change will be performed for the UE. To perform the serving cell change, the RAN configures the UE to send layer 3 (L3) measurement results. Based on the L3 measurement results received from the UE, the RAN sends an RRC reconfiguration message, which configures a reconfiguration with synchronization (e.g., the RRC reconfiguration message includes a ReconfigurationWithSync IE) for the change of the serving cell (e.g., the PCell or the PSCell). In the case where the UE operates in carrier aggregation (CA) of at least one secondary cell (SCell) with the PCell or the PSCell, due to the change of the PCell or the PSCell, the RAN must release the at least one SCell. The serving cell change involves a complete L2 (and L1) reset, resulting in longer latency, greater overhead, and longer interruption time. Therefore, it is desirable to develop new mobility technologies to reduce the latency and overhead for fast serving cell change. However, it is not clear how to develop and implement fast serving cell change. Summary of the Invention

[0009] An example embodiment of the technology of the present disclosure is a method in a centralized unit (CU) of a distributed base station, the distributed base station including a CU, a source distributed unit (DU), and a target DU. The method includes: receiving, from the target DU, a configuration related to a target cell for a serving cell change of a user equipment (UE) currently communicating with the CU via the source DU, the serving cell change to the target cell being initiated after a measurement report from the UE; and sending the configuration to the UE via the source DU.

[0010] Another example embodiment of these technologies is a method in a centralized unit (CU) of a distributed base station, the distributed base station including a CU and a distributed unit (DU). The method includes: receiving, from the DU, a configuration related to a target cell for a serving cell change of a user equipment (UE) currently communicating with the CU via a serving cell, the serving cell change to the target cell being initiated after a measurement report from the UE; and sending the configuration to the UE via the DU.

[0011] Yet another example embodiment of these technologies is a radio access network (RAN) component including processing hardware configured to implement one of the above methods. Brief Description of the Drawings

[0012] Figure 1A is a block diagram of an example system in which a radio access network (RAN) and a user device can implement the technology of the present disclosure for managing a conditional process related to a secondary node (SN);

[0013] Figure 1B is a block diagram of an exemplary base station including a central unit (CU) and a distributed unit (DU) that can operate in a Figure 1A system;

[0014] Figure 2 is Figure 1A a block diagram of an exemplary protocol stack according to which a UE communicates with a base station;

[0015] Figure 3 is a messaging diagram of an exemplary scenario in which a base station configures a UE to perform a lower layer procedure for a cell change operation;

[0016] Figure 4 is a messaging diagram of an exemplary scenario in which a base station configures a UE to perform a lower layer procedure for an inter-DU inter-cell change operation;

[0017] Figure 5A is a messaging diagram of an exemplary scenario in which an MN operates with an SN under DC to perform a lower layer procedure for a cell change operation;

[0018] Figure 5B is related to Figure 5A a messaging diagram of a similar exemplary scenario, but in which the MN directly configures the UE;

[0019] Figure 6A is related to Figure 5A a messaging diagram of a similar exemplary scenario, but in which the cell change operation is an inter-DU cell change operation;

[0020] Figure 6B is related to Figure 5B a messaging diagram of a similar exemplary scenario, but in which the cell change operation is an inter-DU cell change operation;

[0021] Figure 7A is related to Figure 5A a messaging diagram of a similar exemplary scenario, but in which the base station operates as an MN (e.g., M-DU) and an SN (e.g., S-DU) to perform a cell change operation;

[0022] Figure 7B is related to Figure 7A a messaging diagram of a similar exemplary scenario, but in which the MN directly configures the UE;

[0023] Figure 8A is related to Figure 7A a messaging diagram of a similar exemplary scenario, but in which the cell change operation is an inter-DU cell change operation;

[0024] Figure 8B is related to Figure 7BMessage passing diagram of a similar example scenario, but where the cell change operation is an inter-DU cell change operation;

[0025] Figure 9 Is a flowchart depicting an example method implemented in the CU, where the CU receives a first configuration for later activation and sends the first configuration to the UE;

[0026] Figure 10 Is a flowchart depicting Figure 9 A flowchart of a similar example method, but where the CU receives the first configuration from a second DU;

[0027] Figure 11A Is a flowchart depicting an example method implemented in the CU, where the CU determines whether to include an IE in a message to the DU to indicate that the CU requests a configuration for later activation;

[0028] Figure 11B Is a flowchart depicting Figure 11A A flowchart of a similar example method, but where the CU sends a message to a second DU;

[0029] Figure 12A Is a flowchart depicting an example method implemented in the CU, where the CU determines whether to include the configuration in a container IE based on whether the configuration is for later activation;

[0030] Figure 12B Is a flowchart depicting Figure 12A A flowchart of a similar example method, but where the CU receives a configuration from a second DU;

[0031] Figure 13 Is a flowchart depicting an example method implemented in the DU, where the DU sends a first configuration for later activation to the CU and the UE;

[0032] Figure 14 Is a flowchart depicting an example method implemented in the DU, where the DU determines whether to send a configuration activation command to the UE based on whether the configuration is for later activation;

[0033] Figure 15 Is a flowchart depicting an example method implemented in the DU, where the DU determines whether to include the configuration in a first field or a second field based on whether the configuration is for later activation;

[0034] Figure 16 Is a flowchart depicting an example method implemented in the CU, where the CU receives a configuration from the DU, assigns an ID to the configuration, and sends the ID and the configuration to the UE;

[0035] Figure 17 Is a flowchart depicting Figure 16Flowchart of a similar example method, but where the CU receives configuration from a second DU;

[0036] Figure 18 is a flowchart depicting a method similar to Figure 16 and Figure 17 Flowchart of a similar example method, but where the CU receives configuration from multiple DUs;

[0037] Figure 19A is a flowchart depicting an example method implemented in a DU, where the DU receives an ID identifying a specific configuration, sends an activation command to the UE, and retains or releases the remainder of the configuration.

[0038] Figure 19B is a flowchart depicting a method similar to Figure 19A but where the DU generates the configuration; and

[0039] Figure 20 is a flowchart depicting an example method implemented in a DU, where the DU receives an ID identifying a specific configuration and sends a configuration activation command for that configuration to the UE. DETAILED DESCRIPTION

[0040] Figure 1A Depicts an example wireless communication system 100 in which a communication device may 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 is initially connected to the base station 104. In some scenarios, the base station 104 may perform SN addition to configure the UE 102 to operate with the base station 104 and the base station 106 under dual connectivity (DC). The base stations 104 and 106 operate as the MN and SN of the UE 102, respectively.

[0041] In various configurations of the wireless communication system 100, the base station 104 may be implemented as a master eNB (MeNB) or a master gNB (MgNB), and the base station 106 may be implemented as a secondary gNB (SgNB). The UE 102 may communicate with the base stations 104 and 106 via the same RAT (such as EUTRA or NR) or different RATs. When the base station 104 is a MeNB and the base station 106 is an SgNB, the UE 102 may be under EUTRA-NR DC (EN-DC) with the MeNB and the SgNB.

[0042] In some cases, the MeNB or SeNB is implemented as an ng-eNB instead of an eNB. When base station 104 is the master ng-eNB (Mng-eNB) and base station 106 is the SgNB, the UE 102 can be under the next-generation (NG) EUTRA-NR DC (NGEN-DC) with the Mng-eNB and the SgNB. When base station 104 is the MgNB and base station 106 is the SgNB, the UE 102 can be under the NR-NR DC (NR-DC) with the MgNB and the SgNB. When base station 104 is the MgNB and base station 106 is the secondary ng-eNB (Sng-eNB), the UE 102 can be under the NR-EUTRA DC (NE-DC) with the MgNB and the Sng-eNB.

[0043] In the scenario where the UE 102 hands over from base station 104 to base station 106, base stations 104 and 106 operate as the source base station (S-BS) and the target base station (T-BS), respectively. The UE 102 can, for example, operate under DC with base station 104 and an additional base station ( Figure 1A not shown in the figure) before the handover. After the handover is completed, the UE 102 can continue to operate under DC with base station 106 and the additional base station, or operate with base station 106 under single connection (SC). In this case, base stations 104 and 106 operate as the source MN (S-MN) and the target MN (T-MN), respectively.

[0044] The core network (CN) 110 can be the evolved packet core (EPC) 111 or the fifth-generation core (5GC) 160, both of which are Figure 1Ais depicted. The base station 104 can be an eNB that supports the S1 interface for communicating with the EPC 111, an ng-eNB that supports the NG interface for communicating with the 5GC 160, or a gNB that supports the NR radio interface and the NG interface for communicating with the 5GC 160. To directly exchange messages with each other in the scenarios discussed below, the base stations 104 and 106 can support the X2 or Xn interface. Among other components, the EPC 111 can include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. The SGW 112 is generally configured to forward 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., the Internet network and / or the Internet Protocol (IP) Multimedia Subsystem (IMS) network). The 5GC 160 includes a User Plane Function (UPF) 162, an Access and Mobility Management (AMF) 164, and / or a Session Management Function (SMF) 166. The UPF 162 is generally configured to forward user plane packets related to audio calls, video calls, Internet services, 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.

[0045] As Figure 1A shown, the base station 104 supports the cell 124A, and the base station 106 supports the cell 126. The cells 124A and 126 can partially overlap such that the UE 102 can communicate with the base stations 104 and 106 under DC, where one of the base stations 104 and 106 is the MN and the other is the SN. The base station 104 can support additional cells, such as cells 124B and 124C, and the base station 106 can support additional cells ( Figure 1A not shown in the figure). The cells 124A, 124B, and 124C can partially overlap such 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 Transmission and Reception Points (TRP). More specifically, when the UE 102 is under DC with the base stations 104 and 106, one of the base stations 104 and 106 operates as a MeNB, Mng-eNB, or MgNB, and the other operates as an SgNB or Sng-eNB.

[0046] Generally speaking, the wireless communication network 100 may include any suitable number of base stations that support NR cells and / or EUTRA cells. More specifically, the EPC 111 or 5GC 160 may be connected to any suitable number of base stations that support NR cells and / or EUTRA cells. Although the examples below specifically relate to particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), generally, the techniques of the present disclosure may also be applicable 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.

[0047] Continuing to refer Figure 1A , the base station 104 is equipped with processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and a non-transitory computer-readable memory that stores instructions executed by the one or more general-purpose processors. Additionally or alternatively, the processing hardware 130 may include a dedicated processing unit. The processing hardware 130 may include a PHY controller 132, which is configured to transmit data and control signals on physical downlink (DL) channels and DL reference signals to / from one or more user devices (e.g., UE 102) via one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs. The PHY controller 132 is also configured to receive data and control signals on physical uplink (UL) channels and / or UL reference signals from one or more user devices via one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs. The processing hardware 130 in an example implementation includes a MAC controller 134, which is configured to perform MAC functions with one or more user devices. The MAC functions include random access (RA) procedures, managing UL timing advance for one or more user devices, and / or communicating UL / DL MAC PDUs with one or more user devices. The processing hardware 130 may further include an RRC controller 136 to implement procedures and 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 support necessary operations when the base station 104 operates as an MN with respect to an SN or as an SN with respect to an MN. The base station 106 may include processing hardware 140 similar to the processing hardware 130. In particular, components 142, 144, and 146 may be similar to components 132, 134, and 136, respectively.

[0048] The UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors (such as a CPU), and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or a dedicated processing unit. The PHY controller 152 is also configured to receive data and control signals from the base station 104 or 106 on physical DL channels and / or DL reference signals via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. The PHY controller 152 is also configured to transmit data and control signals to the base station 104 or 106 on physical UL channels and / or UL reference signals via one or more cells (e.g., cells 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, which is configured to perform MAC functions with the base station 104 or 106. For example, MAC functions include random access procedures, managing UL timing advance for one or more user devices, and communicating UL / DL MAC PDUs with the base station 104 or 106. The processing hardware 150 may further include an RRC controller 156 to implement procedures and messaging at the RRC sublayer of the protocol communication stack.

[0049] In operation, the UE 102 under DC may use radio bearers (e.g., DRB or SRB) that terminate at the MN 104 or the SN 106 at different times. When communicating on a radio bearer in the uplink (UL) (from the UE 102 to the base station) and / or downlink (from the base station to the UE 102) direction, the UE 102 may apply one or more security keys.

[0050] Figure 1BIllustrates an example distributed implementation of a base station such as base station 104 or 106. In this implementation, the base station may include a Centralized Unit (CU) 172 and one or more Distributed Units (DUs) 174. The CU 172 is equipped with processing hardware that may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or a dedicated processing unit. In one example, the CU 172 is equipped with processing hardware 130. In another example, the CU 172 is equipped with processing hardware 140. The processing hardware 140 in the 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 may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or a dedicated processing unit. In some examples, the processing hardware in the example implementation includes a Media Access Control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., random access procedures) and a Radio Link Control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station 106 operates as an MN or SN. The processing hardware may further include a Physical Layer controller configured to manage or control one or more physical layer operations or procedures.

[0051] Next, Figure 2 Illustrates in a simplified manner a radio protocol stack according to which the UE 102 may communicate with an eNB / ng-eNB or gNB. Each of the base stations 104 or 106 may be an eNB / ng-eNB or gNB.

[0052] The physical layer (PHY) 202A of EUTRA provides a transport channel to the EUTRA media access control (MAC) sublayer 204A, which in turn provides a logical channel to the EUTRA radio link control (RLC) sublayer 206A, and the EUTRA RLC sublayer in turn provides an RLC channel to the EUTRA PDCP sublayer 208 and in some cases to the NR PDCP sublayer 210. Similarly, the PHY 202B of NR provides a transport channel to the NR MAC sublayer 204B, which in turn provides a logical channel to the NR RLC sublayer 206B, and the NR RLC sublayer 206B in turn provides an RLC channel to the NR PDCP sublayer 210. In some implementations, the UE 102 supports both the EUTRA and NR stacks to support handovers between EUTRA and NR base stations and / or DC implemented via EUTRA and NR interfaces. Additionally, as Figure 2 shown in A, the UE 102 may support the layering of NR PDCP 210 on EUTRA RLC 206A.

[0053] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets that may be referred to as service data units (SDUs) (e.g., from an Internet protocol (IP) layer that is directly or indirectly layered on the PDCP layer 208 or 210), and output packets that may be referred to as protocol data units (PDUs) (e.g., output to the RLC layer 206A or 206B). Except where the differences between SDUs and PDUs are relevant, for simplicity, this disclosure refers to both SDUs and PDUs as "packets".

[0054] For example, on the control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 provide SRBs to exchange radio resource control (RRC) messages. On the user plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 provide DRBs to support data exchange.

[0055] When the UE 102 operates under EUTRA / NR DC (EN-DC) with the base station 104 operating as the MeNB and the base station 106 operating as the SgNB, the network may provide the UE 102 with a bearer terminated at the MN using EUTRA PDCP 208 or a bearer terminated at the MN using NR PDCP 210. In various scenarios, the network may also provide the UE 102 with a bearer terminated at the SN using only NR PDCP 210. The bearer terminated at the MN may be an MCG bearer or a split bearer. The bearer terminated at the SN may be an SCG bearer or a split bearer. The bearer terminated at the MN may be an SRB (e.g., SRB1 or SRB2) or a DRB. The bearer terminated at the SN may be an SRB (e.g., SRB) or a DRB.

[0056] Next are several example scenarios in which the base station operating in the Figure 1A system sends a configuration to the UE 102 and later activates the configuration for communication between the UE 102 and the base station. Generally, Figures 3 to 7B similar events in Figure 4 A and Figure 4 B are labeled with similar reference numbers (e.g., event 316 is similar to Figure 5A event 416 in Figure 5B A, Figure 6A event 516 in Figure 6B A, Figure 7A event 517 in Figure 7B A,

[0057] First, referring to Figure 3 , in scenario 300, the base station 104 includes a CU 172 and a DU 174, and the DU 174 operates cell 124A. The UE 102 initially communicates with the base station 104 on cell 124A using a first configuration 302. In some implementations, the UE 102 in carrier aggregation (CA) uses the first configuration on cell 124A and other cells (e.g., Figure 1Acommunicates with the DU 174 on a cell 124D) not shown. The DU 174 operates other cells. In other implementations, the UE 102 communicates with the DU 174 only on the cell 124A. In some implementations, the UE 102 communicates with the DU 174 on the cell 124A and / or other cells via one or more TRPs. In some implementations, the cell 124A is a PCell. In such cases, the other cells include SCell and / or additional cells associated with the PCell or SCell. In other implementations, the cell 124A is an SCell and one of the other cells is a PCell. In such cases, the other cells include SCell and / or additional cells associated with the PCell or SCell. In the following description, the base station 104 may be the DU 174, the CU 172, or both the DU 174 and the CU 172.

[0058] In some implementations, in 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 cells via one or more TRPs. In some implementations, the UE 102 conveys UL PDUs and / or DL PDUs to the base station 104 via a radio bearer including SRB and / or DRB. In further implementations, the base station 104 configures the radio bearer for the UE 102. In some implementations, the UL control signal includes UL control information, channel state information, hybrid automatic repeat request (HARQ) acknowledgement (ACK), HARQ negative ACK, scheduling request, and / or sounding reference signal. Similarly, in further implementations, the UE 102 receives DL PDUs and / or DL control signals from the base station 104 on the cell 124A and / or other cells via one or more TRPs. In some implementations, the DL control signal includes downlink control information (DCI) and reference signals (e.g., synchronization signal block), channel state information reference signal (CSI-RS), and / or tracking reference signal. In some implementations, the base station 104 transmits DCI on the physical downlink control channel (PDCCH) monitored by the UE 102 on the cell 124A and / or other cells via one or more TRPs.

[0059] 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 CSI-MeasConfig IE, a MeasConfig IE, and / or a RadioBearerConfig IE (e.g., defined in 3GPP specification 38.331) or includes configuration parameters in the CSI-MeasConfig IE, the MeasConfig IE, and / or the RadioBearerConfig IE. In some implementations, the UE 102 receives configuration parameters from the base station 104. In other implementations, the UE 102 receives a part of the configuration parameters from a base station other than the base station 104 and receives the remaining part of the configuration parameters from the base station 104.

[0060] When communicating with base station 104, UE 102 sends 304 at least one measurement report to DU 174. In some implementations, the at least one measurement report includes layer 1 (L1) measurement reports and / or layer 3 (L3) measurement reports for at least one serving cell and / or at least one non-serving cell of UE 102. For each of the L3 measurement reports, DU 174 sends 306 a DU-to-CU message including the L3 measurement report to CU172. In some implementations, the DU-to-CU message for event 306 is an F1 Application Protocol (F1AP) message (e.g., UL RRC message transfer message). In some implementations, UE 102 does not send or avoids sending L1 measurement reports to CU 172. The at least one serving cell includes cell 124A and / or other cells, and the at least one non-serving cell includes cell 124B and / or cell 124C. In some implementations, the first configuration includes at least one measurement configuration. In some implementations, UE 102 receives one or more RRC messages (e.g., RRCReconfiguration message) including the at least one measurement configuration from CU 172 via DU 174 in event 302. According to the at least one measurement configuration, UE 102 performs measurements and sends 304 the at least one measurement report to DU 174. In some implementations, the at least one measurement configuration includes an L3 measurement configuration (e.g., MeasConfig IE) and / or an L1 measurement configuration. For example, the L1 measurement configuration (e.g., CSI-MeasConfig IE) includes CSI resource configuration (e.g., CSI-ResourceConfig IE) and / or CSI report configuration (e.g., CSI-ReportConfig IE). UE 102 sends an L3 measurement report to CU 172 via DU 174 according to the L3 measurement configuration. UE 102 sends an L1 measurement report to DU 174 according to the L1 measurement configuration. In some implementations, the at least one measurement configuration includes a new measurement configuration for fast serving cell change (e.g., a new RRC IE (e.g., as defined in 3GPP specification 38.331 v18.0.0 and / or later)). For example, the new measurement configuration includes CSI resource configuration (e.g., CSI-ResourceConfig IE) and / or a new report configuration. In such implementations, the at least one measurement report includes a new measurement report associated with the new measurement configuration. UE 102 sends the new measurement report to DU 174 according to the new measurement configuration. In some implementations, each of the new report configurations includes a trigger event configuration that configures a trigger event to trigger UE102 to send a new measurement report. If UE 102 detects the trigger event, UE 102 sends the new measurement report to DU 174.

[0061] In some implementations, the L1 measurement report includes at least one L1 measurement result. In some implementations, the at least one L1 measurement result includes at least one L1 - Reference Signal Received Power (L1 - RSRP) value and / or at least one L1 - Signal to Interference plus Noise Ratio (L1 - SINR) value. In some implementations, for each of the L1 measurement reports, UE 102 sends a PUCCH transmission including the L1 measurement report to DU 174. That is, UE 102 sends each of the L1 measurement reports to DU 174 on the PUCCH. In other implementations, for each of the L1 measurement reports, UE 102 sends a PUSCH transmission including the L1 measurement report to DU 174. That is, UE 102 sends each of the L1 measurement reports to DU 174 on the PUSCH. In still other implementations, UE 102 sends a part of the L1 measurement report to DU 174 on the PUCCH and sends the remaining part of the L1 measurement report on the Physical Uplink Shared Channel (PUSCH). That is, for each of the parts of the L1 measurement report, UE 102 sends a PUCCH transmission including the L1 measurement report to DU 174, and for each of the remaining parts of the L1 measurement report, UE 102 sends a PUSCH transmission including the L1 measurement report to DU 174. In some implementations, each of the L1 measurement reports is part of the Channel State Information (CSI) (i.e., a CSI component) or CSI. In some implementations, UE 102 includes other CSI components in the above - mentioned PUCCH transmission and / or PUSCH transmission. In some implementations, the other CSI components include components such as Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), CSI - RS Resource Indicator (CRI), Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) Resource Block Indicator (SSBRI), Layer Indicator (LI), and / or Rank Indicator (RI).

[0062] In some implementations, each of the L3 measurement reports includes at least one L3 measurement result. In some implementations, the at least one L3 measurement result includes at least one RSRP (value) and / or at least one SINR (value). In some implementations, UE 102 sends each of the L3 measurement reports to CU 172 on the PUSCH via DU 174. In some implementations, each of the L3 measurement reports is an RRC message (e.g., MeasurementReport message). In some implementations, each of the L3 measurement configurations includes a specific measurement identifier (e.g., measId), and each of the L3 measurement reports includes the specific measurement identifier in the specific L3 measurement configuration. In some implementations, when CU 172 receives from UE 102 via DU 174 an L3 measurement report including a measurement identifier and an L3 measurement result, CU 172 determines that the L3 measurement report is associated with the L3 measurement configuration identified by the measurement identifier.

[0063] In some alternative implementations, for each of at least one measurement report (e.g., L1 measurement report and / or new measurement report), UE 102 sends a MAC control element (CE) including the measurement report to DU 174 in event 304. To send the MAC CE, UE 102 generates one or more MAC PDUs for DU 174 in event 304, each MAC PDU including one or more MAC CEs.

[0064] In some implementations, UE 102 performs measurements on one or more reference signals according to at least one measurement configuration. In further implementations, the one or more reference signals include one or more synchronization signals (SS) / physical broadcast channel (PBCH) resource blocks (SSB) and / or one or more CSI-RS. UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurements. DU 174 sends one or more reference signals on cells 124A and 124B, and in some implementations, sends one or more reference signals on cell 124C and / or other cells.

[0065] After receiving one or some of at least one measurement report from UE 102 (e.g., in response thereto), base station 104 (i.e., CU 172 or DU 174) determines to prepare cell 124B for UE 102. In some implementations, base station 104 determines to prepare cell 124B for UE 102 because at least one measurement report indicates that cell 124B can be used by base station 104 to communicate with UE 102. In some implementations, base station 104 determines to prepare cell 124B for UE 102 because at least one measurement report indicates that cell 124B is eligible for communication with UE 102. In some implementations, if the L3 measurement report indicates that the signal strength and / or quality of cell 124B is higher than a first predetermined threshold and / or better (e.g., higher) than cell 124A, then CU 172 determines to prepare cell 124B for UE 102. In other implementations, if the L1 measurement report or a new type of measurement report indicates that the signal strength and / or quality of cell 124B is higher than a first predetermined threshold and / or better (e.g., higher) than cell 124A, then DU 174 determines to prepare cell 124B for UE 102. Alternatively, base station 104 determines to prepare cell 124B for UE 102 regardless of whether a measurement report is received from UE 102.

[0066] In some implementations, if CU 172 determines to prepare cell 124B, then CU 172 sends 308 a first CU-to-DU message to DU 174 to prepare cell 124B for UE 102. In some implementations, CU 172 includes the cell identifier (ID) of cell 124B in the first CU-to-DU message. For example, the cell ID is a cell global identifier (CGI). In another example, the cell ID is a physical cell ID (PCI). In response, DU 174 generates a second configuration for configuring cell 124B (which may be referred to as "configuration 1" in this document), and sends 310 a first DU-to-CU message including the second configuration to CU 172. In further implementations, if DU 174 determines to prepare cell 124B, then DU 174 initiates the transmission of a first DU-to-CU message to CU 172.

[0067] After receiving the first DU-to-CU message, CU 172 generates an RRC reconfiguration message (e.g., RRCReconfiguration message) including Configuration 1, and sends a second CU-to-DU message including the RRC reconfiguration message to DU 174. Subsequently, DU 174 sends the RRC reconfiguration message to UE 102. In response, UE 102 sends a 320 RRC reconfiguration complete message (e.g., RRCReconfigurationComplete message) to DU 174, and DU 174 then sends a second DU-to-CU message including the RRC reconfiguration complete message to CU 172. In some implementations, CU 172 performs security protection (e.g., integrity protection and / or encryption) on the RRC reconfiguration message. For example, CU 172 generates a message authentication code for integrity (MAC-I) for the RRC reconfiguration message in events 316 and 318, encrypts the RRC reconfiguration message and MAC-I to obtain an encrypted RRC reconfiguration message and an encrypted MAC-I, and sends a PDCP PDU including the encrypted RRC reconfiguration message and the encrypted MAC-I to UE 102 via DU 174. When UE 102 receives the PDCP PDU from CU 172 via DU 174 (i.e., events 316 and 318), UE 102 decrypts the encrypted RRC reconfiguration and the encrypted MAC-I to obtain the RRC reconfiguration message and MAC-I, and UE 102 verifies whether the MAC-I is valid. If UE 102 verifies that the MAC-I is invalid, UE 102 discards or ignores the RRC reconfiguration message. In some implementations, UE 102 performs an RRC connection reconstruction process in response to an invalid MAC-I. Otherwise, in a further implementation, if UE 102 verifies that the MAC-I is valid, UE 102 processes the RRC reconfiguration. UE 102 avoids applying (i.e., executing) Configuration 1 until it receives a configuration activation command that activates Configuration 1 (e.g., event 330).

[0068] In some implementations, the first CU-to-DU message is a UE Context Modification Request message, and the first DU-to-CU message is a UE Context Modification Response message or a UE Context Modification Required message. In some cases for the UE Context Modification Required message, CU 172 sends a UE Context Modification Confirm message to DU 174 in response to the UE Context Modification Required message. In some implementations, the second CU-to-DU message is a DL RRC Message Transfer message. In other implementations, the second CU-to-DU message is a UE Context Modification Request message, and DU 174 sends a second DU-to-CU message (e.g., a UE Context Modification Response message) to CU 172 in response to the second CU-to-DU message.

[0069] Events 308 and 310 are collectively referred to as the serving cell preparation procedure 390 in Figure 3 the following.

[0070] In some implementations, CU 172 includes a field or IE in the RRC reconfiguration messages of events 316 and 318 to indicate to UE 102 not to apply configuration 1 immediately. In some implementations, the field or IE is currently defined (e.g., in 3GPP specification 38.331 v18.0.0 and / or later versions). In further implementations, the field or IE is newly defined (e.g., in the 3GPP 6G specification). In some implementations, the field or IE is an indicator. If the RRC reconfiguration message of event 318 includes the indicator, UE 102 avoids applying configuration 1 immediately. Otherwise, if the RRC reconfiguration message of event 318 does not include the indicator, UE 102 applies configuration 1 immediately. In other implementations, the field or IE is a container (e.g., the first container and / or the second container described below). For example, UE 102 receives an RRC reconfiguration message (e.g., the RRC reconfiguration message of event 318) including a configuration (e.g., configuration 1). If the configuration is included in the container, UE 102 avoids applying the configuration immediately. Otherwise, if the configuration is not included in the container, UE 102 applies the configuration immediately.

[0071] In some implementations, after receiving Configuration 1 in Event 310, CU 172 generates a first container that includes Configuration 1, includes the first container in an RRC reconfiguration message, and sends the RRC reconfiguration message to UE 102 in Event 316. Alternatively, DU 174 generates the first container and includes the first container in a 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, MobilityConfigToAddModListIE, or CellGroupConfigToAddModList IE). The base station 104 includes Configuration 1 in a first element of the first addition or modification list (referred to herein as Element 1). For example, 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 UE 102 receives the first addition or modification list, UE 102 stores the first addition or modification list (e.g., in a variable in random access memory (RAM)).

[0072] In some implementations, CU 172 includes a first ID (referred to herein as ID 1) for identifying Configuration 1 in the RRC reconfiguration message. In some implementations, CU 172 includes ID 1 in the first container or Element 1. In some implementations, CU 172 assigns ID 1 to Configuration 1. In other implementations, CU 172 receives ID 1 from DU 174 in a first DU-to-CU message, as described below.

[0073] In some implementations, CU 172 sends ID 1 to DU 174 such that DU 174 associates ID 1 with Configuration 1. In some implementations, CU 172 includes ID 1 in a first CU-to-DU message. In a further implementation, CU 172 sends 312 a third CU-to-DU message that includes ID 1 to DU 174. In some such cases, CU 172 includes Configuration 1 in the third CU-to-DU message to indicate the association between ID 1 and Configuration 1. In a further implementation, DU174 sends 314 a third DU-to-CU message to CU 172 in response to the third CU-to-DU message. Events 312 and 314 are in Figure 3are collectively referred to as the ID allocation process 392 in

[0074] In some implementations, when CU 172 includes ID 1 in the first CU-to-DU message, DU 174 includes ID 1 in Configuration 1. In such cases, CU 172 does not include ID 1 in the RRC reconfiguration message, the first container, and / or Element 1.

[0075] In some alternative implementations, DU 174 assigns ID 1 to identify Configuration 1. In some implementations, DU 174 includes ID 1 in the first DU-to-CU message. In further implementations, CU 172 includes ID 1 in the RRC reconfiguration message. In other implementations, DU 174 includes ID 1 in Configuration 1. Therefore, CU 172 does not include the ID identifying Configuration 1 in the RRC reconfiguration message, the first container, and / or Element 1.

[0076] In some implementations, Configuration 1 includes multiple configurations for UE 102 to communicate with DU 174 on cell 124B. In some implementations, the multiple configurations include physical layer configuration parameters (e.g., PhysicalCellGroupConfigIE), MAC layer configuration parameters (e.g., MAC-CellGroupConfig IE), and / or RLC configuration parameters (e.g., RLC-BearerConfig IE). In some further implementations, the multiple configurations include special cell configurations (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE).

[0077] In some implementations, DU 174 includes the random access configuration in Configuration 1. In other implementations, DU 174 does not include the random access configuration in Configuration 1. In some implementations, if cell 124A and cell 124B are not synchronized, then DU 174 determines to include the random access configuration in Configuration 1. Otherwise, if cell 124A and cell 124B are synchronized, then DU 174 determines not to include the random access configuration in Configuration 1. In other implementations, if DU 174 determines that UE102 has not synchronized with cell 124B in the UL, then DU 174 determines to include the random access configuration in Configuration 1. Otherwise, if DU 174 determines that UE 102 has synchronized with cell 124B in the UL, then DU 174 determines not to include the random access configuration in Configuration 1. If Configuration 1 includes the random access configuration, then UE 102 performs a random access procedure according to the random access configuration in Event 332, as described below. Otherwise, if Configuration 1 does not include the random access configuration, then UE 102 skips the random access procedure for Event 332 in response to Configuration 1 excluding the random access configuration.

[0078] In some implementations, DU 174 includes the random access configuration in Configuration 1 regardless of whether cell 124A and 124B are synchronized. In some implementations, if cell 124A and cell 124B are synchronized, then DU 174 determines to include a first indication in Configuration 1, where the first indication configures UE 102 not to perform a random access procedure on cell 124B. Otherwise, if cell 124A and cell 124B are not synchronized, then DU 174 determines not to include the first indication in Configuration 1. In other implementations, if DU 174 determines that UE 102 has synchronized with cell 124B in the UL, then DU 174 determines to include the first indication in Configuration 1. Otherwise, if DU 174 determines that UE 102 has not synchronized with cell 124B in the UL, then DU 174 determines not to include the first indication in Configuration 1. If Configuration 1 includes the first indication, then UE 102 skips the random access procedure for Event 332 according to or in response to the first indication. Otherwise, if Configuration 1 does not include the first indication, then in response to Configuration 1 excluding the first indication, UE 102 performs a random access procedure according to the random access procedure in Event 332, as described below.

[0079] In some implementations, the DU 174 includes a reconfiguration with a synchronization configuration (e.g., ReconfigurationWithSync IE) in Configuration 1 or a special cell configuration. In other implementations, the DU 174 does not include a reconfiguration with a synchronization configuration (e.g., ReconfigurationWithSync IE) in Configuration 1 or a special cell configuration. In some implementations, if cell 124A and cell 124B are not synchronized, the base station 104 determines to include a reconfiguration with a synchronization configuration in Configuration 1. Otherwise, if cell 124A and cell 124B are synchronized, the DU 174 determines not to include a reconfiguration with a synchronization configuration in Configuration 1. In other implementations, if the DU 174 determines that the UE 102 has not synchronized with cell 124B in the UL, the DU 174 determines to include a reconfiguration with a synchronization configuration in Configuration 1. Otherwise, if the DU 174 determines that the UE 102 has already synchronized with cell 124B in the UL, the DU 174 determines not to include a reconfiguration with a synchronization configuration in Configuration 1. In some implementations, if Configuration 1 includes a reconfiguration with a synchronization configuration, the UE 102 performs a random access procedure in event 332 in response to or according to the reconfiguration with a synchronization configuration, as described below. Otherwise, if Configuration 1 does not include a reconfiguration with a synchronization configuration, the UE 102 skips the random access procedure for event 332. In some implementations, the DU 174 includes the cell ID of cell 1 (i.e., cell 124B) (i.e., cell ID 1) in Configuration 1. In some implementations, cell ID 1 is a PCI. In further implementations, cell ID 1 is a CGI. In some further implementations, Configuration 1 includes a cell index 1 (e.g., serving cell index) that indexes cell ID 1 or cell 124B.

[0080] In some implementations, after receiving one or some of at least one measurement report of event 304 (e.g., in response thereto), the base station 104 (i.e., CU 172 or DU 174) determines to prepare other cells of the base station 104 for the UE 102. In some implementations, the base station 104 determines to prepare other cells because at least one measurement report indicates that the other cells can be used by the base station 104 to communicate with the UE 102. In some implementations, the other cells include cell 124C and / or cells other than cells 124A, 124B, and 124C. In some implementations, if the L3 measurement report indicates that the signal strength and / or quality of a specific cell among the other cells is higher than a corresponding predetermined threshold and / or better (e.g., higher) than cell 124A, the CU 172 determines to prepare the specific cell for the UE 102. In other implementations, if the L1 measurement report or a new measurement report indicates that the signal strength and / or quality of a specific cell among the other cells is higher than a first predetermined threshold and / or better (e.g., higher) than cell 124A, the DU 174 determines to prepare the specific cell for the UE 102. In some implementations, the corresponding predetermined threshold of the other cells is different from the first predetermined threshold. In further implementations, the corresponding predetermined threshold of the other cells is the same as the first predetermined threshold. In some implementations, the corresponding predetermined thresholds of the other cells are the same or different. Alternatively, the base station 104 determines to prepare other cells for the UE 102 regardless of whether a measurement report is received from the UE 102.

[0081] In some implementations, in response to determining to prepare other cells, the CU 172 and the DU 174 perform at least one other serving cell preparation process to prepare the other cells, where each of the at least one other serving cell preparation processes is similar to process 390. In further implementations, the CU 172 includes the cell IDs of the other cells in at least one CU-to-DU message similar to the first CU-to-DU message of the at least one serving cell preparation process. In some implementations, the CU 172 and the DU 174 perform additional serving cell preparation processes similar to process 390 to prepare each of the other cells. In some such cases, the CU 172 includes the cell ID of a specific cell among the other cells in the CU-to-DU message similar to the first CU-to-DU message of the serving cell preparation process. In the serving cell preparation process, the DU 174 generates configurations 2...N, each of which configures a specific cell among the other cells, and sends the configurations 2...N to the CU 172, as described for configuration 1. "N" is an integer and greater than one. For example, "N" is 2, 4, 6, 8, 10, 12, 14, or 16. The examples and implementations of configuration 1 can be applicable to configurations 2...N.

[0082] In other implementations, the CU 172 determines to prepare other cells in process 390. In some such cases, the CU 172 includes the cell ID for each of the other cells in the first CU-to-DU message, and the DU 174 includes configurations 2...N in the first DU-to-CU message. In still other implementations, the DU 174 determines to prepare other cells in process 390 and includes configurations 2...N in the first DU-to-CU message.

[0083] In some implementations, after receiving configurations 2...N from the DU 174, the CU 172 includes configurations 2...N in the first container. In some implementations, the CU 172 includes configurations 2...N in elements 2...N and includes elements 2...N in the first container. In some implementations, the CU 172 includes IDs 2...N used to respectively identify configurations 2...N in the RRC reconfiguration message. In some implementations, the CU 172 includes IDs 2...N in the first container. For example, the CU 172 includes IDs 2...N and configurations 2...N in elements 2...N in the first addition or modification list.

[0084] In some implementations, the CU 172 assigns IDs 2...N to configurations...N. In other implementations, the CU 172 receives IDs 2...N from the DU 174 in the first DU-to-CU message of process 390 or in the DU-to-CU message of at least one other serving cell preparation process or additional serving cell preparation process.

[0085] In some implementations, the CU 172 performs an ID assignment process for each of configurations 2...N with the DU 174, similar to process 392. In such cases, the DU 174 includes IDs 2...N in configurations 2...N. In such cases, the CU 172 does not include IDs 2...N in the RRC reconfiguration message, the first container, and / or elements 2...N.

[0086] In some alternative implementations, the DU 174 assigns IDs 2...N in configurations 2...N. In some implementations, the DU 174 includes IDs 2...N in the first DU-to-CU message of process 390 or in the DU-to-CU message of at least one other serving cell preparation process or additional serving cell preparation process. The CU 172 includes IDs 2...M in the RRC reconfiguration message. In other implementations, the DU 174 includes IDs 2...N in configurations 2...N. Therefore, the CU 172 does not include the IDs identifying each of configurations 2...N in the RRC reconfiguration message, the first container, and / or element 1.

[0087] In some alternative implementations, instead of using the first container, CU 172 generates a second container that includes configurations 2...N or elements 2...N. Alternatively, DU 174 generates the second container and includes the second container in the first DU-to-CU message or the DU-to-CU message of another serving cell preparation procedure. Then, CU 172 sends an additional RRC reconfiguration message including the second container to UE 102 via DU 174, similar to events 316 and 318. In response, UE 102 sends an additional RRC reconfiguration complete message to CU 172 via DU 174, similar to 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 elements 2...N is an addition or modification IE (e.g., ConfigToAddMod IE, ReconfigToAddMod IE, CellConfigToAddMod IE, MobilityToAddMod IE, MobilityConfigToAddMod IE, or CellGroupConfigToAddMod IE). In some implementations, when UE 102 receives the second addition or modification list, 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).

[0088] In some implementations, DU 174 includes cell IDs 2...N in configurations 2...N respectively. The cell IDs 2...N identify cells 2...N respectively. In some implementations, each of the cell IDs 2...N is a PCI. In some further implementations, the configurations 2...N include cell indices 2...N (e.g., serving cell index) that index the cell IDs 2...N or cells 2...N respectively.

[0089] In some implementations, each of configurations 1 and / or 2...N is a CellGroupConfig IE. In such implementations, the following is an example structure 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.

[0090] In some implementations, the CU 172 sends a release list to the UE 102 via the DU 174 to release one or more of the configurations in configurations 1...N. For example, the CU 172 sends an RRC reconfiguration message including the release list to the UE 102 via the DU 174. In response, the UE 102 sends an RRC reconfiguration complete message to the CU 172 via the DU 174. In some implementations, the base station 104 includes the IDs of one or more of the configurations in the release list to indicate one or more of the configurations to be released. The UE 102 identifies one or more of the configurations based on the IDs and releases one or more of the configurations in response to the release list.

[0091] In some implementations, the base station 104 sends a third addition or modification list that is empty or does not include configurations to the UE 102 to release all of the configurations in configurations 1...N. In some implementations, the base station 104 sends an RRC reconfiguration message including the third addition or modification list to the UE 102. In response, the UE 102 sends an RRC reconfiguration complete message to the CU 172 via the DU 174. The UE 102 releases all of the configurations in configurations 1...N in response to the third addition or modification list.

[0092] In some implementations, the CU 172 determines to release one configuration, multiple configurations, or all of the configurations in configurations 1...N and sends a CU-to-DU message to the DU 174 to instruct the DU 174 to release one, multiple, or all of the configurations in configurations 1...N. For example, the CU 172 includes one, multiple, or all of the IDs 1...N in the CU-to-DU message to instruct the DU 174 to release one, multiple, or all of the configurations in configurations 1...N. Depending on the implementation, each of the cell IDs 1...N is a CGI or a PCI. In some implementations, in response, the DU 174 releases one, multiple, or all of the configurations in configurations 1...N and sends a DU-to-CU message to the CU 172. In other implementations, the DU 174 determines to release one, multiple, or all of the configurations in configurations 1...N and sends a DU-to-CU message including the IDs of one, multiple, or all of the configurations in configurations 1...N to the CU 172. After receiving the DU-to-CU message (e.g., in response thereto), the CU 172 generates a release list or a third addition or modification list to release one, multiple, or all of the configurations in configurations 1...N.

[0093] In other implementations, the DU 174 generates a release list or a third addition or modification list. In some such cases, the DU 174 sends a DU-to-CU message including the release list or the third addition or modification list to the CU 172. In some implementations, in response, the CU 172 sends a CU-to-DU message to the DU 174. In some implementations, the DU 174 determines one, more, or all of the release configurations 1...N. In other implementations, the DU 174 receives a CU-to-DU message from the CU 172 including the ID of one, more, or all of the configurations 1...N to indicate one, more, or all of the release configurations 1...N.

[0094] Example implementation 1

[0095]

[0096] For example, the first addition or modification list is the first CellGroupConfigToAddModList IE, and the second addition or modification list is the second CellGroupConfigToAddModList IE. Element 1 is CellGroupConfigToAddMod IE 1, and elements 2...N are CellGroupConfigToAddMod IE2...N respectively. ID 1 and configuration 1 are the ConfigId and CellGroupConfigIE in CellGroupConfigToAddMod IE 1 respectively. ID 2...N and configuration 2...N are the ConfigId and CellGroupConfig IE in CellGroupConfigToAddMod IE 2...N respectively. In some implementations, the first CellGroupConfigToAddModList IE includes CellGroupConfigToAddMod IE 1, and the second CellGroupConfigToAddModList IE includes CellGroupConfigToAddMod IE 2...N. In a further implementation, the first CellGroupConfigToAddModList IE includes CellGroupConfigToAddModIE 1...N.

[0097] In some implementations, the release list is the CellGroupConfigToReleaseList IE. In further implementations, the base station 104 includes one or more ConfigID IEs in the CellGroupConfigToReleaseList IE to release one or more of the CellGroupConfigToAddMod IEs 1...N in the CellGroupConfigToAddMod IE. One or more CellGroupConfigToAddMod IEs are identified by one or more ConfigID IEs.

[0098] Example implementation 2

[0099] Example implementation 2 is similar to example implementation 1, except that the CellGroupConfigToAddMod IE does not include the ConfigId.

[0100]

[0101] In some implementations, IDs 1...N are implicitly indicated by the order of CellGroupConfigToAddMod IEs 1...N in the first or second CellGroupConfigToAddModList. For example, CellGroupConfigToAddMod IE 1 is the first IE in the first CellGroupConfigToAddModList IE, which implicitly indicates that ID 1 has a value X. X can be zero or one. If the first CellGroupConfigToAddModList IE sequentially includes CellGroupConfigToAddMod IEs 1...N, then IDs 1...N have values X, X + 1...X+(N - 1). In some implementations, if base station 104 sends the second CellGroupConfigToAddModList IE to UE 102, UE 102 and base station 104 replace the first CellGroupConfigToAddModList IE with the second CellGroupConfigToAddModList IE. If the second CellGroupConfigToAddModList IE sequentially includes CellGroupConfigToAddMod IEs 2...N, then IDs 2...N are values X, X + 1...X+N - 2. If the second CellGroupConfigToAddModList IE sequentially includes CellGroupConfigToAddMod IEs 1...N, then IDs 1...N are values X, X + 1...X+N - 1. In some alternative implementations, IDs 1...N are cell IDs 1...N.

[0102] In some implementations, base station 104 sends a CellGroupConfigToAddModList IE that includes zero CellGroupConfigToAddMod IEs to release all of CellGroupConfigToAddMod IEs 1...N.

[0103] In exemplary implementations 1 and 2, "CellGroupConfigToAddModList", "CellGroupConfigToAddMod", "configId", "ConfigId", "cellGroupConfig", "CellGroupConfigToReleaseList", and "maxNrofConfigCells" are merely exemplary and should not be regarded as limiting the scope and application of the present invention.

[0104] In other implementations, each of Configuration 1 and / or 2... N is an RRCRec onfiguration message. In such implementations, the following (i.e., Example Implementations 3-6) are example structures of the first or second addition or modification list.

[0105] Example Implementation 3

[0106] In Example Implementation 3, the first or second addition or modification list is a CondReconfigToAddModList-r16 IE (e.g., as defined by Release 16 in 3GPP specification 38.331), and the CondReconfigToAddMod IE is an element of the list.

[0107]

[0108] For example, the first addition or modification list is the first CondReconfigToAddModList-r16IE and the second CondReconfigToAddModList-r16 IE. Element 1 is a CondRec onfigToAddMod-r16 IE 1, and Elements 2... N are CondReconfigTo AddMod-r16 IE 2... N respectively. ID 1 and Configuration 1 are the CondReconfigId and the RRCReconfiguration message in CondReconfigToAdd Mod IE 1 respectively. ID 2... N and Configuration 2... N are the CondReconfigId and the RRCReconfiguration message in CondReconfigToAddMod IE 2... N respectively. In some implementations, the first CondReconfigToAddModList-r16 IE includes CondReconfigToAddMod-r16IE 1, and the second CondReconfigToAddModList-r16 IE includes CondReconfi gToAddMod-r16 IE 2... N. In a further implementation, the first CondReconfigToAddModList-r16 IE includes CondReconfigToAddMod-r16 IE 1... N.

[0109] In this example implementation, the base station 104 includes a conditional configuration (i.e., condExecution Cond-r16) in at least one of the CondReconfigToAddMod-r16 IEs. 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)), then the UE 102 evaluates one or more conditions configured in the condExecutionCond-r16 field for the conditional procedure. If the UE 102 detects that at least one or all of one or more conditions in the condExecutionCond-r16 field in a particular CondReconfigToAddMod-r16 IE are satisfied, then the UE 102 immediately applies the configuration in the RRC Reconfiguration message in the CondReconfigToAddMod-r16 IE (e.g., as described in 3GPP specification 38.331). In some implementations, the base station 104 does not include a conditional configuration (i.e., condExecutionCond-r16) in any or some of the CondReconfigToAddMod-r16 IEs. Thus, for a CondRec onfigToAddMod-r16 IE that does not include a conditional configuration (i.e., condExecutionCond-r16), the UE 102 is not configured to perform or not perform any evaluation (i.e., detection or determination) of the conditions for a conditional procedure (e.g., conditional handover).

[0110] In some implementations, the release list is the CondReconfigToRemoveList-r16 IE. In a further implementation, the base station 104 includes one or more CondReconfigID IEs in the CondReconfigToRemoveList-r16 IE to release one or more CondReconfigToAdd Mod-r16 IEs among CondRec onfigToAddMod-r16 IEs 1...N. One or more CondReconfigToAddMod-r16 IEs are identified by one or more CondReconfigID IEs.

[0111] Example implementation 4

[0112] Example implementation 4 is similar to example implementation 3, except that in some implementations, a new indicator (e.g., the fastServingCellChange-r18 field) is optionally included in the CondReconfigToAddMod-r16 IE. In some implementations, the new indicator indicates that the CondReconfigToAddMod-r16 IE (i.e., the RRCReconfiguration message or condRRCReconfig-r16 in the IE) is configured for fast serving cell change (i.e., see the description for event 312). If the base station 104 does not include the new indicator in the CondReconfigToAddMod-r16 IE, then the CondReconfigToAddMod-r16 IE is not configured for fast serving cell change.

[0113]

[0114] CondReconfigToRemoveList-r16::=SEQUENCE(SIZE(1..ma xNrofCondCells-r16))OF CondReconfigId-r16.

[0115] Example implementation 5

[0116] Some implementations in 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 conditional procedures, then the base station 104 does not configure or enable fast serving cell change for the UE 102. Thus, example implementation 5 is decoupled from conditional procedures.

[0117]

[0118] In some implementations, the first addition or modification list is the first ReconfigToAdd ModList IE, and the second addition or modification list is the second ReconfigToAddModList IE. Element 1 is ReconfigToAddMod IE1, and elements 2...N are ReconfigToAddMod IE 2...N respectively. ID 1 and Configuration 1 are the ConfigId and RRCReconfiguration IE in ReconfigToAddMod IE 1. ID 2...N and Configuration 2...N are the ConfigId and RRCReconfiguration IE in ReconfigToAddMod IE 2...N respectively. In some implementations, the first ReconfigToAddModList IE includes ReconfigToAddMod IE 1, and the second ReconfigToAddModList IE includes ReconfigToAddMod IE 2...N. In a further implementation, the first ReconfigToAddModList IE includes ReconfigToAddMod IE 1...N.

[0119] In some implementations, the release list is the ReconfigToReleaseList IE. In a further implementation, the base station 104 includes one or more ConfigID IEs in the ReconfigToReleaseList IE to release one or more ReconfigToAddMod IEs among ReconfigToAddMod IEs 1...N. One or more ReconfigToAddMod IEs are identified by one or more ConfigID IEs.

[0120] Example implementation 6

[0121]

[0122] Example implementation 6 is similar to example implementation 5, except that the ReconfigTo AddMod IE does not include the ConfigId. In some implementations, IDs 1... N are implicitly indicated by the order of the ReconfigToAddMod IEs 1... N in the first or second ReconfigToAddModList. For example, ReconfigToAddMod IE 1 is the first IE in the first Reconfig ToAddModList IE, which implicitly indicates that ID 1 has the value X. X can be zero or one. If the first ReconfigToAddModList IE sequentially includes ReconfigT oAddMod IEs 1... N, then IDs 1... N have the values X, X + 1... X+(N - 1). In some implementations, if the base station 104 sends the second ReconfigToAddModList IE to the UE 102, then the UE 102 and the base station 104 replace the first ReconfigToAddModList IE with the second ReconfigToAddModList IE. If the second ReconfigToAddMod List IE sequentially includes ReconfigToAddMod IEs 2... N, then IDs 2... N are the values X, X + 1... X+N - 2. If the second ReconfigToAddModList IE sequentially includes ReconfigToAddMod IEs 1... N, then IDs 1... N have the values X, X + 1... X+N - 1. In some alternative implementations, IDs 1... N are the cell IDs 1... N.

[0123] In some implementations, the base station 104 sends a ReconfigToAddModList IE that includes zero ReconfigToAddMod IEs to release all of the ReconfigToAddMod IEs 1... N.

[0124] In example implementations 5 and 6, "ReconfigToAddModList", "Reconfig ToAddMod", "configId", "ConfigId", "cellGroupConfig", "ReconfigT oReleaseList", and "maxNrofConfigCells" are exemplary and should not limit the scope and application of the present invention.

[0125] Example implementation 7

[0126] Example implementation 7 is a combination of example implementations 1 and 5, as follows. Depending on the implementation, any one of configurations 1...N is a CellGroupConfig IE or an RRC Reconfiguration message. The examples and implementations described for example implementations 1 and 5 can be applied to example implementation 7.

[0127]

[0128] maxNrofConfigCells::=8 After receiving an RRC reconfiguration message in event 318 or sending an RRC reconfiguration complete message in event 320, UE 102 sends 324 at least one measurement report to DU 174, similar to event 304. In some implementations, DU 174 sends 326 a DU-to-CU message including at least one measurement report to CU 172, similar to event 306. In other implementations, DU 174 does not send at least one measurement report to CU 172. In some implementations, at least one measurement report for event 324 includes an L1 measurement report, an L3 measurement report, and / or a new type of measurement report, as described for event 304. In some implementations, UE 102 sends 324 at least one measurement report to DU 174 on PUCCH and / or PUSCH, similar to event 304. In other implementations, UE 102 sends 324 at least one MAC CE including at least one measurement report to DU 174, similar to event 304. In some implementations, each of at least one measurement report for event 324 is not an RRC message.

[0129] In some implementations, the UE 102 sends at least one measurement report to the DU 174 according to at least one measurement configuration. The at least one measurement configuration configures the UE 102 to perform measurements and report the measurement results. The CU 172 sends at least one measurement configuration to the UE 102 via the DU 174. For example, the CU 172 sends one or more RRC messages (e.g., RRCReconfiguration messages) including at least one measurement configuration to the UE 102 via the DU 174 after event 306 or 316. Depending on the implementation, the one or more RRC messages include or do not include the RRC reconfiguration message for event 316. According to 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 at least one L1 measurement result and / or at least one L3 measurement result from the measurements, and includes the at least one L1 measurement result and / or at least one L3 measurement result in the measurement report for event 324. The DU 174 sends one or more reference signals on cells 124A and 124B, and in some implementations, sends one or more reference signals on cell 124C and / or other cells. In some implementations, the measurement configuration includes an L3 measurement configuration (e.g., MeasConfig IE), an L1 measurement configuration (e.g., CSI-MeasConfig IE), and / or a new measurement configuration, as described for event 304.

[0130] In some implementations, the new measurement configuration described for events 304 and 324 is similar to the L3 measurement configuration. For example, the new measurement configuration includes a part of the configuration parameters defined in the MeasConfig IE. In other implementations, the new measurement configuration described for events 304 and 324 is similar to the L1 measurement configuration. For example, the new measurement configuration includes a part of the configuration parameters (e.g., CSI-ResourceConfig IE and / or CSI-ReportConfig IE) defined in the CSI-MeasConfig IE.

[0131] After receiving at least one measurement report in event 324 (e.g., in response thereto), the DU 174 sends a first configuration activation command 330 to the UE 102 to activate Configuration 1. For example, the base station 104 sends the first configuration activation command on cell 124A. In another example, the base station 104 sends the first configuration activation command on cell 124D. In some implementations, the DU 174 includes ID 1 in the first configuration activation command. The UE 102 determines and activates Configuration 1 based on the first configuration activation command and ID 1. In other implementations, the DU 174 includes cell index 1 (e.g., serving cell index) or cell ID 1 included in Configuration 1 in the first configuration activation command. The UE 102 determines and activates Configuration 1 based on the first configuration activation command and cell index 1 or cell ID 1.

[0132] In still other implementations, the DU 174 includes a bitmap instead of ID 1, cell ID 1, or cell index 1 in the first configuration activation command to activate Configuration 1. The number of bits in the bitmap is greater than or equal to "N". In some implementations, bits 1...N respectively correspond to Configurations 1...N, and the DU 174 sets the corresponding bit (e.g., bit 1) in the bitmap to a first value to indicate ID 1 or Configuration 1. In a further implementation, bits 0...N - 1 respectively correspond to Configurations 1...N, and the DU 174 sets the corresponding bit (e.g., bit 0) in the bitmap to a first value to indicate ID 1 or Configuration 1. Thus, the UE 102 can determine a specific ID or a specific configuration based on bit 1 or bit 0 set to the first value in the bitmap. In such implementations, the DU 174 sets the remaining bits in the bitmap to a second value to indicate that the reset of Configurations 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 some implementations, if the DU 174 determines to activate another configuration (e.g., Configuration K) in addition to Configuration 1, the DU 174 sets the corresponding bit (e.g., bit K or bit K - 1) in the bitmap to the first value, where 1 <= K <= N.

[0133] In some implementations, at least one measurement report of event 324 (e.g., an L1 measurement report or a new measurement report) includes at least one measurement result of cell 124B. The DU 174 determines to activate configuration 1 because at least one measurement result indicates that the signal strength or quality of cell 124B is higher than a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In some implementations, the second predetermined threshold is greater than the first predetermined threshold. In such implementations, at least one measurement report of event 324 indicates that the signal strength or quality of cell 124B is suitable for communicating with the UE 102. In a further implementation, the second predetermined threshold is equal to the first predetermined threshold. In such implementations, at least one measurement report of event 324 indicates that the signal strength or quality of cell 124B has been continuously higher than the second predetermined threshold or the first predetermined threshold. This also indicates that cell 124B is suitable for communicating with the UE 102. Therefore, the DU 174 determines to activate configuration 1 (i.e., a fast serving cell change to cell 124B) in response to determining that the signal strength or quality of cell 124B is higher than the second predetermined threshold.

[0134] In some implementations, at least one measurement report of events 324 and 326 (e.g., an L3 measurement report) includes at least one measurement result of cell 124B. The CU 172 determines to activate configuration 1 because at least one measurement result indicates that the signal strength or quality of cell 124B is higher than a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In some implementations, the second predetermined threshold is greater than the first predetermined threshold. In such implementations, at least one measurement report of event 326 indicates that the signal strength or quality of cell 124B is suitable for communicating with the UE 102. In a further implementation, the second predetermined threshold is equal to the first predetermined threshold. In the implementation, at least one measurement report of event 326 indicates that the signal strength or quality of cell 124B has been continuously higher than the second predetermined threshold or the first predetermined threshold. This also indicates that cell 124B is suitable for communicating with the UE 102. Therefore, the CU 172 determines to activate configuration 1 (i.e., a fast serving cell change to cell 124B) in response to determining that the signal strength or quality of cell 124B is higher than the second predetermined threshold.

[0135] In response to this determination, the CU 172 sends a 328 fourth CU-to-DU message to the DU 174 to activate Configuration 1. In response to the fourth CU-to-DU message, the DU 174 sends a 330 first configuration activation command to the UE 102 and optionally sends a fourth DU-to-CU message to the CU 172. In some implementations, the CU 172 includes cell index 1 (e.g., serving cell index) in the fourth CU-to-DU message. Thus, the DU 174 can determine to activate Configuration 1 based on (serving) cell index 1. In other implementations, the CU 172 includes cell ID 1 in the fourth CU-to-DU message. Thus, the DU 174 can determine to activate Configuration 1 based on the cell ID. In still other implementations, the CU 172 includes ID 1 in the fourth CU-to-DU message. Thus, the DU 174 can determine to activate Configuration 1 based on ID 1. In some implementations, the fourth CU-to-DU message and the fourth DU-to-CU message are a UE context modification request message and a UE context modification response message, respectively. In other implementations, the fourth CU-to-DU message is a new interface message (e.g., an F1 application protocol (F1AP) message (e.g., defined in 3GPP specification 38.473 v18.0.0 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 v18.0.0 and / or later versions)).

[0136] In some implementations, the first configuration activation command is a MAC CE included in a MAC PDU received by the UE 102 from the DU 174 in event 330. In some implementations, the MAC CE is a new MAC CE (e.g., defined in 3GPP specification 38.321 v18.0.0 and / or later versions). In some implementations, the DU 174 includes a sub-header that identifies the MAC CE in the MAC PDU, and the UE 102 identifies the MAC CE in the MAC PDU based on this sub-header. Depending on the implementation, the sub-header includes a logical channel ID or an extended logical channel ID (e.g., defined in 3GPP specifications) to identify the MAC CE. For example, the logical channel ID or the extended logical channel ID is newly defined (e.g., in 3GPP specification 38.321 v18.0.0 and / or later versions). In other implementations, the first configuration activation command is a DCI received by the UE 102 on the PDCCH in event 330. The DU 174 generates a CRC for the DCI, scrambles the CRC with the first C-RNTI of the UE 102, and transmits the DCI and the scrambled CRC on the PDCCH in event 330. In some implementations, the format of the DCI is an existing DCI format (e.g., defined in 3GPP specifications (e.g., 38.212)). In further implementations, the format of the DCI is a new DCI format (e.g., defined in 3GPP specifications (e.g., 38.212 v18.0.0 or later versions)).

[0137] 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 accelerates the processing of the first configuration activation command in the UE 102 because the UE 102 does not spend time performing security checks (e.g., decryption and / or integrity checks) on the first configuration activation command.

[0138] In some implementations, after receiving the first configuration activation command, the UE 102 sends a 331 acknowledgement to the DU 174 on cell 124A or cell 124D to indicate that the UE 102 has received 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 v17.1.0). In another example, the MAC CE is a new MAC CE (e.g., defined in 3GPP specification 38.321 v18.0.0 and / or later versions). In still other implementations, the acknowledgement is a PUCCH transmission.

[0139] In some implementations, the CU 172 sends a 316 RRC reconfiguration message in response to an L3 measurement report for cell 124B received by the CU 172 in event 306. In a further implementation, the CU 172 sends a first RRC reconfiguration message including a MeasConfig IE to the UE 102 to configure the UE 102 to send an L3 measurement report. In some implementations, the DU 174 sends a 330 first configuration activation command in response to an L1 measurement report for cell 124B received by the DU 174 in event 324. In a further implementation, the CU 172 sends a second RRC reconfiguration message including a CSI-MeasConfig IE to the UE 102 to configure the UE 102 to send an L1 measurement report. In some implementations, the first RRC reconfiguration message and the second RRC reconfiguration message are the same message (i.e., the same instance). In other implementations, the first RRC reconfiguration message and the second RRC reconfiguration message are different messages. In some implementations, the second RRC reconfiguration message is the RRC reconfiguration message for event 316. In other implementations, the second RRC reconfiguration message is different from the RRC reconfiguration message for event 316.

[0140] After receiving the first configuration activation command (e.g., in response thereto), the UE 102 identifies a specific configuration (e.g., Configuration 1) based on a specific ID (e.g., ID1) and immediately applies Configuration 1. In some implementations, the UE 102 performs a 332 random access procedure with the DU 174 on cell 124B in response to applying Configuration 1. In some implementations, the UE 102 disconnects from cell 124A after receiving the first configuration activation command or sending an acknowledgement (e.g., in response thereto). In other words, the UE 102 stops communicating on cell 124A in response to receiving the 330 first configuration activation command or sending the 331 acknowledgement. In such cases, the UE 102 performs a 332 random access procedure after disconnecting from cell 124A. In some implementations, the UE 102 determines whether to perform a random access procedure based on Configuration 1. In some implementations, if Configuration 1 configures the UE 102 to perform a random access procedure, the UE 102 performs a random access procedure in event 332. For example, Configuration 1 includes a reconfiguration with a synchronization configuration (e.g., ReconfigurationWithSync IE) to configure the UE 102 to perform a random access procedure. Otherwise, if Configuration 1 does not configure the UE 102 to perform a random access procedure or configures the UE 102 to skip the random access procedure, the UE 102 avoids performing a random access procedure with the DU 174 when receiving the first configuration activation command. In such cases, the UE 102 skips event 316. For example, if Configuration 1 excludes a reconfiguration with a synchronization configuration, 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.

[0141] In the case where the UE 102 performs the random access procedure 332, the UE 102 communicates with the DU 174 on the cell 124B using Configuration 1 336 and communicates with the CU 172 via the DU 174 after successfully completing the random access procedure. For example, the UE 102 conveys UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) to the base station 104 in event 318. In such cases, when the UE 102 receives contention resolution from the DU 174, the UE 102 successfully completes the random access procedure. In the case where the random access procedure is a four-step random access procedure, the UE 102 sends a message 3 including the UE identifier to the DU 174 via the cell 124B during the random access procedure. In the case where the random access procedure is a two-step random access procedure, the UE 102 sends a message A including the UE identifier to the DU 174 via the cell 124B during the random access procedure. In some implementations, if Configuration 1 includes a second C-RNTI, the UE identifier is the second C-RNTI of the UE 102. Otherwise, if Configuration 1 does not include a C-RNTI, the UE identifier is the first C-RNTI. In the case where the random access procedure is a contention-free random access procedure, the UE 102 sends a dedicated random access preamble to the DU 174 via the cell 124B. In such cases, Configuration 1 includes the dedicated random access preamble.

[0142] The DU 174 identifies or determines that the UE 102 is connected to the cell 124B when receiving the UE identifier or the dedicated preamble from the UE 102 during the random access procedure.

[0143] In some implementations, the UE 102 sends an RRC message (e.g., an RRC reconfiguration complete message) to the CU 172 via the DU 174 and the cell 124B to indicate that the UE 102 applies Configuration 1. In some implementations, the UE 102 includes the RRC message in message 3. In further implementations, the UE 102 includes the RRC message in message A. In further implementations, the UE 102 sends the RRC message after completing the random access procedure. In other implementations, if the UE 102 maintains communication with the base station 104 on the cell 124A (i.e., the UE 102 does not disconnect from the cell 124A), the UE 102 sends an RRC message to the base station 104 via the cell 124A. In still other implementations, the UE 102 avoids sending an RRC message to the base station 104 in response to applying Configuration 1 or receiving a first configuration activation command.

[0144] In some cases where the UE 102 skips the random access procedure, the UE 102 communicates directly with the base station 104 on cell 124B according to Configuration 1 after receiving (e.g., in response to) the first configuration activation command. For example, the UE 102 conveys UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) to the base station 104 in event 318. In some such cases, after receiving (e.g., in response to) the first configuration activation command, the UE 102 sends at least one PUCCH transmission to the DU 174 on cell 124B according to Configuration 1. In some implementations, the DU 174 sends at least one DCI to the UE 102 on the PDCCH on cell 124B to command the UE 102 to send at least one PUCCH or PUSCH transmission after sending the first configuration activation command. The DU 174 identifies or determines that the UE 102 is connected to cell 124B when receiving the PUCCH or PUSCH transmission. In other implementations, the UE 102 sends at least one PUCCH or PUSCH transmission regardless of receiving DCI on the PDCCH on cell 124B. The DU 174 identifies or determines that the UE 102 is connected to cell 124B when receiving the PUCCH or PUSCH transmission. In some implementations, the UE 102 sends an RRC message (e.g., an RRC reconfiguration complete message) to the CU 172 via the DU 174 and cell 124B to indicate that the UE 102 applies Configuration 1. The CU 172 identifies or determines that the UE 102 is connected to cell 124B when receiving the RRC message. In other implementations, if the UE 102 maintains communication with the base station 104 on cell 124A (i.e., the UE 102 does not disconnect from cell 124A), the UE 102 sends an RRC message to the base station 104 via cell 124A. In still other implementations, the UE 102 avoids sending an RRC message to the base station 104 in response to applying Configuration 1 or receiving the first configuration activation command.

[0145] In some implementations, when the DU 174 determines in event 332 or 336 that the UE 102 has successfully connected to cell 124B, the DU 174 sends a 334 DU-to-CU message (e.g., an access success message) to the CU 172. In some implementations, the DU 174 includes the cell ID of cell 124B in the DU-to-CU message of event 334. The cell ID can be a PCI or a CGI. Thus, the CU 172 determines that the UE 102 is connected to cell 124B when receiving the DU-to-CU message of event 334. In a further implementation, when the DU 174 determines in event 332 or 336 that the UE 102 has successfully connected to cell 124B, the DU 174 sends a DL data delivery status message or frame to the CU 172.

[0146] In some implementations, when it is determined that the UE 102 is connected to cell 124B, the 330 first configuration activation command is sent, or the 331 confirmation is received, the DU 174 stops communicating with the UE 102 on cell 124A. In some implementations, when it is determined that the UE 102 is connected to cell 124B, the 330 first configuration activation command is sent, or the 331 confirmation is received, the DU 174 releases the resources configured for the UE 102 on cell 124A.

[0147] Events 304, 306, 390, 392, 316, 318, 320, 322, 324, 326, 328, 330, 331, 332, 334, 336, 394 are Figure 3 collectively referred to as the fast serving cell configuration procedure 380.

[0148] In some implementations, DU 174 generates Configuration 1 and / or Configuration 2... N as a complete configuration that replaces the first configuration or a specific configuration in the first configuration. In some implementations, if Configuration 1 is a complete configuration, UE 102 and DU 174 communicate with each other 336 according to Configuration 1 instead of the first configuration or the specific configuration. In some implementations, DU 174 includes an indication that Configuration 1 is a complete configuration in Configuration 1. In other implementations, the RRC reconfiguration messages of events 316, 318 include an indication that Configuration 1 is a complete configuration. In still other implementations, the first container includes an indication that Configuration 1 is a complete configuration. In still other implementations, Element 1 (e.g., ConfigToAddMod IE, CellGroupConfigToAddMod, MobilityToAddMod IE, MobilityConfigToAddMod IE, or CellGroupConfigToAddMod IE) includes an indication that Configuration 1 is a complete configuration. In some implementations, UE 102 determines that Configuration 1 is a complete configuration based on the indication that Configuration 1 is a complete configuration. In some implementations, there is an indication that Configuration 1 is different from the fullConfig field (e.g., defined in the current 3GPP specification). In other implementations, Configuration 1 is an indication of the fullConfig field (e.g., defined in the current 3GPP specification) in the RRCReconfiguration message.

[0149] In other implementations, DU 174 generates Configuration 1 and / or Configuration 2... N as an incremental configuration that enhances at least a part of the first configuration. In other words, DU 174 generates Configuration 1... N on top of the first configuration. For example, if Configuration 1 is an incremental configuration, UE 102 and DU 174 enhance at least a part of the first configuration with Configuration 1. Thus, UE 102 and base station 104 communicate with each other 336 according to Configuration 1 and the unenhanced part of the first configuration. In some implementations, Configuration 1 includes an indication that Configuration 1 is an incremental configuration. In other implementations, the first container includes an indication that Configuration 1 is an incremental configuration. In still other implementations, Element 1 includes an indication that Configuration 1 is an incremental configuration. In some implementations, UE 102 determines that Configuration 1 is a complete configuration based on the indication that Configuration 1 is an incremental configuration. In some alternative implementations, Configuration 1, the first container, or Element 1 excludes the indication that Configuration 1 is a complete configuration to indicate that Configuration 1 is an incremental configuration. In further implementations, UE102 determines that Configuration 1 is an incremental configuration based on the exclusion of the indication in Configuration 1, the first container, or Element 1.

[0150] In some implementations, if Configuration 1 is a complete configuration, UE 102 releases the first configuration or a specific configuration in the first configuration after receiving the first configuration activation command at 330, sending an acknowledgement at 331, successfully executing the random access procedure at 332, or receiving the first DCI on a PDCCH addressed to the UE identity of UE 102 on cell 124B (e.g., in response thereto). In some implementations, if Configuration 1 is a complete configuration, DU 174 releases the first configuration or a specific configuration in the first configuration after sending the first configuration activation command at 330, receiving an acknowledgement at 331, successfully executing the random access procedure at 332, or receiving a specific transmission from UE 102 on cell 124B (e.g., in response thereto). In some implementations, the specific transmission is a PUCCH transmission. In a further implementation, the transmission is a PUSCH transmission. In some implementations, after sending the first configuration activation command, DU 174 generates a DCI and the CRC of the DCI, scrambles the CRC with the UE identity of UE 102, and sends the DCI and the scrambled CRC on a PDCCH on cell 124B. When UE 102 receives the DCI and the scrambled CRC and verifies that the scrambled CRC is valid using the UE identity, UE 102 sends a PUSCH transmission to DU 174 on cell 124B.

[0151] In some implementations, the first configuration or the specific configuration is a first CellGroupConfig IE (i.e., the first configuration includes configuration parameters defined in the first CellGroupConfig IE), and Configuration 1 is a second CellGroupConfig IE.

[0152] In some implementations, UE 102 uses a UE MAC entity (e.g., MAC 204B) to communicate with DU 174 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). In some implementations, base station 104 configures whether UE 102 resets the UE MAC entity when receiving the first configuration activation command. In some implementations, base station 104 includes a MAC reset indication in Configuration 1 or Element 1 to configure UE 102 to reset the UE MAC entity, and base station 104 excludes the MAC reset indication from Configuration 1 or Element 1 to configure UE 102 not to reset the UE MAC entity. If Configuration 1 or Element 1 includes a MAC reset indication, UE 102 resets the UE MAC entity in response to the MAC reset indication when receiving the first configuration activation command.

[0153] Otherwise, if Configuration 1 or Element 1 does not include a MAC reset indication, UE 102 avoids resetting the UE MAC entity when or upon receiving the first configuration activation command. In some implementations, if Configuration 1 or Element 1 does not include a MAC reset indication but includes an indication that the configuration is a complete configuration, UE 102 resets the UE MAC entity when or upon receiving the first configuration activation command. Otherwise, if Configuration 1 or Element 1 does not include a MAC reset indication and an indication that the configuration is a complete configuration, UE 102 avoids resetting the UE MAC entity when or upon receiving the first configuration activation command.

[0154] In some implementations, base station 104 (e.g., DU 174 or CU 172) uses the DU MAC entity (e.g., NR MAC 204B) to communicate with UE 102 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). If base station 104 includes a MAC reset indication in Configuration 1 or Element 1, DU 174 resets the DU MAC entity in response to the MAC reset indication after sending the first configuration activation command at 330, receiving the confirmation at 331, or determining that UE 102 is connected to cell 124B in event 332 or 336.

[0155] Otherwise, if Configuration 1 or Element 1 does not include a MAC reset indication, DU 174 avoids resetting the DU MAC entity after sending the first configuration activation command at 330 (e.g., in response thereto). Thus, after sending the first configuration activation command at 330, receiving the confirmation at 331, or determining that UE 102 is connected to cell 124B in event 332 or 336, DU 174 continues to communicate with UE 102 using the reserved (i.e., non-reset) DU MAC entity.

[0156] In some implementations, DU 174 includes the MAC reset indication in the MAC-CellGroupConfig IE (e.g., CellGroupConfig IE) in Configuration 1. In other implementations, DU 174 includes the MAC reset indication in the CellGroupConfig IE and outside of the MAC-CellGroupConfig IE. In yet other implementations, DU 174 includes the MAC reset indication in Element 1 and outside of Configuration 1.

[0157] In some implementations, if Configuration 1 or Element 1 does not include a MAC reset indication but includes an indication that Configuration 1 is a complete configuration, then the DU 174 resets the DU MAC entity after sending the first configuration activation command 330, receiving the confirmation 331, or determining that the UE 102 is connected to cell 124B in event 332 or 336. Alternatively, instead of resetting the DU MAC entity, the DU 174 releases the DU MAC entity and establishes a new DU MAC entity for communicating with the UE 102 via cell 124B. Otherwise, if Configuration 1 or Element 1 does not include a MAC reset indication and an indication that Configuration 1 is a complete configuration, then the DU 174 avoids resetting the DU MAC entity after sending the first configuration activation command 330 (e.g., in response thereto).

[0158] In an alternative implementation, the base station 104 (e.g., DU 174 or CU 172) includes a MAC retention indication in a configuration or element (e.g., Configuration 1 or Element 1) to configure the UE 102 not to 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, then the UE 102 avoids resetting the UE MAC entity in response to the MAC retention indication when 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, then the UE 102 resets the UE MAC entity when or upon receiving the configuration activation command.

[0159] The DU 174 uses the DU MAC entity (e.g., NR MAC 204B) to communicate with the UE 102 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). If the base station 104 includes the MAC retention indication in a configuration or element (e.g., Configuration 1 or Element 1), then the DU 174 avoids resetting the DU MAC entity in response to the MAC retention indication after sending a configuration activation command (e.g., the first configuration activation command) to the UE 102. Thus, after sending the first configuration activation command 330, receiving the confirmation 331, or determining that the UE 102 is connected to cell 124B at event 332 or 336, the DU 174 continues to communicate with the UE 102 using the retained (i.e., not reset) DU MAC entity.

[0160] In some implementations, DU 174 includes the MAC reservation indication in the MAC-CellGroupConfig IE (e.g., CellGroupConfig IE) in Configuration 1. In other implementations, DU 174 includes the MAC reservation indication in the CellGroupConfig IE and outside the MAC-CellGroupConfig IE. In still other implementations, DU 174 includes the MAC reservation indication in Element 1 and outside Configuration 1.

[0161] Otherwise, if Configuration 1 or Element 1 does not include the MAC reservation indication, DU 174 resets the DU MAC entity after sending the first configuration activation command 330 (e.g., in response thereto).

[0162] In some implementations, the base station 104 includes or does not include an indication that Configuration 1 is a complete configuration. If the base station 104 includes an indication that Configuration 1 is a complete configuration in Configuration 1 or Element 1, the base station 104 avoids including the MAC reservation indication in Configuration 1 or Element 1. Otherwise, if the base station 104 does not include an indication that Configuration 1 is a complete configuration in Configuration 1 or Element 1, the base station 104 includes the MAC reservation indication in Configuration 1 or Element 1.

[0163] In an alternative implementation, the base station 104 (e.g., DU 174 or CU 172) includes a MAC partial reset indication in a configuration or an element (e.g., Configuration 1 or Element 1) to configure the UE 102 to partially reset the UE MAC entity, and excludes the MAC partial reset indication from the configuration or the element to configure the UE 102 to fully reset the UE MAC entity. If the configuration or the element includes the MAC partial reset indication, the UE 102 partially resets the UE MAC entity when receiving a configuration activation command (e.g., the first configuration activation command). Otherwise, if the configuration or the element does not include the MAC partial reset indication, the UE 102 fully resets the UE MAC entity after receiving the configuration activation command (e.g., in response thereto). In some implementations, when the UE partially resets the UE MAC entity, the UE 102 retains (e.g., maintains or keeps) the operating 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.

[0164] If the base station 104 includes the MAC partial reset indication in a configuration or an element (e.g., Configuration 1 or Element 1), DU 174 partially resets the DU MAC entity in response to the MAC partial reset indication after sending the configuration activation command (e.g., the first configuration activation command) to the UE 102.

[0165] In some implementations, DU 174 includes the MAC part reset indication in the MAC-CellGroupConfig IE (e.g., CellGroupConfig IE) in Configuration 1. In other implementations, DU 174 includes the MAC part reset indication in the CellGroupConfig IE and outside the MAC-CellGroupConfig IE. In still other implementations, DU 174 includes the MAC part reset indication in Element 1 and outside Configuration 1.

[0166] Otherwise, if Configuration 1 or Element 1 does not include the MAC part reset indication, DU 174 fully resets the DU MAC entity after sending the first configuration activation command (e.g., in response thereto). In some implementations, the base station 104 includes or does not include an indication that Configuration 1 is a complete configuration. In some implementations, if the base station 104 includes an indication that Configuration 1 is a complete configuration in Configuration 1 or Element 1, the base station 104 avoids including the MAC part reset indication in Configuration 1 or Element 1. Otherwise, in further implementations, if the base station 104 does not include an indication that Configuration 1 is a complete configuration in Configuration 1 or Element 1, the base station 104 includes the MAC part reset indication in Configuration 1 or Element 1. In some alternative implementations, in the case where the base station 104 includes an indication that Configuration 1 is a complete configuration in Configuration 1 or Element 1, the base station 104 includes the MAC part reset indication.

[0167] In some implementations, the base station 104 (e.g., DU 174 or CU 172) does not include an indication related to resetting the UE MAC entity in a configuration or element (e.g., Configuration 1 or Element 1) or in an RRC message (e.g., Event 316, 318) including the configuration or element. In such cases, after receiving the first configuration activation command (e.g., in response thereto), the UE 102 partially resets the UE MAC entity. In such cases, DU 174 partially resets the DU MAC entity after sending the first configuration activation command, receiving an acknowledgment, performing a random access procedure with the UE 102, or determining that the UE 102 is connected to Cell 124B.

[0168] In some implementations, when the UE 102 determines to reset the UE MAC entity as described above or the UE 102 resets the UE MAC entity as described above, the UE 102 resets the UE MAC entity before performing the 332 random access procedure or communicating with the base station 104 via the cell 124B as described in 336. 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) initializes Bj of the configured logical channels to zero; (ii) stops one or more timers; (iii) considers the timeAlignmentTimer expired if the UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1); (iv) sets the new data indicator (NDI) of the UL HARQ process to the value 0; (v) sets the NDI of the HARQ process ID to the value 0 for monitoring the PDCCH in the sidelink resource allocation mode 1; (vi) flushes the Msg3 buffer; (vii) flushes the MSGA buffer; (viii) cancels the triggered scheduling request procedure (if any); (ix) cancels the triggered buffer status report procedure (if any); (x) cancels the triggered power headroom report procedure (if any); (xi) cancels the triggered consistent LBT failure (if any); (xii) cancels the triggered BFR (if any); (xiii) cancels the triggered sidelink buffer status report procedure (if any); (xiv) cancels the triggered preemptive buffer status report procedure (if any); (xv) cancels the triggered timing advance report procedure (if any); (xvi) cancels the triggered recommended bitrate query procedure (if any); (xvii) cancels the triggered configured uplink grant confirmation (if any); (xviii) cancels the triggered configured sidelink grant confirmation (if any); (xix) cancels the triggered desired guard symbol query (if any); (xx) cancels the triggered positioning measurement gap activation / deactivation request procedure (if any); (xxi) flushes the soft buffer for the DL HARQ process; (xxii) for each of the DL HARQ processes, considers the next received transmission of the TB as the first transmission; (xxiii) releases the temporary C-RNTI (if any); (xiv) resets one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER); (xxv) and so on.

[0169] In some implementations, when DU 174 resets the DU MAC entity, 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) stops one or more timers; (ii) if UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), considers the timeAlignmentTimer started and / or maintained by DU 174 for UE 102 to have expired; (iii) sets the NDI of the DL HARQ process to the value 0; (iv) flushes the soft buffers of the UL HARQ process; (v) for each of the UL HARQ processes, considers the next received transmission of the TB as the first transmission; (vi) resets one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER); (vii) and so on.

[0170] Depending on the implementation, UE 102 determines to partially or fully reset the UE MAC entity. In some implementations, when UE 102 resets the UE MAC entity as described above, UE 102 fully resets the UE MAC entity (i.e., full UE MAC reset). In a full UE MAC reset, UE 102 performs some or all of the actions described above. In other implementations, when UE 102 resets the UE MAC entity as described above, UE 102 partially resets the UE MAC entity (i.e., partial UE MAC reset). In a partial UE MAC reset, UE 102 performs a subset or part of some or all of the actions in a full UE MAC reset.

[0171] In some implementations, a partial UE MAC reset includes at least one of the following actions: (i) if UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), considers the timeAlignmentTimer of UE 102 to have expired; (ii) flushes the Msg3 buffer; (iii) flushes the MSGA buffer; (iv) releases (if any) the temporary C-RNTI; and / or (v) resets one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0172] In some implementations, partial UE MAC reset further includes at least one of the following actions: (i) canceling (if any) the triggered scheduling request procedure; (ii) canceling (if any) the triggered buffer status report procedure; (iii) canceling (if any) the triggered power headroom report procedure; (iv) canceling (if any) the triggered coherent LBT failure; (v) canceling (if any) the triggered BFR; (vi) canceling (if any) the triggered sidelink buffer status report procedure; (vii) canceling (if any) the triggered preemptive buffer status report procedure; (viii) canceling (if any) the triggered timing advance report procedure; (ix) canceling (if any) the triggered recommended bitrate query procedure; (x) canceling (if any) the triggered configured uplink grant confirmation; (xi) canceling (if any) the triggered configured sidelink grant confirmation; (xii) canceling (if any) the triggered desired protection symbol query; and / or (xiii) canceling (if any) the triggered positioning measurement gap activation / deactivation request procedure.

[0173] In some implementations, partial UE MAC reset further includes at least one of the following actions: (i) stopping a first part of one or more timers and retaining the remaining part of one or more timers; (ii) setting the new data indicator (NDI) of the UL HARQ process to the value 0; (iii) setting the NDI of the HARQ process ID to the value 0 for monitoring the PDCCH in sidelink resource allocation mode 1; (iv) flushing the soft buffer for the DL HARQ process; and / or (v) for each of the DL HARQ processes, treating the next received transmission of the TB as the first transmission.

[0174] Depending on the implementation, DU 174 determines to partially or fully reset the DU MAC entity. In some implementations, when DU 174 resets the DU MAC entity as described above, DU 174 fully resets the DU MAC entity (i.e., full DU MAC reset). In a full DU MAC reset, DU 174 performs some or all of the actions described above. In other implementations, when DU 174 resets the DU MAC entity as described above, DU 174 partially resets the DU MAC entity (i.e., partial DU MAC reset). In a partial DU MAC reset, DU 174 performs a subset or part of some or all of the actions in a full DU MAC reset.

[0175] In some implementations, partial DU MAC reset includes at least one of the following actions in the partial MAC reset: (i) if UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), consider the timeAlignmentTimer started and / or maintained by DU 174 for UE 102 to expire; and / or (ii) reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0176] In some implementations, partial DU MAC reset includes at least one of the following actions for the MAC entity (i.e., DU MAC reset): (i) stop the first part of one or more timers and retain the remaining part of one or more timers; (ii) set the NDI of the DL HARQ process to the value 0; (iii) flush the soft buffer for the UL HARQ process; (iv) for each of the UL HARQ processes, consider the next received transmission of the TB as the first transmission; and / or (v) reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0177] In some implementations, configuration 1 includes or does not include one or more RLC reconstruction indications (e.g., reestablishRLC field) that configure UE 102 to reconstruct one or more RLC entities (e.g., RLC206B) that UE 102 uses to communicate with DU174 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). If configuration 1 includes an RLC reconstruction indication that configures UE 102 to reconstruct an RLC entity (e.g., RLC 206B) that UE 102 uses to convey RLC PDUs to the base station 104 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331), then UE 102 reconstructs the RLC entity in response to the RLC reconstruction indication. In some implementations, UE 102 reconstructs the RLC entity before performing the 332 random access procedure or communicating 336 with the base station 104 via cell 124B. In other implementations, UE 102 reconstructs the RLC entity while or after performing the 332 random access procedure. In some implementations, when UE 102 reconstructs the RLC entity, UE 102 performs at least one of the following actions for the RLC entity: (i) discard RLC SDUs, RLC SDU segments, and RLC PDUs (if any); (ii) stop and reset the timer (if running); (iii) reset the state variable to its initial value. In some implementations, the state variable and the timer are currently defined (e.g., in 3GPP specification 38.322).

[0178] Otherwise, if Configuration 1 does not include an RLC reestablishment indication for the RLC entity, UE 102 avoids reestablishing the RLC entity when or upon receiving the first configuration activation command. In other words, UE 102 avoids performing actions for reestablishing the RLC entity of UE 102 when or upon receiving the first configuration activation command. In some implementations, if Configuration 1 or Element 1 does not include an RLC reestablishment indication but includes an indication that Configuration 1 is a complete configuration, UE 102 reestablishes the RLC entity of UE 102 when or upon receiving the first configuration activation command. Otherwise, if Configuration 1 or Element 1 does not include an RLC reestablishment indication and an indication that Configuration 1 is a complete configuration, UE 102 avoids reestablishing the RLC entity when or upon receiving the first configuration activation command.

[0179] Similarly, DU 174 reestablishes the RLC entity (e.g., NR RLC 206B) that DU 174 uses to communicate with the RLC entity of UE 102 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331) in response to the RLC reestablishment indication. In some implementations, DU 174 reestablishes the RLC entity after sending the first configuration activation command, receiving an acknowledgement of the first configuration activation command from UE 102, or determining that UE 102 is connected to cell 124B. In some implementations, the acknowledgement is a HARQ ACK. In other implementations, the acknowledgement is a MAC CE. In still other implementations, the acknowledgement is a PUCCH transmission. In some implementations, when the base station 104 reestablishes the RLC entity, DU 174 performs at least one of the following actions for the RLC entity: (i) discards RLC SDUs, RLC SDU segments, and RLC PDUs (if any); (ii) stops and resets the timer (if running); and / or (iii) resets the state variable to its initial value. In some implementations, the state variable and the timer are currently defined (e.g., in 3GPP specification 38.322).

[0180] In some implementations, the above description of Configuration 1 also applies to Configurations 2... N.

[0181] In some implementations, after determining that UE 102 is connected to cell 124B (e.g., in response thereto), CU 172 sends a 338 CU-to-DU message (e.g., UE context modification request message) to DU 174 to instruct DU 174 to stop communicating with UE 102 and / or release or suspend the resources configured for UE 102 in cell 124A. In response, in some implementations, DU 174 stops communicating with UE 102 on cell 124A and / or releases or suspends the resources configured for UE 102 in cell 124A, and sends a 340 DU-to-CU message (e.g., UE context modification response message) to CU-172. Events 338 and 340 are collectively referred to as procedure 394 (e.g., UE context modification procedure) in Figure 3 .

[0182] Next, referring to Figure 4 , in scenario 400, base station 104 includes CU 172, source DU (S-DU) 174A, and target DU (T-DU) 174B. S-DU 174A operates cell 124A and, in some implementations, cell 124B, while T-DU 174B operates cell 124C. Scenario 400 is similar to scenario 300. Thus, the description for scenario 300 generally applies to scenario 400. In particular, the description for cell 124B in scenario 300 applies to cell 124C. Additionally, it will be understood that some of the descriptions regarding scenario 300 apply to scenario 400 but apply to one or both of S-DU 174A or T-DU 174B (e.g., events 408, 410, 432, 434, etc.).

[0183] In some implementations, after determining that the UE 102 is connected to cell 124B (e.g., in response thereto), the CU 172 sends a 438 CU-to-DU message (e.g., a UE Context Release Command message) to the S-DU 174A to release the UE context of the UE 102. In response, the S-DU 174A releases the UE context of the UE 102 and sends a 440 DU-to-CU message (e.g., a UE Context Release Complete message) to the CU-172. Alternatively, the CU 172 sends a 438 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 release or suspend the resources configured for the UE 102 in cell 124A. In response, in further implementations, the S-DU 174A stops communicating with the UE 102 on cell 124A and / or releases or suspends the resources configured for the UE 102 in cell 124A, and sends a 440 DU-to-CU message (e.g., a UE context modification response message) to the CU-172.

[0184] Next, referring to Figure 5A , in scenario 500A, the base station 106 operates as the MN, and the base station 104 operates as the SN. The SN 104 includes the CU 172 and the DU 174. Scenario 500A is similar to scenario 300, except that scenario 500A is a DC scenario and scenario 300 is a single connection (SC) scenario. Initially, the UE 102 under DC communicates with the MN 106 and the SN 104. In event 502, the UE 102 communicates with the DU 174 on cell 124A using a first configuration and communicates with the CU 172 via the DU 174, similar to event 302. In some implementations, the UE 102 under DC conveys 502 UL PDUs and / or DL PDUs to the MN 106 and / or the SN 104 via radio bearers including SRBs and / or DRBs. In some implementations, the MN 106 and / or the SN 104 configure radio bearers for the UE 102.

[0185] The UE 102 under DC communicates 502 UL PDUs and / or DL PDUs with the SN 104 on the SCG configured for communication with the UE 102. The UE 102 under DC communicates UL PDUs and / or DL PDUs with the MN 106 on the MCG according to the MN configuration (i.e., MCG configuration). In some implementations, the first configuration is the 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., cell 126 and / or other cells) operated by the MN 106. In the first configuration, the SN 106A configures the SCG, which includes at least one serving cell (e.g., cell 124A and / or other cells) 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) configured by the MN 106 or SN104 to exchange RRC messages between the UE 102 and the SN 104.

[0186] In some implementations, when communicating with the MN 106 and the SN 104 under DC, the MN 106 performs a 580 fast serving cell configuration procedure with the UE 102, similar to procedure 380. In some implementations, when communicating with the MN 106 and the SN 104 under DC, the UE 102 sends at least one measurement report to the CU 172 via the DU 174 and cell 124A in events 504 and 506, respectively, similar to events 304 and 306. In other implementations, when communicating with the MN 106 and the SN 104 under DC, the UE102 sends 505 at least one measurement report to the MN 106 via cell 126. The MN 106 then sends 507 at least one measurement report to the CU 172. In some implementations, the MN 106 generates at least one SN message including at least one measurement report and sends the at least one SN message to the CU 172 in event 507. In some implementations, the at least one SN message includes an RRC Transfer message and / or an SN Modification Request message.

[0187] After receiving at least one measurement report (e.g., in response thereto) or when the base station 104 communicates with the UE 102, the base station 104 determines to prepare cell 124B for the UE 102, as for Figure 3As described. Events 590, 592, 516, 518, 520, 522, 524, 526, 528, 530, 531, 532, 534, 536, and 594 are similar to events 390, 392, 316, 318, 320, 322, 324, 326, 328, 330, 331, 332, 334, 336, and 394. After receiving the first configuration activation command, sending an acknowledgement, or determining that UE 102 is connected to cell 124B, UE 102 operating with MN 106 and SN 104 under DC communicates with SN 104 on cell 124B according to Configuration 1 in event 536, similar to event 336.

[0188] Next, referring to Figure 5B , scenario 500B is generally similar to scenario 500A, except that SN 104 sends 517, 519 RRC reconfiguration messages to UE 102 via MN106 and receives 521, 523 RRC reconfiguration complete messages from UE 102 via MN 106. In some implementations, SN 104 generates a first SN message including an RRC reconfiguration message (e.g., SN Modification Required message, SN Modification Required message, or RRC transfer message) and sends the first SN message to MN 106 in event 517. In some implementations, MN 106 generates a second SN message including an RRC reconfiguration complete message (e.g., SN Reconfiguration Complete message or RRC transfer message) and sends the second SN message to SN 104 in event 523.

[0189] Next, referring to Figure 6A , in scenario 600A, base station 106 operates as an MN and base station 104 operates as an SN, similar to scenarios 300 - 500B. SN 104 includes CU 172, S-DU 174A, and T-DU 174B, similar to base station 104 in scenario 400. Additionally, it will be understood that some descriptions regarding scenarios 300 - 500B may apply to scenario 600A, but apply to one or both of S-DU174A or T-DU 174B (e.g., events 608, 610, 632, 634, etc.).

[0190] Next, referring to Figure 6B , scenario 600B is similar to scenarios 300 - 500B and 600A, except that SN 104 sends 617, 619 RRC reconfiguration messages to UE 102 via MN 106 and receives 621, 623 RRC reconfiguration complete messages from UE 102 via MN 106.

[0191] Next, referring to Figure 7A , in scenario 700A, base station 104 operates as both an MN and an SN, similar to scenarios 300 - 600B. 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 the MN, similar to the base station 104 in Figure 3 or the MN 106 in Figures 5A to 6B , and the CU 172 operates with the S-DU 174B as the SN, similar to the SN 104 in Figures 5A to 6B .

[0192] In scenario 700A, the UE 102 initially communicates 702 with the M-DU 174A and the S-DU 174B under DC, and the UE 102 communicates 702 with the CU 172 via the M-DU 174A and the S-DU 174B. In event 702, the UE 102 communicates with the S-DU 174B on cell 124A using a first configuration and communicates with the CU 172 via the S-DU 174B. Events 704 and 706 are similar to events 304 and 306. In some implementations, the UE 102 sends 705 at least one measurement report to the M-DU 174A, similar to event 304. Similar to event 306, the M-DU 174A then sends 707 at least one DU-to-CU message including at least one measurement report to the CU 172.

[0193] Next, referring to Figure 7B , scenario 700B is similar to scenarios 300 - 600B and 700A, except that the CU 172 sends 717, 719 RRC reconfiguration messages to the UE 102 via the M-DU 174A and receives 721, 723 RRC reconfiguration complete messages from the UE 102 via the M-DU 174A.

[0194] Next, referring to Figure 8A , in scenario 800A, base station 104 operates as both an MN and an SN, similar to scenarios 300 - 700B. 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 the MN and with the S-DU 174B as the SN. Additionally, it will be understood that some of the descriptions regarding scenarios 300 - 700B may apply to scenario 800A, but apply to one or both of the S-DU 174A or the T-DU 174B (e.g., events 808, 810, 832, 834, etc.).

[0195] Next, referring to Figure 8B , scenario 800B is similar to scenarios 300 - 700B and 800A, except that the CU 172 sends 817, 819 RRC reconfiguration messages to the UE 102 via the M-DU 174A and receives 821, 823 RRC reconfiguration complete messages from the UE 102 via the M-DU 174A.

[0196] Next, continuing to refer to Figures 9 to 15 discusses several example methods that can be implemented in one or more RAN nodes such as base stations, DUs, or CUs, or in the RAN, to support configuring a configuration and later activating that configuration. For Figures 3 to 8B the examples and implementations described can be applied to Figures 9 to 15 .

[0197] Figure 9 Illustrates method 900 for configuring and activating a configuration for a UE (e.g., UE 102) that can be implemented by a CU (e.g., CU 172).

[0198] Method 900 begins at block 902, where the CU communicates with the UE via a first DU (e.g., events 302, 380, 502, 580, 702, 780). In some implementations, at block 904, the CU sends a first CU-to-DU message including a first cell ID and an IE to the first DU to request a configuration for later activation (e.g., events 308, 390, 380, 508, 590, 580, 708, 790, 780). At block 906, the CU receives a first DU-to-CU message including a first configuration for later activation, where the first configuration is configured for the UE to communicate with the first DU via a first cell identified by the first cell ID (e.g., events 310, 390, 380, 510, 590, 580, 710, 790, 780). At block 908, the CU generates a first RRC message including a container IE that includes the first configuration. At block 910, the CU sends the first RRC message to the UE via the first DU (e.g., events 316, 318, 380, 516, 518, 580, 716, 718, 780).

[0199] In some implementations, the first cell ID is an NR CGI. In other implementations, the first cell ID is a physical cell ID. In further implementations, if the first cell ID is an NR CGI, the first configuration includes a second cell ID (e.g., PCI). In some implementations, the second cell ID is determined based on the first cell ID.

[0200] In some implementations, the CU includes an additional cell ID in the first CU-to-DU message to request additional configuration for later activation. In some such cases, the first DU-to-CU message includes the additional configuration for later activation, and the CU includes the additional configuration in a container IE. In other implementations, the CU sends an additional CU-to-DU message including the additional cell ID to the first DU. In some implementations, the CU receives an additional DU-to-CU message including the additional configuration for later activation from the first DU. In a further implementation, the CU includes the additional configuration in a container IE. In some implementations, the first cell ID and the additional cell ID are cell ID 1 and cell ID 2... N, respectively, as described above. In some implementations, the first configuration and the additional configuration are configuration 1 and configuration 2... N, respectively, as described above.

[0201] In some implementations, the first CU-to-DU message and / or the additional CU-to-DU message is a UE context modification request message. In some implementations, the first DU-to-CU message and / or the additional DU-to-CU message is a UE context modification response message or a UE context modification required message.

[0202] Figure 10 Method 1000, which can be implemented by a CU (e.g., CU 172), for configuring and activating a serving cell configuration for a UE (e.g., UE102) is shown.

[0203] Method 1000 begins at block 1002, where the CU communicates with the UE via a first DU (e.g., events 402, 480, 602, 680, 802, 880). In some implementations, at block 1004, the CU sends a first CU-to-DU message including a first cell ID and an IE to a second DU to request a configuration for later activation (e.g., events 408, 490, 608, 690, 680, 808, 890, 880). At block 1006, the CU receives a first DU-to-CU message including a first configuration for later activation, where the first configuration is configured for the UE to communicate with the first DU via a first cell identified by the first cell ID (e.g., events 410, 490, 610, 690, 680, 810, 890, 880). At block 1008, the CU generates a first RRC message including a container IE that includes the first configuration. At block 1010, the CU sends the first RRC message to the UE via the first DU (e.g., events 416, 418, 616, 618, 680, 816, 818, 880).

[0204] In some implementations, the first CU-to-DU message is a UE Context Setup Request message. In some implementations, the first DU-to-CU message is a UE Context Setup Response message. In other implementations, the first CU-to-DU message is a UE Context Modification Request message. In some implementations, the first DU-to-CU message is a UE Context Modification Response message.

[0205] In some implementations, the first cell ID is an NR CGI. In other implementations, the first cell ID is a Physical Cell ID. In further implementations, if the first cell ID is an NR CGI, the first configuration includes a second cell ID (e.g., PCI). In some implementations, the second cell ID is determined based on the first cell ID.

[0206] In some implementations, the CU includes an additional cell ID in the first CU-to-DU message to request an additional configuration for later activation. In some such cases, the first DU-to-CU message includes the additional configuration for later activation, and the CU includes the additional configuration in a container IE. In other implementations, the CU sends an additional CU-to-DU message including the additional cell ID to a second DU. In some implementations, the CU receives an additional DU-to-CU message including the additional configuration for later activation from the second DU. In further implementations, the CU includes the additional configuration in a container IE. In some implementations, the first cell ID and the additional cell ID are Cell ID 1 and Cell ID 2...N respectively, as described above. In some implementations, the first configuration and the additional configuration are Configuration 1 and Configuration 2...N respectively, as described above.

[0207] In some implementations, the additional CU-to-DU message and the additional DU-to-CU message are a UE Context Modification Request message and a UE Context Modification Response message respectively. In other implementations, the additional CU-to-DU message and the additional DU-to-CU message are a UE Context Setup Request message and a UE Context Setup Response message respectively.

[0208] In some implementations, methods 900 and 1000 can be combined. In some such cases, the CU sends a single RRC message including a single container received from the first DU and the second DU to the UE, and the single container includes a configuration for later activation. Alternatively, the CU sends separate RRC messages (i.e., a first RRC message and a second RRC message) including the configuration for later activation received from the first DU and the second DU to the UE.

[0209] Figure 11AShown is a method 1100A for configuring a serving cell configuration for a UE (e.g., UE 102) that may be implemented by a CU (e.g., CU 172).

[0210] Method 1100A begins at block 1102, where the CU communicates with the UE via a first DU (e.g., events 302, 380, 402, 480, 502, 580, 602, 680, 702, 780, 802, 880). At block 1104, the CU determines a request for configuration of a first cell. At block 1106, in response to the determination, the CU includes a first cell ID of the first cell in a first CU-to-DU message. At block 1108, the CU determines whether a configuration for later activation is requested. If the CU determines that a configuration for later activation is requested, the flow proceeds to block 1110. At block 1110, the CU includes an IE in the first CU-to-DU message to indicate that the CU requests a configuration for later activation. Otherwise, if the CU determines that a configuration for later activation is not requested, the flow proceeds to block 1112. At block 1112, the CU refrains from including the IE in the first CU-to-DU message. The flow proceeds from block 1110 and from block 1112 to block 1114. At block 1114, the CU sends the first CU-to-DU message to the first DU (e.g., events 308, 390, 380, 508, 590, 580, 708, 790, 780). At block 1116, the CU receives from the first DU a first DU-to-CU message including a first configuration for the UE to communicate with the first DU via the first cell (e.g., events 310, 390, 380, 510, 590, 580, 710, 790, 780). At block 1118, the CU sends an RRC message including the first configuration to the UE via the first DU (e.g., events 316, 318, 380, 416, 418, 516, 518, 580, 616, 618, 680, 716, 718, 780, 816, 818, 880).

[0211] For Figure 9 the examples and implementations described can be applied to Figure 11A . The first cell is operated by the first DU.

[0212] Figure 11Bis a flowchart of example method 1100B, which is similar to method 1100A, except that method 1100B includes blocks 1115 and 1117 instead of blocks 1114 and 1116. At block 1115, the CU sends a first CU-to-DU message (e.g., events 408, 490, 608, 690, 680, 808, 890, 880) to the second DU. At block 1117, the CU receives a first DU-to-CU message (e.g., events 410, 490, 610, 690, 680, 810, 890, 880) from the second DU that includes a first configuration for the UE to communicate with the second DU via the first cell.

[0213] For Figure 10 the example and implementation described can be applied to Figure 11B . The first cell is operated by the second DU.

[0214] Figure 12A illustrates method 1200A for configuring a serving cell configuration for a UE (e.g., UE 102) that can be implemented by a CU (e.g., CU 172).

[0215] Method 1200A begins at block 1202, where the CU communicates with the UE via a first DU (e.g., events 302, 380, 402, 480, 502, 580, 602, 680, 702, 780, 802, 880). At block 1204, the CU receives a first DU-to-CU message (e.g., events 310, 390, 380, 510, 590, 580, 710, 790, 780) from the first DU that includes a first configuration for the UE to communicate with the first DU via the first cell. At block 1206, the CU determines whether the first configuration is for later activation. If the CU determines that the first configuration is for later activation, the flow proceeds to block 1208. At block 1208, the CU includes the first configuration in a container IE and includes the container IE in an RRC message. Otherwise, if the CU determines that the first configuration is not for later activation, the flow proceeds to block 1210. At block 1210, the CU avoids including the first configuration in a container IE and includes the configuration in an RRC message. At block 1212, the CU sends the RRC message to the UE via the first DU (e.g., 316, 318, 380, 416, 418, 516, 518, 580, 616, 618, 680, 716, 718, 780, 816, 818, 880). The flow proceeds from block 1210 as well as from block 1208 to block 1212 (e.g., events 316, 318, 380, 516, 518, 580, 716, 718, 780).

[0216] For Figure 9 and / or Figure 11AThe described examples and implementations can be applicable to Figure 12A . The first cell is operated by the first DU.

[0217] Figure 12B is a flowchart of an example method 1200B, which is similar to method 1200A, except that method 1200B includes block 1205 instead of block 1204. At block 1205, the CU receives a first DU-to-CU message from the second DU that includes a first configuration for the UE to communicate with the second DU via the first cell (e.g., events 410, 490, 610, 690, 680, 810, 890, 880).

[0218] For Figure 10 and / or Figure 11B The described examples and implementations can be applicable to Figure 12B . The first cell is operated by the second DU.

[0219] Figure 13 Illustrates a method 1300 for configuring and activating a serving cell configuration for a UE (e.g., UE102) that can be implemented by a DU (e.g., DU 174).

[0220] Method 1300 begins at block 1302, where the DU communicates with the UE and the CU (e.g., events 302, 380, 402, 480, 502, 580, 602, 680, 702, 780, 802, 880). In some implementations, at block 1304, the DU receives a first CU-to-DU message from the CU that includes a first cell ID and an IE to request a configuration for later activation (e.g., events 308, 390, 380, 508, 590, 580, 708, 790, 780). At block 1306, the DU sends a first DU-to-CU message to the CU that includes a first configuration for later activation, where the first configuration is configured for the UE to communicate with the DU via a first cell identified by the first cell ID (e.g., events 310, 390, 380, 510, 590, 580, 710, 790, 780). At block 1308, the DU sends the first configuration to the UE (e.g., events 316, 318, 380, 516, 518, 580, 716, 718, 780). At block 1310, the DU sends a configuration activation command to the UE to command the UE to apply the first configuration (e.g., events 330, 380, 530, 580, 730, 780). At block 1312, the DU communicates with the UE according to the first configuration (e.g., events 332, 336, 380, 532, 536, 580, 732, 736, 780).

[0221] For Figures 9 to 12B The described examples and implementations can be applicable toFigure 13 The first cell is operated by the first DU.

[0222] Figure 14 Shown is method 1400 for configuring and activating a serving cell configuration for a UE (e.g., UE 102) that can be implemented by a DU (e.g., DU 174).

[0223] Method 1400 begins at block 1402 where the DU communicates with the UE and the CU (e.g., events 302, 380, 502, 580, 702, 780). At block 1404, the DU sends a first DU-to-CU message to the CU that includes a first configuration for the UE to communicate with the DU via the first cell (e.g., events 310, 390, 380, 510, 590, 580, 710, 790, 780). At block 1406, the DU sends the first configuration to the UE (e.g., events 316, 318, 380, 516, 518, 580, 716, 718, 780). At block 1408, the DU determines whether the first configuration is for later activation. If the DU determines that the first configuration is for later activation, the flow proceeds to block 1410. At block 1410, the DU sends a configuration activation command to the UE to command the UE to apply the first configuration (e.g., events 330, 380, 530, 580, 730, 780). Otherwise, if the DU determines that the first configuration is not for later activation, the flow proceeds to block 1412. At block 1412, the DU refrains from sending a configuration activation command to the UE. The flow proceeds from block 1410 and from block 1412 to block 1414. At block 1414, the DU communicates with the UE according to the first configuration (e.g., events 332, 336, 380, 532, 536, 580, 732, 736, 780).

[0224] For Figures 9 to 13 The examples and implementations described can be applicable to Figure 14 。The first cell is operated by the first DU. In the case where the first configuration is not for later activation, the DU applies the first configuration immediately after sending the first configuration to the UE, receiving from the UE an acknowledgement indicating that the UE has received the first configuration, receiving from the CU a CU-to-DU message indicating that the UE has received the first configuration, or receiving from the CU a CU-to-DU message indicating application of the first configuration (e.g., in response thereto).

[0225] Figure 15 Shown is method 1500 for configuring and activating a serving cell configuration for a UE (e.g., UE 102) that can be implemented by a DU (e.g., DU 174).

[0226] Method 1500 starts at block 1502, where the DU generates a first configuration for the UE. At block 1504, the DU determines whether the first configuration is for later activation. If the DU determines that the first configuration is for later activation, the process proceeds to block 1506. At block 1506, the DU includes the first configuration in a first field of a first DU-to-CU message. Otherwise, if the DU determines that the first configuration is not for later activation, the process proceeds to block 1508. At block 1508, the DU includes the first configuration in a second field of the first DU-to-CU message. The process proceeds from block 1508 and from block 1506 to block 1510. At block 1510, the DU sends the first DU-to-CU message to the CU (e.g., event 310, 390, 380, 410, 490, 510, 590, 580, 510, 690, 680, 710, 790, 780, 810, 890, 880).

[0227] Next, referring to Figures 16 to 20 several example methods are discussed that can be implemented in one or more RAN nodes such as a base station, DU, or CU or in the RAN to support configuring a configuration for later activation. For Figures 3 to 8B the examples and implementations described can be applicable to Figures 16 to 20 .

[0228] Figure 16 Method 1600, which can be implemented by the CU (e.g., CU 172), for configuring and activating a configuration for the UE (e.g., UE102) is shown.

[0229] Method 1600 starts at block 1602, where the CU communicates with a first DU and the UE (e.g., event 302, 380, 502, 580, 702, 780). At block 1604, the CU receives configurations 1...N from the first DU, where N is an integer greater than zero. At block 1606, the CU assigns IDs 1...N to configurations 1...N respectively (e.g., event 310, 390, 380, 510, 590, 580, 710, 790, 780). At block 908, the CU sends IDs 1...N and configurations 1...N to the UE via the first protocol and the first DU (e.g., event 316, 318, 380, 516, 518, 580, 716, 718, 780). At block 1610, the CU sends IDs 1...N to the first DU via a second protocol (e.g., event 308, 390, 312, 392, 380, 508, 590, 512, 592, 708, 790, 712, 792).

[0230] In some implementations, the first protocol and the second protocol are the RRC protocol and the F1 Application Protocol (F1AP).

[0231] Figure 17 Illustrates method 1700 for configuring and activating configurations for a UE (e.g., UE 102) that can be implemented by a CU (e.g., CU 174).

[0232] Method 1700 begins at block 1702, where the CU communicates with a first DU and the UE (e.g., events 302, 380, 402, 502, 580, 602, 680, 702, 780, 802, 880). At block 1704, the CU receives configurations 1...P from a second DU, where P is an integer greater than zero (e.g., events 410, 490, 480, 610, 690, 680, 810, 890, 880). At block 1706, the CU assigns IDs 1...P to configurations 1...P respectively. At block 1708, the CU sends IDs 1...P and configurations 1...P to the UE via a first protocol and the first DU (e.g., events 416, 418, 480, 616, 618, 680, 816, 818, 880). At block 1710, the CU sends IDs 1...P to the first DU via a second protocol (e.g., events 412, 492, 612, 692, 812, 892).

[0233] In some implementations, the first protocol and the second protocol are the RRC protocol and the F1 application protocol (F1AP).

[0234] Figure 18 Illustrates method 1800 for configuring configurations for a UE (e.g., UE 102) that can be implemented by a CU (e.g., CU 172).

[0235] Method 1800 begins at block 1802, where the CU communicates with a first DU and the UE (e.g., events 302, 380, 402, 502, 580, 602, 680, 702, 780, 802, 880). At block 1804, the CU receives X1 configurations, X2 configurations... X M configurations from DUs 1...M respectively, where M is an integer greater than zero, and each of X1, X2... X M is a positive integer or zero, and at least one of X1, X2... X M is greater than zero (e.g., events 310, 390, 380, 410, 490, 480, 510, 590, 580, 610, 690, 680, 710, 790, 780, 810, 890, 880). At block 1806, the CU assigns an ID to each of the X1, X2... X M configurations. At block 1808, the CU sends the IDs and X1, X2... X MConfigurations (e.g., events 316, 318, 380, 416, 418, 480, 516, 518, 580, 616, 618, 680, 716, 718, 780, 816, 818, 880). At block 1810, the CU sends an ID (e.g., events 308, 390, 312, 392, 412, 492, 508, 590, 512, 592, 612, 692, 708, 790, 712, 792, 812, 892) to the first DU via a second protocol.

[0236] In some implementations, DU 1...M includes the first DU and / or other DUs. In some implementations, the first protocol and the second protocol are the RRC protocol and the F1 Application Protocol (F1AP).

[0237] Figure 19A Method 1900A for configuring a configuration for a UE (e.g., UE 102) that may be implemented by a DU (e.g., DU 174) is shown.

[0238] Method 1900 begins at block 1902, where the DU communicates with the UE using a first configuration (e.g., events 302, 380, 502, 580, 702, 780). At block 1904, the DU sends at least one configuration to the CU. At block 1906, the DU receives at least one ID from the CU, each ID identifying a specific configuration among the at least one configuration (e.g., events 308, 390, 312, 392, 508, 590, 512, 592, 708, 790, 712, 792). At block 1908, the DU sends at least one ID and at least one configuration to the UE (e.g., events 318, 380, 518, 580, 718, 780). At block 1910, the DU sends a first configuration activation command including a first ID among the at least one ID to activate the first configuration identified by the first ID (e.g., events 330, 380, 530, 580, 730, 780). At block 1912, the DU communicates with the UE using the first configuration after sending the first configuration activation command (e.g., events 332, 336, 380, 532, 536, 580, 732, 736, 780). Depending on the implementation, the process then proceeds to block 1914 or block 1920. At block 1914, the DU retains the remainder of the at least one configuration after sending the configuration activation command. At block 1916, the DU sends a second configuration activation command including a second ID among the at least one first ID to activate the second configuration identified by the second ID. At block 1918, the DU communicates with the UE using the second configuration after sending the second configuration activation command. At block 1920, the DU releases the remainder of the at least one configuration in response to sending the first configuration activation command.

[0239] Figure 19B is a flowchart of an example method 1900B, which is similar to method 1900A, except that method 1900B includes blocks 1905 and 1907 instead of blocks 1904 and 1906. At block 1905, the DU generates at least one configuration. At block 1907, the DU assigns at least one ID, each ID identifying a specific configuration in at least one configuration.

[0240] Figure 20 illustrates a method 2000 for configuring and activating a configuration for a UE (e.g., UE 102) that can be implemented by a DU (e.g., DU 174).

[0241] Method 2000 begins at block 2002, where the DU communicates with the UE. At block 2004, the DU receives at least one configuration (e.g., events 302, 380, 402, 480, 502, 580, 602, 680, 702, 780, 802, 880) from the CU. At block 2006, the DU receives at least one ID from the CU, each ID identifying a specific configuration in at least one configuration (e.g., events 308, 390, 312, 392, 412, 492, 508, 590, 512, 592, 612, 692, 708, 790, 712, 792, 812, 892). At block 1308, the DU sends at least one ID and at least one configuration to the UE (e.g., events 318, 380, 418, 480, 518, 580, 618, 680, 718, 780, 818, 880). At block 2010, the DU sends a configuration activation command including a first ID in at least one ID to activate the configuration identified by the first ID (e.g., events 330, 380, 430, 480, 530, 580, 630, 680, 730, 780, 830, 880). At block 2012, the DU stops communicating with the UE after sending the configuration activation command. Depending on the implementation, the flow then proceeds to block 2014 or 2016. At block 2014, the DU retains the remainder of at least one configuration after sending the configuration activation command. At block 2016, the DU releases the remainder of at least one configuration in response to sending the configuration activation command.

[0242] The following description may apply to the above description.

[0243] Generally speaking, the description of one of the above-mentioned drawings can be applied to another one of the above-mentioned drawings. If there is no conflict, the above examples, implementation manners and methods can be combined. The events or boxes described above can be optional or omitted. For example, the events or boxes with dashed lines in the drawings can be optional. In some implementation manners, "message" is used and "message" can be replaced by "information element (IE)", and vice versa. In some implementation manners, "IE" is used and "IE" can be replaced by "field", and vice versa. In some implementation manners, "configuration" can be replaced by "configurations" or "configuration parameters", and vice versa. In some implementation manners, "configuration activation command" can be replaced by "serving cell change command", "layer 1 / layer 2 handover command", "lower layer handover command" or "lower layer serving cell change command". "Fast serving cell configuration process" can be replaced by "fast serving cell change process".

[0244] The user equipment (e.g., UE 102) in which the technology of the present disclosure can be implemented can be any suitable device capable of wireless communication, such as a smart phone, a tablet computer, a laptop computer, a mobile game 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 smart watch, a wireless hotspot, a femtocell or a broadband router. Further, in some cases, the user equipment can be embedded in an electronic system, such as a headunit of a vehicle or an advanced driver assistance system (ADAS). Still further, the user equipment can operate as an Internet of Things (IoT) device or a mobile Internet device (MID). Depending on the type, the user equipment 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.

[0245] Certain embodiments are described in the present disclosure as including logic or a plurality of components or modules. A module can be a software module (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing certain operations and can be configured or arranged in a particular manner. A hardware module can include dedicated circuitry or logic (e.g., as a dedicated processor, such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.) that is permanently configured to perform certain operations. A hardware module can also include programmable logic or circuitry (e.g., as included within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module as dedicated and permanently configured circuitry or as temporarily configured circuitry (e.g., configured by software) can be driven by cost and time considerations.

[0246] When implemented in software, these techniques can be provided as part of an 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 dedicated processors.

[0247] Upon reading this disclosure, those skilled in the art will appreciate additional and alternative structural and functional designs for handling mobility between base stations through the principles disclosed herein. Accordingly, while specific embodiments and applications have been shown and described, it should be understood that the disclosed embodiments are not limited to the exact construction and components disclosed herein. Various modifications, changes, and variations to the arrangement, operation, and details of the methods and devices disclosed herein will be apparent to those of ordinary skill in the art without departing from the spirit and scope defined in the appended claims.

Claims

1. A method in a Centralized Unit (CU) of a distributed base station, the distributed base station including a CU, a source Distributed Unit (DU), and a target DU, the method comprising: Receiving, from the target DU, a configuration related to a target cell for a User Equipment (UE) currently communicating with the CU via the source DU to perform a serving cell change to the target cell, the serving cell change to the target cell being initiated after a measurement report from the UE; And Sending, via the source DU, the configuration to the UE.

2. The method according to claim 1, further comprising: Sending a request for the configuration related to the target cell to the target DU, the request including an identifier of the target cell; Wherein receiving the configuration from the target DU is in response to the sending of the DU.

3. The method according to claim 2, wherein: The sending of the request includes sending a request to establish a context for the UE, and The receiving of the configuration includes receiving a response to the request.

4. The method according to claim 2 or 3, wherein the cell identifier is a Global Cell Identifier (CGI).

5. The method according to any one of claims 2 to 4, further comprising: Receiving, via the source DU, a Layer 3 (L3) measurement report from the UE for a plurality of cells; Wherein the sending of the request is in response to the L3 measurement report.

6. The method according to any one of claims 2 to 5, wherein the request indicates that the configuration related to the target cell is for later activation at the UE, and the UE does not immediately apply the configuration identifier for later activation.

7. The method according to any one of the preceding claims, wherein the configuration includes a random access configuration, and the UE accesses the target cell according to the random access configuration.

8. The method according to any one of the preceding claims, wherein the configuration includes a Channel State Information (CSI) resource configuration.

9. The method according to any one of the preceding claims, wherein the configuration includes one or more of the following: (i) Physical layer configuration parameters, (ii) Medium Access Control (MAC) layer configuration parameters, or (iii) Radio Link Control (RLC) configuration parameters.

10. The method according to any one of the preceding claims, wherein sending the configuration to the UE includes: Sending the configuration and an identifier (ID) assigned by the CU to the configuration.

11. The method according to any one of the preceding claims, wherein sending the configuration to the UE includes: Sending the configuration and an indication that the UE does not immediately apply the configuration.

12. The method according to any one of the preceding claims, further comprising: After sending the configuration to the UE, receiving the measurement report including a Layer 1 (L1) measurement report; And Sending, via the source DU, a command to activate the serving cell change to the target cell to the UE.

13. The method according to claim 12, wherein the command for activating the serving cell change to the target cell identifies at least one of (i) the target cell or (ii) the configuration associated with the target cell.

14. The method according to any one of the preceding claims, wherein sending the configuration to the UE comprises: sending the configuration and an identifier (ID) assigned by the CU to the configuration.

15. A method in a central unit (CU) of a distributed base station, the distributed base station comprising a CU and a distributed unit (DU), the method comprising: receiving from the DU a configuration related to a target cell for a user equipment (UE) currently communicating with the CU via a serving cell, the serving cell change to the target cell being initiated after a measurement report from the UE; and sending the configuration to the UE via the DU.

16. The method according to claim 1, further comprising: sending a request for the configuration related to the target cell to the DU, the request comprising an identifier of the target cell; wherein receiving the configuration from the DU is in response to the sending by the DU.

17. The method according to claim 15 or 16, wherein: the sending of the request comprises sending a request to establish a context for the UE, and the receiving of the configuration comprises receiving a response to the request.

18. The method according to any one of claims 15 to 17, further comprising: receiving from the UE via the DU a layer 3 (L3) measurement report for a plurality of cells; wherein the sending of the request is in response to the L3 measurement report.

19. The method according to any one of claims 15 to 18, wherein the configuration comprises one or more of the following: (i) a random access configuration according to which the UE accesses the target cell, (ii) a channel state information (CSI) resource configuration, (iii) physical layer configuration parameters, (iv) media access control (MAC) layer configuration parameters, or (v) radio link control (RLC) configuration parameters.

20. The method according to any one of claims 15 to 19, further comprising: after sending the configuration to the UE, receiving the measurement report comprising a layer 1 (L1) measurement report; and sending a command for activating the serving cell change to the target cell to the UE via the DU.

21. A radio access network (RAN) component comprising processing hardware configured to implement the method according to any one of the preceding claims.

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