Managing data communications in serving cell change scenarios

Abstract

Comprising the CU and a distributed unit, DU, sends (1006), via the DU, a configuration in the first cell to a user equipment, UE, for performing a serving cell change to the second cell after the activation command; and suspending (1010) DL transmission of data packets to the UE in response to receiving (1008, 1009) a DU-to-CU message after sending the configuration but before receiving an indication that the UE has connected to the second cell.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of the filing date of provisional U.S. patent application No. 63 / 377,719, entitled “MANAGING DATA COMMUNICATION IN A SERVING CELL CHANGE SCENARIO,” filed on September 29, 2022. The entire contents of this provisional application are hereby expressly incorporated herein by reference. Technical Field

[0003] The present disclosure relates to wireless communications, and more particularly to managing data communications in a serving cell change for a user equipment (UE) and a decomposed base station. Background Art

[0004] This background description is provided for the purpose of generally presenting the context of the present disclosure. The work of the inventors mentioned by name (to the extent that it is described in this background section) and aspects of the specification that might not have been considered prior art at the time of filing are neither explicitly nor implicitly admitted to be prior art to the present disclosure.

[0005] In a telecommunication system, the Packet Data Convergence Protocol (PDCP) sublayer of the radio protocol stack provides services such as user plane data delivery, 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 sequencing of protocol data units (PDUs) in the uplink direction (from a user device (also referred to as user equipment (UE)) to a base station) and in the downlink direction (from a base station to a UE). Further, the PDCP sublayer provides signaling radio bearers (SRBs) and data radio bearers (DRBs) to the radio resource control (RRC) sublayer. Generally speaking, in some scenarios, the UE and 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 under dual connectivity (DC), the cell associated with the base station operating the master node (MN) defines a master cell group (MCG), and the cell associated with the base station acting as a secondary node (SN) defines a secondary cell group (SCG). SRB1 resources carry RRC messages including NAS messages on a dedicated control channel (DCCH) in some cases, while SRB2 resources support RRC messages including recorded 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 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 SN to exchange RRC messages related to the SN, and can be referred to as SCG SRBs. Split SRBs allow the UE to exchange RRC messages directly with the MN via the lower layer resources of the MN and SN. Further, a DRB using only the lower layer resources of the MN may be referred to as an MCG DRB, a DRB using only the lower layer resources of the SN may be referred to as an SCG DRB, and a DRB using the lower layer resources of both the MCG and the SCG may be referred to as a split DRB.

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

[0008] When a UE moves from the coverage area of ​​one cell in the RAN to another cell, a serving cell change will be performed for the UE at some point. In order 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 (e.g., the RRC reconfiguration message includes a ReconfigurationWithSync IE) configured with synchronized reconfiguration to change the serving cell (e.g., PCell or PSCell). In the case where the UE operates in carrier aggregation (CA) of at least one secondary cell (SCell) with a PCell or PSCell, the RAN must release the at least one SCell due to the change of the PCell or PSCell. The serving cell change involves a full L2 (and L1) reset, resulting in longer latency, greater overhead, and longer interruption time. Therefore, it is expected to develop new mobile technologies to reduce the latency and overhead of fast serving cell changes. However, it is not clear how to develop and implement fast serving cell changes. Summary of the invention

[0009] An example embodiment of the technology disclosed herein is a method in a CU of a distributed base station including a CU and a DU, the method comprising: sending a configuration for performing a service cell change to a second cell after an activation command to a UE in a first cell via the DU; and suspending downlink (DL) transmission of data packets to the UE in response to receiving a DU to CU message after sending the configuration but before receiving an indication that the UE is connected to the second cell.

[0010] Another example embodiment of these technologies is a method in a DU of a distributed base station including the DU and the CU, the method comprising: communicating with a user equipment (UE) in a first cell according to a first configuration parameter; sending a configuration to the UE for performing a serving cell change to a second cell after an activation command; sending the activation command to the UE in response to a measurement report; and sending an indication to the CU to suspend downlink (DL) transmission of data packets to the UE in response to sending the activation command.

[0011] Yet another example embodiment of the techniques is a node in a radio access network (RAN), the node comprising processing hardware and configured to implement one of the methods described above. 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 may implement the disclosed techniques for managing conditional procedures associated with a secondary node (SN);

[0013] Figure 1B Yes, you can Figure 1A A block diagram of an example base station including a centralized unit (CU) and a distributed unit (DU) operating in a system of FIG.

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

[0015] Figure 3 is a message passing diagram for an example scenario of lower layer procedures in which a base station configures a UE to perform a cell change operation;

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

[0017] Figure 5A is a message transfer diagram of an example scenario in which a MN and a SN operate under a DC to perform lower layer procedures of a cell change operation;

[0018] Figure 5B is with Figure 5A Message passing diagram for an example scenario similar to but in which the MN directly configures the UE;

[0019] Fig. 6A is with Figure 5A The scenario is similar to the message passing diagram of the example scenario where the cell change operation is an inter-DU cell change operation;

[0020] Figure 6B is with Figure 5B The scenario is similar to the message passing diagram of the example scenario where the cell change operation is an inter-DU cell change operation;

[0021] Fig. 7A is with Figure 5A A message transfer diagram for an example scenario similar to that of FIG. 1 but in which the base station acts as a MN (e.g., M-DU) and a SN (e.g., S-DU) to perform a cell change operation;

[0022] Figure 7B is with Fig. 7A Message passing diagram for an example scenario similar to but in which the MN directly configures the UE;

[0023] Fig. 8A is with Fig. 7A The scenario is similar to the message passing diagram of the example scenario where the cell change operation is an inter-DU cell change operation;

[0024] Figure 8B is with Figure 7BThe scenario is similar to the message passing diagram of the example scenario where the cell change operation is an inter-DU cell change operation;

[0025] Fig. 9A is a flow chart depicting an example method implemented in a DU, wherein the DU sends a configuration to a UE for later activation, and sends a message to a CU to indicate initiation of a cell change after activating the configuration;

[0026] Fig. 9B It is depicted with Fig. 9A A flowchart of an example method similar to the method of but wherein the DU sends a message to the CU to suspend downlink data transmission after activating the configuration;

[0027] Fig. 10A is a flow chart depicting an example method implemented in a CU, wherein the CU sends a configuration for later activation to a UE via a DU and receives an indication to initiate a cell change from the DU;

[0028] Fig. 10B It is depicted with Fig. 10A A flowchart of an example method similar to the method of but in which the CU receives an indication from the DU to suspend downlink data transmission;

[0029] Fig.11 is a flow chart depicting an example method implemented in a UE, wherein the UE receives a configuration for later activation, receives a configuration activation command, and suspends radio bearers;

[0030] Fig. 12A is a flowchart depicting an example method implemented in a CU, wherein the CU determines whether to obtain a configuration of a UE from a DU based on whether a second cell (eg, to be operated) is operated by a DU connected to the CU; and

[0031] Fig. 12B It is depicted with Fig. 12A Flow diagram of an example method that is similar to the method of but in which the CU makes a determination based on whether the second cell is operated by another base station. DETAILED DESCRIPTION

[0032] Figure 1A An example wireless communication system 100 is depicted 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 an SN addition to configure the UE 102 to operate in dual connectivity (DC) with the base station 104 and the base station 106. The base stations 104 and 106 act as a MN and a SN, respectively, for the UE 102.

[0033] 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 station 104 and the base station 106 via the same RAT (such as EUTRA or NR) or via different RATs. When the base station 104 is a MeNB and the base station 106 is an SgNB, the UE 102 may be in EUTRA-NR DC (EN-DC) with the MeNB and the SgNB.

[0034] In some cases, the MeNB or SeNB is implemented as an ng-eNB instead of an eNB. When the base station 104 is a master ng-eNB (Mng-eNB) and the base station 106 is an SgNB, the UE 102 can be in the next generation (NG) EUTRA-NRDC (NGEN-DC) with the Mng-eNB and the SgNB. When the base station 104 is a MgNB and the base station 106 is an SgNB, the UE 102 can be in NR-NR DC (NR-DC) with the MgNB and the SgNB. When the base station 104 is a MgNB and the base station 106 is a secondary ng-eNB (Sng-eNB), the UE 102 can be in NR-EUTRA DC (NE-DC) with the MgNB and the Sng-eNB.

[0035] In a scenario where UE 102 is handed over from base station 104 to base station 106, base stations 104 and 106 act as a source base station (S-BS) and a target base station (T-BS), respectively. For example, before the handover, UE 102 may communicate with base station 104 and an additional base station ( Figure 1A After the handover is completed, UE 102 may continue to operate with base station 106 and the additional base station in DC, or operate with base station 106 in a single connection (SC). In this case, base stations 104 and 106 act as a source MN (S-MN) and a target MN (T-MN), respectively.

[0036] The core network (CN) 110 may be an evolved packet core (EPC) 111 or a fifth generation core (5GC) 160, both of which are Figure 1A. The base station 104 may be an eNB supporting an S1 interface for communicating with the EPC 111, an ng-eNB supporting an NG interface for communicating with the 5GC 160, or a gNB supporting an NR radio interface and an NG interface for communicating with the 5GC 160. In order to exchange messages directly with each other during the scenarios discussed below, the base stations 104 and 106 may support an X2 or Xn interface. Among other components, the EPC 111 may include a serving gateway (SGW) 112, a mobility management entity (MME) 114, and a packet data network gateway (PGW) 116. The SGW 112 is generally configured to deliver user plane packets associated with audio calls, video calls, Internet services, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The PGW 116 provides a connection from the UE to one or more external packet data networks (e.g., an Internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network). 5GC 160 includes a user plane function (UPF) 162 and an access and mobility management (AMF) 164, and / or a session management function (SMF) 166. UPF 162 is generally configured to deliver user plane packets related to audio calls, video calls, Internet services, etc., AMF 164 is configured to manage authentication, registration, paging and other related functions, and SMF 166 is configured to manage PDU sessions.

[0037] like Figure 1A As shown, base station 104 supports cell 124A, and base station 106 supports cell 126A. Cells 124A and 126 may partially overlap, so that UE 102 may communicate with base station 104 and base station 106 under DC, where one of base stations 104 and 106 is a MN and the other is a SN. Base station 104 may support additional cells (such as cells 124B and 124C), and base station 106 may support additional cells ( Figure 1A 124B and 124C may partially overlap so that the UE 102 may communicate with the base station 104 in carrier aggregation (CA). The base station 104 may operate the cells 124A, 124B and 124C via one or more transmit and receive points (TRPs). More specifically, when the UE 102 operates with the base station 104 and the base station 106 in DC, one of the base stations 104 and 106 acts as a MeNB, Mng-eNB or MgNB, and the other acts as a SgNB or Sng-eNB.

[0038] In general, the wireless communication network 100 may include any suitable number of base stations supporting NR cells and / or EUTRA cells. More specifically, the EPC 111 or the 5GC 160 may be connected to any suitable number of base stations supporting NR cells and / or EUTRA cells. Although the following examples specifically refer to specific CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, 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.

[0039] Continue 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 non-transitory computer-readable memory storing instructions executed by one or more general-purpose processors. In addition 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 send data and control signals on a physical downlink (DL) channel and send DL reference signals with 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 and / or receive UL reference signals on a physical uplink (UL) channel with one or more user devices via one or more cells (e.g., cells 124A, 124B, and / or 124C) and / or one or more TRPs. In an example implementation, the processing hardware 130 includes a MAC controller 134, which is configured to perform MAC functions with one or more user devices. MAC functions include random access (RA) procedures, managing UL timing advance of one or more user devices, and / or transmitting UL / DL MAC PDUs with one or more user devices. Processing hardware 130 may further include an RRC controller 136 to implement procedures and message delivery at the RRC sublayer of the protocol communication stack. For example, the RRC controller 132 may be configured to support RRC message delivery associated with a handover process, and / or to support necessary operations when the base station 104 acts as a MN relative to the SN or acts as a SN relative to the MN. The base station 106 may include processing hardware 140 similar to the processing hardware 130. Specifically, components 142, 144, and 146 may be similar to components 132, 134, and 136, respectively.

[0040] UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors (such as CPUs), and non-transitory computer-readable memory storing machine-readable instructions that can be executed on one or more general-purpose processors, and / or dedicated processing units. PHY controller 152 is also configured to receive data and control signals on a physical DL channel with base station 104 or 106 via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs, and / or receive DL reference signals. PHY controller 152 is also configured to send data and control signals on a physical UL channel with base station 104 or 106 via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs, and / or send UL reference signals. In an example implementation, processing hardware 150 includes a MAC controller 154, which is configured to perform MAC functions with 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 base station 104 or 106. Processing hardware 150 may further include RRC controller 156 to implement procedures and messaging at the RRC sublayer of the protocol communication stack.

[0041] In operation, a UE 102 in DC may use radio bearers (e.g., DRBs or SRBs) that terminate at different times at the MN 104 or the SN 106. The UE 102 may apply one or more security keys when communicating on the radio bearers in the uplink (UL) (from the UE 102 to the base station) and / or downlink (from the base station to the UE 102) directions.

[0042] Figure 1BAn example distributed implementation of a base station, such as base station 104 or 106, is depicted. In this implementation, the base station may include a centralized unit (CU) 172 and one or more distributed units (DUs) 174. CU 172 is equipped with processing hardware, which may include one or more general-purpose processors (such as CPUs), and non-transitory computer-readable memory storing machine-readable instructions that can be executed on one or more general-purpose processors, and / or dedicated processing units. In one example, CU 172 is equipped with processing hardware 130. In another example, CU 172 is equipped with processing hardware 140. In an example implementation, processing hardware 140 includes an SN RRC controller 142, which is configured to manage or control one or more RRC configurations and / or RRC processes when base station 106 acts as an SN. DU 174 is also equipped with processing hardware, which may include one or more general-purpose processors (such as CPUs) and non-transitory computer-readable memory storing machine-readable instructions that can be executed on one or more general-purpose processors, and / or dedicated processing units. In some examples, in an example implementation, the processing hardware includes: a medium access control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., a random access procedure); and a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station 106 acts as a 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.

[0043] Next, Figure 2 The radio protocol stack according to which the UE 102 can communicate with the eNB / ng-eNB or gNB is shown in a simplified manner. Each of the base stations 104 or 106 can be an eNB / ng-eNB or a gNB.

[0044] The physical layer (PHY) 202A of EUTRA provides transport channels to the EUTRA medium access control (MAC) sublayer 204A, which in turn provides logical channels to the EUTRA radio link control (RLC) sublayer 206A, and the EUTRA RLC sublayer in turn provides RLC channels to the EUTRA PDCP sublayer 208 and, in some cases, to the NR PDCP sublayer 210. Similarly, the PHY 202B of NR provides transport channels to the NR MAC sublayer 204B, which in turn provides logical channels to the NR RLC sublayer 206B, and the NR RLC sublayer 206B in turn provides RLC channels to the NR PDCP sublayer 210. In some implementations, the UE 102 supports both EUTRA and NR stacks to support handover between EUTRA and NR base stations and / or to support DC over the EUTRA and NR interfaces. Further, as Figure 2 As shown in Figure A, the UE 102 can support NR PDCP 210 layered on EUTRA RLC 206A.

[0045] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets, which may be referred to as service data units (SDUs) (e.g., from an Internet Protocol (IP) layer layered directly or indirectly on the PDCP layer 208 or 210), and output packets, which may be referred to as protocol data units (PDUs) (e.g., to the RLC layer 206A or 206B). For simplicity, this disclosure refers to both SDUs and PDUs as "packets", except where the difference between SDUs and PDUs is relevant.

[0046] 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.

[0047] When the UE 102 operates under EUTRA / NR DC (EN-DC) with the base station 104 acting as a MeNB and the base station 106 acting as an SgNB, the network may provide the UE 102 with a MN terminated bearer using EUTRA PDCP 208 or a MN terminated bearer using NR PDCP 210. In various scenarios, the network may provide the UE 102 with an SN terminated bearer using only NR PDCP 210. The MN terminated bearer may be an MCG bearer or a split bearer. The SN terminated bearer may be an SCG bearer or a split bearer. The MN terminated bearer may be an SRB (e.g., SRB1 or SRB2) or a DRB. The SN terminated bearer may be an SRB (e.g., SRB2) or a DRB.

[0048] Next, several example scenarios, including Figure 1A A base station operating in the system sends a configuration to UE 102, and the configuration is later activated for communication between UE 102 and the base station. Figures 3 to 7B Similar events in the same file are marked with similar reference numbers (for example, event 316 is similar to Figure 4 A and Figure 4 B's event 416, Figure 5A Event 516, Figure 5B Event 517, Fig. 6A Event 616, Figure 6B Event 617, Fig. 7A Event 716 and Figure 7B Event 717 of FIG. 1 ), differences will be discussed below where appropriate. In addition to the differences shown in the figures and discussed below, any of the alternative implementations discussed with respect to a particular event (e.g., for message delivery and processing) may apply to events labeled with similar reference numbers in other figures.

[0049] First reference Figure 3 In scenario 300, base station 104 includes CU 172 and DU 174, and DU 174 operates cell 124A. UE 102 initially communicates 302 with base station 104 on cell 124A using a first configuration. In some implementations, UE 102 in carrier aggregation (CA) uses the first configuration to communicate in cell 124A and other cells (e.g., Figure 1A 124D) is used to communicate with DU 174. DU 174 operates other cells. In other implementations, UE 102 communicates with DU 174 only on cell 124A. In some implementations, UE 102 communicates with DU 174 on cell 124A and / or other cells via one or more TRPs. In some implementations, cell 124A is a PCell. In such cases, other cells include SCells and / or additional cells associated with PCell or SCell. In other implementations, cell 124A is an SCell, and one of the other cells is a PCell. In such cases, the remaining cells in the cell include SCells and / or additional cells associated with PCell or SCell. In the following description, base station 104 can be DU 174, CU 172, or DU 174 and CU 172.

[0050] In some implementations, in event 302, UE 102 sends UL PDUs and / or UL control signals to base station 104 via one or more TRPs on cell 124A and / or other cells. In some implementations, UE 102 transmits UL PDUs and / or DL ​​PDUs with base station 104 via radio bearers, and in further implementations, these radio bearers include SRBs and / or DRBs. In some implementations, base station 104 configures radio bearers to UE 102. In some implementations, the UL control signal includes UL control information, channel state information, hybrid automatic repeat request (HARQ) acknowledgment (ACK), HARQ negative ACK, scheduling request and / or sounding reference signal. Similarly, in further implementations, UE 102 receives DL PDUs and / or DL ​​control signals from base station 104 on 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 blocks, channel state information reference signals (CSI-RS) and / or tracking reference signals). In further implementations, the base station 104 sends the DCI on a physical downlink control channel (PDCCH) monitored by the UE 102 on the cell 124A and / or other cells via one or more TRPs.

[0051] 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 CellGroupConfig IE (e.g., defined in 3GPP specification 38.331) or configuration parameters in CellGroupConfig IE. In some implementations, the first configuration includes CSI-MeasConfig IE, MeasConfig IE, and / or RadioBearerConfig IE (e.g., defined in 3GPP specification 38.331) or configuration parameters in CSI-MeasConfig IE, MeasConfig IE, and / or RadioBearerConfig IE. In some implementations, UE 102 receives the configuration parameters from base station 104. In other implementations, UE 102 receives a portion of the configuration parameters from a base station other than base station 104 and receives the remainder of the configuration parameters from base station 104.

[0052] While communicating with the base station 104, the UE 102 sends 304 at least one measurement report to the DU 174. In some implementations, the at least one measurement report includes a layer 1 (L1) measurement report and / or a layer 3 (L3) measurement report for at least one serving cell and / or at least one non-serving cell of the UE 102. For each of the L3 measurement reports, the DU 174 sends 306 a DU to CU message including the L3 measurement report to the CU 172. In some implementations, the DU to CU message of event 306 is an F1 application protocol (F1AP) message (e.g., an UL RRC messaging message). In some implementations, the UE 102 does not send or avoids sending the L1 measurement report to the CU 172. The at least one serving cell includes the cell 124A and / or other cells, and the at least one non-serving cell includes the cell 124B and / or the cell 124C. In some implementations, the first configuration includes at least one measurement configuration. In some implementations, the UE 102 receives one or more RRC messages (e.g., RRCReconfiguration messages) including at least one measurement configuration from the CU 172 via the DU 174 in event 302. According to the at least one measurement configuration, the UE 102 performs measurement and sends 304 at least one measurement report to the DU 174. In some implementations, the at least one measurement configuration includes an L3 measurement configuration (e.g., MeasConfig IE) and / or an L1 measurement configuration. For example, the L1 measurement configuration (e.g., CSI-MeasConfig IE) includes a CSI resource configuration (e.g., CSI-ResourceConfig IE) and / or a CSI report configuration (e.g., CSI-ReportConfig IE). The UE 102 sends the L3 measurement report to the CU 172 via the DU 174 according to the L3 measurement configuration. The UE 102 sends the L1 measurement report to the DU 174 according to the L1 measurement configuration. In some implementations, 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 higher)). For example, the new measurement configuration includes a CSI resource configuration (e.g., CSI-ResourceConfig IE) and / or a new report configuration. In such implementations, 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 the trigger event to trigger UE 102 to send the new measurement report. If UE 102 detects a trigger event, UE 102 sends the new measurement report to DU 174.

[0053] 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 and noise ratio (L1-SINR) value. In some implementations, for each of the L1 measurement reports, the UE 102 sends a PUCCH transmission including the L1 measurement report to the DU 174. That is, the UE 102 sends each of the L1 measurement reports to the DU 174 on the PUCCH. In other implementations, for each of the L1 measurement reports, the UE 102 sends a PUSCH transmission including the L1 measurement report to the DU 174. That is, the UE 102 sends each of the L1 measurement reports to the DU 174 on the PUSCH. In yet other implementations, the UE 102 sends a portion of the L1 measurement report on the PUCCH and sends the remainder of the L1 measurement report to the DU 174 on the physical UL shared channel (PUSCH). That is, for each of the parts of the L1 measurement report, the UE 102 sends a PUCCH transmission including the L1 measurement report to the DU 174, and for each of the remaining parts of the L1 measurement report, the UE 102 sends a PUSCH transmission including the L1 measurement report to the DU 174. In some implementations, each of the L1 measurement reports is a channel state information (CSI) (i.e., a CSI component) or a part of the CSI. In some implementations, the 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 a channel quality indicator (CQI), a precoding matrix indicator (PMI), a CSI-RS resource indicator (CRI), a synchronization signal (SS) / physical broadcast channel (PBCH) resource block indicator (SSBRI), a layer indicator (LI) and / or a rank indicator (RI).

[0054] In some implementations, each of the L3 measurement reports includes at least one L3 measurement result. In some implementations, 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 PUSCH via DU 174. In some implementations, each of the L3 measurement reports is an RRC message (e.g., a 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 a specific measurement identifier in a specific L3 measurement configuration. In some implementations, when CU 172 receives an L3 measurement report including a measurement identifier and an L3 measurement result from UE 102 via DU 174, CU 172 determines that the L3 measurement report is associated with the L3 measurement configuration identified by the measurement identifier.

[0055] In some alternative implementations, for each of at least one measurement report (e.g., an L1 measurement report and / or a new type measurement report), the UE 102 sends a MAC control element (CE) including the measurement report to the DU 174 at event 304. To send the MAC CE, at event 304, the UE 102 generates one or more MAC PDUs to the DU 174, each MAC PDU including one or more of the MAC CEs.

[0056] In some implementations, the 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 (SSBs) and / or one or more CSI-RS. The UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurement. The DU 174 transmits one or more reference signals on cells 124A and 124B and optionally on cell 124C and / or other cells.

[0057] After receiving one or more of the at least one measurement report from the UE 102 (e.g., in response thereto), the base station 104 (i.e., the CU 172 or the DU 174) determines to prepare the cell 124B for the UE 102. In some implementations, the base station 104 determines to prepare the cell 124B for the UE 102 because the at least one measurement report indicates that the base station 104 can use the cell 124B to communicate with the UE 102. In some implementations, the base station 104 determines to prepare the cell 124B for the UE 102 because the at least one measurement report indicates that the cell 124B is eligible for communication with the UE 102. In some implementations, the CU 172 determines to prepare the cell 124B for the UE 102 if the L3 measurement report indicates that the signal strength and / or quality of the cell 124B is above a first predetermined threshold and / or better than the cell 124A. In other implementations, if the L1 measurement report or the new type measurement report indicates that the signal strength and / or quality of the cell 124B is above the first predetermined threshold and / or is better (e.g., higher) than the cell 124A, the DU 174 determines to prepare the cell 124B for the UE 102. Alternatively, the base station 104 determines to prepare the cell 124B for the UE 102 regardless of whether the measurement report is received from the UE 102.

[0058] In some implementations, if CU 172 determines to prepare cell 124B, 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 a 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 (referred to herein as configuration 1) to configure cell 124B, and sends 310 a first DU-to-CU message including the second configuration to CU 172. In a further implementation, if DU 174 determines to prepare cell 124B, DU 174 initiates the sending of the first DU-to-CU message to CU 172.

[0059] After receiving the first DU-to-CU message, CU 172 generates an RRC reconfiguration message (e.g., an RRCReconfiguration message) including configuration 1, and sends 316 a second CU-to-DU message including the RRC reconfiguration message to DU 174. DU 174 in turn sends 318 the RRC reconfiguration message to UE 102. In response, UE 102 sends 320 an RRC reconfiguration complete message (e.g., an RRCReconfigurationComplete message) to DU 174, which in turn sends 322 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 ciphering) on ​​the RRC reconfiguration message. For example, CU 172 generates an integrity message authentication code (MAC-I) for the RRC reconfiguration message, encrypts the RRC reconfiguration message and the MAC-I to obtain an encrypted RRC reconfiguration message and the 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 in events 316 and 318. 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 the MAC-I, and 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 reestablishment procedure in response to an invalid MAC-I. Otherwise, in a further implementation, if UE 102 verifies that MAC-I is valid, UE 102 processes the RRC reconfiguration. UE 102 avoids applying (ie, executing) Configuration 1 until a configuration activation command is received to activate Configuration 1 (eg, event 330).

[0060] 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 (UE Context ModificationRequired) message. In some implementations, in the case of a UE context modification required message, CU 172 sends a UE context modification confirmation 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.

[0061] Events 308 and 310 in Figure 3 It is collectively referred to as the service cell preparation process 390.

[0062] In some implementations, CU 172 includes a field or IE in the RRC reconfiguration message of events 316 and 318 to indicate that UE 102 should not apply configuration 1 immediately. In some implementations, the field or IE is currently defined (e.g., defined in 3GPP specification 38.331 v18.0.0 and / or higher). In further implementations, the field or IE is newly defined (e.g., defined in 3GPP 6G specifications). 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., an 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.

[0063] In some implementations, after receiving configuration 1 in event 310, CU 172 generates a first container including 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). Base station 104 includes configuration 1 in a first element (referred to herein as element 1) of the first addition or modification list. For example, element 1 is an addition or modification IE (e.g., ConfigToAddModIE, 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 (eg, in a variable in random access memory (RAM)).

[0064] 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 a first container or element 1. In some implementations, CU 172 assigns ID 1 to configuration 1. In other implementations, CU 172 receives ID 1 in a first DU-to-CU message from DU 174, as described below.

[0065] In some implementations, CU 172 sends ID 1 to DU 174 so that DU 174 can associate ID 1 with Configuration 1. In some implementations, CU 172 includes ID 1 in the first CU-to-DU message. In further implementations, CU 172 sends 312 a third CU-to-DU message including 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 further implementations, DU 174 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 described in detail in detail below. Figure 3It is collectively referred to as the ID allocation process 392.

[0066] In some implementations, in cases where 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.

[0067] 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 an ID identifying configuration 1 in the RRC reconfiguration message, the first container, and / or element 1.

[0068] In some implementations, configuration 1 includes multiple configurations for enabling UE 102 to communicate with DU 174 on cell 124B. In some implementations, the multiple configurations include physical layer configuration parameters (e.g., PhysicalCellGroupConfig IE), MAC layer configuration parameters (e.g., MAC-CellGroupConfig IE), and / or RLC configuration parameters (e.g., RLC-BearerConfig IE). 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).

[0069] In some implementations, DU 174 includes a random access configuration in configuration 1. In other implementations, DU 174 does not include a random access configuration in configuration 1. In some implementations, if cell 124A and cell 124B are not synchronized, DU 174 determines to include a random access configuration in configuration 1. Otherwise, if cell 124A and cell 124B are synchronized, DU 174 determines to not include a random access configuration in configuration 1. In other implementations, if DU 174 determines that UE 102 is not synchronized with cell 124B in the UL, DU 174 determines to include a random access configuration in configuration 1. Otherwise, if DU 174 determines that UE 102 is synchronized with cell 124B in the UL, DU 174 determines to not include a random access configuration in configuration 1. If configuration 1 includes a random access configuration, UE 102 performs a random access procedure in event 332 according to the random access configuration, as described below. Otherwise, if configuration 1 does not include a random access configuration, UE 102 skips the random access procedure of event 332 in response to configuration 1 not including a random access configuration.

[0070] In some implementations, regardless of whether cells 124A and 124B are synchronized, DU 174 includes the random access configuration in configuration 1. In some implementations, if cell 124A and cell 124B are synchronized, DU 174 determines to include a first indication in configuration 1, which configures UE 102 not to perform a random access procedure on cell 124B. Otherwise, if cell 124A is not synchronized with cell 124B, DU 174 determines not to include the first indication in configuration 1. In other implementations, if DU 174 determines that UE 102 is synchronized with cell 124B in UL, DU 174 determines to include the first indication in configuration 1. Otherwise, if DU 174 determines that UE 102 is not synchronized with cell 124B in UL, DU 174 determines not to include the first indication in configuration 1. If configuration 1 includes the first indication, UE 102 skips the random access procedure of event 332 based on or in response to the first indication. Otherwise, if configuration 1 does not include the first indication, UE 102 performs a random access procedure according to a random access procedure in event 332 in response to configuration 1 not including the first indication, as described below.

[0071] In some implementations, DU 174 includes a reconfiguration with synchronization configuration (e.g., ReconfigurationWithSync IE) in configuration 1 or special cell configuration. In other implementations, DU 174 does not include a reconfiguration with synchronization configuration (e.g., ReconfigurationWithSync IE) in configuration 1 or special cell configuration. In some implementations, if cell 124A and cell 124B are not synchronized, base station 104 determines to include a reconfiguration with synchronization configuration in configuration 1. Otherwise, if cell 124A and cell 124B are synchronized, DU 174 determines not to include a reconfiguration with synchronization configuration in configuration 1. In other implementations, if DU 174 determines that UE 102 has not yet synchronized with cell 124B in UL, DU 174 determines to include a reconfiguration with synchronization configuration in configuration 1. Otherwise, if DU 174 determines that UE 102 has synchronized with cell 124B in UL, DU 174 determines not to include a reconfiguration with synchronization configuration in configuration 1. In some implementations, if configuration 1 includes reconfiguration with synchronization configuration, UE 102 performs the random access procedure in event 332 as described below in response to or according to the reconfiguration with synchronization configuration. Otherwise, if configuration 1 does not include reconfiguration with synchronization configuration, UE 102 skips the random access procedure of event 332. In some implementations, DU 174 includes a cell ID (i.e., cell ID 1) of cell 1 (i.e., cell 124B) 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., a serving cell index) that indexes cell ID 1 or cell 124B.

[0072] In some implementations, after receiving one or more of the at least one measurement report of event 304 (e.g., in response thereto), the base station 104 (i.e., the CU 172 or the 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 the at least one measurement report indicates that the base station 104 can use other cells to communicate with the UE 102. In further implementations, the other cells include the cell 124C and / or cells other than the 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 in the other cells is higher than a corresponding predetermined threshold and / or better than (e.g., higher than) the cell 124A, the CU 172 determines to prepare the specific cell for the UE 102. In other implementations, if the L1 measurement report or the new measurement report indicates that the signal strength and / or quality of a particular cell in the other cells is higher than the first predetermined threshold and / or better than (e.g., higher than) the cell 124A, the DU 174 determines to prepare the other cells for the UE 102. In some implementations, the corresponding predetermined thresholds for the other cells are different from the first predetermined threshold. In further implementations, the corresponding predetermined thresholds for the other cells are the same as the first predetermined threshold. In some implementations, the corresponding predetermined thresholds for the other cells are the same or different. Alternatively, the base station 104 determines to prepare the other cells for the UE 102 regardless of whether the measurement report is received from the UE 102.

[0073] In some implementations, in response to a determination to prepare other cells, CU 172 and DU 174 perform at least one other serving cell preparation process to prepare the other cells, wherein each of the at least one other serving cell preparation process is similar to process 390. In some implementations, CU 172 includes a cell ID of the other cells in at least one CU-to-DU message of at least one serving cell preparation process, which is similar to the first CU-to-DU message. In some implementations, CU 172 and DU 174 perform additional serving cell preparation processes to prepare each of the other cells, similar to process 390. In some such cases, CU 172 includes a cell ID of a specific cell in the other cells in a CU-to-DU message of the serving cell preparation process, which is similar to the first CU-to-DU message. In the serving cell preparation process, DU 174 generates configurations 2, ..., N, each of which configures a specific cell in the other cells, and sends configurations 2, ..., N to CU 172, as described for configuration 1. "N" is an integer and is greater than one. For example, "N" is 2, 4, 6, 8, 10, 12, 14, or 16. The examples and implementations of Configuration 1 may be applicable to Configuration 2, ..., N.

[0074] In other implementations, CU 172 determines to prepare other cells in process 390. In some such cases, CU 172 includes a cell ID of each of the other cells in the first CU to DU message, and DU 174 includes configuration 2, ..., N in the first DU to CU message. In still other implementations, DU 174 determines to prepare other cells in process 390 and includes configuration 2, ..., N in the first DU to CU message.

[0075] In some implementations, after receiving configurations 2, ..., N from DU 174, CU 172 includes configurations 2, ..., N in the first container. In some implementations, CU 172 includes configurations 2, ..., N in elements 2, ..., N, and includes elements 2, ..., N in the first container. In some implementations, CU 172 includes IDs 2, ..., N for identifying configurations 2, ..., N, respectively, in the RRC reconfiguration message. In some implementations, CU 172 includes IDs 2, ..., N in the first container. For example, CU 172 includes IDs 2, ..., N and configurations 2, ..., N in elements 2, ..., N in the first addition or modification list.

[0076] In some implementations, CU 172 assigns IDs 2, ..., N for configurations, ..., N. In other implementations, CU 172 receives IDs 2, ..., N from DU 174 in a first DU to CU message of process 390 or in a DU to CU message of at least one other serving cell preparation process or additional serving cell preparation process.

[0077] In some implementations, CU 172 and DU 174 perform an ID allocation process for each of configurations 2, ..., N, similar to process 392. In such a case, DU 174 includes IDs 2, ..., N in configurations 2, ..., N. In such a case, CU 172 does not include IDs 2, ..., N in the RRC reconfiguration message, the first container, and / or elements 2, ..., N.

[0078] In some alternative implementations, DU 174 assigns IDs 2, ..., N for configurations 2, ..., N. In some implementations, DU 174 includes IDs 2, ..., N in a first DU to CU message of process 390 or in a DU to CU message of at least one other serving cell preparation process or additional serving cell preparation process. In further implementations, CU 172 includes IDs 2, ..., N in an RRC reconfiguration message. In other implementations, DU 174 includes IDs 2, ..., N in configurations 2, ..., N. Thus, CU 172 includes an ID identifying each of configurations 2, ..., N in an RRC reconfiguration message, a first container, and / or element 1.

[0079] In some alternative implementations, CU 172 generates a second container including configuration 2, ..., N or elements 2, ..., N instead of using the first container. Alternatively, DU 174 generates the second container and includes the second container in the first DU to CU message or in a DU to CU message of another serving cell preparation process. 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-CP 172A 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, MobilityConfigToAddModListIE, or CellGroupConfigToAddModList IE), and in further implementations, each of 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 RAM).

[0080] In some implementations, the 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 indexes 2, ..., N (e.g., serving cell indexes) that index the cell IDs 2, ..., N or the cells 2, ..., N, respectively.

[0081] 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 a first or second add or modify list (e.g., CellGroupConfigToAddModList IE), and the CellGroupConfigToAddMod IE is an element of the first or second add or modify list.

[0082] In some implementations, CU 172 sends a release list to UE 102 via DU 174 to release one or more configurations in configuration 1, ..., N. For example, CU 172 sends an RRC reconfiguration message including the release list to UE 102 via DU 174. In response, UE 102 sends an RRC reconfiguration complete message to CU 172 via DU 174. In some implementations, base station 104 includes one or more IDs of configurations in the release list to indicate one or more of the configurations to be released. UE 102 identifies one or more of the configurations according to the IDs, and releases one or more of the configurations in response to the release list.

[0083] In some implementations, the base station 104 sends a third addition or modification list to the UE 102, which is empty or does not include a configuration to release all 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 configurations 1, ..., N in response to the third addition or modification list.

[0084] In some implementations, CU 172 determines to release one, some, or all of configurations 1, ..., N, and in further implementations, sends a CU-to-DU message to DU 174 to instruct DU 174 to release one, some, or all of configurations 1, ..., N. For example, CU 172 includes one, some, or all of IDs 1, ..., N in the CU-to-DU message to instruct DU 174 to release one, some, or all of configurations 1, ..., N. Depending on the implementation, each of the cell IDs 1, ..., N is a CGI or a PCI. In response, DU 174 releases one, some, or all of configurations 1, ..., N, and in some implementations, sends a DU-to-CU message to CU 172. In other implementations, DU 174 determines to release one, some, or all of configurations 1, ..., N, and sends a DU-to-CU message to CU 172, including the IDs of one, some, or all of configurations 1, ..., N. After receiving the DU to CU message (eg, in response thereto), CU 172 generates a release list or a third addition or modification list to release one, some, or all of configurations 1, . . . , N.

[0085] In yet other implementations, DU 174 generates a release list or a third addition or modification list. In some such cases, DU 174 sends a DU to CU message including the release list or the third addition or modification list to CU 172. In a further implementation, CU 172 sends a CU to DU message to DU 174 in response. In some implementations, DU 174 determines to release one, some, or all of configurations 1, ..., N. In other implementations, DU 174 receives a CU to DU message from CU 172, which includes the ID of one, some, or all of configurations 1, ..., N to indicate that one, some, or all of configurations 1, ..., N are released.

[0086] Example Implementation 1

[0087]

[0088] 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 ConfigId and CellGroupConfig IE in CellGroupConfigToAddMod IE 1, respectively. ID 2, ..., N and configuration 2, ..., N are ConfigId and CellGroupConfig IE in CellGroupConfigToAddMod IE2, ..., 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.

[0089] In some implementations, the release list is a CellGroupConfigToReleaseList IE. In further implementations, the base station 104 includes one or more ConfigID IEs in the CellGroupConfigToReleaseList IE to release one or more CellGroupConfigToAddMod IEs in CellGroupConfigToAddMod IEs 1, ..., N. The one or more CellGroupConfigToAddMod IEs are identified by one or more ConfigID IEs.

[0090] Example Implementation 2

[0091] Example implementation 2 is similar to example implementation 1, except that CellGroupConfigToAddModIE does not include ConfigId.

[0092]

[0093] In some implementations, ID 1, ..., N is implicitly indicated by the order of CellGroupConfigToAddMod IE 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 of X. X can be zero or one. If the first CellGroupConfigToAddModList IE includes CellGroupConfigToAddMod IE 1, ..., N in order, then ID 1, ..., N has values ​​of X, X+1, ..., X+(N-1). In some implementations, if the base station 104 sends the second CellGroupConfigToAddModList IE to the UE 102, the UE 102 and the base station 104 replace the first CellGroupConfigToAddModList IE with the second CellGroupConfigToAddModList IE. If the second CellGroupConfigToAddModList IE includes CellGroupConfigToAddMod IEs 2, ..., N in order, then ID 2, ..., N is a value of X, X+1, ..., X+N-2. If the second CellGroupConfigToAddModList IE includes CellGroupConfigToAddMod IEs 1, ..., N in order, then ID 1, ..., N is a value of X, X+1, ..., X+N-1. In some alternative implementations, ID 1, ..., N is a cell ID 1, ..., N.

[0094] In some implementations, the base station 104 sends a CellGroupConfigToAddModList IE including zero CellGroupConfigToAddMod IEs to release all CellGroupConfigToAddMod IEs 1, . . . , N.

[0095] In example implementations 1 and 2, "CellGroupConfigToAddModList", "CellGroupConfigToAddMod", "configId", "ConfigId", "cellGroupConfig", "CellGroupConfigToReleaseList" and "maxNrofConfigCells" are merely exemplary and should not be construed as limiting the scope and application of the present invention.

[0096] In other implementations, each of configurations 1 and / or 2, ..., N is an RRCReconfiguration message. In such implementations, the following (ie, example implementations 3 to 6) are example structures of the first or second addition or modification list.

[0097] Example Implementation 3

[0098] In example implementation 3, the first or second add or modify list is a CondReconfigToAddModList-r16 IE (eg, as defined in 3GPP specification 38.331 Release 16), and the CondReconfigToAddMod IE is an element of the list.

[0099]

[0100] For example, the first addition or modification list is the first CondReconfigToAddModList-r16 IE and the second CondReconfigToAddModList-r16 IE. Element 1 is CondReconfigToAddMod-r16 IE 1, and elements 2, ..., N are CondReconfigToAddMod-r16 IE 2, ..., N, respectively. ID 1 and configuration 1 are CondReconfigId and RRCReconfiguration message in CondReconfigToAddMod IE 1, respectively. ID 2, ..., N and configuration 2, ..., N are CondReconfigId and RRCReconfiguration message in CondReconfigToAddMod IE 2, ..., N, respectively. In some implementations, the first CondReconfigToAddModList-r16 IE includes CondReconfigToAddMod-r16 IE 1, and the second CondReconfigToAddModList-r16 IE includes CondReconfigToAddMod-r16 IE 2, ..., N. In further implementations, the first CondReconfigToAddModList-r16 IE includes CondReconfigToAddMod-r16 IE 1, ..., N.

[0101] In this example implementation, the base station 104 includes a conditional configuration in at least one of the CondReconfigToAddMod-r16 IEs (i.e., condExecutionCond-r16). In some implementations, if the UE 102 supports a conditional procedure (e.g., conditional handover (CHO), conditional PSCell addition (CPA), or conditional PSCell change (CPC)), the UE 102 evaluates one or more conditions configured in the condExecutionCond-r16 field for the conditional procedure. If the UE 102 detects that at least one or all of the one or more conditions in the condExecutionCond-r16 field in a particular CondReconfigToAddMod-r16 IE are met, the UE 102 immediately applies the configuration in the RRCReconfiguration 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 the conditional configuration (i.e., condExecutionCond-r16) in any one or some of the CondReconfigToAddMod-r16 IEs. Therefore, the UE 102 is not configured to perform or does not perform any evaluation (i.e., detection or determination) of the condition of the conditional procedure (e.g., conditional handover) that does not include the CondReconfigToAddMod-r16 IE of the conditional configuration (i.e., condExecutionCond-r16).

[0102] In some implementations, the release list is a CondReconfigToRemoveList-r16 IE. In further implementations, the base station 104 includes one or more CondReconfigID IEs in the CondReconfigToRemoveList-r16 IE to release one or more CondReconfigToAddMod-r16 IEs in CondReconfigToAddMod-r16 IEs 1, ..., N. The one or more CondReconfigToAddMod-r16 IEs are identified by one or more CondReconfigID IEs.

[0103] Example Implementation 4

[0104] Example implementation 4 is similar to example implementation 3, except that in some implementations, a new indicator (e.g., 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 of event 312). If the base station 104 does not include the new indicator in the CondReconfigToAddMod-r16 IE, the CondReconfigToAddMod-r16 IE is not configured for fast serving cell change.

[0105]

[0106]

[0107] CondReconfigToRemoveList-r16 ::= SEQUENCE (SIZE (1..maxNrofCondCells-r16)) OF CondReconfigId-r16

[0108] Example Implementation 5

[0109] Some of the example implementations 3 and 4 may involve the UE 102 supporting conditional procedures (e.g., conditional handover (CHO), conditional PSCell addition (CPA), and / or conditional PSCell change (CPC)). If the UE 102 does not support the conditional procedures, the base station 104 does not configure or enable fast serving cell change for the UE 102. Therefore, example implementation 5 is separate from the conditional procedures.

[0110]

[0111] In some implementations, the first addition or modification list is a first ReconfigToAddModList IE, and the second addition or modification list is a second ReconfigToAddModList IE. Element 1 is ReconfigToAddMod IE 1, and elements 2, ..., N are ReconfigToAddMod IE 2, ..., N, respectively. ID 1 and configuration 1 are ConfigId and RRCReconfiguration IE in ReconfigToAddMod IE 1, respectively. ID 2, ..., N and configuration 2, ..., N are 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 further implementations, the first ReconfigToAddModList IE includes ReconfigToAddMod IE 1, ..., N.

[0112] In some implementations, the release list is a ReconfigToReleaseList IE. In further implementations, the base station 104 includes one or more ConfigID IEs in the ReconfigToReleaseList IE to release one or more ReconfigToAddMod IEs in ReconfigToAddMod IEs 1, ..., N. The one or more ReconfigToAddMod IEs are identified by one or more ConfigID IEs.

[0113] Example Implementation 6

[0114]

[0115] Example implementation 6 is similar to example implementation 5, except that the ReconfigToAddMod IE does not include ConfigId. In some implementations, ID 1, ..., N is implicitly indicated by the order of ReconfigToAddMod IE 1, ..., N in the first or second ReconfigToAddModList. For example, ReconfigToAddMod IE 1 is the first IE in the first ReconfigToAddModList IE, which implicitly indicates that ID 1 has a value of X. X can be zero or one. If the first ReconfigToAddModList IE includes ReconfigToAddMod IE 1, ..., N in order, then ID 1, ..., N has values ​​X, X+1, ..., X+(N-1). In some implementations, if the base station 104 sends the second ReconfigToAddModList IE to the UE 102, the UE 102 and the base station 104 replace the first ReconfigToAddModList IE with the second ReconfigToAddModList IE. If the second ReconfigToAddModList IE includes ReconfigToAddMod IEs 2, ..., N in order, then ID 2, ..., N is a value of X, X+1, ..., X+N-2. If the second ReconfigToAddModList IE includes ReconfigToAddMod IEs 1, ..., N in order, then ID 1, ..., N has a value of X, X+1, ..., X+N-1. In some alternative implementations, ID 1, ..., N is a cell ID 1, ..., N.

[0116] In some implementations, the base station 104 sends a ReconfigToAddModList IE including zero ReconfigToAddMod IEs to release all ReconfigToAddMod IEs 1, . . . , N.

[0117] In example implementations 5 and 6, “ReconfigToAddModList,” “ReconfigToAddMod,” “configId,” “ConfigId,” “cellGroupConfig,” “ReconfigToReleaseList,” and “maxNrofConfigCells” are exemplary and should not limit the scope and application of the present invention.

[0118] Example Implementation 7

[0119] Example implementation 7 is a combination of example implementations 1 and 5, as shown below. Depending on the implementation, any of configurations 1, ..., N is a CellGroupConfig IE or an RRCReconfiguration message. The examples and implementations described for example implementations 1 and 5 may be applicable to example implementation 7.

[0120]

[0121] maxNrofConfigCells ::= 8 After receiving the RRC reconfiguration in event 318 or sending the RRC reconfiguration complete message in event 320, the UE 102 sends 324 at least one measurement report to the DU 174, similar to event 304. In some implementations, the DU 174 sends 326 a DU-to-CU message including the at least one measurement report to the CU 172, similar to event 306. In other implementations, the DU 174 does not send the at least one measurement report to the CU 172. In some implementations, the at least one measurement report of event 324 includes an L1 measurement report, an L3 measurement report, and / or a new type measurement report, as described for event 304. In some implementations, the UE 102 sends 324 at least one measurement report to the DU 174 on the PUCCH and / or PUSCH, similar to event 304. In other implementations, the UE 102 sends 324 at least one MAC CE including the at least one measurement report to the DU 174, similar to event 304. In some implementations, each of the at least one measurement report of event 324 is not an RRC message.

[0122] In some implementations, the UE 102 sends 324 at least one measurement report to the DU 174 according to the at least one measurement configuration. The at least one measurement configuration configures the UE 102 to perform measurements and report measurement results. The CU 172 sends the at least one measurement configuration to the UE 102 via the DU 174. For example, after event 306 or 316, the CU 172 sends one or more RRC messages (e.g., RRCReconfiguration messages) including the at least one measurement configuration to the UE 102 via the DU 174. The one or more RRC messages may or may not include the RRC reconfiguration message of 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 measurement, and the UE 102 includes the at least one L1 measurement result and / or at least one L3 measurement result in the at least one measurement report of event 324. DU 174 transmits one or more reference signals on cells 124A and 124B and in some implementations on cell 124C and / or other cells. In some implementations, at least one 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.

[0123] In some implementations, the new measurement configuration described for events 304 and 324 is similar to an L3 measurement configuration. For example, the new measurement configuration includes a portion 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 an L1 measurement configuration. For example, the new measurement configuration includes a portion of the configuration parameters defined in the CSI-MeasConfig IE (e.g., CSI-ResourceConfig IE and / or CSI-ReportConfig IE).

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

[0125] In yet other implementations, DU 174 includes a bitmap in the first configuration activation command instead of ID 1, cell ID 1, or cell index 1 (e.g., serving cell index) to activate configuration 1. The number of bits in the bitmap is greater than or equal to "N". In some implementations, bits 1, ..., N correspond to configurations 1, ..., N, respectively, and DU 174 sets the corresponding bit in the bitmap (e.g., bit 1) to a first value to indicate ID 1 or configuration 1. In further implementations, bits 0, ..., N-1 correspond to configurations 1, ..., N, respectively, and DU 174 sets the corresponding bit in the bitmap (e.g., bit 0) to a first value to indicate ID 1 or configuration 1. Therefore, 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, 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 DU 174 determines to activate another configuration (e.g., configuration K) in addition to configuration 1, DU 174 sets the corresponding bit in the bitmap (e.g., bit K or bit K-1) to a first value, where 1<=K<=N.

[0126] In some implementations, at least one measurement report (e.g., L1 measurement report or new measurement report) of event 324 includes at least one measurement result for cell 124B. 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 an implementation, at least one measurement report of event 324 indicates that the signal strength or quality of cell 124B is suitable for communication with UE 102. In a further implementation, the second predetermined threshold is equal to the first predetermined threshold. In such an implementation, 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 communication with UE 102. Therefore, DU 174 determines to activate configuration 1 (i.e., the fast serving cell is changed to cell 124B) in response to the signal strength or quality of cell 124B being higher than the second predetermined threshold.

[0127] In some implementations, at least one measurement report (e.g., L3 measurement report) of events 324 and 326 includes at least one measurement result for cell 124B. 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 an implementation, at least one measurement report of event 326 indicates that the signal strength or quality of cell 124B is suitable for communicating with UE 102. In a further implementation, the second predetermined threshold is equal to the first predetermined threshold. In such an 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. The at least one measurement report also indicates that cell 124B is suitable for communicating with UE 102. Therefore, CU 172 determines to activate configuration 1 (i.e., the fast serving cell is changed to cell 124B) in response to determining that the signal strength or quality of cell 124B is higher than the second predetermined threshold.

[0128] In response to the determination, CU 172 sends 328 a fourth CU-to-DU message to DU 174 to activate configuration 1. In response to the fourth CU-to-DU message, DU 174 sends 330 a first configuration activation command to UE 102, and in some implementations, sends a fourth DU-to-CU message to CU 172. In some implementations, CU 172 includes a cell index 1 (e.g., a serving cell index) in the fourth CU-to-DU message. Thus, in some such implementations, DU 174 determines to activate configuration 1 based on cell index 1. In other implementations, CU 172 includes cell ID 1 in the fourth CU-to-DU message. Thus, in some such implementations, DU 174 determines to activate configuration 1 based on cell ID. In yet other implementations, CU 172 includes ID 1 in the fourth CU-to-DU message. Thus, in some such implementations, DU 174 determines 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).

[0129] In some implementations, when DU 174 determines to activate configuration 1 or sends the first configuration activation command as described above, DU 174 sends 329 a fifth DU to CU message to CU 172. In some implementations, CU 172 suspends or stops DL data transmission of UE 102 in response to the fifth DU to CU message. In further implementations, when suspending or stopping DL data transmission of UE 102, CU 172 buffers DL data of UE 102 received by CU 172 from the core network or edge server in further implementations. In some implementations, in the fifth DU to CU message, DU 174 indicates that a serving cell change has occurred (e.g., the serving cell is changed from cell 124A to cell 124B). In other implementations, in the fifth DU to CU message, DU 174 indicates that DL transmission of UE 102 is suspended or stopped.

[0130] In some implementations, the fifth DU to CU message is an existing F1AP message (e.g., as defined in 3GPP specification 38.473). In other implementations, the fifth DU to CU message is a dedicated F1AP message specifically defined to indicate the stop of DL transmission (e.g., defined in 3GPP specification 38.473 v18.0.0 and / or higher). In yet other implementations, the fifth DU to CU message is an existing frame (e.g., as defined in 3GPP specification 38.474). In yet other implementations, the fifth DU to CU message is a dedicated frame specifically defined to indicate the stop of DL transmission (e.g., defined in 3GPP specification 38.474 v18.0.0 and / or higher).

[0131] In some implementations, the first configuration activation command is a MAC CE included in a MAC PDU received by UE 102 from 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 higher). In some implementations, DU 174 includes a subheader identifying the MAC CE in the MAC PDU, and UE 102 identifies the MAC CE in the MAC PDU based on the subheader. In further implementations, the subheader includes a logical channel ID or an extended logical channel ID (e.g., defined in a 3GPP specification) to identify the MAC CE. For example, the logical channel ID or the extended logical channel ID is newly defined (e.g., defined in 3GPP specification 38.321 v18.0.0 and / or higher). In other implementations, the first configuration activation command is a DCI received by UE 102 on the PDCCH in event 330. DU 174 generates a CRC for the DCI, scrambles the CRC with the first C-RNTI of UE 102, and sends the DCI and the scrambled CRC on the PDCCH at event 330. In some implementations, the format of the DCI is an existing DCI format (e.g., defined in a 3GPP specification (e.g., 38.212)). In further implementations, the format of the DCI is a new DCI format (e.g., defined in a 3GPP specification (e.g., 38.212 v18.0.0 or later)).

[0132] In some implementations, DU 174 does not perform security protection (e.g., integrity protection and / or encryption) on the first configuration activation command. Avoiding such operations speeds up processing of the first configuration activation command in UE 102 because UE 102 does not need to spend time performing security checks (e.g., decryption and / or integrity checks) on the first configuration activation command.

[0133] In some implementations, after receiving the first configuration activation command, UE 102 sends 331 confirmation to DU 174 on cell 124A or cell 124D to indicate that UE 102 received the first configuration activation command. In some implementations, the confirmation is a HARQ ACK. In other implementations, the confirmation 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 higher). In yet other implementations, the confirmation is a PUCCH transmission.

[0134] In some implementations, CU 172 sends 316 the RRC reconfiguration message in response to the L3 measurement report for cell 124B received by CU 172 in event 306. In further implementations, CU 172 sends a first RRC reconfiguration message including a MeasConfig IE to UE 102 to configure UE 102 to send the L3 measurement report. In some implementations, DU 174 sends 330 a first configuration activation command in response to the L1 measurement report for cell 124B received by DU 174 in event 324. In further implementations, CU 172 sends a second RRC reconfiguration message including a CSI-MeasConfig IE to UE 102 to configure UE 102 to send the L1 measurement report. In some implementations, the first RRC reconfiguration message and the second RRC reconfiguration message are the same message (e.g., 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 of event 316. In other implementations, the second RRC reconfiguration message is different from the RRC reconfiguration message of event 316.

[0135] After receiving the first configuration activation command (e.g., in response thereto), the UE 102 identifies a specific configuration (e.g., configuration 1) according to a specific ID (e.g., ID1) and immediately applies configuration 1. In some implementations, the UE 102 performs 332 a random access procedure with the DU 174 on the cell 124B in response to applying configuration 1. In some implementations, the UE 102 disconnects from the cell 124A after receiving the first configuration activation command or sending an acknowledgement (e.g., in response thereto). In other words, after receiving 330 the first configuration activation command or sending 331 an acknowledgement (e.g., in response thereto), the UE 102 stops communicating on the cell 124A. In such a case, the UE 102 performs 332 a random access procedure after disconnecting from the cell 124A. In some implementations, the UE 102 determines whether to perform a random access procedure according to configuration 1. In some implementations, if configuration 1 configures UE 102 to perform a random access procedure, UE 102 performs a random access procedure in event 332. For example, configuration 1 includes a reconfiguration with synchronization configuration (e.g., ReconfigurationWithSync IE) to configure UE 102 to perform a random access procedure. Otherwise, if configuration 1 does not configure UE 102 to perform a random access procedure or configures UE 102 to skip a random access procedure, UE 102 avoids performing a random access procedure with DU 174 upon receiving a first configuration activation command. In such a case, UE 102 skips event 316. For example, if configuration 1 does not include a reconfiguration with synchronization configuration, configuration 1 configures 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.

[0136] In the case where the UE 102 performs 332 a random access procedure, the UE 102 communicates 336 with the DU 174 on the cell 124B using configuration 1, and communicates with the CU 172 via the DU 174 after successfully completing the random access procedure. For example, in event 318, the UE 102 transmits UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) with the base station 104. In such a case, when the UE 102 receives a 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 a UE identity 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 a UE identity 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 identity is the second C-RNTI of UE 102. Otherwise, if configuration 1 does not include a C-RNTI, the UE identity is the first C-RNTI. In the case where the random access procedure is a contention-free random access procedure, UE 102 sends a dedicated random access preamble to DU 174 via cell 124B. In such a case, configuration 1 includes a dedicated random access preamble.

[0137] Upon receiving the UE identification or dedicated preamble from UE 102 during the random access procedure, DU 174 identifies or determines that UE 102 is connected to cell 124B.

[0138] 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 instruct the UE 102 to apply 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 yet 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 is not disconnected from the cell 124A), the UE 102 sends the RRC message to the base station 104 via the cell 124A. In yet 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.

[0139] In some cases where the UE 102 skips the random access procedure, the UE 102, after (e.g., in response to) receiving the first configuration activation command, communicates 336 directly with the base station 104 on the cell 124B according to configuration 1. For example, in event 318, the UE 102 transmits UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) with the base station 104. In some such cases, after (e.g., in response to) receiving the first configuration activation command, the UE 102 sends 336 at least one PUCCH transmission to the DU 174 on the cell 124B according to configuration 1. In some implementations, after sending the first configuration activation command, the DU 174 sends at least one DCI on the PDCCH on the cell 124B to the UE 102 to command the UE 102 to send at least one PUCCH or PUSCH transmission. The DU 174 identifies or determines that the UE 102 is connected to the cell 124B after receiving the PUCCH or PUSCH transmission. In other implementations, the UE 102 sends at least one PUCCH or PUSCH transmission regardless of whether the DCI is received on the PDCCH on the cell 124B. The DU 174 identifies or determines that the UE 102 is connected to the cell 124B after 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 the cell 124B to instruct the UE 102 to apply configuration 1. The CU 172 identifies or determines that the UE 102 is connected to the cell 124B after receiving the RRC message. In other implementations, if the UE 102 maintains communication with the base station 104 on the cell 124A (i.e., the UE 102 is not disconnected from the cell 124A), the UE 102 sends the RRC message to the base station 104 via the cell 124A. In yet other implementations, UE 102 refrains from sending an RRC message to base station 104 in response to applying configuration 1 or receiving the first configuration activation command.

[0140] In some implementations, when DU 174 determines that UE 102 is successfully connected to cell 124B in event 332 or 336, DU 174 sends 334 a DU to CU message (e.g., an access success message) to CU 172. In some implementations, DU 174 includes the cell ID of cell 124B in the DU to CU message of event 334. Depending on the implementation, the cell ID is a PCI or a CGI. Therefore, CU 172 determines that UE 102 is connected to cell 124B upon receiving the DU to CU message of event 334. In further implementations, when DU 174 determines that UE 102 is successfully connected to cell 124B in event 332 or 336, DU 174 sends a DL data delivery status message or frame to CU 172. In some implementations, when CU 172 receives 334 the DU to CU message, CU 172 resumes or continues DL data transmission of UE 102. In further implementations, after resuming or continuing DL data transmission of UE 102 (eg, in response thereto), CU 172 sends the DL data of UE 102 to DU 174 , which in turn sends the DL data to UE 102 at event 336 .

[0141] In some implementations, upon determining that UE 102 is connected to cell 124B, sending 330 a first configuration activation command, or receiving 331 an acknowledgement, DU 174 stops communicating with UE 102 on cell 124A. In some implementations, upon determining that UE 102 is connected to cell 124B, sending 330 a first configuration activation command, or receiving 331 an acknowledgement, DU 174 releases resources of cell 124A configured for UE 102.

[0142] Events 304, 306, 390, 392, 316, 318, 320, 322 Figure 3 are collectively referred to as serving cell configuration process 380. Events 324, 326, 328, 330, 331, 332, 334, 336, 394 are Figure 3 It is collectively referred to as the service cell change process 382.

[0143] In some implementations, DU 174 generates configuration 1 and / or configuration 2, ..., N as a complete configuration, replacing 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 336 with each other 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 message of events 316, 318 includes an indication that configuration 1 is a complete configuration. In yet other implementations, the first container includes an indication that configuration 1 is a complete configuration. In yet 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, the indication of configuration 1 is different from the fullConfig field (e.g., defined in the current 3GPP specification). In other implementations, the indication of configuration 1 is the fullConfig field (e.g., defined in the current 3GPP specification) in the RRCReconfiguration message.

[0144] In other implementations, DU 174 generates configuration 1 and / or configuration 2, ..., N as incremental configurations, enhancing at least a portion 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 use configuration 1 to enhance at least a portion of the first configuration. Therefore, UE 102 and base station 104 communicate 336 with each other based on configuration 1 and the unenhanced portion 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 yet 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 full configuration based on the indication that configuration 1 is an incremental configuration. In some alternative implementations, configuration 1, the first container, or element 1 does not include an indication that configuration 1 is a full configuration to indicate that configuration 1 is an incremental configuration. In a further implementation, UE 102 determines that configuration 1 is an incremental configuration based on determining that the indication is not included in configuration 1, the first container, or element 1.

[0145] In some implementations, if configuration 1 is a full configuration, the UE 102 releases the first configuration or a specific configuration in the first configuration after (e.g., in response to) receiving 330 a first configuration activation command, sending 331 an acknowledgement, successfully performing 332 a random access procedure, or receiving a first DCI on a PDCCH addressed to a UE identity of the UE 102 on the cell 124B. In some implementations, if configuration 1 is a full configuration, the DU 174 releases the first configuration or a specific configuration in the first configuration after (e.g., in response to) sending 330 a first configuration activation command, receiving 331 an acknowledgement, successfully performing 332 a random access procedure, or receiving a specific transmission from the UE 102 on the cell 124B. In some implementations, the specific transmission is a PUCCH transmission. In further implementations, the transmission is a PUSCH transmission. In some implementations, after sending the first configuration activation command, DU 174 generates a DCI and a CRC for the DCI, scrambles the CRC using the UE identity of UE 102, and sends the DCI and the scrambled CRC on the 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.

[0146] In some implementations, the first configuration or the specific configuration is a first CellGroupConfig IE (ie, the first configuration includes configuration parameters defined in the first CellGroupConfig IE), and Configuration 1 is a second CellGroupConfig IE.

[0147] In some implementations, the UE 102 communicates with the DU 174 using a UE MAC entity (e.g., MAC 204B) (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). In some implementations, the base station 104 configures whether the UE 102 resets the UE MAC entity after receiving the first configuration activation command. In some implementations, the base station 104 includes a MAC reset indication in configuration 1 or element 1 to configure the UE 102 to reset the UE MAC entity, and does not include a MAC reset indication in configuration 1 or element 1 to configure the UE 102 not to reset the UE MAC entity. If configuration 1 or element 1 includes a MAC reset indication, the UE 102 resets the UE MAC entity in response to the MAC reset indication after receiving the first configuration activation command.

[0148] Otherwise, if configuration 1 or element 1 does not include a MAC reset indication, the UE 102 avoids resetting the UE MAC entity after receiving the first configuration activation command 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 full configuration, the UE 102 resets the UE MAC entity after receiving 330 to the first configuration activation command or upon receiving 330 to 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 full configuration, the UE 102 avoids resetting the UE MAC entity after receiving 330 to the first configuration activation command or upon receiving 330 to the first configuration activation command.

[0149] In some implementations, the base station 104 (e.g., DU 174 or CU 172) uses a DU MAC entity (e.g., NRMAC 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 a MAC reset indication in configuration 1 or element 1, the DU 174 resets the DU MAC entity in response to the MAC reset indication after sending 330 a first configuration activation command, receiving 331 an acknowledgement, or determining in events 332 or 336 that the UE 102 is connected to the cell 124B.

[0150] Otherwise, if configuration 1 or element 1 does not include a MAC reset indication, DU 174 avoids resetting the DU MAC entity after (e.g., in response to) sending 330 the first configuration activation command. Thus, after sending 330 the first configuration activation command, receiving 331 an acknowledgement, or determining in event 332 or 336 that UE 102 is connected to cell 124B, DU 174 continues to communicate with UE 102 using the retained (i.e., non-reset) DU MAC entity.

[0151] In some implementations, the DU 174 includes a MAC reset indication in a MAC-CellGroupConfig IE (e.g., CellGroupConfig IE) in Configuration 1. In other implementations, the DU 174 includes a MAC reset indication in the CellGroupConfig IE and outside the MAC-CellGroupConfig IE. In still other implementations, the DU 174 includes a MAC reset indication in Element 1 and outside Configuration 1.

[0152] In some implementations, if configuration 1 or element 1 does not include a MAC reset indication and includes an indication that configuration 1 is a full configuration, the DU 174 resets the DU MAC entity after sending 330 the first configuration activation command, receiving 331 an acknowledgement, or determining in event 332 or 336 that the UE 102 is connected to the cell 124B. Alternatively, the DU 174 releases the DU MAC entity and establishes a new DU MAC entity to communicate with the UE 102 via the cell 124B, rather than resetting the DU MAC entity. Otherwise, if configuration 1 or element 1 does not include a MAC reset indication and an indication that configuration 1 is a full configuration, the DU 174 avoids resetting the DU MAC entity after (e.g., in response to) sending 330 the first configuration activation command.

[0153] 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 the base station 104 does not include a MAC retention indication in the configuration or element to configure the UE 102 to reset the UE MAC entity. If the configuration or element includes the MAC retention indication, the UE 102 avoids resetting the UE MAC entity in response to the MAC retention indication after receiving a configuration activation command (e.g., a first configuration activation command). Otherwise, if the configuration or element does not include the MAC retention indication, the UE 102 resets the UE MAC entity after or when receiving the configuration activation command.

[0154] DU 174 communicates with UE 102 using a DU MAC entity (e.g., NR MAC 204B) (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). If base station 104 includes a MAC retention indication in a configuration or element (e.g., configuration 1 or element 1), DU 174 avoids resetting the DU MAC entity in response to the MAC retention indication after sending a configuration activation command (e.g., a first configuration activation command) to UE 102. Therefore, after sending 330 the first configuration activation command, receiving 331 an acknowledgment, or determining at event 332 or 336 that UE 102 is connected to cell 124B, DU 174 continues to communicate with UE 102 using the retained (i.e., non-reset) DU MAC entity.

[0155] In some implementations, the DU 174 includes the MAC reservation indication in a MAC-CellGroupConfig IE (e.g., CellGroupConfig IE) in Configuration 1. In other implementations, the DU 174 includes the MAC reservation indication in the CellGroupConfig IE and outside the MAC-CellGroupConfig IE. In still other implementations, the DU 174 includes the MAC reservation indication in Element 1 and outside Configuration 1.

[0156] Otherwise, if configuration 1 or element 1 does not include a MAC retention indication, the DU 174 resets the DU MAC entity after (eg, in response to) sending 330 the first configuration activation command.

[0157] 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 in configuration 1 or element 1 that configuration 1 is a complete configuration, the base station 104 avoids including a MAC reservation indication in configuration 1 or element 1. Otherwise, in further implementations, if the base station 104 does not include an indication in configuration 1 or element 1 that configuration 1 is a complete configuration, the base station 104 includes a MAC reservation indication in configuration 1 or element 1.

[0158] In some alternative implementations, the base station 104 (e.g., DU 174 or CU 172) includes a MAC partial reset indication in a configuration or element (e.g., configuration 1 or element 1) to configure the UE 102 to partially reset the UE MAC entity, and the base station 104 does not include a MAC partial reset indication in the configuration or element to configure the UE 102 to completely reset the UE MAC entity. If the configuration or element includes a MAC partial reset indication, the UE 102 partially resets the UE MAC entity upon receiving a configuration activation command (e.g., a first configuration activation command). Otherwise, if the configuration or element does not include a MAC partial reset indication, the UE 102 completely resets the UE MAC entity after (e.g., in response to) receiving the configuration activation command. In some implementations, when the UE partially resets the UE MAC entity, the UE 102 retains (e.g., maintains or keeps) the operating state of the UE MAC entity, or omits one or more actions that the UE 102 performs when the UE 102 completely resets the UE MAC entity in some implementations.

[0159] If the base station 104 includes a MAC partial reset indication in a configuration or element (e.g., configuration 1 or element 1), the DU 174 partially resets the DU MAC entity in response to the MAC partial reset indication after sending a configuration activation command (e.g., a first configuration activation command) to the UE 102.

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

[0161] Otherwise, if configuration 1 or element 1 does not include a MAC partial reset indication, the DU 174 completely resets the DU MAC entity after (e.g., in response to) sending 330 the first configuration activation command. 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 a MAC partial 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 a MAC partial 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 a MAC partial reset indication.

[0162] 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 an RRC message (e.g., events 316, 318) including the configuration or element. In such a case, the UE 102 partially resets the UE MAC entity after (e.g., in response to) receiving the first configuration activation command. In such a case, the DU 174 partially resets the DU MAC entity after sending the first configuration activation command, receiving 331 an acknowledgment, performing 336 a random access procedure with the UE 102, or determining that the UE 102 is connected to the cell 124B.

[0163] In some implementations, when the UE 102 determines to reset or reset the UE MAC entity as described above, the UE 102 resets the UE MAC entity before performing 332 a random access procedure or communicating 336 with the base station 104 via the cell 124B. In some implementations, when the UE 102 resets the UE MAC entity, the UE 102 performs at least one of the following actions on the UE MAC entity (i.e., a UE MAC reset or a complete UE MAC reset): (i) initializes Bj of the configured logical channel to zero; (ii) stops one or more timers; (iii) if the UE 102 is configured to perform a random access procedure (e.g., event 332) in the configuration (e.g., configuration 1), then the timeAlignmentTimer is considered to have expired; (iv) sets the UL (v) Set the New Data Indicator (NDI) of the HARQ process ID to a value of 0; (vi) Set the NDI of the HARQ process ID to a value of 0 to monitor the PDCCH in sidelink resource allocation mode 1; (vi) Refresh the Msg3 buffer; (vii) Refresh the MSGA buffer; (viii) Cancel (if any) the triggered scheduling request process; (ix) Cancel (if any) the triggered buffer status report process; (x) Cancel (if any) the triggered power headroom report process; (xi) Cancel (if any) the triggered consistent LBT failure; (xii) Cancel (if any) the triggered BFR; (xiii) Cancel (if any) the triggered (x) cancel (if any) the triggered sidelink buffer status reporting process; (xiv) cancel (if any) the triggered preemption buffer status reporting process; (xv) cancel (if any) the triggered timing advance reporting process; (xvi) cancel (if any) the triggered recommended bit rate query process; (xvii) cancel (if any) the triggered configured uplink grant confirmation; (xviii) cancel (if any) the triggered configured sidelink grant confirmation; (xix) cancel (if any) the triggered required protection symbol query; (xx) cancel (if any) the triggered positioning measurement gap activation / deactivation request process; (xxi) refresh the soft buffer of the DL HARQ process; (xxii) for each of the DL HARQ processes, regard the next received transmission of the TB as the first transmission; (xxiii) release (if any) the temporary C-RNTI; (xiv) reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER); (xxv), etc.

[0164] In some implementations, when DU 174 resets the DU MAC entity, DU 174 performs at least one of the following actions on the DU MAC entity (i.e., a DU MAC reset or a full DU MAC reset): (i) stops one or more timers; (ii) if in the configuration (e.g., configuration 1) UE 102 is configured to perform a random access process (e.g., event 332), then the timeAlignmentTimer started and / or maintained by DU 174 for UE 102 is considered to have expired; (iii) the NDI of the DL HARQ process is set to a value of 0; (iv) the soft buffer of the UL HARQ process is refreshed; (v) for each of the UL HARQ processes, the next received transmission of the TB is considered to be the first transmission; (vi) one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER) are reset; (vii), etc.

[0165] Depending on the implementation, the UE 102 determines to partially or completely reset the UE MAC entity. In some implementations, when the UE 102 resets the UE MAC entity as described above, the UE 102 completely resets the UE MAC entity (i.e., a complete UE MAC reset). In a complete UE MAC reset, the UE 102 performs some or all of the above actions. In other implementations, when the UE 102 resets the UE MAC entity as described above, the UE 102 partially resets the UE MAC entity (i.e., a partial UE MAC reset). In a partial UE MAC reset, the UE 102 performs a subset or portion of some or all of the actions in a complete UE MAC reset.

[0166] In some implementations, the 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), then the timeAlignmentTimer of UE 102 is considered to have expired; (ii) flushing the Msg3 buffer; (iii) flushing the MSGA buffer; (iv) releasing (if any) the temporary C-RNTI; and / or (v) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0167] In some implementations, the partial UE MAC reset further includes at least one of the following actions: (i) cancelling (if any) the triggered scheduling request process; (ii) cancelling (if any) the triggered buffer status reporting process; (iii) cancelling (if any) the triggered power headroom reporting process; (iv) cancelling (if any) the triggered consistent LBT failure; (v) cancelling (if any) the triggered BFR; (vi) cancelling (if any) the triggered sidelink buffer status reporting process; (vii) cancelling (if any) the triggered preemption buffer status reporting process; (viii) cancelling (if any) the triggered timing advance reporting process; (ix) cancelling (if any) the triggered recommended bit rate query process; (x) cancelling (if any) the triggered configured uplink grant confirmation; (xi) cancelling (if any) the triggered configured sidelink grant confirmation; (xii) cancelling (if any) the triggered required protection symbol query; and / or (xiii) cancelling (if any) the triggered positioning measurement gap activation / deactivation request process.

[0168] In some implementations, the partial UE MAC reset further includes at least one of the following actions: (i) stopping a first portion of one or more timers and retaining the remainder of one or more timers; (ii) setting a new data indicator (NDI) for the UL HARQ process to a value of 0; (iii) setting the NDI for the HARQ process ID to a value of 0 in order to monitor the PDCCH in sidelink resource allocation mode 1; (iv) flushing soft buffers for the DL HARQ processes; and / or (v) for each of the DL HARQ processes, treating the next received transmission of the TB as the first transmission.

[0169] Depending on the implementation, DU 174 determines to partially or completely reset the DU MAC entity. In some implementations, when DU 174 resets the DU MAC entity as described above, DU 174 completely resets the DU MAC entity (i.e., a complete DU MAC reset). In a complete 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 UE MAC entity (i.e., a partial DU MAC reset). In a partial DU MAC reset, DU 174 performs a subset or portion of some or all of the actions in a complete DU MAC reset.

[0170] In some implementations, the 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 the configuration (e.g., configuration 1), then the timeAlignmentTimer started and / or maintained by DU 174 for UE 102 is deemed to have expired; and / or (ii) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0171] In some implementations, a partial DU MAC reset includes performing at least one of the following actions on the MAC entity (i.e., a DU MAC reset): (i) stopping a first portion of one or more timers and retaining the remainder of one or more timers; (ii) setting the NDI for the DL HARQ process to a value of 0; (iii) flushing the soft buffers for the UL HARQ processes; (iv) for each of the UL HARQ processes, treating the next received transmission of the TB as the first transmission; and / or (v) resetting one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0172] In some implementations, configuration 1 includes or does not include one or more RLC reestablishment indications (e.g., reestablishRLC fields) that configure the UE 102 to reestablish one or more RLC entities (e.g., RLC 206B) that the UE 102 uses to communicate with the DU 174 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). If configuration 1 includes an RLC reestablishment indication that configures the UE 102 to reestablish an RLC entity (e.g., RLC 206B) that the UE 102 uses to transmit RLC PDUs with the base station 104 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331), the UE 102 reestablishes the RLC entity in response to the RLC reestablishment indication. In some implementations, the UE 102 reestablishes the RLC entity before performing 332 a random access procedure or communicating 336 with the base station 104 via the cell 124B. In other implementations, the UE 102 reestablishes the RLC entity when or after performing the random access procedure 332. In some implementations, when the UE 102 reestablishes the RLC entity, the UE 102 performs at least one of the following actions on the RLC entity: (i) discarding the RLC SDU, RLC SDU fragment, and RLC PDU (if any); (ii) stopping and resetting the timer (if running); (iii) resetting the state variable to an initial value. In some implementations, the state variables and timers are currently defined (e.g., defined in 3GPP specification 38.322).

[0173] Otherwise, if configuration 1 does not include an RLC re-establishment indication for the RLC entity, the UE 102 avoids re-establishing the RLC entity after receiving the first configuration activation command or upon receiving the first configuration activation command. In other words, the UE 102 avoids performing an action to re-establish the RLC entity of the UE 102 after receiving the first configuration activation command or upon receiving the first configuration activation command. In some implementations, if configuration 1 or element 1 does not include an RLC re-establishment indication and includes an indication that configuration 1 is a complete configuration, the UE 102 re-establishes the RLC entity of the UE 102 after receiving the first configuration activation command or upon receiving the first configuration activation command. Otherwise, if configuration 1 or element 1 does not include an RLC re-establishment indication and an indication that configuration 1 is a complete configuration, the UE 102 avoids re-establishing the RLC entity after receiving the first configuration activation command or upon receiving the first configuration activation command.

[0174] Similarly, DU 174 reestablishes the RLC entity (e.g., NR RLC 206B) used by DU 174 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 acknowledgment of the first configuration activation command from UE 102, or determining that UE 102 is connected to cell 124B. In some implementations, the acknowledgment is a HARQ ACK. In other implementations, the acknowledgment is a MAC CE. In yet other implementations, the acknowledgment is a PUCCH transmission. In some implementations, when the base station 104 reestablishes the RLC entity, the DU 174 performs at least one of the following actions on the RLC entity: (i) discarding the RLC SDU, RLC SDU fragment, and RLC PDU (if any); (ii) stopping and resetting the timer (if running); and / or (iii) resetting the state variable to an initial value. In some implementations, the state variables and timers are currently defined (e.g., defined in 3GPP specification 38.322).

[0175] In some implementations, the above description for configuration 1 also applies to configuration 2, ..., N.

[0176] In some implementations, after determining that UE 102 is connected to cell 124B (e.g., in response thereto), CU 172 sends 338 a CU-to-DU message (e.g., a UE context modification request message) to DU 174 to instruct DU 174 to cease communicating with UE 102 and / or release or suspend resources of cell 124A configured for UE 102. In further implementations, in response, DU 174 ceases communicating with UE 102 on cell 124A, releases or suspends resources of cell 124A configured for UE 102, and / or sends 340 a DU-to-CU message (e.g., a UE context modification response message) to CU 172. Events 338 and 340 occur at the same time. Figure 3 are collectively referred to as process 394 (e.g., UE context modification process).

[0177] Next reference 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 operates cell 124B, while T-DU 174B operates cell 124C. Scenario 400 is similar to scenario 300. Therefore, the description of scenario 300 can generally apply to scenario 400. Specifically, the description of cell 124B in scenario 300 can apply to cell 124C. Events 404, 406, 490, 492, 416, 418, 420, 422 are described in detail in FIG. Figure 4 are collectively referred to as serving cell configuration process 480. Events 424, 426, 428, 430, 431, 432, 434, 436, 494 are Figure 4 It is collectively referred to as the service cell change process 482.

[0178] In some implementations, after determining that the UE 102 is connected to the cell 124C (e.g., in response thereto), the CU 172 sends 438 a 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 440 a DU-to-CU message (e.g., a UE context release complete message) to the CU-172. Alternatively, the CU 172 sends 438 a CU-to-DU message (e.g., a UE context modification request message) to the S-DU 174A to instruct the S-DU 174A to stop communicating with the UE 102 and / or to release or suspend resources of the cell 124A configured for the UE 102. In response, in some such implementations, the S-DU 174A ceases communicating with the UE 102 on the cell 124A, releases or suspends resources of the cell 124A configured for the UE 102, and / or sends 440 a DU to CU message (e.g., a UE Context Modification Response message) to the CU-172.

[0179] Next reference Figure 5AIn scenario 500A, base station 106 acts as a MN and base station 104 acts as a SN. SN 104 includes CU 172 and DU 174. Scenario 500A is similar to scenario 300, except that scenario 500A is a DC scenario, while scenario 300 is a single connection (SC) scenario. Initially, UE 102 in DC communicates with MN 106 and SN 104. In event 502, UE 102 communicates with DU 174 on cell 124A using a first configuration, and communicates with CU 172 via DU 174, similar to event 302. In some implementations, UE 102 in DC transmits 502 UL PDUs and / or DL ​​PDUs with MN 106 and / or SN 104 via radio bearers, and in some further implementations, these radio bearers include SRBs and / or DRBs. In a further implementation, the MN 106 and / or the SN 104 configure a radio bearer to the UE 102. The UE 102 in DC transmits 502 UL PDUs and / or DL ​​PDUs with the SN 104 on the SCG that the SN 104 configures for communicating with the UE 102. The UE 102 in DC transmits UL PDUs and / or DL ​​PDUs with the MN 106 on the MCG according to the MN configuration (i.e., the MCG configuration). In some implementations, the first configuration is the SN configuration (i.e., the SCG configuration). In the MN configuration, the MN 106 configures an MCG that includes at least one service cell operated by the MN 106 (e.g., the cell 126 and / or other cells). In the first configuration, the SN 106A configures an SCG that includes at least one service cell operated by the SN 104 (e.g., the cell 124A and / or other cells). In some implementations, the MN configuration includes a plurality of configuration parameters, and UE 102 receives the configuration parameters in one or more RRC messages from MN 106. In other implementations, the first configuration includes a plurality of configuration parameters, and UE 102 receives the configuration parameters in one or more RRC messages from SN 104 (e.g., via MN 106) or on an SRB (e.g., SRB3) that MN 106 or SN 104 configures for exchanging RRC messages between UE 102 and SN 104.

[0180] In some implementations, when communicating with MN 106 and SN 104 under DC, MN 106 performs 580 a fast serving cell configuration procedure with UE 102, similar to process 380. In some implementations, when communicating with MN 106 and SN 104 under DC, UE 102 sends at least one measurement report to CU 172 via DU 174 and cell 124A in events 504 and 506, similar to events 304 and 306, respectively. In other implementations, when communicating with MN 106 and SN 104 under DC, UE 102 sends 505 at least one measurement report to MN 106 via cell 126. MN 106 in turn sends 507 at least one measurement report to CU 172. In some implementations, MN 106 generates at least one SN message including at least one measurement report, and sends at least one SN message to 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.

[0181] After receiving at least one measurement report (e.g., in response thereto) or while base station 104 is communicating with UE 102, base station 104 determines to prepare cell 124B for UE 102, such as for Figure 3 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, respectively. After receiving the first configuration activation command, sending an acknowledgment, or determining that UE 102 is connected to cell 124B, UE 102 operating with MN 106 and SN 104 in DC communicates 536 with SN 104 on cell 124B according to configuration 1, similar to event 336.

[0182] Events 504, 506, 505, 507, 590, 592, 516, 518, 520, 522 Figure 5A Events 524, 526, 528, 530, 531, 532, 534, 536, 594 are collectively referred to as serving cell configuration process 581A. Figure 5A It is collectively referred to as the service cell change process 583.

[0183] Next reference Figure 5B, scenario 500B is substantially similar to scenario 500A, except that SN 104 sends 517, 519 RRC reconfiguration messages to UE 102 via MN 106 and receives 521, 523 RRC reconfiguration complete messages from UE 102 via MN 106. In some implementations, SN 104 generates a first SN message (e.g., an SN modification required message, an SN modification required message, or an RRC transfer message) that includes the RRC reconfiguration message, and sends the first SN message to MN 106 at event 517. In some implementations, MN 106 generates a second SN message (e.g., an SN reconfiguration complete message or an RRC transfer message) that includes the RRC reconfiguration complete message, and sends the second SN message to SN 104 at event 523.

[0184] Events 504, 506, 505, 507, 590, 592, 517, 519, 521, 523 Figure 5B It is collectively referred to as the service cell configuration process 581B.

[0185] Next reference Fig. 6A In scenario 600A, base station 106 acts as a MN and base station 104 acts as a SN, similar to scenarios 300 to 500B. SN 104 includes CU 172, S-DU 174A, and T-DU 174B, similar to base station 104 in scenario 400. Events 604, 606, 605, 607, 690, 692, 616, 618, 620, 622 are Fig. 6A Events 624, 626, 628, 630, 631, 632, 634, 636, 694 are collectively referred to as serving cell configuration process 681A. Fig. 6A 600A, but also one or both of the S-DU 174A or T-DU 174B (e.g., events 608, 610, 632, 634, etc.).

[0186] Next reference Figure 6B Scenario 600B is similar to scenarios 300 to 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. Events 604, 606, 605, 607, 690, 692, 617, 619, 621, 623 are Figure 6B It is collectively referred to as the service cell configuration process 681B.

[0187] Next reference Fig. 7A In scenario 700A, base station 104 acts as a MN and a SN, similar to scenarios 300 to 600B. Base station 104 includes CU 172, a master DU (M-DU) 174A, and a secondary DU (S-DU) 174B. CU 172 and M-DU 174A act as a MN, similar to Figure 3 Base station 104 or FIG. 5A to FIG. 6B MN 106 in, and CU 172 and S-DU 174B act as SN, similar to FIG. 5A to FIG. 6B SN 104 in.

[0188] In scenario 700A, UE 102 initially communicates 702 with M-DU 174A and S-DU 174B in DC, and communicates 702 with CU 172 via M-DU 174A and S-DU 174B. At event 702, UE 102 communicates with S-DU 174B on cell 124A and communicates with CU 172 via S-DU 174B using a first configuration. Events 704 and 706 are similar to events 304 and 306. In some implementations, UE 102 sends 705 at least one measurement report to M-DU 174A, similar to event 304. M-DU 174A in turn sends 707 at least one DU-to-CU message including at least one measurement report to CU 172, similar to event 306.

[0189] Events 704, 706, 705, 707, 790, 792, 716, 718, 720, 722 Fig. 7A Events 724, 726, 728, 730, 731, 732, 734, 736, 794 are collectively referred to as serving cell configuration process 781A. Fig. 7A It is collectively referred to as the service cell change process 783.

[0190] Next reference Figure 7B Scenario 700B is similar to scenarios 300 to 600B and 700A, except that CU 172 sends 717, 719 RRC reconfiguration messages to UE 102 via M-DU 174A and receives 721, 723 RRC reconfiguration complete messages from UE 102 via M-DU 174A. Events 704, 706, 705, 707, 790, 792, 717, 719, 721, 723 are Figure 7B It is collectively referred to as the service cell configuration process 781B.

[0191] Next reference Fig. 8AIn scenario 800A, base station 104 acts as a MN and a SN, similar to scenarios 300 to 700B. Base station 104 includes CU 172, master DU (M-DU) 174A, secondary DU (S-DU) 174B, and T-DU 174C. CU 172 acts as a MN with M-DU 174A and as a SN with S-DU 174B. Events 804, 806, 805, 807, 890, 892, 816, 818, 820, 822 are described in detail in detail. Fig. 8A Events 824, 826, 828, 830, 831, 832, 834, 836, 894 are collectively referred to as serving cell configuration process 881A. Fig. 8A 800A, but may also be applicable to one, some or all of the M-DU 174A, S-DU 174B or T-DU 174C (e.g., events 808, 810, 832, 834, etc.).

[0192] Next reference Figure 8B Scenario 800B is similar to scenarios 300 to 700B and 800A, except that CU 172 sends 817, 819 RRC reconfiguration messages to UE 102 via M-DU 174A and receives 821, 823 RRC reconfiguration complete messages from UE 102 via M-DU 174A. Events 804, 806, 805, 807, 890, 892, 817, 819, 821, 823 are Fig. 8A It is collectively referred to as the service cell configuration process 881B.

[0193] Next, refer to 9A to 12B Several example methods that may be implemented in a UE (e.g., UE 102) or a RAN node (e.g., base station 104 / 106 or DU 174) to handle data communications in a serving cell change are discussed. Figures 3 to 8B The examples and implementations described can be applied to 9A to 12B .

[0194] Fig. 9A An example method 900A is shown that may be implemented by a DU (eg, DU 174) for handling data communications in a serving cell change with a UE (eg, UE 102).

[0195] Method 900A begins at block 902, where the DU communicates with the UE via a first cell using a first plurality of configuration parameters (e.g., events 302, 380, 402, 480, 502, 580, 582, 581A, 581B, 602, 680, 682, 681A, 681B, 702, 780, 782, 781A, 781B, 802, 880, 882, 881A, 881B). At box 904, the DU sends a configuration for later activation to the UE and the CU, where the configuration configures the second cell (e.g., events 310, 316, 318, 380, 410, 416, 418, 480, 510, 516, 518, 517, 519, 580, 581A, 581B, 610, 616, 618, 617, 619, 680, 681A, 681B, 710, 716, 718, 717, 719, 780, 781A, 781B, 810, 816, 818, 817, 819, 880, 881A, 881B). At block 906, the DU sends a configuration activation command to the UE to activate the configuration (e.g., events 330, 382, ​​430, 482, 530, 583, 582, 630, 683, 682, 730, 783, 782, 830, 883, 882). At block 908, the DU sends a DU-to-CU message to the CU to indicate that a serving cell change is or will be initiated in response to the activation of the configuration (e.g., events 329, 382, ​​429, 482, 529, 583, 582, 629, 683, 682, 729, 783, 782, 829, 883, 882).

[0196] Fig. 9B is a flow chart of an example method 900B that is similar to method 900A, except that method 900B includes block 909 instead of block 908. At block 909, the DU sends a DU-to-CU message to the CU to suspend DL data transmission to the DU in response to activating the configuration (e.g., events 329, 382, ​​429, 482, 529, 583, 582, 629, 683, 682, 729, 783, 782, 829, 883, 882).

[0197] Fig. 10A An example method 1000A is shown that may be implemented by a CU (eg, CU 172) for handling data communications in a serving cell change with a UE (eg, UE 102).

[0198] Method 1000A begins at box 1002, where the CU communicates with the UE via a first DU and a first cell (e.g., events 302, 380, 402, 480, 502, 580, 582, 581A, 581B, 602, 680, 682, 681A, 681B, 702, 780, 782, 781A, 781B, 802, 880, 882, 881A, 881B). At box 1004, the CU receives a configuration for later activation from the first DU or the second DU, where the configuration configures the second cell (e.g., events 310, 380, 410, 480, 510, 580, 581A, 581B, 680, 681A, 681B, 710, 780, 781A, 781B, 810, 880, 881A, 881B). At box 1006, the CU sends a configuration for later activation (e.g., events 316, 318, 380, 416, 418, 480, 516, 518, 517, 519, 580, 581A, 581B, 616, 618, 617, 619, 680, 681A, 681B, 716, 718, 717, 719, 780, 781A, 781B, 816, 818, 817, 819, 880, 881A, 881B) to the UE via the first DU. At box 1008, the CU receives a first DU-to-CU message from the first DU, the first DU-to-CU message indicating that a serving cell change is initiated or is to be initiated for the UE (e.g., events 329, 382, ​​429, 482, 529, 583, 582, 629, 683, 682, 729, 783, 782, 829, 883, 882). At box 1010, the CU suspends DL transmission for the UE after (e.g., in response to) the first DU-to-CU message. At box 1012, the CU receives a second DU-to-CU message from the first DU or the second DU, the second DU-to-CU message indicating that the UE is connected to a second cell (e.g., events 334, 382, ​​434, 482, 534, 583, 582, 634, 683, 682, 734, 783, 782, 834, 883, 882). At block 1014, the CU resumes DL transmission to the UE after (e.g., in response to) the second DU-to-CU message (e.g., events 336, 382, ​​436, 482, 536, 583, 582, 636, 683, 682, 736, 783, 782, 836, 883, 882).

[0199] Fig. 10Bis a flow chart of an example method 1000A similar to method 1000B, except that method 1000B includes block 1009 instead of block 1008. At block 1009, the CU receives a first DU-to-CU message from a first DU, the first DU-to-CU message indicating a pause or stop of DL data transmission for the UE (e.g., events 329, 382, ​​429, 482, 529, 583, 582, 629, 683, 682, 729, 783, 782, 829, 883, 882).

[0200] Fig.11 A method 1100 is shown that can be implemented by a UE (e.g., UE 102) for managing data communications with a RAN (e.g., DU 174, CU 172, base station 104 / 106, or RAN 105).

[0201] Method 1100A begins at box 1102, where the UE transmits data with the RAN via a first cell and radio bearer using a first configuration (e.g., events 302, 380, 402, 480, 502, 580, 582, 581A, 581B, 602, 680, 682, 681A, 681B, 702, 780, 782, 781A, 781B, 802, 880, 882, 881A, 881B). At block 1104, the UE receives from the RAN a second configuration for later activation, the second configuration configuring a serving cell change from the first cell to the second cell (e.g., events 316, 318, 380, 416, 418, 480, 516, 518, 517, 519, 580, 581A, 581B, 616, 618, 617, 619, 680, 681A, 681B, 716, 718, 717, 719, 780, 781A, 781B, 816, 818, 817, 819, 880, 881A, 881B). At block 1106, the UE continues to communicate data with the RAN via the first cell and the radio bearer before receiving a configuration activation command to activate the second configuration. At block 1108, the UE receives a configuration activation command from the RAN to activate the second configuration (e.g., events 330, 382, ​​430, 482, 530, 583, 582, 630, 683, 682, 730, 783, 782, 830, 883, 882). At block 1110, the UE suspends the radio bearers. In some implementations, at block 1112, the UE performs a random access procedure with the RAN via the second cell in response to the configuration activation command (e.g., events 332, 382, ​​432, 482, 532, 583, 582, 632, 683, 682, 732, 783, 782, 832, 883, 882). At block 1114, the UE resumes the radio bearers after connecting to the second cell. At block 1116, the UE communicates data with the RAN via the second cell and radio bearer using the second configuration (e.g., events 336, 382, ​​436, 482, 536, 583, 582, 636, 683, 682, 736, 783, 782, 836, 883, 882).

[0202] Fig. 12A An example method 1200A is shown that may be implemented by a CU (eg, CU 172) for handling data communications in a serving cell change with a UE (eg, UE 102).

[0203] Method 1200A begins at box 1202, where the CU communicates with the UE via a first DU and a first cell (e.g., events 302, 380, 402, 480, 502, 580, 582, 581A, 581B, 602, 680, 682, 681A, 681B, 702, 780, 782, 781A, 781B, 802, 880, 882, 881A, 881B). At block 1204, the CU receives measurement results for the second cell from the UE (e.g., events 304, 306, 380, 404, 406, 480, 504, 506, 505, 507, 580, 581A, 581B, 604, 606, 605, 607, 680, 681A, 681B, 704, 706, 705, 707, 780, 781A, 781B, 804, 806, 805, 807, 880, 881A, 881B). At block 1206, the CU determines whether the second cell is operated by a DU connected to the CU. If the CU determines at block 1206 that the second cell is operated by a DU connected to the CU, the process proceeds to block 1208. At box 1208, the CU obtains a configuration for later activation of the UE (e.g., events 310, 380, 410, 480, 510, 580, 581A, 581B, 680, 681A, 681B, 710, 780, 781A, 781B, 810, 880, 881A, 881B) from a DU (e.g., a first DU or a second DU). At block 1210, the CU sends a configuration for later activation to the UE via the first DU (e.g., events 316, 318, 380, 416, 418, 480, 516, 518, 517, 519, 580, 581A, 581B, 616, 618, 617, 619, 680, 681A, 681B, 716, 718, 717, 719, 780, 781A, 781B, 816, 818, 817, 819, 880, 881A, 881B). Otherwise, if the CU determines at block 1206 that the second cell is not operated by the DU connected to the CU, the flow proceeds to block 1212. At block 1212, the CU avoids obtaining a configuration for configuring the second cell and later activation for the UE. In some implementations, at block 1214, the CU sends an RRC message to the UE to hand over the UE to the second cell.

[0204] Fig. 12B1 is a flow chart of an example method 1200A similar to method 1200B, except that method 1200B includes block 1207 instead of block 1206. At block 1207, the CU determines whether the second cell is operated by another base station. If the CU determines at block 1207 that the second cell is operated by another base station, the flow proceeds to block 1208. Otherwise, if the CU determines that the second cell is not operated by another base station (i.e., the second cell is operated by the base station), the flow proceeds to block 1212.

[0205] The following description may be applicable to the above description.

[0206] In general, the description of one of the above figures may apply to another figure in the above figures. If there is no conflict, the above examples, implementations and methods may be combined. The events or boxes described above may be optional or omitted. For example, the events or boxes with dashed lines in the figure may be optional. In some implementations, "message" is used and "information element (IE)" can be used to replace "message", and vice versa. In some implementations, "IE" is used and "field" can be used to replace "IE", and vice versa. In some implementations, "configuration" can be replaced by "multiple configurations" or "configuration parameters", and vice versa. In some implementations, "configuration activation command" can be replaced by "serving cell change command", "layer 1 / layer 2 switching command", "lower layer switching command" or "lower layer serving cell change command". "Fast serving cell configuration process" can be replaced by "fast serving cell change process".

[0207] The user device (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. In addition, in some cases, the user device can be embedded in an electronic system (such as a head unit of a vehicle or an advanced driver assistance system (ADAS)). Further, the user device can be operated as an Internet of Things (IoT) device or a mobile Internet device (MID). Depending on the type, the user device may include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0208] Certain embodiments are described in the present disclosure as including logic or multiple components or modules. A module may be a software module (e.g., a code or machine-readable instruction stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit that is capable of performing certain operations and may be configured or arranged in a certain manner. A hardware module may include a dedicated circuit system or logic that is permanently configured to perform certain operations (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.). A hardware module may also include a programmable logic or circuit system (e.g., as contained in a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in a dedicated and permanently configured circuit system or in a temporarily configured circuit system (e.g., configured by software) may be driven by cost and time considerations.

[0209] When implemented in software, the techniques may be provided as part of an operating system, as a library used by multiple applications, as a specific software application, etc. The software may be executed by one or more general-purpose processors or by one or more special-purpose processors.

Claims

1. A method in a distributed base station comprising a centralized unit CU and a distributed unit DU, the method comprising: sending, via the DU, to a user equipment UE in a first cell, a configuration for performing a serving cell change to a second cell after an activation command; as well as In response to receiving a DU to CU message after sending the configuration but before receiving an indication that the UE is connected to the second cell, downlink (DL) transmission of data packets to the UE is suspended.

2. The method of claim 1, further comprising: In response to receiving the indication that the UE is connected to the second cell, resuming the DL transmission of the data packets to the UE.

3. The method of claim 1 or 2, wherein pausing the DL transmission comprises: The data packets are buffered at the CU.

4. The method according to any one of the preceding claims, further comprising: After sending the configuration, sending the activation command to the UE.

5. The method of claim 4, further comprising: sending, together with the configuration, an identifier assigned to the configuration, The identifier is included in the activation command.

6. The method of claim 5, wherein: The configuration and the identifier assigned to the configuration are sent in a Radio Resource Control, RRC, message.

7. The method according to any one of claims 4 to 6, wherein sending the activation command is in response to receiving a layer 1 L1 measurement report from the UE.

8. The method of claim 7, further comprising: An L1 measurement configuration is provided to the UE, wherein the L1 measurement report is generated according to the L1 measurement configuration.

9. The method of any one of the preceding claims, wherein the DU to CU message includes an indication to initiate the serving cell change.

10. The method of any one of claims 1 to 8, wherein the DU to CU message comprises a request to suspend the DL transmission of data packets.

11. A method as claimed in any one of the preceding claims, wherein the DU is a first DU; The method further comprises: Before sending the configuration, communicating with the UE in the first cell via the first DU; as well as The configuration for performing the serving cell change is received from the second DU.

12. A method as claimed in any one of the preceding claims, wherein: The distributed base station acts as a secondary node SN to support dual activities of the UE via a master node MN and the SN.

13. A method as claimed in any one of the preceding claims, wherein: The distributed base station acts as a MN to support dual activities of the UE via the MN and the SN.

14. A method in a distributed base station comprising a distributed unit DU and a centralized unit CU, the method comprising: communicating with a user equipment UE in a first cell according to a first configuration parameter; sending, to the UE, a configuration for performing a serving cell change to a second cell after an activation command; sending the activation command to the UE in response to the measurement report; as well as In response to sending the activation command, an indication to suspend downlink (DL) transmission of data packets to the UE is sent to the CU.

15. A node in a Radio Access Network, RAN, comprising processing hardware and configured to implement the method of any preceding claim.

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