Managing communication failures in user equipment

Abstract

A user equipment (UE) communicates with a RAN in a first cell according to a first configuration. The UE receives, from the RAN, a message including a configuration for performing a serving cell change to the second cell after the activation command; detecting a communication failure with the RAN prior to receiving the activation command; and in response to the detection, performing at least one of (i) performing the RRC reestablishment process, or releasing the second configuration.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit and priority of the filing date of the provisional U.S. Patent Application No. 63 / 377,723, filed on September 29, 2022, entitled "MANAGING RADIO LINK CONTROL PROTOCOL OPERATION FOR A FAST SERVING CELL CHANGE". The entire content of the provisional application is hereby incorporated by reference in its entirety. Technical Field

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

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

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

[0006] Depending on the scenario, the UE uses several types of SRBs and DRBs. When operating in dual connectivity (DC), the cell associated with the base station operating as the master node (MN) defines the master cell group (MCG), and the cell associated with the base station operating as the secondary node (SN) defines the secondary cell group (SCG). SRB1 resources carry RRC messages that include NAS messages on a dedicated control channel (DCCH) in some cases, and SRB2 resources support RRC messages that include logged measurement information or NAS messages also on the DCCH but with a lower priority than SRB1 resources. More generally, SRB1 and SRB2 resources allow the UE and the MN to exchange RRC messages related to the MN and embed RRC messages related to the SN, and can be referred to as MCG SRBs. SRB3 allows the UE and the SN to exchange RRC messages related to the SN, and can be referred to as SCG SRBs. Split SRBs allow the UE to directly exchange RRC messages with the MN via the lower layer resources of the MN and the SN. Further, a DRB that uses only the lower layer resources of the MN can be referred to as an MCG DRB, a DRB that uses only the lower layer resources of the SN can be referred to as an SCG DRB, and a DRB that uses the lower layer resources of both the MCG and the SCG can be referred to as a split DRB.

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

[0008] When a UE moves from the coverage area of one cell in the RAN to another cell, at a certain moment, a serving cell change will be performed for the UE. To perform the serving cell change, the RAN configures the UE to send layer 3 (L3) measurement results. Based on the L3 measurement results received from the UE, the RAN sends an RRC reconfiguration message configured with synchronized reconfiguration (e.g., the RRC reconfiguration message includes a ReconfigurationWithSync IE) to change the serving cell (e.g., the PCell or the PSCell). In a case where the UE operates in carrier aggregation (CA) of at least one secondary cell (SCell) with the PCell or the PSCell, the RAN must release at least one SCell due to the change of the PCell or the PSCell. The serving cell change involves a complete L2 (and L1) reset, resulting in longer latency, greater overhead, and longer interruption time. Therefore, it is desirable to develop new mobility technologies to reduce the latency and overhead 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 of the present disclosure is a method implemented in a UE. The method includes communicating with the RAN in a first cell according to a first configuration; receiving, from the RAN, a message including a configuration for performing a serving cell change to a second cell after an activation command; detecting a communication failure with the RAN before receiving the activation command; and in response to the detection, performing at least one of the following: (i) performing a radio resource control (RRC) reconstruction process, or releasing a second configuration.

[0010] Another example embodiment of these technologies is a method implemented in a UE. The method includes communicating with the RAN in a first cell according to a first configuration; receiving, from the RAN, a message including a configuration for performing a serving cell change to a second cell after an activation command; detecting a communication failure with the RAN before receiving the activation command; in response to the detection, retaining the second configuration; and connecting to the second cell according to the second configuration.

[0011] Yet another example implementation of these technologies is a UE, which includes: a transceiver; and processing hardware configured to implement the method according to any one of the foregoing claims. Brief Description of the Drawings

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

[0013] Figure 1B is included inFigure 1A Block diagram of an example base station with a Centralized Unit (CU) and a Distributed Unit (DU) operating in a system;

[0014] Figure 2 is Figure 1A Block diagram of an example protocol stack by which a UE communicates with a base station; and

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

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

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

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

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

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

[0021] Figure 7A is with Figure 5A a messaging diagram of an example scenario similar to the example scenario, but in which the base station operates 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 Figure 7A a messaging diagram of an example scenario similar to the example scenario, but in which the MN directly configures the UE;

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

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

[0025] Figure 9A is a message passing diagram of an example scenario where the split base station configures the UE to perform the lower layer procedures of the cell change operation and performs additional RRC procedures with the UE after the UE determines the failure of the cell change operation;

[0026] Figure 9B is similar to Figure 9A A message passing diagram of an example scenario similar to the example scenario, but where the base station releases the UE context instead of modifying the UE context;

[0027] Figure 9C is similar to Figure 9A A message passing diagram of an example scenario similar to the example scenario, but where the UE communicates with the prepared cell or performs a recovery process;

[0028] Figure 9D is similar to Figure 9C A message passing diagram of an example scenario similar to the example scenario, but where the target DU communicates with the UE on the prepared cell;

[0029] Figure 10A is a flowchart depicting an example method implemented in the UE, where the UE determines that a communication failure has occurred, performs protocol procedures, and releases the configuration for later activation;

[0030] Figure 10B is a flowchart depicting an example method similar to Figure 10A the example method, but where the UE retains the configuration for later activation;

[0031] Figure 10C is a flowchart depicting an example method similar to Figure 10A and Figure 10B the example method, but where the UE determines whether to release or retain the configuration based on whether the communication failure is with the MN or SN of the RAN;

[0032] Figure 10D is a flowchart depicting an example method similar to Figure 10C the example method, but where the UE determines whether to activate the configuration or perform protocol procedures based on whether the selected cell is configured in the configuration;

[0033] Figure 11A is a flowchart depicting an example method implemented in the UE, where the UE activates the configuration for later activation, performs a random access procedure, and communicates with the RAN using the previous configuration;

[0034] Figure 11B is a flowchart depicting an example method similar toFigure 11A The flowchart of an example method similar to the example method, but where the UE determines whether to communicate with the RAN or execute a protocol procedure based on whether the random access procedure fails;

[0035] Figure 12 is a flowchart depicting an example method implemented in a UE, where the UE determines whether to activate a configuration for later activation based on whether the UE receives a configuration activation command or a communication failure occurs. Detailed implementation

[0036] Figure 1A Depicts an example wireless communication system 100 in which a communication device may implement these techniques. The wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106, and a core network (CN) 110. The UE 102 is initially connected to the base station 104. In some scenarios, the base station 104 may perform SN addition to configure the UE 102 to operate with the base station 104 and the base station 106 under dual connectivity (DC). The base stations 104 and 106 operate as the MN and SN for the UE 102, respectively.

[0037] 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 under EUTRA-NR DC (EN-DC) with the MeNB and the SgNB.

[0038] 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 may be under next-generation (NG) EUTRA-NR DC (NGEN-DC) with the Mng-eNB and the SgNB. When the base station 104 is an MgNB and the base station 106 is an SgNB, the UE 102 may be under NR-NR DC (NR-DC) with the MgNB and the SgNB. When the base station 104 is an MgNB and the base station 106 is a secondary ng-eNB (Sng-eNB), the UE 102 may be under NR-EUTRA DC (NE-DC) with the MgNB and the Sng-eNB.

[0039] In a scenario where UE 102 hands over from base station 104 to base station 106, base stations 104 and 106 operate as a source base station (S-BS) and a target base station (T-BS), respectively. For example, before the handover, UE 102 may operate with base station 104 and an additional base station ( Figure 1A not shown in the figure) under DC. After the handover is completed, UE 102 may continue to operate with base station 106 and the additional base station under DC or operate with base station 106 under single connection (SC). In this case, base stations 104 and 106 operate as a source MN (S-MN) and a target MN (T-MN), respectively.

[0040] The core network (CN) 110 may be an evolved packet core (EPC) 111 or a fifth-generation core (5GC) 160, both of which are depicted in Figure 1A the figure. Base station 104 may be an eNB that supports the S1 interface for communication with EPC 111, an ng-eNB that supports the NG interface for communication with 5GC 160, or a gNB that supports the NR radio interface and the NG interface for communication with 5GC 160. To directly exchange messages with each other during the scenarios discussed below, base stations 104 and 106 may support the X2 or Xn interface. Among other components, EPC 111 may include a serving gateway (SGW) 112, a mobility management entity (MME) 114, and a packet data network gateway (PGW) 116. SGW 112 is generally configured to forward user plane packets related to audio calls, video calls, Internet traffic, etc., and MME 114 is configured to manage authentication, registration, paging, and other related functions. PGW 116 provides connectivity from the UE to one or more external packet data networks (e.g., the Internet network and / or the Internet Protocol (IP) Multimedia Subsystem (IMS) network). 5GC 160 includes a user plane function (UPF) 162, an access and mobility management (AMF) 164, and / or a session management function (SMF) 166. UPF 162 is generally configured to forward user plane packets related to audio calls, video calls, Internet traffic, etc., AMF 164 is configured to manage authentication, registration, paging, and other related functions, and SMF 166 is configured to manage PDU sessions.

[0041] As Figure 1A illustrated, base station 104 supports cell 124A, and base station 106 supports cell 126. Cells 124A and 126 may partially overlap such that UE 102 may communicate with base station 104 and base station 106 under DC, where one of base stations 104 and 106 is the MN and the other is the SN. Base station 104 may support additional cells such as cells 124B and 124C, and base station 106 may support additional cells (Figure 1A (not shown in the figure). Cells 124A, 124B, and 124C may partially overlap such that UE 102 can communicate with base station 104 in carrier aggregation (CA). Base station 104 may operate cells 124A, 124B, and 124C via one or more transmit and receive points (TRPs). More specifically, when UE 102 is in DC with base stations 104 and 106, one of base stations 104 and 106 operates as a MeNB, Mng-eNB, or MgNB and the other operates as an SgNB or Sng-eNB.

[0042] Generally, wireless communication network 100 may include any suitable number of base stations that support NR cells and / or EUTRA cells. More specifically, EPC 111 or 5GC 160 may be connected to any suitable number of base stations that support NR cells and / or EUTRA cells. Although the examples below specifically relate to particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), generally, the techniques of the present disclosure may also be applicable to other suitable radio access and / or core network technologies, such as sixth generation (6G) radio access and / or 6G core network or 5G NR - 6G DC.

[0043] Continuing to refer to Figure 1A, the base station 104 is equipped with processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and a non-transitory computer-readable memory storing instructions executed by the one or more general-purpose processors. Additionally or alternatively, the processing hardware 130 may include a dedicated processing unit. The processing hardware 130 may include a PHY controller 132, which is configured to transmit data and control signals on a physical downlink (DL) channel and DL reference signals associated 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 on a physical uplink (UL) channel and / or UL reference signals associated 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. The processing hardware 130 in an example implementation includes a MAC controller 134, which is configured to perform MAC functions with one or more user devices. The MAC functions include random access (RA) procedures, managing UL timing advance for one or more user devices, and / or communicating UL / DL MAC PDUs with one or more user devices. The processing hardware 130 may further include an RRC controller 136, which is used to implement procedures and message passing at the RRC sublayer of the protocol communication stack. For example, the RRC controller 132 may be configured to support RRC message passing associated with handover procedures, and / or support necessary operations when the base station 104 operates as an MN with respect to an SN or as an SN with respect to an MN. The base station 106 may include processing hardware 140 similar to the processing hardware 130. In particular, components 142, 144, and 146 may be similar to components 132, 134, and 136, respectively.

[0044] UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or a dedicated processing unit. The PHY controller 152 is also configured to receive data and control signals on a physical DL channel and / or DL reference signals with the base station 104 or 106 via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. The PHY controller 152 is also configured to transmit data and control signals on a physical UL channel and / or UL reference signals with the base station 104 or 106 via one or more cells (e.g., cells 124A, 124B, 124C, and / or 126) and / or one or more TRPs. The processing hardware 150 in an example implementation includes a MAC controller 154, which is configured to perform MAC functions with the base station 104 or 106. For example, the MAC functions include a random access procedure, managing UL timing advance for one or more user devices, and communicating UL / DL MAC PDUs with the base station 104 or 106. The processing hardware 150 may further include an RRC controller 156, which is used to implement procedures and messaging at the RRC sublayer of the protocol communication stack.

[0045] In operation, the UE 102 under DC may use radio bearers (e.g., DRB or SRB) that terminate at the MN 104 or SN 106 at different times. When communicating on a radio bearer in the uplink (UL) (from the UE 102 to the base station) and / or downlink (from the base station to the UE 102) direction, the UE 102 may apply one or more security keys.

[0046] Figure 1BDepict an example distributed implementation of a base station such as base station 104 or 106. In this implementation, the base station may include a Centralized Unit (CU) 172 and one or more Distributed Units (DUs) 174. The CU 172 is equipped with processing hardware that may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or a dedicated processing unit. In one example, the CU 172 is equipped with processing hardware 130. In another example, the CU 172 is equipped with processing hardware 140. In an example implementation, the processing hardware 140 includes an SN RRC controller 142 configured to manage or control one or more RRC configurations and / or RRC procedures when base station 106 operates as an SN. The DU 174 is also equipped with processing hardware that may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or a dedicated processing unit. In some examples, in an example implementation, the processing hardware includes: a Media Access Control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., random access procedures); and a Radio Link Control (RLC) controller configured to manage or control one or more RLC operations or procedures when base station 106 operates as an MN or SN. The processing hardware may further include a Physical Layer controller configured to manage or control one or more Physical Layer operations or procedures.

[0047] Next, Figure 2 Illustrate in a simplified manner a radio protocol stack according to which the UE 102 may communicate with an eNB / ng-eNB or a gNB. Each of base stations 104 or 106 may be an eNB / ng-eNB or a gNB.

[0048] The physical layer (PHY) 202A of EUTRA provides transport channels to the EUTRA media 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 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 the EUTRA and NR stacks to support handovers between EUTRA and NR base stations and / or DC via the EUTRA and NR interfaces. Further, as Figure 2 illustrated in A, the UE 102 may support the layering of NR PDCP 210 over EUTRA RLC 206A.

[0049] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 (e.g., receive packets that may be referred to as service data units (SDUs) from an Internet protocol (IP) layer that is directly or indirectly layered on the PDCP layer 208 or 210), and output (e.g., to the RLC layer 206A or 206B) packets that may be referred to as protocol data units (PDUs). Except where the differences between SDUs and PDUs are relevant, for simplicity, this disclosure refers to both SDUs and PDUs as "packets".

[0050] On the control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 provide SRBs to exchange, for example, 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.

[0051] When the UE 102 operates with the base station 104 operating as a MeNB and the base station 106 operating as an SgNB under EUTRA / NR DC (EN-DC), the network may provide the UE 102 with a bearer terminated at the MN using EUTRA PDCP 208, or a bearer terminated at the MN using NR PDCP 210. In various scenarios, the network may also provide the UE 102 with a bearer terminated at the SN using only NR PDCP 210. The bearer terminated at the MN may be an MCG bearer or a split bearer. The bearer terminated at the SN may be an SCG bearer or a split bearer. The bearer terminated at the MN may be an SRB (e.g., SRB1 or SRB2) or a DRB. The bearer terminated at the SN may be an SRB (e.g., SRB) or a DRB.

[0052] Next, several example scenarios in which a base station operating in a Figure 1A system sends a configuration to the UE 102 and later activates the configuration for communication between the UE 102 and the base station. In general, Figures 3 to 7B similar event markings in Figure 4 A and Figure 4 B's event 416, Figure 5A 's event 516, Figure 5B 's event 517, Figure 6A 's event 616, Figure 6B 's event 617, Figure 7A 's event 716 and Figure 7B 's event 717), and the differences will be discussed below as appropriate. In addition to the differences shown in the figures and discussed below, any alternative implementations discussed for a particular event (e.g., for message passing and handling) may be applicable to events marked with similar reference numerals in other figures.

[0053] First, referring to Figure 3 , in scenario 300, the base station 104 includes a CU 172 and a DU 174, and the DU 174 operates cell 124A. The UE 102 initially communicates with the base station 104 on cell 124A using a first configuration 302. In some implementations, the UE 102 in carrier aggregation (CA) uses the first configuration on cell 124A and other cells (e.g., Figure 1Acommunicates with DU 174 on cell 124D) not shown. 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 SCell and / or additional cells associated with the 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 SCell and / or additional cells associated with the PCell or SCell. In the following description, base station 104 may be DU 174, CU 172, or DU 174 and CU 172.

[0054] In some implementations, in event 302, UE 102 transmits UL PDUs and / or UL control signals to base station 104 on cell 124A and / or other cells via one or more TRPs. In some implementations, UE 102 communicates UL PDUs and / or DL PDUs with base station 104 via a radio bearer, which in further implementations includes SRB and / or DRB. In some implementations, base station 104 configures the radio bearer for UE 102. In some implementations, the UL control signal includes UL control information, channel state information, hybrid automatic repeat request (HARQ) acknowledgement (ACK), HARQ negative ACK, scheduling request, and / or sounding reference signal. Similarly, in further implementations, 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 block, channel state information reference signal (CSI-RS), and / or tracking reference signal). In further implementations, base station 104 transmits DCI on the physical downlink control channel (PDCCH) monitored by UE 102 on cell 124A and / or other cells via one or more TRPs.

[0055] In some implementations, the first configuration includes physical layer configuration parameters, MAC configuration parameters, RLC configuration parameters, PDCP configuration parameters, measurement configuration parameters, and / or radio bearer configuration parameters. In some implementations, the first configuration includes a CellGroupConfig IE (e.g., defined in 3GPP specification 38.331) or configuration parameters in the CellGroupConfig IE. In some implementations, the first configuration includes a CSI-MeasConfig IE, a MeasConfig IE, and / or a RadioBearerConfig IE (e.g., defined in 3GPP specification 38.331) or includes configuration parameters in the CSI-MeasConfig IE, the MeasConfig IE, and / or the RadioBearerConfig IE. In some implementations, the UE 102 receives configuration parameters from the base station 104. In other implementations, the UE 102 receives a part of the configuration parameters from a base station other than the base station 104 and receives the remaining part of the configuration parameters from the base station 104.

[0056] When communicating with base station 104, UE 102 sends 304 at least one measurement report to DU 174. In some implementations, the at least one measurement report includes layer 1 (L1) measurement reports and / or layer 3 (L3) measurement reports for at least one serving cell and / or at least one non-serving cell of UE 102. For each L3 measurement report in the L3 measurement reports, DU 174 sends 306 a DU-to-CU message including the L3 measurement report to CU 172. In some implementations, the DU-to-CU message for event 306 is an F1 Application Protocol (F1AP) message (e.g., UL RRC message transfer message). In some implementations, UE102 does not send or avoids sending L1 measurement reports to CU 172. The at least one serving cell includes cell 124A and / or other cells, and the at least one non-serving cell includes cell 124B and / or cell 124C. In some implementations, the first configuration includes at least one measurement configuration. In some implementations, UE 102 receives, in event 302, one or more RRC messages (e.g., RRCReconfiguration message) including at least one measurement configuration from CU172 via DU 174, as described above. According to the at least one measurement configuration, UE 102 performs measurements and sends 304 at least one measurement report to DU 174. In some implementations, the at least one measurement configuration includes an L3 measurement configuration (e.g., MeasConfig IE) and / or an L1 measurement configuration. For example, the L1 measurement configuration (e.g., CSI-MeasConfig IE) includes a CSI resource configuration (e.g., CSI-ResourceConfig IE) and / or a CSI report configuration (e.g., CSI-ReportConfig IE). UE 102 sends an L3 measurement report to CU 172 via DU 174 according to the L3 measurement configuration. UE 102 sends an L1 measurement report to DU 174 according to the L1 measurement configuration. In some implementations, the at least one measurement configuration includes a new measurement configuration for fast serving cell change (e.g., a new RRC IE (e.g., as defined in 3GPP specification 38.331 v18.0.0 and / or later versions)). 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, the at least one measurement report includes a new measurement report associated with the new measurement configuration. UE 102 sends a new measurement report to DU 174 according to the new measurement configuration. In some implementations, each new report configuration in the new report configuration includes a trigger event configuration that configures a trigger event for triggering UE 102 to send a new measurement report.If the UE 102 detects a triggering event, the UE 102 sends a new measurement report to the DU 174.

[0057] In some implementations, the L1 measurement report includes at least one L1 measurement result. In some implementations, the at least one L1 measurement result includes at least one L1 reference signal received power (L1-RSRP) value and / or at least one L1 signal-to-interference-plus-noise ratio (L1-SINR) value. In some implementations, for each L1 measurement report in the L1 measurement report, the UE 102 sends a PUCCH transmission including the L1 measurement report to the DU 174. That is, the UE 102 sends each L1 measurement report in the L1 measurement report to the DU 174 on the PUCCH. In other implementations, for each L1 measurement report in the L1 measurement report, the UE 102 sends a PUSCH transmission including the L1 measurement report to the DU 174. That is, the UE 102 sends each L1 measurement report in the L1 measurement report to the DU 174 on the PUSCH. In still other implementations, the UE 102 sends a part of the L1 measurement report on the PUCCH and sends the rest of the L1 measurement report to the DU 174 on the physical uplink shared channel (PUSCH). That is, for each of such 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 rest 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 L1 measurement report in the L1 measurement report is part of the channel state information (CSI) (i.e., a CSI component) or CSI. In some implementations, the UE 102 includes other CSI components in the above 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).

[0058] In some implementations, each L3 measurement report in the L3 measurement reports includes at least one L3 measurement result. In some implementations, the at least one L3 measurement result includes at least one RSRP value and / or at least one SINR value. In some implementations, UE 102 sends each L3 measurement report in the L3 measurement reports to CU 172 via DU 174 on the PUSCH. In some implementations, each L3 measurement report in the L3 measurement reports is an RRC message (e.g., MeasurementReport message). In some implementations, each L3 measurement configuration in the L3 measurement configurations includes a specific measurement identifier (e.g., measId), and each L3 measurement report in the L3 measurement reports includes the specific measurement identifier in the specific L3 measurement configuration. In some implementations, when CU 172 receives from UE 102 via DU 174 an L3 measurement report including a measurement identifier and an L3 measurement result, CU 172 determines that the L3 measurement report is associated with the L3 measurement configuration identified by the measurement identifier.

[0059] In some alternative implementations, for each measurement report in at least one measurement report (e.g., L1 measurement report and / or new measurement report), UE 102 sends a MAC control element (CE) including the measurement report to DU 174 in event 304. To send the MAC CE, UE 102 generates one or more MAC PDUs in event 304 to DU 174, each MAC PDU including one or more MAC CEs in the MAC CE.

[0060] In some implementations, UE 102 performs measurements on one or more reference signals according to at least one measurement configuration. In further implementations, the one or more reference signals include one or more synchronization signals (SS) / physical broadcast channel (PBCH) resource blocks (SSB) and / or one or more CSI-RS. UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurements. DU 174 sends the one or more reference signals on cells 124A and 124B and optionally cells 124C and / or other cells.

[0061] After receiving one or more measurement reports in at least one measurement report from UE 102 (e.g., in response thereto), base station 104 (i.e., CU 172 or DU 174) determines to prepare cell 124B for UE 102. In some implementations, base station 104 determines to prepare cell 124B for UE 102 because at least one measurement report indicates that cell 124B can be used by base station 104 to communicate with UE 102. In some implementations, base station 104 determines to prepare cell 124B for UE 102 because at least one measurement report indicates that cell 124B is eligible for communication with UE 102. In some implementations, if the L3 measurement report indicates that the signal strength and / or quality of cell 124B is higher than a first predetermined threshold and / or better than cell 124A, CU 172 determines to prepare cell 124B for UE 102. In other implementations, if the L1 measurement report or a new type of measurement report indicates that the signal strength and / or quality of cell 124B is higher than a first predetermined threshold and / or better than (e.g., higher than) cell 124A, DU 174 determines to prepare cell 124B for UE 102. Alternatively, regardless of whether a measurement report is received from UE 102, base station 104 determines to prepare cell 124B for UE 102.

[0062] In some implementations, if CU 172 determines to prepare cell 124B, CU 172 sends a first CU-to-DU message 308 to DU 174 to prepare cell 124B for UE 102. In some implementations, CU 172 includes the cell identifier (ID) of cell 124B in the first CU-to-DU message. For example, the cell ID is a cell global identifier (CGI). In another example, the cell ID is a physical cell ID (PCI). In response, DU 174 generates a second configuration (referred to herein as configuration 1) that configures cell 124B and sends a first DU-to-CU message 310 including the second configuration to CU 172. In a further implementation, if DU 174 determines to prepare cell 124B, DU 174 initiates the transmission of the first DU-to-CU message to CU 172.

[0063] After receiving the first DU-to-CU message, CU 172 generates an RRC reconfiguration message (e.g., RRCReconfiguration message) including Configuration 1, and sends a second CU-to-DU message including the RRC reconfiguration message to DU 174. Subsequently, DU 174 sends the RRC reconfiguration message to UE 102. In response, UE 102 sends a RRC reconfiguration complete message (e.g., RRCReconfigurationComplete message) to DU 174, and the DU then sends a second DU-to-CU message including the RRC reconfiguration complete message to CU 172. In some implementations, CU 172 performs security protection (e.g., integrity protection and / or encryption) on the RRC reconfiguration message. For example, CU 172 generates 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 an encrypted MAC-I, and sends a PDCP PDU including the encrypted RRC reconfiguration message and the encrypted MAC-I to UE 102 via DU 174 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 re-establishment procedure in response to an invalid MAC-I. Otherwise, in further implementations, if UE 102 verifies that the MAC-I is valid, UE 102 processes the RRC reconfiguration. UE 102 avoids applying (i.e., executing) Configuration 1 until it receives a configuration activation command (e.g., event 330) that activates Configuration 1.

[0064] 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 requirement message. In some implementations, in the case of a UE context modification requirement message, CU 172 sends a UE context modification confirmation message to DU 174 in response to the UE context modification requirement 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.

[0065] Events 308 and 310 are collectively referred to as the serving cell preparation procedure 390 in Figure 3 the following.

[0066] In some implementations, the CU 172 includes a field or IE in the RRC reconfiguration messages for events 316 and 318 to indicate to the UE 102 not to apply configuration 1 immediately. In some implementations, the field or IE is currently defined (e.g., in 3GPP specification 38.331 v18.0.0 and / or later versions). In further implementations, the field or IE is newly defined (e.g., in 3GPP 6G specifications). In some implementations, the field or IE is an indicator. If the RRC reconfiguration message for event 318 includes the indicator, the UE 102 avoids applying configuration 1 immediately. Instead, the UE 102 waits for a subsequent activation command (see, for example, the discussion of event 330 below). Otherwise, if the RRC reconfiguration message for event 318 does not include the indicator, the 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, the UE 102 receives an RRC reconfiguration message (e.g., the RRC reconfiguration message for event 318) that includes a configuration (e.g., configuration 1). If the configuration is included in the container, the UE 102 avoids applying the configuration immediately. Otherwise, if the configuration is not included in the container, the UE 102 applies the configuration immediately.

[0067] 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, MobilityConfigToAddModList IE, or CellGroupConfigToAddModList IE). Base station 104 includes Configuration 1 in a first element of the first addition or modification list (referred to herein as Element 1). For example, Element 1 is an addition or modification IE (e.g., ConfigToAddMod IE, CellConfigToAddMod IE, MobilityToAddMod IE, MobilityConfigToAddMod IE, or CellGroupConfigToAddMod IE). In some implementations, when UE 102 receives the first addition or modification list, UE 102 stores the first addition or modification list (e.g., in a variable in random access memory (RAM)).

[0068] In some implementations, CU 172 includes a first ID (referred to herein as ID 1) for identifying Configuration 1 in the RRC reconfiguration message. In some implementations, CU 172 includes ID 1 in the first container or Element 1. In some implementations, CU 172 assigns ID 1 to Configuration 1. In other implementations, CU 172 receives ID 1 from DU 174 in a first DU-to-CU message, as described below.

[0069] In some implementations, CU 172 sends ID 1 to DU 174 such that DU 174 can associate ID 1 with Configuration 1. In some implementations, CU 172 includes ID 1 in a first CU-to-DU message. In a further implementation, CU 172 sends 312 a third CU-to-DU message 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 a further implementation, 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 in Figure 3Collectively referred to as the ID allocation process 392 in the present disclosure.

[0070] In some implementations, when the CU 172 includes ID 1 in the first CU-to-DU message, the DU 174 includes ID 1 in Configuration 1. In such cases, the CU 172 does not include ID 1 in the RRC reconfiguration message, the first container, and / or Element 1.

[0071] In some alternative implementations, the DU 174 assigns ID 1 to identify Configuration 1. In some implementations, the DU 174 includes ID 1 in the first DU-to-CU message. In further implementations, the CU 172 includes ID 1 in the RRC reconfiguration message. In other implementations, the DU 174 includes ID 1 in Configuration 1. Therefore, the CU 172 does not include the ID identifying Configuration 1 in the RRC reconfiguration message, the first container, and / or Element 1.

[0072] In some implementations, Configuration 1 includes multiple configurations for the UE 102 to communicate with the DU 174 on Cell 124B. In some implementations, the multiple configurations include physical layer configuration parameters (e.g., PhysicalCellGroupConfigIE), MAC layer configuration parameters (e.g., MAC-CellGroupConfig IE), and / or RLC configuration parameters (e.g., RLC-BearerConfig IE). In some further implementations, the multiple configurations include special cell configurations (e.g., SpCellConfig IE) and / or one or more SCell configurations (e.g., SCellConfig IE).

[0073] In some implementations, DU 174 includes the random access configuration in Configuration 1. In other implementations, DU 174 does not include the random access configuration in Configuration 1. In some implementations, if cell 124A and cell 124B are not synchronized, then DU 174 determines to include the random access configuration in Configuration 1. Otherwise, if cell 124A and cell 124B are synchronized, then DU 174 determines not to include the random access configuration in Configuration 1. In other implementations, if DU 174 determines that UE102 is not synchronized with cell 124B in the UL, then DU 174 determines to include the random access configuration in Configuration 1. Otherwise, if DU174 determines that UE 102 has been synchronized with cell 124B in the UL, then DU 174 determines not to include the random access configuration in Configuration 1. If Configuration 1 includes the random access configuration, then UE 102 performs the random access procedure in Event 332 according to the random access configuration, as described below. Otherwise, if Configuration 1 excludes the random access configuration, then UE 102 skips the random access procedure of Event 332 in response to Configuration 1 excluding the random access configuration.

[0074] In some implementations, regardless of whether cell 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, then DU 174 determines to include a first indication in Configuration 1, and the first indication configures UE 102 not to perform a random access procedure on cell 124B. Otherwise, if cell 124A is not synchronized with cell 124B, then DU 174 determines not to include the first indication in Configuration 1. In other implementations, if DU 174 determines that UE 102 has been synchronized with cell 124B in the UL, then DU 174 determines to include the first indication in Configuration 1. Otherwise, if DU 174 determines that UE 102 has not been synchronized with cell 124B in the UL, then DU 174 determines not to include the first indication in Configuration 1. If Configuration 1 includes the first indication, then UE 102 skips the random access procedure of Event 332 according to or in response to the first indication. Otherwise, if Configuration 1 excludes the first indication, then UE 102 performs the random access procedure in Event 332 according to the random access configuration in response to Configuration 1 excluding the first indication, as described below.

[0075] In some implementations, the DU 174 includes a reconfiguration configuration with synchronization (e.g., ReconfigurationWithSync IE) in Configuration 1 or the special cell configuration. In other implementations, the DU 174 does not include a reconfiguration configuration with synchronization (e.g., ReconfigurationWithSync IE) in Configuration 1 or the special cell configuration. In some implementations, if cell 124A and cell 124B are not synchronized, the base station 104 determines to include a reconfiguration configuration with synchronization in Configuration 1. Otherwise, if cell 124A and cell 124B are synchronized, the DU 174 determines not to include a reconfiguration configuration with synchronization in Configuration 1. In other implementations, if the DU 174 determines that the UE 102 has not been synchronized with cell 124B in the UL, the DU 174 determines to include a reconfiguration configuration with synchronization in Configuration 1. Otherwise, if the DU 174 determines that the UE 102 has been synchronized with cell 124B in the UL, the DU 174 determines not to include a reconfiguration configuration with synchronization in Configuration 1. In some implementations, if Configuration 1 includes a reconfiguration configuration with synchronization, the UE 102 performs the random access procedure in event 332 as described below in response to or according to the reconfiguration configuration with synchronization. Otherwise, if Configuration 1 does not include a reconfiguration configuration with synchronization, the UE 102 skips the random access procedure for event 332. In some implementations, the DU 174 includes the cell ID of cell 1 (i.e., cell 124B) (i.e., cell ID 1) in Configuration 1. In some implementations, cell ID 1 is the PCI. In further implementations, cell ID 1 is the CGI. In some further implementations, Configuration 1 includes a cell index 1 (e.g., serving cell index) that indexes cell ID 1 or cell 124B.

[0076] In some implementations, after receiving one or more measurement reports in at least one measurement report of event 304 (e.g., in response thereto), base station 104 (i.e., CU 172 or DU 174) determines to prepare other cells of base station 104 for UE 102. In some implementations, base station 104 determines to prepare other cells because at least one measurement report indicates that the other cells can be used by base station 104 to communicate with UE 102. In further implementations, the other cells include cell 124C and / or cells other than cells 124A, 124B, and 124C. In some implementations, if the L3 measurement report indicates that the signal strength and / or quality of a specific cell in the other cells is higher than a corresponding predetermined threshold and / or better than (e.g., higher than) cell 124A, CU 172 determines to prepare the specific cell for UE 102. In other implementations, if the L1 measurement report or a new measurement report indicates that the signal strength and / or quality of a specific cell in the other cells is higher than a first predetermined threshold and / or better than (e.g., higher than) cell 124A, DU 174 determines to prepare the specific cell for UE 102. In some implementations, the corresponding predetermined threshold of the other cells is different from the first predetermined threshold. In further implementations, the corresponding predetermined threshold of the other cells is the same as the first predetermined threshold. In some implementations, the corresponding predetermined thresholds of the other cells are the same or different. Alternatively, regardless of whether a measurement report is received from UE 102, base station 104 determines to prepare other cells for UE 102.

[0077] In some implementations, in response to the determination to prepare other cells, CU 172 and DU 174 perform at least one other serving cell preparation process to prepare the other cells, where each other serving cell preparation process in the at least one other serving cell preparation process is similar to process 390. In some implementations, CU 172 includes the cell ID of the other cells in at least one CU-to-DU message of the at least one serving cell preparation process, and the at least one CU-to-DU message is similar to the first CU-to-DU message. In some implementations, CU 172 and DU 174 perform an additional serving cell preparation process to prepare each of the other cells, similar to process 390. In some such cases, CU 172 includes the cell ID of a specific cell in the other cells in the CU-to-DU message of the serving cell preparation process, and the CU-to-DU message is similar to the first CU-to-DU message. During the serving cell preparation process, DU 174 generates configurations 2,..., N, each configuration configuring 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 greater than one. For example, "N" is 2, 4, 6, 8, 10, 12, 14, or 16. Examples and implementations of configuration 1 may be applicable to configurations 2,..., N.

[0078] In other implementations, the CU 172 determines to prepare other cells in process 390. In some such cases, the CU 172 includes the cell ID of each of the other cells in the first CU-to-DU message, and the DU 174 includes configurations 2, …, N in the first DU-to-CU message. In still other implementations, the DU 174 determines to prepare other cells in process 390, and includes configurations 2, …, N in the first DU-to-CU message.

[0079] In some implementations, after receiving configurations 2, …, N from the DU 174, the CU 172 includes configurations 2, …, N in the first container. In some implementations, the CU 172 includes configurations 2, …, N in elements 2, …, N, and includes elements 2, …, N in the first container. In some implementations, the CU 172 includes IDs 2, …, N in the RRC reconfiguration message to respectively identify configurations 2, …, N. In some implementations, the CU 172 includes IDs 2, …, N in the first container. For example, the CU 172 includes IDs 2, …, N and configurations 2, …, N in elements 2, …, N in the first addition or modification list.

[0080] In some implementations, the CU 172 assigns IDs 2, …, N to configurations 2, …, N. In other implementations, the CU 172 receives IDs 2, …, N from the DU 174 in the first DU-to-CU message of process 390 or in the DU-to-CU message of at least one other serving cell preparation process or additional serving cell preparation process.

[0081] In some implementations, the CU 172 and the DU 174 perform an ID allocation process for each of the configurations 2, …, N, similar to process 392. In such cases, the DU 174 includes IDs 2, …, N in configurations 2, …, N. In such cases, the CU 172 does not include IDs 2, …, N in the RRC reconfiguration message, the first container, and / or elements 2, …, N.

[0082] In some alternative implementations, DU 174 assigns IDs 2, …, N in configurations 2, …, N. In some implementations, DU 174 includes IDs 2, …, N in the first DU-to-CU message of procedure 390 or in the DU-to-CU messages of at least one other serving cell preparation procedure or additional serving cell preparation procedure. In a further implementation, CU 172 includes IDs 2, …, M in the RRC reconfiguration message. In other implementations, DU 174 includes IDs 2, …, N in configurations 2, …, N. Accordingly, CU 172 does not include the IDs identifying each of the configurations 2, …, N in the RRC reconfiguration message, the first container, and / or element 1.

[0083] In some alternative implementations, CU 172 generates a second container including configurations 2, …, N or elements 2, …, N to replace the use of the first container. Alternatively, DU 174 generates the second container and includes the second container in the first DU-to-CU message or in the DU-to-CU messages of other serving cell preparation procedures. Then, CU 172 sends an additional RRC reconfiguration message including the second container to UE 102 via DU 174, similar to events 316 and 318. In response, UE 102 sends an additional RRC reconfiguration complete message to CU 172 via DU 174, similar to events 320, 322. In some implementations, the second container is a second addition or modification list (e.g., ConfigToAddModList IE, CellConfigToAddModList IE, MobilityToAddModList IE, MobilityConfigToAddModList IE, or CellGroupConfigToAddModList IE), and in a further implementation, each of the elements 2, …, N is an addition or modification IE (e.g., ConfigToAddMod IE, ReconfigToAddMod IE, CellConfigToAddMod IE, MobilityToAddMod IE, MobilityConfigToAddMod IE, or CellGroupConfigToAddMod IE). In some implementations, when UE 102 receives the second addition or modification list, UE 102 stores the second addition or modification list together with the first addition or modification list (e.g., in a variable in the RAM).

[0084] In some implementations, DU 174 includes cell IDs 2, …, N in configurations 2, …, N respectively. The cell IDs 2, …, N identify cells 2, …, N respectively. In some implementations, each of the cell IDs 2, …, N is a PCI. In some further implementations, configurations 2, …, N include cell indexes 2, …, N (e.g., serving cell indexes) that index cell IDs 2, …, N or cells 2, …, N respectively.

[0085] In some implementations, each of the configurations 1, …, N and / or 2, …, N is a CellGroupConfig IE. In such implementations, the following is an example structure of a first or second addition or modification list (e.g., CellGroupConfigToAddModList IE), and the CellGroupConfigToAddMod IE is an element of the first or second addition or modification list.

[0086] In some implementations, CU 172 sends a release list to UE 102 via DU 174 to release one or more of the configurations 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, the base station 104 includes the IDs of one or more 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 based on the IDs and releases one or more of the configurations in response to the release list.

[0087] In some implementations, the base station 104 sends an empty or configuration - free third addition or modification list to UE 102 to release all of the configurations 1, …, N. In some implementations, the base station 104 sends an RRC reconfiguration message including the third addition or modification list to UE 102. In response, UE 102 sends an RRC reconfiguration complete message to CU 172 via DU 174. UE 102 releases all of the configurations 1, …, N in response to the third addition or modification list.

[0088] In some implementations, the CU 172 determines to release one, some, or all of the configurations 1, …, N, and in further implementations, sends a CU-to-DU message to the DU 174 to instruct the DU 174 to release one, some, or all of the configurations 1, …, N. For example, the CU 172 includes one, some, or all of the IDs 1, …, N in the CU-to-DU message to instruct the DU 174 to release one, some, or all of the configurations 1, …, N. Depending on the implementation, each of the cell IDs 1, …, N is a CGI or a PCI. In response, the DU 174 releases one, some, or all of the configurations 1, …, N, and in some implementations, sends a DU-to-CU message to the CU 172. In other implementations, the DU 174 determines to release one, some, or all of the configurations 1, …, N, and sends a DU-to-CU message including the IDs of one, some, or all of the configurations 1, …, N to the CU 172. After receiving the DU-to-CU message (e.g., in response thereto), the CU 172 generates a release list or a third addition or modification list to release one, some, or all of the configurations 1, …, N.

[0089] In still other implementations, the DU 174 generates a release list or a third addition or modification list. In some such cases, the DU 174 sends a DU-to-CU message including the release list or the third addition or modification list to the CU 172. In further implementations, in response, the CU 172 sends a CU-to-DU message to the DU 174. In some implementations, the DU 174 determines to release one, some, or all of the configurations 1, …, N. In other implementations, the DU 174 receives from the CU172 a CU-to-DU message including the IDs of one, some, or all of the configurations 1, …, N to instruct the release of one, some, or all of the configurations 1, …, N.

[0090] Example implementation 1

[0091]

[0092] For example, the first addition or modification list is the first CellGroupConfigToAddModList IE, and the second addition or modification list is the second CellGroupConfigToAddModList IE. Element 1 is CellGroupConfigToAddMod IE 1, and elements 2, …, N are CellGroupConfigToAddMod IE2, …, N respectively. ID 1 and configuration 1 are the ConfigId and CellGroupConfig IE in CellGroupConfigToAddMod IE 1 respectively. ID 2, …, N and configurations 2, …, N are the 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 further implementations, the first CellGroupConfigToAddModList IE includes CellGroupConfigToAddMod IE1, …, N.

[0093] In some implementations, the release list is the CellGroupConfigToReleaseList IE. In further implementations, the base station 104 includes one or more ConfigID IEs in the CellGroupConfigToReleaseList IE to release one or more of the CellGroupConfigToAddMod IEs in CellGroupConfigToAddMod IE 1, …, N. One or more CellGroupConfigToAddMod IEs are identified by one or more ConfigID IEs.

[0094] Example implementation 2

[0095] Example implementation 2 is similar to example implementation 1, except that the CellGroupConfigToAddMod IE does not include a ConfigId.

[0096]

[0097] In some implementations, IDs 1, …, N are implicitly indicated by the order of the CellGroupConfigToAddMod IEs 1, …, N in the first or second CellGroupConfigToAddModList. For example, CellGroupConfigToAddMod IE 1 is the first IE in the first CellGroupConfigToAddModList IE, which implicitly indicates that ID 1 has a value X. X can be zero or one. If the first CellGroupConfigToAddModList IE includes the CellGroupConfigToAddMod IEs 1, …, N in sequence, then IDs 1, …, N have the values X, X + 1, …, X + (N - 1). In some implementations, if base station 104 sends the second CellGroupConfigToAddModList IE to UE 102, then UE 102 and base station 104 replace the first CellGroupConfigToAddModList IE with the second CellGroupConfigToAddModList IE. If the second CellGroupConfigToAddModList IE includes the CellGroupConfigToAddMod IEs 2, …, N in sequence, then IDs 2, …, N are the values X, X + 1, …, X + N - 2. If the second CellGroupConfigToAddModList IE includes the CellGroupConfigToAddMod IEs 1, …, N in sequence, then IDs 1, …, N are the values X, X + 1, …, X + N - 1. In some alternative implementations, IDs 1, …, N are cell IDs 1, …, N.

[0098] In some implementations, base station 104 sends a CellGroupConfigToAddModList IE that includes zero CellGroupConfigToAddMod IEs to release all of the IEs in CellGroupConfigToAddMod IEs 1, …, N.

[0099] In Example Implementations 1 and 2, "CellGroupConfigToAddModList", "CellGroupConfigToAddMod", "configId", "ConfigId", "cellGroupConfig", "CellGroupConfigToReleaseList", and "maxNrofConfigCells" are merely exemplary and should not be regarded as limiting the scope and application of the present invention.

[0100] In other implementations, each of Configurations 1, …, N and / or Configurations 2, …, N is an RRCReconfiguration message. In such implementations, the following (i.e., Example Implementations 3 to 6) are example structures of the first or second addition or modification list.

[0101] Example Implementation 3

[0102] In Example Implementation 3, the first or second addition or modification list is a CondReconfigToAddModList-r16 IE (e.g., as defined in 3GPP Specification 38.331 from Release 16), and the CondReconfigToAddModIE is an element of the list.

[0103]

[0104] 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 the CondReconfigId and the RRCReconfiguration message in CondReconfigToAddMod IE 1. IDs 2, …, N and Configurations 2, …, N are the CondReconfigId and the RRCReconfiguration message in CondReconfigToAddMod IEs 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 IEs 2, …, N. In further implementations, the first CondReconfigToAddModList-r16 IE includes CondReconfigToAddMod-r16 IEs 1, …, N.

[0105] In this example implementation, the base station 104 includes a conditional configuration (i.e., condExecutionCond-r16) in at least one of the CondReconfigToAddMod-r16 IEs. In some implementations, if the UE 102 supports a conditional procedure (e.g., conditional handover (CHO), conditional PSCell addition (CPA), or conditional PSCell change (CPC)), the UE 102 evaluates one or more conditions configured for the conditional procedure in the condExecutionCond-r16 field. 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 satisfied, 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 a conditional configuration (i.e., condExecutionCond-r16) in any or some of the CondReconfigToAddMod-r16 IEs. Thus, for a CondReconfigToAddMod-r16 IE that does not include a conditional configuration (i.e., condExecutionCond-r16), the UE 102 is not configured to perform or not perform any evaluation (i.e., detection or determination) of the conditions for a conditional procedure (e.g., conditional handover).

[0106] In some implementations, the release list is the CondReconfigToRemoveList-r16 IE. In a further implementation, the base station 104 includes one or more CondReconfigID IEs in the CondReconfigToRemoveList-r16 IE to release one or more of the CondReconfigToAddMod-r16 IEs in CondReconfigToAddMod-r16 IEs 1, …, N. One or more CondReconfigToAddMod-r16 IEs are identified by one or more CondReconfigID IEs.

[0107] Example implementation 4

[0108] Example implementation 4 is similar to Example implementation 3, except that in some implementations, a new indicator (e.g., the fastServingCellChange-r18 field) is optionally included in the CondReconfigToAddMod-r16 IE. In some implementations, the new indicator indicates that the CondReconfigToAddMod-r16 IE (i.e., condRRCReconfig-r16 in the RRCReconfiguration message or IE) is configured for fast serving cell change (i.e., see the description for event 312). If the base station 104 does not include the new indicator in the CondReconfigToAddMod-r16 IE, the CondReconfigToAddMod-r16 IE is not configured for fast serving cell change.

[0109]

[0110] CondReconfigToRemoveList-r16 ::= SEQUENCE (SIZE (1..maxNrofCondCells-r16)) OF CondReconfigId-r16.

[0111] Example implementation 5

[0112] Some implementations in Example implementations 3 and 4 may involve the UE 102 supporting conditional procedures (e.g., conditional handover (CHO), conditional PSCell addition (CPA), and / or conditional PSCell change (CPC)). If the UE 102 does not support conditional procedures, the base station 104 does not configure or enable fast serving cell change for the UE 102. Thus, Example implementation 5 is decoupled from conditional procedures.

[0113]

[0114] In some implementations, the first add or modify list is the first ReconfigToAddModList IE, and the second add or modify list is the 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 the ConfigId and RRCReconfiguration IE in ReconfigToAddMod IE 1 respectively. ID 2, …, N and Configuration 2, …, N are the ConfigId and RRCReconfiguration IE in ReconfigToAddMod IE 2, …, N respectively. In some implementations, the first ReconfigToAddModList IE includes ReconfigToAddMod IE 1, and the second ReconfigToAddModList IE includes ReconfigToAddMod IE 2, …, N. In further implementations, the first ReconfigToAddModList IE includes ReconfigToAddMod IE 1, …, N.

[0115] In some implementations, the release list is the 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 among ReconfigToAddMod IE 1, …, N. One or more ReconfigToAddMod IEs are identified by one or more ConfigID IEs.

[0116] Example implementation 6

[0117]

[0118] Example implementation 6 is similar to example implementation 5, except that the ReconfigToAddMod IE does not include the ConfigId. In some implementations, the IDs 1, …, N are implicitly indicated by the order of the ReconfigToAddMod IEs 1, …, N in the first or second ReconfigToAddModList. For example, ReconfigToAddMod IE 1 is the first IE in the first ReconfigToAddModList IE, which implicitly indicates that ID 1 has the value X. X can be zero or one. If the first ReconfigToAddModList IE includes the ReconfigToAddMod IEs 1, …, N in sequence, then the IDs 1, …, N have the values X, X + 1, …, X+(N - 1). In some implementations, if the base station 104 sends the second ReconfigToAddModList IE to the UE 102, then the UE 102 and the base station 104 replace the first ReconfigToAddModList IE with the second ReconfigToAddModList IE. If the second ReconfigToAddModList IE includes the ReconfigToAddMod IEs 2, …, N in sequence, then the IDs 2, …, N have the values X, X + 1, …, X+N - 2. If the second ReconfigToAddModList IE includes the ReconfigToAddMod IEs 1, …, N in sequence, then the IDs 1, …, N have the values X, X + 1, …, X+N - 1. In some alternative implementations, the IDs 1, …, N are the cell IDs 1, …, N.

[0119] In some implementations, the base station 104 sends a ReconfigToAddModList IE that includes zero ReconfigToAddMod IEs to release all of the IEs in the ReconfigToAddMod IEs 1, …, N.

[0120] 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.

[0121] Example implementation 7

[0122] Example implementation 7 is a combination of example implementations 1 and 5, as follows. Depending on the implementation, any one of Configurations 1, …, N is a CellGroupConfig IE or an RRCReconfiguration message. The examples and implementations described for example implementations 1 and 5 may apply to example implementation 7.

[0123]

[0124] maxNrofConfigCells ::= 8. After receiving an RRC reconfiguration in event 318 or sending an RRC reconfiguration complete message in event 320, UE 102 sends 324 at least one measurement report to DU 174, similar to event 304. In some implementations, DU 174 sends 326 a DU-to-CU message including at least one measurement report to CU 172, similar to event 306. In other implementations, DU 174 does not send at least one measurement report to CU 172. In some implementations, at least one measurement report for event 324 includes an L1 measurement report, an L3 measurement report, and / or a new type of measurement report, as described for event 304. In some implementations, UE 102 sends 324 at least one measurement report to DU 174 on PUCCH and / or PUSCH, similar to event 304. In other implementations, UE 102 sends 324 at least one MAC CE including at least one measurement report to DU 174, similar to event 304. In some implementations, each measurement report in at least one measurement report for event 324 is not an RRC message.

[0125] In some implementations, the UE 102 sends at least one measurement report to the DU 174 according to at least one measurement configuration. The at least one measurement configuration configures the UE 102 to perform measurements and report the measurement results. The CU 172 sends at least one measurement configuration to the UE 102 via the DU 174. For example, after event 306 or 316, the CU 172 sends one or more RRC messages (e.g., RRCReconfiguration message) including 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 for event 316. According to the at least one measurement configuration, the UE 102 performs measurements on one or more reference signals. In some implementations, the one or more reference signals include one or more SSBs and / or one or more CSI-RSs. The UE 102 obtains at least one L1 measurement result and / or at least one L3 measurement result from the measurements, and the UE 102 includes the at least one L1 measurement result and / or the at least one L3 measurement result in at least one measurement report for event 324. The DU 174 sends one or more reference signals on cells 124A and 124B and in some implementations on cell 124C and / or other cells. In some implementations, the 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.

[0126] In some implementations, the new measurement configuration as described for events 304 and 324 is similar to the L3 measurement configuration. For example, the new measurement configuration includes a part of the configuration parameters defined in the MeasConfig IE. In other implementations, the new measurement configuration as described for events 304 and 324 is similar to the L1 measurement configuration. For example, the new measurement configuration includes a part of the configuration parameters defined in the CSI-MeasConfig IE (e.g., CSI-ResourceConfig IE and / or CSI-ReportConfig).

[0127] After receiving at least one measurement report in event 324 (e.g., in response thereto), the DU 174 sends a first configuration activation command 330 to the UE 102 to activate configuration 1. For example, the base station 104 sends the first configuration activation command on cell 124A. In another example, the base station 104 sends the first configuration activation command on cell 124D. In some implementations, the DU 174 includes ID 1 in the first configuration activation command. The UE 102 determines and activates configuration 1 based on the first configuration activation command and ID 1. In other implementations, the DU 174 includes in the first configuration activation command the cell index 1 (e.g., serving cell index) or cell ID 1 included in configuration 1. The UE 102 determines and activates configuration 1 based on the first configuration activation command and the cell index 1 or cell ID 1.

[0128] In still other implementations, instead of ID 1, cell ID 1, or cell index 1 (e.g., serving cell index), the DU 174 includes a bitmap in the first configuration activation command to activate configuration 1. The number of bits in the bitmap is greater than or equal to "N". In some implementations, bits 1, …, N correspond to configurations 1, …, N respectively, and the DU 174 sets the corresponding bit (e.g., bit 1) in the bitmap to a first value to indicate ID 1 or configuration 1. In a further implementation, bits 0, …, N - 1 correspond to configurations 1, …, N respectively, and the DU 174 sets the corresponding bit (e.g., bit 0) in the bitmap to a first value to indicate ID 1 or configuration 1. Thus, the UE 102 can determine a specific ID or a specific configuration based on bit 1 or bit 0 set to the first value in the bitmap. In such implementations, the DU 174 sets the remaining bits in the bitmap to a second value to indicate that the reset of configurations 1, …, N is not activated. In some implementations, the first value is one, and the second value is zero. In other implementations, the first value is zero, and the second value is one. In some implementations, if the DU 174 determines to activate another configuration (e.g., configuration K) in addition to configuration 1, the DU 174 sets the corresponding bit (e.g., bit K or bit K - 1) in the bitmap to the first value, where 1 <= K <= N.

[0129] In some implementations, at least one measurement report of event 324 (e.g., L1 measurement report or new measurement report) includes at least one measurement result for cell 124B. The DU 174 determines to activate configuration 1 because at least one measurement result indicates that the signal strength or quality of cell 124B is higher than a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In some implementations, the second predetermined threshold is greater than the first predetermined threshold. In such 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 the 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 the UE 102. Therefore, in response to the signal strength or quality of cell 124B being higher than the second predetermined threshold, the DU 174 determines to activate configuration 1 (i.e., fast serving cell change to cell 124B).

[0130] In some implementations, at least one measurement report of events 324 and 326 (e.g., L3 measurement report) includes at least one measurement result for cell 124B. The CU 172 determines to activate configuration 1 because at least one measurement result indicates that the signal strength or quality of cell 124B is higher than a second predetermined threshold. The second predetermined threshold is different from the first predetermined threshold. In some implementations, the second predetermined threshold is greater than the first predetermined threshold. In such an implementation, at least one measurement report of event 326 indicates that the signal strength or quality of cell 124B is suitable for communication with the 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. At least one measurement report also indicates that cell 124B is suitable for communication with the UE 102. Therefore, in response to determining that the signal strength or quality of cell 124B is higher than the second predetermined threshold, the CU 172 determines to activate configuration 1 (i.e., fast serving cell change to cell 124B).

[0131] In response to this determination, CU 172 sends a 328 fourth CU-to-DU message to DU 174 to activate Configuration 1. In response to the fourth CU-to-DU message, DU 174 sends a 330 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 cell index 1 (e.g., 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 the cell ID. In still 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).

[0132] In some implementations, when DU 174 determines to activate Configuration 1 or sends the first configuration activation command as described above, DU 174 sends a 329 fifth DU-to-CU message to CU 172. In some implementations, CU 172 pauses or stops DL data transmission for UE 102 in response to the fifth DU-to-CU message. In further implementations, when pausing or stopping DL data transmission for UE 102, CU 172 buffers the DL data of UE 102 that CU 172 receives from the core network or the 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 changes from cell 124A to cell 124B). In other implementations, in the fifth DU-to-CU message, DU 174 indicates pausing or stopping DL transmission for UE 102.

[0133] In some implementations, the fifth DU-to-CU message is an existing F1AP message (e.g., defined in 3GPP specification 38.473). In other implementations, the fifth DU-to-CU message is a new F1AP message (e.g., defined in 3GPP specification 38.473 v18.0.0 and / or later versions). In still other implementations, the fifth DU-to-CU message is an existing frame (e.g., defined in 3GPP specification 38.474). In still other implementations, the fifth DU-to-CU message is a new frame (e.g., defined in 3GPP specification 38.474 v18.0.0 and / or later versions).

[0134] In some implementations, the first configuration activation command is a MAC CE included in a MAC PDU that UE 102 receives 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 later versions). In some implementations, DU 174 includes a sub-header that identifies the MAC CE in the MAC PDU, and UE 102 identifies the MAC CE in the MAC PDU based on this sub-header. In a further implementation, the sub-header includes a logical channel ID or an extended logical channel ID for identifying the MAC CE (e.g., defined in 3GPP specifications). For example, the logical channel ID or the extended logical channel ID is newly defined (e.g., in 3GPP specification 38.321 v18.0.0 and / or later). In other implementations, the first configuration activation command is a DCI that UE 102 receives on a PDCCH in event 330. DU 174 generates a CRC for the DCI, scrambles the CRC with the first C-RNTI of UE 102, and transmits the DCI and the scrambled CRC on the PDCCH in event 330. In some implementations, the format of the DCI is an existing DCI format (e.g., defined in 3GPP specifications (e.g., 38.212)). In a further implementation, the format of the DCI is a new DCI format (e.g., defined in 3GPP specifications (e.g., 38.212 v18.0.0 or later versions)).

[0135] In some implementations, DU 174 does not perform security protection (e.g., integrity protection and / or encryption) on the first configuration activation command. Avoiding this accelerates the processing of the first configuration activation command in UE 102 because UE 102 does not spend time performing security checks (e.g., decryption and / or integrity checks) on the first configuration activation command.

[0136] In some implementations, after receiving the first configuration activation command, UE 102 sends a 331 confirmation to DU 174 on cell 124A or cell 124D to indicate that UE 102 has 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 later versions). In still other implementations, the confirmation is a PUCCH transmission.

[0137] In some implementations, CU 172 sends a 316 RRC reconfiguration message in response to the L3 measurement report for cell 124B received by CU 172 in event 306. In a further implementation, CU 172 sends a first RRC reconfiguration message including a MeasConfig IE to UE 102 to configure UE 102 to send an L3 measurement report. In some implementations, DU 174 sends a 330 first configuration activation command in response to the L1 measurement report for cell 124B received by DU 174 in event 324. In a further implementation, CU 172 sends a second RRC reconfiguration message including a CSI-MeasConfig IE to UE 102 to configure UE 102 to send an L1 measurement report. In some implementations, the first and second RRC reconfiguration messages are the same message (i.e., the same instance). In other implementations, the first and second RRC reconfiguration messages are different messages. In some implementations, the second RRC reconfiguration message is the RRC reconfiguration message for event 316. In other implementations, the second RRC reconfiguration message is different from the RRC reconfiguration message for event 316.

[0138] After receiving a first configuration activation command (e.g., in response thereto), the UE 102 identifies a specific configuration (e.g., Configuration 1) based on a specific ID (e.g., ID1) and immediately applies Configuration 1. In some implementations, the UE 102 performs a random access procedure with the DU 174 on cell 124B in response to applying Configuration 1. In some implementations, after receiving the first configuration activation command or sending an acknowledgement (e.g., in response thereto), the UE 102 disconnects from cell 124A. In other words, after receiving the first configuration activation command or sending the acknowledgement (e.g., in response thereto), the UE 102 stops communicating on cell 124A. In such cases, the UE 102 performs a random access procedure after disconnecting from cell 124A. In some implementations, the UE 102 determines whether to perform a random access procedure based on Configuration 1. In some implementations, if Configuration 1 configures the UE 102 to perform a random access procedure, the UE 102 performs a random access procedure in event 332. For example, Configuration 1 includes a reconfiguration configuration with synchronization (e.g., ReconfigurationWithSync IE) to configure the UE 102 to perform a random access procedure. Otherwise, if Configuration 1 does not configure the UE 102 to perform a random access procedure or configures the UE 102 to skip the random access procedure, the UE 102 avoids performing a random access procedure with the DU 174 when receiving the first configuration activation command. In such cases, the UE 102 skips event 316. For example, if Configuration 1 excludes a reconfiguration configuration with synchronization, Configuration 1 configures the UE 102 not to perform a random access procedure. In some implementations, the random access procedure is a four-step random access procedure. In other implementations, the random access procedure is a two-step random access procedure. In some implementations, the random access procedure is a contention-free random access procedure. In other implementations, the random access procedure is a contention-based random access procedure.

[0139] In the case where the UE 102 performs the random access procedure 332, after successfully completing the random access procedure, the UE 102 communicates with the DU 174 on the cell 124B using Configuration 1 336 and communicates with the CU 172 via the DU 174. For example, the UE 102 communicates UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) with the base station 104 in event 318. In such cases, 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 the UE identifier to the DU 174 via the cell 124B during the random access procedure. In the case where the random access procedure is a two-step random access procedure, the UE 102 sends a message A including the UE identifier to the DU 174 via the cell 124B during the random access procedure. In some implementations, if Configuration 1 includes a second C-RNTI, the UE identifier is the second C-RNTI of the UE 102. Otherwise, if Configuration 1 does not include a C-RNTI, the UE identifier is the first C-RNTI. In the case where the random access procedure is a contention-free random access procedure, the UE 102 sends a dedicated random access preamble to the DU 174 via the cell 124B. In such cases, Configuration 1 includes the dedicated random access preamble.

[0140] When the DU 174 receives the UE identifier or the dedicated preamble from the UE 102 during the random access procedure, it identifies or determines that the UE 102 is connected to the cell 124B.

[0141] In some implementations, the UE 102 sends an RRC message (e.g., an RRC reconfiguration complete message) to the CU 172 via the DU 174 and the cell 124B to indicate that the UE 102 applies Configuration 1. In some implementations, the UE 102 includes the RRC message in message 3. In further implementations, the UE 102 includes the RRC message in message A. In still further implementations, the UE 102 sends the RRC message after completing the random access procedure. In other implementations, if the UE 102 maintains communication with the base station 104 on the cell 124A (i.e., the UE 102 does not disconnect from the cell 124A), the UE 102 sends an RRC message to the base station 104 via the cell 124A. In still other implementations, the UE 102 avoids sending an RRC message to the base station 104 in response to applying Configuration 1 or receiving a first configuration activation command.

[0142] In some cases where the UE 102 skips the random access procedure, the UE 102 communicates directly with the base station 104 on cell 124B according to Configuration 1 after receiving the first configuration activation command (e.g., in response thereto). For example, the UE 102 communicates UL PDUs, DL PDUs, and / or physical layer signals (e.g., PUCCH transmissions and PDCCH transmissions) with the base station 104 in event 318. In some such cases, the UE 102 transmits at least one PUCCH transmission to the DU 174 on cell 124B according to Configuration 1 after receiving the first configuration activation command (e.g., in response thereto). In some implementations, the DU 174 transmits at least one DCI to the UE 102 on the PDCCH on cell 124B to command the UE 102 to transmit at least one PUCCH or PUSCH transmission after the first configuration activation command is sent. The DU 174 identifies or determines that the UE 102 is connected to cell 124B when the PUCCH or PUSCH transmission is received. In other implementations, the UE 102 transmits at least one PUCCH or PUSCH transmission regardless of whether DCI is received on the PDCCH on cell 124B. The DU 174 identifies or determines that the UE 102 is connected to cell 124B when the PUCCH or PUSCH transmission is received. In some implementations, the UE 102 sends an RRC message (e.g., an RRC reconfiguration complete message) to the CU 172 via the DU 174 and cell 124B to indicate that the UE 102 applies Configuration 1. The CU 172 identifies or determines that the UE 102 is connected to cell 124B when the RRC message is received. In other implementations, if the UE 102 maintains communication with the base station 104 on cell 124A (i.e., the UE 102 does not disconnect from cell 124A), the UE 102 sends an RRC message to the base station 104 via cell 124A. In still other implementations, the UE 102 avoids sending an RRC message to the base station 104 in response to applying Configuration 1 or receiving the first configuration activation command.

[0143] In some implementations, when the DU 174 determines in event 332 or 336 that the UE 102 has successfully connected to cell 124B, the DU 174 sends a 334 DU-to-CU message (e.g., an access success message) to the CU 172. In some implementations, the DU 174 includes the cell ID of cell 124B in the DU-to-CU message of event 334. Depending on the implementation, the cell ID is a PCI or a CGI. Thus, the CU 172 determines that the UE 102 is connected to cell 124B when receiving the DU-to-CU message of event 334. In a further implementation, when the DU 174 determines in event 332 or 336 that the UE 102 has successfully connected to cell 124B, the DU 174 sends a DL data delivery status message or frame to the CU 172. In some implementations, when the CU 172 receives the 334 DU-to-CU message, the CU 172 resumes or continues the DL data transmission for the UE 102. In a further implementation, after resuming or continuing the DL data transmission for the UE 102 (e.g., in response thereto), the CU 172 sends the DL data for the UE 102 to the DU 174, which in turn sends the DL data to the UE 102 in event 336.

[0144] In some implementations, when it is determined that the UE 102 is connected to cell 124B, the 330 first configuration activation command is sent, or the 331 confirmation is received, the DU 174 stops communicating with the UE 102 on cell 124A. In some implementations, when it is determined that the UE 102 is connected to cell 124B, the 330 first configuration activation command is sent, or the 331 confirmation is received, the DU 174 releases the resources of cell 124A configured for the UE 102.

[0145] Events 304, 306, 390, 392, 316, 318, 320, 322 are Figure 3 collectively referred to as the serving cell configuration procedure 380. Events 324, 326, 328, 330, 331, 332, 334, 336, 394 are Figure 3 collectively referred to as the serving cell change procedure 382.

[0146] In some implementations, DU 174 generates Configuration 1 and / or Configuration 2, …, N as full configurations, thereby replacing the first configuration or a specific configuration in the first configuration. In some implementations, if Configuration 1 is a full configuration, UE 102 and DU 174 communicate with each other 336 according to Configuration 1 instead of the first configuration or the specific configuration. In some implementations, DU 174 includes an indication that Configuration 1 is a full configuration in Configuration 1. In other implementations, the RRC reconfiguration messages for events 316, 318 include an indication that Configuration 1 is a full configuration. In still other implementations, the first container includes an indication that Configuration 1 is a full 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 full configuration. In some implementations, UE 102 determines that Configuration 1 is a full configuration based on the indication that Configuration 1 is a full configuration. In some implementations, there is an indication that Configuration 1 is different from the fullConfig field (e.g., as defined in the current 3GPP specification). In other implementations, there is an indication that Configuration 1 is the fullConfig field (e.g., as defined in the current 3GPP specification) in the RRCReconfiguration message.

[0147] In other implementations, DU 174 generates Configuration 1 and / or Configuration 2, …, N as delta configurations that augment at least a part of the first configuration. In other words, DU 174 generates Configuration 1, …, N on top of the first configuration. For example, if Configuration 1 is a delta configuration, UE 102 and DU 174 use Configuration 1 to augment at least a part of the first configuration. Thus, UE 102 and base station 104 communicate with each other 336 according to Configuration 1 and the unaugmented part of the first configuration. In some implementations, Configuration 1 includes an indication that Configuration 1 is a delta configuration. In other implementations, the first container includes an indication that Configuration 1 is a delta configuration. In still other implementations, Element 1 includes an indication that Configuration 1 is a delta configuration. In some implementations, UE 102 determines that Configuration 1 is a full configuration based on the indication that Configuration 1 is a delta configuration. In some alternative implementations, Configuration 1, the first container, or Element 1 excludes the indication that Configuration 1 is a full configuration to indicate that Configuration 1 is a delta configuration. In further implementations, UE 102 determines that Configuration 1 is a delta configuration based on the determination that the indication is excluded in Configuration 1, the first container, or Element 1.

[0148] In some implementations, if Configuration 1 is a full configuration, then after the UE 102 receives 330 the first configuration activation command, sends 331 an acknowledgement, successfully executes 332 a random access procedure, or receives 332 the first DCI on a PDCCH addressed to the UE identity of the UE 102 on cell 124B (e.g., in response thereto), the UE 102 releases the first configuration or a specific configuration in the first configuration. In some implementations, if Configuration 1 is a full configuration, then after the DU 174 sends 330 the first configuration activation command, receives 331 an acknowledgement, successfully executes 332 a random access procedure, or receives 332 a specific transmission from the UE 102 on cell 124B (e.g., in response thereto), the DU 174 releases the first configuration or a specific configuration in the first configuration. In some implementations, the specific transmission is a PUCCH transmission. In a further implementation, the transmission is a PUSCH transmission. In a further implementation, after sending the first configuration activation command, the DU 174 generates a DCI and a CRC for the DCI, scrambles the CRC with the UE identity of the UE 102, and sends the DCI and the scrambled CRC on a PDCCH on cell 124B. When the UE 102 receives the DCI and the scrambled CRC and verifies that the scrambled CRC is valid using the UE identity, the UE 102 sends a PUSCH transmission to the DU 174 on cell 124B.

[0149] In some implementations, the first configuration or the specific configuration is a first CellGroupConfig IE (i.e., the first configuration includes configuration parameters defined in the first CellGroupConfig IE), and Configuration 1 is a second CellGroupConfig IE.

[0150] In some implementations, the UE 102 uses a UE MAC entity (e.g., MAC 204B) to communicate with the DU 174 (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 when 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 excludes the 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, then when receiving the first configuration activation command, the UE 102 resets the UE MAC entity in response to the MAC reset indication.

[0151] Otherwise, if Configuration 1 or Element 1 does not include a MAC reset indication, UE 102 avoids resetting the UE MAC entity when or upon receiving the first configuration activation command. In some implementations, if Configuration 1 or Element 1 does not include a MAC reset indication and includes an indication that the configuration is a full configuration, UE 102 resets the UE MAC entity when or upon receiving the first configuration activation command. Otherwise, if Configuration 1 or Element 1 does not include a MAC reset indication and the configuration is a full configuration indication, UE 102 avoids resetting the UE MAC entity when or upon receiving the first configuration activation command.

[0152] In some implementations, base station 104 (e.g., DU 174 or CU 172) uses the DU MAC entity (e.g., NR MAC 204B) to communicate with UE 102 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). If base station 104 includes a MAC reset indication in Configuration 1 or Element 1, then after transmitting the first configuration activation command, receiving an acknowledgement, or determining that UE 102 is connected to cell 124B in event 332 or 336, DU 174 resets the DU MAC entity in response to the MAC reset indication.

[0153] Otherwise, if Configuration 1 or Element 1 does not include a MAC reset indication, DU 174 avoids resetting the DU MAC entity after transmitting the first configuration activation command (e.g., in response thereto). Thus, after transmitting the first configuration activation command, receiving an acknowledgement, or determining that UE 102 is connected to cell 124B in event 332 or 336, DU 174 continues to use the reserved (i.e., not reset) DU MAC entity to communicate with UE 102.

[0154] In some implementations, DU 174 includes the MAC reset indication in the MAC-CellGroupConfig IE (e.g., CellGroupConfig IE) in Configuration 1. In other implementations, DU 174 includes the MAC reset indication in the CellGroupConfig IE and outside of the MAC-CellGroupConfig IE. In yet other implementations, DU 174 includes the MAC reset indication in Element 1 and outside of Configuration 1.

[0155] 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, then after sending the first configuration activation command 330, receiving an acknowledgement 331, or determining at event 332 or 336 that UE 102 is connected to cell 124B, DU 174 resets the DU MAC entity. Alternatively, instead of resetting the DU MAC entity, DU 174 releases the DU MAC entity and establishes a new DU MAC entity for communicating with UE 102 via cell 124B. Otherwise, if Configuration 1 or Element 1 does not include a MAC reset indication and Configuration 1 is a full configuration, then DU 174 avoids resetting the DU MAC entity after sending the first configuration activation command 330 (e.g., in response thereto).

[0156] 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 UE 102 not to reset the UE MAC entity, and the base station 104 excludes the MAC retention indication in the configuration or element to configure UE 102 to reset the UE MAC entity. If the configuration or element includes the MAC retention indication, then upon receiving a configuration activation command (e.g., the first configuration activation command), UE 102 avoids resetting the UE MAC entity in response to the MAC retention indication. Otherwise, if the configuration or element does not include the MAC retention indication, then UE 102 resets the UE MAC entity when or upon receiving the configuration activation command.

[0157] DU 174 uses the DU MAC entity (e.g., NR MAC 204B) to communicate with UE 102 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). If the base station 104 includes the MAC retention indication in a configuration or element (e.g., Configuration 1 or Element 1), then after sending a configuration activation command (e.g., the first configuration activation command) to UE 102, DU 174 avoids resetting the DU MAC entity in response to the MAC retention indication. Accordingly, after sending the first configuration activation command 330, receiving an acknowledgement 331, or determining at event 332 or 336 that UE 102 is connected to cell 124B, DU 174 continues to use the retained (i.e., not reset) DU MAC entity to communicate with UE 102.

[0158] In some implementations, DU 174 includes the MAC reservation indication in the MAC-CellGroupConfig IE (e.g., CellGroupConfig IE) in Configuration 1. In other implementations, DU 174 includes the MAC reservation indication in the CellGroupConfig IE and outside the MAC-CellGroupConfig IE. In still other implementations, DU 174 includes the MAC reservation indication in Element 1 and outside Configuration 1.

[0159] Otherwise, if Configuration 1 or Element 1 does not include the MAC reservation indication, DU 174 resets the DU MAC entity after sending the first configuration activation command 330 (e.g., in response thereto).

[0160] In some implementations, the base station 104 includes or does not include an indication that Configuration 1 is a full configuration. If the base station 104 includes an indication that Configuration 1 is a full configuration in Configuration 1 or Element 1, the base station 104 avoids including the MAC reservation 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 full configuration in Configuration 1 or Element 1, the base station 104 includes the MAC reservation indication in Configuration 1 or Element 1.

[0161] 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 an 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 excludes the MAC partial reset indication in the configuration or the element to configure the UE 102 to fully reset the UE MAC entity. If the configuration or the element includes the MAC partial reset indication, the UE 102 partially resets the UE MAC entity when receiving a configuration activation command (e.g., the first configuration activation command). Otherwise, if the configuration or the element does not include the MAC partial reset indication, the UE 102 fully resets the UE MAC entity after receiving the configuration activation command (e.g., in response thereto). In some implementations, when the UE partially resets the UE MAC entity, the UE 102 retains (e.g., maintains or keeps) the operating state of the UE MAC entity, or omits one or more actions that the UE 102 performs when the UE 102 fully resets the UE MAC entity in some implementations.

[0162] If the base station 104 includes the MAC partial reset indication in a configuration or an element (e.g., Configuration 1 or Element 1), after sending the configuration activation command (e.g., the first configuration activation command) to the UE 102, the DU 174 partially resets the DU MAC entity in response to the MAC partial reset indication.

[0163] In some implementations, DU 174 includes the MAC part reset indication in the MAC-CellGroupConfig IE (e.g., CellGroupConfig IE) in Configuration 1. In other implementations, DU 174 includes the MAC part reset indication in the CellGroupConfig IE and outside the MAC-CellGroupConfig IE. In still other implementations, DU 174 includes the MAC part reset indication in Element 1 and outside Configuration 1.

[0164] Otherwise, if Configuration 1 or Element 1 does not include the MAC part reset indication, DU 174 fully resets the DU MAC entity after sending the first configuration activation command (e.g., in response thereto). In some implementations, Base Station 104 includes or does not include an indication that Configuration 1 is a full configuration. In some implementations, if Base Station 104 includes an indication that Configuration 1 is a full configuration in Configuration 1 or Element 1, Base Station 104 avoids including the MAC part reset indication in Configuration 1 or Element 1. Otherwise, in further implementations, if Base Station 104 does not include an indication that Configuration 1 is a full configuration in Configuration 1 or Element 1, Base Station 104 includes the MAC part reset indication in Configuration 1 or Element 1. In some alternative implementations, in cases where Base Station 104 includes an indication that Configuration 1 is a full configuration in Configuration 1 or Element 1, Base Station 104 includes the MAC part reset indication.

[0165] In some implementations, Base Station 104 (e.g., DU 174 or CU 172) does not include an indication related to resetting the UE MAC entity in a configuration or element (e.g., Configuration 1 or Element 1) or in an RRC message (e.g., Event 316, 318) that includes the configuration or element. In such cases, UE 102 partially resets the UE MAC entity after receiving the first configuration activation command (e.g., in response thereto). In such cases, after sending the first configuration activation command, receiving an acknowledgement, performing a random access procedure with UE 102, or determining that UE 102 is connected to Cell 124B, DU 174 partially resets the DU MAC entity.

[0166] In some implementations, when the UE 102 determines to reset the UE MAC entity or resets the UE MAC entity as described above, the UE 102 resets the UE MAC entity before performing the 332 random access procedure or communicating with the base station 104 via the cell 124B 336. In some implementations, when the UE 102 resets the UE MAC entity, the UE 102 performs at least one of the following actions for the UE MAC entity (i.e., UE MAC reset or full UE MAC reset): (i) initialize Bj of the configured logical channels to zero; (ii) stop one or more timers; (iii) consider the timeAlignmentTimer expired if the UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1); (iv) set the new data indicator (NDI) for the UL HARQ process to the value 0; (v) set the NDI for the HARQ process ID to the value 0 for monitoring the PDCCH in the sidelink resource allocation mode 1; (vi) flush the Msg3 buffer; (vii) flush the MSGA buffer; (viii) cancel the triggered scheduling request procedure (if any); (ix) cancel the triggered buffer status report procedure (if any); (x) cancel the triggered power headroom report procedure (if any); (xi) cancel the triggered consistent LBT failure (if any); (xii) cancel the triggered BFR (if any); (xiii) cancel the triggered sidelink buffer status report procedure (if any); (xiv) cancel the triggered preemption buffer status report procedure (if any); (xv) cancel the triggered timing advance report procedure (if any); (xvi) cancel the triggered recommended bitrate query procedure (if any); (xvii) cancel the triggered configured uplink grant confirmation (if any); (xviii) cancel the triggered configured sidelink grant confirmation (if any); (xix) cancel the triggered desired guard symbol query (if any); (xx) cancel the triggered positioning measurement gap activation / deactivation request procedure (if any); (xxi) flush the soft buffer for the DL HARQ process; (xxii) for each DL HARQ process in the DL HARQ process, consider the next received transmission of the TB as the first transmission; (xxiii) release the temporary C-RNTI (if any); (xiv) reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER); (xxv) and so on.

[0167] In some implementations, when DU 174 resets the DU MAC entity, DU 174 performs at least one of the following actions for the DU MAC entity (i.e., DU MAC reset or full DU MAC reset): (i) stops one or more timers; (ii) if UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), considers the timeAlignmentTimer started and / or maintained by DU 174 for UE 102 to be expired; (iii) sets the NDI for the DL HARQ process to the value 0; (iv) flushes the soft buffer for the UL HARQ process; (v) for each UL HARQ process in the UL HARQ process, considers the next received transmission of the TB to be the first transmission; (vi) resets one or more counters (e.g., BFI_COUNTER / or LBT_COUNTER); (vii) and so on.

[0168] Depending on the implementation, UE 102 determines to partially or fully reset the UE MAC entity. In some implementations, when UE 102 resets the UE MAC entity as described above, UE 102 fully resets the UE MAC entity (i.e., full UE MAC reset). In a full UE MAC reset, UE 102 performs some or all of the actions described above. In other implementations, when UE102 resets the UE MAC entity as described above, UE 102 partially resets the UE MAC entity (i.e., partial UE MAC reset). In a partial UE MAC reset, UE 102 performs a subset or part of some or all of the actions in a full UE MAC reset.

[0169] In some implementations, a partial UE MAC reset includes at least one of the following actions: (i) if UE102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), considers the timeAlignmentTimer of UE 102 to be expired; (ii) flushes the Msg3 buffer; (iii) flushes the MSGA buffer; (iv) releases (if any) the temporary C-RNTI; and / or (v) resets one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0170] In some implementations, partial UE MAC reset further includes at least one of the following actions: (i) canceling (if any) the triggered scheduling request procedure; (ii) canceling (if any) the triggered buffer status report procedure; (iii) canceling (if any) the triggered power headroom report procedure; (iv) canceling (if any) the triggered consistent LBT failure; (v) canceling (if any) the triggered BFR; (vi) canceling (if any) the triggered sidelink buffer status report procedure; (vii) canceling (if any) the triggered pre-emption buffer status report procedure; (viii) canceling (if any) the triggered timing advance report procedure; (ix) canceling (if any) the triggered recommended bit rate query procedure; (x) canceling (if any) the triggered configured uplink grant confirmation; (xi) canceling (if any) the triggered configured sidelink grant confirmation; (xii) canceling (if any) the triggered desired guard symbol query; and / or (xiii) canceling (if any) the triggered positioning measurement gap activation / deactivation request procedure.

[0171] In some implementations, partial UE MAC reset further includes at least one of the following actions: (i) stopping a first part of one or more timers and retaining the remaining part of one or more timers; (ii) setting the new data indicator (NDI) for the UL HARQ procedure to the value 0; (iii) setting the NDI for the HARQ process ID to the value 0 for monitoring the PDCCH in sidelink resource allocation mode 1; (iv) flushing the soft buffer for the DL HARQ procedure; and / or (v) for each DL HARQ procedure in the DL HARQ procedure, treating the next received transmission of the TB as the first transmission.

[0172] Depending on the implementation, DU 174 determines to partially or fully reset the DU MAC entity. In some implementations, when DU 174 resets the DU MAC entity as described above, DU 174 fully resets the DU MAC entity (i.e., full DU MAC reset). In a full DU MAC reset, DU 174 performs some or all of the actions described above. In other implementations, when DU174 resets the DU MAC entity as described above, DU 174 partially resets the DU MAC entity (i.e., partial DU MAC reset). In a partial DU MAC reset, DU 174 performs a subset or part of some or all of the actions in a full DU MAC reset.

[0173] In some implementations, partial DU MAC reset includes at least one of the following actions in the partial MAC reset: (i) if UE 102 is configured to perform a random access procedure (e.g., event 332) in a configuration (e.g., configuration 1), consider the timeAlignmentTimer started and / or maintained by DU 174 for UE 102 as expired; and / or (ii) reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0174] In some implementations, partial DU MAC reset includes at least one of the following actions for the MAC entity (i.e., DU MAC reset): (i) stop a first part of one or more timers and retain the remaining part of one or more timers; (ii) set the NDI for the DL HARQ process to the value 0; (iii) flush the soft buffer for the UL HARQ process; (iv) for each UL HARQ process in the UL HARQ process, consider the next received transmission of the TB as the first transmission; and / or (v) reset one or more counters (e.g., BFI_COUNTER and / or LBT_COUNTER).

[0175] In some implementations, Configuration 1 includes or does not include one or more RLC reestablishment indications (e.g., the reestablishRLC field) for configuring UE 102 to reestablish one or more RLC entities (e.g., RLC 206B) that UE 102 uses to communicate with DU 174 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331). If Configuration 1 includes an RLC reestablishment indication for an RLC entity (e.g., RLC 206B) that configures UE 102 to reestablish RLC PDUs (e.g., events 302, 304, 318, 320, 324, 330, and / or 331) that UE 102 uses to communicate with base station 104, then UE 102 reestablishes the RLC entity in response to the RLC reestablishment indication. In some implementations, UE 102 reestablishes the RLC entity before performing the 332 random access procedure or communicating 336 with base station 104 via cell 124B. In other implementations, UE 102 reestablishes the RLC entity during or after performing the 332 random access procedure. In some implementations, when UE 102 reestablishes the RLC entity, UE 102 performs at least one of the following actions for the RLC entity: (i) discarding RLC SDUs, RLC SDU segments, and RLC PDUs (if any); (ii) stopping and resetting the timer (if running); (iii) resetting the state variable to its initial value. In some implementations, the state variable and the timer are currently defined (e.g., in 3GPP specification 38.322).

[0176] Otherwise, if Configuration 1 does not include an RLC reestablishment indication for the RLC entity, then UE 102 avoids reestablishing the RLC entity when or upon receiving the first configuration activation command. In other words, UE 102 avoids performing actions for reestablishing the RLC entity of UE 102 when or upon receiving the first configuration activation command. In some implementations, if Configuration 1 or Element 1 does not include an RLC reestablishment indication and includes an indication that Configuration 1 is a full configuration, then UE 102 reestablishes the RLC entity of UE 102 when or upon receiving the first configuration activation command. Otherwise, if Configuration 1 or Element 1 does not include an RLC reestablishment indication and Configuration 1 is an indication of a full configuration, then UE 102 avoids reestablishing the RLC entity when or upon receiving the first configuration activation command.

[0177] Similarly, DU 174 reconstructs the RLC entity (e.g., NR RLC 206B) that DU 174 uses to communicate with the RLC entity of UE 102 (e.g., events 302, 304, 318, 320, 324, 330, and / or 331) in response to an RLC re - establishment indication. In some implementations, DU 174 reconstructs the RLC entity after sending the first configuration activation command, receiving an acknowledgement for the first configuration activation command from UE 102, or determining that UE 102 is connected to cell 124B. In some implementations, the acknowledgement is a HARQ ACK. In other implementations, the acknowledgement is a MAC CE. In still other implementations, the acknowledgement is a PUCCH transmission. In some implementations, when the base station 104 reconstructs the RLC entity, DU 174 performs at least one of the following actions for the RLC entity: (i) discards RLC SDUs, RLC SDU segments, and RLC PDUs (if any); (ii) stops and resets the timer (if it is running); and / or (iii) resets the state variable to its initial value. In some implementations, the state variable and the timer are currently defined (e.g., in 3GPP specification 38.322).

[0178] In some implementations, the above description for configuration 1 also applies to configurations 2, …, N.

[0179] In some implementations, after determining that UE 102 is connected to cell 124B (e.g., in response thereto), CU 172 sends a 338 CU - to - DU message (e.g., UE context modification request message) to DU 174 to instruct DU 174 to stop communicating with UE 102 and / or release or suspend the resources of cell 124A that are configured for UE 102. In a further implementation, in response, DU 174 stops communicating with UE 102 on cell 124A, releases or suspends the resources of cell 124A that are configured for UE 102, and / or sends a 340 DU - to - CU message (e.g., UE context modification response message) to CU - 172. Events 338 and 340 are collectively referred to as procedure 394 (e.g., UE context modification procedure) in Figure 3 which.

[0180] Next, refer to Figure 4, in scenario 400, base station 104 includes CU 172, source DU (S-DU) 174A, and target DU (T-DU) 174B. S-DU 174A operates cell 124A and, in some implementations, cell 124B, while T-DU 174B operates cell 124C. Scenario 400 is similar to scenario 300. Thus, the description for scenario 300 generally applies to scenario 400. Specifically, the description for cell 124B in scenario 300 applies to cell 124C. Events 404, 406, 490, 492, 416, 418, 420, and 422 are collectively referred to as the fast serving cell configuration procedure 480 in Figure 4 Events 424, 426, 428, 430, 431, 432, 434, 436, 494 are collectively referred to as the serving cell change procedure 482 in Figure 4 .

[0181] In some implementations, after determining that UE 102 is connected to cell 124C (e.g., in response thereto), CU 172 sends a 438 CU-to-DU message (e.g., UE context release command message) to S-DU 174A to release the UE context of UE 102. In response, S-DU 174A releases the UE context of UE 102 and sends a 440 DU-to-CU message (e.g., UE context release complete message) to CU-172. Alternatively, CU 172 sends a 438 CU-to-DU message (e.g., UE context modification request message) to S-DU 174A to instruct S-DU 174A to stop communicating with UE 102 and / or release or suspend the resources of cell 124A configured for UE 102. In response, in some such implementations, S-DU 174A stops communicating with UE 102 on cell 124A, releases or suspends the resources of cell 124A configured for UE 102, and / or sends a 440 DU-to-CU message (e.g., UE context modification response message) to CU-172.

[0182] Next, refer to Figure 5A, in scenario 500A, base station 106 operates as an MN, and base station 104 operates as an SN. SN 104 includes a CU 172 and a DU 174. Scenario 500A is similar to scenario 300, except that scenario 500A is a DC scenario and scenario 300 is a single connection (SC) scenario. Initially, UE 102 under 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 under DC communicates 502 UL PDUs and / or DL PDUs with MN 106 and / or SN 104 via a radio bearer, which may include an SRB and / or a DRB in further implementations. In further implementations, MN 106 and / or SN 104 configure the radio bearer for UE 102. UE 102 under DC communicates 502 UL PDUs and / or DL PDUs with SN 104 on the SCG configured by SN 104 for communicating with UE 102. UE 102 under DC communicates UL PDUs and / or DL PDUs with MN 106 on the MCG according to the MN configuration (i.e., MCG configuration). In some implementations, the first configuration is an SN configuration (i.e., SCG configuration). In the MN configuration, MN 106 configures the MCG, which includes at least one serving cell operated by MN 106 (e.g., cell 126 and / or other cells). In the first configuration, SN 106A configures the SCG, which includes at least one serving cell operated by SN 104 (e.g., cell 124A and / or other cells). In some implementations, the MN configuration includes multiple 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 multiple configuration parameters, and UE 102 (e.g., via MN 106) receives the configuration parameters in one or more RRC messages from SN 104 or on an SRB (e.g., SRB3) configured by MN 106 or SN 104 for exchanging RRC messages between UE 102 and SN 104.

[0183] In some implementations, when communicating with MN 106 and SN 104 under DC, MN 106 performs the fast serving cell configuration procedure 580 with UE102, similar to procedure 380. In some implementations, when communicating with MN 106 and SN104 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 then 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, at least one SN message includes an RRC transfer message and / or an SN modification request message.

[0184] After receiving at least one measurement report (e.g., in response thereto) or when the base station 104 communicates with UE 102, the base station 104 determines to prepare cell 124B for UE 102, as described 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 acknowledgement, or determining that UE 102 is connected to cell 124B, UE 102 operating with MN 106 and SN 104 under DC communicates 536 with SN 104 on cell 124B according to configuration 1, similar to event 336.

[0185] Events 504, 506, 505, 507, 590, 592, 516, 518, 520, 522 are Figure 5A collectively referred to as the serving cell configuration procedure 581A in Figure 5A Events 524, 526, 528, 530, 531, 532, 534, 536, 594 are

[0186] Next, refer to Figure 5B, Scenario 500B is generally similar to Scenario 500A, except that SN 104 sends 517, 519 RRC reconfiguration messages to UE 102 via MN106 and receives 521, 523 RRC reconfiguration complete messages from UE 102 via MN 106. In some implementations, SN 104 generates a first SN message (e.g., SN modification request message, SN modification required message, or RRC transfer message) including the RRC reconfiguration message, and sends the first SN message to MN 106 in event 517. In some implementations, MN 106 generates a second SN message (e.g., SN reconfiguration complete message or RRC transfer message) including the RRC reconfiguration complete message, and sends the second SN message to SN 104 in event 523.

[0187] Events 504, 506, 505, 507, 590, 592, 517, 519, 521, 523 are collectively referred to as the serving cell configuration procedure 581B in Figure 5B the following.

[0188] Next, referring to Figure 6A , in Scenario 600A, base station 106 operates as an MN, and base station 104 operates as an SN, similar to Scenarios 300 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 collectively referred to as the serving cell configuration procedure 681A in Figure 6A the following. Events 624, 626, 628, 630, 631, 632, 634, 636, 694 are collectively referred to as the serving cell change procedure 683 in Figure 6A the following. Further, it will be understood that some of the descriptions regarding Scenarios 300 to 500B may apply to Scenario 600A, but apply to one or both of S-DU 174A or T-DU 174B (e.g., events 608, 610, 632, 634, etc.).

[0189] Next, referring to Figure 6B , Scenario 600B is similar to Scenarios 300 to 500B and Scenario 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 collectively referred to as the serving cell configuration procedure 681B in Figure 6B the following.

[0190] Next, referring to Figure 7A , in scenario 700A, base station 104 operates as both an MN and an SN, similar to scenarios 300 through 600B. Base station 104 includes a CU 172, a master DU (M-DU) 174A, and a secondary DU (S-DU) 174B. The CU 172 operates with the M-DU 174A as the MN, similar to the base station 104 in Figure 3 or the MN 106 in Figures 5A to 6B , and the CU 172 operates with the S-DU 174B as the SN, similar to the SN 104 in Figures 5A to 6B .

[0191] In scenario 700A, the UE 102 initially communicates 702 with the M-DU 174A and the S-DU 174B under DC and communicates 702 with the CU 172 via the M-DU 174A and the S-DU 174B. In event 702, the UE 102 communicates with the S-DU 174B on cell 124A using a first configuration and communicates with the CU 172 via the S-DU 174B. Events 704 and 706 are similar to events 304 and 306. In some implementations, the UE 102 sends 705 at least one measurement report to the M-DU 174A, similar to event 304. The M-DU 174A then sends 707 at least one DU-to-CU message including at least one measurement report to the CU 172, similar to event 306.

[0192] Events 704, 706, 705, 707, 790, 792, 716, 718, 720, 722 are collectively referred to as the serving cell configuration procedure 781A in Figure 7A . Events 724, 726, 728, 730, 731, 732, 734, 736, 794 are collectively referred to as the serving cell change procedure 783 in Figure 7A .

[0193] Next, referring to Figure 7B , scenario 700B is similar to scenarios 300 through 600B and scenario 700A, except that the CU 172 sends 717, 719 RRC reconfiguration messages to the UE 102 via the M-DU 174A and receives 721, 723 RRC reconfiguration complete messages from the UE 102 via the M-DU 174A. Events 704, 706, 705, 707, 790, 792, 717, 719, 721, 723 are collectively referred to as the serving cell configuration procedure 781B in Figure 7B .

[0194] Next, referring to Figure 8A, in scenario 800A, base station 104 operates as both an MN and an SN, similar to scenarios 300 to 700B. Base station 104 includes a CU 172, a master DU (M-DU) 174A, a secondary DU (S-DU) 174B, and a T-DU 174C. The CU 172 operates with the M-DU 174A as the MN and with the S-DU 174B as the SN. Events 804, 806, 805, 807, 890, 892, 816, 818, 820, 822 are Figure 8A collectively referred to as the serving cell configuration procedure 881A in Figure 8A . Events 824, 826, 828, 830, 831, 832, 834, 836, 894 are Figure 8A collectively referred to as the serving cell change procedure 883. Further, it will be understood that some descriptions regarding scenarios 300 to 700B may apply to scenario 800A, but apply 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.).

[0195] Next, referring to Figure 8B , scenario 800B is similar to scenarios 300 to 700B and scenario 800A, except that the CU 172 sends RRC reconfiguration messages 817, 819 to the UE 102 via the M-DU 174A and receives RRC reconfiguration complete messages 821, 823 from the UE 102 via the M-DU 174A. Events 804, 806, 805, 807, 890, 892, 817, 819, 821, 823 are Figure 8A collectively referred to as the serving cell configuration procedure 881B.

[0196] Next, referring to Figure 9A , in scenario 900A, base station 104 includes a CU 172, a source DU (S-DU) 174A, and a target DU (T-DU) 174B, similar to scenarios 300 and 400. The differences between scenario 900A, 300, and 400 are described below.

[0197] In some scenarios or implementations, the UE 102 receives configurations 1, …, N from the base station 104 in procedure 380 and / or receives configurations N+1, …, N+P from the base station 104 in procedure 480. Depending on the implementation, each of “N” and “P” is an integer greater than zero. Before activating one of the configurations, the UE 102 determines 902 that communication with the base station 104 has failed. In response to the communication failure, the UE 102 initiates 906 an RRC connection reestablishment procedure to recover from the communication failure. In response to this initiation, the UE 102 selects a cell that operates on the S-DU 174A and performs 904 a random access procedure with the S-DU 174A on that cell. In some scenarios or implementations, the cell is cell 124A. In other scenarios or implementations, the cell is a cell other than cell 124A. In some implementations, the communication failure is a radio link failure, an integrity check failure, or a reconfiguration failure with synchronization.

[0198] In some implementations, the random access procedure is a four-step random access procedure or a two-step random access procedure. In the four-step random access procedure, the UE 102 sends a random access preamble to the S-DU 174A, and in response, the S-DU 174A sends a random access response to the UE 102. Then, the UE 102 sends message 3 including an RRC reestablishment request message to the S-DU 174A according to the uplink grant included in the random access response. The S-DU 174A then sends the RRC reestablishment request message to the CU 172. In some implementations, the S-DU 174A sends a first MAC PDU including a contention resolution MAC CE to the UE 102 in response to message 3.

[0199] In response to the RRC reestablishment request message, the CU 172 sends an RRC reestablishment message to the UE 102 via the S-DU 174A. In some implementations, the S-DU 174A includes the RRC reestablishment message in the first MAC PDU. In other implementations, the S-DU 174A sends a second MAC PDU including the RRC reestablishment message. In response to the RRC reestablishment message, the UE 102 sends an RRC reestablishment complete message to the CU 172 via the S-DU 174A. After sending the RRC reestablishment message or receiving the RRC connection reestablishment complete message, the CU 172 then performs an RRC reconfiguration procedure 908 with the UE 102 via the S-DU 174A. During the RRC reconfiguration procedure, the CU 172 sends an RRC reconfiguration message including configuration parameters to the UE 102 via the S-DU 174A. In response, the UE 102 sends an RRC reconfiguration complete message to the CU 172 via the S-DU 174A. After performing the RRC reconfiguration procedure, the UE 102 communicates 922 with the S-DU 174A using the configuration parameters and communicates with the CU 172 via the S-DU 174A.

[0200] In some implementations, the CU 172 performs a UE context modification procedure 912 with the S-DU 174A when or after performing the RRC connection reestablishment procedure (e.g., in response thereto) to obtain configuration parameters for the UE 102. In some implementations, the CU 172 initiates the procedure 912 by sending a UE context modification request message to the S-DU 174A. In response, the S-DU 174A sends a UE context modification response message including the configuration parameters to the CU 172. The CU 172 includes the configuration parameters in the RRC reconfiguration message of the procedure 908. In other implementations, the S-DU 174A initiates the UE context modification procedure by sending a UE context modification requirement message including the configuration parameters to the CU 172. In response, the CU 172 sends a UE context modification confirmation message to the S-DU 174A. The CU 172 includes the configuration parameters in the RRC reconfiguration message of the procedure 908.

[0201] In some implementations, the UE 102 releases 910 configurations 1, …, N and / or configurations N+1, …, N+P in response to a communication failure 902 or an RRC connection reestablishment procedure 906. Alternatively, the CU 172A includes a release indication in the RRC reconfiguration message of procedure 908 to release configurations 1, …, N and / or configurations N+1, …, N+P. Accordingly, the UE 102 releases 910 configurations 1, …, N and / or configurations N+1, …, N+P in response to the release indication. In some implementations, the S-DU 174A releases 914 configurations 1, …, N in response to a UE context modification procedure. In some implementations, the CU 172 includes a release indication in the UE context modification request message to instruct the S-DU 174A to release the configurations for later activation, and the S-DU 174A releases configurations 1, …, N in response to the release indication. In a further implementation, the S-DU 174A releases configurations 1, …, N in response to a UE context modification request message, regardless of whether the UE context modification request message includes a release indication for the S-DU 174A to release the configurations for later activation.

[0202] In some implementations, the CU 172 sends 916 a UE context release command message to the T-DU 174B to release configurations N+1, …, N+P. In response, the T-DU 174B sends 918 a UE context release complete message to the S-DU 174A and releases 920 configurations N+1, …, N+P.

[0203] In other implementations, the UE 102 retains configurations 1, …, N and / or configurations N+1, …, N+P after determining a communication failure 902 or performing an RRC connection reestablishment procedure 906 (e.g., in response thereto). In some such cases, the S-DU 174A retains configurations 1, …, N in response to procedure 912. Similarly, in a further implementation, the CU 172 does not send a UE context release command message to the T-DU 174B, such that the T-DU 174B retains configurations N+1, …, N+P.

[0204] Events 904, 906, 908, 910, 912, 914, 916, 918, 920, and 922 are collectively referred to as a recovery procedure 970 in Figure 9A the

[0205] Next, refer to Figure 9B, Scenario 900B is similar to Scenario 900A, except that the random access procedure 905 occurs between UE 102 and T-DU 174B, and the RRC connection reestablishment procedure 907 and the RRC reconfiguration procedure 909 occur among UE 102, T-DU 174B, and CU 172. By replacing S-DU 174A with T-DU 174B, Figure 9A the descriptions of the random access procedure, the RRC connection reestablishment procedure, and the RRC reconfiguration procedure are applicable to Figure 9B . After performing the RRC reconfiguration procedure, UE 102 communicates with T-DU 174B using the configuration parameters of the RRC reconfiguration message of the RRC reconfiguration procedure and communicates with CU 172 via T-DU 174B.

[0206] In some implementations, in Scenario 900B, CU 172 sends a 911 UE context release command message to S-DU 174A in response to the RRC connection reestablishment procedure to release the UE context of UE 102. In response, S-DU 174A sends a 913 UE context release complete message to CU 172 and releases the UE context of UE 102. In some implementations, the UE context includes a first configuration or a part of the first configuration. In a further implementation, S-DU 174A further releases configurations 1, …, N in response to the UE context release command message. Alternatively, CU 172 does not send a UE context release command message to S-DU 174A, so that S-DU 174A retains the first configuration and configurations 1, …, N. In a further alternative implementation, CU 172 performs a UE context modification procedure with S-DU 174A to release or retain configurations 1, …, N, similar to procedure 912.

[0207] In some implementations, CU 172 performs a UE context modification procedure with T-DU 174B to release configurations N+1, …, N+P, similar to procedure 912. In response to the UE context modification procedure, T-DU 174B releases configurations N+1, …, N+P.

[0208] Events 905, 907, 909, 911, 913, 914, 920, and 923 are collectively referred to as the connection reestablishment procedure 971 in Figure 9B .

[0209] Next, refer to Figure 9C, Scenario 900C is similar to Scenario 900A. After determining that communication fails at 902 or initiating an RRC connection reestablishment procedure with the base station 104 (e.g., in response thereto), the UE 102 selects 903C a suitable cell. If the suitable cell is prepared or configured in Configurations 1, …, N, the UE 102 connects to the cell. In some scenarios or implementations, the suitable cell is the Figure 3 cell 1 described in, and the UE 102 connects to cell 1 as described for Figure 3 . Otherwise, if the UE 102 selects a cell that is not prepared or not configured in Configurations 1, …, N, the UE 102 performs procedure 970.

[0210] Next, referring to Figure 9D , Scenario 900D is similar to Scenarios 900B and 900C. After determining that communication fails at 902 or initiating an RRC connection reestablishment procedure with the base station 104 (e.g., in response thereto), the UE 102 selects 903D a suitable cell. If the suitable cell is a cell that is prepared or configured in Configurations N+1, …, N+P, the UE 102 connects to the cell. In some scenarios or implementations, the suitable cell is the Figure 4 cell 1 described in, and the UE 102 connects to cell 1 as described for Figure 4 . Otherwise, if the UE 102 selects a cell that is not prepared or not configured in Configurations N+1, …, N+P, the UE 102 performs procedure 971.

[0211] Next, referring to Figures 10A to 12 discusses several example methods that can be implemented in a UE (e.g., UE 102) to handle communication failures and configurations for later activation. The examples and implementations described for Figures 3 to 9D can be applicable to Figures 10A to 12 .

[0212] Figure 10A Illustrates method 1000A for a UE (e.g., UE 102) to manage communication failures with a RAN (e.g., DU 174, CU 172, base station 104 / 106, or RAN 105).

[0213] Method 1000A begins at block 1002, where the UE communicates with the RAN using a first configuration (e.g., events 302, 402, 502, 602, 702, 802). At block 1004, the UE receives a second configuration from the RAN (e.g., events 316, 318, 416, 418, 516, 518, 517, 519, 616, 618, 617, 619, 716, 718, 717, 719, 816, 818, 817, 819). At block 1006, the UE determines a communication failure with the base station before receiving a configuration activation command to activate the second configuration (e.g., event 902). At block 1008, the UE performs a protocol procedure with the RAN to recover from the communication failure (e.g., events 906, 970, 907, 971). In some implementations, at block 1010, the UE retains a first part of the first configuration in response to the communication failure or the protocol procedure. In further implementations, at block 1012, the UE releases a second part of the first configuration in response to the communication failure or the protocol procedure.

[0214] In some implementations, the protocol procedure is an RRC connection reestablishment procedure. In other implementations, when the UE's MN and SN with the RAN are under DC (e.g., events 502, 581A, 581B, 602, 681A, 681B, 702, 781A, 781B, 802, 881A, 881B), the protocol procedure is an RRC reconfiguration procedure for primary cell group (MCG) fast recovery. In some implementations, during the RRC reconfiguration procedure, the UE receives an RRC reconfiguration message from the SN to recover from the communication failure. In response, the UE connects to the cell of the MN and sends an RRC reconfiguration complete message to the MN via that cell. In still other implementations, when the UE's MN and SN with the RAN are under DC (e.g., events 502, 581A, 581B, 602, 681A, 681B, 702, 781A, 781B, 802, 881A, 881B), the protocol procedure is an SCG failure information procedure. During the SCG failure information procedure, the UE sends SCG failure information to the MN (e.g., an SCGFailureInformation message or an SCGFailureInformationNR message). In further implementations, the MN sends an SN message to the SN. In some implementations, the MN includes the SCG failure message in the SN message.

[0215] Figure 10BIt is a flowchart of an exemplary method 1000B similar to method 1000A, except that method 1000B includes blocks 1011 and 1016 instead of block 1010. At block 1011, the UE retains a second configuration for later activation in response to a communication failure or a protocol procedure. At block 1016, the UE activates the second configuration to communicate with the RAN (e.g., events 330, 332, 336, 382, 430, 432, 436, 482, 530, 532, 536, 582, 583, 630, 632, 636, 682, 683, 730, 732, 736, 782, 783, 830, 832, 836, 882, 883) after the communication failure is recovered.

[0216] Figure 10C It is a flowchart of an exemplary method 1000C similar to methods 1000A and 1000B, except that method 1000C includes block 1009. At block 1009, the UE determines whether the communication failure is with the MN or the SN of the RAN. If the UE determines that the communication failure is with the MN, the process proceeds to block 1010 and, in some implementations, to blocks 1012 and 1014. Otherwise, if the UE determines that the communication failure is with the SN, the process proceeds to block 1011 and, in some implementations, to blocks 1012, 1014, and 1016.

[0217] Figure 10D It is a flowchart of an exemplary method 1000D similar to methods 1000A and 1000B, except that method 1000D includes blocks 1005 and 1007. At block 1005, the UE selects a cell (e.g., events 903C, 903D) in response to a communication failure or a protocol procedure. At block 1007, the UE determines whether the cell is configured in the second configuration (e.g., events 903C, 903D). If the UE determines at block 1007 that the cell is configured in the second configuration, the process proceeds to block 1016. Otherwise, if the UE determines that the cell is not configured in the second configuration, the process proceeds to block 1008.

[0218] Figure 11A Illustrates a method 1100A that can be implemented by a UE (e.g., UE 102) for managing communication failures with a RAN (e.g., DU 174, CU 172, base station 104 / 106, or RAN 105).

[0219] Method 1100A starts from blocks 1002 and 1004 as Figure 10A described. At block 1104, the UE activates a second configuration in response to a communication failure. In some implementations, at block 1106, the UE avoids initiating a protocol procedure in response to a communication failure. For example, in some implementations, the protocol procedure is as forFigure 10A As described. At block 1108, the UE performs a random access procedure with the RAN on a cell, where the first configuration includes an ID identifying the cell (e.g., Figure 9C event 332 of Figure 9D or event 432, events 532, 632, 732, 832). At block 1110, after successfully performing the random access procedure (e.g., in response thereto), the UE communicates with the RAN using the first configuration (e.g., Figure 9C event 336 of Figure 9D or event 436, events 536, 636, 736, 836).

[0220] Figure 11B is a flowchart of an example method 1100B similar to method 1100A, except that method 1100B includes blocks 1107 and 1112. At block 1107, the UE determines whether the UE has failed to complete the random access procedure. If the UE determines at block 1107 that the UE has successfully completed the random access procedure, the flow proceeds to block 1110. If the UE determines at block 1107 that the UE has failed to complete the random access procedure, the flow proceeds to block 1112. At block 1112, the UE performs a protocol procedure in response to the failure of the random access procedure.

[0221] For Figure 10A the examples and implementations described above may be applicable to Figures 11A to 11B .

[0222] Figure 12 Illustrates a method 1200 for managing communication failures with a RAN (e.g., DU 174, CU 172, base station 104 / 106, or RAN 105) that may be implemented by a UE (e.g., UE 102).

[0223] Method 1200 starts from blocks 1002, 1004 as Figure 10A described. At block 1202, the UE determines whether the UE has received a configuration activation command from the RAN to activate a second configuration. If the UE determines at block 1202 that the UE has received a configuration activation command from the RAN to activate a second configuration, the flow proceeds to block 1016. Otherwise, if the UE determines at block 1202 that the UE has not received a configuration activation command from the RAN to activate a second configuration, the flow proceeds to block 1204. At block 1204, the UE determines whether a communication failure with the RAN has occurred. If the UE determines at block 1204 that a communication failure with the RAN has occurred, the flow proceeds to block 1016. Otherwise, if the UE determines at block 1204 that a communication failure with the RAN has not occurred, the flow returns to block 1202.

[0224] The following description may apply to the above description.

[0225] Generally speaking, the description of one of the above-mentioned drawings is applicable to another one of the above-mentioned drawings. If there is no conflict, the above examples, implementation manners and methods can be combined. The events or boxes described above can be optional or omitted. For example, the events or boxes with dashed lines in the drawings can be optional. In some implementation manners, "message" is used and "information element (IE)" can replace "message", and vice versa. In some implementation manners, "IE" is used and "field" can replace "IE", and vice versa. In some implementation manners, "configurations" or "configuration parameters" can replace "configuration", and vice versa. In some implementation manners, "configuration activation command" can be replaced by "serving cell change command", "layer 1 / layer 2 handover command", "lower layer handover command" or "lower layer serving cell change command". "Fast serving cell change procedure" can replace "fast serving cell configuration procedure".

[0226] The user equipment (e.g., UE 102) in which the technology of the present disclosure can be implemented can be any suitable device capable of wireless communication, such as a smart phone, a tablet computer, a laptop computer, a mobile game console, a point of sale (POS) terminal, a health monitoring device, a drone, a camera, a media streaming dongle or another personal media device, a wearable device such as a smart watch, a wireless hotspot, a femtocell or a broadband router. Further, in some cases, the user equipment can be embedded in a host unit such as a vehicle or an electronic system of an advanced driver assistance system (ADAS). Still further, the user equipment can operate as an Internet of Things (IoT) device or a mobile Internet device (MID). Depending on the type, the user equipment can include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0227] Certain embodiments are described in the present disclosure as including logic or a plurality of components or modules. A module can be a software module (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing certain operations and can be configured or arranged in some manner. A hardware module can include dedicated circuitry 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 can also include programmable logic or circuitry that is temporarily configured by software to perform certain operations (e.g., as included within a general-purpose processor or other programmable processor). The decision to implement a hardware module in dedicated and permanently configured circuitry or in temporarily configured circuitry (e.g., configured by software) can be driven by cost and time considerations.

[0228] When implemented in software, the techniques can be provided as part of an operating system, a library used by multiple applications, a particular software application, etc. The software can be executed by one or more general-purpose processors or one or more dedicated processors.

[0229] After reading this disclosure, those skilled in the art will appreciate additional and alternative structural and functional designs for handling mobility between base stations through the principles disclosed herein. Thus, while specific embodiments and applications have been shown and described, it should be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes, and variations to the arrangements, operations, and details of the methods and devices disclosed herein will be apparent to those of ordinary skill in the art without departing from the spirit and scope defined in the appended claims.

Claims

1. A method implemented in a user equipment (UE), the method comprising: Communicating with a radio access network (RAN) in a first cell according to a first configuration; Receiving from the RAN a message comprising a configuration for performing a serving cell change to a second cell after an activation command; Detecting a communication failure with the RAN before receiving the activation command; and In response to the detection, performing at least one of the following: Performing a radio resource control (RRC) reestablishment procedure, or Releasing the second configuration.

2. The method according to claim 1, wherein the detection of the communication failure comprises detecting a radio link failure (RLF).

3. The method according to claim 1, wherein the detection of the communication failure comprises detecting a security check failure.

4. The method according to claim 3, wherein the detection of the security check failure comprises: Determining that an integrity message authentication code (MAC-I) of the message is invalid.

5. The method according to claim 4, further comprising: Receiving the message and the MAC-I in encrypted form.

6. The method according to claim 1, wherein the detection of the communication failure comprises detecting a reconfiguration failure with synchronization.

7. A method implemented in a user equipment (UE), the method comprising: Communicating with a radio access network (RAN) in a first cell according to a first configuration; Receiving from the RAN a message comprising a configuration for performing a serving cell change to a second cell after an activation command; Detecting a communication failure with the RAN before receiving the activation command; In response to the detection, retaining the second configuration; and Connecting to the second cell according to the second configuration.

8. The method according to claim 7, further comprising: Receiving the activation command; wherein the connecting to the second cell is in response to the activation command.

9. The method according to claim 8, further comprising: Receiving in the message comprising the configuration an identifier assigned to the configuration; and Determining that the activation command comprises the identifier to perform the serving cell change.

10. The method according to claim 7 or 8, wherein the receiving of the activation command is in response to sending a layer 1 (L1) measurement report to the RAN.

11. The method according to claim 7, wherein: The retaining of the second configuration is in response to determining that the communication failure is with a second node (SN).

12. The method according to claim 7, further comprising: Selecting the second cell after the communication failure; and Connecting to the second cell in response to determining that the second configuration is applicable to the second cell.

13. The method according to claim 7, wherein the detection of the communication failure comprises detecting an RLF.

14. The method according to claim 7, wherein the detection of the communication failure comprises detecting a security check failure.

15. A user equipment (UE) comprising: A transceiver; and Processing hardware configured to implement the method according to any one of the preceding claims.

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