Method and apparatus for implementing mbs multicast service continuity during ue movement in rrc state

Abstract

The application discloses a method for realizing MBS multicast service continuity during UE movement in a communication network system in an RRC inactive state, comprising configuring a RAN-based notification area (RNA) for a UE by an existing service radio access network (RAN) node through RRC signaling, and the configuration contains RNA configuration for multicast or unicast service or both. When the UE moves out of the configured multicast and / or unicast RNA area, the UE requests to indicate its movement mode to the RAN node and / or indicates that the RAN node should update the RNA and / or receive the configured service through RRC signaling, so that the RAN node can update the RNA and / or service reception configuration for the UE, and when the UE moves to a new cell, the newly updated RNA area and / or service reception configuration are considered.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless communication systems, and more particularly to a method and apparatus for providing a radio access network (RAN) notification mechanism for multicast service continuity for multicast / broadcast service (MBS) during user equipment (UE) mobility in a radio resource control (RRC) inactive state. BACKGROUND

[0002] New radio (NR) MBS is expected to cover a wide range of applications and services, including public safety, mission critical, vehicle-to-everything communication (V2X), IPv4 / IPv6 multicast transparent transmission, IPTV, wireless software transmission, group communication, and Internet of Things applications in the 5G era. At the 3GPP RAN 88-e meeting (June 29 to July 3, 2020), a new working item (WID) was approved to support MBS functions in R17 5G specifications. For R17 NR MBS, two transmission modes have been defined, the broadcast transmission mode focuses on meeting lower UE quality of service (QoS) requirements, and the target users include devices in RRC connected, RRC inactive, and RRC idle states. The multicast transmission mode can meet higher UE QoS requirements, and the target users are devices in the RRC connected state. At the RAN 94-e meeting (December 6-17, 2021), it is proposed in the discussion of the R18 NR MBS working item that the power consumption efficiency of multicast reception in the RRC connected state is low and may not fully meet the requirements of MBS mission critical services, especially when the number of UEs in the cell exceeds the cell access capacity according to the requirements of SA1 TR 23.774. Therefore, it is recommended to support UE multicast reception in the RRC inactive state, and the following goals are studied: specification support for UE to receive multicast in RRC inactive state [RAN2, RAN3]; study of point-to-multipoint (PTM) configuration for receiving multicast in RRC inactive state [RAN2]; study of the impact of UE mobility and state transition when receiving multicast in RRC inactive state (without requiring seamless / non-lossy mobility) [RAN2, RAN3].

[0003] According to SA1 TR 23.774, for MBS mission critical scenarios where the number of users in a cell exceeds the normal access control limit, it is required that the UE, radio access network (RAN) node and core network (CN) are able to quickly, temporarily reconnect the UE (i.e. triggered by user request or inter-cell mobility) to guarantee the service continuity of MBS multicast radio bearers in different RRC operation states (such as connected, inactive and idle states). However, according to the R17 MBS specification, only multicast reception in RRC connected mode is defined. Therefore, when a mobility occurs during the UE is receiving multicast service in RRC inactive state, the UE needs to be moved to RRC connected state first by the network (RAN node), and then the RAN node performs handover operation for the UE to guarantee the service continuity of multicast bearers. However, this mobility option of moving the UE to RRC connected state only may not be the best choice for R18 NR MBS multicast service, especially for mission critical service, as the service requires fast / immediate reconnection time according to the requirement of TR 23.774 to avoid service interruption. SUMMARY

[0004] It is an object of the present application to propose a method and apparatus for achieving continuity of multicast / broadcast service (MBS) multicast service during mobility of a user equipment (UE) in a radio resource control (RRC) inactive state.

[0005] In a first aspect of the present application, a method for implementing multicast service continuity of multicast / broadcast service (MBS) during user equipment (UE) mobility in a radio resource control (RRC) inactive state, comprising: configuring a UE with a RAN-based notification area (RNA) configuration including a multicast RNA and / or a unicast RNA via RRC initial signaling by an existing serving radio access network (RAN) node; when the UE moves or performs a reselection procedure and reselects a cell belonging to the configured multicast RNA and / or unicast RNA, the UE continues to receive multicast and / or unicast services normally according to the existing reception configuration provided by the existing serving RAN node; when the UE moves or reselects a cell not belonging to the configured multicast RNA and / or unicast RNA, the UE triggers RRC signaling request to the existing serving RAN node indicating whether to resume RRC connection for multicast and / or unicast service reception; the UE receives RRC signaling response generated based on the UE indication from the existing serving RAN node or a new serving RAN node, the UE indication carrying multicast and / or unicast RNA update and / or multicast and / or unicast reception configuration; and the UE applies the multicast and / or unicast reception configuration to receive multicast and / or unicast service data according to the UE request and considers the updated RNA configuration when moving or reselecting to a new cell.

[0006] In a second aspect of the present application, a communication network system includes a memory, a transceiver, and a processor coupled to the memory and the transceiver. The processor is configured to perform the above method.

[0007] In a third aspect of the present application, a non-transitory machine-readable storage medium having stored thereon instructions that, when executed by a computer, cause the computer to perform the above method.

[0008] In a fourth aspect of the present application, a chip includes a processor configured to invoke and run a computer program stored in a memory to cause a device installed with the chip to perform the above method.

[0009] In a fifth aspect of the present application, a computer-readable storage medium having stored therein a computer program, wherein the computer program causes a computer to perform the above method.

[0010] In a sixth aspect of the present application, a computer program product includes a computer program, wherein the computer program causes a computer to perform the above method.

[0011] In a seventh aspect of the present application, a computer program, wherein the computer program causes a computer to execute the above method. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the embodiments or related technologies of the present application, the following briefly introduces the drawings to be described in the embodiments. Obviously, the drawings only illustrate some of the embodiments of the present application, and the ordinary skilled in the art can obtain other drawings from these drawings without any cost.

[0013] Figure 1 FIG. 1 is a schematic diagram illustrating an example of possible mobility patterns of a NR UE in a multicast service reception period in an inactive state according to an embodiment of the present application.

[0014] Figure 2 FIG. 2 is a block diagram illustrating one or more user equipment (UE) and base stations (such as gNB) communicating in a communication network system according to an embodiment of the present application.

[0015] Figure 3 FIG. 3 is a flowchart illustrating a method of implementing multicast service continuity of a multicast / broadcast service (MBS) during movement of a user equipment (UE) in a radio resource control (RRC) inactive state according to an embodiment of the present application.

[0016] Figure 4 FIG. 4 is an example of a UE RRC signaling request message information element according to an embodiment of the present application.

[0017] Figure 5 FIG. 5 is an example of a RAN node RRC signaling response information element configured with a multicast RAN notification area (RNA) according to an embodiment of the present application.

[0018] Figure 6 FIG. 6 is an example of a multicast RNA configuration provided in a RRC signaling response according to an embodiment of the present application.

[0019] Figure 7 FIG. 7 is an example of RRC inactive state movement between two cells under the same gNB during multicast service reception according to an embodiment of the present application.

[0020] Figure 8 FIG. 8 is an example of handling inactive state movement between two cells under the same gNB during multicast service reception according to an embodiment of the present application.

[0021] Figure 9 FIG. 2 is an example illustrating RRC inactive state mobility between two cells under different gNBs during multicast service reception according to embodiments of the present application.

[0022] Figure 10 FIG. 3 is an example illustrating handling mobility between two cells under different gNBs during multicast service reception according to embodiments of the present application.

[0023] Figure 11 FIG. 4 is a system block diagram for wireless communication according to embodiments of the present application. DETAILED DESCRIPTION

[0024] The technical content, structural features, and achieved purposes and effects of the present application are described in detail below in conjunction with the accompanying drawings. Specifically, the terms in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not a limitation on the present application.

[0025] In Rel-17 NR, the way of handling UE mobility is different in different RRC states. The characteristics of UE mobility in different RRC states in NR are summarized in Table 1. According to Table 1, in the RRC connected state, the UE context (i.e., the parameters required for communication between the UE and the network) has been established in the UE and the network, and the RAN node or cell to which the UE belongs can be known through a temporary identity (i.e., C-RNTI, used to identify the UE in the RAN node). In the RRC connected state, the mobility of the UE is based on cell-level information, i.e., the UE provides the RAN node with measurement information of neighboring cells, and the RAN node instructs the UE to perform a handover operation accordingly. In the RRC idle state, there is no UE context in the RAN, and the UE is not registered to a specific cell. In the RRC idle state, mobility is based on the tracking area management provided by the core network (CN), and the UE manages mobility by cell selection and reselection when moving out of the provided tracking area. In the RRC inactive state, the UE context is saved in the UE and the RAN node (e.g., gNB), and both the user plane connection (i.e., N3 interface) and the control connection (i.e., N2 interface) between the RAN node and the CN are reserved only for the UE, but the RAN node releases the RRC connection with the UE.

[0026] Table 1: Mobility handling in different RRC states in 5G

[0027]

[0028] Based on the above discussion, the possible handling options for UE service continuity guarantee for receiving MBS multicast in RRC inactive state are as follows. One general possible solution option is to reuse the concept of Rel-17 core network (CN) tracking area (i.e., track UE mobility based on configured MBS service area), which is also used for MBS broadcast mobility. However, this option might not meet the target of fast reconnection of UE for multicast reception (as per the requirement of TR 23.774) as it relies on UE interaction with core network. Another possible solution option is to adopt a RAN notification area (RNA) based solution (i.e., track UE mobility by updating reconfigurable RAN notification area), which is used for NR unicast inactive state mobility. This option is able to meet the service continuity requirement for multicast and achieve the fast reconnection target as per TR 23.774 requirement as it relies on UE and RAN node interaction. Reusing this inactive state mobility solution for MBS multicast might require the following enhancements to the existing NR unicast solution: 1) As in NR MBS, multicast service reception is cell-based, it is currently unclear how the existing mechanism can ensure inactive state mobility service continuity when moving from one cell to a new cell for a UE receiving only multicast service, only unicast service, or both multicast and unicast service when considering reusing the existing unicast RNA based inactive state mobility solution for MBS multicast. 2) It is currently unclear how the existing unicast RNA based solution handles this specific mobility pattern as shown in Figure 1 The following embodiments of the present application discuss a set of methods and enhancement solutions to address these issues.

[0029] To address the above issues, some embodiments of the present application provide a set of methods and signaling enhancements, including introducing the concept of service and scenario specific RAN notification area mobility mechanism, and defining related UE and RAN node signaling enhancements, to guarantee the continuity of multicast and / or unicast services when the UE is moving in inactive state, and to allow fast reconnection for time sensitive multicast services according to the requirements of TR 23.774. In these example methods, a UE is configured by a serving RAN node (e.g. gNB or gNB-CU node) with RAN notification areas, including multicast RAN notification areas (RNAs) or unicast RAN notification areas, or a combination of both, through RRC signaling messages (e.g. RRC release message with suspend configuration). When the UE moves to a new cell, the UE evaluates whether the cell belongs to one of the configured multicast or unicast RAN notification areas. If the cell belongs to at least one RAN notification area, the UE continues the MBS multicast and / or unicast reception in the new cell normally based on the existing reception configuration provided by the gNB node. If the cell does not belong to any configured RAN notification area, the UE will initiate / trigger a RRC signaling request to the gNB, where the RRC signaling request includes an inactive-radio network temporary identifier (I-RNTI) value of the same or different RAN node, a resume cause indicating RAN notification area update, and / or an indication about whether the connection is resumed for multicast service, unicast service, or both. Based on the RRC signaling request provided by the UE, the gNB node configures a RRC signaling response, which carries the reception configuration for multicast or unicast or both according to the UE indication, and the updated RNA area configuration according to the gNB decision of UE intra-gNB mobility mode or UE inter-different-gNB mobility mode according to some embodiments or according to another set of embodiments. Subsequently, the gNB transmits the configured RRC response signaling to the UE, followed by the transmission of unicast and / or multicast service data to the UE. Upon receiving the RRC response message, the UE applies the multicast and / or unicast reception configuration to receive the multicast and / or unicast service data as requested by the UE, and considers the updated RNA configuration when moving or performing cell reselection. According to the above procedure, the UE is able to continue receiving multicast and unicast services when moving between different cells based on the interaction with the RAN node only, regardless of the deployment scenario (e.g. intra-gNB mobility or inter-different-gNB mobility).

[0030] Figure 2It is illustrated that one or more user equipment (UE) 10, a first RAN node (e.g., gNB or gNB-DU) 20 and a second RAN node (e.g., gNB or gNB-DU) 30 provided in a communication network system 40 according to an embodiment of the present application. The communication network system 40 includes one or more UEs 10, a first base station 20 and a second RAN node 30. The one or more UEs 10 can include a memory 12, a transceiver 13 and a processor 11 coupled with the memory 12 and the transceiver 13. The first RAN node 20 can include a memory 22, a transceiver 23 and a processor 21 coupled with the memory 22 and the transceiver 23. The second base station 30 can include a memory 32, a transceiver 33 and a processor 31 coupled with the memory 32 and the transceiver 33. The processor 11, 21 or 31 can be configured to implement proposed functions, procedures and / or methods in the present description. Layers of radio interface protocol can be implemented in the processor 11, 21 or 31. The memory 12, 22 or 32 is operatively coupled with the processor 11, 21 or 31 and stores information related to operations of the processor 11, 21 or 31. The transceiver 13, 23 or 33 is operatively coupled with the processor 11, 21 or 31 and is used for transmitting and / or receiving a radio signal.

[0031] The processor 11, 21 or 31 can include an application-specific integrated circuit (ASIC), other chip sets, logic circuit and / or a data processing device. The memory 12, 22 or 32 can include a read-only memory (ROM), a random access memory (RAM), a flash memory, a memory card, a storage medium and / or other storage devices. The transceiver 13, 23 or 33 can include a baseband circuit for processing a radio frequency signal. When the embodiments are implemented in software, the techniques described herein can be implemented by modules (for example, procedures, functions and so on) that perform the functions described herein. These modules can be stored on the memory 12, 22 or 32 and executed by the processor 11, 21 or 31. The memory 12, 22 or 32 can be implemented within, or external to, the processor 11, 21 or 31, and coupled to the processor 11, 21 or 31 via various known means.

[0032] In some embodiments, the communication network system 40 is configured to perform the following method to achieve continuity of multicast / broadcast service (MBS) multicast service in a mobility procedure of a user equipment (UE) in a radio resource control (RRC) inactive state. The method comprises: the UE is configured by an existing serving radio access network (RAN) node through RRC initial signaling to contain a RAN-based notification area (RNA) configuration of multicast RAN notification area and / or unicast RAN notification area; when the UE moves or performs a reselection procedure and reselects to a cell belonging to the configured multicast RAN notification area and / or the configured unicast RAN notification area, the UE normally continues to receive the MBS multicast and / or unicast on the cell based on the existing reception configuration provided by the existing serving RAN node; when the UE moves or reselects to a cell not belonging to the configured multicast RAN notification area and / or the configured unicast RAN notification area, the UE triggers an RRC signaling request to the existing serving RAN node, indicating whether to resume the RRC connection for MBS multicast and / or unicast reception; the UE receives an RRC signaling response generated based on the UE indication from the existing serving RAN node or a new serving RAN node, the response carrying a multicast and / or unicast RNA update and / or a multicast and / or unicast reception configuration; the UE applies the multicast and / or unicast reception configuration to receive the multicast and / or unicast service data indicated by the UE and considers the updated RNA configuration when moving or performing cell reselection to a new cell.

[0033] In some embodiments, the existing serving RAN node and / or the new serving RAN node can be a gNB node, a gNB-central unit (gNB-CU) or a gNB-distributed unit (gNB-DU). In some embodiments, the RRC initial signaling is an RRC release or RRC reconfiguration message carrying multicast and / or unicast RAN notification area (RNA) configuration and / or multicast and / or unicast service reception configuration. In some embodiments, the RRC signaling request is an RRC resume request or RRC resume request 1 message containing a radio network temporary identifier (RNTI) value, a resume cause indicating an RNA update, and / or an indication indicating whether the RRC connection is resumed for multicast service reception and / or unicast service reception. In some embodiments, the indication indicating whether the RRC connection is resumed for multicast service and / or unicast service contains in a spare bit field of the RRC resume request or RRC resume request 1 message.

[0034] In some embodiments, the RRC signaling response is an RRC release message or an RRC reconfiguration message carrying multicast and / or unicast RAN notification area (RNA) update and / or multicast and / or unicast service reception configuration. In some embodiments, both the RRC initial signaling and the RRC signaling response are RRC reconfiguration or RRC release with suspend messages containing a multicast RAN notification area and / or a unicast RAN notification area. In some embodiments, the multicast RAN notification area is configured as: one cell list, in which the UE is provided with an explicit list of one or more cells constituting the multicast RAN notification area; and / or one RAN area list, in which the UE is provided with at least one RAN area ID, a RAN area being a subset of a core network (CN) tracking area, equal to a CN tracking area, or a set of cells under a gNB-distributed unit (DU). In some embodiments, a RAN area is specified by a RAN area ID, which includes a tracking area code (TAC) and / or a RAN area code.

[0035] In some embodiments, the indication indicating whether the RRC connection is resumed for multicast service and / or unicast service is as follows: a spare bit value of zero indicates that the RRC is resumed for unicast, a spare bit value of one indicates that the RRC is resumed for unicast, and if the field is absent, the field indicates that the RRC is resumed for both unicast and multicast.

[0036] In some embodiments, the RRC signaling request triggered by the UE to the existing serving RAN node can contain a resume cause indicating an RNA area update, an indication indicating whether the RRC connection is for multicast and / or unicast service resume, and / or an RNTI value of the same or different RAN node.

[0037] In some embodiments, if the existing RAN node receives the RRC signaling request from the UE and contains the RNTI value of the same RAN node, the existing RAN node assumes that the UE’s movement is an intra-gNB movement from the last serving gNB distributed unit (gNB-DU) to a new gNB-DU. In some embodiments, the last gNB-DU encapsulates the RRC signaling request in a non-UE associated message (i.e., initial uplink RRC transfer message) and transmits the initial uplink RRC transfer message to the existing gNB-CU. In some embodiments, based on the indication provided by the UE in the RRC signaling request, the gNB-CU sends a UE context setup request message to the new gNB-DU that the UE moves to, to create a UE unicast context and / or a UE multicast context, and to setup one or more multicast and / or data bearers. In some embodiments, the UE context setup request message contains a request to the new gNB-DU to include the cell group configuration information of the target cell in the UE context setup response message. In some embodiments, the new gNB-DU responds to the existing gNB-CU with a UE context setup response message containing the UE unicast and / or multicast context, multicast and / or data bearer configuration, and updated cell group information containing the identity of the target cell, which is requested by the last gNB-CU. In some embodiments, the gNB-CU generates an RRC reconfiguration or release message containing the updated unicast / multicast RNA area based on the updated cell group information and multicast and / or unicast reception configuration; then encapsulates the RRC reconfiguration or release message in an RRC downlink transfer message and sends the RRC downlink transfer message to the new gNB-DU. In some embodiments, the new gNB-DU forwards the RRC response message to the UE and further forwards the multicast and / or unicast service data to the UE according to the content indicated in the UE request.

[0038] In some embodiments, if the existing serving RAN node receives an RRC signaling request containing another serving RAN node RNTI, the serving RAN node assumes that the UE’s movement is a cross-gNB movement from the existing gNB node to the new gNB node. In some embodiments, the new gNB sends a context retrieval request to the existing RAN node to retrieve the UE unicast context (if the resume value indicated in the UE RRC signaling request is zero), or to retrieve the UE multicast context (if the spare bit value in the UE RRC signaling request is zero), or to retrieve both the UE multicast and unicast contexts if no spare bit indication is provided. In some embodiments, if the new gNB successfully retrieves the UE unicast and / or multicast context, the new gNB uses the UE’s unicast and / or multicast context; otherwise, the new gNB establishes new UE unicast and / or multicast context. In some embodiments, the new gNB responds to the UE with an RRC connection release message to keep the UE in RRC inactive state, or sends an RRC connection resume message to change the UE state to RRC connected state by looking at the RRC response signaling carrying the multicast and / or unicast service reception configuration and the updated RNA area configuration according to the retrieved or newly established UE unicast and / or multicast context. In some embodiments, the new gNB further contacts the service access and mobility management function (AMF) to switch the N2 and N3 tunnels to the new gNB, and the new gNB further transmits the multicast and / or unicast service data to the UE according to the content indicated in the UE request. In some embodiments, upon receiving the RRC signaling response from the existing serving RAN node or the new serving RAN node, the UE applies the multicast and / or unicast reception configuration to receive the multicast and / or unicast service data and considers the updated RNA configuration when moving or reselecting to a new cell.

[0039] Figure 3 Figure 1 is a flow chart illustrating a method for implementing multicast service continuity for a user equipment (UE) in a wireless communication network system when the UE moves in a radio resource control (RRC) inactive state, according to an embodiment of the present application. Figure 3It is illustrated that, in some embodiments, the method comprises the following steps: configuring, by an existing serving radio access network (RAN) node, a RAN-based notification area configuration containing a multicast RAN notification area and / or a unicast RAN notification area for the UE through RRC initial signaling; when the UE moves or performs a reselection procedure and reselects a cell belonging to the configured multicast RAN notification area and / or unicast RAN notification area, the UE normally continues MBS multicast and / or unicast reception on the cell according to the existing reception configuration provided by the existing serving RAN node; when the UE moves or reselects to a cell not belonging to the configured multicast RAN notification area and / or unicast RAN notification area, the UE triggers an RRC signaling request to the existing serving RAN node, indicating whether to restore RRC connection for MBS multicast and / or unicast reception; the UE receives an RRC signaling response generated according to the UE indication from the existing serving RAN node or a new serving RAN node, and the signaling response contains multicast and / or unicast RAN notification area (RNA) update and / or multicast and / or unicast reception configuration; then, the UE applies the multicast and / or unicast reception configuration to receive multicast and / or unicast service data indicated in the UE request, and considers the updated RNA configuration when moving or performing reselection to a new cell.

[0040] In the above exemplary method group, the RRC signaling request of the UE is an RRC resume request or an RRC resume request 1, which includes an inactive radio network temporary identifier (I-RNTI) value, a resume cause indicating RNA update, and / or an indication of whether the connection is resumed for groupcast service, unicast service, or both types of services. In the above exemplary method group, the indication of whether the connection is resumed for groupcast service, unicast service, or both types of services is provided in a spare bit field of the RRC resume request or the RRC resume request 1.

[0041] Figure 4 An example of a UE signaling request message contained in a paging information element is shown according to an embodiment of the present application. Figure 5 An example of a groupcast RNA configuration signaling message information element is shown according to an embodiment of the present application. Figure 4 And Figure 5 It is illustrated that, in the above exemplary method group, the RRC signaling message is an RRC connection release message with suspend configuration containing a groupcast RAN notification area, a unicast RAN notification area, or a combination of both.

[0042] In the above example method set, the multicast RAN notification area can be configured as: 1. Cell list, where the UE is provided with an explicit list of one or more cells that constitute the RAN notification area. 2. RAN area list, where the UE is provided with at least one RAN area ID, which is a subset of a core network (CN) tracking area, equal to one CN tracking area, or a group of cells under one gNB-DU. The RAN area is specified by a RAN area ID, including a TAC (Tracking Area Code) and an optional RAN area code, as shown in Figure 6

[0043] In the above example method set, the UE indicates to the gNB whether the connection is resumed for multicast service, unicast service, or both types of service in the following way: a spare bit value of zero indicates RRC resume for unicast, a spare bit value of one indicates RRC resume for multicast, and if the field is missing, it indicates RRC resume for both unicast and multicast, as shown in Table 2.

[0044] In the above example method set, the operation of the RAN node on the received RRC signaling request containing the spare bit indicated by the UE can be: if the spare bit value is zero, configure the RRC release or reconfiguration message for unicast reception configuration and / or unicast RNA area update; if the spare bit value is one, configure the RRC release or reconfiguration message for multicast reception configuration and / or multicast RNA area update; if the spare bit is not indicated, configure the RRC release or reconfiguration message for both unicast and multicast reception configuration and unicast and multicast RNA update, as shown in Table 2.

[0045] Table 2: Indication provided by the UE in the RRC signaling request through the spare bit

[0046]

[0047] In the above example method set, if the RAN node (gNB) receives an RRC signaling request containing the RNTI of the same RAN node, the RAN node can assume that the UE's mobility mode is intra-gNB mobility and can respond according to the following embodiments. In the above example method set, if the gNB receives an RRC signaling request containing the RNTI of another RAN node, the gNB can assume that the UE's mobility mode is inter-gNB mobility and the other node can respond according to the following embodiments.

[0048] Intra-gNB mobility between two cells under the same gNB:

[0003] Figure 7 An example of RRC inactive state mobility between two cells under the same gNB during multicast service reception by the UE is shown, according to one embodiment of the present application. Figure 8 ​An example of handling inactive state mobility between two cells under the same gNB during multicast service reception is shown according to one embodiment of the application. Figure 7 and Figure 8 It is illustrated that in certain embodiments, according to the example method groups described above, if a RAN node (gNB) receives a RRC signaling request containing the RNTI of the same RAN node, the RAN node can assume the mobility mode of the UE as intra-gNB mobility as shown in Figure 7 and can respond according to Figure 8 .

[0049] Figure 8 It is illustrated that in some embodiments, the UE triggers a RRC signaling request to the last gNB-DU, which contains the RNTI value of the same gNB, a resume cause indicating RNA update, and / or an indication indicating whether the RRC connection is resumed for multicast service, unicast service, or both. The last gNB-DU encapsulates the RRC signaling request in a non-UE related (initial uplink RRC message transmission) message and transmits the RRC signaling request to the gNB-CU. According to the indication provided in the RRC resume message, the gNB-CU sends a UE context setup request message to the new gNB-DU where the UE exists to create a UE unicast context and / or a UE multicast context and to setup one or more multicast and / or data bearers. The UE context setup request contains a request asking the new gNB-DU to include the cell group configuration information of the target cell where the UE is located. The new gNB-DU responds to the gNB-CU with a UE context setup response message, which contains the unicast context and / or the UE multicast context, the multicast and / or data bearers, and the target cell ID, which is requested by the gNB-CU. The gNB-CU generates a RRC reconfiguration or release message carrying the updated RNA area configuration based on the new cell group, the multicast and / or unicast reception configuration, and encapsulates the RRC reconfiguration or release message in a downlink RRC message transmission and sends it to the new gNB-DU. The new gNB-DU forwards the RRC message to the UE and then forwards the multicast and / or unicast service data to the UE according to the content indicated in the UE request.

[0050] Mobility between two cells under different gNBs (or gNB-CUs):

[0051] Figure 9 An example of RRC inactive state mobility between two cells under different gNBs during multicast service reception by a UE is shown according to one embodiment of the application. Figure 10 An example of handling mobility between two cells under different gNBs during multicast service reception is shown according to one embodiment of the application. Figure 9 and Figure 10As illustrated, in certain embodiments, according to the example method group above, if a RAN node (gNB) receives an RRC signaling request containing RNTI of a different RAN node, the RAN node can assume the UE’s mobility mode as inter-gNB mobility, as Figure 9 illustrated, and can respond accordingly. Figure 10

[0052] Figure 10 As illustrated, in certain embodiments, a UE triggers an RRC signaling request containing the last gNB’s RNTI value, a resume cause indicating RNA update, and / or an indication indicating whether the RRC connection is resumed for multicast service, unicast service, or both, to a new gNB. The new gNB uses the I-RNTI to retrieve the last serving gNB’s contact information and sends a request to retrieve the UE’s unicast context (if the spare bit value in the RRC resume request is zero) or the UE’s MBS multicast context (if the spare bit value in the RRC resume request is one), or both when no spare bit indication is provided in the RRC resume request. If the new gNB successfully retrieves the context, it uses the context; otherwise, the new gNB establishes new UE unicast and / or multicast context. The new gNB replies to the UE with an RRC connection release message (keeping the UE in RRC inactive state) or an RRC connection resume message (changing its state to RRC connected state) carrying the reception configuration for multicast, unicast, or both services according to the UE’s indication, and the updated RNA area configuration according to the retrieved context or newly established UE unicast and / or multicast context. The new gNB also contacts the serving AMF to switch N2 and N3 tunnels to the new gNB. Subsequently, the new gNB transmits multicast and / or unicast service data to the UE according to the content indicated in the UE’s request.

[0053] In summary, certain embodiments of the present application provide a method to configure MBS multicast service continuity during UE’s mobility in RRC inactive state based on RAN notification mechanism. The main advantages of the new example method include: 1. The new example method introduces a RAN notification area concept mechanism for multicast, enabling the UE to quickly reconnect to the network to ensure MBS multicast service continuity, in line with the Rel-18 WID requirement for MBS mission critical service. 2. The new example mechanism provides signaling enhancements, allowing the UE to move flexibly in RRC inactive state, crossing different RAN deployment scenarios (e.g., intra-gNB mobility and inter-gNB mobility) during multicast and / or unicast reception, based only on UE’s interaction with RAN nodes, without relying on the core network (CN).

[0054] Figure 11 ​is a block diagram of a wireless communication example system 700 according to embodiments of the present application. Embodiments described herein can be implemented into a system using any suitably configured hardware and / or software. Figure 11 The system 700 is shown comprising radio frequency (RF) circuitry 710, baseband circuitry 720, application circuitry 730, a memory / storage 740, a display 750, a camera 760, a sensor 770, and an input / output (I / O) interface 780, which are all communicatively coupled via one another, as shown. The application circuitry 730 can include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processors can include any combination of general-purpose processors and dedicated processors, such as graphics processors, application processors. The processors can be coupled with memory / storage and configured to execute instructions stored in the memory / storage to enable various applications and / or operating systems to run on the system.

[0055] While the present application has been described in connection with the embodiments described, it is to be understood that the application is not to be limited to those embodiments. On the contrary, it is intended to cover various arrangements known to those skilled in the art, falling within the scope of the appended claims, which are to be accorded the widest interpretation so as to encompass all equivalent combinations of features.

Claims

1. A method for ensuring the continuity of multicast / broadcast services (MBS) during the movement of a user equipment (UE) in an inactive Radio Resource Control (RRC) state, characterized in that, include: Configure the RAN-based notification area configuration, which includes multicast RAN notification areas and / or unicast RAN notification areas, for the UE via RRC initial signaling through the existing serving radio access network RAN ​​node; When the UE moves or performs a reselection procedure and reselects a cell belonging to the configured multicast RAN notification area and / or unicast RAN notification area, the UE continues to receive multicast and / or unicast services normally according to the existing reception configuration provided by the existing serving RAN node. When the UE moves or reselects a cell that does not belong to the configured multicast RAN notification area and / or unicast RAN notification area, the UE triggers an RRC signaling request to the existing serving RAN node to indicate whether to restore the RRC connection for the multicast and / or unicast service reception. The UE receives an RRC signaling response generated based on the UE's instruction from the existing serving RAN node or the new serving RAN node. The RRC signaling response carries multicast and / or unicast RAN notification area RNA update and / or multicast and / or unicast reception configuration. as well as The UE applies the multicast and / or unicast receive configuration to receive multicast and / or unicast service data according to the UE request, and considers the updated RNA configuration when moving or reselecting to a new cell.

2. The method according to claim 1, characterized in that, The existing serving RAN node and / or the new serving RAN node are gNB nodes or gNB central unit (gNB-CU) nodes.

3. The method according to claim 1, characterized in that, The initial RRC signaling is an RRC release or RRC reconfiguration message carrying multicast and / or unicast RAN notification area RNA configuration and / or the multicast and / or unicast service receive configuration.

4. The method according to claim 1, characterized in that, The RRC signaling request is an RRC recovery request or RRC recovery request 1 message that includes the Radio Network Temporary Identifier (RNTI) value, the reason for the recovery of the RNA update, and / or an indication of whether the RRC connection is recovered for multicast service reception and / or unicast service reception.

5. The method according to claim 4, characterized in that, Instructions regarding whether to restore the RRC connection for the multicast service reception and / or unicast service reception are provided in the spare bit field of the RRC recovery request or the RRC recovery request 1 message.

6. The method according to claim 1, characterized in that, The RRC signaling response is an RRC release message or RRC reconfiguration message carrying the multicast and / or unicast RAN notification area RNA update and / or the multicast and / or unicast service receive configuration.

7. The method according to claim 6, characterized in that, Both the initial RRC signaling and the RRC signaling response are RRC reconfiguration or RRC release with a pause message that includes the multicast RAN notification area and / or the unicast RAN notification area.

8. The method according to claim 7, characterized in that, The multicast RAN notification area is configured as follows: Cell list, wherein the UE is provided with an explicit list of one or more cells constituting a multicast RAN notification area; and / or A list of RAN regions, wherein the UE is provided with at least one RAN region ID, and the RAN region is a subset of the core network (CN) tracking area or equivalent to the CN tracking area or a group of cells managed by a gNB distribution unit (DU).

9. The method according to claim 8, characterized in that, The RAN region is designated by a RAN region ID, which contains the Tracking Area Code (TAC) and / or the RAN region code.

10. The method according to claim 1, characterized in that, The instructions regarding whether to restore the RRC connection for multicast and / or unicast service reception are as follows: A spare bit with a value of 0 indicates unicast RRC recovery, a spare bit with a value of 1 indicates multicast RRC recovery, and if the field does not exist, it means that both unicast and multicast are recovered simultaneously.

11. The method according to claim 1, characterized in that, If an existing RAN node receives the RRC signaling request from the UE, and the RRC signaling request contains the RNTI value of the same RAN node, then the existing RAN node assumes that the UE's movement is a movement within the gNB from the last serving gNB distributed unit gNB-DU to the new gNB-DU.

12. The method according to claim 11, characterized in that, The UE triggers the RRC signaling request to the existing gNB-CU through the last gNB-DU. The RRC signaling request includes the RNTI value of the same gNB, the reason for the recovery of the RNA region update, and / or an indication of whether the RRC connection is recovered for multicast and / or unicast service reception.

13. The method according to claim 12, characterized in that, The final gNB-DU includes the RRC signaling request in a non-UE associated message, namely the initial uplink RRC transmission message, and transmits the initial uplink RRC transmission message to the existing gNB-CU.

14. The method according to claim 13, characterized in that, Based on the indication provided by the UE in the RRC signaling request, the gNB-CU sends a UE context establishment request message to the new gNB-DU to which the UE has moved, in order to create a UE unicast context and / or a UE multicast context, and set up one or more multicast and / or data bearers.

15. The method according to claim 14, characterized in that, The UE context establishment request message includes a request for the new gNB-DU to include the target cell's group configuration information in the UE context establishment response message.

16. The method according to claim 15, characterized in that, The new gNB-DU responds to the existing gNB-CU with the UE context establishment response message, which includes the UE unicast context and / or the UE multicast context, as well as multicast and / or data bearer configuration and update group configuration information including the target cell identifier.

17. The method according to claim 16, characterized in that, The gNB-CU generates an RRC reconfiguration or release message, which includes an updated unicast / multicast RNA region based on the update group configuration information, and includes multicast and / or unicast receive configuration; then, the RRC reconfiguration or release message is encapsulated in an RRC downlink transmission message and sent to the new gNB-DU.

18. The method according to claim 17, characterized in that, The new gNB-DU forwards the RRC response message to the UE, and further forwards the multicast and / or unicast service data to the UE according to the content indicated in the UE request.

19. The method according to claim 1, characterized in that, If a serving RAN node receives an RRC signaling request that includes the RNTI of another serving RAN node, the serving RAN node assumes that the UE's movement is an inter-gNB movement from an existing gNB node to a new gNB node.

20. The method according to claim 1, characterized in that, The UE triggers the RRC signaling request to the new gNB node. The RRC signaling request includes the RNTI value of the existing gNB node, the reason for the recovery of the RNA region update, and / or an indication of whether the RRC connection is recovered for multicast and / or unicast service reception.

21. The method according to claim 20, characterized in that, The new gNB node sends a context retrieval request to the existing RAN node to retrieve the UE unicast context. If the indication recovery value in the RRC signaling request is zero, or if the UE multicast context is retrieved, if the spare bit value in the RRC signaling request is zero, or if the spare bit indication is not provided in the RRC signaling request, then the UE multicast and unicast contexts are retrieved.

22. The method according to claim 21, characterized in that, If the new gNB node successfully retrieves the UE unicast and / or multicast context, the new gNB node uses the UE unicast and / or multicast context; otherwise, the new gNB node establishes a new UE unicast and / or multicast context.

23. The method according to claim 22, characterized in that, The new gNB node responds to the UE via RRC connection release to keep the UE in an RRC inactive state, or changes the UE state to an RRC connected state via an RRC connection recovery message, based on the multicast and / or unicast service reception configuration carried in the RRC response signaling and the RNA region configuration updated according to the retrieved or newly established UE unicast and / or multicast context.

24. The method according to claim 23, characterized in that, The new gNB node further contacts the Service Access and Mobility Management Function (AMF) to switch the N2 and N3 tunnels to the new gNB node, and the new gNB node further transmits the multicast and / or unicast service data to the UE according to the content indicated in the UE request.

25. The method according to claim 1, characterized in that, Upon receiving the RRC signaling response from the existing serving RAN node or the new serving RAN node, the UE applies a multicast and / or unicast receive configuration to receive the multicast and / or unicast service data, and considers the new updated RNA configuration when moving or reselecting to a new cell.

26. A communication network system, characterized in that, include: Memory; transceiver; as well as A processor coupled to the memory and the transceiver; The processor is configured to perform the method of any one of claims 1 to 25.

27. A non-transitory machine-readable storage medium, characterized in that, It stores instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 25.

28. A chip, characterized in that, include: A processor configured to invoke and run a computer program stored in memory to cause a device on which the chip is mounted to perform the method of any one of claims 1 to 25.

29. A computer-readable storage medium, characterized in that, It contains a computer program that causes the computer to perform the method of any one of claims 1 to 25.

30. A computer program product, characterized in that, Includes a computer program, wherein the computer program causes a computer to perform the method of any one of claims 1 to 25.

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