Method and apparatus for receiving multicast service during UE mobility and RRC state handover

Abstract

The invention discloses a method and equipment for carrying out multicast service / session receiving during the switching period of UE (user equipment) mobility and radio resource control (RRC) states. The method executed by UE (User Equipment) comprises the following steps: in an RRC (Radio Resource Control) connection state, the UE sends an RRC message containing a non-access stratum (NAS) multicast service / session join request to an access and mobility management function (AMF) entity of a core network through a radio access network (RAN) node; and the UE receiving an RRC reconfiguration message from the RAN node, the message indicating that the MBS can be received without changing the RRC state and comprising MBS multicast service configuration; or receiving an RRC connection release message indicating an RRC state switch for the MBS and including RRC suspend configuration information including MBS multicast service configuration and neighbor cell auxiliary information to help the UE reselect an optimal cell providing multicast service interested by the UE, or to receive an RRC connection release message, the message indicating an RRC state switch for the MBS, and including RRC suspend configuration information including MBS multicast service configuration and neighbor cell auxiliary information.

Description

Technical Field

[0001] The present application relates to the field of wireless communication systems, and more specifically to a method and device for receiving a multicast service / session during user equipment (UE) mobility and radio resource control (RRC) state switching. For example, it particularly relates to receiving a multicast / broadcast service (MBS) by a UE during an RRC switching process in which the UE switches from an RRC connected state to an RRC inactive state. Background Art

[0002] New Radio (NR) Multicast / Broadcast Service (MBS) is expected to cover a wide variety of applications and services in the 5G era, including public safety, mission-critical communications, V2X, transparent IPv4 / IPv6 multicast transmission, IPTV, wireless software distribution, group communications, and IoT applications. During the 3GPP Radio Access Network (RAN) 88-e meeting (June 29-July 3, 2020), a new working item (WID) was approved to support RAN support for MBS in the 5G specifications of Release 17. For NR MBS in Release 17, two transmission modes have been specified: broadcast transmission mode, which focuses on meeting lower UE QoS requirements and targets to support UEs in RRC Connected, RRC Inactive, and RRC Idle states, and multicast transmission mode, which focuses on meeting higher UE QoS requirements and targets to support UEs in RRC Connected state. During the discussion on Release 18 NR MBS work items at the RAN 94e meeting (December 6-17, 2021), it was suggested that multicast reception in the RRC connected state may not fully meet the needs of mission-critical services, especially in large cells where the number of UEs exceeds the cell access capacity. In addition, the RRC connected state also has an adverse effect on the power efficiency of the UE because it requires the UE to stay awake all the time to receive multicast.

[0003] Therefore, it is recommended to support multicast reception for UEs in RRC inactive (RRC_INACTIVE) state in Release 18 NR MBS, and to study the following objectives: Standardize the ability to support UEs in RRC_INACTIVE state to receive multicast services (involving RAN2 and RAN3), including: a) Study the point to multipoint (PTM) configuration of UEs receiving multicast services in RRC_INACTIVE state (involving RAN2), b) Study the impact of mobility and state switching of UEs receiving multicast services in RRC_INACTIVE state (involving RAN2 and RAN3).

[0004] Since the RAN node cannot directly know the association between UE session joining and the actual state of the multicast session in the current Release 17 NR MBS specification (i.e., it cannot clearly know whether the MBS multicast session is active or inactive when the UE joins), it is unclear how and / or based on what criteria the RAN node or gNB will decide to move / transition the UE from the RRC connected (RRC_CONNECTED) state to the RRC inactive (RRC_INACTIVE) state for multicast reception. In addition, how to ensure service continuity of multicast bearers during RRC state switching (i.e., switching from RRC connected state to RRC inactive state) and when the UE moves between different multicast-capable cells within the MBS service area. Summary of the invention

[0005] The purpose of the present application is to propose a method and device for receiving a multicast service / session during user equipment (UE) mobility and radio resource control (RRC) state switching.

[0006] In a first aspect of the present application, a method for receiving a multicast service / session during mobility and radio resource control (RRC) state switching of a user equipment (UE) is performed by a UE, comprising: in an RRC connected state, the UE sends an RRC message containing a non-access stratum (NAS) request for joining a multicast service / session to an access and mobility management function (AMF) entity of a core network through a radio access network (RAN) node, and the UE receives an RRC reconfiguration message from the RAN node, the RRC reconfiguration message indicating that multicast / broadcast service (MBS) reception does not require an RRC state change and includes an MBS multicast service configuration, or indicates an RRC connection release message, the RRC connection release message indicates an RRC state switch for MBS and includes an RRC suspension configuration message including an MBS multicast service configuration and neighboring auxiliary information.

[0007] In a second aspect of the present application, a method for receiving a multicast service / session during user equipment (UE) mobility and RRC state switching is performed by a base station, comprising: receiving a session join request from a UE, wherein the base station, the RAN, or the RAN associated with a core network evaluates resource availability to accept an MBS multicast session join request from a new UE by evaluating at least one of the following configuration parameters when receiving the session join request: whether the number of unicast, multicast and / or broadcast radio bearers, and / or the number of active multicast services / sessions, and / or the number of UEs joining active multicast services / sessions exceeds a predefined limit, deciding to keep the UE in an RRC connected state for MBS reception by sending an RRC reconfiguration message to the UE if the at least one configuration parameter does not exceed the predefined limit; or deciding to switch, if the at least one configuration parameter exceeds a predefined limit The base station may further include at least one of the following in the RRC suspension configuration information: providing a neighboring cell frequency list of the multicast service / session of interest to the UE, and / or providing an absolute cell priority and / or cell level of a certain multicast service / session of interest to the UE, and / or providing an MBS area cell list of a certain multicast service / session of interest to the UE, so as to assist the UE in reselecting the best neighboring cell frequency for providing the multicast service / session of interest to the UE.

[0008] In a third aspect of the present application, a user equipment (UE) includes a memory, a transceiver, and a processor coupled to the memory and the transceiver. The processor is configured to execute the above method.

[0009] In a fourth aspect of the present application, a base station includes a memory, a transceiver, and a processor coupled to the memory and the transceiver. The processor is configured to execute the above method.

[0010] In a fifth aspect of the present application, a non-transitory machine-readable storage medium stores instructions thereon, and when a computer executes the instructions, the instructions cause the computer to execute the above method.

[0011] In a sixth aspect of the present application, a chip includes a processor configured to call and run a computer program stored in a memory so that a device equipped with the chip executes the above method.

[0012] In a seventh aspect of the present application, a computer-readable storage medium stores a computer program, wherein the computer program enables a computer to execute the above method.

[0013] In an eighth aspect of the present application, a computer program product comprises a computer program, wherein the computer program enables a computer to execute the above method.

[0014] In a ninth aspect of the present application, a computer program is provided, wherein the computer program enables a computer to execute the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or related technologies, the following briefly introduces the drawings to be described in the embodiments. Obviously, the drawings are only some embodiments of the present application, and ordinary technicians in this field can obtain other drawings based on these drawings without paying any price.

[0016] Figure 1 It is a schematic diagram showing an example of 5G RRC state switching mapping according to an embodiment of the present application.

[0017] Figure 2 It is a block diagram showing communication between one or more user equipment (UE) and a base station (such as a gNB) in a communication network system according to an embodiment of the present application.

[0018] Figure 3 The present invention is a flowchart showing a method for receiving a multicast service / session during user equipment (UE) mobility and radio resource control (RRC) state switching performed by a UE according to an embodiment of the present application.

[0019] Figure 4 The present invention is a flowchart showing a method for receiving a multicast service / session during user equipment (UE) mobility and radio resource control (RRC) state switching performed by a base station according to an embodiment of the present application.

[0020] Figure 5 It is a schematic diagram showing an example of mobility of a UE during RRC switching from a connected state to an inactive state according to an embodiment of the present application.

[0021] Figure 6 The flowchart shows an example of processing multicast reception during RAN switching from a connected state to an inactive state based on UE mobility and RRC according to an embodiment of the present application.

[0022] Figure 7 The flowchart shows an example of processing multicast reception during UE mobility and RRC switching from a connected state to an inactive state based on RAN and CN association according to an embodiment of the present application.

[0023] Figure 8 is a block diagram of a system for wireless communication according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] The technical content, structural features, objectives 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 used to describe the purpose of specific embodiments, and are not intended to limit the present application.

[0025] In Rel-17 NR, UE mobility is handled differently in different RRC states. The characteristics of UE mobility in different RRC states in NR are summarized in Table 1. According to the table, in the RRC connected state, the UE context (i.e., the parameters required for communication) is established between the UE and the network, and the RAN node or the cell to which the UE belongs can identify the UE through a temporary identifier that identifies the UE, i.e., the cell radio network temporary identifier (C-RNTI). In this state, the UE mobility is based on cell-level information, i.e., the UE provides neighboring cell measurement information to the RAN node, and the RAN node instructs or commands the UE to switch based on the measurement information. In the RRC_IDLE state, there is no UE context in the radio access network (RAN) and the UE is not registered to a specific cell. In this state, mobility is based on the tracking area code provided by the core network (CN), and when the UE moves out of the provided tracking area, it manages mobility by itself through the cell selection and reselection process. In the RRC_INACTIVE state, the UE context is maintained in the UE and RAN nodes (e.g., gNB), and the core network connection is also retained. In this state, mobility is controlled by cell reselection in the tracking area configured by the RAN node (e.g. gNB). On the other hand, the RRC state switching for a specific UE in 5G NR is handled as follows: When the UE starts, it enters the RRC_IDLE state. The UE can switch from the RRC_IDLE state to the RRC connected state through an initial attach or RRC connection setup / establishment request. If the UE is inactive for a period of time, the network can move the UE from the RRC connected state to the RRC_INACTIVE state through an RRC release message with a suspended configuration, and can switch it back to the RRC connected state through the UE's RRC resume request or the network's paging message. In addition, the network can also move the UE from the RRC connected state or RRC_INACTIVE state to the RRC_IDLE state when the link fails through the RRC release message, such as Figure 1 shown.

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

[0027] RRC Status Mobility Processing Mobility level RRC connection status RAN-based handover Cell level RRC inactive state UE-based cell reselection RAN Tracking Area Level RRC Idle State UE-based cell selection and reselection Core Network Tracking Region Level

[0028] Some embodiments of the present application focus on multicast session reception during UE mobility and switching from RRC connected state to RRC inactive state. According to TS23.247, an MBS multicast session specifies the following states.

[0029] 1. Active state: The multicast service / session has been established and MBS data can be transmitted to the UEs that have joined the multicast service / session. Radio resources are allocated for the multicast service / session. In order to receive the multicast MBS service / session data, the UEs that have joined the multicast service / session must be in the connected state (CM-CONNECTED) of the connection management to receive the data of the multicast service / session. The UE is allowed to join the multicast service / session (subject to authorization check). For the UEs that have joined the multicast service / session, 5GC resources and radio resources will be reserved for them.

[0030] 2. Inactive state: The multicast service / session has been established, but no MBS data is transmitted to the UEs that have joined the multicast service / session. The radio resources of the multicast service / session are released, and the UEs that have joined the multicast service / session can be in the CM-CONNECTED state or the CM-IDLE state. The UE is allowed to join the multicast service / session (subject to authorization check).

[0031] The above multicast state model allows UEs to join multicast services / sessions regardless of the actual data transmission status, which may lead to overload of RAN nodes or cells. On the other hand, since the joining process of a multicast service / session is a non-access stratum (NAS) signaling process (i.e., between the UE and the core network), it is transparent to the RAN nodes or gNBs. Therefore, the RAN nodes cannot directly know the association between the UE joining and the actual state of the multicast service / session (i.e., it is not known whether the multicast service / session joined by the UE is in an active or inactive state). In this case, it is unclear how and based on what criteria or measures the gNB should decide to switch the UE from the RRC CONNECTED state to the RRC INACTIVE state for multicast reception (e.g., in the scenario where the number of UEs in a cell exceeds the cell access capacity according to the WID requirement). In addition, it is also a challenge to ensure the multicast bearer service continuity of the UE during the RRC state switch (i.e., switching from the RRC CONNECTED state to the RRC INACTIVE state) and in the mobility between different neighboring MBS cells. The following embodiments of the present application provide a method and device for receiving a multicast service / session during user equipment (UE) mobility and RRC state switching to solve the above-mentioned problems.

[0032] Figure 2It is illustrated that in some embodiments, the communication network system 40 includes one or more user equipment (UE) 10 and a base station (e.g., gNB) 20. In an embodiment of the present application, the communication network system 40 includes one or more UEs 10 and a base station 20 (e.g., a first base station or a second base station). One or more UEs 10 may include a memory 12, a transceiver 13, and a processor 11 coupled to the memory 12 and the transceiver 13. The base station 20 may include a memory 22, a transceiver 23, and a processor 21 coupled to the memory 22 and the transceiver 23. The processor 11 or 21 may be configured to implement the functions, procedures, and / or methods proposed in this description. The various layers of the wireless interface protocol may be implemented in the processor 11 or 21. The memory 12 or 22 is operatively coupled to the processor 11 or 21 to store various information required to operate the processor 11 or 21. The transceiver 13 or 23 is operatively coupled to the processor 11 or 21, and the transceiver 13 or 23 is used to send and / or receive wireless signals.

[0033] The processor 11 or 21 may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits and / or data processing devices. The memory 12 or 22 may 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 or 23 may include a baseband circuit for processing radio frequency signals. When these embodiments are implemented in software form, the techniques described in this application may be implemented by modules (such as programs, functions, etc.) to perform the functions described herein. The modules may be stored in the memory 12 or 22 and executed by the processor 11 or 21. The memory 12 or 22 may be integrated inside the processor 11 or 21, or may be implemented outside the processor 11 or 21, in which case it may be connected to the processor 11 or 21 by various known communication methods.

[0034] In some embodiments, the transceiver 13 is configured to send an RRC message including a non-access stratum (NAS) request for multicast service / session joining to an access and mobility management function (AMF) entity of a core network through a radio access network (RAN) node when the UE 10 is in an RRC connected state. The transceiver 13 is also configured to receive an RRC reconfiguration message from the RAN node, the RRC reconfiguration message indicating that multicast / broadcast service (MBS) reception does not require an RRC state change and includes an MBS multicast service configuration, or indicates an RRC connection release message, the RRC connection release message indicating an RRC state switch for the MBS and including an RRC suspend configuration message including an MBS multicast service configuration and neighboring auxiliary information.

[0035] In some embodiments, the transceiver 23 is configured to receive an RRC message carrying a multicast session from the UE 10 via the base station 20, wherein the base station 20, the RAN node, or the RAN node associated with the core network evaluates resource availability to accept the MBS multicast session joining request of the new UE by evaluating at least one of the following configuration parameters upon receiving the session joining request: whether the number of unicast, multicast and / or broadcast radio bearers, and / or the number of active multicast services / sessions, and / or the number of UEs joining the active multicast services / sessions exceeds predefined limits of these parameters; decides to keep the UE 10 in the RRC connected state to receive the MBS multicast session by sending an RRC reconfiguration message to the UE 10 if at least one configuration parameter does not exceed its predefined limit; and decides to switch the RRC state of the UE 10 from the RRC connected state to the RRC inactive state to receive the MBS multicast session by sending an RRC connection release message containing RRC suspension configuration information to the UE 10 if at least one configuration parameter exceeds the predefined limit. If the base station decides to switch the RRC state of UE 10 from the RRC connected state to the RRC inactive state to receive the multicast service / session, the base station includes at least one of the following in the RRC suspension configuration information: providing a list of neighboring cell frequencies for the multicast service / session of interest to UE 10, and / or providing an absolute cell priority and / or cell level of a certain multicast service / session of interest to UE 10 by the neighboring cells, and / or providing a list of MBS area cells for a certain multicast service / session of interest to UE 10, so as to assist UE 10 in reselecting the best neighboring cell frequency providing the multicast service / session of interest to UE 10.

[0036] In some embodiments, the MBS multicast service configuration is related to the multicast service / session that the UE is interested in receiving, and the neighboring auxiliary information is related to the neighboring frequency that provides the same MBS multicast service / session that the UE is interested in receiving. In some embodiments, if the UE is configured to switch from the RRC connected state to the RRC inactive state to receive the multicast service / session, after receiving the RRC suspension configuration information including the neighboring auxiliary information, the UE evaluates the reference signal received quality (RSRQ) or reference signal received power (RSRP) of the neighboring frequency, and reselects the best cell that provides the multicast service / session that the UE is interested in receiving and resides in it. In some embodiments, the NAS request includes a multicast service / session identifier (ID) or a protocol data unit (PDU) ID related to the multicast service / session that the UE is interested in receiving. In some embodiments, the neighboring auxiliary information is the neighboring frequency that provides the multicast service / session that the UE is interested in receiving.

[0037] In some embodiments, the UE is configured to remain in the RRC connected state to receive the multicast service / session by the RAN node by receiving the RRC reconfiguration message containing the MBS multicast service configuration of interest to the UE, the UE is further configured to receive the multicast service / session data using shared or dedicated transmission resources, and when the availability of RAN radio bearer resources and / or the number of UEs per active MBS multicast service / session does not exceed a predefined limit of a given cell or the RAN node, the UE receives the multicast service / session data through the configured transmission resources. In some embodiments, the UE is configured to switch from the RRC connected state to the RRC inactive state to receive the multicast service / session by receiving the RRC connection release message containing the neighboring cell assistance information and the RRC suspension configuration information, the UE is further configured to receive the multicast service / session data using shared or dedicated transmission resources, and if the availability of RAN radio bearer resources and / or the number of UEs per active service / session exceeds a predefined limit of a given cell or the RAN node, the UE receives the multicast service / session data.

[0038] In some embodiments, the UE is further configured to receive neighbor assistance information, which includes at least one of the following: a list of neighbor frequencies providing a certain multicast service / session of interest to the UE, and / or an absolute cell priority and / or cell level of a certain multicast service / session of interest to the UE, and / or a list of MBS area cells providing a certain multicast service / session of interest to the UE. In some embodiments, when the availability of RAN radio bearer resources and / or the number of UEs with active services / sessions for a given cell or RAN node exceeds a predefined RAN node limit, the UE is further configured to receive neighbor assistance information to assist it in reselecting the best neighbor frequency providing a certain multicast service / session of interest to the UE.

[0039] In some embodiments, if no other UE is receiving or interested in receiving the multicast service / session of interest to the UE, the UE receives the multicast service / session data via dedicated transmission resources; if other UEs are receiving or interested in receiving the multicast service / session of interest to the UE, the UE receives the multicast service / session data via shared transmission resources. In some embodiments, the RRC message containing the NAS multicast service / session join request includes a list containing MBS multicast, broadcast and / or unicast session identifiers mapped to MBS radio bearers (MBS radio bearers, MRBs) and / or unicast data radio bearers (data radio bearers, DRBs), or a list of NAS dedicated messages mapped to MRBs and / or DRBs.

[0040] In some embodiments, the shared transmission resources include at least one of: MBS radio bearer (MBS radiobearer, MRB) configuration, discontinuous reception (discontinues reception, DRX) mode and / or point to multipoint (point to multipoint, PTM) RAN protocol and configuration of transmission logic and physical channels. In some embodiments, the dedicated transmission resources include at least one of: MRB configuration, unicast data radio bearer (data radio bearer, DRB) configuration, DRX mode and / or point to point (point to point, PTP) RAN protocol and configuration of transmission logic and physical channels.

[0041] In some embodiments, evaluating resource availability to accept a new UE multicast service / session join request can be selectively performed directly by the RAN node when the RAN node receives an RRC message containing a UE multicast service / session join request; or indirectly after the RAN node establishes an association with the AMF entity of the core network.

[0042] In some embodiments, the RAN node-based direct evaluation of resource availability to accept a new UE multicast service / session joining request includes, after receiving an RRC message containing a NAS request for multicast service / session joining from the UE, evaluating whether the number of currently configured multicast / broadcast radio bearers exceeds a predefined MRB and / or DRB value, or a network-set MRB / DRB limit value, which serves as a threshold for switching the UE's RRC state from an RRC connected state to an RRC inactive state. In some embodiments, the RAN node-based direct evaluation also includes the RAN node sending an MBS / multicast session resource setup request containing NAS multicast service / conference information provided by the UE to the core network AMF entity, and receiving information from the AMF about a list of MBS area cells that provide the multicast service / session requested by the UE. In some embodiments, the direct evaluation based on the RAN node also includes the RAN node determining the neighboring cell frequency providing the multicast session or the service of interest to the UE based on the MBS area cell list and multicast session ID information provided by the AMF entity, and including the MBS area cell list and multicast association information in the RRC connection release message, as well as the RRC suspension configuration information sent to the UE, if the base station decides to switch the UE from the RRC connected state to the RRC inactive state for multicast service / session reception.

[0043] In some embodiments, indirectly evaluating resource availability based on association of a RAN node with a core network node to accept a new UE multicast service / session join request includes: sending, by the RAN node, an MBS / multicast session resource setup request containing NAS information provided by the UE to an AMF entity of the core network, receiving information about the requested multicast session activity and a list of MBS area cells, and evaluating, by the RAN node, based on the session activity information provided by the AMF entity. If the number of currently active multicast sessions or the number of UEs per active multicast service / session multiplied by the number of active multicast services / sessions exceeds a predefined value, or the number of UEs per active multicast service / session per RAN node exceeds a threshold set by the network or the RAN node, then deciding whether to switch the UE from an RRC connected state to an RRC inactive state for multicast service / session reception. In some embodiments, the indirect evaluation based on the association between the RAN node and the core network node also includes: based on the MBS area cell list and session ID information provided by the AMF entity, determining the neighboring cell frequency that provides the multicast session ID or the service of interest to the UE, and including this information and the RRC suspension configuration information in the RRC connection release message to the UE, if the base station decides to switch the UE from the RRC connected state to the RRC inactive state for multicast service / session reception.

[0044] The present application provides a method for defining a standard for switching the RRC state of a UE from an RRC connected state (RRCCONNECTED) to an RRC inactive state (RRCINACTIVE) to receive multicast service / session data, and determining how to ensure service continuity of the UE multicast bearer during the RRC state switching (i.e., switching from the RRC connected state to the RRC inactive state) and when moving between different cells supporting MBS. In the method, when a UE in the RRC_CONNECTED state wishes to receive a multicast service, the UE may send a request to the core network through the gNB, which includes a service / session identity (ID) or a PDU service / session ID related to the multicast service / session that the UE wishes to join. Upon receiving the request from the UE, the gNB or the gNB in ​​collaboration with the core network (CN) evaluates the UE's request by evaluating at least one of the following parameters: the total number of currently configured unicast, multicast and broadcast sessions, the number of UEs joining an active multicast session, and / or whether the availability of RAN resources (e.g., the number of configured multicast radio bearers (MRBs) and / or unicast data radio bearers (DRBs)) exceeds a predefined limit set by the RAN node / gNB / cell for switching the UE's RRC connected state. Based on the evaluation result, if the availability of RAN resources (MRBs / DRBs) allows, and / or the number of UEs per active service / session does not exceed the predefined limit set by the RAN node, the RAN node maintains the UE in the RRC connected state for multicast reception by sending to the UE an RRC reconfiguration message containing the MBS configuration associated with the multicast session that the UE wishes to join. Otherwise, if the availability of RAN resources (MRB / DRB) is insufficient, and / or the number of UEs per active service / session exceeds a predefined limit set by the RAN node, the RAN node switches the UE to the RRC inactive state for multicast reception by sending an RRC release message containing the suspension configuration to the UE. If the gNB decides to switch the UE to the RRC inactive state for multicast reception, in order to ensure service continuity of the multicast bearer during UE mobility and state switching, the gNB may include some assistance information, such as a list of neighboring cell frequencies that provide the same multicast service / session that the UE wishes to receive, the absolute priority or ranking of the neighboring cells providing the same multicast service of interest to the UE, to assist the UE in reselecting the best neighboring cell frequency that provides the multicast service / session it wishes to receive (e.g. Figure 3 and Figure 4As shown). The method provided in the present application also considers the mobility scenario of the UE during RRC switching from the RRC connected state to the RRC inactive state. In this scenario, NR signaling and data protocols operate between the UE, RAN nodes and the core network (CN), including a user plane protocol for transmitting MBS service / session data between the network (i.e., the user plane function (UPF) entity of the core network) and the UE, and a control plane protocol for transmitting control signaling information between the network (i.e., the access and mobility management function (AMF) entity), the RAN node and the UE. These NR signaling and data protocols include a non-access stratum (NAS) protocol, which terminates between the UE and the core network AMF entity and is used for core network-related functions such as UE session management; and an access stratum protocol, which terminates between the UE and the RAN node and is used for functions such as transmitting user data, controlling transmission resources and switching (such as Figure 5 shown).

[0045] Figure 3 The present invention is a flowchart showing a method for receiving a multicast service / session during a user equipment (UE) mobility and radio resource control (RRC) state switching performed by a UE according to an embodiment of the present application. The method comprises: in an RRC connected state, the UE sends an RRC message containing a non-access stratum (NAS) request for joining a multicast service / session to an access and mobility management function (AMF) entity of a core network through a radio access network (RAN) node, and the UE receives an RRC reconfiguration message from the RAN node, the RRC reconfiguration message indicating that multicast / broadcast service (MBS) reception does not require an RRC state change and contains an MBS multicast service configuration, or indicates an RRC connection release message, the RRC connection release message indicates an RRC state switching for MBS and includes an RRC suspension configuration message containing an MBS multicast service configuration and neighboring auxiliary information.

[0046] Figure 4The present invention is a flowchart showing a method for receiving a multicast service / session during the mobility and radio resource control (RRC) state switching of a user equipment (UE) performed by a base station according to an embodiment of the present application. The method includes: receiving a session joining request from a UE, wherein the base station, the RAN, or the RAN associated with the core network evaluates resource availability to accept the MBS multicast session joining request of the new UE by evaluating at least one of the following configuration parameters when receiving the session joining request: whether the number of unicast, multicast and / or broadcast radio bearers, and / or the number of active multicast services / sessions, and / or the number of UEs joining the active multicast services / sessions exceeds a predefined limit, and decides to keep the UE in an RRC connected state for MBS reception by sending an RRC reconfiguration message to the UE if the at least one configuration parameter does not exceed the predefined limit; or decides to switch, and if the at least one configuration parameter exceeds the predefined limit, sends a RRC suspend configuration message to the UE, The base station sends an RRC connection release message with configuration information, switches the RRC state of the UE from the RRC connected state to the RRC inactive state for MBS reception. If the base station decides to switch the RRC state of the UE from the RRC connected state to the RRC inactive state to receive the multicast service / session, the base station includes at least one of the following in the RRC suspension configuration information: providing a neighboring frequency list of the multicast service / session of interest to the UE, and / or a neighboring absolute cell priority and / or cell level of a multicast service / session of interest to the UE, and / or providing an MBS area cell list of a multicast service / session of interest to the UE, so as to assist the UE in reselecting the best neighboring frequency that provides the multicast service / session of interest to the UE.

[0047] Figure 5 The example shows the mobility of a UE during RRC switching from a connected state to an inactive state according to an embodiment of the present application. The example considers a scenario in which a UE in an RRC connected state wishes to receive an MBS multicast service through a source RAN node cell and moves to another NG-RAN node / cell (i.e., a target cell or RAN node).

[0048] In the above scenario, the UE in RRC_CONNECTED state sends a NAS request containing the multicast service / session ID and / or the relevant PDU ID to the AMF entity of the core network through the RAN node. The RAN node or a RAN node associated with the core network then evaluates the UE's request and makes a decision based on information such as the number of unicast, multicast and broadcast services / sessions, the status of the service / session the UE is joining and / or the availability of RAN resources for the session.

[0049] If the RAN resource availability and / or the number of UEs or active sessions for a given cell or RAN node does not exceed predefined limits, the RAN node shall do the following:

[0050] Maintain the RRC connection state of the UE to receive multicast services.

[0051] Configure shared or dedicated transmission resources (e.g., radio bearers (MRB / DRB), discontinuous reception (DRX) mode, transmission logical channels and physical channels).

[0052] Send an RRC reconfiguration message containing the relevant MBS multicast service / session reception configuration to the UE.

[0053] Transmit multicast service / session data to UE via configured transmission resources.

[0054] If the RAN resource availability and / or the number of UEs or active sessions for a given cell or RAN node exceeds predefined limits, the RAN node shall perform the following actions:

[0055] Switch the UE from the RRC connected state to the RRC inactive state to receive the multicast service.

[0056] Configure shared or dedicated transmission resources (e.g., radio bearers (MRB / DRB), discontinuous reception (DRX) mode, transmission logical channels, and physical channels) for multicast session transmission.

[0057] An RRC release suspension configuration message including the relevant MBS multicast session reception configuration is sent to the UE.

[0058] The RAN node may also include some auxiliary information, such as a list of neighboring cell frequencies that provide the same multicast service / session, and the absolute priority or level of the neighboring cells that provide the same multicast service of interest to the UE, to assist the UE in reselecting the best neighboring cell frequency that provides the multicast service or session it wishes to receive.

[0059] If no other UE receives the same multicast service / session data, the multicast data is transmitted to the UE via the configured dedicated resources; if other UE receives the same service / session, the multicast data is transmitted via point-to-multipoint (PTM) mode.

[0060] Specifically, in some embodiments, the shared transmission resources include at least one of the following: MBS radio bearer (MRB) configuration, discontinuous reception (DRX) mode and / or point-to-multipoint (PTM) RAN protocol and configuration of transmission logical and physical channels. In some embodiments, the dedicated transmission resources include at least one of the following: MRB configuration, unicast data radio bearer (DRB) configuration, DRX mode and / or point-to-point (PTP) RAN protocol and configuration of transmission logical and physical channels. In some embodiments, if no other UE receives the multicast service / session of interest to the UE, the UE receives the multicast service / session data through the dedicated transmission resources; if other UEs receive or are interested in receiving the multicast service / session of interest to the UE, the UE receives the data through the shared transmission resources.

[0061] When the UE switches from the RRC_CONNECTED state to the RRC_INACTIVE state and moves to another RAN node, the UE measures the reference signal received power (RSRP) and reference signal received quality (RSRQ) of the neighbor MBS frequency list provided in the RRC suspension configuration information to find the best cell providing the target multicast service among these cells (based on RSRQ / RSRP) and reselects to this cell to continue the multicast service / session reception in the RRC inactive state (while the UE switches to the new cell, the neighbor frequencies can be received).

[0062] In the above method, the RRC session join message of the UE may include a list of MBS multicast, broadcast and / or unicast session identifiers mapped to MRBs / DRBs, or a list of NAS dedicated messages mapped to MRBs / DRBs.

[0063] In the above method, evaluating the RAN resource availability of the MBS session includes the following operations: the RAN node directly evaluates whether to accept the new UE to join the multicast service / session after receiving the UE RRC message carrying the session joining request, such as Figure 6 shown.

[0064] Evaluate whether the number of currently configured multicast / broadcast radio bearers exceeds a predefined MRB / DRB value (or a threshold limit set by the network as a switch for switching the UE from the RRC connected state to the RRC inactive state).

[0065] The RAN node sends an MBS / multicast service / session resource setup request containing the NAS information provided by the UE to the AMF of the core network.

[0066] Receive information about a list of cells in an MBS service area requesting a multicast session.

[0067] Based on the MBS area cell list and session ID information provided by the AMF, the neighboring cell frequencies that provide these multicast session IDs or services of interest to the UE are determined and sent to the UE including the suspension configuration information in the RRC release message if the gNB decides to switch this particular UE to RRC inactive state to receive multicast services.

[0068] In the above method, evaluating the RAN resource availability of the MBS service / session includes the following steps (eg Figure 7 As shown), after associating with the core network AMF entity, evaluate whether to accept the new UE to join the multicast service / session:

[0069] The RAN node sends an MBS / multicast service / session resource setup request containing the NAS information provided by the UE to the core network AMF.

[0070] Receive information about the requested multicast service / session activity status (ie, whether the service / session is in RRC inactive state or RRC active state) and the MBS service area cell list.

[0071] The RAN node performs an evaluation based on the service / session activity information provided by the AMF and decides whether to keep the UE in the RRC connected state or switch it to the RRC inactive state to receive the multicast service / session data if the number of currently active multicast services / sessions or the number of UEs for each active multicast service / session multiplied by the number of active services / sessions exceeds a predefined value (i.e., the limit on the number of UEs allowed to join an active multicast service / session per RAN node / gNB / cell, which is set by the network as the threshold for switching the UE from the RRC connected state to the RRC inactive state).

[0072] Based on the MBS area cell list and service / session ID information provided by the AMF, determine the frequencies of neighboring cells that provide these multicast services / session IDs or services of interest to the UE and include this information in the RRC release message along with the suspension configuration information to the UE if the gNB decides to switch this particular UE to RRC inactive state to receive multicast services.

[0073] In summary, the present application provides a method for defining a standard for switching the RRC state of a UE from an RRC connected state (RRCCONNECTED) to an RRC inactive state (RRCINACTIVE) to receive multicast service / session data, and determining how to ensure the continuity of the UE's multicast bearer service during RRC state switching (i.e., from an RRC connected state to an RRC inactive state) and movement across different MBS-supporting cells. In the method, when a UE in an RRC_CONNECTED state wishes to receive a multicast service, the UE may send a request to a core network through a gNB, including a service / session identifier (ID) or a PDU service / session ID related to the multicast service / session that the UE wishes to join. Upon receiving the request from the UE, the gNB or the gNB associated with the core network evaluates the UE's request and makes a decision based on at least one of the following parameters: the total number of currently configured unicast, multicast, and broadcast sessions, the number of UEs joining the active multicast service / session, and the RAN resource availability (e.g., the number of configured radio bearers) for the multicast service / session, to decide whether to keep the UE in the RRC connected state or switch it to the RRC inactive state to receive the multicast service.

[0074] If the gNB decides to switch the UE to RRC inactive state to receive multicast services, in order to ensure service continuity of multicast bearers during the mobility and state switching of the UE, the gNB may include some auxiliary information, such as a list of neighboring cell frequencies that provide the same multicast services / sessions that the UE is interested in, the absolute priority or cell level of the neighboring cells, to assist the UE in reselecting the best neighboring cell frequency that provides the multicast services / sessions it wishes to receive.

[0075] In the above method, the present application provides a method for UE to receive multicast services during RRC state switching (i.e., from RRC connected state to RRC inactive state) and moving across different MBS or multicast supporting cells. The main advantages of this new method include:

[0076] 1. This method defines the criteria or measures used by the gNB to decide the state handover of a specific UE within a cell / RAN node, helping to avoid the problem of cell / RAN node overload in scenarios with a large number of UEs.

[0077] 2. This method introduces a mechanism to provide the UE with information about neighboring MBS multicast cells, so that the UE can ensure the continuity of multicast service / session reception during mobility and RRC state switching, and support mobility across different RAN nodes.

[0078] 3. This method allows the UE to receive multicast service / session data in the RRC inactive state, which helps to improve the power consumption saving capability of the UE.

[0079] Figure 8 7 is a block diagram of an exemplary wireless communication system 700 according to an embodiment of the present application. The embodiments described herein may be implemented into a system using any appropriately configured hardware and / or software. Figure 8 A system 700 is shown, which includes a radio frequency (RF) circuit 710, a baseband circuit 720, an application circuit 730, a memory / storage device 740, a display 750, a camera 760, a sensor 770, and an input / output (I / O) interface 780, which are coupled to each other at least as shown. The application circuit 730 may include circuits, such as but not limited to one or more single-core or multi-core processors. The processor may include any combination of general-purpose processors and special-purpose processors, such as a graphics processor, an application processor. The processor may be coupled to a memory / storage device and configured to execute instructions stored in the memory / storage device to enable various applications and / or operating systems to run on the system.

[0080] While the present disclosure has been described in connection with what is considered to be the most practical and preferred embodiment, it is to be understood that the present disclosure is not limited to the disclosed embodiment, but is intended to cover various arrangements made without departing from the scope of the broadest interpretation of the appended claims.

Claims

1. A method for receiving a multicast service / session during mobility and radio resource control (RRC) state switching of a user equipment (UE), performed by the UE, characterized in that: include: In the RRC connected state, the UE sends an RRC message containing a non-access layer NAS request for multicast service / session joining to an access and mobility management function AMF entity of the core network through a radio access network RAN ​​node; The UE receives an RRC reconfiguration message from the RAN node, the RRC reconfiguration message indicating that multicast / broadcast service MBS reception does not require an RRC state change and includes an MBS multicast service configuration, or indicates an RRC connection release message, the RRC connection release message indicates an RRC state switch for the MBS and includes an RRC suspension configuration information including an MBS multicast service configuration and neighboring cell assistance information.

2. The method according to claim 1, characterized in that The MBS multicast service configuration is related to the multicast service / session that the UE is interested in receiving, and the neighboring cell auxiliary information is related to the neighboring cell frequency that provides the same MBS multicast service / session that the UE is interested in receiving.

3. The method according to claim 1 or 2, characterized in that: If the UE is configured to switch from the RRC connected state to the RRC inactive state to receive a multicast service / session, after receiving the RRC suspension configuration information including the neighboring cell assistance information, the UE evaluates the reference signal received quality RSRQ or reference signal received power RSRP of the neighboring cell frequency, and reselects the best cell that provides the multicast service / session that the UE is interested in receiving and resides in it.

4. The method according to any one of claims 1 to 3, characterized in that The NAS request includes a multicast service / session identifier ID or a protocol data unit PDU ID related to the multicast service / session that the UE is interested in.

5. The method according to any one of claims 1 to 4, characterized in that The neighboring cell auxiliary information is the neighboring cell frequency that provides the multicast service / session that the UE is interested in.

6. The method according to any one of claims 1 to 5, characterized in that The UE is configured to remain in the RRC connected state and receive the multicast service / session by the RAN node by receiving the RRC reconfiguration message containing the MBS multicast service configuration of the UE, and the UE is also configured to receive the multicast service / session data using shared or dedicated transmission resources, and when the availability of RAN radio bearer resources and / or the number of UEs per active MBS multicast service / session does not exceed a predefined limit of a given cell or the RAN node, the UE receives the multicast service / session data through the configured transmission resources.

7. The method according to claim 6, characterized in that The UE is configured to switch from the RRC connected state to the RRC inactive state to receive the multicast service / session by receiving the RRC connection release message including the neighboring cell assistance information and the RRC suspension configuration information. The UE is also configured to receive the multicast service / session data using shared or dedicated transmission resources. If the availability of RAN radio bearer resources and / or the number of UEs per active service / session exceeds a predefined limit of a given cell or the RAN node, the UE receives the multicast service / session data.

8. The method according to claim 6 or 7, characterized in that: The shared transmission resources include at least one of the following: MBS radio bearer MRB configuration, discontinuous reception DRX mode and / or point-to-multipoint PTM RAN protocol and configuration of transmission logic and physical channels.

9. The method according to claim 6 or 7, characterized in that: The dedicated transmission resources include at least one of the following: MRB configuration, unicast data radio bearer DRB configuration, DRX mode and / or point-to-point PTP RAN protocol and configuration of transmission logic and physical channels.

10. The method according to claim 7, characterized in that The UE is also configured to receive the neighboring cell assistance information, and the neighboring cell assistance information includes at least one of the following: a neighboring cell frequency list providing multicast services / sessions of interest to the UE, an absolute cell priority and / or cell level of neighboring cells, and an MBS area cell list providing multicast services / sessions of interest to the UE.

11. The method according to claim 7, characterized in that The UE is also configured to receive the neighbor cell assistance information to assist the UE in reselecting the best neighbor cell frequency providing the multicast service / session of interest to the UE when the availability of RAN radio bearer resources and / or the number of UEs with active services / sessions for a given cell or the RAN node exceeds a predefined RAN node limit.

12. The method according to claims 6 and 7, characterized in that If no other UE is receiving or interested in receiving the multicast service / session of interest to the UE, the UE receives the multicast service / session data via dedicated transmission resources; or, if other UEs are receiving or interested in receiving the multicast service / session of interest to the UE, the UE receives the multicast service / session data via shared transmission resources.

13. The method according to any one of claims 1 to 12, characterized in that The RRC message containing the NAS request for multicast service / session join includes a list containing MBS multicast, broadcast and / or unicast session identifiers mapped to MRBs and / or DRBs, or a NAS dedicated message list mapped to MRBs and / or DRBs.

14. The method according to any one of claims 6 to 12, characterized in that Evaluating the availability of RAN radio bearer resources for directly accepting new UEs to join a multicast service / session by the RAN node is performed after receiving the RRC message containing the NAS request for joining a multicast service / session.

15. The method according to claim 14, characterized in that Evaluating the availability of the RAN radio bearer resources for multicast service / session reception comprises, after receiving the RRC message containing the NAS request for joining the multicast service / session, evaluating the number of currently configured multicast / broadcast radio bearers and comparing it with a predefined value of MRB and / or DRB or a limit set by the network, the limit serving as a threshold for switching the RRC state of the UE from the RRC connected state to the RRC inactive state.

16. The method according to claim 15, characterized in that Evaluating the availability of the RAN radio bearer resources for multicast service / session reception also includes sending an MBS / multicast session resource setup request by the RAN node to the AMF entity of the core network, wherein the MBS / multicast session resource setup request includes NAS multicast conference information provided by the UE.

17. The method according to claim 16, characterized in that Evaluating the availability of the RAN radio bearer resources for multicast service / session reception further comprises receiving information on a list of MBS area cells providing the requested multicast service / session.

18. The method according to claim 17, characterized in that Evaluating the availability of the RAN radio bearer resources for multicast service / session reception also includes determining, based on the MBS regional cell list and multicast session ID information provided by the AMF entity, a neighboring cell frequency that provides the multicast session or service of interest to the UE, and including the regional cell list and multicast association information in an RRC connection release message, as well as RRC suspension configuration information to the UE, if the base station decides to switch the UE from the RRC connected state to the RRC inactive state to receive the multicast service / session.

19. The method according to any one of claims 6 to 12, characterized in that Evaluating the availability of the RAN radio bearer resources for receiving a multicast service / session is used to accept new UEs to join a multicast service / session after establishing an association with the AMF entity of the core network.

20. The method according to claim 19, characterized in that Evaluating the availability of the RAN radio bearer resources for multicast service / session reception also includes sending, by the RAN node to the AMF entity of the core network, an MBS / multicast session resource setup request including the NAS information provided by the UE.

21. The method according to claim 20, characterized in that Evaluating the availability of the RAN radio bearer resources for multicast service / session reception also includes receiving information about the requested multicast session activity and MBS area cell list.

22. The method according to claim 21, characterized in that Evaluating the availability of the RAN radio bearer resources for receiving the multicast service / session also includes the RAN node performing an evaluation based on the session activity information provided by the AMF entity, and if the number of currently active multicast sessions or the number of UEs for each active multicast service / session multiplied by the number of active multicast services / sessions exceeds a predefined value, deciding whether to keep the UE in the RRC connected state or switch the UE from the RRC connected state to the RRC inactive state to receive the multicast service / session.

23. The method according to claim 19, characterized in that The predefined value includes a limit set by the network on the number of UEs allowed to join an active multicast service / session per RAN node, base station and / or cell, the limit serving as a threshold for switching the UE from the RRC connected state to the RRC inactive state to receive the multicast service / session.

24. The method according to claim 22 or 23, characterized in that Evaluating the availability of the RAN radio bearer resources for receiving multicast services / sessions also includes determining, based on the MBS area cell list and session ID information provided by the AMF entity, the neighboring cell frequency that provides the multicast session ID or the service of interest to the UE, and if the base station decides to switch the UE from the RRC connected state to the RRC inactive state to receive the multicast service / session, including the information in the RRC connection release message and the RRC suspension configuration information and sending it to the UE.

25. A method for receiving a multicast service / session during a user equipment UE mobility and a radio resource control RRC state switching, performed by a base station, characterized in that: include: receiving a session join request from a UE, wherein the base station, the RAN, or the RAN associated with a core network evaluates resource availability to accept the MBS multicast session join request of the new UE by evaluating at least one of the following configuration parameters upon receiving the session join request: the number of unicast, multicast and / or broadcast radio bearers, and / or the number of active multicast services / sessions, and / or whether the number of UEs joining an active multicast service / session exceeds a predefined limit; Decide to keep the UE in an RRC connected state for MBS reception by sending an RRC reconfiguration message to the UE if the at least one configuration parameter does not exceed a predefined limit; or decide to switch, if the at least one configuration parameter exceeds a predefined limit, switch the RRC state of the UE from the RRC connected state to the RRC inactive state for MBS reception by sending an RRC connection release message containing RRC suspension configuration information to the UE. If the base station decides to switch the RRC state of the UE from the RRC connected state to the RRC inactive state to receive a multicast service / session, the base station includes at least one of the following in the RRC suspension configuration information: provide a list of neighboring cell frequencies for the multicast service / session of interest to the UE, and / or provide an absolute cell priority and / or cell level of a certain multicast service / session of interest to the UE in a neighboring cell, and / or provide a list of MBS area cells for a certain multicast service / session of interest to the UE, so as to assist the UE in reselecting the best neighboring cell frequency for providing the multicast service / session of interest to the UE.

26. A user equipment, characterized in that: include: Memory; Transceiver; as well as a processor coupled to the memory and the transceiver; The processor is configured to execute the method according to any one of claims 1 to 24.

27. A base station, characterized in that: include: Memory; Transceiver; as well as a processor coupled to the memory and the transceiver; Wherein, the processor is configured to execute the method of claim 25.

28. A non-transitory machine-readable storage medium, characterized in that Instructions are stored thereon, and when a computer executes the instructions, the instructions cause the computer to perform the method of any one of claims 1 to 25.

29. A chip, characterized in that: include: A processor configured to call and run a computer program stored in a memory so that a device equipped with the chip executes a method according to any one of claims 1 to 25.

30. A computer-readable storage medium, characterized in that: A computer program is stored therein, wherein the computer program causes a computer to execute the method of any one of claims 1 to 25.

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

32. A computer program, characterized in that The computer program causes a computer to execute the method according to any one of claims 1 to 25.

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