WO2022170963A1 - 用于实现多播广播业务切换的方法及相关设备 - Google Patents

用于实现多播广播业务切换的方法及相关设备 Download PDF

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Publication number
WO2022170963A1
WO2022170963A1 PCT/CN2022/073688 CN2022073688W WO2022170963A1 WO 2022170963 A1 WO2022170963 A1 WO 2022170963A1 CN 2022073688 W CN2022073688 W CN 2022073688W WO 2022170963 A1 WO2022170963 A1 WO 2022170963A1
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session
mbs
mbs session
smf
base station
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PCT/CN2022/073688
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English (en)
French (fr)
Inventor
熊春山
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腾讯科技（深圳）有限公司
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Publication of WO2022170963A1 publication Critical patent/WO2022170963A1/zh
Priority to US17/987,789 priority Critical patent/US20230077191A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/16—Performing reselection for specific purposes
    • H04W36/165—Performing reselection for specific purposes for reducing network power consumption
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W28/00—Network traffic management; Network resource management
    • H04W28/02—Traffic management, e.g. flow control or congestion control
    • H04W28/0268—Traffic management, e.g. flow control or congestion control using specific QoS parameters for wireless networks, e.g. QoS class identifier [QCI] or guaranteed bit rate [GBR]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/06—Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0007—Control or signalling for completing the hand-off for multicast or broadcast services, e.g. MBMS
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0011—Control or signalling for completing the hand-off for data sessions of end-to-end connection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/26—Reselection being triggered by specific parameters by agreed or negotiated communication parameters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0011—Control or signalling for completing the hand-off for data sessions of end-to-end connection
    • H04W36/0019—Control or signalling for completing the hand-off for data sessions of end-to-end connection adapted for mobile IP [MIP]

Definitions

  • the present disclosure relates to the field of communication technologies, and in particular, to a method for implementing multicast broadcast service switching, a session management function device, a multicast broadcast session management function device, a computer-readable storage medium, and a computer program product.
  • Unicast (Unicast) is a one-to-one communication.
  • the Unicast Source (Unicast Source) transmits multiple different content to different User Equipment (UE) through the router.
  • UE User Equipment
  • Figure 1 it is assumed that five different The content is transmitted to UE 1, UE 2, UE 3, UE 4, and UE 5 respectively.
  • the advantage of unicast communication is that different content can be transmitted to different users.
  • Multicast can also be called “multicast”, which is to transmit the same content to multiple authorized user equipments.
  • the Multicast Source in Figure 1 transmits the same content to Authorized UE 6, UE 7 and UE 8.
  • Application scenarios such as online video conferencing and online video-on-demand are particularly suitable for multicasting.
  • the multicast mode it is possible to transmit data to all target nodes at one time, or to transmit data only to specific objects (authorized UEs).
  • Broadcasting also transmits the same content to multiple user devices. But it does not make the selection of the user's device.
  • MBS multi-cast broadcast service, multicast broadcasting service
  • the RAN Radio Access Network, Radio Access Network
  • a 5G base station hereinafter referred to as the target base station, or target RAN
  • the The UE needs to switch to the unicast transmission mode, and after activating the MBS service transmission, continues to transmit the data corresponding to the MBS service through the unicast transmission mode, so as to realize the continuity of the MBS service.
  • Embodiments of the present disclosure provide a method for implementing multicast broadcast service switching, a session management function device, a multicast broadcast session management function device, a computer-readable storage medium, and a computer program product, which can be used in user equipment from a mobile device that supports MBS services.
  • a session management function device a multicast broadcast session management function device
  • a computer-readable storage medium a computer program product
  • An embodiment of the present disclosure provides a method for implementing multicast broadcast service handover, which is applied to SMF corresponding to user equipment, the source base station accessed by the user equipment before handover supports MBS, and the user equipment
  • the source base station establishes an MBS session (MBS Session, abbreviation for a multicast session or a broadcast session, i.e. a multicast or broadcast session, which can also be called a multicast broadcast service session), and the user equipment accesses after switching.
  • MBS Session abbreviation for a multicast session or a broadcast session, i.e. a multicast or broadcast session, which can also be called a multicast broadcast service session
  • the target base station does not support MBS, and the core network accessed by the target base station supports MBS.
  • the method includes: acquiring a PDU (Protocol Data Unit, protocol data unit) session associated with the MBS session, wherein the S-NSSAI (Single Network Slice Selection Assistance Information of the PDU session, single network slice selection assistance information) is the same as the S-NSSAI of the MBS session, and the DNN (Data Network Name, data network name) of the PDU session is the same as the DNN of the MBS session; obtain the MBS session identifier of the MBS session; according to the The MBS session identifier obtains the QoS flow information corresponding to the activated MBS session from the MB-SMF (for example, it may be all QoS flow information corresponding to the activated MBS session), wherein the QoS flow information corresponding to the activated MBS session
  • the quality of service flow information corresponding to the session includes one or more quality of service flow information; according to the quality of service flow information corresponding to the activated MBS session, establish on the PDU session corresponding to the activated MBS session A quality of service
  • An embodiment of the present disclosure provides a session management function device, including: one or more processors; a storage device configured to store one or more programs, when the one or more programs are stored by the one or more processors When executed, the one or more processors are caused to implement the methods described in the above embodiments.
  • An embodiment of the present disclosure provides a method for implementing multicast broadcast service handover, which is applied to MB-SMF corresponding to user equipment, the source base station accessed by the user equipment before handover supports MBS, and the user equipment before handover An MBS session has been established at the source base station, the target base station accessed by the user equipment after handover does not support MBS, and the core network accessed by the target base station supports MBS.
  • the method includes: after the user equipment is handed over from the source base station to the target base station, transmitting to the SMF QoS flow information corresponding to the activated MBS session (for example, it may be related to the activated MBS session).
  • All quality of service flow information corresponding to the activated MBS session including one or more quality of service flow information, so that the SMF according to the activated MBS session Corresponding QoS flow information, establishing a QoS flow corresponding to the activated MBS session on the PDU session associated with the MBS session, wherein the QoS flow corresponding to the activated MBS session includes one or Multiple quality of service streams.
  • the S-NSSAI of the PDU session is the same as the S-NSSAI of the MBS session
  • the DNN of the PDU session is the same as the DNN of the MBS session.
  • An embodiment of the present disclosure provides a multicast broadcast session management function device, including: one or more processors; and a storage device configured to store one or more programs, when the one or more programs are stored by the one or more programs When executed by a plurality of processors, the one or more processors are caused to implement the methods described in the above embodiments.
  • An embodiment of the present disclosure provides a computer-readable storage medium, where the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, implements the method described in the foregoing embodiments.
  • Embodiments of the present disclosure provide a computer program product or computer program, where the computer program product or computer program includes computer instructions, and the computer instructions are stored in a computer-readable storage medium.
  • the processor of the computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device performs the methods provided by the various embodiments above.
  • the SMF can directly obtain the QoS Flow (Quality of Service Flow, quality of service flow) information corresponding to the activated MBS session through the MB-SMF corresponding to the MBS session (for example, it can be related to the activated MBS session). All QoS Flow information corresponding to the session), thereby simplifying the process of SMF acquiring the QoS Flow information of the activated MBS session.
  • QoS Flow Quality of Service Flow, quality of service flow
  • this method has minor modifications to the 5G system, which enables the UE to switch the MBS session to the unicast PDU session when switching between the source base station that supports the MBS service and the target base station that does not support the MBS service. Continuity of MBS business.
  • FIG. 1 is a schematic diagram showing a comparison between unicast and multicast IP transmission in the related art.
  • FIG. 2 shows a reference architecture diagram of a 5G MBS in the related art.
  • FIG. 3 schematically shows a flowchart of a method for implementing multicast broadcast service switching according to an embodiment of the present disclosure.
  • FIG. 4 schematically shows a schematic diagram of handover between NG-RANs based on Xn interface without UPF reallocation according to an embodiment of the present disclosure.
  • FIG. 5 schematically shows a schematic diagram of an execution stage of implementing NG-RAN handover through an N2 node according to an embodiment of the present disclosure.
  • FIG. 6 schematically shows a schematic diagram of a process of triggering the establishment of a PDU session on the target NG-RAN side according to an embodiment of the present disclosure.
  • FIG. 7 schematically shows a schematic diagram of a process of triggering the establishment of a PDU session on the target NG-RAN side according to another embodiment of the present disclosure.
  • FIG. 8 schematically shows a schematic diagram of a PDU session modification process according to an embodiment of the present disclosure.
  • FIG. 9 schematically shows a process diagram of the SMF discovering the MB-SMF according to an embodiment of the present disclosure.
  • FIG. 10 schematically shows a process diagram of an MB-SMF discovery by an SMF according to another embodiment of the present disclosure.
  • FIG. 11 schematically shows a block diagram of a session management function device according to an embodiment of the present disclosure.
  • FIG. 12 schematically shows a block diagram of a multicast broadcast session management function device according to an embodiment of the present disclosure.
  • UPF User Plane Function, user plane function
  • SMF Session Management Function, session management function
  • MB-N9 Multicast Broadcast-N9, Multicast Broadcast N9
  • MB-UPF Multicast Broadcast-UPF, Multicast Broadcast User Plane Function
  • receives MBS service data and can also send MBS service data to NG-RAN (5G Radio Access Network, the RAN node in Figure 2) through the N3 interface.
  • NG-RAN 5G Radio Access Network, the RAN node in Figure 2
  • the UPF and the MB-UPF can be logically independent, but can also share the same UPF entity.
  • the SMF can select MB-SMF (Multicast Broadcast SMF, Multicast Broadcast Session Management Function) for the MBS session, and can interact with the MB-SMF to obtain information related to the MBS session.
  • SMF and MB-SMF are logically independent, but can also share the same entity.
  • UDR Unified Data Repository, Unified Data Storage
  • NRF Network Function, Network Function
  • Network Storage Function support to discover MB-SMF for MBS Session, and store the selected MB-SMF ID (identity, ID, i.e. MB-SMF ID).
  • MBSF Multicast Broadcast Service Function, Multicast Broadcast Service Function
  • MBSF-U MBSF User Plane Function
  • MBSF-C MBSF Control Plane Function, MBSF Control Plane Function
  • MBSF-C/U is not necessary, but they are necessary under the following two conditions: the first condition, when 5G MBS and 4G or 3G MBMS (Multimedia Broadcast/Multicast Service, Multimedia Broadcast/Multicast When the business) is interconnected, that is, when the 5G AF (Application Function, application function) and the 4G or 3G MBMS AS (Application Server, application server) are the same entity, see Figure 2.
  • the second condition is when the operator needs to perform media processing on the MBS service (eg, perform video transcoding or content inspection, etc.).
  • SMF and UPF can participate in the process of 5G MBS Session, and there are related descriptions in the following embodiments.
  • NEF in Figure 2 is Network Exposure Function, that is, the network opening function.
  • PCF Policy Control Function, which is the policy control function
  • Npcf refers to the Npcf message that obtains the services provided by PCF.
  • AMF Access and Mobility Management Function, that is, access mobility management function.
  • FIG. 3 schematically shows a flowchart of a method for implementing multicast broadcast service switching according to an embodiment of the present disclosure.
  • the method provided in the embodiment of FIG. 3 can be applied to the SMF corresponding to the user equipment UE.
  • the source base station accessed by the user equipment before handover supports MBS, and the user equipment has established an MBS session at the source base station before the handover.
  • the target base station accessed by the user equipment after handover does not support MBS, and the core network accessed by the target base station (in the following embodiments, the 5G core network is used as an example for illustration, but the present disclosure is not limited to This) supports MBS.
  • the base station that the UE accesses before handover is called the source base station
  • the base station that the UE accesses after the handover is called the target base station.
  • the NG-RAN in the 5G system respectively referred to as the source NG-RAN (or S-NG-RAN) and the target NG-RAN (or T-NG-RAN), are taken as examples to illustrate, but the present disclosure is not limited to here.
  • the MBS Session in the embodiment of the present disclosure may include an MBS Multicast Session and/or an MBS Broadcast Session, that is, an MBS Multicast Session and/or an MBS Broadcast Session.
  • MBS Multicast Session MBS Multicast Session
  • MBS Broadcast Session MBS Broadcast Session
  • the method provided by the embodiment of the present disclosure may include the following steps.
  • step S310 acquire a PDU session associated with the MBS session, wherein the S-NSSAI of the PDU session is the same as the S-NSSAI of the MBS session, and the DNN of the PDU session is the same as the DNN of the MBS session .
  • the PDU session (PDU Session) associated with the MBS session can be established either on the side of the source base station or on the side of the target base station, which is not limited in the present disclosure.
  • the PDU Session established on the target base station side/source base station side is used to replace the MBS Session on the source base station, such as MBS Multicast/Broadcast Session, so the combination of S-NSSAI and DNN of the PDU Session is the same as the S-NSSAI of the original MBS Multicast/Broadcast Session.
  • -NSSAI and DNN combination are the same, so that the continuity of MBS service can be maintained.
  • a corresponding PDU session is associated with each MBS session, and the S-NSSAI of each MBS session is associated with the corresponding PDU session.
  • the S-NSSAI of the PDU session corresponding to the MBS session is the same, and the DNN of each MBS session is the same as the DNN of the PDU session corresponding to the MBS session.
  • step S320 the MBS session identifier (that is, the MBS Session ID) of the MBS session is obtained.
  • step S330 obtain the QoS flow information corresponding to the activated MBS session from the MB-SMF according to the MBS session identifier, wherein the QoS flow information corresponding to the activated MBS session includes one or more Quality of service flow information.
  • the QoS flow information acquired by the SMF may be all QoS flow information corresponding to the activated MBS session, and correspondingly, the QoS flow information established on the PDU session associated with the MBS session
  • the quality of service flows may be all quality of service flows corresponding to the activated MBS session.
  • each MBS session may be activated before the handover, or may be activated after the handover, which is not limited in the present disclosure.
  • the actions that the UE wants to join the MBS explicitly but have not started the service data transmission are defined as “register”, “join” or “establish”.
  • the action of starting the transmission of MBS service data is defined as “activation” or “service activation”, that is, only the MBS session established by the QoS Flow is "activated”; if the QoS Flow is not established, there is no MB-UPF. MBS sessions are just established.
  • step S340 according to the QoS flow information corresponding to the activated MBS session, a QoS flow corresponding to the activated MBS session is established on the PDU session, wherein the QoS flow corresponding to the activated MBS session is established on the PDU session.
  • the quality of service flow corresponding to the session includes one or more quality of service flows.
  • the user equipment may have activated the MBS session at the source base station before handover, and has not yet established a PDU session associated with the MBS session.
  • acquiring the PDU session associated with the MBS session may include: after the user equipment is handed over from the source base station to the target base station, executing the user equipment-triggered establishment of the target base station side The process of a PDU session.
  • acquiring the MBS session identifier of the activated MBS session may include: in the process of establishing the PDU session on the side of the target base station, receiving a PDU session establishment session management context request message from the AMF, the PDU session establishment The session management context request message includes the MBS session identifier.
  • the PDU session establishment session management context request message may further include the S-NSSAI, the DNN, a request type, and an N1 session management container.
  • the request type is indicated as an existing MBS session.
  • the N1 session management container carries a PDU session establishment request.
  • acquiring the QoS flow information corresponding to the activated MBS session from the MB-SMF according to the MBS session identifier may include: in the process of establishing the PDU session on the side of the target base station , sending a first MBS session creation request message to the MB-SMF, where the first MBS session creation request message carries the MBS session identifier; receiving the MBS session creation request message that is returned by the MB-SMF in response to the first MBS session creation request message
  • the first MBS session creation response message includes the quality of service flow information corresponding to the activated MBS session.
  • establishing a quality of service flow corresponding to the activated MBS session on the PDU session according to the quality of service flow information corresponding to the activated MBS session may include: During the establishment of the PDU session, a first communication N1N2 message transmission message is sent to the AMF, so that the AMF establishes the DPU session according to the quality of service flow information corresponding to the activated MBS session. The quality of service flow corresponding to the MBS session.
  • the process of establishing a PDU session at the target base station side after handover can refer to the following figure for details 6 and Fig. 7.
  • the user equipment may have not activated the MBS session at the source base station before handover, and has not established a PDU session associated with the MBS session.
  • the method may further include: establishing the PDU on the side of the target base station after the handover During the session, send a second MBS session creation request message to the MB-SMF, where the second MBS session creation request message carries the MBS session identifier; receive the MB-SMF response to the second MBS session creation The second MBS session creation response message returned from the request message; if the second MBS session creation response message does not carry the QoS flow information corresponding to the MBS session, it is determined that the MBS session has not been activated.
  • acquiring the quality of service flow information corresponding to the activated MBS session from the MB-SMF according to the MBS session identifier may include: after the MBS session is activated, executing the MB-SMF The modification process of the PDU session triggered by the SMF; in the modification process of the PDU session, an MBS session update request message sent by the MB-SMF is received, and the MBS session update request message carries the same message as the activated MBS The quality of service flow information corresponding to the session; returning an MBS session update response message responding to the MBS session update request message to the MB-SMF.
  • establishing a quality of service flow corresponding to the activated MBS session on the PDU session according to the quality of service flow information corresponding to the activated MBS session may include: During the modification process of the PDU session, a second communication N1N2 message transmission message is sent to the AMF, so that the AMF establishes the DPU session according to the quality of service flow information corresponding to the activated MBS session. The quality of service flow corresponding to the MBS session.
  • the method may further include: in the establishment process of the PDU session , determine the UE-UDM according to the SUPI of the user equipment; obtain the MBS session management subscription data of the MBS session from the UE-UDM according to the SUPI; determine the S-UDM according to the MBS session management subscription data
  • the NSSAI and the DNN have signed up at the UE-UDM. The specific process of judging whether the S-NSSAI and the DNN have signed a contract can be seen in Figure 6 below.
  • the method may further include: sending the first NF to the NRF Discovery request message, the first NF discovery request message carries the MBS session identifier and the network type indicated as MBS UDM; receiving the first NF discovery request response message returned by the NRF in response to the first NF discovery request message , the first NF discovery request response message carries the MB-UDM identifier; according to the MB-UDM identifier, send an MBS session context acquisition request message to the MB-UDM, where the MBS session context acquisition request message carries the MBS session identifier ; Receive the MBS session context acquisition response message returned by the MB-UDM in response to the MBS session context acquisition request message, and the MBS session context acquisition response message carries the MB-SMF MB-SMF corresponding to the MBS session identifier.
  • SMF logo The process of SMF discovering MB
  • the method may further include: sending a second NF to the NRF a discovery request message, where the second NF discovery request message carries the MBS session identifier and the network type indicated as MBS SMF; receiving a second NF discovery request response message returned by the NRF in response to the second NF discovery request message, The second NF discovery request response message carries the MB-SMF identifier of the MB-SMF corresponding to the MBS session identifier.
  • Fig. 10 for details.
  • the user equipment may not have activated the MBS session at the source base station before handover, and has established a PDU session associated with the MBS session.
  • acquiring the quality of service flow information corresponding to the activated MBS session from the MBS session according to the MBS session identifier may include: when the user equipment is handed over from the source base station to the target base station, and the After the MBS session is activated after the handover, the modification process of the PDU session is triggered; in the modification process of the PDU session, the activated MBS session is obtained from the MB-SMF according to the MBS session identifier. Corresponding quality of service flow information.
  • the specific process of implementing multicast broadcast service handover can be seen in Figure 10 below.
  • the SMF can directly obtain the QoS Flow (Quality of Service Flow) information of the activated MBS session through the MB-SMF corresponding to the MBS session, thus simplifying the SMF to obtain the activated QoS Flow (Quality of Service Flow) information.
  • QoS Flow Quality of Service Flow
  • this method makes little modification to the 5G system, and realizes that when the UE switches between the source base station that supports MBS service and the target base station that does not support MBS service, the MBS session is switched to the unicast PDU session. Continuity of MBS business.
  • the registration process for example, step 9 in FIG. 4 or step 12 in FIG. 5 , even as shown in FIG. 4 , there may be no registration process, that is, the registration process is optional) or The PDU session establishment process is added later.
  • the 5G radio access network mainly includes two types of nodes: gNB and ng-eNB, between gNB and gNB, between gNB and ng-eNB, and between ng-eNB and gNB, the interfaces are all Xn interfaces, and Xn interfaces are Xn interfaces. Refers to the network interface between NG-RAN nodes.
  • the PDU session establishment process can be preferentially executed after the registration process , but the present disclosure is not limited to this. In this case, the PDU session establishment process may also be performed before the registration process.
  • the PDU session establishment process can be preferentially executed before the registration process, but this disclosure does not Limited to this, in this case, the PDU session establishment process can also be performed after the registration process.
  • the UE has established multiple MBS sessions at the source base station before handover to the target base station, it is assumed that some of the MBS sessions have been activated before the handover, that is, the QoS Flow has been established; the other part of the MBS sessions have not been activated before the handover. , that is, the QoS Flow has not been established, the PDU session establishment process corresponding to this part of the MBS session that has been activated before the handover can be performed before the registration process, and the PDU session corresponding to the other part of the MBS session that has not been activated before the handover is preferentially executed.
  • the PDU session establishment process is executed after the registration process, so that the MBS session that already has service data can be preferentially switched to the PDU session, which can improve the response speed of the service and meet the timeliness of service switching, but the present disclosure is not limited to this. .
  • the execution of multiple PDU session establishment procedures corresponding to multiple MBS sessions may be performed in parallel and independently, and there is no constraint relationship between them.
  • FIG. 4 schematically shows a schematic diagram of an Xn interface based inter NG-RAN handover without UPF re-allocation according to an embodiment of the present disclosure.
  • the UE switches from the source NG-RAN to the target NG-RAN, where the source NG-RAN supports MBS Multicast/Broadcast Session, and the target NG-RAN does not support MBS Multicast/Broadcast Session.
  • the target NG-RAN will send a handover completion indication to the UE.
  • the UE receives the handover completion indication, it can know that it has successfully accessed the target NG-RAN. After that, the UE can trigger the PDU session establishment process as shown in FIG. 6 and FIG. 7 .
  • the handover completion indication may be in any form, for example, the target base station sends the relevant physical layer, media access control (Media Access Control, MAC) layer, radio link control (Radio Link Control, The indication of the RLC) layer or the message of the radio resource control (Radio Resource Control, RRC) layer, the present disclosure does not limit the form of the handover completion indication, as long as the UE can be informed that the UE has successfully accessed the target base station.
  • media access control Media Access Control, MAC
  • Radio Link Control Radio Link Control
  • the indication of the RLC Radio Link Control
  • RRC Radio Resource Control
  • the registration process of step 9 in the embodiment of FIG. 4 and step 12 in the embodiment of FIG. 5 means that after the UE receives the handover completion instruction sent by the target base station, if the UE changes to a new tracking area (Tracking Area), it executes A registration procedure (Registration Procedure) for registering the user equipment to the network.
  • the UE may trigger the establishment of the PDU session on the side of the target base station before the registration process or after the registration process.
  • the execution type is Mobility Registration Procedure of Registration Update (mobility registration update), so that the UE is re-registered to a network such as 5GS (5G system, 5G system) in a new TA.
  • 5GS 5G system, 5G system
  • the UE if the user equipment moves from the source base station to the target base station in an idle state (Connection Management-IDLE, CM-IDLE), the UE triggers the establishment of the target base station side Before the PDU session, the UE may also trigger a service request (Service Request) process to make the user equipment enter a connection state (Connection Management-CONNECTED, CM-CONNECTED).
  • Service Request Service Request
  • the UE can enter the CM-CONNECTED state through Service Request. Then, execute the PDU Session Establishment process.
  • the UE may also perform a registration process whose registration type is mobility registration update, so that the user equipment enters a connected state.
  • the UE For example, if the UE is in the CM-IDLE state and moves from a source base station that supports MBS Multicast/Broadcast Session to another target base station that does not support MBS Multicast/Broadcast Session, and the UE also finds that the current TAI is not in the registered TAI List , the UE first performs the registration process with the registration type Mobility Registration Update (Mobility Registration Update), and then performs the PDU session establishment (PDU Session Establishment) process when the signaling connection is not released.
  • Mobility Registration Update Mobility Registration Update
  • PDU Session Establishment PDU Session Establishment
  • the UE can trigger the PDU session establishment process at any time between step 1a and step 8 in FIG. 4 . , that is, the PDU session establishment process shown in FIG. 5 can be triggered before step 9 in FIG. 4, or the PDU session establishment process shown in FIG. 5 can be triggered after step 9 in FIG. 4. In addition, the steps in FIG. 4 9 is optional.
  • Step 1a in Figure 4 is optional, if the PLMN (Public Land Mobile Network) has been configured with a secondary RAT (Radio Access Technology, Radio Access Technology) usage report, the source in the handover execution phase NG-RAN node can provide RAN usage data report to AMF, namely RAN usage data Report(N2 SM Information(Secondary RAT usage data), Handover Flag, Source to Target transparent container).
  • the Handover Flag indicates that the AMF should buffer N2 Session Management Information (N2 Session Management Information, N2 SM Information) before forwarding, where the N2 SM information includes usage data reports.
  • Source to Target transparent container refers to the source to target transparent container.
  • Step 1b in Figure 4 is optional, the target NG-RAN sends an N2 path switch request, namely N2 Path Switch Request, to the AMF to notify the UE that it has moved (moved) to a new target cell, and provides a The PDU Sessions list is used for switching.
  • N2 path switch request namely N2 Path Switch Request
  • step 2 in FIG. 4 the AMF sends an Nsmf_PDUSession_UpdateSMContext request, that is, a PDU session update session management context request, to the SMF.
  • step 3 in Figure 4 the SMF sends an N4 session modification request, namely the N4 Session Modification Request, to the UPF.
  • the UPF sends an N4 Session Modification response (Response) to the SMF, that is, an N4 session modification response.
  • N4 Session Modification response Response
  • Step 5 in Figure 4 in order to assist the reordering function in the target NG-RAN, the UPF sends one or more "end marker packets" for each N3 tunnel.
  • the UPF Start sending downlink data to the target NG-RAN.
  • step 6 in FIG. 4 the SMF sends an Nsmf_PDUSession_UpdateSMContext response, that is, a PDU session update session management context response, to the AMF.
  • step 7 in Figure 4 the AMF sends the N2 Path Switch Request Ack (ie, the N2 Path Switch Request Ack) to the target NG-RAN.
  • N2 Path Switch Request Ack ie, the N2 Path Switch Request Ack
  • step 8 in Fig. 4 the target NG-RAN confirms that the handover is successful by sending a release resource message to the source NG-RAN.
  • the target NG-RAN then triggers the resource release of the source NG-RAN.
  • the registration procedure (Registration procedure) of step 9 in Figure 4 is optional.
  • FIG. 5 schematically shows a schematic diagram of an execution phase (inter NG-RAN node N2 based handover, execution phase) implemented by an N2 node according to an embodiment of the present disclosure. Before Figure 5, it can also include Inter NG-RAN node N2 based handover, Preparation phase (that is, the preparation phase for realizing NG-RAN handover through the N2 node).
  • execution phase inter NG-RAN node N2 based handover, execution phase
  • Preparation phase that is, the preparation phase for realizing NG-RAN handover through the N2 node.
  • the S-NG-RAN in FIG. 5 refers to the source NG-RAN supporting MBS, which can also be expressed as S-RAN, corresponding to S-AMF and S-UPF.
  • T-NG-RAN refers to a target NG-RAN that does not support MBS, and can also be expressed as T-RAN, corresponding to T-AMF (target AMF) and T-UPF (target UPF).
  • the PSA in UPF(PSA) is the PDU Session Anchor, which is the PDU Session Anchor.
  • step 1 in Figure 5 the S-AMF sends a handover command (Handover Command) to the S-RAN.
  • a handover command Handover Command
  • Step 2 in Figure 5 S-RAN sends Handover Command to UE
  • Step 2a in FIG. 5 is optional, and the S-RAN sends an Uplink RAN Status Transfer (Uplink RAN Status Transfer) message to the S-AMF.
  • Uplink RAN Status Transfer Uplink RAN Status Transfer
  • Step 2b in Figure 5 the S-AMF sends the Namf_Communication_N1N2MessageTransfer service operation to the T-AMF, and the T-AMF confirms it.
  • Step 2c in Figure 5 is optional, the S-AMF or, if the AMF is relocated, the T-AMF sends a Downlink RAN Status Transfer message to the T-RAN.
  • Uplink packets go from T-RAN to T-UPF and UPF (PSA). Downlink packets are sent to S-RAN from UPF (PSA) via S-UPF.
  • the S-RAN should start forwarding downlink data to the T-RAN. This can be through direct data forwarding (step 3a in Figure 5) or indirect data forwarding (step 3b in Figure 5). Steps 3a and 3b in Figure 5 are optional.
  • the UE synchronizes to a new cell (new cell, that is, the target cell corresponding to the target base station).
  • the UE sends a Handover Confirm (Handover Confirm) message to the T-RAN, that is, the UE indicates to the network that the UE has been handed over to the target RAN.
  • the UE sends a Handover Confirm message to the T-RAN.
  • the handover confirmation message it is considered that the UE has been handed over successfully.
  • the UE can trigger the PDU session establishment process as described in the embodiment of FIG. 5 at any time, so as to establish the PDU session on the target base station side.
  • step 5 in Figure 5 the T-RAN sends a Handover Notify (handover notification) to the T-AMF.
  • Step 6a in Figure 5 is optional, the T-AMF sends Namf_Communication_N2InfoNotify to the S-AMF.
  • Step 6b in Figure 5 is optional, the S-AMF sends a Namf_Communication_N2InfoNotify ACK (acknowledgement) to the T-AMF.
  • Step 6c in Figure 5 the S-AMF sends the Nsmf_PDUSession_ReleaseSMContext Request (request) to the SMF.
  • step 7 in Figure 5 the T-AMF sends an Nsmf_PDUSession_UpdateSMContext Request to the SMF.
  • Step 8a in Figure 5 is optional, the SMF sends an N4 Session Modification Request (N4 Session Modification Request) to the T-UPF.
  • N4 Session Modification Request N4 Session Modification Request
  • Step 8b in Figure 5 is optional, the T-UPF sends an N4 Session Modification Response to the SMF.
  • Step 9a in Figure 5 is optional, the SMF sends an N4 Session Modification Request to the S-UPF.
  • Step 9b in Figure 5 is optional, the S-UPF sends the N4 Session Modification Response to the SMF.
  • Step 10a in Figure 5 is optional, the SMF sends an N4 Session Modification Request to the UPF (PSA).
  • Step 10b in Figure 5 is optional, UPF (PSA) sends N4 Session Modification Response to SMF.
  • PSA PSA
  • step 11 in Figure 5 the SMF sends the Nsmf_PDUSession_UpdateSMContext Response to the T-AMF.
  • step 12 in Figure 5 the UE triggers the Registration procedure.
  • the UE may trigger the PDU session establishment process described in the following Figures 6 and 7 before the registration process in Step 12 in Figure 5 or after the registration process in Step 12.
  • Step 13a in Figure 5 is optional, the SMF sends an N4 Session Release Request (N4 Session Release Request) to the S-UPF.
  • N4 Session Release Request N4 Session Release Request
  • Step 13b in Figure 5 is optional, the S-UPF sends an N4 Session Release Response (N4 Session Release Response) to the SMF.
  • N4 Session Release Response N4 Session Release Response
  • step 14a in Figure 5 the AMF sends the UE Context Release Command(), that is, the UE context release command, to the S-RAN.
  • step 14b in Figure 5 the S-RAN sends the UE Context Release Command Complete() to the AMF, that is, the UE context release command is completed.
  • Step 15a in Figure 5 is optional, the SMF sends an N4 Session Modification Request to the T-UPF.
  • Step 15b in Figure 5 is optional, the T-UPF sends the N4 Session Modification Response to the SMF.
  • the UE if the PDU session associated with the MBS session is not established at the source base station side, the UE triggers the establishment of the PDU session at the target base station side after determining that the target base station does not support MBS.
  • the UE determining that the target base station does not support MBS may include: the UE receiving a system message block broadcast by the target base station, and determining according to the system message block that the target base station does not support MBS; or, acquiring the target service of MBS area, and determining that the target base station does not support MBS according to the target service area.
  • the UE can know whether the target cell is or not through the SIB (system information block, system message block) message broadcast by the target cell system corresponding to the target base station.
  • SIB system information block, system message block
  • the SIB message broadcasted by the target base station can indicate: MBS is not supported at all, which S-NSSAI does not support, or which DNN does not support, or which S-NSSAI and DNN combination does not support MBS Session, then the UE can according to the broadcast SIB message
  • the indication information determines that the corresponding one or more PDU Sessions are established at the target base station.
  • the present disclosure does not limit the manner in which the UE determines whether the target base station supports MBS.
  • each MBS Multicast/Broadcast Session corresponds to a combination of S-NSSAI and DNN
  • the UE can determine the target location according to the indication information in the broadcast SIB message.
  • the NG-RAN side establishes the corresponding PDU Session.
  • These multiple MBS Multicast/Broadcast Sessions can be switched to their corresponding PDU Sessions in parallel, or the switching sequence can be determined according to whether there is a service (that is, whether the MBS Session has been activated and whether there is the QoS Flow of the MBS Session).
  • the UE has 5 MBS Multicast/Broadcast Sessions
  • these 5 MBS Multicast/Broadcast Sessions can be switched to their corresponding PDU Sessions at the same time.
  • the switching process of /Broadcast Session can be carried out independently, for example, it can be parallel, and there is no sequential relationship between each other, or some of the 5 MBS Multicast/Broadcast Sessions, such as 3 with services, switch first, and the other part, such as 2 without
  • the post-switching of the service can ensure the real-time switching of the MBS Multicast/Broadcast Session with the service and maintain the continuity of the service.
  • the UE can directly switch the activated MBS session of the source base station to the MBS session of the target base station to achieve service continuity.
  • FIG. 6 and FIG. 7 it is assumed that the source base station accessed by the UE before handover supports MBS, the UE has established an MBS session at the source base station before handover to the target base station, and the MBS session has been activated, while the UE has not established a PDU session associated with the MBS session before handover.
  • the target base station after the handover does not support MBS
  • the 5G core network accessed by the target base station supports MBS.
  • FIG. 6 and FIG. 7 schematically illustrate a process of triggering the establishment of a PDU session on the target NG-RAN side according to an embodiment of the present disclosure.
  • Step 1 in Figure 6 the UE sends a non-access stratum message (Non-Access Stratum Message, abbreviated as NAS Message) to the AMF, and the NAS Message can carry a request type (Request Type), wherein the request type indicates that there is an existing MBS Session (Existing MBS Session), so that AMF selects SMF for the new PDU session according to the value of Request Type.
  • NAS Message Non-Access Stratum Message
  • Request Type request type
  • the NAS Message may also carry the S-NSSAI, the DNN and the MBS session identifier of the MBS session, so that the SMF can perform the S-NSSAI, the DNN and the MBS session according to the S-NSSAI, the DNN and the MBS session Identifies establishing the PDU session.
  • the NAS message may further carry a PDU session ID (PDU Session ID) of the PDU session and an N1 session management (Session Management, SM) container (Container), where the N1 session management container carries the PDU session Establishment request (PDU Session Establishment Request).
  • PDU Session ID PDU session ID
  • N1 session management container Container
  • the UE may initiate a PDU Session Establishment process to establish a PDU Session on the target base station side.
  • the UE can send a NAS message to the AMF, and carry the following parameters in the NAS message: S-NSSAI, DNN, PDU Session ID, Request Type, MBS Session ID (for example, it can include MBS Multicast Session/Broadcast Session ID, hereinafter in order to communicate with Corresponding to the original source base station, it can also be recorded as Old MBS Multicast/Broadcast Session ID) and N1 SM Container, in which PDU Session Establishment Request is carried.
  • S-NSSAI S-NSSAI
  • DNN DNN
  • PDU Session ID for example, it can include MBS Multicast Session/Broadcast Session ID, hereinafter in order to communicate with Corresponding to the original source base station, it can also be recorded as Old MBS Multicast/Broadcast Session ID
  • MBS Session ID for example, it can include MBS Multicast Session/Broadcast Session ID, hereinafter in order to communicate
  • NAS Message S-NSSAI(s), UE Requested DNN, PDU Session ID, Request type, Old MBS Session ID, N1 SM container(PDU Session Establishment Request, [Port Management Information Container])).
  • Request Type be indicated as Existing MBS Session
  • Existing MBS Session may include Existing MBS Multicast/Broadcast Session (an existing MBS Multicast/Broadcast session).
  • the Request Type indicates that the Existing MBS Multicast/Broadcast Session is treated as a new PDU Session, that is, a new SMF is selected.
  • the AMF can establish a PDU Session through interaction with the SMF, and establish one or more QoS Flows corresponding to the activated MBS Session in the PDU Session.
  • the Old MBS Session ID indicates that the Old MBS Multicast/Broadcast Session ID indicates the MBS Multicast/Broadcast Session ID corresponding to the MBS Multicast/Broadcast Session (in some places below, it is directly represented by the MBS Multicast/Broadcast Session ID).
  • the Old MBS Session ID indicated as Old MBS Multicast Session ID indicates that the switch is an MBS multicast service
  • the Old MBS Session ID indicated as Old MBS Broadcast Session ID indicates that the switch is an MBS broadcast service.
  • the N1 SM container is the N1 session management container that carries the PDU Session Establishment Request (PDU session establishment request).
  • Port Management Information Container represents the port management information container.
  • the S-NSSAI and DNN combination in the NAS message is the S-NSSAI and DNN combination corresponding to the Old MBS Multicast/Broadcast Session.
  • the PDU Session established on the target NG-RAN side is used to replace the MBS Multicast/Broadcast Session on the source NG-RAN side.
  • the S-NSSAI and DNN of the PDU Session on the target NG-RAN are combined with the original MBS Multicast/Broadcast Session's S-NSSAI, like the DNN combination, can maintain business continuity.
  • a NAS message carries S-NSSAI, DNN, PDU Session ID, Request Type, MBS Session ID and N1 SM Container at the same time as an example for illustration, the present disclosure is not limited to Therefore, in other embodiments, the UE may directly or indirectly send multiple NAS messages to the AMF, and each NAS message carries at least a part of the above contents, or the UE may directly or indirectly send one of the other forms to the AMF.
  • the AMF it is sufficient to inform the AMF that a PDU session needs to be created at present, and the PDU session is used to replace the MBS session that has been established but not yet activated on the source base station side.
  • the value and expression form of the information are also not limited to the above examples.
  • MB-PCF Multicast Broadcast Policy Control function
  • UE-PCF User Equipment Policy Control Function
  • SMF and MB-SMF are logically independent, but may also be the same SMF entity.
  • UPF and MB-UPF are logically completely independent, but may be the same UPF entity.
  • AMF indicates that the Request Type is Existing MBS Multicast/Broadcast Session as a new PDU Session to process, that is, selects a new SMF (SMF in Figure 6 is different from MB-SMF).
  • the AMF selects an SMF according to the S-NSSAI and DNN provided by the UE.
  • the AMF sends a Nsmf_PDUSession_CreateSMContext request message (that is, a protocol data unit session establishment session management context request message, referred to as a PDU session establishment session management context request message) to the selected SMF, and the Nsmf_PDUSession_CreateSMContext request message carries the DNN, S -NSSAI, Request Type, Old MBS Session ID and N1 SM container, ie Nsmf_PDUSession_CreateSMContext Request(SUPI,selected DNN,UE requested DNN,S-NSSAI(s),PDU Session ID,AMF ID,Request Type(indicated as Existing MBS Multicast /Broadcast Session),Old MBS Session ID,PCF ID,Priority Access,[Small Data Rate Control Status],N1 SM container(PDU Session Establishment Request),User location information,Access Type,RAT Type
  • Priority Access means priority access
  • Small Data Rate Control Status means small data rate control status
  • User location information means user location information
  • Access Type means access type
  • RAT Type means RAT type
  • PEI is the abbreviation of Permanent Equipment Identifier, That is, the permanent device identifier
  • GPSI is the abbreviation of Generic Public Subscription Identifier, that is, the general public user identifier
  • UE presence in LADN service area indicates that the UE exists in the LADN (Local Area Data Network, local data network) service area
  • Subscription For PDU Session Status Notification means defining PDU session status notification
  • DNN Selection Mode means DNN selection mode
  • Trace Requirements means tracing requirements
  • Optimisation indication means control plane CIoT (Cell Internet of Things, cellular Internet of Things) 5GS optimization indication
  • Control Plane Only indicator represents a control surface only indicator.
  • Nsmf_PDUSession_CreateSMContext Request message directly sends a Nsmf_PDUSession_CreateSMContext Request message to SMF, and a Nsmf_PDUSession_CreateSMContext Request message carries DNN, S-NSSAI, Request Type, Old MBS Multicast/Broadcast Session ID and N1SM container at the same time.
  • Nsmf_PDUSession_CreateSMContext Request message carries DNN, S-NSSAI, Request Type, Old MBS Multicast/Broadcast Session ID and N1SM container at the same time.
  • the AMF may directly or indirectly send one or more Nsmf_PDUSession_CreateSMContext Request messages to the SMF, and each Nsmf_PDUSession_CreateSMContext Request message carries at least a part of all the above information respectively, Or other message forms may also be used, which is not limited in the present disclosure, as long as the SMF can finally obtain the above-mentioned required information.
  • Step X.1 in FIG. 6 may include steps X.1.a to X.1.i as follows.
  • step X.1.a the SMF sends the Nnrf_NFDiscovery request message (the network function discovery request message, namely the NF discovery request message) to the NRF, and the Nnrf_NFDiscovery request message carries the SUPI and NF type (NF Type) of the UE, and The NF Type is indicated as UDM to indicate that the ID of the UDM is obtained from the NRF.
  • the Nnrf_NFDiscovery request message the network function discovery request message, namely the NF discovery request message
  • the Nnrf_NFDiscovery request message carries the SUPI and NF type (NF Type) of the UE, and
  • the NF Type is indicated as UDM to indicate that the ID of the UDM is obtained from the NRF.
  • step X.1.b when the NRF receives the above Nnrf_NFDiscovery request message (SUPI, NF Type indicates UDM) from SMF, it responds to the Nnrf_NFDiscovery request message (SUPI, NF Type indicates UDM), and finds the corresponding UE The ID (identity, identification) of the UDM, which is called UE-UDM ID (that is, the user equipment unified data management function identifier corresponding to the user equipment unified data management function), and returns the Nnrf_NFDiscovery response message (UE-UDM ID) to the SMF , that is, the NF discovery response message.
  • UE-UDM ID the Nnrf_NFDiscovery response message
  • step X.1.c after the SMF receives the Nnrf_NFDiscovery response message from the NRF, it can know the UDM corresponding to the UE according to the UE-UDM ID carried in the Nnrf_NFDiscovery response message. Therefore, the SMF can report the UE-UDM ID to the UE-UDM ID.
  • the corresponding UE-UDM sends a Nudm_SDM_Get request message (data management acquisition request message), and the Nudm_SDM_Get request message carries the UE-UDM ID and the SUPI of the UE.
  • step X.1.d after the UE-UDM receives the Nudm_SDM_Get request message from the SMF, the UE-UDM may send a Nudr_DM_Query request message (data management query request message) to the UE-UDR, and carry the Nudr_DM_Query request message in the Nudr_DM_Query request message.
  • UE's SUPI UE's SUPI.
  • the UDR corresponding to the UE-UDM is referred to as UE-UDR, that is, user equipment unified data storage.
  • the UDM corresponding to MBS Session such as MBS Multicast/Broadcast Session mentioned below is called MB-UDM, which is the unified data management function of multicast broadcasting
  • the UDR corresponding to MB-UDM is called MB-UDR, which is the unified multicast broadcast. data storage.
  • the MB-UDR and the UE-UDR may be the same UDR, or may be different UDRs.
  • the response message includes MBS session management subscription data of the MBS Multicast/Broadcast Session.
  • step X.1.f after the UE-UDM receives the Nudr_DM_Query response message returned by the UE-UDR, the UE-UDM may respond to the Nudm_SDM_Get request message and return a Nudm_SDM_Get response message (data management get response message) to the SMF, where the The Nudm_SDM_Get response message carries the MBS session management subscription data of the MBS Multicast/Broadcast Session.
  • step X.1.h after the UE-UDM receives the Nudm_SDM_Subscribe request message, it can send a Nudr_DM_Subscribe message (data management subscription message) to the UE-UDR, and the Nudr_DM_Subscribe message carries the MBS session management of the MBS Multicast/Broadcast Session contract data.
  • the UE-UDM may return a Nudm_SDM_Subscribe response message (data management subscription response message) to the SMF.
  • Step X.1 in the embodiment of FIG. 6 Nudm_SDM_Get (including request and response messages) and (including request and response messages) Session Management Subscription data (session management subscription data) in Nudm_SDM_Subscribe are indicated as MBS Session Management Subscription data (that is, multiple broadcast broadcast service session management subscription data).
  • MBS Session Management Subscription data that is, multiple broadcast broadcast service session management subscription data.
  • the Session Management Subscription data in Nudr_DM_Query (including request and response messages) and Nudr_DM_Subscribe (including request and response messages) is indicated as MBS Session Management Subscription data.
  • Step X.1 in the embodiment of FIG. 6 is that the SMF queries the NRF through the SUPI of the UE to obtain the UE-UDM.
  • the UE-UDM in the step X.1 in the embodiment of FIG. 6 is used to store the MBS session management subscription data of the UE. , according to these MBS session management subscription data, it can be known whether the S-NSSAI and the DNN have signed a contract, if not, the following steps in FIG. 6 are refused to be executed. That is, the X.1 step checks (check) whether the establishment of a PDU session is allowed, and the MBS session management subscription data includes a lot of information, such as the maximum allowed bandwidth, charging, and the like.
  • the UE executes the entire process shown in Figure 6 and Figure 7 for each PDU Session, because each MBS Multicast/Broadcast The S-NSSAI and DNN of the PDU Session corresponding to the Session are specified in all processes.
  • step 3b of FIG. 6 the SMF returns an Nsmf_PDUSession_CreateSMContext response message (that is, a protocol data unit session establishment session management context response message, abbreviated as PDU session establishment session management context response message) to the AMF in response to the Nsmf_PDUSession_CreateSMContext request message.
  • Nsmf_PDUSession_CreateSMContext response message that is, a protocol data unit session establishment session management context response message, abbreviated as PDU session establishment session management context response message
  • step 4 of FIG. 6 PDU session authentication/authorization (Authentication/Authorization) is performed.
  • step 5 of FIG. 6 the SMF selects the UPF, wherein if the SMF finds that it is the MB-SMF, the SMF directly selects the MB-UPF as the UPF.
  • step 6a of Figure 6 the SMF sends an N4 Session Establishment Request (N4 Session Establishment Request) message to the selected UPF.
  • N4 Session Establishment Request N4 Session Establishment Request
  • step 6b of Figure 6 the UPF returns an N4 Session Establishment Response (N4 Session Establishment Response) message to the SMF for confirmation.
  • N4 Session Establishment Response N4 Session Establishment Response
  • step 7a in FIG. 7 if the PCF is deployed and the dynamic policy is used, in step 7a in FIG. 7, the SMF selects the PCF (ie, selects the UE-PCF in FIG. 8).
  • the SMF can reuse the MB-PCF selected by the MBS Multicast/Broadcast Session as the UE-PCF, or can re-select a PCF different from the MB-PCF as the UE-PCF for the UE.
  • the MB-PCF is preferably selected as the UE-PCF according to the MBS Multicast/Broadcast Session ID.
  • Step 7b in Figure 7 is optional. If the PCF is deployed and the dynamic policy is used, then in Step 7b in Figure 7, the SM Policy Association Establishment procedure is performed to obtain the Default PCC of the PDU Session. Rule.
  • Step 7c in Figure 7 is optional, the SMF subscribes the UE-UDM for the PDU Session.
  • step X.2 for the SMF to discover the MB-SMF, so as to perform subsequent steps, as shown in FIG. 9 and FIG. 10 below. It should be noted that, step X.2 only needs to be completed before step 8, and has no time relationship with other steps.
  • step 8 in FIG. 7 the SMF sends an Nsmf_MBSSession_Create request (Request) message to the MB-SMF corresponding to the MBS session found in step X.2, that is, the first MBS session creation request message, and the Nsmf_MBSSession_Create Request message can carry all the The MBS session ID corresponding to the above-mentioned MBS session, that is, the old (old) MBS session ID in FIG. 7 .
  • the Nsmf_MBSSession_Create Request message can also carry SUPI, GPSI, DNN, S-NSSAI, PDU session ID, SMF ID, UPF CN-Tunnel-Info (core network tunnel information, where CN is the abbreviation of Core Network), PDU Session type, PCF ID and AMF ID.
  • step 9a in FIG. 7 optionally, the MB-SMF sends an N4 session establishment request message to the MB-UPF.
  • the MB-UPF responds to the N4 session establishment request message and returns an N4 session establishment response message to the MB-SMF. If the SMF provides the UPF CN-Tunnel-Info, the MB-UPF can establish a transport tunnel to the UPF.
  • the UPF establishes a user plane connection with the MB-UPF, for example, the UPF joins the transport layer IP multicast address allocated by the MB-UPF. Through this transport layer IP multicast address and C-TEID (common TEID (Tunnel Endpoint Identity, tunnel endpoint identity)), UPF starts to receive the downlink data sent by MB-UPF. For UPF, this is the first received data.
  • a downlink data First Downlink Data
  • the MB-SMF responds to the Nsmf_MBSSession_Create Request message in the above step 8, and sends an Nsmf_MBSSession_Create response (Response) message to the SMF, that is, the first MBS session creation response message.
  • the Nsmf_MBSSession_Create Response message carries the MBS QoS Flow parameter List (List) and MBS CN tunnel transmission information of MB-UPF, wherein the MBS QoS Flow parameter list further includes MBS QFI (MBS QoS Flow ID, namely QoS Flow identification), MBS QFI QoS rules (Rules), MBS QFI QoS Configuration (Profile), that is, all QoS Flow information corresponding to the activated MBS session, all QoS Flow information includes one or more.
  • MBS QoS Flow parameter List further includes MBS QFI (MBS QoS Flow ID, namely QoS Flow identification), MBS QFI QoS rules (Rules), MBS QFI QoS Configuration (Profile), that is, all QoS Flow information corresponding to the activated MBS session, all QoS Flow information includes one or more.
  • the SMF can determine that the MBS session has been activated. Therefore, in Figure 6 And the QoS Flow corresponding to the MBS Session is established during the establishment of the PDU Session in Figure 7.
  • Step 11 in FIG. 7 is optional. If the PCF is deployed and the dynamic policy is used, then in step 11 in FIG. 7 , the SMF triggers the SM policy association modification process.
  • the SMF provides the selected PCF with the QoS information (Packet Filter, 5QI, ARP, etc.) of each QoS Flow corresponding to the MBS Session service flow obtained from the MB-UDM, and requests the PCF to check (check) the QoS information of these MBS Session service flows Whether it complies with the Policy (policy) rules of the user and the network.
  • QoS information Packet Filter, 5QI, ARP, etc.
  • PCF issues new authorized Policy rules according to the policies of users and networks, that is, the QoS information (Packet Filter, 5QI, ARP, etc.) of each MBS Session service flow. Even if no QoS information is modified, PCF still needs to transfer SMF The QoS information of the provided MBS Session service flow is sent to the SMF again.
  • QoS information Packet Filter, 5QI, ARP, etc.
  • the MBS Session ID is indicated as the MBS Multicast/Broadcast Session ID to indicate that it is used for the MBS Multicast/Broadcast Session, And it corresponds to the ID of the MBS Multicast/Broadcast Session, so that MB-PCF can use the corresponding authorized Policy Rules (policy rules) to SMF according to the user, network and MBS Multicast/Broadcast Session ID.
  • the PCF still needs to send the QoS information of the MBS Session service flow provided by the SMF to the SMF again.
  • step 12 in Figure 7 SMF sends Namf_Communication_N1N2MessageTransfer (that is, the first communication N1N2 message transfer message) to AMF, SMF requests AMF to transfer the message on N1 interface and the message on N2 interface, SMF wants AMF to send UE and target NG respectively -RAN forwards the relevant information about the SM, and the SMF establishes one or more corresponding MBS Multicast/Broadcast Sessions on the PDU Session according to the dynamic Policy RuleQoS information provided by the PCF or the QoS Flow information of the MBS Multicast/Broadcast Session provided by the MB-UDM QoS Flow.
  • Namf_Communication_N1N2MessageTransfer that is, the first communication N1N2 message transfer message
  • SMF requests AMF to transfer the message on N1 interface and the message on N2 interface
  • SMF triggers Namf_Communication_N1N2MessageTransfer([N2 SM information](PDU Session ID, QFI(s), QoS Profile(s), [Alternative QoS Profile(s)], Session-AMBR, [CN Tunnel Info(s)], QoS Monitoring indication,QoS Monitoring reporting frequency,[TSCAI(s)]),N1 SM container(PDU Session Modification Command(PDU Session ID,QoS rule(s),QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s), QoS rule operation and QoS Flow level QoS parameters operation, Session-AMBR))).
  • N2 SM information PDU Session ID, QFI(s), QoS Profile(s), [Alternative QoS Profile(s)], Session-AMBR, [CN Tunnel Info(s)], QoS Monitoring indication,QoS Monitoring reporting frequency,[
  • the PDU Session ID in Namf_Communication_N1N2MessageTransfer is to let AMF know which Session of the UE to provide the Transfer service for.
  • N2 SM information (N2 session management information) is for the target NG-RAN.
  • the main contents include: PDU Session ID, QFI(s), QoS Profile(s), CN Tunnel Info (core network tunnel information), Session-AMBR ( Session-Aggregate Maximum Bit Rate, session aggregation maximum bit rate), PDU Session Type (PDU session type).
  • the QoS Profile(s) is used for the target NG-RAN to configure multiple QoS Flows for a Session; CN Tunnel Info is used to identify the node on the UPF side of the N3 interface for this Session.
  • N1 SM container (N1 session management container) is for UE to see, it is an SM message, namely Session Established Accept, the main contents include: QoS Rule(s), S-NSSAI(s), DNN, IP address and Session-AMBR .
  • the QoS Rule(s) is used for the UE to configure multiple QoS Flows in one Session; the IP address is used for the data routing after the UE exits from the UPF.
  • the QoS Profile(s) and QoS Rule(s) are mentioned here, which refer to the QoS Profile and QoS Rule corresponding to each QoS Flow. If there are multiple QoS Flows, one message contains the QoS Profile and QoS Rule corresponding to each QoS Flow. In 5G, multiple QoS Flows of a session are configured at one time in this way, which greatly improves the signaling efficiency.
  • step 13 of Figure 7 the AMF sends an N2 PDU Session Request (N2 PDU Session Request) message to the target NG-RAN.
  • N2 PDU Session Request N2 PDU Session Request
  • N2 PDU Session Request (N2 SM information, NAS message(PDU Session ID, N1 SM container(PDU Session Establishment Accept)), [CN assisted RAN parameters tuning]). That is, the N2 PDU Session Request sent by the AMF to the target NG-RAN includes the NAS message and the N2 SM information received from the SMF, where the NAS message includes the PDU Session ID and PDU Session Establishment Accept for sending to the UE.
  • step 14 of FIG. 7 RRC (Radio Resource Control, Radio Resource Control) reconfiguration is performed between the target NG-RAN and the UE.
  • RRC Radio Resource Control, Radio Resource Control
  • step 15 of Figure 7 the target NG-RAN sends an N2 PDU Session Request Ack message to the AMF.
  • step 16 of FIG. 7 the AMF sends a Nsmf_PDUSession_UpdateSMContext request message to the SMF.
  • AMF sends Nsmf_PDUSession_UpdateSMContext Request(SM Context ID, N2 SM information, Request Type) to SMF.
  • AMF uses the update SM context service provided by SMF to deliver N2 SM information to SMF.
  • step 17a of Figure 7 the SMF sends the N4 Session Modification Request message to the UPF, hoping to transmit the AN Tunnel Info (access network tunnel information) from the target NG-RAN to open the downlink tunnel of N3, and Finally, the UPF is informed of the downlink forwarding rules.
  • AN Tunnel Info There is a parameter in the N2 SM information: AN Tunnel Info, which identifies the target NG-RAN side node of the Session on the N3 interface. Once the AN Tunnel Info is delivered by the SMF to the UPF, the downlink tunnel of the Session on the N3 interface is opened.
  • step 17b of FIG. 7 the UPF responds to the N4 Session Modification Request message and returns an N4 Session Modification Response (N4 Session Modification Response) message to the SMF.
  • N4 Session Modification Response N4 Session Modification Response
  • step 18 of FIG. 7 the SMF responds to the Nsmf_PDUSession_UpdateSMContext request message and returns an Nsmf_PDUSession_UpdateSMContext response message to the AMF.
  • step 19 in Figure 7 the SMF sends the Nsmf_PDUSession_SMContextStatusNotify message to the AMF.
  • the UPF sends the IPv6 (Internet Protocol Version 6, Internet Protocol Version 6) address configuration to the target NG-RAN, and the target NG-RAN sends the IPv6 address configuration to the UE.
  • the UPF sends the first downlink data to the UE.
  • the SMF may also send a Nsmf_MBSSession_Update request message to the MB-SMF.
  • the UE when the source base station of the UE before the switching has activated the MBS session and has not established the PDU session associated with the MBS session, the UE starts from After the source base station that supports MBS switches to the target base station that does not support MBS, it triggers the establishment of a PDU session on the side of the target base station that does not support MBS.
  • the SMF directly establishes all the QoS Flows corresponding to the activated MBS sessions on the source base station side on the PDU session associated with the MBS session, which simplifies the process of obtaining the QoS Flows by the SMF.
  • all QoS Flows corresponding to the activated MBS sessions may include one or more QoS Flows.
  • this method has minimal modification to the 5G system, and enables the UE to switch the activated MBS session to a unicast PDU session when switching between a source base station that supports MBS and a target base station that does not support MBS.
  • the SMF sends an Nsmf_MBSSession_Create request (Request) message, that is, a second MBS session creation request message, to the MB-SMF corresponding to the MBS session, and the Nsmf_MBSSession_Create Request message may carry the corresponding MBS session The MBS session ID.
  • Request Nsmf_MBSSession_Create request
  • the MB-SMF responds to the Nsmf_MBSSession_Create Request message in step 8 in FIG. 7 and sends an Nsmf_MBSSession_Create response (Response) message to the SMF, that is, the second MBS session creation response message, in the Nsmf_MBSSession_Create Response message.
  • the MBS CN tunneling information that does not carry the list (List) and the MB-UPF, that is, the second MBS session creation response message does not carry all the QoS Flow information corresponding to the activated MBS session, so the SMF can determine that the MBS session is here not yet activated. Therefore, if the MBS session has not been activated before the handover, the QoS Flow corresponding to the MBS Session is not established during the establishment of the PDU Session in FIG. 7 .
  • step 12 in the above-mentioned Figure 7 SMF sends Namf_Communication_N1N2MessageTransfer (communication N1N2 message transfer message) to AMF. Since all QoS Flow information corresponding to the activated MBS session has not been obtained, SMF is not established on the PDU Session in this step. One or more QoS Flows corresponding to MBS Multicast/Broadcast Session.
  • the UE in the process of modifying the triggered PDU session, the UE will cause the SMF to obtain all the QoS Flow information corresponding to the MBS session from the MB-SMF, so that the SMF can modify the MBS session corresponding to the activated MBS session. All QoS Flows are established on this PDU session to realize the continuity of MBS service data transmission.
  • FIG. 8 schematically shows a schematic diagram of a PDU session modification process according to an embodiment of the present disclosure.
  • step 1 of FIG. 8 after the PDU session has been established on the target RAN or the target NG-RAN side, the MBS session is activated.
  • step 2a you can choose to execute step 2a or 2b, if triggered by 2b, execute step 3.
  • step 2a of FIG. 8 the MB-PCF sends a policy control message related to the MBS Session to the MB-SMF, which triggers the modification of the MBS Session policy association.
  • step 2a may be a part of the MBS session activation process in step 1.
  • step 2b of Figure 8 the MB-SMF triggers a QoS update.
  • MB-SMF triggers SM policy association modification. Policy for MB-SMF to acquire new MBS session from MB-PCF.
  • MB-SMF triggers SM Policy Association Modification (SMF initiated SM Policy Association Modification).
  • the MB-SMF provides the QoS information (Packet Filter, 5QI, ARP, etc.) of each QoS Flow corresponding to the MBS Session service flow to the MB-PCF, and requests the MB-PCF to check (check) whether the QoS information of these MBS Session service flows conforms to the user Policy rules with the network.
  • QoS information Packet Filter, 5QI, ARP, etc.
  • MB-PCF issues new authorized Policy rules according to the policies of users and networks, that is, the QoS information (Packet Filter, 5QI, ARP, etc.) of each MBS Session service flow, even without any modification of QoS information, MB-PCF It is still necessary to send the QoS information of the MBS Session service flow provided by the MB-SMF to the MB-SMF again.
  • QoS information Packet Filter, 5QI, ARP, etc.
  • the MB-SMF sends an Nsmf_MBSSession_Update request message (ie, an MBS session update request message) to the SMF, and the MBS session update request message carries all QoS flow information corresponding to the activated MBS session.
  • Nsmf_MBSSession_Update request message ie, an MBS session update request message
  • the MB-SMF sends an N4 Session Modification Request (N4 Session Modification Request) to the MB-UPF.
  • N4 Session Modification Request Send one or more N4Rules corresponding to each QoS Flow to the MB-UPF. For each QoS Flow, there may be multiple N4Rules.
  • the MB-UPF sends an N4 Session Modification Response (N4 Session Modification Response) to the MB-SMF.
  • N4 Session Modification Response N4 Session Modification Response
  • step 6 of FIG. 8 the SMF initiates a session management (SM) policy association modification of the PDU Session to the UE-PCF.
  • SM session management
  • the SMF triggers the SM policy association modification (SMF initiated SM Policy Association Modification).
  • the SMF provides the QoS information (Packet Filter, 5QI, ARP, etc.) of each QoS Flow of the MBS Session service flow provided by the MB-SMF to the UE-PCF, and requests the UE-PCF to check (check) whether the QoS information of these MBS Session service flows is not Comply with the Policy (policy) rules of the user and the network.
  • QoS information Packet Filter, 5QI, ARP, etc.
  • the UE-PCF issues new authorized Policy rules according to the policies of the user and the network, that is, the QoS information (Packet Filter, 5QI, ARP, etc.) of each MBS Session service flow, even if no QoS information is modified, the UE-PCF It is still necessary to send the QoS information of the MBS Session service flow provided by the SMF to the SMF again.
  • the QoS information Packet Filter, 5QI, ARP, etc.
  • step 7 of FIG. 8 SMF sends Namf_Communication_N1N2MessageTransfer (ie, the second communication N1N2 message transfer message) to AMF, SMF requests AMF to transmit the message on N1 interface and the message on N2 interface, SMF wants AMF to send UE and target respectively
  • the NG-RAN forwards relevant information about the SM.
  • SMF triggers Namf_Communication_N1N2MessageTransfer([N2 SM information](PDU Session ID, QFI(s), QoS Profile(s), [Alternative QoS Profile(s)], Session-AMBR, [CN Tunnel Info(s)], QoS Monitoring indication,QoS Monitoring reporting frequency,[TSCAI(s)]),N1 SM container(PDU Session Modification Command(PDU Session ID,QoS rule(s),QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s), QoS rule operation and QoS Flow level QoS parameters operation, Session-AMBR))).
  • N2 SM information PDU Session ID, QFI(s), QoS Profile(s), [Alternative QoS Profile(s)], Session-AMBR, [CN Tunnel Info(s)], QoS Monitoring indication,QoS Monitoring reporting frequency,[
  • the PDU Session ID in Namf_Communication_N1N2MessageTransfer is to let AMF know which Session of the UE to provide the Transfer service for.
  • N2 SM information (N2 session management information) is for the target NG-RAN.
  • the main contents include: PDU Session ID, QFI(s), QoS Profile(s), CN Tunnel Info (core network tunnel information), Session-AMBR ( Session-Aggregate Maximum Bit Rate, session aggregation maximum bit rate), PDU Session Type (PDU session type).
  • the QoS Profile(s) is used for the target NG-RAN to configure multiple QoS Flows for a Session; CN Tunnel Info is used to identify the node on the UPF side of the N3 interface for this Session.
  • N1 SM container (N1 session management container) is for UE to see, it is an SM message, namely Session Established Accept, the main contents include: QoS Rule(s), S-NSSAI(s), DNN, IP address and Session-AMBR .
  • the QoS Rule(s) is used for the UE to configure multiple QoS Flows in one Session; the IP address is used for the data routing after the UE exits from the UPF.
  • the QoS Profile(s) and QoS Rule(s) are mentioned here, which refer to the QoS Profile and QoS Rule corresponding to each QoS Flow. If there are multiple QoS Flows, one message contains the QoS Profile and QoS Rule corresponding to each QoS Flow. In 5G, multiple QoS Flows can be configured for one session at a time in this way, which greatly improves signaling efficiency.
  • Each QoS Flow and its parameters correspond to the MBS QoS Flow and its parameters corresponding to the MBS Session respectively, that is, the SMF maps each MBS QoS Flow and its parameters corresponding to the MBS Session to a QoS of this PDU Session. Flow and its parameters.
  • step 8 of Fig. 8 the AMF sends an N2 session request message to the target RAN. Command the target RAN to establish the previous QoS Flows.
  • the UE sends an AN-specific (designated) resource modification transmission to the target RAN (including a PDU session modification command, and a radio-specific resource modification message, such as an RRC Reconfiguration message to establish a DRB (Data Data) that transmits each QoS Flow. Radio Bearer, data radio bearer)).
  • a radio-specific resource modification message such as an RRC Reconfiguration message to establish a DRB (Data Data) that transmits each QoS Flow. Radio Bearer, data radio bearer)).
  • the target RAN sends an N2 session response message to the AMF to confirm that the radio resources corresponding to each QoS Flow have been allocated.
  • step 11 of FIG. 8 the AMF sends an Nsmf_PDUSession_UpdateSMContext request message, that is, a PDU session update session management context request message, to the SMF.
  • step 12a of Fig. 8 the SMF sends an N4 session modification request message to the UPF/PSA.
  • step 12b of FIG. 8 the UPF/PSA responds to the N4 session modification request message and returns an N4 session modification response message to the SMF.
  • the SMF responds to the Nsmf_PDUSession_UpdateSMContext request message, and sends an Nsmf_PDUSession_UpdateSMContext response message, that is, a PDU session update session management context response message, to the AMF.
  • step 14 of FIG. 8 the UE sends a PDU Session Modification Command Ack (PDU Session Modification Command Ack) to the target RAN.
  • PDU Session Modification Command Ack PDU Session Modification Command Ack
  • step 15 of Figure 8 the target RAN sends an N2 NAS uplink transfer to the AMF.
  • step 16 of FIG. 8 the AMF sends an Nsmf_PDUSession_UpdateSMContext request message to the SMF.
  • step 17 of FIG. 8 the SMF responds to the Nsmf_PDUSession_UpdateSMContext request message and sends an Nsmf_PDUSession_UpdateSMContext response message to the AMF.
  • step 18 in FIG. 8 the SMF responds to the Nsmf_MBSSession_Update request message in step 4 in FIG. 8 and returns an Nsmf_MBSSession_Update response message to the MB-SMF.
  • step 19a of FIG. 8 the MB-SMF sends an N4 session modification request message to the MB-UPF.
  • step 19b of FIG. 8 the MB-UPF sends an N4 session modification response to the MB-SMF in response to the N4 session modification request message.
  • the UE when the UE is handed over from a source base station supporting MBS to a target base station not supporting MBS, the MBS session established on the side of the source base station has not been activated, And the 5G core network accessed by the target base station supports MBS, after the UE switches from the source base station that supports MBS to the target base station that does not support MBS, triggers the establishment of a PDU session on the target base station side, and then activates the MBS session.
  • the QoS Flow information corresponding to the activated MBS session is transmitted to the SMF through the MB-SMF, so that the SMF can transfer the QoS Flow corresponding to the activated MBS session in the MBS session. It is established on the PDU session associated with the session, which simplifies the process for SMF to obtain QoS Flow information. At the same time, when the MBS session is established, there is no need to associate the PDU session, which saves the resources of the PDU session and maintains the continuity of the service.
  • this method has minimal modification to the 5G system, and enables the UE to switch the MBS session to a unicast PDU session when switching between a source base station that supports MBS and a target base station that does not support MBS.
  • the UE supports the establishment of a unicast PDU session in an asynchronous manner after the UE switches to a target base station that does not support MBS.
  • the embodiment of the present disclosure establishes the PDU session associated with the MBS session after the UE switches to the target base station, when the MBS session is established, there is no need to associate the PDU session, which saves the resources of the PDU session, and can keep the Continuity of MBS business.
  • the UE is required to associate the MBS Session with a PDU Session before switching, and then make the PDU Session switch to the target cell or target RAN, and then transmit the service data corresponding to the MBS Session through the PDU Session.
  • the UE since the UE does not know when the handover occurs in advance (for example, the handover is triggered by the 5G network), in order to support the handover that may occur at any time, when activating an MBS Session, it needs to establish a PDU Session immediately, and in the Before the UE switches to the target RAN, it needs to associate the MBS Session with the PDU Session. This causes a lot of waste of resources, because the UE may not switch to the target base station that does not support MBS, or switch to the target base station that does not support MBS after a long time, such as 2 hours.
  • the method provided by the embodiment of the present disclosure can also be adapted to, before the UE is handed over from the source base station to the target base station, the MBS session and the PDU session have been established on the source base station side, and the UE has already been handed over.
  • the UDM corresponding to the MBS Session such as the MBS Multicast/Broadcast Session is called MB-UDM (Multicast Broadcast Unified Data Manager, multicast broadcast unified data management).
  • MB-UDM Multicast Broadcast Unified Data Manager, multicast broadcast unified data management
  • FIG. 9 schematically shows a process diagram of the SMF discovering the MB-SMF according to an embodiment of the present disclosure.
  • step 1 of Figure 9 the UE has joined an MBS Multicast/Broadcast Session, which has been established and has not been activated.
  • MB-SMF sends Nnrf_NFDiscovery_Request message (third NF discovery request message) to NRF, and the Nnrf_NFDiscovery_Request message carries MBS Session ID indication as MBS Multicast/Broadcast Session ID and NF Type indication for MBS UDM.
  • step Y.1.b of FIG. 9 after receiving the Nnrf_NFDiscovery_Request message, the NRF finds the corresponding MB-UDM ID according to the MBS Multicast/Broadcast Session ID and NF Type carried in the Nnrf_NFDiscovery_Request message as MBS UDM, And return the Nnrf_NFDiscovery_Request response message (the third NF discovery request response message) to the MB-SMF, and the MB-UDM ID is carried in the Nnrf_NFDiscovery_Request response message.
  • the MB-SMF can send a Nudm_MBSSessionContextRegisteration request (MBS session Context registration request message), carry the MBS Session ID (indicated as MBS Multicast/Broadcast Session ID) and the MB-SMF ID in the Nudm_MBSSessionContextRegisteration request.
  • MBS session Context registration request message MBS Session ID (indicated as MBS Multicast/Broadcast Session ID) and the MB-SMF ID in the Nudm_MBSSessionContextRegisteration request.
  • Notification Correlation ID is to let SMF know the PDU Session corresponding to which UE.
  • step Y.2.b of FIG. 9 after receiving the Nudm_MBSSessionContextRegisteration request, the MB-UDM registers the MB-SMF in the MB-UDM, and returns a Nudm_MBSSessionContextRegisteration response, that is, an MBS session context registration response message, to the MB-SMF.
  • the corresponding MB-SMFs may also be different. Therefore, through the above steps, the MBs registered to the MB-UDM -SMF may be multiple.
  • step 2 of FIG. 9 the methods described in the embodiments of FIG. 6 and FIG. 7 may be used to establish a PDU session.
  • step Y.3.a of Figure 9 the SMF sends the Nnrf_NFDiscovery_Request message (the first NF discovery request message) to the NRF, and the Nnrf_NFDiscovery_Request message carries the MBS Session ID to indicate the MBS Multicast/Broadcast Session ID and the NF Type to indicate the MBS UDM.
  • step Y.3.b of Figure 9 after receiving the Nnrf_NFDiscovery_Request message, the NRF finds the corresponding MB-UDM ID according to the MBS Multicast/Broadcast Session ID and NF Type carried in the Nnrf_NFDiscovery_Request message, indicating that it is MBS UDM, And return the Nnrf_NFDiscovery_Request response message (the first NF discovery request response message) to the MB-SMF, and the MB-UDM ID is carried in the Nnrf_NFDiscovery_Request response message.
  • step Y.4.a of FIG. 9 after receiving the Nnrf_NFDiscovery_Request response message, the SMF can send a Nudm_MBSSessionContextGet request (MBS session context acquisition request) to the corresponding MB-UDM according to the MB-UDM ID carried in the Nnrf_NFDiscovery_Request response message message), carry MBS Session ID (indicated as MBS Multicast/Broadcast Session ID), Notification Correlation ID (Notification Correlation ID) and MB-SMF ID in the Nudm_MBSSessionContextGet request.
  • MBS Session ID indicated as MBS Multicast/Broadcast Session ID
  • Notification Correlation ID Notification Correlation ID
  • MB-SMF ID MB-SMF ID in the Nudm_MBSSessionContextGet request.
  • step Y.4.b of FIG. 9 after receiving the Nudm_MBSSessionContextGet request message, the MB-UDM returns a Nudm_MBSSessionContextGet response message, that is, the MBS session context acquisition response message, to the SMF, and the Nudm_MBSSessionContextGet response message carries the MBS session ID and the MB-SMF. ID.
  • FIG. 10 schematically shows a process diagram of an MB-SMF discovery by an SMF according to another embodiment of the present disclosure.
  • step 1 of Figure 10 the UE has joined an MBS Multicast/Broadcast Session, which has been established and has not been activated.
  • the MB-SMF sends the Nnrf_NFManagement_NFRegister_request message (NF management NF registration request message) to the NRF, and the Nnrf_NFManagement_NFRegister_request message carries the MBS Session ID (indicated as MBS Multicast/Broadcast Session ID), Notification Correlation ID (notification Association ID) and MB-SMF ID.
  • MBS Session ID indicated as MBS Multicast/Broadcast Session ID
  • Notification Correlation ID notification Association ID
  • MB-SMF ID MBS Session ID
  • step 3 of FIG. 10 after receiving the Nnrf_NFManagement_NFRegister_request message, the NRF stores the NF configuration, that is, the MBS Session ID and the MB-SMF ID are stored in the NRF in association.
  • the NRF sends the Nnrf_NFManagement_NFRegister_response message (NF management NF registration response message) to the MB-SMF in response to the Nnrf_NFManagement_NFRegister_request message.
  • step 5 of FIG. 10 the method described in the embodiments of FIG. 6 and FIG. 7 may be used to establish a PDU session.
  • step 6 of Fig. 10 SMF sends Nnrf_NFDiscovery_Request message (second NF discovery request message) to NRF, carries MBS Session ID in this Nnrf_NFDiscovery_Request message and indicates MBS Multicast/Broadcast Session ID, and NF Type indicates MBS SMF.
  • the NRF After receiving the Nnrf_NFDiscovery_Request message, the NRF indicates that it is MBS SMF according to the MBS Multicast/Broadcast Session ID and NF Type carried in the Nnrf_NFDiscovery_Request message, authorizes NF service discovery, and finds the same MBS Multicast/Broadcast
  • the NF Type corresponding to the Session ID indicates the MB-SMF ID of the MBS SMF.
  • step 8 of FIG. 10 the NRF returns an Nnrf_NFDiscovery_Request response message (ie, the second NF discovery request response message) to the SMF, and the Nnrf_NFDiscovery_Request response message carries the MB-SMF ID.
  • Nnrf_NFDiscovery_Request response message ie, the second NF discovery request response message
  • an embodiment of the present disclosure also provides a method for implementing multicast broadcast service handover, which is applied to MB-SMF corresponding to user equipment, and the source base station accessed by the user equipment before handover supports MBS, and the The user equipment has established an MBS session at the source base station before the handover, the target base station accessed by the user equipment after the handover does not support MBS, and the core network accessed by the target base station supports MBS.
  • the method may include: after the user equipment is handed over from the source base station to the target base station, transmitting to the SMF the quality of service flow information corresponding to the activated MBS session, wherein the information corresponding to the activated MBS session is
  • the quality of service flow information corresponding to the MBS session may include one or more quality of service flow information, so that the SMF, according to the quality of service flow information corresponding to the activated MBS session, in the PDU session associated with the MBS session establishing a quality of service flow corresponding to the activated MBS session, wherein the quality of service flow corresponding to the activated MBS session includes one or more quality of service flows.
  • the S-NSSAI of the PDU session is the same as the S-NSSAI of the MBS session, and the DNN of the PDU session is the same as the DNN of the MBS session.
  • the user equipment may have activated the MBS session at the source base station before handover, and has not yet established a PDU session associated with the MBS session.
  • transmitting the QoS flow information corresponding to the activated MBS session to the SMF may include: after the user equipment is handed over from the source base station to the target base station, executing the user equipment-triggered The process of establishing the PDU session on the target base station side; in the process of establishing the PDU session on the target base station side, receiving the first MBS session creation request message sent by the SMF, the first MBS session creation request message Carrying the MBS session identifier of the MBS session; sending a first MBS session creation response message generated in response to the first MBS session creation request message to the SMF, where the first MBS session creation response message includes an QoS flow information corresponding to the MBS session.
  • the user equipment may have not activated the MBS session at the source base station before handover, and has not established a PDU session associated with the MBS session.
  • the method may further include: after the user equipment is handed over from the source base station to the target base station, executing the user equipment The process of establishing the PDU session on the target base station side triggered by the device; in the process of establishing the PDU session on the target base station side, receiving a second MBS session creation request message sent by the SMF, the second The MBS session creation request message carries the MBS session identifier; and sends a second MBS session creation response message generated in response to the second MBS session creation request message to the SMF, the second MBS session creation response message does not carry The quality of service flow information corresponding to the MBS session, so that the SMF determines that the MBS session has not been activated according to the second MBS session creation response message.
  • transmitting the QoS flow information corresponding to the activated MBS session to the SMF may include: after the MBS session is activated, triggering a modification process of the PDU session; During the session modification process, send an MBS session update request message to the SMF, where the MBS session update request message carries the quality of service flow information corresponding to the activated MBS session; receive the SMF response to the MBS session update The MBS session update response message returned by the request message.
  • the method may further include: sending a third NF discovery request message to the NRF, where the third NF discovery request message carries the MBS session identifier and network type indicated as MBS UDM; receive a third NF discovery request response message returned by the NRF in response to the third NF discovery request message, and the third NF discovery request response message carries the MB-UDM identifier ;
  • the MB-UDM identifier send an MBS session context registration request message to the MB-UDM, where the MBS session context registration request message carries the MBS session identifier and the MBS of the MB-SMF corresponding to the MBS session identifier - SMF identification, so as to store the MBS session identification and the MB-SMF identification in the MB-UDM in association; receive the MBS session context registration response returned by the MB-UDM in response to the MBS session context registration request message information.
  • the method may further include: sending an NF management NF registration request message to the NRF, where the NF management NF registration request message carries the The MBS session ID and the MB-SMF ID of the MB-SMF corresponding to the MBS session ID are stored in the NRF in association with the MBS session ID and the MB-SMF ID; receiving the NRF response to the The NF management NF registration response message returned by the NF management NF registration request message, the NF management NF registration response message carries the MB-SMF identifier of the MB-SMF.
  • FIG. 11 schematically shows a block diagram of a session management function device according to an embodiment of the present disclosure.
  • the session management function device 1100 provided by this embodiment of the present disclosure may include: one or more processors 1101 ; and a memory 1103 configured to store one or more programs, when the one or more programs are When executed by the one or more processors 1101, the one or more processors 1101 are caused to implement the method described in any of the foregoing embodiments.
  • the source base station accessed by the user equipment before handover supports MBS
  • the user equipment has established an MBS session at the source base station before the handover
  • the target base station accessed by the user equipment after the handover does not support MBS
  • the core network accessed by the target base station supports MBS.
  • the program may be specifically used for: acquiring a PDU session associated with the MBS session, wherein the S-NSSAI of the PDU session is the same as the S-NSSAI of the MBS session, and the DNN of the PDU session is the same as the MBS session obtain the MBS session identifier of the MBS session; obtain the QoS flow information corresponding to the activated MBS session from the MB-SMF according to the MBS session identifier, which corresponds to the activated MBS session
  • the QoS flow information includes one or more QoS flow information; according to the QoS flow information corresponding to the activated MBS session, the QoS corresponding to the activated MBS session is established on the PDU session flow, wherein the quality of service flow corresponding to the activated MBS session includes one or more quality of service flows.
  • the program may further include: a PDU session acquisition unit 11031, which may be configured to acquire a PDU session associated with the MBS session, wherein the S-NSSAI of the PDU session is the same as the S-NSSAI of the MBS session, so The DNN of the PDU session is the same as the DNN of the MBS session; the MBS session identifier acquisition unit 11032 can be used to acquire the MBS session identifier of the MBS session; the quality of service flow information acquisition unit 11033 can be used to obtain the MBS session The identifier obtains the QoS flow information corresponding to the activated MBS session from the MB-SMF, wherein the QoS flow information corresponding to the activated MBS session includes one or more QoS flow information; the QoS flow establishment
  • the unit 11034 can be configured to, according to the quality of service flow information corresponding to the activated MBS session, establish a quality of service flow corresponding to the activated MBS session on the PDU session, wherein the quality of service flow
  • the user equipment has activated the MBS session at the source base station before handover, and has not yet established a PDU session associated with the MBS session.
  • the PDU session acquisition unit 11031 may be configured to: after the user equipment is handed over from the source base station to the target base station, execute a process of establishing the PDU session on the target base station side triggered by the user equipment.
  • the MBS session identifier acquisition unit 11032 may be configured to: in the process of establishing the PDU session on the target base station side, receive a PDU session establishment session management context request message from the AMF, where the PDU session establishment session management context request message is included in the PDU session establishment session management context request message. Including the MBS session identifier.
  • the PDU session establishment session management context request message further includes the S-NSSAI, the DNN, a request type, and an N1 session management container, wherein the request type indicates an existing MBS session, so
  • the N1 session management container carries a PDU session establishment request.
  • the quality of service flow information obtaining unit 11033 may be configured to: in the process of establishing the PDU session on the side of the target base station, send a first MBS session creation request message to the MB-SMF, the The first MBS session creation request message carries the MBS session identifier; receiving a first MBS session creation response message returned by the MB-SMF in response to the first MBS session creation request message, the first MBS session creation response message Include QoS flow information corresponding to the activated MBS session.
  • the quality of service flow establishment unit 11034 may be configured to: in the establishment process of the PDU session, send a first communication N1N2 message transmission message to the AMF, so that the AMF The quality of service flow information corresponding to the MBS session, and the quality of service flow corresponding to the MBS session is established on the DPU session.
  • the user equipment has not activated the MBS session at the source base station before handover, and has not established a PDU session associated with the MBS session.
  • the program may further include: a second MBS session creation request message sending unit, which may be configured to, before acquiring the quality of service flow information corresponding to the activated MBS session from the MBS session identifier according to the MBS session identifier, before switching
  • the target base station side sends a second MBS session creation request message to the MB-SMF, where the second MBS session creation request message carries the MBS session identifier; the second MBS session creation request message carries the MBS session identifier;
  • a session creation response message receiving unit which can be configured to receive a second MBS session creation response message returned by the MB-SMF in response to the second MBS session creation request message;
  • the second MBS session creation response message does not carry the quality of service flow information corresponding to the MBS session, and it is determined that the
  • the quality of service flow information acquisition unit 11033 may be configured to: after the MBS session is activated, execute the modification process of the PDU session triggered by the MB-SMF; During the process, an MBS session update request message sent by the MB-SMF is received, and the MBS session update request message carries the quality of service flow information corresponding to the activated MBS session; and a response is returned to the MB-SMF. MBS session update response message of MBS session update request message.
  • the quality of service flow establishing unit 11034 may be configured to: in the modification process of the PDU session, send a second communication N1N2 message transmission message to the AMF, so that the AMF The quality of service flow information corresponding to the MBS session, and the quality of service flow corresponding to the MBS session is established on the DPU session.
  • the program may further include: a UE-UDM determination unit, which may be configured to, before acquiring the quality of service flow information corresponding to the activated MBS session from the MB-SMF according to the MBS session identification, in During the establishment of the PDU session, the UE-UDM is determined according to the SUPI of the user equipment; the MBS session management subscription data acquisition unit can be used to acquire the MBS session of the MBS session from the UE-UDM according to the SUPI Manage subscription data; a subscribed judging unit may be configured to manage subscription data according to the MBS session, and determine that the S-NSSAI and the DNN have subscribed in the UE-UDM.
  • a UE-UDM determination unit which may be configured to, before acquiring the quality of service flow information corresponding to the activated MBS session from the MB-SMF according to the MBS session identification, in During the establishment of the PDU session, the UE-UDM is determined according to the SUPI of the user equipment; the MBS session management subscription data
  • the program may further include: a first NF discovery request message sending unit, which may be configured to determine that the S-NSSAI and the DNN have After the UDM is signed, the first NF discovery request message is sent to the NRF, and the first NF discovery request message carries the MBS session identifier and the network type indicated as MBS UDM; the first NF discovery request response message receiving unit can be used for Receive the first NF discovery request response message returned by the NRF in response to the first NF discovery request message, where the first NF discovery request response message carries the MB-UDM identifier; the MBS session context acquisition request message sending unit can use sending an MBS session context acquisition request message to the MB-UDM according to the MB-UDM identifier, where the MBS session context acquisition request message carries the MBS session identifier; the MBS session context acquisition response message receiving unit can be used to receive all The MBS session context acquisition response message returned by the MB-UDM in response to the MBS session context acquisition request message, where the
  • the program may further include: a second NF discovery request message sending unit, which may be configured to determine, according to the MBS session management subscription data, that the S-NSSAI and the DNN are already in the UE-UDM After signing the contract, send a second NF discovery request message to the NRF, where the second NF discovery request message carries the MBS session identifier and the network type indicated as MBS SMF; the second NF discovery request response message receiving unit can be used to receive A second NF discovery request response message returned by the NRF in response to the second NF discovery request message, where the second NF discovery request response message carries the MB-SMF identifier of the MB-SMF corresponding to the MBS session identifier .
  • a second NF discovery request message sending unit which may be configured to determine, according to the MBS session management subscription data, that the S-NSSAI and the DNN are already in the UE-UDM After signing the contract, send a second NF discovery request message to the NRF, where the second NF discovery request
  • FIG. 12 schematically shows a block diagram of a multicast broadcast session management function device according to an embodiment of the present disclosure.
  • FIG. 12 schematically shows a block diagram of a multicast broadcast session management function device according to an embodiment of the present disclosure.
  • the multicast broadcast session management function device 1200 provided by this embodiment of the present disclosure may include: one or more processors 1201 ; and a memory 1203 configured to store one or more programs, when the one or more When the program is executed by the one or more processors 1201, the one or more processors 1201 implement the method described in any of the above embodiments.
  • FIG. 12 schematically shows a block diagram of a multicast broadcast session management function device according to an embodiment of the present disclosure.
  • FIG. 12 schematically shows a block diagram of a multicast broadcast session management function device according to an embodiment of the present disclosure.
  • the multicast broadcast session management function device 1200 provided by this embodiment of the present disclosure may include: one or more processors 1201 ; and a memory 1203 configured to store one or more programs, when
  • the source base station accessed by the user equipment before handover supports MBS
  • the user equipment has established an MBS session at the source base station before the handover
  • the target base station accessed by the user equipment after the handover does not support MBS
  • the core network accessed by the target base station supports MBS.
  • the program may be specifically configured to: after the user equipment is handed over from the source base station to the target base station, transmit to the SMF the quality of service flow information corresponding to the activated MBS session, wherein the information corresponding to the activated MBS session is
  • the quality of service flow information corresponding to the MBS session includes one or more quality of service flow information, so that the SMF, according to the quality of service flow information corresponding to the activated MBS session, on the PDU session associated with the MBS session A quality of service flow corresponding to the activated MBS session is established, wherein the quality of service flow corresponding to the activated MBS session includes one or more quality of service flows.
  • the S-NSSAI of the PDU session is the same as the S-NSSAI of the MBS session
  • the DNN of the PDU session is the same as the DNN of the MBS session.
  • the program may further include: a quality of service flow information transmission unit 12031, which may be configured to transmit to the SMF after the user equipment is handed over from the source base station to the target base station, corresponding to the activated MBS session
  • the quality of service flow information wherein the quality of service flow information includes one or more, so that the SMF establishes a connection with the PDU session associated with the MBS session according to the quality of service flow information corresponding to the activated MBS session.
  • the quality of service flow corresponding to the activated MBS session wherein the quality of service flow corresponding to the activated MBS session includes one or more quality of service flows.
  • the user equipment has activated the MBS session at the source base station before handover, and has not yet established a PDU session associated with the MBS session.
  • the quality of service flow information transmission unit 12031 may be configured to: after the user equipment is handed over from the source base station to the target base station, execute the user equipment-triggered process of establishing the PDU session on the target base station side The process: in the process of establishing the PDU session on the target base station side, receiving a first MBS session creation request message sent by the SMF, where the first MBS session creation request message carries the MBS session identifier of the MBS session; sending a first MBS session creation response message generated in response to the first MBS session creation request message to the SMF, where the first MBS session creation response message includes a quality of service flow corresponding to the activated MBS session information.
  • the user equipment has not activated the MBS session at the source base station before handover, and has not established a PDU session associated with the MBS session.
  • the program may further include: a PDU session establishment execution process, which may be used to transmit the QoS flow information corresponding to the activated MBS session to the SMF, before the user equipment is handed over from the source base station to the target After the base station, execute the process of establishing the PDU session on the target base station side triggered by the user equipment;
  • the second MBS session creation request message receiving unit can be used for the process of establishing the PDU session on the target base station side , receiving a second MBS session creation request message sent by the SMF, where the second MBS session creation request message carries the MBS session identifier;
  • the second MBS session creation response message sending unit can be used to send the SMF to the SMF A second MBS session creation response message generated in response to the second MBS session creation request message, the second MBS session creation response message does not carry the QoS flow information
  • the quality of service flow information transmission unit 12031 may be configured to: when the MBS session is activated, trigger the modification process of the PDU session; during the modification process of the PDU session, send a message to the SMF Sending an MBS session update request message, where the MBS session update request message carries quality of service flow information corresponding to the activated MBS session; and receiving an MBS session update response message returned by the SMF in response to the MBS session update request message .
  • the program may further include: a third NF discovery request message sending unit, which may be configured to send a third NF discovery request message to the NRF before the user equipment triggers the establishment process of the PDU session, where
  • the third NF discovery request message carries the MBS session identifier and the network type indicated as MBS UDM;
  • the third NF discovery request response message receiving unit can be configured to receive the NRF in response to the third NF discovery request message and return The third NF discovery request response message, the third NF discovery request response message carries the MB-UDM identifier;
  • the MBS session context registration request message sending unit can be used to send the MBS to the MB-UDM according to the MB-UDM identifier
  • a session context registration request message where the MBS session context registration request message carries the MBS session ID and the MB-SMF ID of the MB-SMF corresponding to the MBS session ID, so that the MBS session ID and the MBS - The SMF identifier is associated and stored in the MB
  • the program may further include: an NF management NF registration request message sending unit, which may be configured to send an NF management NF registration request message to the NRF before the user equipment triggers the establishment process of the PDU session, so that The NF management NF registration request message carries the MBS session ID and the MB-SMF ID of the MB-SMF corresponding to the MBS session ID, so that the MBS session ID and the MB-SMF ID are associated and stored in the The NRF; the NF management NF registration response message receiving unit can be configured to receive the NF management NF registration response message returned by the NRF in response to the NF management NF registration request message, and the NF management NF registration response message carries the MB - MB-SMF logo for SMF.
  • an NF management NF registration request message sending unit which may be configured to send an NF management NF registration request message to the NRF before the user equipment triggers the establishment process of the PDU session, so that The NF management NF registration request message carries the MBS session ID
  • FIG. 11 and FIG. 12 there are shown schematic structural diagrams of the session management function device 1100 and the multicast broadcast session management function device 1200 suitable for implementing the embodiment of the present application.
  • the structures shown in FIG. 11 and FIG. 12 are only an example, and should not impose any limitations on the functions and scope of use of the embodiments of the present application.
  • the session management function device 1100 and the multicast broadcast session management function device 1200 provided by the embodiments of the present disclosure may further include: communication interfaces (1102, 1202) and communication buses (1104, 1204).
  • the processor (1101, 1201), the communication interface (1102, 1202) and the memory (1103, 1203) complete the communication with each other through the communication bus (1104, 1204).
  • the communication interface (1102, 1202) may be an interface of a communication module, such as an interface of a GSM (Global System for Mobile communications, global system for mobile communications) module.
  • a GSM Global System for Mobile communications, global system for mobile communications
  • Processors (1101, 1201) are used to execute programs.
  • the memories (1103, 1203) are used to store programs.
  • a program may include a computer program including computer operating instructions.
  • the processor (1101, 1201) may be a central processing unit (CPU), or a specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present disclosure.
  • CPU central processing unit
  • ASIC Application Specific Integrated Circuit
  • the memories (1103, 1203) may include high-speed RAM (random access memory, random access memory) memory, and may also include non-volatile memory (non-volatile memory), such as at least one disk memory.
  • a computer-readable storage medium storing a computer program, when the computer program is executed by a processor, implements the method described in any of the above embodiments.
  • embodiments of the present disclosure include a computer program product comprising a computer program carried on a computer-readable storage medium, the computer program containing program code for performing the method illustrated in the flowchart.
  • the computer-readable storage medium shown in the present disclosure may be a computer-readable signal medium or a computer-readable storage medium, or any combination of the above two.
  • the present application also provides a computer-readable storage medium.
  • the computer-readable storage medium may be included in the electronic device described in the above embodiments; in electronic equipment.
  • the above-mentioned computer-readable storage medium carries one or more programs, and when the above-mentioned one or more programs are executed by an electronic device, the electronic device enables the electronic device to implement the methods described in the following embodiments.

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Abstract

本公开实施例提供了一种用于实现多播广播业务切换的方法及相关设备。该方法应用于用户设备对应的SMF，用户设备在切换前接入的源基站支持MBS，用户设备在切换前已在源基站建立MBS会话，用户设备切换后接入的目标基站不支持MBS，目标基站接入的核心网支持MBS，该方法包括：获取与MBS会话关联的PDU会话，PDU会话的S-NSSAI和MBS会话的S-NSSAI相同，PDU会话的DNN与MBS会话的DNN相同；获取MBS会话的MBS会话标识；根据MBS会话标识从MB-SMF获取与已激活的MBS会话对应的服务质量流信息；根据已激活的MBS会话对应的服务质量流信息，在PDU会话上建立与已激活的MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。

Description

用于实现多播广播业务切换的方法及相关设备
本申请要求于2021年2月10日提交中国专利局、申请号为202110184912.9、申请名称为“用于实现多播广播业务切换的方法及相关设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本公开涉及通信技术领域，具体而言，涉及一种用于实现多播广播业务切换的方法、会话管理功能设备、多播广播会话管理功能设备、计算机可读存储介质和计算机程序产品。
背景技术
单播(Unicast)是一对一的通信，单播源(Unicast Source)将多份不同的内容经由路由器传输给不同的用户设备(User Equipment，UE)，例如图1中假设将五份不同的内容分别传输给UE 1、UE 2、UE 3、UE 4、UE 5。单播通信的优点是可以给不同的用户传输不同的内容。
“多播(Multicast)”也可以称为“组播”，是将相同的内容传输给被授权的多个用户设备，例如图1中的多播源(Multicast Source)将同一份内容同时传输给被授权的UE 6、UE 7和UE 8。网上视频会议、网上视频点播等应用场景特别适合采用多播方式。采用多播方式，既可以实现一次向所有目标节点传送数据，也可以达到只对特定对象(被授权的UEs)传送数据的目的。
广播(Broadcast)也是将相同的内容传输给多个用户设备。但是它没有进行用户设备的选择。
在5G(5th generation mobile networks或5th generation wireless systems、5th-Generation，第五代移动通信技术)MBS(multi-cast broadcast service，多播广播业务)中存在的一个问题，就是在一个5G网络中，可能只有部分基站支持MBS，另一部分基站可能不支持MBS业务(例如MBS多播业务和/或MBS广播业务)，当UE从一个支持MBS业务的5G的基站(下文称之为源基站，或者源RAN(Radio Access Network，无线接入网))或小区移动到一个不支持MBS业务的5G的基站(下文称之为目标基站，或者目标RAN)或小区时，若UE事先已经加入MBS业务，则UE需要切换到单播的传输方式，然后在激活了MBS业务传输之后，通过该单播的传输方式来继续传输MBS业务对应的数据，从而实现MBS业务的连续性。
发明内容
本公开实施例提供一种用于实现多播广播业务切换的方法、会话管理功能设备、多播广播会话管理功能设备、计算机可读存储介质和计算机程序产品，能够在用户设备从支持MBS业务的源基站切换至不支持MBS业务的目标基站的过程中，实现MBS业务的连续性。
本公开实施例提供一种用于实现多播广播业务切换的方法，应用于用户设备对应的SMF，所述用户设备在切换前接入的源基站支持MBS，所述用户设备在切换前已在所述源基站建立MBS会话(MBS Session，a multicast session or a broadcast session的简写，即一个多播或广播会话，也可以称之为多播广播业务会话)，所述用户设备切换后接入的目标基站不支持MBS，且所述目标基站接入的核心网支持MBS。其中，所述方法包括：获取与所述MBS会话关联的PDU(Protocol Data Unit，协议数据单元)会话，其中所述PDU会话的S-NSSAI(Single Network Slice Selection Assistance Information，单网络分片选择辅助信息)和所述MBS会话的S-NSSAI相同，所述PDU会话的DNN(Data Network Name，数据网络名称)与所述MBS会话的DNN相同；获取所述MBS会话的MBS会话标识；根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息(例如可以是与该已激活的MBS会话对应的所有服务质量流信息)，其中与已激活的所述MBS会话对应的服务质量流信息包括一个或多个服务质量流信息；根据与已激活的所述MBS会话对应的服务质量流信息，在所述PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。
本公开实施例提供一种会话管理功能设备，包括：一个或多个处理器；存储装置，配置为存储一个或多个程序，当所述一个或多个程序被所述一个或多个处理器执行时，使得所述一个或多个处理器实现如上述实施例所述的方法。
本公开实施例提供一种用于实现多播广播业务切换的方法，应用于用户设备对应的MB-SMF，所述用户设备在切换前接入的源基站支持MBS，所述用户设备在切换前已在所述源基站建立MBS会话，所述用户设备切换后接入的目标基站不支持MBS，且所述目标基站接入的核心网支持MBS。其中，所述方法包括：在所述用户设备从所述源基站切换至所述目标基站之后，向SMF传输与已激活的所述MBS会话对应的服务质量流信息(例如，可以是与该已激活的MBS会话对应的所有服务质量流信息)，其中与该已激活的MBS会话对应的服务质量流信息包括一个或多个服务质量流信息，以便所述SMF根据与已激活的所述MBS会话对应的服务质量流信息，在与所述MBS会话关联的PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。其中所述PDU会话的S-NSSAI和所述MBS会话的S-NSSAI相同，所述PDU会话的DNN与所述MBS会话的DNN相同。
本公开实施例提供一种多播广播会话管理功能设备，包括：一个或多个处理器；存储装置，配置为存储一个或多个程序，当所述一个或多个程序被所述一个或多个处理器执行时，使得所述一个或多个处理器实现如上述实施例所述的方法。
本公开实施例提供一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，所述计算机程序被处理器执行时实现如上述实施例所述的方法。
本公开实施例提供一种计算机程序产品或计算机程序，该计算机程序产品或计算机程序包括计算机指令，该计算机指令存储在计算机可读存储介质中。计算机设备的处理器从计算机可读存储介质读取该计算机指令，处理器执行该计算机指令，使得该计算机设备执行上述各种实施例提供的方法。
在本公开实施例所提供的技术方案中，一方面，当UE从支持MBS业务的源基站切换至不支持MBS业务的目标基站后，若该目标基站接入的核心网例如5G核心网支持MBS业务，则SMF可以直接通过与该MBS会话对应的MB-SMF，获取与已激活的该MBS会话对应的QoS Flow(Quality of Service Flow，服务质量流)信息(例如，可以是与该激活的MBS会话对应的所有QoS Flow信息)，从而简化了SMF获取与已激活的该MBS会话的QoS Flow信息的过程。另一方面，这种方式对5G系统的修改较小，实现了UE在支持MBS业务的源基站与不支持MBS业务的目标基站之间切换时，将MBS会话切换到单播的PDU会话，实现了MBS业务的连续性。
附图说明
图1示出了相关技术中一种单播与多播的IP传输的比较示意图。
图2示出了相关技术中一种5G MBS的参考架构图。
图3示意性示出了根据本公开的一实施例的用于实现多播广播业务切换的方法的流程图。
图4示意性示出了根据本公开的一实施例的没有UPF重新分配的基于Xn接口的NG-RAN之间的切换的示意图。
图5示意性示出了根据本公开的一实施例的通过N2节点实现NG-RAN切换的执行阶段的示意图。
图6示意性示出了根据本公开的一实施例的触发在目标NG-RAN侧建立PDU会话的过程示意图。
图7示意性示出了根据本公开的另一实施例的触发在目标NG-RAN侧建立PDU会话的过程示意图。
图8示意性示出了根据本公开的一实施例的PDU会话修改过程的示意图。
图9示意性示出了根据本公开的一实施例的SMF发现MB-SMF的过程示意图。
图10示意性示出了根据本公开的另一实施例的SMF发现MB-SMF的过程示意图。
图11示意性示出了根据本公开的一实施例的会话管理功能设备的框图。
图12示意性示出了根据本公开的一实施例的多播广播会话管理功能设备的框图。
具体实施方式
5G MBS的架构如图2所示。如图2所示，UPF(User Plane Function，用户面功能)通过N4接口与SMF(Session Management Function，会话管理功能)交互，并通过MB-N9(Multicast Broadcast- N9，多播广播N9)接口从MB-UPF(Multicast Broadcast-UPF，多播广播用户面功能)接收MBS业务数据，还可以通过N3接口向NG-RAN(5G无线接入网，图2中的RAN节点)发送MBS业务数据。其中UPF和MB-UPF在逻辑上可以是独立的，但也可以合用同一个UPF实体。SMF可以为MBS会话选择MB-SMF(Multicast Broadcast SMF，多播广播会话管理功能)，并可以与MB-SMF交互以获得MBS会话相关的信息。SMF和MB-SMF在逻辑上是独立的，但也可以合用同一个实体。UDR(Unified Data Repository，统一数据存储)或NRF(NF(Network Function，网络功能)Repository Function，网络存储功能)支持为MBS Session发现MB-SMF，并存储所选择的MB-SMF的ID(identity，标识，即MB-SMF ID)。
其中，MBSF(Multicast Broadcast Service Function，多播广播业务功能)可以包括MBSF-U(MBSF User Plane Function，MBSF用户面功能)和MBSF-C(MBSF Control Plane Function，MBSF控制面功能)。其中MBSF-C/U不是必需的，然而在下面的两个条件下，它们是必需的：第一个条件，当5G MBS与4G或3G的MBMS(Multimedia Broadcast/Multicast Service，多媒体广播/多播业务)的业务是互联互通时，即5G的AF(Application Function，应用功能)与4G或3G的MBMS AS(Application Server，应用服务器)是同一个实体时，见图2。或，第二个条件，当运营商需要对MBS的业务进行媒体的处理时(如对视频进行转码或内容的检查等处理)。
注意，SMF和UPF可以参与到5G MBS Session的过程中，下面的实施例中有相关的说明。
其中，图2中的NEF的英文全称是Network Exposure Function，即网络开放功能。PCF的英文全称是Policy Control Function，即策略控制功能，Npcf是指获取PCF提供的服务的Npcf消息。AMF的英文全称是Access and Mobility Management Function，即接入移动管理功能。
图3示意性示出了根据本公开的一实施例的用于实现多播广播业务切换的方法的流程图。图3实施例提供的方法可以应用于用户设备UE对应的SMF，所述用户设备在切换前接入的源基站支持MBS，所述用户设备在切换前已在所述源基站建立MBS会话，所述用户设备切换后接入的目标基站不支持MBS，且所述目标基站接入的核心网(在下面的实施例中，均以5G核心网为例进行举例说明，但本公开并不限定于此)支持MBS。
本公开实施例中，该UE在切换前接入的基站称之为源基站，该UE在切换后接入的基站称之为目标基站，在下面的举例说明中，以源基站和目标基站均为5G系统中的NG-RAN，分别称之为源NG-RAN(或者S-NG-RAN)和目标NG-RAN(或者T-NG-RAN)为例进行举例说明，但本公开并不限定于此。
本公开实施例中的MBS Session可以包括MBS Multicast Session和/或MBS Broadcast Session，即MBS多播会话和/或MBS广播会话。需要说明的是，本公开实施例提供的方案既可以适用于MBS Muliticast Session(MBS多播会话)，也可以适用于MBS Broadcast Session(MBS广播会话)。在下面的举例说明中，若以MBS多播会话为例进行举例说明，则可以扩展至MBS广播会话，进行对应参数和消息的适应性修改。
如图3所示，本公开实施例提供的方法可以包括以下步骤。
在步骤S310中，获取与所述MBS会话关联的PDU会话，其中所述PDU会话的S-NSSAI和所述MBS会话的S-NSSAI相同，所述PDU会话的DNN与所述MBS会话的DNN相同。
本公开实施例中，与MBS会话关联的PDU会话(PDU Session)既可以在源基站侧建立，也可以在目标基站侧建立，本公开对此不做限定。在目标基站侧/源基站侧建立的PDU Session是用于取代源基站上的MBS Session例如MBS Multicast/Broadcast Session的，因此PDU Session的S-NSSAI与DNN组合与原来的MBS Multicast/Broadcast Session的S-NSSAI与DNN组合是一样的，这样可以保持MBS业务的连续性。
本公开实施例中，若所述用户设备在切换前，已在所述源基站建立多个MBS会话，则针对每个MBS会话分别关联对应的PDU会话，每个MBS会话的S-NSSAI与该MBS会话对应的PDU会话的S-NSSAI相同，每个MBS会话的DNN与该MBS会话对应的PDU会话的DNN相同。
在步骤S320中，获取所述MBS会话的MBS会话标识(即MBS Session ID)。
在步骤S330中，根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务 质量流信息，其中与已激活的所述MBS会话对应服务质量流信息包括一个或多个服务质量流信息。
需要说明的是，本公开实施例中，SMF获取的服务质量流信息可以是与该已激活的MBS会话对应的所有服务质量流信息，对应的，在与该MBS会话关联的PDU会话上建立的服务质量流可以是与该已激活的MBS会话对应的所有服务质量流。
本公开实施例中，每个MBS会话可以在切换前激活，也可以在切换后激活，本公开对此不做限定。UE要明确地加入MBS，但还没有开始业务数据传输的动作定义为“注册”、“加入”或“建立”。UE加入MBS后，并启动MBS业务数据的传输的动作定义为“激活”或“业务启动”，即只有QoS Flow建立了的MBS会话才是“激活”；没有建立QoS Flow，没有MB-UPF的MBS会话只是建立。
在步骤S340中，根据与已激活的所述MBS会话对应的服务质量流信息，在所述PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。
在示例性实施例中，所述用户设备可以在切换前已在所述源基站激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话。其中，获取与所述MBS会话关联的PDU会话，可以包括：在所述用户设备从所述源基站切换至所述目标基站后，执行所述用户设备触发的在所述目标基站侧建立所述PDU会话的过程。其中，获取已激活的所述MBS会话的MBS会话标识，可以包括：在所述目标基站侧建立所述PDU会话的过程中，从AMF接收PDU会话建立会话管理上下文请求消息，所述PDU会话建立会话管理上下文请求消息中包括所述MBS会话标识。
在示例性实施例中，所述PDU会话建立会话管理上下文请求消息还可以包括所述S-NSSAI、所述DNN、请求类型和N1会话管理容器。其中所述请求类型指示为已存在MBS会话。所述N1会话管理容器中携带有PDU会话建立请求。
在示例性实施例中，根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息，可以包括：在所述目标基站侧建立所述PDU会话的过程中，向所述MB-SMF发送第一MBS会话创建请求消息，所述第一MBS会话创建请求消息携带所述MBS会话标识；接收所述MB-SMF响应所述第一MBS会话创建请求消息而返回的第一MBS会话创建响应消息，所述第一MBS会话创建响应消息中包括与已激活的所述MBS会话对应的服务质量流信息。
在示例性实施例中，根据与已激活的所述MBS会话对应的服务质量流信息，在所述PDU会话上建立与已激活的所述MBS会话对应的服务质量流，可以包括：在所述PDU会话的建立过程中，向所述AMF发送第一通信N1N2消息传输消息，以使得所述AMF根据与已激活的所述MBS会话对应的服务质量流信息，在所述DPU会话上建立所述MBS会话对应的服务质量流。
当所述用户设备在切换前已在所述源基站激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话时，切换后在目标基站侧建立PDU会话的过程具体可以参见下图6和图7。
在示例性实施例中，所述用户设备可以在切换前在所述源基站尚未激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话。其中，在根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息之前，所述方法还可以包括：在切换后的所述目标基站侧建立所述PDU会话的过程中，向所述MB-SMF发送第二MBS会话创建请求消息，所述第二MBS会话创建请求消息携带所述MBS会话标识；接收所述MB-SMF响应所述第二MBS会话创建请求消息而返回的第二MBS会话创建响应消息；若所述第二MBS会话创建响应消息中未携带所述MBS会话对应的服务质量流信息，则判定所述MBS会话尚未激活。
在示例性实施例中，根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息，可以包括：当所述MBS会话被激活后，执行所述MB-SMF触发的所述PDU会话的修改过程；在所述PDU会话的修改过程中，接收所述MB-SMF发送的MBS会话更新请求消息，所述MBS会话更新请求消息携带与已激活的所述MBS会话对应的服务质量流信息；向所述MB-SMF返回响应所述MBS会话更新请求消息的MBS会话更新响应消息。
在示例性实施例中，根据与已激活的所述MBS会话对应的服务质量流信息，在所述PDU会话上建立与已激活的所述MBS会话对应的服务质量流，可以包括：在所述PDU会话的修改过程中，向所述AMF发送第二通信N1N2消息传输消息，以使得所述AMF根据与已激活的所述MBS会话对应的 服务质量流信息，在所述DPU会话上建立所述MBS会话对应的服务质量流。
当所述用户设备在切换前在所述源基站尚未激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话时，在切换后的目标基站侧建立PDU会话的过程具体参见下图6和图7以及PDU会话修改的过程具体可以参见下图8。
在示例性实施例中，在根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息之前，所述方法还可以包括：在所述PDU会话的建立过程中，根据所述用户设备的SUPI确定UE-UDM；根据所述SUPI从所述UE-UDM获取所述MBS会话的MBS会话管理签约数据；根据所述MBS会话管理签约数据，确定所述S-NSSAI和所述DNN已在所述UE-UDM签约。判断S-NSSAI和DNN是否已签约的具体过程可以参见下图6。
在示例性实施例中，在根据所述MBS会话管理签约数据，确定所述S-NSSAI和所述DNN已在所述UE-UDM签约之后，所述方法还可以包括：向NRF发送第一NF发现请求消息，所述第一NF发现请求消息携带所述MBS会话标识和指示为MBS UDM的网络类型；接收所述NRF响应所述第一NF发现请求消息而返回的第一NF发现请求响应消息，所述第一NF发现请求响应消息携带MB-UDM标识；根据所述MB-UDM标识，向MB-UDM发送MBS会话上下文获取请求消息，所述MBS会话上下文获取请求消息携带所述MBS会话标识；接收所述MB-UDM响应所述MBS会话上下文获取请求消息而返回的MBS会话上下文获取响应消息，所述MBS会话上下文获取响应消息携带所述MBS会话标识对应的所述MB-SMF的MB-SMF标识。SMF发现MB-SMF的过程具体可以参见下图9。
在示例性实施例中，在根据所述MBS会话管理签约数据，确定所述S-NSSAI和所述DNN已在所述UE-UDM签约之后，所述方法还可以包括：向NRF发送第二NF发现请求消息，所述第二NF发现请求消息携带所述MBS会话标识和指示为MBS SMF的网络类型；接收所述NRF响应所述第二NF发现请求消息返回的第二NF发现请求响应消息，所述第二NF发现请求响应消息携带所述MBS会话标识对应的所述MB-SMF的MB-SMF标识。SMF发现MB-SMF的另一过程具体可以参见下图10。
在示例性实施例中，所述用户设备可以在切换前在所述源基站尚未激活所述MBS会话，且已建立与所述MBS会话关联的PDU会话。其中，根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息，可以包括：当所述用户设备从所述源基站切换至所述目标基站，且所述MBS会话在切换后被激活后，触发所述PDU会话的修改过程；在所述PDU会话的修改过程中，根据所述MBS会话标识从所述MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息。当所述用户设备可以在切换前在所述源基站尚未激活所述MBS会话，且已建立与所述MBS会话关联的PDU会话时，实现多播广播业务切换的具体过程可以参见下图10。
本公开实施例提供的用于实现多播广播业务切换的方法，一方面，当UE从支持MBS业务的源基站切换至不支持MBS业务的目标基站后，若该目标基站接入的核心网例如5G核心网支持MBS业务，则SMF可以直接通过与该MBS会话对应的MB-SMF获取已激活的该MBS会话的QoS Flow(Quality of Service Flow，服务质量流)信息，从而简化了SMF获取已激活的该MBS会话的QoS Flow信息的过程。另一方面，这种方式对5G系统修改较小，实现了UE在支持MBS业务的源基站与不支持MBS业务的目标基站之间切换时，将MBS会话切换到单播的PDU会话，实现了MBS业务的连续性。
UE在3GPP(3rd Generation Partnership Project，第三代合作伙伴计划)内部的切换的过程，有多种切换情形，本公开实施例通过图4和图5列出了其中两种情形，但本公开实施例提供的方法并不限于这两种情形，例如还可以适用于“Xn based inter NG-RAN handover with insertion of intermediate UPF(插入中间UPF的基于Xn接口的NG-RAN之间的切换)”和“Xn based inter NG-RAN handover with intermediate UPF re-allocation(中间UPF重新分配的基于Xn接口的NG-RAN之间的切换)”这两种情形。本公开实施例所提供的方法，在注册过程(例如图4的步骤9或者图5的步骤12，甚至如图4所示，也可以不存在注册过程，即注册过程是可选的)前或者后增加PDU会话建立过程。
其中，5G无线接入网主要包括两种节点：gNB和ng-eNB，gNB和gNB之间，gNB和ng-eNB之间，ng-eNB和gNB之间的接口都为Xn接口，Xn接口是指NG-RAN节点之间的网络接口。
本公开实施例中，若UE切换至目标NG-RAN之前，已经在源NG-RAN侧建立但尚未激活MBS  Session，即尚未建立任何的QoS Flow，可以优先让PDU会话建立过程在注册过程之后执行，但本公开并不限定于此，在这种情况下，也可以使得PDU会话建立过程在注册过程之前执行。若UE切换至目标NG-RAN之前，已经在源NG-RAN侧建立且已激活MBS Session，即切换前已建立QoS Flow，可以优先让PDU会话建立过程在注册过程之前执行，但本公开并不限定于此，在这种情况下，也可以将PDU会话建立过程放到注册过程之后执行。
本公开实施例中，若UE切换至目标基站之前，在源基站已建立多个MBS会话，假设其中部分MBS会话在切换前已激活，即已经建立QoS Flow；另一部分MBS会话在切换前尚未激活，即还没有建立QoS Flow，则可以优先将与这部分在切换前已激活的MBS会话对应的PDU会话建立过程放到注册过程之前执行，优先将与另一部分在切换前尚未激活的MBS会话对应的PDU会话建立过程放到注册过程之后执行，这样可以让已经有业务数据的MBS会话优先切换至PDU会话，能够提高业务的响应速度，满足业务切换的及时性，但本公开并不限定于此。多个MBS会话对应的多个PDU会话建立过程的执行之间可以是并行的、独立的，彼此之间没有约束关系的。
图4示意性示出了根据本公开的一实施例的没有UPF重新分配的基于Xn接口的NG-RAN之间的切换(Xn based inter NG-RAN handover without UPF re-allocation)的示意图。
如图4所示，通过切换准备阶段(handover preparation phase)和切换执行阶段(handover execution phase)，UE从源NG-RAN切换至目标NG-RAN，其中，源NG-RAN是支持MBS Multicast/Broadcast Session的，而目标NG-RAN是不支持MBS Multicast/Broadcast Session的。当UE从源NG-RAN切换至目标NG-RAN后，目标NG-RAN会向UE发送切换完成指示，UE接收到该切换完成指示之后，即可获知其已经成功地接入目标NG-RAN，此后，UE即可触发如图6和图7所示的PDU会话建立过程。
本公开实施例中，所述切换完成指示可以以任意的形式，例如目标基站给UE发送相关的物理层，媒体接入控制(Media Access Control，MAC)层，无线链路控制(Radio Link Control，RLC)层的指示或无线资源控制(Radio Resource Control，RRC)层的消息，本公开对切换完成指示的形式不做限定，只要能够告知该UE已经成功地接入目标基站即可。
图4实施例中的步骤9和图5实施例中的步骤12的注册过程，是指UE在接收目标基站发送的切换完成指示之后，若UE改变至新的跟踪区域(Tracking Area)，则执行将所述用户设备注册至网络的注册过程(Registration Procedure)。其中，UE可以在所述注册过程之前或者所述注册过程之后触发在所述目标基站侧建立所述PDU会话。
具体地，当由于UE的移动导致其进入到一个新的TA，且该新的TA超出了该UE当前的服务区域(Registration Areas)(由一个或多个TA组成)时，需要执行类型为Mobility Registration Update(移动性注册更新)的Registration Procedure，以使得该UE在新的TA再次注册至网络例如5GS(5G system，5G系统)。
在示例性实施例中，若所述用户设备是在空闲状态(Connection Management-IDLE,CM-IDLE)从所述源基站移动至所述目标基站，则UE在触发在所述目标基站侧建立所述PDU会话之前，UE还可以触发服务请求(Service Request)过程以使所述用户设备进入连接状态(Connection Management-CONNECTED,CM-CONNECTED)。
例如，若UE是在CM-IDLE状态下，从一个支持MBS Multicast/Broadcast Session的源基站移动到另一个不支持MBS Multicast/Broadcast Session的目标基站，则UE可以通过Service Request进入CM-CONNECTED状态，然后，再执行PDU Session Establishment过程。
在示例性实施例中，若所述用户设备是在空闲状态从所述源基站移动至所述目标基站，且所述用户设备的当前跟踪区域标识(Tracking Area Identity，TAI)不在注册的跟踪区域标识列表(TAI List)中，则UE在触发在所述目标基站侧建立PDU会话之前，还可以执行注册类型为移动性注册更新的注册过程，以使所述用户设备进入连接状态。
例如，若UE是在CM-IDLE状态下，从一个支持MBS Multicast/Broadcast Session的源基站移动到另一个不支持MBS Multicast/Broadcast Session的目标基站，且UE同时发现当前TAI不在注册的TAI List中，则UE先执行注册类型为Mobility Registration Update(移动性注册更新)的注册过程，在 信令连接未被释放的情形下，然后，再执行PDU会话建立(PDU会Session Establishment)过程。
由于UE触发的图6和图7所示的PDU会话建立过程独立于图4中网络侧的通信过程，因此，UE可以在图4的步骤1a和步骤8之间的任意时刻触发PDU会话建立过程，即可以在图4中的步骤9之前触发图5所示的PDU会话建立过程，也可以在图4中的步骤9之后触发图5所示的PDU会话建立过程，此外，图4中的步骤9是可选的。
下面对图4中的步骤进行简单说明。
图4中的步骤1a是可选的，如果PLMN(Public Land Mobile Network，公共陆地移动网)已配置辅助(secondary)RAT(Radio Access Technology，无线接入技术)使用情况报告，在切换执行阶段源NG-RAN节点可以提供RAN使用数据报告至AMF，即RAN usage data Report(N2 SM Information(Secondary RAT usage data),Handover Flag,Source to Target transparent container)。Handover Flag(切换标识)指示AMF应当在转发之前缓冲N2会话管理信息(N2 Session Management Information，N2 SM Information)，其中，N2 SM信息包括使用数据报告。Source to Target transparent container是指源至目标透明容器。
图4中的步骤1b是可选的，目标NG-RAN向AMF发送N2路径切换请求，即N2 Path Switch Request，以用于通知UE已经移动(moved)至一个新的目标小区，并提供了一个PDU Sessions列表用于切换。
图4中的步骤2，AMF向SMF发送Nsmf_PDUSession_UpdateSMContext请求，即PDU会话更新会话管理上下文请求。
图4中的步骤3，SMF向UPF发送N4会话修改请求，即N4 Session Modification Request。
图4中的步骤4，UPF向SMF发送N4 Session Modification响应(Response)，即N4会话修改响应。
图4中的步骤5，为了辅助目标NG-RAN中的重新订购功能(reordering function)，UPF针对每个N3隧道(tunnel)发送一个或多个“结束标识(end marker)包(packets)。UPF开始发送下行数据至目标NG-RAN。
图4中的步骤6，SMF向AMF发送Nsmf_PDUSession_UpdateSMContext响应，即PDU会话更新会话管理上下文响应。
图4中的步骤7，AMF向目标NG-RAN发送N2 Path Switch Request Ack(即N2路径切换请求确认)。
图4中的步骤8，通过向源NG-RAN发送一个释放资源消息，目标NG-RAN确认切换成功。目标NG-RAN然后触发源NG-RAN的资源释放。
图4中的步骤9的注册过程(Registration procedure)是可选的。
图5示意性示出了根据本公开的一实施例的通过N2节点实现NG-RAN切换的执行阶段(inter NG-RAN node N2 based handover,execution phase)的示意图。在图5之前，还可以包括Inter NG-RAN node N2 based handover,Preparation phase(即通过N2节点实现NG-RAN切换的准备阶段)。
图5中的S-NG-RAN是指支持MBS的源NG-RAN，也可以表示为S-RAN，对应S-AMF和S-UPF。T-NG-RAN是指不支持MBS的目标NG-RAN，也可以表示为T-RAN，对应T-AMF(目标AMF)和T-UPF(目标UPF)。UPF(PSA)中的PSA是PDU Session Anchor，即PDU会话锚点。
图5中的步骤1，S-AMF向S-RAN发送切换指令(Handover Command)。
图5中的步骤2，S-RAN向UE发送Handover Command
图5中的步骤2a是可选的，S-RAN向S-AMF发送上行RAN状态传输(Uplink RAN Status Transfer)消息。
图5中的步骤2b是可选的，S-AMF向T-AMF发送Namf_Communication_N1N2MessageTransfer服务操作，T-AMF确认。
图5中的步骤2c是可选的，S-AMF或者，如果AMF重新设置(relocation)，则T-AMF向T-RAN发送下行RAN状态传输消息(Downlink RAN Status Transfer message)。
图5中上行包(Uplink packets)从T-RAN至T-UPF和UPF(PSA)。下行包(Downlink packets)通过S-UPF从UPF(PSA)发送S-RAN。S-RAN应当开始转发下行数据(downlink data)至T-RAN。这可以通过直接数据转发(direct data forwarding，图5中的步骤3a)或者间接数据转发(indirect data forwarding，图5中的步骤3b)。图5中的步骤3a和3b是可选的。UE同步至新小区(new cell，即目标基站对应的目标小区)。
图5中的步骤4，UE向T-RAN发送切换确认(Handover Confirm)消息，即UE指示给网络，该UE已经切换到目标RAN了。在UE已经成功地同步至目标小区(target cell)之后，UE向T-RAN发送Handover Confirm message。根据该切换确认消息认为该UE已经成功切换。在UE已经同步至新小区或者UE已经确认切换成功之后，UE可以随时触发如上图5实施例所述的PDU会话建立过程，以用于在目标基站侧建立PDU会话。
图5中的步骤5，T-RAN向T-AMF发送Handover Notify(切换通知)。
图5中的步骤6a是可选的，T-AMF向S-AMF发送Namf_Communication_N2InfoNotify。
图5中的步骤6b是可选的，S-AMF向T-AMF发送Namf_Communication_N2InfoNotify ACK(确认)。
图5中的步骤6c是可选的，S-AMF向SMF发送Nsmf_PDUSession_ReleaseSMContext Request(请求)。
图5中的步骤7，T-AMF向SMF发送Nsmf_PDUSession_UpdateSMContext Request。
图5中的步骤8a是可选的，SMF向T-UPF发送N4 Session Modification Request(N4会话修改请求)。
图5中的步骤8b是可选的，T-UPF向SMF发送N4 Session Modification Response(响应)。
图5中的步骤9a是可选的，SMF向S-UPF发送N4 Session Modification Request。
图5中的步骤9b是可选的，S-UPF向SMF发送N4 Session Modification Response。
图5中的步骤10a是可选的，SMF向UPF(PSA)发送N4 Session Modification Request。
图5中的步骤10b是可选的，UPF(PSA)向SMF发送N4 Session Modification Response。
图5中的步骤11，SMF向T-AMF发送Nsmf_PDUSession_UpdateSMContext Response。
图5中的步骤12，UE触发Registration procedure。
需要说明的是，UE可以在图5步骤12的注册过程之前或者步骤12的注册过程之后触发如下图6和图7所述的PDU会话建立过程。
图5中的步骤13a是可选的，SMF向S-UPF发送N4 Session Release Request(N4会话释放请求)。
图5中的步骤13b是可选的，S-UPF向SMF发送N4 Session Release Response(N4会话释放响应)。
图5中的步骤14a，AMF向S-RAN发送UE Context Release Command()，即UE上下文释放指令。
图5中的步骤14b，S-RAN向AMF发送UE Context Release Command Complete()，即UE上下文释放指令完成。
图5中的步骤15a是可选的，SMF向T-UPF发送N4 Session Modification Request。
图5中的步骤15b是可选的，T-UPF向SMF发送N4 Session Modification Response。
本公开实施例中，若未在源基站侧建立与MBS会话关联的PDU会话，则UE确定所述目标基站不支持MBS后，触发在所述目标基站侧建立PDU会话。其中，UE确定所述目标基站不支持MBS，可以包括：UE接收所述目标基站广播的系统消息块，以及根据所述系统消息块确定所述目标基站不支持MBS；或者，获取MBS的目标服务区域，以及根据所述目标服务区域确定所述目标基站不支持MBS。
具体地，当UE从支持MBS的源基站切换至不支持MBS的目标基站后，UE可以通过目标基站对应的目标小区系统广播的SIB(system information block，系统消息块)消息，获知目标小区是不支持MBS Multicast/Broadcast Session的。例如，目标基站广播的SIB消息可以指示：完全不支持MBS，哪 个S-NSSAI不支持，或哪个DNN不支持，或哪个S-NSSAI与DNN组合不支持MBS Session，则UE可以根据广播的SIB消息的指示信息确定在目标基站建立相应的一个或多个PDU Session。或者，可以通过其它方式获得，例如根据MBS Multicast/Broadcast Session的目标服务区域来判断目标基站是否支持MBS Multicast/Broadcast Session。本公开对UE如何确定目标基站是否支持MBS的方式不作限定。
需要说明的是，若同时建立了多个MBS Multicast/Broadcast Session时，每个MBS Multicast/Broadcast Session对应于一个S-NSSAI与DNN组合，则UE根据广播的SIB消息中的指示信息可以确定在目标NG-RAN侧建立相应的PDU Session。这些多个MBS Multicast/Broadcast Session可以并行地切换至各自对应的PDU Session，也可以按照有无业务(即MBS Session是否已经激活，有无MBS Session的QoS Flow)来决定切换的先后顺序。
例如，若UE有5个MBS Multicast/Broadcast Session，则由于目标NG-RAN不支持MBS Multicast/Broadcast Session，则这5个MBS Multicast/Broadcast Session可以同时切换至各自对应的PDU Session，每个MBS Multicast/Broadcast Session的切换过程可以是独立进行的，例如可以是并行的，彼此之间没有先后关系，或者5个MBS Multicast/Broadcast Session中部分例如3个有业务的先切换，另一部分例如2个无业务的后切换，这样可以保证有业务的MBS Multicast/Broadcast Session实时切换，保持业务的连续性。
在其他实施例中，若UE确定该切换后的目标基站也支持MBS，则可以直接将源基站已激活的MBS会话切换至该目标基站的MBS会话，即可实现业务的连续性。
图6和图7的实施例中，假设该UE在切换前接入的源基站支持MBS，该UE在切换至目标基站之前，已经在该源基站建立MBS会话，且该MBS会话在切换前已激活，同时该UE在切换前尚未建立与该MBS会话关联的PDU会话。此外，切换后的目标基站虽然不支持MBS，但该目标基站接入的5G核心网却是支持MBS的。图6和图7示意性示出了根据本公开的一实施例的触发在目标NG-RAN侧建立PDU会话的过程示意图。
图6中的步骤1，UE向AMF发送非接入层消息(Non-Access Stratum Message，简写为NAS Message)，NAS Message可携带请求类型(Request Type)，其中所述请求类型指示为已存在MBS会话(Existing MBS Session)，以便AMF根据Request Type的取值，为新建PDU会话选择SMF。
在示例性实施例中，NAS Message还可以携带所述S-NSSAI、所述DNN和所述MBS会话的MBS会话标识，以便所述SMF根据所述S-NSSAI、所述DNN和所述MBS会话标识建立所述PDU会话。
在示例性实施例中，NAS Message还可以携带所述PDU会话的PDU会话标识(PDU Session ID)和N1会话管理(Session Management，SM)容器(Container)，所述N1会话管理容器中携带PDU会话建立请求(PDU Session Establishment Request)。
例如，在UE切换至不支持MBS的目标基站，且确定目标基站不支持MBS之后，UE可以发起PDU Session Establishment过程，以在目标基站侧建立PDU Session。UE可以向AMF发送NAS消息，并在该NAS消息中携带以下参数：S-NSSAI、DNN、PDU Session ID、Request Type、MBS Session ID(例如可以包括MBS Multicast Session/Broadcast Session ID，在下文中为了与原来的源基站对应，也可以记录为Old MBS Multicast/Broadcast Session ID)和N1 SM Container，在该N1 SM Container中携带PDU Session Establishment Request。即可表示为NAS Message(S-NSSAI(s),UE Requested DNN,PDU Session ID,Request type,Old MBS Session ID,N1 SM container(PDU Session Establishment Request,[Port Management Information Container]))。
本公开实施例中，让Request Type指示为Existing MBS Session，Existing MBS Session可以包括Existing MBS Multicast/Broadcast Session(已存在MBS多播/广播会话)。当AMF接收到UE发送的NAS消息之后，Request Type指示为Existing MBS Multicast/Broadcast Session当做新建PDU Session来处理，即选择一个新的SMF。AMF通过与该SMF的交互可以建立PDU Session，并将与已激活的MBS Session对应的一个或多个QoS Flow在该PDU Session中建立起来。
其中，Old MBS Session ID指示为Old MBS Multicast/Broadcast Session ID表示MBS Multicast/Broadcast Session对应的MBS多播/广播会话标识(下文中有些地方直接用MBS  Multicast/Broadcast Session ID表示)。其中Old MBS Session ID指示为Old MBS Multicast Session ID表示切换的是一个MBS多播业务，Old MBS Session ID指示为Old MBS Broadcast Session ID表示切换的是一个MBS广播业务。
N1 SM container即N1会话管理容器中携带PDU Session Establishment Request(PDU会话建立请求)。Port Management Information Container表示端口管理信息容器。
NAS消息中的S-NSSAI和DNN组合是与Old MBS Multicast/Broadcast Session对应的S-NSSAI和DNN组合。在目标NG-RAN侧建立的PDU Session是用于取代源NG-RAN侧的MBS Multicast/Broadcast Session的，通过目标NG-RAN上的PDU Session的S-NSSAI和DNN组合与原来的MBS Multicast/Broadcast Session的S-NSSAI和DNN组合一样，能够保持业务的连续性。
需要说明的是，虽然上述举例中，以一个NAS消息中同时携带S-NSSAI、DNN、PDU Session ID、Request Type、MBS Session ID和N1 SM Container为例进行举例说明，但本公开并不限定于此，在其他实施例中，可以是UE直接或间接向AMF发送多个NAS消息，每个NAS消息中分别携带上述内容中的至少一部分，也可以是UE直接或间接向AMF发送其他形式的一个或多个消息，只要能将上述信息传递给AMF即可，告知AMF当前需要创建一个PDU会话，且该PDU会话是用于取代源基站侧已建立且尚未激活的MBS会话的即可，具体上述信息的取值和表达形式也不限于上述举例。
图6和图7实施例中，SMF与PCF之间有接口，即图6和图7中可以出现两个PCF，一个PCF与MB-SMF连接，称之为MB-PCF(多播广播策略控制功能)，可以用于提供MBS Multicast/Broadcast Session的上下文信息，是用于整个5G MBS Session的策略控制，另一个与SMF连接的PCF称之为UE-PCF(用户设备策略控制功能)，是用于控制PDU Session的Policy(策略)。可以理解的是，MB-PCF和UE-PCF是逻辑上独立的，但也有可能是同一个PCF实体。SMF与MB-SMF是逻辑上独立的，但也可能是同一个SMF实体。同样的，UPF与MB-UPF是逻辑上完全独立的，但可能是同一个UPF实体。
图6中的步骤2，AMF将Request Type指示为Existing MBS Multicast/Broadcast Session当做新建PDU Session来处理，即选择一个新的SMF(图6中的SMF不同于MB-SMF)。AMF根据UE提供的S-NSSAI与DNN选择出一个SMF。
图6中的步骤3a，AMF向所选择的SMF发送Nsmf_PDUSession_CreateSMContext请求消息(即协议数据单元会话建立会话管理上下文请求消息，简称为PDU会话建立会话管理上下文请求消息)，该Nsmf_PDUSession_CreateSMContext请求消息携带DNN、S-NSSAI、Request Type、Old MBS Session ID和N1 SM container，即Nsmf_PDUSession_CreateSMContext Request(SUPI,selected DNN,UE requested DNN,S-NSSAI(s),PDU Session ID,AMF ID,Request Type(指示为Existing MBS Multicast/Broadcast Session),Old MBS Session ID,PCF ID,Priority Access,[Small Data Rate Control Status],N1 SM container(PDU Session Establishment Request),User location information,Access Type,RAT Type,PEI,GPSI,UE presence in LADN service area,Subscription For PDU Session Status Notification,DNN Selection Mode,Trace Requirements,Control Plane CIoT 5GS Optimisation indication,or Control Plane Only indicator)。
其中，Nsmf_PDUSession_CreateSMContext Request中携带SUPI(Subscription Permanent Identifier，用户身份标识符)，DNN和S-NSSAI，Request type(＝Existing MBS Multicast//Broadcast Session)和Old MBS Session ID＝Old MBS Multicast/Broadcast Session ID等。其中，Priority Access表示优先接入，Small Data Rate Control Status表示小数据速率控制状态，User location information表示用户位置信息，Access Type表示接入类型，RAT Type表示RAT类型，PEI是Permanent Equipment Identifier的简写，即永久设备标识符,GPSI是Generic Public Subscription Identifier的简写，即通用公共用户标识)，UE presence in LADN service area表示UE存在于LADN(Local Area Data Network，本地数据网络)服务区，Subscription For PDU Session Status Notification表示定义PDU会话状态通知，DNN Selection Mode表示DNN选择模式，Trace Requirements表示追踪要求，Control Plane CIoT 5GS Optimisation indication表示控制面CIoT(Cell Internet of Things，蜂窝物联网)5GS优化指示，Control Plane Only indicator表示仅控制面指示器。
需要说明的是，虽然上述举例说明中，AMF直接向SMF发送一个 Nsmf_PDUSession_CreateSMContext Request消息，且在一个Nsmf_PDUSession_CreateSMContext Request消息中同时携带DNN、S-NSSAI、Request Type、Old MBS Multicast/Broadcast Session ID和N1SM container等多种信息，但本公开并不限定于此，在其他实施例中，AMF可以直接或者间接向SMF发送一个或多个Nsmf_PDUSession_CreateSMContext Request消息，每个Nsmf_PDUSession_CreateSMContext Request消息分别携带上述全部信息中的至少一部分，或者还可以采用其他消息形式，本公开对此不做限定，只要SMF最终能够获取到上述所需的信息即可。
图6中的步骤X.1可以包括如下的步骤X.1.a至X.1.i。
在步骤X.1.a中，SMF向NRF发送Nnrf_NFDiscovery请求消息(网络功能发现请求消息，即NF发现请求消息)，并在该Nnrf_NFDiscovery请求消息中携带UE的SUPI和NF类型(NF Type)，且NF Type指示为UDM以指示从NRF获取的是UDM的ID。
在步骤X.1.b中，当NRF从SMF接收到上述Nnrf_NFDiscovery请求消息(SUPI，NF Type指示为UDM)后，响应该Nnrf_NFDiscovery请求消息(SUPI，NF Type指示为UDM)，查找到该UE对应的UDM的ID(identity，标识)，这里称之为UE-UDM ID(即用户设备统一数据管理功能对应的用户设备统一数据管理功能标识)，并向SMF返回Nnrf_NFDiscovery响应消息(UE-UDM ID)，即NF发现响应消息。
在步骤X.1.c中，当SMF从NRF接收到Nnrf_NFDiscovery响应消息后，根据Nnrf_NFDiscovery响应消息中携带的UE-UDM ID即可获知该UE对应的UDM，因此，SMF可以向该UE-UDM ID对应的UE-UDM发送Nudm_SDM_Get请求消息(数据管理获取请求消息)，在该Nudm_SDM_Get请求消息中携带UE-UDM ID和该UE的SUPI。
在步骤X.1.d中，当UE-UDM从SMF接收到Nudm_SDM_Get请求消息后，UE-UDM可以向UE-UDR发送Nudr_DM_Query请求消息(数据管理查询请求消息)，在该Nudr_DM_Query请求消息中携带该UE的SUPI。
需要说明的是，本公开实施例中，将与UE-UDM对应的UDR称之为UE-UDR即用户设备统一数据存储。下文中提及的与MBS Session例如MBS Multicast/Broadcast Session对应的UDM称之为MB-UDM即多播广播统一数据管理功能，与MB-UDM对应的UDR称之为MB-UDR即多播广播统一数据存储。
可以理解的是，在本公开实施例中，MB-UDR和UE-UDR可以是同一个UDR，也可以是不同的UDR。
在步骤X.1.e中，当UE-UDR从UE-UDM接收到Nudr_DM_Query请求消息后，可以响应该Nudr_DM_Query请求消息而向UE-UDM返回Nudr_DM_Query响应消息(数据管理查询响应消息)，在该Nudr_DM_Query响应消息中包括MBS Multicast/Broadcast Session的MBS会话管理签约数据。
在步骤X.1.f中，当UE-UDM接收到UE-UDR返回的Nudr_DM_Query响应消息后，UE-UDM可以响应Nudm_SDM_Get请求消息而向SMF返回Nudm_SDM_Get响应消息(数据管理获取响应消息)，在该Nudm_SDM_Get响应消息中携带MBS Multicast/Broadcast Session的MBS会话管理签约数据。
在步骤X.1.g中，SMF接收到Nudm_SDM_Get响应消息后，可以向UE-UDM发送Nudm_SDM_Subscribe请求消息(数据管理订阅请求消息)，在该Nudm_SDM_Subscribe请求消息中携带SUPI、MBS Multicast/Broadcast Session的MBS会话管理签约数据、DNN和S-NSSAI。
在步骤X.1.h中，当UE-UDM接收到Nudm_SDM_Subscribe请求消息后，可以向UE-UDR发送Nudr_DM_Subscribe消息(数据管理订阅消息)，在该Nudr_DM_Subscribe消息中携带MBS Multicast/Broadcast Session的MBS会话管理签约数据。
在步骤X.1.i中，UE-UDM可以向SMF返回Nudm_SDM_Subscribe响应消息(数据管理订阅响应消息)。
图6实施例中的步骤X.1，Nudm_SDM_Get(包括请求和响应消息)与(包括请求和响应消息)Nudm_SDM_Subscribe中的Session Management Subscription data(会话管理签约数据)指示为MBS Session Management Subscription data(即多播广播业务会话管理签约数据)。同样的，Nudr_DM_Query (包括请求和响应消息)与Nudr_DM_Subscribe(包括请求和响应消息)中的Session Management Subscription data指示为MBS Session Management Subscription data。
图6实施例中的步骤X.1是SMF通过UE的SUPI查询NRF得到UE-UDM，图6实施例中的步骤X.1中的UE-UDM是用于存储UE的MBS会话管理签约数据的，根据这些MBS会话管理签约数据可以获知S-NSSAI与DNN是否已经签约，如果未签约，则拒绝执行图6中下面的步骤。即X.1步骤检查(check)是否允许建立PDU会话，MBS会话管理签约数据包括很多信息，例如允许的最大带宽、计费等。
需要说明的是，若UE有多个MBS Multicast/Broadcast Session同时切换到单播的相应的PDU Session上来，UE为每个PDU Session执行图6和图7的整个流程，因每个MBS Multicast/Broadcast Session对应的PDU Session的S-NSSAI及DNN在所有的流程中作了指定。
图6的步骤3b中，SMF向AMF返回响应Nsmf_PDUSession_CreateSMContext请求消息的Nsmf_PDUSession_CreateSMContext响应消息(即协议数据单元会话建立会话管理上下文响应消息，简写为PDU会话建立会话管理上下文响应消息)。
图6的步骤4中，进行PDU会话验证/授权(Authentication/Authorization)。
图6的步骤5中，SMF进行UPF的选择，其中若SMF发现自己就是MB-SMF，则SMF就直接选择MB-UPF作为UPF。
图6的步骤6a中，SMF向所选择的UPF发送N4 Session Establishment Request(N4会话建立请求)消息。
图6的步骤6b中，UPF向SMF返回N4 Session Establishment Response(N4会话建立响应)消息，进行确认。
图7中的步骤7a，若PCF被部署且动态策略被使用，则在图7的步骤7a中，SMF进行PCF的选择(即选择图8中的UE-PCF)。SMF可以重用MBS Multicast/Broadcast Session选择的MB-PCF作为UE-PCF，也可以为该UE重新选择一个不同于MB-PCF的PCF作为UE-PCF。本公开实施例中，优选根据MBS Multicast/Broadcast Session ID来选择MB-PCF作为UE-PCF。
图7中的步骤7b是可选的，若PCF被部署且动态策略被使用，则在图7的步骤7b中，进行SM策略关联建立过程(SM Policy Association Establishment procedure)，获取PDU Session的Default PCC Rule。
图7中的步骤7c是可选的，SMF为PDU Session订阅UE-UDM。
本公开实施例还增加一个称为X.2的步骤，用于SMF发现MB-SMF，以执行后续的步骤，具体参见下图9和图10。需要说明的是，步骤X.2只需要在步骤8前完成，与其它步骤没有时间前后的关系。
图7中的步骤8，SMF向步骤X.2发现的所述MBS会话对应的MB-SMF发送Nsmf_MBSSession_Create请求(Request)消息，即第一MBS会话创建请求消息，且该Nsmf_MBSSession_Create Request消息中可以携带所述MBS会话对应的MBS会话ID，即图7中的旧(old)MBS会话ID。
进一步地，该Nsmf_MBSSession_Create Request消息中还可以携带SUPI，GPSI，DNN，S-NSSAI，PDU会话ID，SMF ID，UPF CN-Tunnel-Info(核心网隧道信息，其中CN是Core Network的简写)，PDU会话类型，PCF ID和AMF ID。
图7中的步骤9a，可选的，MB-SMF向MB-UPF发送N4会话建立请求消息。
图7中的步骤9b，可选的，MB-UPF响应所述N4会话建立请求消息，向所述MB-SMF返回N4会话建立响应消息。若SMF提供了UPF CN-Tunnel-Info，则MB-UPF可建立到UPF的传输隧道。
UPF与MB-UPF建立用户面连接，例如UPF通过加入MB-UPF所分配的传输层IP多播地址。通过这个传输层IP多播地址及C-TEID(通用TEID(Tunnel Endpoint Identity，隧道端点标识))，UPF开始接收到MB-UPF发送的下行数据，对于UPF而言，这是其接收到的第一个下行数据(First Downlink Data)。
在图7中的步骤10中，MB-SMF响应上述步骤8的Nsmf_MBSSession_Create Request消息，向 SMF发送Nsmf_MBSSession_Create响应(Response)消息，即第一MBS会话创建响应消息，该Nsmf_MBSSession_Create Response消息中携带MBS QoS Flow参数列表(List)和MB-UPF的MBS CN隧道传输信息，其中该MBS QoS Flow参数列表中进一步包括MBS QFI(MBS QoS Flow ID，即QoS Flow标识)，MBS QFI QoS规则(Rules)，MBS QFI QoS配置(Profile)，即与该已激活的MBS会话对应的所有QoS Flow信息，所有QoS Flow信息包括一个或多个。
需要说明的是，因MB-SMF发送给SMF的第一MBS会话创建响应消息中包含与已激活的MBS会话对应的所有QoS Flow信息，则SMF可以判定该MBS会话已激活，因此，在图6和图7的PDU Session建立过程中建立与MBS Session对应的QoS Flow。
图7中的步骤11是可选的，若PCF被部署且动态策略被使用，则在图7的步骤11中，SMF触发SM策略关联修改过程。SMF向选择的PCF提供从MB-UDM所获取的对应MBS Session业务流的各个QoS Flow的QoS信息(Packet Filter，5QI，ARP等)，请求PCF来Check(检查)这些MBS Session业务流的QoS信息是否符合用户与网络的Policy(策略)规则。PCF根据用户与网络的Policy下发新的授权的Policy规则，即每个MBS Session业务流的QoS信息(Packet Filter，5QI，ARP等)，即使不作任何的QoS信息的修改，PCF仍然需要将SMF提供的MBS Session业务流的QoS信息再次发送给SMF。
若选择的PCF为MB-PCF，且SMF在发送给MB-PCF的消息Npcf_SMPolicyControlCreate Request中还包含MBS Session ID，MBS Session ID指示为MBS Multicast/Broadcast Session ID以指明是用于MBS Multicast/Broadcast Session，且对应MBS Multicast/Broadcast Session的ID，这样MB-PCF就可以依据用户、网络及MBS Multicast/Broadcast Session ID采用对应的授权的Policy Rules(策略规则)给SMF。即每个MBS Session业务流的QoS信息(Packet Filter，5QI，ARP等)，即使不作任何的QoS信息的修改，PCF仍然需要将SMF提供的MBS Session业务流的QoS信息再次发送给SMF。
图7中的步骤12，SMF向AMF发送Namf_Communication_N1N2MessageTransfer(即第一通信N1N2消息传输消息)，SMF向AMF请求传输N1接口上的消息与N2接口上的消息，SMF想让AMF分别给UE和目标NG-RAN转发有关SM的相关信息，SMF根据PCF提供的动态Policy RuleQoS信息或MB-UDM提供的MBS Multicast/Broadcast Session的QoS Flow信息，在PDU Session上建立MBS Multicast/Broadcast Session对应的一个或多个QoS Flow。
具体地，SMF触发Namf_Communication_N1N2MessageTransfer([N2 SM information](PDU Session ID,QFI(s),QoS Profile(s),[Alternative QoS Profile(s)],Session-AMBR,[CN Tunnel Info(s)],QoS Monitoring indication,QoS Monitoring reporting frequency,[TSCAI(s)]),N1 SM container(PDU Session Modification Command(PDU Session ID,QoS rule(s),QoS Flow level QoS parameters if needed for the QoS Flow(s)associated with the QoS rule(s),QoS rule operation and QoS Flow level QoS parameters operation,Session-AMBR)))。
其中，Namf_Communication_N1N2MessageTransfer中的PDU Session ID是让AMF知道为UE的哪个Session提供Transfer服务。
N2 SM information(N2会话管理信息)是给目标NG-RAN的，主要内容包含：PDU Session ID，QFI(s)，QoS Profile(s)，CN Tunnel Info(核心网隧道信息)，Session-AMBR(Session-Aggregate Maximum Bit Rate，会话聚合最大比特率)，PDU Session Type(PDU会话类型)。其中QoS Profile(s)用于目标NG-RAN对一个Session多个QoS Flow的配置；CN Tunnel Info则用于标识此Session在N3接口UPF侧节点。
N1 SM container(N1会话管理容器)是给UE看的，是一个SM消息，即Session Established Accept，主要内容包含：QoS Rule(s)、S-NSSAI(s)、DNN、IP地址以及Session-AMBR。其中，QoS Rule(s)用于UE对一个Session多个QoS Flow的配置；IP地址用于UE从UPF出口以后的数据路由。
这里提到了QoS Profile(s)与QoS Rule(s)，是指每个QoS Flow对应的QoS Profile与QoS Rule。若有多个QoS Flow，则在一个消息中包含有每个QoS Flow对应的QoS Profile与QoS Rule。5G中以这种方式一次性配置一个Session的多个QoS Flow，大大提高了信令效率。
在图7的步骤13中，AMF向目标NG-RAN发送N2 PDU会话请求(N2 PDU Session Request)消息。
具体地，N2 PDU Session Request(N2 SM information,NAS message(PDU Session ID,N1 SM container(PDU Session Establishment Accept)),[CN assisted RAN parameters tuning])。即AMF向目标NG-RAN发送的N2 PDU Session Request中包括NAS message和从SMF接收到的N2 SM information，其中NAS message包括用于发送给UE的PDU Session ID和PDU Session Establishment Accept。
在图7的步骤14中，目标NG-RAN和UE之间进行RRC(Radio Resource Control，无线资源控制)重配置(reconfiguration)。
在图7的步骤15中，目标NG-RAN向AMF发送N2 PDU会话请求确认(N2 PDU Session Request Ack)消息。
在图7的步骤16中，AMF向SMF发送Nsmf_PDUSession_UpdateSMContext请求消息。
AMF向SMF发送Nsmf_PDUSession_UpdateSMContext Request(SM Context ID,N2 SM information,Request Type)，AMF使用SMF提供的更新SM上下文服务，向SMF交付N2 SM information。N2 SM information中有一些关于QoS Flow(s)的参数，SMF可以及时更新Session上下文的内容。
在图7的步骤17a中，SMF向UPF发送N4会话修改请求(N4 Session Modification Request)消息，希望传输来自目标NG-RAN的AN Tunnel Info(接入网隧道信息)来打通N3的下行隧道，并最终将下行的转发规则告知UPF。N2 SM information中有一个参数：AN Tunnel Info，这个标识了Session在N3接口的目标NG-RAN侧节点。一旦AN Tunnel Info由SMF交付给UPF，Session在N3接口上的下行隧道就打通了。
在图7的步骤17b中，UPF响应N4 Session Modification Request消息，向SMF返回N4会话修改响应(N4 Session Modification Response)消息。
在图7的步骤18中，SMF响应Nsmf_PDUSession_UpdateSMContext请求消息，向AMF返回Nsmf_PDUSession_UpdateSMContext响应消息。
图7中的步骤19中，SMF向AMF发送Nsmf_PDUSession_SMContextStatusNotify消息。
图7中的步骤20中，UPF向目标NG-RAN发送IPv6(Internet Protocol Version 6，互联网协议第6版)地址配置，目标NG-RAN向UE发送IPv6地址配置。UPF向UE发送第一个下行数据。
图7中的步骤21中，SMF还可以向MB-SMF发送Nsmf_MBSSession_Update请求消息。
本公开实施方式提供的用于实现多播广播业务切换的方法，一方面，当UE在切换前的源基站已激活MBS会话且尚未建立与该MBS会话关联的PDU会话的情形下，在UE从支持MBS的源基站切换至不支持MBS的目标基站之后，再触发在该不支持MBS的目标基站侧建立一个PDU会话，由于该目标基站接入的5G核心网支持MBS，因此，可以通过MB-SMF直接在该与MBS会话关联的PDU会话上建立源基站侧已激活的MBS会话对应的所有QoS Flow，简化了SMF获取QoS Flow的流程。其中，与已激活的MBS会话对应的所有QoS Flow可以包括一个或多个QoS Flow。另一方面，这种方式对5G系统修改的最小，实现了UE在支持MBS的源基站与不支持MBS的目标基站之间切换时，将已激活的MBS会话切换到单播的PDU会话。
需要说明的是，上述对图7的PDU会话建立过程的描述，是针对在切换前该MBS会话已激活的情形，若该MBS会话在从源基站切换至目标基站之前尚未激活的情形，则上述图7实施例中的步骤8，SMF向所述MBS会话对应的MB-SMF发送Nsmf_MBSSession_Create请求(Request)消息，即第二MBS会话创建请求消息，且该Nsmf_MBSSession_Create Request消息中可以携带所述MBS会话对应的MBS会话ID。
且在图7中的步骤10中，MB-SMF响应上述图7中的步骤8的Nsmf_MBSSession_Create Request消息，向SMF发送Nsmf_MBSSession_Create响应(Response)消息，即第二MBS会话创建响应消息，该Nsmf_MBSSession_Create Response消息中未携带列表(List)和MB-UPF的MBS CN隧道传输信息，即第二MBS会话创建响应消息未携带与已激活的MBS会话对应的所有QoS Flow信息，SMF由此可以确定该MBS会话在此时尚未激活。因此，若切换前尚未激活MBS会话，则在图7的PDU Session建立过程中也就没有建立与MBS Session对应的QoS Flow。
同时，上述图7中的步骤12，SMF向AMF发送Namf_Communication_N1N2MessageTransfer(通 信N1N2消息传输消息)，由于未获取到与已激活的MBS会话对应的所有QoS Flow信息，在该步骤SMF未在PDU Session上建立MBS Multicast/Broadcast Session对应的一个或多个QoS Flow。
当利用如上图7所示实施例的方法在目标RAN或者目标NG-RAN侧已经建立PDU会话，且在图7实施例中没有任何的QoS Flow的建立。图8实施例中，UE从源基站切换至目标基站成功后，当切换前接入的源基站侧建立的MBS会话在切换之后被激活，SMF会触发已建立的PDU会话的修改(PDU Session Modification)过程，UE在执行被触发的PDU会话的修改过程中，会使SMF从MB-SMF获取到该与的MBS会话对应的所有QoS Flow信息，从而使得该SMF能够将与已激活的MBS会话对应的所有QoS Flow在该PDU会话上建立，实现MBS业务数据传输的连续性。
图8示意性示出了根据本公开的一实施例的PDU会话修改过程的示意图。
图8的步骤1，在目标RAN或者目标NG-RAN侧已经建立PDU会话后，MBS会话被激活。
图8中可以选择执行步骤2a或者2b，若由2b触发，则执行步骤3。
在图8的步骤2a中，MB-PCF向MB-SMF发送MBS Session相关的策略控制消息，触发MBS Session策略关联修改。
需要说明的是，步骤2a可能是步骤1中MBS会话激活过程中的一部分。
在图8的步骤2b中，MB-SMF触发QoS更新。
在图8的步骤3中，MB-SMF触发SM策略关联修改。MB-SMF从MB-PCF获取新的MBS会话的策略。
若MB-PCF被部署且动态策略被使用，则MB-SMF触发SM策略关联修改(SMF initiated SM Policy Association Modification)。MB-SMF向MB-PCF提供对应MBS Session业务流的各个QoS Flow的QoS信息(Packet Filter，5QI，ARP等)，请求MB-PCF来Check(检查)这些MBS Session业务流的QoS信息是否符合用户与网络的Policy(策略)规则。MB-PCF根据用户与网络的Policy下发新的授权的Policy规则，即每个MBS Session业务流的QoS信息(Packet Filter，5QI，ARP等)，即使不作任何的QoS信息的修改，MB-PCF仍然需要将MB-SMF提供的MBS Session业务流的QoS信息再次发送给MB-SMF。
在图8的步骤4中，MB-SMF向SMF发送Nsmf_MBSSession_Update请求消息(即MBS会话更新请求消息)，所述MBS会话更新请求消息携带与已激活的所述MBS会话对应的所有服务质量流信息。
图8的步骤5a，MB-SMF向MB-UPF发送N4会话修改请求(N4 Session Modification Request)。将各个QoS Flow对应的一个或多个N4Rule发送给MB-UPF。对于每个QoS Flow，可能存在着多个N4Rules。
图8的步骤5b，MB-UPF向MB-SMF发送N4会话修改响应(N4 Session Modification Response)。
图8的步骤6，SMF向UE-PCF发起PDU Session的会话管理(SM)策略关联修改。
若UE-PCF被部署且动态策略被使用，则SMF触发SM策略关联修改(SMF initiated SM Policy Association Modification)。SMF向UE-PCF提供MB-SMF提供的MBS Session业务流的各个QoS Flow的QoS信息(Packet Filter，5QI，ARP等)，请求UE-PCF来Check(检查)这些MBS Session业务流的QoS信息是否符合用户与网络的Policy(策略)规则。UE-PCF根据用户与网络的Policy下发新的授权的Policy规则，即每个MBS Session业务流的QoS信息(Packet Filter，5QI，ARP等)，即使不作任何的QoS息的修改，UE-PCF仍然需要将SMF提供的MBS Session业务流的QoS信息再次发送给SMF。
在图8的步骤7中，SMF向AMF发送Namf_Communication_N1N2MessageTransfer(即第二通信N1N2消息传输消息)，SMF向AMF请求传输N1接口上的消息与N2接口上的消息，SMF想让AMF分别给UE和目标NG-RAN转发有关SM的相关信息。
具体地，SMF触发Namf_Communication_N1N2MessageTransfer([N2 SM information](PDU Session ID,QFI(s),QoS Profile(s),[Alternative QoS Profile(s)],Session-AMBR,[CN Tunnel Info(s)],QoS Monitoring indication,QoS Monitoring reporting frequency,[TSCAI(s)]),N1 SM container(PDU Session Modification Command(PDU Session ID,QoS rule(s),QoS Flow level QoS parameters if needed for the QoS  Flow(s)associated with the QoS rule(s),QoS rule operation and QoS Flow level QoS parameters operation,Session-AMBR)))。
其中，Namf_Communication_N1N2MessageTransfer中的PDU Session ID是让AMF知道为UE的哪个Session提供Transfer服务。
N2 SM information(N2会话管理信息)是给目标NG-RAN的，主要内容包含：PDU Session ID，QFI(s)，QoS Profile(s)，CN Tunnel Info(核心网隧道信息)，Session-AMBR(Session-Aggregate Maximum Bit Rate，会话聚合最大比特率)，PDU Session Type(PDU会话类型)。其中QoS Profile(s)用于目标NG-RAN对一个Session多个QoS Flow的配置；CN Tunnel Info则用于标识此Session在N3接口UPF侧节点。
N1 SM container(N1会话管理容器)是给UE看的，是一个SM消息，即Session Established Accept，主要内容包含：QoS Rule(s)、S-NSSAI(s)、DNN、IP地址以及Session-AMBR。其中，QoS Rule(s)用于UE对一个Session多个QoS Flow的配置；IP地址用于UE从UPF出口以后的数据路由。
这里提到了QoS Profile(s)与QoS Rule(s)，是指每个QoS Flow对应的QoS Profile与QoS Rule。若有多个QoS Flow，则在一个消息中包含有每个QoS Flow对应的QoS Profile与QoS Rule。5G中以这种方式一次性可以配置一个Session多个QoS Flow，大大提高了信令效率。而这里的每个QoS Flow及其参数都是分别对应于MBS Session对应的MBS QoS Flow及其参数，即SMF将MBS Session对应的每个MBS QoS Flow及其参数分别映射到这个PDU Session的一个QoS Flow及其参数。
图8的步骤8，AMF向目标RAN发送N2会话请求消息。命令目标RAN建立前面的各个QoS Flow。
图8的步骤9，UE向目标RAN发送AN-specific(指定)资源修改的传输(包括PDU会话修改指令，以及无线特定的资源修改消息，如RRC Reconfiguration消息来建立传输各个QoS Flow的DRB(Data Radio Bearer，数据无线承载))。
图8的步骤10，目标RAN向AMF发送N2会话响应消息,确认对应于各个QoS Flow的无线资源已经被分配。
图8的步骤11，AMF向SMF发送Nsmf_PDUSession_UpdateSMContext请求消息，即PDU会话更新会话管理上下文请求消息。
图8的步骤12a，SMF向UPF/PSA发送N4会话修改请求消息。
图8的步骤12b，UPF/PSA响应所述N4会话修改请求消息，向所述SMF返回N4会话修改响应消息。
图8的步骤13，SMF响应Nsmf_PDUSession_UpdateSMContext请求消息，向AMF发送Nsmf_PDUSession_UpdateSMContext响应消息，即PDU会话更新会话管理上下文响应消息。
图8的步骤14，UE向目标RAN发送PDU会话修改指令确认(PDU Session Modification Command Ack)。
图8的步骤15，目标RAN向AMF发送N2 NAS上行传输(N2 NAS uplink transfer)。
图8的步骤16，AMF向SMF发送Nsmf_PDUSession_UpdateSMContext请求消息。
图8的步骤17，SMF响应Nsmf_PDUSession_UpdateSMContext请求消息，向AMF发送Nsmf_PDUSession_UpdateSMContext响应消息。
图8的步骤18，SMF响应图8中的步骤4的Nsmf_MBSSession_Update请求消息，向MB-SMF返回Nsmf_MBSSession_Update响应消息。
图8的步骤19a，MB-SMF向MB-UPF发送N4会话修改请求消息。
图8的步骤19b，MB-UPF响应于N4会话修改请求消息，向MB-SMF发送N4会话修改响应。
本公开实施方式提供的用于实现多播广播业务切换的方法，一方面，若当UE从支持MBS的源基站切换至不支持MBS的目标基站时，源基站侧已建立的MBS会话尚未激活，且该目标基站接入的5G核心网支持MBS，则在UE从支持MBS的源基站切换至不支持MBS的目标基站之后，触发在目标基站侧建立一个PDU会话，然后再在该MBS会话被激活后，在该PDU会话的修改过程中，通过MB-SMF将与已激活的MBS会话对应的QoS Flow信息传输至SMF，从而使得SMF可以将与已激活 的MBS会话对应的QoS Flow在与该MBS会话关联的PDU会话上建立起来，简化了SMF获取QoS Flow信息的流程。同时，使得在MBS会话建立时，不需要关联PDU会话，节省了PDU会话的资源，同时可以保持业务的连续性。另一方面，这种方式对5G系统修改的最小，实现了UE在支持MBS的源基站与不支持MBS的目标基站之间切换时，将MBS会话切换到单播的PDU会话。此外，本公开实施例提供的方案，UE即使在其MBS会话的传输面没有建立时，也支持UE切换到不支持MBS的目标基站后，通过异步的方式来实现单播的PDU会话的建立。
同时，由于本公开实施例是在UE切换至目标基站之后才建立与该MBS会话关联的PDU会话的，因此在MBS会话建立时，不需要关联PDU会话，节省了PDU会话的资源，同时可以保持MBS业务的连续性。而在相关技术中，要求UE在切换前，让MBS Session关联一个PDU Session，然后再让PDU Session切换到目标小区或目标RAN，然后，再通过这个PDU Session来传输MBS Session对应的业务数据。但由于事先UE不知道什么时间发生切换(例如切换是由5G网络来触发的)，因此，为了支持随时可能发生的切换，则在激活一个MBS Session时，就需要立即建立一个PDU Session，并在UE切换至目标RAN之前就需要将该MBS Session与该PDU Session关联。这就造成了很多资源的浪费，因为UE可能不切换到不支持MBS的目标基站，或在很长时间，如2小时后才切换到不支持MBS的目标基站。
需要说明的是，本公开实施例提供的方法还可以适应于，在UE从源基站切换至目标基站之前，已经在该源基站侧建立了MBS会话，并建立了PDU会话，且在切换前已经将该PDU会话与该MBS会话关联起来了的情形。
本公开实施例中，与MBS Session例如MBS Multicast/Broadcast Session对应的UDM称之为MB-UDM(Multicast Broadcast Unified Data Manager，多播广播统一数据管理)。
在上述的实施例中，SMF向MB-SMF发送第一MBS会话创建请求消息或者第二MBS会话创建请求消息之前，SMF需要先执行MB-SMF的发现过程。图9和图10提供了两种不同的发现过程。
图9示意性示出了根据本公开的一实施例的SMF发现MB-SMF的过程示意图。
在图9的步骤1中，UE已加入一个MBS Multicast/Broadcast Session，该MBS会话已建立且尚未激活。
在图9的步骤Y.1.a中，MB-SMF向NRF发送Nnrf_NFDiscovery_Request消息(第三NF发现请求消息)，在该Nnrf_NFDiscovery_Request消息中携带MBS Session ID指示为MBS Multicast/Broadcast Session ID和NF Type指示为MBS UDM。
在图9的步骤Y.1.b中，NRF接收到该Nnrf_NFDiscovery_Request消息后，根据该Nnrf_NFDiscovery_Request消息中携带的MBS Multicast/Broadcast Session ID和NF Type指示为MBS UDM，查找到对应的MB-UDM ID，并向MB-SMF返回Nnrf_NFDiscovery_Request响应消息(第三NF发现请求响应消息)，在该Nnrf_NFDiscovery_Request响应消息中携带该MB-UDM ID。
在图9的步骤Y.2.a中，MB-SMF接收到该Nnrf_NFDiscovery_Request响应消息后，根据该Nnrf_NFDiscovery响应消息中携带的MB-UDM ID，即可向对应的MB-UDM发送Nudm_MBSSessionContextRegisteration请求(MBS会话上下文注册请求消息)，在Nudm_MBSSessionContextRegisteration请求中携带MBS Session ID(指示为MBS Multicast/Broadcast Session ID)和MB-SMF ID。
需要说明的是，SMF可能是多个。对于不同的SMF，执行其对应的不同的PDU Session修改过程。Notification Correlation ID就是让SMF知道对应于哪个UE的PDU Session。
在图9的步骤Y.2.b中，MB-UDM接收到Nudm_MBSSessionContextRegisteration请求后，将MB-SMF注册至MB-UDM中，并向MB-SMF返回Nudm_MBSSessionContextRegisteration响应，即MBS会话上下文注册响应消息。
需要说明的是，因为可能存在着多个MBS会话切换到不支持MBS的(可能不同的)目标RAN上，对应的MB-SMF也可能分别不同，因此通过上述步骤，注册到MB-UDM的MB-SMF可能是多个。
在图9的步骤2中，可以采用上述图6和图7实施例所述的方法，建立PDU会话。
在图9的步骤Y.3.a中，SMF向NRF发送Nnrf_NFDiscovery_Request消息(第一NF发现请求消息)，在该Nnrf_NFDiscovery_Request消息中携带MBS Session ID指示为MBS Multicast/Broadcast Session ID和NF Type指示为MBS UDM。
在图9的步骤Y.3.b中，NRF接收到该Nnrf_NFDiscovery_Request消息后，根据该Nnrf_NFDiscovery_Request消息中携带的MBS Multicast/Broadcast Session ID和NF Type指示为MBS UDM，查找到对应的MB-UDM ID，并向MB-SMF返回Nnrf_NFDiscovery_Request响应消息(第一NF发现请求响应消息)，在该Nnrf_NFDiscovery_Request响应消息中携带该MB-UDM ID。
在图9的步骤Y.4.a中，SMF接收到该Nnrf_NFDiscovery_Request响应消息后，根据该Nnrf_NFDiscovery_Request响应消息中携带的MB-UDM ID，可向对应的MB-UDM发送Nudm_MBSSessionContextGet请求(MBS会话上下文获取请求消息)，在Nudm_MBSSessionContextGet请求中携带MBS Session ID(指示为MBS Multicast/Broadcast Session ID)，Notification Correlation ID(通知关联标识)和MB-SMF ID。
在图9的步骤Y.4.b中，MB-UDM接收到Nudm_MBSSessionContextGet请求消息后，向SMF返回Nudm_MBSSessionContextGet响应消息，即MBS会话上下文获取响应消息，该Nudm_MBSSessionContextGet响应消息携带该MBS会话ID和MB-SMF ID。
图10示意性示出了根据本公开的另一实施例的SMF发现MB-SMF的过程示意图。
在图10的步骤1中，UE已加入一个MBS Multicast/Broadcast Session，该MBS会话已建立且尚未激活。
在图10的步骤2中，MB-SMF向NRF发送Nnrf_NFManagement_NFRegister_request消息(NF管理NF注册请求消息)，在该Nnrf_NFManagement_NFRegister_request消息中携带MBS Session ID(指示为MBS Multicast/Broadcast Session ID)，Notification Correlation ID(通知关联标识)和MB-SMF ID。
在图10的步骤3中，NRF接收到该Nnrf_NFManagement_NFRegister_request消息后，存储NF配置，即将MBS Session ID和MB-SMF ID关联地存储在NRF中。
在图10的步骤4中，NRF响应该Nnrf_NFManagement_NFRegister_request消息，向MB-SMF发送该Nnrf_NFManagement_NFRegister_response消息(NF管理NF注册响应消息)。
在图10的步骤5中，可以采用上述图6和图7实施例所述的方法，建立PDU会话。
在图10的步骤6中，SMF向NRF发送Nnrf_NFDiscovery_Request消息(第二NF发现请求消息)，在该Nnrf_NFDiscovery_Request消息中携带MBS Session ID指示为MBS Multicast/Broadcast Session ID，NF Type指示为MBS SMF。
在图10的步骤7中，NRF接收到该Nnrf_NFDiscovery_Request消息后，根据该Nnrf_NFDiscovery_Request消息中携带的MBS Multicast/Broadcast Session ID及NF Type指示为MBS SMF，授权NF服务发现，查找到与该MBS Multicast/Broadcast Session ID对应的NF Type指示为MBS SMF的MB-SMF ID。
在图10的步骤8中，NRF向SMF返回Nnrf_NFDiscovery_Request响应消息(即第二NF发现请求响应消息)，该Nnrf_NFDiscovery_Request响应消息携带MB-SMF ID。
进一步地，本公开实施方式还提供了一种用于实现多播广播业务切换的方法，应用于用户设备对应的MB-SMF，所述用户设备在切换前接入的源基站支持MBS，所述用户设备在切换前已在所述源基站建立MBS会话，所述用户设备切换后接入的目标基站不支持MBS，且所述目标基站接入的核心网支持MBS。其中，所述方法可以包括：在所述用户设备从所述源基站切换至所述目标基站之后，向SMF传输与已激活的所述MBS会话对应的服务质量流信息，其中与已激活的所述MBS会话对应的服务质量流信息可以包括一个或多个服务质量流信息，以便所述SMF根据与已激活的所述MBS会话对应的服务质量流信息，在与所述MBS会话关联的PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。
其中所述PDU会话的S-NSSAI和所述MBS会话的S-NSSAI相同，所述PDU会话的DNN与所述MBS会话的DNN相同。
在示例性实施例中，所述用户设备可以在切换前已在所述源基站激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话。其中，向SMF传输与已激活的所述MBS会话对应的服务质量流信息，可以包括：在所述用户设备从所述源基站切换至所述目标基站后，执行所述用户设备触发的在所述目标基站侧建立所述PDU会话的过程；在所述目标基站侧建立所述PDU会话的过程中，接收所述SMF发送的第一MBS会话创建请求消息，所述第一MBS会话创建请求消息携带所述MBS会话的MBS会话标识；向所述SMF发送响应所述第一MBS会话创建请求消息而生成的第一MBS会话创建响应消息，所述第一MBS会话创建响应消息中包括与已激活的所述MBS会话对应的服务质量流信息。
在示例性实施例中，所述用户设备可以在切换前在所述源基站尚未激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话。其中，向SMF传输与已激活的所述MBS会话对应的服务质量流信息之前，所述方法还可以包括：在所述用户设备从所述源基站切换至所述目标基站后，执行所述用户设备触发的在所述目标基站侧建立所述PDU会话的过程；在所述目标基站侧建立所述PDU会话的过程中，接收所述SMF发送的第二MBS会话创建请求消息，所述第二MBS会话创建请求消息携带所述MBS会话标识；向所述SMF发送响应所述第二MBS会话创建请求消息而生成的第二MBS会话创建响应消息，所述第二MBS会话创建响应消息中未携带所述MBS会话对应的服务质量流信息，以便于所述SMF根据所述第二MBS会话创建响应消息，确定所述MBS会话尚未激活。
在示例性实施例中，向SMF传输与已激活的所述MBS会话对应的服务质量流信息，可以包括：当所述MBS会话被激活后，触发所述PDU会话的修改过程；在所述PDU会话的修改过程中，向所述SMF发送MBS会话更新请求消息，所述MBS会话更新请求消息携带与已激活的所述MBS会话对应的服务质量流信息；接收所述SMF响应所述MBS会话更新请求消息返回的MBS会话更新响应消息。
在示例性实施例中，在所述用户设备触发所述PDU会话的建立过程之前，所述方法还可以包括：向NRF发送第三NF发现请求消息，所述第三NF发现请求消息携带所述MBS会话标识和指示为MBS UDM的网络类型；接收所述NRF响应所述第三NF发现请求消息而返回的第三NF发现请求响应消息，所述第三NF发现请求响应消息携带MB-UDM标识；根据所述MB-UDM标识，向MB-UDM发送MBS会话上下文注册请求消息，所述MBS会话上下文注册请求消息携带所述MBS会话标识和所述MBS会话标识对应的所述MB-SMF的MB-SMF标识，以便将所述MBS会话标识和所述MB-SMF标识关联存储至所述MB-UDM；接收所述MB-UDM响应所述MBS会话上下文注册请求消息而返回的MBS会话上下文注册响应消息。
在示例性实施例中，在所述用户设备触发所述PDU会话的建立过程之前，所述方法还可以包括：向NRF发送NF管理NF注册请求消息，所述NF管理NF注册请求消息携带所述MBS会话标识和所述MBS会话标识对应的所述MB-SMF的MB-SMF标识，以便将所述MBS会话标识和所述MB-SMF标识关联存储至所述NRF；接收所述NRF响应所述NF管理NF注册请求消息而返回的NF管理NF注册响应消息，所述NF管理NF注册响应消息携带所述MB-SMF的MB-SMF标识。
本公开实施例提供的用于实现多播广播业务切换的方法的具体实现可以参照上述其它实施例中用于实现多播广播业务切换的方法中的内容，在此不再赘述。
图11示意性示出了根据本公开的一实施例的会话管理功能设备的框图。如图11所示，本公开实施例提供的会话管理功能设备1100可以包括：一个或多个处理器1101；存储器1103，配置为存储一个或多个程序，当所述一个或多个程序被所述一个或多个处理器1101执行时，使得所述一个或多个处理器1101实现如上述任一实施例所述的方法。图11实施例中，用户设备在切换前接入的源基站支持MBS，所述用户设备在切换前已在所述源基站建立MBS会话，所述用户设备切换后接入的目标基站不支持MBS，且所述目标基站接入的核心网支持MBS。
其中，程序可具体用于：获取与所述MBS会话关联的PDU会话，其中所述PDU会话的S-NSSAI和所述MBS会话的S-NSSAI相同，所述PDU会话的DNN与所述MBS会话的DNN相同；获取所述MBS会话的MBS会话标识；根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息，其中与已激活的所述MBS会话对应的服务质量流信息包括一个或多个服务质量 流信息；根据与已激活的所述MBS会话对应的服务质量流信息，在所述PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。
参考图11，程序可进一步包括：PDU会话获取单元11031，可以用于获取与所述MBS会话关联的PDU会话，其中所述PDU会话的S-NSSAI和所述MBS会话的S-NSSAI相同，所述PDU会话的DNN与所述MBS会话的DNN相同；MBS会话标识获取单元11032，可以用于获取所述MBS会话的MBS会话标识；服务质量流信息获取单元11033，可以用于根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息，其中与已激活的所述MBS会话对应的服务质量流信息包括一个或多个服务质量流信息；服务质量流建立单元11034，可以用于根据与已激活的所述MBS会话对应的服务质量流信息，在所述PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。
在示例性实施例中，所述用户设备在切换前已在所述源基站激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话。其中，PDU会话获取单元11031可配置为：在所述用户设备从所述源基站切换至所述目标基站后，执行所述用户设备触发的在所述目标基站侧建立所述PDU会话的过程。其中，MBS会话标识获取单元11032可配置为：在所述目标基站侧建立所述PDU会话的过程中，从AMF接收PDU会话建立会话管理上下文请求消息，所述PDU会话建立会话管理上下文请求消息中包括所述MBS会话标识。
在示例性实施例中，所述PDU会话建立会话管理上下文请求消息还包括所述S-NSSAI、所述DNN、请求类型和N1会话管理容器，其中所述请求类型指示为已存在MBS会话，所述N1会话管理容器中携带PDU会话建立请求。
在示例性实施例中，服务质量流信息获取单元11033可配置为：在所述目标基站侧建立所述PDU会话的过程中，向所述MB-SMF发送第一MBS会话创建请求消息，所述第一MBS会话创建请求消息携带所述MBS会话标识；接收所述MB-SMF响应所述第一MBS会话创建请求消息而返回的第一MBS会话创建响应消息，所述第一MBS会话创建响应消息中包括与已激活的所述MBS会话对应的服务质量流信息。
在示例性实施例中，服务质量流建立单元11034可配置为：在所述PDU会话的建立过程中，向所述AMF发送第一通信N1N2消息传输消息，以使得所述AMF根据与已激活的所述MBS会话对应的服务质量流信息，在所述DPU会话上建立所述MBS会话对应的服务质量流。
在示例性实施例中，所述用户设备在切换前在所述源基站尚未激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话。其中，程序可进一步包括：第二MBS会话创建请求消息发送单元，可以用于在根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息之前，在切换后的所述目标基站侧建立所述PDU会话的过程中，向所述MB-SMF发送第二MBS会话创建请求消息，所述第二MBS会话创建请求消息携带所述MBS会话标识；第二MBS会话创建响应消息接收单元，可以用于接收所述MB-SMF响应所述第二MBS会话创建请求消息而返回的第二MBS会话创建响应消息；MBS会话尚未激活判定单元，可以用于若所述第二MBS会话创建响应消息中未携带所述MBS会话对应的服务质量流信息，则判定所述MBS会话尚未激活。
在示例性实施例中，服务质量流信息获取单元11033可配置为：当所述MBS会话被激活后，执行所述MB-SMF触发的所述PDU会话的修改过程；在所述PDU会话的修改过程中，接收所述MB-SMF发送的MBS会话更新请求消息，所述MBS会话更新请求消息携带与已激活的所述MBS会话对应的服务质量流信息；向所述MB-SMF返回响应所述MBS会话更新请求消息的MBS会话更新响应消息。
在示例性实施例中，服务质量流建立单元11034可配置为：在所述PDU会话的修改过程中，向所述AMF发送第二通信N1N2消息传输消息，以使得所述AMF根据与已激活的所述MBS会话对应的服务质量流信息，在所述DPU会话上建立所述MBS会话对应的服务质量流。
在示例性实施例中，程序可进一步包括：UE-UDM确定单元，可以用于在根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息之前，在所述PDU会话的建立过程中，根据所述用户设备的SUPI确定UE-UDM；MBS会话管理签约数据获取单元，可以用于根据所 述SUPI从所述UE-UDM获取所述MBS会话的MBS会话管理签约数据；已签约判定单元，可以用于根据所述MBS会话管理签约数据，确定所述S-NSSAI和所述DNN已在所述UE-UDM签约。
在示例性实施例中，程序可进一步包括：第一NF发现请求消息发送单元，可以用于在根据所述MBS会话管理签约数据，确定所述S-NSSAI和所述DNN已在所述UE-UDM签约之后，向NRF发送第一NF发现请求消息，所述第一NF发现请求消息携带所述MBS会话标识和指示为MBS UDM的网络类型；第一NF发现请求响应消息接收单元，可以用于接收所述NRF响应所述第一NF发现请求消息而返回的第一NF发现请求响应消息，所述第一NF发现请求响应消息携带MB-UDM标识；MBS会话上下文获取请求消息发送单元，可以用于根据所述MB-UDM标识，向MB-UDM发送MBS会话上下文获取请求消息，所述MBS会话上下文获取请求消息携带所述MBS会话标识；MBS会话上下文获取响应消息接收单元，可以用于接收所述MB-UDM响应所述MBS会话上下文获取请求消息而返回的MBS会话上下文获取响应消息，所述MBS会话上下文获取响应消息携带所述MBS会话标识对应的所述MB-SMF的MB-SMF标识。
在示例性实施例中，程序可进一步包括：第二NF发现请求消息发送单元，可以用于在根据所述MBS会话管理签约数据确定所述S-NSSAI和所述DNN已在所述UE-UDM签约之后，向NRF发送第二NF发现请求消息，所述第二NF发现请求消息携带所述MBS会话标识和指示为MBS SMF的网络类型；第二NF发现请求响应消息接收单元，可以用于接收所述NRF响应所述第二NF发现请求消息而返回的第二NF发现请求响应消息，所述第二NF发现请求响应消息携带所述MBS会话标识对应的所述MB-SMF的MB-SMF标识。
本公开实施例提供的会话管理功能设备的具体实现可以参照上述用于实现多播广播业务切换的方法中的内容，在此不再赘述。
图12示意性示出了根据本公开的一实施例的多播广播会话管理功能设备的框图。图12示意性示出了根据本公开的一实施例的多播广播会话管理功能设备的框图。如图12所示，本公开实施例提供的多播广播会话管理功能设备1200可以包括：一个或多个处理器1201；存储器1203，配置为存储一个或多个程序，当所述一个或多个程序被所述一个或多个处理器1201执行时，使得所述一个或多个处理器1201实现如上述任一实施例所述的方法。图12实施例中，用户设备在切换前接入的源基站支持MBS，所述用户设备在切换前已在所述源基站建立MBS会话，所述用户设备切换后接入的目标基站不支持MBS，且所述目标基站接入的核心网支持MBS。
其中，程序可具体用于：在所述用户设备从所述源基站切换至所述目标基站之后，向SMF传输与已激活的所述MBS会话对应的服务质量流信息，其中与已激活的所述MBS会话对应的服务质量流信息包括一个或多个服务质量流信息，以便所述SMF根据与已激活的所述MBS会话对应的服务质量流信息，在与所述MBS会话关联的PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。其中所述PDU会话的S-NSSAI和所述MBS会话的S-NSSAI相同，所述PDU会话的DNN与所述MBS会话的DNN相同。
参考图12，程序可进一步包括：服务质量流信息传输单元12031，可以用于在所述用户设备从所述源基站切换至所述目标基站之后，向SMF传输与已激活的所述MBS会话对应的服务质量流信息，其中服务质量流信息包括一个或多个，以便所述SMF根据与已激活的所述MBS会话对应的服务质量流信息，在与所述MBS会话关联的PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。
在示例性实施例中，所述用户设备在切换前已在所述源基站激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话。其中，服务质量流信息传输单元12031可配置为：在所述用户设备从所述源基站切换至所述目标基站后，执行所述用户设备触发的在所述目标基站侧建立所述PDU会话的过程；在所述目标基站侧建立所述PDU会话的过程中，接收所述SMF发送的第一MBS会话创建请求消息，所述第一MBS会话创建请求消息携带所述MBS会话的MBS会话标识；向所述SMF发送响应所述第一MBS会话创建请求消息而生成的第一MBS会话创建响应消息，所述第一MBS会话创建响应消息中包括与已激活的所述MBS会话对应的服务质量流信息。
在示例性实施例中，所述用户设备在切换前在所述源基站尚未激活所述MBS会话，且尚未建立 与所述MBS会话关联的PDU会话。其中，程序可进一步包括：PDU会话建立执行过程，可以用于向SMF传输与已激活的所述MBS会话对应的服务质量流信息之前，在所述用户设备从所述源基站切换至所述目标基站后，执行所述用户设备触发的在所述目标基站侧建立所述PDU会话的过程；第二MBS会话创建请求消息接收单元，可以用于在所述目标基站侧建立所述PDU会话的过程中，接收所述SMF发送的第二MBS会话创建请求消息，所述第二MBS会话创建请求消息携带所述MBS会话标识；第二MBS会话创建响应消息发送单元，可以用于向所述SMF发送响应所述第二MBS会话创建请求消息而生成的第二MBS会话创建响应消息，所述第二MBS会话创建响应消息中未携带所述MBS会话对应的服务质量流信息，以便于所述SMF根据所述第二MBS会话创建响应消息，确定所述MBS会话尚未激活。
在示例性实施例中，服务质量流信息传输单元12031可配置为：当所述MBS会话被激活后，触发所述PDU会话的修改过程；在所述PDU会话的修改过程中，向所述SMF发送MBS会话更新请求消息，所述MBS会话更新请求消息携带与已激活的所述MBS会话对应的服务质量流信息；接收所述SMF响应所述MBS会话更新请求消息而返回的MBS会话更新响应消息。
在示例性实施例中，程序可进一步包括：第三NF发现请求消息发送单元，可以用于在所述用户设备触发所述PDU会话的建立过程之前，向NRF发送第三NF发现请求消息，所述第三NF发现请求消息携带所述MBS会话标识和指示为MBS UDM的网络类型；第三NF发现请求响应消息接收单元，可以用于接收所述NRF响应所述第三NF发现请求消息而返回的第三NF发现请求响应消息，所述第三NF发现请求响应消息携带MB-UDM标识；MBS会话上下文注册请求消息发送单元，可以用于根据所述MB-UDM标识，向MB-UDM发送MBS会话上下文注册请求消息，所述MBS会话上下文注册请求消息携带所述MBS会话标识和所述MBS会话标识对应的所述MB-SMF的MB-SMF标识，以便将所述MBS会话标识和所述MB-SMF标识关联存储至所述MB-UDM；MBS会话上下文注册响应消息接收单元，可以用于接收所述MB-UDM响应所述MBS会话上下文注册请求消息而返回的MBS会话上下文注册响应消息。
在示例性实施例中，程序可进一步包括：NF管理NF注册请求消息发送单元，可以用于在所述用户设备触发所述PDU会话的建立过程之前，向NRF发送NF管理NF注册请求消息，所述NF管理NF注册请求消息携带所述MBS会话标识和所述MBS会话标识对应的所述MB-SMF的MB-SMF标识，以便将所述MBS会话标识和所述MB-SMF标识关联存储至所述NRF；NF管理NF注册响应消息接收单元，可以用于接收所述NRF响应所述NF管理NF注册请求消息而返回的NF管理NF注册响应消息，所述NF管理NF注册响应消息携带所述MB-SMF的MB-SMF标识。
本公开实施例提供的多播广播会话管理功能设备的具体实现可以参照上述用于实现多播广播业务切换的方法中的内容，在此不再赘述。
需要说明的是，参考上述图11和图12，其示出了适于用来实现本申请实施例的会话管理功能设备1100和多播广播会话管理功能设备1200的结构示意图。图11和图12示出的结构仅仅是一个示例，不应对本申请实施例的功能和使用范围带来任何限制。
参照图11和图12，本公开实施例提供的会话管理功能设备1100和多播广播会话管理功能设备1200还可以分别包括：通信接口(1102、1202)和通信总线(1104、1204)。
其中处理器(1101、1201)、通信接口(1102、1202)和存储器(1103、1203)通过通信总线(1104、1204)完成相互间的通信。
可选的，通信接口(1102、1202)可以为通信模块的接口，如GSM(Global System for Mobile communications，全球移动通信系统)模块的接口。处理器(1101、1201)用于执行程序。存储器(1103、1203)用于存放程序。程序可以包括计算机程序，该计算机程序包括计算机操作指令。
处理器(1101、1201)可以是一个中央处理器CPU，或者是特定集成电路ASIC(Application Specific Integrated Circuit)，或者是被配置成实施本公开实施例的一个或多个集成电路。
存储器(1103、1203)可以包含高速RAM(random access memory，随机存取存储器)存储器，也可以还包括非易失性存储器(non-volatile memory)，例如至少一个磁盘存储器。
一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，所述计算机程序被处理 器执行时实现如上述任一实施例中所述的方法。
特别地，根据本公开的实施例，下文参考流程图描述的过程可以被实现为计算机软件程序。例如，本公开的实施例包括一种计算机程序产品，其包括承载在计算机可读存储介质上的计算机程序，该计算机程序包含用于执行流程图所示的方法的程序代码。
需要说明的是，本公开所示的计算机可读存储介质可以是计算机可读信号介质或者计算机可读存储介质或者是上述两者的任意组合。
作为另一方面，本申请还提供了一种计算机可读存储介质，该计算机可读存储介质可以是上述实施例中描述的电子设备中所包含的；也可以是单独存在，而未装配入该电子设备中。上述计算机可读存储介质承载有一个或者多个程序，当上述一个或者多个程序被一个该电子设备执行时，使得该电子设备实现如下述实施例中所述的方法。

Claims (21)

  1. 一种用于实现多播广播业务切换的方法，应用于用户设备对应的SMF，所述用户设备在切换前接入的源基站支持MBS，所述用户设备在切换前已在所述源基站建立MBS会话，所述用户设备切换后接入的目标基站不支持MBS，且所述目标基站接入的核心网支持MBS；其中，所述方法包括：
    获取与所述MBS会话关联的PDU会话，其中所述PDU会话的S-NSSAI和所述MBS会话的S-NSSAI相同，所述PDU会话的DNN与所述MBS会话的DNN相同；
    获取所述MBS会话的MBS会话标识；
    根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息，其中与已激活的所述MBS会话对应的服务质量流信息包括一个或多个服务质量流信息；
    根据与已激活的所述MBS会话对应的服务质量流信息，在所述PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流。
  2. 根据权利要求1所述的方法，其中，所述用户设备在切换前已在所述源基站激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话；其中，所述获取与所述MBS会话关联的PDU会话，包括：
    在所述用户设备从所述源基站切换至所述目标基站后，执行所述用户设备触发的在所述目标基站侧建立所述PDU会话的过程；
    其中，所述获取已激活的所述MBS会话的MBS会话标识，包括：
    在所述目标基站侧建立所述PDU会话的过程中，从AMF接收PDU会话建立会话管理上下文请求消息，所述PDU会话建立会话管理上下文请求消息中包括所述MBS会话标识。
  3. 根据权利要求2所述的方法，其中，所述PDU会话建立会话管理上下文请求消息还包括所述S-NSSAI、所述DNN、请求类型和N1会话管理容器，其中所述请求类型指示为已存在MBS会话，所述N1会话管理容器中携带PDU会话建立请求。
  4. 根据权利要求2所述的方法，其中，所述根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息，包括：
    在所述目标基站侧建立所述PDU会话的过程中，向所述MB-SMF发送第一MBS会话创建请求消息，所述第一MBS会话创建请求消息携带所述MBS会话标识；
    接收所述MB-SMF响应所述第一MBS会话创建请求消息而返回的第一MBS会话创建响应消息，所述第一MBS会话创建响应消息中包括与已激活的所述MBS会话对应的服务质量流信息。
  5. 根据权利要求4所述的方法，其中，所述根据与已激活的所述MBS会话对应的服务质量流信息，在所述PDU会话上建立与已激活的所述MBS会话对应的服务质量流，包括：
    在所述PDU会话的建立过程中，向所述AMF发送第一通信N1N2消息传输消息，以使得所述AMF根据与已激活的所述MBS会话对应的服务质量流信息，在所述DPU会话上建立所述MBS会话对应的服务质量流。
  6. 根据权利要求1所述的方法，其中，所述用户设备在切换前在所述源基站尚未激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话；其中，在根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息之前，所述方法还包括：
    在切换后的所述目标基站侧建立所述PDU会话的过程中，向所述MB-SMF发送第二MBS会话创建请求消息，所述第二MBS会话创建请求消息携带所述MBS会话标识；
    接收所述MB-SMF响应所述第二MBS会话创建请求消息而返回的第二MBS会话创建响应消息；
    若所述第二MBS会话创建响应消息中未携带所述MBS会话对应的服务质量流信息，则判定所述MBS会话尚未激活。
  7. 根据权利要求6所述的方法，其中，所述根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息，包括：
    当所述MBS会话被激活后，执行所述MB-SMF触发的所述PDU会话的修改过程；
    在所述PDU会话的修改过程中，接收所述MB-SMF发送的MBS会话更新请求消息，所述MBS会话更新请求消息携带与已激活的所述MBS会话对应的服务质量流信息；
    向所述MB-SMF返回响应所述MBS会话更新请求消息的MBS会话更新响应消息。
  8. 根据权利要求7所述的方法，其中，所述根据与已激活的所述MBS会话对应的服务质量流信息，将与已激活的所述MBS会话对应的服务质量流在所述PDU会话上建立，包括：
    在所述PDU会话的修改过程中，向所述AMF发送第二通信N1N2消息传输消息，以使得所述AMF根据与已激活的所述MBS会话对应的服务质量流信息，在所述DPU会话上建立所述MBS会话对应的服务质量流。
  9. 根据权利要求2至8任一项所述的方法，其中，在根据所述MBS会话标识从MB-SMF获取与已激活的所述MBS会话对应的服务质量流信息之前，所述方法还包括：
    在所述PDU会话的建立过程中，根据所述用户设备的SUPI确定UE-UDM；
    根据所述SUPI从所述UE-UDM获取所述MBS会话的MBS会话管理签约数据；
    根据所述MBS会话管理签约数据，确定所述S-NSSAI和所述DNN已在所述UE-UDM签约。
  10. 根据权利要求9所述的方法，其中，在根据所述MBS会话管理签约数据，确定所述S-NSSAI和所述DNN已在所述UE-UDM签约之后，所述方法还包括：
    向NRF发送第一NF发现请求消息，所述第一NF发现请求消息携带所述MBS会话标识和指示为MBS UDM的网络类型；
    接收所述NRF响应所述第一NF发现请求消息而返回的第一NF发现请求响应消息，所述第一NF发现请求响应消息携带MB-UDM标识；
    根据所述MB-UDM标识，向MB-UDM发送MBS会话上下文获取请求消息，所述MBS会话上下文获取请求消息携带所述MBS会话标识；
    接收所述MB-UDM响应所述MBS会话上下文获取请求消息而返回的MBS会话上下文获取响应消息，所述MBS会话上下文获取响应消息携带所述MBS会话标识对应的所述MB-SMF的MB-SMF标识。
  11. 根据权利要求9所述的方法，其中，在根据所述MBS会话管理签约数据，确定所述S-NSSAI和所述DNN已在所述UE-UDM签约之后，所述方法还包括：
    向NRF发送第二NF发现请求消息，所述第二NF发现请求消息携带所述MBS会话标识和指示为MBS SMF的网络类型；
    接收所述NRF响应所述第二NF发现请求消息而返回的第二NF发现请求响应消息，所述第二NF发现请求响应消息携带所述MBS会话标识对应的所述MB-SMF的MB-SMF标识。
  12. 一种用于实现多播广播业务切换的方法，应用于用户设备对应的MB-SMF，所述用户设备在切换前接入的源基站支持MBS，所述用户设备在切换前已在所述源基站建立MBS会话，所述用户设备切换后接入的目标基站不支持MBS，且所述目标基站接入的核心网支持MBS；其中，所述方法包括：
    在所述用户设备从所述源基站切换至所述目标基站之后，向SMF传输与已激活的所述MBS会话对应的服务质量流信息，其中与已激活的所述MBS会话对应的服务质量流信息包括一个或多个服务质量流信息，以便所述SMF根据与已激活的所述MBS会话对应的服务质量流信息，在与所述MBS会话关联的PDU会话上建立与已激活的所述MBS会话对应的服务质量流，其中与已激活的所述MBS会话对应的服务质量流包括一个或多个服务质量流；
    其中所述PDU会话的S-NSSAI和所述MBS会话的S-NSSAI相同，所述PDU会话的DNN与所述MBS会话的DNN相同。
  13. 根据权利要求12所述的方法，其中，所述用户设备在切换前已在所述源基站激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话；其中，所述向SMF传输与已激活的所述MBS会话对应的服务质量流信息，包括：
    在所述用户设备从所述源基站切换至所述目标基站后，执行所述用户设备触发的在所述目标基站侧建立所述PDU会话的过程；
    在所述目标基站侧建立所述PDU会话的过程中，接收所述SMF发送的第一MBS会话创建请求消息，所述第一MBS会话创建请求消息携带所述MBS会话的MBS会话标识；
    向所述SMF发送响应所述第一MBS会话创建请求消息而生成的第一MBS会话创建响应消息，所述第一MBS会话创建响应消息中包括与已激活的所述MBS会话对应的服务质量流信息。
  14. 根据权利要求12所述的方法，其中，所述用户设备在切换前在所述源基站尚未激活所述MBS会话，且尚未建立与所述MBS会话关联的PDU会话；其中，所述向SMF传输与已激活的所述MBS会话对应的服务质量流信息之前，所述方法还包括：
    在所述用户设备从所述源基站切换至所述目标基站后，执行所述用户设备触发的在所述目标基站侧建立所述PDU会话的过程；
    在所述目标基站侧建立所述PDU会话的过程中，接收所述SMF发送的第二MBS会话创建请求消息，所述第二MBS会话创建请求消息携带所述MBS会话标识；
    向所述SMF发送响应所述第二MBS会话创建请求消息而生成的第二MBS会话创建响应消息，所述第二MBS会话创建响应消息中未携带所述MBS会话对应的服务质量流信息，以便于所述SMF根据所述第二MBS会话创建响应消息，确定所述MBS会话尚未激活。
  15. 根据权利要求14所述的方法，其中，所述向SMF传输与已激活的所述MBS会话对应的服务质量流信息，包括：
    当所述MBS会话被激活后，触发所述PDU会话的修改过程；
    在所述PDU会话的修改过程中，向所述SMF发送MBS会话更新请求消息，所述MBS会话更新请求消息携带与已激活的所述MBS会话对应的服务质量流信息；
    接收所述SMF响应所述MBS会话更新请求消息而返回的MBS会话更新响应消息。
  16. 根据权利要求13至15任一项所述的方法，其中，在所述用户设备触发所述PDU会话的建立过程之前，所述方法还包括：
    向NRF发送第三NF发现请求消息，所述第三NF发现请求消息携带所述MBS会话标识和指示为MBS UDM的网络类型；
    接收所述NRF响应所述第三NF发现请求消息而返回的第三NF发现请求响应消息，所述第三NF发现请求响应消息携带MB-UDM标识；
    根据所述MB-UDM标识，向MB-UDM发送MBS会话上下文注册请求消息，所述MBS会话上下文注册请求消息携带所述MBS会话标识和所述MBS会话标识对应的所述MB-SMF的MB-SMF标识，以便将所述MBS会话标识和所述MB-SMF标识关联存储至所述MB-UDM；
    接收所述MB-UDM响应所述MBS会话上下文注册请求消息而返回的MBS会话上下文注册响应消息。
  17. 根据权利要求13至15任一项所述的方法，其中，在所述用户设备触发所述PDU会话的建立过程之前，所述方法还包括：
    向NRF发送NF管理NF注册请求消息，所述NF管理NF注册请求消息携带所述MBS会话标识和所述MBS会话标识对应的所述MB-SMF的MB-SMF标识，以便将所述MBS会话标识和所述MB-SMF标识关联存储至所述NRF；
    接收所述NRF响应所述NF管理NF注册请求消息而返回的NF管理NF注册响应消息，所述NF管理NF注册响应消息携带所述MB-SMF的MB-SMF标识。
  18. 一种会话管理功能设备，包括：
    一个或多个处理器；
    存储装置，配置为存储一个或多个程序，当所述一个或多个程序被所述一个或多个处理器执行时，使得所述一个或多个处理器实现如权利要求1至11中任一项所述的方法。
  19. 一种多播广播会话管理功能设备，包括：
    一个或多个处理器；
    存储装置，配置为存储一个或多个程序，当所述一个或多个程序被所述一个或多个处理器执行时，使得所述一个或多个处理器实现如权利要求12至17中任一项所述的方法。
  20. 一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，其中，所述计算机程序被处理器执行时，实现如权利要求1至11中任一项所述的方法，或者如权利要求12至17中任一项所述的方法。
  21. 一种计算机程序产品，该计算机程序产品包括计算机指令，该计算机指令存储在计算机可读存储介质中；计算机设备的处理器从计算机可读存储介质读取该计算机指令，处理器执行该计算机指令，使得该计算机设备执行如权利要求1至11中任一项所述的方法或者如权利要求12至17中任一项所述的方法。
PCT/CN2022/073688 2021-02-10 2022-01-25 用于实现多播广播业务切换的方法及相关设备 WO2022170963A1 (zh)

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