WO2022012247A1 - 多播广播业务的通信方法、装置、介质及电子设备 - Google Patents

多播广播业务的通信方法、装置、介质及电子设备 Download PDF

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Publication number
WO2022012247A1
WO2022012247A1 PCT/CN2021/100085 CN2021100085W WO2022012247A1 WO 2022012247 A1 WO2022012247 A1 WO 2022012247A1 CN 2021100085 W CN2021100085 W CN 2021100085W WO 2022012247 A1 WO2022012247 A1 WO 2022012247A1
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Prior art keywords
user plane
mbs
plane node
multicast
node
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PCT/CN2021/100085
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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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Priority to JP2022556242A priority Critical patent/JP7378636B2/ja
Priority to KR1020227035155A priority patent/KR20220152306A/ko
Priority to EP21841515.6A priority patent/EP4099730A4/en
Publication of WO2022012247A1 publication Critical patent/WO2022012247A1/zh
Priority to US17/954,088 priority patent/US20230025793A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/30—Resource management for broadcast services
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/40—Connection management for selective distribution or broadcast
    • 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
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/02—Details
    • H04L12/16—Arrangements for providing special services to substations
    • H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
    • H04L12/189—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast in combination with wireless systems
    • 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
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/12—Setup of transport tunnels

Definitions

  • the present application relates to the field of computer and communication technologies, and in particular, to a communication method, apparatus, medium and electronic device for a multicast broadcast service.
  • the control plane and the user plane are separated, that is, the control plane node and the user plane node are no longer the same network node. In this case, the user plane is established.
  • MBS session transmission tree will face various problems.
  • the embodiments of the present application provide a communication method, apparatus, medium and electronic device for a multicast broadcast service, so that the user plane MBS session transmission can be realized at least to a certain extent under the communication system architecture in which the control plane and the user plane are separated
  • the establishment of the tree can also improve the transmission efficiency of MBS service data.
  • I-SMF Intermediate-Session Management Function, intermediate session management function entity
  • a method for communicating a multicast broadcast service comprising: receiving a first user plane multicast broadcast service MBS session establishment request sent by an intermediate session management function entity I-SMF,
  • the intermediate user plane node can establish a connection with the i-th level user plane node and the user plane functional entity managed by the sub-control plane node;
  • the first interaction unit is configured to send the first interaction unit to the intermediate user plane node.
  • a third interaction unit configured to send a second user plane to an i-th level user plane node selected
  • the plane node sends a second MBS session start request, where the second MBS session start request is used to instruct the sub-control plane node to allocate a sub-user plane node to the intermediate user plane node, and make the sub-user plane node receive the The MBS service data sent by the
  • the second MBS IP multicast transport address and the second C-TEID, the second MBS IP multicast transport address is used for the sub-user plane node of the intermediate user plane node to join the second MBS IP multicast transport address a corresponding multicast transmission group to receive the MBS service data transmitted by the intermediate user plane node through multicast;
  • the processing unit is configured to support receiving the i-th level user plane node through multicast at the intermediate user plane node In the case of the sent MBS service data, join the multicast transmission group corresponding to the first MBS IP multicast transmission address to receive the MBS service data sent by the i-th level user plane node through multicast.
  • a computer-readable medium on which a computer program is stored, and when the computer program is executed by a processor, implements the communication method for a multicast broadcast service described in the foregoing embodiments .
  • an electronic device including: one or more processors; and a storage device for storing 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 made to implement the communication method for a multicast broadcast service as described in the above embodiments.
  • 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 executes the communication methods for multicast broadcasting services provided in the above-mentioned various optional embodiments.
  • the i-th level control plane node selects the I-SMF, and then sends a first MBS session start request to the I-SMF to instruct the I-SMF to establish a user interface with the intermediate user plane node
  • the intermediate user plane node can join the multicast transmission group corresponding to the first MBS IP multicast transmission address assigned by the i-th level user plane node to receive the MBS service data sent by the i-th level user plane node through multicast
  • the I-SMF may send a second MBS session start request to the sub-control plane node provided by the i-th control plane node to instruct the sub-control plane node to allocate the sub-user plane node for the intermediate user plane node, and the intermediate user plane node for the intermediate user plane node.
  • the allocated sub-user plane node may join the multicast transmission group corresponding to the second MBS IP multicast transmission address allocated by the intermediate user plane node to receive the MBS service data sent by the intermediate user plane node. It can be seen that the technical solutions of the embodiments of the present application can realize the establishment of the MBS session transmission tree of the user plane under the communication system architecture in which the control plane and the user plane are separated, and since the intermediate user plane nodes can access the
  • the multicast transmission group corresponding to the first MBS IP multicast transmission address receives the MBS service data sent by the i-th level user plane node through multicast, and the sub-user plane nodes of the intermediate user plane node can be added to the data allocated by the intermediate user plane node.
  • the multicast transmission group corresponding to the second MBS IP multicast transmission address receives the MBS service data sent by the intermediate user plane node in a multicast manner, so the transmission efficiency of the MBS service data can be improved.
  • FIG. 1 shows a schematic diagram of a data transmission flow in a unicast communication system and a multicast communication system
  • FIG. 2 shows a schematic diagram of a multicast context activation process of MBMS
  • Fig. 3 shows the classification schematic diagram of IPv4 network address
  • Fig. 4 shows the structure schematic diagram of the multicast address of IPv4
  • Fig. 5 shows the structure schematic diagram of the multicast address of IPv6
  • Figure 6 shows a schematic structural diagram of an IPv4 header
  • Fig. 7 shows the protocol header format of IGMPv1, the protocol header format of IGMPv2 and the schematic diagram of the format of member report message in IGMPv3;
  • FIG. 8 shows a schematic diagram of the MBMS registration process of the MBMS multicast service
  • Figure 9 shows a schematic diagram of an MBMS session start process
  • Figure 10 shows a schematic diagram of an MBS system architecture
  • FIG. 11 shows a schematic structural diagram of an MBS system
  • FIG. 12 shows a flowchart of a communication method for a multicast broadcast service according to an embodiment of the present application
  • FIG. 13 shows a flowchart of a method for communicating a multicast broadcast service according to an embodiment of the present application
  • FIG. 14 shows a flowchart of a method for communicating a multicast broadcast service according to an embodiment of the present application
  • 16 shows a flowchart of an MBS communication method in which the control plane and the user plane are separated according to an embodiment of the present application
  • Figure 17 shows a schematic diagram of the connection relationship between gNB and 5GC in NG-RAN
  • FIG. 18 shows a flowchart of an MBS communication method in which the control plane and the user plane are separated according to an embodiment of the present application
  • FIG. 19 shows a schematic diagram of a cascaded manner of the technical solutions of the embodiments of the present application.
  • FIG. 20 shows a flowchart of an MBS communication method in which the control plane and the user plane are separated according to an embodiment of the present application
  • FIG. 21 shows a flowchart of an MBS communication method in which the control plane and the user plane are separated according to an embodiment of the present application
  • FIG. 22 shows a flowchart of an MBS communication method in which the control plane and the user plane are separated according to an embodiment of the present application
  • FIG. 23 shows a flowchart of an MBS communication method in which the control plane and the user plane are separated according to an embodiment of the present application
  • FIG. 24 shows a block diagram of a communication apparatus for a multicast broadcast service according to an embodiment of the present application
  • FIG. 25 shows a block diagram of a communication apparatus for a multicast broadcast service according to an embodiment of the present application
  • FIG. 26 shows a block diagram of a communication apparatus for a multicast broadcast service according to an embodiment of the present application
  • Fig. 27 shows a schematic structural diagram of a computer system suitable for implementing the electronic device of the embodiment of the present application.
  • Example embodiments will now be described more fully with reference to the accompanying drawings.
  • Example embodiments can be embodied in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art.
  • the wireless communication systems of 2G (second generation mobile communication technology), 3G (third generation mobile communication technology) and 4G (fourth generation mobile communication technology) support MBMS (Multimedia Broadcast and Multicast Service), this Services are divided into two types: Broadcast (broadcast) and Multicast (multicast).
  • Broadcast Broadcast
  • Multicast Multicast
  • 2G and 3G systems support multicast services
  • 4G systems do not support them in standards
  • 2G, 3G and 4G systems all support broadcast services.
  • unicast is a one-to-one communication.
  • the advantage is that the sender can transmit different content to different receivers, but if the sender needs to transmit the same content to multiple receivers, it needs to end-to-end separately. It is less efficient to transmit multiple copies of the same data.
  • a unicast source sends data to multiple receivers in a unicast manner, it needs to transmit multiple copies of the same data in an end-to-end manner (different line types in Figure 1 represent different data flow).
  • Multicast also known as “multicast” is when a sender transmits the same content to multiple receivers.
  • Online video conferencing and online video-on-demand are especially suitable for multicast, because if unicast is used, there will be as many transmissions as there are receivers, which is obviously extremely inefficient; ,
  • the broadcast mode of all sending although the data can be transmitted at one time, it cannot achieve the purpose of distinguishing specific data recipients. It can be seen that, by using the multicast method, the same data can be sent to multiple receivers at one time, and the purpose of transmitting data only to a specific object can be achieved.
  • a multicast source can send the same data to multiple receivers at one time.
  • Broadcasting also transmits the same content to multiple recipients, but does not select the recipients during transmission, so there may be unnecessary devices that also transmit data, resulting in a waste of network resources.
  • some receivers may not be “interested” in the content of the broadcast, so after receiving the content of the broadcast, they have to discard the received data packets, which also results in a waste of terminal resources.
  • the fundamental difference between the broadcast service and the multicast service is that all UEs (User Equipment, user equipment) in the system can participate in the broadcast service without signing a contract, while the UE of the multicast service can participate only after signing a contract and being authenticated.
  • the UE joins the multicast group of the corresponding service through the IP multicast address.
  • the broadcast service corresponding to a broadcast group has its specific service area.
  • the MBMS multicast context activation process is defined in Section 8.2 of TS23.246 of the 3GPP (3rd Generation Partnership Project) protocol, as shown in Figure 2, including the following steps:
  • Step S201 the UE selects an APN (Access Point Name, access point name) to establish a PDP (Packet Data Protocol, packet data protocol) context (Context), and then assigns an Internet Protocol (IP) address to the UE, in order to facilitate subsequent Described, the APN selected by the UE in this step is identified by APN0.
  • APN Access Point Name, access point name
  • PDP Packet Data Protocol, packet data protocol
  • IP Internet Protocol
  • Step S202 the UE selects an IP Multicast Address (the IP multicast address is used to identify a multicast service), and then sends an IGMP joint (Join) data packet to the GGSN (Gateway GPRS Support Node, gateway GPRS support node) to indicate the UE To join this multicast group.
  • IP Multicast Address the IP multicast address is used to identify a multicast service
  • IGMP joint Join
  • Step S203 the GGSN sends an MBMS authorization request to the BM-SC (Broadcast Multicast Service Center, Broadcast Multicast Service Center), and receives an MBMS authorization response fed back by the BM-SC.
  • the BM-SC verifies whether the UE can join the multicast group according to the subscription data of the UE. If it is confirmed that the UE can join the multicast group, the APN (the APN that the UE will use to join the multicast group) is given in the MBMS authorization response.
  • the APN is identified by APN1), and then the APN1 to be used by the UE is delivered to the UE through steps S204a, S204b, and S205.
  • Step S206 the UE initiates a new MBMS session (Session) according to the APN1 provided by the BM-SC, that is, sends a request for activating the MBMS context, and the request for activating the MBMS context includes IP Multicast Address, APN1 and the MBMS capability of the UE.
  • the MBMS capability may be, for example, a QoS (Quality of Service, quality of service) capability.
  • Step S207 the SGSN (Serving GPRS Support Node, Serving GPRS Support Node) verifies whether the UE has subscribed to APN1, if the verification fails, the SGSN sends an MBMS notification rejection request to the GGSN, and the GGSN sends a notification rejection response to the MBMS.
  • the subscription data of the UE is stored in the HSS (Home Subscriber Server, Home Subscriber Server), and the interaction process between the SGSN and the HSS is not shown in FIG. 2 .
  • the specific process of step S208 and step S209 in FIG. 2 please refer to the MBMS context activation process defined in Section 8.2 of TS23.246.
  • Step S210 if the SGSN checks that the UE passes, then the SGSN selects another GGSN (that is, a GGSN that supports the Multicast service) according to APN1, and sends a request message for creating an MBMS context to the GGSN, which contains the ID of the UE, UE Location ID, IP Multicast Address, APN1 and UE access information (such as 2G or 3G).
  • GGSN that is, a GGSN that supports the Multicast service
  • the ID of the UE can be IMSI (International Mobile Subscriber Identity, International Mobile Subscriber Identity) or MSISDN (Mobile Station International Integrated Service Digital Network Number, Mobile Station International Integrated Service Digital Network Number).
  • the UE location (Location) ID may be a RAT (Radio Access Technology, radio access technology) ID or a CGI (Common Gateway Interface, public gateway interface) or a SAI (Service Area Identity, service area identifier) and the like.
  • Step S211 the GGSN sends an MBMS authorization request to the BM-SC, and the BM-SC authorizes the UE according to the subscription information of the UE, and feeds back the MBMS authorization response to the GGSN.
  • Step S212 if the authorization allows access, and there is no context of any UE indicated by the IP Multicast Address on the GGSN, that is, the UE is the first to access the multicast service identified by the IP Multicast Address on the GGSN, then to its superior node.
  • the BM-SC is registered to indicate that the multicast service data sent to the IP multicast Address subsequently needs to be sent to this GGSN. (Note that different UEs may select different GGSNs, so when the BM-SC sends multicast data down, it needs to send the same multicast data to these GGSNs at the same time).
  • Step S213 the GGSN creates an MBMS UE context corresponding to the IP Multicast Address of the UE, and then sends a Create MBMS Context Response to the SGSN to indicate that the MBMS context is successfully created.
  • Step S214 similar to step S212, if there is no context of any UE indicated by the IP Multicast Address on the SGSN, that is, the UE is the first to access the multicast service identified by the IP Multicast Address on the SGSN, then the upper node GGSN will be sent to the GGSN. Register to indicate that the multicast service data sent to the IP multicast Address subsequently needs to be sent to this SGSN. (Note that different UEs may select different SGSNs, so when the GGSN sends multicast data downward, it needs to send the same multicast data to these SGSNs at the same time).
  • step S215 For the specific process from step S215 to step S217 in FIG. 2 , please refer to the MBMS context activation process defined in Section 8.2 of TS23.246.
  • the 2G or 3G UE first establishes a PDP Context through APN0, assigns an IP address, and then sends an IGMP Join packet to the network with this IP address.
  • the GGSN will intercept this IGMP data packets, and then send a signaling (ie, MBMS authorization request) to the MB-SC, and then the BM-SC allocates an APN1 to the UE, and then the UE sends a request MBMS context activation message with this APN1, so as to activate an MBMS context.
  • IP multicast address may be an IPv4 multicast address or an IPv6 multicast address.
  • IPv4 network addresses are divided into class A addresses, class B addresses, class C addresses, class D addresses, and class E addresses.
  • the first byte (8 bits) in the class A address is the network number, and the other 3 bytes (24 bits) are the host number.
  • the range of the class A address is: 0.0.0.0 to 127.255.255.255.
  • the first byte and the second byte in the class B address are the network number, and the other two bytes are the host number.
  • the range of the class B address is: 128.0.0.0 to 191.255.255.255.
  • the first 3 bytes in the class C address are the network number, and the fourth byte is the host number.
  • the range of the class C address is: 192.0.0.0 to 223.255.255.255.
  • Class D addresses are multicast addresses.
  • the first 4 bits of this class address are "1110".
  • the range of class D addresses is: 224.0.0.0 to 239.255.255.255.
  • Class E addresses are reserved addresses.
  • the first 5 bits of this class address are "11110".
  • the range of class E addresses is: 240.0.0.0 to 247.255.255.255.
  • IPv4 multicast addresses can have three structures, which are respectively applicable to Well-Known multicast addresses, Globally-Scoped multicast addresses and local scopes. (Locally-Scoped) multicast address.
  • the structure of an IPv6 multicast address is shown in Figure 5.
  • the first byte (8 bits) indicates that the address is a multicast address, the next 4 bits are the Flag field, and the next 4 bits are the range (Scope) field, the last 112-bit group identifier (Group ID).
  • the first bit of the flag bit field is 0, which is reserved for future use; the second bit indicates whether the multicast address is embedded with RP (Rendezvous Point, aggregation point), RP is the specified multicast stream in the multicast network. For example, when the value of the second bit is 0, it means that the aggregation point is not embedded, and when the value of the second bit is 1, it means that the aggregation point is embedded.
  • the third bit of the flag field indicates whether prefix information is embedded in the multicast address. For example, when the third bit value is 0, it means that the prefix information is not embedded, and when the third bit value is 1, it means that the prefix information is embedded. prefix information.
  • the last bit of the flag field indicates whether the multicast address is a permanently assigned multicast address (permanently assigned address) or a temporary multicast address (transient multicast address). When the last bit value is 1, it means it is a temporary multicast address.
  • the multicast address can only be used as the destination IP address (that is, the destination IP address in the IP header), and the multicast address cannot be used as the source IP address.
  • the multicast data packets are all sent down by the network side to the UE, that is, the multicast data packets are all DL (Downlink, downlink) data packets, and the UE Data cannot be sent to the network side through the corresponding multicast address. That is to say, the UE cannot use the multicast address as the destination IP address to send an uplink IP packet, that is, there is no UL (Uplink, uplink) multicast data.
  • IP packet transmitted in the network is composed of IP header and data.
  • the structure of IPv4 header is shown in Figure 6, which mainly includes: “version” field, "header length” field, “service type” field, “total length” field. " field, “Identity” field, “Flag” field, “Slice Offset” field, “Time to live” field, "Protocol” field, "Header Checksum” field, "Source Address” field, “Destination Address” field , "Optional Fields”.
  • the "version” field occupies 4 bits, and refers to the version of the IP protocol, for example, the version number is 4 (ie, IPv4).
  • the "Header Length” field occupies 4 bits.
  • the "Service Type” field occupies 8 bits and is used to obtain better service.
  • the "total length” field occupies 16 bits and refers to the length of the sum of the header and data.
  • the "Identity” field occupies 16 bits and is a counter used to generate the datagram's identity.
  • the "slice offset” field occupies 12 bits, and refers to the relative position of a certain slice in the original packet after the longer packet is fragmented.
  • the "Time To Live” field is TTL (Time To Live), which occupies 8 bits.
  • the TTL field is a field initially set by the sender.
  • the "protocol” field occupies 8 bits and is used to indicate which protocol the data carried in this datagram uses.
  • the value of "1" indicates that it is the ICMP (Internet Control Message Protocol, Internet Control Message Protocol) protocol; the value is "2" Indicates IGMP protocol; a value of "6” indicates a TCP (Transmission Control Protocol) protocol; a value of "17” indicates a UDP (User Datagram Protocol) protocol; a value of "50” indicates It is an ESP (Encapsulating Security Payload, encapsulating security payload) protocol; a value of "51” indicates an AH (Authentication header, authentication header) protocol.
  • the "header checksum” field occupies 16 bits, only the header of the datagram is checked, and the data part is not checked.
  • the "source address” field and the “destination address” field occupy 4 bytes respectively, and are used to record the source address and the destination address respectively.
  • IGMPv1 For the IGMP protocol mentioned above, there are three protocol versions, namely IGMPv1, IGMPv2 and IGMPv3, and the corresponding standards are RFC1054, RFC2236 and RFC3376 respectively.
  • the protocol header format of IGMPv1 and the protocol header format of IGMPv2 are shown in Figure 7.
  • the protocol header of IGMPv1 includes a 4-bit IGMP version field and a 4-bit IGMP message type field (the value of this field is 1 means yes Host Membership Query, that is, the host member query type; a value of 2 means Host Membership Report, that is, the host member report type), 8-bit unused field (this field is filled with 0 when sending, and ignored when receiving), 16-bit IGMP Checksum field (this checkword is calculated and inserted into this field when a message is transmitted; when a packet is received, this field is checked before processing the packet), and a 32-bit multicast address field.
  • the protocol header of IGMPv2 includes an 8-bit message type field, an 8-bit maximum response time field, a 16-bit IGMP checksum field, and a 32-bit multicast address field.
  • IGMPv2 the old 4-bit version field and the old 4-bit type field are combined into a new 8-bit type field.
  • the type codes are set to 0x11 and 0x12 to maintain backward compatibility with the IGMP version 1 and version 2 packet formats.
  • the maximum response time field in the protocol header of IGMPv2 is used to indicate the maximum time (in units of 1/10 second) before sending a response report, and the default value is 10 seconds. Similar to IGMPv1, when a message is transmitted, the checksum is calculated and filled in the checksum field in the protocol header of IGMPv2. When a message is received, the checksum is checked before the message is processed to determine whether the IGMP message is in the Whether an error occurred during the transfer.
  • the IGMP Join data packet shown in Figure 2 is realized by the Membership Report message of IGMP.
  • the destination IP address in the IP packet of the IGMP Joint message is not the IP multicast address to be joined, but the IP multicast address to be joined is included in the parameters of the message.
  • Section 8.4 of the standard TS23.246 defines the MBMS registration process applicable to the MBMS multicast service, as shown in Figure 8, including the following steps: Step S801, the RNC (Radio Network Controller, Radio Network Controller) sends the MBMS registration to the SGSN Step S802, the SGSN sends an MBMS registration request to the GGSN; Step S803, the GGSN sends an MBMS registration request to the BM-SC; Step S804, the BM-SC feeds back the MBMS registration response to the GGSN, and can perform the MBMS session start process at the same time; Step S805, The GGSN feeds back the MBMS registration response to the SGSN, and at the same time can perform the MBMS session start process; in step S806, the SGSN feeds back the MBMS registration response to the RNC, and at the same time can perform the MBMS session start process.
  • Step S801 the RNC (Radio Network Controller, Radio Network Controller) sends the MBMS registration to the
  • the main function of the MBMS registration process is to form a signaling tree that controls bearer establishment (MBMS Bearer Context) from top to bottom. Since the control plane and the user plane are not separated in the 2G and 3G standards, forming a transmission tree carrying the MBMS control plane on the control plane is equivalent to establishing a top-to-bottom MBMS-bearing transmission tree (note that MBMS The transport tree of the bearer is established using the MBMS Session Start procedure). In addition, since 4G does not support multicast services, there is no MBMS registration process in the 4G standard.
  • Section 8.3 of the standard TS23.246 defines the MBMS session start process, as shown in Figure 9, including the following steps: Step S901, the BM-SC sends an MBMS session start request to the GGSN, and the GGSN feeds back the MBMS session start response to the BM-SC; Step S902, the GGSN sends an MBMS session start request to the SGSN, and then the SGSN feeds back the MBMS session start response to the GGSN; Step S903, the SGSN sends an MBMS session start request to the BSC (Base Station Controller, base station controller)/RNC, and then the BSC/ The RNC feeds back the MBMS session start response to the SGSN; in step S904, the MBMS session initiation process is performed between the UE and the RSC/RNC; in step S903a, the BSC/RNC sends an IGMPv3 member report message.
  • Step S901 the BM-SC sends an MBMS session start request to
  • the MBMS registration process and the MBS session start process are both Per IP Multicast (each IP multicast) process, which is to establish a top-to-bottom MBMS control plane for this IP Multicast
  • the signaling tree of the bearer context is the same as a transport tree of the MBMS bearer from top to bottom, not Per UE Per IP Multicast.
  • the MBS session start process is a Per IP Broadcast (each IP broadcast) process, which establishes a top-to-bottom MBMS bearer context for the control plane of this IP Broadcast.
  • the signaling tree is the same as a top-to-bottom MBMS bearer transmission tree, rather than Per UE Per IP Broadcast.
  • part of the MBMS registration process may be performed together, such as steps S212 and S214 shown in FIG. 2 , but This is only performed when the first UE in the SGSN and GGSN activates the IP Multicast service.
  • steps S212 and S214 shown in FIG. 2 .
  • an important function is to form the transmission tree of the user plane of the multicast service and the broadcast service, so as to prevent the formation of the transmission ring of the user plane (that is, there are multiple different paths when reaching a certain node).
  • the transmission path but also to prevent the occurrence of MBMS fragmentation (that is, the occurrence of a node without downstream nodes).
  • GGSN does not define Pool in the standard, in actual deployment, there is a GGSN Pool to provide high reliability of the system.
  • BSC/RNC access the same BSC/RNC and activate the same MBMS IP Multicast
  • they may be selected by the BSC/RNC to different SGSNs in the same SGSN Pool.
  • APNs used by these UEs are the same, different SGSNs in the same SGSN Pool will select different GGSNs, but the SGSNs may be connected to the same GGSN.
  • the 3GPP standard stipulates that when the RNC uses the Iu interface, it is allowed to choose to use the SGSN Pool, and for the MBMS, the GGSN needs to use the GTP-U (GPRS Tunneling Protocol-User plane, CPRS Tunneling Protocol User plane) to directly connect to the RNC , the user plane is not allowed to pass through the SGSN. In this way, even if different users on the same RNC use the same APN and IP Multicast and select different SGSNs, their user planes are ultimately the same, and there will not be multiple different user planes.
  • GTP-U GPRS Tunneling Protocol-User plane, CPRS Tunneling Protocol User plane
  • the standard TS23.236 defines that the BSC/RNC rejects the MBMS session start request messages of other SGSNs to achieve only the A user plane.
  • the SGSN can only select one GGSN to establish a bearer plane, thereby preventing the occurrence of MBMS transmission loops.
  • the BSC/RNC rejects the establishment of the bearer plane of an SGSN, it may cause the SGSN to have no downstream nodes.
  • the SGSN has to use the DeRegistration (deregistration) technology (for details, please refer to Section 8.6.0 of the standard TS23.236). ) to delete itself from the downstream nodes of the GGSN, so as to prevent the GGSN from sending MBMS multicast data to the SGSN, but the SGSN cannot transmit down, and avoid MBMS transmission breakage.
  • the SGSN refuses the establishment of the bearer plane of the GGSN, it may cause the GGSN to have no downstream nodes. In this case, the GGSN has to use the DeRegistration technology to delete itself from the downstream nodes of the BM-SC, thereby preventing the The SC sends MBMS multicast data to the GGSN to avoid MBMS transmission breakage.
  • any node has a downstream node. If a node has no downstream nodes, the node should leave the transport tree (corresponding to the DeRegistration procedure). For example, when all MBMS UEs under a base station move to other base stations, the base station needs to perform DeRegistration operation to the SGSN; when all MBMS connected base stations under an SGSN perform DeRegistration operation, the SGSN needs to perform DeRegistration operation to the GGSN; When all MBMSs under a GGSN are connected to the SGSN to perform the DeRegistration operation, the GGSN needs to perform the Deregistration operation to the BM-SC.
  • the transmission path of MBMS services is a tree structure, and each parent node is under one or more child nodes, the bearing between the parent node and the child node can be based on the relationship between the parent node and the child node.
  • GTP Tunnel GTP Tunnel
  • the parent node can assign a local IP Multicast address (this address is not the Multicast address in the MBMS Multicast service), and the IP Multicast address of the transport layer is used for the child node ( Efficient transmission of MBMS service data between the base station) and the parent node (such as the MBMS GW or GGSN).
  • the parent node only needs to send the MBMS service data through the multicast address of the transport layer, and all child nodes can receive the MBMS service data, thus greatly reducing the data processing volume of the parent node.
  • the parent node needs to assign a local IP Multicast transport layer address. After the child node receives the IP Multicast transport layer address assigned by the parent node, it needs to join the transmission through the IGMP Join process. Layer multicast group. Because some sub-nodes do not support multicast, some sub-nodes may use transport layer multicast to receive MBMS service data, and other sub-nodes use point-to-point GTP tunnel mode. Allocate the IP address and TEID of the downstream GTP-U. Of course, if the parent node finds that the number of child nodes is relatively small, it can also decide not to use the multicast transmission method.
  • the network nodes Since the control plane and the user plane are not separated in the MBMS system, that is, the network nodes contain both the user plane and the control plane functions. Therefore, when a network node does not support the multicast transmission technology, it directly replies with a GTP-U IP address. and TEID, the parent node can know that this node does not support multicast transmission. However, in the 5G MBS system, the control plane and the user plane are separated, and the control plane and the user plane are no longer the same network node. In this case, establishing an MBS session transmission tree will face various problems.
  • the latest 5G MBS research report defines two system architectures as shown in Figure 10 and Figure 11.
  • the system architecture shown in Figure 10 is to superimpose functions on the current 5G architecture, that is, without modifying the current 5G architecture.
  • 5G MBS services are supported by enhancing the functions and interfaces of the 5G architecture.
  • the advantage of this architecture is that 5G MBS can be supported through software upgrades.
  • the system architecture shown in Figure 11 is a brand new architecture, that is, adding some new network function nodes while the current 5G architecture remains unchanged.
  • NG-RAN Next Generation Radio Access Network
  • AMF Access and Mobility Management Function, access and mobility management function
  • UDM Unified Data Management, unified data management
  • UDR User Data Repository, user data warehouse
  • NEF Network Exposure Function, network open function
  • PCF PCF
  • SMF in Figure 10 is Session Management Function, namely session management function; UPF is User Plane Function, namely user plane function; AF is Application Function, namely application function.
  • MB-UPF in Figure 11 is Multicast/Broadcast-UPF; MB-SMF is Multicast/Broadcast-SMF; MBSU is Multicast/Broadcast Service User Plane (multicast/broadcast service user plane); MBSF is Multicast/Broadcast-SMF Broadcast Service Function (multicast broadcast business entity).
  • FIG. 12 shows a flowchart of a method for communicating a multicast broadcast service according to an embodiment of the present application.
  • the method for communicating the multicast broadcast service can be performed by the I-SMF, and the method for communicating the multicast broadcast service at least includes: Steps S1210 to S1230 are described in detail as follows:
  • a first MBS session start request sent by the i-th level control plane node in the MBS session transmission tree is received, where the first MBS session start request includes the information of the sub-control plane node provided by the i-th level control plane node. information, the identification information of the i-th level user plane node selected by the i-th level control plane node, the first MBS IP multicast transmission address allocated by the i-th level user plane node, and the first MBS IP multicast transmission address for transmitting MBS service data by multicast.
  • a C-TEID, i 1,...,N, where N is a positive integer.
  • the i-th level control plane node may select one or more user plane functional entities from the managed user plane functional entities as the first i-level user plane node.
  • the i-th level control plane node determines, according to the information of the sub-control plane nodes of the i-th level control plane node, that the user plane functional entity managed by the i-th level control plane node cannot communicate with the sub-control plane nodes of the i-th level control plane node.
  • the managed user plane functional entity establishes a transmission path, then an SMF capable of communicating with the i-th level control plane node and the sub-control plane nodes of the i-th level control plane node can be selected as the I-SMF.
  • the i-th level control plane node can select an I-SMF, which needs to be able to communicate with the i-th level control plane node and with the I-SMF.
  • the child control plane nodes of the i-th level control plane node communicate with each other.
  • the i-th level control plane node may perform a user plane MBS session establishment process with the i-th level user plane node, that is, to the i-th level user plane node.
  • Send the user plane MBS session establishment request and receive the user plane MBS session establishment response fed back by the i-th level user plane node, and then obtain the i-th level user plane node from the user plane MBS session establishment response fed back by the i-th level user plane node.
  • the assigned first MBS IP multicast transport address and the first C-TEID is the assigned to the i-th level user plane node.
  • the i-th level control plane node After the i-th level control plane node determines the information, it sends the above-mentioned first MBS session start request to the selected I-SMF, and adds these information to the first MBS session start request, that is, the i-th level is added.
  • an intermediate user plane node is selected according to the information of the i-th level control plane node and the information of the sub-control plane nodes provided by the i-th level control plane node.
  • the user plane functional entities managed by the sub-control plane nodes of the i-level control plane nodes establish connections.
  • the information of the i-th level control plane node may include the service area of the i-th level control plane node
  • the information of the sub-control plane nodes provided by the i-th level control plane node may include the i-th level control plane
  • the service area of the sub-control plane node provided by the node, the I-SMF selects the user plane function entity that can be managed by the i-th level user plane node and the sub-control plane node provided by the i-th level control plane node according to this information
  • step S1230 send a first user plane MBS session establishment request to the intermediate user plane node, and receive a first user plane MBS session establishment response fed back by the intermediate user plane node, where the first user plane MBS session establishment request includes the first user plane MBS session establishment request.
  • An MBS IP multicast transport address and a first C-TEID the first MBS IP multicast transport address is used to enable the intermediate user plane node to join the multicast transport group corresponding to the first MBS IP multicast transport address to receive the i-th level MBS service data sent by user plane nodes through multicast.
  • the I-SMF sends the data to the intermediate user plane node.
  • the first user plane MBS session establishment request includes indication information requesting to allocate an F-TEID to the intermediate user plane node.
  • the first user plane MBS session establishment response fed back by the intermediate user plane node includes the intermediate user plane.
  • the F-TEID allocated by the plane node, the F-TEID is used to enable the intermediate user plane node to receive the MBS service data sent by the i-th level user plane node in a point-to-point manner.
  • the intermediate user plane node may indicate through the first user plane MBS session establishment response that the intermediate user plane node does not support multicast, but supports receiving the i-th level user plane node through point-to-point mode
  • the sent MBS service data includes the F-TEID allocated by the intermediate user plane node.
  • the first MBS session start request sent by the I-SMF to the intermediate user plane node includes each The respective identification information of the i-th level user plane node, the first MBS IP multicast transmission address and the first C-TEID allocated by each i-th level user plane node.
  • the first MBS IP multicast transmission addresses allocated by different i-th level user plane nodes are different.
  • a second MBS session start request is sent to the sub-control plane node provided by the i-th level control plane node to indicate that the sub-control plane node provided by the i-th level control plane node is an intermediate user
  • the plane node assigns a sub-user plane node
  • the second MBS session start request includes the identification information of the intermediate user plane node, and the second MBS IP multicast transmission address and the second C-TEID assigned by the intermediate user plane node.
  • the second MBS IP multicast transport address is used to enable the sub-user plane node to join the multicast transport group corresponding to the second MBS IP multicast transport address to receive the MBS service data sent by the intermediate user plane node through multicast.
  • the I-SMF may obtain the second MBS IP multicast transmission address and the second C- TEID.
  • the first user plane MBS session establishment request sent by the I-SMF to the intermediate user plane node includes instruction information for instructing the intermediate user plane node to allocate new MBS IP multicast distribution information, and the intermediate user plane node feeds back
  • the first user plane MBS session establishment response of the I-SMF contains the second MBS IP multicast transmission address and the second C-TEID allocated by the intermediate user plane node.
  • the I-SMF after sending the second MBS session start request to the sub-control plane node provided by the i-th level control plane node, the I-SMF also needs to receive the sub-control plane node provided by the i-th level control plane node
  • the second MBS session start response fed back to the second MBS session start request includes the first indication information.
  • the content included in the first indication information may include the following situations:
  • the first indication information includes the identification information of the intermediate user plane node, the first F-TEID list information, and the first field information used to indicate that multicast transmission is started,
  • the first field information indicates that there is a sub-user plane node that supports receiving MBS service data sent by the intermediate user plane node through multicast among the sub-user plane nodes allocated by the sub-control plane node provided by the i-th level control plane node to the intermediate user plane node.
  • the first F-TEID list information contains the F-TEID of the sub-user plane node that does not support multicasting but supports receiving MBS service data sent by the intermediate user plane node in a point-to-point manner, and the F-TEID is used for
  • the sub-user plane nodes of the intermediate user plane node receive the MBS service data sent by the intermediate user plane node in a point-to-point manner.
  • the first indication information includes the identification information of the intermediate user plane node, and does not include the above-mentioned first F-TEID list information and the above-mentioned first field information, in this case , the first indication information is used to instruct that the sub-control plane nodes provided by the i-th control plane node and the sub-user plane nodes allocated to the intermediate user plane nodes all support receiving MBS service data sent by the intermediate user plane nodes through multicast.
  • the first indication information includes the identification information of the intermediate user plane node, the above-mentioned first F-TEID list information, and does not include the above-mentioned first field information, in this case , the first indication information is used to indicate that the sub-control plane nodes provided by the i-th level control plane nodes are all sub-user-plane nodes allocated by the intermediate user-plane nodes that do not support multicasting, but support receiving intermediate user-plane nodes in a point-to-point manner. Sent MBS service data.
  • the first indication information includes the identification information of the intermediate user plane node and the field information for disabling multicast transmission, and does not include the above-mentioned first F-TEID list information.
  • the first indication information is used to indicate that the sub control plane node provided by the i-th level control plane node does not allocate a sub user plane node to the intermediate user plane node.
  • the field information for disabling multicast transmission may be setting the value of Multicast Enable to Disable.
  • the second MBS session start response fed back by the sub-control plane node provided by the i-th level control plane node to the I-SMF includes: There is a first indication information list, and the first indication information list includes first indication information corresponding to all intermediate user plane nodes respectively.
  • the second MBS session start response fed back by the sub-control plane node of the i-th control plane node to the I-SMF may also include a list of failed identification information, and the failed identification information list is used to the target intermediate user plane node indicating no sub-user plane node is assigned.
  • the I-SMF determines, according to the second MBS session start response fed back by the sub-control plane node of the i-th control plane node, that there is a target intermediate user plane node that is not assigned a sub-user plane node, then Send a user plane MBS session deletion request to the target intermediate user plane node.
  • the technical solution of this embodiment is to delete the broken branch in the transmission tree of the MBS session on the user plane.
  • the I-SMF may also receive a user plane MBS session fed back by the target intermediate user plane node Deletion response, the user plane MBS session deletion response is sent by the target intermediate user plane node after receiving the user plane MBS session deletion request, wherein, if the target intermediate user plane node has joined the first MBS IP multicast transmission address corresponding to the multicast address.
  • the multicast transmission group after receiving the user plane MBS session deletion request, exit the multicast transmission group corresponding to the first MBS IP multicast transmission address.
  • the I-SMF receives the second feedback respectively fed back by all the sub-control plane nodes provided by the i-th level control plane node. After the MBS session starts to respond, it is then determined whether there is a target intermediate user plane node that has not been assigned a sub-user plane node, so as to avoid the response to the second MBS session that has received feedback from part of the sub-control plane nodes. There is a deviation in the judgment of the target intermediate user plane node of the plane node.
  • the I-SMF may respond to the second MBS session according to the second MBS session
  • the start response determines the method by which the intermediate user plane node transmits the MBS service data to the sub-user plane nodes of the intermediate user plane node respectively.
  • the I-SMF sends the information to the intermediate user plane node according to the identification information of the intermediate user plane node contained in the first indication information.
  • the user plane node sends a user plane MBS session modification request to instruct the intermediate user plane node to transmit MBS service data to sub-user plane nodes corresponding to each F-TEID included in the first F-TEID list information in a point-to-point manner.
  • the user plane MBS session modification request is further used to instruct the intermediate user plane node to simultaneously use multicast transmission to the child user plane nodes of the intermediate user plane node Sending MBS service data; if the first indication information does not contain the above-mentioned first field information, the user plane MBS session modification request is also used to indicate that the intermediate user plane node does not need to use multicast transmission to transmit to the child of the intermediate user plane node. The user plane node sends MBS service data.
  • the intermediate user plane node can transmit MBS service data to all sub-user plane nodes of the intermediate user plane node through multicast transmission.
  • the I-SMF may, according to the first indication information corresponding to each intermediate user plane node included in the second MBS session start response, , and send the user plane MBS session modification request to the intermediate user plane node that needs to send the user plane MBS session modification request.
  • some sub-user plane nodes of an intermediate user plane node do not support the multicast mode, but support the point-to-point mode
  • Receiving the MBS service data sent by the intermediate user plane node indicates that the intermediate user plane node is an intermediate user plane node that needs to send a user plane MBS session modification request.
  • the I-SMF can also use the second MBS session according to the second MBS session start response. Start response, and feed back the first MBS session start response for the first MBS session start request to the i-th level control plane node. If the i-th level control plane node provides at least two sub-control plane nodes, then the I-SMF needs to send the second MBS session start response to the feedback from all sub-control plane nodes provided by the i-th level control plane node. The i-th level control plane node feeds back the first MBS session start response.
  • the first MBS session start response fed back by the I-SMF to the i-th level control plane node contains second indication information.
  • the content contained in the second indication information may be in the following situations:
  • the second indication information includes the identification information of the i-th level user plane node, the second F-TEID list information, and the second field used to indicate that multicast transmission is started information
  • the second field information indicates that there is an intermediate user plane node that supports receiving MBS service data sent by the i-th level user plane node through multicast
  • the second F-TEID list information includes information that does not support multicast, but Supports the F-TEID of the intermediate user plane node that receives the MBS service data sent by the i-th user plane node in a point-to-point manner.
  • the F-TEID is used to enable the intermediate user plane node to receive the data sent by the i-th user plane node through MBS business data.
  • the second indication information includes the identification information of the i-th level user plane node, and does not include the above-mentioned second F-TEID list information and the above-mentioned second field information.
  • the second indication information is used to indicate that all intermediate user plane nodes support receiving MBS service data sent by the i-th level user plane node through multicast.
  • the second indication information includes the identification information of the i-th level user plane node, the above-mentioned second F-TEID list information, and does not include the above-mentioned second field information, in this case
  • the second indication information is used to indicate that none of the intermediate user plane nodes support the multicast mode, but support to receive the MBS service data sent by the i-th level user plane node in the point-to-point mode.
  • the first MBS session start response fed back by the I-SMF to the level i control plane node includes the following: A second indication information list, where the second indication information list includes the second indication information corresponding to all the i-th level user plane nodes respectively.
  • FIG. 12 illustrates the communication method of the multicast broadcast service according to the embodiment of the present application from the perspective of the I-SMF.
  • the following describes the communication method of the multicast broadcast service according to the embodiment of the present application from the perspective of the i-th control plane node with reference to FIG. 13 . Further explanation:
  • FIG. 13 shows a flowchart of a method for communicating a multicast broadcast service according to an embodiment of the present application, and the method for communicating the multicast broadcast service may be performed by an i-th level control plane node, for example, the SMF in FIG. 10 .
  • the communication method of the multicast broadcast service includes at least steps S1310 to S1320, and the details are as follows:
  • step S1310 send a second user plane MBS session establishment request to the i-th level user plane node selected by the i-th level control plane node, and receive a second user plane MBS session establishment response fed back by the i-th level user plane node, the
  • the i-th level control plane node may select one or more user plane functional entities from the managed user plane functional entities as the first i-level user plane node.
  • the i-th level control plane node may perform a user plane MBS session establishment process with the i-th level user plane node, that is, send a second user plane MBS session establishment request to the i-th level user plane node , and receive the second user plane MBS session establishment response fed back by the i-th user plane node, and then obtain the allocated The first MBS IP multicast transport address and the first C-TEID.
  • step S1320 an intermediate session management function entity I-SMF is selected, and a first MBS session start request is sent to the I-SMF, where the first MBS session start request includes the information of the sub-control plane node provided by the i-th control plane node. information, the identification information of the i-th level user plane node, the first MBS IP multicast transmission address and the first C-TEID allocated by the i-th level user plane node.
  • the first MBS session start request is used to trigger the I-SMF to select a user plane function entity that can be managed with the i-th level user plane node and the sub-control plane node provided by the i-th level control plane node
  • the intermediate user plane node that establishes the connection and is used to trigger the I-SMF to send a second MBS session start request to the sub-control plane node provided by the i-th control plane node, where the intermediate user plane node is used to join the first MBS IP multicast transmission
  • the multicast transmission group corresponding to the address is used to receive the MBS service data sent by the i-th level user plane node through multicast, and the second MBS session start request is used to indicate that the sub-control plane node provided by the i-th level control plane node is an intermediate user
  • the plane node allocates a sub-user plane node, and enables the sub-user plane node to receive the MBS service data sent by the intermediate user plane node.
  • the first MBS session start request sent by the level i control plane node to the I-SMF includes A list of child control plane nodes may be included, and the list includes information of all child control plane nodes provided by the i-th level control plane node.
  • the purpose of selecting the intermediate session management function entity I-SMF by the i-th level control plane node is: if the i-th level control plane node determines that the user plane function entity managed by the i-th level control plane node cannot communicate with The user plane functional entity managed by the sub-control plane node of the i-th level control plane node establishes a transmission path, then the SMF that can communicate with the i-th level control plane node and the sub-control plane node of the i-th level control plane node can be selected as the I-SMF.
  • This method makes it impossible to establish a directly connected user plane between the i-th level user plane node and the downstream user plane node (usually the base station or the distributed unit (DU) of the base station) during the establishment of the user plane MBS session.
  • the I-SMF can be inserted, and then the I-SMF can select an intermediate user plane node to complete the establishment of the user plane MBS session transmission tree, effectively realizing the optimization of the user plane transmission resources.
  • the i-th control plane node may further receive the first MBS session start feedback from the I-SMF for the first MBS session start request In response, in this case, the i-th level control plane node may determine whether to send a user plane MBS session modification request to the i-th level user plane node according to the content contained in the first MBS session start response.
  • a user plane MBS session modification request needs to be sent to the i-th level user plane node.
  • FIG. 13 illustrates the communication method of the multicast broadcast service according to the embodiment of the present application from the perspective of the i-th control plane node.
  • the following describes the communication method of the multicast broadcast service according to the embodiment of the present application from the perspective of the intermediate user plane node with reference to FIG. 14 .
  • FIG. 14 For further clarification:
  • FIG. 14 shows a flowchart of a method for communicating a multicast broadcast service according to an embodiment of the present application.
  • the method for communicating the multicast broadcast service may be performed by an intermediate user plane node, such as the UPF in FIG. 10 or FIG. 11 .
  • the MB-UPF in the multicast broadcast service includes at least steps S1410 to S1430, and the details are as follows:
  • a first user plane MBS session establishment response is fed back to the I-SMF, where the first user plane MBS session establishment response includes the second MBS IP multicast transmission address and the second C- TEID, the second MBS IP multicast transmission address is used for the sub-user plane node of the intermediate user plane node to join the multicast transmission group corresponding to the second MBS IP multicast transmission address to receive the information transmitted by the intermediate user plane node through multicast.
  • MBS business data is used for the sub-user plane node of the intermediate user plane node to join the multicast transmission group corresponding to the second MBS IP multicast transmission address to receive the information transmitted by the intermediate user plane node through multicast.
  • step S1430 if the intermediate user plane node supports receiving the MBS service data sent by the i-th level user plane node through multicast, join the multicast transmission group corresponding to the first MBS IP multicast transmission address to receive the i-th level user The MBS service data sent by the plane node through multicast.
  • the intermediate user plane node if the intermediate user plane node does not support multicasting, but supports receiving the MBS service data sent by the i-th level user plane node in a point-to-point manner, the intermediate user plane node can be assigned to receive the MBS service data in a point-to-point manner.
  • F-TEID of the MBS service data sent by the i-th level user plane node if the intermediate user plane node does not support multicasting, but supports receiving the MBS service data sent by the i-th level user plane node in a point-to-point manner.
  • the intermediate user plane node may also receive a user plane MBS session modification request sent by the I-SMF.
  • the user plane MBS session The modification request includes first F-TEID list information, where the first F-TEID list information includes sub-user plane nodes that do not support multicasting but support receiving MBS service data sent by intermediate user plane nodes in a point-to-point manner.
  • the intermediate user plane node can transmit MBS to the sub-user plane nodes corresponding to each F-TEID included in the first F-TEID list information in a point-to-point manner based on the first F-TEID list information.
  • the intermediate user plane node if it receives the user plane MBS session deletion request sent by the I-SMF, it sends a user plane MBS session deletion response to the I-SMF; wherein, if the intermediate user plane node has joined the In the multicast transmission group corresponding to the first MBS IP multicast transmission address, after receiving the user plane MBS session deletion request, exit the multicast transmission group corresponding to the first MBS IP multicast transmission address.
  • the technical solution of this embodiment is to delete the broken branch in the transmission tree of the MBS session on the user plane.
  • the intermediate user plane node if it receives multiple user plane MBS session establishment requests, it feeds back the user plane MBS for one user plane MBS session establishment request among the multiple user plane MBS session establishment requests A session establishment response is sent, and a rejection message is fed back for other user plane MBS session establishment requests in the multiple user plane MBS session establishment requests, so as to indicate that the user plane node has been selected.
  • the multiple user plane MBS session establishment requests received by the intermediate user plane node at the same time may be sent by the same I-SMF (corresponding to the case where the same I-SMF is selected by different control plane nodes), or It may also be sent by different I-SMFs (corresponding to the case where different control plane nodes select different I-SMFs).
  • the technical solution of this embodiment enables one user plane node to be selected only as a child node of another user plane node, but cannot be selected as a child node of multiple user plane nodes.
  • the intermediate user plane node after feeding back the first user plane MBS session establishment response to the I-SMF, receives again a sub-user plane for selecting the intermediate user plane node as another user plane node If the user plane MBS session establishment request of the node is received, a rejection message is fed back for the user plane MBS session establishment request received again to indicate that the user plane node has been selected.
  • the user plane MBS session establishment request received by the intermediate user plane node again may be sent by other I-SMFs, or may be sent by the I-SMF that the intermediate user plane node feeds back the first user plane MBS session establishment response.
  • the user plane MBS session establishment request received again is used to select the intermediate user plane node as the child user plane node of other user plane nodes.
  • the technical solution of this embodiment also enables one user plane node to be selected only as a child node of another user plane node, but cannot be selected as a child node of multiple user plane nodes.
  • the 5G MBS session transmission tree needs to ensure that each user plane has only one parent user plane node.
  • the parent control plane node of the control plane may appear.
  • the child control plane node can provide different one or more child user plane nodes to different parent control plane nodes respectively, that is, even different parent users corresponding to the same parent control plane node
  • the plane node and its child user plane nodes are also independent of each other.
  • the sub-user plane node that does not support receiving multicast transmission data can assign the IP address of GTP-U + TEID (represented by F-TEID) , to transmit MBS service data to these sub-user plane nodes in a point-to-point manner.
  • FIG. 15 shows an MBS communication method in which the control plane and the user plane are separated according to an embodiment of the present application, wherein the F-CP in the following content represents the Father-Control Plane (parent control plane), the S- CP stands for Son-Control Plane (child control plane), F-UP stands for Father-User Plane (parent user plane), and S-UP stands for Son-User Plane (child user plane).
  • the F-CP in the following content represents the Father-Control Plane (parent control plane)
  • the S- CP stands for Son-Control Plane (child control plane)
  • F-UP stands for Father-User Plane (parent user plane)
  • S-UP stands for Son-User Plane (child user plane).
  • Step S1501 F-CP1 receives an MBS session start request (ie Nfcp_MBSSessionStart Request) sent by the parent control plane node of F-CP1, and the MBS session start request includes TMGI (Temporary Mobile Group Identity, temporary group identity), MBS Session Duration (MBS session duration), MBS QFIs (QoS Flow Identifier, QoS flow identifier), QoS Profile (QoS configuration), UP ID (the UP ID is the user plane node at the same level as the parent control plane node of F-CP1 ID), MBS IP Multicast Distribution (MBS IP multicast distribution information), MBS Time to Data Transfer (MBS service data transmission time), and MBS Service Area (MBS service area).
  • MBS session start request ie Nfcp_MBSSessionStart Request
  • MBS session start request includes TMGI (Temporary Mobile Group Identity, temporary group identity), MBS Session Duration (MBS session duration), MBS QFIs (QoS
  • TMGI represents a multicast or broadcast temporary group identifier
  • MBS Session Duration represents the duration of this MBS session
  • MBS Time to Data Transfer represents the time when MBS service data starts to be sent
  • QoS Profile includes 5QI (5G QoS Identifier, 5G QoS indicator), MFBR (Maximum Flow Bit Rate, maximum bit rate), GFBR (Guaranteed Flow Bit Rate, guaranteed flow bit rate), ARP (Allocation and Retention Priority, allocation and retention priority), etc.
  • MBS IP Multicast Distribution Contains the IP multicast transmission address (the IP multicast transmission address is the IP multicast transmission assigned by the user plane node at the same level as the parent control plane node of the F-CP1 (that is, the user plane node identified by the aforementioned UP ID).
  • MBS Service Area is the service area when this MBS service is a broadcast service.
  • Step S1502 the F-CP1 determines to select one or more F-UPFs from the multiple F-UPFs as user plane nodes of the same level as the F-CP1 according to the information of the sub-control plane nodes of the F-CP1.
  • F-UP11 only one user plane node (referred to as F-UP11) at the same level as F-CP1 is selected, and then F-CP1 sends a user plane MBS session establishment request (ie N4 MBSSessionEstablishment Request) to F-UP11.
  • -UP11 feeds back the user plane MBS session establishment response (ie N4 MBSSessionEstablishment Response) to the F-CP1.
  • the information of the sub-control plane nodes of the F-CP1 is composed of each MBS UE Context; for the MBS broadcast service, the sub-control plane nodes of the F-CP1 The information is provided by the parent control plane node of the F-CP1 or obtained by the network according to the service area configuration.
  • the information of the sub-control plane nodes of the F-CP1 includes the number and location information of the sub-control plane nodes of the F-CP1, and the like.
  • the user plane MBS session establishment request sent by the F-CP1 to the selected F-UP11 may include PDR (Packet Detection Rule, packet detection rule), QER (QoS Enforcement Rule, QoS enforcement) Rules), FAR (Forwarding Action Rule, forwarding execution rules), MBS IP Multicast Distribution, Allocate New MBS IP Multicast Distribution for Downlink Node (assign new MBS IP multicast distribution information for downlink nodes) instructions, request allocation of F-TEID instruct.
  • PDR Packet Detection Rule, packet detection rule
  • QER QoS Enforcement Rule, QoS enforcement
  • FAR Forwarding Action Rule, forwarding execution rules
  • MBS IP Multicast Distribution Allocate New MBS IP Multicast Distribution for Downlink Node (assign new MBS IP multicast distribution information for downlink nodes) instructions, request allocation of F-TEID instruct.
  • the user plane MBS session establishment response fed back by F-UP11 includes Allocate MBS IP Multicast Distribution for Downlink node and F-TEID.
  • the PDR in the user plane MBS session establishment request includes one or more MBS IP Multicast Address+UDP Port to indicate one or more different MBS QoS Flows;
  • QER includes MFBR, GFBR and DL Flow Level Marking ( Downstream level mark);
  • MBS IP Multicast Distribution is the MBS IP Multicast Distribution corresponding to TMGI, which comes from F-CP1 receiving the MBS session start request sent by the parent control plane node of F-CP1, which contains MBS IP Multicast Distribution
  • the broadcast transport address is IP1.
  • the Allocate New MBS IP Multicast Distribution for Downlink Node indication in the user plane MBS session establishment request is used to indicate that F-UP11 has sub-user plane nodes, so F-UP11 needs to allocate a new MBS IP Multicast Distribution, user plane MBS session
  • the Allocate MBS IP Multicast Distribution for Downlink node in the establishment response contains the new MBS IP Multicast Distribution allocated by F-UP11, and the new MBS IP Multicast Distribution contains the new IP multicast transmission address (for the convenience of distinction, this new The IP multicast transport address is recorded as IP2) and C-TEID.
  • MBS IP Multicast Distribution is allocated by each parent user plane node to all child user plane nodes of each parent user plane node. Different parent user plane nodes will be allocated different MBS IP Multicast Distributions.
  • the user plane MBS session establishment request message sent by F-CP1 contains the request for allocation Indication of the F-TEID to request the F-UP11 to allocate an F-TEID in order to receive the MBS service data sent by the parent user plane node of the F-UP11 in a point-to-point manner.
  • the allocated F-TEID is carried in the MBS session establishment response.
  • the F-UP11 If the user plane MBS session establishment request does not contain an instruction to request F-TEID allocation, that is, the F-CP1 does not make a decision, but the user plane node F-UP11 does not support receiving data transmitted based on multicast, then the F-UP11 also needs to Allocate an F-TEID, and carry the allocated F-TEID in the user plane MBS session establishment response.
  • Step S1503 if the F-UP11 supports receiving data transmitted by multicast, it applies to join the multicast transmission group corresponding to the IP multicast transmission address IP1 to receive the MBS service data sent by the parent user plane node of the F-UP11.
  • Step S1504 F-CP1 sends an MBS session start request (ie Nscp_MBSSessionStart Request) to each sub-control plane sub-node respectively according to the information of the sub-control plane nodes of F-CP1, that is, steps S1504 to S1508 are for each sub-control plane node respectively. If it is performed independently, in this embodiment, sending to a sub-control plane node S-CP is taken as an example for description.
  • the MBS session start request sent by F-CP1 to the sub-control plane node S-CP of F-CP1 contains the following parameters: TMGI, MBS Session Duration, MBS QFIs, QoS Profile, F-UP11 ID, MBS IP Multicast Distribution, MBS Time to Data Transfer, MBS Service Area.
  • TMGI MBS Session Duration
  • MBS QFIs MBS QFIs
  • QoS Profile QoS Profile
  • F-UP11 ID F-UP11 ID
  • MBS IP Multicast Distribution MBS Time to Data Transfer
  • MBS Service Area MBS Service Area
  • step S1502 the S-CP selects one or more of the F-UP11 from the multiple S-UPs according to the information of the sub-control plane nodes of the S-CP. Multiple S-UPs, it is assumed that S-UP1 and S-UP2 are selected in this embodiment. Then step S1505a and step S1505b are executed respectively.
  • Step S1505a the S-CP sends a user plane MBS session establishment request to the selected S-UP1, and the S-UP1 feeds back a user plane MBS session establishment response to the S-CP.
  • the user plane MBS session establishment request sent by the S-CP may also include PDR, QER, FAR, MBS IP Multicast Distribution, F-UP11 ID, Allocate New MBS IP Multicast Distribution for Downlink Node Indication, request for allocation of F-TEID, etc.
  • the user plane MBS session establishment response fed back by the S-UP1 includes the Allocate MBS IP Multicast Distribution for Downlink node and the F-TEID.
  • the MBS IP Multicast Distribution in the user plane MBS session establishment request sent by the S-CP comes from the MBS session start request received in step S1504, and the IP multicast transmission address contained therein is IP2.
  • the Allocate New MBS IP Multicast Distribution for Downlink Node indication in the user plane MBS session establishment request sent by the S-CP to the S-UP1 is used to instruct the S-UP1 to allocate a new MBS IP Multicast Distribution for multicast transmission.
  • the specific process of allocation by S-UP1 is described with reference to step S1502. Similarly, if the S-UP1 does not support multicast transmission, an F-TEID can be assigned and is also assigned by the S-UP1.
  • Step S1505b the S-CP sends a user plane MBS session establishment request to the selected S-UP2, and the S-UP2 feeds back a user plane MBS session establishment response to the S-CP.
  • the specific process is similar to step S1505a and will not be repeated here.
  • Step S1506 if S-UP1 and S-UP2 support receiving data based on multicast transmission, then respectively join the multicast transmission group corresponding to the IP multicast transmission address (ie IP2) allocated by F-UP11 to receive F- MBS service data sent by UP11.
  • IP2 IP multicast transmission address
  • Step S1507 the S-CP sends an MBS session start response (ie, Nscp_MBSSessionStart Response) to the F-CP1, and the MBS session start response contains the F-UP11 ID.
  • MBS session start response ie, Nscp_MBSSessionStart Response
  • the MBS session start response sent by S-CP to F-CP1 contains List of F-TEID (due to It is for the sub-user plane node. For the convenience of distinguishing, it is hereinafter denoted as List of F-TEIDsup), and corresponds to F-UP11.
  • the List of F-TEIDsup contains the F-TEIDs allocated by S-UP1 and S-UP2 that do not support receiving multicast transmission but support receiving MBS service data in a point-to-point manner.
  • S-UPs in S-UP1 and S-UP2 support receiving multicast transmission, it needs to include Multicast Enable in the MBS session start response to indicate that F-UP11 needs to use both multicast transmission and point-to-point transmission technology to transmit to F-UP11
  • the sub-user plane nodes of UP11 transmit MBS service data.
  • the MBS session start response sent by the S-CP to the F-CP1 does not contain the List of F-TEIDsup, it means that all sub-user plane nodes selected by the S-CP support the reception of multicast-based data. Therefore, The identifier of Multicast Enable does not need to be carried in the MBS session start response.
  • the MBS session start response sent by S-CP to F-CP1 contains List of F-TEIDsup, but does not contain the identifier of Multicast Enable, it means that all sub-user plane nodes selected by S-CP do not support receiving
  • the data is transmitted based on multicast, but supports receiving MBS service data transmitted by point-to-point.
  • the sub control plane node S-CP can also indicate by returning a Failure Code through the MBS session start response.
  • the MBS session start response sent by the S-CP to the F-CP1 can also be used. Does not contain the List of F-TEIDsup, but only contains the F-TEID allocated by this sub-user plane node.
  • Step S1508 if the MBS session start response in step S1507 contains the F-UP11 ID and F-TEID parameters (such as the F-TEID allocated by a certain S-UP, or the List of F-TEIDsup corresponding to some S-UPs) ), then F-CP1 sends a user plane MBS session modification request (ie, N4 MBSSessionModification Request) to F-UP11, and F-UP11 feeds back a user plane MBS session modification response to F-CP1.
  • a user plane MBS session modification request ie, N4 MBSSessionModification Request
  • the user plane MBS session modification request includes a List of F-TEIDsup corresponding to the S-UP that does not support receiving multicast transmission but supports receiving MBS service data in a point-to-point manner, to instruct F-UP11 to increase the use of point-to-point mode
  • the MBS service data are respectively transmitted to the S-UPs that do not support receiving multicast transmission but support receiving MBS service data in a point-to-point manner. If the MBS session start response in step S1507 does not contain the indication of Multicast Enable, it indicates that the F-UP11 no longer uses the multicast transmission mode. If the MBS session start response in step S1507 contains the indication of Multicast Enable, it indicates that the F-UP11 should use the multicast transmission and the point-to-point transmission at the same time.
  • the F-UP11 can only use the point-to-point way to transmit MBS service data to the S-UP corresponding to the F-TEID; at the same time, the F-UP11 can use the multicast transmission address (ie IP2) to send MBS to other S-UPs at the same time according to the user plane MBS session modification request in step S1508.
  • the multicast transmission address ie IP2
  • step S1507 If the MBS session start response in step S1507 does not contain the F-TEID, and Multicast Enable is not set to Disable, it means that the F-UP11 continues to use the multicast transmission mode, and step S1508 is not required at this time.
  • step S1509 after steps S1504 to S1508 are executed for each child control plane node, F-CP1 sends an MBS session start response to the parent control plane node of F-CP1 according to the MBS session start responses fed back by all child control plane nodes (that is, Nfcp_MBSSessionStart Response).
  • the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 contains the UP ID (the UP ID is the identifier of the user plane node at the same level as the parent control plane node of F-CP1 ), and may also include List of F-TEID (for the convenience of distinction, it is recorded as List of F-TEIDfup), since F-CP1 only selects a user plane node F-UP11 of the same level, so if F- The MBS session start response that CP1 replies to the parent control plane node of F-CP1 contains the List of F-TEIDfup, so it also contains only the F-TEID allocated by F-UP11.
  • the UP ID is the identifier of the user plane node at the same level as the parent control plane node of F-CP1
  • List of F-TEIDfup for the convenience of distinction, it is recorded as List of F-TEIDfup
  • steps S1501 to S1509 are the processing procedures after the F-CP1 receives the MBS session start request sent by the parent control plane node of the F-CP1.
  • the F-CP1 selects a user plane node of the same level F-UP11, and its child control plane node S-CP selects two child user plane nodes S-UP1 and S-UP2 that are at the same level as the S-CP.
  • Step S1510 F-CP2 receives the MBS session start request sent by the parent control plane node of F-CP2, and the MBS session start request includes TMGI, MBS Session Duration, MBS QFIs, QoS Profile, UPx ID, MBS IP Multicast Distribution , MBS Time to Data Transfer, MBS Service Area.
  • the meaning of the specific parameters refers to the description in the aforementioned step S1501.
  • the IP multicast transmission address included in the MBS IP Multicast Distribution in the MBS session start request received by the F-CP2 can be recorded as IPx.
  • Step S1511 the F-CP2 determines to select one or more F-UPFs from the multiple F-UPFs as user plane nodes of the same level as the F-CP2 according to the information of the sub-control plane nodes of the F-CP2.
  • F-CP2 sends a user plane MBS session establishment request to F-UP21, and F-UP21 feeds back the user plane MBS session to F-CP2 Build a response.
  • step S1502. Similar to step S1502, the F-CP2 and the F-UP21 interact between the user plane MBS session establishment request and the user plane MBS session establishment response, and the F-UP21 allocates a new IP multicast transmission address (for the convenience of distinction, denoted as IP3).
  • IP3 IP multicast transmission address
  • the F-UP21 allocates an F-TEID for receiving MBS service data in a point-to-point manner, and carries it in the user plane MBS session establishment response Assigned F-TEID.
  • Step S1512 if the F-UP21 supports receiving data transmitted by multicast, it applies to join the multicast transmission group corresponding to the IP multicast transmission address IPx to receive the MBS service data sent by the parent user plane node of the F-UP21.
  • step S1513 the F-CP2 sends an MBS session start request to each sub-control plane sub-node respectively according to the information of the sub-control plane nodes of the F-CP2, that is, steps S1513 to S1517 are performed separately for each sub-control plane node.
  • sending to a sub-control plane node S-CP is taken as an example for description.
  • the MBS session start request sent by F-CP2 to the sub-control plane node S-CP of F-CP2 also includes MBS IP Multicast Distribution, and the MBS IP Multicast Distribution is allocated in step S1511, and its corresponding
  • the user plane node identifier is the F-UP21 ID, and the IP multicast transmission address contained in it is IP3.
  • step S1513 and step S1504 there is no sequence relationship between step S1513 and step S1504, and they may be steps executed in parallel by F-CP2 and F-CP1 respectively.
  • the S-CP After the S-CP receives the MBS session start request sent by the F-CP2, the S-CP selects one or more S-UPs for the F-UP21 according to the information of the sub-control plane nodes of the S-CP according to the information of the sub-control plane nodes of the S-CP. For multiple S-UPs, in this embodiment, it is assumed that S-UP3 and S-UP4 are selected, and then step S1514a and step S1514b are executed respectively.
  • the S-UP selected by the S-CP for the F-UP21 is different from the S-CP selected by the S-CP for the F-UP11.
  • a child control plane node on the control plane may have multiple parent control plane nodes, for example, the child control plane node S-CP has two parent control plane nodes F-CP1 and F- CP2, but a child user plane node is not allowed to have multiple parent user plane nodes. In this way, when a child user plane node already has a parent user plane node, it can no longer participate in the selection of child user plane nodes.
  • S-CP can only select S-UP3 and S-UP4 for F-UP21, and S-UP1 and S-UP2 have been selected as sub-user plane nodes of F-UP11, so S-CP can no longer select S-UP1 With S-UP2 as the child user plane node of F-UP21.
  • Step S1514a the S-CP sends a user plane MBS session establishment request to the selected S-UP3, and the S-UP3 feeds back a user plane MBS session establishment response to the S-CP.
  • Step S1514b the S-CP sends a user plane MBS session establishment request to the selected S-UP4, and the S-UP4 feeds back a user plane MBS session establishment response to the S-CP.
  • the specific process is similar to step S1505a and will not be repeated here.
  • Step S1515 if S-UP3 and S-UP4 support receiving data transmitted based on multicast, then join the corresponding multicast transmission group of the IP multicast transmission address (i.e. IP3) allocated by F-UP21 to receive F- MBS service data sent by UP21.
  • IP3 IP multicast transmission address
  • Step S1516 the S-CP sends an MBS session start response to the F-CP2, where the MBS session start response contains the F-UP21 ID.
  • the specific description of this step is similar to the foregoing step S1507, and will not be repeated here.
  • Step S1517 the F-CP2 sends a user plane MBS session modification request to the F-UP21, and the F-UP21 feeds back a user plane MBS session modification response to the F-CP2.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • Step S1518 after steps S1513 to S1517 are performed for each child control plane, F-CP2 sends an MBS session start response to the parent control plane node of F-CP2 according to the MBS session start responses fed back by all child control planes.
  • the specific description of this step is similar to that of the foregoing step S1509, and will not be repeated here.
  • steps S1510 to S1518 are the processing procedures after the F-CP2 receives the MBS session start request sent by the parent control plane node of the F-CP2, and in the processing procedure, the F-CP2 selects a user plane node of the same level F-UP21, and the sub-control plane node S-CP of F-CP2 selects two sub-user plane nodes S-UP3 and S-UP4 that are at the same level as the S-CP.
  • the child control plane node S-CP has multiple parent control plane nodes F-CP1 and F-CP2, and the child user plane node S-CP controlled by the S-CP has multiple parent control plane nodes F-CP1 and F-CP2.
  • UP has only one parent user plane node.
  • step S1501 and the message in step S1510 may be sent in parallel, therefore, steps S1501-S1509 and steps S1510-S1518 may be executed in parallel.
  • a user plane node may be sent a user plane MBS session establishment request message by two control plane nodes at the same time, or after being selected by one control plane node, it may receive another control plane node.
  • the user plane MBS session establishment request message sent by the plane node may be sent by the plane node.
  • the user plane node can In the MBS session establishment response message, normally respond to the user plane MBS session establishment request sent by one of the control plane nodes, and in the other user plane MBS session establishment response message, reject the other control plane node to indicate the user.
  • the face node has been selected. If a user plane node already has a parent user plane node through a control plane node, and receives a user plane MBS session establishment request message sent by another control plane node, the other user plane MBS session establishment response message in the Reject the other control plane node to indicate that the user plane node has been selected.
  • Step S1519a the F-UP11 receives the downlink MBS service data sent by the parent user plane node of the F-UP11. Then, the received downlink MBS service data is transmitted to S-UP1 and S-UP2 through step S1520a.
  • the MBS service data needs to be received in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps. For example, for S-UP1 and S-UP2, if it is determined that only multicast transmission is used, then S-UP1 and S-UP2 receive the MBS service data sent by F-UP11 through multicast transmission; In the point-to-point transmission mode, the S-UP1 and S-UP2 respectively receive the MBS service data sent by the F-UP11 through the point-to-point transmission mode.
  • the MBS service data For each user plane node having sub-user plane nodes, the MBS service data needs to be transmitted to each sub-user plane node in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps. For example, for the F-UP11, if it is determined that only the multicast transmission mode is adopted, the F-UP11 transmits the MBS service data to all the sub-user plane nodes of the F-UP11 (the S-UP11 in this embodiment) through the multicast mode.
  • the F-UP11 sends to each sub-user plane node of the F-UP11 (S-UP1 and S-UP2 in this embodiment) respectively to transmit the point-to-point transmission through the point-to-point transmission. way to transmit MBS service data.
  • Step S1519b the F-UP21 receives the downlink MBS service data sent by the parent user plane node of the F-UP21. Then, the received downlink MBS service data is transmitted to S-UP3 and S-UP4 through step S1520b.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps
  • each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • the MBS session start request sent by the parent control plane node to the child control plane node only includes the information of one parent user plane node.
  • Another embodiment of the present application is introduced below with reference to FIG. 16 .
  • the MBS session start request sent by the parent control plane node to the child control plane node may include information of multiple parent user plane nodes.
  • FIG. 16 shows an MBS communication method in which the control plane and the user plane are separated according to an embodiment of the present application.
  • F-CP in the following content represents Father-Control Plane (parent control plane)
  • S -CP stands for Son-Control Plane (child control plane)
  • F-UP stands for Father-User Plane (parent user plane)
  • S-UP stands for Son-User Plane (child user plane).
  • Step S1601 the F-CP1 receives an MBS session start request sent by the parent control plane node of the F-CP1.
  • the specific process is similar to the foregoing step S1501 and will not be repeated here.
  • the IP multicast transmission address included in the MBS IP Multicast Distribution in the MBS session start request is recorded as IP1.
  • the F-CP1 may determine to select one or more F-UPFs from the multiple F-UPFs according to the information of the child control plane nodes of the F-CP1 As the user plane nodes at the same level as the F-CP1, it is assumed in this embodiment that two user plane nodes are selected, denoted as F-UP11 and F-UP12. Then step S1602a and step S1602b are executed respectively.
  • Step S1602a the F-CP1 sends a user plane MBS session establishment request to the F-UP11, and the F-UP11 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP11 in step S1602a is recorded as IP2.
  • Step S1602b the F-CP1 sends a user plane MBS session establishment request to the F-UP12, and the F-UP12 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be described again, wherein the IP multicast transmission address allocated by the F-UP12 in step S1602b is recorded as IP3.
  • Step S1603 if F-UP11 and F-UP12 support receiving data transmitted based on multicast, then apply to join the multicast transmission group corresponding to IP multicast transmission address IP1 to receive the parent users of F-UP11 and F-UP12 MBS service data sent by the plane node.
  • step S1604 the F-CP1 sends an MBS session start request to each sub-control plane sub-node according to the information of the sub-control plane nodes of the F-CP1, that is, steps S1604 to S1608 are performed separately for each sub-control plane node.
  • sending to a sub-control plane node S-CP is taken as an example for description.
  • the MBS session start request sent by F-CP1 to the sub-control plane node S-CP of F-CP1 contains the following parameters: TMGI, MBS Session Duration, MBS QFIs, QoS Profile, MBS Time to Data Transfer, List of ⁇ F- UP ID, MBS transmission information ⁇ , MBS Service Area.
  • the MBS transmission information is MBS IP Multicast Distribution (IP Multicast Distribution address, C-TEID).
  • F-CP1 selects two user plane nodes F-UP11 and F-UP12 at the same level as F-CP1
  • the List of ⁇ F-UP ID, MBS transmission information ⁇ contains F-UP11 and F-UP12.
  • MBS IP Multicast Distribution corresponding to UP11 ID and F-UP11 ID and MBS IP Multicast Distribution corresponding to F-UP12 ID and F-UP12 ID.
  • the MBS IP Multicast Distribution corresponding to the F-UP11 ID is allocated by F-UP11, and the IP multicast transmission address contained in it is IP2; the MBS IP Multicast Distribution corresponding to the F-UP12 ID is allocated by F-UP12, including The IP multicast transport address is IP3.
  • the IP multicast transmission address IP3 allocated by the F-UP12 and the IP multicast transmission address IP2 allocated by the F-UP11 cannot be the same, but the allocated C-TEIDs can be the same.
  • the S-CP After the S-CP receives the MBS session start request sent by the F-CP1, similar to step S1502, the S-CP selects one or more S-UPs for the F-UP11 according to the information of the sub-control plane nodes of the S-CP. Multiple S-UPs, and selecting one or more S-UPs for F-UP12, it is assumed in this embodiment that S-UP11 and S-UP12 are selected for F-UP11, and S-UP21 and S are selected for F-UP12 -UP22, that is, different sub-user plane nodes are selected for F-UP11 and F-UP12. Then step S1605a and step S1605b are executed respectively.
  • Step S1605a the S-CP sends a user plane MBS session establishment request to the selected S-UP11 and S-UP12 respectively, and the user plane MBS session establishment request includes the IP multicast transmission address IP2 allocated by the F-UP11, and the S-UP11 and S-UP12 respectively feed back the user plane MBS session establishment response to the S-CP (to save layout, S-UP11 and S-UP12 are drawn together in FIG. 16 ).
  • the specific process is similar to step S1505a and will not be repeated here.
  • Step S1605b the S-CP sends a user plane MBS session establishment request to the selected S-UP21 and S-UP22 respectively, and the user plane MBS session establishment request includes the IP multicast transmission address IP3 allocated by the F-UP12, and the S-UP21 and S-UP22 respectively feed back the user plane MBS session establishment response to the S-CP (in order to save layout, S-UP21 and S-UP22 are drawn together in FIG. 16 ).
  • the specific process is similar to step S1505a and will not be repeated here.
  • Step S1606a if S-UP11 and S-UP12 support the reception of data transmitted based on multicast, then respectively join the multicast transmission group corresponding to the IP multicast transmission address (ie IP2) allocated by F-UP11 to receive F- MBS service data sent by UP11.
  • IP2 IP multicast transmission address
  • Step S1606b if S-UP21 and S-UP22 support receiving data based on multicast transmission, then respectively join the multicast transmission group corresponding to the IP multicast transmission address (ie IP3) allocated by F-UP12 to receive F- MBS service data sent by UP12.
  • IP3 IP multicast transmission address
  • Step S1607 the S-CP sends an MBS session start response to the F-CP1.
  • the MBS session start response contains the F-TEID allocated by the S-UP and corresponds to the F-UP, thus forming a List of ⁇ F-UP ID ,List of F-TEIDsup,Multicast Enable ⁇ .
  • List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contains List of F-TEIDsup and Multicast Enable for F-UP11, and List of F-TEIDsup for F-UP12 and Multicast Enable.
  • step S1507 since some S-UPs support receiving data transmitted based on multicast, while other S-UPs do not support receiving data transmitted based on multicast, this List F-TEIDsup only corresponds to those that do not support receiving Multicast transmission, but supports S-UP for receiving MBS service data in a point-to-point manner. Therefore, when all S-UPs of an F-UP support the reception of data transmitted based on multicast, the List of F-TEIDsup corresponding to this F-UP does not exist, and other descriptions refer to the relevant content of step S1507.
  • the S-CP decides not to allocate any sub-user plane nodes to one/some of the F-UP IDs
  • the Multicast Enable corresponding to this/these F-UP IDs can be set to Disable.
  • Failed List ⁇ F-UP ⁇ may also be used in the MBS session start response to indicate the parent user plane node to which the child user plane node is not allocated.
  • Step S1608a F-CP1 sends a user plane MBS session modification request to F-UP11 according to the List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contained in the MBS session start response, and F-UP11 sends F-CP1 Feedback user plane MBS session modification response.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • Step S1608b F-CP1 sends a user plane MBS session modification request to F-UP12 according to the List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ included in the MBS session start response, and F-UP12 sends F-CP1 Feedback user plane MBS session modification response.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • step S1609 after steps S1604 to S1608 are performed for each child control plane, the F-CP1 sends an MBS session start response to the parent control plane node of the F-CP1 according to the MBS session start responses fed back by all the child control planes.
  • F-CP1 selects two user plane nodes F-UP11 and F-UP12 that are at the same level as F-CP1
  • F-UPs in F-UP11 and F-UP12 have F-UPs, they do not support receiving multicast-based transmission.
  • the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 contains List of F-TEID (because it is for the parent user plane node, for ease of distinction, it will be recorded as List below of F-TEIDfup), and corresponds to the UP ID of the parent user plane node of F-UP11 and F-UP12.
  • the List of F-TEIDfup includes the F-TEIDs allocated by F-UP11 and F-UP12 that do not support receiving multicast transmission but support receiving MBS service data in a point-to-point manner. If some F-UPs in F-UP11 and F-UP12 support receiving data transmitted based on multicast, the MBS session start response needs to include Multicast Enable to indicate that the parent user plane nodes of F-UP11 and F-UP12 are at the same time It is necessary to use multicast transmission and point-to-point transmission technology to transmit MBS service data to F-UP11 and F-UP12.
  • the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 does not contain List of F-TEIDfup, it means that the user plane nodes selected by F-CP1 at the same level as F-CP1 support all Receive data transmitted based on multicast, so the MBS session start response does not need to carry the Multicast Enable identifier.
  • the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 contains List of F-TEIDfup, but does not contain the Multicast Enable flag, it means that all selected by F-CP1 are related to F-CP1.
  • the user plane nodes at the same level of CP1 do not support receiving data transmitted in multicast mode, but support receiving MBS service data transmitted in point-to-point mode.
  • the F-CP1 may also indicate by returning a Failure Code through the MBS session start response.
  • the MBS session start response may not include List of F-TEIDfup , but only the F-TEID allocated by the user plane node that does not support receiving multicast transmission but supports receiving MBS service data in a point-to-point manner.
  • steps S1601 to S1609 are the processing procedures after F-CP1 receives the MBS session start request sent by the parent control plane node of F-CP1.
  • Two user plane nodes F-UP11 and F-UP12, and the sub-control plane node S-CP of F-CP1 selects two sub-user plane nodes S-UP11 and S- For UP12, two sub-user plane nodes S-UP21 and S-UP22, which are at the same level as the S-CP, are selected for F-UP12.
  • Step S1610 F-CP2 receives the MBS session start request sent by the parent control plane node of F-CP2, and the MBS session start request includes TMGI, MBS Session Duration, MBS QFIs, QoS Profile, UPx ID, MBS IP Multicast Distribution , MBS Time to Data Transfer, MBS Service Area.
  • the meaning of the specific parameters refers to the description in the aforementioned step S1501.
  • the IP multicast transmission address included in the MBS IP Multicast Distribution in the MBS session start request received by the F-CP2 can be recorded as IPx.
  • Step S1611 the F-CP2 determines to select one or more F-UPFs from the multiple F-UPFs as user plane nodes at the same level as the F-CP2 according to the information of the sub-control plane nodes of the F-CP2.
  • F-CP2 sends a user plane MBS session establishment request to F-UP21, and F-UP21 feeds back the user plane MBS session to F-CP2 Build a response.
  • step S1502. Similar to step S1502, the F-CP2 and the F-UP21 interact between the user plane MBS session establishment request and the user plane MBS session establishment response, and the F-UP21 allocates a new IP multicast transmission address (for the convenience of distinction, denoted as IP4).
  • IP4 IP multicast transmission address
  • the F-UP21 allocates an F-TEID for receiving MBS service data in a point-to-point manner, and carries the allocation in the user plane MBS session establishment response F-TEID.
  • Step S1612 if the F-UP21 supports receiving data transmitted by multicast, it applies to join the multicast transmission group corresponding to the IP multicast transmission address IPx to receive the MBS service data sent by the parent user plane node of the F-UP21.
  • step S1613 the F-CP2 sends an MBS session start request to each sub-control plane sub-node according to the information of the sub-control plane nodes of the F-CP2, that is, steps S1613 to S1617 are performed separately for each sub-control plane node.
  • sending to a sub-control plane node S-CP is taken as an example for description.
  • the MBS session start request sent by F-CP2 to the sub-control plane node S-CP of F-CP2 also includes MBS IP Multicast Distribution, and the MBS IP Multicast Distribution is allocated in step S1611, and its corresponding
  • the user plane node identifier is the F-UP21 ID, and the IP multicast transmission address it contains is IP4.
  • step S1613 and step S1604 do not have a sequential relationship, and they may be steps executed in parallel by F-CP2 and F-CP1 respectively.
  • the S-CP After the S-CP receives the MBS session start request sent by the F-CP2, the S-CP selects one or more S-UPs for the F-UP21 according to the information of the sub-control plane nodes of the S-CP according to the information of the sub-control plane nodes of the S-CP. For multiple S-UPs, it is assumed that S-UP31 and S-UP32 are selected in this embodiment, and then step S1614 is executed.
  • a child control plane node on the control plane may have multiple parent control plane nodes, for example, the child control plane node S-CP has two parent control plane nodes F-CP1 and F- CP2, but a child user plane node is not allowed to have multiple parent user plane nodes. In this way, when a child user plane node already has a parent user plane node, it can no longer participate in the selection of child user plane nodes. .
  • Step S1614 the S-CP sends a user plane MBS session establishment request to the selected S-UP31 and S-UP32 respectively, and the S-UP31 and S-UP32 respectively feed back a user plane MBS session establishment response to the S-CP.
  • the specific process is similar to step S1505a and will not be repeated here.
  • Step S1615 if S-UP31 and S-UP32 support receiving data transmitted based on multicast, then join the corresponding multicast transmission group of the IP multicast transmission address (i.e. IP4) allocated by F-UP21 to receive F- MBS service data sent by UP21.
  • IP4 IP multicast transmission address
  • Step S1616 the S-CP sends an MBS session start response to the F-CP2, where the MBS session start response contains the F-UP21 ID.
  • the specific description of this step is similar to the foregoing step S1507, and will not be repeated here.
  • Step S1617 the F-CP2 sends a user plane MBS session modification request to the F-UP21, and the F-UP21 feeds back a user plane MBS session modification response to the F-CP2.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • Step S1618 after steps S1613 to S1617 are performed for each child control plane, F-CP2 sends an MBS session start response to the parent control plane node of F-CP2 according to the MBS session start responses fed back by all child control planes.
  • the specific description of this step is similar to that of the foregoing step S1509, and will not be repeated here.
  • steps S1610 to S1618 are the processing procedures after F-CP2 receives the MBS session start request sent by the parent control plane node of F-CP2.
  • the user plane node F-UP21 of F-CP2, and the sub control plane node S-CP of F-CP2 selects two sub user plane nodes S-UP31 and S-UP32 that are at the same level as the S-CP.
  • the child control plane node S-CP has multiple parent control plane nodes F-CP1 and F-CP2, and the child user plane node S-CP controlled by the S-CP has multiple parent control plane nodes F-CP1 and F-CP2.
  • UP has only one parent user plane node.
  • step S1601 and the message in step S1610 may be sent in parallel, therefore, steps S1601-S1609 and steps S1610-S1618 may be executed in parallel.
  • a user plane node may be sent a user plane MBS session establishment request message by two control plane nodes at the same time, or after being selected by one control plane node, it may receive another control plane node.
  • the user plane MBS session establishment request message sent by the plane node may be sent in parallel, therefore, steps S1601-S1609 and steps S1610-S1618 may be executed in parallel.
  • the user plane node can In the MBS session establishment response message, normally respond to the user plane MBS session establishment request sent by one of the control plane nodes, and in the other user plane MBS session establishment response message, reject the other control plane node to indicate the user.
  • the face node has been selected. If a user plane node already has a parent user plane node through a control plane node, and receives a user plane MBS session establishment request message sent by another control plane node, the other user plane MBS session establishment response message in the Reject the other control plane node to indicate that the user plane node has been selected.
  • Step S1619a the F-UP11 receives the downlink MBS service data sent by the parent user plane node of the F-UP11. Then, the received downlink MBS service data is transmitted to S-UP11 and S-UP12 through step S1620a.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps
  • each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • Step S1619b the F-UP12 receives the downlink MBS service data sent by the parent user plane node of the F-UP12. Then, the received downlink MBS service data is transmitted to S-UP21 and S-UP22 through step S1620b.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps
  • each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • Step S1619c the F-UP21 receives the downlink MBS service data sent by the parent user plane node of the F-UP21. Then, the received downlink MBS service data is transmitted to S-UP31 and S-UP32 through step S1620c.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps, and each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • the MBS session start request sent by the parent control plane node to the child control plane node includes information of multiple parent user plane nodes.
  • the NR (New Radio) base station (gNB) can be separated from the control plane and the user plane, that is, the gNB-CU (Centralized Unit, centralized unit) can be used as a sub-control plane node, and the gNB-DU ( Distributed Unit, distributed unit) can be used as a sub-user plane node, and the control plane of one base station can control the user plane of one or more base stations.
  • the gNB-CU Centralized Unit, centralized unit
  • the gNB-DU Distributed Unit, distributed unit
  • the gNB in the NG-RAN is connected to the 5GC (5g Core network, 5G core network) through the NG interface.
  • the gNB in the NG-RAN can be separated from the control plane and the user plane.
  • the base station control plane ie The interface between the gNB-CU) and the user plane of the base station (that is, the gNB-DU) may be the F1 interface, and the interface between the gNBs may be the Xn-C interface.
  • the embodiment shown in FIG. 18 can be obtained. Since the network node SMF or MB-SMF cannot It communicates directly with the NR base station, so AMF is introduced for interaction.
  • Step S1801 the F-CP1 receives an MBS session start request sent by the parent control plane node of the F-CP1.
  • the specific process is similar to the foregoing step S1501 and will not be repeated here.
  • the IP multicast transmission address included in the MBS IP Multicast Distribution in the MBS session start request is recorded as IP1.
  • the F-CP1 After receiving the MBS session start request sent by the parent control plane node of the F-CP1, the F-CP1 can determine to select one or more F-UPFs according to the information of the gNB corresponding to the F-CP1 (such as the location and number, etc.) There are multiple user plane nodes at the same level as the F-CP1. In this embodiment, it is assumed that two user plane nodes are selected, denoted as F-UP11 and F-UP12. Then step S1802a and step S1802b are executed respectively.
  • Step S1802a the F-CP1 sends a user plane MBS session establishment request to the F-UP11, and the F-UP11 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP11 in step S1802a is recorded as IP2.
  • Step S1802b the F-CP1 sends a user plane MBS session establishment request to the F-UP12, and the F-UP12 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP12 in step S1802b is recorded as IP3.
  • Step S1803 if F-UP11 and F-UP12 support receiving data transmitted based on multicast, then apply to join the multicast transmission group corresponding to the IP multicast transmission address IP1 to receive the parent users of F-UP11 and F-UP12 MBS service data sent by the plane node.
  • Step S1804a the F-CP1 sends an information transfer message (namely Namf_Communication_NonUeN2MessageTransfer) to the AMF.
  • an information transfer message namely Namf_Communication_NonUeN2MessageTransfer
  • the F-CP1 sends an information transfer message to the AMF containing the following parameters: RAN ID, N2 MBS Session Container (MBS session container).
  • N2 MBS Session Container contains (N2 MBS Session Start Request(TMGI, MBS QFIs, QoS Profile, List of ⁇ F-UP ID, MBS transmission information ⁇ )).
  • MBS transmission information is MBS IP Multicast Distribution (IP Multicast Distribution address, C-TEID).
  • the List of ⁇ F-UP ID, MBS transmission information ⁇ contains F-UP11 and F-UP12.
  • MBS IP Multicast Distribution corresponding to UP11 ID and F-UP11 ID and MBS IP Multicast Distribution corresponding to F-UP12 ID and F-UP12 ID.
  • the MBS IP Multicast Distribution corresponding to the F-UP11 ID is allocated by F-UP11, and the IP multicast transmission address contained in it is IP2; the MBS IP Multicast Distribution corresponding to the F-UP12 ID is allocated by F-UP12, including The IP multicast transport address is IP3.
  • the IP multicast transmission address IP3 allocated by the F-UP12 and the IP multicast transmission address IP2 allocated by the F-UP11 cannot be the same, but the allocated C-TEIDs can be the same.
  • the MBS session container included in the information transfer message sent by F-CP1 to AMF indicates that AMF is to send the relevant content of N2 MBS Session Start Request (TMGI, MBS QFIs, QoS Profile, List of ⁇ F-UP ID, MBS transmission information ⁇ ) to the gNB identified by the RAN ID.
  • TMGI MBS Session Start Request
  • MBS QFIs MBS QFIs
  • QoS Profile List of ⁇ F-UP ID
  • MBS transmission information ⁇ MBS transmission information
  • step S1804b the AMF sends an MBS session start request to the corresponding gNB-CU according to the RAN ID contained in the information transfer message in step S1804a, which includes the parameters in step S1804a, that is, TMGI, MBS QFIs, QoS Profile, List of ⁇ F-UP ID, MBS transfer information ⁇ .
  • the gNB-CU After the gNB-CU receives the MBS session start request sent by the AMF, the gNB-CU determines the number and location of the registered MBS Multicast Service UEs (for the MBS Multicast Service) or the MBS Broadcast Service Area (for the MBS Broadcast Service) One or more gNB-DUs are selected for F-UP11 and F-UP12 from among multiple gNB-DUs, respectively. In this embodiment, it is assumed that gNB-DU11 and gNB-DU12 are selected for F-UP11, and gNB-DU21 and gNB-DU22 are selected for F-UP12, that is, different gNB-DUs are selected for F-UP11 and F-UP12. Then step S1805a and step S1805b are executed respectively.
  • Step S1805a the gNB-CU sends a user plane MBS session establishment request (that is, F1 MBS Session Establishment Request) to the selected gNB-DU11 and gNB-DU12 respectively, and the user plane MBS session establishment request includes the IP address allocated by the F-UP11.
  • broadcast transport address IP2 gNB-DU11 and gNB-DU12 feed back user plane MBS session establishment responses to gNB-CU respectively (to save layout, gNB-DU11 and gNB-DU12 are drawn together in Figure 18).
  • the specific process is similar to the interaction process between the S-CP and the S-UP in step S1505a, and will not be repeated here.
  • Step S1805b the gNB-CU sends the user plane MBS session establishment request (that is, the F1 MBS Session Establishment Request) to the selected gNB-DU21 and gNB-DU22 respectively, and the user plane MBS session establishment request includes the IP address allocated by the F-UP12.
  • broadcast transport address IP3, gNB-DU21 and gNB-DU22 feed back user plane MBS session establishment responses to gNB-CU respectively (to save layout, gNB-DU21 and gNB-DU22 are drawn together in Figure 18).
  • the specific process is similar to the interaction process between the S-CP and the S-UP in step S1505a, and will not be repeated here.
  • Step S1806a if gNB-DU11 and gNB-DU12 support receiving data transmitted based on multicast, then join the multicast transmission group corresponding to the IP multicast transmission address (ie IP2) allocated by F-UP11 to receive F- MBS service data sent by UP11.
  • IP2 IP multicast transmission address
  • Step S1806b if gNB-DU21 and gNB-DU22 support the reception of data transmitted based on multicast, then respectively join the multicast transmission group corresponding to the IP multicast transmission address (ie IP3) allocated by F-UP12 to receive F- MBS service data sent by UP12.
  • IP3 IP multicast transmission address
  • the gNB-DU does not support receiving data transmitted based on multicast, but supports receiving MBS service data in a point-to-point manner, the corresponding F-TEID needs to be allocated,
  • the F-TEID is allocated by the gNB-CU, or allocated by the gNB-DU.
  • step S1807a the gNB allocates wireless air interface resources according to the QFIs and QoS Profile contained in the information transfer message received in step S1804a.
  • Step S1807b the gNB-CU sends an MBS session start response to the AMF.
  • the MBS session start response includes the F-TEID allocated by the gNB-DU (for the convenience of distinction, it is recorded as F-TEIDgnb-du), and the corresponding in F-UP, thus forming a List of ⁇ F-UP ID,List of F-TEIDgnb-du,Multicast Enable ⁇ .
  • List of ⁇ F-UP ID, List of F-TEIDgnb-du, Multicast Enable ⁇ contains List of F-TEIDgnb-du and Multicast Enable for F-UP11, and List for F-UP12 of F-TEIDgnb-du and Multicast Enable.
  • this List F-TEIDgnb-du only corresponds to those that do not Supports gNB-DUs that receive multicast transmissions, but support MBS service data in a point-to-point manner. Therefore, when all gNB-DUs of an F-UP support the reception of data transmitted based on multicast, the List of F-TEID gnb-du corresponding to this F-UP is gone. For other instructions, refer to the relevant content of step S1507 .
  • the Multicast Enable corresponding to this/these F-UP IDs may be set to Disable.
  • Failed List ⁇ F-UP ⁇ may also be used in the MBS session start response to indicate the parent user plane node to which the gNB-DU is not allocated.
  • the AMF sends an information notification message Namf_Communication_NonUeN2InfoNotify to the F-CP1 according to the MBS session start response received in step S1807b.
  • the information notification message includes N2 MBS Session container(N2 MBS Session Start Response(List of(F-UP ID,List of F-TEIDgnb-du,Multicast Enable))).
  • Step S1808a F-CP1 sends a user plane MBS session modification request to F-UP11 according to the List of ⁇ F-UP ID, List of F-TEIDgnb-du, Multicast Enable ⁇ contained in the received information notification message, and F-UP11 Feedback the user plane MBS session modification response to the F-CP1.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • Step S1808b F-CP1 sends a user plane MBS session modification request to F-UP12 according to the List of ⁇ F-UP ID, List of F-TEIDgnb-du, Multicast Enable ⁇ contained in the received information notification message, and F-UP12 Feedback the user plane MBS session modification response to the F-CP1.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • Step S1809 after performing steps S1804a to S1808b for each gNB identified by the RAN ID, the F-CP1 sends an MBS session start response to the parent control plane node of the F-CP1 according to the MBS session start responses fed back by all gNB-CUs. .
  • the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 includes the UP ID of the user plane node at the same level as the parent control plane node of F-CP1, and may also include List of F-TEIDfup and Multicast Enable.
  • steps S1801 to S1809 are the processing procedures after F-CP1 receives the MBS session start request sent by the parent control plane node of F-CP1.
  • Two user plane nodes F-UP11 and F-UP12, and the gNB-CU corresponding to F-CP1 selects two sub-user plane nodes gNB-DU11 and gNB-DU12 at the same level as gNB-CU for F-UP11, which are F-UP12 selects two sub-user plane nodes gNB-DU21 and gNB-DU22 that are at the same level as gNB-CU.
  • Step S1810 the F-CP2 receives the MBS session start request sent by the parent control plane node of the F-CP2.
  • the specific process is similar to the foregoing step S1501 and will not be repeated here.
  • the IP multicast transmission address included in the MBS IP Multicast Distribution in the MBS session start request is recorded as IPx.
  • Step S1811 after receiving the MBS session start request sent by the parent control plane node of the F-CP2, the F-CP2 can determine, according to the information (such as the location and number, etc.) of the gNB corresponding to the F-CP2, from the multiple F-UPFs. Select one or more user plane nodes at the same level as the F-CP2. In this embodiment, it is assumed that only one user plane node F-UP21 is selected, then F-CP2 sends a user plane MBS session establishment request to F-UP21, and F-UP21 feeds back a user plane MBS session establishment response to F-CP2.
  • step S1502. Similar to step S1502, the F-CP2 and the F-UP21 interact through the user plane MBS session establishment request and the user plane MBS session establishment response, and the F-UP21 allocates a new IP multicast transmission address (for the convenience of distinction, denoted as IP4).
  • IP4 IP multicast transmission address
  • the F-UP21 allocates an F-TEID for receiving MBS service data in a point-to-point manner, and carries the allocation in the user plane MBS session establishment response F-TEID.
  • Step S1812 if the F-UP21 supports receiving data transmitted by multicast, it applies to join the multicast transmission group corresponding to the IP multicast transmission address IPx to receive the MBS service data sent by the parent user plane node of the F-UP21.
  • Step S1813a the F-CP2 sends an information transfer message (namely Namf_Communication_NonUeN2MessageTransfer) to the AMF.
  • an information transfer message namely Namf_Communication_NonUeN2MessageTransfer
  • the information transmission message contains the F-UP21 ID and the MBS IP Multicast Distribution corresponding to the F-UP21 ID.
  • the IP multicast transmission address contained in the MBS IP Multicast Distribution is IP4.
  • step S1813a and step S1804a have no sequential relationship, and they may be steps performed in parallel by F-CP2 and F-CP1 respectively.
  • step S1813b the AMF sends an MBS session start request to the corresponding gNB-CU according to the RAN ID contained in the information transfer message in step S1813a, including the parameters in step S1813a.
  • the gNB-CU After the gNB-CU receives the MBS session start request sent by the AMF, the gNB-CU determines the number and location of the registered MBS Multicast Service UEs (for the MBS Multicast Service) or the MBS Broadcast Service Area (for the MBS Broadcast Service) One or more gNB-DUs selected for F-UP21 from multiple gNB-DUs, respectively.
  • gNB-DU31 and gNB-DU32 are selected for F-UP21, that is, the gNB-DU selected for F-UP21 is different from the gNB-DU selected for F-UP11 and F-UP12.
  • Step S1814 gNB-CU sends a user plane MBS session establishment request (that is, F1 MBS Session Establishment Request) to the selected gNB-DU31 and gNB-DU32 respectively, and the user plane MBS session establishment request includes the IP address allocated by F-UP21. IP4 broadcast transport address, gNB-DU31 and gNB-DU32 feed back user plane MBS session establishment responses to gNB-CU respectively (to save layout, gNB-DU31 and gNB-DU32 are drawn together in Figure 18). The specific process is similar to step S1505a and will not be repeated here.
  • a user plane MBS session establishment request that is, F1 MBS Session Establishment Request
  • Step S1815 if gNB-DU31 and gNB-DU32 support receiving data transmitted based on multicast, then join the multicast transmission group corresponding to the IP multicast transmission address (ie IP4) allocated by F-UP21 to receive F- MBS service data sent by UP21.
  • IP4 IP multicast transmission address
  • the gNB-DU does not support receiving data transmitted based on multicast, but supports receiving MBS service data in a point-to-point manner, the corresponding F-TEID needs to be allocated,
  • the F-TEID is allocated by the gNB-CU, or allocated by the gNB-DU.
  • step S1816a the gNB allocates wireless air interface resources according to the QFIs and QoS Profile contained in the information transfer message received in step S1813a.
  • Step S1816b the gNB-CU sends an MBS session start response to the AMF. If a gNB-DU does not support receiving data transmitted based on multicast, the MBS session start response includes the F-TEIDgnb-du allocated by this gNB-DU, and corresponds to F-UP21. For other descriptions, please refer to the related content of step S1507.
  • the AMF sends an information notification message Namf_Communication_NonUeN2InfoNotify to the F-CP2 according to the MBS session start response received in step S1816b.
  • the information notification message includes (N2 MBS Session container(N2 MBS Session Start Response(F-UP21 ID,List of F-TEIDgnb-du,Multicast Enable))).
  • Step S1817 F-CP2 sends a user plane MBS session modification request to F-UP21 according to the F-UP21 ID and List of F-TEIDgnb-du contained in the received information notification message, and F-UP21 feeds back the user plane to F-CP2 MBS session modification response.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • Step S1818 after performing steps S1813b to S1817 for each gNB identified by the RAN ID, the F-CP2 sends an MBS session start response to the parent control plane node of the F-CP2 according to the MBS session start responses fed back by all gNB-CUs. .
  • the MBS session start response that F-CP2 replies to the parent control plane node of F-CP2 includes the UPx ID of the user plane node at the same level as the parent control plane node of F-CP2, and may also include List of F-TEIDfup.
  • steps S1810 to S1818 are the processing procedures after F-CP2 receives the MBS session start request sent by the parent control plane node of F-CP2.
  • the user plane node F-UP21, and the gNB-CU corresponding to the F-CP2 selects two sub-user plane nodes gNB-DU31 and gNB-DU32 that are at the same level as the gNB-CU.
  • the gNB-CU may have multiple parent control plane nodes F-CP1 and F-CP2, while the gNB-DU controlled by the gNB-CU has only one parent user plane node .
  • step S1801 and the message in step S1810 may be sent in parallel, therefore, steps S1801-S1809 and steps S1810-S1818 may be executed in parallel.
  • a user plane node may be sent a user plane MBS session establishment request message by two control plane nodes at the same time, or after being selected by one control plane node, it may receive another control plane node.
  • the user plane node can In the MBS session establishment response message, normally respond to the user plane MBS session establishment request sent by one of the control plane nodes, and in the other user plane MBS session establishment response message, reject the other control plane node to indicate the user.
  • the face node has been selected. If a user plane node already has a parent user plane node through a control plane node, and receives a user plane MBS session establishment request message sent by another control plane node, the other user plane MBS session establishment response message in the Reject the other control plane node to indicate that the user plane node has been selected.
  • Step S1819a the F-UP11 receives the downlink MBS service data sent by the parent user plane node of the F-UP11. Then, the received downlink MBS service data is transmitted to gNB-DU11 and gNB-DU12 through step S1820a.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps, and each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps. .
  • Step S1819b the F-UP12 receives the downlink MBS service data sent by the parent user plane node of the F-UP12. Then, the received downlink MBS service data is transmitted to gNB-DU21 and gNB-DU22 through step S1820b.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps, and each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps. .
  • Step S1819c the F-UP21 receives the downlink MBS service data sent by the parent user plane node of the F-UP21. Then, the received downlink MBS service data is transmitted to gNB-DU31 and gNB-DU32 through step S1820c.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps, and each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps. .
  • the technical solution of the embodiment shown in FIG. 18 is mainly a process of establishing a control plane transmission tree and a user plane transmission tree after introducing the NR base station into the MBS session transmission tree.
  • FIG. 15 , FIG. 16 and FIG. 18 only the interaction process between two-level nodes in the MBS session transmission tree is introduced.
  • the interaction process between any two-level nodes can be implemented with reference to the embodiments shown in FIG. 15 , FIG. 16 or FIG. 18 .
  • the two-level nodes shown in 1901 and 1902 may be the two-level nodes shown in FIG. 15 or FIG. 16 .
  • a three-level MBS session transmission tree can be implemented, in which the GF-CP is the parent control plane node of F-CP, and GF-UP is the parent user plane node of F-UP. In this way, any level of MBS session transmission tree can be realized.
  • the embodiment shown in FIG. 18 can also be combined with the embodiments shown in FIG. 15 and FIG. An MBS session transmission tree at any level of the base station.
  • Figure 15, Figure 16, and Figure 18 show the establishment process of the MBS session transmission tree according to the embodiment of the present application.
  • the user plane transmission tree may also be broken, so it is also necessary to delete the branch. Branch operation.
  • Step S2001 the F-CP1 receives an MBS session start request sent by the parent control plane node of the F-CP1.
  • the specific process is similar to the foregoing step S1501 and will not be repeated here.
  • the IP multicast transmission address included in the MBS IP Multicast Distribution in the MBS session start request is recorded as IP1.
  • the F-CP1 may determine to select one or more F-UPFs from the multiple F-UPFs according to the information of the child control plane nodes of the F-CP1 As user plane nodes at the same level as F-CP1, it is assumed in this embodiment that two user plane nodes F-UP11 and F-UP12 are selected. Then step S1602a and step S1602b are executed respectively.
  • Step S2002a the F-CP1 sends a user plane MBS session establishment request to the F-UP11, and the F-UP11 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP11 in step S2002a is recorded as IP2.
  • Step S2002b the F-CP1 sends a user plane MBS session establishment request to the F-UP12, and the F-UP12 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP12 in step S2002b is recorded as IP3.
  • Step S2003 if F-UP11 and F-UP12 support receiving data transmitted based on multicast, apply to join the multicast transmission group corresponding to IP multicast transmission address IP1 to receive the parent users of F-UP11 and F-UP12 MBS service data sent by the plane node.
  • step S2004 the F-CP1 sends an MBS session start request to each sub-control plane sub-node respectively according to the information of the sub-control plane node of the F-CP1, that is, steps S2004 to S2008 are performed separately for each sub-control plane node.
  • sending to a sub-control plane node S-CP is taken as an example for description.
  • the MBS session start request sent by F-CP1 to the sub-control plane node S-CP of F-CP1 contains the following parameters: TMGI, MBS Session Duration, MBS QFIs, QoS Profile, MBS Time to Data Transfer, List of ⁇ F- UP ID, MBS transmission information ⁇ , MBS Service Area.
  • the MBS transmission information is MBS IP Multicast Distribution (IP Multicast Distribution address, C-TEID).
  • F-CP1 selects two user plane nodes F-UP11 and F-UP12 at the same level as F-CP1
  • the List of ⁇ F-UP ID, MBS transmission information ⁇ contains F-UP11 and F-UP12.
  • MBS IP Multicast Distribution corresponding to UP11 ID and F-UP11 ID and MBS IP Multicast Distribution corresponding to F-UP12 ID and F-UP12 ID.
  • the MBS IP Multicast Distribution corresponding to the F-UP11 ID is allocated by F-UP11, and the IP multicast transmission address contained in it is IP2; the MBS IP Multicast Distribution corresponding to the F-UP12 ID is allocated by F-UP12, including The IP multicast transport address is IP3.
  • the IP multicast transmission address IP3 allocated by the F-UP12 and the IP multicast transmission address IP2 allocated by the F-UP11 cannot be the same, but the allocated C-TEIDs can be the same.
  • the S-CP After the S-CP receives the MBS session start request sent by the F-CP1, similar to step S1502, the S-CP selects one or more S-UPs for the F-UP11 according to the information of the sub-control plane nodes of the S-CP. Multiple S-UPs, and selection of one or more S-UPs for F-UP12, in this example it is assumed that S-UP11 and S-UP12 are selected for F-UP11, but no sub-user plane is selected for F-UP12 node. Then step S2005 is executed.
  • Step S2005 the S-CP sends a user plane MBS session establishment request to the selected S-UP11 and S-UP12 respectively, and the user plane MBS session establishment request includes the IP multicast transmission address IP2 allocated by the F-UP11, and the S-UP11 and S-UP12 respectively feed back a user plane MBS session establishment response to the S-CP (to save layout, S-UP11 and S-UP12 are drawn together in FIG. 20 ).
  • the specific process is similar to step S1505a and will not be repeated here.
  • Step S2006 if S-UP11 and S-UP12 support receiving data transmitted based on multicast, then respectively join the corresponding multicast transmission group of the IP multicast transmission address (ie IP2) allocated by F-UP11 to receive F- MBS service data sent by UP11.
  • IP2 IP multicast transmission address
  • Step S2007 the S-CP sends an MBS session start response to the F-CP1.
  • the MBS session start response contains the F-TEID allocated by the S-UP and corresponds to the F-UP, thus forming a List of ⁇ F-UP ID ,List of F-TEIDsup,Multicast Enable ⁇ .
  • List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ includes List of F-TEIDsup and Multicast Enable for F-UP11, and Multicast Enable (value for F-UP12) to Disable). Since the F-UP12 is not allocated an F-TEID, and the corresponding Multicast Enable is set to Disable, it indicates that the sub-user plane node is not selected for the F-UP12.
  • step S1507 since some S-UPs support receiving data transmitted based on multicast, while other S-UPs do not support receiving data transmitted based on multicast, this List F-TEIDsup only corresponds to those that do not support receiving Multicast transmission, but supports S-UP for receiving MBS service data in a point-to-point manner. Therefore, when all S-UPs of an F-UP support the reception of data transmitted based on multicast, the List of F-TEIDsup corresponding to this F-UP does not exist, and other descriptions refer to the relevant content of step S1507.
  • the Failed List ⁇ F-UP ⁇ may be used in the MBS session start response to indicate the parent user plane node to which no child user plane node is assigned.
  • Step S2008a F-CP1 sends a user plane MBS session modification request to F-UP11 according to the List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contained in the MBS session start response, and F-UP11 sends F-CP1 Feedback user plane MBS session modification response.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • F-CP1 determines that all sub-control plane nodes of F-CP1 have not allocated sub-user plane nodes to F-UP11, F-CP1 sends a user plane MBS session deletion request to F-UP11, and F-UP11 After receiving the user plane MBS session deletion request, it sends out an IGMP Leave data packet and deletes it from the multicast transport group indicated by the multicast transport address IP1 assigned by the parent user plane node of F-UP11, and F-UP11 sends F-UP11 to F - CP1 replies with a user plane MBS session delete response (this process is not identified in the figure).
  • Step S2008b after receiving the MBS session start responses from all the sub-control plane nodes of the F-CP1, the F-CP1 determines that all the sub-control plane nodes of the F-CP1 have not allocated sub-user plane nodes to the F-UP12, and then sends the F-UP12 sends a user plane MBS session delete request (ie, N4 MBSSessionDelete Request).
  • F-UP12 After receiving the user plane MBS session delete request, F-UP12 sends an IGMP Leave data packet, indicating that the corresponding parent user plane node from the F-UP12
  • the multicast transport address ie IP1 indicates that the multicast transport group is deleted, and the F-UP12 replies the user plane MBS session deletion response to the F-CP1.
  • Steps S2004 to S2008 are performed separately for each sub-control plane node of F-CP1, and it cannot be just because the MBS session start response returned by a sub-control plane node of F-CP1 in step S2007 indicates that there is no Allocating the sub-user plane node to the F-UP 12 starts to execute the operation of deleting the MBS session in step S2008b. Instead, F-CP1 should determine whether to delete the MBS session with this user plane node after judging which user plane node has not been allocated a child user plane node after receiving the replies from all sub-control plane nodes.
  • Step S2009 after steps S2004 to S2008 are performed for each child control plane, the F-CP1 sends an MBS session start response to the parent control plane node of the F-CP1 according to the MBS session start responses fed back by all the child control planes.
  • the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 contains the UP ID of the user plane node at the same level as the parent control plane node of F-CP1, and may also contain List of F-TEID (for the convenience of distinction, it is recorded as List of F-TEIDfup), since F-CP1 selects two user plane nodes F-UP11 and F-UP12 at the same level as F-CP1, but S-CP1 The child user plane node is not allocated to F-UP12, so if the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 contains List of F-TEIDfup, then it also contains only the one allocated by F-UP11. F-TEID.
  • the MBS session start response returned by F-CP1 to the parent control plane node of F-CP1 may not include the F-TEID allocated by F-UP11, in this case, it means that F-UP11 supports receiving multiple-based In this case, the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 does not need to include Multicast Enable; if the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 starts The response contains the F-TEID allocated by F-UP11, which means that F-UP11 does not support receiving data transmitted based on multicast, but supports MBS service data sent by point-to-point.
  • Step S2010 the F-UP11 receives the downlink MBS service data sent by the parent user plane node of the F-UP11. Then, the received downlink MBS service data is transmitted to S-UP11 and S-UP12 through step S2011.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps
  • each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • F-CP1 selects two user plane nodes F-UP11 and F-UP12 that are at the same level as F-CP1
  • the sub-control plane node S-CP of F-CP1 does not F-UP12 allocates sub-user plane nodes, that is, there is a broken branch in the user plane transmission tree, so the existing broken branch needs to be deleted.
  • a non-PSA Protocol Data Unit (PDU) Session Anchor, PDU Session Anchor
  • PDU Session Anchor PDU Session Anchor
  • a user plane MBS is established.
  • the process of the transmission tree can be referred to as shown in Figure 21, including the following steps:
  • Step S2101 the F-CP1 receives the MBS session start request sent by the parent control plane node of the F-CP1.
  • the specific process is similar to the foregoing step S1501 and will not be repeated here.
  • the IP multicast transmission address included in the MBS IP Multicast Distribution in the MBS session start request is recorded as IP1.
  • the F-CP1 may determine to select one or more F-UPFs from the multiple F-UPFs according to the information of the child control plane nodes of the F-CP1 As the user plane nodes at the same level as the F-CP1, it is assumed in this embodiment that two user plane nodes are selected, denoted as F-UP11 and F-UP12. Then step S2102a and step S2102b are executed respectively.
  • Step S2102a the F-CP1 sends a user plane MBS session establishment request to the F-UP11, and the F-UP11 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP11 in step S2102a is recorded as IP2.
  • Step S2102b the F-CP1 sends a user plane MBS session establishment request to the F-UP12, and the F-UP12 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP12 in step S2102b is recorded as IP3.
  • Step S2103 if F-UP11 and F-UP12 support receiving data transmitted based on multicast, then apply to join the multicast transmission group corresponding to the IP multicast transmission address IP1 to receive the parent users of F-UP11 and F-UP12 MBS service data sent by the plane node.
  • F-CP1 can choose to perform the following steps S2104a, S2104b and S2104c, and select user plane nodes F-UP21, F-UP22, F-UP23 (the user plane nodes selected by F-CP1 (and the number is only an example), the purpose of this is to enable F-UP11 and F-UP12 to perform offload or optimize transmission through F-UP21, F-UP22, and F-UP23.
  • the F-UP11 directly transfers the MBS service data If it is transmitted to the next-level user plane node of the F-UP11, the transmission efficiency is very low.
  • the MBS service data can be sent by the F-UP11 to the next-level user through the F-UF21. This can effectively improve the efficiency of data transmission.
  • Steps S2104a, S2104b and S2104c are described below:
  • Step S2104a the F-CP1 sends a user plane MBS session establishment request to the F-UP21, and the F-UP21 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here.
  • the F-UP21 further allocates a new IP multicast transmission address for transmitting MBS service data to the sub-user plane node of the F-UP21, which is identified as IP4 in this embodiment.
  • the F-UP21 will allocate an F-TEID to receive the MBS service data from the F-UP11 in a point-to-point manner.
  • Step S2104b the F-CP1 sends a user plane MBS session establishment request to the F-UP22, and the F-UP22 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here.
  • the F-UP22 further allocates a new IP multicast transmission address for transmitting MBS service data to the sub-user plane node of the F-UP22, which is identified as IP5 in this embodiment.
  • the F-UP22 will allocate an F-TEID to receive the MBS service data from the F-UP11 in a point-to-point manner.
  • the multicast transmission address in the MBS IP Multicast Distribution included in the user plane MBS session establishment request in step S2104a and step S2104b is the multicast transmission address IP2 in step S2102a.
  • Step S2104c the F-CP1 sends a user plane MBS session establishment request to the F-UP23, and the F-UP23 feeds back a user plane MBS session establishment response to the F-CP1.
  • the F-UP23 also allocates a new IP multicast transmission address for transmitting MBS service data to the sub-user plane node of the F-UP23, which is identified as IP6 in this embodiment. This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here.
  • the multicast transmission address in the MBS IP Multicast Distribution included in the user plane MBS session establishment request in step S2104c is the multicast transmission address IP3 in step S2102b.
  • the new multicast transmission address determined in step S2104c is allocated by the F-UP23 to the sub-user plane nodes of the F-UP23 (ie, S-UP31 and S-UP32 in FIG. 21 ).
  • the F-UP23 does not support receiving the MBS service data sent by the F-UP12 through multicast, the F-UP23 will allocate an F-TEID to receive the MBS service data from the F-UP12 in a point-to-point manner.
  • Step S2105a if F-UP21 and F-UP22 support receiving data transmitted based on multicast, apply to join the multicast transmission group corresponding to IP multicast transmission address IP2 to receive MBS service data sent by F-UP11.
  • Step S2105b if the F-UP23 supports receiving data transmitted based on multicast, it applies to join the multicast transmission group corresponding to the IP multicast transmission address IP3 to receive the MBS service data sent by the F-UP12.
  • Step S2106a if there are user plane nodes in F-UP21 and F-UP22 that do not support receiving multicast transmission but support receiving MBS service data in a point-to-point manner, then F-CP1 sends a user plane MBS session modification request to F-UP11, The F-UP11 feeds back the user plane MBS session modification response to the F-CP1.
  • the user plane MBS session modification request includes the F-TEID allocated by the user plane node in F-UP21 and F-UP22 that does not support receiving multicast transmission but supports receiving MBS service data in a point-to-point manner, to indicate the F-TEID.
  • UP11 adds the point-to-point mode to transmit MBS service data to the user plane nodes in F-UP21 and F-UP22 that do not support receiving multicast transmission but support the point-to-point mode for receiving MBS service data.
  • Step S2106b if the F-UP23 does not support receiving the data transmitted based on the multicast mode, but supports receiving the MBS service data in the point-to-point mode, the F-CP1 sends a user plane MBS session modification request to the F-UP12, and the F-UP12 sends the F-UP12 to the F-UP12. CP1 feeds back a user plane MBS session modification response.
  • the user plane MBS session modification request includes the F-TEID allocated by the F-UP23 to instruct the F-UP12 to transmit the MBS service data to the F-UP23 in a point-to-point manner.
  • Step S2107 the F-CP1 sends an MBS session start request to the child control plane node S-CP1 of the F-CP1 according to the information of the child control plane node of the F-CP1.
  • the MBS session start request sent by F-CP1 to the sub-control plane node S-CP1 of F-CP1 contains the following parameters: TMGI, MBS Session Duration, MBS QFIs, QoS Profile, MBS Time to Data Transfer, List of ⁇ F- UP ID, MBS transmission information ⁇ , MBS Service Area.
  • the MBS transmission information is MBS IP Multicast Distribution (IP Multicast Distribution address, C-TEID).
  • List of ⁇ F-UP ID, MBS transmission information ⁇ includes F-UP21 ID and MBS IP Multicast Distribution corresponding to F-UP21 ID, and MBS corresponding to F-UP22 ID and F-UP22 ID IP Multicast Distribution.
  • the MBS IP Multicast Distribution corresponding to F-UP21ID is allocated by F-UP21, and the IP multicast transmission address contained in it is the new IP multicast transmission address IP4 allocated by F-UP21 in step S2104a;
  • F-UP22 ID corresponds to The MBS IP Multicast Distribution is allocated by F-UP22, and the IP multicast transmission address contained therein is the new IP multicast transmission address IP5 allocated by F-UP22 in step S2104b, and allocated by F-UP21 in step S2104a
  • the new IP multicast transmission address IP4 is different from the new IP multicast transmission address IP5 allocated by the F-UP22 in step S2104b.
  • Step S2108 after receiving the MBS session start request sent by the F-CP1, the S-CP1 performs a user plane MBS session establishment process. Specifically, the S-CP1 selects one or more S-UPs for the F-UP21 and one or more S-UPs for the F-UP22 from the plurality of S-UPs according to the information of the sub-control plane nodes of the S-CP1 , in this embodiment, it is assumed that S-UP11 and S-UP12 are selected for F-UP21, and S-UP21 and S-UP22 are selected for F-UP22, that is, different sub-user planes are selected for F-UP21 and F-UP22 node.
  • the S-CP1 then sends a user plane MBS session establishment request to the sub-user plane nodes (ie S-UP11, S-UP12, S-UP21 and S-UP22) selected for the F-UP21 and F-UP22 respectively, and receives these sub-user plane nodes.
  • the user plane MBS session establishment response fed back by the user plane node.
  • these sub-user plane nodes can join the corresponding multicast transmission group to receive MBS service data (that is, S-UP11 and S-UP12 join the multicast transmission group corresponding to IP4, S-UP21 and S-UP21 and S-UP22 joins the multicast transmission group corresponding to IP5); if some of these sub-user plane nodes do not support receiving data transmitted based on multicast, but support receiving MBS service data in point-to-point mode, they do not support
  • the sub-user plane node that receives the data transmitted based on the multicast mode but supports the use of point-to-point mode to receive the MBS service data can allocate the F-TEID to receive the MBS service data by the point-to-point mode.
  • the specific process is similar to step S1505a and step S1506, no longer Repeat.
  • Step S2109 the S-CP1 sends an MBS session start response to the F-CP1.
  • the MBS session start response includes the F-TEID allocated by the S-UP, and corresponds to the F-UP.
  • List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contains List of F-TEIDsup and Multicast Enable for F-UP21, and List of F-TEIDsup for F-UP22 and Multicast Enable.
  • step S1507 since some S-UPs support receiving data transmitted based on multicast, while other S-UPs do not support receiving data transmitted based on multicast, this List F-TEIDsup only corresponds to those that do not support receiving Multicast transmission, but supports S-UP for receiving MBS service data in a point-to-point manner. Therefore, when all S-UPs of an F-UP support the reception of data transmitted based on multicast, the List of F-TEIDsup corresponding to this F-UP does not exist, and other descriptions refer to the relevant content of step S1507.
  • the S-CP1 decides not to allocate any sub-user plane nodes to one/some of the F-UP IDs
  • the Multicast Enable corresponding to this/these F-UP IDs can be set to Disable.
  • Failed List ⁇ F-UP ⁇ may also be used in the MBS session start response to indicate the F-UP that is not assigned a sub-user plane node.
  • Step S2110a the F-CP1 sends a user plane MBS session modification request to the F-UP21 according to the List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contained in the MBS session start response fed back by the S-CP1, and the F- The UP21 feeds back the user plane MBS session modification response to the F-CP1.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • Step S2110b F-CP1 sends a user plane MBS session modification request to F-UP22 according to the List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ included in the MBS session start response fed back by S-CP1, and F- The UP22 feeds back the user plane MBS session modification response to the F-CP1.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • Step S2111 the F-CP1 sends an MBS session start request to the child control plane node S-CP2 of the F-CP1 according to the information of the child control plane node of the F-CP1.
  • the MBS session start request sent by F-CP1 to the sub-control plane node S-CP2 of F-CP1 contains the following parameters: TMGI, MBS Session Duration, MBS QFIs, QoS Profile, MBS Time to Data Transfer, List of ⁇ F- UP ID, MBS transmission information ⁇ , MBS Service Area.
  • the MBS transmission information is MBS IP Multicast Distribution (IP Multicast Distribution address, C-TEID).
  • the List of ⁇ F-UP ID, MBS transmission information ⁇ includes the F-UP23ID and the MBS IP Multicast Distribution corresponding to the F-UP23ID.
  • the MBS IP Multicast Distribution corresponding to the F-UP23ID is allocated by the F-UP23, and the IP multicast transmission address contained therein is the new IP multicast transmission address IP6 allocated by the F-UP23 in step S2104c.
  • step S2111 and step S2107 do not have a sequential relationship, and they may be steps executed by the F-CP1 in parallel.
  • Step S2112 After receiving the MBS session start request sent by the F-CP1, the S-CP2 performs a user plane MBS session establishment process. Specifically, the S-CP2 selects one or more S-UPs for the F-UP23 from the multiple S-UPs according to the information of the sub-control plane nodes of the S-CP2. In this embodiment, it is assumed that an S-UP is selected for the F-UP23. UP31 and S-UP32, that is, the sub-user plane nodes selected for F-UP23 are different from the sub-user plane nodes selected for F-UP21 and F-UP22.
  • S-CP2 sends a user plane MBS session establishment request to the sub-user plane nodes (ie S-UP31 and S-UP32) selected for F-UP23 respectively, and receives the user plane MBS sessions fed back by S-UP31 and S-UP32 respectively Build a response.
  • sub-user plane nodes ie S-UP31 and S-UP32
  • S-UP31 and S-UP32 can join the multicast transmission group corresponding to the new IP multicast transmission address IP6 allocated by F-UP23 in step S2104c to receive the MBS sent by F-UP23 Service data; if some sub-user plane nodes in S-UP31 and S-UP32 do not support receiving data based on multicast transmission, but support receiving MBS service data in point-to-point mode, S-UP31 and S-UP32 do not support The sub-user plane node that receives the data transmitted based on the multicast mode but supports the use of point-to-point mode to receive the MBS service data can allocate an F-TEID to receive the MBS service data sent by the F-UP23 in a point-to-point mode.
  • the specific process is the same as steps S1505a and S1505a. S1506 is similar and will not be repeated here.
  • Step S2113, S-CP2 sends an MBS session start response to F-CP1.
  • the MBS session start response includes the F-TEID allocated by the S-UP. , and corresponds to F-UP, thus forming a List of ⁇ F-UP ID,List of F-TEIDsup,Multicast Enable ⁇ .
  • List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contains List of F-TEIDsup and Multicast Enable for F-UP23.
  • step S1507 since some S-UPs support receiving data transmitted based on multicast, while other S-UPs do not support receiving data transmitted based on multicast, this List F-TEIDsup only corresponds to those that do not support receiving Multicast transmission, but supports S-UP for receiving MBS service data in a point-to-point manner. Therefore, when all S-UPs of an F-UP support the reception of data transmitted based on multicast, the List of F-TEIDsup corresponding to this F-UP does not exist, and other descriptions refer to the relevant content of step S1507.
  • the S-CP2 decides not to allocate any sub-user plane nodes to one/some F-UP IDs
  • the Multicast Enable corresponding to this/these F-UP IDs can be set to Disable.
  • Failed List ⁇ F-UP ⁇ may also be used in the MBS session start response to indicate the F-UP that is not assigned a sub-user plane node.
  • Step S2114 F-CP1 sends a user plane MBS session modification request to F-UP23 according to the List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contained in the MBS session start response fed back by S-CP2, and F- The UP23 feeds back the user plane MBS session modification response to the F-CP1.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • Step S2115 after the F-CP1 receives the MBS session start responses fed back by all the S-CPs, the F-CP1 sends the MBS session start responses to the parent control plane node of the F-CP1 according to the MBS session start responses fed back by all the S-CPs.
  • the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 contains the UP ID (the UP ID is the identifier of the user plane node at the same level as the parent control plane node of F-CP1 ), and may also contain List of F-TEIDfup and Multicast Enable.
  • F-CP1 has two sub-control plane nodes S-CP1 and S-CP2, and F-CP1 selects the next-level user plane node F- UP21 and F-UP22, F-CP1 selects the next-level user plane node F-UP23 for F-UP12, and S-CP1 selects sub-user plane nodes S-UP11 and S-UP12 for F-UP21, S-CP1 Sub-user plane nodes S-UP21 and S-UP22 are selected for F-UP22, and sub-user plane nodes S-UP31 and S-UP32 are selected for F-UP23 by S-CP2.
  • a user plane node in the process of establishing a user plane MBS session, there may be a user plane node that is simultaneously sent a user plane MBS session establishment request message by two control plane nodes, or has been selected by a control plane node and then receives the message.
  • User plane MBS session establishment request message sent by another control plane node. If a user plane node simultaneously receives the user plane MBS session establishment request messages sent by two control plane nodes (of course, there may be more, and two are used as an example here), the user plane node can In the MBS session establishment response message, normally respond to the user plane MBS session establishment request sent by one of the control plane nodes, and in the other user plane MBS session establishment response message, reject the other control plane node to indicate the user.
  • the face node has been selected. If a user plane node already has a parent user plane node through a control plane node, and receives a user plane MBS session establishment request message sent by another control plane node, the other user plane MBS session establishment response message in the Reject the other control plane node to indicate that the user plane node has been selected.
  • Step S2116a the F-UP11 receives the downlink MBS service data sent by the parent user plane node of the F-UP11. Then, the received downlink MBS service data is transmitted to the F-UP21 through step S2117a, and the downlink MBS service data received through step S2117b is transmitted to the F-UP22.
  • F-UP21 transmits the received downlink MBS service data to S-UP11 and S-UP12 through step S2118a.
  • F-UP22 transmits the received downlink MBS service data to S-UP21 and S-UP22 through step S2118b.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps, and each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • Step S2116b the F-UP12 receives the downlink MBS service data sent by the parent user plane node of the F-UP12. Then, the received downlink MBS service data is transmitted to the F-UP23 through step S2117c, and the F-UP23 transmits the received downlink MBS service data to S-UP31 and S-UP32 through step S2118c.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps
  • each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • Step S2201 the F-CP1 receives an MBS session start request sent by the parent control plane node of the F-CP1.
  • the specific process is similar to the aforementioned step S1501, and will not be repeated here.
  • the IP multicast transmission address included in the MBS IP Multicast Distribution in the MBS session start request is recorded as IP1.
  • the F-CP1 may determine to select one or more F-UPFs from the multiple F-UPFs according to the information of the child control plane nodes of the F-CP1 As the user plane nodes at the same level as the F-CP1, it is assumed in this embodiment that two user plane nodes are selected, denoted as F-UP11 and F-UP12. Then step S2202a and step S2202b are executed respectively.
  • Step S2202a the F-CP1 sends a user plane MBS session establishment request to the F-UP11, and the F-UP11 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP11 in step S2202a is recorded as IP2.
  • Step S2202b the F-CP1 sends a user plane MBS session establishment request to the F-UP12, and the F-UP12 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP12 in step S2202b is recorded as IP3.
  • Step S2203 if the F-UP11 and the F-UP12 support receiving the data transmitted based on the multicast mode, then apply to join the multicast transmission group corresponding to the IP multicast transmission address IP1 to receive the parent user of the F-UP11 and the F-UP12 MBS service data sent by the plane node.
  • F-CP1 can choose to perform the following steps S2204a, S2204b and S2204c, and select user plane nodes F-UP21, F-UP22, F-UP23 (the user plane nodes selected by F-CP1 (and the number is only an example), the purpose of this is to enable F-UP11 and F-UP12 to perform offload or optimize transmission through F-UP21, F-UP22, and F-UP23.
  • the F-UP11 directly transfers the MBS service data If it is transmitted to the next-level user plane node of the F-UP11, the transmission efficiency is very low.
  • the MBS service data can be sent by the F-UP11 to the next-level user through the F-UF21. This can effectively improve the efficiency of data transmission.
  • Steps S2204a, S2204b and S2204c are described below:
  • Step S2204a the F-CP1 sends a user plane MBS session establishment request to the F-UP21, and the F-UP21 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here.
  • the F-UP21 also allocates a new IP multicast transmission address for transmitting MBS service data to the sub-user plane node of the F-UP21, which is identified as IP4 in this embodiment.
  • the F-UP21 will allocate an F-TEID to receive the MBS service data from the F-UP11 in a point-to-point manner.
  • Step S2204b the F-CP1 sends a user plane MBS session establishment request to the F-UP22, and the F-UP22 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here.
  • the F-UP22 further allocates a new IP multicast transmission address for transmitting MBS service data to the sub-user plane node of the F-UP22, which is identified as IP5 in this embodiment.
  • the F-UP22 will allocate an F-TEID to receive the MBS service data from the F-UP11 in a point-to-point manner.
  • the multicast transmission address in the MBS IP Multicast Distribution included in the user plane MBS session establishment request in step S2204a and step S2204b is the multicast transmission address IP2 in step S2202a.
  • Step S2204c the F-CP1 sends a user plane MBS session establishment request to the F-UP23, and the F-UP23 feeds back a user plane MBS session establishment response to the F-CP1.
  • the F-UP23 also allocates a new IP multicast transmission address for transmitting MBS service data to the sub-user plane node of the F-UP23, which is identified as IP6 in this embodiment. This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here.
  • the multicast transmission address in the MBS IP Multicast Distribution included in the user plane MBS session establishment request in step S2204c is the multicast transmission address IP3 in step S2202b.
  • the new multicast transmission address determined in step S2204c is IP6 allocated by F-UP23 to the sub-user plane nodes of F-UP23 (ie, S-UP31 and S-UP32 in FIG. 22 ).
  • the F-UP23 will allocate an F-TEID to receive the MBS service data from the F-UP12 in a point-to-point manner.
  • Step S2205a if F-UP21 and F-UP22 support receiving data transmitted based on multicast, apply to join the multicast transmission group corresponding to IP multicast transmission address IP2 to receive MBS service data sent by F-UP11.
  • Step S2205b if the F-UP23 supports receiving data transmitted by multicast, it applies to join the multicast transmission group corresponding to the IP multicast transmission address IP3 to receive the MBS service data sent by the F-UP12.
  • Step S2206a if there are user plane nodes in F-UP21 and F-UP22 that do not support receiving multicast transmission but support receiving MBS service data in a point-to-point manner, then F-CP1 sends a user plane MBS session modification request to F-UP11, The F-UP11 feeds back the user plane MBS session modification response to the F-CP1.
  • the user plane MBS session modification request includes the F-TEID allocated by the user plane node in F-UP21 and F-UP22 that does not support receiving multicast transmission but supports receiving MBS service data in a point-to-point manner, to indicate the F-TEID.
  • UP11 adds the point-to-point mode to transmit MBS service data to the user plane nodes in F-UP21 and F-UP22 that do not support receiving multicast transmission but support the point-to-point mode for receiving MBS service data.
  • F-CP1 does not allocate a subordinate user plane node for F-UP11
  • F-CP1 sends a user plane MBS session deletion request to F-UP11
  • F-UP11 receives the user plane MBS session deletion request after receiving the user plane MBS session deletion request.
  • send out an IGMP Leave packet and exit from the multicast transport group indicated by the multicast transport address IP1 assigned by the parent user plane node of F-UP11
  • F-UP11 replies to F-CP1 with a user plane MBS session deletion response (this process is not identified in the figure).
  • Step S2206b if the F-UP23 does not support receiving data based on multicast transmission, but supports receiving MBS service data in a point-to-point manner, then the F-CP1 sends a user plane MBS session modification request to the F-UP12, and the F-UP12 sends the F-UP12 to the F-UP12. CP1 feeds back a user plane MBS session modification response.
  • the user plane MBS session modification request includes the F-TEID allocated by the F-UP23 to instruct the F-UP12 to transmit the MBS service data to the F-UP23 in a point-to-point manner.
  • F-CP1 does not allocate a subordinate user plane node to F-UP12
  • F-CP1 sends a user plane MBS session deletion request to F-UP12
  • F-UP12 receives the user plane MBS session deletion request after receiving the user plane MBS session deletion request.
  • send out an IGMP Leave data packet and exit from the multicast transport group indicated by the multicast transport address IP1 assigned by the parent user plane node of F-UP12
  • F-UP12 replies to F-CP1 with a user plane MBS session deletion response (this process is not identified in the figure).
  • Step S2207 the F-CP1 sends an MBS session start request to the child control plane node S-CP1 of the F-CP1 according to the information of the child control plane node of the F-CP1.
  • the MBS session start request sent by F-CP1 to the sub-control plane node S-CP1 of F-CP1 contains the following parameters: TMGI, MBS Session Duration, MBS QFIs, QoS Profile, MBS Time to Data Transfer, List of ⁇ F- UP ID, MBS transmission information ⁇ , MBS Service Area.
  • the MBS transmission information is MBS IP Multicast Distribution (IP Multicast Distribution address, C-TEID).
  • List of ⁇ F-UP ID, MBS transmission information ⁇ includes F-UP21 ID and MBS IP Multicast Distribution corresponding to F-UP21 ID, and MBS corresponding to F-UP22 ID and F-UP22 ID IP Multicast Distribution.
  • the MBS IP Multicast Distribution corresponding to the F-UP21 ID is allocated by the F-UP21, and the IP multicast transmission address contained therein is the new IP multicast transmission address IP4 allocated by the F-UP21 in step S2204a; the F-UP22 ID
  • the corresponding MBS IP Multicast Distribution is allocated by F-UP22, and the IP multicast transmission address contained therein is the new IP multicast transmission address IP5 allocated by F-UP22 in step S2204b, and in step S2204a by F-UP21
  • the assigned new IP multicast transport address IP4 is different from the new IP multicast transport address IP5 assigned by the F-UP 22 in step S2204b.
  • Step S2208 After receiving the MBS session start request sent by the F-CP1, the S-CP1 performs a user plane MBS session establishment process. Specifically, the S-CP1 selects one or more S-UPs for the F-UP21 and several S-UPs for the F-UP22 from the multiple S-UPs according to the information of the sub-control plane nodes of the S-CP1, the In the embodiment, it is assumed that S-UP11 and S-UP12 are selected for F-UP21, and no sub-user plane node is selected for F-UP22.
  • the S-CP1 sends a user plane MBS session establishment request to the S-UP11 and S-UP12 respectively, and receives the user plane MBS session establishment response fed back by the S-UP11 and S-UP12 respectively.
  • S-UP11 and S-UP12 support receiving multicast transmission, they can join the multicast transmission group corresponding to the new IP multicast transmission address IP4 allocated by F-UP21 in step S2204a to receive the MBS service sent by F-UP21 Data; if some sub-user plane nodes in S-UP11 and S-UP12 do not support receiving data based on multicast transmission, but support receiving MBS service data in point-to-point mode, then S-UP11 and S-UP12 do not support receiving data.
  • a user plane node that supports receiving MBS service data in a point-to-point manner based on the data transmitted in multicast mode can allocate an F-TEID to receive the MBS service data sent by F-UP21 in a point-to-point manner.
  • the specific process is similar to step S1505a and step S1506 ,No longer.
  • Step S2209 the S-CP1 sends an MBS session start response to the F-CP1.
  • the MBS session start response includes the F-TEID allocated by the S-UP, and corresponds to the F-UP.
  • List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contains List of F-TEIDsup and Multicast Enable for F-UP21, and List of F-TEIDsup for F-UP22 and Multicast Enable.
  • the S-CP1 does not select a sub-user plane node for F-UP22, the List of F-TEIDsup for F-UP22 does not contain any F-TEID, and the value of Multicast Enable for F-UP22 is Disable. Or there is no List of F-TEIDsup for F-UP22 in the MBS session start response sent by S-CP1 to F-CP1, and the value of Multicast Enable for F-UP22 is Disable.
  • the S-CP1 may also return a Failure Code (such as Failed List ⁇ F-UP22 ⁇ ) in the MBS session start response to indicate that the sub-user plane node is not selected to the F-UP22.
  • step S1507 since some S-UPs support receiving data transmitted based on multicast, while other S-UPs do not support receiving data transmitted based on multicast, the List F-TEIDsup for F-UP21 only corresponds to For those S-UPs that do not support receiving multicast transmission but support receiving MBS service data in a peer-to-peer manner, refer to the relevant content of step S1507 for other descriptions.
  • Step S2210a F-CP1 sends a user plane MBS session modification request to F-UP21 according to the List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ included in the MBS session start response fed back by S-CP1, and F- The UP21 feeds back the user plane MBS session modification response to the F-CP1.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • F-CP1 determines that F-UP21 is not assigned any lower-level user plane node
  • F-CP1 sends a user plane MBS session deletion request to F-UP21
  • F-UP21 receives the user plane MBS session after receiving the user plane MBS session.
  • After the delete request send out an IGMP Leave packet, and exit from the multicast transport group indicated by the multicast transport address IP2 assigned by the F-UP11, and the F-UP21 replies to the F-CP1 with a user plane MBS session deletion response (this process is not identified in the figure).
  • Step S2210b after receiving the MBS session start responses from all sub-control plane nodes of F-CP1, F-CP1 determines that all sub-control plane nodes of F-CP1 do not select sub-user plane nodes for F-UP22, then F- CP1 sends a user plane MBS session deletion request to F-UP22, and after receiving the user plane MBS session deletion request, F-UP22 sends an IGMP Leave data packet, and the multicast transmission indicated by the multicast transmission address IP2 assigned by F-UP11 is transmitted. is deleted from the group, and the F-UP22 replies the user plane MBS session deletion response to the F-CP1.
  • Step S2211 the F-CP1 sends an MBS session start request to the child control plane node S-CP2 of the F-CP1 according to the information of the child control plane node of the F-CP1.
  • the MBS session start request sent by F-CP1 to the sub-control plane node S-CP2 of F-CP1 contains the following parameters: TMGI, MBS Session Duration, MBS QFIs, QoS Profile, MBS Time to Data Transfer, List of ⁇ F- UP ID, MBS transmission information ⁇ , MBS Service Area.
  • the MBS transmission information is MBS IP Multicast Distribution (IP Multicast Distribution address, C-TEID).
  • the List of ⁇ F-UP ID, MBS transmission information ⁇ includes the F-UP23ID and the MBS IP Multicast Distribution corresponding to the F-UP23ID.
  • the MBS IP Multicast Distribution corresponding to the F-UP23ID is allocated by the F-UP23, and the IP multicast transmission address contained therein is the new IP multicast transmission address IP6 allocated by the F-UP23 in step S2204c.
  • step S2211 and step S2207 do not have a sequential relationship, and they may be steps executed by the F-CP1 in parallel.
  • Step S2212 after receiving the MBS session start request sent by the F-CP1, the S-CP2 performs a user plane MBS session establishment process. Specifically, the S-CP2 selects one or more S-UPs for the F-UP23 from the multiple S-UPs according to the information of the sub-control plane nodes of the S-CP2. In this embodiment, it is assumed that an S-UP is selected for the F-UP23. UP31 and S-UP32, that is, the sub-user plane nodes selected for F-UP23 are different from the sub-user plane nodes selected for F-UP21 and F-UP22.
  • S-CP2 sends a user plane MBS session establishment request to the sub-user plane nodes (ie S-UP31 and S-UP32) selected for F-UP23 respectively, and receives the user plane MBS sessions fed back by S-UP31 and S-UP32 respectively Build a response.
  • sub-user plane nodes ie S-UP31 and S-UP32
  • S-UP31 and S-UP32 can join the multicast transmission group corresponding to the new IP multicast transmission address IP6 allocated by F-UP23 in step S2204c to receive the MBS sent by F-UP23 Service data; if some sub-user plane nodes in S-UP31 and S-UP32 do not support receiving data based on multicast transmission, but support receiving MBS service data in point-to-point mode, S-UP31 and S-UP32 do not support The sub-user plane node that receives the data transmitted based on the multicast mode but supports the use of point-to-point mode to receive the MBS service data can allocate the F-TEID to receive the MBS service data sent by the F-UP23 in a point-to-point mode.
  • the specific process is the same as steps S1505a and S1505a. S1506 is similar and will not be described again.
  • Step S2213 the S-CP2 sends an MBS session start response to the F-CP1.
  • the MBS session start response includes the F-TEID allocated by the S-UP. , and corresponds to F-UP, thus forming a List of ⁇ F-UP ID,List of F-TEIDsup,Multicast Enable ⁇ .
  • List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contains List of F-TEIDsup and Multicast Enable for F-UP23.
  • step S1507 since some S-UPs support receiving data transmitted based on multicast, while other S-UPs do not support receiving data transmitted based on multicast, this List F-TEIDsup only corresponds to those that do not support receiving Multicast transmission, but supports S-UP for receiving MBS service data in a point-to-point manner. Therefore, when all S-UPs of an F-UP support the reception of data transmitted based on multicast, the List of F-TEIDsup corresponding to this F-UP does not exist, and other descriptions refer to the relevant content of step S1507.
  • the S-CP2 decides not to allocate any sub-user plane nodes to one/some F-UP IDs
  • the Multicast Enable corresponding to this/these F-UP IDs can be set to Disable.
  • Failed List ⁇ F-UP ⁇ may also be used in the MBS session start response to indicate the F-UP that is not assigned a sub-user plane node.
  • Step S2214 F-CP1 sends a user plane MBS session modification request to F-UP23 according to the List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contained in the MBS session start response fed back by S-CP2, and F- The UP23 feeds back the user plane MBS session modification response to the F-CP1.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • F-CP1 determines that F-UP23 is not assigned any lower-level user plane node
  • F-CP1 sends a user plane MBS session deletion request to F-UP23
  • F-UP23 receives the user plane MBS session after receiving the user plane MBS session.
  • After the delete request send out an IGMP Leave data packet, and exit from the multicast transport group indicated by the multicast transport address IP3 assigned by the F-UP12, and the F-UP23 replies to the F-CP1 with a user plane MBS session deletion response (this process is not identified in the figure).
  • Step S2215 after the F-CP1 receives the MBS session start responses fed back by all the S-CPs, the F-CP1 sends the MBS session start responses to the parent control plane node of the F-CP1 according to the MBS session start responses fed back by all the S-CPs.
  • the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 contains the UP ID (the UP ID is the identifier of the user plane node at the same level as the parent control plane node of F-CP1 ), and may also contain List of F-TEIDfup and Multicast Enable.
  • F-CP1 has two sub-control plane nodes S-CP1 and S-CP2, and F-CP1 selects the next-level user plane node F- UP21 and F-UP22, F-CP1 selects the next-level user plane node F-UP23 for F-UP12, and S-CP1 selects sub-user plane nodes S-UP11 and S-UP12 for F-UP21, S-CP2 Sub-user plane nodes S-UP31 and S-UP32 are selected for F-UP23.
  • the S-CP1 does not select a sub-user plane node for the F-UP22, the F-UP22 needs to be deleted from the user plane MBS transmission tree.
  • a user plane node in the process of establishing a user plane MBS session, there may be a user plane node that is simultaneously sent a user plane MBS session establishment request message by two control plane nodes, or has been selected by a control plane node and then receives the message.
  • User plane MBS session establishment request message sent by another control plane node. If a user plane node simultaneously receives the user plane MBS session establishment request messages sent by two control plane nodes (of course, there may be more, and two are used as an example here), the user plane node can In the MBS session establishment response message, normally respond to the user plane MBS session establishment request sent by one of the control plane nodes, and in the other user plane MBS session establishment response message, reject the other control plane node to indicate the user.
  • the face node has been selected. If a user plane node already has a parent user plane node through a control plane node, and receives a user plane MBS session establishment request message sent by another control plane node, the other user plane MBS session establishment response message in the Reject the other control plane node to indicate that the user plane node has been selected.
  • Step S2216a the F-UP11 receives the downlink MBS service data sent by the parent user plane node of the F-UP11. Then, the received downlink MBS service data is transmitted to the F-UP21 through step S2217a. F-UP21 transmits the received downlink MBS service data to S-UP11 and S-UP12 through step S2218a.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps
  • each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • Step S2216b the F-UP12 receives the downlink MBS service data sent by the parent user plane node of the F-UP12. Then, the received downlink MBS service data is transmitted to the F-UP23 through step S2217c, and the F-UP23 transmits the received downlink MBS service data to S-UP31 and S-UP32 through step S2218c.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps
  • each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • chapter 5.3.4.2.2 of the standard TS23.501 defines one or more I-SMFs and one or more I-UPFs (Intermediate-UPF, intermediate user plane function entities) in a non-roaming situation to participate in a Architecture of the PDU session.
  • I-SMF Intermediate-UPF, intermediate user plane function entities
  • the name of the UPF controlled by SMF remains unchanged, and is still called UPF, while the UPF controlled by I-SMF is called I-UPF.
  • the embodiments of the present application propose that the I-SMF and the I-UPF can participate in the MBS session.
  • the specific process of establishing the MBS transmission tree on the user plane can be referred to as shown in FIG. 23 , including the following steps:
  • Step S2301 the F-CP1 receives an MBS session start request sent by the parent control plane node of the F-CP1.
  • the specific process is similar to the aforementioned step S1501, and will not be repeated here.
  • the IP multicast transmission address included in the MBS IP Multicast Distribution in the MBS session start request is recorded as IP1.
  • the F-CP1 may determine to select one or more F-UPFs from the multiple F-UPFs according to the information of the child control plane nodes of the F-CP1 As the user plane nodes at the same level as the F-CP1, it is assumed in this embodiment that two user plane nodes are selected, denoted as F-UP11 and F-UP12. Then step S2302a and step S2302b are executed respectively.
  • Step S2302a the F-CP1 sends a user plane MBS session establishment request to the F-UP11, and the F-UP11 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP11 in step S2302a is recorded as IP2.
  • Step S2302b the F-CP1 sends a user plane MBS session establishment request to the F-UP12, and the F-UP12 feeds back a user plane MBS session establishment response to the F-CP1.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here, wherein the IP multicast transmission address allocated by the F-UP12 in step S2302b is recorded as IP3.
  • Step S2303 if F-UP11 and F-UP12 support receiving data transmitted based on multicast, then apply to join the multicast transmission group corresponding to the IP multicast transmission address IP1 to receive the parent users of F-UP11 and F-UP12 MBS service data sent by the plane node.
  • F-CP1 determines that the UPF managed by F-CP1 and the UPF managed by the sub control plane node of F-CP1 cannot directly establish a transmission path according to the service area information of the sub-control plane node (usually the NR base station) of F-CP1, then The F-CP1 selects an I-SMF, wherein the selected I-SMF can communicate with the F-CP1 and the sub-control plane nodes of the F-CP1. In this embodiment, it is assumed that an I-SMF is selected, and then step S2304 is executed.
  • Step S2304 the F-CP1 sends an MBS session start request (ie, Nscp_MBSSessionStart Request) to the I-SMF.
  • MBS session start request ie, Nscp_MBSSessionStart Request
  • the MBS session start request sent by F-CP1 to I-SMF contains the following parameters: TMGI, MBS Session Duration, List of S-CP, MBS QFIs, QoS Profile, MBS Time to Data Transfer, List of ⁇ F-UP ID , MBS transmission information ⁇ , MBS Service Area.
  • F-CP1 includes the sub-control plane node information List of S-CP provided by F-CP1 in the MBS session start request sent to I-SMF is mainly because I-SMF is dynamically selected and added by F-CP1 For MBS service management, I-SMF does not have any MBS UE Context (for MBS multicast service) or user plane node information.
  • List of ⁇ F-UP ID, MBS Transport Information ⁇ only includes the ID of F-UP11 and the MBS IP Multicast Distribution corresponding to the ID of F-UP11.
  • the MBS IP Multicast Distribution corresponding to the F-UP11 ID is allocated by the F-UP11, which includes the new IP multicast transport address IP2 and C-TEID allocated by the F-UP11 in step S2302a.
  • step S2305a and step S2305b are performed.
  • Step S2305a the I-SMF sends user plane MBS session establishment requests to I-UPF11 and I-UPF12 respectively, and I-UPF11 and I-UPF12 respectively feed back user plane MBS session establishment responses to I-SMF.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here.
  • I-UPF11 and I-UPF12 are respectively allocated new IP multicast transmission addresses, which are respectively recorded as IP4 and IP5 in this embodiment, and the new IP multicast transmission address IP4 allocated by I-UPF11 is used for It transmits MBS service data to the sub-user plane node of I-UPF11 (that is, S-UP11 in Figure 23); the new IP multicast transmission address IP5 allocated by I-UPF12 is used to transmit the MBS service data to the sub-user plane node of I-UPF12 (ie S-UP12 in Fig. 23) to transmit MBS service data.
  • the I-UPF11 does not support receiving the MBS service data sent by the F-UP11 through multicast, then the I-UPF11 will allocate an F-TEID to receive the MBS service data from the F-UP11 in a point-to-point manner; similarly, if the I-UPF12 does not support receiving the MBS service data sent by the F-UP11 through multicast, so the I-UPF12 will allocate an F-TEID to receive the MBS service data from the F-UP11 in a point-to-point manner.
  • Step S2305b the I-SMF sends a user plane MBS session establishment request to the I-UPF21 and I-UPF22 respectively, and the I-UPF21 and I-UPF22 respectively feed back the user plane MBS session establishment response to the I-SMF.
  • This process is similar to the process of step S1502 in the foregoing embodiment, and will not be repeated here.
  • I-UPF21 and I-UPF22 are respectively allocated new IP multicast transmission addresses, which are respectively recorded as IP6 and IP7 in this embodiment, and the new IP multicast transmission address IP6 allocated by I-UPF21 is used for It transmits MBS service data to the sub-user plane node of I-UPF21 (that is, S-UP21 in Figure 23 ); the new IP multicast transmission address IP7 allocated by I-UPF22 is used to transmit the MBS service data to the sub-user plane node of I-UPF22 (ie S-UP22 in Fig. 23) to transmit MBS service data.
  • I-UPF21 does not support receiving MBS service data sent by F-UP11 through multicast
  • I-UPF21 will allocate an F-TEID to receive MBS service data from F-UP11 in a point-to-point manner
  • the I-UPF22 does not support receiving the MBS service data sent by the F-UP11 through multicast, so the I-UPF22 will allocate an F-TEID to receive the MBS service data from the F-UP11 in a point-to-point manner.
  • the IP multicast transmission address in the MBS IP Multicast Distribution included in the user plane MBS session establishment request in steps S2305a and S2305b is the IP allocated by F-UP11 in step S2302a Multicast transport address IP2.
  • I-UPF11 and I-UPF12 are drawn together, I-UPF21 and I-UPF22 are drawn together, S-UP11 and S-UP12 are drawn together, and S-UPF11 and S-UP12 are drawn together.
  • -UP21 and S-UP22 are drawn together.
  • Step S2306a if the I-UPF11 and the I-UPF12 support receiving data transmitted based on multicast, apply to join the multicast transmission group corresponding to the IP multicast transmission address IP2 to receive the MBS service data sent by the F-UP11.
  • Step S2306b if I-UPF21 and I-UPF22 support receiving data transmitted based on multicast, apply to join the multicast transmission group corresponding to IP multicast transmission address IP2 to receive MBS service data sent by F-UP11.
  • Step S2307 the I-SMF sends an MBS session start request to the sub-control plane node S-CP1 provided by the F-CP1.
  • the MBS session start request sent by I-SMF to S-CP1 contains the following parameters: TMGI, MBS QFIs, QoS Profile, List of ⁇ I-UPF ID, MBS transmission information ⁇ , MBS Service Area.
  • the List of ⁇ I-UPF ID, MBS transmission information ⁇ contains the IDs corresponding to I-UPF11, I-UPF12, I-UPF21, and I-UPF22, respectively, as well as I-UPF11, I-UPF12, MBS transmission information corresponding to I-UPF21 and I-UPF22 respectively.
  • the IP multicast transmission address contained in the MBS transmission information corresponding to I-UPF11 is IP4, and the IP multicast transmission address contained in the MBS transmission information corresponding to I-UPF12 is IP5, and the MBS transmission information corresponding to I-UPF21 contains The IP multicast transmission address is IP6, and the IP multicast transmission address included in the MBS transmission information corresponding to I-UPF22 is IP7, and IP4, IP5, IP6 and IP7 are different.
  • S-CP1 sends user plane MBS session establishment requests to S-UP11, S-UP12, S-UP21 and S-UP22 respectively, and receives user feedback from S-UP11, S-UP12, S-UP21 and S-UP22 respectively face MBS session establishment response.
  • the S-UP11 supports receiving multicast transmission, it can join the multicast transmission group corresponding to the IP multicast transmission address IP4 allocated by the I-UPF11 to receive the MBS service data sent by the I-UPF11; if the S-UP12 supports receiving multiple If the S-UP21 supports receiving multicast transmission, you can join the I-UPF21
  • the multicast transmission group corresponding to the assigned IP multicast transmission address IP6 is used to receive the MBS service data sent by the I-UPF21; if the S-UP22 supports receiving multicast transmission, it can be added to the IP multicast transmission address IP7 assigned by the I-UPF22.
  • the specific process is similar to step S1505a and step S1506, and will not be repeated.
  • Step S2309 the S-CP1 sends an MBS session start response to the I-SMF. If any S-UP in S-UP11, S-UP12, S-UP21 and S-UP22 does not support receiving data based on multicast transmission, but supports receiving MBS service data in point-to-point mode, then S-CP1 sends I-SMF
  • the sent MBS session start response contains the F-TEID allocated by the S-UP, and corresponds to the corresponding I-UPF, thus forming a List of ⁇ I-UPF ID, List of F-TEIDsup, Multicast Enable ⁇ .
  • List of ⁇ I-UPF ID, List of F-TEIDsup, Multicast Enable ⁇ contains List of F-TEIDsup and Multicast for I-UPF11, I-UPF12, I-UPF21, I-UPF22, respectively Enable.
  • this List F-TEIDsup only corresponds to those that do not support receiving Multicast transmission, but supports S-UP for receiving MBS service data in a peer-to-peer manner. For other descriptions, refer to the related content of step S1507.
  • the S-CP1 decides not to allocate any sub-user plane nodes to one/some of the I-UPF IDs
  • the Multicast Enable corresponding to this/these I-UPF IDs can be set to Disable.
  • Failed List ⁇ I-UPF ⁇ may also be used in the MBS session start response to indicate the I-UPFs that are not assigned sub-user plane nodes.
  • Step S2310a the I-SMF sends a user plane MBS session modification request to the I-UPF 11/12 according to the List of ⁇ I-UPF ID, List of F-TEIDsup, Multicast Enable ⁇ contained in the MBS session start response fed back by the S-CP1 respectively.
  • the I-UPF 11/12 feeds back the user plane MBS session modification response to the I-SMF.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • the I-SMF determines that the I-UPF11 or I-UPF12 is not assigned any sub-user plane node, the I-SMF sends a user plane MBS session deletion request to the I-UPF11 or I-UPF12, and the I-UPF11 Or I-UPF12, after receiving the user plane MBS session deletion request, sends out an IGMP Leave data packet, exits from the multicast transport group indicated by the multicast transport address IP2 assigned by F-UP11, and I-UPF11 or I-UPF12 Reply to the I-SMF with a user plane MBS session deletion response (this process is not identified in the figure).
  • Step S2310b the I-SMF sends a user plane MBS session modification request to the I-UPF 21/22 according to the List of ⁇ I-UPF ID, List of F-TEIDsup, Multicast Enable ⁇ contained in the MBS session start response fed back by the S-CP1 respectively.
  • the I-UPF 21/22 feeds back the user plane MBS session modification response to the I-SMF.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • the I-SMF determines that the I-UPF21 or I-UPF22 is not assigned any sub-user plane node, the I-SMF sends a user plane MBS session deletion request to the I-UPF21 or I-UPF22, and the I-UPF21 Or I-UPF22, after receiving the user plane MBS session deletion request, sends out an IGMP Leave data packet, exits from the multicast transport group indicated by the multicast transport address IP2 assigned by F-UP11, and I-UPF21/22 sends IGMP Leave - The SMF replies with a user plane MBS session delete response (this process is not identified in the figure).
  • Step S2311 the I-SMF sends an MBS session start response to the F-CP1. If any I-UPF in I-UPF11, I-UPF12, I-UPF21, and I-UPF22 does not support receiving data transmitted by multicast, but supports receiving MBS service data by point-to-point, then I-SMF sends F-CP1
  • the sent MBS session start response contains the F-TEID allocated by this I-UPF and corresponds to F-UP11, thus forming a List of ⁇ F-UP ID, List of F-TEIDiupf, Multicast Enable ⁇ .
  • List of ⁇ F-UP ID, List of F-TEIDiupf, Multicast Enable ⁇ contains List of F-TEIDiufp and Multicast Enable for F-UP11.
  • this List F-TEIDiupf only corresponds to those that do not support receiving Multicast transmission, but supports I-UPF for receiving MBS service data in a peer-to-peer manner. For other descriptions, refer to the related content of step S1507.
  • Step S2312 if I-UPF11, I-UPF12, I-UPF21, and I-UPF22 have I-UPFs that do not support receiving multicast transmission but support receiving MBS service data in a point-to-point manner, then F-CP1 sends F-UP11 Send the user plane MBS session modification request, and the F-UP11 feeds back the user plane MBS session modification response to the F-CP1.
  • the user plane MBS session modification request sent by F-CP1 to F-UP11 includes I-UPF11, I-UPF12, I-UPF21, and I-UPF22, which do not support receiving multicast transmission, but support using point-to-point mode to receive MBS
  • the F-TEID of the I-UPF of the service data is used to instruct the F-UP11 to increase the use of point-to-point to I-UPF11, I-UPF12, I-UPF21, I-UPF22. It does not support receiving multicast transmission, but supports the use of point-to-point mode
  • the I-UPF receiving the MBS service data transmits the MBS service data.
  • F-CP1 determines that F-UP11 is not assigned any lower-level user plane node
  • F-CP1 sends a user plane MBS session deletion request to F-UP11
  • F-UP11 receives the user plane MBS session after receiving the user plane MBS session.
  • After the delete request send an IGMP Leave packet, and exit from the multicast transport group indicated by the multicast transport address IP1 assigned by the parent user plane node of F-UP11, and F-UP11 replies to F-CP1 to delete the user plane MBS session Response (this process is not identified in the diagram).
  • Step S2313 the F-CP1 sends an MBS session start request to the child control plane node S-CP2 of the F-CP1 according to the information of the child control plane node of the F-CP1.
  • the MBS session start request sent by F-CP1 to the sub-control plane node S-CP2 of F-CP1 contains the following parameters: TMGI, MBS Session Duration, MBS QFIs, QoS Profile, MBS Time to Data Transfer, List of ⁇ F- UP ID, MBS transmission information ⁇ , MBS Service Area.
  • the MBS transmission information is MBS IP Multicast Distribution (IP Multicast Distribution address, C-TEID).
  • the List of ⁇ F-UP ID, MBS transmission information ⁇ includes the F-UP12 ID and the MBS IP Multicast Distribution corresponding to the F-UP12 ID.
  • the MBS IP Multicast Distribution corresponding to the F-UP12 ID is allocated by the F-UP12, and the IP multicast transmission address contained therein is the new IP multicast transmission address IP3 allocated by the F-UP12 in step S2302b.
  • step S2313 and step S2304 do not have a sequential relationship, and they may be steps executed by the F-CP1 in parallel.
  • Step S2314 after receiving the MBS session start request sent by the F-CP1, the S-CP2 performs a user plane MBS session establishment process. Specifically, the S-CP2 selects one or more S-UPs for the F-UP12 from the multiple S-UPs according to the information of the sub-control plane nodes of the S-CP2. In this embodiment, it is assumed that an S-UP is selected for the F-UP12. UP31 and S-UP32. Then S-CP2 sends user plane MBS session establishment requests to S-UP31 and S-UP32 respectively, and receives the user plane MBS session establishment responses fed back by S-UP31 and S-UP32 respectively.
  • S-UP31 and S-UP32 support Receiving the multicast transmission
  • the sub-user plane node that receives the MBS service data in a point-to-point manner can allocate an F-TEID to receive the MBS service data sent by the F-UP12 in a point-to-point manner.
  • Step S2315 S-CP2 sends an MBS session start response to F-CP1. If there are S-UPs in S-UP31 and S-UP32 that do not support receiving data based on multicast transmission, but support receiving MBS service data in point-to-point mode, the MBS session start response sent by S-CP2 to F-CP1 contains The F-TEID allocated by this S-UP corresponds to the F-UP, thus forming a List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ . In this embodiment, List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ contains List of F-TEIDsup and Multicast Enable for F-UP12.
  • this List F-TEIDsup only corresponds to those that do not support receiving Multicast transmission, but supports S-UP for receiving MBS service data in a peer-to-peer manner. For other descriptions, refer to the related content of step S1507.
  • Step S2316 F-CP1 sends a user plane MBS session modification request to F-UP12 according to the List of ⁇ F-UP ID, List of F-TEIDsup, Multicast Enable ⁇ included in the MBS session start response fed back by S-CP2, and F- The UP12 feeds back the user plane MBS session modification response to the F-CP1.
  • the specific description of this step is similar to that of the foregoing step S1508, and will not be repeated here.
  • F-CP1 determines that F-UP12 is not assigned any lower-level user plane node
  • F-CP1 sends a user plane MBS session deletion request to F-UP12
  • F-UP12 receives the user plane MBS session after receiving the user plane MBS session.
  • After the delete request send an IGMP Leave packet, and exit from the multicast transport group indicated by the multicast transport address IP1 assigned by the parent user plane node of F-UP12, and F-UP12 replies to F-CP1 to delete the user plane MBS session Response (this process is not identified in the diagram).
  • Step S2317 after the F-CP1 receives the MBS session start responses fed back by all the sub-control plane nodes of the F-CP1, the F-CP1 starts responding to the F-CP1 according to the MBS session start responses fed back by all the sub-control plane nodes of the F-CP1.
  • the parent control plane node sends an MBS session start response.
  • the MBS session start response that F-CP1 replies to the parent control plane node of F-CP1 contains the UP ID (the UP ID is the identifier of the user plane node at the same level as the parent control plane node of F-CP1 ), and may also contain List of F-TEIDfup and Multicast Enable.
  • F-CP1 has two sub-control plane nodes S-CP1 and S-CP2, F-CP1 selects I-SMF, and I-SMF selects I-UPF11 , I-UPF12, I-UPF21, I-UPF22.
  • S-CP1 selects S-UP11 for I-UPF11, S-UP12 for I-UPF12, S-UP21 for I-UPF21, S-UP22 for I-UPF22, and S-CP2 for F- UP12 chose S-UP31 and S-UP32.
  • the same I-SMF sends two user plane MBS session establishment requests (corresponding to the case where different control plane nodes select the same I-SMF), or two different I-SMFs send a
  • the user plane MBS session establishment request (corresponding to the case where different control plane nodes select different I-SMFs)
  • the intermediate user plane node can normally respond to one of the user plane MBS session establishment requests, In a response message of a user plane MBS session establishment request, another control plane node is rejected (Reject) to indicate that the user plane node has been selected.
  • the response to the other user plane MBS session establishment request Reject another control plane node in the message to indicate that the user plane node has been selected.
  • Step S2318a the F-UP11 receives the downlink MBS service data sent by the parent user plane node of the F-UP11. Then, the received downlink MBS service data is transmitted to I-UPF11 and I-UPF12 through step S2319a, and the received downlink MBS service data is transmitted to I-UPF21 and I-UPF22 through step S2319b. Then in step S2320a, the I-UPF11 transmits the downlink MBS service data to the S-UP11, and the I-UPF12 transmits the downlink MBS service data to the S-UP12.
  • step S2320b the I-UPF21 transmits the downlink MBS service data to the S-UP21, and the I-UPF22 transmits the downlink MBS service data to the S-UP22.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps, and at the same time, each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps.
  • Step S2318b the F-UP12 receives the downlink MBS service data sent by the parent user plane node of the F-UP12. Then, the received downlink MBS service data is transmitted to S-UP31 and S-UP32 through step S2319c.
  • each user plane node transmits the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps, and at the same time, each user plane node receives the MBS service data in the multicast transmission mode or the point-to-point transmission mode determined in the previous steps. .
  • F-CP represents a parent control plane node
  • F-UP represents a parent user plane node
  • S-CP represents a child control plane node
  • S-UP represents a child user plane node.
  • the SMF can be replaced by the F-CP and the UPF can be replaced by the F-UP, in which case the S-CP and the S-UP are combined to replace the access network node.
  • MB-SMF can be replaced by S-CP and MB-UPF can be replaced by S-UP .
  • the MB-SMF can be replaced by the F-CP and the MB-UPF by the F-UP, in which case the S-CP is combined with the S-UP to replace the NG-RAN.
  • Figures 10 and 11 show the basic architecture diagrams of two 5G MBSs, in which enhancement processing can be performed.
  • the technical solution shown in FIG. 21 or FIG. 22 can be used to establish a user plane MBS session tree; when an extra MB-SMF or SMF occurs (at this time, an extra UPF occurs) , the user plane MBS session tree can be established by using the technical solution shown in FIG. 23 .
  • the technical solutions of the above embodiments of the present application implement the process of establishing a user plane MBS session, which can prevent the occurrence of a transmission loop of the user plane MBS session, and avoid the problem of broken branches in the transmission tree of the user plane MBS session.
  • the same parent control plane provides multiple parent user plane nodes at the same time when the control plane and the user plane are separated during the establishment of the user plane MBS session.
  • the same control plane node can manage different user plane nodes to form parent and child transmission, which optimizes the user plane transmission resources, and can not be established between the parent user plane node and the base station during the establishment of the user plane MBS session.
  • I-SMF and I-UPF are found and inserted to complete the establishment of the user plane transmission tree, which effectively realizes the optimization of the user plane transmission resources.
  • FIG. 24 shows a block diagram of a communication apparatus of a multicast broadcast service according to an embodiment of the present application, and the communication apparatus of the multicast broadcast service may be set in the I-SMF.
  • a communication apparatus 2400 for a multicast broadcast service includes: a first receiving unit 2402 , a selection unit 2404 , a first interaction unit 2406 and a second interaction unit 2408 .
  • the first receiving unit 2402 is configured to receive a first MBS session start request sent by the i-th level control plane node in the MBS session transmission tree, where the first MBS session start request includes the i-th level control plane
  • the information of the child control plane node provided by the node, the identification information of the i-th level user plane node corresponding to the i-th level control plane node, the first MBS IP multicast transmission address allocated by the i-th level user plane node and the The first C-TEID used to transmit MBS service data by multicast, i 1, . . .
  • the selection unit 2404 is configured to The information of the sub control plane node provided by the i-th level control plane node selects an intermediate user plane node, and the intermediate user plane node can be established with the i-th level user plane node and the user plane function entity managed by the sub control plane node.
  • the first interaction unit 2406 is configured to send a first user plane MBS session establishment request to the intermediate user plane node, and receive a first user plane MBS session establishment response fed back by the intermediate user plane node, the first user
  • the first MBS IP multicast transport address and the first C-TEID are included in the request for establishing a plane MBS session, and the first MBS IP multicast transport address is used to make the intermediate user plane node join the first MBS
  • the multicast transmission group corresponding to the IP multicast transmission address receives the MBS service data sent by the i-th level user plane node through multicast
  • the control plane node sends a second MBS session start request to instruct the sub control plane node provided by the i-th level control plane node to allocate a sub user plane node to the intermediate user plane node, and the second MBS session start request includes There is the identification information of the intermediate user plane node, and the second MBS IP multicast transmission address and the second C-TEID allocated by the intermediate user plane node, and the second
  • the first user plane MBS session establishment request includes instruction information for instructing the intermediate user plane node to allocate new MBS IP multicast distribution information;
  • the first user plane MBS session establishment request includes instruction information for instructing the intermediate user plane node to allocate new MBS IP multicast distribution information;
  • a user plane MBS session establishment response includes the second MBS IP multicast transmission address and the second C-TEID allocated by the intermediate user plane node.
  • the A user plane MBS session establishment request includes indication information requesting to allocate an F-TEID (Fully qualified Tunnel Endpoint Identifier) to the intermediate user plane node
  • the first user plane MBS session establishment response includes There is an F-TEID allocated by the intermediate user plane node, and the F-TEID is used to enable the intermediate user plane node to receive the MBS service data sent by the i-th level user plane node in a point-to-point manner
  • the first user plane MBS session establishment response indicates that the intermediate user plane node does not support multicasting, but supports receiving the MBS service data of the i-th level user plane node in a point-to-point manner, and includes the intermediate user plane node.
  • the F-TEID assigned by the user plane node is not limited to the following three-points:
  • the second interaction unit 2408 is further configured to: after sending the second MBS session start request to the sub-control plane node provided by the i-th level control plane node, receive the The sub-control plane node feeds back a second MBS session start response to the second MBS session start request, where the second MBS session start response includes the first indication information;
  • the first indication information includes identification information of the intermediate user plane node, first F-TEID list information, and first field information used to indicate that multicast transmission is started, and the first field information indicates Among the sub-user plane nodes allocated by the sub-control plane node to the intermediate user-plane node, there is a sub-user-plane node that supports receiving MBS service data sent by the intermediate user-plane node in a multicast manner, and the first F- The TEID list information includes the F-TEID of the sub-user plane node that does not support multicast, but supports receiving the MBS service data sent by the intermediate user plane node in a point-to-point manner; or
  • the first indication information includes the identification information of the intermediate user plane node, and does not include the first F-TEID list information and the first field information, then the first indication information is used to indicate the The sub-user plane nodes allocated by the sub-control plane node to the intermediate user plane node all support receiving MBS service data sent by the intermediate user plane node through multicast; or
  • the first indication information includes the identification information of the intermediate user plane node, the first F-TEID list information, and does not include the first field information, then the first indication information is used to indicate the The sub-user plane nodes allocated by the sub-control plane node to the intermediate user plane node do not support multicasting but support receiving MBS service data sent by the intermediate user plane node in a point-to-point manner; or
  • the first indication information includes the identification information of the intermediate user plane node and the field information for disabling multicast transmission, and does not include the first F-TEID list information, then the first indication information is used to indicate The child control plane node does not allocate a child user plane node to the intermediate user plane node.
  • the second MBS session start response includes a first indication information list, and the first indication information list The first indication information corresponding to all intermediate user plane nodes is included.
  • the second MBS session start response further includes a list of failed identification information, where the failed identification information list is used to indicate a target that is not assigned a sub-user plane node Intermediate user plane node.
  • the first interaction unit 2406 is further configured to: if it is determined according to the second MBS session start response that there is a target intermediate user plane node that is not assigned a sub-user plane node, send the The target intermediate user plane node sends a user plane MBS session deletion request.
  • the first interaction unit 2406 is further configured to: receive a user plane MBS session deletion response fed back by the target intermediate user plane node, where the user plane MBS session deletion response is the Sent by the target intermediate user plane node after receiving the user plane MBS session deletion request, wherein, if the target intermediate user plane node has joined the multicast transmission group corresponding to the first MBS IP multicast transmission address, Then exit the multicast transmission group corresponding to the first MBS IP multicast transmission address after receiving the user plane MBS session deletion request.
  • the first interaction unit 2406 is configured to: after receiving the level i control plane After the second MBS session start response fed back by all the sub-control plane nodes provided by the node, it is determined whether there is a target intermediate user plane node that is not assigned a sub-user plane node.
  • the first interaction unit 2406 is further configured to: after receiving the second MBS session start response fed back by the sub control plane node for the second MBS session start request, if The first indication information includes the first F-TEID list information, and the user plane MBS session modification is sent to the intermediate user plane node according to the identification information of the intermediate user plane node contained in the first indication information request, to instruct the intermediate user plane node to transmit MBS service data to the sub-user plane nodes corresponding to each F-TEID included in the first F-TEID list information in a point-to-point manner;
  • the user plane MBS session modification request is further used to instruct the intermediate user plane node to simultaneously use multicast transmission to the intermediate user
  • the sub-user plane node of the plane node sends MBS service data
  • the user plane MBS session modification request is further used to indicate that the intermediate user plane node does not need to use multicast transmission to send the information to the intermediate user plane node
  • the sub-user plane node sends MBS service data.
  • the first interaction unit 2406 is further configured to: if at least two intermediate user plane nodes are selected, start each intermediate user included in the response according to the second MBS session The first indication information corresponding to the plane node sends the user plane MBS session modification request to the intermediate user plane node that needs to send the user plane MBS session modification request.
  • the second interaction unit 2408 is further configured to: after receiving the second MBS session start response fed back by the sub-control plane node for the second MBS session start request, according to The sub control plane node feeds back a second MBS session start response, and feeds back a first MBS session start response to the first MBS session start request to the i-th level control plane node.
  • the second interaction unit 2408 is configured to: if the level i control plane node provides at least two sub-control plane nodes, after receiving the level i control plane After the second MBS session start response fed back by all the sub-control plane nodes provided by the node, the first MBS session start response is fed back to the i-th level control plane node.
  • the first MBS session start response includes second indication information
  • the second indication information includes the identification information of the i-th level user plane node, the second F-TEID list information, and the second field information used to indicate that multicast transmission is started.
  • the second field The information indicates that there is an intermediate user plane node that supports receiving the MBS service data sent by the i-th user plane node through multicast, and the second F-TEID list information includes information that does not support multicast, but supports point-to-point The F-TEID of the intermediate user plane node that receives the MBS service data sent by the i-th level user plane node; or
  • the second indication information includes the identification information of the i-th user plane node and does not include the second F-TEID list information and the second field information, then the second indication information is used to indicate
  • the intermediate user plane nodes all support receiving MBS service data sent by the i-th level user plane node through multicast; or
  • the second indication information includes the identification information of the i-th level user plane node, the second F-TEID list information, and does not include the second field information, then the second indication information is used to indicate None of the intermediate user plane nodes supports multicasting, but supports receiving MBS service data sent by the i-th level user plane nodes in a point-to-point manner.
  • the first MBS session start response includes second indication information
  • the second indication information list includes the second indication information corresponding to all the i-th level user plane nodes respectively.
  • the first MBS session start request includes each level i The respective identification information of the level user plane nodes, and the first MBS IP multicast transmission address and the first C-TEID assigned by each level i user plane node; wherein, the first MBS assigned by different level i user plane nodes IP multicast transport addresses are not the same.
  • FIG. 25 shows a block diagram of a communication apparatus for a multicast broadcast service according to an embodiment of the present application, and the communication apparatus for the multicast broadcast service may be set in an i-th level control plane node.
  • a communication apparatus 2500 for a multicast broadcast service includes: a third interaction unit 2502 and a fourth interaction unit 2504 .
  • the four-interaction unit 2504 is configured to select an intermediate session management function entity I-SMF, and send a first MBS session start request to the I-SMF, where the first MBS session start request includes the information provided by the i-th level control plane node.
  • An MBS session start request is used to instruct the I-SMF to select an intermediate user plane node capable of establishing a connection with the i-th level user plane node and the user plane functional entity managed by the sub-control plane node, and to communicate with the intermediate user plane node.
  • the user plane node establishes a user plane MBS session, so that the intermediate user plane node joins the multicast transmission group corresponding to the first MBS IP multicast transmission address to receive the information sent by the i-th level user plane node through multicast.
  • the node assigns a sub-user plane node, and enables the sub-user plane node to receive the MBS service data sent by the intermediate user plane node.
  • the fourth interaction unit 2504 is further configured to: after sending the first MBS session start request to the I-SMF, receive the I-SMF for the first MBS The first MBS session start response fed back by the session start request; according to the content contained in the first MBS session start response, it is determined whether to send a user plane MBS session modification request to the i-th level user plane node.
  • the fourth interaction unit 2504 is configured to: if the information of the sub-control plane node provided by the i-th level control plane node is used to determine the management of the i-th level control plane node If the user plane functional entity cannot directly establish a transmission path with the user plane functional entity managed by the sub control plane node, the SMF that can communicate with the i-th level control plane node and the sub control plane node is selected as the described I-SMF.
  • FIG. 26 shows a block diagram of a communication apparatus for a multicast broadcast service according to an embodiment of the present application, and the communication apparatus for the multicast broadcast service may be set in an intermediate user plane node.
  • a communication apparatus 2600 for a multicast broadcast service includes: a second receiving unit 2602 , a sending unit 2604 and a processing unit 2606 .
  • the second receiving unit 2602 is configured to receive a first user plane MBS session establishment request sent by the I-SMF, where the first user plane MBS session establishment request includes the first MBS IP address allocated by the i-th level user plane node.
  • the sending unit 2604 is configured to feed back the first user plane MBS session establishment response to the I-SMF
  • the MBS session establishment response includes the second MBS IP multicast transport address and the second C-TEID allocated by the intermediate user plane node, and the second MBS IP multicast transport address is used for the sub-user plane of the intermediate user plane node
  • the node joins the multicast transmission group corresponding to the second MBS IP multicast transmission address to receive the MBS service data transmitted by the intermediate user plane node through multicast;
  • the processing unit 2606 is configured to support the intermediate user plane node through In the case of receiving the MBS service data sent by the i-th level user plane
  • the processing unit 2606 is further configured to: if the intermediate user plane node does not support multicast, but supports point-to-point reception of the data sent by the i-th level user plane node For MBS service data, the F-TEID for receiving the MBS service data sent by the i-th level user plane node in a point-to-point manner is allocated.
  • the second receiving unit 2602 is further configured to: after the sending unit 2604 feeds back a first user plane MBS session establishment response to the I-SMF, receive the I-SMF transmission
  • the user plane MBS session modification request contains the first F-TEID list information
  • the first F-TEID list information contains information that does not support multicast, but supports point-to-point receiving the F-TEID of the sub-user plane node of the MBS service data sent by the intermediate user plane node;
  • the processing unit 2606 is further configured to: based on the first F-TEID list information, respectively transmit MBS service data to the sub-user plane nodes corresponding to each F-TEID included in the first F-TEID list information in a point-to-point manner , and determine, according to the user plane MBS session modification request, whether to simultaneously use multicast transmission to send MBS service data to the sub-user plane nodes of the intermediate user plane node.
  • the sending unit 2604 is further configured to: when receiving the user plane MBS session deletion request sent by the I-SMF, send the user plane MBS session deletion to the I-SMF Response; wherein, if you have joined the multicast transmission group corresponding to the first MBS IP multicast transmission address, after receiving the user plane MBS session deletion request, exit the first MBS IP multicast transmission address The corresponding multicast transport group.
  • the processing unit 2606 is further configured to: if multiple user plane MBS session establishment requests are received, for a user plane MBS among the multiple user plane MBS session establishment requests The session establishment request feeds back a user plane MBS session establishment response, and returns a reject message for other user plane MBS session establishment requests in the multiple user plane MBS session establishment requests to indicate that the user plane node has been selected; or
  • FIG. 27 shows a schematic structural diagram of a computer system suitable for implementing the electronic device of the embodiment of the present application.
  • the computer system 2700 includes a central processing unit (Central Processing Unit, CPU) 2701, which can be loaded into a random device according to a program stored in a read-only memory (Read-Only Memory, ROM) 2702 or from a storage part 2708
  • a program in a memory (Random Access Memory, RAM) 2703 is accessed to perform various appropriate actions and processes, such as performing the methods described in the above embodiments.
  • RAM 2703 Random Access Memory
  • various programs and data required for system operation are also stored.
  • the CPU 2701, the ROM 2702, and the RAM 2703 are connected to each other through a bus 2704.
  • An Input/Output (I/O) interface 2705 is also connected to the bus 2704 .
  • the following components are connected to the I/O interface 2705: an input section 2706 including a keyboard, a mouse, etc.; an output section 2707 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker, etc. ; a storage part 2708 including a hard disk and the like; and a communication part 2709 including a network interface card such as a LAN (Local Area Network) card, a modem, and the like.
  • the communication section 2709 performs communication processing via a network such as the Internet.
  • Drivers 2710 are also connected to I/O interface 2705 as needed.
  • a removable medium 2711 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is mounted on the drive 2710 as needed so that a computer program read therefrom is installed into the storage section 2708 as needed.
  • embodiments of the present application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program comprising a computer program for performing the method illustrated in the flowchart.
  • the computer program may be downloaded and installed from the network through the communication portion 2709, and/or installed from the removable medium 2711.
  • CPU central processing unit
  • the computer-readable medium shown in the embodiments of the present application may be a computer-readable signal medium or a computer-readable storage medium, or any combination of the above two.
  • the computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, or a combination of any of the above.
  • Computer readable storage media may include, but are not limited to, electrical connections with one or more wires, portable computer disks, hard disks, random access memory (RAM), read only memory (ROM), erasable Erasable Programmable Read Only Memory (EPROM), flash memory, optical fiber, portable Compact Disc Read-Only Memory (CD-ROM), optical storage device, magnetic storage device, or any suitable of the above The combination.
  • a computer-readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.
  • a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying a computer-readable computer program therein.
  • Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the foregoing.
  • a computer-readable signal medium can also be any computer-readable medium other than a computer-readable storage medium that can transmit, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device .
  • a computer program embodied on a computer-readable medium may be transmitted using any suitable medium, including but not limited to: wireless, wired, etc., or any suitable combination of the foregoing.
  • each block in the flowchart or block diagram may represent a module, program segment, or part of code, and the above-mentioned module, program segment, or part of code contains one or more executables for realizing the specified logical function instruction.
  • the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.
  • the units involved in the embodiments of the present application may be implemented in software or hardware, and the described units may also be provided in a processor. Among them, the names of these units do not constitute a limitation on the unit itself under certain circumstances.
  • the present application also provides a computer-readable medium.
  • the computer-readable medium may be included in the electronic device described in the above embodiments; it may also exist alone without being assembled into the electronic device. middle.
  • the above-mentioned computer-readable medium carries one or more programs, and when the above-mentioned one or more programs are executed by an electronic device, enables the electronic device to implement the methods described in the above-mentioned embodiments.
  • the exemplary embodiments described herein may be implemented by software, or may be implemented by software combined with necessary hardware. Therefore, the technical solutions according to the embodiments of the present application may be embodied in the form of software products, and the software products may be stored in a non-volatile storage medium (which may be CD-ROM, U disk, mobile hard disk, etc.) or on the network , which includes several instructions to cause a computing device (which may be a personal computer, a server, a touch terminal, or a network device, etc.) to execute the method according to the embodiments of the present application.
  • a computing device which may be a personal computer, a server, a touch terminal, or a network device, etc.

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Abstract

本申请的实施例提供了一种多播广播业务的通信方法、装置、介质及电子设备。该方法包括：接收多播广播业务MBS会话传输树中的第i级控制面节点发送的第一MBS会话开始请求，i＝1,…,N，N为正整数；选择中间用户面节点，向中间用户面节点发送第一用户面MBS会话建立请求，该第一用户面MBS会话建立请求中包含有第一MBS网际互联协议IP多播传输地址和第一通用隧道端点标识C-TEID；向子控制面节点发送第二MBS会话开始请求，以指示子控制面节点为中间用户面节点分配子用户面节点，该第二MBS会话开始请求中包含有中间用户面节点的标识信息，以及中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID。

Description

多播广播业务的通信方法、装置、介质及电子设备
本申请要求于2020年7月17日提交中国专利局、申请号为202010694105.7、申请名称为“多播广播业务的通信方法、装置、介质及电子设备”的中国专利申请的优先权。
技术领域
本申请涉及计算机及通信技术领域，具体而言，涉及一种多播广播业务的通信方法、装置、介质及电子设备。
发明背景
在5G MBS(Multicast and Broadcast Service，多播广播业务)系统中，控制面与用户面是分离的，即控制面节点与用户面节点不再是同一个网络节点，在这种情况下建立用户面MBS会话传输树将面临多种问题。
发明内容
本申请的实施例提供了一种多播广播业务的通信方法、装置、介质及电子设备，进而至少在一定程度上可以在控制面与用户面分离的通信系统架构下，实现用户面MBS会话传输树的建立，并且也可以提高MBS业务数据的传输效率。
本申请的其他特性和优点将通过下面的详细描述变得显然，或部分地通过本申请的实践而习得。
根据本申请实施例的一个方面，提供了一种多播广播业务的通信方法，所述方法包括：接收多播广播业务MBS会话传输树中的第i级控制面节点发送的第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级控制面节点选择的第i级用户面节点的标识信息、所述第i级用户面节点所分配的第一MBS网际互联协议IP多播传输地址与用于通过多播方式传输MBS业务数据的第一通用隧道端点标识C-TEID，i＝1,…,N，N为正整数；根据所述第i级控制面节点的信息及所述第i级控制面节点提供的子控制面节点的信息选择中间用户面节点，所述中间用户面节点能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接；向所述中间用户面节点发送第一用户面MBS会话建立请求，并接收所述中间用户面节点反馈的第一用户面MBS会话建立响应，所述第一用户面MBS会话建立请求中包含有所述第一MBS IP多播传输地址和第一C-TEID，所述第一MBS IP多播传输地址用于使所述中间用户面节点加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据；向所述第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求，以指示所述第i级控制面节点提供的子控制面节点为所述中间用户面节点分配子用户面节点，所述第二MBS会话开始请求中包含有所述中间用户面节点的标识信息，以及所述中间用户面节点分配的第二MBS IP多播传 输地址和第二C-TEID，所述第二MBS IP多播传输地址用于使所述子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式发送的MBS业务数据。
根据本申请实施例的一个方面，提供了一种多播广播业务的通信方法，所述方法包括：向第i级控制面节点选择的第i级用户面节点发送第二用户面多播广播业务MBS会话建立请求，并接收所述第i级用户面节点反馈的第二用户面MBS会话建立响应，所述第i级控制面节点是MBS会话传输树中除最后一级控制面节点之外的任一级控制面节点，i＝1,…,N，N为正整数；选择I-SMF(Intermediate-Session Management Function，中间会话管理功能实体)，向所述I-SMF发送第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级用户面节点的标识信息、所述第i级用户面节点分配的第一MBS网际互连协议IP多播传输地址和第一通用隧道端点标识C-TEID；其中，所述第一MBS会话开始请求用于触发所述I-SMF选择能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接的中间用户面节点，并用于触发所述I-SMF向所述子控制面节点发送第二MBS会话开始请求，所述中间用户面节点用于加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据，所述第二MBS会话开始请求用于指示所述子控制面节点为所述中间用户面节点分配子用户面节点，并使所述子用户面节点接收所述中间用户面节点发送的MBS业务数据。
根据本申请实施例的一个方面，提供了一种多播广播业务的通信方法，所述方法包括：接收中间会话管理功能实体I-SMF发送的第一用户面多播广播业务MBS会话建立请求，所述第一用户面MBS会话建立请求中包含有第i级用户面节点分配的第一MBS网际互连协议IP多播传输地址和第一通用隧道端点标识C-TEID，i＝1,…,N，N为正整数；向所述I-SMF反馈第一用户面MBS会话建立响应，所述第一用户面MBS会话建立响应中包含有中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，所述第二MBS IP多播传输地址用于所述中间用户面节点的子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式传输的MBS业务数据；若所述中间用户面节点支持通过多播方式接收所述第i级用户面节点发送的MBS业务数据，则加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据。
根据本申请实施例的一个方面，提供了一种多播广播业务的通信装置，包括：第一接收单元，配置为接收多播广播业务MBS会话传输树中的第i级控制面节点发送的第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级控制面节点对应的第i级用户面节点的标识信息、所述第i级用户面节点所分配的第一MBS网际互连协议IP多播传输地址与用于通过多播方式传输MBS业务数据的第一通用隧道端点标识C-TEID， i＝1,…,N，N为正整数；选择单元，配置为根据所述第i级控制面节点的信息及所述第i级控制面节点提供的子控制面节点的信息选择中间用户面节点，所述中间用户面节点能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接；第一交互单元，配置为向所述中间用户面节点发送第一用户面MBS会话建立请求，并接收所述中间用户面节点反馈的第一用户面MBS会话建立响应，所述第一用户面MBS会话建立请求中包含有所述第一MBS IP多播传输地址和第一C-TEID，所述第一MBS IP多播传输地址用于使所述中间用户面节点加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据；第二交互单元，配置为向所述第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求，以指示所述第i级控制面节点提供的子控制面节点为所述中间用户面节点分配子用户面节点，所述第二MBS会话开始请求中包含有所述中间用户面节点的标识信息，以及所述中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，所述第二MBS IP多播传输地址用于使所述子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式发送的MBS业务数据。
根据本申请实施例的一个方面，提供了一种多播广播业务的通信装置，包括：第三交互单元，配置为向第i级控制面节点选择的第i级用户面节点发送第二用户面多播广播业务MBS会话建立请求，并接收所述第i级用户面节点反馈的第二用户面MBS会话建立响应，所述第i级控制面节点是MBS会话传输树中除最后一级控制面节点之外的任一级控制面节点，i＝1,…,N，N为正整数；第四交互单元，配置为选择中间会话管理功能实体I-SMF，向所述I-SMF发送第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级用户面节点的标识信息、所述第i级用户面节点分配的第一MBS网际互连协议IP多播传输地址和第一通用隧道端点标识C-TEID；其中，所述第一MBS会话开始请求用于指示所述I-SMF选择能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接的中间用户面节点，且与所述中间用户面节点建立用户面MBS会话，以使所述中间用户面节点加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据，并用于指示所述I-SMF向所述子控制面节点发送第二MBS会话开始请求，所述第二MBS会话开始请求用于指示所述子控制面节点为所述中间用户面节点分配子用户面节点，并使所述子用户面节点接收所述中间用户面节点发送的MBS业务数据。
根据本申请实施例的一个方面，提供了一种多播广播业务的通信装置，包括：第二接收单元，配置为接收中间会话管理功能实体I-SMF发送的第一用户面多播广播业务MBS会话建立请求，所述第一用户面MBS会话建立请求中包含有第i级用户面节点分配的第一MBS网际互连协议IP多播传输地址和第一通用隧道端点标识C-TEID，i＝1,…,N，N为正整数；发送单元，配置为向所述I-SMF反馈第一用户面MBS会话建立响应，所述第一用户面MBS会话建立响应中包含有中间用户面节点分 配的第二MBS IP多播传输地址和第二C-TEID，所述第二MBS IP多播传输地址用于所述中间用户面节点的子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式传输的MBS业务数据；处理单元，配置为在所述中间用户面节点支持通过多播方式接收所述第i级用户面节点发送的MBS业务数据的情况下，加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据。
根据本申请实施例的一个方面，提供了一种计算机可读介质，其上存储有计算机程序，所述计算机程序被处理器执行时实现如上述实施例中所述的多播广播业务的通信方法。
根据本申请实施例的一个方面，提供了一种电子设备，包括：一个或多个处理器；存储装置，用于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中所述的多播广播业务的通信方法。
根据本申请实施例的一个方面，提供了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可选实施例中提供的多播广播业务的通信方法。
在本申请的一些实施例所提供的技术方案中，第i级控制面节点选择I-SMF，然后向I-SMF发送第一MBS会话开始请求，以指示I-SMF与中间用户面节点建立用户面MBS会话，中间用户面节点可以加入第i级用户面节点分配的第一MBS IP多播传输地址对应的多播传输组来接收第i级用户面节点通过多播方式发送的MBS业务数据，同时，I-SMF可以向第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求来指示该子控制面节点为中间用户面节点分配子用户面节点，而为中间用户面节点分配的子用户面节点可以加入中间用户面节点分配的第二MBS IP多播传输地址对应的多播传输组来接收中间用户面节点发送的MBS业务数据。可见，本申请实施例的技术方案可以在控制面与用户面分离的通信系统架构下，实现用户面MBS会话传输树的建立，并且由于中间用户面节点可以接入第i级用户面节点分配的第一MBS IP多播传输地址对应的多播传输组来接收第i级用户面节点通过多播方式发送的MBS业务数据，且中间用户面节点的子用户面节点可以加入中间用户面节点分配的第二MBS IP多播传输地址对应的多播传输组来接收中间用户面节点通过多播方式发送的MBS业务数据，因此可以提高MBS业务数据的传输效率。
应当理解的是，以上的一般描述和后文的细节描述仅是示例性和解释性的，并不能限制本申请。
附图简要说明
此处的附图被并入说明书中并构成本说明书的一部分，示出了符合本申请的实施例，并与说明书一起用于解释本申请的原理。显而易见地，下面描述中的附图仅 仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。在附图中：
图1示出了单播通信系统及多播通信系统的数据传输流程示意图；
图2示出了MBMS的多播上下文激活过程示意图；
图3示出了IPv4网络地址的分类示意图；
图4示出了IPv4的多播地址的结构示意图；
图5示出了IPv6的多播地址的结构示意图；
图6示出了IPv4首部的结构示意图；
图7示出了IGMPv1的协议头部格式、IGMPv2的协议头部格式和IGMPv3中成员报告消息的格式示意图；
图8示出了MBMS多播业务的MBMS注册过程示意图；
图9示出了MBMS会话开始过程示意图；
图10示出了一种MBS系统架构示意图；
图11示出了一种MBS系统结构示意图；
图12示出了根据本申请的一个实施例的多播广播业务的通信方法的流程图；
图13示出了根据本申请的一个实施例的多播广播业务的通信方法的流程图；
图14示出了根据本申请的一个实施例的多播广播业务的通信方法的流程图；
图15示出了根据本申请的一个实施例的控制面与用户面分离的MBS通信方法的流程图；
图16示出了根据本申请的一个实施例的控制面与用户面分离的MBS通信方法的流程图；
图17示出了NG-RAN中gNB与5GC之间的连接关系示意图；
图18示出了根据本申请的一个实施例的控制面与用户面分离的MBS通信方法的流程图；
图19示出了本申请实施例的技术方案的级联方式示意图；
图20示出了根据本申请的一个实施例的控制面与用户面分离的MBS通信方法的流程图；
图21示出了根据本申请的一个实施例的控制面与用户面分离的MBS通信方法的流程图；
图22示出了根据本申请的一个实施例的控制面与用户面分离的MBS通信方法的流程图；
图23示出了根据本申请的一个实施例的控制面与用户面分离的MBS通信方法的流程图；
图24示出了根据本申请的一个实施例的多播广播业务的通信装置的框图；
图25示出了根据本申请的一个实施例的多播广播业务的通信装置的框图；
图26示出了根据本申请的一个实施例的多播广播业务的通信装置的框图；
图27示出了适于用来实现本申请实施例的电子设备的计算机系统的结构示意 图。
实施方式
现在将参考附图更全面地描述示例实施方式。然而，示例实施方式能够以多种形式实施，且不应被理解为限于在此阐述的范例；相反，提供这些实施方式使得本申请将更加全面和完整，并将示例实施方式的构思全面地传达给本领域的技术人员。
此外，所描述的特征、结构或特性可以以任何合适的方式结合在一个或更多实施例中。在下面的描述中，提供许多具体细节从而给出对本申请的实施例的充分理解。然而，本领域技术人员将意识到，可以实践本申请的技术方案而没有特定细节中的一个或更多，或者可以采用其它的方法、组元、装置、步骤等。在其它情况下，不详细示出或描述公知方法、装置、实现或者操作以避免模糊本申请的各方面。
附图中所示的方框图仅仅是功能实体，不一定必须与物理上独立的实体相对应。即，可以采用软件形式来实现这些功能实体，或在一个或多个硬件模块或集成电路中实现这些功能实体，或在不同网络和/或处理器装置和/或微控制器装置中实现这些功能实体。
附图中所示的流程图仅是示例性说明，不是必须包括所有的内容和操作/步骤，也不是必须按所描述的顺序执行。例如，有的操作/步骤还可以分解，而有的操作/步骤可以合并或部分合并，因此实际执行的顺序有可能根据实际情况改变。
需要说明的是：在本文中提及的“多个”是指两个或两个以上。“和/或”描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。字符“/”一般表示前后关联对象是一种“或”的关系。
2G(第二代移动通信技术)、3G(第三代移动通信技术)与4G(第四代移动通信技术)的无线通信系统支持MBMS(Multimedia Broadcast and Multicast Service，多媒体广播组播业务)，这个业务分为Broadcast(广播)与Multicast(组播)两种业务。但是，只有2G与3G系统支持多播业务，4G系统在标准上不支持，并且2G、3G和4G系统都支持广播业务。
除了广播和组播业务之外，网络节点之间的通信方式还包括单播。“单播”为一对一的通信，其优点是发送方可以向不同的接收方传输不同的内容，但是如果发送方需要向多个接收方传输相同的内容，那么就需要端到端地分别传输多份相同的数据，效率较低。具体如图1中所示，单播源以单播的方式向多个接收方发送数据时，需要以端到端的方式分别传输多份相同的数据(图1中不同的线型表示不同的数据流)。
“组播”也可以称为“多播”，是发送方将相同的内容传输给多个接收方。网上视频会议、网上视频点播特别适合采用多播方式，因为如果采用单播方式，那么有多少个接收方，就会有多少次传送过程，这种方式显然效率极低；而如果采用不区分目标、全部发送的广播方式，虽然一次可以传送完数据，但是达不到区分特定数据接收方的目的。可见，采用多播方式，既可以实现一次向多个接收方发送相同的数据，也可以达到只对特定对象传送数据的目的。具体如图1中所示，多播源一次可以向多个 接收方发送数据相同的数据。
“广播”也是将相同的内容传输给多个接收方，但是在传输的时候没有进行接收方的选择，因此可能存在着对不必要的设备也进行了数据的传输而造成网络资源的浪费。另外，有些接收方可能对广播的内容没有“兴趣”，那么在接收到广播的内容之后，也不得不丢弃掉接收到的数据包，进而也造成了终端资源的浪费。
广播业务与多播业务的根本区别在于系统中的UE(User Equipment，用户设备)都可以参加广播业务且无需签约，而多播业务的UE在签约与认证后才能参加。同时需要注意的是：多播业务与广播业务有很多种，对于多播业务，UE是通过IP多播地址加入相应业务的多播组。一个广播群对应的广播业务有其特定的服务区域。
在3GPP(3rd Generation Partnership Project，第三代合作伙伴计划)协议的TS23.246章节8.2中定义了MBMS的多播上下文激活过程，具体如图2所示，包括如下步骤：
步骤S201，UE选择一个APN(Access Point Name，接入点名称)建立一个PDP(Packet Data Protocol，分组数据协议)上下文(Context)，然后分配一个网际互联协议(IP)地址给UE，为便于后续描述，该步骤中UE选择的APN用APN0来进行标识。
步骤S202，UE选择一个IP Multicast Address(该IP多播地址用于标识一个多播业务)，然后向GGSN(Gateway GPRS Support Node，网关GPRS支持节点)发送IGMP联合(Join)数据包，以指示UE要加入这个多播组。
步骤S203，GGSN向BM-SC(Broadcast Multicast Service Center，广播多播业务中心)发送MBMS授权请求，并接收BM-SC反馈的MBMS授权响应。其中，BM-SC根据UE的签约数据认证UE是否可以加入这个多播组，如果确认UE可以加入这个多播组，则在MBMS授权响应中给出UE加入这个多播组所要使用的APN(该APN以APN1来进行标识)，然后通过步骤S204a、S204b、S205将UE所要使用的APN1传递给UE。
步骤S206，UE根据BM-SC提供的APN1发起一个新的MBMS会话(Session)，即发送激活MBMS上下文请求，该激活MBMS上下文请求中包含有IP Multicast Address、APN1和UE的MBMS能力。该MBMS能力比如可以是QoS(Quality of Service，服务质量)能力。
步骤S207，SGSN(Serving GPRS Support Node，服务GPRS支持节点)校验UE是否有签约APN1，若校验不能通过，则SGSN向GGSN发送MBMS通知拒绝请求，GGSN向MBMS发送通知拒绝响应。需要说明的是，UE的签约数据保存在HSS(Home Subscriber Server，归属用户服务器)中，图2中没有示出SGSN与HSS的交互过程。另外，图2中的步骤S208和步骤S209的具体过程请参见TS23.246章节8.2中定义的MBMS上下文激活过程。
步骤S210，若SGSN校验UE通过，则SGSN根据APN1选择另外一个GGSN(即支持Multicast业务的GGSN)，向该GGSN发送创建MBMS上下文请求消息，此消息中包含有UE的ID、UE Location ID、IP Multicast Address、APN1和UE的接入信息(比如是2G还是3G)。
其中，UE的ID可以是IMSI(International Mobile Subscriber Identity，国际移动用 户识别码)或MSISDN(Mobile Station International Integrated Service Digital Network Number，移动台国际综合业务数字网络号码)。UE位置(Location)ID可以是RAT(Radio Access Technology，无线接入技术)ID或者CGI(Common Gateway Interface，公共网关接口)或者SAI(Service Area Identity，服务区域标识)等。
步骤S211，GGSN向BM-SC发送MBMS授权请求，BM-SC根据UE的签约信息对UE进行授权，并向GGSN反馈MBMS授权响应。
步骤S212，若授权允许接入，且GGSN上没有IP Multicast Address指示的任何UE的上下文，即此UE是此GGSN上第一个接入IP Multicast Address所标识的多播业务，则向其上级节点BM-SC作注册，以指示后续发送给IP multicast Address的多播业务数据时，需要发送到此GGSN上。(注意，不同的UE可能选择到不同的GGSN上，因此BM-SC向下发送多播数据时，需要向这些GGSN同时发送相同的多播数据)。
步骤S213，GGSN创建此UE的对应于此IP Multicast Address的MBMS UE上下文，然后向SGSN发送创建MBMS上下文响应，以指示MBMS上下文创建成功。
步骤S214，类似于步骤S212，若SGSN上没有IP Multicast Address指示的任何UE的上下文，即此UE是此SGSN上第一个接入IP Multicast Address所标识的多播业务，则向上级节点GGSN作注册，以指示后续发送给IP multicast Address的多播业务数据时，需要发送到此SGSN上。(注意，不同的UE可能选择到不同的SGSN上，因此该GGSN向下发送多播数据时，需要向这些SGSN同时发送相同的多播数据)。
图2中的步骤S215至步骤S217的具体过程请参见TS23.246章节8.2中定义的MBMS上下文激活过程。
由图2所示的流程可知：2G或3G的UE先是通过APN0建立一个PDP Context，分配得到一个IP地址，然后以此IP地址发送一个加入多播的IGMP Join数据包给网络，GGSN要截获这个IGMP数据包，然后向MB-SC发送一个信令(即MBMS授权请求)，进而BM-SC向UE分配一个APN1，然后UE再以这个APN1发送请求MBMS上下文激活消息，从而才能激活一个MBMS上下文。
前述的IP多播地址可能是IPv4多播地址，也可以IPv6多播地址。如图3所示，IPv4的网络地址分为A类地址、B类地址、C类地址、D类地址和E类地址。其中，A类地址中的第1字节(8位)为网络号，其它3个字节(24位)为主机号，A类地址的范围是：0.0.0.0到127.255.255.255。B类地址中的第1字节和第2字节为网络号，其它2个字节为主机号，B类地址的范围是：128.0.0.0到191.255.255.255。C类地址中的前3个字节为网络号，第4个字节为主机号，C类地址的范围是：192.0.0.0到223.255.255.255。D类地址是多播地址，该类地址最前面4位是“1110”，D类地址的范围是：224.0.0.0到239.255.255.255。E类地址是保留地址，该类地址最前面5位是“11110”，E类地址的范围是：240.0.0.0到247.255.255.255。
如图4所示，IPv4的多播地址又可以具有三种结构，这三种结构分别适用于众所周知(Well-Known)的多播地址，全局范围(Globally-Scoped)的多播地址和本地范围(Locally-Scoped)的多播地址。
IPv6多播地址的结构如图5所示，第一个字节(8比特)表示该地址是多播地址，接下来的4比特是标志位(Flag)字段，再接下来的4比特是范围(Scope)字段，最后的112比特位组标识符(Group ID)。
其中，标志位字段的第一个比特为0，保留给将来使用；第二个比特指示该多播地址是否内嵌了RP(Rendezvous Point，聚合点)，RP是多播网络中指定多播流的分发点，比如第二个比特值为0时，表示未内嵌聚合点，第二个比特值为1时，表示内嵌了聚合点。标志位字段的第三个比特指示该多播地址是否内嵌了前缀信息，比如第三个比特值为0时，表示未内嵌前缀信息，第三个比特值为1时，表示内嵌了前缀信息。标志位字段的最后一个比特指示该多播地址是永久分配的多播地址(permanently assigned address)还是临时多播地址(transient multicast address)，比如最后一个比特值为0时，表示是永久分配的多播地址，最后一个比特值为1时，表示是临时多播地址。
范围(Scope)字段的作用是限定多播地址的范围，取值与描述如表1所示：
Figure PCTCN2021100085-appb-000001
表1
在多播通信中，多播地址只能作为目的IP地址(即IP头中的目的IP地址)，多播地址不能作为源IP地址。在MBMS(2G、3G)与MBS(5G)的多播业务中，多播数据包都是网络侧向下发送给UE的，即多播数据包都是DL(Downlink，下行)数据包，UE不能通过对应的多播地址向网络侧发送数据。也就是说UE不能将此多播地址作为目的IP地址发送上行的IP包，即没有UL(Uplink，上行)的多播数据。
网络中传输的IP包是由IP首部和数据两部分组成的，IPv4首部的结构如图6所示，主要包括：“版本”字段、“首部长度”字段、“服务类型”字段、“总长度” 字段、“标识”字段、“标志”字段、“片偏移”字段、“生存时间”字段、“协议”字段、“首部校验和”字段、“源地址”字段、“目的地址”字段、“可选字段”。
其中，“版本”字段占4位，指IP协议的版本，比如版本号为4(即IPv4)。“首部长度”字段占4位。“服务类型”字段占8位，用来获得更好的服务。“总长度”字段占16位，指首部和数据之和的长度。“标识”字段占16位，它是一个计数器，用来产生数据报的标识。“标志”字段占3位，“标志”字段的最低位是MF(More Fragment)，如果MF＝1则表示后面“还有分片”，如果MF＝0则表示是最后一个分片；“标志”字段中间的一位是DF(Don't Fragment)，只有当DF＝0时才允许分片。“片偏移”字段占12位，指较长的分组在分片后某片在原分组中的相对位置。“生存时间”字段即为TTL(Time To Live)，其占8位，TTL字段是由发送端初始设置一个字段。“协议”字段占8位，用于指示此数据报携带的数据使用何种协议，其中值为“1”表示是ICMP(Internet Control Message Protocol，Internet控制报文协议)协议；值为“2”表示是IGMP协议；值为“6”表示是TCP(Transmission Control Protocol，传输控制协议)协议；值为“17”表示是UDP(User Datagram Protocol，用户数据报协议)协议；值为“50”表示是ESP(Encapsulating Security Payload，封装安全载荷)协议；值为“51”表示是AH(Authentication header，认证头)协议。“首部校验和”字段占16位，只检验数据报的首部，不检验数据部分。“源地址”字段和“目的地址”字段分别占4字节，用于分别记录源地址和目的地址。
对于上述提到的IGMP协议，其有三个协议版本，分别为IGMPv1、IGMPv2和IGMPv3，对应的标准分别是RFC1054、RFC2236和RFC3376。IGMPv1的协议头部格式和IGMPv2的协议头部格式如图7所示，其中，IGMPv1的协议头部包括4比特的IGMP版本字段、4比特的IGMP报文类型字段(该字段值为1表示是Host Membership Query，即主机成员查询类型；值为2表示是Host Membership Report，即主机成员报告类型)、8比特的未用字段(该字段在发送时填0，接收时忽略)、16比特的IGMP校验和字段(当传送报文时，计算该校验字并插入到该字段中去；当接收包时，该字段在处理包之前进行检验)，以及32位的组播地址字段。
IGMPv2的协议头部包括8比特的报文类型字段、8比特的最大响应时间字段、16比特的IGMP校验和字段，以及32位的组播地址字段。
其中，IGMPv2的协议头部中的报文类型字段所指示的类型有如下几种：0x11＝Membership Query，表示的是IGMP成员查询消息；0x12＝Version 1 Membership Report，表示的是IGMPv1的成员报告消息；0x16＝Version 2 Membership Report，表示的是IGMPv2的成员报告消息；0x17＝Leave Group表示的是离开消息。在IGMPv2中，旧的4位版本字段和旧的4位类型字段拼成了一个新的8位类型字段，通过分别将成员查询消息(版本1和版本2的)及版本1的成员报告消息的类型代码置为0x11和0x12，保持了IGMP版本1和版本2包格式的向后兼容。
IGMPv2的协议头部中的最大响应时间字段用于指示在发出响应报告前的最长时间(以1/10秒为单位)，缺省值为10秒。类似于IGMPv1，在传送报文时，计算校验 和并填入IGMPv2的协议头部中的校验和字段中，接收报文时，在处理报文之前检验校验和，以判断IGMP消息在传输过程中是否发生了错误。
继续参照图7所示，IGMPv3中成员报告消息(Membership Report)的格式包括类型字段(由于是成员报告消息，因此类型＝0x22)、保留字段、校验和字段、组记录数量字段以及组记录字段。其中，图2中所示的IGMP Join数据包就是IGMP的Membership Report消息来实现的。对IGMPv3而言，IGMP Joint消息的IP包中的目的IP地址不是要加入的IP多播地址，而是在消息的参数中包含了其要加入的IP多播地址。
标准TS23.246的章节8.4定义了适用于MBMS多播业务的MBMS注册过程，具体如图8所示，包括如下步骤：步骤S801，RNC(Radio Network Controller，无线网络控制器)向SGSN发送MBMS注册请求；步骤S802，SGSN向GGSN发送MBMS注册请求；步骤S803，GGSN向BM-SC发送MBMS注册请求；步骤S804，BM-SC向GGSN反馈MBMS注册响应，同时可以执行MBMS会话开始过程；步骤S805，GGSN向SGSN反馈MBMS注册响应，同时可以执行MBMS会话开始过程；步骤S806，SGSN向RNC反馈MBMS注册响应，同时可以执行MBMS会话开始过程。可见，MBMS注册过程的主要功能是形成了从上到下的一个控制承载建立(MBMS Bearer Context)的信令树。由于2G、3G的标准中是控制面与用户面不分离，因此在控制面上形成了MBMS承载控制面的传输树就等同于后续可以建立一个从上到下的MBMS承载的传输树(注意MBMS承载的传输树是用MBMS Session Start过程建立)。另外，由于4G不支持多播业务，所以4G标准中不存在着MBMS注册过程。
标准TS23.246的章节8.3定义了MBMS会话开始过程，具体如图9所示，包括如下步骤：步骤S901，BM-SC向GGSN发送MBMS会话开始请求，GGSN向BM-SC反馈MBMS会话开始响应；步骤S902，GGSN向SGSN发送MBMS会话开始请求，然后由SGSN向GGSN反馈MBMS会话开始响应；步骤S903，SGSN向BSC(Base Station Controller，基站控制器)/RNC发送MBMS会话开始请求，然后由BSC/RNC向SGSN反馈MBMS会话开始响应；步骤S904，UE与RSC/RNC之间进行MBMS会话开始过程；步骤S903a，BSC/RNC发送IGMPv3成员报告消息。
其中，对于MBMS的多播业务而言，MBMS注册过程与MBS会话开始过程都是Per IP Multicast(每个IP组播)过程，它是为这个IP Multicast建立一个从上到下的控制面的MBMS承载上下文的信令树与一个从上到下的MBMS承载的传输树，而不是Per UE Per IP Multicast。对于MBMS的广播业务而言，没有MBMS注册过程，且MBS会话开始过程都是Per IP Broadcast(每个IP广播)过程，它是为这个IP Broadcast建立一个从上到下的控制面的MBMS承载上下文的信令树与一个从上到下的MBMS承载的传输树，而不是Per UE Per IP Broadcast。
但是，对于MBMS的多播业务而言，为了优化注册流程，在UE进行MBMS UE Context激活过程中，可以一并执行MBMS注册的部分过程，比如图2中所示的步骤S212和步骤S214，但这仅仅是当SGSN与GGSN中的第一个UE激活这个IP Multicast业务时执行的，当有第二个UE在相同的SGSN与GGSN上激活这个IP Multicast时，就不 再执行图2中所示的步骤S212和步骤S214。
对于MBMS的多播业务与广播业务而言，一个重要的功能是要形成多播业务与广播业务的用户面的传输树，防止形成用户面的传输环(即到达某个节点存在着多条不同的传输路径)，同时也防止MBMS断枝的出现(即出现某个节点没有下游节点)。
在2G～3G系统中，多个SGSN可以组成一个Pool(池)。虽然GGSN在标准上没有定义Pool，但是在实际部署时，存在着一个GGSN Pool以提供系统的高可靠性。这样，不同的UE接入到同一个BSC/RNC，并激活相同的MBMS IP Multicast时，有可能被BSC/RNC选择到同一个SGSN Pool中的不同SGSN上。但由于这些UE使用的APN是相同的，因此这些同一个SGSN Pool中的不同SGSN将选择到不同的GGSN，但可能SGSN是连接到相同的GGSN。3GPP的标准是这样规定的，当RNC使用Iu接口时，才允许选择使用SGSN Pool，且对于MBMS需要GGSN使用GTP-U(GPRS Tunneling Protocol-User plane，CPRS隧道协议用户面)直接连接到RNC上，用户面不允许经过SGSN。这样即使在同一个RNC上的不同用户使用相同的APN和IP Multicast选择了不同的SGSN，但其用户面最终是相同的，不会存在着多条不同的用户面。
但是，对于BSC而言，可能存在着多个SGSN向其发送MBMS会话开始请求消息，对于这种情况，标准TS23.236中定义了通过BSC/RNC拒绝其它SGSN的MBMS会话开始请求消息来实现只有一条用户面。同样的，当多个GGSN向一个SGSN发送MBMS会话开始请求消息时，SGSN也只能选择一个GGSN建立承载面，进而防止MBMS传输环的出现。
当BSC/RNC拒绝了一个SGSN的承载面建立，就可能造成这个SGSN没有下游节点，在这种情况下，SGSN只好通过DeRegistration(取消注册)技术(具体可以参照标准TS23.236的章节8.6.0)来实现将自身从GGSN的下游节点中删除，从而防止GGSN给这个SGSN发送MBMS的多播数据，而这个SGSN却不能往下传输的问题，避免出现MBMS传输断枝。同样的，当SGSN拒绝GGSN的承载面建立时，可能造成这个GGSN没有下游节点，在这种情况下，GGSN只好通过DeRegistration技术来实现将自身从BM-SC的下游节点中删除，从而防止BM-SC给这个GGSN发送MBMS的多播数据，避免出现MBMS传输断枝。
即对于MBMS多播业务而言，除了最终的传输点UE外，任何节点都有一个下游节点。若一个节点没有下游节点，则这个节点应当离开这个传输树(对应于DeRegistration过程)。例如，当一个基站下的MBMS UE全部移动到其它基站时，则这个基站需要向SGSN进行DeRegistration操作；当一个SGSN下的所有MBMS连接基站进行了DeRegistration操作，则这个SGSN需要向GGSN进行DeRegistration操作；当一个GGSN下的所有MBMS连接SGSN进行了DeRegistration操作，则这个GGSN需要向BM-SC进行Deregistration操作。
此外，由于MBMS业务(包含广播业务和多播业务)的传输路径是一个树状结构，每个父节点下面是一个或多个子节点，父节点与子节点的承载可以是基于父与子之间的GTP Tunnel(GTP隧道)。但当子节点数量特别多时，父节点就需要同时向很多的 子节点发送同样的IP Multicast数据，显然通过GTP隧道传输的方式效率非常低。为了提升网络侧父节点与子节点之间的传输效率，父节点可以分配一个本地的IP Multicast地址(这个地址不是MBMS Multicast业务中的Multicast地址)，这个传输层的IP Multicast地址用于子节点(如基站)同父节点(如MBMS GW或GGSN)之间高效传输MBMS业务数据。在这种情况下，父节点只需要将MBMS业务数据通过这个传输层的多播地址发送出去，所有的子节点都可以接收MBMS业务数据，从而大大地减轻了父节点的数据处理量。
要使用上述基于多播的承载传输优化技术，需要父节点分配一个本地的IP Multicast传输层地址，子节点在收到这个父节点分配的IP Multicast传输层地址后，需要通过IGMP Join过程加入这个传输层的多播组。因有些子节点不支持多播，因此可能存在着一部分子节点使用传输层多播的方式接收MBMS业务数据，另外一部分子节点分别使用点到点的GTP Tunnel方式，在这种情形下是由子节点分配下行GTP-U的IP地址及TEID。当然，父节点若发现子节点的数目比较少，则也可以决定不采用多播传输方式。
由于MBMS系统中控制面与用户面不分离，也就是网络节点都是同时包含用户面与控制面功能，因此当某个网络节点不支持多播传输技术后，直接回复一个GTP-U的IP地址及TEID后，父节点就可以知道这个节点不支持多播传输。但是在5G MBS系统中，控制面与用户面是分离的，控制面与用户面不再是同一个网络节点，在这种情况下建立MBS会话传输树将面临多种问题。
并且5G MBS最新的研究报告中定义了如图10和图11所示的两种系统架构，其中，图10所示的系统架构是在目前5G架构上叠加功能，即在不修改目前5G架构的情形下，通过增强5G架构的功能与接口来支持5G MBS业务，这种架构的好处是通过软件升级就可以支持5G MBS。图11所示的系统架构是一个全新的架构，即在目前5G架构不变的情形下，增加一些新的网络功能节点。这种架构的好处是对目前的5G的架构影响最小化，但是有些网络功能节点可能还是需要进行增强，如NG-RAN(Next Generation Radio Access Network，下一代无线接入网)、AMF(Access and Mobility Management Function，接入和移动性管理功能)、UDM(Unified Data Management，统一数据管理)、UDR(User Data Repository，用户数据仓库)、NEF(Network Exposure Function，网络开放功能)、PCF等。
图10中的SMF是Session Management Function，即会话管理功能；UPF是User Plane Function，即用户面功能；AF是Application Function，即应用功能。图11中的MB-UPF即为Multicast/Broadcast-UPF；MB-SMF即为Multicast/Broadcast-SMF；MBSU即为Multicast/Broadcast Service User Plane(多播/广播业务用户面)；MBSF即为Multicast/Broadcast Service Function(多播广播业务实体)。
以下实施例将介绍针对5G MBS系统的用户面MBS会话传输树的相关技术内容，详细阐述如下：
图12示出了根据本申请的一个实施例的多播广播业务的通信方法的流程图，该多 播广播业务的通信方法可以由I-SMF来执行，该多播广播业务的通信方法至少包括步骤S1210至步骤S1230，详细介绍如下：
在步骤S1210中，接收MBS会话传输树中的第i级控制面节点发送的第一MBS会话开始请求，该第一MBS会话开始请求中包含有第i级控制面节点提供的子控制面节点的信息、第i级控制面节点选择的第i级用户面节点的标识信息、第i级用户面节点所分配的第一MBS IP多播传输地址与用于通过多播方式传输MBS业务数据的第一C-TEID，i＝1,…,N，N为正整数。
在本申请的一个实施例中，第i级控制面节点可以根据第i级控制面节点的子控制面节点的信息，从管理的用户面功能实体中选取一个或多个用户面功能实体作为第i级用户面节点。同时，如果第i级控制面节点根据第i级控制面节点的子控制面节点的信息，确定第i级控制面节点管理的用户面功能实体不能与第i级控制面节点的子控制面节点管理的用户面功能实体建立传输通路，那么可以选择能够与第i级控制面节点及与第i级控制面节点的子控制面节点进行通信的SMF作为I-SMF。
比如，若第i级控制面节点的服务区域是A，而第i级控制面节点的子控制面节点的服务区域是C，即第i级控制面节点所管理的用户面功能实体不能直接与第i级控制面节点的子控制面节点所管理的用户面功能实体进行通信，那么第i级控制面节点可以选择一个I-SMF，该I-SMF需要能够与第i级控制面节点及与第i级控制面节点的子控制面节点进行通信。
在本申请的一个实施例中，第i级控制面节点在选择出第i级用户面节点之后，可以与第i级用户面节点进行用户面MBS会话建立过程，即向第i级用户面节点发送用户面MBS会话建立请求，并接收第i级用户面节点反馈的用户面MBS会话建立响应，然后从第i级用户面节点反馈的用户面MBS会话建立响应中获取到第i级用户面节点所分配的第一MBS IP多播传输地址与第一C-TEID。当第i级控制面节点确定出这些信息之后，向选择出的I-SMF发送上述的第一MBS会话开始请求，并在该第一MBS会话开始请求中添加这些信息，即添加了第i级控制面节点提供的子控制面节点的标识信息、第i级用户面节点的标识信息、第i级用户面节点所分配的第一MBS IP多播传输地址与第一C-TEID。
在步骤S1220中，根据第i级控制面节点的信息及第i级控制面节点提供的子控制面节点的信息选择中间用户面节点，该中间用户面节点能够与第i级用户面节点和第i级控制面节点的子控制面节点管理的用户面功能实体建立连接。
在本申请的一个实施例中，第i级控制面节点的信息可以包括第i级控制面节点的服务区域，第i级控制面节点提供的子控制面节点的信息可以包括第i级控制面节点提供的子控制面节点的服务区域，I-SMF根据这些信息选择出能够与第i级用户面节点，以及能够与第i级控制面节点提供的子控制面节点所管理的用户面功能实体建立连接的中间用户面节点。
在步骤S1230中，向中间用户面节点发送第一用户面MBS会话建立请求，并接收中间用户面节点反馈的第一用户面MBS会话建立响应，该第一用户面MBS会话建立请 求中包含有第一MBS IP多播传输地址和第一C-TEID，该第一MBS IP多播传输地址用于使中间用户面节点加入第一MBS IP多播传输地址对应的多播传输组来接收第i级用户面节点通过多播方式发送的MBS业务数据。
在本申请的一个实施例中，如果中间用户面节点不支持通过多播方式、但支持通过点对点方式接收第i级用户面节点发送的MBS业务数据，那么I-SMF向中间用户面节点发送的第一用户面MBS会话建立请求中包含有请求为中间用户面节点分配F-TEID的指示信息，在这种情况下，中间用户面节点反馈的第一用户面MBS会话建立响应中包含有中间用户面节点分配的F-TEID，该F-TEID用于使中间用户面节点通过点对点的方式接收第i级用户面节点发送的MBS业务数据。
在本申请的一个实施例中，如果I-SMF并不知晓中间用户面节点是否不支持接收基于多播方式传输的数据，或者I-SMF即便知晓中间用户面节点不支持接收基于多播方式传输的数据，但是也不进行决策，那么中间用户面节点可以通过第一用户面MBS会话建立响应指示中间用户面节点不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点发送的MBS业务数据，并包含有中间用户面节点分配的F-TEID。
在本申请的一个实施例中，若第i级控制面节点选择了至少两个第i级用户面节点，则I-SMF向中间用户面节点发送的第一MBS会话开始请求中包含有每个第i级用户面节点各自的标识信息、每个第i级用户面节点分配的第一MBS IP多播传输地址和第一C-TEID。其中，不同的第i级用户面节点分配的第一MBS IP多播传输地址不相同。
继续参照图12所示，在步骤S1240中，向第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求，以指示第i级控制面节点提供的子控制面节点为中间用户面节点分配子用户面节点，该第二MBS会话开始请求中包含有中间用户面节点的标识信息，以及中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，该第二MBS IP多播传输地址用于使子用户面节点加入第二MBS IP多播传输地址对应的多播传输组来接收中间用户面节点通过多播方式发送的MBS业务数据。
在本申请的一个实施例中，I-SMF可以从中间用户面节点反馈的第一用户面MBS会话建立响应中获取到中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID。具体而言，I-SMF向中间用户面节点发送的第一用户面MBS会话建立请求中包含有用于指示中间用户面节点分配新的MBS IP多播分发信息的指示信息，中间用户面节点反馈给I-SMF的第一用户面MBS会话建立响应中包含有中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID。
在本申请的一个实施例中，I-SMF在向第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求之后，还需要接收第i级控制面节点提供的子控制面节点针对第二MBS会话开始请求反馈的第二MBS会话开始响应，该第二MBS会话开始响应中包含有第一指示信息。该第一指示信息中包含的内容可以有如下几种情况：
情况1：在本申请的一个实施例中，该第一指示信息中包含有中间用户面节点的标识信息、第一F-TEID列表信息和用于表示启动多播方式传输的第一字段信息，该第一字段信息表示第i级控制面节点提供的子控制面节点为中间用户面节点分配的子用户 面节点中存在支持通过多播方式接收中间用户面节点发送的MBS业务数据的子用户面节点，该第一F-TEID列表信息包含有不支持通过多播方式、但支持通过点对点方式接收中间用户面节点发送的MBS业务数据的子用户面节点的F-TEID，该F-TEID用于使中间用户面节点的子用户面节点通过点对点的方式接收中间用户面节点发送的MBS业务数据。
情况2：在本申请的一个实施例中，该第一指示信息包含有中间用户面节点的标识信息、且不包含上述第一F-TEID列表信息和上述第一字段信息，在这种情况下，该第一指示信息用于指示第i级控制面节点提供的子控制面节点为中间用户面节点分配的子用户面节点均支持通过多播方式接收中间用户面节点发送的MBS业务数据。
情况3：在本申请的一个实施例中，该第一指示信息包含有中间用户面节点的标识信息、上述第一F-TEID列表信息，且不包含上述第一字段信息，在这种情况下，该第一指示信息用于指示第i级控制面节点提供的子控制面节点为中间用户面节点分配的子用户面节点均不支持通过多播方式、但支持通过点对点方式接收中间用户面节点发送的MBS业务数据。
情况4：在本申请的一个实施例中，该第一指示信息包含有中间用户面节点的标识信息和停用多播传输的字段信息、且不包含上述第一F-TEID列表信息，在这种情况下，该第一指示信息用于指示第i级控制面节点提供的子控制面节点没有为中间用户面节点分配子用户面节点。可选地，停用多播传输的字段信息可以是将Multicast Enable的值设置为Disable。
在本申请的一个实施例中，若I-SMF选择了至少两个中间用户面节点，则第i级控制面节点提供的子控制面节点向I-SMF反馈的第二MBS会话开始响应中包含有第一指示信息列表，该第一指示信息列表中包含有所有中间用户面节点分别对应的第一指示信息。
在本申请的一个实施例中，第i级控制面节点的子控制面节点向I-SMF反馈的第二MBS会话开始响应中还可能包含有失败的标识信息列表，该失败的标识信息列表用于指示未被分配子用户面节点的目标中间用户面节点。
在本申请的一个实施例中，如果I-SMF根据第i级控制面节点的子控制面节点反馈的第二MBS会话开始响应确定存在未被分配子用户面节点的目标中间用户面节点，则向目标中间用户面节点发送用户面MBS会话删除请求。该实施例的技术方案即是删除用户面MBS会话传输树中的断枝。
在本申请的一个实施例中，I-SMF在向未被分配子用户面节点的目标中间用户面节点发送用户面MBS会话删除请求之后，还可以接收目标中间用户面节点反馈的用户面MBS会话删除响应，该用户面MBS会话删除响应是目标中间用户面节点在接收到用户面MBS会话删除请求之后发送的，其中，若目标中间用户面节点已加入第一MBS IP多播传输地址对应的多播传输组中，则在接收到用户面MBS会话删除请求之后退出第一MBS IP多播传输地址对应的多播传输组。
在本申请的一个实施例中，如果第i级控制面节点提供了至少两个子控制面节点， 则I-SMF在接收到第i级控制面节点提供的所有子控制面节点分别反馈的第二MBS会话开始响应之后，再确定是否存在未被分配子用户面节点的目标中间用户面节点，避免根据接收到部分子控制面节点反馈的第二MBS会话开始响应导致对是否存在未被分配子用户面节点的目标中间用户面节点的判断出现偏差。
在本申请的一个实施例中，I-SMF在接收第i级控制面节点提供的子控制面节点针对第二MBS会话开始请求反馈的第二MBS会话开始响应之后，可以根据该第二MBS会话开始响应确定中间用户面节点通过哪种方式分别向中间用户面节点的子用户面节点传输MBS业务数据。
具体而言，如果第二MBS会话开始响应中的第一指示信息包含有上述第一F-TEID列表信息，则I-SMF根据该第一指示信息中包含的中间用户面节点的标识信息向中间用户面节点发送用户面MBS会话修改请求，以指示中间用户面节点通过点对点的方式向第一F-TEID列表信息所包含的各个F-TEID对应的子用户面节点分别传送MBS业务数据。其中，如果该第一指示信息中还包含有上述第一字段信息，则该用户面MBS会话修改请求还用于指示中间用户面节点同时使用多播传输方式向中间用户面节点的子用户面节点发送MBS业务数据；若该第一指示信息中不包含上述第一字段信息，则该用户面MBS会话修改请求还用于指示中间用户面节点不需要使用多播传输方式向中间用户面节点的子用户面节点发送MBS业务数据。
需要说明的是，如果第二MBS会话开始响应中的第一指示信息不包含上述第一F-TEID列表信息和上述第一字段信息，则说明中间用户面节点的子用户面节点都支持接收多播传输，那么中间用户面节点可以通过多播传输的方式向中间用户面节点的所有子用户面节点传输MBS业务数据。
在本申请的一个实施例中，如果I-SMF选择了至少两个中间用户面节点，则I-SMF可以根据第二MBS会话开始响应中包含的每个中间用户面节点对应的第一指示信息，向需要发送用户面MBS会话修改请求的中间用户面节点发送用户面MBS会话修改请求。具体地，如果根据第i级控制面节点提供的子控制面节点反馈的第二MBS会话开始响应确定某个中间用户面节点的部分子用户面节点不支持通过多播方式、但支持通过点对点方式接收该中间用户面节点发送的MBS业务数据，那说明该中间用户面节点是需要发送用户面MBS会话修改请求的中间用户面节点。
在本申请的一个实施例中，I-SMF在接收第i级控制面节点的子控制面节点针对第二MBS会话开始请求反馈的第二MBS会话开始响应之后，还可以根据该第二MBS会话开始响应，向第i级控制面节点反馈针对第一MBS会话开始请求的第一MBS会话开始响应。如果第i级控制面节点提供了至少两个子控制面节点，那么I-SMF需要在接收到第i级控制面节点提供的所有子控制面节点分别反馈的第二MBS会话开始响应之后，再向第i级控制面节点反馈第一MBS会话开始响应。
类似于第i级控制面节点提供的子控制面节点反馈的第二MBS会话开始响应，在本申请的一个实施例中，I-SMF向第i级控制面节点反馈的第一MBS会话开始响应中包含有第二指示信息。该第二指示信息中包含的内容可以有如下几种情况：
情况1：在本申请的一个实施例中，该第二指示信息中包含有第i级用户面节点的标识信息、第二F-TEID列表信息和用于表示启动多播方式传输的第二字段信息，该第二字段信息表示存在支持通过多播方式接收第i级用户面节点发送的MBS业务数据的中间用户面节点，该第二F-TEID列表信息包含有不支持通过多播方式、但支持通过点对点方式接收第i级用户面节点发送的MBS业务数据的中间用户面节点的F-TEID，该F-TEID用于使中间用户面节点通过点对点的方式接收第i级用户面节点发送的MBS业务数据。
情况2：在本申请的一个实施例中，该第二指示信息包含有第i级用户面节点的标识信息、且不包含上述第二F-TEID列表信息和上述第二字段信息，在这种情况下，该第二指示信息用于指示中间用户面节点均支持通过多播方式接收第i级用户面节点发送的MBS业务数据。
情况3：在本申请的一个实施例中，该第二指示信息包含有第i级用户面节点的标识信息、上述第二F-TEID列表信息，且不包含上述第二字段信息，在这种情况下，该第二指示信息用于指示中间用户面节点均不支持通过多播方式、但支持通过点对点方式接收第i级用户面节点发送的MBS业务数据。
在本申请的一个实施例中，如果第i级控制面节点选择了至少两个第i级用户面节点，那么I-SMF向第i级控制面节点反馈的第一MBS会话开始响应中包含有第二指示信息列表，该第二指示信息列表中包含有所有第i级用户面节点分别对应的第二指示信息。
图12是从I-SMF的角度对本申请实施例的多播广播业务的通信方法进行阐述，以下结合图13从第i级控制面节点的角度对本申请实施例的多播广播业务的通信方法进行进一步说明：
图13示出了根据本申请的一个实施例的多播广播业务的通信方法的流程图，该多播广播业务的通信方法可以由第i级控制面节点来执行，例如，图10中的SMF或图11中的MB-SMF，该多播广播业务的通信方法至少包括步骤S1310至步骤S1320，详细介绍如下：
在步骤S1310中，向第i级控制面节点选择的第i级用户面节点发送第二用户面MBS会话建立请求，并接收第i级用户面节点反馈的第二用户面MBS会话建立响应，该第i级控制面节点是MBS会话传输树中除最后一级控制面节点之外的任一级控制面节点，i＝1,…,N，N为正整数。
在本申请的一个实施例中，第i级控制面节点可以根据第i级控制面节点的子控制面节点的信息，从管理的用户面功能实体中选取一个或多个用户面功能实体作为第i级用户面节点。第i级控制面节点在选择出第i级用户面节点之后，可以与第i级用户面节点进行用户面MBS会话建立过程，即向第i级用户面节点发送第二用户面MBS会话建立请求，并接收第i级用户面节点反馈的第二用户面MBS会话建立响应，然后从第i级用户面节点反馈的第二用户面MBS会话建立响应中获取到第i级用户面节点所分配的第一MBS IP多播传输地址与第一C-TEID。
在步骤S1320中，选择中间会话管理功能实体I-SMF，向I-SMF发送第一MBS会话开始请求，该第一MBS会话开始请求中包含有第i级控制面节点提供的子控制面节点的信息、第i级用户面节点的标识信息、第i级用户面节点分配的第一MBS IP多播传输地址和第一C-TEID。
在本申请的一个实施例中，第一MBS会话开始请求用于触发I-SMF选择能够与第i级用户面节点和第i级控制面节点提供的子控制面节点所管理的用户面功能实体建立连接的中间用户面节点，并用于触发I-SMF向第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求，该中间用户面节点用于加入第一MBS IP多播传输地址对应的多播传输组来接收第i级用户面节点通过多播方式发送的MBS业务数据，该第二MBS会话开始请求用于指示第i级控制面节点提供的子控制面节点为中间用户面节点分配子用户面节点，并使该子用户面节点接收中间用户面节点发送的MBS业务数据。
在本申请的一个实施例中，如果第i级控制面节点提供了两个或两个以上的子控制面节点，那么第i级控制面节点向I-SMF发送的第一MBS会话开始请求中可以包含有子控制面节点的列表，该列表中包含有第i级控制面节点提供的所有子控制面节点的信息。
在本申请的一个实施例中，第i级控制面节点选择中间会话管理功能实体I-SMF的目的是：假如第i级控制面节点确定第i级控制面节点管理的用户面功能实体不能与第i级控制面节点的子控制面节点管理的用户面功能实体建立传输通路，那么可以选择能够与第i级控制面节点及与第i级控制面节点的子控制面节点进行通信的SMF作为I-SMF。这种方式使得在用户面MBS会话建立过程中第i级用户面节点与下游的用户面节点(通常是基站或基站的分布单元(Distributed Unit，简称DU))之间无法建立直接连接的用户面传输时，可以插入I-SMF，进而I-SMF可以选择中间用户面节点来完成用户面MBS会话传输树的建立，有效实现了用户面传输资源的优化。
在本申请的一个实施例中，第i级控制面节点在向I-SMF发送第一MBS会话开始请求之后，还可能接收到I-SMF针对第一MBS会话开始请求反馈的第一MBS会话开始响应，在这种情况下，第i级控制面节点可以根据该第一MBS会话开始响应中包含的内容，确定是否向第i级用户面节点发送用户面MBS会话修改请求。具体地，如果根据I-SMF反馈的第一MBS会话开始响应确定某个/某些中间用户面节点不支持通过多播方式、但支持通过点对点方式接收第i级用户面节点发送的MBS业务数据，那么需要向第i级用户面节点发送用户面MBS会话修改请求。
图13是从第i级控制面节点的角度对本申请实施例的多播广播业务的通信方法进行阐述，以下结合图14从中间用户面节点的角度对本申请实施例的多播广播业务的通信方法进行进一步说明：
图14示出了根据本申请的一个实施例的多播广播业务的通信方法的流程图，该多播广播业务的通信方法可以由中间用户面节点来执行，例如图10中的UPF或者图11中的MB-UPF，该多播广播业务的通信方法至少包括步骤S1410至步骤S1430，详细介绍如下：
在步骤S1410中，接收I-SMF发送的第一用户面MBS会话建立请求，该第一用户面MBS会话建立请求中包含有第i级用户面节点分配的第一MBS IP多播传输地址和第一C-TEID，i＝1,…,N，N为正整数。
在步骤S1420中，向I-SMF反馈第一用户面MBS会话建立响应，该第一用户面MBS会话建立响应中包含有中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，该第二MBS IP多播传输地址用于该中间用户面节点的子用户面节点加入第二MBS IP多播传输地址对应的多播传输组来接收中间用户面节点通过多播方式传输的MBS业务数据。
在步骤S1430中，若中间用户面节点支持通过多播方式接收第i级用户面节点发送的MBS业务数据，则加入第一MBS IP多播传输地址对应的多播传输组来接收第i级用户面节点通过多播方式发送的MBS业务数据。
在本申请的一个实施例中，如果中间用户面节点不支持通过多播方式、但支持通过点对点方式接收第i级用户面节点发送的MBS业务数据，则中间用户面节点可以分配通过点对点方式接收第i级用户面节点发送的MBS业务数据的F-TEID。
在本申请的一个实施例中，中间用户面节点在向I-SMF反馈第一用户面MBS会话建立响应之后，还可能接收到I-SMF发送的用户面MBS会话修改请求，该用户面MBS会话修改请求中包含有第一F-TEID列表信息，该第一F-TEID列表信息包含有不支持通过多播方式、但支持通过点对点方式接收中间用户面节点发送的MBS业务数据的子用户面节点的F-TEID，然后中间用户面节点可以基于该第一F-TEID列表信息，通过点对点的方式向该第一F-TEID列表信息包含的各个F-TEID所对应的子用户面节点分别传送MBS业务数据，并根据该用户面MBS会话修改请求确定是否同时使用多播传输方式向中间用户面节点的子用户面节点发送MBS业务数据。具体请参照前述实施例的技术方案，不再赘述。
在本申请的一个实施例中，如果中间用户面节点接收到I-SMF发送的用户面MBS会话删除请求，则向I-SMF发送用户面MBS会话删除响应；其中，若中间用户面节点已加入第一MBS IP多播传输地址对应的多播传输组中，则在接收到该用户面MBS会话删除请求之后，退出该第一MBS IP多播传输地址对应的多播传输组。该实施例的技术方案即为删除用户面MBS会话传输树中的断枝。
在本申请的一个实施例中，如果中间用户面节点接收到多个用户面MBS会话建立请求，则针对这多个用户面MBS会话建立请求中的一个用户面MBS会话建立请求来反馈用户面MBS会话建立响应，并针对这多个用户面MBS会话建立请求中的其它用户面MBS会话建立请求反馈拒绝消息，以指示此用户面节点已被选择。需要说明的是：中间用户面节点同时接收到的多个用户面MBS会话建立请求可能是同一个I-SMF发送的(对应于不同的控制面节点选择了同一个I-SMF的情况)，或者也可能是不同的I-SMF发送的(对应于不同的控制面节点选择不同的I-SMF的情况)。该实施例的技术方案使得一个用户面节点只能被选择作为另外一个用户面节点的子节点，而不能被选择作为多个用户面节点的子节点。
在本申请的一个实施例中，如果中间用户面节点在向I-SMF反馈第一用户面MBS会话建立响应之后，再次接收到用于将中间用户面节点选择为其它用户面节点的子用户面节点的用户面MBS会话建立请求，则针对再次接收到的用户面MBS会话建立请求反馈拒绝消息，以指示此用户面节点已被选择。需要说明的是：中间用户面节点再次接收到的用户面MBS会话建立请求可能是其它I-SMF发送的，也可能是中间用户面节点反馈第一用户面MBS会话建立响应的I-SMF发送的，但是再次接收到的用户面MBS会话建立请求是用于将中间用户面节点选择为其它用户面节点的子用户面节点的。该实施例的技术方案同样使得一个用户面节点只能被选择作为另外一个用户面节点的子节点，而不能被选择作为多个用户面节点的子节点。
以上分别从I-SMF、第i级控制面节点、中间用户面节点的角度对本申请实施例的技术方案进行了说明，以下从各个实体交互的角度对本申请实施例的技术方案的实现细节进行详细阐述。
在本申请的一个实施例中，5G的MBS会话传输树需要保证每个用户面的父用户面节点只能是一个，但由于用户面由控制面来控制，可能出现控制面的父控制面节点不是只有一个，在这种情况下，子控制面节点可以向不同的父控制面节点分别提供不同的一个或多个子用户面节点，也就是，即使是同一个父控制面节点对应的不同父用户面节点，其子用户面节点也是互相独立的。
其中，如果为一个父控制面节点分配了多个子用户面节点，而这多个子用户面节点中一部分子用户面节点支持接收基于多播方式传输的数据，而另外一部分子用户面节点不支持接收基于多播方式传输的数据，但是支持通过点对点的方式接收MBS业务数据，那么不支持接收多播传输数据的子用户面节点可以分配GTP-U的IP地址+TEID(用F-TEID来表示)，以通过点对点的方式向这些子用户面节点传输MBS业务数据。
具体地，图15示出了根据本申请的一个实施例的控制面与用户面分离的MBS通信方法，其中，以下内容中出现的F-CP表示Father-Control Plane(父控制面)，S-CP表示Son-Control Plane(子控制面)，F-UP表示Father-User Plane(父用户面)，S-UP表示Son-User Plane(子用户面)。
参照图15所示，包括如下步骤：
步骤S1501，F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求(即Nfcp_MBSSessionStart Request)，该MBS会话开始请求中包含有TMGI(Temporary Mobile Group Identity，临时群组标识)、MBS Session Duration(MBS会话持续时间)、MBS QFIs(QoS Flow Identifier，QoS流标识)、QoS Profile(QoS配置)、UP ID(该UP ID是与F-CP1的父控制面节点同级的用户面节点的标识)、MBS IP Multicast Distribution(MBS IP多播分发信息)、MBS Time to Data Transfer(MBS业务数据传输时间)、MBS Service Area(MBS服务区域)。
其中，TMGI表示一个多播或广播的临时组标识；MBS Session Duration表示这次MBS会话的时间长度；MBS Time to Data Transfer表示MBS业务数据开始发送的时间；QoS Profile包括5QI(5G QoS Identifier，5G QoS指示符)、MFBR(Maximum Flow Bit  Rate，最大比特流速率)、GFBR(Guaranteed Flow Bit Rate，保证流比特率)、ARP(Allocation and Retention Priority，分配与保持优先级)等；MBS IP Multicast Distribution包含了IP多播传输地址(该IP多播传输地址是与F-CP1的父控制面节点同级的用户面节点(即前述的UP ID所标识的用户面节点)所分配的IP多播传输地址，为便于区分，将其记为IP1)和C-TEID(为了简化，图15中没有画出F-CP1和F-CP2的父控制面节点，也没有画出F-UP11和F-UP21的父用户面节点)；MBS Service Area是当此MBS业务是广播业务时的服务区域。
步骤S1502，F-CP1根据F-CP1的子控制面节点的信息确定从多个F-UPF中选取一个或多个F-UPF作为与F-CP1同级的用户面节点。该实施例中假定只选取了一个与F-CP1同级的用户面节点(记为F-UP11)，然后F-CP1向F-UP11发送用户面MBS会话建立请求(即N4 MBSSessionEstablishment Request)，F-UP11向F-CP1反馈用户面MBS会话建立响应(即N4 MBSSessionEstablishment Response)。
在本申请的一个实施例中，对于MBS多播业务而言，F-CP1的子控制面节点的信息是由各个MBS UE Context组成；对于MBS广播业务而言，F-CP1的子控制面节点的信息是由F-CP1的父控制面节点提供或由网络根据服务区域配置得到。F-CP1的子控制面节点的信息包括F-CP1的子控制面节点的数量及位置信息等。
在本申请的一个实施例中，F-CP1向选取的F-UP11发送的用户面MBS会话建立请求中可能包含有PDR(Packet Detection Rule，报文检测规则)、QER(QoS Enforcement Rule，QoS执行规则)、FAR(Forwarding Action Rule，转发执行规则)、MBS IP Multicast Distribution、Allocate New MBS IP Multicast Distribution for Downlink Node(为下行节点分配新的MBS IP多播分发信息)指示、请求分配F-TEID的指示。F-UP11反馈的用户面MBS会话建立响应中包含有Allocate MBS IP Multicast Distribution for Downlink node、F-TEID。
其中，用户面MBS会话建立请求中的PDR包含一个或多个MBS IP Multicast Address+UDP Port来指示一个或多个不同的MBS QoS Flow；QER包含与PDR对应的MFBR、GFBR及DL Flow Level Marking(下行流等级标记)；MBS IP Multicast Distribution是TMGI所对应的MBS IP Multicast Distribution，其来自于F-CP1接收到由F-CP1的父控制面节点发送的MBS会话开始请求，其中包含的MBS IP多播传输地址即为IP1。
用户面MBS会话建立请求中的Allocate New MBS IP Multicast Distribution for Downlink Node指示是用于指示F-UP11存在着子用户面节点，因此F-UP11需要分配一个新的MBS IP Multicast Distribution，用户面MBS会话建立响应中的Allocate MBS IP Multicast Distribution for Downlink node则包含F-UP11所分配的新的MBS IP Multicast Distribution，该新的MBS IP Multicast Distribution包含了新的IP多播传输地址(为便于区分，该新的IP多播传输地址记为IP2)与C-TEID。
需要说明的是，MBS IP Multicast Distribution是每个父用户面节点为每个父用户面节点的所有子用户面节点所分配的，不同的父用户面节点会分配不同的MBS IP Multicast Distribution。
此外，若根据网络配置，F-UP11不支持接收基于多播方式传输的MBS业务数据，但是支持通过点对点的方式接收MBS业务数据，则F-CP1发送的用户面MBS会话建立请求消息包含请求分配F-TEID的指示，以请求F-UP11为了通过以点对点方式接收F-UP11的父用户面节点发送的MBS业务数据而分配一个F-TEID，F-UP11在分配F-TEID之后，在用户面MBS会话建立响应中携带分配的F-TEID。
若用户面MBS会话建立请求中没有包含请求分配F-TEID的指示，即F-CP1不进行决策，但用户面节点F-UP11不支持接收基于多播方式传输的数据，那么F-UP11同样需要分配一个F-TEID，并在用户面MBS会话建立响应中携带分配的F-TEID。
步骤S1503，若F-UP11支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP1对应的多播传输组中，以接收F-UP11的父用户面节点发送的MBS业务数据。
步骤S1504，F-CP1根据F-CP1的子控制面节点的信息，向每个子控制面子节点分别发送MBS会话开始请求(即Nscp_MBSSessionStart Request)，即步骤S1504至步骤S1508是针对每个子控制面节点分别单独执行的，该实施例中以向一个子控制面节点S-CP发送为例进行说明。
F-CP1发送给F-CP1的子控制面节点S-CP的MBS会话开始请求中包含了如下参数：TMGI、MBS Session Duration、MBS QFIs、QoS Profile、F-UP11 ID，MBS IP Multicast Distribution、MBS Time to Data Transfer、MBS Service Area。其中，F-CP1发送的MBS会话开始请求中的MBS IP Multicast Distribution是在步骤S1502中分配的，其中包含的IP多播传输地址即为IP2。
S-CP在接收到F-CP1发送的MBS会话开始请求之后，类似于步骤S1502，S-CP根据S-CP的子控制面节点的信息从多个S-UP中选取F-UP11的一个或多个S-UP，该实施例中假定选取了S-UP1与S-UP2。然后分别执行步骤S1505a和步骤S1505b。
步骤S1505a，S-CP向选取的S-UP1发送用户面MBS会话建立请求，S-UP1向S-CP反馈用户面MBS会话建立响应。
在本申请的一个实施例中，S-CP发送的用户面MBS会话建立请求中也可能包含有PDR、QER、FAR、MBS IP Multicast Distribution、F-UP11 ID、Allocate New MBS IP Multicast Distribution for Downlink Node指示、请求分配F-TEID的指示等。S-UP1反馈的用户面MBS会话建立响应中包含有Allocate MBS IP Multicast Distribution for Downlink node和F-TEID。
其中，S-CP发送的用户面MBS会话建立请求中的MBS IP Multicast Distribution来自于步骤S1504接收到的MBS会话开始请求，其中包含的IP多播传输地址即为IP2。S-CP发送给S-UP1的用户面MBS会话建立请求中的Allocate New MBS IP Multicast Distribution for Downlink Node指示是用于指示S-UP1来分配一个新的MBS IP Multicast Distribution，以便于以多播传输方式发送MBS业务数据到S-UP1的子用户面节点。具体由S-UP1分配的过程参照步骤S1502所述。类似的，如果S-UP1不支持多播传输，则可以分配一个F-TEID，并且也是由S-UP1分配的。
步骤S1505b，S-CP向选取的S-UP2发送用户面MBS会话建立请求，S-UP2向S-CP反馈用户面MBS会话建立响应。具体过程与步骤S1505a类似，不再赘述。
步骤S1506，S-UP1和S-UP2若支持接收基于多播方式传输的数据，则分别加入F-UP11分配的IP多播传输地址(即IP2)对应的多播传输组中，以接收F-UP11发送的MBS业务数据。
步骤S1507，S-CP向F-CP1发送MBS会话开始响应(即Nscp_MBSSessionStart Response)，该MBS会话开始响应中包含有F-UP11 ID。
其中，若S-UP1和S-UP2中有S-UP不支持接收基于多播方式传输的数据，则S-CP向F-CP1发送的MBS会话开始响应中包含有List of F-TEID(由于是针对子用户面节点的，为便于区分，以下将其记为List of F-TEIDsup)，且对应于F-UP11。该List of F-TEIDsup包含有S-UP1和S-UP2中不支持接收多播传输但支持使用点对点方式接收MBS业务数据的S-UP所分配的F-TEID。若S-UP1和S-UP2中有部分S-UP支持接收多播传输，则需要在MBS会话开始响应中包含Multicast Enable以指示F-UP11同时需要使用多播传输与点对点传输技术来向F-UP11的子用户面节点传输MBS业务数据。
特别地，若S-CP向F-CP1发送的MBS会话开始响应中不包含List of F-TEIDsup，则表明S-CP选择的所有子用户面节点都支持接收基于多播方式传输的数据，因此MBS会话开始响应中无需携带Multicast Enable这个标识。
特别地，若S-CP向F-CP1发送的MBS会话开始响应中包含有List of F-TEIDsup，但没有包含Multicast Enable这个标识，则说明S-CP选择的所有子用户面节点都不支持接收基于多播方式传输的数据，但支持接收通过点对点方式传输的MBS业务数据。
特别地，若S-CP向F-CP1发送的MBS会话开始响应中不包含List of F-TEIDsup，且Multicast Enable设置为Disable，则表明子控制面节点S-CP没有为F-UP11分配对应的子用户面节点(一个可能的原因是要选择的子用户面节点已经分配了父用户面节点，此时，就不能选择这些子用户面节点了)。在这种情况下，子控制面节点S-CP也可以通过MBS会话开始响应来返回Failure Code来指示。
需要说明的是，如果S-CP选择的子用户面节点中只有一个子用户面节点不支持接收基于多播方式传输的数据，那么S-CP向F-CP1发送的MBS会话开始响应中也可以不包含List of F-TEIDsup，而是只包含这个子用户面节点分配的F-TEID。
步骤S1508，若步骤S1507中的MBS会话开始响应中包含有F-UP11 ID及F-TEID参数(如某个S-UP分配的F-TEID，或者某些S-UP对应的List of F-TEIDsup)，则F-CP1向F-UP11发送用户面MBS会话修改请求(即N4 MBSSessionModification Request)，F-UP11向F-CP1反馈用户面MBS会话修改响应。其中，该用户面MBS会话修改请求中包含有不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP对应的List of F-TEIDsup，以指示F-UP11增加使用点对点的方式分别向不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP传送MBS业务数据。若步骤S1507中的MBS会话开始响应中不包含Multicast Enable的指示，则指示F-UP11不再使用多播传输方式。若步骤S1507中的MBS会话开始响应中包含有Multicast Enable的指 示，则指示F-UP11同时要使用多播传输与点对点传输方式。
需要说明的是：如果步骤S1507中的MBS会话开始响应中只包含有一个F-TEID，而F-UP11不知道F-UP11的子用户面节点的具体数量，那么F-UP11可以只使用点对点的方式向这个F-TEID对应的S-UP传送MBS业务数据；同时F-UP11可以根据步骤S1508中的用户面MBS会话修改请求同时使用多播传输地址(即IP2)向其它的S-UP发送MBS业务数据。
如果步骤S1507中的MBS会话开始响应中不包含F-TEID，且Multicast Enable不是设置为Disable，则表示F-UP11继续使用多播传输方式，此时无需执行步骤S1508。
步骤S1509，当针对每个子控制面节点都执行步骤S1504至步骤S1508之后，F-CP1根据所有子控制面节点反馈的MBS会话开始响应向F-CP1的父控制面节点发送MBS会话开始响应(即Nfcp_MBSSessionStart Response)。
类似于步骤S1507，F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有UP ID(该UP ID是与F-CP1的父控制面节点同级的用户面节点的标识)，并且可能还包含有List of F-TEID(为便于区分，将其记为List of F-TEIDfup)，由于F-CP1仅选择了一个同级的用户面节点F-UP11，因此如果F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有List of F-TEIDfup，那么其中也只包含F-UP11分配的F-TEID。
需要说明的是，由于在该实施例中F-CP1仅选择了一个同级的用户面节点F-UP11，因此F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中如果不包含F-UP11分配的F-TEID，在这种情况下说明F-UP11支持接收基于多播方式传输的数据，此时F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中无需包含Multicast Enable；如果F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含F-UP11分配的F-TEID，则说明F-UP11不支持接收基于多播方式传输的数据，在这种情况下由于F-CP1只有一个同级的用户面节点F-UP11，因此F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中也无需包含Multicast Enable。
其中，步骤S1501至步骤S1509是F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求之后的处理过程，在该处理过程中，F-CP1选择了一个同级的用户面节点F-UP11，并且其子控制面节点S-CP选择了两个与S-CP同级的子用户面节点S-UP1和S-UP2。
继续参照图15所示，还包括如下步骤：
步骤S1510，F-CP2接收到F-CP2的父控制面节点发送的MBS会话开始请求，该MBS会话开始请求中包含有TMGI、MBS Session Duration、MBS QFIs、QoS Profile、UPx ID、MBS IP Multicast Distribution、MBS Time to Data Transfer、MBS Service Area。其中，具体参数的含义参照前述步骤S1501中的说明，为便于区分，F-CP2接收到的MBS会话开始请求中的MBS IP Multicast Distribution包含的IP多播传输地址可以记为IPx。
步骤S1511，F-CP2根据F-CP2的子控制面节点的信息确定从多个F-UPF中选取一 个或多个F-UPF作为与F-CP2同级的用户面节点。该实施例中假定只选取一个与F-CP2同级的用户面节点F-UP21，然后F-CP2向F-UP21发送用户面MBS会话建立请求，F-UP21向F-CP2反馈用户面MBS会话建立响应。
具体说明参见前述步骤S1502的相关内容，类似于步骤S1502，F-CP2与F-UP21之间通过用户面MBS会话建立请求与用户面MBS会话建立响应之间的交互，F-UP21分配了新的IP多播传输地址(为便于区分，记为IP3)。
此外，类似地，若F-UP21不支持接收基于多播方式传输的数据，则F-UP21分配一个用于通过点对点方式接收MBS业务数据的F-TEID，并在用户面MBS会话建立响应中携带分配的F-TEID。
步骤S1512，若F-UP21支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IPx对应的多播传输组中，以接收F-UP21的父用户面节点发送的MBS业务数据。
步骤S1513，F-CP2根据F-CP2的子控制面节点的信息，向每个子控制面子节点分别发送MBS会话开始请求，即步骤S1513至步骤S1517是针对每个子控制面节点分别单独执行的，该实施例中以向一个子控制面节点S-CP发送为例进行说明。
类似地，F-CP2发送给F-CP2的子控制面节点S-CP的MBS会话开始请求中同样包含了MBS IP Multicast Distribution，且该MBS IP Multicast Distribution是在步骤S1511中分配的，其对应的用户面节点标识是F-UP21 ID，其中包含的IP多播传输地址即为IP3。
需要说明的是：步骤S1513与步骤S1504之间并没有先后关系，它们可以是F-CP2与F-CP1并行分别执行的步骤。
S-CP在接收到F-CP2发送的MBS会话开始请求之后，类似于前述步骤，S-CP根据S-CP的子控制面节点的信息从多个S-UP中为F-UP21选择一个或多个S-UP，该实施例中假定选取了S-UP3与S-UP4，然后分别执行步骤S1514a和步骤S1514b。
需要说明的是，S-CP为F-UP21选取的S-UP不同于S-CP为F-UP11选择的S-CP。换句话说，本申请的实施例中，在控制面上一个子控制面节点可以有多个父控制面节点，比如子控制面节点S-CP具有两个父控制面节点F-CP1和F-CP2，但是一个子用户面节点是不允许有多个父用户面节点的，这样，当一个子用户面节点已经有一个父用户面节点后，不能再参与子用户面节点的选择。因此S-CP为F-UP21只能选择S-UP3与S-UP4，而S-UP1与S-UP2已经被选择为F-UP11的子用户面节点，因此S-CP不能再选择S-UP1与S-UP2作为F-UP21的子用户面节点了。
步骤S1514a，S-CP向选取的S-UP3发送用户面MBS会话建立请求，S-UP3向S-CP反馈用户面MBS会话建立响应。步骤S1514b，S-CP向选取的S-UP4发送用户面MBS会话建立请求，S-UP4向S-CP反馈用户面MBS会话建立响应。具体过程与步骤S1505a类似，不再赘述。
步骤S1515，S-UP3和S-UP4若支持接收基于多播方式传输的数据，则分别加入F-UP21分配的IP多播传输地址(即IP3)对应的多播传输组中，以接收F-UP21发送的MBS业务数据。
步骤S1516，S-CP向F-CP2发送MBS会话开始响应，该MBS会话开始响应中包含有F-UP21 ID。该步骤的具体说明与前述步骤S1507类似，不再赘述。
步骤S1517，F-CP2向F-UP21发送用户面MBS会话修改请求，F-UP21向F-CP2反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S1518，当针对每个子控制面都执行步骤S1513至步骤S1517之后，F-CP2根据所有子控制面反馈的MBS会话开始响应向F-CP2的父控制面节点发送MBS会话开始响应。该步骤的具体说明与前述步骤S1509类似，不再赘述。
其中，步骤S1510至步骤S1518是F-CP2接收到F-CP2的父控制面节点发送的MBS会话开始请求之后的处理过程，在该处理过程中，F-CP2选择了一个同级的用户面节点F-UP21，并且F-CP2的子控制面节点S-CP选择了两个与S-CP同级的子用户面节点S-UP3和S-UP4。
通过步骤S1501至步骤S1518可知，在本申请的实施例中，子控制面节点S-CP有多个父控制面节点F-CP1和F-CP2，而S-CP控制的子用户面节点S-UP只有一个父用户面节点。
另外，步骤S1501中的消息与步骤S1510中的消息可能是并行发下来的，因此，步骤S1501～S1509与步骤S1510～S1518可能是并行执行的。这样，在用户面MBS会话建立过程中，可能存在着一个用户面节点同时被两个控制面节点发送用户面MBS会话建立请求消息，或已经被一个控制面节点选择后、又接收到另一个控制面节点发送的用户面MBS会话建立请求消息。如果一个用户面节点同时收到两个控制面节点(当然也可以是更多个，此处以两个为例进行说明)发送的用户面MBS会话建立请求消息，那么该用户面节点可以在用户面MBS会话建立响应消息中，正常响应其中一个控制面节点发送的用户面MBS会话建立请求，并且在另一个用户面MBS会话建立响应消息中，拒绝(Reject)另外一个控制面节点，以指示此用户面节点已经被选择。如果一个用户面节点通过一个控制面节点已经有了父用户面节点后，又收到另外一个控制面节点发送的用户面MBS会话建立请求消息时，则在另一个用户面MBS会话建立响应消息中Reject该另外一个控制面节点，以指示此用户面节点已经被选择。
当这种MBS会话传输树建立完成之后，可以执行如下步骤：
步骤S1519a，F-UP11接收到F-UP11的父用户面节点发送的下行MBS业务数据。然后通过步骤S1520a将接收到的该下行MBS业务数据传输给S-UP1和S-UP2。
需要说明的是：对于有父用户面节点的各个用户面节点，需要以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。比如，对于S-UP1和S-UP2而言，若确定是只采用多播传输方式，则S-UP1和S-UP2通过多播传输方式接收F-UP11发送的MBS业务数据；若确定是只采用点对点传输方式，则S-UP1和S-UP2分别通过点对点传输方式接收F-UP11发送的MBS业务数据。
对于有子用户面节点的各个用户面节点，需要以前面步骤所确定的多播传输方式或点对点传输方式向每个子用户面节点传送MBS业务数据。比如，对于F-UP11而言，若确定是只采用多播传输方式，则F-UP11通过多播方式传送MBS业务数据给F-UP11 的所有子用户面节点(该实施例中即为S-UP1和S-UP2)；若确定是只采用点对点传输方式，则F-UP11分别向F-UP11的每个子用户面节点(该实施例中即为S-UP1和S-UP2)以通过点对点传输方式传送MBS业务数据。
步骤S1519b，F-UP21接收到F-UP21的父用户面节点发送的下行MBS业务数据。然后通过步骤S1520b将接收到的该下行MBS业务数据传输给S-UP3和S-UP4。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
在图15所示的实施例中，父控制面节点向子控制面节点发送的MBS会话开始请求中仅包含了一个父用户面节点的信息，以下结合图16介绍在本申请的另一个实施例中，父控制面节点向子控制面节点发送的MBS会话开始请求中可以包含多个父用户面节点的信息。
具体地，图16示出了根据本申请的一个实施例的控制面与用户面分离的MBS通信方法，类似地，以下内容中出现的F-CP表示Father-Control Plane(父控制面)，S-CP表示Son-Control Plane(子控制面)，F-UP表示Father-User Plane(父用户面)，S-UP表示Son-User Plane(子用户面)。
参照图16所示，包括如下步骤：
步骤S1601，F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求。具体过程与前述步骤S1501类似，不再赘述。其中，该MBS会话开始请求中的MBS IP Multicast Distribution包含的IP多播传输地址记为IP1。
F-CP1在接收到F-CP1的父控制面节点发送的MBS会话开始请求之后，可以根据F-CP1的子控制面节点的信息确定从多个F-UPF中选取一个或多个F-UPF作为与F-CP1同级的用户面节点，该实施例中假定选取了两个用户面节点，记为F-UP11和F-UP12。然后分别执行步骤S1602a和步骤S1602b。
步骤S1602a，F-CP1向F-UP11发送用户面MBS会话建立请求，F-UP11向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S1602a中F-UP11分配的IP多播传输地址记为IP2。
步骤S1602b，F-CP1向F-UP12发送用户面MBS会话建立请求，F-UP12向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S1602b中F-UP12分配的IP多播传输地址记为IP3。
步骤S1603，若F-UP11与F-UP12支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP1对应的多播传输组中，以接收F-UP11与F-UP12的父用户面节点发送的MBS业务数据。
步骤S1604，F-CP1根据F-CP1的子控制面节点的信息，向每个子控制面子节点分别发送MBS会话开始请求，即步骤S1604至步骤S1608是针对每个子控制面节点分别单独执行的，该实施例中以向一个子控制面节点S-CP发送为例进行说明。
F-CP1发送给F-CP1的子控制面节点S-CP的MBS会话开始请求中包含了如下参数： TMGI、MBS Session Duration、MBS QFIs、QoS Profile、MBS Time to Data Transfer、List of{F-UP ID，MBS传输信息}、MBS Service Area。其中，MBS传输信息即为MBS IP Multicast Distribution(IP Multicast Distribution address,C-TEID)。在该实施例中，由于F-CP1选择了两个与F-CP1同级的用户面节点F-UP11和F-UP12，因此List of{F-UP ID，MBS传输信息}中包含了F-UP11 ID及F-UP11 ID对应的MBS IP Multicast Distribution，以及F-UP12 ID及F-UP12 ID对应的MBS IP Multicast Distribution。F-UP11 ID对应的MBS IP Multicast Distribution是F-UP11所分配的，其中包含的IP多播传输地址即为IP2；F-UP12 ID对应的MBS IP Multicast Distribution是F-UP12所分配的，其中包含的IP多播传输地址即为IP3。
需要说明的是：F-UP12分配的IP多播传输地址IP3与F-UP11分配的IP多播传输地址IP2不能相同，但是所分配的C-TEID可以相同。
S-CP在接收到F-CP1发送的MBS会话开始请求之后，类似于步骤S1502，S-CP根据S-CP的子控制面节点的信息从多个S-UP中为F-UP11选择一个或多个S-UP，以及为F-UP12选择一个或多个S-UP，该实施例中假定为F-UP11选取了S-UP11与S-UP12，为F-UP12选取了S-UP21与S-UP22，即为F-UP11和F-UP12选择了不同的子用户面节点。然后分别执行步骤S1605a和步骤S1605b。
步骤S1605a，S-CP向选取的S-UP11和S-UP12分别发送用户面MBS会话建立请求，该用户面MBS会话建立请求中包含有F-UP11分配的IP多播传输地址IP2，S-UP11和S-UP12分别向S-CP反馈用户面MBS会话建立响应(为了节省版面，图16中将S-UP11与S-UP12画在了一起)。具体过程与步骤S1505a类似，不再赘述。
步骤S1605b，S-CP向选取的S-UP21和S-UP22分别发送用户面MBS会话建立请求，该用户面MBS会话建立请求中包含有F-UP12分配的IP多播传输地址IP3，S-UP21和S-UP22分别向S-CP反馈用户面MBS会话建立响应(为了节省版面，图16中将S-UP21与S-UP22画在了一起)。具体过程与步骤S1505a类似，不再赘述。
步骤S1606a，S-UP11和S-UP12若支持接收基于多播方式传输的数据，则分别加入F-UP11分配的IP多播传输地址(即IP2)对应的多播传输组中，以接收F-UP11发送的MBS业务数据。
步骤S1606b，S-UP21和S-UP22若支持接收基于多播方式传输的数据，则分别加入F-UP12分配的IP多播传输地址(即IP3)对应的多播传输组中，以接收F-UP12发送的MBS业务数据。
步骤S1607，S-CP向F-CP1发送MBS会话开始响应。若有S-UP不支持接收基于多播方式传输的数据，则MBS会话开始响应中包含此S-UP分配的F-TEID，且对应于F-UP，从而形成一个List of{F-UP ID,List of F-TEIDsup,Multicast Enable}。在该实施例中，List of{F-UP ID,List of F-TEIDsup,Multicast Enable}包含了针对F-UP11的List of F-TEIDsup和Multicast Enable，以及针对F-UP12的List of F-TEIDsup和Multicast Enable。
类似于步骤S1507，由于有些S-UP支持接收基于多播方式传输的数据，而另外一些S-UP不支持接收基于多播方式传输的数据，所以这个List F-TEIDsup只是对应于那 些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP。因此，当一个F-UP的所有S-UP都支持接收基于多播方式传输的数据，则对应于这个F-UP的List of F-TEIDsup就没有了，其它说明参照步骤S1507的相关内容。
此外，当S-CP决定不向其中某个/某些F-UP ID分配任何的子用户面节点时，则可以将这个/这些F-UP ID对应的Multicast Enable设置为Disable。当然，也可以在MBS会话开始响应中采用Failed List{F-UP}来指示没有被分配子用户面节点的父用户面节点。
步骤S1608a，F-CP1根据MBS会话开始响应中包含的List of{F-UP ID,List of F-TEIDsup,Multicast Enable}向F-UP11发送用户面MBS会话修改请求，F-UP11向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S1608b，F-CP1根据MBS会话开始响应中包含的List of{F-UP ID,List of F-TEIDsup,Multicast Enable}向F-UP12发送用户面MBS会话修改请求，F-UP12向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S1609，当针对每个子控制面都执行步骤S1604至步骤S1608之后，F-CP1根据所有子控制面反馈的MBS会话开始响应向F-CP1的父控制面节点发送MBS会话开始响应。
其中，由于F-CP1选择了两个与F-CP1同级的用户面节点F-UP11和F-UP12，因此若F-UP11和F-UP12中有F-UP不支持接收基于多播方式传输的数据，则F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有List of F-TEID(由于是针对父用户面节点的，为便于区分，以下将其记为List of F-TEIDfup)，且对应于F-UP11和F-UP12的父用户面节点的UP ID。该List of F-TEIDfup包含有F-UP11和F-UP12中不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的F-UP所分配的F-TEID。若F-UP11和F-UP12中有部分F-UP支持接收基于多播方式传输的数据，则需要在MBS会话开始响应中包含Multicast Enable以指示F-UP11和F-UP12的父用户面节点同时需要使用多播传输与点对点传输技术来向F-UP11和F-UP12传输MBS业务数据。
特别地，若F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中不包含List of F-TEIDfup，则表明F-CP1选择的与F-CP1同级的用户面节点都支持接收基于多播方式传输的数据，因此该MBS会话开始响应中无需携带Multicast Enable这个标识。
特别地，若F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有List of F-TEIDfup，但没有包含Multicast Enable这个标识，则说明F-CP1选择的所有与F-CP1同级的用户面节点都不支持接收基于多播方式传输的数据、但支持接收点对点方式传输的MBS业务数据。
特别地，若F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中不包含List of F-TEIDfup，且Multicast Enable设置为Disable，则表明F-CP1没有选择与F-CP1同级的用户面节点。在这种情况下，F-CP1也可以通过MBS会话开始响应来返回Failure Code来指示。
需要说明的是，如果F-CP1选择的与F-CP1同级的用户面节点中只有一个不支持接收基于多播方式传输的数据，那么MBS会话开始响应中也可以不包含List of F-TEIDfup，而是只包含这个不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的用户面节点所分配的F-TEID。
其中，步骤S1601至步骤S1609是F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求之后的处理过程，在该处理过程中，F-CP1选择了与F-CP1同级的两个用户面节点F-UP11和F-UP12，并且F-CP1的子控制面节点S-CP为F-UP11选择了两个与S-CP同级的子用户面节点S-UP11和S-UP12，为F-UP12选择了两个与S-CP同级的子用户面节点S-UP21和S-UP22。
继续参照图16所示，还包括如下步骤：
步骤S1610，F-CP2接收到F-CP2的父控制面节点发送的MBS会话开始请求，该MBS会话开始请求中包含有TMGI、MBS Session Duration、MBS QFIs、QoS Profile、UPx ID、MBS IP Multicast Distribution、MBS Time to Data Transfer，MBS Service Area。其中，具体参数的含义参照前述步骤S1501中的说明，为便于区分，F-CP2接收到的MBS会话开始请求中的MBS IP Multicast Distribution包含的IP多播传输地址可以记为IPx。
步骤S1611，F-CP2根据F-CP2的子控制面节点的信息确定从多个F-UPF中选取一个或多个F-UPF作为与F-CP2同级的用户面节点。该实施例中假定只选取一个与F-CP2同级的用户面节点F-UP21，然后F-CP2向F-UP21发送用户面MBS会话建立请求，F-UP21向F-CP2反馈用户面MBS会话建立响应。
具体说明参见前述步骤S1502的相关内容，类似于步骤S1502，F-CP2与F-UP21之间通过用户面MBS会话建立请求与用户面MBS会话建立响应之间的交互，F-UP21分配了新的IP多播传输地址(为便于区分，记为IP4)。
此外，类似地，若F-UP21不支持接收基于多播方式传输的数据，F-UP21分配一个用于通过点对点方式接收MBS业务数据的F-TEID，并在用户面MBS会话建立响应中携带分配的F-TEID。
步骤S1612，若F-UP21支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IPx对应的多播传输组中，以接收F-UP21的父用户面节点发送的MBS业务数据。
步骤S1613，F-CP2根据F-CP2的子控制面节点的信息，向每个子控制面子节点分别发送MBS会话开始请求，即步骤S1613至步骤S1617是针对每个子控制面节点分别单独执行的，该实施例中以向一个子控制面节点S-CP发送为例进行说明。
类似地，F-CP2发送给F-CP2的子控制面节点S-CP的MBS会话开始请求中同样包含了MBS IP Multicast Distribution，且该MBS IP Multicast Distribution是在步骤S1611中分配的，其对应的用户面节点标识是F-UP21 ID，其包含的IP多播传输地址即为IP4。
需要说明的是：步骤S1613与步骤S1604之间并没有先后关系，它们可以是F-CP2与F-CP1并行分别执行的步骤。
S-CP在接收到F-CP2发送的MBS会话开始请求之后，类似于前述步骤，S-CP根据S-CP的子控制面节点的信息从多个S-UP中为F-UP21选择一个或多个S-UP，该实施例中假定选取了S-UP31与S-UP32，然后执行步骤S1614。
需要说明的是，S-CP为F-UP21选取的S-UP不同于S-CP为F-UP11和F-UP12选择的S-CP。换句话说，本申请的实施例中，在控制面上一个子控制面节点可以有多个父控制面节点，比如子控制面节点S-CP具有两个父控制面节点F-CP1和F-CP2，但是一个子用户面节点是不允许有多个父用户面节点的，这样，当一个子用户面节点已经有一个父用户面节点后，不能再参与子用户面节点的选择。。
步骤S1614，S-CP向选取的S-UP31和S-UP32分别发送用户面MBS会话建立请求，S-UP31和S-UP32分别向S-CP反馈用户面MBS会话建立响应。具体过程与步骤S1505a类似，不再赘述。
步骤S1615，S-UP31和S-UP32若支持接收基于多播方式传输的数据，则分别加入F-UP21分配的IP多播传输地址(即IP4)对应的多播传输组中，以接收F-UP21发送的MBS业务数据。
步骤S1616，S-CP向F-CP2发送MBS会话开始响应，该MBS会话开始响应中包含有F-UP21 ID。该步骤的具体说明与前述步骤S1507类似，不再赘述。
步骤S1617，F-CP2向F-UP21发送用户面MBS会话修改请求，F-UP21向F-CP2反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S1618，当针对每个子控制面都执行步骤S1613至步骤S1617之后，F-CP2根据所有子控制面反馈的MBS会话开始响应向F-CP2的父控制面节点发送MBS会话开始响应。该步骤的具体说明与前述步骤S1509类似，不再赘述。
其中，步骤S1610至步骤S1618是F-CP2接收到F-CP2的父控制面节点发送的MBS会话开始请求之后的处理过程，在该处理过程中，F-CP2选择了一个与F-CP2同级的用户面节点F-UP21，并且F-CP2的子控制面节点S-CP选择了两个与S-CP同级的子用户面节点S-UP31和S-UP32。
通过步骤S1601至步骤S1618可知，在本申请的实施例中，子控制面节点S-CP有多个父控制面节点F-CP1和F-CP2，而S-CP控制的子用户面节点S-UP只有一个父用户面节点。
另外，步骤S1601中的消息与步骤S1610中的消息可能是并行发下来的，因此，步骤S1601～S1609与步骤S1610～S1618可能是并行执行的。这样，在用户面MBS会话建立过程中，可能存在着一个用户面节点同时被两个控制面节点发送用户面MBS会话建立请求消息，或已经被一个控制面节点选择后、又接收到另一个控制面节点发送的用户面MBS会话建立请求消息。如果一个用户面节点同时收到两个控制面节点(当然也可以是更多个，此处以两个为例进行说明)发送的用户面MBS会话建立请求消息，那么该用户面节点可以在用户面MBS会话建立响应消息中，正常响应其中一个控制面节点发送的用户面MBS会话建立请求，并且在另一个用户面MBS会话建立响应消息中，拒绝(Reject)另外一个控制面节点，以指示此用户面节点已经被选择。如果一个用户 面节点通过一个控制面节点已经有了父用户面节点后，又收到另外一个控制面节点发送的用户面MBS会话建立请求消息时，则在另一个用户面MBS会话建立响应消息中Reject该另外一个控制面节点，以指示此用户面节点已经被选择。
当这种MBS会话传输树建立完成之后，可以执行如下步骤：
步骤S1619a，F-UP11接收到F-UP11的父用户面节点发送的下行MBS业务数据。然后通过步骤S1620a将接收到的该下行MBS业务数据传输给S-UP11和S-UP12。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
步骤S1619b，F-UP12接收到F-UP12的父用户面节点发送的下行MBS业务数据。然后通过步骤S1620b将接收到的该下行MBS业务数据传输给S-UP21和S-UP22。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
步骤S1619c，F-UP21接收到F-UP21的父用户面节点发送的下行MBS业务数据。然后通过步骤S1620c将接收到的该下行MBS业务数据传输给S-UP31和S-UP32。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
在图16所示的实施例中，父控制面节点向子控制面节点发送的MBS会话开始请求中包含了多个父用户面节点的信息。可选地，在5G系统中，NR(New Radio)基站(gNB)可以是控制面与用户面分离的，即gNB-CU(Centralized Unit，集中单元)可以作为子控制面节点，gNB-DU(Distributed Unit，分布单元)可以作为子用户面节点，并且一个基站的控制面可以控制一个或多个基站的用户面。具体如图17所示，NG-RAN中的gNB通过NG接口连接到5GC(5g Core network，5G核心网)，NG-RAN中的gNB可以是控制面与用户面分离的，基站控制面(即gNB-CU)与基站用户面(即gNB-DU)之间的接口可以是F1接口，gNB之间的接口可以是Xn-C接口。
在本申请的一个实施例中，在将gNB-CU和gNB-DU应用到图16所示的实施例中之后，可以得到图18所示的实施例，由于网络节点SMF或MB-SMF是不能直接与NR基站进行通信的，因此引入了AMF来进行交互。
参照图18所示，可以包括如下步骤：
步骤S1801，F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求。具体过程与前述步骤S1501类似，不再赘述。其中，该MBS会话开始请求中的MBS IP Multicast Distribution包含的IP多播传输地址记为IP1。
F-CP1在接收到F-CP1的父控制面节点发送的MBS会话开始请求之后，可以根据F-CP1对应的gNB的信息(如位置和数量等)确定从多个F-UPF中选取一个或多个作为与F-CP1同级的用户面节点，该实施例中假定选取了两个用户面节点，记为F-UP11 和F-UP12。然后分别执行步骤S1802a和步骤S1802b。
步骤S1802a，F-CP1向F-UP11发送用户面MBS会话建立请求，F-UP11向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S1802a中F-UP11分配的IP多播传输地址记为IP2。
步骤S1802b，F-CP1向F-UP12发送用户面MBS会话建立请求，F-UP12向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S1802b中F-UP12分配的IP多播传输地址记为IP3。
步骤S1803，若F-UP11与F-UP12支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP1对应的多播传输组中，以接收F-UP11与F-UP12的父用户面节点发送的MBS业务数据。
步骤S1804a，F-CP1向AMF发送信息传送消息(即Namf_Communication_NonUeN2MessageTransfer)。
F-CP1向AMF发送信息传送消息包含了如下参数：RAN ID、N2 MBS Session Container(MBS会话容器)。其中，N2 MBS Session Container包含了(N2 MBS Session Start Request(TMGI,MBS QFIs,QoS Profile,List of{F-UP ID，MBS传输信息}))。MBS传输信息即为MBS IP Multicast Distribution(IP Multicast Distribution address,C-TEID)。在该实施例中，由于F-CP1选择了两个与F-CP1同级的用户面节点F-UP11和F-UP12，因此List of{F-UP ID，MBS传输信息}中包含了F-UP11 ID及F-UP11 ID对应的MBS IP Multicast Distribution，以及F-UP12 ID及F-UP12 ID对应的MBS IP Multicast Distribution。F-UP11 ID对应的MBS IP Multicast Distribution是F-UP11所分配的，其中包含的IP多播传输地址即为IP2；F-UP12 ID对应的MBS IP Multicast Distribution是F-UP12所分配的，其中包含的IP多播传输地址即为IP3。
需要说明的是：F-UP12分配的IP多播传输地址IP3与F-UP11分配的IP多播传输地址IP2不能相同，但是所分配的C-TEID可以相同。
F-CP1向AMF发送信息传送消息包含的MBS会话容器表示是要AMF将N2 MBS Session Start Request(TMGI,MBS QFIs,QoS Profile,List of{F-UP ID，MBS传输信息})的相关内容发送给RAN ID所标识的gNB。当F-CP1中的MBS Session Context中记录有多个RAN ID时，则后续的步骤S1804b至步骤S1808b是针对每个RAN ID所标识的gNB分别执行的。
步骤S1804b，AMF根据步骤S1804a中的信息传送消息所包含的RAN ID向对应的gNB-CU发送MBS会话开始请求，包含有步骤S1804a中的各项参数，即包含有TMGI、MBS QFIs、QoS Profile、List of{F-UP ID，MBS传输信息}。
gNB-CU在接收到AMF发送的MBS会话开始请求之后，gNB-CU根据注册的MBS Multicast Service UE的数量及位置(对于MBS Multicast Service而言)或MBS Broadcast Service Area(对于MBS Broadcast Service而言)分别从多个gNB-DU中为F-UP11和F-UP12选择一个或多个gNB-DU。该实施例中假定为F-UP11选取了gNB-DU11与gNB-DU12，为F-UP12选取了gNB-DU21与gNB-DU22，即为F-UP11和F-UP12选择 了不同的gNB-DU。然后分别执行步骤S1805a和步骤S1805b。
步骤S1805a，gNB-CU向选取的gNB-DU11和gNB-DU12分别发送用户面MBS会话建立请求(即F1 MBS Session Establishment Request)，该用户面MBS会话建立请求中包含有F-UP11分配的IP多播传输地址IP2，gNB-DU11和gNB-DU12分别向gNB-CU反馈用户面MBS会话建立响应(为了节省版面，图18中将gNB-DU11与gNB-DU12画在了一起)。具体过程与步骤S1505a中S-CP与S-UP之间的交互过程类似，不再赘述。
步骤S1805b，gNB-CU向选取的gNB-DU21和gNB-DU22分别发送用户面MBS会话建立请求(即F1 MBS Session Establishment Request)，该用户面MBS会话建立请求中包含有F-UP12分配的IP多播传输地址IP3，gNB-DU21和gNB-DU22分别向gNB-CU反馈用户面MBS会话建立响应(为了节省版面，图18中将gNB-DU21与gNB-DU22画在了一起)。具体过程与步骤S1505a中S-CP与S-UP之间的交互过程类似，不再赘述。
步骤S1806a，gNB-DU11和gNB-DU12若支持接收基于多播方式传输的数据，则分别加入F-UP11分配的IP多播传输地址(即IP2)对应的多播传输组中，以接收F-UP11发送的MBS业务数据。
步骤S1806b，gNB-DU21和gNB-DU22若支持接收基于多播方式传输的数据，则分别加入F-UP12分配的IP多播传输地址(即IP3)对应的多播传输组中，以接收F-UP12发送的MBS业务数据。
需要说明的是：类似于前述实施例，若根据网络配置，gNB-DU不支持接收基于多播方式传输的数据，但支持通过点对点的方式接收MBS业务数据，则需要分配对应的F-TEID，该F-TEID由gNB-CU分配，或由gNB-DU分配。
步骤S1807a，gNB根据步骤S1804a中接收到的信息传送消息中包含的QFIs与QoS Profile分配无线空口资源。
步骤S1807b，gNB-CU向AMF发送MBS会话开始响应。若有gNB-DU不支持接收基于多播方式传输的数据，则MBS会话开始响应中包含此gNB-DU分配的F-TEID(为便于区分，将其记为F-TEIDgnb-du)，且对应于F-UP，从而形成一个List of{F-UP ID,List of F-TEIDgnb-du,Multicast Enable}。在该实施例中，List of{F-UP ID,List of F-TEIDgnb-du,Multicast Enable}包含了针对F-UP11的List of F-TEIDgnb-du和Multicast Enable，以及针对F-UP12的List of F-TEIDgnb-du和Multicast Enable。
类似于步骤S1507，由于有些gNB-DU支持接收基于多播方式传输的数据，而另外一些gNB-DU不支持接收基于多播方式传输的数据，所以这个List F-TEIDgnb-du只是对应于那些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的gNB-DU。因此，当一个F-UP的所有gNB-DU都支持接收基于多播方式传输的数据，则对应于这个F-UP的List of F-TEIDgnb-du就没有了，其它说明参照步骤S1507的相关内容。
此外，当gNB-CU决定不向其中某个/某些F-UP ID分配任何的子用户面节点时， 则可以将这个/这些F-UP ID对应的Multicast Enable设置为Disable。当然，也可以在MBS会话开始响应中采用Failed List{F-UP}来指示没有被分配gNB-DU的父用户面节点。
步骤S1807c，AMF根据步骤S1807b中收到的MBS会话开始响应向F-CP1发送信息通知消息Namf_Communication_NonUeN2InfoNotify。其中，该信息通知消息包含N2 MBS Session container(N2 MBS Session Start Response(List of(F-UP ID,List of F-TEIDgnb-du,Multicast Enable)))。
步骤S1808a，F-CP1根据接收到的信息通知消息中包含的List of{F-UP ID,List of F-TEIDgnb-du,Multicast Enable}向F-UP11发送用户面MBS会话修改请求，F-UP11向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S1808b，F-CP1根据接收到的信息通知消息中包含的List of{F-UP ID,List of F-TEIDgnb-du,Multicast Enable}向F-UP12发送用户面MBS会话修改请求，F-UP12向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S1809，当针对每个RAN ID所标识的gNB都执行步骤S1804a至步骤S1808b之后，F-CP1根据所有gNB-CU反馈的MBS会话开始响应向F-CP1的父控制面节点发送MBS会话开始响应。
类似于步骤S1609，F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有与F-CP1的父控制面节点同级的用户面节点的UP ID，并且可能还包含有List of F-TEIDfup和Multicast Enable。
其中，步骤S1801至步骤S1809是F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求之后的处理过程，在该处理过程中，F-CP1选择了与F-CP1同级的两个用户面节点F-UP11和F-UP12，并且F-CP1对应的gNB-CU为F-UP11选择了两个与gNB-CU同级的子用户面节点gNB-DU11和gNB-DU12，为F-UP12选择了两个与gNB-CU同级的子用户面节点gNB-DU21和gNB-DU22。
继续参照图18所示，还包括如下步骤：
步骤S1810，F-CP2接收到F-CP2的父控制面节点发送的MBS会话开始请求。具体过程与前述步骤S1501类似，不再赘述。其中，该MBS会话开始请求中的MBS IP Multicast Distribution包含的IP多播传输地址记为IPx。
步骤S1811，F-CP2在接收到F-CP2的父控制面节点发送的MBS会话开始请求之后，可以根据F-CP2对应的gNB的信息(如位置和数量等)确定从多个F-UPF中选取一个或多个作为与F-CP2同级的用户面节点。该实施例中假定只选取一个用户面节点F-UP21，然后F-CP2向F-UP21发送用户面MBS会话建立请求，F-UP21向F-CP2反馈用户面MBS会话建立响应。
具体说明参见前述步骤S1502的相关内容，类似于步骤S1502，F-CP2与F-UP21之间通过用户面MBS会话建立请求与用户面MBS会话建立响应之间的交互，F-UP21 分配了新的IP多播传输地址(为便于区分，记为IP4)。
此外，类似地，若F-UP21不支持接收基于多播方式传输的数据，F-UP21分配一个用于通过点对点方式接收MBS业务数据的F-TEID，并在用户面MBS会话建立响应中携带分配的F-TEID。
步骤S1812，若F-UP21支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IPx对应的多播传输组中，以接收F-UP21的父用户面节点发送的MBS业务数据。
步骤S1813a，F-CP2向AMF发送信息传送消息(即Namf_Communication_NonUeN2MessageTransfer)。该信息传送消息的具体说明类似于前述步骤S1804a，不再赘述。但是需要说明的是：由于F-CP2选择了一个与F-CP2同级的用户面节点F-UP21，因此信息传送消息中包含了F-UP21 ID和对应于F-UP21 ID的MBS IP Multicast Distribution，该MBS IP Multicast Distribution中所包含的IP多播传输地址即为IP4。当F-CP2中的MBS Session Context中记录有多个RAN ID时，则后续的步骤S1813b至步骤S1817是针对每个RAN ID所标识的gNB分别执行的。
需要说明的是：步骤S1813a与步骤S1804a之间并没有先后关系，它们可以是F-CP2与F-CP1并行分别执行的步骤。
步骤S1813b，AMF根据步骤S1813a中的信息传送消息所包含的RAN ID向对应的gNB-CU发送MBS会话开始请求，包含有步骤S1813a中的各项参数。
gNB-CU在接收到AMF发送的MBS会话开始请求之后，gNB-CU根据注册的MBS Multicast Service UE的数量及位置(对于MBS Multicast Service而言)或MBS Broadcast Service Area(对于MBS Broadcast Service而言)分别从多个gNB-DU中为F-UP21选取的一个或多个gNB-DU。该实施例中假定为F-UP21选取了gNB-DU31与gNB-DU32，即为F-UP21选择的gNB-DU不同于为F-UP11与F-UP12选择的gNB-DU。
步骤S1814，gNB-CU向选取的gNB-DU31和gNB-DU32分别发送用户面MBS会话建立请求(即F1 MBS Session Establishment Request)，该用户面MBS会话建立请求中包含有F-UP21分配的IP多播传输地址IP4，gNB-DU31和gNB-DU32分别向gNB-CU反馈用户面MBS会话建立响应(为了节省版面，图18中将gNB-DU31与gNB-DU32画在了一起)。具体过程与步骤S1505a类似，不再赘述。
步骤S1815，gNB-DU31和gNB-DU32若支持接收基于多播方式传输的数据，则分别加入F-UP21分配的IP多播传输地址(即IP4)对应的多播传输组中，以接收F-UP21发送的MBS业务数据。
需要说明的是：类似于前述实施例，若根据网络配置，gNB-DU不支持接收基于多播方式传输的数据，但支持通过点对点的方式接收MBS业务数据，则需要分配对应的F-TEID，该F-TEID由gNB-CU分配，或由gNB-DU分配。
步骤S1816a，gNB根据步骤S1813a中接收到的信息传送消息中包含的QFIs与QoS Profile分配无线空口资源。
步骤S1816b，gNB-CU向AMF发送MBS会话开始响应。若有gNB-DU不支持接 收基于多播方式传输的数据，则MBS会话开始响应中包含此gNB-DU分配的F-TEIDgnb-du，且对应于F-UP21。其它说明可参照步骤S1507的相关内容。
步骤S1816c，AMF根据步骤S1816b中收到的MBS会话开始响应向F-CP2发送信息通知消息Namf_Communication_NonUeN2InfoNotify。其中，该信息通知消息包含(N2 MBS Session container(N2 MBS Session Start Response(F-UP21 ID,List of F-TEIDgnb-du,Multicast Enable)))。
步骤S1817，F-CP2根据接收到的信息通知消息中包含的F-UP21 ID和List of F-TEIDgnb-du向F-UP21发送用户面MBS会话修改请求，F-UP21向F-CP2反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S1818，当针对每个RAN ID所标识的gNB都执行步骤S1813b至步骤S1817之后，F-CP2根据所有gNB-CU反馈的MBS会话开始响应向F-CP2的父控制面节点发送MBS会话开始响应。
类似于步骤S1509，F-CP2向F-CP2的父控制面节点回复的MBS会话开始响应中包含有与F-CP2的父控制面节点同级的用户面节点的UPx ID，并且可能还包含有List of F-TEIDfup。
其中，步骤S1810至步骤S1818是F-CP2接收到F-CP2的父控制面节点发送的MBS会话开始请求之后的处理过程，在该处理过程中，F-CP2选择了一个与F-CP2同级的用户面节点F-UP21，并且F-CP2对应的gNB-CU选择了两个与gNB-CU同级的子用户面节点gNB-DU31和gNB-DU32。
通过步骤S1801至步骤S1818可知，在本申请的实施例中，gNB-CU可以有多个父控制面节点F-CP1和F-CP2，而gNB-CU控制的gNB-DU只有一个父用户面节点。
另外，步骤S1801中的消息与步骤S1810中的消息可能是并行发下来的，因此，步骤S1801～S1809与步骤S1810～S1818可能是并行执行的。这样，在用户面MBS会话建立过程中，可能存在着一个用户面节点同时被两个控制面节点发送用户面MBS会话建立请求消息，或已经被一个控制面节点选择后、又接收到另一个控制面节点发送的用户面MBS会话建立请求消息。如果一个用户面节点同时收到两个控制面节点(当然也可以是更多个，此处以两个为例进行说明)发送的用户面MBS会话建立请求消息，那么该用户面节点可以在用户面MBS会话建立响应消息中，正常响应其中一个控制面节点发送的用户面MBS会话建立请求，并且在另一个用户面MBS会话建立响应消息中，拒绝(Reject)另外一个控制面节点，以指示此用户面节点已经被选择。如果一个用户面节点通过一个控制面节点已经有了父用户面节点后，又收到另外一个控制面节点发送的用户面MBS会话建立请求消息时，则在另一个用户面MBS会话建立响应消息中Reject该另外一个控制面节点，以指示此用户面节点已经被选择。
当这种MBS会话传输树建立完成之后，可以执行如下步骤：
步骤S1819a，F-UP11接收到F-UP11的父用户面节点发送的下行MBS业务数据。然后通过步骤S1820a将接收到的该下行MBS业务数据传输给gNB-DU11和gNB-DU12。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送 MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
步骤S1819b，F-UP12接收到F-UP12的父用户面节点发送的下行MBS业务数据。然后通过步骤S1820b将接收到的该下行MBS业务数据传输给gNB-DU21和gNB-DU22。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
步骤S1819c，F-UP21接收到F-UP21的父用户面节点发送的下行MBS业务数据。然后通过步骤S1820c将接收到的该下行MBS业务数据传输给gNB-DU31和gNB-DU32。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
图18所示实施例的技术方案主要是将NR基站引入到MBS会话传输树中之后建立控制面传输树与用户面传输树的过程。需要说明的是，在图15、图16和图18所示的实施例中，只介绍了MBS会话传输树中的两级节点之间的交互过程，对于包含三级或三级以上节点的MBS会话传输树而言，其中的任意两级节点之间的交互过程都可以参照图15、图16或图18所示的实施例来实现。比如，如图19所示，1901和1902所示的两级节点可以是图15或图16中所示的两级节点，在将1901中的子控制面节点S-CP和子用户面节点S-UP与1902中的父控制面F-CP节点和父用户面节点F-UP分别叠加为同一个实体之后，如图19中1903所示可以实现一个三级的MBS会话传输树，其中GF-CP是F-CP的父控制面节点，GF-UP是F-UP的父用户面节点。基于这种方式，可以实现任意级的MBS会话传输树。
对于图18所示的实施例，由于基站只能作为网络侧的最后一级，因此也可以通过将图18所示的实施例与图15和图16所示的实施例进行组合，以实现包含基站的任意级的MBS会话传输树。
图15、图16和图18示出了根据本申请实施例的MBS会话传输树的建立过程，而MBS会话在建立过程中用户面传输树也可能出现断枝的情况，因此也需要进行删除断枝的操作。
具体如图20所示，可以包括如下步骤：
步骤S2001，F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求。具体过程与前述步骤S1501类似，不再赘述。其中，该MBS会话开始请求中的MBS IP Multicast Distribution包含的IP多播传输地址记为IP1。
F-CP1在接收到F-CP1的父控制面节点发送的MBS会话开始请求之后，可以根据F-CP1的子控制面节点的信息确定从多个F-UPF中选取一个或多个F-UPF作为与F-CP1同级的用户面节点，该实施例中假定选取了两个用户面节点F-UP11和F-UP12。然后分别执行步骤S1602a和步骤S1602b。
步骤S2002a，F-CP1向F-UP11发送用户面MBS会话建立请求，F-UP11向F-CP1 反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S2002a中F-UP11分配的IP多播传输地址记为IP2。
步骤S2002b，F-CP1向F-UP12发送用户面MBS会话建立请求，F-UP12向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S2002b中F-UP12分配的IP多播传输地址记为IP3。
步骤S2003，若F-UP11与F-UP12支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP1对应的多播传输组中，以接收F-UP11与F-UP12的父用户面节点发送的MBS业务数据。
步骤S2004，F-CP1根据F-CP1的子控制面节点的信息，向每个子控制面子节点分别发送MBS会话开始请求，即步骤S2004至步骤S2008是针对每个子控制面节点分别单独执行的，该实施例中以向一个子控制面节点S-CP发送为例进行说明。
F-CP1发送给F-CP1的子控制面节点S-CP的MBS会话开始请求中包含了如下参数：TMGI、MBS Session Duration、MBS QFIs、QoS Profile、MBS Time to Data Transfer、List of{F-UP ID，MBS传输信息}、MBS Service Area。其中，MBS传输信息即为MBS IP Multicast Distribution(IP Multicast Distribution address,C-TEID)。在该实施例中，由于F-CP1选择了两个与F-CP1同级的用户面节点F-UP11和F-UP12，因此List of{F-UP ID，MBS传输信息}中包含了F-UP11 ID及F-UP11 ID对应的MBS IP Multicast Distribution，以及F-UP12 ID及F-UP12 ID对应的MBS IP Multicast Distribution。F-UP11 ID对应的MBS IP Multicast Distribution是F-UP11所分配的，其中包含的IP多播传输地址即为IP2；F-UP12 ID对应的MBS IP Multicast Distribution是F-UP12所分配的，其中包含的IP多播传输地址即为IP3。
需要说明的是：F-UP12分配的IP多播传输地址IP3与F-UP11分配的IP多播传输地址IP2不能相同，但是所分配的C-TEID可以相同。
S-CP在接收到F-CP1发送的MBS会话开始请求之后，类似于步骤S1502，S-CP根据S-CP的子控制面节点的信息从多个S-UP中为F-UP11选择一个或多个S-UP，以及为F-UP12选择一个或多个S-UP，该实施例中假定为F-UP11选取了S-UP11与S-UP12，但是没有为F-UP12选择任何子用户面节点。然后执行步骤S2005。
步骤S2005，S-CP向选取的S-UP11和S-UP12分别发送用户面MBS会话建立请求，该用户面MBS会话建立请求中包含有F-UP11分配的IP多播传输地址IP2，S-UP11和S-UP12分别向S-CP反馈用户面MBS会话建立响应(为了节省版面，图20中将S-UP11与S-UP12画在了一起)。具体过程与步骤S1505a类似，不再赘述。
步骤S2006，S-UP11和S-UP12若支持接收基于多播方式传输的数据，则分别加入F-UP11分配的IP多播传输地址(即IP2)对应的多播传输组中，以接收F-UP11发送的MBS业务数据。
步骤S2007，S-CP向F-CP1发送MBS会话开始响应。若有S-UP不支持接收基于多播方式传输的数据，则MBS会话开始响应中包含此S-UP分配的F-TEID，且对应于F-UP，从而形成一个List of{F-UP ID,List of F-TEIDsup,Multicast Enable}。在该实施例中，List  of{F-UP ID,List of F-TEIDsup,Multicast Enable}包含了针对F-UP11的List of F-TEIDsup和Multicast Enable，以及针对F-UP12的Multicast Enable(取值为Disable)。由于F-UP12没有分配F-TEID，同时对应的Multicast Enable设置为Disable，则表明没有为F-UP12选择子用户面节点。
类似于步骤S1507，由于有些S-UP支持接收基于多播方式传输的数据，而另外一些S-UP不支持接收基于多播方式传输的数据，所以这个List F-TEIDsup只是对应于那些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP。因此，当一个F-UP的所有S-UP都支持接收基于多播方式传输的数据，则对应于这个F-UP的List of F-TEIDsup就没有了，其它说明参照步骤S1507的相关内容。
此外，当S-CP决定不向其中某个/某些F-UP ID分配任何的子用户面节点时，除了可以将这个/这些F-UP ID对应的Multicast Enable参数设置为Disable之外，还可以在MBS会话开始响应中采用Failed List{F-UP}来指示没有被分配子用户面节点的父用户面节点。
步骤S2008a，F-CP1根据MBS会话开始响应中包含的List of{F-UP ID,List of F-TEIDsup,Multicast Enable}向F-UP11发送用户面MBS会话修改请求，F-UP11向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
需要说明的是：若F-CP1确定F-CP1的所有子控制面节点都没有向F-UP11分配子用户面节点，则F-CP1向F-UP11发送用户面MBS会话删除请求，F-UP11在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，并从F-UP11的父用户面节点分配的多播传输地址IP1指示的多播传输组中删除，并且F-UP11向F-CP1回复用户面MBS会话删除响应(此过程未在图中标识)。
步骤S2008b，F-CP1在收到F-CP1的所有子控制面节点回复的MBS会话开始响应之后，确定F-CP1的所有子控制面节点都没有向F-UP12分配子用户面节点，则向F-UP12发送用户面MBS会话删除请求(即N4 MBSSessionDelete Request)，F-UP12在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，指示从F-UP12的父用户面节点对应的多播传输地址(即IP1)指示的多播传输组中删除，并且F-UP12向F-CP1回复用户面MBS会话删除响应。
需要说明的是：步骤S2004至步骤S2008是针对F-CP1的每个子控制面节点分别单独执行的，不能仅仅由于F-CP1的一个子控制面节点在步骤S2007中回复的MBS会话开始响应指示没有向F-UP12分配子用户面节点就启动执行步骤S2008b的删除MBS会话的操作。而应该是F-CP1在收到所有子控制面节点的回复后再判断没有为哪个用户面节点分配子用户面节点，以决定是否要删除与这个用户面节点之间的MBS会话。
步骤S2009，当针对每个子控制面都执行步骤S2004至步骤S2008之后，F-CP1根据所有子控制面反馈的MBS会话开始响应向F-CP1的父控制面节点发送MBS会话开始响应。
类似于步骤S1509，F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有与F-CP1的父控制面节点同级的用户面节点UP ID，并且可能还包含有List of  F-TEID(为便于区分，将其记为List of F-TEIDfup)，由于F-CP1选择了两个与F-CP1同级的用户面节点F-UP11和F-UP12，但是S-CP未向F-UP12分配子用户面节点，因此如果F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有List of F-TEIDfup，那么其中也只包含F-UP11分配的F-TEID。
需要说明的是，如果F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中可以不包含F-UP11分配的F-TEID，在这种情况下说明F-UP11支持接收基于多播方式传输的数据，此时F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中无需包含Multicast Enable；如果F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含F-UP11分配的F-TEID，则说明F-UP11不支持接收基于多播方式传输的数据、但是支持通过点对点方式发送的MBS业务数据，在这种情况下由于只有一个与F-CP1同级的用户面节点F-UP11，因此F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中也无需包含Multicast Enable。
当MBS会话传输树建立完成之后，可以执行如下步骤：
步骤S2010，F-UP11接收到F-UP11的父用户面节点发送的下行MBS业务数据。然后通过步骤S2011将接收到的该下行MBS业务数据传输给S-UP11和S-UP12。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
在图20所示的实施例中，虽然F-CP1选择了两个与F-CP1同级的用户面节点F-UP11和F-UP12，但是F-CP1的子控制面节点S-CP没有向F-UP12分配子用户面节点，即用户面传输树中出现了断枝的情况，因此需要删除存在的断枝。
在本申请的一个实施例中，还可以由非PSA(PDU(Protocol Data Unit，分组数据单元)Session Anchor，PDU会话锚点)的UPF来参与MBS会话，在这种情况下，建立用户面MBS传输树的过程可以参照图21所示，包括如下步骤：
步骤S2101，F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求。具体过程与前述步骤S1501类似，不再赘述。其中，该MBS会话开始请求中的MBS IP Multicast Distribution包含的IP多播传输地址记为IP1。
F-CP1在接收到F-CP1的父控制面节点发送的MBS会话开始请求之后，可以根据F-CP1的子控制面节点的信息确定从多个F-UPF中选取一个或多个F-UPF作为与F-CP1同级的用户面节点，该实施例中假定选取了两个用户面节点，记为F-UP11和F-UP12。然后分别执行步骤S2102a和步骤S2102b。
步骤S2102a，F-CP1向F-UP11发送用户面MBS会话建立请求，F-UP11向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S2102a中F-UP11分配的IP多播传输地址记为IP2。
步骤S2102b，F-CP1向F-UP12发送用户面MBS会话建立请求，F-UP12向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S2102b中F-UP12分配的IP多播传输地址记为IP3。
步骤S2103，若F-UP11与F-UP12支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP1对应的多播传输组中，以接收F-UP11与F-UP12的父用户面节点发送的MBS业务数据。
在执行步骤S2102a和步骤S2102b之后，F-CP1可以选择执行如下步骤S2104a、步骤S2104b和步骤S2104c，并选择用户面节点F-UP21、F-UP22、F-UP23(F-CP1选择的用户面节点及数量仅为示例)，这样做的目的在于可以使得F-UP11和F-UP12通过F-UP21、F-UP22、F-UP23来进行分流或优化传输。
例如，当F-UP11与F-UP11的下一级用户面节点之间的距离较远，且F-UP11的下一级用户面节点的数量非常多时，如果由F-UP11直接将MBS业务数据传输给F-UP11的下一级用户面节点，那么这种传输效率非常低。而通过在F-UP11与F-UP11的下一级用户面节点之间引入诸如F-UP21、F-UP22等，则可以由F-UP11将MBS业务数据通过F-UF21发送给下一级用户面节点，这样可以有效提升数据传输效率。
以下介绍步骤S2104a、步骤S2104b和步骤S2104c：
步骤S2104a，F-CP1向F-UP21发送用户面MBS会话建立请求，F-UP21向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述。在步骤S2104a中F-UP21还分配了一个向F-UP21的子用户面节点传输MBS业务数据的新的IP多播传输地址，该实施例中标识为IP4。并且，如果F-UP21不支持接收F-UP11通过多播方式发送的MBS业务数据，那么F-UP21会分配一个F-TEID来通过点对点的方式从F-UP11接收MBS业务数据。
步骤S2104b，F-CP1向F-UP22发送用户面MBS会话建立请求，F-UP22向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述。在步骤S2104b中F-UP22还分配了一个向F-UP22的子用户面节点传输MBS业务数据的新的IP多播传输地址，该实施例中标识为IP5。并且，如果F-UP22不支持接收F-UP11通过多播方式发送的MBS业务数据，那么F-UP22会分配一个F-TEID来通过点对点的方式从F-UP11接收MBS业务数据。
需要说明的是，在本申请的一个实施例中，步骤S2104a和步骤S2104b中的用户面MBS会话建立请求包含的MBS IP Multicast Distribution中的多播传输地址为步骤S2102a中的多播传输地址IP2。
步骤S2104c，F-CP1向F-UP23发送用户面MBS会话建立请求，F-UP23向F-CP1反馈用户面MBS会话建立响应。同时，F-UP23还分配了一个向F-UP23的子用户面节点传输MBS业务数据的新的IP多播传输地址，该实施例中标识为IP6。该过程与前述实施例中步骤S1502的过程类似，不再赘述。
在本申请的一个实施例中，步骤S2104c中的用户面MBS会话建立请求包含的MBS IP Multicast Distribution中的多播传输地址为步骤S2102b中的多播传输地址IP3。其中，步骤S2104c中确定的新的多播传输地址是F-UP23分配给F-UP23的子用户面节点的(即图21中的S-UP31和S-UP32)。并且，如果F-UP23不支持接收F-UP12通过多播方式发送的MBS业务数据，那么F-UP23会分配一个F-TEID来通过点对点的方式从F-UP12 接收MBS业务数据。
步骤S2105a，若F-UP21与F-UP22支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP2对应的多播传输组中，以接收F-UP11发送的MBS业务数据。
步骤S2105b，若F-UP23支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP3对应的多播传输组中，以接收F-UP12发送的MBS业务数据。
步骤S2106a，若F-UP21和F-UP22中有不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的用户面节点，则F-CP1向F-UP11发送用户面MBS会话修改请求，F-UP11向F-CP1反馈用户面MBS会话修改响应。其中，该用户面MBS会话修改请求中包含有F-UP21和F-UP22中不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的用户面节点分配的F-TEID，以指示F-UP11增加使用点对点的方式向F-UP21和F-UP22中不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的用户面节点传送MBS业务数据。
步骤S2106b，若F-UP23不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则F-CP1向F-UP12发送用户面MBS会话修改请求，F-UP12向F-CP1反馈用户面MBS会话修改响应。其中，该用户面MBS会话修改请求中包含有F-UP23分配的F-TEID，以指示F-UP12通过点对点的方式向F-UP23传送MBS业务数据。
步骤S2107，F-CP1根据F-CP1的子控制面节点的信息，向F-CP1的子控制面节点S-CP1发送MBS会话开始请求。
F-CP1发送给F-CP1的子控制面节点S-CP1的MBS会话开始请求中包含了如下参数：TMGI、MBS Session Duration、MBS QFIs、QoS Profile、MBS Time to Data Transfer、List of{F-UP ID，MBS传输信息}、MBS Service Area。其中，MBS传输信息即为MBS IP Multicast Distribution(IP Multicast Distribution address,C-TEID)。在该实施例中，List of{F-UP ID，MBS传输信息}中包含了F-UP21 ID及F-UP21 ID对应的MBS IP Multicast Distribution，以及F-UP22 ID及F-UP22 ID对应的MBS IP Multicast Distribution。F-UP21ID对应的MBS IP Multicast Distribution是F-UP21所分配的，其中包含的IP多播传输地址即为步骤S2104a中由F-UP21分配的新的IP多播传输地址IP4；F-UP22 ID对应的MBS IP Multicast Distribution是F-UP22所分配的，其中包含的IP多播传输地址即为步骤S2104b中由F-UP22分配的新的IP多播传输地址IP5，且步骤S2104a中由F-UP21分配的新的IP多播传输地址IP4和步骤S2104b中由F-UP22分配的新的IP多播传输地址IP5不相同。
步骤S2108，S-CP1在接收到F-CP1发送的MBS会话开始请求之后，进行用户面MBS会话建立过程。具体地，S-CP1根据S-CP1的子控制面节点的信息从多个S-UP中为F-UP21选择一个或多个S-UP，以及为F-UP22选择一个或多个S-UP，该实施例中假定为F-UP21选取了S-UP11与S-UP12，为F-UP22选取了S-UP21与S-UP22，即为F-UP21和F-UP22选择了不同的子用户面节点。然后S-CP1分别向为F-UP21和F-UP22选择的子用户面节点(即S-UP11、S-UP12、S-UP21与S-UP22)发送用户面MBS会话建立请 求，并接收这些子用户面节点反馈的用户面MBS会话建立响应。同时，如果这些子用户面节点支持接收多播传输，则可以加入相应的多播传输组来接收MBS业务数据(即S-UP11和S-UP12加入IP4对应的多播传输组，S-UP21和S-UP22加入IP5对应的多播传输组)；如果这些子用户面节点中的一些子用户面节点不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据的子用户面节点可以分配F-TEID来通过点对点的方式接收MBS业务数据，具体过程与步骤S1505a及步骤S1506类似，不再赘述。
步骤S2109，S-CP1向F-CP1发送MBS会话开始响应。若有S-UP不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则MBS会话开始响应中包含此S-UP分配的F-TEID，且对应于F-UP，从而形成一个List of{F-UP ID,List of F-TEIDsup,Multicast Enable}。在该实施例中，List of{F-UP ID,List of F-TEIDsup,Multicast Enable}包含了针对F-UP21的List of F-TEIDsup和Multicast Enable，以及针对F-UP22的List of F-TEIDsup和Multicast Enable。
类似于步骤S1507，由于有些S-UP支持接收基于多播方式传输的数据，而另外一些S-UP不支持接收基于多播方式传输的数据，所以这个List F-TEIDsup只是对应于那些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP。因此，当一个F-UP的所有S-UP都支持接收基于多播方式传输的数据，则对应于这个F-UP的List of F-TEIDsup就没有了，其它说明参照步骤S1507的相关内容。
此外，当S-CP1决定不向其中某个/某些F-UP ID分配任何的子用户面节点时，则可以将这个/这些F-UP ID对应的Multicast Enable设置为Disable。当然，也可以在MBS会话开始响应中采用Failed List{F-UP}来指示没有被分配子用户面节点的F-UP。
步骤S2110a，F-CP1根据S-CP1反馈的MBS会话开始响应中包含的List of{F-UP ID,List of F-TEIDsup,Multicast Enable}向F-UP21发送用户面MBS会话修改请求，F-UP21向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S2110b，F-CP1根据S-CP1反馈的MBS会话开始响应中包含的List of{F-UP ID,List of F-TEIDsup,Multicast Enable}向F-UP22发送用户面MBS会话修改请求，F-UP22向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S2111，F-CP1根据F-CP1的子控制面节点的信息，向F-CP1的子控制面节点S-CP2发送MBS会话开始请求。
F-CP1发送给F-CP1的子控制面节点S-CP2的MBS会话开始请求中包含了如下参数：TMGI、MBS Session Duration、MBS QFIs、QoS Profile、MBS Time to Data Transfer、List of{F-UP ID，MBS传输信息}、MBS Service Area。其中，MBS传输信息即为MBS IP Multicast Distribution(IP Multicast Distribution address,C-TEID)。在该实施例中，List of{F-UP ID，MBS传输信息}中包含了F-UP23ID及F-UP23ID对应的MBS IP Multicast  Distribution。F-UP23ID对应的MBS IP Multicast Distribution是F-UP23所分配的，其中包含的IP多播传输地址即为步骤S2104c中由F-UP23分配的新的IP多播传输地址IP6。
需要说明的是：步骤S2111与步骤S2107之间并没有先后关系，它们可以是F-CP1并行分别执行的步骤。
步骤S2112，S-CP2在接收到F-CP1发送的MBS会话开始请求之后，进行用户面MBS会话建立过程。具体地，S-CP2根据S-CP2的子控制面节点的信息从多个S-UP中为F-UP23选择一个或多个S-UP，该实施例中假定为F-UP23选取了S-UP31与S-UP32，即为F-UP23选取的子用户面节点与为F-UP21和F-UP22选择的子用户面节点不相同。然后S-CP2分别向为F-UP23选择的子用户面节点(即S-UP31与S-UP32)发送用户面MBS会话建立请求，并接收S-UP31与S-UP32分别反馈的用户面MBS会话建立响应。同时，如果S-UP31与S-UP32支持接收多播传输，则可以加入步骤S2104c中由F-UP23分配的新的IP多播传输地址IP6对应的多播传输组来接收F-UP23发送的MBS业务数据；如果S-UP31与S-UP32中的一些子用户面节点不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则S-UP31与S-UP32中不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据的子用户面节点可以分配F-TEID来通过点对点的方式接收F-UP23发送的MBS业务数据，具体过程与步骤S1505a及步骤S1506类似，不再赘述。
步骤S2113，S-CP2向F-CP1发送MBS会话开始响应。若S-UP31与S-UP32中有S-UP不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则MBS会话开始响应中包含此S-UP分配的F-TEID，且对应于F-UP，从而形成一个List of{F-UP ID,List of F-TEIDsup,Multicast Enable}。在该实施例中，List of{F-UP ID,List of F-TEIDsup,Multicast Enable}包含了针对F-UP23的List of F-TEIDsup和Multicast Enable。
类似于步骤S1507，由于有些S-UP支持接收基于多播方式传输的数据，而另外一些S-UP不支持接收基于多播方式传输的数据，所以这个List F-TEIDsup只是对应于那些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP。因此，当一个F-UP的所有S-UP都支持接收基于多播方式传输的数据，则对应于这个F-UP的List of F-TEIDsup就没有了，其它说明参照步骤S1507的相关内容。
此外，当S-CP2决定不向其中某个/某些F-UP ID分配任何的子用户面节点时，则可以将这个/这些F-UP ID对应的Multicast Enable设置为Disable。当然，也可以在MBS会话开始响应中采用Failed List{F-UP}来指示没有被分配子用户面节点的F-UP。
步骤S2114，F-CP1根据S-CP2反馈的MBS会话开始响应中包含的List of{F-UP ID,List of F-TEIDsup,Multicast Enable}向F-UP23发送用户面MBS会话修改请求，F-UP23向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
步骤S2115，当F-CP1接收到所有S-CP反馈的MBS会话开始响应之后，F-CP1根据所有S-CP反馈的MBS会话开始响应向F-CP1的父控制面节点发送MBS会话开始响 应。
类似于步骤S1609，F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有UP ID(该UP ID是与F-CP1的父控制面节点同级的用户面节点的标识)，并且可能还包含有List of F-TEIDfup和Multicast Enable。
通过步骤S2101至步骤S2115可知，在本申请的实施例中，F-CP1有两个子控制面节点S-CP1和S-CP2，F-CP1为F-UP11选择了下一级用户面节点F-UP21和F-UP22，F-CP1为F-UP12选择了下一级用户面节点F-UP23，同时S-CP1为F-UP21选择了子用户面节点S-UP11和S-UP12，S-CP1为F-UP22选择了子用户面节点S-UP21和S-UP22，S-CP2为F-UP23选择了子用户面节点S-UP31和S-UP32。
需要说明的是：在用户面MBS会话建立过程中，可能存在着一个用户面节点同时被两个控制面节点发送用户面MBS会话建立请求消息，或已经被一个控制面节点选择后、又接收到另一个控制面节点发送的用户面MBS会话建立请求消息。如果一个用户面节点同时收到两个控制面节点(当然也可以是更多个，此处以两个为例进行说明)发送的用户面MBS会话建立请求消息，那么该用户面节点可以在用户面MBS会话建立响应消息中，正常响应其中一个控制面节点发送的用户面MBS会话建立请求，并且在另一个用户面MBS会话建立响应消息中，拒绝(Reject)另外一个控制面节点，以指示此用户面节点已经被选择。如果一个用户面节点通过一个控制面节点已经有了父用户面节点后，又收到另外一个控制面节点发送的用户面MBS会话建立请求消息时，则在另一个用户面MBS会话建立响应消息中Reject该另外一个控制面节点，以指示此用户面节点已经被选择。
当这种MBS会话传输树建立完成之后，可以执行如下步骤：
步骤S2116a，F-UP11接收到F-UP11的父用户面节点发送的下行MBS业务数据。然后通过步骤S2117a将接收到的该下行MBS业务数据传输给F-UP21，并通过步骤S2117b接收到的该下行MBS业务数据传输给F-UP22。F-UP21通过步骤S2118a将接收到的该下行MBS业务数据传输给S-UP11和S-UP12。F-UP22通过步骤S2118b将接收到的该下行MBS业务数据传输给S-UP21和S-UP22。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
步骤S2116b，F-UP12接收到F-UP12的父用户面节点发送的下行MBS业务数据。然后通过步骤S2117c将接收到的该下行MBS业务数据传输给F-UP23，F-UP23通过步骤S2118c将接收到的该下行MBS业务数据传输给S-UP31和S-UP32。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
对于图21中所示的由非PSA的UPF来参与MBS会话的应用场景而言，同样需要防止出现断枝的出现，具体过程可以参照图22所示，包括如下步骤：
步骤S2201，F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求。具体 过程与前述步骤S1501类似，不再赘述。其中，该MBS会话开始请求中的MBS IP Multicast Distribution包含的IP多播传输地址记为IP1。
F-CP1在接收到F-CP1的父控制面节点发送的MBS会话开始请求之后，可以根据F-CP1的子控制面节点的信息确定从多个F-UPF中选取一个或多个F-UPF作为与F-CP1同级的用户面节点，该实施例中假定选取了两个用户面节点，记为F-UP11和F-UP12。然后分别执行步骤S2202a和步骤S2202b。
步骤S2202a，F-CP1向F-UP11发送用户面MBS会话建立请求，F-UP11向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S2202a中F-UP11分配的IP多播传输地址记为IP2。
步骤S2202b，F-CP1向F-UP12发送用户面MBS会话建立请求，F-UP12向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S2202b中F-UP12分配的IP多播传输地址记为IP3。
步骤S2203，若F-UP11与F-UP12支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP1对应的多播传输组中，以接收F-UP11与F-UP12的父用户面节点发送的MBS业务数据。
在执行步骤S2202a和步骤S2202b之后，F-CP1可以选择执行如下步骤S2204a、步骤S2204b和步骤S2204c，并选择用户面节点F-UP21、F-UP22、F-UP23(F-CP1选择的用户面节点及数量仅为示例)，这样做的目的在于可以使得F-UP11和F-UP12通过F-UP21、F-UP22、F-UP23来进行分流或优化传输。
例如，当F-UP11与F-UP11的下一级用户面节点之间的距离较远，而F-UP11的下一级用户面节点的数量非常多时，如果由F-UP11直接将MBS业务数据传输给F-UP11的下一级用户面节点，那么这种传输效率非常低。而通过在F-UP11与F-UP11的下一级用户面节点之间引入诸如F-UP21、F-UP22等，则可以由F-UP11将MBS业务数据通过F-UF21发送给下一级用户面节点，这样可以有效提升数据传输效率。
以下介绍步骤S2204a、步骤S2204b和步骤S2204c：
步骤S2204a，F-CP1向F-UP21发送用户面MBS会话建立请求，F-UP21向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述。在步骤S2204a中F-UP21还分配了一个向F-UP21的子用户面节点传输MBS业务数据的新的IP多播传输地址，该实施例中标识为IP4。并且，如果F-UP21不支持接收F-UP11通过多播方式发送的MBS业务数据，那么F-UP21会分配一个F-TEID来通过点对点的方式从F-UP11接收MBS业务数据。
步骤S2204b，F-CP1向F-UP22发送用户面MBS会话建立请求，F-UP22向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述。步骤S2104b中F-UP22还分配了一个向F-UP22的子用户面节点传输MBS业务数据的新的IP多播传输地址，该实施例中标识为IP5。并且，如果F-UP22不支持接收F-UP11通过多播方式发送的MBS业务数据，那么F-UP22会分配一个F-TEID来通过点对点的方式从F-UP11接收MBS业务数据。
需要说明的是，在本申请的一个实施例中，步骤S2204a和步骤S2204b中的用户面MBS会话建立请求包含的MBS IP Multicast Distribution中的多播传输地址为步骤S2202a中的多播传输地址IP2。
步骤S2204c，F-CP1向F-UP23发送用户面MBS会话建立请求，F-UP23向F-CP1反馈用户面MBS会话建立响应。同时，F-UP23还分配了一个向F-UP23的子用户面节点传输MBS业务数据的新的IP多播传输地址，该实施例中标识为IP6。该过程与前述实施例中步骤S1502的过程类似，不再赘述。
在本申请的一个实施例中，步骤S2204c中的用户面MBS会话建立请求包含的MBS IP Multicast Distribution中的多播传输地址为步骤S2202b中的多播传输地址IP3。其中，步骤S2204c中确定的新的多播传输地址是F-UP23分配给F-UP23的子用户面节点的(即图22中的S-UP31和S-UP32)IP6。并且，如果F-UP23不支持接收F-UP12通过多播方式发送的MBS业务数据，那么F-UP23会分配一个F-TEID来通过点对点的方式从F-UP12接收MBS业务数据。
步骤S2205a，若F-UP21与F-UP22支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP2对应的多播传输组中，以接收F-UP11发送的MBS业务数据。
步骤S2205b，若F-UP23支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP3对应的多播传输组中，以接收F-UP12发送的MBS业务数据。
步骤S2206a，若F-UP21和F-UP22中有不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的用户面节点，则F-CP1向F-UP11发送用户面MBS会话修改请求，F-UP11向F-CP1反馈用户面MBS会话修改响应。其中，该用户面MBS会话修改请求中包含有F-UP21和F-UP22中不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的用户面节点分配的F-TEID，以指示F-UP11增加使用点对点的方式向F-UP21和F-UP22中不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的用户面节点传送MBS业务数据。
需要说明的是：若F-CP1没有为F-UP11分配下级用户面节点，则F-CP1向F-UP11发送用户面MBS会话删除请求，F-UP11在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，并从F-UP11的父用户面节点分配的多播传输地址IP1指示的多播传输组中退出，并且F-UP11向F-CP1回复用户面MBS会话删除响应(此过程未在图中标识)。
步骤S2206b，若F-UP23不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则F-CP1向F-UP12发送用户面MBS会话修改请求，F-UP12向F-CP1反馈用户面MBS会话修改响应。其中，该用户面MBS会话修改请求中包含有F-UP23分配的F-TEID，以指示F-UP12通过点对点的方式向F-UP23传送MBS业务数据。
需要说明的是：若F-CP1没有为F-UP12分配下级用户面节点，则F-CP1向F-UP12发送用户面MBS会话删除请求，F-UP12在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，并从F-UP12的父用户面节点分配的多播传输地址IP1指示 的多播传输组中退出，并且F-UP12向F-CP1回复用户面MBS会话删除响应(此过程未在图中标识)。
步骤S2207，F-CP1根据F-CP1的子控制面节点的信息，向F-CP1的子控制面节点S-CP1发送MBS会话开始请求。
F-CP1发送给F-CP1的子控制面节点S-CP1的MBS会话开始请求中包含了如下参数：TMGI、MBS Session Duration、MBS QFIs、QoS Profile、MBS Time to Data Transfer、List of{F-UP ID，MBS传输信息}、MBS Service Area。其中，MBS传输信息即为MBS IP Multicast Distribution(IP Multicast Distribution address,C-TEID)。在该实施例中，List of{F-UP ID，MBS传输信息}中包含了F-UP21 ID及F-UP21 ID对应的MBS IP Multicast Distribution，以及F-UP22 ID及F-UP22 ID对应的MBS IP Multicast Distribution。F-UP21 ID对应的MBS IP Multicast Distribution是F-UP21所分配的，其中包含的IP多播传输地址即为步骤S2204a中由F-UP21分配的新的IP多播传输地址IP4；F-UP22 ID对应的MBS IP Multicast Distribution是F-UP22所分配的，其中包含的IP多播传输地址即为步骤S2204b中由F-UP22分配的新的IP多播传输地址IP5，且步骤S2204a中由F-UP21分配的新的IP多播传输地址IP4和步骤S2204b中由F-UP22分配的新的IP多播传输地址IP5不相同。
步骤S2208，S-CP1在接收到F-CP1发送的MBS会话开始请求之后，进行用户面MBS会话建立过程。具体地，S-CP1根据S-CP1的子控制面节点的信息从多个S-UP中为F-UP21选择一个或多个S-UP，以及为F-UP22选择若干个S-UP，该实施例中假定为F-UP21选取了S-UP11与S-UP12，为F-UP22没有选择子用户面节点。然后S-CP1分别向S-UP11与S-UP12发送用户面MBS会话建立请求，并接收S-UP11与S-UP12分别反馈的用户面MBS会话建立响应。同时如果S-UP11与S-UP12支持接收多播传输，则可以加入F-UP21在步骤S2204a中分配的新的IP多播传输地址IP4对应的多播传输组来接收F-UP21发送的MBS业务数据；如果S-UP11与S-UP12中的一些子用户面节点不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则S-UP11与S-UP12中不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据的用户面节点可以分配F-TEID来通过点对点的方式接收F-UP21发送的MBS业务数据，具体过程与步骤S1505a及步骤S1506类似，不再赘述。
步骤S2209，S-CP1向F-CP1发送MBS会话开始响应。若有S-UP不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则MBS会话开始响应中包含此S-UP分配的F-TEID，且对应于F-UP，从而形成一个List of{F-UP ID,List of F-TEIDsup,Multicast Enable}。在该实施例中，List of{F-UP ID,List of F-TEIDsup,Multicast Enable}包含了针对F-UP21的List of F-TEIDsup和Multicast Enable，以及针对F-UP22的List of F-TEIDsup和Multicast Enable。由于S-CP1没有为F-UP22选择子用户面节点，因此针对F-UP22的List of F-TEIDsup中不包含任何F-TEID，且针对F-UP22的Multicast Enable值为Disable。或者S-CP1向F-CP1发送的MBS会话开始响应中没有针对F-UP22的List of F-TEIDsup，且针对F-UP22的Multicast Enable值为Disable。当 然，S-CP1也可以通过MBS会话开始响应中返回Failure Code(比如Failed List{F-UP22})来指示未向F-UP22选择子用户面节点。
类似于步骤S1507，由于有些S-UP支持接收基于多播方式传输的数据，而另外一些S-UP不支持接收基于多播方式传输的数据，所以针对F-UP21的List F-TEIDsup只是对应于那些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP，其它说明参照步骤S1507的相关内容。
步骤S2210a，F-CP1根据S-CP1反馈的MBS会话开始响应中包含的List of{F-UP ID,List of F-TEIDsup,Multicast Enable}向F-UP21发送用户面MBS会话修改请求，F-UP21向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
需要说明的是：若F-CP1确定F-UP21没有被分配任何的下级用户面节点，则F-CP1向F-UP21发送用户面MBS会话删除请求，F-UP21在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，并从F-UP11分配的多播传输地址IP2指示的多播传输组中退出，并且F-UP21向F-CP1回复用户面MBS会话删除响应(此过程未在图中标识)。
步骤S2210b，F-CP1在收到F-CP1的所有子控制面节点回复的MBS会话开始响应之后，确定F-CP1的所有子控制面节点没有为F-UP22选择子用户面节点，则F-CP1向F-UP22发送用户面MBS会话删除请求，F-UP22在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，从F-UP11分配的多播传输地址IP2指示的多播传输组中删除，并且F-UP22向F-CP1回复用户面MBS会话删除响应。
步骤S2211，F-CP1根据F-CP1的子控制面节点的信息，向F-CP1的子控制面节点S-CP2发送MBS会话开始请求。
F-CP1发送给F-CP1的子控制面节点S-CP2的MBS会话开始请求中包含了如下参数：TMGI、MBS Session Duration、MBS QFIs、QoS Profile、MBS Time to Data Transfer、List of{F-UP ID，MBS传输信息}、MBS Service Area。其中，MBS传输信息即为MBS IP Multicast Distribution(IP Multicast Distribution address,C-TEID)。在该实施例中，List of{F-UP ID，MBS传输信息}中包含了F-UP23ID及F-UP23ID对应的MBS IP Multicast Distribution。F-UP23ID对应的MBS IP Multicast Distribution是F-UP23所分配的，其中包含的IP多播传输地址即为步骤S2204c中由F-UP23分配的新的IP多播传输地址IP6。
需要说明的是：步骤S2211与步骤S2207之间并没有先后关系，它们可以是F-CP1并行分别执行的步骤。
步骤S2212，S-CP2在接收到F-CP1发送的MBS会话开始请求之后，进行用户面MBS会话建立过程。具体地，S-CP2根据S-CP2的子控制面节点的信息从多个S-UP中为F-UP23选择一个或多个S-UP，该实施例中假定为F-UP23选取了S-UP31与S-UP32，即为F-UP23选取的子用户面节点与为F-UP21和F-UP22选择的子用户面节点不相同。然后S-CP2分别向为F-UP23选择的子用户面节点(即S-UP31与S-UP32)发送用户面MBS会话建立请求，并接收S-UP31与S-UP32分别反馈的用户面MBS会话建立响应。 同时，如果S-UP31与S-UP32支持接收多播传输，则可以加入步骤S2204c中由F-UP23分配的新的IP多播传输地址IP6对应的多播传输组来接收F-UP23发送的MBS业务数据；如果S-UP31与S-UP32中的一些子用户面节点不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则S-UP31与S-UP32中不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据的子用户面节点可以分配F-TEID来通过点对点的方式接收F-UP23发送的MBS业务数据，具体过程与步骤S1505a及步骤S1506类似，不再赘述。
步骤S2213，S-CP2向F-CP1发送MBS会话开始响应。若S-UP31与S-UP32中有S-UP不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则MBS会话开始响应中包含此S-UP分配的F-TEID，且对应于F-UP，从而形成一个List of{F-UP ID,List of F-TEIDsup,Multicast Enable}。在该实施例中，List of{F-UP ID,List of F-TEIDsup,Multicast Enable}包含了针对F-UP23的List of F-TEIDsup和Multicast Enable。
类似于步骤S1507，由于有些S-UP支持接收基于多播方式传输的数据，而另外一些S-UP不支持接收基于多播方式传输的数据，所以这个List F-TEIDsup只是对应于那些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP。因此，当一个F-UP的所有S-UP都支持接收基于多播方式传输的数据，则对应于这个F-UP的List of F-TEIDsup就没有了，其它说明参照步骤S1507的相关内容。
此外，当S-CP2决定不向其中某个/某些F-UP ID分配任何的子用户面节点时，则可以将这个/这些F-UP ID对应的Multicast Enable设置为Disable。当然，也可以在MBS会话开始响应中采用Failed List{F-UP}来指示没有被分配子用户面节点的F-UP。
步骤S2214，F-CP1根据S-CP2反馈的MBS会话开始响应中包含的List of{F-UP ID,List of F-TEIDsup,Multicast Enable}向F-UP23发送用户面MBS会话修改请求，F-UP23向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
需要说明的是：若F-CP1确定F-UP23没有被分配任何的下级用户面节点，则F-CP1向F-UP23发送用户面MBS会话删除请求，F-UP23在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，并从F-UP12分配的多播传输地址IP3指示的多播传输组中退出，并且F-UP23向F-CP1回复用户面MBS会话删除响应(此过程未在图中标识)。
步骤S2215，当F-CP1接收到所有S-CP反馈的MBS会话开始响应之后，F-CP1根据所有S-CP反馈的MBS会话开始响应向F-CP1的父控制面节点发送MBS会话开始响应。
类似于步骤S1609，F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有UP ID(该UP ID是与F-CP1的父控制面节点同级的用户面节点的标识)，并且可能还包含有List of F-TEIDfup和Multicast Enable。
通过步骤S2201至步骤S2215可知，在本申请的实施例中，F-CP1有两个子控制面 节点S-CP1和S-CP2，F-CP1为F-UP11选择了下一级用户面节点F-UP21和F-UP22，F-CP1为F-UP12选择了下一级用户面节点F-UP23，同时S-CP1为F-UP21选择了子用户面节点S-UP11和S-UP12，S-CP2为F-UP23选择了子用户面节点S-UP31和S-UP32。同时，由于S-CP1没有为F-UP22选择子用户面节点，因此需要将F-UP22从用户面MBS传输树中删除。
需要说明的是：在用户面MBS会话建立过程中，可能存在着一个用户面节点同时被两个控制面节点发送用户面MBS会话建立请求消息，或已经被一个控制面节点选择后、又接收到另一个控制面节点发送的用户面MBS会话建立请求消息。如果一个用户面节点同时收到两个控制面节点(当然也可以是更多个，此处以两个为例进行说明)发送的用户面MBS会话建立请求消息，那么该用户面节点可以在用户面MBS会话建立响应消息中，正常响应其中一个控制面节点发送的用户面MBS会话建立请求，并且在另一个用户面MBS会话建立响应消息中，拒绝(Reject)另外一个控制面节点，以指示此用户面节点已经被选择。如果一个用户面节点通过一个控制面节点已经有了父用户面节点后，又收到另外一个控制面节点发送的用户面MBS会话建立请求消息时，则在另一个用户面MBS会话建立响应消息中Reject该另外一个控制面节点，以指示此用户面节点已经被选择。
当这种MBS会话传输树建立完成之后，可以执行如下步骤：
步骤S2216a，F-UP11接收到F-UP11的父用户面节点发送的下行MBS业务数据。然后通过步骤S2217a将接收到的该下行MBS业务数据传输给F-UP21。F-UP21通过步骤S2218a将接收到的该下行MBS业务数据传输给S-UP11和S-UP12。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
步骤S2216b，F-UP12接收到F-UP12的父用户面节点发送的下行MBS业务数据。然后通过步骤S2217c将接收到的该下行MBS业务数据传输给F-UP23，F-UP23通过步骤S2218c将接收到的该下行MBS业务数据传输给S-UP31和S-UP32。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
此外，在标准TS23.501的5.3.4.2.2章节定义了非漫游情形下的一个或多个I-SMF与一个或多个I-UPF(Intermediate-UPF，中间用户面功能实体)参与到一个PDU会话的架构。对于一个非漫游的PDU会话，只有一个SMF。若有多个SMF，则控制PSA的SMF为了保持与规范的一致性，仍然称之为SMF，其它的SMF称为I-SMF。其中，被SMF控制的UPF的命名不变，仍然称之为UPF，而被I-SMF控制的UPF称为I-UPF。
在该情形下，本申请的实施例提出了可以由I-SMF及I-UPF参与到MBS会话中，具体建立用户面MBS传输树的过程可以参照图23所示，包括如下步骤：
步骤S2301，F-CP1接收到F-CP1的父控制面节点发送的MBS会话开始请求。具体 过程与前述步骤S1501类似，不再赘述。其中，该MBS会话开始请求中的MBS IP Multicast Distribution包含的IP多播传输地址记为IP1。
F-CP1在接收到F-CP1的父控制面节点发送的MBS会话开始请求之后，可以根据F-CP1的子控制面节点的信息确定从多个F-UPF中选取一个或多个F-UPF作为与F-CP1同级的用户面节点，该实施例中假定选取了两个用户面节点，记为F-UP11和F-UP12。然后分别执行步骤S2302a和步骤S2302b。
步骤S2302a，F-CP1向F-UP11发送用户面MBS会话建立请求，F-UP11向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S2302a中F-UP11分配的IP多播传输地址记为IP2。
步骤S2302b，F-CP1向F-UP12发送用户面MBS会话建立请求，F-UP12向F-CP1反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述，其中步骤S2302b中F-UP12分配的IP多播传输地址记为IP3。
步骤S2303，若F-UP11与F-UP12支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP1对应的多播传输组中，以接收F-UP11与F-UP12的父用户面节点发送的MBS业务数据。
之后，F-CP1根据F-CP1的子控制面节点(通常是NR基站)的服务区域信息确定F-CP1管理的UPF与F-CP1的子控制面节点管理的UPF不能直接建立传输通路，则F-CP1选择一个I-SMF，其中选择出的I-SMF能够与F-CP1和F-CP1的子控制面节点进行通信。该实施例中，假设选择了一个I-SMF，之后执行步骤S2304。
步骤S2304，F-CP1向I-SMF发送MBS会话开始请求(即Nscp_MBSSessionStart Request)。
F-CP1发送给I-SMF的MBS会话开始请求中包含了如下参数：TMGI、MBS Session Duration、List of S-CP、MBS QFIs、QoS Profile、MBS Time to Data Transfer、List of{F-UP ID,MBS传输信息}、MBS Service Area。F-CP1之所以在发送给I-SMF的MBS会话开始请求中包含有F-CP1提供的子控制面节点信息List of S-CP，主要是因为I-SMF是被F-CP1动态选择后加入到MBS业务管理的，I-SMF没有任何MBS UE Context(对于MBS多播业务而言)或用户面节点的信息。在该实施例中，List of{F-UP ID,MBS Transport Information}只包含了F-UP11的ID及F-UP11 ID对应的MBS IP Multicast Distribution。F-UP11 ID对应的MBS IP Multicast Distribution是F-UP11所分配的，其中包含了步骤S2302a中F-UP11分配的新的IP多播传输地址IP2和C-TEID。
I-SMF在接收到MBS会话开始请求之后，基于接收到的MBS会话开始请求，根据查询或网络匹配的F-CP1的服务区域及F-CP1提供的List of S-CP的服务区域，确定并选择I-UPF11、I-UPF12、I-UPF21、I-UPF22。然后执行步骤S2305a和步骤S2305b。
步骤S2305a，I-SMF分别向I-UPF11和I-UPF12发送用户面MBS会话建立请求，I-UPF11和I-UPF12分别向I-SMF反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述。其中，步骤S2305a中I-UPF11和I-UPF12分别分配了新的IP多播传输地址，该实施例中分别记为IP4和IP5，I-UPF11分配的新的 IP多播传输地址IP4是用于向I-UPF11的子用户面节点(即图23中的S-UP11)传输MBS业务数据的；I-UPF12分配的新的IP多播传输地址IP5是用于向I-UPF12的子用户面节点(即图23中的S-UP12)传输MBS业务数据的。并且，如果I-UPF11不支持接收F-UP11通过多播方式发送的MBS业务数据，那么I-UPF11会分配一个F-TEID来通过点对点的方式从F-UP11接收MBS业务数据；类似地，如果I-UPF12不支持接收F-UP11通过多播方式发送的MBS业务数据，那么I-UPF12会分配一个F-TEID来通过点对点的方式从F-UP11接收MBS业务数据。
步骤S2305b，I-SMF分别向I-UPF21和I-UPF22发送用户面MBS会话建立请求，I-UPF21和I-UPF22分别向I-SMF反馈用户面MBS会话建立响应。该过程与前述实施例中步骤S1502的过程类似，不再赘述。其中，步骤S2305a中I-UPF21和I-UPF22分别分配了新的IP多播传输地址，该实施例中分别记为IP6和IP7，I-UPF21分配的新的IP多播传输地址IP6是用于向I-UPF21的子用户面节点(即图23中的S-UP21)传输MBS业务数据的；I-UPF22分配的新的IP多播传输地址IP7是用于向I-UPF22的子用户面节点(即图23中的S-UP22)传输MBS业务数据的。并且，如果I-UPF21不支持接收F-UP11通过多播方式发送的MBS业务数据，那么I-UPF21会分配一个F-TEID来通过点对点的方式从F-UP11接收MBS业务数据；类似地，如果I-UPF22不支持接收F-UP11通过多播方式发送的MBS业务数据，那么I-UPF22会分配一个F-TEID来通过点对点的方式从F-UP11接收MBS业务数据。
需要说明的是，在本申请的一个实施例中，步骤S2305a和步骤S2305b中的用户面MBS会话建立请求包含的MBS IP Multicast Distribution中的IP多播传输地址为步骤S2302a中F-UP11分配的IP多播传输地址IP2。且图23中由于版面原因，将I-UPF11和I-UPF12画在了一起，将I-UPF21和I-UPF22画在了一起，并将S-UP11和S-UP12画在了一起，将S-UP21和S-UP22画在了一起。
步骤S2306a，若I-UPF11和I-UPF12支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP2对应的多播传输组中，以接收F-UP11发送的MBS业务数据。
步骤S2306b，若I-UPF21和I-UPF22支持接收基于多播方式传输的数据，则申请加入IP多播传输地址IP2对应的多播传输组中，以接收F-UP11发送的MBS业务数据。
步骤S2307，I-SMF向F-CP1提供的子控制面节点S-CP1发送MBS会话开始请求。
I-SMF发送给S-CP1的MBS会话开始请求中包含了如下参数：TMGI、MBS QFIs、QoS Profile、List of{I-UPF ID,MBS传输信息}、MBS Service Area。在该实施例中，List of{I-UPF ID,MBS传输信息}中包含了I-UPF11、I-UPF12、I-UPF21、I-UPF22分别对应的ID，以及I-UPF11、I-UPF12、I-UPF21、I-UPF22分别对应的MBS传输信息。I-UPF11对应的MBS传输信息中包含的IP多播传输地址即为IP4、I-UPF12对应的MBS传输信息中包含的IP多播传输地址即为IP5、I-UPF21对应的MBS传输信息中包含的IP多播传输地址即为IP6、I-UPF22对应的MBS传输信息中包含的IP多播传输地址即为IP7，且IP4、IP5、IP6和IP7不相同。
步骤S2308，S-CP1在接收到I-SMF发送的MBS会话开始请求之后，进行用户面 MBS会话建立过程。具体地，S-CP1从多个S-UP中为I-UPF11选择一个或多个S-UP、为I-UPF12选择一个或多个S-UP、为I-UPF21选择一个或多个S-UP，以及为I-UPF22选择一个或多个S-UP，该实施例中假定S-CP1为I-UPF11选择了S-UP11、为I-UPF12选择了S-UP12、为I-UPF21选择了S-UP21、为I-UPF22选择了S-UP22。然后S-CP1分别向S-UP11、S-UP12、S-UP21和S-UP22发送用户面MBS会话建立请求，并接收S-UP11、S-UP12、S-UP21和S-UP22分别反馈的用户面MBS会话建立响应。同时，如果S-UP11支持接收多播传输，则可以加入I-UPF11分配的IP多播传输地址IP4对应的多播传输组来接收I-UPF11发送的MBS业务数据；如果S-UP12支持接收多播传输，则可以加入I-UPF12分配的IP多播传输地址IP5对应的多播传输组来接收I-UPF12发送的MBS业务数据；如果S-UP21支持接收多播传输，则可以加入I-UPF21分配的IP多播传输地址IP6对应的多播传输组来接收I-UPF21发送的MBS业务数据；如果S-UP22支持接收多播传输，则可以加入I-UPF22分配的IP多播传输地址IP7对应的多播传输组来接收I-UPF22发送的MBS业务数据，具体过程与步骤S1505a及步骤S1506类似，不再赘述。
步骤S2309，S-CP1向I-SMF发送MBS会话开始响应。若S-UP11、S-UP12、S-UP21和S-UP22中有S-UP不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则S-CP1向I-SMF发送的MBS会话开始响应中包含此S-UP分配的F-TEID，且对应于相应的I-UPF，从而形成一个List of{I-UPF ID,List of F-TEIDsup,Multicast Enable}。在该实施例中，List of{I-UPF ID,List of F-TEIDsup,Multicast Enable}包含了分别针对I-UPF11、I-UPF12、I-UPF21、I-UPF22的List of F-TEIDsup和Multicast Enable。
类似于步骤S1507，由于有些S-UP支持接收基于多播方式传输的数据，而另外一些S-UP不支持接收基于多播方式传输的数据，所以这个List F-TEIDsup只是对应于那些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP，其它说明参照步骤S1507的相关内容。
此外，当S-CP1决定不向其中某个/某些I-UPF ID分配任何的子用户面节点时，则可以将这个/这些I-UPF ID对应的Multicast Enable设置为Disable。当然，也可以在MBS会话开始响应中采用Failed List{I-UPF}来指示没有被分配子用户面节点的I-UPF。
步骤S2310a，I-SMF根据S-CP1反馈的MBS会话开始响应中包含的List of{I-UPF ID,List of F-TEIDsup,Multicast Enable}分别向I-UPF11/12发送用户面MBS会话修改请求，I-UPF11/12向I-SMF反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
需要说明的是：若I-SMF确定I-UPF11或I-UPF12没有被分配任何的子用户面节点，则I-SMF向I-UPF11或I-UPF12发送用户面MBS会话删除请求，I-UPF11或I-UPF12在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，从F-UP11分配的多播传输地址IP2指示的多播传输组中退出，并且I-UPF11或I-UPF12向I-SMF回复用户面MBS会话删除响应(此过程未在图中标识)。
步骤S2310b，I-SMF根据S-CP1反馈的MBS会话开始响应中包含的List of{I-UPF ID, List of F-TEIDsup,Multicast Enable}分别向I-UPF21/22发送用户面MBS会话修改请求，I-UPF21/22向I-SMF反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
需要说明的是：若I-SMF确定I-UPF21或I-UPF22没有被分配任何的子用户面节点，则I-SMF向I-UPF21或I-UPF22发送用户面MBS会话删除请求，I-UPF21或I-UPF22在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，从F-UP11分配的多播传输地址IP2指示的多播传输组中退出，并且I-UPF21/22向I-SMF回复用户面MBS会话删除响应(此过程未在图中标识)。
步骤S2311，I-SMF向F-CP1发送MBS会话开始响应。若I-UPF11、I-UPF12、I-UPF21、I-UPF22中有I-UPF不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则I-SMF向F-CP1发送的MBS会话开始响应中包含此I-UPF分配的F-TEID，且对应于F-UP11，从而形成一个List of{F-UP ID,List of F-TEIDiupf,Multicast Enable}。在该实施例中，List of{F-UP ID,List of F-TEIDiupf,Multicast Enable}包含了针对F-UP11的List of F-TEIDiufp和Multicast Enable。
类似于步骤S1507，由于有些I-UPF支持接收基于多播方式传输的数据，而另外一些I-UPF不支持接收基于多播方式传输的数据，所以这个List F-TEIDiupf只是对应于那些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的I-UPF，其它说明参照步骤S1507的相关内容。
步骤S2312，若I-UPF11、I-UPF12、I-UPF21、I-UPF22中有不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的I-UPF，则F-CP1向F-UP11发送用户面MBS会话修改请求，F-UP11向F-CP1反馈用户面MBS会话修改响应。其中，F-CP1向F-UP11发送的用户面MBS会话修改请求中包含有I-UPF11、I-UPF12、I-UPF21、I-UPF22中不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的I-UPF的F-TEID，以指示F-UP11增加使用点对点的方式向I-UPF11、I-UPF12、I-UPF21、I-UPF22中不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的I-UPF传送MBS业务数据。
需要说明的是：若F-CP1确定F-UP11没有被分配任何的下级用户面节点，则F-CP1向F-UP11发送用户面MBS会话删除请求，F-UP11在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，并从F-UP11的父用户面节点分配的多播传输地址IP1指示的多播传输组中退出，并且F-UP11向F-CP1回复用户面MBS会话删除响应(此过程未在图中标识)。
步骤S2313，F-CP1根据F-CP1的子控制面节点的信息，向F-CP1的子控制面节点S-CP2发送MBS会话开始请求。
F-CP1发送给F-CP1的子控制面节点S-CP2的MBS会话开始请求中包含了如下参数：TMGI、MBS Session Duration、MBS QFIs、QoS Profile、MBS Time to Data Transfer、List of{F-UP ID，MBS传输信息}、MBS Service Area。其中，MBS传输信息即为MBS IP Multicast Distribution(IP Multicast Distribution address,C-TEID)。在该实施例中，List  of{F-UP ID，MBS传输信息}中包含了F-UP12 ID及F-UP12 ID对应的MBS IP Multicast Distribution。F-UP12 ID对应的MBS IP Multicast Distribution是F-UP12所分配的，其中包含的IP多播传输地址即为步骤S2302b中由F-UP12分配的新的IP多播传输地址IP3。
需要说明的是：步骤S2313与步骤S2304之间并没有先后关系，它们可以是F-CP1并行分别执行的步骤。
步骤S2314，S-CP2在接收到F-CP1发送的MBS会话开始请求之后，进行用户面MBS会话建立过程。具体地，S-CP2根据S-CP2的子控制面节点的信息从多个S-UP中为F-UP12选择一个或多个S-UP，该实施例中假定为F-UP12选取了S-UP31与S-UP32。然后S-CP2分别向S-UP31与S-UP32发送用户面MBS会话建立请求，并接收S-UP31与S-UP32分别反馈的用户面MBS会话建立响应，同时如果S-UP31与S-UP32支持接收多播传输，则可以加入步骤S2302b中由F-UP12分配的新的IP多播传输地址IP3对应的多播传输组来接收F-UP12发送的MBS业务数据；如果S-UP31与S-UP32中的一些子用户面节点不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则S-UP31与S-UP32中不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据的子用户面节点可以分配F-TEID来通过点对点的方式接收F-UP12发送的MBS业务数据，具体过程与步骤S1505a及步骤S1506类似，不再赘述。
步骤S2315，S-CP2向F-CP1发送MBS会话开始响应。若S-UP31与S-UP32中有S-UP不支持接收基于多播方式传输的数据、但支持使用点对点方式接收MBS业务数据，则S-CP2向F-CP1发送的MBS会话开始响应中包含此S-UP分配的F-TEID，且对应于F-UP，从而形成一个List of{F-UP ID,List of F-TEIDsup,Multicast Enable}。在该实施例中，List of{F-UP ID,List of F-TEIDsup,Multicast Enable}包含了针对F-UP12的List of F-TEIDsup和Multicast Enable。
类似于步骤S1507，由于有些S-UP支持接收基于多播方式传输的数据，而另外一些S-UP不支持接收基于多播方式传输的数据，所以这个List F-TEIDsup只是对应于那些不支持接收多播传输、但支持使用点对点方式接收MBS业务数据的S-UP，其它说明参照步骤S1507的相关内容。
步骤S2316，F-CP1根据S-CP2反馈的MBS会话开始响应中包含的List of{F-UP ID,List of F-TEIDsup,Multicast Enable}向F-UP12发送用户面MBS会话修改请求，F-UP12向F-CP1反馈用户面MBS会话修改响应。该步骤的具体说明与前述步骤S1508类似，不再赘述。
需要说明的是：若F-CP1确定F-UP12没有被分配任何的下级用户面节点，则F-CP1向F-UP12发送用户面MBS会话删除请求，F-UP12在接收到该用户面MBS会话删除请求之后，发出IGMP Leave数据包，并从F-UP12的父用户面节点分配的多播传输地址IP1指示的多播传输组中退出，并且F-UP12向F-CP1回复用户面MBS会话删除响应(此过程未在图中标识)。
步骤S2317，当F-CP1接收到F-CP1的所有子控制面节点反馈的MBS会话开始响 应之后，F-CP1根据F-CP1的所有子控制面节点反馈的MBS会话开始响应向F-CP1的父控制面节点发送MBS会话开始响应。
类似于步骤S1609，F-CP1向F-CP1的父控制面节点回复的MBS会话开始响应中包含有UP ID(该UP ID是与F-CP1的父控制面节点同级的用户面节点的标识)，并且可能还包含有List of F-TEIDfup和Multicast Enable。
通过步骤S2301至步骤S2315可知，在本申请的实施例中，F-CP1有两个子控制面节点S-CP1和S-CP2，F-CP1选择了I-SMF，I-SMF选择了I-UPF11、I-UPF12、I-UPF21、I-UPF22。同时S-CP1为I-UPF11选择了S-UP11、为I-UPF12选择了S-UP12、为I-UPF21选择了S-UP21、为I-UPF22选择了S-UP22，S-CP2为F-UP12选择了S-UP31和S-UP32。
需要说明的是：在用户面MBS会话建立过程中，可能存在着一个中间用户面节点同时接收到两个用户面MBS会话建立请求的情况(当然也可以是更多个，此处以两个为例进行说明)，比如同一个I-SMF发送了两个用户面MBS会话建立请求(对应于不同的控制面节点选择同一个I-SMF的情况)，或者两个不同的I-SMF分别发送了一个用户面MBS会话建立请求(对应于不同的控制面节点选择不同的I-SMF的情况)，在这种情况下，中间用户面节点可以正常响应其中一个用户面MBS会话建立请求，而在针对另一个用户面MBS会话建立请求的响应消息中拒绝(Reject)另外一个控制面节点，以指示此用户面节点已经被选择。
如果一个中间用户面节点通过一个用户面MBS会话建立请求已经有了父用户面节点后，又收到另外一个用户面MBS会话建立请求时，则在针对该另一个用户面MBS会话建立请求的响应消息中Reject另外一个控制面节点，以指示此用户面节点已经被选择。
当这种MBS会话传输树建立完成之后，可以执行如下步骤：
步骤S2318a，F-UP11接收到F-UP11的父用户面节点发送的下行MBS业务数据。然后通过步骤S2319a将接收到的该下行MBS业务数据传输给I-UPF11和I-UPF12，并通过步骤S2319b接收到的该下行MBS业务数据传输给I-UPF21和I-UPF22。然后在步骤S2320a中，I-UPF11将下行MBS业务数据传输给S-UP11、I-UPF12将下行MBS业务数据传输给S-UP12。在步骤S2320b中，I-UPF21将下行MBS业务数据传输给S-UP21、I-UPF22将下行MBS业务数据传输给S-UP22。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
步骤S2318b，F-UP12接收到F-UP12的父用户面节点发送的下行MBS业务数据。然后通过步骤S2319c将接收到的该下行MBS业务数据传输给S-UP31和S-UP32。其中，各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来传送MBS业务数据，同时各个用户面节点以前面步骤所确定的多播传输方式或点对点传输方式来接收MBS业务数据。
在本申请上述实施例的技术方案中，用F-CP表示父控制面节点，F-UP表示父用户面节点，S-CP表示子控制面节点，S-UP表示子用户面节点。在图10所示的系统架 构中，可以用F-CP代替SMF、用F-UP代替UPF，在这种情况下，S-CP与S-UP联合起来代替接入网节点。
在图11所示的系统架构中，可以用F-CP代替MBSF、用F-UP代替MBSU时，在这种情况下，可以用S-CP代替MB-SMF、用S-UP代替MB-UPF。或者可以用F-CP代替MB-SMF、用F-UP代替MB-UPF，在这种情况下，S-CP与S-UP联合起来代替NG-RAN。
需要说明的是：图10和图11示出了两个5G MBS的基本架构图，在该基本架构图中可以进行增强处理，比如对于图10所示的架构，可以出现多个UPF、多个SMF；对于图11所示的架构，MB-SMF与MB-UPF也可分别出现多个。当出现额外的UPF或MB-UPF时，可以采用图21或图22所示的技术方案来建立用户面MBS会话树；当出现额外的MB-SMF或SMF时(此时，出现额外的UPF)，可以采用图23所示的技术方案来建立用户面MBS会话树。
本申请上述实施例的技术方案实现了用户面MBS会话建立过程，可以防止出现用户面MBS会话的传输环，并避免用户面MBS会话传输树中出现断枝的问题。同时可以解决用户面MBS会话建立过程中控制面与用户面分离时，同一个父控制面同时提供多个父用户面节点的问题。此外可以实现同一个控制面节点通过管理不同的用户面节点来形成父与子的传输，优化了用户面传输资源，并且可以在用户面MBS会话建立过程中父用户面节点与基站之间无法建立直接连接的用户面传输时，发现并插入I-SMF及I-UPF，以完成用户面传输树的建立，有效实现了用户面传输资源的优化。
以下介绍本申请的装置实施例，可以用于执行本申请上述实施例中的多播广播业务的通信方法。对于本申请装置实施例中未披露的细节，请参照本申请上述的多播广播业务的通信方法的实施例。
图24示出了根据本申请的一个实施例的多播广播业务的通信装置的框图，该多播广播业务的通信装置可以设置在I-SMF内。
参照图24所示，根据本申请的一个实施例的多播广播业务的通信装置2400，包括：第一接收单元2402、选择单元2404、第一交互单元2406和第二交互单元2408。
其中，第一接收单元2402，配置为接收MBS会话传输树中的第i级控制面节点发送的第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级控制面节点对应的第i级用户面节点的标识信息、所述第i级用户面节点所分配的第一MBS IP多播传输地址与用于通过多播方式传输MBS业务数据的第一C-TEID，i＝1,…,N，N为正整数；选择单元2404，配置为根据所述第i级控制面节点的信息及所述第i级控制面节点提供的子控制面节点的信息选择中间用户面节点，所述中间用户面节点能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接；第一交互单元2406配置为向所述中间用户面节点发送第一用户面MBS会话建立请求，并接收所述中间用户面节点反馈的第一用户面MBS会话建立响应，所述第一用户面MBS会话建立请求中包含有所述第一MBS IP多播传输地址和第一C-TEID，所述第一MBS IP多播传输地址用于使所述中间用户面节点加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节 点通过多播方式发送的MBS业务数据；第二交互单元2408配置为向所述第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求，以指示所述第i级控制面节点提供的子控制面节点为所述中间用户面节点分配子用户面节点，所述第二MBS会话开始请求中包含有所述中间用户面节点的标识信息，以及所述中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，所述第二MBS IP多播传输地址用于使所述子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式发送的MBS业务数据。
在本申请的一些实施例中，基于前述方案，所述第一用户面MBS会话建立请求中包含有用于指示所述中间用户面节点分配新的MBS IP多播分发信息的指示信息；所述第一用户面MBS会话建立响应中包含有所述中间用户面节点分配的所述第二MBS IP多播传输地址和第二C-TEID。
在本申请的一些实施例中，基于前述方案，若所述中间用户面节点不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点的MBS业务数据，则所述第一用户面MBS会话建立请求中包含有请求为所述中间用户面节点分配F-TEID(Fully qualified Tunnel Endpoint Identifier，全量隧道端点标识)的指示信息，所述第一用户面MBS会话建立响应中包含有所述中间用户面节点分配的F-TEID，所述F-TEID用于使所述中间用户面节点通过点对点的方式接收所述第i级用户面节点发送的MBS业务数据；或者
所述第一用户面MBS会话建立响应中指示所述中间用户面节点不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点的MBS业务数据，并包含有所述中间用户面节点分配的F-TEID。
在本申请的一些实施例中，基于前述方案，第二交互单元2408还配置为：在向所述第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求之后，接收所述子控制面节点针对所述第二MBS会话开始请求反馈的第二MBS会话开始响应，所述第二MBS会话开始响应中包含有第一指示信息；
其中，所述第一指示信息中包含有所述中间用户面节点的标识信息、第一F-TEID列表信息和用于表示启动多播方式传输的第一字段信息，所述第一字段信息表示所述子控制面节点为所述中间用户面节点分配的子用户面节点中存在支持通过多播方式接收所述中间用户面节点发送的MBS业务数据的子用户面节点，所述第一F-TEID列表信息包含有不支持通过多播方式、但支持通过点对点方式接收所述中间用户面节点发送的MBS业务数据的子用户面节点的F-TEID；或者
所述第一指示信息包含有所述中间用户面节点的标识信息、且不包含所述第一F-TEID列表信息和所述第一字段信息，则所述第一指示信息用于指示所述子控制面节点为所述中间用户面节点分配的子用户面节点均支持通过多播方式接收所述中间用户面节点发送的MBS业务数据；或者
所述第一指示信息包含有所述中间用户面节点的标识信息、所述第一F-TEID列表信息，且不包含所述第一字段信息，则所述第一指示信息用于指示所述子控制面节点 为所述中间用户面节点分配的子用户面节点均不支持通过多播方式、但支持通过点对点方式接收所述中间用户面节点发送的MBS业务数据；或者
所述第一指示信息包含有所述中间用户面节点的标识信息和停用多播传输的字段信息、且不包含所述第一F-TEID列表信息，则所述第一指示信息用于指示所述子控制面节点没有为所述中间用户面节点分配子用户面节点。
在本申请的一些实施例中，基于前述方案，若选择了至少两个中间用户面节点，则所述第二MBS会话开始响应中包含有第一指示信息列表，所述第一指示信息列表中包含有所有中间用户面节点分别对应的所述第一指示信息。
在本申请的一些实施例中，基于前述方案，所述第二MBS会话开始响应中还包含有失败的标识信息列表，所述失败的标识信息列表用于指示未被分配子用户面节点的目标中间用户面节点。
在本申请的一些实施例中，基于前述方案，第一交互单元2406还配置为：若根据所述第二MBS会话开始响应确定存在未被分配子用户面节点的目标中间用户面节点，则向所述目标中间用户面节点发送用户面MBS会话删除请求。
在本申请的一些实施例中，基于前述方案，第一交互单元2406还配置为：接收所述目标中间用户面节点反馈的用户面MBS会话删除响应，所述用户面MBS会话删除响应是所述目标中间用户面节点在接收到所述用户面MBS会话删除请求之后发送的，其中，若所述目标中间用户面节点已加入所述第一MBS IP多播传输地址对应的多播传输组中，则在接收到所述用户面MBS会话删除请求之后退出所述第一MBS IP多播传输地址对应的多播传输组。
在本申请的一些实施例中，基于前述方案，若所述第i级控制面节点提供了至少两个子控制面节点，则第一交互单元2406配置为：在接收到所述第i级控制面节点提供的所有子控制面节点分别反馈的第二MBS会话开始响应之后，确定是否存在未被分配子用户面节点的目标中间用户面节点。
在本申请的一些实施例中，基于前述方案，第一交互单元2406还配置为：在接收所述子控制面节点针对所述第二MBS会话开始请求反馈的第二MBS会话开始响应之后，若所述第一指示信息中包含有所述第一F-TEID列表信息，则根据所述第一指示信息中包含的中间用户面节点的标识信息向所述中间用户面节点发送用户面MBS会话修改请求，以指示所述中间用户面节点通过点对点的方式向所述第一F-TEID列表信息所包含的各个F-TEID对应的子用户面节点分别传送MBS业务数据；
其中，若所述第一指示信息中还包含有所述第一字段信息，则所述用户面MBS会话修改请求还用于指示所述中间用户面节点同时使用多播传输方式向所述中间用户面节点的子用户面节点发送MBS业务数据；
若所述第一指示信息中不包含所述第一字段信息，则所述用户面MBS会话修改请求还用于指示所述中间用户面节点不需要使用多播传输方式向所述中间用户面节点的子用户面节点发送MBS业务数据。
在本申请的一些实施例中，基于前述方案，第一交互单元2406还配置为：若选择 了至少两个中间用户面节点，则根据所述第二MBS会话开始响应中包含的每个中间用户面节点对应的第一指示信息，向需要发送所述用户面MBS会话修改请求的中间用户面节点发送所述用户面MBS会话修改请求。
在本申请的一些实施例中，基于前述方案，第二交互单元2408还配置为：在接收所述子控制面节点针对所述第二MBS会话开始请求反馈的第二MBS会话开始响应之后，根据所述子控制面节点反馈的第二MBS会话开始响应，向所述第i级控制面节点反馈针对所述第一MBS会话开始请求的第一MBS会话开始响应。
在本申请的一些实施例中，基于前述方案，第二交互单元2408配置为：若所述第i级控制面节点提供了至少两个子控制面节点，则在接收到所述第i级控制面节点提供的所有子控制面节点分别反馈的第二MBS会话开始响应之后，再向所述第i级控制面节点反馈所述第一MBS会话开始响应。
在本申请的一些实施例中，基于前述方案，所述第一MBS会话开始响应中包含有第二指示信息；
其中，所述第二指示信息中包含有所述第i级用户面节点的标识信息、第二F-TEID列表信息和用于表示启动多播方式传输的第二字段信息，所述第二字段信息表示存在支持通过多播方式接收所述第i级用户面节点发送的MBS业务数据的中间用户面节点，所述第二F-TEID列表信息包含有不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点发送的MBS业务数据的中间用户面节点的F-TEID；或者
所述第二指示信息包含有所述第i级用户面节点的标识信息、且不包含所述第二F-TEID列表信息和所述第二字段信息，则所述第二指示信息用于指示所述中间用户面节点均支持通过多播方式接收所述第i级用户面节点发送的MBS业务数据；或者
所述第二指示信息包含有所述第i级用户面节点的标识信息、所述第二F-TEID列表信息，且不包含所述第二字段信息，则所述第二指示信息用于指示所述中间用户面节点均不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点发送的MBS业务数据。
在本申请的一些实施例中，基于前述方案，若所述第i级控制面节点选择了至少两个第i级用户面节点，则所述第一MBS会话开始响应中包含有第二指示信息列表，所述第二指示信息列表中包含有所有第i级用户面节点分别对应的所述第二指示信息。
在本申请的一些实施例中，基于前述方案，若所述第i级控制面节点选择了至少两个第i级用户面节点，则所述第一MBS会话开始请求中包含有每个第i级用户面节点各自的标识信息、及每个第i级用户面节点分配的第一MBS IP多播传输地址和第一C-TEID；其中，不同的第i级用户面节点分配的第一MBS IP多播传输地址不相同。
图25示出了根据本申请的一个实施例的多播广播业务的通信装置的框图，该多播广播业务的通信装置可以设置在第i级控制面节点内。
参照图25所示，根据本申请的一个实施例的多播广播业务的通信装置2500，包括：第三交互单元2502和第四交互单元2504。
其中，第三交互单元2502配置为向第i级控制面节点选择的第i级用户面节点发 送第二用户面MBS会话建立请求，并接收所述第i级用户面节点反馈的第二用户面MBS会话建立响应，所述第i级控制面节点是MBS会话传输树中除最后一级控制面节点之外的任一级控制面节点，i＝1,…,N，N为正整数；第四交互单元2504配置为选择中间会话管理功能实体I-SMF，向所述I-SMF发送第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级用户面节点的标识信息、所述第i级用户面节点分配的第一MBS IP多播传输地址和第一C-TEID；其中，所述第一MBS会话开始请求用于指示所述I-SMF选择能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接的中间用户面节点，且与所述中间用户面节点建立用户面MBS会话，以使所述中间用户面节点加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据，并用于指示所述I-SMF向所述子控制面节点发送第二MBS会话开始请求，所述第二MBS会话开始请求用于指示所述子控制面节点为所述中间用户面节点分配子用户面节点，并使所述子用户面节点接收所述中间用户面节点发送的MBS业务数据。
在本申请的一些实施例中，基于前述方案，第四交互单元2504还配置为：在向所述I-SMF发送第一MBS会话开始请求之后，接收所述I-SMF针对所述第一MBS会话开始请求反馈的第一MBS会话开始响应；根据所述第一MBS会话开始响应中包含的内容，确定是否向所述第i级用户面节点发送用户面MBS会话修改请求。
在本申请的一些实施例中，基于前述方案，第四交互单元2504配置为：若根据所述第i级控制面节点提供的子控制面节点的信息，确定所述第i级控制面节点管理的用户面功能实体不能直接与所述子控制面节点管理的用户面功能实体建立传输通路，则选择能够与所述第i级控制面节点及与所述子控制面节点进行通信的SMF作为所述I-SMF。
图26示出了根据本申请的一个实施例的多播广播业务的通信装置的框图，该多播广播业务的通信装置可以设置在中间用户面节点内。
参照图26所示，根据本申请的一个实施例的多播广播业务的通信装置2600，包括：第二接收单元2602、发送单元2604和处理单元2606。
其中，第二接收单元2602配置为接收I-SMF发送的第一用户面MBS会话建立请求，所述第一用户面MBS会话建立请求中包含有第i级用户面节点分配的第一MBS IP多播传输地址和第一C-TEID，i＝1,…,N，N为正整数；发送单元2604配置为向所述I-SMF反馈第一用户面MBS会话建立响应，所述第一用户面MBS会话建立响应中包含有中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，所述第二MBS IP多播传输地址用于所述中间用户面节点的子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式传输的MBS业务数据；处理单元2606配置为在所述中间用户面节点支持通过多播方式接收所述第i级用户面节点发送的MBS业务数据的情况下，加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据。
在本申请的一些实施例中，基于前述方案，处理单元2606还配置为：若所述中间用户面节点不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点发送的MBS业务数据，则分配通过点对点方式接收所述第i级用户面节点发送的MBS业务数据的F-TEID。
在本申请的一些实施例中，基于前述方案，第二接收单元2602还配置为：在发送单元2604向所述I-SMF反馈第一用户面MBS会话建立响应之后，接收所述I-SMF发送的用户面MBS会话修改请求，所述用户面MBS会话修改请求中包含有第一F-TEID列表信息，所述第一F-TEID列表信息包含有不支持通过多播方式、但支持通过点对点方式接收所述中间用户面节点发送的MBS业务数据的子用户面节点的F-TEID；
处理单元2606还配置为：基于所述第一F-TEID列表信息，通过点对点的方式向所述第一F-TEID列表信息包含的各个F-TEID所对应的子用户面节点分别传送MBS业务数据，并根据所述用户面MBS会话修改请求确定是否同时使用多播传输方式向所述中间用户面节点的子用户面节点发送MBS业务数据。
在本申请的一些实施例中，基于前述方案，发送单元2604还配置为：在接收到所述I-SMF发送的用户面MBS会话删除请求时，向所述I-SMF发送用户面MBS会话删除响应；其中，若已加入所述第一MBS IP多播传输地址对应的多播传输组中，则在接收到所述用户面MBS会话删除请求之后，退出所述第一MBS IP多播传输地址对应的多播传输组。
在本申请的一些实施例中，基于前述方案，处理单元2606还配置为：若接收到多个用户面MBS会话建立请求，则针对所述多个用户面MBS会话建立请求中的一个用户面MBS会话建立请求反馈用户面MBS会话建立响应，并针对所述多个用户面MBS会话建立请求中的其它用户面MBS会话建立请求反馈拒绝消息，以指示此用户面节点已被选择；或者
在向所述I-SMF反馈第一用户面MBS会话建立响应之后，若再次接收到用于将所述中间用户面节点选择为其它用户面节点的子用户面节点的用户面MBS会话建立请求，则针对再次接收到的用户面MBS会话建立请求反馈拒绝消息，以指示此用户面节点已被选择。
图27示出了适于用来实现本申请实施例的电子设备的计算机系统的结构示意图。
需要说明的是，图27示出的电子设备的计算机系统2700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。
如图27所示，计算机系统2700包括中央处理单元(Central Processing Unit，CPU)2701，其可以根据存储在只读存储器(Read-Only Memory，ROM)2702中的程序或者从存储部分2708加载到随机访问存储器(Random Access Memory，RAM)2703中的程序而执行各种适当的动作和处理，例如执行上述实施例中所述的方法。在RAM 2703中，还存储有系统操作所需的各种程序和数据。CPU 2701、ROM 2702以及RAM 2703通过总线2704彼此相连。输入/输出(Input/Output，I/O)接口2705也连接至总线2704。
以下部件连接至I/O接口2705：包括键盘、鼠标等的输入部分2706；包括诸如阴极射线管(Cathode Ray Tube，CRT)、液晶显示器(Liquid Crystal Display，LCD)等以及扬声器等的输出部分2707；包括硬盘等的存储部分2708；以及包括诸如LAN(Local Area Network，局域网)卡、调制解调器等的网络接口卡的通信部分2709。通信部分2709经由诸如因特网的网络执行通信处理。驱动器2710也根据需要连接至I/O接口2705。可拆卸介质2711，诸如磁盘、光盘、磁光盘、半导体存储器等等，根据需要安装在驱动器2710上，以便于从其上读出的计算机程序根据需要被安装入存储部分2708。
特别地，根据本申请的实施例，上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，本申请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计算机程序。在这样的实施例中，该计算机程序可以通过通信部分2709从网络上被下载和安装，和/或从可拆卸介质2711被安装。在该计算机程序被中央处理单元(CPU)2701执行时，执行本申请的系统中限定的各种功能。
需要说明的是，本申请实施例所示的计算机可读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。计算机可读存储介质例如可以是——但不限于——电、磁、光、电磁、红外线、或半导体的系统、装置或器件，或者任意以上的组合。计算机可读存储介质的更具体的例子可以包括但不限于：具有一个或多个导线的电连接、便携式计算机磁盘、硬盘、随机访问存储器(RAM)、只读存储器(ROM)、可擦式可编程只读存储器(Erasable Programmable Read Only Memory，EPROM)、闪存、光纤、便携式紧凑磁盘只读存储器(Compact Disc Read-Only Memory，CD-ROM)、光存储器件、磁存储器件、或者上述的任意合适的组合。在本申请中，计算机可读存储介质可以是任何包含或存储程序的有形介质，该程序可以被指令执行系统、装置或者器件使用或者与其结合使用。而在本申请中，计算机可读的信号介质可以包括在基带中或者作为载波一部分传播的数据信号，其中承载了计算机可读的计算机程序。这种传播的数据信号可以采用多种形式，包括但不限于电磁信号、光信号或上述的任意合适的组合。计算机可读的信号介质还可以是计算机可读存储介质以外的任何计算机可读介质，该计算机可读介质可以发送、传播或者传输用于由指令执行系统、装置或者器件使用或者与其结合使用的程序。计算机可读介质上包含的计算机程序可以用任何适当的介质传输，包括但不限于：无线、有线等等，或者上述的任意合适的组合。
附图中的流程图和框图，图示了按照本申请各种实施例的系统、方法和计算机程序产品的可能实现的体系架构、功能和操作。其中，流程图或框图中的每个方框可以代表一个模块、程序段、或代码的一部分，上述模块、程序段、或代码的一部分包含一个或多个用于实现规定的逻辑功能的可执行指令。也应当注意，在有些作为替换的实现中，方框中所标注的功能也可以以不同于附图中所标注的顺序发生。例如，两个接连地表示的方框实际上可以基本并行地执行，它们有时也可以按相反的顺序执行，这依所涉及的功能而定。也要注意的是，框图或流程图中的每个方框、以及框图或流 程图中的方框的组合，可以用执行规定的功能或操作的专用的基于硬件的系统来实现，或者可以用专用硬件与计算机指令的组合来实现。
描述于本申请实施例中所涉及到的单元可以通过软件的方式实现，也可以通过硬件的方式来实现，所描述的单元也可以设置在处理器中。其中，这些单元的名称在某种情况下并不构成对该单元本身的限定。
作为另一方面，本申请还提供了一种计算机可读介质，该计算机可读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上述实施例中所述的方法。
应当注意，尽管在上文详细描述中提及了用于动作执行的设备的若干模块或者单元，但是这种划分并非强制性的。实际上，根据本申请的实施方式，上文描述的两个或更多模块或者单元的特征和功能可以在一个模块或者单元中具体化。反之，上文描述的一个模块或者单元的特征和功能可以进一步划分为由多个模块或者单元来具体化。
通过以上的实施方式的描述，本领域的技术人员易于理解，这里描述的示例实施方式可以通过软件实现，也可以通过软件结合必要的硬件的方式来实现。因此，根据本申请实施方式的技术方案可以以软件产品的形式体现出来，该软件产品可以存储在一个非易失性存储介质(可以是CD-ROM，U盘，移动硬盘等)中或网络上，包括若干指令以使得一台计算设备(可以是个人计算机、服务器、触控终端、或者网络设备等)执行根据本申请实施方式的方法。
本领域技术人员在考虑说明书及实践这里公开的实施方式后，将容易想到本申请的其它实施方案。本申请旨在涵盖本申请的任何变型、用途或者适应性变化，这些变型、用途或者适应性变化遵循本申请的一般性原理并包括本申请未公开的本技术领域中的公知常识或惯用技术手段。
应当理解的是，本申请并不局限于上面已经描述并在附图中示出的精确结构，并且可以在不脱离其范围进行各种修改和改变。本申请的范围仅由所附的权利要求来限制。

Claims (29)

  1. 一种多播广播业务的通信方法，其特征在于，所述方法包括：
    接收多播广播业务MBS会话传输树中的第i级控制面节点发送的第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级控制面节点选择的第i级用户面节点的标识信息、所述第i级用户面节点所分配的第一MBS网际互联协议IP多播传输地址与用于通过多播方式传输MBS业务数据的第一通用隧道端点标识C-TEID，i＝1,…,N，N为正整数；
    根据所述第i级控制面节点的信息及所述第i级控制面节点提供的子控制面节点的信息选择中间用户面节点，所述中间用户面节点能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接；
    向所述中间用户面节点发送第一用户面MBS会话建立请求，并接收所述中间用户面节点反馈的第一用户面MBS会话建立响应，所述第一用户面MBS会话建立请求中包含有所述第一MBS IP多播传输地址和第一C-TEID，所述第一MBS IP多播传输地址用于使所述中间用户面节点加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据；
    向所述第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求，以指示所述第i级控制面节点提供的子控制面节点为所述中间用户面节点分配子用户面节点，所述第二MBS会话开始请求中包含有所述中间用户面节点的标识信息，以及所述中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，所述第二MBS IP多播传输地址用于使所述子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式发送的MBS业务数据。
  2. 根据权利要求1所述的多播广播业务的通信方法，其中，所述第一用户面MBS会话建立请求中包含有用于指示所述中间用户面节点分配新的MBS IP多播分发信息的指示信息；
    所述第一用户面MBS会话建立响应中包含有所述中间用户面节点分配的所述第二MBS IP多播传输地址和第二C-TEID。
  3. 根据权利要求1所述的多播广播业务的通信方法，其中，
    若所述中间用户面节点不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点的MBS业务数据，则所述第一用户面MBS会话建立请求中包含有请求为所述中间用户面节点分配全量隧道端点标识F-TEID的指示信息，所述第一用户面MBS会话建立响应中包含有所述中间用户面节点分配的F-TEID，所述F-TEID用于使所述中间用户面节点通过点对点的方式接收所述第i级用户面节点发送的MBS业务数据；或者
    所述第一用户面MBS会话建立响应中指示所述中间用户面节点不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点的MBS业务数据，并包含有所述中间用户面节点分配的F-TEID。
  4. 根据权利要求1所述的多播广播业务的通信方法，其中，在向所述第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求之后，所述多播广播业务的通信方法还包括：
    接收所述子控制面节点针对所述第二MBS会话开始请求反馈的第二MBS会话开始响应，所述第二MBS会话开始响应中包含有第一指示信息；
    其中，所述第一指示信息中包含有所述中间用户面节点的标识信息、第一全量隧道端点标识F-TEID列表信息和用于表示启动多播方式传输的第一字段信息，所述第一字段信息表示所述子控制面节点为所述中间用户面节点分配的子用户面节点中存在支持通过多播方式接收所述中间用户面节点发送的MBS业务数据的子用户面节点，所述第一F-TEID列表信息包含有不支持通过多播方式、但支持通过点对点方式接收所述中间用户面节点发送的MBS业务数据的子用户面节点的F-TEID；或者
    所述第一指示信息包含有所述中间用户面节点的标识信息、且不包含所述第一F-TEID列表信息和所述第一字段信息，则所述第一指示信息用于指示所述子控制面节点为所述中间用户面节点分配的子用户面节点均支持通过多播方式接收所述中间用户面节点发送的MBS业务数据；或者
    所述第一指示信息包含有所述中间用户面节点的标识信息、所述第一F-TEID列表信息，且不包含所述第一字段信息，则所述第一指示信息用于指示所述子控制面节点为所述中间用户面节点分配的子用户面节点均不支持通过多播方式、但支持通过点对点方式接收所述中间用户面节点发送的MBS业务数据；或者
    所述第一指示信息包含有所述中间用户面节点的标识信息和停用多播传输的字段信息、且不包含所述第一F-TEID列表信息，则所述第一指示信息用于指示所述子控制面节点没有为所述中间用户面节点分配子用户面节点。
  5. 根据权利要求4所述的多播广播业务的通信方法，其中，若选择了至少两个中间用户面节点，则所述第二MBS会话开始响应中包含有第一指示信息列表，所述第一指示信息列表中包含有所有中间用户面节点分别对应的所述第一指示信息。
  6. 根据权利要求5所述的多播广播业务的通信方法，其中，所述第二MBS会话开始响应中还包含有失败的标识信息列表，所述失败的标识信息列表用于指示未被分配子用户面节点的目标中间用户面节点。
  7. 根据权利要求4至6中任一项所述的多播广播业务的通信方法，还包括：
    若根据所述第二MBS会话开始响应确定存在未被分配子用户面节点的目标中间用户面节点，则向所述目标中间用户面节点发送用户面MBS会话删除请求。
  8. 根据权利要求7所述的多播广播业务的通信方法，还包括：
    接收所述目标中间用户面节点反馈的用户面MBS会话删除响应，所述用户面MBS会话删除响应是所述目标中间用户面节点在接收到所述用户面MBS会话删除请求之后发送的，其中，若所述目标中间用户面节点已加入所述第一MBS IP多播传输地址对应的多播传输组中，则在接收到所述用户面MBS会话删除请求之后退出所 述第一MBS IP多播传输地址对应的多播传输组。
  9. 根据权利要求7所述的多播广播业务的通信方法，其中，若所述第i级控制面节点提供了至少两个子控制面节点，则所述多播广播业务的通信方法还包括：
    在接收到所述第i级控制面节点提供的所有子控制面节点分别反馈的第二MBS会话开始响应之后，确定是否存在未被分配子用户面节点的目标中间用户面节点。
  10. 根据权利要求4所述的多播广播业务的通信方法，其中，在接收所述子控制面节点针对所述第二MBS会话开始请求反馈的第二MBS会话开始响应之后，所述多播广播业务的通信方法还包括：
    若所述第一指示信息中包含有所述第一F-TEID列表信息，则根据所述第一指示信息中包含的中间用户面节点的标识信息向所述中间用户面节点发送用户面MBS会话修改请求，以指示所述中间用户面节点通过点对点的方式向所述第一F-TEID列表信息所包含的各个F-TEID对应的子用户面节点分别传送MBS业务数据；
    其中，若所述第一指示信息中还包含有所述第一字段信息，则所述用户面MBS会话修改请求还用于指示所述中间用户面节点同时使用多播传输方式向所述中间用户面节点的子用户面节点发送MBS业务数据；
    若所述第一指示信息中不包含所述第一字段信息，则所述用户面MBS会话修改请求还用于指示所述中间用户面节点不需要使用多播传输方式向所述中间用户面节点的子用户面节点发送MBS业务数据。
  11. 根据权利要求10所述的多播广播业务的通信方法，还包括：
    若选择了至少两个中间用户面节点，则根据所述第二MBS会话开始响应中包含的每个中间用户面节点对应的第一指示信息，向需要发送所述用户面MBS会话修改请求的中间用户面节点发送所述用户面MBS会话修改请求。
  12. 根据权利要求4所述的多播广播业务的通信方法，其中，在接收所述子控制面节点针对所述第二MBS会话开始请求反馈的第二MBS会话开始响应之后，所述多播广播业务的通信方法还包括：
    根据所述子控制面节点反馈的第二MBS会话开始响应，向所述第i级控制面节点反馈针对所述第一MBS会话开始请求的第一MBS会话开始响应。
  13. 根据权利要求12所述的多播广播业务的通信方法，其中，若所述第i级控制面节点提供了至少两个子控制面节点，则在接收到所述第i级控制面节点提供的所有子控制面节点分别反馈的第二MBS会话开始响应之后，再向所述第i级控制面节点反馈所述第一MBS会话开始响应。
  14. 根据权利要求12所述的多播广播业务的通信方法，其中，所述第一MBS会话开始响应中包含有第二指示信息；
    其中，所述第二指示信息中包含有所述第i级用户面节点的标识信息、第二F-TEID列表信息和用于表示启动多播方式传输的第二字段信息，所述第二字段信息表示存在支持通过多播方式接收所述第i级用户面节点发送的MBS业务数据的中间用户面节点，所述第二F-TEID列表信息包含有不支持通过多播方式、但支持通过 点对点方式接收所述第i级用户面节点发送的MBS业务数据的中间用户面节点的F-TEID；或者
    所述第二指示信息包含有所述第i级用户面节点的标识信息、且不包含所述第二F-TEID列表信息和所述第二字段信息，则所述第二指示信息用于指示所述中间用户面节点均支持通过多播方式接收所述第i级用户面节点发送的MBS业务数据；或者
    所述第二指示信息包含有所述第i级用户面节点的标识信息、所述第二F-TEID列表信息，且不包含所述第二字段信息，则所述第二指示信息用于指示所述中间用户面节点均不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点发送的MBS业务数据。
  15. 根据权利要求14所述的多播广播业务的通信方法，其中，若所述第i级控制面节点选择了至少两个第i级用户面节点，则所述第一MBS会话开始响应中包含有第二指示信息列表，所述第二指示信息列表中包含有所有第i级用户面节点分别对应的所述第二指示信息。
  16. 根据权利要求1所述的多播广播业务的通信方法，其中，若所述第i级控制面节点选择了至少两个第i级用户面节点，则所述第一MBS会话开始请求中包含有每个第i级用户面节点各自的标识信息、及每个第i级用户面节点分配的第一MBS IP多播传输地址和第一C-TEID；
    其中，不同的第i级用户面节点分配的第一MBS IP多播传输地址不相同。
  17. 一种多播广播业务的通信方法，其特征在于，所述方法包括：
    向第i级控制面节点选择的第i级用户面节点发送第二用户面多播广播业务MBS会话建立请求，并接收所述第i级用户面节点反馈的第二用户面MBS会话建立响应，所述第i级控制面节点是MBS会话传输树中除最后一级控制面节点之外的任一级控制面节点，i＝1,…,N，N为正整数；
    选择中间会话管理功能实体I-SMF，向所述I-SMF发送第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级用户面节点的标识信息、所述第i级用户面节点分配的第一MBS网际互连协议IP多播传输地址和第一通用隧道端点标识C-TEID；
    其中，所述第一MBS会话开始请求用于触发所述I-SMF选择能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接的中间用户面节点，并用于触发所述I-SMF向所述子控制面节点发送第二MBS会话开始请求，所述中间用户面节点用于加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据，所述第二MBS会话开始请求用于指示所述子控制面节点为所述中间用户面节点分配子用户面节点，并使所述子用户面节点接收所述中间用户面节点发送的MBS业务数据。
  18. 根据权利要求17所述的多播广播业务的通信方法，其中，在向所述I-SMF发送第一MBS会话开始请求之后，所述多播广播业务的通信方法还包括：
    接收所述I-SMF针对所述第一MBS会话开始请求反馈的第一MBS会话开始响应；
    根据所述第一MBS会话开始响应中包含的内容，确定是否向所述第i级用户面节点发送用户面MBS会话修改请求。
  19. 根据权利要求17所述的多播广播业务的通信方法，其中，所述选择中间会话管理功能实体I-SMF，包括：
    若根据所述第i级控制面节点提供的子控制面节点的信息，确定所述第i级控制面节点管理的用户面功能实体不能直接与所述子控制面节点管理的用户面功能实体建立传输通路，则选择能够与所述第i级控制面节点及与所述子控制面节点进行通信的SMF作为所述I-SMF。
  20. 一种多播广播业务的通信方法，其特征在于，所述方法包括：
    接收中间会话管理功能实体I-SMF发送的第一用户面多播广播业务MBS会话建立请求，所述第一用户面MBS会话建立请求中包含有第i级用户面节点分配的第一MBS网际互连协议IP多播传输地址和第一通用隧道端点标识C-TEID，i＝1,…,N，N为正整数；
    向所述I-SMF反馈第一用户面MBS会话建立响应，所述第一用户面MBS会话建立响应中包含有中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，所述第二MBS IP多播传输地址用于所述中间用户面节点的子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式传输的MBS业务数据；
    若所述中间用户面节点支持通过多播方式接收所述第i级用户面节点发送的MBS业务数据，则加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据。
  21. 根据权利要求20所述的多播广播业务的通信方法，还包括：
    若所述中间用户面节点不支持通过多播方式、但支持通过点对点方式接收所述第i级用户面节点发送的MBS业务数据，则分配通过点对点方式接收所述第i级用户面节点发送的MBS业务数据的全量隧道端点标识F-TEID。
  22. 根据权利要求20所述的多播广播业务的通信方法，其中，在向所述I-SMF反馈第一用户面MBS会话建立响应之后，所述多播广播业务的通信方法还包括：
    接收所述I-SMF发送的用户面MBS会话修改请求，所述用户面MBS会话修改请求中包含有第一全量隧道端点标识F-TEID列表信息，所述第一F-TEID列表信息包含有不支持通过多播方式、但支持通过点对点方式接收所述中间用户面节点发送的MBS业务数据的子用户面节点的F-TEID；
    基于所述第一F-TEID列表信息，通过点对点的方式向所述第一F-TEID列表信息包含的各个F-TEID所对应的子用户面节点分别传送MBS业务数据，并根据所述用户面MBS会话修改请求确定是否同时使用多播传输方式向所述中间用户面节点的子用户面节点发送MBS业务数据。
  23. 根据权利要求20所述的多播广播业务的通信方法，还包括：
    若接收到所述I-SMF发送的用户面MBS会话删除请求，则向所述I-SMF发送用户面MBS会话删除响应；
    其中，若已加入所述第一MBS IP多播传输地址对应的多播传输组中，则在接收到所述用户面MBS会话删除请求之后，退出所述第一MBS IP多播传输地址对应的多播传输组。
  24. 根据权利要求20所述的多播广播业务的通信方法，其中，
    若接收到多个用户面MBS会话建立请求，则针对所述多个用户面MBS会话建立请求中的一个用户面MBS会话建立请求反馈用户面MBS会话建立响应，并针对所述多个用户面MBS会话建立请求中的其它用户面MBS会话建立请求反馈拒绝消息，以指示此用户面节点已被选择；或者
    在向所述I-SMF反馈第一用户面MBS会话建立响应之后，若再次接收到用于将所述中间用户面节点选择为其它用户面节点的子用户面节点的用户面MBS会话建立请求，则针对再次接收到的用户面MBS会话建立请求反馈拒绝消息，以指示此用户面节点已被选择。
  25. 一种多播广播业务的通信装置，其特征在于，包括：
    第一接收单元，配置为接收多播广播业务MBS会话传输树中的第i级控制面节点发送的第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级控制面节点对应的第i级用户面节点的标识信息、所述第i级用户面节点所分配的第一MBS网际互连协议IP多播传输地址与用于通过多播方式传输MBS业务数据的第一通用隧道端点标识C-TEID，i＝1,…,N，N为正整数；
    选择单元，配置为根据所述第i级控制面节点的信息及所述第i级控制面节点提供的子控制面节点的信息选择中间用户面节点，所述中间用户面节点能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接；
    第一交互单元，配置为向所述中间用户面节点发送第一用户面MBS会话建立请求，并接收所述中间用户面节点反馈的第一用户面MBS会话建立响应，所述第一用户面MBS会话建立请求中包含有所述第一MBS IP多播传输地址和第一C-TEID，所述第一MBS IP多播传输地址用于使所述中间用户面节点加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据；
    第二交互单元，配置为向所述第i级控制面节点提供的子控制面节点发送第二MBS会话开始请求，以指示所述第i级控制面节点提供的子控制面节点为所述中间用户面节点分配子用户面节点，所述第二MBS会话开始请求中包含有所述中间用户面节点的标识信息，以及所述中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，所述第二MBS IP多播传输地址用于使所述子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式 发送的MBS业务数据。
  26. 一种多播广播业务的通信装置，其特征在于，包括：
    第三交互单元，配置为向第i级控制面节点选择的第i级用户面节点发送第二用户面多播广播业务MBS会话建立请求，并接收所述第i级用户面节点反馈的第二用户面MBS会话建立响应，所述第i级控制面节点是MBS会话传输树中除最后一级控制面节点之外的任一级控制面节点，i＝1,…,N，N为正整数；
    第四交互单元，配置为选择中间会话管理功能实体I-SMF，向所述I-SMF发送第一MBS会话开始请求，所述第一MBS会话开始请求中包含有所述第i级控制面节点提供的子控制面节点的信息、所述第i级用户面节点的标识信息、所述第i级用户面节点分配的第一MBS网际互连协议IP多播传输地址和第一通用隧道端点标识C-TEID；
    其中，所述第一MBS会话开始请求用于指示所述I-SMF选择能够与所述第i级用户面节点和所述子控制面节点管理的用户面功能实体建立连接的中间用户面节点，且与所述中间用户面节点建立用户面MBS会话，以使所述中间用户面节点加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据，并用于指示所述I-SMF向所述子控制面节点发送第二MBS会话开始请求，所述第二MBS会话开始请求用于指示所述子控制面节点为所述中间用户面节点分配子用户面节点，并使所述子用户面节点接收所述中间用户面节点发送的MBS业务数据。
  27. 一种多播广播业务的通信装置，其特征在于，包括：
    第二接收单元，配置为接收中间会话管理功能实体I-SMF发送的第一用户面多播广播业务MBS会话建立请求，所述第一用户面MBS会话建立请求中包含有第i级用户面节点分配的第一MBS网际互连协议IP多播传输地址和第一通用隧道端点标识C-TEID，i＝1,…,N，N为正整数；
    发送单元，配置为向所述I-SMF反馈第一用户面MBS会话建立响应，所述第一用户面MBS会话建立响应中包含有中间用户面节点分配的第二MBS IP多播传输地址和第二C-TEID，所述第二MBS IP多播传输地址用于所述中间用户面节点的子用户面节点加入所述第二MBS IP多播传输地址对应的多播传输组来接收所述中间用户面节点通过多播方式传输的MBS业务数据；
    处理单元，配置为在所述中间用户面节点支持通过多播方式接收所述第i级用户面节点发送的MBS业务数据的情况下，加入所述第一MBS IP多播传输地址对应的多播传输组来接收所述第i级用户面节点通过多播方式发送的MBS业务数据。
  28. 一种计算机可读介质，其上存储有计算机程序，其特征在于，所述计算机程序被处理器执行时实现如权利要求1至16中任一项所述的多播广播业务的通信方法，或实现如权利要求17至19中任一项所述的多播广播业务的通信方法，或实现如权利要求20至24中任一项所述的多播广播业务的通信方法。
  29. 一种电子设备，其特征在于，包括：
    一个或多个处理器；
    存储装置，用于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16中任一项所述的多播广播业务的通信方法，或实现如权利要求17至19中任一项所述的多播广播业务的通信方法，或实现如权利要求20至24中任一项所述的多播广播业务的通信方法。
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