Service handover method, apparatus and system

Abstract

This application discloses a service switching method, apparatus, and system. The method includes: a first session management network element receiving a first message from a first mobility management network element requesting context information of an EPS bearer corresponding to a PDU session of a first terminal. The first mobility management network element is located in a first network, the PDU session is provided by the first session management network element, and the PDU session is associated with a multicast service; the first session management network element sends the EPS bearer context information to the first mobility management network element according to the first message, the EPS bearer context information including the context of the EPS bearer corresponding to the multicast service. This application solution can be used in the fields of communication technology, artificial intelligence, vehicle networking, and smart home networking.

Description

[0001] This application claims priority to Chinese patent application filed on May 8, 2020, with application number 202010383295.0 and entitled "Business Switching Method, Apparatus and System", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communication technology, and in particular to service switching methods, apparatus and systems. Background Technology

[0003] In the 3rd generation partnership project (3GPP), with the rapid development of wireless communication technology, the fifth generation (5G) mobile communication network (referred to as 5G network) has emerged. The 5G network can coexist with the existing fourth generation (4G) network, and the two can interoperate.

[0004] In 5G networks, there is a need for network-side equipment to simultaneously send the same service data to multiple terminals, i.e., point-to-multipoint multicast service transmission requirements. To meet this requirement, existing methods use multicast broadcast / multicast to share the same user plane function (UPF) for the same multicast service data sent to multiple terminals, and then send the multicast service data to multiple terminals through the same UPF.

[0005] When a terminal moves from a 5G network to the coverage area of ​​a 4G network base station, if the terminal receives multicast service data via multicast broadcast / multicast in the 5G network, then how the terminal can receive the multicast service data via the 4G network base station when it moves to the coverage area of ​​the 4G network, and how to ensure the continuity of the multicast service data sent to the terminal, becomes an urgent problem to be solved. Summary of the Invention

[0006] This application provides a service switching method, apparatus, and system to switch multicast services from a first network to a second network, and transmit multicast service data through the evolved packet system (EPS) in the second network.

[0007] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0008] In a first aspect, embodiments of this application provide a service switching method, which may include: a first session management network element receiving a first message from a first mobility management network element requesting context information of an EPS bearer corresponding to a PDU session; the first session management network element sending the EPS bearer context information to the first mobility management network element according to the first message; the EPS bearer context information including the context of the EPS bearer corresponding to a multicast service. Wherein, the first mobility management network element is located in a first network, the PDU session is a PDU session of a first terminal, the PDU session is provided by the first session management network element, and the PDU session is associated with a multicast service.

[0009] Based on the method described in the first aspect, the first session management network element determines the context information of the EPS bearer corresponding to the multicast service. When the first terminal switches networks, the first session management network element sends the context information of the EPS bearer corresponding to the multicast service to the first mobility management network element. This allows the first mobility management network element to trigger the second mobility management network element to establish a tunnel for the EPS bearer corresponding to the multicast service. When the first terminal switches to the second network, the application server sends multicast service data to the first terminal through this EPS bearer, ensuring the continuity of multicast service transmission. Simultaneously, when the first terminal moves out of the area corresponding to the EPS bearer to the MBMS area, the transmission of multicast service data via the EPS bearer is stopped, and the transmission is switched to the MBMS bearer, improving data transmission performance.

[0010] In one possible design, the context of the EPS bearer includes the context of at least one EPS bearer corresponding to the multicast service, and the context of each EPS bearer includes the identifier of the EPS bearer and the QoS parameters of the EPS bearer.

[0011] Based on this possible design, the context of one or more EPS bearers can be determined, and the data of the multicast service can be transmitted through one or more EPS bearers corresponding to the multicast service to meet the transmission requirements of the multicast service.

[0012] In one possible design, the method further includes: the first session management network element determining the context of the EPS bearer corresponding to the multicast service.

[0013] Based on this possible design, the first session management network element determines the context of the EPS bearer corresponding to the multicast service, reducing the signaling overhead of obtaining the context information of the EPS bearer and extracting the context of the EPS bearer from the obtained context information.

[0014] In one possible design, the first session management network element determines the context of the EPS bearer corresponding to the multicast service by: the first session management network element determining whether the multicast service can be switched to the second network, and the first session management network element determining the context of the EPS bearer corresponding to the multicast service.

[0015] Based on this possible design, when the multicast service supports switching to the second network, the context of the EPS bearer corresponding to the multicast service can be determined. This allows the first terminal to receive multicast service data through the EPS bearer after switching to the second network, ensuring the continuity of service transmission and improving the utilization of transmission resources.

[0016] In one possible design, the method further includes: a first session management network element receiving first indication information to indicate permission for multicast services to switch to a second network. For example, the first session management network element obtains a first PCC rule, which includes the first indication information.

[0017] Based on this possible design, the first session management network element can obtain first indication information from other network elements, which can effectively and flexibly indicate whether to allow multicast services to switch to the second network.

[0018] In one possible design, the first session management network element determines the context of the EPS bearer corresponding to the multicast service by: the first session management network element obtaining the first PCC rule corresponding to the multicast service, including the QoS parameters of at least one service data stream SDF corresponding to the multicast service when the application server sends the multicast service in a multicast manner, and mapping at least one SDF to at least one EPS bearer according to the QoS parameters of at least one SDF.

[0019] Based on this possible design, the first session management network element can obtain the first PCC rule when establishing a multicast session corresponding to a multicast service, and determine the context of the EPS bearer corresponding to the multicast service according to the first PCC rule, which is simple and easy to implement.

[0020] In one possible design, the first session management network element determines the context of the EPS bearer corresponding to the multicast service by: the first session management network element mapping at least one QoS flow corresponding to the multicast service to at least one EPS bearer according to the QoS flow information of the multicast service; wherein, the QoS flow information includes the QoS parameters of at least one QoS flow, and the at least one QoS flow is used by the application server to send the multicast service data in a multicast manner.

[0021] Based on this possible design, the first session management network element can obtain the QoS flow information of multicast services and determine the context of the EPS bearer corresponding to the multicast service according to the QoS flow information of the multicast service, which is simple and easy to implement.

[0022] In one possible design, the method further includes: the first session management network element obtaining QoS flow information of the multicast service from the second session management network element that manages the multicast service.

[0023] Based on this possible design, the first session management network element can obtain the QoS flow information of multicast services from the second session management network element that manages multicast services, simplifying the system design.

[0024] In one possible design, the first session management network element determines the context of the EPS bearer corresponding to the multicast service by: the first session management network element mapping at least one SDF corresponding to the multicast service to at least one EPS bearer according to a second PCC rule, which includes the QoS parameters of at least one service data stream SDF corresponding to the multicast service when the application server sends the multicast service in unicast mode.

[0025] Based on this possible design, the first session management network element can determine the context of the EPS bearer according to the PCC rules when sending multicast services in unicast mode, so that the determined EPS bearer meets the QoS parameters for sending multicast services in unicast mode, which is simple and easy to implement.

[0026] In one possible design, the method further includes: the first session management network element sending a first event notification to the application server to notify the first terminal to join the multicast session corresponding to the multicast service, and receiving a second PCC rule.

[0027] Based on this possible design, the first session management network element notifies the application server that the first terminal has joined the multicast session. This allows the application server to send the second description information corresponding to the terminal that has joined the multicast session to the first network element. As a result, the policy control network element further determines the second PCC rule based on the second description information. The first session management network element receives the second PCC rule and determines the context information of the EPS bearer corresponding to the multicast service related to the terminal. This makes it possible to switch the multicast service to the second network, ensuring the continuity of multicast service transmission.

[0028] In one possible design, the method further includes: a first session management network element receiving a first subscription request for requesting to notify the application server of a first event, wherein the first event is that a terminal joins a multicast session corresponding to a multicast service, and the terminal includes a first terminal.

[0029] Based on this possible design, the first session management network element can receive subscription requests for the first event and send the first event notification to the application server upon receiving the subscription request, thereby improving the user experience.

[0030] In one possible design, the method further includes: a first session management network element receiving second indication information to indicate that the handover of the first terminal is complete, and sending a second message to a first user plane network element to establish a first mapping relationship between the identification information of the multicast service flow and the tunnel information carried by the EPS, wherein the identification information of the multicast service flow is used to identify the multicast service flow corresponding to the multicast service, and the first mapping relationship is used to instruct the first user plane network element to send the multicast service data through the EPS.

[0031] Based on this possible design, after the first terminal handover is completed, the first session management network element can send the first mapping relationship between the identification information of the multicast service flow and the tunnel information of the EPS bearer to the first user plane network element. This will allow the application server to send the data packets of the multicast service to the first user plane network element, and the first user plane network element to send the received data to the SGW / target access network device through the corresponding EPS bearer according to the first mapping relationship.

[0032] In one possible design, the method further includes: a first session management network element receiving second indication information to indicate that the handover of the first terminal is complete, and sending a second message to a first user plane network element including a second mapping relationship between the identifier of the QoS flow and the tunnel information of the EPS bearer, the second mapping relationship being used to instruct the first user plane network element to send the data packet corresponding to the QoS flow through the EPS bearer.

[0033] Based on this possible design, after the first terminal handover is completed, the first session management network element can send the second mapping relationship between the QoS flow identifier and the tunnel information of the EPS bearer to the first user plane network element. This allows the application server to send the multicast service data packets to the second user plane network element, and the second user plane network element to send the received data packets and QFI together to the first user plane network element. After receiving the data packets containing multicast service data transmitted through the tunnel, the first user plane network element, according to the second mapping relationship, the QFI corresponding to the data packet, and the identifier of the EPS bearer, sends the multicast service data to the SGW / target access network device through one or more EPS bearers.

[0034] In one possible design, the second message is also used to obtain downlink tunnel information of the first user plane network element. The downlink tunnel information of the first user plane network element is used to establish a tunnel for transmitting multicast service data between the first user plane network element and the second user plane network element. The second user plane network element is used to transmit multicast services in the first network. The method further includes: the first session management network element sending the downlink tunnel information of the first user plane network element to the second user plane network element.

[0035] Based on this possible design, the downlink tunnel information of the first user plane network element can be obtained through the second message and sent to the second user plane network element, which simplifies the system design and reduces signaling overhead.

[0036] In one possible design, the method further includes: the first session management network element sending a second event notification to the application server, the second event notification being used to notify the first terminal that it is about to switch to the second network or that the switch to the second network has been completed.

[0037] Based on this possible design, a second event notification can be sent to the application server when the first terminal is about to switch to the second network or when the switch to the second network is completed. Upon receiving the second event notification, the application server prepares to begin sending multicast service data packets to the first user plane network element via unicast or multicast, and also sends a third message to the first terminal to notify it to receive multicast service data via EPS bearer or to notify it to receive multicast service data via unicast session. In this way, preparation for sending multicast service data via unicast can begin during the first terminal's switch from the first network to the second network, avoiding packet loss and ensuring the continuity of data transmission after the first terminal successfully switches to the second network.

[0038] In one possible design, the first session management network element is also used to receive a second subscription request from the application server. The second subscription request is used to request that a second event be notified to the application server. The second event is that the first terminal is about to switch to the second network, or the switch to the second network is completed, or the first terminal is switching to the second network, or the first terminal is in the process of switching to the second network.

[0039] Based on this possible design, the first session management network element can send a second event notification to the application server upon the application server's subscription request, thereby improving the user experience. At the same time, it can promptly notify the application server of the terminal's switching status, so that the application server can prepare in time to send multicast service data to the terminal, avoid packet loss, and ensure the continuity of data transmission after the first terminal successfully switches to the second network.

[0040] In one possible design, the method further includes: the first session management network element sending context information of the EPS bearer to the source access network device; and / or, the first session management network element sending the identifier of the EPS bearer to the first terminal, or the identifier of the EPS bearer and the packet filter of the EPS bearer.

[0041] Based on this possible design, the first session management network element can send EPS bearer-related information to the source access network device and the first terminal, so that the source access network device and the first terminal can accurately receive the multicast service data sent by the application server according to the received EPS bearer-related information, thereby improving the reliability of multicast service transmission.

[0042] In one possible design, the method further includes: a first session management network element receiving third indication information for instructing to stop sending multicast service data to a first terminal via EPS bearer or for instructing the first terminal to receive multicast service data via MBMS bearer, and sending first configuration information to a first user plane network element for notifying the first user plane network element to stop sending multicast service data to the first terminal via EPS bearer.

[0043] Alternatively, the method further includes: the first session management network element receiving from the first terminal an eighth indication message for instructing the deletion of the EPS bearer, or for instructing the first terminal to receive multicast service data through the MBMS bearer; and, based on the eighth indication message, sending to the first user plane network element first configuration information for notifying the first user plane network element to stop sending multicast service data to the first terminal through the EPS bearer.

[0044] Based on this possible design, the first session management network element can send the first configuration information to the first user plane when it stops sending multicast service data to the first terminal through the EPS bearer. This allows the first user plane network element to stop sending multicast service data to the first terminal through the EPS bearer, thereby releasing transmission resources and improving transmission resource utilization.

[0045] In one possible design, the method further includes: a first session management network element receiving fourth indication information for instructing the transmission of multicast service data to a first terminal via EPS bearer, and sending second configuration information to a first user plane network element for notifying the first user plane network element to transmit multicast service data to the first terminal via EPS bearer.

[0046] Based on this possible design, when sending multicast service data to the first terminal again via EPS, the second configuration information is sent to the first user plane network element so that the first user plane network element can send multicast service data to the first terminal via EPS, adjust the multicast service transmission method in a timely manner, and improve data transmission reliability.

[0047] Secondly, this application provides a communication device, which can be a first session management network element or a chip or system-on-a-chip within the first session management network element. It can also be a module or unit within the first session management network element used to implement the service switching method described in the embodiments of this application, or other modules or units capable of implementing the method executed by the first session management network element. This communication device can implement the functions performed by the first session management network element in the first aspect or various possible designs. In one design, the communication device may include module units or means corresponding to each of the methods / operations / steps / actions described in the first aspect. These modules, units, or means can be implemented in hardware, software, or by hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the aforementioned functions.

[0048] Thirdly, a communication device is provided. This device can be a first session management network element, a chip or system-on-a-chip within the first session management network element, or other modules or units capable of implementing the methods of the first session management network element. This communication device can implement the functions performed by the first session management network element in the first aspect or any possible design described above, and these functions can be implemented in hardware. In one possible design, the communication device may include a processor and a communication interface. The processor can be used to support the communication device in implementing the functions involved in the first aspect or any possible design of the first aspect. For example, the processor can receive a first message from the first mobility management network element requesting context information of the EPS bearer corresponding to a PDU session through the communication interface, and according to the first message, send the context information of the EPS bearer to the first mobility management network element through the communication interface. The context information of the EPS bearer includes the context of the EPS bearer corresponding to a multicast service. In yet another possible design, the communication device may also include a memory for storing computer instructions and / or data. When the communication device is running, the processor executes the computer instructions stored in the memory to cause the communication device to perform the service switching method described in the first aspect or any possible design of the first aspect. In the embodiments of this application, the communication interface may be a transceiver, interface circuit, bus interface, pin, or other device capable of transmitting and receiving functions.

[0049] Fourthly, a computer-readable storage medium is provided that stores instructions which, when executed on a computer, enable the computer to perform the service switching method described in the first aspect or any possible design of the above aspects.

[0050] Fifthly, a computer program product including instructions is provided, which may include program instructions that, when the computer program product is run on a computer, enable the computer to perform the service switching method described in the first aspect or any possible design of the above aspects.

[0051] Sixthly, a chip system is provided, comprising a processor and a communication interface. This chip system can be used to implement the functions performed by the first session management network element in the first aspect or any possible design of the first aspect. For example, the processor is used to receive a first message from the first mobility management network element requesting context information of the EPS bearer corresponding to a PDU session via the communication interface. Based on the first message, the processor sends the EPS bearer context information to the first mobility management network element via the communication interface. The EPS bearer context information includes the context of the EPS bearer corresponding to a multicast service. In one possible design, the chip system further includes a memory for storing program instructions and / or data. When the chip system is running, the processor executes the program instructions stored in the memory to cause the chip system to perform the service switching method described in the first aspect or any possible design of the first aspect. The chip system can be composed of chips or may include chips and other discrete devices, without limitation.

[0052] In a seventh aspect, embodiments of this application also provide a service switching method, the method comprising: an application server receiving a first report from a first terminal indicating that the first terminal enters a multicast service area in a second network, and sending a fifth indication message to a first network element indicating to stop sending multicast service data to the first terminal through the evolved packet system (EPS) bearer in the second network.

[0053] Based on the method described in the seventh aspect, when the first terminal enters the MBMS area of ​​the multicast service in the second network, the application server can switch the way of sending multicast service data from EPS bearer to MBMS bearer, so that the first terminal switches the reception of the multicast service from receiving via EPS bearer (i.e. unicast bearer) to receiving via MBMS bearer, and adjust the transmission mode of multicast service in a timely manner to ensure the continuity of service transmission.

[0054] In one possible design, the method further includes: the application server receiving a second report from the first terminal indicating that the first terminal moves out of the MBMS area of ​​the multicast service, and sending a sixth indication message indicating that the multicast service data is sent to the first terminal via the EPS bearer.

[0055] Based on this possible design, when the terminal moves out of the MBMS area of ​​the multicast service, the transmission method can be switched from MBMS bearer to EPS bearer, so that the first terminal can switch the reception of the multicast service from receiving via MBMS bearer to receiving via EPS bearer (i.e. unicast bearer), and adjust the transmission method of the multicast service in a timely manner to ensure the continuity of service transmission.

[0056] In one possible design, the method further includes: the application server sending multicast service data packets, including multicast service data and the multicast address of the multicast service, to the first user plane network element via EPS bearer, that is, sending multicast service data via multicast mode without switching the sending mode to unicast mode, which is simple and easy to implement.

[0057] In one possible design, the method further includes: the application server sending first description information of the multicast service for formulating a first PCC rule to the first network element, the first PCC rule including QoS parameters of at least one service data stream SDF corresponding to the multicast service when the application server sends the multicast service in a multicast manner.

[0058] Based on this possible design, when sending multicast service data in multicast mode, the application server sends first description information for formulating first PCC rules, so that the context of the EPS bearer determined according to the first PCC rules meets the QoS parameters specified in the first description information, that is, the QoS parameters when sending in multicast mode, without affecting the terminal's experience when switching to the EPS bearer to receive multicast service data.

[0059] In one possible design, the first description information includes first indication information for indicating whether multicast service is allowed to switch to the second network. That is, the first description information indicates whether multicast service is allowed to switch to the second network. This design is simple and reduces signaling overhead.

[0060] In one possible design, the method further includes: the application server sending a multicast service data packet, including multicast service data and the address information of the first terminal, to the first user plane network element via EPS bearer.

[0061] Based on this possible design, the application server can selectively send multicast service data to the first terminal via unicast, thereby improving the utilization of transmission resources.

[0062] In one possible design, the fifth instruction information is also used to instruct the first network element to delete the second description information when the multicast service corresponding to the multicast service is transmitted through unicast bearer, and the second description information is used to formulate the second PCC rule corresponding to the multicast service; the sixth instruction information includes the second description information.

[0063] Based on this possible design, when the terminal moves into the MBMS area of ​​the multicast service, the second description information can be deleted through the fifth indication information to improve resource utilization; when the terminal moves out of the MBMS area of ​​the multicast service and switches to receiving multicast service data through EPS bearer, the second description information can be indicated to the first network element again through the sixth indication information so that the second PCC rule can be specified again according to the second description information, and the context of EPS bearer can be determined according to the second PCC rule to ensure the accuracy and continuity of multicast service transmission.

[0064] In one possible design, the method further includes: after receiving a first event notification from a first network element to notify the first terminal to join the multicast session corresponding to the multicast service, the application server sends second description information corresponding to the multicast service to the first network element. That is, after learning that the first terminal has joined the multicast session, the second description information is sent so that a second PCC rule can be executed according to the second description information, an EPS bearer can be determined according to the second PCC rule, and multicast service data can be sent to the first terminal through the EPS bearer to ensure the continuity of multicast service transmission.

[0065] In one possible design, the method further includes: the application server sending a first subscription request to the first network element to request that a first event be notified to the application server, wherein the first event is that a terminal joins the multicast session corresponding to the multicast service, and the terminal includes the first terminal.

[0066] In one possible design, the method further includes: the application server receiving a second event notification from a first session management network element, notifying the first terminal that it is about to switch to the second network or that the switch to the second network is complete, and sending a third message to the first terminal, notifying the first terminal to receive multicast service data via EPS. Further, after receiving the second event notification, the application server begins sending multicast service data packets including multicast service data and the address information of the first terminal.

[0067] Based on this possible design, the application server can begin preparing to send multicast service data in unicast mode when the first terminal switches from the first network to the second network, avoiding packet loss and ensuring the continuity of data transmission after the first terminal successfully switches to the second network.

[0068] In one possible design, the method further includes: the application server sending a second subscription request to the first network element to request that a second event be notified to the application server, wherein the second event is that the first terminal is about to switch to the second network or the switch to the second network is completed.

[0069] Eighthly, this application provides a communication device, which can be an application server, a chip or system-on-a-chip within the application server, a module or unit within the application server for implementing the data transmission method described in the embodiments of this application, or other modules or units capable of implementing the application server side. This communication device can implement the functions performed by the application server in the seventh aspect or various possible designs. In one design, the communication device may include module units or means corresponding to each of the methods / operations / steps / actions described in the seventh aspect. These modules, units, or means can be implemented in hardware, software, or by hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the aforementioned functions.

[0070] A ninth aspect provides a communication device, which can be an application server, a chip or system-on-a-chip within an application server, or other modules or units capable of implementing the application server side. This communication device can implement the functions performed by the application server in the seventh aspect or any possible design described above, and these functions can be implemented in hardware. In one possible design, the communication device may include a processor and a communication interface. The processor can be used to support the communication device in implementing the functions involved in the seventh aspect or any possible design of the seventh aspect. For example, the processor is used to receive, through the communication interface, a first report from a first terminal indicating that the first terminal has entered a multicast service area in a second network, and to send a fifth indication message to a first network element indicating to stop sending multicast service data to the first terminal via the Evolved Packet System (EPS) bearer in the second network. In yet another possible design, the communication device may further include a memory for storing computer instructions and / or data. When the communication device is running, the processor executes the computer instructions stored in the memory to cause the communication device to perform the data transmission method described in the seventh aspect or any possible design of the seventh aspect.

[0071] In a tenth aspect, a computer-readable storage medium is provided, which stores instructions that, when executed on a computer, cause the computer to perform the data transmission method described in the seventh aspect or any possible design of the preceding aspects.

[0072] In an eleventh aspect, a computer program product comprising instructions is provided, the computer program product including program instructions that, when the computer program product is run on a computer, enable the computer to perform the data transmission method described in the seventh aspect or any possible design of the above aspects.

[0073] In a twelfth aspect, a chip system is provided, comprising a processor and a communication interface. This chip system can be used to implement the functions performed by the application server in the seventh aspect or any possible design of the seventh aspect. For example, the processor is used to receive, via the communication interface, a first report from a first terminal indicating that the first terminal has entered a multicast service area in a second network (MBMS area), and to send a fifth indication to a first network element indicating to stop transmitting multicast service data to the first terminal via an Evolved Packet System (EPS) bearer in the second network. In one possible design, the chip system further includes a memory for storing program instructions and / or data. When the chip system is running, the processor executes the program instructions stored in the memory to cause the chip system to perform the data transmission method described in the seventh aspect or any possible design of the seventh aspect. The chip system can be composed of chips or may include chips and other discrete devices, without limitation.

[0074] In a thirteenth aspect, embodiments of this application also provide a communication system, the communication system including the communication device as described in the second or third aspect, or the communication device as described in the eighth or ninth aspect. Attached Figure Description

[0075] Figure 1a An architecture diagram of a communication system provided in an embodiment of this application;

[0076] Figure 1b This is a schematic diagram of the architecture of another communication system provided in an embodiment of this application;

[0077] Figure 2 A schematic diagram of an architecture for 4G and 5G network interoperability provided in an embodiment of this application;

[0078] Figure 3 A schematic diagram illustrating the composition of a communication device 300 provided in an embodiment of this application;

[0079] Figure 4 A flowchart illustrating a service switching method provided in an embodiment of this application;

[0080] Figure 5 A flowchart illustrating a service switching method provided in an embodiment of this application;

[0081] Figure 6 A flowchart illustrating yet another service switching method provided in this application embodiment;

[0082] Figure 7 A flowchart illustrating yet another service switching method provided in this application embodiment;

[0083] Figure 8A schematic diagram illustrating the composition of a communication device 80 provided in an embodiment of this application;

[0084] Figure 9 This is a schematic diagram of the composition of a communication device 90 provided in an embodiment of this application. Detailed Implementation

[0085] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. In the description of this application, unless otherwise stated, " / " indicates that the objects before and after are in an "or" relationship. For example, A / B can represent A or B. "And / or" in this application is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone, where A and B can be singular or plural. Furthermore, in the description of this application, unless otherwise stated, "multiple" refers to two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple. Furthermore, to facilitate a clear description of the technical solutions in the embodiments of this application, the terms "first" and "second" are used in the embodiments of this application to distinguish identical or similar items with substantially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that "first" and "second" are not necessarily different. Meanwhile, in the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is being used as an example, illustration, or description. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of terms such as "exemplary" or "for example" is intended to present related concepts in a concrete manner for ease of understanding.

[0086] Furthermore, the network architecture and business scenarios described in the embodiments of this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. As those skilled in the art will know, with the evolution of network architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0087] The service switching method provided in this application is applicable to communication systems where a first network and a second network are interconnected, so as to switch multicast services transmitted in the first network to a transmission channel in the second network for transmission. In this application, the multicast service can be a multicast type service, a multicast type service, or a broadcast type service, such as a broadcast service, etc., and is not limited thereto.

[0088] like Figure 1a The diagram illustrates a communication system 10 provided in this application embodiment. This communication system 10 is an interconnected system between a first network and a second network. The communication system 10 includes a first mobility management network element and a first session management network element. Further, it may also include a first user plane network element, a second mobility management network element, or an application server. The first mobility management network element is located in the first network. The first session management network element and the first user plane network element are shared / co-located network elements between the first and second networks. The second mobility management network element is located in the second network. The application server is located in the data network (DN).

[0089] The first mobility management network element is configured to send a first message to the first session management network element requesting context information of the EPS bearer corresponding to the protocol data unit (PDU) session. The first session management network element is configured to receive the first message from the first mobility management network element requesting context information of the EPS bearer corresponding to the PDU session, and, based on the first message, send the EPS bearer context information to the first mobility management network element, so that the first mobility management network element triggers the second mobility management network element to establish an EPS bearer based on the EPS bearer context information.

[0090] Specifically, the first mobility management network element is used to send a first message to the first session management network element when it receives a handover request that instructs the first terminal to perform a handover.

[0091] Furthermore, the first session management network element is also used to obtain a first PCC rule, and map at least one SDF to at least one EPS bearer according to the QoS parameters of at least one SDF included in the first PCC rule; or, obtain QoS flow information of multicast services, and map at least one QoS flow corresponding to the multicast service to the at least one EPS bearer according to the QoS flow information of the multicast service; or, obtain a second PCC rule, and map at least one SDF to at least one EPS bearer according to the QoS parameters of at least one SDF included in the second PCC rule.

[0092] Furthermore, the first session management network element is also used to send a second event notification to the application server. This second event notification is used to notify the first terminal that it is about to receive multicast service data via EPS bearer, or that it is about to switch to the second network or that the switch to the second network is complete, or that it notifies the application server that the first terminal is receiving multicast service data via unicast session. The application server is used to receive the second event notification and, based on the second event notification, send a third message to the first terminal. This third message is used to notify the first terminal that it is receiving multicast service data via EPS bearer.

[0093] Furthermore, the first session management network element is also used to receive a second subscription request from the application server. The second subscription request is used to request that a second event be notified to the application server. The second event is that the first terminal is about to switch to the second network, or the switch to the second network is completed, or the first terminal is in the process of switching to the second network.

[0094] Furthermore, the application server is also used to start sending multicast service data packets after receiving the second event notification. The data packets include multicast service data and a destination address, wherein the destination address includes the address information of the first terminal.

[0095] based on Figure 1a In the communication system shown, the first session management network element can determine the context information of the EPS bearer. The context information of the EPS bearer includes the context of the EPS bearer corresponding to the multicast service. When the first terminal switches, the context information of the EPS bearer is sent to the first mobility management network element so that the first mobility management network element can trigger other network elements to establish a tunnel for the EPS bearer. This allows the application server to send the multicast service data to the first terminal through the EPS bearer when the first terminal switches to the second network, ensuring the continuity of multicast service transmission.

[0096] Furthermore, such as Figure 1b As shown, the communication system 10 may further include: a first terminal, a source access network device, a second access network device, a second session management network element, a second user plane network element, a multicast / multicast service controller, a multicast / multicast gateway, a serving gateway (SGW), a second mobility management network element, and first network elements: a network storage network element, a policy control network element, and a network open function network element, etc. Taking the first terminal as terminal 1 as an example, Figure 1bIn the system shown, the transmission path for multicast service data in the first network can be called a multicast session. The transmission path corresponding to this multicast session can be: Application Server <-> First User Plane Network Element <-> Source Access Network Device <-> Multiple Terminals, including Terminal 1; or, Application Server <-> Second User Plane Network Element <-> First User Plane Network Element <-> Source Access Network Device <-> Multiple Terminals, including Terminal 1. The transmission path for multicast service data in the second network can include EPS bearers and MBMS bearers. The transmission path for the EPS bearer is: Application Server <-> First User Plane Network Element <-> Serving Gateway <-> Target Access Network Device <-> Terminal 1. The transmission path corresponding to the MBMS bearer is: Application Server <-> Multicast / Multicast Service Controller <-> Multicast / Multicast Gateway <-> Target Access Network Device <-> Terminal 1. Figure 1b In the system shown, the transmission path for signaling interaction between the terminal and the application server in the second network is: application server <-> first user plane network element <-> source access network device <-> terminal 1.

[0097] Furthermore, in Figure 1b In the communication system shown, the application server is also used to receive a first report from the first terminal, which instructs the first terminal to enter the multicast / broadcast media service (MBMS) area of ​​the multicast service in the second network, in which the first terminal can receive the multicast service data through the MBMS bearer; and to send a fifth indication information to the first network element, which instructs to stop sending the multicast service data to the first terminal through the evolved packet system (EPS) bearer in the second network or instructs the first terminal to receive the multicast service data through the MBMS bearer.

[0098] Furthermore, the first session management network element is also used to receive a request message to add the first terminal to the multicast session corresponding to the multicast service, and during the process of adding the first terminal to the multicast session corresponding to the multicast service, obtain the first policy and charging control (PCC) rule corresponding to the multicast service from the policy control network element, and determine the context of the EPS bearer corresponding to the multicast service according to the first PCC rule; or, obtain the QoS flow information corresponding to the multicast service from the second session management network element, and determine the context of the EPS bearer corresponding to the multicast service according to the quality of service (QoS) flow corresponding to the multicast service; or, obtain the second PCC rule from the policy control network element, and determine the context of the EPS bearer corresponding to the multicast service according to the second PCC rule.

[0099] Furthermore, the QoS flow information corresponding to the first PCC rule and / or multicast service includes first indication information, which is used to indicate that the multicast service is allowed to switch to the second network.

[0100] Furthermore, the application server is also used to send first description information to the first network element, the first description information including first indication information, so that the policy control network element can obtain the first description information and formulate the first PCC rule.

[0101] Furthermore, the first session management network element is also used to send a first event notification to the application server during the process of the first terminal joining the multicast session corresponding to the multicast service. The application server is also used to send second description information to the first network element after receiving the first event notification, so that the policy control network element can obtain the second description information to formulate a second PCC rule.

[0102] Optionally, the terminal device in this application embodiment can be a device for implementing wireless communication functions, such as a terminal or a chip that can be used in a terminal. The terminal can be a user equipment (UE), access terminal, terminal unit, terminal station, mobile station, mobile station, remote station, remote terminal, mobile device, wireless communication device, terminal agent, or terminal apparatus in a 5G network or future evolved communication system. Access terminals can be cellular phones, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, personal digital assistants (PDAs), handheld devices with wireless communication capabilities, computing devices or other processing devices connected to a wireless modem, in-vehicle devices or wearable devices, virtual reality (VR) terminal devices, augmented reality (AR) terminal devices, wireless terminals in industrial control, wireless terminals in self-driving, wireless terminals in remote medical care, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, etc. Terminals can be mobile or fixed.

[0103] Optionally, the source access network device and target access network device in this application embodiment are mainly used to implement physical layer functions, resource scheduling and management, terminal access control, and mobility management. The source access network device and target access network device can be devices supporting wired access or devices supporting wireless access. For example, the source access network device can be a next-generation radio access network (NG-RAN) device, an access network (AN) / radio access network (RAN), composed of multiple 5G-AN / 5G-RAN nodes. The 5G-AN / 5G-RAN nodes can be: next-generation base stations (NR nodeB, gNB), transmission reception points (TRPs), transmission points (TPs), or some other access nodes, etc. The target access network equipment can be an evolved universal terrestrial radioaccess network (E-UTRAN) device, such as an access point (AP), a base station (nodeB, NB), an enhanced nodeB (eNB), or some other access node.

[0104] Optionally, the mobility management network element in this application embodiment is mainly responsible for terminal access authentication, mobility management, signaling interaction between various functional network elements, such as managing user registration status, user connection status, user registration and network access, tracking area updates, cell handover user authentication and key security.

[0105] Optionally, the session management network element in this application embodiment is mainly used to implement user plane transmission logical channels, such as session management functions such as the establishment, release, and modification of PDU sessions.

[0106] Optionally, the user plane network element in this embodiment can serve as an anchor point on the user plane transmission logical channel to perform functions such as routing and forwarding user plane data. For example, it can establish a channel (i.e., the user plane transmission logical channel) with the terminal, forward data packets between the terminal and the DN on the channel, and be responsible for filtering data packets of the terminal, forwarding data, rate control, and generating billing information.

[0107] Optionally, the network open function network element in this embodiment can be used for functions such as opening core network events and capabilities, translating core network external parameters and internal parameters, receiving and storing information provided by core network external network elements, and selecting core network devices. The core network external network element may include application servers, etc.

[0108] Optionally, the policy control network element in this application embodiment can be used to provide policies to the mobility management network element and the session management network element, such as quality of service policies, slice selection policies, etc.

[0109] Optionally, the network storage element in this embodiment can be used to store user data, such as user subscription information, authentication or authorization data, etc. The network storage element can be a unified data management (UDM), a network repository function (NRF), or a unified data repository (UDR), etc.

[0110] Optionally, the service gateway and multicast / broadcast service-gateway (MBSC-GW) in this embodiment can route and forward data packets under the control of the second mobility management network element, that is, forward the received user data to the designated network element. The service gateway can be as follows: Figure 1b As shown, it can be deployed independently in the communication system or integrated into other network elements. For example, the user plane function of the service gateway can be integrated into the first user plane network element, and the data plane function of the service gateway can be integrated into the first session management network element, without restriction.

[0111] Optionally, the multicast / broadcast service controller (MBSC) in this embodiment of the application has service management functions such as group management, security management, and service announcement.

[0112] Optionally, the DN in this embodiment can be a carrier network that provides data transmission services to users, such as a carrier network that provides IP multimedia service (IMS) to users. An application server (AS) can be deployed in the DN, which can provide data transmission services to users.

[0113] It should be noted that, Figure 1b This is merely an illustrative architecture diagram, except... Figure 1bIn addition to the functional units shown, the system may also include other functional network elements, such as operation and management (O&M) network elements, etc., which are not limited in this application embodiment. Furthermore, Figure 1b The names of the various devices in the text are not restricted, except... Figure 1b In addition to the names shown, each device can also be named with other names, such as replacing them with network element names that have the same or similar functions, without restriction.

[0114] in, Figure 1a , Figure 1b The first and second networks in this context are different communication networks that support different radio access technologies (RATs). For example, the first network could be a 5th generation (5G) network or a new radio (NR) network, supporting NR technology. The second network could be a long-term evolution (LTE) network or a 4th generation (4G) network, supporting LTE technology. The following section will combine... Figure 2 The above communication system is described using the example of a 5G network as the first network and a 4G network as the second network.

[0115] like Figure 2As shown, this is a communication system for the interconnection of 5G and 4G networks. The network element corresponding to the first user plane network element may be a PDN gateway userplane function (PGW-U) + UPF, and the network element corresponding to the first session management network element may be a PDN gateway control plane function (PGW-C) + SMF. The network element or entity corresponding to the second session management network element can be the session management function (SMF)1, the network element or entity corresponding to the second user plane network element can be the user plane function (UPF)1, the network element or entity corresponding to the source access network device can be gNB, the network element or entity corresponding to the destination access network device can be eNB, the network element or entity corresponding to the first mobility management network element can be the access and mobility management function (AMF), the network element or entity corresponding to the second mobility management network element can be the mobility management entity (MME), the policy control network element can be the policy control function (PCF), the network element or entity corresponding to the network exposure function network element can be the network exposure function (NEF), the network element or entity corresponding to the network slice selection network element can be the network slice selection function, and the network element or entity corresponding to the network storage network element can be NRF, UDR, or UDM. Here, "+" indicates co-location. For example, in PGW-U+UPF, UPF is the user plane function of the first network, and PGW-U is the gateway user plane function of the second network; in PGW-C+SMF, SMF is the session management function of the first network, and PGW-C is the gateway control plane function in the second network corresponding to SMF. In the embodiments of this application, the network device after co-location can also be called by other names, and the embodiments of this application do not specifically limit it.

[0116] Optionally, the first session management network element and the application server in the embodiments of this application may also be referred to as communication devices, which may be a general-purpose device or a special-purpose device. The embodiments of this application do not specifically limit this.

[0117] Optionally, the functions of the first session management network element or application server in this application embodiment can be implemented by one device, multiple devices, or one or more functional modules within a device. This application embodiment does not specifically limit this. It is understood that the above functions can be network elements in hardware devices, software functions running on dedicated hardware, a combination of hardware and software, or virtualization functions instantiated on a platform (e.g., a cloud platform).

[0118] In practical implementation, the devices in the communication system described above, such as the first session management network element and the application server, can all be adopted. Figure 3 The shown composition structure, or including Figure 3 The components shown. Figure 3 This is a schematic diagram illustrating the composition of a communication device 300 provided in an embodiment of this application. The communication device 300 may include a processor 301, a communication line 302, and a communication interface 303. Furthermore, the communication device 300 may also include a memory 304. The processor 301, memory 304, and communication interface 303 can be connected via the communication line 302.

[0119] Processor 301 may be a central processing unit (CPU), a general-purpose processor, a network processor (NP), a digital signal processor (DSP), a microprocessor, a microcontroller, a programmable logic device (PLD), or any combination thereof. Processor 301 may also be other devices with processing functions, such as circuits, devices, or software modules, without limitation.

[0120] Communication line 302 is used to transmit information between the components included in communication device 300.

[0121] Communication interface 303 is used for communicating with other devices or other communication networks. These other communication networks can be Ethernet, radio access network (RAN), wireless local area networks (WLAN), etc. Communication interface 303 can be a module, circuit, transceiver, or any device capable of enabling communication.

[0122] Memory 304 is used to store instructions. These instructions can be computer programs.

[0123] The memory 304 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and / or instructions; it may also be a random access memory (RAM) or other type of dynamic storage device capable of storing information and / or instructions; it may also be an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs), magnetic disk storage media, or other magnetic storage devices, without limitation.

[0124] It should be noted that the memory 304 can exist independently of the processor 301, or it can be integrated with the processor 301. The memory 304 can be used to store instructions, program code, or some data, etc. The memory 304 can be located inside or outside the communication device 300, without restriction.

[0125] Processor 301 is configured to execute instructions stored in memory 304 to implement the service switching method provided in the following embodiments of this application. For example, when communication device 300 is a session management network element or a chip or system-on-a-chip within a session management network element, processor 301 executes the instructions stored in memory 304 to implement the steps performed by the session management network element in the following embodiments of this application. As another example, when communication device 300 is a mobility management network element or a chip or system-on-a-chip within a mobility management network element, processor 301 can execute the instructions stored in memory 304 to implement the steps performed by the mobility management network element in the following embodiments of this application.

[0126] In one example, processor 301 may include one or more CPUs, for example Figure 3 CPU0 and CPU1 in the CPU.

[0127] As an optional implementation, the communication device 300 includes multiple processors, for example, besides Figure 3 In addition to processor 301, it may also include processor 307.

[0128] As an optional implementation, the communication device 300 also includes an output device 305 and an input device 306. For example, the input device 306 is a device such as a keyboard, mouse, microphone, or joystick, and the output device 305 is a device such as a display screen or speaker.

[0129] It should be noted that the communication device 300 can be a desktop computer, laptop computer, network server, mobile phone, tablet computer, wireless terminal, embedded device, chip system, or something else. Figure 3 Equipment with a similar structure. Furthermore... Figure 3 The structural composition shown does not constitute a limitation on the communication device, except... Figure 3 In addition to the components shown, the communication device may include more or fewer components than illustrated, or combine certain components, or have different component arrangements.

[0130] In this embodiment of the application, the chip system may be composed of chips or may include chips and other discrete devices.

[0131] The following is combined Figure 1b The communication system shown illustrates the service switching method provided in the embodiments of this application. Each network element in the following embodiments may possess... Figure 3 The components shown are not described in detail. It should be noted that the actions, terminology, etc., involved in the various embodiments of this application can be referenced interchangeably without limitation. The message names or parameter names in the messages exchanged between various devices in the embodiments of this application are merely examples; other names can be used in specific implementations without limitation. For example, multicast described in the embodiments of this application can be replaced with broadcast, multicast, multicast communication, multicast / broadcast, etc. Determining in the embodiments of this application can also be understood as creating or generating; "including" in the embodiments of this application can also be understood as "carrying"; "stop" in this application can also be understood as "no longer" or "about to be unable to"; multicast service in this application can also be replaced with group service or broadcast service, etc. This is uniformly stated here, and the embodiments of this application do not specifically limit this.

[0132] Figure 4 This is a flowchart illustrating a service switching method provided in an embodiment of this application. The method describes the process of switching multicast services transmitted via PDU sessions in a first network to transmission via EPS bearers in a second network. Figure 4 As shown, the method includes:

[0133] S401: The first terminal establishes a PDU session.

[0134] The first terminal can be Figure 1bIn the communication system shown, any terminal supporting multicast service transmission, or alternatively, any terminal that can be described as the first terminal, can be any multicast group corresponding to the multicast service. In this application, the PDU session of the first terminal can be called a unicast PDU session. The first terminal can transmit data or signaling with the application server through this PDU session. The anchor point of this PDU session or the user plane network element corresponding to this PDU session can be the first user plane network element, and the session management network element corresponding to this PDU session is the first session management network element. That is, the PDU session can be provided by the first session management network element, such as providing services like PDU session establishment, PDU session modification, and PDU maintenance. For example, assuming the first terminal is terminal 1, in... Figure 1b In the communication system shown, the transmission path of this PDU session is: application server <-> first user plane network element <-> source access network device <-> terminal 1; Figure 2 In the communication system shown, the transmission path of the PDU session is: AS<->PGW-U+UPF<->gNB<->Terminal 1. One or more intermediate UPF (I-UPF) network elements can be inserted between the source access network device (or PGW-U+UPF) and the source access network device (or gNB) along the transmission path of the PDU session; this embodiment does not limit this.

[0135] Specifically, the first terminal can register with the first network through the first mobility management network element (MMI). After registering with the first network, the first terminal sends a PDU session establishment request to the MMI. Upon receiving the PDU session establishment request, the MMI selects the first session management network element and sends the PDU session establishment request to it. After receiving the PDU session establishment request, the first session management network element determines the Quality of Service (QoS) flow (QF), selects the first user plane network element as the anchor point for the PDU session, and establishes the PDU session. The detailed process of establishing a PDU session can be found in existing technologies and will not be elaborated upon here.

[0136] Furthermore, after the first terminal successfully establishes a PDU session, the first mobility management network element can save the correspondence between the identification information of the PDU session and the identification information of the first session management network element. The first session management network element can save the correspondence between the identification information of the PDU session and the identification information of the first user plane network element, for example, by saving the correspondence between the identification information of the PDU session and the identification information of the first user plane network element in the context of the PDU session.

[0137] The identification information of the PDU session can be used to identify the PDU session, and the identification information of the PDU session can be the identifier (ID) of the PDU session. The identification information of the PDU session can be configured by the first terminal and sent to the first mobility management network element and other core network devices in the PDU session establishment request.

[0138] The identification information of the first session management network element can be used to identify the first session management network element. For example, the identification information of the first session management network element can be the Internet protocol (IP) address, the media access control (MAC) address, or the fully qualified domain name (FQDN) of the first session management network element, or other identifiers that can identify the first session management network element, without restriction.

[0139] The first user plane network element can be referred to as the user plane network element corresponding to the PDU session, or it can be described as a UPF that is directly connected to the DN and transmits data of the first terminal, or a UPF that receives data of the first terminal sent by the application server, or a UPF that serves as the N6 interface endpoint for data transmission of the first terminal, or an entry network element of the core network user plane that receives data of the first terminal. The identification information of the first user plane network element can be used to identify the first user plane network element. For example, the identification information of the first user plane network element can be the IP address, MAC address, or FQDN of the first user plane network element, or other identifiers that can identify the first user plane network element, without limitation.

[0140] S402: The first terminal joins the multicast session corresponding to the multicast service.

[0141] Multicast services can be directed to multiple terminals (two or more terminals), and the data recipients for a multicast service can be two or more terminals. For example, when a multicast service is directed to multiple terminals in a group, all terminals in that group can be authorized to receive the multicast service data. A multicast group can be a combination of multiple terminals receiving the same multicast service data, such as a convoy receiving orders from the same command center or a group of users receiving the same television program. When the multicast service is a broadcast service, broadcast service data can be sent to multiple terminals via broadcast. In this case, the multiple terminals receiving the broadcast service data do not need to be authorized to receive the multicast service data.

[0142] A multicast session, also known as a multicast PDU session or multicast broadcast session, serves as a logical channel for transmitting multicast service data. Through this session, multicast service data can be sent to terminals within a multicast group. The transmission path of a multicast session can include the transmission path between the user plane network element corresponding to the multicast session and the source access network device, as well as the transmission path between the source access network device and the first terminal. Multicast sessions can be provided by a multicast session management network element, which can select the user plane network element corresponding to the multicast session to complete the establishment, modification, and maintenance of the multicast session.

[0143] In this application, the multicast session management network element managing multicast services can be either a first session management network element or a second session management network element, and the first session management network element and the second session management network element are different. For example, if the first session management network element has the function of managing multicast services, then the first session management network element can be used as the session management network element corresponding to the multicast session; if the first session management network element does not have the ability to manage multicast services, and the second session management network element does have the function of managing multicast services, then the second session management network element can be used as the session management network element corresponding to the multicast session. The anchor point of the multicast session or the user plane network element corresponding to the multicast session can be either a first user plane network element or a second user plane network element, and the first user plane network element and the second user plane network element are different. For example, if the first user plane network element has the function of transmitting multicast service data (for example, the first user plane network element can directly obtain multicast service data from the application server), then the first user plane network element can be used as the anchor point of the multicast session; if the first user plane network element does not have the function of transmitting multicast service data, then the second user plane network element can be used as the anchor point of the multicast session.

[0144] For example, assuming the first terminal is terminal 1, if the first user plane network element has the function of transmitting multicast service data, then in Figure 1b In the communication system shown, the transmission path of this multicast session is: application server <-> first user plane network element <-> source access network device <-> terminal, which includes terminal 1. Figure 2 In the system shown, the transmission path for this multicast session is: AS <-> PGW-U+UPF <-> gNB <-> terminal, where the terminal includes terminal 1. If the first user plane network element cannot directly receive multicast service data from the AS, but the second user plane network element can directly receive multicast service data from the AS, then in Figure 1b In the communication system shown, the transmission path of this multicast session is: application server <-> second user plane network element <-> source access network device <-> terminal, which includes terminal 1; Figure 2In the system shown, the transmission path of the multicast session is: AS<->UPF1<->gNB<->Terminal, where the terminal includes Terminal 1. It should be noted that in various embodiments of this application, intermediate user plane network elements may also exist along the transmission path of the multicast session. For example, a first user plane network element may be inserted / deployed as an intermediate user plane network element between the second user plane network element and the source access network device; this is not limited.

[0145] It should be noted that in the various embodiments of this application, a transmission tunnel may be established between the application server and the user plane network element corresponding to the multicast session, or the application server may directly send the multicast service data to the user plane network element corresponding to the multicast session using multicast, without limitation.

[0146] In one possible design, the first terminal can be added to the multicast session when the multicast session is established. For example, when the first terminal is the first terminal to join the multicast session corresponding to the multicast service, and no multicast session has been established before the first terminal joins the multicast session, the first terminal can trigger the establishment of the multicast session and join the multicast session.

[0147] Method 1: The first terminal can initiate a request to establish a multicast session and join the multicast session through the PDU session described in S401. Specifically, this implementation method may include:

[0148] The first terminal sends a join request to the first session management network element corresponding to the PDU session, requesting to join the multicast session. The first session management network element receives the join request, triggers the establishment of the multicast session, and adds the first terminal to the multicast session corresponding to the multicast service. The establishment of the multicast session can be triggered by the first session management network element, and during the process, the first session management network element may need to interact with the session management network element managing the multicast service. For example, if the session management network element managing the multicast service is the second session management network element, the first session management network element selects / determines the second session management network element and obtains relevant information from it, such as the quality of service (QoS) flow information corresponding to the multicast session. Establishing a multicast session may include establishing the transmission path for the multicast session.

[0149] As mentioned above, the transmission path of a multicast session can include the path from the user plane network element corresponding to the multicast session to the source access network device, in order to Figure 1bFor example, the user plane network element corresponding to the multicast session is the second user plane network element, meaning the transmission path of the multicast session is the path between the second user plane network element and the source access network device. Establishing the transmission path between the second user plane network element and the source access network device requires obtaining the tunnel information of the source access network device and configuring the tunnel information of the source access network device into the second user plane network element so that the second user plane network element can use the tunnel to send multicast service data to the source access network device. The transmission path of the multicast session may also include the transmission path between the source access network device and the first terminal. Establishing the transmission path between the source access network device and the first terminal may include: sending the QoS flow information of the multicast session to the source access network device, and requesting the source access network device to configure radio resources for the first terminal so that the multicast service data can be sent from the source access network device to the first terminal.

[0150] In various embodiments of this application, the functions of the first session management network element and the second session management network element differ depending on the method used to establish the multicast session. Taking the session management network element that manages the multicast service as the second session management network element as an example, in one implementation, the first session management network element sends a request message to the second session management network element, requesting to obtain the QoS flow information of the multicast service. The second session management network element receives the request message, sends the QoS flow information of the multicast service to the first session management network element, and the first session management network element sends the QoS flow information to the source access network device, and requests the source access network device to configure the radio resources of the multicast session for the first terminal. In the method of this embodiment, the second session management network element also sends first indication information when sending the QoS flow information to the first session management network element, or the QoS flow information includes the first indication information. It should be noted that the second session management network element determines the QoS flow information of the multicast service based on the first PCC rule. The second session management network element obtains the first PCC rule from the PCF. If the PCF also sends the first indication information when sending the first PCC rule to the second session management network element, then the second session management network element also sends the first indication information when sending the QoS flow information to the first session management network element. The first session management network element receives the tunnel information corresponding to the multicast session from the source access network device. The first session management network element sends this tunnel information to the second session management network element, which then configures the tunnel information on the user plane network element corresponding to the multicast session, i.e., the second user plane network element. In this way, the second user plane network element can use the tunnel information to send data to the source access network device. After receiving the data, the source access network device can use the configured radio resources to send it to the terminal.

[0151] In another implementation, the second session management network element sends the QoS flow information of the multicast service to the source access network device and directly receives the tunnel information corresponding to the multicast session from the source access network device. The second session management network element can trigger the above process after receiving the above request message sent by the first session management network element. Alternatively, the second session management network element can send the QoS flow information to the first session management network element after receiving the above request message, and the first session management network element can be responsible for subsequently notifying the source access network device to configure the radio resources for the multicast session for the first terminal.

[0152] Of course, there may be other methods for establishing multicast sessions, and this application does not limit them.

[0153] In addition, establishing a multicast session may also include: the session management network element managing the multicast service selecting the user plane network element for the multicast service, i.e., the aforementioned second user plane network element, and performing the following process: the session management network element managing the multicast service sending the correspondence between the identification information of the multicast service flow and the QoS flow information (i.e., the Quality of Service Flow Identifier (QFI)) to the second user plane network element; the second user plane network element receiving and storing the correspondence between the identification information of the multicast service flow and the QoS flow information. It should be noted that the multicast service flow described in the embodiments of this application may refer to one or more service flows corresponding to the multicast service, such as: service data flow (SDF).

[0154] If the AS and the second user plane network element adopt a tunneling method, the establishment of a multicast session may also include: the session management network element that manages the multicast service obtains the tunnel information of the second user plane network element and sends the tunnel information of the second user plane network element to the application server; the application server receives and saves the tunnel information of the second user plane network element and establishes a transmission tunnel between the application server and the second user plane network element.

[0155] It should be noted that if the first session management network element itself can manage multicast services, and is thus a session management network element for managing multicast services, then the establishment of a multicast session does not require the participation of the second session management network element; that is, the first session management network element possesses the functions of the second session management network element. In this case, the first session management network element obtains the first PCC rule corresponding to the multicast service. Furthermore, the first PCC rule includes first indication information, or the first session management network element receives the first indication information simultaneously with the first PCC rule.

[0156] The process of the first session management network element selecting / determining the second session management network element is based on existing technology and will not be described in detail here.

[0157] The aforementioned joining request may include identification information of the multicast service flow, identification information of the first terminal, identification information of the PDU session, and other information, without limitation. The identification information of the multicast service flow can be used to uniquely identify the multicast service, and can be configured by the application layer or application server of the first terminal. The identification information of the multicast service flow may be the temporary mobile group identifier (TMGI) of the multicast session corresponding to the multicast service, or the Internet Protocol (IP) address of the application server providing the multicast service, or the service identifier (serviceID) of the multicast service, or the packet filter information of the multicast service, or the service data flow (SDF) identification rules of the multicast service, or the ID of the multicast session used to transmit the multicast service.

[0158] The identification information of the first terminal can be used to identify the first terminal. The identification information of the first terminal may include the IP address, MAC address, International Mobile Subscriber Identity (IMSI), Globally Unique Temporary UE Identity (GUTI), Subscription Permanent Identifier (SUPI), Generic Public Subscription Identifier (GPSI), etc.

[0159] For example, when the first terminal determines to join a multicast session, it sends a join request to the first session management network element corresponding to the PDU session. The process of the first terminal determining to join the multicast session may include: receiving a user's instruction to join a specific multicast session, selecting a multicast service of interest from a locally stored multicast service list, and determining to join the multicast session corresponding to that service. For instance, the first terminal may display the multicast service list to the user, who can then select a multicast service of interest from the list via a human-machine interface. The first terminal then determines to join the multicast session corresponding to that service based on the user's selection.

[0160] The multicast service list can include information about one or more multicast services, such as service identifiers. The multicast service list can be pre-configured on the first terminal or dynamically configured to the first terminal by the network side. For example, assuming the multicast service list can include information about multicast sessions, such as TV programs like CCTV1 and CCTV2, and the first terminal is a set-top box (STB) 1, STB1 can display the relevant information of these TV programs to the user. The user can manually select the TV program they want to watch, such as selecting CCTV1, and send the selection result to STB1. Based on the selection result, STB1 sends a join request carrying the identifier information of CCTV1 to the first session management network element.

[0161] The first terminal sending a join request to the first session management network element corresponding to the PDU session may include either Example 1 or Example 2 below:

[0162] Example 1: The first terminal sends a join request to the first session management network element through the user corresponding to the PDU session.

[0163] For example, the first terminal sends an join request to the source access network device through a PDU session. The source access network device receives the join request and sends it to the first user plane network element. The first user plane network element receives the join request and sends it to the first session management network element. In Example 1, the join request can be a user plane message.

[0164] Example 2: The first terminal sends a join request to the first session management network element through the control interface corresponding to the PDU session.

[0165] For example, the first terminal sends an join request to the first mobility management network element; the first mobility management network element receives the join request and, based on the correspondence between the identification information of the PDU session in the context of the locally stored PDU session and the identification information of the first session management network element, sends the join request to the first session management network element.

[0166] In Example 2, the join request can be a PDU session modification request, a PDU session establishment request, or other control plane signaling.

[0167] Method 2: The application server triggers the addition of the first terminal to the multicast session. Specifically, this process may include:

[0168] The application server sends a message (A) to the first network element to add the first terminal to the multicast session. The first network element then forwards message (A) to the policy control network element, which is the PCF corresponding to the PDU session of the first terminal. Alternatively, the application server can first send message (A) to the NEF, which then sends it to the UDR, and the UDR sends it to the PCF corresponding to the PDU session of the first terminal. Upon receiving message (A), the policy control network element requests the first session management network element to add the first terminal to the multicast session. After receiving the request from the policy control network element, the first session management network element triggers the execution of the process described in Method 1 or Method 2 above to establish the multicast session and add the first terminal to the multicast session, which will not be elaborated further.

[0169] Alternatively, the application server sends a message (B) to the first network element to add the terminal to the multicast session. The terminal includes the first terminal, but may also include all terminals in the aforementioned terminal list. Upon receiving message (B), the first network element can send it to the policy control network elements corresponding to all terminals in the terminal list. For example, the application server can first send message (B) to the NEF, and then the NEF can send it to the PCFs corresponding to all terminals in the terminal list. Taking the first terminal as an example, the message (B) is also sent to the PCF corresponding to the first terminal's PDU session. Subsequently, upon receiving message (B), the PCF corresponding to the first terminal's PDU session requests the first session management network element to execute the process described in Method 1 or Method 2 to establish a multicast session and add the first terminal to the multicast session. This process will not be elaborated further.

[0170] In either Method 1 or Method 2 above, the session management network element managing the multicast service needs to determine the QoS flow information of the multicast session. Specifically, determining the QoS flow information of the multicast session by the session management network element may include: obtaining a first policy and charging control (PCC) rule from the policy control network element, and determining the QoS flow information corresponding to the multicast service based on the obtained first PCC rule. The process by which the policy control network element determines the first PCC rule is as follows:

[0171] The application server sends the first description information of the multicast service to the policy control network element (such as the PCF). Upon receiving the first description information, the policy control network element formulates the first PCC rule for the application server to send the multicast service data via multicast based on the first description information. It should be noted that the application server can send the first description information directly to the policy control network element, or it can send the first description information to the policy control network element through another first network element. For example, the application server can send the first description information to the NEF, which will then save it to the UDR. The PCF can then retrieve the first description information from the UDR, or the UDR can push the first description information to the PCF.

[0172] The first description information of the multicast service specifies the transmission requirements when the application server sends data for the multicast service via multicast. This first description information may include: information about one or more service data flows (SDFs) of the multicast service sent by the application server via multicast, and the corresponding quality of service (QoS) requirements (such as bandwidth requirements, latency requirements, error rate, etc.). In addition, the first description information may also include one or more of the following: communication area, start and / or end time of sending data for the multicast service via multicast, and application server address information. If the multicast service supports switching to a second network (such as 4G), the first description information also includes first indication information, which can be used to indicate the service support status of the multicast service (such as whether switching the multicast service to a second network is allowed).

[0173] The first PCC rule can include at least one SDF corresponding to the multicast service when the application server sends the multicast service using multicast, and the QoS parameters (e.g., bandwidth size, latency budget, error rate, etc.) of each SDF. If the first description information includes first indication information, the first PCC rule can also include the aforementioned first indication information and other information, without limitation. Specifically, the relevant description of the first PCC rule can refer to the existing technology and will not be repeated here. The QoS flow information determined according to the first PCC rule can include the identifiers of one or more Quality of Service flows (QFs), the QoS parameters of each QF, etc. The identifier of the QF can be a 5G QoS flow identifier (5QI) or a 5G QoS ID, etc., without limitation. One or more SDFs corresponding to the multicast service can correspond to one QF. The QoS parameters of the QF can be determined based on the QoS parameters of one or more SDFs corresponding to the QF. For example, the value of the QoS parameters of the QF can be equal to the sum of the values ​​of the QoS parameters of one or more SDFs corresponding to the QF. For example, assuming that the SDF corresponding to multicast service 1 includes SDF1, SDF2, and SDF3, the session management network element that manages the multicast service can map SDF1 and SDF2 to QF1 and SDF3 to QF2.

[0174] It should be noted that, in the embodiments of this application, if the first PCC rule or the first description information includes the first indication information, the session management network element managing the multicast service also sends the first indication information when sending the QoS flow information of the multicast service to the first session management network element, or the session management network element managing the multicast service includes the first indication information in the QoS flow information of the multicast service sent to the first session management network element.

[0175] It should be noted that this application is not limited to establishing a multicast session through either Method 1 or Method 2 alone. It can also combine Method 1 and Method 2 to establish a multicast session. For example, a transmission tunnel between the application server and the second user plane network element can be established first through Method 2, without establishing a transmission tunnel between the source access network device and the second user plane network element. Subsequently, when the first terminal requests to establish a multicast session through Method 1, it is not necessary to establish a transmission tunnel between the application server and the second user plane network element. Instead, the establishment of a transmission tunnel between the source access network device and the second user plane network element is sufficient.

[0176] At this point, multicast sessions have been successfully established between the application server and the second user plane network element, between the second user plane network element and the source access network device, and between the source access network device and the first terminal, with the first terminal successfully added to the multicast session. Subsequently, the application server can send multicast service data to the second user plane network element based on its identification information. The second user plane network element receives and identifies the multicast service data sent by the application server and sends it to the source access network device via a QoS stream. The source access network device then uses the air interface transmission resources corresponding to the QoS stream information to send the multicast service data to the first terminal that has joined the multicast session.

[0177] In another possible design, the multicast session has already been established / is ready to be established before the first terminal joins the multicast session. In this case, it is not necessary to establish the multicast session again by executing Method 1 and / or Method 2. In this case, corresponding to Method 1 or Method 2, it is only necessary to notify the source access network device to allocate the radio resources corresponding to the multicast session for the first terminal. For details, please refer to the description of Method 1 or Method 2.

[0178] Optionally, after or during the execution of S402, the network-side device may also notify the application server that the first terminal has joined the multicast session. For example, in one implementation, the application server may send a first subscription request to the first network element, requesting notification of a first event, which is that a terminal has joined the multicast session, including the first terminal. Exemplarily, the first subscription request may be sent to the first network element along with first description information (i.e., in a single message). Subsequently, after or during the execution of S402 to add the first terminal to the multicast session, the session management network element (such as the first session management network element or the second session management network element) may send a first event notification to the application server. This first event notification is used to notify the application server that the first terminal has joined the multicast session. The first event notification may include the identification information of the first terminal, such as the IP address of the first terminal. Furthermore, the application server can send second description information for formulating the second PCC rule to the first network element. The first network element then sends the second description information to the policy control network element, so that the policy control network element can formulate the second PCC rule based on the second description information and trigger the first session management network element to establish the EPS bearer context according to the second PCC rule. In this way, the application server can know which terminals have joined the multicast session, so that the application server can send the second description information corresponding to the terminals that have joined the multicast session to the first network element. This allows the core network to further determine the second PCC rule and the EPS bearer context information corresponding to the multicast service of the terminal based on the second description information, making it possible to switch the multicast service to the second network.

[0179] The descriptions of the second description information and the second PCC rule can be found in S403. It should be noted that in S402, when the application server sends the second description information to the policy control network element through the first network element, it can also instruct that radio resources not be allocated according to the second description information. That is, when the first terminal moves from the first network to the second network, the radio resources carried by EPS will be allocated according to the second PCC rule corresponding to the second description information. In other words, the second description information is only used to formulate the second PCC rule and trigger the core network device to determine the context information of the EPS bearer for multicast services according to the second PCC rule. The core network device does not actually allocate radio resources carried by EPS in the second network or radio resources in the first network to the first terminal according to the second description information.

[0180] S403: The first session management element determines the context of the EPS bearer corresponding to the multicast service.

[0181] The EPS bearer can be a logical channel in the second network used to transmit data for multicast services. The context of the EPS bearer can include at least the identifier of at least one EPS bearer corresponding to the multicast service and the QoS parameters of the EPS bearer. It can also include other information, such as the downlink tunnel information of the first user plane network element, etc., without limitation.

[0182] In one example, the first session management network element is a session management network element that manages multicast services. During the process of adding a first terminal to a multicast session, the first session management network element can determine the context of the EPS bearer corresponding to the multicast service according to the first PCC rule. For example, during the process of the first terminal joining the multicast session, if the first session management network element determines that the multicast service should be switched to the second network, it will trigger the first session management network element to determine the context of the EPS bearer corresponding to the multicast service according to the first PCC rule. It should be noted that in this example, the first session management network element can be a session management network element that manages multicast services.

[0183] The first session management network element can determine whether to allow the multicast service to switch to the second network based on the aforementioned first indication information. The first indication information may be included in the first PCC rule, and the first session management network element can obtain the first indication information from the first PCC rule. For example, the policy control network element can send the first indication information when sending the first PCC rule to the first session management network element, that is, send the first PCC rule and the first indication information to the first session management network element in one message. Alternatively, if the first PCC rule does not contain the first indication information, the first session management network element can also obtain the first indication information from other sources, such as storing it in the subscription information of the first terminal. The first session management network element can obtain the first indication information from the subscription information of the first terminal. For example, the subscription information of the first terminal may include an identifier of the multicast service that is allowed to switch. The identifier of the multicast service can be used to identify the multicast service. The first session management network element can determine whether to allow the multicast service to switch to the second network based on the subscription information of the first terminal. If the identifier of the multicast service is included in the subscription information of the first terminal, then the multicast service is allowed to switch to the second network.

[0184] In this application, allowing multicast services to switch to the second network can also be described as multicast services being able to be transmitted through either the first network or the second network, without restriction.

[0185] Specifically, the first session management network element determines the context of the EPS bearer corresponding to the multicast service according to the first PCC rule, which may include: the first session management network element maps at least one SDF to at least one EPS bearer according to the QoS parameters of at least one SDF included in the first PCC rule, one or more SDFs can be mapped to one EPS bearer, and at the same time, configures the identifier of the EPS bearer for each EPS bearer, and configures the value of the QoS parameter of each EPS bearer to be equal to the sum of the values ​​of the QoS parameters of all SDFs corresponding to the EPS bearer.

[0186] For example, assuming that the SDF corresponding to multicast service 1 includes SDF1, SDF2, and SDF3, the first session management network element can map SDF1 and SDF2 to EPS bearer 1 and map SDF3 to EPS bearer 2.

[0187] It should be noted that in the example above, the first session management network element obtains the first PCC rule. For example, if the first session management network element has the functionality of the second session management network element, the first session management network element will obtain the first PCC rule.

[0188] In another example, the first session management network element is not the session management network element managing multicast services, while the second session management network element is. The first session management network element can determine the context of the EPS bearer corresponding to the multicast service based on the QoS flow information of the multicast service during the process of the first terminal joining the multicast session. For example, if the first session management network element determines that the multicast service should be switched to the second network during the process of the first terminal joining the multicast session, it will be triggered to determine the context of the EPS bearer corresponding to the multicast service based on the QoS flow information.

[0189] The first session management network element can obtain QoS flow information from the second session management network element.

[0190] In this scenario, the first session management network element can determine whether to allow the multicast service to switch to the second network based on the first indication information. For example, the first session management network element can obtain the first indication information from the second session management network element, such as obtaining the first indication information when acquiring QoS flow information, or the QoS flow information includes the first indication information; alternatively, the first session management network element can also obtain the first indication information from other network elements, such as obtaining the subscription information of the first terminal carrying the first indication information from other network elements, and determining whether to allow the multicast service to switch to the second network based on the subscription information of the first terminal. Specifically, this method can be described in the description of one example above.

[0191] Specifically, the first session management network element's determination of the EPS bearer context corresponding to the multicast service based on QoS flow information may include: The first session management network element maps one or more QoS flows to one or more EPS bearers based on the QoS flow information of the multicast service. One or more QoS flows can be mapped to one EPS bearer. Simultaneously, it configures an EPS bearer identifier for each EPS bearer and configures the QoS parameter value of each EPS bearer to be equal to the sum of the QoS parameter values ​​of all QoS flow bearers corresponding to that EPS bearer. Here, the multicast service corresponds to one or more QoS flows, one or more SDFs of the multicast service can be mapped to those one or more QoS flows, and one or more SDFs can be mapped to one QoS flow.

[0192] For example, assuming that the SDF corresponding to multicast service 1 includes SDF1, SDF2, and SDF3, and SDF1 and SDF2 are mapped to QoS flow 1 and SDF3 is mapped to QoS flow 2, then the first session management network element can map QoS flow 1 and QoS flow 2 to EPS bearer 1; or, map QoS flow 1 to EPS bearer 1 and QoS flow 2 to EPS bearer 2.

[0193] In another example, the first session management network element can obtain a second PCC rule from the policy control network element after the first terminal joins the multicast session or during the process of the first terminal joining the multicast session, and determine the context of the EPS bearer corresponding to the multicast service based on the second PCC rule. For example, when the first session management network element learns / discovers that the first terminal has joined the multicast session, the first session management network element sends a first event notification to the application server. The application server receives the first event notification and sends second description information to the first network element. The policy control network element formulates a second PCC rule based on the second description information and sends it to the first session management network element. The first session management network element receives the second PCC rule and determines the context of the EPS bearer corresponding to the multicast service based on the second PCC rule.

[0194] Specifically, the first session management network element determines the context of the EPS bearer corresponding to the multicast service according to the second PCC rule, which may include: the first session management network element maps at least one SDF included in the second PCC rule to one or more EPS bearers, one or more SDFs can be mapped to one EPS bearer, and at the same time, configures the EPS bearer identifier for each EPS bearer, and configures the QoS parameter value of each EPS bearer to be equal to the sum of the QoS parameter values ​​of all SDFs corresponding to that EPS bearer.

[0195] The second PCC rule can be determined by the policy control network element based on the second description information of the multicast service. The second description information of the multicast service can be used to specify the transmission requirements when the application server sends the multicast service data via unicast. The second description information of the multicast service may include: description information of one or more SDFs corresponding to the multicast service, and the QoS requirements (such as bandwidth requirements, latency requirements, error rate, etc.) of each SDF when the application server sends the multicast service via unicast. The second description information of the multicast service may correspond to the first terminal, and may also include the address information of the first terminal, such as the IP address of the first terminal.

[0196] For example, after determining that the first terminal has joined the multicast session, the application server can send second description information to the policy control network element. In one implementation, the application server receives a first event notification, which is used to notify the first terminal that it has joined the multicast session. Upon receiving this notification, the application server determines that the first terminal has joined the multicast session and sends the second description information corresponding to the multicast service to the first network element. The first session management network element can send the first event notification to the application server during the process of the first terminal joining the multicast session.

[0197] In this application, the first network element can be any one of the following: a network open function network element, a network storage network element, a policy control network element, and a first session management network element. The first network element can also be described as a core network element. The network open function network element can be NEF, the network storage network element can be UDM, UDR, or URF, and the policy control network element can be PCF.

[0198] Optionally, the first session management network element includes the context of the EPS bearer corresponding to the multicast service in the context information of the EPS bearer corresponding to the PDU session, and saves the correspondence between the PDU session identifier and the context information of the EPS bearer.

[0199] Further optionally, after the first session management network element determines the context of the EPS bearer corresponding to the multicast service, the first session management network element sends the identifier of the EPS bearer corresponding to the multicast service and the QoS parameters corresponding to the EPS bearer to the source access network device, and / or, the first session management network element sends the identifier of the EPS bearer corresponding to the multicast service to the first terminal. Optionally, the first session management network element may also send a packet filter of the EPS bearer to the terminal, the packet filter being used to match the data packets of the multicast service to the EPS bearer.

[0200] S404: The source access network device determines that the first terminal has been switched and sends a switch request to the first mobility management network element.

[0201] Among them, the source access network device can be the access network device in the first network that provides network services to the first terminal.

[0202] The handover (HO) request can be used to request the first terminal to be switched to the second network. The handover request may include the identification information of the first terminal and the identification information of the target access network device, and may also include other information, such as: when the first session management network element sends the context of the EPS bearer to the source access network device, the handover request may also include the identifier of the EPS bearer corresponding to the multicast service, or the identifier of the EPS bearer corresponding to the multicast service and the QoS parameters of the EPS bearer.

[0203] For example, the source access network device can carry the identifier of the EPS bearer corresponding to the multicast service, or the identifier of the EPS bearer corresponding to the multicast service and the QoS parameters of the EPS bearer in a container. This container is transparent to the first mobility management network element. The first mobility management network element cannot parse the information carried in the container. It only needs to transmit the container to the target access network device through the second mobility management network element.

[0204] The identification information of the target access network device can be used to identify the target access network device, which can be the access network device in the second network that provides network services to the first terminal.

[0205] S405: The first mobility management element receives the handover request and sends the first message to the first session management element.

[0206] The first message can be used to request the context information of the EPS bearer corresponding to the PDU session, and can also be used to instruct the first terminal to switch to the second network where the target access network device is located.

[0207] S406: The first session management network element receives the first message and sends the context information of the EPS bearer to the first mobility management network element.

[0208] In one example, the first session management network element can send the context information of the EPS bearer corresponding to the PDU session to the first mobility management network element. The context information of the EPS bearer includes the context of the EPS bearer corresponding to the multicast service. The context of the EPS bearer can, as described above, include the context of at least one EPS bearer corresponding to the multicast service. The context of each EPS bearer includes the identifier of the EPS bearer and the QoS parameters of the EPS bearer, and may also include downlink tunnel information of the first user plane network element corresponding to the EPS bearer, etc.

[0209] Optionally, after receiving the first message, the first session management network element can send a second event notification to the application server. This second event notification can be used to notify the application server that the first terminal is about to switch to the second network, or that the switch to the second network is complete; or it can be used to notify the application server that the first terminal is about to receive multicast service data via EPS bearer; or it can be used to notify the application server that the first terminal is receiving multicast service data via unicast session. Further, after receiving the second event notification, the application server prepares to start sending multicast service data packets to the first user plane network element via unicast, the destination address of which is the address information of the first terminal; or, the application server can still use multicast to send multicast service data packets, which may include multicast service data and the multicast address of the multicast service. Further, after receiving the second event notification, the application server can also send a third message to the first terminal. This third message can be used to notify the first terminal to receive multicast service data via EPS bearer or to notify the first terminal to receive multicast service data via unicast session. In this way, the application server can begin preparing to send multicast service data via unicast during the process of the first terminal switching from the first network to the second network, avoiding packet loss and ensuring the continuity of data transmission after the first terminal successfully switches to the second network.

[0210] It should be noted that the embodiments of this application are not limited to the timing of sending the second event notification. Optionally, the first session management network element may also send the second event notification to the application server after the first terminal handover is completed, such as sending the second event notification to the application server in S411 below, without limitation.

[0211] The second event notification can be a notification message triggered after a second event occurs. For example, the application server can send a second subscription request to the first session management network element, requesting the first session management network element to notify the application server of the second event. The second event can be the first terminal switching from the first network to the second network, the start of the switch, or the successful switch. This allows the first session management network element to be aware that the first terminal has switched, is about to switch, or has successfully switched, and then send the second event notification to the application server.

[0212] S407: The first mobility management element receives the context information of the EPS bearer and sends the context information of the EPS bearer to the second mobility management element.

[0213] The second mobility management element can be a mobility management element (MME) in the second network that manages the target access network device. For example, the first mobility management element can select the second mobility management element from one or more mobility management elements in the second network that manage the target access network device based on the identification information of the target access network device.

[0214] Furthermore, the first mobility management network element can also send the identification information of the target access network device to the second mobility management network element.

[0215] S408: The second mobility management network element receives the context information of the EPS bearer from the first mobility management network element, and establishes a tunnel for each EPS bearer according to the context information of the EPS bearer.

[0216] The tunnel carried by the EPS can include a tunnel between the first user plane network element and the target access network device. When the serving gateway and the first user plane network element are deployed separately, the tunnel carried by the EPS can include: a tunnel between the serving gateway and the first user plane network element, and a tunnel between the serving gateway and the target access network device. When the serving gateway and the first user plane network element are co-located, the tunnel carried by the EPS can include a tunnel between the first user plane network element and the target access network device.

[0217] The following explanation uses the Service Gateway (SGW) as an example, with the SGW and the first user plane network element deployed separately. The second mobility management network element can send a session establishment request to the SGW, which includes the identifier of each EPS bearer and the identifier information of the first session management network element. After receiving the session establishment message, the SGW allocates downlink tunnel information for each EPS bearer according to the EPS bearer's identifier, and in S410, sends the downlink tunnel information of the SGW to the first session management network element according to the identifier information of the first session management network element. The first session management network element then sends the downlink tunnel information of the SGW to the first user plane network element, establishing a tunnel between the first user plane network element and the SGW.

[0218] In this system, the downlink tunnel information of the SGW corresponds to the EPS bearer, with one EPS bearer corresponding to one downlink tunnel information of the SGW. The downlink tunnel information of the SGW is used by the SGW to receive data corresponding to the EPS bearer / data transmitted on the EPS bearer from the first user plane network element. The downlink tunnel information of the SGW can be the SGW's IP address and / or tunnel endpoint identifier (TEID).

[0219] It should be noted that the EPS bearer corresponding to the multicast service described in this application is used to transmit downlink data. In this case, since there is no uplink data on the EPS bearer or it is not used to transmit uplink data, the SGW does not need to allocate uplink tunnel information. However, if the EPS bearer is also used to transmit uplink data, after receiving the session establishment request, the SGW can allocate uplink tunnel information. The uplink tunnel information of the SGW can be used by the SGW to receive data from the EPS bearer from the target access network device. In this case, the context of the EPS bearer also includes the downlink tunnel information of the first user plane network element. Correspondingly, the session establishment request can also include / carry the downlink tunnel information of the first user plane network element, so that the SGW can send the uplink data transmitted on the EPS bearer to the first user plane network element according to the downlink tunnel information of the first user plane network element.

[0220] In this application, downlink data and uplink data are relative concepts. Downlink data can refer to data sent from the application server to the terminal via EPS, while uplink data can refer to data sent from the terminal to the application server via EPS.

[0221] It should be noted that if the service gateway and the first user plane network element are co-located, and the tunnel carried by the EPS includes the tunnel between the first user plane network element and the target access network device, after executing S407, execute S409, and there is no need to execute S408.

[0222] S409: The second mobility management network element requests the target access network device to allocate radio resources for the EPS bearer, and obtains information on the radio resources corresponding to the EPS bearer and the tunnel information of the target access network device from the target access network device.

[0223] Among them, radio resources can be the air interface transmission resources used for transmitting multicast service data between the target access network and the first terminal. The information of the radio resources corresponding to the EPS bearer can be used to indicate the radio resources corresponding to the EPS bearer.

[0224] For example, the second mobility management network element can send the EPS bearer identifier and the corresponding QoS information of the EPS bearer from the context of the EPS bearer obtained from the first mobility management network element to the target access network device. Furthermore, if uplink data exists, it will also send the uplink tunnel information of the SGW to the target access network device. It should be noted that if the handover request sent by the source access network device to the first mobility management network element in S404 carries a container, then the container is also sent by the first mobility management network element to the second mobility management network element, which then sends it to the target access network device. The target access network device allocates radio resources for each EPS bearer based on the container and / or the EPS bearer identifier and the corresponding QoS information of the EPS bearer in the context of the EPS bearer. The target access network device also allocates downlink tunnel information for the EPS bearer. The target access network device carries the information of the radio resources allocated for the EPS bearer in a container and sends the container along with the downlink tunnel information to the second mobility management network element.

[0225] Specifically, the downlink tunnel information of the target access network device corresponds to the EPS bearer. One EPS bearer corresponds to one downlink tunnel information of the target access network device. The downlink tunnel information of the target access network device is used by the target access network device to receive data corresponding to the EPS bearer / data transmitted on the EPS bearer. The downlink tunnel information of the target access network device can be the IP address and / or TEID of the target access network device.

[0226] The aforementioned wireless resource information can be used to instruct the target access network equipment on the wireless resources allocated to the EPS bearer.

[0227] Furthermore, after the above process is completed, the second mobility management network element can send a transparent container carrying information about the radio resources allocated by the target access network device for the EPS bearer to the source access network device through the first mobility management network element. The source access network device then configures the first terminal based on this transparent container, such as by sending the transparent container to the first terminal in a handover command (HO command). After receiving the information about the radio resources allocated by the target access network device for the EPS bearer, the first terminal accesses the target access network device according to the information about the radio resources allocated by the target access network device. After the target access network device detects the access of the first terminal, it sends a notification message to the second mobility management network element, notifying the second mobility management network element that the first terminal has accessed from the target access network device.

[0228] S410: The second mobility management network element sends a second instruction message to the first session management network element.

[0229] The second indication information can be used to indicate whether the first terminal has completed the handover or the handover was successful.

[0230] In one example, when the SGW is deployed independently, the second mobility management network element can send a second indication message to the first session management network element through the SGW. For instance, the second mobility management network element sends a second indication message to the SGW, which includes a handover indication indicating that the first terminal's handover is complete or successful. After receiving the second indication message, the SGW sends a message to the first session management network element indicating that the first terminal's handover is complete, such as a seventh indication message. The seventh indication message also includes a handover indication indicating that the first terminal's handover is complete or successful. It should be noted that the seventh indication message and the second indication message can be different types of messages; both can indicate that the first terminal's handover is complete or successful. For example, both the seventh and second indication messages can carry a handover indication indicating that the first terminal's handover is complete.

[0231] The second indication information may include downlink tunnel information of the target access network device, so that the SGW can obtain and save the downlink tunnel information of the target access network device from the second indication information, establish a tunnel between the SGW and the target access network device, and send the data transmitted on the EPS bearer to the target access network device according to the downlink tunnel information of the target access network device.

[0232] The seventh indication information may include downlink tunnel information allocated by the SGW for each EPS bearer, such as the downlink tunnel information of the SGW. The first session management network element sends the received downlink tunnel information of the SGW to the first user plane network element so that the first user plane network element can receive and save the downlink tunnel information of the SGW, establish a tunnel between the SGW and the first user plane network element, and send the data transmitted on the EPS bearer to the SGW according to the downlink tunnel information of the SGW.

[0233] In another example, when the SGW's user plane function is co-located with the user plane network element and its control plane function is co-located with the first session management network element (i.e., the SGW is integrated with other network elements and the SGW is not present in the communication system), the second mobility management network element can directly send the second indication information to the first session management network element. In this case, the second indication information may include downlink tunnel information of the target access network device. The first session management network element sends the received downlink tunnel information of the target access network device to the first user plane network element, so that the first user plane network element receives and stores the downlink tunnel information of the target access network device, establishes a tunnel between the target access network device and the first user plane network element, and sends the data transmitted on the EPS bearer to the target access network device based on the downlink tunnel information of the target access network device.

[0234] S411: The first session management network element receives the second instruction information or the seventh instruction information and sends the second message to the first user plane network element.

[0235] In one example, when the first user plane network element is the anchor point corresponding to a multicast session, the second message may include a first mapping relationship between the identification information of the multicast service flow and the tunnel information of the EPS bearer (i.e., the downlink tunnel information of the SGW or the downlink tunnel information of the target access network device). The identification information of the multicast service flow is used to identify the multicast service flow. The first mapping relationship can be used to instruct the first user plane network element to send multicast service data through the EPS bearer corresponding to the multicast service. Further, the first user plane network element receives and saves the first mapping relationship. At this point, a transmission tunnel for transmitting multicast service data between the application server and the first user plane network element, and between the first user plane network element and the SGW / target access network device, is successfully established. Subsequently, after the application server sends the multicast service data packets to the first user plane network element, the first user plane network element sends the received data to the SGW / target access network device through the corresponding EPS bearer according to the first mapping relationship.

[0236] In another example, where the first user plane network element is not the anchor point corresponding to the multicast session, but the second user plane network element is, the second message may include a second mapping relationship between the identifier of the QoS flow and the tunnel information of the EPS bearer (i.e., the downlink tunnel information of the SGW or the downlink tunnel information of the target access network device). This second mapping relationship can be used to map the QoS flow corresponding to the multicast service to the EPS bearer corresponding to the multicast service. Further, the first user plane network element receives and saves the second mapping relationship. Further still, in this example, the second message is also used to obtain the downlink tunnel information of the first user plane network element. After obtaining the downlink tunnel information of the first user plane network element, the first session management network element sends the downlink tunnel information of the first user plane network element to the second user plane network element. The downlink tunnel information of the first user plane network element is used to establish a tunnel for transmitting multicast service data between the first user plane network element and the second user plane network element. The downlink tunnel information of the first user plane network element may include the IP address and / or the TEID of the first user plane network element.

[0237] It should be noted that, in the embodiments of this application, when the SGW is deployed independently, the tunnel information carried by the EPS is the downlink tunnel information of the SGW; when the SGW is co-located with the first user plane network element, the tunnel information carried by the EPS is the downlink tunnel information of the target access network device.

[0238] The process by which the first session management network element sends downlink tunnel information of the first user plane network element to the second user plane network element may include:

[0239] When the first session management network element can manage the second user plane network element, it directly sends the downlink tunnel information of the first user plane network element to the second user plane network element. When the first session management network element cannot directly manage the second user plane network element, it sends the downlink tunnel information of the first user plane network element to the session management network element that manages the second user plane network element. For example, as mentioned above, if the session management network element managing the second user plane network element is the second session management network element itself, then the first session management network element sends the downlink tunnel information of the first user plane network element to the second session management network element. The second session management network element then sends this tunnel information to the second user plane network element.

[0240] In addition, the session management network element managing the second user plane network element can also send the identification information of the multicast service flow, the QFI corresponding to the identification information of the multicast service flow, and the downlink tunnel information of the first user plane network element corresponding to the identification information of the multicast service flow to the second user plane network element. Here, the identification information of the multicast service flow and the QFI are used to map the service data flow of the multicast service to the QoS flow of the multicast service. When the second user plane network element receives a data packet of the multicast service that matches the identification information of the multicast service flow, the second user plane network element sends the QFI corresponding to the identification information and the data packet together to the first user plane network element through the tunnel corresponding to the tunnel information.

[0241] Furthermore, the second user plane network element can store the correspondence between the multicast service flow identification information, the QFI corresponding to the multicast service flow identification information, and the downlink tunnel information of the first user plane network element. The first user plane network element stores the second mapping relationship. At this point, transmission tunnels for transmitting multicast service data are successfully established between the application server and the second user plane network element, between the second user plane network element and the first user plane network element, and between the first user plane network element and the SGW / target access network device. Subsequently, the application server can send multicast service data packets carrying multicast service flow identification information to the second user plane network element. The second user plane network element, based on the correspondence between the multicast service flow identification information, the QFI, and the downlink tunnel information of the first user plane network element, sends the received data packets and the QFI together to the first user plane network element. After receiving the data packets containing multicast service data transmitted through the tunnel, the first user plane network element, based on the second mapping relationship, the QFI corresponding to the data packet, and the identifier of the EPS bearer, sends the multicast service data to the SGW / target access network device through one or more EPS bearers.

[0242] Furthermore, after receiving the second or seventh instruction information, the first session management network element learns that the first terminal handover is complete or has been successful, and can send a second event notification to the application server. The relevant description of the second event notification can be found in S406 and will not be repeated here.

[0243] Furthermore, after receiving the second event notification, the application server prepares to send data packets containing multicast service information via unicast, with the destination address of the multicast service data packets being the address information of the first terminal; alternatively, the application server may still use multicast to send multicast service data packets, which may include multicast service data and the multicast address of the multicast service. Furthermore, after receiving the second event notification, the application server may also send a third message to the first terminal. This third message can be used to notify the first terminal to receive multicast service data via EPS bearer or to notify the first terminal to receive multicast service data via unicast session. In this way, the application server can begin preparing to send multicast service data after the first terminal's handover is complete, avoiding packet loss and ensuring the continuity of data transmission after the first terminal successfully switches to the second network.

[0244] At this point, the first terminal successfully switched to the second network, connected to the target access network device in the second network, and received multicast service data through the EPS bearer.

[0245] In this application, the target access network device can be an access network device that supports MBMS bearer or an access network device that does not support MBMS bearer. If the target access network device supports transmitting the multicast service data via MBMS bearer, or if there are other access network devices at the location of the first terminal that support sending the multicast service data via MBMS bearer, then the first terminal can switch its multicast service reception from receiving via EPS bearer (i.e., unicast bearer) to receiving via MBMS bearer. The MBMS area can refer to an area that supports receiving the multicast service data via MBMS bearer. The process of switching the first terminal's multicast service reception from receiving via EPS bearer to receiving via MBMS bearer can be referred to in S412 to S414 below:

[0246] S412: The first terminal detects that it has entered the MBMS area of ​​the multicast service.

[0247] For example, the first terminal can obtain the MBMS information corresponding to the multicast service in advance, such as the TMGI of the multicast service. The first terminal can listen to the wireless channel based on the MBMS information corresponding to the multicast service to determine whether the first terminal has entered the MBMS area of ​​the multicast service. If it hears the MBMS information of the multicast service (such as the TMGI of the multicast service) being sent through the MBMS bearer, it is determined that it has entered the MBMS area of ​​the multicast service.

[0248] The MBMS information may include the TMGI of the multicast service, as well as the radio configuration information corresponding to the MBMS bearer and other information. For example... Figure 1bAs shown, the transmission path carried by MBMS is: application server to BMSC, BMSC to MBSC-GW, MBSC-GW to target access network device, and target access network device to first terminal.

[0249] S413: The first terminal sends the first report to the application server.

[0250] The first report can be used to instruct the first terminal to enter the MBMS area corresponding to the multicast service in the second network, and to receive multicast service data through the MBMS bearer in the second network, or to support receiving multicast service data through the MBMS bearer in the second network. The first report may include the identification information of the first terminal.

[0251] For example, the first terminal can send a first report to the application server via the EPS bearer of the first terminal.

[0252] S414: The application server receives the first report and sends the fifth instruction information to the first network element.

[0253] The fifth instruction information can be used to instruct the first terminal to stop receiving multicast service data through the EPS bearer in the second network. This application is not limited to the content of the fifth instruction information; alternatively, the content of the fifth instruction information can also be any of the following: instructing the cessation of sending multicast service data to the first terminal through the EPS bearer; instructing that multicast service data will no longer be sent through the EPS bearer; instructing that the first terminal is receiving multicast service data through the MBMS bearer; instructing the first network element that the first terminal can receive the multicast service data through the MBMS bearer; or instructing that the first terminal no longer needs to receive the multicast service data through the EPS bearer. These instructions involved in the fifth instruction information have the same meaning and can indirectly or directly instruct that multicast service data will no longer be sent to the first terminal through the EPS bearer, but instead be sent through the MBMS bearer. These instructions can be used interchangeably; for example, the fifth instruction information instructing the cessation of receiving multicast service data through the EPS bearer in the second network can be replaced by describing it as instructing the cessation of sending multicast service data through the EPS bearer to the first terminal.

[0254] Furthermore, if the application server receives the first event notification and sends the second description information to the first network element, the fifth indication information can also be used to indicate the deletion of the second description information corresponding to the multicast service. In this case, the fifth indication information is an indication to delete the second description information.

[0255] At this point, the first terminal receives multicast service data in the second network via MBMS.

[0256] Furthermore, if the fifth indication information is used to indicate the deletion of the second description information corresponding to the multicast service, then after receiving the fifth indication information, the first network element can also trigger the policy control network element to delete the second description information and delete the second PCC rule generated based on the second description information. During the process of deleting the second PCC rule, the first network element sends the third indication information to the first session management network element. At this time, for the first session management network element, the third indication information can be used to indicate the deletion of the second PCC rule. The first session management network element deletes / releases the radio resources allocated according to the second PCC rule for transmitting the EPS bearer corresponding to the multicast service. After receiving the third indication information, the first session management network element releases the radio resources used for transmitting the EPS bearer corresponding to the multicast service. Here, deleting the second PCC rule means also deleting / releasing the transmission resources corresponding to the EPS bearer determined according to the second PCC rule, so that the data of the multicast service can no longer be transmitted through the EPS bearer.

[0257] Furthermore, if the fifth indication information is only used to indicate the cessation of sending multicast service data to the first terminal via the EPS bearer (i.e., not used to indicate the deletion of the second description information); or, used to indicate that the first terminal is receiving multicast service data via the MBMS bearer; or, used to indicate that the first terminal can receive data for the multiple services via the MBMS bearer, then the first network element sends a third indication information to the first session management network element. The third indication information can be used to indicate the cessation of sending multicast service data to the first terminal via the EPS bearer; or, used to indicate that the first terminal is receiving multicast service data via the MBMS bearer; or, used to indicate that the first terminal can receive data for the multiple services via the MBMS bearer. Further, the first session management network element determines, based on the third indication information, to stop / no longer send multicast service data to the first terminal via the EPS bearer, and the first session management network element can deactivate the radio resources of the EPS bearer used for transmitting the multicast service data.

[0258] Furthermore, after receiving the third instruction information, the first session management network element sends first configuration information to the first user plane network element. This first configuration information can be used to notify the first user plane network element to stop / no longer send multicast service data to the first terminal via the EPS bearer. Upon receiving the first configuration information, the first user plane network element stops / no longer sends multicast service data to the downlink node corresponding to the EPS bearer, such as the SGW / target access network device, via the EPS bearer. Furthermore, the first configuration information can also be used to instruct the first user plane network element to delete the first mapping relationship or second mapping relationship previously received and saved by the first user plane network element.

[0259] Furthermore, the first terminal is mobile; after moving to the MBMS area, it may move out of the MBMS area, making it unable to receive multicast service data via MBMS. For example, ... Figure 1b As shown, terminal 1 moves out of the MBMS area in the second network and cannot receive multicast service data via MBMS bearer. When the first terminal moves out of the MBMS area, the multicast service data can be switched back to transmission via EPS bearer, specifically including:

[0260] The first terminal detects that it has moved out of the MBMS area and sends a second report to the application server. The second report can be used to instruct the first terminal to move out of the MBMS area of ​​the multicast service, that is, to no longer support receiving multicast service data through the MBMS area in the second network.

[0261] The application server receives the second report from the first terminal and sends a sixth instruction to the first network element. The sixth instruction can be used to instruct the creation of corresponding resources for the first terminal to receive multicast services through EPS bearer or to instruct the first terminal to receive multicast service data through EPS bearer.

[0262] Furthermore, when the fifth instruction information is used to instruct the deletion of the second description information, the sixth instruction information may carry the second description information. That is, the application server can resend the second description information to the first network element to request the allocation of corresponding EPS bearer radio resources for multicast service transmission via unicast bearer. For example, after receiving the sixth instruction information, the first network element triggers the policy control network element to formulate a second PCC rule based on the second description information and send a fourth instruction information to the first session management network element. The fourth instruction information may be used to instruct the transmission of multicast service data to the first terminal via EPS bearer or to instruct the creation of corresponding resources for the first terminal to receive multicast services via EPS bearer. In this case, the fourth instruction information may include / is the second PCC rule. Further, the first session management network element determines the EPS bearer required for transmitting the multicast service based on the second PCC rule.

[0263] Alternatively, the sixth indication information may not carry the second description information. After receiving the sixth indication information, the first network element sends the fourth indication information to the first session management network element. The fourth indication information can be used to indicate that multicast service data is sent to the first terminal through the EPS bearer or to indicate that corresponding resources are created for the first terminal to receive multicast services through the EPS bearer. The fourth indication information does not include the second PCC rule. At this time, the first session management network element can determine the EPS bearer required for the multicast service flow according to the first PCC rule stored locally. The first session management network element includes the correspondence between the identification information of the multicast service flow and the tunnel information of the EPS bearer in the second configuration information.

[0264] Furthermore, after receiving the fourth instruction information, the first session management network element sends second configuration information to the first user plane network element. This second configuration information notifies the first user plane network element to transmit multicast service data via the EPS bearer. Upon receiving the second configuration information, the first user plane network element continues / re-transmits the multicast service data via the EPS bearer. Furthermore, the second configuration information can also be used to send a first mapping relationship or a second mapping relationship to the first user plane network element, so that the first user plane network element can transmit the received multicast service data via the EPS bearer corresponding to the multicast service according to the first mapping relationship or the second mapping relationship.

[0265] Furthermore, the first session management network element can also notify the SGW and the access network equipment accessed by the first terminal in the second network to allocate resources for the EPS bearer of the multicast service. For details, please refer to existing technologies, which will not be elaborated here.

[0266] During the processes described in steps S412 to S414 above, after the first terminal moves to the MBMS area of ​​the multicast service, the first terminal sends a first report to the application server. This triggers the application server to notify the first session management network element, through the first network element, to stop / no longer transmit multicast service data via the EPS bearer, delete the radio resources of the EPS bearer, and switch from transmitting multicast service data via the EPS bearer to transmitting multicast service data via the MBMS bearer. In other words, the application server triggers the first session management network element to switch between the EPS bearer and the MBMS bearer. Furthermore, when the first terminal moves out of the MBMS area, the application server is triggered to notify the first session management network element to stop / no longer transmit multicast service data via the MBMS bearer and switch to transmitting multicast service data via the EPS bearer.

[0267] Alternatively, this application also provides a method in which, when the first terminal moves to the MBMS area, the first terminal directly sends an indication message to the first session management network element, indicating that it will stop / no longer transmit multicast service data through the EPS bearer and switch to the MBMS bearer to transmit multicast service data, thereby reducing the latency of switching from the EPS bearer to the MBMS bearer. Specifically, this process may include:

[0268] The first terminal detects that it has entered the MBMS area of ​​the multicast service, or the first terminal determines that the data of the multicast service is sent through the EPS bearer (i.e. the EPS bearer connected to the PDN).

[0269] The first terminal sends the eighth instruction information to the first session management network element. Further, the first session management network element receives the eighth instruction information and performs corresponding actions based on it, such as deactivating the radio resources carried by the EPS used to transmit data for the multicast service.

[0270] The eighth indication information can be used to instruct the deletion of the EPS bearer corresponding to the multicast service, or it can be used to instruct the first terminal to receive multicast service data via MBMS. The eighth indication information can be an EPS bearer modification or deletion request message, or it can be carried within an EPS bearer modification or deletion request message. The eighth indication information can carry the identification information of the multicast service, for example, it can carry the TMGI of the multicast service, the multicast address of the multicast service, or the EPS bearer identifier (EBI) of the EPS bearer corresponding to the multicast service.

[0271] In one implementation, the eighth indication information is the EPS bearer modification or EPS bearer deletion request message. In this implementation, the identification information of the multicast service is included in the flow description information to be deleted (such as the packet filter corresponding to the multicast service), or in the EPS bearer identification field of the EPS bearer modification or EPS bearer deletion request message.

[0272] Furthermore, when the first terminal moves out of the MBMS area corresponding to the multicast service again, the first terminal cannot receive the multicast service data through the MBMS bearer. At this time, the first terminal can send a ninth indication message to the first session management network element, indicating to stop / no longer send multicast service data through the MBMS bearer, and switch to the EPS bearer to send multicast service data, thereby reducing the latency of switching from the MBMS bearer to the EPS bearer.

[0273] The ninth instruction information is used to instruct the first terminal to move out of the MBMS area of ​​the multicast service, or for the first terminal to receive the multicast service data via the EPS bearer (i.e., the first terminal cannot receive the multicast service data via the MBMS bearer), or to request the creation of an EPS bearer for the multicast service. The ninth instruction information may include the identifier of the multicast service, for example, it may carry the TMGI of the multicast service, the multicast address of the multicast service, or the EPS bearer identifier (EBI) of the EPS bearer corresponding to the multicast service.

[0274] In one implementation, the ninth indication information may be an EPS bearer allocation or modification request message or may be carried in an EPS bearer allocation or modification request message. The identifier of the multicast service may be included in the flow description information, such as the flow description information including the multicast address of the multicast service and optional source address and optional source and / or destination port numbers.

[0275] based on Figure 4The method allows the first session management network element to determine the context information of the EPS bearer corresponding to the multicast service when the first terminal joins a multicast session. When the first terminal switches networks, the first session management network element sends this context information to the first mobility management network element, which then triggers the second mobility management network element to establish a tunnel for the EPS bearer corresponding to the multicast service. This ensures that when the first terminal switches to the second network, the application server sends multicast service data to the first terminal via the EPS bearer, guaranteeing the continuity of multicast service transmission. Furthermore, when the first terminal moves out of the area corresponding to the EPS bearer to the MBMS area, the transmission of multicast service data via the EPS bearer is stopped, and the transmission is switched to the MBMS bearer, improving data transmission performance.

[0276] The following is combined Figure 2 Taking a 5G network as the first network, a 4G network as the second network, a terminal 1 as the first terminal, a session management network element (PGW+C+SMF) as the first session management network element (PGW-U+UPF) as the first user plane network element (the anchor point for multicast sessions), a session management network element (PGW+C+SMF) for managing multicast services, and the first user plane network element having the function of transmitting multicast service data, a mobility management network element (AMF) as the first mobility management network element (MME) as the second mobility management network element (MME), a source access network device (gNB) as the source access network device (gNB), a target access network device (eNB) as the target access network device (eNB), an independently deployed SGW, an application server (AS), a NEF / PCF as the first network element, and EPS bearers used for transmitting downlink data / EPS bearers corresponding to downlink data, and an AS sending multicast service data via multicast as an example, the following is an example. Figure 4 The method shown will be described in detail.

[0277] Figure 5 A flowchart of a service switching method provided in an embodiment of this application is shown below. Figure 5 As shown, it may include:

[0278] S501: Terminal 1 establishes a PDU session for Terminal 1.

[0279] The transmission path of the PDU session in terminal 1 is: AS<->PGW-U+UPF<->gNB<->Terminal 1. The specific execution process of S501 can be referred to in S401, and will not be repeated here.

[0280] S502: Terminal 1 requests to join the multicast session from PGW-C+SMF. PGW-C+SMF establishes a multicast session (optional) and joins the multicast session corresponding to the multicast service.

[0281] The transmission path for the multicast session is: AS<->PGW-U+UPF<->gNB<->Terminal, where the terminal includes Terminal 1. The specific execution process of S502 can be referred to in S402 and will not be repeated here.

[0282] S503: When PGW-C+SMF joins a multicast session on terminal 1, it determines the context of the EPS bearer corresponding to the multicast service.

[0283] Specifically, PGW-C+SMF can determine the context of the EPS bearer corresponding to the multicast service based on the first PCC rule. The specific execution process of S503 and the relevant description of the EPS bearer can be found in S403 and will not be repeated here.

[0284] S504: gNB determines that terminal 1 has switched from 5G network to 4G network and sends a handover request to AMF.

[0285] The relevant description of the switching request and the specific execution process of S504 can be referred to in S404, and will not be repeated here.

[0286] S505: The AMF receives a handover request, learns from the handover request that terminal 1 has been handed over, and sends a first message to the PGW-C+SMF to request the context information of the EPS bearer corresponding to the multicast service.

[0287] The description of the first message and the specific execution process of S505 can be referred to in S405, and will not be repeated here.

[0288] S506: PGW-C+SMF receives the first message and sends the context information carried by EPS to AMF.

[0289] S506 can be referred to in S406, and will not be repeated here.

[0290] S507: The AMF receives the context information of the EPS bearer and sends the context information of the EPS bearer to the MME.

[0291] S507 can be referred to in S407, and will not be repeated here.

[0292] S508: The MME receives the context information of the EPS bearer and sends a session establishment request to the SGW based on the context information of the EPS bearer, requesting the SGW to establish a tunnel for each EPS bearer.

[0293] The description of the session establishment request and the specific execution process of S508 are the same as those described in S408, and will not be repeated here.

[0294] S509: The SGW allocates downlink tunnel information for the EPS bearer and sends a session establishment response to the MME, which carries the downlink tunnel information of the SGW.

[0295] S510: The MME requests the eNB to allocate radio resources for the EPS bearer and the eNB's downlink tunnel information.

[0296] S510 can be referred to in S409, and will not be repeated here.

[0297] S511: The eNB receives the request from the MME, allocates radio resources for the EPS bearer and allocates downlink tunnel information for the eNB, and sends the radio resource information of the EPS bearer together with the downlink tunnel information of the eNB to the MME in a transparent container.

[0298] S512: The MME receives the transparent container and downlink tunnel information of the eNB from the eNB, and sends the transparent container to the AMF.

[0299] S513: The AMF receives the transparent container from the MME and sends the transparent container to the gNB.

[0300] S514: The gNB receives the transparent container and sends a handover command to Terminal 1. The handover command carries information about the radio resources carried by the EPS.

[0301] S515: Terminal 1 receives a handover command from the gNB, connects to the eNB based on the radio resource information carried by the EPS, and disconnects from the gNB.

[0302] S516: The eNB sends a notification message to the MME, notifying the MME terminal 1 that the handover is complete.

[0303] S517: The MME receives a notification from the eNB and sends a second indication message to the SGW. The second indication message carries a handover indication and contains the downlink tunnel information of the eNB received by the MME in S512.

[0304] S518: The SGW receives the second indication information, saves the downlink tunnel information of the eNB, and sends the seventh indication information to the PGW-C+SMF according to the identification information of the PGW-C+SMF carried in the session establishment request. The seventh indication information also carries a handover indication and the downlink tunnel information of the SGW.

[0305] S519: The PGW-C+SMF receives the seventh indication information, learns that the handover of terminal 1 is complete, and sends a second message carrying the first mapping relationship to the PGW-U+UPF. Accordingly, the PGW-U+UPF receives and saves the first mapping relationship.

[0306] In this embodiment, the AS sends multicast service data packets to the PGW-U+UPF. These data packets include multicast service data and the multicast address. In this case, a single multicast service data packet received by the PGW-U+UPF may be sent to multiple terminals. For example, terminal 2 also establishes an EPS bearer to the PGW-U+UPF and receives the multicast service data packets through this EPS bearer. Therefore, the second message can also be used to instruct the PGW-U+UPF to copy the multicast service data packet after receiving it and send it through the EPS bearer of terminal 1 (i.e., using the downlink tunnel information of the SGW). If terminal 2 is also present, the PGW-U+UPF will also copy the data packet after receiving it and send it through the EPS bearer of terminal 2.

[0307] The description of the first mapping relationship and the specific execution process of S519 are described in S411. In this embodiment, the identification information of the multicast service flow in the first mapping relationship is used to identify the description information of one or more SDFs of the multicast service when the AS sends it in a multicast manner.

[0308] At this point, the transmission path carried by EPS is established as follows: AS<->PGW-U+UPF<->SGW<->eNB<->Terminal 1.

[0309] S520: PGW-C+SMF sends a second event notification to AS.

[0310] The second event notification can be used to notify terminal 1 that it is about to switch to the 4G network or that the switch to the 4G network has been completed. For a detailed description of the second event notification, please refer to [link / reference needed]. Figure 4 As described above, I will not repeat it here.

[0311] S521: AS receives the second event notification and sends a third message to terminal 1. The third message is used to notify terminal 1 to receive multicast service data through EPS bearer.

[0312] Furthermore, AS sends multicast service data packets to PGW-U+UPF, PGW-U+UPF receives the multicast service data packets, and sends the multicast service data packets to terminal 1 via EPS bearer.

[0313] Alternatively, the second event notification described in S520 can also be sent to AS after PGW-C+SMF receives the first message in S506. That is, S520 and S521 can be executed in S506, or sent at any time between S506 and S520, without restriction.

[0314] Subsequently, if terminal 1 moves from the unicast area / EPS bearer area to the MBMS area of ​​the multicast service, then S522 to S526 will be executed.

[0315] S522: Terminal 1 detected that it has entered the MBMS area for multicast services.

[0316] The specific execution process of S522 can be referred to in S412, and will not be repeated here.

[0317] S523: Terminal 1 sends the first report to AS.

[0318] The relevant descriptions in the first report and the specific implementation process of S523 can be referred to S413, and will not be repeated here.

[0319] S524: AS receives the first report and sends the fifth instruction information to NEF / PCF.

[0320] The description of the fifth instruction information can be found in S414. The fifth instruction information can be used to instruct terminal 1 to stop receiving multicast service data through the EPS bearer in the second network, or to notify the cessation of sending multicast service data through the EPS bearer, or to instruct that multicast service data will no longer be sent through the EPS bearer, or to instruct the first terminal to receive multicast service data through the MBMS bearer.

[0321] S525: NEF / PCF receives the fifth instruction information and sends the third instruction information to PGW-C+SMF.

[0322] S526: The PGW-C+SMF receives third indication information, deletes / releases radio resources used for transmitting the EPS bearer corresponding to the multicast service, and sends first configuration information to the first user plane network element. The first configuration information can be used to notify the first user plane network element to stop / no longer transmit multicast service data through the EPS bearer. Upon receiving the first configuration information, the first user plane network element stops / no longer transmits multicast service data to the SGW / target access network device through the EPS bearer. Figure 5 In the illustrated embodiment, the first configuration information can also be used to instruct PGW-U+UPF to delete the first mapping relationship.

[0323] Furthermore, if terminal 1 moves from the MBMS area to the unicast area, causing it to be unable to receive multicast service data via the MBMS bearer, the method further includes: terminal 1 detects that it has moved out of the MBMS area of ​​the multicast service and sends a second report to the AS indicating that terminal 1 has moved out of the MBMS area of ​​the multicast service; the AS receives the second report from terminal 1 and sends a sixth indication message to the NEF / PCF, instructing terminal 1 to receive multicast service data via the EPS bearer. The NEF / PCF receives the sixth indication message and sends a fourth indication message to the PGW-C+SMF; the PGW-C+SMF receives the fourth indication message and sends a second configuration message to the PGW-U+UPF, the second configuration message being used to notify the PGW-U+UPF to send multicast service data via the EPS bearer. After receiving the second configuration message, the PGW-U+UPF continues / re-sends multicast service data via the EPS bearer. Figure 5 In the illustrated embodiment, the second configuration information can also be used to send the first mapping relationship to the PGW-U+UPF. For example, the second configuration information can carry the first mapping relationship so that the PGW-U+UPF can send the received multicast service data packets through the EPS bearer corresponding to the multicast service according to the first mapping relationship.

[0324] The descriptions of the second report, third instruction information, fourth instruction information, fifth instruction information, sixth instruction information, and second configuration information can be found in [reference needed]. Figure 4 As described above, I will not repeat it here.

[0325] based on Figure 5 The method shown allows PGW-C+SMF to determine the context information of the EPS bearer when terminal 1 joins a multicast session. When terminal 1 switches over, the PGW-C+SMF sends this context information to the AMF, which then triggers the MME to establish a tunnel for the EPS bearer. This ensures that when terminal 1 switches to the second network, the AS can send multicast service data to terminal 1 via the EPS bearer, guaranteeing the continuity of multicast service transmission. Simultaneously, when terminal 1 moves out of the area corresponding to the EPS bearer to the MBMS area, the transmission of multicast service data via the EPS bearer is stopped, and the transmission is switched to the MBMS bearer, improving data transmission performance.

[0326] The following is combined Figure 2Taking a 5G network as the first network, a 4G network as the second network, and terminal 1 as terminal 1, the first session management network element is PGW+C+SMF, the first user plane network element is PGW-U+UPF, UPF1 is the anchor point for the multicast session (i.e., the second user plane network element), SMF1 is the session management network element for managing multicast services (i.e., the second session management network element), the first mobility management network element is AMF, the second mobility management network element is MME, the source access network device is gNB, the target access network device is eNB, the SGW is deployed independently, the application server is AS, the first network element is NEF / PCF, EPS bearer is used to transmit downlink data / EPS bearer corresponding downlink data, and AS sends multicast service data through multicast as an example. Figure 4 The method shown will be described in detail.

[0327] Figure 6 A flowchart illustrating a service switching method provided in an embodiment of this application. Figure 6 and Figure 5 The difference is: Figure 5 The PGW-U+UPF can connect directly to the AS, and serves as the downlink entry point for multicast service data. Figure 6 The UPF1 is directly connected to the AS, and the UPF1 serves as the downlink entry point for multicast service data. Figure 6 The session management network element corresponding to the multicast session is SMF1, which manages UPF1. For example... Figure 6 As shown, the service switching method may include:

[0328] S601: Terminal 1 establishes a PDU session for Terminal 1.

[0329] The transmission path of the PDU session in terminal 1 is: AS<->PGW-U+UPF<->gNB<->Terminal 1. The specific execution process of S601 can be referred to in S401, and will not be repeated here.

[0330] S602: Terminal 1 requests to join the multicast session from PGW-C+SMF. PGW-C+SMF triggers SMF1 to establish the multicast session corresponding to the multicast service and join the multicast session corresponding to the multicast service.

[0331] The transmission path for the multicast session is: AS<->UPF1<->gNB<->Terminal, where the terminal includes Terminal 1. The specific execution process of S602 can be referred to in S402 and will not be repeated here.

[0332] S603: When PGW-C+SMF joins a multicast session on terminal 1, it obtains the QoS flow information corresponding to the multicast service from SMF1 and determines the context of the EPS bearer corresponding to the multicast service based on the QoS flow information corresponding to the multicast service.

[0333] The specific execution process of S603 and the relevant description of EPS carrying can be referred to in S403, and will not be repeated here.

[0334] S604: gNB determines that terminal 1 has switched from 5G network to 4G network and sends a handover request to AMF.

[0335] The relevant description of the switching request and the specific execution process of S604 can be referred to in S404, and will not be repeated here.

[0336] S605: The AMF receives a handover request, learns from the handover request that terminal 1 has been handed over, and sends a first message to the PGW-C+SMF to request the context information of the EPS bearer corresponding to the multicast service.

[0337] The description of the first message and the specific execution process of S605 can be referred to in S405, and will not be repeated here.

[0338] S606: PGW-C+SMF receives the first message and sends the context information carried by EPS to AMF.

[0339] S606 can be referred to in S406, and will not be repeated here.

[0340] S607: The AMF receives the context information of the EPS bearer and sends the context information of the EPS bearer to the MME.

[0341] S607 can be referred to in S407, and will not be repeated here.

[0342] S608: The MME receives the context information of the EPS bearer and sends a session establishment request to the SGW based on the context information of the EPS bearer, requesting the SGW to establish a tunnel for each EPS bearer.

[0343] The description of the session establishment request and the specific execution process of S608 are the same as those described in S408, and will not be repeated here.

[0344] S609: The SGW allocates downlink tunnel information for the EPS bearer and sends a session establishment response to the MME, which carries the downlink tunnel information of the SGW.

[0345] S610: The MME requests the eNB to allocate radio resources and downlink tunnel information for the EPS bearer.

[0346] S610 can be referred to in S409, and will not be repeated here.

[0347] S611: The eNB receives the request from the MME, allocates radio resources for the EPS bearer and allocates downlink tunnel information for the eNB, and sends the information of the radio resources of the EPS bearer together with the downlink tunnel information of the eNB to the MME in a transparent container.

[0348] S612: The MME receives the transparent container and the downlink tunnel information of the eNB from the eNB, and sends the transparent container to the AMF.

[0349] S613: The AMF receives the transparent container from the MME and sends the transparent container to the gNB.

[0350] S614: The gNB receives the transparent container and sends a handover command to Terminal 1. The handover command carries information about the radio resources carried by the EPS.

[0351] S615: Terminal 1 receives a handover command from the gNB, connects to the eNB based on the radio resource information carried by the EPS, and disconnects from the gNB.

[0352] S616: The eNB sends a notification message to the MME to notify terminal 1 that the handover is complete.

[0353] S617: The MME receives a notification from the eNB and sends a second indication message to the SGW. The second indication message indicates that the handover of terminal 1 is complete. The second indication message carries the downlink tunnel information of the eNB received by the MME.

[0354] S618: The SGW receives the second indication information, saves the downlink tunnel information of the eNB, and sends the seventh indication information to the PGW-C+SMF according to the identification information of the PGW-C+SMF carried in the session establishment request. The seventh indication information also indicates that the handover of terminal 1 is complete. The seventh indication information carries the downlink tunnel information of the SGW.

[0355] S619: The PGW-C+SMF receives the seventh indication information, learns that the handover of terminal 1 is complete, and sends a second message carrying the second mapping relationship to the PGW-U+UPF. Accordingly, the PGW-U+UPF receives and saves the second mapping relationship.

[0356] The second message is also used to obtain downlink tunnel information of PGW-U+UPF, so that PGW-C+SMF can send the obtained downlink tunnel information of PGW-U+UPF to UPF1 to establish a transmission tunnel between UPF1 and PGW-U+UPF.

[0357] The description of the second mapping relationship and the specific execution process of S619 are the same as those described in S411 and will not be repeated here.

[0358] S620: PGW-C+SMF sends downlink tunnel information of PGW-U+UPF to SMF1.

[0359] S621: SMF1 receives downlink tunnel information from PGW-U+UPF and sends downlink tunnel information from PGW-U+UPF to UPF1. Correspondingly, UPF1 receives and stores the downlink tunnel information from PGW-U+UPF.

[0360] Thus, the transmission path carried by EPS is established as follows: AS<->UPF1<->PGW-U+UPF<->SGW<->eNB<->Terminal 1.

[0361] S622: PGW-C+SMF sends a second event notification to AS.

[0362] The second event notification can be used to notify terminal 1 that it is about to switch to the 4G network or that the switch to the 4G network has been completed. For a detailed description of the second event notification, please refer to [link / reference needed]. Figure 4 As described above, I will not repeat it here.

[0363] S623: AS receives the second event notification and sends a third message to terminal 1. The third message is used to notify terminal 1 to receive multicast service data through EPS bearer.

[0364] Furthermore, AS sends multicast service data to UPF1, UPF1 receives the multicast service data, and sends multicast service data to PGW-U+UPF according to the downlink tunnel information of PGW-U+UPF. PGW-U+UPF receives the multicast service data and sends the multicast service data to terminal 1 through EPS bearer according to the second mapping relationship.

[0365] Alternatively, the second event notification described in S620 can also be sent to AS after PGW-C+SMF receives the first message in S606. That is, S620 and S621 can be executed in S606 or at any time between steps S606 and S621 without restriction.

[0366] Subsequently, if terminal 1 moves from the unicast area / EPS bearer area to the MBMS area of ​​the multicast service, then S624 to S628 will be executed.

[0367] S624: Terminal 1 detected that it has entered the MBMS area for multicast services.

[0368] The specific execution process of S624 can be referred to in S412, and will not be repeated here.

[0369] S625: Terminal 1 sends the first report to AS.

[0370] The relevant descriptions in the first report and the specific implementation process of S625 can be referred to S413, and will not be repeated here.

[0371] S626: AS receives the first report and sends the fifth instruction information to NEF / PCF.

[0372] The description of the fifth instruction information can be found in S414. The fifth instruction information can be used to instruct terminal 1 to stop receiving multicast service data through the EPS bearer in the second network, or to notify the first network element to stop sending multicast service data through the EPS bearer, or to instruct that multicast service data will no longer be sent through the EPS bearer. Figure 6 In the illustrated embodiment, the first configuration information can also be used to instruct PGW-U+UPF to delete the second mapping relationship.

[0373] S627: NEF / PCF receives the fifth instruction information and sends the third instruction information to PGW-C+SMF.

[0374] S628: The PGW-C+SMF receives the third indication information, deletes / releases the radio resources used for transmitting the EPS bearer corresponding to the multicast service, and sends the first configuration information to the first user plane network element. The first configuration information can be used to notify the first user plane network element to stop / no longer transmit multicast service data through the EPS bearer. Upon receiving the first configuration information, the first user plane network element stops / no longer transmits multicast service data to the SGW / target access network device through the EPS bearer.

[0375] Furthermore, if terminal 1 moves from the MBMS area to the unicast area, causing it to be unable to receive multicast service data via the MBMS bearer, the method further includes: terminal 1 detects that it has moved out of the MBMS area of ​​the multicast service and sends a second report to the AS indicating that terminal 1 has moved out of the MBMS area of ​​the multicast service; the AS receives the second report from terminal 1 and sends a sixth indication message to the NEF / PCF, instructing terminal 1 to receive multicast service data via the EPS bearer. The NEF / PCF receives the sixth indication message and sends a fourth indication message to the PGW-C+SMF; the PGW-C+SMF receives the fourth indication message and sends a second configuration message to the PGW-U+UPF, the second configuration message being used to notify the PGW-U+UPF to send multicast service data via the EPS bearer. After receiving the second configuration message, the PGW-U+UPF continues / re-sends multicast service data via the EPS bearer. Figure 6In the illustrated embodiment, the second configuration information can also be used to send the second mapping relationship to the PGW-U+UPF. For example, the second configuration information can carry the second mapping relationship so that the PGW-U+UPF can send the received multicast service data packets through the EPS bearer corresponding to the multicast service according to the second mapping relationship.

[0376] The descriptions of the second report, third instruction information, fourth instruction information, fifth instruction information, sixth instruction information, and second configuration information can be found in [reference needed]. Figure 4 As described above, I will not repeat it here.

[0377] based on Figure 6 The method shown allows the PGW-C+SMF to obtain QoS flow information corresponding to the multicast service from SMF1 when terminal 1 joins a multicast session. Based on this QoS flow information, it determines the context information of the EPS bearer corresponding to the multicast service. When terminal 1 switches over, the PGW-C+SMF sends this context information to the AMF, which then triggers the MME to establish a tunnel for the EPS bearer. This ensures that when terminal 1 switches to the second network, the AS sends multicast service data to the PGW-U+SMF via UPF1, and the PGW-U+SMF then sends the multicast service data back to terminal 1 via the EPS bearer, guaranteeing the continuity of multicast service transmission. Simultaneously, when terminal 1 moves from the area corresponding to the EPS bearer to the MBMS area, it stops sending multicast service data via the EPS bearer and switches to sending multicast service data via the MBMS bearer, improving data transmission performance.

[0378] The following is combined Figure 2 Taking a 5G network as the first network, a 4G network as the second network, and terminal 1 as terminal 1, the first session management network element is PGW+C+SMF, the first user plane network element is PGW-U+UPF, the first user plane network element is the anchor point for multicast sessions, PGW+C+SMF is the session management network element for managing multicast services, the first user plane network element has the function of transmitting multicast service data, the first mobility management network element is AMF, the second mobility management network element is MME, the source access network device is gNB, the target access network device is eNB, the SGW is independently deployed, the application server is AS, the first network element is NEF / PCF, EPS bearer is used to transmit downlink data / EPS bearer corresponding downlink data, and the AS sends multicast service data through unicast as an example. Figure 4 The method shown will be described in detail.

[0379] Figure 7 A flowchart illustrating a service switching method provided in an embodiment of this application. Figure 7 and Figure 5 and Figure 6 The difference is: Figure 7 The PGW+C+SMF determines the context of the EPS bearer based on the second PCC rule corresponding to the multicast service. The AS sends the multicast service data to the PGW-U+UPF via unicast. Figure 5 and Figure 6 The AS in the middle sends multicast service data via multicast. For example... Figure 7 As shown, the service switching method may include:

[0380] S701: Terminal 1 establishes a PDU session for Terminal 1.

[0381] The transmission path of the PDU session in terminal 1 is: AS<->PGW-U+UPF<->gNB<->Terminal 1. The specific execution process of S701 can be referred to in S401, and will not be repeated here.

[0382] S702: The application server sends the first subscription request to the NEF / PCF. The subscription request will notify the AS of the first event. The first event is that a terminal joins the multicast session corresponding to the multicast service. The terminal includes terminal 1.

[0383] The execution order of S701 and S702 is unrestricted; S702 can be executed before or after S701.

[0384] S703: Terminal 1 requests to join the multicast session from PGW-C+SMF. PGW-C+SMF establishes a multicast session and joins the multicast session corresponding to the multicast service.

[0385] In this embodiment, the PGW-C+SMF can obtain a first PCC rule from the PCF, and the first PCC rule includes a first subscription request. It should be noted that this embodiment uses the PGW-C+SMF creating a multicast session as an example. If the multicast session is created by another SMF (e.g., by SMF1), the PGW-C+SMF can obtain the QoS flow information of the multicast service from SMF1, and the first subscription request is included in the response message containing the QoS flow of the multicast service. Alternatively, the PGW-C+SMF may send the identification information of terminal 1 joining the multicast session to SMF1, and SMF1 may send a first event notification corresponding to the first subscription request.

[0386] The transmission path for the multicast session is: AS<->PGW-U+UPF<->gNB<->Terminal, where the terminal includes Terminal 1. The specific execution process of S502 can be referred to in S402 and will not be repeated here.

[0387] S704: PGW-C+SMF determines that terminal 1 has joined the multicast session and sends the first event notification to AS.

[0388] The first event notification is used to notify AS terminal 1 that it has joined the multicast session. The first event notification may carry the address information of terminal 1 and other information. If the first PCC rule includes a first subscription request, the PGW-C+SMF sends the first event notification to the AS. If the response message of the QoS flow including multicast services obtained by the PGW-C+SMF from the PCF includes the first subscription request, the PGW-C+SMF can send the first event notification to the AS, or the PGW-C+SMF can send the identification information of terminal 1 that has joined the multicast session to SMF1, and SMF1 can then send the first event notification to the AS; there is no restriction on this.

[0389] S705: AS receives the first event notification and sends the second description information to PCF via NEF.

[0390] The relevant descriptions of the second descriptive information are as described above and will not be repeated here.

[0391] S706: The PCF receives the second description information and formulates the second PCC rule based on the second description information.

[0392] S707: PGW-C+SMF obtains the second PCC rule from the PCF and determines the context of the EPS bearer corresponding to the multicast service based on the second PCC rule.

[0393] The process by which PGW-C+SMF determines the context of the EPS bearer corresponding to the multicast service according to the second PCC rule can be referred to in S403 and will not be repeated here.

[0394] S708: gNB determines that terminal 1 has switched from 5G network to 4G network and sends a handover request to AMF.

[0395] The relevant description of the switching request and the specific execution process of S708 can be referred to in S404, and will not be repeated here.

[0396] S709: The AMF receives a handover request, learns from the handover request that terminal 1 has been handed over, and sends a first message to the PGW-C+SMF to request the context information of the EPS bearer corresponding to the multicast service.

[0397] The description of the first message and the specific execution process of S709 can be referred to in S405, and will not be repeated here.

[0398] S710: PGW-C+SMF receives the first message and sends the context information of the EPS bearer to AMF.

[0399] S710 can be referred to in S406, and will not be repeated here.

[0400] S711: The AMF receives the context information of the EPS bearer and sends the context information of the EPS bearer to the MME.

[0401] S711 can be referred to in S407, and will not be repeated here.

[0402] S712: The MME receives the context information of the EPS bearer and sends a session establishment request to the SGW based on the context information of the EPS bearer, requesting the SGW to establish a tunnel for each EPS bearer.

[0403] The description of the session establishment request and the specific execution process of S712 are as described in S408 and will not be repeated here.

[0404] S713: The SGW allocates downlink tunnel information for the EPS bearer and sends a session establishment response to the MME, which carries the downlink tunnel information of the SGW.

[0405] S714: The MME requests the eNB to allocate radio resources and eNB downlink tunnel information for the EPS bearer.

[0406] S714 can be referred to in S409, and will not be repeated here.

[0407] S715: The eNB receives the request from the MME, allocates radio resources for the EPS bearer and allocates downlink tunnel information for the eNB, and sends the radio resource information of the EPS bearer along with the downlink tunnel information of the eNB to the MME in a transparent container.

[0408] S716: The MME receives the transparent container and downlink tunnel information of the eNB from the eNB, and sends the transparent container to the AMF.

[0409] S717: The AMF receives the transparent container from the MME and sends the transparent container to the gNB.

[0410] S718: gNB receives the transparent container and sends a handover command to terminal 1. The handover command carries information about the radio resources carried by the EPS.

[0411] S719: Terminal 1 receives a handover command from the gNB, connects to the eNB based on the radio resource information carried by the EPS, and disconnects from the gNB.

[0412] S720: The eNB sends a notification message to the MME to notify terminal 1 that the handover is complete.

[0413] S721: The MME receives a notification from the eNB and sends a second indication message to the SGW. The second indication message indicates that the handover of terminal 1 is complete. The second indication message carries the downlink tunnel information of the eNB received by the MME.

[0414] S722: The SGW receives the second indication information, saves the downlink tunnel information of the eNB, and sends the seventh indication information to the PGW-C+SMF according to the identification information of the PGW-C+SMF carried in the session establishment request. The seventh indication information also indicates that the handover of terminal 1 is complete. The seventh indication information carries the downlink tunnel information of the SGW.

[0415] S723: The PGW-C+SMF receives the seventh indication information, learns that the handover of terminal 1 is complete, and sends a second message carrying the first mapping relationship to the PGW-U+UPF. Accordingly, the PGW-U+UPF receives and saves the first mapping relationship.

[0416] The description of the first mapping relationship and the specific execution process of S723 are as described in S411. It should be noted that, in Figure 7 In the illustrated embodiment, the identification information of the multicast service flow in the first mapping relationship is used to identify the description information of one or more SDFs of the multicast service when the AS sends it in unicast mode.

[0417] At this point, the transmission path carried by EPS is established as follows: AS<->PGW-U+UPF<->SGW<->eNB<->Terminal 1.

[0418] S724: PGW-C+SMF sends a second event notification to AS.

[0419] The second event notification can be used to notify terminal 1 that it is about to switch to the 4G network or that the switch to the 4G network has been completed. For a detailed description of the second event notification, please refer to [link / reference needed]. Figure 4 As described above, I will not repeat it here.

[0420] S725: AS receives the second event notification and sends a third message to terminal 1. The third message is used to notify terminal 1 to receive multicast service data through EPS bearer.

[0421] Furthermore, the AS sends a data packet carrying the address information of terminal 1 and the multicast service data to the PGW-U+UPF. The PGW-U+UPF receives the data packet and sends the multicast service data to terminal 1 through the EPS bearer according to the address information of terminal 1.

[0422] Alternatively, the second event notification described in S724 can also be sent to AS after PGW-C+SMF receives the first message in S710. That is, S724 and S725 can be executed in S710, or at any time between steps S710 and S725, without restriction.

[0423] Subsequently, if terminal 1 moves from the unicast area / EPS bearer area to the MBMS area of ​​the multicast service, then S726 to S730 will be executed.

[0424] S726: Terminal 1 detected that it has entered the MBMS area for multicast services.

[0425] The specific execution process of S726 can be referred to in S412, and will not be repeated here.

[0426] S727: Terminal 1 sends the first report to AS.

[0427] The relevant descriptions in the first report and the specific implementation process of S723 can be referred to S413, and will not be repeated here.

[0428] S728: AS receives the first report and sends the fifth instruction information to NEF / PCF.

[0429] The description of the fifth instruction information can be referred to in S414. The fifth instruction information can be used to instruct terminal 1 to stop receiving multicast service data through the EPS bearer in the second network, or to notify the first network element to stop sending multicast service data through the EPS bearer, or to instruct that multicast service data will no longer be sent through the EPS bearer. The fifth instruction information can be an instruction to delete the second description information.

[0430] S729: NEF / PCF receives the fifth instruction information, deletes the second description information, and sends the third instruction information to PGW-C+SMF.

[0431] The third instruction information may be an instruction to delete the second PCC rule.

[0432] S730: The PGW-C+SMF receives third indication information, deletes the second PCC rule, deletes / releases the radio resources used for transmitting the EPS bearer corresponding to the multicast service, and sends first configuration information to the first user plane network element. The first configuration information can be used to notify the first user plane network element to stop / no longer transmit multicast service data through the EPS bearer. Upon receiving the first configuration information, the first user plane network element stops / no longer transmits multicast service data to the SGW / target access network device through the EPS bearer. Figure 7 In the illustrated embodiment, the first configuration information can also be used to instruct PGW-U+UPF to delete the first mapping relationship.

[0433] Furthermore, if terminal 1 moves from the MBMS area to the unicast area, causing it to be unable to receive multicast service data via the MBMS bearer, the method further includes: terminal 1 detects that it has moved out of the MBMS area of ​​the multicast service and sends a second report to the AS indicating that terminal 1 has moved out of the MBMS area of ​​the multicast service; the AS receives the second report from terminal 1 and sends a sixth indication message to the NEF / PCF, instructing terminal 1 to receive multicast service data via the EPS bearer; the sixth indication message may carry second description information. The NEF / PCF receives the sixth indication message and sends a fourth indication message to the PGW-C+SMF; the fourth indication message may carry a second PCC rule. The PGW-C+SMF receives the fourth indication message and sends second configuration information to the PGW-U+UPF; the second configuration information is used to notify the PGW-U+UPF to send multicast service data via the EPS bearer. After receiving the second configuration information, the PGW-U+UPF continues / re-sends multicast service data via the EPS bearer. Figure 7 In the illustrated embodiment, the second configuration information can also be used to send the first mapping relationship to the PGW-U+UPF. For example, the second configuration information can also carry the first mapping relationship so that the PGW-U+UPF can send the received multicast service data packets through the corresponding EPS bearer according to the first mapping relationship.

[0434] Specifically, the descriptions of the second report, third instruction information, fourth instruction information, fifth instruction information, sixth instruction information, and the second configuration information can be found in [reference needed]. Figure 4 As described above, I will not repeat it here.

[0435] based on Figure 7 The method shown allows the PGW-C+SMF to obtain the second PCC rule corresponding to the multicast service from the PCF after terminal 1 joins the multicast session. Based on the second PCC rule, it determines the context information of the EPS bearer and sends this context information to the AMF when terminal 1 switches over. This allows the AMF to trigger the MME to establish a tunnel for the EPS bearer. When terminal 1 switches to the second network, the AS sends multicast service data to the PGW-U+SMF via unicast, and the PGW-U+SMF then sends the multicast service data to terminal 1 through the EPS bearer, ensuring the continuity of multicast service transmission. Simultaneously, when terminal 1 moves out of the area corresponding to the EPS bearer to the MBMS area, it stops sending multicast service data via the EPS bearer and switches to sending multicast service data via the MBMS bearer, improving data transmission performance.

[0436] The above is alternative. Figures 5-7In any of the embodiments shown, after terminal 1 enters the MBMS area of ​​the multicast service, terminal 1 can directly instruct the PGW-C+SMF to stop receiving multicast service data through the EPS bearer in the second network. For example, with Figure 5 For example, Figure 5 S523 to S525 in the text can be replaced with:

[0437] Step (a): Terminal 1 sends an eighth indication message to PGW-C+SMF. The eighth indication message is used to indicate the deletion of the EPS bearer corresponding to the multicast service, or the eighth indication message is used to indicate that Terminal 1 is receiving the multicast service through MBMS, so that PGW-C+SMF will execute the action shown in S526 after receiving the eighth indication message.

[0438] For a specific description of the eighth instruction information, please refer to [link / reference]. Figure 4 As described above, I will not repeat it here.

[0439] akin, Figure 6 S625 to S627 in the above text can also be replaced by step (a), and Figure 7 S727 to S729 can also be replaced by step (a) as described above. It should be understood that replacing S523 to S525 with step (a) in this embodiment of the application can mean executing steps (a) and S526 after completing S522. Replacing S625 to S627 with step (a) in this embodiment of the application can mean executing steps (a) and S628 after completing S624. Replacing S727 to S729 with step (a) in this embodiment of the application can mean executing steps (a) and S730 after completing S726.

[0440] Furthermore, when terminal 1 moves out of the MBMS area corresponding to the service again, terminal 1 cannot receive the multicast service data through the MBMS bearer. At this time, terminal 1 can send a ninth indication message to the PGW-C+SMF. The ninth indication message is used to instruct terminal 1 to move out of the MBMS area of ​​the multicast service, or terminal 1 needs to receive the multicast service through the bearer (i.e., terminal 1 cannot receive the multicast service through the MBMS bearer), or to request the creation of a bearer for the multicast service, so that the GW-C+SMF can delete the radio resources related to the MBMS bearer according to the ninth indication message and switch to the EPS bearer to transmit the multicast service data.

[0441] For a specific description of the ninth instruction information, please refer to [link / reference]. Figure 4 As described above, I will not repeat it here.

[0442] The above mainly describes the solution provided by the embodiments of this application from the perspective of interaction between various nodes. It is understood that each node, such as the first session management network element and the application server, includes corresponding hardware structures and / or software modules to execute the above functions. Those skilled in the art should readily recognize that, in conjunction with the algorithm steps of the examples described in the embodiments disclosed herein, the methods of the embodiments of this application can be implemented in hardware, software, or a combination of hardware and computer software. Whether a function is executed by hardware or by computer software driving hardware depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0443] This application embodiment can divide the first session management network element and application server into functional modules according to the above method example. For example, each function can be divided into a separate functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware or as a software functional module. It should be noted that the module division in this application embodiment is illustrative and only represents one logical functional division. In actual implementation, there may be other division methods.

[0444] Figure 8 A structural diagram of a communication device 80 is shown. This communication device 80 can be a first session management network element, a chip within the first session management network element, a system-on-a-chip, or other devices capable of implementing the functions of the first session management network element in the above-described method. This communication device 80 can be used to execute the functions of the first session management network element involved in the above-described method embodiments. As one possible implementation, Figure 8 The communication device 80 shown includes: a receiving unit 801 and a transmitting unit 802;

[0445] The receiving unit 801 receives a first message from a first mobility management network element, containing context information carried by the EPS corresponding to a request PDU session. The first mobility management network element is located in a first network, the PDU session is a PDU session of a first terminal, the PDU session is provided by a first session management network element, and the PDU session is associated with a multicast service. For example, the receiving unit 801 supports the communication device 80 in performing the actions of receiving the first message in S406, S506, S606, and S710.

[0446] The sending unit 802 is configured to send context information of the EPS bearer, including the context of the EPS bearer corresponding to the multicast service, to the first mobility management network element according to the first message. For example, the sending unit 802 may support the communication device 80 in performing the actions of sending the context information of the EPS bearer in S406, S506, S606 and S710.

[0447] Further optional, such as Figure 8 As shown, the communication device 80 may also include a processing unit 803.

[0448] The processing unit 803 is configured to obtain a first PCC rule through the receiving unit 801, and map at least one SDF to at least one EPS bearer according to the QoS parameters of at least one SDF included in the first PCC rule to obtain the context of the EPS bearer corresponding to the multicast service; or, map at least one QoS flow corresponding to the multicast service to at least one EPS bearer according to the QoS flow information of the multicast service to obtain the context of the EPS bearer corresponding to the multicast service; or, map at least one SDF corresponding to the multicast service to at least one EPS bearer according to the second PCC rule to obtain the context of the EPS bearer corresponding to the multicast service.

[0449] Optionally, the sending unit 802 is further configured to send a first event notification to the application server, notifying the first terminal to join the multicast session corresponding to the multicast service. The receiving unit 801 is further configured to receive a second PCC rule.

[0450] Optionally, the receiving unit 801 is further configured to receive second indication information indicating that the handover of the first terminal is complete. The sending unit 802 is further configured to send a second message to the first user plane network element, the second message including a first mapping relationship between the identification information of the multicast service flow and the tunnel information carried by the EPS, or the second message including a second mapping relationship between the identifier of the QoS flow and the tunnel information carried by the EPS.

[0451] Further optionally, the sending unit 802 is also used to send a second event notification to the application server, notifying the first terminal that it is about to switch to the second network or that the switch to the second network has been completed.

[0452] Optionally, the receiving unit 801 is further configured to receive third indication information for instructing the cessation of sending multicast service data to the first terminal via the EPS bearer. The sending unit 802 is further configured to send first configuration information to the first user plane network element according to the third indication information, notifying the first user plane network element to stop sending multicast service data to the first terminal via the EPS bearer.

[0453] Optionally, the receiving unit 801 is further configured to receive fourth indication information indicating that data for multicast services is to be sent to the first terminal via the EPS bearer. The sending unit 802 is further configured to send second configuration information to the first user plane network element according to the fourth indication information, notifying the first user plane network element to send data for multicast services to the first terminal via the EPS bearer.

[0454] Specifically, the above Figures 4-7 All relevant content regarding each step in the illustrated method embodiment can be found in the functional descriptions of the corresponding functional modules, and will not be repeated here. The communication device 80 is used to execute... Figures 4-7 The first session management network element in the service switching method shown in the diagram has the same function as the service switching method described above, and therefore can achieve the same effect.

[0455] In this embodiment, the communication device 80 can also be presented in an integrated manner, divided into various functional modules. Here, "functional module" can refer to an application-specific integrated circuit (ASIC), a circuit, a processor and memory executing one or more software or firmware programs, integrated logic circuits, and / or other devices that can provide the above-mentioned functions. In a simple embodiment, those skilled in the art will understand that the communication device 80 can adopt... Figure 3 The communication device 300 shown is in the form of [example device].

[0456] for example, Figure 3 The processor 301 in the communication device 300 shown can execute the service switching method in the above method embodiment by calling the computer execution instructions stored in the memory 304.

[0457] Specifically, Figure 8 The functions / implementation process of the receiving unit 801 and the transmitting unit 802 can be obtained through Figure 3 The processor 301 in the communication device 300 shown calls computer execution instructions stored in the memory 304 to implement the function. Figure 8 The functions / implementation process of the receiving unit 801 and the transmitting unit 802 can be obtained through Figure 3 This is achieved through the communication interface 303 in the communication device 300 shown. Figure 8 The function / implementation process of the processing unit 803 in the middle can be achieved through Figure 3 This is implemented by the processor 301 in the communication device 300 shown.

[0458] Figure 9A structural diagram of a communication device 90 is shown. This communication device 90 can be an application server, a chip within the application server, a system-on-a-chip, or other devices capable of implementing the functions of the application server in the above-described method. This communication device 90 can be used to execute the functions of the application server involved in the above-described method embodiments. As one possible implementation method... Figure 9 The communication device 90 shown includes: a receiving unit 901 and a transmitting unit 902;

[0459] The receiving unit 901 is configured to receive a first report from the first terminal indicating that the first terminal has entered the MBMS area of ​​multicast services in the second network. For example, the receiving unit 901 is configured to support the communication device 90 in performing the actions of receiving the first report in S413, S524, S626, and S728.

[0460] The sending unit 902 is configured to send a fifth indication message to the first network element, indicating to stop sending multicast service data to the first terminal via the EPS bearer in the second network. For example, the sending unit 902 is configured to support the communication device 90 in performing the actions of sending the fifth indication message in S413, S524, S626, and S728.

[0461] The fifth instruction information can also be used to instruct the first network element to delete the second description information corresponding to the multicast service; the sixth instruction information can also include the second description information.

[0462] Optionally, the receiving unit 901 is further configured to receive a second report from the first terminal instructing the first terminal to move out of the MBMS area of ​​the multicast service. The sending unit 902 is further configured to send a sixth indication message to the first network element, instructing the transmission of multicast service data to the first terminal via EPS bearer.

[0463] Optionally, the sending unit 902 is further configured to send data packets including multicast service data and multicast addresses of the multicast service to the first user plane network element via EPS bearer.

[0464] Optionally, the transmitting unit 902 is further configured to transmit data packets, including multicast service data and address information of the first terminal, to the first user plane network element via EPS bearer.

[0465] Optionally, the receiving unit 901 is further configured to receive a second event notification from the first session management network element, which notifies the first terminal that it is about to switch to the second network or that the switch to the second network is complete. The sending unit 902 is further configured to send a third message to the first terminal according to the second event notification, notifying the first terminal to receive multicast service data through the EPS bearer.

[0466] Specifically, the above Figures 4-7All relevant content regarding each step in the illustrated method embodiment can be found in the functional descriptions of the corresponding functional modules, and will not be repeated here. The communication device 80 is used to execute... Figures 4-7 The method shown uses the application server's functionality to achieve the same effect as the aforementioned business switching method.

[0467] In this embodiment, the communication device 90 is presented in an integrated manner, divided into various functional modules. Here, "functional module" can refer to an ASIC, circuitry, a processor and memory executing one or more software or firmware programs, integrated logic circuitry, and / or other devices that can provide the aforementioned functions. In a simplified embodiment, those skilled in the art will recognize that the communication device 90 can employ... Figure 3 The communication device 300 shown is in the form of [example device].

[0468] for example, Figure 3 The processor 301 in the communication device 300 shown can execute the service switching method in the above method embodiment by calling the computer execution instructions stored in the memory 304.

[0469] Specifically, Figure 9 The functions / implementation process of the receiving unit 901 and the transmitting unit 902 can be obtained through Figure 3 The processor 301 in the communication device 300 shown calls computer execution instructions stored in the memory 304 to implement the function. Figure 9 The functions / implementation process of the receiving unit 901 and the transmitting unit 902 can be obtained through Figure 3 This is achieved through the communication interface 303 in the communication device 300 shown.

[0470] This application also provides a computer-readable storage medium. All or part of the processes in the above method embodiments can be implemented by a computer program instructing related hardware. This program can be stored in the computer-readable storage medium, and when executed, it can include the processes of the above method embodiments. The computer-readable storage medium can be a terminal device of any of the foregoing embodiments, such as an internal storage unit including a data sending end and / or a data receiving end, such as a hard disk or memory of the terminal device. The computer-readable storage medium can also be an external storage device of the terminal device, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the terminal device. Further, the computer-readable storage medium can include both the internal storage unit and the external storage device of the terminal device. The computer-readable storage medium is used to store the computer program and other programs and data required by the terminal device. The computer-readable storage medium can also be used to temporarily store data that has been output or will be output.

[0471] This application also provides computer instructions. All or part of the processes in the above method embodiments can be executed by computer instructions to instruct related hardware (such as computers, processors, network devices, and terminals). The program can be stored in the aforementioned computer-readable storage medium.

[0472] It should be understood that in the embodiments of this application, "B corresponding to A" means that B is associated with A. For example, B can be determined based on A. It should also be understood that determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information. Furthermore, the term "connection" in the embodiments of this application refers to various connection methods, such as direct connection or indirect connection, to achieve communication between devices, and the embodiments of this application do not impose any limitations on this.

[0473] Unless otherwise specified, the term "transmission" in the embodiments of this application refers to bidirectional transmission, encompassing the actions of sending and / or receiving. Specifically, "transmission" in the embodiments of this application includes sending data, receiving data, or both sending and receiving data. In other words, data transmission here includes uplink and / or downlink data transmission. Data may include channels and / or signals; uplink data transmission refers to uplink channel and / or uplink signal transmission, and downlink data transmission refers to downlink channel and / or downlink signal transmission. The terms "network" and "system" in the embodiments of this application refer to the same concept; a communication system is a communication network.

[0474] Through the above description of the embodiments, those skilled in the art can clearly understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0475] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0476] The units described as separate components may or may not be physically separate. A component shown as a unit can be one or more physical units; that is, it can be located in one place or distributed in multiple different locations. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0477] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0478] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solutions of this application, in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a device, such as a microcontroller, chip, or processor, to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.

[0479] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A service handover method characterized by comprising: The method further comprises: The first session management network element receives a first message from a first mobility management network element, the first message being used to request context information of an evolved packet system (EPS) bearer corresponding to a protocol data unit (PDU) session, the first mobility management network element being located in a first network, the PDU session being a PDU session of a first terminal, the PDU session being served by the first session management network element, and the PDU session being associated with a multicast service; The first session management network element sends, to the first mobility management network element, the context information of the EPS bearer according to the first message, the context information of the EPS bearer including context of at least one EPS bearer corresponding to the multicast service.

2. The method of claim 1, wherein, The context of the EPS bearer includes context of at least one EPS bearer corresponding to the multicast service, and each context of the EPS bearer includes an identifier of the EPS bearer and a quality of service (QoS) parameter of the EPS bearer.

3. The method according to claim 1 or 2, characterized in that, The method further comprises: The first session management network element determines the context of the EPS bearer corresponding to the multicast service.

4. The method of claim 3, wherein, The first session management network element determining the context of the EPS bearer corresponding to the multicast service comprises: The first session management network element determines that the multicast service is allowed to switch to a second network. The first session management network element determines the context of the EPS bearer corresponding to the multicast service.

5. The method of claim 4, wherein, The method further comprises: The first session management network element receives first indication information, the first indication information being used to indicate that the multicast service is allowed to switch to the second network.

6. The method of claim 3, wherein, The first session management network element determining the context of the EPS bearer corresponding to the multicast service comprises: The first session management network element acquires first policy and charging control (PCC) rules corresponding to the multicast service, the first PCC rules including QoS parameters of at least one service data flow (SDF) corresponding to the multicast service when an application server sends the multicast service in a multicast manner; The first session management network element maps the at least one SDF to the at least one EPS bearer according to the QoS parameters of the at least one SDF.

7. The method of claim 3, wherein, The first session management network element determining the context of the EPS bearer corresponding to the multicast service comprises: The first session management network element maps at least one QoS flow corresponding to the multicast service to the at least one EPS bearer according to QoS flow information of the multicast service; The QoS flow information includes QoS parameters of the at least one QoS flow, and the at least one QoS flow is used to send data of the multicast service in a multicast manner by an application server.

8. The method of claim 7, wherein, The method further comprises: The first session management network element acquires the QoS flow information of the multicast service from a second session management network element, the second session management network element being a session management network element for managing the multicast service.

9. The method of claim 3, wherein, The first session management network element determining the context of the EPS bearer corresponding to the multicast service comprises: The first session management network element maps at least one SDF corresponding to the multicast service to the at least one EPS bearer according to a second PCC rule, the second PCC rule comprising a QoS parameter of at least one service data flow SDF corresponding to the multicast service when the application server sends the multicast service in a unicast manner.

10. The method of claim 9, wherein, The method further comprises: The first session management network element sends a first event notification to the application server, the first event notification being used to notify the first terminal to join a multicast session corresponding to the multicast service; The first session management network element receives the second PCC rule.

11. The method of claim 10, wherein, The method further comprises: The first session management network element receives a first subscription request, the first subscription request being used to request to notify the application server of a first event, the first event being that a terminal joins a multicast session corresponding to the multicast service, the terminal comprising the first terminal.

12. The method of any one of claims 1-2, 4-11, wherein, The method further comprises: The first session management network element receives second indication information, the second indication information being used to indicate that the first terminal completes handover; The first session management network element sends a second message to a first user plane network element, the second message comprising a first mapping relationship between identification information of a multicast service flow and tunnel information of the EPS bearer, the identification information of the multicast service flow being used to identify a multicast service flow corresponding to the multicast service, and the first mapping relationship being used to instruct the first user plane network element to send data of the multicast service through the EPS bearer.

13. The method of any one of claims 1-2, 4-11, wherein, The method further comprises: The first session management network element receives second indication information, the second indication information being used to indicate that the first terminal completes handover; The first session management network element sends a second message to a first user plane network element, the second message comprising a second mapping relationship between identification of a QoS flow and tunnel information of the EPS bearer, the second mapping relationship being used to instruct the first user plane network element to send a data packet corresponding to the QoS flow through the EPS bearer.

14. The method of claim 13, wherein, The second message is further used to obtain downlink tunnel information of the first user plane network element, the downlink tunnel information of the first user plane network element being used to establish a tunnel between the first user plane network element and a second user plane network element for transmitting data of the multicast service, the second user plane network element being used to transmit the multicast service in the first network; The method further comprises: the first session management network element sends the downlink tunnel information of the first user plane network element to the second user plane network element.

15. The method of any one of claims 1-2, 4-11, 14, wherein, The method further comprises: The first session management network element sends a second event notification to an application server, the second event notification being used to notify the first terminal that the first terminal is about to hand over to a second network or has completed handover to the second network.

16. The method of any one of claims 1-2, 4-11, 14, wherein, The method further comprises: The first session management network element sends context information of the EPS bearer to a source access network device; and / or, The first session management network element sends identification of the EPS bearer to the first terminal, or identification of the EPS bearer and a packet filter of the EPS bearer.

17. The method of any one of claims 1-2, 4-11, 14, wherein, The method further comprises: The first session management network element receives third indication information, and the third indication information is used to indicate that the data of the multicast service is stopped from being sent to the first terminal through the EPS bearer. The first session management network element sends first configuration information to a first user plane network element according to the third indication information, and the first configuration information is used to inform the first user plane network element to stop sending the data of the multicast service to the first terminal through the EPS bearer.

18. The method of any one of claims 1-2, 4-11, 14, wherein, The method further comprises: The first session management network element receives third indication information, and the third indication information is used to indicate that the first terminal receives the data of the multicast service through a multicast / broadcast media service (MBMS) bearer. The first session management network element sends first configuration information to a first user plane network element according to the third indication information, and the first configuration information is used to inform the first user plane network element to stop sending the data of the multicast service to the first terminal through the EPS bearer.

19. The method of any one of claims 1-2, 4-11, 14, wherein, The method further comprises: The first session management network element receives eighth indication information from the first terminal, and the eighth indication information is used to indicate that the EPS bearer is deleted or the eighth indication information is used to indicate that the first terminal receives the data of the multicast service through an MBMS bearer. The first session management network element sends first configuration information to a first user plane network element according to the eighth indication information, and the first configuration information is used to inform the first user plane network element to stop sending the data of the multicast service to the first terminal through the EPS bearer.

20. The method of claim 19, wherein, Further comprising: The eighth indication information comprises identification information of the multicast service.

21. The method of any one of claims 1-2, 4-11, 14, 20, wherein, The method further comprises: The first session management network element receives fourth indication information, and the fourth indication information is used to indicate that the data of the multicast service is sent to the first terminal through the EPS bearer. The first session management network element sends second configuration information to a first user plane network element according to the fourth indication information, and the second configuration information is used to inform the first user plane network element to send the data of the multicast service to the first terminal through the EPS bearer.

22. The method of any one of claims 1-2, 4-11, 14, 20, wherein, The method further comprises: An application server receives a first report from the first terminal, and the first report is used to indicate that the first terminal enters a multicast / broadcast media service (MBMS) area of a multicast service in a second network. The application server sends fifth indication information to a first network element, and the fifth indication information is used to indicate that the data of the multicast service is stopped from being sent to the first terminal through an evolved packet system (EPS) bearer in the second network.

23. The method of claim 22, wherein, The method further comprises: The application server receives a second report of the first terminal, and the second report is used to indicate that the first terminal moves out of an MBMS area of the multicast service. The application server sends sixth indication information to the first network element, and the sixth indication information is used to indicate that the data of the multicast service is sent to the first terminal through the EPS bearer.

24. The method of claim 22, wherein, The method further comprises: The application server sends, to a first user plane network element, a data packet of the multicast service through the EPS bearer, the data packet of the multicast service comprising data of the multicast service and a destination address, the destination address comprising a multicast address of the multicast service.

25. The method of claim 24, wherein, The method further comprises: The application server sends, to the first network element, first description information of the multicast service, the first description information being used to formulate a first policy and charging control (PCC) rule, the first PCC rule comprising a QoS parameter of at least one service data flow (SDF) corresponding to the multicast service when the application server sends the multicast service in a multicast manner.

26. The method of claim 25, wherein, The first description information comprises first indication information, the first indication information being used to indicate that the multicast service is allowed to switch to the second network.

27. The method of claim 23, wherein, The method further comprises: The application server sends, to a first user plane network element, a data packet of the multicast service through the EPS bearer, the data packet of the multicast service comprising data of the multicast service and a destination address, the destination address comprising an address of the first terminal.

28. The method of claim 27, wherein The fifth indication information is further used to indicate that the first network element deletes second description information corresponding to the multicast service, the second description information being description information when the multicast service is transmitted through a unicast bearer, and the second description information being used to formulate a second PCC rule corresponding to the multicast service; The sixth indication information comprises the second description information.

29. The method of claim 27 or 28, wherein, The method further comprises: The application server receives a first event notification from the first network element; If the first event notification is used to notify that the first terminal joins a multicast session corresponding to the multicast service, the application server sends, to the first network element, second description information corresponding to the multicast service.

30. The method of claim 29, wherein, The method further comprises: The application server sends, to the first network element, a first subscription request, the first subscription request being used to request that a first event be notified to the application server, the first event being that a terminal joins a multicast session corresponding to the multicast service, the terminal comprising the first terminal.

31. The method of any one of claims 23-28, 30, wherein, The method further comprises: The application server receives a second event notification from a first session management network element, the second event notification being used to notify that the first terminal is about to switch to the second network or has completed switching to the second network; The application server sends, to the first terminal, a third message according to the second event notification, the third message being used to notify the first terminal to receive data of the multicast service through the EPS bearer.

32. The method of claim 31, wherein, The method further comprises: The application server sends, to the first network element, a second subscription request, the second subscription request being used to request that a second event be notified to the application server, the second event being that the first terminal is about to switch to the second network or has completed switching to the second network.

33. A first session management network element, the first session management network element configured to: The first session management network element comprises a module or unit for executing the service switching method of any one of claims 1-21.

34. An application server, characterized by The application server comprises a module or unit for performing the service switching method of any one of claims 22-32.

35. A communication system, characterized by The communication system comprises a first session management network element and a first mobility management network element; The first mobility management network element is configured to send a first message to the first session management network element, the first message being used to request context information of an EPS bearer corresponding to a protocol data unit (PDU) session, the first mobility management network element being located in a first network, the PDU session being a PDU session of a first terminal, the PDU session being served by the first session management network element, and the PDU session being associated with a multicast service. The first session management network element is configured to receive the first message and send the context information of the EPS bearer to the first mobility management network element according to the first message, the context information of the EPS bearer comprising context of an EPS bearer corresponding to the multicast service.

36. The communication system of claim 35, wherein, The communication system further comprises an application server and a first network element; The application server is configured to receive a first report from the first terminal, the first report being used to indicate that the first terminal enters a multicast / broadcast media service (MBMS) area of a multicast service in a second network, and send fifth indication information to the first network element, the fifth indication information being used to indicate that the data of the multicast service is stopped from being sent to the first terminal through an evolved packet system (EPS) bearer in the second network. The first network element is configured to send third indication information to the first session management network element in response to the fifth indication information. The first session management network element is configured to receive the third indication information from the first network element, and send first configuration information to a first user plane network element according to the third indication information, the third indication information being used to indicate that the data of the multicast service is stopped from being sent to the first terminal through the EPS bearer, and the first configuration information being used to notify the first user plane network element to stop sending the data of the multicast service to the first terminal through the EPS bearer.

37. The communication system of claim 35, wherein, The communication system further comprises a first network element; The first network element is configured to receive fifth indication information from an application server, the fifth indication information being used to indicate that the first terminal receives the data of the multicast service through an MBMS bearer. The first network element is configured to send third indication information to the first session management network element in response to the fifth indication information. The first session management network element is configured to receive the third indication information from the first network element, and send first configuration information to a first user plane network element according to the third indication information. The third indication information is used to indicate that the first terminal receives the data of the multicast service through an MBMS bearer, and the first configuration information is used to notify the first user plane network element to stop sending the data of the multicast service to the first terminal through the EPS bearer.

38. The communication system of claim 37, wherein, The communication system further comprises the application server; The application server is configured to receive a first report from the first terminal, and send the fifth indication information to the first network element; the first report is configured to indicate that the first terminal enters an MBMS area in a second network.

39. The communication system of any of claims 36-38, wherein, The application server is further configured to receive a second report from the first terminal, the second report is configured to indicate that the first terminal moves out of an MBMS area of the multicast service; and send sixth indication information to the first network element, the sixth indication information is configured to indicate that the data of the multicast service is sent to the first terminal through the EPS bearer. The first network element is configured to send fourth indication information to the first session management network element in response to the sixth indication information. The first session management network element is further configured to receive the fourth indication information, and send second configuration information to the first user plane network element according to the fourth indication information, the fourth indication information is configured to indicate that the data of the multicast service is sent to the first terminal through the EPS bearer, and the second configuration information is configured to notify the first user plane network element to send the data of the multicast service to the first terminal through the EPS bearer.

40. The communication system of claim 35, wherein, The first session management network element is further configured to receive eighth indication information from the first terminal, the eighth indication information is configured to indicate that the EPS bearer is deleted, or the eighth indication information is configured to indicate that the first terminal receives the data of the multicast service through an MBMS bearer. The first session management network element is further configured to send first configuration information to the first user plane network element according to the eighth indication information, the first configuration information is configured to notify the first user plane network element to stop sending the data of the multicast service to the first terminal through the EPS bearer.

41. The communication system of any of claims 36-38, 40, wherein, The first session management network element is further configured to send a second event notification to the application server, the second event notification is configured to notify that the first terminal is about to switch to a second network or has completed switching to the second network. The application server is further configured to receive the second event notification from the first session management network element, and send a third message to the first terminal according to the second event notification, the third message is configured to notify the first terminal to receive the data of the multicast service through the EPS bearer.

42. A computer-readable storage medium, characterized in that, The computer readable storage medium stores instructions, when the instructions are run on a computer, the computer is caused to perform the service switching method of any of claims 1-21.

43. A computer program product comprising instructions, wherein: The computer program product can include program instructions, when the computer program product is run on a computer, the computer is caused to perform the service switching method of any of claims 1-21.

44. A computer-readable storage medium, comprising: The computer readable storage medium stores instructions, when the instructions are run on a computer, the computer is caused to perform the service switching method of any of claims 22-32.

45. A computer program product comprising instructions, wherein: The computer program product can include program instructions that, when executed on a computer, cause the computer to perform the method of any of claims 22-32.

Images