CN113630822B

CN113630822B - Method and device for switching multicast service

Info

Publication number: CN113630822B
Application number: CN202010756685.8A
Authority: CN
Inventors: 宗在峰; 朱奋勤
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-05-08
Filing date: 2020-07-31
Publication date: 2023-05-02
Anticipated expiration: 2040-07-31
Also published as: WO2021223745A1; CN113630822A

Abstract

The embodiment of the application provides a method and a device for switching multicast service, when a signal of a multicast area where a terminal device in a first network is located is weak, a first session management network element receives first indication information, the first indication information is used for indicating a data packet for sending the service to the terminal device through unicast bearing, the first session management network element sends second indication information to a first user plane network element, the second indication information is used for indicating the data packet to the terminal device through unicast bearing, and when the terminal device is accessed through a second network, the second session management network element adds the terminal device into a multicast session corresponding to the service. By switching the service data from the multicast path of the first network to the unicast bearer of the first network, and switching the unicast bearer of the first network to the multicast session of the second network, the continuity of the multicast service data in the cell switching process can be ensured.

Description

Method and device for switching multicast service

The present application claims priority from chinese patent office, application number 202010383204.3, application name "method and apparatus for multicast service switching" filed on day 5 and 8 of 2020, the entire contents of which are incorporated herein by reference.

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a method and an apparatus for switching multicast services.

Background

In a long term evolution (Long Term Evolution, LTE) system network, for group communication (Group Communication) services, an application server (Application Services) may send multicast broadcast service data (also referred to as MBMS service) to a terminal device in two ways: multimedia broadcast/multicast service (Multimedia Broadcast/Multicast Services, MBMS) bearer or unicast bearer.

When the terminal device is located in the coverage area of the fifth generation mobile communication (5G) network, the terminal device may also receive multicast broadcast service data in a multicast broadcast manner, and the 5G network is also called a New Radio (New Radio) system. In a 5G network, the AS may also send multicast broadcast service data to the terminal device in two ways: a 5G multicast broadcast path or a unicast path.

In an LTE system, an MBMS has a certain service area, and when a terminal device moves from the MBMS area to the coverage area of a 5G base station, how to ensure continuity of multicast and broadcast service data in a handover process is a key problem to be solved.

Disclosure of Invention

The embodiment of the application provides a method and a device for switching multicast service, which can ensure that the multicast service data received by a terminal device through a multicast path of a first network keeps service continuity in the switching process in the process of switching the terminal device from the first network to a second network.

The first aspect of the present application provides a method for switching multicast services, including: the first session management network element receives first indication information, where the first indication information is used to indicate a data packet for sending a service to a terminal device located in a first network through a unicast bearer. The first session management network element sends second indication information to the first user plane network element, wherein the second indication information is used for indicating to send the data packet to the terminal equipment through the unicast bearer. When the terminal equipment is accessed through a second network, the first session management network element adds the terminal equipment into the multicast session corresponding to the service.

In the method, the data of the service is firstly switched from the multicast path of the first network to the unicast bearer of the first network, and the multicast session is switched from the unicast bearer of the first network to the multicast session of the second network, so that the continuity of the service can be maintained in the switching process of the multicast service data received by the terminal equipment through the multicast path of the first network in the process of switching the terminal equipment from the first network to the second network.

In an exemplary manner, the method further comprises: and the first session management network element acquires the multicast QoS flow information of the service and determines unicast bearing of the data packet for transmitting the service according to the multicast QoS flow information of the service.

In an exemplary manner, the first session management network element receives first indication information, including: the first session management network element receives a first message, where the first message includes the first indication information and a multicast service identifier of the service. Correspondingly, the first session management network element obtains the multicast QoS flow information of the service, including: and the first session management network element acquires the multicast QoS flow information of the service according to the multicast service identifier.

In another exemplary manner, the first indication information includes a multicast service identifier of the service, and the first session management network element obtains multicast QoS flow information of the service, including: and the first session management network element acquires the multicast QoS flow information of the service according to the multicast service identifier.

In an exemplary manner, the method further comprises: and if the first session management network element receives eighth indication information, wherein the eighth indication information indicates that the service supports service continuity, the first session management network element determines a unicast QoS flow corresponding to the service according to the information of the multicast QoS flow.

In an exemplary manner, the first session management network element joins the terminal device to the multicast session corresponding to the service, specifically: and in the process of switching the terminal equipment from the first network to the second network, the first session management network element switches the data packet of the service from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through a protocol data unit PDU session. After the terminal device is switched from the first network to the second network, the first session management network element joins the terminal device in the multicast session, and the data packet of the service is switched from being sent to the terminal via the PDU session to being sent to the terminal device via the multicast session.

The PDU session is a unicast path in the second network, the data packet transmitted in the multicast mode in the first network is firstly switched from the multicast mode to the unicast path of the first network, then switched from the unicast path of the first network to the unicast path of the second network, and then switched from the unicast path of the second network to the multicast path of the second network, thereby ensuring that the multicast service of the terminal equipment maintains the continuity of the service in the cell switching process.

Optionally, after the terminal device joins the multicast session, the first user plane network element is notified to stop sending the data of the service to the terminal device through the PDU session.

In another exemplary manner, the first session management network element joins the terminal device to the multicast session corresponding to the service, specifically: and in the process of switching the terminal equipment from the first network to the second network, the first session management network element adds the terminal equipment into the multicast session, and the data packet of the service is switched from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through the multicast session.

The method switches the data packet transmitted by the multicast mode in the first network from the multicast mode to the unicast path of the first network, and then switches the unicast path of the first network to the multicast path of the second network, thereby ensuring that the multicast service of the terminal equipment maintains the continuity of the service in the cell switching process.

Optionally, before the first session management network element joins the terminal device in the multicast session, the first session management network element determines that the service supports multicast transmission through the second network.

Optionally, the determining, by the first session management network element, that the service supports sending by the multicast manner of the second network may be: the first session management network element receives a first rule corresponding to the service, wherein the first rule is used for controlling, strategy or charging, and the first rule comprises third indication information which is used for indicating the service to support multicast mode transmission.

Optionally, the first rule further includes a multicast service identifier corresponding to the service.

Optionally, the third indication information is a multicast service identifier corresponding to the service.

In an exemplary manner, the first indication information and the first rule are carried in the same message, or the first session management network element receives the first rule before receiving the first indication information.

Optionally, before the first session management network element joins the terminal device in the multicast session, it is determined that the terminal device supports multicast in the second network, and/or a target access network device supports multicast, where the terminal device accesses the second network through the target access network device.

Optionally, the determining, by the first session management network element, that the terminal device supports multicast in the second network may be: and the first session management network element receives multicast capability indication information sent by the terminal equipment in the process of establishing packet data network PDN connection of the terminal equipment, wherein the multicast capability indication information is used for indicating the multicast capability of the terminal equipment in the second network. And the first session management network element determines that the terminal equipment supports multicast in the second network according to the multicast capability indication information.

Optionally, if the multicast session corresponding to the service is not yet established, the first session management network element triggers to establish the multicast session.

In an exemplary manner, the first session management network element joins the terminal device to the multicast session, including: the first session management network element receives a request message sent by an access and mobility management function AMF, the request message being used to create or update a PDU session, the PDU session being associated with the service. The first session management network element determines that the service sent through the unicast bearer supports multicast mode sending, and the terminal device supports multicast service in the second network, and the first session management network element instructs a target access network device in the second network to join the terminal device into the multicast session.

In an exemplary manner, when the terminal device moves into the MBMS area or after moving into the MBMS area, the first session management network element receives fourth indication information, where the fourth indication information is used to indicate that the data of the service is stopped being sent through the unicast bearer, and the first session management network element notifies the first user plane network element to stop sending the data of the service through the unicast bearer according to the fourth indication information.

In an exemplary manner, the second indication information includes a first mapping relationship between information of a first tunnel and an identifier QFI of a multicast QoS flow of the service, where the first tunnel is a tunnel corresponding to the unicast bearer, the QFI is a QFI of a data packet of the service received by the first user plane network element, and the first mapping relationship is used by the first user plane network element to determine the first tunnel for sending the data packet of the service.

Correspondingly, after the first session management network element sends the second indication information to the first user plane network element, the first session management network element receives the information of the second tunnel from the first user plane network element, the first user plane network element receives the data packet of the service from the second user plane network element or the application server through the second tunnel, and the first session management network element sends the second tunnel information to the second user plane network element or the application server.

In an exemplary manner, the second indication information includes the multicast address, and the second indication information is used to instruct the first user plane network element to send a data packet with a destination address being the multicast address to the terminal device through the unicast bearer.

In an exemplary manner, after the terminal device switches to the second network, the first session management network element sends a first notification message to an AS, where the first notification message is used to notify the AS that the AS supports sending data of the service to the terminal device using a multicast manner. Correspondingly, the first session management network element joins the terminal device into the multicast session corresponding to the service, specifically: the first session management network element receives fifth indication information, where the fifth indication information is used to indicate that the terminal device joins the multicast session corresponding to the service, and the first session management network element joins the terminal device into the multicast session corresponding to the service according to the fifth indication information.

Optionally, before the first session management network element sends the first notification message to the AS, the first session management network element receives sixth indication information, where the sixth indication information is used to indicate that, when supporting sending service data to the terminal device by using a multicast mode, the first notification message is sent to the AS.

Optionally, the first message includes the first indication information and the sixth indication information are carried in the first message.

Optionally, before the first session management network element joins the terminal in the multicast session corresponding to the service according to the fifth indication information, the first session management network element determines that the terminal device supports multicast in the second network, and/or a target access network device supports multicast, where the terminal device accesses the second network through the target access network device.

A second aspect of the present application provides a method for switching multicast services, including: a first session management network element obtains a multicast service identifier of a service, and the first session management network element provides service for PDN connection of terminal equipment;

the first session management network element obtains multicast QoS flow information of the service according to the multicast service identifier;

when the terminal equipment is accessed through a second network, the first session management network element adds the terminal equipment into the multicast session corresponding to the service.

In the method, the first session management network element obtains the multicast service identifier of the service received by the terminal equipment through the multicast path of the first network in advance, and obtains the multicast QoS stream information of the service according to the multicast service identifier, so that when the terminal equipment is accessed through the second network, the first session management network element can add the terminal equipment into the multicast session corresponding to the service, thereby ensuring that the continuity of the service is maintained in the switching process of the multicast service data received by the terminal equipment through the multicast path of the first network in the process of switching the terminal equipment from the first network to the second network.

In an exemplary manner, the first session management network element joins the terminal device to the multicast session corresponding to the service, specifically: in the process of switching the terminal equipment from the first network to the second network, the first session management network element creates a unicast QoS flow in the second network according to the multicast QoS flow information, the unicast QoS flow belongs to a PDU session, the PDU session corresponds to the PDN connection, and the service is sent to the terminal equipment through the PDU session. After the terminal device is switched from the first network to the second network, the first session management network element joins the terminal device in the multicast session, and the data packet of the service is switched from being sent to the terminal device through the PDU session to being sent to the terminal device through the multicast session of the second network.

The PDU session is a unicast path in the second network, the data transmitted by the multicast mode in the first network is switched to the unicast path of the second network, and then the unicast path of the second network is switched to the multicast path of the second network, thereby ensuring that the multicast service of the terminal equipment maintains the continuity of the service in the cell switching process.

In another exemplary manner, the first session management network element joins the terminal device to the multicast session corresponding to the service, specifically: in the process of switching the terminal equipment from the first network to the second network, the first session management network element adds the terminal equipment into the multicast session according to the multicast service identifier, and the data packet of the service is switched from being sent to the terminal equipment in a multicast mode through the first network to being sent to the terminal equipment in a multicast session through the second network.

The method directly switches the data packet transmitted by the multicast mode in the first network to the multicast path of the second network, thereby ensuring that the multicast service of the terminal equipment maintains the continuity of the service in the cell switching process.

In an exemplary manner, the method further comprises: the first session management network element receives the multicast service identification from the terminal device, or the first session management network element receives the multicast service identification from the AS.

In an exemplary manner, the method further comprises: the first session management network element receiving the multicast service identification from the terminal device comprises the terminal device sending the multicast service identification to the first session management network element through the PDN connection.

The terminal device sends the identifier of the multicast service through the PDN connection, so that the first session management network element associates the service with the PDN connection, so that when the terminal device is switched to the second network, the first session management network element can associate the service with a PDU session corresponding to the PDN connection, and the terminal device can be added into the multicast session through the PDU session.

In an exemplary manner, the method further comprises: the first session management network element determines that the terminal device is accessed through the first network, and after receiving the multicast service identifier from the terminal device, the first session management network element does not join the terminal device into the multicast session and/or does not create a unicast bearer for the terminal device in the first network.

A third aspect of the present application provides a method for switching multicast services, including: the AS receives a first report from the terminal device, the first report being used to instruct the terminal device to move out of the MBMS area. The AS determines, according to the first report, a data packet for sending a service to the terminal device through a unicast bearer, and sends first indication information to a core network device and/or a first session management network element, where the first indication information is used to indicate that the data packet for sending the service to the terminal device through the unicast bearer.

When the signal of the MBMS area of the terminal equipment is weak, the method enables the AS to trigger to establish a unicast bearer by sending a first report to the AS, switches the service from the MBMS bearer to the unicast bearer, and further switches the service from the unicast bearer to a multicast session of a second network, thereby ensuring the continuity of the multicast service in the cell switching process.

Optionally, the AS further sends a multicast service identifier corresponding to the service to the core network device and/or the first session management network element.

In an exemplary manner, the first indication information includes a multicast service identifier corresponding to the service.

In another exemplary manner, the AS sends a first message to the first session management network element, where the first message includes the first indication information and a multicast service identifier corresponding to the service. Or the AS sends a second message to the core network equipment, wherein the second message comprises the first indication information and a multicast service identifier corresponding to the service.

Optionally, the AS further sends the eighth indication information to the core network device and/or the first session management network element, where the eighth indication information indicates that the service supports service continuity.

Optionally, the AS further sends third indication information to the core network device and/or the first session management network element, where the third indication information is used to indicate that the service supports multicast mode sending.

Optionally, the AS sends third indication information to the core network device, including: and the AS sends a second message to the core network equipment, wherein the second message comprises the third indication information and a multicast service identifier corresponding to the service.

Optionally, the AS further sends eighth indication information to the core network device or the first session management network element, where the eighth indication information is used to indicate that the service supports service continuity.

Optionally, the AS sends sixth indication information to the core network device, where the sixth indication information is used to indicate that the first notification message is sent to the AS when data that supports sending services to the terminal device in a multicast manner is supported.

Optionally, the first indication information and the sixth indication information are carried in a first message or a second message.

In an exemplary manner, the AS receives a first notification message, where the first notification message is used to notify data supporting sending the service to the terminal device using a multicast manner, and in response to the first notification message, the AS sends a second notification message to the terminal device, where the second notification message is used to notify the terminal device to receive the data of the service using the multicast session.

In another exemplary manner, the AS receives a first notification message, where the first notification message is used to notify data supporting sending the service to the terminal device using a multicast manner, and in response to the first notification message, the AS sends fifth indication information to the first session management network element or the core network device, where the fifth indication information is used to indicate that the terminal device is joined to a multicast session corresponding to the service.

In an exemplary manner, when the terminal device moves from the non-MBMS area into the MBMS area, the AS receives a second report from the terminal device, the second report being used to inform the AS that the terminal device is capable of receiving data of the service through an MBMS bearer. Correspondingly, the AS sends fourth indication information to the core network device, where the fourth indication information is used to indicate to stop sending the data of the service through the unicast bearer.

A fourth aspect of the present invention provides a method for switching multicast services, where in a process of establishing a PDN connection, a terminal device sends multicast capability indication information to a first session management network element, where the multicast capability indication information is used to indicate multicast capability of the terminal device in the second network. The terminal equipment receives configuration information of wireless resources allocated to the terminal equipment by target access network equipment in the second network from source access network equipment in the first network, wherein the configuration information of the wireless resources is used for receiving data of the service by the terminal equipment in the second network in a multicast mode, and the terminal equipment receives the data of the service according to the configuration information of the wireless resources.

In an exemplary manner, the terminal device receives a fourth notification message from the application server AS, the fourth notification message being used to inform the terminal device to receive data of the service using the multicast session in the second network.

A fifth aspect of the present application provides a method for switching multicast services, including: the target access network device receives seventh indication information from the first session management network element, where the seventh indication information is used to indicate that the terminal device is added to a multicast session corresponding to a service. And the target access network equipment acquires the parameters of the multicast QoS flow of the multicast session, and allocates wireless resources for the multicast QoS flow according to the seventh indication information and the parameters of the multicast QoS flow. The target access network device sends the configuration information of the wireless resources of the multicast QoS stream to the terminal device through a source access network device, wherein the source access network device is the access network device which the terminal device accesses before accessing the target access network device.

Optionally, the seventh indication information and QoS information of the multicast session are sent by the first session management network element via a message.

A sixth aspect of the present application provides a first session management network element, comprising: the receiving module is used for receiving first indication information, wherein the first indication information is used for indicating a data packet for sending service to terminal equipment positioned in a first network through unicast bearing; a sending module, configured to send second indication information to a first user plane network element, where the second indication information is used to indicate to send the data packet to the terminal device through the unicast bearer; and the joining module is used for joining the terminal equipment into the multicast session corresponding to the service when the terminal equipment is accessed through the second network.

Optionally, the network element further includes: an acquisition module, configured to acquire multicast quality of service QoS flow information of the service; and the first determining module is used for determining unicast bearing of the data packet for sending the service according to the multicast QoS flow information of the service.

Optionally, the receiving module is specifically configured to: receiving a first message, wherein the first message comprises the first indication information and a multicast service identifier of the service; the acquisition module is specifically configured to: and acquiring the multicast QoS flow information of the service according to the multicast service identifier.

Optionally, the first indication information includes a multicast service identifier of the service, and the obtaining module is specifically configured to: and acquiring the multicast QoS flow information of the service according to the multicast service identifier.

The first determining module is further configured to: and if the first session management network element receives eighth indication information, wherein the eighth indication information indicates that the service supports service continuity, determining a unicast QoS flow corresponding to the service according to the information of the multicast QoS flow.

In an exemplary manner, the joining module is specifically configured to: and switching the data packet of the service from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through a protocol data unit PDU session in the process of switching the terminal equipment from the first network to the second network, joining the terminal equipment into the multicast session after the terminal equipment is switched from the first network to the second network, and switching the data packet of the service from being sent to the terminal through the PDU session to being sent to the terminal equipment through the multicast session.

Optionally, after the terminal device joins the multicast session, the sending module is further configured to: and notifying the first user plane network element to stop sending the data of the service to the terminal equipment through the PDU session.

In another exemplary manner, the joining module is specifically configured to: and in the process of switching the terminal equipment from the first network to the second network, adding the terminal equipment into the multicast session, and switching the data packet of the service from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through the multicast session.

Optionally, the method further comprises: and the second determining module is used for determining that the service support is sent in a multicast mode of the second network before the first session management network element joins the terminal equipment into the multicast session.

Optionally, the second determining module is specifically configured to: and receiving a first rule corresponding to the service, wherein the first rule is used for controlling, strategy or charging, and the first rule comprises third indication information which is used for indicating the service to support multicast mode transmission.

Optionally, the method further comprises a third determining module, configured to determine that the terminal device supports multicast in the second network, and/or that a target access network device supports multicast, where the terminal device accesses the second network through the target access network device.

Optionally, the third determining module is specifically configured to: and in the process that the terminal equipment establishes packet data network PDN connection, receiving multicast capability indication information sent by the terminal equipment, wherein the multicast capability indication information is used for indicating the multicast capability of the terminal equipment in the second network, and determining that the terminal equipment supports multicast in the second network according to the multicast capability indication information.

Optionally, the method further comprises: and the establishing module is used for triggering the establishment of the multicast session under the condition that the multicast session corresponding to the service is not established yet.

In an exemplary manner, the joining module is specifically configured to: receiving a request message sent by an access and mobility management function AMF, wherein the request message is used for creating or updating a PDU session, the PDU session is associated with the service, the service sent through the unicast bearer is determined to support multicast mode sending, the terminal equipment supports multicast service in the second network, and a target access network equipment in the second network is instructed to join the terminal equipment into the multicast session.

In an exemplary manner, when the terminal device moves into the MBMS area or after moving into the MBMS area, the receiving module is further configured to: and receiving fourth indication information, wherein the fourth indication information is used for indicating that the transmission of the data of the service through the unicast bearer is stopped. And the sending module is further configured to notify the first user plane network element to stop sending the data of the service through the unicast bearer according to the fourth indication information.

Correspondingly, the receiving module is further configured to: and after the sending module sends the second indication information to the first user plane network element, receiving information of a second tunnel from the first user plane network element, and receiving the data packet of the service from the second user plane network element or an application server by the first user plane network element through the second tunnel. The sending module is further configured to: and sending the second tunnel information to the second user plane network element or the application server.

In an exemplary manner, after the terminal device switches to the second network, the sending module is further configured to: and sending a first notification message to an AS, wherein the first notification message is used for notifying the AS to support sending the service data to the terminal equipment by using a multicast mode. Correspondingly, the adding module is specifically configured to: and receiving fifth indication information, wherein the fifth indication information is used for indicating the terminal equipment to join the multicast session corresponding to the service, and the terminal is joined to the multicast session corresponding to the service according to the fifth indication information.

Optionally, before the sending module sends the first notification message to the AS, the receiving module is further configured to: and receiving sixth indication information, wherein the sixth indication information is used for indicating to send the first notification message to the AS when supporting to send service data to the terminal equipment by using a multicast mode.

Optionally, the method further includes a determining module, before the joining module joins the terminal into the multicast session corresponding to the service according to the fifth indication information, the determining module determines that the terminal device supports multicast in the second network, and/or a target access network device supports multicast, where the terminal device accesses the second network through the target access network device.

A seventh aspect of the present application provides an AS, comprising: a receiving module, configured to receive a first report from a terminal device, where the first report is used to instruct the terminal device to move out of an MBMS area; a determining module, configured to determine, according to the first report, a data packet for sending a service to the terminal device through a unicast bearer; and the sending module is used for sending first indication information to the core network equipment and/or the first session management network element, wherein the first indication information is used for indicating to send the data packet of the service to the terminal equipment through unicast bearing.

Optionally, the sending module is further configured to: and sending third indication information to the core network equipment and/or the first session management network element, wherein the third indication information is used for indicating the service to support the multicast mode to send.

Optionally, the sending module sends third indication information to the core network device, specifically: and sending a second message to the core network equipment, wherein the second message comprises the third indication information and the multicast service identifier corresponding to the service.

Optionally, the sending module is further configured to: and sending the multicast service identifier corresponding to the service to the core network equipment and/or the first session management network element.

Optionally, the sending module is further configured to: and sending the eighth indication information to the core network equipment and/or the first session management network element, wherein the eighth indication information indicates that the service supports service continuity.

Optionally, the sending module is further configured to: and sending sixth indication information to the core network equipment, wherein the sixth indication information is used for indicating to send the first notification message to the AS when supporting sending service data to the terminal equipment in a multicast mode.

Optionally, the first indication information and the sixth indication information are carried in a first message.

In an exemplary manner, the receiving module is further configured to: receiving a first notification message, where the first notification message is used to notify data supporting sending the service to the terminal device by using a multicast mode, and the sending module is further configured to: and responding to the first notification message, sending a second notification message to the terminal equipment, wherein the second notification message is used for notifying the terminal equipment to receive the data of the service by using the multicast session.

In another exemplary manner, the receiving module is further configured to: receiving a first notification message, where the first notification message is used to notify data supporting sending the service to the terminal device by using a multicast mode, and the sending module is further configured to: and responding to the first notification message, and sending fifth indication information to the first session management network element or the core network equipment, wherein the fifth indication information is used for indicating the terminal equipment to join the multicast session corresponding to the service.

In an exemplary manner, the receiving module is further configured to: and when the terminal equipment moves into the MBMS area from the non-MBMS area, receiving a second report from the terminal equipment, wherein the second report is used for informing the AS that the terminal equipment can receive the data of the service through the MBMS bearing. Correspondingly, the sending module is further configured to: and sending fourth indication information to the core network equipment, wherein the fourth indication information is used for indicating that the sending of the data of the service through the unicast bearer is stopped.

An eighth aspect of the present application provides a terminal device, including: a sending module, configured to send multicast capability indication information to a first session management network element in a process of establishing a PDN connection for the terminal device, where the multicast capability indication information is used to indicate multicast capability of the terminal device in the second network; a receiving module, configured to receive, from a source access network device in a first network, configuration information of a radio resource allocated by a target access network device in a second network to the terminal device, where the configuration information of the radio resource is used for the terminal device to receive data of the service in the second network by multicast mode; the receiving module is further configured to receive data of the service according to the configuration information of the radio resource.

In an exemplary manner, the receiving module is further configured to: and receiving a fourth known message from the application server AS, wherein the fourth known message is used for notifying the terminal equipment to receive the data of the service by using the multicast session in the second network.

A ninth aspect of the present application provides a target access network device, including: a receiving module, configured to receive seventh indication information from a first session management network element, where the seventh indication information is used to indicate that the terminal device is added to a multicast session corresponding to a service; an acquisition module, configured to acquire parameters of a multicast QoS flow of the multicast session; a resource allocation module, configured to allocate radio resources for the multicast QoS flow according to the seventh indication information and parameters of the multicast QoS flow; and the sending module is used for sending the configuration information of the wireless resources of the multicast QoS stream to the terminal equipment through source access network equipment, wherein the source access network equipment is access network equipment which is accessed by the terminal equipment before the terminal equipment is accessed to the target access network equipment.

A tenth aspect of the present application provides a first session management network element comprising a processor, a memory for storing instructions, and a transceiver for communicating with other devices, the processor being configured to execute the instructions stored in the memory to cause the first session management network element to perform a method according to the first aspect or any of the aspects of the present application.

An eleventh aspect of the present application provides an AS comprising a processor, a memory for storing instructions, and a transceiver for communicating with other devices, the processor being configured to execute the instructions stored in the memory to cause the AS to perform a method AS described in the second aspect or any of the aspects of the present application.

A twelfth aspect of the present application provides a terminal device comprising a processor, a memory for storing instructions, and a transceiver for communicating with other devices, the processor being adapted to execute the instructions stored in the memory to cause the terminal device to perform a method as described in the third aspect or any of the aspects of the present application.

A thirteenth aspect of the present application provides a target access network device comprising a processor, a memory for storing instructions, and a transceiver for communicating with other devices, the processor being configured to execute the instructions stored in the memory to cause the target access network device to perform a method as claimed in the fourth aspect or any of the present application.

A fourteenth aspect of the present application provides a computer readable storage medium storing instructions which, when executed, cause a computer to perform the method of the first, second, third, fourth or any of the aspects of the present application.

A fifteenth aspect of the present application provides a computer program product comprising instructions which, when executed, cause a computer to perform the method of the first, second, third, fourth or any of the aspects of the present application.

A sixteenth aspect of the present application provides a communication system comprising a first session management network element for performing the method according to the first aspect or any of the modes of the first aspect of the present application, and an AS for performing the method according to the second aspect or any of the modes of the second aspect of the present application.

Optionally, the communication system further includes: a first user plane network element.

When the signal of the multicast area where the terminal equipment is located in the first network is weak, the first session management network element receives first indication information, the first indication information is used for indicating a data packet for sending the service to the terminal equipment through unicast bearing, the first session management network element sends second indication information to the first user plane network element, the second indication information is used for indicating the data packet for sending the data packet to the terminal equipment through unicast bearing, and when the terminal equipment is accessed through the second network, the second session management network element adds the terminal equipment into a multicast session corresponding to the service. By switching the data of the service from the multicast path of the first network to the unicast bearer of the first network, and switching the unicast bearer of the first network to the multicast session of the second network, the continuity of the service can be maintained in the switching process of the multicast service data received by the terminal device through the multicast path of the first network in the process of switching the terminal device from the first network to the second network.

Drawings

Fig. 1 is a schematic architecture diagram of an LTE system;

FIG. 2 is a schematic architecture diagram of a 5G network;

fig. 3 is a schematic diagram of a conventional MBMS-supporting 4G network architecture;

fig. 4 is a schematic diagram of a conventional architecture of a 5G network supporting multicast mode;

fig. 5 is a schematic diagram of a network architecture applicable to an embodiment of the present application;

fig. 6 is a flowchart of a method for switching multicast service according to the first embodiment of the present application;

fig. 7 is a flowchart of a method for switching multicast service according to the second embodiment of the present application;

fig. 8 is a signaling flow chart of a method for switching multicast service according to the third embodiment of the present application;

fig. 9 is a signaling flow chart of a method for switching multicast service according to the fourth embodiment of the present application;

fig. 10 is a signaling flow chart of a method for switching multicast service provided in the fifth embodiment of the present application;

fig. 11 is a signaling flow chart of a method for switching multicast service provided in the sixth embodiment of the present application;

fig. 12 is a signaling flow chart of a method for switching multicast service according to the seventh embodiment of the present application;

fig. 13 is a signaling flow chart of a method for switching multicast service according to the eighth embodiment of the present application;

fig. 14 is a schematic structural diagram of a first session management network element provided in a ninth embodiment of the present application;

FIG. 15 is a schematic view of an AS according to embodiment ten of the present application;

Fig. 16 is a schematic structural diagram of a terminal device according to an eleventh embodiment of the present application;

fig. 17 is a schematic structural diagram of a target access network device according to a twelfth embodiment of the present application;

fig. 18 is a schematic structural diagram of a first session management network element according to the thirteenth embodiment of the present application.

Detailed Description

The embodiment of the application provides a method for switching multicast service, which can realize that the multicast service is kept uninterrupted in the process of switching terminal equipment from a fourth generation mobile communication (4-generation, 4G) system to a fifth generation mobile communication system. The 4G network may be an LTE system, and the 5G network is also called a New wireless communication system, a New access technology (NR), or a next generation mobile communication system.

Fig. 1 is a schematic architecture diagram of an LTE system. As shown in fig. 1, the LTE system may include: a User Equipment (UE), an evolved UMTS terrestrial radio access network (Evolved UMTS Terrestrial Radio Access Network, E-UTRAN), a mobility management entity (Mobility Management Entity, MME), a Serving Gateway (SGW), a packet data network Gateway (Packet Data Network Gateway, PGW), a scheme and charging rules function (Policy and Charging Rule Function, PCRF), a home network server (Home Subscriber Server, HSS), and operator IP traffic, among others.

The core network of the LTE network mainly comprises three logic functional bodies of an MME (mobility management entity), an SGW (serving gateway) and a PGW, wherein the MME is a signaling management network element and is responsible for Non-Access Stratum (NAS) signaling encryption, distributing temporary identity for UE (user equipment), selecting core network equipment such as the SGW, the PGW and the like, and providing functions of roaming, tracking, security and the like; the SGW is a mobility anchor point switched between local evolution nodes (eNB) and provides legal monitoring related functions, and the eNB is a base station in an LTE system; the PGW is responsible for the functions of user address allocation, scheme control, charging rule execution, legal monitoring correlation and the like; the HSS is used for storing the subscription information of the user; the PCRF is used to provide the scheme and charging control rules.

Fig. 2 is a schematic architecture diagram of a 5G network, and referring to fig. 2,5G, the access network in the network may be a radio access network (radio access network, (R) AN), and the (R) AN device in the 5G network may be composed of a plurality of 5G- (R) AN nodes, which may include: an access network of non-3 GPP, such as an Access Point (AP) of a WiFi network, a next generation base station (which may be collectively referred to as a new generation radio access network node (NG-RAN node), wherein the next generation base station includes a new air interface base station (NR node b, gNB), a new generation evolved base station (NG-eNB), a gNB in a form of a Central Unit (CU) and a Distributed Unit (DU), etc.), a transceiving point (transmission receive point, TRP), a transmission point (transmission point, TP), or other nodes.

The 5G core network (5G core/new generation core,5 GC/NGC) includes a plurality of functional units including an access and mobility management function (Access and Mobility Management Function, AMF) network element, a session management function (Session Management Function, SMF) network element, a user plane function (User Plane Function, UPF) network element, an authentication server function (Authentication Server Function, AUSF) network element, a policy control function (Policy Control Function, PCF) network element, an application function (Application Function, AF) network element, a unified data management function (unified data management, UDM) network element, a network slice selection function (Network Slice Selection Function, NSSF) network element, and the like.

The AMF network element is mainly responsible for services such as mobility management, access management, etc. The SMF network element is mainly responsible for session management, UE address management and allocation, dynamic host configuration protocol functions, selection and control of user plane functions, etc. The UPF is mainly responsible for packet routing forwarding, packet filtering, performing quality of service (quality of service, qoS) control related functions, etc. for external connection to a Data Network (DN). The AUSF is mainly responsible for authentication functions for terminal devices, etc. The PCF network element is mainly responsible for providing a unified policy framework for network behavior management, providing policy rules for control plane functions, obtaining registration information related to policy decisions, etc. It should be noted that these functional units may work independently, or may be combined to implement some control functions, such as access control and mobility management functions for access authentication, security encryption, location registration, etc. of the terminal device, and session management functions for setting up, releasing, changing, etc. of the user plane transmission path.

The functional units in the 5GC may communicate through a next generation Network (NG) interface, for example: the UE can transmit control plane information with AMF network element through NG interface 1 (N1), the RAN device can establish user plane data transmission channel with UPF through NG interface 3 (N3), the AN/RAN device can establish control plane signaling connection with AMF network element through NG interface 2 (N2), UPF can interact with SMF network element through NG interface 4 (N4), UPF can interact user plane data with data network DN through NG interface 6 (N6), AMF network element can interact with SMF network element through NG interface 11 (N11), SMF network element can interact with PCF network element through NG interface 7 (N7), AMF network element can interact with AUSF through NG interface 12 (N12). It should be noted that fig. 2 is only an exemplary architecture diagram, and the network architecture may include other functional units besides the functional units shown in fig. 2.

UEs in the 4G network and the 5G network are also called terminal equipment, mobile Station (MS), mobile terminal (mobile terminal), terminal (terminal), and the like.

The terminal device may communicate with one or more core networks via the RAN, and thus may also be referred to as a wireless terminal, which may be a device that provides voice and/or data connectivity to a user, a handheld device with wireless connectivity, or other processing device connected to a wireless modem.

For example, the terminal device may be a cellular phone, a cordless phone, a session initiation protocol (session initiation protocol, SIP) phone, a wireless local loop (wireless local loop, WLL) station, a personal digital assistant (personal digital assistant, PDA), a handheld device with wireless communication capabilities, a computing device or other processing device connected to a wireless modem, an in-vehicle device or a wearable device, a Virtual Reality (VR) terminal device, an augmented reality (augmented reality, AR) terminal device, a wireless terminal in industrial control (industrial control), a wireless terminal in self driving (self driving), a wireless terminal in telemedicine (remote media), a wireless terminal in smart grid (smart grid), a wireless terminal in transportation security (transportation safety), a wireless terminal in smart city (smart city), a wireless terminal in smart home (smart home), or the like. The embodiments of the present application are not specifically limited.

In the 4G network, MBMS and eMBMS are introduced for group communication, the eMBMS is the evolution of MBMS, and the MBMS supports two modes of multimedia broadcasting service and multicast service, so that multimedia video information can be directly broadcast to all users, and can also be sent to a group of subscription users for watching, thereby helping operators to develop various commercial applications such as multimedia advertisement, free and charged television channels, multimedia message mass sending and the like. The operator can develop the mobile phone television service with lower network deployment cost.

In order to realize multicast service, on the basis of the existing 4G network, functional entities such as a broadcast multicast service center (Broadcast Multicast Service Center, BM-SC), an MBMS Gateway (MBMS-Gateway), and the like are introduced. Fig. 3 is a schematic diagram of an architecture of a conventional MBMS-supporting 4G network, and AS shown in fig. 3, a group communication application server (Group Communication service Application Server, GCS AS) in an application domain (application domain) provides basic services and supplementary services, multimedia conferences, converged communication, short message gateways, standard attendant console, and other services to UEs.

The GCS AS may send data to the UE in two ways: unicast bearer mode and MBMS bearer mode. The paths corresponding to the unicast bearer (or referred to as unicast paths) are: GCS AS- > S/P-GW- > E-UTRAN (eNB) - > UE, namely GCS AS sends data to S/P-GW through SGi interface, S/P-GW represents SGW and/or PGW, S/P-GW sends the data to E-UTRAN, E-UTRAN sends the data to UE. The path corresponding to the MBMS bearer is: GCSAS- > BM-SC- > MBMS-GW- > E-UTRAN (eNB) - > UE, namely GCS AS sends data to MBMS-GW through MB2-U interface, MBMS-GW sends the data to E-UTRAN, E-UTRAN sends the data to UE.

To send data over the MBMS bearer, the GCS AS first needs to inform the BM-SC to establish a multicast bearer, the process of establishing the multicast bearer will establish the MB2-U interface and establish an interface from the BM-SC to the MBMS-GW and from the MBMS-GW to the E-UTRAN, and inform the E-UTRAN to establish the MBMS air interface bearer. After the MBMS bearer is established, the GCS AS may send the multicast service data to the E-UTRAN over the MBMS bearer and to the UE over the E-UTRAN.

In a 4G network, MBMS has a certain service area, i.e. not all base stations support MBMS bearers. If some base stations do not support the MBMS bearer, multicast service data cannot be sent through the MBMS bearer, and in this case, in order to ensure continuity of the service, the base stations will switch to send data through the unicast bearer, that is, send data through a packet data network (Packet Date Network, PDN) connection, that is, send data through the S/P-GW.

When the UE is about to or has moved out of the MBMS service area, the UE may send a report to the GCS AS, and the GCS AS may notify the UE to receive data of the service through a unicast bearer when knowing that the UE is about to move out of the MBMS service area according to the report, and the GCS-AS sends unicast information corresponding to the service (i.e. the group communication service) to the PCRF through the Rx interface, which triggers the PGW to modify or create the bearer so AS to prepare resources for sending the unicast data of the service.

Correspondingly, when the UE moves into the MBMS service area, the UE may also send a report to the GCS AS, and the GCS AS may notify the UE to receive the data of the service through the MBMS bearer and trigger the PGW to delete the resources of the unicast bearer allocated for the service through the Rx interface when knowing that the UE moves into the MBMS service area according to the report.

In fig. 3, there is a signaling interface between the UE and the GCS AS, and signaling between the UE and the GCS AS is also sent through a PDN connection, i.e. through a unicast bearer. And the MB2-U interface is used for transmitting multicast service data, and the MB2-C interface is used for transmitting signaling related to group communication service.

When the UE is located in the 5G coverage area, the UE may also receive service data by using a 5G multicast method. AS shown in fig. 4, when the UE receives service data in a 5G multicast manner, the multicast service data may be transmitted through a multicast path, for example, the AS (may be GCS AS) transmits the multicast service data to the UPF, and the base station may transmit one set of multicast service data to a plurality of UEs through a shared tunnel between the UPF and the base station (only one set of multicast service data is transmitted to the base station through the tunnel UPF) to transmit the multicast service data to the 5G base station.

The 5G base station may flexibly determine a play mode according to an air interface condition, the number of terminals listening to the service, and the like, where the play mode may be a Point-to-multipoint (Point to multipoint, PTM) mode or a Point-to-Point (PTP) mode. In the PTM mode, the base station only transmits one data, and a plurality of terminal devices can receive the data; in PTP mode, a base station transmits a data which can be received only by one terminal device. For the same multicast service, the base station may enable PTM and PTP modes at the same time, for example, PTM is used for UE1 and UE2, and PTP is used for UE 3.

The 5G multicast path includes: AS- > UPF- >5G AN- > UE. There is also a unicast path in the 5G network, i.e. a path of the PDU session, which includes: AS- > PGW-U+UPF- >5G AN- > UE. If signaling exists between the UE and the AS, the signaling can be sent through the unicast path.

The UPF in FIG. 4 may be controlled by the PGW-C+SMF, or by other SMFs, which may be the same UPF as the PGW-U+UPF, or may be a separate network element. The PGW-u+upf is a network element having both a PGW (PGW-U) function and a UPF function, and the PGW-u+upf may be a combined network element having the PGW-U function and the UPF function, or may be two physically independent network elements. Similarly, PGW-c+smf is a network element having both a PGW (PGW-C) function and an SMF function, and the PGW-c+smf may be a combined network element having the PGW-C function and the SMF function, or may be two physically independent network elements.

In the existing scheme, the UE can switch between the MBMS bearer and the unicast bearer in the 4G network, and similarly, the UE can switch between the 5G multicast path and the unicast path in the 5G network. However, when the UE moves from the MBMS area of 4G to the coverage area of the 5G base station, how to make the UE switch to 5G, the UE maintains service continuity during the switching process through the multicast service data received by the MBMS.

The method for switching the multicast service can ensure that the multicast service data received by the UE through the MBMS bearer keeps service continuity in the switching process after the UE moves from the MBMS area to the 5G network. Fig. 5 is a schematic diagram of a network architecture suitable for the method of the present application, as shown in fig. 5, when a 5G network and a 4G network are in interworking, PGW-C and SMF on a unicast path are combined, which is called PGW-c+smf, and PGW-U and UPF are combined, which is called PGW-u+upf. PCRF in 4G networks is replaced by PCF, which has an interface with PGW-c+smf to receive PCC rules.

In the architecture shown in fig. 5, the path corresponding to the MBMS bearer is the same as the path corresponding to the MBMS bearer in the 4G network shown in fig. 3, and the 5G multicast path shown in fig. 5 is the same as the 5G multicast path in the 5G network shown in fig. 4.

In a 5G network, in one possible implementation, only a specific UPF and an AS have an interface, that is, the AS can only send multicast service data to the specific UPF, in this implementation, the PGW-u+upf of the PDU session of the terminal device may not be able to directly receive the multicast service data from the AS, where if the multicast service data is sent through the PDU session, the PGW-u+upf needs to receive the multicast service data from the specific UPF, that is, needs to establish a path from the specific UPF to the PGW-u+upf. In order to support that multicast service sent through a 5G multicast path may be switched to be sent through a 4G network, in one implementation manner, the embodiment of the present application modifies a path corresponding to a unicast bearer of the multicast service in the 4G network, in a 4G network architecture shown in fig. 3, a unicast path of the multicast service in the 4G network is AS (GCSAS) - > S/P-GW- > eNB- > UE, and in a system architecture diagram shown in fig. 5, a unicast path of the multicast service in the 4G network is changed to: AS- > UPF- > S/P-GW- > eNB- > UE, i.e. in the architecture shown in FIG. 5, multicast traffic needs to pass UPF on the unicast path of the 4G network. In the system architecture diagram shown in fig. 5, unlike the prior art, the destination address of the packet of the multicast service sent through the unicast path of 4G is the multicast address of the multicast service, and not the address of the terminal device.

In addition, in the prior art (i.e., in the architecture diagram shown in fig. 3), the destination address of the multicast service data transmitted by the GCS AS through the unicast bearer in the 4G network is a unicast address (i.e., the address of the terminal device), and the destination address of the multicast service data transmitted through the MBMS bearer is a multicast address. In the architecture diagram shown in fig. 5, in the 4G network, destination addresses of multicast service data sent by the AS through the unicast bearer or the MBMS bearer are the same, that is, the destination addresses are all multicast addresses of the multicast service.

In actual deployment, the UPF shown in fig. 5 may or may not be co-located with the PGW-u+upf, which is not limited in this embodiment, and if the UPF is co-located with the PGW-u+upf, the path from the UPF to the PGW-u+upf does not exist.

In this embodiment of the present application, the 4G multicast mode (or referred to as a 4G multicast path) uses MBMS bearer to transmit data, the 4G unicast mode (or referred to as a 4G unicast path) uses unicast bearer to transmit data, and the unicast bearer transmits data through PDN connection, where the unicast bearer refers to an evolved packet system bearer EPS (Evolved Packet System bearer, EPS bearer) bearer. The 5G multicast mode adopts a 5G multicast session (or called 5G multicast path) to transmit data, and the 5G unicast mode adopts a PDU session to transmit data, and the unicast QoS in the PDU session actually transmits data.

In addition, in the embodiment of the present application, a multicast service is described as an example, but the method of the embodiment of the present application is also applicable to a broadcast service, and multicast may be replaced by broadcast.

Based on the system architecture shown in fig. 3 or fig. 5, in this embodiment, the first network is a 4G network, and the second network is a 5G network, but the first network and the second network are not limited to the 4G network and the 5G network, and may be other networks supporting multicast services, for example, as the network evolves, the second network may be a next generation network. Fig. 6 is a flowchart of a method for switching multicast services according to an embodiment of the present application, as shown in fig. 6, where the method provided in the embodiment includes the following steps:

s101, a first session management network element receives first indication information, wherein the first indication information is used for indicating a data packet for sending service to terminal equipment located in a first network through unicast bearing.

The terminal device currently receives service data in a multicast manner, wherein the first session management network element may be PGW-c+smf, and the first indication information is sent to PGW-c+smf after the PCF receives the second message from the AS, or the AS directly sends the second message to PGW-c+smf. When the AS knows that the signal of the MBMS area of the service where the terminal equipment is currently located is weak, or the AS determines that the terminal equipment is about to move out of the MBMS area of the service or has moved out of the MBMS area of the service, the AS directly sends first indication information to the PGW-C+SMF, or after the AS sends a second message to the PCF, the PCF sends the first indication information to the PGW-C+SMF.

The AS may determine that the terminal device is about to be moved out of the MBMS area of the service or has been moved out of the MBMS area of the service by receiving a first report of the terminal device, or learn that the signal of the MBMS area of the service in which the terminal device is currently located is weak, where the first report is used to indicate that the terminal device is moved out of or is about to be moved out of the MBMS area of the service or that the signal of the MBMS area of the service in which the terminal device is currently located is weak.

The first indication information is used for indicating the first session management network element to send a data packet of a service to a terminal located in the first network by adopting a unicast bearer, or is used for indicating to distribute the unicast bearer for the service of the terminal equipment in the first network, or is used for indicating to switch or migrate the service of the terminal equipment from the MBMS bearer to the unicast bearer.

Wherein, the data packet for sending the service to the terminal device located in the first network through the unicast bearer is divided into two cases:

in a first case, based on the architecture of fig. 5, the data packet of the service sent by the AS includes the data of the service and the destination address, where the destination address is the multicast address of the service.

In the second case, based on the architecture of fig. 5, the data packet of the service sent by the AS includes the data of the service and the destination address, where the destination address is the IP address of the terminal device.

For the first case, the first indication information may further include a first rule, or the first indication information is sent to the first session management network element together with the first rule, or the first indication information is the first rule. The first rule may be a policy control and charging (Policy Control and Charging, PCC) rule corresponding to the service when the AS sends data of the service in a case one manner, and correspondingly, the first indication information is used to instruct the first session management network element to create a unicast bearer according to the first rule. The first rule is determined by the PCF according to first description information, and the first description information is corresponding service information when the service is sent in a mode of passing through the service, and comprises identification information of the service and corresponding QoS parameters. The identification information of the service is used to identify the service, and may include any one of a source or destination address, a source or destination port number, and a protocol number of a packet of the service, for example.

In one possible method, the first session management network element has acquired the first rule before receiving the first indication information, in which case the first indication information does not include the first rule, and the first indication information includes identification information of the service, so that the first session management network element determines the first rule and/or the second indication information according to the identification information of the service, and the description of the second indication information is referred to in S102. The service identification information may be a multicast service identification corresponding to the service, or a unicast service identification corresponding to the service, or other information for identifying the service, which is not limited in this implementation.

Further, in this case, the first rule may further include third indication information, where the third indication information is used to indicate that the service supports multicast mode transmission. Further, the first rule further includes a multicast service identifier corresponding to the service. In one implementation, the third indication information is a multicast service identifier corresponding to the service.

For the second case, the first indication information may further include a second rule, or the first indication information is sent to the first session management network element together with the second rule, or the first indication information is the second rule. The second rule may be a PCC rule corresponding to the service when the AS sends data of the service in the second case, different from the first rule, where the second rule may include no third indication information, and the first indication information is used to instruct the first session management network element to create a unicast bearer according to the second rule. The second rule is determined by the PCF according to second description information, and the second description information is corresponding service information when the service is sent in a second mode, and comprises identification information of the service and corresponding QoS parameters.

It will be appreciated that both cases one and two are based on the architecture shown in fig. 5, but that there are differences: in the first case, a second tunnel needs to be established between the AS and the first user plane network element, and in the second case, the second tunnel does not need to be established between the AS and the first user plane network element.

Optionally, in the embodiment of the present application, after receiving the first indication information, the first session management network element obtains multicast QoS flow information of the service from the UDM or the UDR or the second session management network element, and determines a unicast bearer for sending the service according to the multicast QoS flow information of the service. The first session management network element may obtain multicast QoS flow information of the service from the UDM or the UDR or the second session management network element according to a multicast service identifier, where the multicast service identifier may be AS or the core network device and the first indication information are sent to the first session management network element, or the first indication information includes the multicast service identifier.

The QoS flow information of a service includes information of one or more QoS flows of the service, where the information of one QoS flow includes QFI of the QoS flow, service identification information mapped to the QoS flow (e.g., a quintuple or service identifier, where a destination address in the quintuple information is a multicast IP address of the service), a QoS parameter of the QoS flow (e.g., 5QI, a maximum bandwidth requirement, etc. corresponding to the QoS flow).

Optionally, the first session management network element further receives eighth indication information from the second session management network element or the UDM or the UDR, where the eighth indication information indicates that the service needs to support service continuity when switching across systems, and service continuity refers to ensuring that data packets of the service are not lost as much as possible and/or are sent in sequence when the terminal device moves. If the first session management network element receives the eighth indication information, determining a unicast QoS flow corresponding to the service according to the information of the multicast QoS flow.

S102, the first session management network element sends second indication information to the first user plane network element according to the first indication information, wherein the second indication information is used for indicating to send the data packet of the service to the terminal equipment through the unicast bearer.

For the second case, the second indication information includes a third mapping relationship between the service identification information and the information of the first tunnel when the AS transmits the data of the service in the second case. Optionally, the service identification information includes an IP address of the terminal device. When receiving a data packet of a service, the first user plane network element determines information of a first tunnel for transmitting the data packet according to service identification information of the data packet and the third mapping relation. Wherein, each unicast bearer corresponds to the information of a first tunnel, the information of the first tunnel is the tunnel information of a downlink node, and the downlink node is an SGW or an access network device (when the SGW is set together with other network elements).

For the first case, the second indication information includes a second mapping relationship between the service identification information and the information of the first tunnel when the AS transmits the data of the service in the first case, or a first mapping relationship between the identifier QFI of the multicast QoS flow of the service and the information of the first tunnel. For the architecture described in fig. 5, when the unicast path is AS- > PGW-u+upf- > eNB- > UE, the second mapping relationship is included in the second indication information; for the architecture shown in fig. 5, when the unicast path is AS- > UPF- > PGW-u+upf- > eNB- > UE, the second indication information includes the first mapping relationship, where the first mapping relationship is used for determining, by the first user plane network element, information of a first tunnel used for sending the data packet according to the QFI in the data packet received from the UPF, that is, determining a unicast bearer corresponding to the data packet. Wherein, each unicast bearer corresponds to the information of a first tunnel, the information of the first tunnel is the tunnel information of a downlink node, and the downlink node is an SGW or an access network device (when the SGW is set together with other network elements).

When the unicast path is AS- > UPF- > PGW-U+UPF- > eNB- > UE, further, the second indication information is further used for obtaining information of a second tunnel, the information of the second tunnel is used for the first user plane network element to receive a data packet of a service from the second user plane network element or an application server, and the first session management network element receives the information of the second tunnel from the first user plane network element AS a response message and sends the information of the second tunnel to the second user plane network element or the AS.

Or when the unicast path is AS- > UPF- > PGW-U+UPF- > eNB- > UE, the second indication information further comprises second tunnel information, so that after the first user plane network element receives the data packet from the second tunnel, the first tunnel information used for sending the data packet is determined according to the first mapping relation.

In addition to this, the first session management unit requests the other nodes to create unicast bearers, for example PGW-c+smf sends a message to SMF to create unicast bearers, and correspondingly SGW sends a message to MME and MME sends a message to access network device to create unicast bearers. Since the above method is the same as the prior art, the description of this embodiment is omitted.

For the first case, when the unicast path is AS- > PGW-u+upf- > eNB- > UE, a second tunnel from AS to PGW-u+upf needs to be established, and then PGW-c+smf needs to further send information of the second tunnel to AS. The PGW-c+smf may carry information of the second tunnel in a fifth notification message, where the fifth notification message is used to notify the AS to send data of the service using the information of the second tunnel. Further, the fifth notification message is further configured to notify that a unicast bearer for sending data of the service is established, and the AS may further send a sixth notification message to the terminal device according to the fifth notification message, where the sixth notification message is configured to notify the terminal device to use the unicast bearer to receive the data of the service.

For the first case, when the unicast path is AS- > UPF- > PGW-u+upf- > eNB- > UE, the first session management network element sends the information of the second tunnel to the second user plane network element, including, if the first session management network element is a session management network element for managing the second user plane network element, directly sending the information of the second tunnel to the second user plane network element by the first session management network element; if the first session management network element is not the session management network element for managing the second user plane network element, the first session management network element sends the information of the second tunnel to the session management network element for managing the second user plane network element, and the session management network element for managing the second user plane network element sends the information of the second tunnel to the second user plane network element.

S103, when the terminal equipment is accessed through the second network, the first session management network element adds the terminal equipment into the multicast session corresponding to the service.

In order to support switching of data of the service transmitted through the MBMS bearer of the first network to transmission through the second network and maintain continuity of the service, in this embodiment, before switching the terminal device to the second network, the data of the service is switched from transmission through the MBMS bearer to transmission through the unicast bearer (i.e., EPS bearer) to transmission to the terminal device. Specifically by steps S101 and S102. In order for the terminal device to send the first report in time so that there is enough time to switch the service to the second network after the unicast bearer, an appropriate MBMS signal strength threshold may be configured for the terminal device, and when the terminal device detects that the MBMS signal is below the threshold, the terminal device sends the first report.

In this embodiment, the following three service switching modes are provided to realize the switching of multicast services:

the first multicast service switching mode: in the switching process of the terminal equipment from the first network to the second network, the first session management unit switches the data packet of the service from being sent to the terminal equipment through a unicast bearer to being sent to the terminal equipment through a PDU session, and after the terminal equipment is switched from the first network to the second network, the first session management network element adds the terminal equipment into a multicast session corresponding to the service, and the data packet of the service is switched from being sent to the terminal through the PDU session to being sent to the terminal equipment through the multicast session.

The PDU session is a unicast path in a second network, taking a first network as a 4G network and a second network as a 5G network as an example, the method switches a data packet transmitted through an MBMS bearer from the MBMS bearer to the unicast path of the 4G network, then switches the unicast path of the 4G network to the unicast path of the 5G network, and then switches the unicast path of the 5G network to the multicast path of the 5G network, thereby ensuring the continuity of multicast service in the switching process of the service of the terminal equipment from the MBMS bearer transmission through the 4G network to the multicast session transmission through the 5G network. The unicast path from the 4G network to the unicast path of the 5G network may refer to the description of the 4G-to-5G switching procedure in the prior art, and will not be repeated.

The 5G multicast session includes a 5G multicast path, the 5G multicast session may further include one or more QoS flows, different QoS flows are used to send service data with different QoS requirements, and of course, the 5G multicast session may further include information such as QoS parameters corresponding to each QoS flow, which is not limited.

The second multicast service switching mode: in the process of switching the terminal equipment from the first network to the second network, the first session management network element adds the terminal equipment into the multicast session corresponding to the service, and the data packet of the service is switched from being sent to the terminal equipment through the unicast bearer of the first network to being sent to the terminal equipment through the multicast session.

The second switching mode is opposite to the first switching mode, the first session management network element directly switches the data packet of the service from the unicast bearer of the first network to the multicast session of the second network, and the first switching mode does not need to switch the data packet of the service from the unicast bearer of the first network to the unicast bearer of the second network and then switches the data packet of the service from the unicast bearer of the second network to the multicast session of the second network.

The two switching modes can ensure the continuity of the multicast service in the process of switching the terminal equipment from the first network to the second network.

Before the first session management network element joins the terminal device in the multicast session, the first session management network element also needs to determine whether the service supports multicast transmission through the second network, and whether the terminal device supports multicast in the second network. When the service supports multicast transmission through the second network and the terminal device supports multicast in the second network, the first session management network element joins the terminal device into a multicast session of the service in the second network.

The first session management network element may determine whether the service supports multicast transmission over the second network by: the first session management network element receives third indication information, where the third indication information is used to indicate that the service supports multicast mode transmission. Further, the third indication information further includes a multicast service identifier of the service, or the third indication information is an identifier of the multicast service.

In one implementation, the first rule includes third indication information.

Taking the first rule as a PCC rule as an example, the PCF sends the first rule to the first session management network element. The third indication information may indicate, in an explicit manner or in an implicit manner, that the service supports multicast transmission of the second network, where the third indication information is an newly added indication in the PCC rule, for example, the PCF may add an indication whether to support multicast transmission in the PCC rule corresponding to each service, or add an indication indicating multicast transmission in the PCC rule corresponding to the service supporting multicast service. Optionally, if the service supports multicast mode transmission, the PCC rule further includes a multicast service identifier. For example, the multicast service identifier may be, but not limited to, a temporary mobile group identity (Temporary Mobile Group Identity, TMGI) of the service or a multicast address of the service when played in a multicast manner in the second network or other identifier for identifying the multicast service.

In the implicit mode, whether the service supports the multicast mode transmission can be indicated through the multicast service identifier, and when the PCC rule of the service comprises the multicast service identifier of the service, the first session management network element determines that the service supports the multicast mode transmission. Or when the destination address of the service included in the PCC rule is a multicast address, determining that the service supports multicast mode transmission.

Optionally, the third indication information may be directly sent to the PGW-c+smf by the AS instead of being carried in the PCC rule, where the AS may send the third indication information to the PGW-c+smf in service information, where the service information may include description information (e.g., five-tuple information such AS IP address, port number, protocol number, etc.) and QoS requirement information (e.g., bandwidth requirement, latency requirement, etc.) of the service.

In one implementation, the first indication information may be sent to the first session management network element in the same message as the first rule, or the first rule may also be used as the first indication information, that is, the first rule indicates, through the first rule, a data packet that sends a service to a terminal device located in the first network through a unicast bearer.

In another implementation, the first indication information and the first rule are carried in different messages, and the first session management network element may receive the first rule before receiving the first indication information. In this implementation manner, the first indication information includes identification information of the service, where the identification information of the service may be a multicast service identifier corresponding to the service. The first session management network element may obtain a first rule during the PDN connection establishment process, or when data of the service is sent to the terminal device for the first time in a unicast bearer manner of the first network, for example, at the above-mentioned occasion, the AS sends information of the service to the PCF, where the information of the service includes indication information for indicating whether the service supports multicast transmission and description information when the service is sent in a case one (a destination address of a data packet is a multicast address), where the description information includes identification information of at least one data traffic flow of the service and QoS requirement information corresponding to the identification information, and the PCF generates the first rule according to the information of the service and sends the first rule to the first session management network element.

Further, the first session management network element determines that the terminal device supports multicast in the second network, by:

the first session management network element may receive multicast capability indication information sent by the terminal device during the process of establishing the PDN connection by the terminal device, where the multicast capability indication information is used to indicate multicast capability of the terminal device in the second network, and the first session management network element determines that the terminal device supports multicast in the second network according to the multicast capability indication information.

Illustratively, the capability indication information is included in session management capability information of the terminal device. The terminal device may indicate whether the terminal device supports the multicast service through indication information of one or more bits. For example, the terminal device indicates whether the terminal device supports the multicast service through the indication information of one bit, when the value of the bit is 1, the terminal device is indicated to support the multicast service in the second network, and when the value of the bit is 0, the terminal device is indicated to not support the multicast service in the second network.

Or when the terminal equipment does not support the multicast service in the second network, the terminal equipment does not carry the multicast capability indication information in the process of establishing the PDN connection. And the first session management unit determines that the terminal equipment does not support the multicast service in the second network if the multicast capability indication information is not received in the process of establishing the PDN connection of the terminal equipment, and determines that the terminal equipment supports the multicast service in the second network if the multicast capability indication information is received.

After the first session management network element determines to join the terminal device into the multicast session corresponding to the service, the multicast session may or may not be established. If the multicast session is not established, the first session management network element triggers the establishment of the multicast session. The first session management network element triggers to establish the multicast session, which is described in the prior art, and this embodiment is not repeated.

In one implementation, a first session management network element receives a request message sent by an AMF, where the request message is used to create or update a PDU session, the first session management network element determines that the service sent through a unicast bearer supports multicast mode sending, and the terminal device supports multicast service in a second network, and then the first session management network element instructs a target access network device in the second network to join the terminal device in the multicast session.

The request message is illustratively a create session request message or an update session request message. In the first multicast service switching manner, the request message may be an update session request message, where the request message indicates that switching is completed, and the first session management network element instructs the target access network device in the second network to join the terminal device in the multicast session after receiving the request message, that is, instructs the target access network device in the second network to join the terminal device in the multicast session after switching is completed.

In the second multicast service switching manner described above, the request message may be a create session request message, and the request message may indicate to switch preparation, where the first session management network element instructs the target access network device in the second network to join the terminal device in the multicast session, and the message is sent to the target access network device in a switch request (HO request) message, that is, the first session management network element instructs the target access network device in the second network to join the terminal device in the multicast session in a switch preparation stage. The switching request message includes seventh indication information, where the seventh indication information is used to indicate that the terminal device joins the multicast session corresponding to the service, and after receiving the switching request message, the target access network device allocates a radio resource for the terminal device according to the seventh indication information in the switching request message, where the radio resource is used to receive data of the service through the multicast session, encapsulates the radio resource in a transparent container, sends the radio resource to the source access network device in the first network, and the source access network device sends the radio resource to the terminal device, so that the terminal device can receive the data of the service from the target access network device according to the radio resource.

Taking the first session management network element as PGW-c+smf, the first network as 4G network, and the second network as 5G network as an example, PGW-c+smf further obtains parameters of multicast QoS flow when the service is sent in a multicast manner in 5G, and sends the parameters of multicast QoS flow to the target access network device in the second network during the process of instructing the target access network device to join the terminal device in the multicast session, or before instructing the target access network device in the second network to join the terminal device in the multicast session.

For the first multicast service switching mode, after the terminal device joins the multicast session, the first session management network element notifies the first user plane network element to stop sending the service data to the terminal device through the PDU session.

For the first or second multicast service switching manner, after the terminal device joins the multicast session, optionally, the first session management network element sends a third notification message to the AS for notifying that the terminal device has switched to the second network, or for notifying that the AS uses the multicast session to send data of the service to the terminal device. After receiving the third notification message, optionally, in response to the third notification message, the AS sends a fourth notification message to the terminal device, where the fourth notification message is used to notify the terminal device to start receiving data of the service using the multicast session.

In the third multicast service switching manner, the process of switching the data of the multicast service from the MBMS bearer to the unicast bearer is the same as the prior art, or the process of establishing the unicast bearer by the first session management network element is the same as the prior art, which is different from the prior art in that: when the first session management network element receives the indication information sent by the AMF and indicating the preparation or completion of the handover, the first session management network element sends a first notification message to the AS, where the first notification message is used to notify support or will support to send data of the service to the terminal device in a multicast mode of the second network, or is used to notify the terminal device to switch to or will switch to the second network, or is used to notify the AS that the service is used to send data of the service to the terminal device in a mode of service condition.

Optionally, before the first session management network element sends the first notification message to the AS, the first session management network element receives sixth indication information, where the sixth indication information is used to indicate that, when supporting or about to support sending data of a service to the terminal device in a multicast manner of the second network, or when the terminal device switches to or about to switch to the second network, the first notification message is sent to the AS. Correspondingly, the first session management network element sends the first notification message to the AS when the terminal device starts to switch to the second network or successfully switches to the second network according to the sixth indication information.

The sixth indication information may be sent to the first session management network element together with the first indication information, for example, the first session management network element receives a first message sent by the AS or the PCF, where the first message includes the first indication information and the sixth indication information.

In the third multicast service switching method, when the terminal device receives the data of the multicast service through the unicast bearer of the first network, the AS sends the data of the multicast service in a second mode (i.e., the destination address is the address of the terminal device). In this way, therefore, the first indication information is the second rule, and the third indication information is not included in the second rule. The sixth indication information is sent together with the first indication information, which may be understood that the second rule includes the sixth indication information, where the sixth indication information may be a subscription request.

In the third multicast service switching manner, the first session management network element adds the terminal device to the multicast session corresponding to the service, which may be: the first session management network element receives fifth indication information, where the fifth indication information is used to indicate that the terminal device joins the multicast session corresponding to the service, and the first session management network element joins the terminal device into the multicast session corresponding to the service according to the fifth indication information.

The fifth indication information may be sent by the core network device or the terminal device to the first session management network element. After receiving the first notification message, the AS may send a request message for joining the terminal device to the multicast session to the core network device, and the core network device sends the fifth indication information to the first session management network element according to the request message. Or, the AS sends a second notification message to the terminal device after receiving the first notification message, where the second notification message is used to notify the terminal device to receive the data of the service using the multicast session, and in response to the second notification message, the terminal device sends the fifth indication information to the first session management network element.

Similarly to the first or second multicast service switching manner, the first session management network element needs to determine whether the terminal device supports multicast in the second network, which can be specifically described with reference to the first or second multicast service switching manner.

In the third multicast service switching manner, the method for the first session management network element to join the terminal device into the multicast session may refer to the first or second multicast service switching manner, which is not described herein.

In the third multicast service switching mode, before the terminal device switches to the second network, the service is sent to the terminal device through the unicast bearer of the first network, and after switching to the second network, the service is switched to the unicast bearer passing through the second network and sent to the terminal device. The first session management network element may delete unicast resources corresponding to the service after joining the terminal device to the multicast session. The first session management network element may delete the corresponding unicast resource after receiving the indication to delete the second rule, in one implementation, the AS sends a request to delete the second description information to the core network device after receiving the first notification message, where the second description information is information of a service when the AS sends data of the service in a second manner, including identification information and QoS parameters of the service, and the core network device sends the indication to delete the second rule to the first session management network element when receiving the request to delete the second description information, where the second rule is generated by the core network device according to the second description information.

In this embodiment, when a signal of a multicast area where a terminal device located in a first network is located is weak, a first session management network element receives first indication information, where the first indication information is used to indicate a data packet for sending a service to the terminal device through a unicast bearer, and the first session management network element sends second indication information to a first user plane network element, where the second indication information is used to indicate that the data packet is sent to the terminal device through the unicast bearer, and when the terminal device is accessed through a second network, the first session management network element joins the terminal device into a multicast session corresponding to the service. The method comprises the steps of switching service data from a multicast path of a first network to a unicast bearer of the first network, switching the service data from the unicast bearer of the first network to a unicast path of a second network, and then switching the service data to a multicast session, or directly switching the service data from the unicast path of the first network to the multicast session of the second network, or notifying an AS in a first session management network element in order to directly notify a core network device by the AS, or notifying the first session management network element by a terminal device, joining the terminal to the multicast session of the second network by the AS, thereby ensuring that multicast service data received by the terminal device through the multicast path of the first network is received through the multicast path of the second network after the terminal device is switched to the second network, and maintaining continuity of the service.

Fig. 7 is a flowchart of a method for switching multicast services provided in the second embodiment of the present application, in which the first embodiment describes the method from the first session management network element side, and the second embodiment describes the method from the AS side, AS shown in fig. 7, and the method provided in this embodiment includes the following steps:

s201, the AS receives a first report from the terminal device, where the first report is used to instruct the terminal device to move out of the MBMS area.

The terminal device may send the first report in case the signal of the MBMS area in which it is currently located is weak, or in case the terminal device is about to or has moved from the MBMS area to the 5G network. In order to support smooth switching of data sent over the MBMS bearer to the multicast path in the second network, it is assumed in this embodiment that a suitable predetermined value is configured for the terminal device, for example, when the signal quality of the MBMS detected by the terminal device is inferior to the predetermined value, the terminal device sends the first report to the AS, the first report being used to instruct the terminal device to move out of the MBMS area, which is the area in the first network.

The network may ensure that the terminal device sends the first report to the AS before a cell handover from the first network to the second network occurs by configuring an appropriate predetermined value.

S202, AS determines a data packet for sending service to the terminal equipment through unicast bearing according to the first report.

The AS determines that the data packet of the service is sent to the terminal device through the unicast bearer of the first network under the condition that the signal of the MBMS area where the terminal device is currently located is weak according to the first report, or under the condition that the AS determines that the terminal device is about to move out of the MBMS area or has moved out of the MBMS area according to the first report.

S203, AS sends first indication information to the core network device and/or the first session management network element, wherein the first indication information is used for indicating to send the data packet of the service to the terminal device through unicast bearing.

The first session management network element may be PGW-c+smf, and the AS may directly send the first indication information to PGW-c+smf, or may send the first indication information to a core network device, where the core network device may send the first indication information to PGW-c+smf, and the core network device may be PCF or NEF.

Optionally, the AS further sends third indication information to the core network device, where the third indication information is used to indicate that the service supports multicast mode sending.

Wherein, the AS sends the data packet of the service to the terminal device located in the first network through the unicast bearer of the first network in two cases:

In the first case, the data packet of the service sent by the AS includes the data of the service and the destination address, where the destination address is a multicast address.

In the second case, the data packet of the service sent by the AS includes the data of the service and the destination address, where the destination address is the IP address of the terminal device.

For the first case, the first indication information may further include a first rule, or the first indication information is sent to the first session management network element together with the first rule, or the first indication information is the first rule. The first rule may be a PCC rule corresponding to the service when the AS sends data of the service in a case one manner. The first rule is determined by the PCF according to first description information, and the first description information is corresponding service information when the service is sent in a mode of passing through the service, and comprises identification information of the service and corresponding QoS parameters. The first indication information is used for indicating the first session management network element to create a unicast bearer according to the first rule. Optionally, the first indication information includes a multicast service identifier.

Further, in this case, the first rule may further include third indication information, where the third indication information is used to indicate that the service supports multicast mode for sending, and when the first indication information does not include a multicast service identifier, the third indication information may be a multicast service identifier corresponding to the service. Or the first rule further comprises a multicast service identifier corresponding to the service besides the third indication information, namely the multicast service identifier exists independently of the first indication information and the third indication information.

For the second case, the first indication information may further include a second rule, or the first indication information is sent to the first session management network element together with the second rule, where the first indication information is the second rule. The second rule may be a PCC rule corresponding to the service when the AS sends data of the service in a second manner. The first indication information is used for indicating the first session management network element to create the unicast bearer according to the second rule. The second rule is determined by the PCF according to second description information, and the second description information is corresponding service information when the service is sent in a second mode, and comprises identification information of the service and corresponding QoS parameters.

In one mode, after receiving the first report, the AS sends a second message to the PCF or the NEF, where the second message carries the first indication information, and the PCF or the NEF sends the first indication information carried in the first message to the PGW-c+smf. The first rule is sent to the PCF, NEF, or PGW-c+smf before sending the first indication. Optionally, the first indication information includes a multicast service identifier, or the second message carries the first indication information and the multicast service identifier. When the second message carries the first indication information and the multicast service identifier, the PCF or the NEF correspondingly sends the first indication information and the multicast service identifier carried in the first message to the PGW-c+smf.

In another way, after receiving the first report, the AS sends a second message to the PCF or the NEF, where the second message carries the first indication information and the first description information, and the PCF or the NEF sends the first indication information and the first rule carried in the first message to the PGW-c+smf, where the first rule may be used AS the first indication information, that is, the first message may include only the first rule. Optionally, the first indication information includes a multicast service identifier, or the second message carries the first indication information, the multicast service identifier, and the first description information, or the multicast service identifier may be carried in the first description information. When the second message carries the first indication information, the multicast service identifier and the first description information, the PCF or the NEF correspondingly carries the first indication information, the first rule and the multicast service identifier in the first message and sends the first indication information, the first rule and the multicast service identifier to the PGW-c+smf, or the multicast service identifier is included in the first rule.

For the second case, the first session management network element sends a first notification message to the AS when determining that the terminal device is ready to switch to the second network or the switch is completed, where the first notification message is used to notify that the terminal device is supported or about to support sending the data of the service in the multicast mode of the second network to the terminal device, or is used to notify that the terminal device is switched to or about to switch to the second network, or is used to notify that the AS uses the first mode to send the data of the service to the terminal device.

Correspondingly, the AS receives the first notification message from the first session management network element, and according to the first notification message, the AS sends a request message for joining the terminal device into the multicast session to the core network device, and according to the request message, the core network device sends the fifth indication information to the first session management network element, and the AS may also send the fifth indication information to the core network device. Or the AS sends a second notification message to the terminal equipment according to the first notification message, wherein the second notification message is used for notifying the terminal equipment to receive the data of the service by using the multicast session, and the terminal equipment sends fifth indication information to the first session management network element after receiving the second notification message.

Optionally, the AS sends sixth indication information to the core network device, where the sixth indication information is used to indicate that, when supporting or about to support sending data of a service to the terminal device in a multicast manner of the second network, or when the terminal device switches to or about to switch to the second network, the first notification message is sent to the AS. The AS may send the first indication information and the sixth indication information to the core network device through the second message.

Optionally, after the unicast bearer is established for the terminal device, the AS receives a fifth notification message from the first session management network element, where the fifth notification message is used to notify the AS to send data of the service using the unicast bearer of the first network. And the AS sends a sixth notification message to the terminal equipment according to the fifth notification message, wherein the sixth notification message is used for notifying the terminal equipment to receive the data of the service by using the unicast bearer of the first network.

In this embodiment, the AS receives a first report from the terminal device, where the first report is used to instruct the terminal device to move out of the MBMS area, and the AS determines, according to the first report, to send a data packet of the service to the terminal device through the unicast bearer of the first network, and sends first indication information to the core network device and/or the first session management network element, to instruct to send the data packet of the service to the terminal device through the unicast bearer of the first network. Therefore, the first session management network element establishes a unicast bearer of the first network for the terminal equipment, the data packet of the service is firstly switched to the unicast bearer in the first network, and then the unicast bearer is switched to the multicast session in the second network, so that the continuity of the service is maintained in the switching process of multicast service data received by the terminal equipment through the MBMS bearer in the process of switching the terminal equipment from the first network to the second network.

Fig. 8 is a signaling flow chart of a method for switching multicast services according to the third embodiment of the present application, where the first multicast service switching manner described above is taken as an example, that is, data transmitted by an MBMS bearer is first switched from an MBMS bearer to a unicast bearer in a 4G network, in a switching process of a terminal device from the 4G network to the 5G network, PGW-c+smf switches data transmitted by the MBMS bearer from the unicast bearer in the 4G network to a PDU session (that is, a unicast path in the 5G network), and PGW-c+smf switches the terminal device to the 5G multicast session after the terminal device is switched from the 4G network to the 5G network, that is, from the unicast path in the 5G network to the 5G multicast path.

In this embodiment, the AS may directly send the data to the PGW-u+upf, or the AS may send the data to the UPF first and then send the data to the PGW-u+upf through the UPF.

Referring to fig. 5 and 8, the method provided in this embodiment includes the following steps:

s301, PDN connection is established.

After the terminal equipment establishes the PDN connection in the 4G network, the terminal equipment can establish signaling connection with the AS through the PDN connection, and the signaling path is AS follows: AS < - > PGW-U < - > eNB < - > UE, the eNB is an access network device in the 4G network. And, if the current location of the terminal device supports MBMS, the AS may inform the terminal device to receive data (e.g., media data) of the service through the MBMS bearer. The path of sending data to the terminal equipment by the AS through the MBMS bearer is AS follows: AS- > BM-SC- > MBMS GW- > eNB- > UE.

The procedure for establishing a PDN connection may refer to the prior art and will not be described in detail here. Unlike the prior art, if the terminal device supports 5G multicast capability, the terminal device carries 5G multicast capability indication information in a protocol configuration option (Protocol Configuration Option, PCO) of the PDN connection establishment request message.

In order to support 4G and 5G interworking, PGW-C selected by MME for the PDN connection is PGW-c+smf, and UPF selected by PGW-c+smf for the PDN connection is PGW-u+upf.

Data between the AS and the terminal device is classified into two types, one is a signaling data stream and the other is a non-signaling data stream (e.g. voice or video or file data), and the AS can decide which data streams are transmitted through the MBMS bearer and which data are transmitted through the unicast bearer. For example, the signaling data stream is sent over a unicast bearer, the non-signaling data stream is sent over an MBMS bearer, although the AS may also decide to send part of the signaling data stream over the MBMS bearer and another part of the signaling data stream over the unicast bearer.

For traffic data streams that are not to be sent over the MBMS bearer, the AS may send these traffic data streams using the IP address (unicast address) of the terminal device. For traffic data flows that may be sent over MBMS bearers, the AS may send using multicast IP addresses. It should be noted that, the service data stream that may be transmitted through the MBMS bearer may also be transmitted through the unicast bearer when the UE moves out of the MBMS area. If the destination address of the packets of the service sent on the MBMS bearer is a multicast IP address, after the packets of the service are switched to be sent over the unicast bearer, the AS does not need to change the format of these packets, i.e. the destination IP address can still use the multicast IP address.

Alternatively, the AS may establish a policy session to the core network device (e.g., PCF/NEF) that is associated with the PDN connection. The AS may send the description information of the service to the core network device through the policy session, so that the mobile network allocates corresponding unicast bearer resources for the service. The description information of the service transmitted to the core network includes identification information (e.g., five-tuple information such as IP address, port number, protocol number, etc.) and QoS requirement information (e.g., bandwidth requirement, latency requirement, etc.) of the service. It should be noted that, the service may include at least one service data flow, and the description information of the service includes description information of the at least one service data flow.

If the AS supports sending the service in a multicast mode (5G multicast mode or MBMS multicast mode), the AS includes third indication information in the description information of the service, where the third indication information is used to indicate that the service supports sending in the multicast mode.

Optionally, even if the service supporting the multicast mode is currently sent through the MBMS bearer, the AS may send the description information of the service to the core network device in advance. The AS indicates that the service is not currently transmitted through the unicast bearer (or is currently transmitted through the MBMS bearer) when transmitting the description information of the service.

This step may also create an interface between the AS and PGW-u+upf for services sent in support of multicast, although the interface may also be created in step S305. In particular, the AS may send the processing requirements of the multicast service to the core network device, for example, the AS may request the core network to perform robust header compression (Robust Header Compression, ROHC) or forward error correction (Forward Error Correction, FEC) coding on the service data. The AS may include the above-described processing requirements in the information of the service.

The PCF may generate a PCC rule (first rule) according to the description information of the service sent by the AS and the processing requirement, and send the PCC rule to the PGW-c+smf corresponding to the PDN connection. If the AS indicates that the service supports the multicast mode, the PCF also transmits the indication information to the PGW-C+SMF so that the PGW-C+SMF can know that the service supports the multicast mode. For example, the PCF may carry third indication information in the PCC rule, where the third indication information is used to indicate whether multicast transmission is supported. If the AS sends the processing requirement to the PCF, the PCF also sends the processing requirement to the PGW-c+smf, e.g., the PCC rule carries the processing requirement. If the service information sent by the AS includes the multicast service identifier, the PCF sends the multicast service identifier to the PGW-c+smf, for example, the PCC rule includes the multicast service identifier.

In this embodiment, when the AS sends a service data packet to a terminal device located in the first network through a unicast bearer, the service data packet sent by the AS includes service data and a destination address, where the destination address is a multicast address.

If the transmission path between the PGW-U+UPF and the AS or UPF is not established, the PGW-C+SMF informs the PGW-U+UPF to establish the path. Specifically, for the second tunnel between the PGW-u+upf and the AS, if the path is based on the MB2-U interface, the PGW-c+smf may allocate or PGW-c+smf requests the PGW-u+upf to allocate information of the MB2-U interface, where the information of the MB2-U interface includes a user packet protocol (User Datagram Protocol, UDP) port number and an IP address for receiving the service data.

The UDP port number+ip address is used to identify a second tunnel between the AS and the PGW-u+upf, through which the service is transported between the AS and the PGW-u+upf, where the UDP port number+ip address may be created for the service or may be created for the service of the terminal device. When the information of the MB2-U interface is created for a service, the PGW-u+upf may be used to send data of the service from the AS to a plurality of terminal devices served by the PGW-u+upf (i.e. the second tunnel between the AS and the PGW-u+upf is a shared tunnel). If the information of the MB2-U interface is created for the service of the terminal device, the data received by the PGW-u+upf from the AS can only be sent to the terminal, i.e. the second tunnel between the AS and the PGW-u+upf is a dedicated tunnel of the terminal device. The path may also be based on other tunneling technologies, for example, a GTP-U based tunnel, and the establishment of the GTP-U based tunnel is similar to the tunnel described above, which is not repeated in this embodiment.

After the PGW-C+SMF acquires the information of the second tunnel, the PGW-C+SMF sends the information of the second tunnel to the AS, so that the AS sends the data packet of the service to the PGW-U+UPF through the second tunnel according to the information of the second tunnel. The PGW-c+smf may carry the information of the second tunnel to the AS in a fifth notification message or in other messages, where the fifth notification message is used to notify the AS to send the data of the service using the unicast bearer.

When the AS sends the data of the service to the UPF and then to the PGW-U+UPF by the UPF, a second tunnel between the PGW-U+UPF and the UPF needs to be established, and for the second tunnel between the PGW-U+UPF and the UPF, the second tunnel can request the PGW-U+SMF to allocate tunnel information of the second tunnel based on the GTP-U, including tunnel endpoint identifiers (Tunnel Endpoint Identifier, TEID) and IP addresses, and send the tunnel information to the UPF, and if the UPF is managed by other SMFs, the PGW-C+SMF sends the information of the second tunnel to the SMF and the SMF to the UPF. In this scenario, the UPF maps the traffic data to a multicast QoS flow and sends it to the PGW-U+UPF through a second tunnel. The SMF managing the UPF may determine at least one multicast QoS flow corresponding to the service according to a first rule of the service, including a QFI of the multicast QoS flow, a data flow of the service mapped to the multicast QoS flow, a QoS parameter of the multicast QoS flow, and the like.

S302, the terminal equipment sends a first report to the AS, wherein the first report is used for indicating the terminal equipment to move out of the MBMS area.

It is assumed that the terminal device is located in the MBMS area of the service and the terminal device receives data of the service through the MBMS bearer in step S301. Then, when the terminal device moves out of the MBMS area, a first report is sent to the AS.

The network may ensure that the terminal device sends the first report to the AS before a cell handover from the 4G network to the 5G network occurs by configuring an appropriate signal predetermined value, e.g. when the terminal device detects that the signal quality of the MBMS is inferior to the signal predetermined value, the terminal device sends the first report to the AS reporting to the AS an event that the MBMS channel quality of the terminal device is inferior to the signal predetermined value.

S303, the AS sends a second message to the PCF, wherein the second message comprises the first indication information.

The first indication information is used for indicating a data packet for sending service to the terminal equipment located in the first network through unicast bearing, and optionally, the first indication information comprises multicast service identification. Or the second message comprises the first indication information and the multicast service identification.

When the service needs to be clear, the service comprises a plurality of service data flows, in one case, all the service data flows in the service are currently sent through the MBMS bearer, in the other case, one part of the service data flows in the service are currently sent through the MBMS bearer, and the other part of the service data flows are currently sent through the unicast bearer. In the embodiment of the application, when the service of the terminal equipment is switched from the MBMS bearing to the unicast bearing, only the service data stream currently sent by the MBMS bearing is switched to the unicast bearing, and the service data stream currently sent by the unicast bearing is not processed.

If the AS has established a policy session associated with the PDN connection (i.e., the PDN connection established in S301), the AS sends a second message over the policy session.

If the AS does not send the description information of the service data flow to be switched to the unicast bearer to the PCF/NEF in step S301, the second message may further include the description information of the service data flow to be switched to the unicast bearer. If the AS has already sent the description information of the service data flow that needs to be switched to the unicast bearer to the PCF/NEF in step S301, the second message may or may not include the description information of the service data flow that needs to be switched to the unicast bearer.

The description information of the service data streams to be switched to the unicast bearer includes third indication information, where the third indication information indicates that the service data streams support transmission in a multicast mode (5G multicast or MBMS multicast). The third indication information may be indicated in a display manner or an implicit manner, and is not described herein in detail with reference to the description related to the first embodiment.

Optionally, the second message further includes processing requirements of the AS on the service data flows, for example, the AS may request the core network to perform header compression (ROHC) or forward redundancy coding (FEC) on the service data. See description of S301, and will not be repeated.

S304, the PCF sends a first message to the PGW-C+SMF, wherein the first message comprises first indication information.

Optionally, the first message includes a PCC rule (i.e., a first rule) corresponding to a service data flow to be switched to the unicast bearer, where the PCC rule includes third indication information, and the PCC rule is generated by the PCF according to description information of the service data flow to be switched to the unicast bearer, which is included in the second message. Alternatively, if PGW-c+smf has obtained PCC rules for these traffic data flows, the first message may include only the first indication information. Optionally, the first message further includes a multicast service identifier.

Alternatively, in other embodiments, the AS may send the second message directly to the PGW-c+smf.

In this embodiment of the present application, the first indication information included in the second message sent by the AS to the core network device is the same AS the first indication information included in the first message sent by the core network device to the PGW-c+smf, and is a data packet for indicating to send a service to the terminal device located in the first network through the unicast bearer, but names of the first message and the second message may be different.

S305, PGW-C+SMF establishes unicast bearer for service sent in multicast mode.

If the second tunnel is not already established, the second tunnel is established in this step, and the description of step S301 may be referred to, which is not repeated here. The step of establishing unicast bearer for the service sent in the multicast supporting mode comprises the following steps:

the PGW-C+SMF establishes a unicast bearer for the service according to the first indication information, and in the establishment process, the PGW-C+SMF sends second indication information to the PGW-U+UPF, wherein the second indication information is used for indicating to send a data packet to the terminal equipment through the unicast bearer. The PGW-u+upf receives the second indication information, and if the transmission path between the PGW-u+upf and the AS is not yet established, for the first case, a second tunnel between the PGW-u+upf and the AS is established according to the step in S301. The description of the first embodiment is referred to for the related information of the second indication information, which is not repeated here.

If the second tunnel is a tunnel between the PGW-u+upf and the AS or the PGW-u+upf directly receives the data of the service from the AS (i.e., the second tunnel is not needed), the second indication information includes a second mapping relationship, where the second mapping relationship is a mapping relationship between service identification information and information of the first tunnel when the AS sends the data of the service in a case one, and the PGW-u+upf may match a packet of the service received from the second tunnel or directly received from the AS with the second mapping relationship, and if the matching is successful, the packet is sent through the matched first tunnel. The PGW-c+smf may determine the bearer corresponding to each service data flow according to the PCC rule of the service, and generate a second mapping relationship according to the identification information of the service data flow and the first tunnel information corresponding to the bearer, and then send the second mapping relationship to the PGW-u+upf, so that the PGW-u+upf determines the tunnel of the bearer corresponding to the received data packet of the service. When mapping a data flow of a service to a unicast bearer, PGW-c+smf may map the service data flow to a new bearer, i.e. create a new bearer for the data flow of the service, or PGW-c+smf may map the data flow of the service to an existing bearer, i.e. modify the existing bearer to add the service data flow.

If the second tunnel is a tunnel between the PGW-u+upf and the UPF, the PGW-c+smf determines a first mapping relationship between the QFI of the multicast QoS flow and the first tunnel information, and sends the first mapping relationship to the PGW-u+upf, so that the PGW-u+upf determines the first tunnel information of the unicast bearer corresponding to the QFI of the data packet received from the second tunnel according to the QFI of the data packet, so that the data packet is sent by using the first tunnel, that is, the second indication information includes the first mapping relationship.

Establishing the unicast bearer also includes informing the SGW, a base station in the first network, etc. to allocate tunnel information for the bearer and allocate corresponding resources. Reference is made in particular to the prior art and is not repeated here.

In addition, in order that the service can be switched from unicast bearer transmission through the first network to PDU session transmission through the second network, in this step, PGW-c+smf further determines parameters of a unicast QoS flow corresponding to the service when the service is transmitted through the PDU session of the second network, for example, PGW-c+smf may map one or more data flows of the service to one unicast QoS flow, determine QoS parameters of the unicast QoS flow according to QoS parameters of the service data flow mapped to the unicast QoS flow, and transmit the parameters of the unicast QoS flow to the terminal device, where the parameters of the unicast QoS flow include QFI of the unicast QoS flow.

S306, the PGW-C+SMF sends a fifth notification message to the AS.

The fifth notification message is used to notify the AS to send the data of the service using the unicast bearer, or to notify the AS network that the service data stream transmitted on the MBMS bearer has been switched or migrated to the unicast bearer.

If the information of the second tunnel between the PGW-u+upf and the AS is allocated in the step S305, the PGW-c+smf includes the information of the second tunnel in the fifth notification message, so that the AS sends the service data to the PGW-u+upf according to the information of the second tunnel.

S307, AS sends a sixth notification message to the terminal device.

In response to the fifth notification message, the AS sends a sixth notification message to the terminal device, where the sixth notification message is used to notify the terminal device that the data of the service is received by using the unicast bearer, or is used to notify the terminal device that the network has switched or migrated the service data stream transmitted on the MBMS bearer to the unicast bearer.

Steps S306 and S307 are optional steps, i.e. after the PGW-c+smf establishes the unicast bearer, the AS and the terminal device may not be notified. Or the PGW-C+SMF sends a fifth notification message to the AS, and the AS does not send a sixth notification message to the terminal equipment.

S308, the terminal equipment is switched from the 4G network to the 5G network.

In the present embodiment, in the cell switching process, a service data stream transmitted on an MBMS bearer is switched from a unicast bearer of a 4G network to a unicast path of a 5G network, where the unicast path of the 5G network is a PDU session, and the data bearer is a unicast QoS stream in the PDU session.

It can be appreciated that data in the 5G network is transmitted through QoS flows, which in this embodiment include two types: a unicast QoS flow and a multicast QoS flow, traffic data flows transmitted on MBMS bearers are mapped to the unicast QoS flow or the multicast QoS flow, wherein the unicast QoS flow is a data bearer in a 5G unicast path and the multicast QoS flow is a data bearer in a 5G multicast path.

S309, joining the terminal equipment into the 5G multicast session corresponding to the service.

If the service support is sent in a multicast mode, after the terminal equipment is successfully switched to the 5G network, the terminal equipment can be added into a 5G multicast session corresponding to the service. It can be appreciated that after the terminal device switches to the 5G network, the 5G multicast session may or may not be established, and if the 5G multicast session is not established, PGW-c+smf triggers to establish the 5G multicast session, and PGW-c+smf triggers to establish the 5G multicast session, which is referred to the prior art and will not be described herein.

And after the terminal equipment is successfully switched to the 5G network, the PGW-C+SMF judges whether the terminal equipment supports the 5G multicast service and the service supports the multicast mode for transmission, and the PGW-C+SMF determines to add the terminal equipment into the 5G multicast session corresponding to the service.

The PGW-c+smf may determine whether the terminal device supports the 5G multicast service according to the 5G multicast capability indication information of the terminal device received in step 301.

The PGW-c+smf may determine whether the service supports multicast transmission according to the third indication information received from the PCF or AS in step 301 or 304.

Optionally, before determining to join the terminal device into the 5G multicast session corresponding to the service, the PGW-c+smf determines that the target base station supports the 5G multicast capability, where the target base station is a base station to which the terminal device is connected in the 5G network. For example, during a handover procedure, the PGW-c+smf may obtain the 5G multicast capability of the target base station, e.g., the PGW-c+smf may obtain the capability of the target base station from the AMF (the capability may be sent to the AMF when the target base station supports 5G multicast service). Or the PGW-c+smf acquires the 5G multicast capability of the target base station in the process of triggering the creation of the multicast session to the target base station (if the multicast session is created successfully, this means that the base station supports the 5G multicast capability).

Optionally, the PGW-c+smf may not acquire the 5G multicast capability of the target base station in the handover process, but request the target base station to join the terminal device into the 5G multicast session if it is determined that the terminal device supports the 5G multicast service and the service is transmitted in a multicast-supporting manner, and agree to join if the target base station supports the 5G multicast service, and fail to join if the target base station does not support the 5G multicast service, and the PGW-c+smf determines that the target base station does not support the 5G multicast service according to a join failure event.

It will be appreciated that joining a terminal device to a 5G multicast session needs to be done jointly by a plurality of network elements, e.g. a base station gNB (i.e. target base station) and PGW-c+smf in a 5G network are required. The PGW-c+smf may notify the target base station to join the terminal device in the 5G multicast session after the 5G multicast session is established, or may notify the target base station to join the terminal device in the 5G multicast session during the 5G multicast session establishment, that is, notify the target base station to join the terminal device in the 5G multicast session when the parameters of the multicast QoS flow of the service are sent to the target base station. When receiving a request for joining the terminal equipment into the 5G multicast session, the target base station configures corresponding wireless resources for the terminal equipment so as to receive service data corresponding to the 5G multicast session from the target base station.

S310, the PGW-C+SMF sends a third notification message to the AS.

In this embodiment, after the PGW-c+smf joins the terminal device in the 5G multicast session corresponding to the service, the PGW-c+smf sends a third notification message to the AS, where the third notification message is used to notify that the terminal device is switched to the second network, or is used to notify the AS to start sending data of the service to the terminal device using the 5G multicast session.

S311, AS sends a fourth notification message to the terminal device.

In response to the third notification message, the AS sends a fourth notification message to the terminal device, where the fourth notification message is used to notify the terminal device to receive data of the service using the 5G multicast session.

S312, deleting the unicast QoS flow.

When PGW-c+smf switches the service data flow of the service to be sent through the 5G multicast session, PGW-c+smf may delete radio resources of the unicast QoS flow previously allocated for the service data flow.

Alternatively, PGW-c+smf may reserve the context of unicast QoS flows, but PGW-c+smf requests the gNB to delete radio resources of these unicast QoS flows to save resources of the gNB.

Optionally, the PGW-c+smf also informs the PGW-u+upf to stop sending traffic data flows to the terminal device that have been migrated to be sent over the 5G multicast session.

Fig. 9 is a signaling flow chart of a method for switching multicast services according to the fourth embodiment of the present application, where the method of the present embodiment may be performed before step S308 in the third embodiment, as shown in fig. 9, and the method provided in the present embodiment includes the following steps:

s401, PDN connection is established.

The specific implementation manner of this step refers to the description of step S301 in the third embodiment, and will not be repeated here. The PDN connection is used for signaling between the terminal device and the AS.

S402, data of the multicast service is transmitted through unicast bearer.

In contrast to the first embodiment, after the PDN connection is established, the multicast service is transmitted through the MBMS bearer, in this embodiment, the multicast service is transmitted through the unicast bearer, and the establishment of the unicast bearer may refer to the description of steps S301 to S307 in the third embodiment, that is, when the terminal device moves out of the MBMS area, the data of these multicast services is migrated to be sent through the unicast bearer.

S403, the terminal equipment sends a second report to the AS, wherein the second report is used for informing the AS that the terminal equipment can receive the data of the service through the MBMS bearing.

When the terminal equipment moves into the MBMS area from the non-MBMS area, the terminal equipment detects an MBMS signal, and detects that data corresponding to the service is being transmitted through an MBMS bearer (a base station can send a TMGI corresponding to the service), the terminal equipment sends a second report to the AS, and the AS acquires a multicast service data stream which can transmit the service to the terminal equipment through the MBMS bearer according to the second report.

S404, the AS sends fourth indication information to the PCF.

The fourth indication information is used for indicating that the sending of the data of the service through the unicast bearer is stopped, or is used for indicating that the terminal equipment can receive the data of the service through the MBMS bearer, or is used for indicating that the core network element deletes the unicast bearer resource corresponding to the multicast service.

In one implementation, the fourth indication information includes description information of service data flows (i.e., multicast service data flows) that need to be deleted from the unicast bearer, so that the PCF deletes unicast bearer resources corresponding to the service data flows.

In another implementation manner, the fourth indication information does not include description information of the service data flow to be deleted, only includes identification information of the service, and the PCF deletes the bearer resource corresponding to the service data flow supporting the multicast mode in the service according to the identification information of the service. It should be understood that the AS indicates which service data flows support the multicast manner in step 402, and the PCF may determine, according to the indication in step 402, which unicast bearer resources corresponding to the service data flows need to be deleted.

And S405, the PCF sends the fourth indication information to the PGW-C+SMF.

Corresponding to the former implementation manner of S404, the PCF informs the PGW-c+smf to delete the PCC rules corresponding to the service data flows through the fourth indication information; corresponding to the latter implementation mode, the PCF only informs the PGW-C+SMF to delete the unicast bearer resources of the service data flow supporting the multicast mode through the fourth indication information, and PCC rules are reserved.

It should be noted that, in the embodiment of the present application, for convenience of description, the indication information sent by the AS to the core network device for indicating that the data of the service is stopped to be sent through the unicast bearer, and the indication information sent by the core network device to the PGW-c+smf for indicating that the data of the service is stopped to be sent through the unicast bearer are both referred to AS fourth indication information, and it can be understood that names of the indication information sent in different messages or between different network elements may be different, and in the embodiment of the present application, names of the indication information in different messages or names of the sending between different network elements are not limited.

S406, deleting unicast bearing resources corresponding to the multicast service.

The PGW-c+smf deletes the unicast bearer resource created in the foregoing step, for example, PGW-c+smf notifies SGW, MME, eNB to delete the resource corresponding to the unicast bearer, which can be seen in the prior art. And, the PGW-c+smf further notifies the PGW-u+upf to stop sending the data of the multicast service through the unicast bearer, for example, notifies the PGW-u+upf to delete the first mapping relationship or the second mapping relationship.

For the previous implementation in steps S404 and S405, PGW-c+smf deletes the corresponding PCC rule. For the latter implementation in steps S404 and S405, PGW-c+smf still retains the corresponding PCC rule.

S407, the AS sends a seventh notification message to the terminal device.

The seventh notification message is used to notify the terminal device to receive the corresponding data through the MBMS bearer. Step S407 is performed after step S406 in this embodiment, and optionally, step S407 may be performed before step S404 in other embodiments of the present application.

Fig. 10 is a signaling flow chart of a method for switching multicast services provided in the fifth embodiment of the present application on the basis of the first embodiment and the second embodiment, which is different from the third embodiment in that: the present embodiment is described by taking the above-mentioned second multicast service switching manner as an example, that is: the data transmitted by the MBMS bearer is firstly switched from the MBMS bearer to the unicast bearer in the 4G network, and in the switching process of the terminal equipment from the 4G network to the 5G network, the PGW-C+SMF switches the data transmitted by the MBMS bearer from the unicast bearer in the 4G network to the 5G multicast session, namely, the unicast bearer in the 4G network is not required to be switched to the unicast bearer in the 5G network, thereby omitting the establishment of the unicast QoS flow in the 5G network. As shown in fig. 10, the method provided in this embodiment includes the following steps:

s501, PDN connection is established.

S502, the terminal equipment sends a first report to the AS, wherein the first report is used for indicating the terminal equipment to move out of the MBMS area.

S503, the AS sends a second message to the PCF, wherein the second message comprises the first indication information.

The first indication information is used for indicating a data packet for sending the service to the terminal equipment through the unicast bearer, and optionally, the first indication information comprises a multicast service identifier, or the second message comprises the first indication information and the multicast service identifier.

S504, the PCF sends a first message to the PGW-C+SMF, wherein the first message comprises first indication information.

It should be noted that, in the embodiment of the present application, for convenience of description, the indication information sent by the AS to the core network device for indicating that the data of the service is sent through the unicast bearer, and the indication information sent by the core network device to the PGW-c+smf for indicating that the data of the service is sent through the unicast bearer are both referred to AS the first indication information, and it can be understood that names of sending the indication information in different messages or between different network elements may be different, and in the embodiment of the present application, the names of sending the indication information in different messages or between different network elements are not limited. Other indications in the present specification are similar and are herein incorporated by reference. Optionally, the first message further includes a multicast service identifier.

S505, PGW-C+SMF establishes unicast bearer for service sent in multicast mode.

S506, the PGW-C+SMF sends a fifth notification message to the AS.

S507, AS sends a sixth notification message to the terminal device.

The specific implementation manner of the steps 501 to 507 refers to the descriptions of the steps S301 to S307 in the third embodiment, and will not be repeated here. In addition to the descriptions of S301 to S307, it is also included in this embodiment:

optionally, in step S501 or step S505, the PGW-c+smf further acquires multicast QoS flow information of the service, and sends parameters of the multicast QoS flow to the terminal device, where the parameters of the multicast QoS flow include QFI of each multicast QoS flow, and optional QoS parameters, and so on. The parameters of the multicast QoS flow are sent to the terminal device for receiving data of the service according to the parameters of the multicast QoS flow after joining the terminal to the multicast session of the second network.

S508, the eNB sends a first switching request to the MME.

The eNB is a base station in a 4G network, also referred to as a source base station, and the first handover request is for requesting a handover to a target base station in a 5G network, i.e. a gNB.

S509, the MME sends a first handover request to the AMF.

The MME may forward the first handover request to the AMF by forwarding a relocation request (Forward Relocation Request) message.

S510, the AMF sends a create session request to the PGW-c+smf (Create SM Context Request).

The specific implementation of S508-S510 refers to the prior art, and will not be described here again.

S511, creating the 5G multicast session corresponding to the service.

If the multicast session corresponding to the service is not established yet, the session creation request message is used for triggering the 5G multicast session for creating the service, and after the PGW-C+SMF receives the session creation request message, the PDN connection is determined to comprise the service supporting the transmission in a 5G multicast mode according to the context of the session. For example, if the PCC rule of the service associated with the PDN connection includes third indication information, the service supports 5G multicast transmission. It should be understood that the service data flows sent in the multicast supporting manner on the PDN connection may correspond to different 5G multicast sessions, and the PGW-c+smf determines whether the service data flows belong to the same 5G multicast session according to PCC rules corresponding to the service data flows.

The establishment of the 5G multicast session is referred to the related description in the prior art, and will not be described in detail here. The establishment of the 5G multicast session includes: the parameters of the multicast QoS flow are sent to the target base station so that the target base station creates a corresponding context, and a first tunnel from the UPF (which may be PGW-u+upf) to the target base station is established, and the first tunnel is used for the UPF to send data of the multicast service.

S512, the PGW-C+SMF sends a create session request response to the AMF.

After the 5G multicast session is established, the PGW-C+SMF sends a create session request response to the AMF, wherein the create session request response comprises a message sent to a target base station in the 5G network, and the message sent to the target base station comprises seventh indication information, and the seventh indication information is used for indicating that the terminal equipment is added into the multicast session corresponding to the service, namely, the 5G multicast session.

Optionally, the create session request response further includes parameters of the multicast QoS flow of the 5G multicast session sent to the target base station.

Optionally, the parameters of the multicast QoS flow may also be sent in step S511, that is, in the 5G multicast session establishment procedure, PGW-c+smf sends the parameters of the multicast QoS flow to the target base station.

S513, the AMF sends a second handover request to the gNB.

And the gNB is a target base station, the AMF carries seventh indication information received from the PGW-C+SMF and sends the second switching request to the gNB, and if the session request response is established to comprise the parameters of the multicast QoS flow, the second switching request comprises the parameters of the multicast QoS flow. And the gNB allocates wireless resources for the multicast QoS flow according to the seventh indication information and the parameters of the multicast QoS flow.

S514, the gNB sends a second handover request response to the AMF.

The second handover request response includes a transparent container (transparent container) including configuration information of radio resources of the multicast QoS flow allocated by the gNB for the terminal device to join the 5G multicast session.

S515, the AMF sends the second handover request response to the eNB through the MME.

S516, the eNB sends a switching command to the terminal equipment.

The eNB acquires configuration information of radio resources allocated by gNB for the multicast QoS flow of the terminal equipment from the transparent container, and sends the configuration information of the radio resources allocated by the multicast QoS flow to the terminal equipment by carrying the configuration information in a switching command.

The terminal equipment configures according to the configuration information of the wireless resources allocated by the multicast QoS flow, and accesses the gNB, and after the configuration is completed, the data of the multicast service can be transmitted through the 5G multicast session.

In S514 to S516, the target base station transmits configuration information of radio resources of the multicast QoS flow to the terminal device through the source base station.

S517, a subsequent switching flow.

The subsequent switching process includes that after the terminal device accesses the gNB, the gNB sends a notification to the AMF, the AMF notifies the PGW-C+SMF switching path, and the like, and compared with the prior art, the embodiment does not modify the subsequent switching process.

And S518, the PGW-C+SMF sends a third notification message to the AS.

S519, the AS sends a sixth notification message to the terminal device.

The specific implementation manner of S518 and S519 may refer to the descriptions related to steps S310 and S311 in the third embodiment, which are not repeated here.

Compared with the third embodiment, in the present embodiment, the data transmitted by the MBMS bearer is directly switched from the unicast bearer in the 4G network to the 5G multicast session, that is, the unicast bearer in the 4G network is not required to be switched from the unicast bearer in the 4G network to the unicast bearer in the 5G network, and then the unicast bearer in the 5G network is switched to the 5G multicast session, so that establishment of the unicast QoS flow in the 5G network is omitted, and time for switching the multicast service from the MBMS bearer to the 5G multicast session is shortened.

Fig. 11 is a signaling flow chart of a method for switching multicast services provided in the sixth embodiment of the present application on the basis of the first embodiment and the second embodiment, which is different from the third embodiment in that: the present embodiment will be described taking the third multicast service switching method as an example. As shown in fig. 11, the method provided in this embodiment includes the following steps:

s601, PDN connection is established.

S602, the terminal equipment sends a first report to the AS, wherein the first report is used for indicating the terminal equipment to move out of the MBMS area.

S603, the AS sends a second message to the PCF, wherein the second message comprises the first indication information and the sixth indication information.

S604, the PCF sends a first message to the PGW-C+SMF, wherein the first message comprises first indication information and sixth indication information.

S605, the PGW-C+SMF establishes a unicast bearer for the service sent in the multicast mode.

S606, the PGW-C+SMF sends a fifth notification message to the AS.

S607, the AS sends a sixth notification message to the terminal device.

Steps 501-507 are substantially similar to steps S301-S307 of embodiment three, except that: in this embodiment, the description information of the service sent by the AS is the second description information sent in the second case, and accordingly, the first indication information includes a second rule, where the second rule is determined by the PCF according to the second description information, and the second rule does not include the third indication information. In the third embodiment, the description information of the service sent by the AS is the first description information when sent in the manner of the first case, the first indication information includes a first rule, the first rule is determined by the PCF according to the first description information, and the first rule includes third indication information. In addition, in this embodiment, the first message and the second message include sixth indication information, and in the third embodiment, the first message and the second message sent by the AS do not include sixth indication information.

S608, the terminal equipment is switched from the 4G network to the 5G network.

S609, the PGW-C+SMF sends a first notification message to the AS.

In this embodiment, after the terminal device successfully switches from the 4G network to the 5G network according to the sixth indication information (i.e., when PGW-c+smf completes the indication information when the first switch is first performed), and when it is determined that the terminal device supports the 5G multicast service, the terminal device sends a first notification message to the AS, where the first notification message is used to notify that data for supporting or about to support sending the service to the terminal device by using the multicast mode, or is used to notify that the terminal device switches to the 5G network, or is used to notify that the AS uses a mode to send the data of the service to the terminal device.

In other embodiments of the present application, the PGW-c+smf may also send the first notification message to the AS when the terminal device prepares to switch, that is, the PGW-c+smf sends the first notification message when receiving the switch preparation indication information.

Of course, the PGW-c+smf may send the first notification message at other time after receiving the handover preparation, which is not limited.

S610, AS sends request message for joining terminal equipment to multicast session to PCF.

The AS determines to join the terminal equipment into the 5G multicast session according to the first notification message, and notifies the core network equipment to join the terminal equipment into the 5G multicast session.

S611, PCF sends fifth indication information to PGW-C+SMF.

And the PCF adds the terminal equipment into the 5G multicast session according to the indication of the AS, and sends fifth indication information to the PGW-C+SMF to indicate the PGW-C+SMF to add the terminal equipment into the 5G multicast session.

And S612, adding the terminal equipment into the 5G multicast session corresponding to the service according to the fifth indication information.

The specific implementation of step S612 may refer to the description of step S309 in the third embodiment, and will not be repeated here.

And S613, the PGW-C+SMF sends a third notification message to the AS.

S614, the AS sends a fourth notification message to the terminal device.

Steps S613 and S614 are optional steps.

S615, deleting the unicast QoS flow.

The specific implementation of steps S613-615 refers to the related descriptions of steps S310-S312 in the third embodiment, and will not be repeated here.

In other embodiments of the present application, after receiving the first notification message, the AS may also send a second notification message to the terminal device, notifying the terminal device to receive data using the 5G multicast session, where the terminal device sends the fifth indication information to the PGW-c+smf according to the second notification message.

Fig. 12 is a signaling flow chart of a method for switching multicast services according to the seventh embodiment of the present application, where the first multicast service switching manner described above is taken as an example, that is, data transmitted by an MBMS bearer is first switched from an MBMS bearer to a unicast bearer in a 4G network, in a switching process of a terminal device from the 4G network to the 5G network, PGW-c+smf switches data transmitted by the MBMS bearer from the unicast bearer in the 4G network to a PDU session (that is, a unicast path in the 5G network), and PGW-c+smf switches the terminal device to the 5G multicast session after the terminal device is switched from the 4G network to the 5G network, that is, from the unicast path in the 5G network to the 5G multicast path.

In this embodiment, the AS sends the data to the UPF, and then sends the data to the PGW-U+UPF through the UPF.

Before the flow of this embodiment, the AS sends multicast service information of the service to the core network device, where the multicast service information includes service description information, such AS quintuple information, when the service is sent in a multicast manner. The destination IP address in the service description information in the multicast service information of the service is illustratively a multicast IP address used when the service is transmitted in a multicast manner. The multicast service information also includes QoS requirement information of the service, such as bandwidth requirement when the service is transmitted in a multicast manner. Here, the core network device refers to PCF or NEF, and when the core network device is the NEF, the NEF receives the multicast service information of the service, then stores the multicast service information in the UDR, and the UDR sends the multicast service information of the service to the PCF. The PCF determines a multicast PCC rule of the service according to multicast service information of the service, and sends the determined multicast PCC rule to the second SMF, where the second SMF may determine multicast QoS flow information of the service according to the multicast service information of the service, where the multicast service information includes a multicast service identifier, and a specific determination process may refer to the prior art and is not described herein.

Optionally, the multicast service information of the service further includes eighth indication information, where the eighth indication information is used to indicate that the service supports service continuity during cross-system handover. If the multicast service information includes the eighth indication information, the PCF sends the eighth indication information to the second SMF, so as to indicate that the service needs to support service continuity during cross-system handover. For simplicity of description, the indication information received by the PCF and the indication information sent by the PCF to the second SMF are both referred to as eighth indication information, and different names may be used in actual application, but the roles are used to indicate that the service needs to support service continuity. Here, service continuity refers to ensuring that data packets of the service are not lost and/or are sent in sequence as much as possible when the terminal equipment moves.

Referring to fig. 5 and 12, the method provided in this embodiment includes the following steps:

s701, PDN connection is established.

S702, the terminal equipment sends a first report to the AS, wherein the first report is used for indicating the terminal equipment to move out of the MBMS area.

The specific implementation of S701-S702 refers to the descriptions of steps S301 and S302 in the third embodiment, and will not be repeated here.

S703, AS sends a second message to PCF, wherein the second message comprises the first indication information and the multicast service identification.

The multicast service identifier may be TMGI, or may be other identifier information, which is not limited in this embodiment. The first indication information is used for indicating a data packet for sending service to a terminal device located in the first network through a unicast bearer.

It should be noted that the multicast service identifier may also be included in the first indication information and sent to the PCF.

S704, the PCF sends a first message to the PGW-C+SMF, wherein the first message comprises first indication information and multicast service identification.

It should be noted that the multicast service identifier may also be included in the first indication information and sent to the PGW-c+smf.

The first message and the second message both carry first indication information, and in specific implementation, different message names may be adopted, but both functions are used to indicate that data of the service is sent to the terminal device through unicast bearer, and for convenience of description, they are referred to as first indication information in this embodiment.

And S705, the PGW-C+SMF acquires the multicast QoS flow information of the service according to the multicast service identifier.

In the embodiment of the application, the PGW-c+smf may obtain the multicast QoS flow information of the service according to the multicast service identifier. The PGW-c+smf may request the multicast QoS flow information of the service to the second SMF according to the multicast service identifier, the second SMF may obtain the multicast service information according to the multicast service identifier, determine the multicast QoS flow information of the service according to the multicast service information, and a specific determination process may refer to the prior art and will not be described again.

The multicast QoS flow information of a service includes information of one or more QoS flows of the service, where the information of one QoS flow includes QFI of the QoS flow, service identification information mapped to the QoS flow (e.g., a quintuple or service identifier, where a destination address in the quintuple information is a multicast IP address of the service), and QoS parameters of the QoS flow (e.g., 5QI, maximum bandwidth requirement, etc. corresponding to the QoS flow).

In one implementation, the PGW-c+smf may obtain the multicast QoS flow information of the service from the UDM/UDR, and specifically, the PGW-c+smf sends the multicast service identifier to the UDM/UDR, so that the UDM/UDR obtains the multicast QoS flow information of the service according to the multicast service identifier. The multicast QoS flow information of the service stored in the UDM/UDR may be stored in the UDM/UDR by the second SMF, for example, the second SMF obtains information of the service from the PCF, for example, PCC rule of the service, and determines the multicast QoS flow information of the service according to the PCC rule of the service obtained from the PCF, and after determining the multicast QoS flow information, the second SMF stores the multicast QoS flow information of the service, the multicast service identifier of the service, and the identifier information of the second SMF together in the UDM/UDR.

In another implementation, the PGW-c+smf obtains multicast QoS flow information for the service from the second SMF. After the PGW-c+smf receives the first message, the PGW-c+smf sends the multicast service identifier to the second SMF, and the second SMF sends the multicast QoS flow information of the service to the PGW-c+smf according to the multicast service identifier. The PGW-C+SMF can obtain the information of the second SMF corresponding to the service from the UDM/UDR according to the multicast service identification so as to obtain the multicast QoS stream information of the service from the second SMF.

If the service needs to support service continuity in the cross-system movement, the second SMF or UDM/UDR sends eighth indication information to the PGW-C+SMF to indicate that the service needs to support service continuity.

S706, PGW-C+SMF establishes unicast bearing for service according to the multicast QoS flow information of service.

The PGW-c+smf determines, according to multicast QoS flow information of a service, a unicast bearer of a data packet for sending the service, where the unicast bearer may be an EPS bearer. Illustratively, PGW-c+smf may map one or more multicast QoS flows to one EPS bearer. The PGW-c+smf may map the multicast QoS flow of the service onto an existing EPS bearer, or may map the multicast QoS flow of the service into a new EPS bearer.

PGW-c+smf may map part of the multicast QoS flows into existing bearers and part of the multicast QoS flows into new bearers; alternatively, PGW-c+smf maps all multicast QoS flows into existing bearers; or PGW-c+smf maps the entire multicast QoS flow to the new bearer, which is not limited by the present embodiment.

In addition, if the PGW-c+smf receives the eighth indication information, that is, the service supports service continuity, in order that the service can be switched from unicast bearer transmission through the first network to PDU session transmission through the second network, in this step, the PGW-c+smf further determines parameters of a unicast QoS flow corresponding to the service when the service is transmitted through the PDU session of the second network, for example, the PGW-c+smf may map one or more multicast QoS flows of the service to one unicast QoS flow, and determine QoS parameters of the unicast QoS flow according to the QoS parameters of the service data flow mapped to the unicast QoS flow. If the unicast QoS flow information does not need to be transmitted to the terminal device, the procedure of determining the unicast QoS flow may be performed at the time of handover, i.e., step S711, and is not limited.

In the embodiment of the present application, establishing a unicast bearer for the service includes modifying the bearer (if the multicast QoS flow of the service is mapped into an existing bearer) and/or creating the bearer (if the multicast QoS of the service is mapped into a new bearer). After the PGW-c+smf establishes the unicast bearer, the PGW-c+smf notifies the SGW to modify the bearer (if the multicast QoS flow of the service is mapped to the existing bearer) and/or create the bearer (if the multicast QoS of the service is mapped to the new bearer), which can be specifically referred to the prior art, and this embodiment is not repeated. In this process, PGW-c+smf acquires first tunnel information of one or more EPS bearers corresponding to the service.

Optionally, in the process of modifying the bearer and/or creating the bearer, the PGW-c+smf sends information of the EPS bearer corresponding to the service, including the bearer identifier, and a unicast QoS flow (including QFI) corresponding to the service to the terminal device.

S707, the PGW-C+SMF sends second indication information to the PGW-U+UPF.

The second indication information is used for indicating to send a data packet to the terminal equipment through a unicast bearer, after the PGW-c+smf establishes the unicast bearer, a first mapping relationship is determined, the first mapping relationship is a mapping relationship between QFI of a multicast QoS flow of a service and information of a first tunnel, the information of the first tunnel is tunnel information of a downlink node, the downlink node is an SGW or an access network device (when the SGW is combined with other network elements), and each unicast bearer corresponds to one first tunnel.

The second indication information includes a first mapping relationship, and is used for determining, according to the first mapping relationship, first tunnel information corresponding to a unicast bearer corresponding to the QFI of data received from a second tunnel (the second tunnel is a tunnel between the PGW-u+upf and the UPF).

If the second tunnel is not established, the PGW-C+SMF requests the PGW-U+UPF to distribute the tunnel information of the second tunnel. And the PGW-U+UPF distributes the tunnel information of the second tunnel and sends the tunnel information to the PGW-C+SMF.

And S708, the PGW-C+SMF sends second tunnel information to a second SMF.

S709, the second SMF sends second tunnel information to the UPF.

The UPF uses the second tunnel information to send the data packet of the service to the GW-U+UPF.

S710, the second SMF sends a response message to the PGW-C+SMF.

After the unicast bearer establishment is completed, the AS may send traffic data over the unicast bearer. Optionally, after step S710, that is, after the PGW-c+smf receives the response message, the PGW-c+smf sends a fifth notification message to the AS, where the fifth notification message is used to notify the AS to send data of the service using the unicast bearer, or is used to notify the AS network that the service data flow transmitted on the MBMS bearer has been switched or migrated to the unicast bearer.

Optionally, in response to the fifth notification message, the AS sends a sixth notification message to the terminal device, where the sixth notification message is used to notify the terminal device that the data of the service is received by using the unicast bearer, or is used to notify the terminal device that the network has switched or migrated the service data stream transmitted on the MBMS bearer to the unicast bearer.

S711, the terminal device switches from the 4G network to the 5G network.

In this embodiment, only when the service supports service continuity, the bearer corresponding to the service is switched to the 5G network. The specific implementation manner of this step refers to the description of step S308 in the third embodiment, and will not be described herein.

It should be noted that, in the process of switching the terminal device from the 4G network to the 5G network, the terminal device may be added to the 5G multicast session corresponding to the service, i.e., steps S711 to S712 may be replaced by steps S508 to S517.

And S712, the terminal equipment is added into the 5G multicast session corresponding to the service.

The specific implementation manner of this step refers to the description of step S310 in the third embodiment, and will not be repeated here.

S713, delete unicast QoS flows.

The specific implementation of step S713 refers to the description of step S312 in the third embodiment, and will not be repeated here.

Optionally, after step S712, the PGW-c+smf sends a third notification message to the AS, where the third notification message is used to notify the terminal device that the terminal device has switched to the 5G network, or is used to notify the AS to start sending data of the service to the terminal device using the 5G multicast session. In response to the third notification message, the AS sends a fourth notification message to the terminal device, where the fourth notification message is used to notify the terminal device to receive data of the service using the 5G multicast session.

Fig. 13 is a signaling flow chart of a method for switching multicast services according to an eighth embodiment of the present application, where the difference between the first embodiment and the seventh embodiment is that: in this embodiment, the data transmitted by the MBMS bearer is not switched from the MBMS bearer to the unicast bearer of the 4G network, but rather, in the switching process of the terminal device from the 4G network to the 5G network, the PGW-c+smf creates a corresponding unicast QoS flow for the service in the 5G network, so that the data can be sent through the unicast QoS flow after the terminal device is switched to the 5G network, and after the terminal device is switched from the 4G network to the 5G network, the PGW-c+smf joins the terminal device into the 5G multicast session, that is, switches from the unicast path in the 5G network to the 5G multicast path. As shown in fig. 13, the method of the present embodiment may include the steps of:

s801, PDN connection is established.

The specific implementation manner of S801 refers to the description of step S301 in the third embodiment, and will not be repeated here.

S802, PGW-C+SMF obtains multicast service identification of the service.

In one implementation, the terminal device sends a message to the PGW-c+smf through the PDN connection, where the message includes a multicast service identifier, for example, the terminal device sends an IGMP Join, the PGW-c+smf receives an IGMP Join message (the message is sent to the PGW-c+smf through the PGW-u+upf), and the IGMP Join includes multicast address information when the service is sent in a multicast manner, where the multicast address information may be used to identify the service (i.e., as a multicast service identifier). It should be noted that the multicast service identity of the service may include a variety of different identities, such as multicast address information (e.g. for identifying the service in IGMP messages), TMGI (for identifying the service in 4G MBMS), or 5G multicast service identity (for identifying the service in 5G network). In this implementation, the terminal device may send a multicast service identifier to the PGW-c+smf when it determines that the service needs to be received, and further, the terminal device may send a multicast service identifier to the PGW-c+smf when it determines that the service needs to support continuity.

The terminal device sends the identifier of the multicast service through the PDN connection, so that the PGW-C+SMF associates the service with the PDN connection, and when the terminal device is switched to the second network, the PGW-C+SMF can associate the service with a PDU session corresponding to the PDN connection, so that the terminal device can be added into the multicast session of the second network through the PDU session.

In another implementation, the PGW-c+smf receives the multicast service identifier from the AS, for example, in a process of performing application layer signaling interaction between the terminal device and the AS through the PDN connection, the AS sends the multicast service identifier of the service to the core network device, and the PCF sends the multicast service identifier to the PGW-c+smf. For example, when sending the applied signaling description information to the core network device, the AS sends the multicast service identifier of the service to the core network device, and when sending the PCC rule corresponding to the signaling, the core network device (for example, PCF) sends the multicast service identifier to the PGW-c+smf. The AS may send a multicast service identity to the core network device when the service needs to support continuity. The AS may send the multicast service identifier of the service to the PGW-c+smf after receiving the message sent by the terminal device and requesting to receive the service.

S803, PGW-C+SMF obtains the multicast QoS stream information of the service according to the multicast service identification.

After the PGW-C+SMF acquires the multicast service identifier, acquiring the multicast QoS flow information of the service according to the multicast service identifier, and storing the multicast QoS flow information. The specific acquisition mode is described in step S705, and will not be described here again. If the PGW-c+smf acquires the multicast service identifier from the terminal device, the PGW-c+smf may determine whether the terminal device is currently accessed through the first network (e.g., the PGW-c+smf may sense that an interface type between the PGW-c+smf and the downlink node is an S5 interface or an S8 interface, thereby determining that the terminal device is accessed through the first network), and if the PGW-c+smf determines that the terminal device is accessed through the first network, the PGW-c+smf only acquires the multicast QoS flow information of the service, and does not establish a unicast bearer for the service.

S804, the terminal equipment is switched from the 4G network to the 5G network, and a unicast QoS flow is created in the 5G network according to the multicast QoS flow information of the service in the switching process.

Since the PGW-c+smf does not create a unicast bearer for the service, that is, steps S702 to S710 in embodiment seven are not performed, in the handover process, the PGW-c+smf determines, according to the multicast QoS flow information of the service, the unicast QoS flow information corresponding to when the PDU session is sent through the second network. And sends a request to the target base station (i.e., the gNB) to create the unicast QoS flow for the traffic at the second network during the handover so that the traffic can be sent over the PDU session of the second network immediately after the handover to the second network. The method for determining unicast QoS flow information according to multicast QoS flow information can be seen in step S706 in embodiment seven.

Optionally, in other embodiments of the present application, the PGW-c+smf may not establish a unicast QoS flow in the process of switching the terminal device from the 4G network to the 5G network, but directly join the terminal device to the 5G multicast session corresponding to the service in the process of switching the terminal device from the 4G network to the 5G network, that is, directly switch the service from the MBMS bearer to the 5G multicast session, without passing through the 4G unicast bearer and the 5G unicast QoS flow in the middle, so as to ensure that the multicast service of the terminal device maintains the continuity of the service in the cell switching process.

S805, joining the terminal equipment into the 5G multicast session corresponding to the service.

It should be noted that, in the process of switching the terminal device from the 4G network to the 5G network, the terminal device may be added to the 5G multicast session corresponding to the service, i.e., steps S804-S805 may be replaced by steps S508-S517.

S806, deleting the unicast QoS flow.

The specific implementation manner of step S806 refers to the description of step S312 in the third embodiment, and will not be repeated here.

Optionally, after step S806, the PGW-c+smf sends a third notification message to the AS, where the third notification message is used to notify the terminal device that the terminal device has switched to the 5G network, or is used to notify the AS to start sending data of the service to the terminal device using the 5G multicast session. In response to the third notification message, the AS sends a fourth notification message to the terminal device, where the fourth notification message is used to notify the terminal device to receive data of the service using the 5G multicast session.

In this manner, PGW-c+smf obtains, in advance, a multicast service identifier of a service received by a terminal device through a multicast path of a first network (e.g. a 4G network), and obtains multicast QoS flow information of the service according to the multicast service identifier, in a process that the terminal device switches from the first network to a second network (e.g. a 5G network), unicast QoS flow information is established in the second network according to the multicast QoS flow information of the service, after the unicast QoS flow is established, the service can be sent to the terminal device through the unicast QoS flow, and subsequently, after the terminal device switches to the second network, the terminal device is added to a 5G multicast session corresponding to the service. The method comprises the steps of firstly switching the service from MBMS transmission to unicast QoS streaming transmission of 5G, and switching the unicast QoS streaming transmission of 5G to 5G multicast session transmission, so as to ensure that multicast service data received by the terminal equipment through a multicast path of a first network is kept in service continuity in the switching process in the process of switching the terminal equipment from the first network to a second network.

It should be noted that the method of the fourth embodiment may be combined with not only the third embodiment but also the fifth embodiment, the sixth embodiment, the seventh embodiment or the eighth embodiment, that is, the method of the fourth embodiment may be performed before step S508 in the fifth embodiment, or the method of the fourth embodiment may be performed before step S608 in the sixth embodiment, or the method of the fourth embodiment may be performed before step S711 in the seventh embodiment, or the method of the fourth embodiment may be performed before step 804 in the eighth embodiment.

Fig. 14 is a schematic structural diagram of a first session management network element provided in the ninth embodiment of the present application, as shown in fig. 14, where the first session management network element 100 includes:

the receiving module 11 is configured to receive first indication information, where the first indication information is used to indicate a data packet that is sent to a terminal device located in a first network through a unicast bearer.

A sending module 12, configured to send second indication information to the first user plane network element, where the second indication information is used to indicate to send the data packet to the terminal device through the unicast bearer.

And the joining module 13 is configured to join the terminal device into the multicast session corresponding to the service when the terminal device accesses through the second network.

Optionally, the first session management network element 100 further includes: an acquisition module, configured to acquire multicast quality of service QoS flow information of the service; and the first determining module is used for determining unicast bearing of the data packet for sending the service according to the multicast QoS flow information of the service.

Optionally, the receiving module 11 is specifically configured to: receiving a first message, wherein the first message comprises the first indication information and a multicast service identifier of the service; the acquisition module is specifically configured to: and acquiring the multicast QoS flow information of the service according to the multicast service identifier.

Or, the first indication information includes a multicast service identifier of the service, and the obtaining module is specifically configured to: and acquiring the multicast QoS flow information of the service according to the multicast service identifier.

Optionally, the first determining module is further configured to: and if the first session management network element receives eighth indication information, wherein the eighth indication information indicates that the service supports service continuity, determining a unicast QoS flow corresponding to the service according to the information of the multicast QoS flow.

In an exemplary manner, the joining module 13 is specifically configured to: and switching the data packet of the service from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through a protocol data unit PDU session in the process of switching the terminal equipment from the first network to the second network, joining the terminal equipment into the multicast session after the terminal equipment is switched from the first network to the second network, and switching the data packet of the service from being sent to the terminal through the PDU session to being sent to the terminal equipment through the multicast session.

Optionally, after the terminal device joins the multicast session, the sending module 12 is further configured to: and notifying the first user plane network element to stop sending the data of the service to the terminal equipment through the PDU session.

In another exemplary manner, the joining module 12 is specifically configured to: and in the process of switching the terminal equipment from the first network to the second network, adding the terminal equipment into the multicast session, and switching the data packet of the service from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through the multicast session.

In an exemplary manner, the joining module 13 is specifically configured to: receiving a request message sent by an access and mobility management function AMF, wherein the request message is used for creating or updating a PDU session, the PDU session is associated with the service, the service sent through the unicast bearer is determined to support multicast mode sending, the terminal equipment supports multicast service in the second network, and a target access network equipment in the second network is instructed to join the terminal equipment into the multicast session.

In an exemplary manner, when the terminal device moves into the MBMS area or after moving into the MBMS area, the receiving module 11 is further configured to: and receiving fourth indication information, wherein the fourth indication information is used for indicating that the transmission of the data of the service through the unicast bearer is stopped. The sending module 12 is further configured to notify, according to the fourth indication information, the first user plane network element to stop sending the data of the service through the unicast bearer.

Correspondingly, the receiving module 11 is further configured to: and after the sending module sends the second indication information to the first user plane network element, receiving information of a second tunnel from the first user plane network element, and receiving the data packet of the service from the second user plane network element or an application server by the first user plane network element through the second tunnel. The transmitting module 12 is further configured to: and sending the second tunnel information to the second user plane network element or the application server.

In an exemplary manner, after the terminal device switches to the second network, the sending module 12 is further configured to: and sending a first notification message to an AS, wherein the first notification message is used for notifying the AS to support sending the service data to the terminal equipment by using a multicast mode. Correspondingly, the joining module 13 is specifically configured to: and receiving fifth indication information, wherein the fifth indication information is used for indicating the terminal equipment to join the multicast session corresponding to the service, and the terminal is joined to the multicast session corresponding to the service according to the fifth indication information.

Optionally, before the sending module 12 sends the first notification message to the AS, the receiving module 11 is further configured to: and receiving sixth indication information, wherein the sixth indication information is used for indicating to send the first notification message to the AS when supporting to send service data to the terminal equipment by using a multicast mode.

The first session management network element of the present embodiment may be used to execute the methods executed by the first session management network element in the first to sixth embodiments of the foregoing methods, and the specific implementation manner and technical effects are similar, and are not repeated here.

Fig. 15 is a schematic structural diagram of an AS provided in embodiment ten of the present application, AS shown in fig. 15, where the AS200 includes:

A receiving module 21, configured to receive a first report from a terminal device, where the first report is used to instruct the terminal device to move out of an MBMS area.

A determining module 22, configured to determine, according to the first report, a data packet for sending a service to the terminal device through a unicast bearer.

A sending module 23, configured to send first indication information to a core network device and/or a first session management network element, where the first indication information is used to indicate to send a data packet of the service to the terminal device through a unicast bearer.

Optionally, the sending module 23 is further configured to: and sending third indication information to the core network equipment and/or the first session management network element, wherein the third indication information is used for indicating the service to support the multicast mode to send.

Optionally, the sending module 23 sends third indication information to the core network device, specifically: and sending a second message to the core network equipment, wherein the second message comprises the third indication information and the multicast service identifier corresponding to the service.

Optionally, the sending module 23 is further configured to: and sending sixth indication information to the core network equipment, wherein the sixth indication information is used for indicating to send the first notification message to the AS when supporting sending service data to the terminal equipment in a multicast mode.

Optionally, the sending module 23 is further configured to send a multicast service identifier corresponding to the service to the core network device and/or the first session management network element.

In another exemplary manner, the sending module 23 sends a first message to the first session management network element, where the first message includes the first indication information and the multicast service identifier corresponding to the service. Or, the sending module 23 sends a second message to the core network device, where the second message includes the first indication information and the multicast service identifier corresponding to the service.

In an exemplary manner, the receiving module 21 is further configured to: receiving a first notification message, where the first notification message is used to notify data supporting sending the service to the terminal device by using a multicast mode, and the sending module 23 is further configured to: and responding to the first notification message, sending a second notification message to the terminal equipment, wherein the second notification message is used for notifying the terminal equipment to receive the data of the service by using the multicast session.

In another exemplary manner, the receiving module 21 is further configured to: receiving a first notification message, where the first notification message is used to notify data supporting sending the service to the terminal device by using a multicast mode, and the sending module 23 is further configured to: and responding to the first notification message, and sending fifth indication information to the first session management network element or the core network equipment, wherein the fifth indication information is used for indicating the terminal equipment to join the multicast session corresponding to the service.

In an exemplary manner, the receiving module 21 is further configured to: and when the terminal equipment moves into the MBMS area from the non-MBMS area, receiving a second report from the terminal equipment, wherein the second report is used for informing the AS that the terminal equipment can receive the data of the service through the MBMS bearing. Correspondingly, the sending module 23 is further configured to: and sending fourth indication information to the core network equipment, wherein the fourth indication information is used for indicating that the sending of the data of the service through the unicast bearer is stopped.

The AS of the present embodiment may be used to execute the methods executed by the AS in the first to sixth embodiments of the foregoing method, and the specific implementation manner and technical effects are similar, and are not repeated here.

Fig. 16 is a schematic structural diagram of a terminal device provided in an eleventh embodiment of the present application, as shown in fig. 16, the terminal device 300 includes:

and the sending module 31 is configured to send, to a first session management network element, multicast capability indication information during a process of establishing a PDN connection for the terminal device, where the multicast capability indication information is used to indicate a multicast capability of the terminal device in the second network.

A receiving module 32, configured to receive, from a source access network device in a first network, configuration information of a radio resource allocated by a target access network device in the second network to the terminal device, where the configuration information of the radio resource is used for the terminal device to receive, in the second network, data of the service by multicast mode; the receiving module is further configured to receive data of the service according to the configuration information of the radio resource.

In an exemplary manner, the receiving module 31 is further configured to: and receiving a fourth known message from the application server AS, wherein the fourth known message is used for notifying the terminal equipment to receive the data of the service by using the multicast session in the second network.

The terminal device of the present embodiment may be used to execute the methods executed by the terminal devices in the first to sixth embodiments of the foregoing method, and the specific implementation manner and technical effects are similar, and are not repeated here.

Fig. 17 is a schematic structural diagram of a target access network device according to the twelfth embodiment of the present application, as shown in fig. 17, where the target access network device 400 includes:

a receiving module 41, configured to receive seventh indication information from the first session management network element, where the seventh indication information is used to indicate that the terminal device is added to a multicast session corresponding to a service.

An obtaining module 42 is configured to obtain parameters of the multicast QoS flow of the multicast session.

A resource allocation module 43, configured to allocate radio resources for the multicast QoS flow according to the seventh indication information and the parameter of the multicast QoS flow.

A sending module 44, configured to send, to the terminal device, configuration information of radio resources of the multicast QoS flow through a source access network device, where the source access network device is an access network device that the terminal device accesses before accessing the target access network device.

The target access network device of the present embodiment may be used to execute the methods executed by the target access network device in the first to sixth embodiments of the foregoing method, and the specific implementation manner and technical effects are similar, and are not repeated here.

Fig. 18 is a schematic structural diagram of a first session management network element provided in the thirteenth embodiment of the present application, as shown in fig. 18, where the first session management network element 500 includes: the processor 51, the memory 52 and the transceiver 53 are connected to communicate with the processor 51 through the bus 54, the memory 52 is used for storing instructions, the transceiver 53 is used for communicating with other devices, and the processor 51 is used for executing the instructions stored in the memory 52, so that the first session management network element 500 executes the method executed by the first session management network element in the first embodiment to the sixth embodiment.

It is understood that the processor used by the first session management network element in the embodiments of the present application may be a Central Processing Unit (CPU), a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, a transistor logic device, a hardware component, or any combination thereof. Which may implement or perform the various exemplary logic blocks, modules, and circuits described in connection with this disclosure. The processor may also be a combination that performs the function of a computation, e.g., a combination comprising one or more microprocessors, a combination of a DSP and a microprocessor, and the like.

The buses described in embodiments of the present application may be industry standard architecture (Industry Standard Architecture, ISA) buses, external device interconnect (Peripheral Component, PCI) buses, or extended industry standard architecture (Extended Industry Standard Architecture, EISA) buses, among others. The buses may be divided into address buses, data buses, control buses, etc. For ease of illustration, the buses in the drawings of the present application are not limited to only one bus or one type of bus.

In the several embodiments provided in this application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of the units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.

The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in hardware plus software functional units.

The integrated units implemented in the form of software functional units described above may be stored in a computer readable storage medium. The software functional unit is stored in a storage medium, and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor (processor) to perform part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a magnetic disk, or an optical disk, or other various media capable of storing program codes.

Claims

1. A method for switching multicast service, comprising:

the first session management network element receives first indication information, wherein the first indication information is used for indicating to send a data packet of the multicast service to terminal equipment positioned in a first network through unicast bearing;

the first session management network element sends second indication information to the first user plane network element, wherein the second indication information is used for indicating to send the data packet received by the first user plane network element from the second user plane network element to the terminal equipment through the unicast bearer;

when the terminal equipment is accessed through a second network, the first session management network element adds the terminal equipment into a multicast session corresponding to the multicast service so that the terminal equipment receives the data packet through a multicast path of the second network;

wherein the second user plane network element is located on a multicast path of the second network.

2. The method as recited in claim 1, further comprising:

the first session management network element acquires multicast quality of service QoS flow information of the service;

and the first session management network element determines unicast bearing of the data packet for sending the service according to the multicast QoS flow information of the service.

3. The method of claim 2, wherein the first session management network element receives first indication information, comprising:

the first session management network element receives a first message, wherein the first message comprises the first indication information and a multicast service identifier of the service;

the first session management network element obtains multicast QoS flow information of the service, including:

and the first session management network element acquires the multicast QoS flow information of the service according to the multicast service identifier.

4. The method of claim 2, wherein the first indication information includes a multicast service identification of the service, and wherein the first session management network element obtains multicast QoS flow information for the service, comprising:

5. The method of any one of claims 2-4, further comprising:

and if the first session management network element receives eighth indication information, wherein the eighth indication information indicates that the service supports service continuity, the first session management network element determines a unicast QoS flow corresponding to the service according to the information of the multicast QoS flow.

6. The method according to any of claims 1-4, wherein the first session management network element joining the terminal device to the multicast session corresponding to the service comprises:

in the process of switching the terminal equipment from the first network to the second network, the first session management network element switches the data packet of the service from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through a protocol data unit PDU session;

after the terminal device is switched from the first network to the second network, the first session management network element joins the terminal device in the multicast session, and the data packet of the service is switched from being sent to the terminal via the PDU session to being sent to the terminal device via the multicast session.

7. The method according to any of claims 1-4, wherein the first session management network element joining the terminal device to the multicast session corresponding to the service comprises:

and in the process of switching the terminal equipment from the first network to the second network, the first session management network element adds the terminal equipment into the multicast session, and the data packet of the service is switched from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through the multicast session.

8. The method of claim 5, wherein the first session management network element joining the terminal device to the multicast session corresponding to the service comprises:

9. The method of claim 5, wherein the first session management network element joining the terminal device to the multicast session corresponding to the service comprises:

10. The method according to any of claims 1, 8 and 9, wherein before the first session management network element joins the terminal device to the multicast session, further comprising:

the first session management network element determines that the service supports multicast mode transmission through the second network.

11. The method of claim 10, wherein the first session management network element determining that the service supports multicast delivery over the second network comprises:

the first session management network element receives a first rule corresponding to the service, wherein the first rule is used for controlling, strategy or charging, and the first rule comprises third indication information which is used for indicating the service to support multicast mode transmission.

12. The method according to claim 8 or 9, wherein before the first session management network element joins the terminal device to the multicast session, further comprising:

the first session management network element determines that the terminal device supports multicast in the second network and/or the target access network device supports multicast, wherein the terminal device accesses the second network through the target access network device.

13. The method as recited in claim 12, further comprising:

the first session management network element receives multicast capability indication information sent by the terminal equipment in the process of establishing packet data network PDN connection of the terminal equipment, wherein the multicast capability indication information is used for indicating the multicast capability of the terminal equipment in the second network;

the first session management network element determining that the terminal device supports multicast in the second network, including:

and the first session management network element determines that the terminal equipment supports multicast in the second network according to the multicast capability indication information.

14. The method of claim 6, wherein after the terminal device joins the multicast session, further comprising:

the first session management network element informs the first user plane network element to stop sending the data of the service to the terminal device through the PDU session.

15. The method of any one of claims 1-4, 8, 9, 11, 13, 14, further comprising:

when the terminal equipment moves into a Multimedia Broadcast Multicast Service (MBMS) area or after moving into the MBMS area, the first session management network element receives fourth indication information, wherein the fourth indication information is used for indicating that the data of the service is stopped to be sent through the unicast bearer;

And the first session management network element informs the first user plane network element of stopping sending the data of the service through the unicast bearer according to the fourth indication information.

16. The method according to claim 1, wherein the second indication information includes a first mapping relationship between information of a first tunnel and an identifier QFI of a multicast quality of service QoS flow of the service, the first tunnel being a tunnel corresponding to the unicast bearer, the QFI being a QFI of a data packet of the service received by the first user plane network element, the first mapping relationship being used by the first user plane network element to determine the first tunnel for sending the data packet of the service.

17. The method of claim 16, wherein after the first session management network element sends the second indication information to the first user plane network element, the method further comprises:

the first session management network element receives information of a second tunnel from the first user plane network element, and the first user plane network element receives a data packet of the service from the second user plane network element or an application server through the second tunnel;

and the first session management network element sends the second tunnel information to the second user plane network element or the application server.

18. The method according to claim 1, wherein the second indication information includes a multicast address, and the second indication information is used to instruct the first user plane network element to send a data packet with a destination address being the multicast address to the terminal device through the unicast bearer.

19. The method of claim 1, further comprising, after the terminal device switches to the second network:

the first session management network element sends a first notification message to an Application Server (AS), wherein the first notification message is used for notifying the AS that the AS supports sending the data of the service to the terminal equipment by using a multicast mode;

the first session management network element joins the terminal device into the multicast session corresponding to the service, including:

the first session management network element receives fifth indication information, wherein the fifth indication information is used for indicating the terminal equipment to join the multicast session corresponding to the service;

and the first session management network element adds the terminal into the multicast session corresponding to the service according to the fifth indication information.

20. The method of claim 19, wherein before the first session management network element sends the first notification message to the application server AS, further comprising:

The first session management network element receives sixth indication information, where the sixth indication information is used to indicate that the first notification message is sent to the AS when supporting sending service data to the terminal device by using a multicast mode.

21. The method according to claim 19 or 20, wherein before the first session management network element joins the terminal device to the multicast session, further comprising:

22. A first session management network element, comprising:

the receiving module is used for receiving first indication information, wherein the first indication information is used for indicating a data packet for sending the multicast service to the terminal equipment positioned in the first network through a unicast bearer;

a sending module, configured to send second indication information to a first user plane network element, where the second indication information is used to indicate that the data packet received by the first user plane network element from a second user plane network element is sent to the terminal device through the unicast bearer;

A joining module, configured to join the terminal device to a multicast session corresponding to the service when the terminal device is accessed through a second network, so that the terminal device receives the data packet through a multicast path of the second network;

23. The network element of claim 22, further comprising:

an acquisition module, configured to acquire multicast quality of service QoS flow information of the service;

and the first determining module is used for determining unicast bearing of the data packet for sending the service according to the multicast QoS flow information of the service.

24. The network element of claim 23, wherein the receiving module is specifically configured to:

receiving a first message, wherein the first message comprises the first indication information and a multicast service identifier of the service;

the acquisition module is specifically configured to:

and acquiring the multicast QoS flow information of the service according to the multicast service identifier.

25. The network element of claim 23, wherein the first indication information includes a multicast service identifier of the service, and the obtaining module is specifically configured to:

26. The network element of any one of claims 23-25, wherein the first determining module is further configured to:

and if the first session management network element receives eighth indication information, wherein the eighth indication information indicates that the service supports service continuity, determining a unicast QoS flow corresponding to the service according to the information of the multicast QoS flow.

27. The network element according to any of the claims 22-25, wherein the joining module is specifically configured to:

switching the data packet of the service from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through a protocol data unit PDU session in the process of switching the terminal equipment from the first network to the second network;

after the terminal device is switched from the first network to the second network, the terminal device is added into the multicast session, and the data packet of the service is switched from being sent to the terminal through the PDU session to being sent to the terminal device through the multicast session.

28. The network element according to any of the claims 22-25, wherein the joining module is specifically configured to:

And in the process of switching the terminal equipment from the first network to the second network, adding the terminal equipment into the multicast session, and switching the data packet of the service from being sent to the terminal equipment through the unicast bearer to being sent to the terminal equipment through the multicast session.

29. The network element of claim 26, wherein the joining module is specifically configured to:

30. The network element of claim 26, wherein the joining module is specifically configured to:

31. The network element according to any of claims 22, 29 and 30, further comprising:

and the second determining module is used for determining that the service supports the multicast mode transmission through the second network before the joining module joins the terminal equipment into the multicast session.

32. The network element of claim 31, wherein the second determining module is specifically configured to:

and receiving a first rule corresponding to the service, wherein the first rule is used for controlling, strategy or charging, and the first rule comprises third indication information which is used for indicating the service to support multicast mode transmission.

33. The network element according to claim 29 or 30, further comprising:

and a third determining module, configured to determine that the terminal device supports multicast in the second network, and/or that a target access network device supports multicast, where the terminal device accesses the second network through the target access network device.

34. The network element of claim 33, wherein the receiving module is further configured to:

receiving multicast capability indication information sent by the terminal equipment, wherein the multicast capability indication information is used for indicating the multicast capability of the terminal equipment in the second network;

The third determining module is specifically configured to:

and determining that the terminal equipment supports multicast in the second network according to the multicast capability indication information.

35. The network element of claim 27, wherein the sending module is further configured to:

after the terminal equipment joins the multicast session, notifying the first user plane network element to stop sending the data of the service to the terminal equipment through the PDU session.

36. The network element of any one of claims 22-25, 29, 30, 32, 34, 35, wherein the receiving module is further configured to:

receiving fourth indication information when the terminal equipment moves into a Multimedia Broadcast Multicast Service (MBMS) area or after the terminal equipment moves into the MBMS area, wherein the fourth indication information is used for indicating that the data of the service is stopped being sent through the unicast bearer;

the sending module is further configured to: and notifying the first user plane network element to stop sending the data of the service through the unicast bearer according to the fourth indication information.

37. The network element of claim 22, wherein the second indication information includes a first mapping relationship between information of a first tunnel and an identifier QFI of a multicast quality of service QoS flow of the service, the first tunnel being a tunnel corresponding to the unicast bearer, the QFI being a QFI of a data packet of the service received by the first user plane network element, the first mapping relationship being used by the first user plane network element to determine the first tunnel for transmitting the data packet of the service.

38. The network element of claim 37, wherein the receiving module is further configured to:

after the sending module sends second indication information to a first user plane network element, receiving information of a second tunnel from the first user plane network element, wherein the first user plane network element receives a data packet of the service from a second user plane network element or an application server through the second tunnel;

the sending module is further configured to: and sending the second tunnel information to the second user plane network element or the application server.

39. The network element of claim 22, wherein the second indication information includes a multicast address, and the second indication information is used to instruct the first user plane network element to send a data packet with a destination address being the multicast address to the terminal device through the unicast bearer.

40. The network element of claim 22, wherein after the terminal device switches to the second network, the sending module is further configured to:

sending a first notification message to an Application Server (AS), wherein the first notification message is used for notifying the AS that the AS supports sending the data of the service to the terminal equipment by using a multicast mode;

The joining module is specifically configured to:

receiving fifth indication information, wherein the fifth indication information is used for indicating the terminal equipment to join the multicast session corresponding to the service;

and according to the fifth indication information, the terminal is added into the multicast session corresponding to the service.

41. The network element of claim 40, wherein the receiving module is further configured to, prior to the sending of the first notification message to the application server AS:

and receiving sixth indication information, wherein the sixth indication information is used for indicating to send the first notification message to the AS when supporting to send service data to the terminal equipment by using a multicast mode.

42. The network element of claim 40 or 41, further comprising:

and the determining module is used for determining that the terminal equipment supports multicast in the second network and/or the target access network equipment supports multicast, wherein the terminal equipment accesses the second network through the target access network equipment.

43. A communication system, comprising: a first session management network element and an application server, AS;

the AS is used for receiving a first report from a terminal device of a first network, wherein the first report is used for indicating the terminal device to move out of a Multimedia Broadcast Multicast Service (MBMS) area; according to the first report, determining a data packet for transmitting the multicast service to the terminal equipment through a unicast bearer; the first indication information is used for indicating to send the data packet of the service to the terminal equipment through unicast bearing;

The first session management network element is configured to receive the first indication information; transmitting second indication information to the first user plane network element, wherein the second indication information is used for indicating the data packet received by the first user plane network element from the second user plane network element to be transmitted to the terminal equipment through the unicast bearer; when the terminal equipment is accessed through a second network, the first session management network element adds the terminal equipment into a multicast session corresponding to the service, so that the terminal equipment receives the data packet through a multicast path of the second network; wherein the second user plane network element is located on a multicast path of the second network.

44. The system of claim 43, further comprising the first user plane network element.

45. The system of claim 43, wherein after the terminal device switches to the second network, the first session management network element is further configured to send a first notification message to an application server, AS, the first notification message being configured to notify the AS that supports sending data of the service to the terminal device using multicast; and the method is specifically used for receiving fifth indication information, wherein the fifth indication information is used for indicating the terminal equipment to join the multicast session corresponding to the service, and the terminal is joined to the multicast session corresponding to the service according to the fifth indication information.