CN113630822A

CN113630822A - Method and device for switching multicast service

Info

Publication number: CN113630822A
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: 2021-11-09
Anticipated expiration: 2040-07-31
Also published as: WO2021223745A1; CN113630822B

Abstract

The embodiment of the application provides a method and a device for switching multicast services, 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, the first indication information is used for indicating a data packet of a service to be sent to the terminal device through unicast bearer, 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 that the data packet is sent to the terminal device through the unicast bearer, and when the terminal device accesses through a second network, the first session management network element adds the terminal device into a multicast session corresponding to the service. The service data is switched from the multicast path of the first network to the unicast bearer of the first network, and the unicast bearer of the first network is switched to the multicast session of the second network, so that 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 the chinese patent application filed on 8/5/2020 and entitled "method and apparatus for multicast service switching" by the chinese patent office, application number 202010383204.3, the entire contents of which are incorporated herein by reference.

Technical Field

The present application 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 (LTE) system network, for a Group Communication (Group Communication) service, an Application server (Application Services) may send multicast broadcast service data (also referred to as MBMS service) to a terminal device in the following two ways: multimedia Broadcast/Multicast Services (MBMS) bearers or unicast bearers.

When the terminal device is located in the coverage of a fifth Generation mobile communication (5Generation, 5G) network, the terminal device may also receive multicast broadcast service data in a multicast broadcast manner, and the 5G network is also referred to as 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 a coverage area of a 5G base station, how to ensure continuity of multicast broadcast service data in a handover process is a key problem to be solved.

Disclosure of Invention

The embodiments of the present application provide a method and an apparatus for switching a multicast service, which can ensure that, in a process of switching a terminal device from a first network to a second network, multicast service data received by the terminal device through a multicast path of the first network maintains service continuity in the switching process.

A first aspect of the present application provides a method for switching multicast services, including: and the first session management network element receives first indication information, wherein the first indication information is used for indicating a data packet of a service to be sent to terminal equipment located in a first network through unicast bearing. And the first session management network element sends second indication information to a first user plane network element, wherein the second indication information is used for indicating that the data packet is sent to the terminal equipment through the unicast bearer. And when the terminal equipment accesses 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 switched from the multicast path of the first network to the unicast bearer of the first network, and the unicast bearer of the first network is switched to the multicast session of the second network, so 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 method further comprises: and the first session management network element acquires the multicast QoS stream information of the service, and determines the unicast bearer of the data packet for sending the service according to the multicast QoS stream information of the service.

In an exemplary manner, the receiving, by the first session management network element, the first indication information includes: and 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. Correspondingly, the acquiring, by the first session management network element, the multicast QoS flow information of the service includes: and the first session management network element acquires the multicast QoS stream 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 acquiring, by the first session management network element, multicast QoS flow information of the service includes: and the first session management network element acquires the multicast QoS stream information of the service according to the multicast service identifier.

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

In an exemplary manner, the adding, by the first session management network element, the terminal device into the multicast session corresponding to the service specifically includes: 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 device 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, and the method switches a data packet transmitted by a multicast mode in the first network from the multicast mode to the unicast path of the first network, then switches the data packet from the unicast path of the first network to the unicast path of the second network, and then switches the data packet 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 keeps service continuity 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 service data to the terminal device through the PDU session.

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

According to the method, the data packet transmitted in the multicast mode in the first network is switched to the unicast path of the first network from the multicast mode, and then is switched to the multicast path of the second network from the unicast path of the first network, so that the continuity of the multicast service of the terminal equipment in the cell switching process is guaranteed.

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

Optionally, the determining, by the first session management network element, that the service supports multicast transmission through the second network may be: and the first session management network element receives a first rule corresponding to the service, wherein the first rule is used for controlling, policy or charging, the first rule comprises third indication information, and the third indication information is used for indicating that the service supports 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 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 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 established, the first session management network element triggers the establishment of the multicast session.

In an exemplary manner, the joining, by the first session management network element, the multicast session by the end device includes: and the first session management network element receives 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, and the PDU session is associated with the service. And the first session management network element determines that the service sent by 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 add the terminal device to 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 sending of the data of the service through the unicast bearer is stopped, 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 quality of service QoS stream 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 for the first user plane network element to determine the first tunnel through which the data packet of the service is sent.

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 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 indicate the first user plane network element to send a data packet with a destination address of the multicast address to the terminal device through the unicast bearer.

In an exemplary manner, after the terminal device is switched 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 the data of the service to the terminal device in a multicast mode. Correspondingly, the adding, by the first session management network element, the terminal device into the multicast session corresponding to the service specifically includes: and the first session management network element receives fifth indication information, wherein the fifth indication information is used for indicating that the terminal equipment is added into 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.

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 the first notification message is sent to the AS when the first session management network element supports sending service data to the terminal device in a multicast mode.

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

Optionally, before the first session management network element adds the terminal to 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 acquires 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 acquires the multicast QoS stream information of the service according to the multicast service identifier;

and when the terminal equipment accesses 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, a first session management network element obtains a multicast service identifier of a service received by a terminal device through a multicast path of a first network in advance, and obtains multicast QoS stream information of the service according to the multicast service identifier, so that when the terminal device accesses through a second network, the first session management network element can add the terminal device into a multicast session corresponding to the service, and therefore, in the process of switching the terminal device from the first network to the second network, the multicast service data received by the terminal device through the multicast path of the first network can keep service continuity in the switching process.

In an exemplary manner, the adding, by the first session management network element, the terminal device into the multicast session corresponding to the service specifically includes: and 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 stream in the second network according to the multicast QoS stream information, wherein the unicast QoS stream 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 the multicast session sent to the terminal device via the PDU session to the multicast session sent to the terminal device via the second network.

The PDU session is a unicast path in the second network, the mode switches data transmitted by a multicast mode in the first network to the unicast path of the second network, and then switches the data 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 keeps service continuity in the cell switching process.

In another exemplary manner, the adding, by the first session management network element, the terminal device into the multicast session corresponding to the service specifically includes: and in the process of switching the terminal device from the first network to the second network, the first session management network element adds the terminal device into the multicast session according to the multicast service identifier, and switches the data packet of the service from the multicast mode sent to the terminal device via the first network to the multicast session sent to the terminal device via 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 keeps the continuity of the service in the process of cell switching.

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

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

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

In an exemplary manner, the method further comprises: and 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 add the terminal device to 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 equipment, wherein the first report is used for indicating that the terminal equipment moves out of the MBMS area. And the AS determines to send a data packet of the service to the terminal equipment through unicast bearer according to the first report, and sends first indication information to core network equipment and/or a 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 bearer.

When the signal of the MBMS area of the terminal equipment is weak, the method enables the AS to trigger and establish unicast bearing by sending a first report to the AS, switches the service from the MBMS bearing to the unicast bearing, and further switches the service from the unicast bearing to the 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 device, where the second message includes 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, where the third indication information includes: 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 and 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 of a service is supported to be sent to the terminal device in a multicast manner.

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 that data of the service is supported to be sent to the terminal device using a multicast mode, 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 that data supporting the service is sent to the terminal device in a multicast manner is supported, 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 added to a multicast session corresponding to the service.

In an exemplary manner, when the terminal device moves from a non-MBMS area to an MBMS area, the AS receives a second report from the terminal device, where the second report is used to notify the AS that the terminal device can receive 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 that sending of the service data through a unicast bearer is stopped.

In a fourth aspect of the present application, 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 a multicast capability of the terminal device in a second network. The terminal device receives configuration information of wireless resources allocated to the terminal device by a target access network device in a second network from a source access network device in a first network, wherein the configuration information of the wireless resources is used for the terminal device to receive the data of the service in the second network in a multicast mode, and the terminal device 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 an application server AS, where the fourth notification message is used to notify the terminal device to receive data of a service using a multicast session in the second network.

A fifth aspect of the present application provides a method for switching multicast services, including: and the target access network equipment receives seventh indication information from the first session management network element, wherein the seventh indication information is used for indicating that the terminal equipment is added into the multicast session corresponding to the service. And the target access network equipment acquires the parameters of the multicast QoS flow of the multicast session, and allocates wireless resources to the multicast QoS flow according to the seventh indication information and the parameters of the multicast QoS flow. And the target access network equipment sends 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 the access network equipment accessed by the terminal equipment before the terminal equipment is accessed to the target access network equipment.

Optionally, the seventh indication information and the QoS information of the multicast session are sent by the first session managing network element through one message.

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

Optionally, the network element further includes: the acquisition module is used for acquiring the multicast service quality QoS stream information of the service; and the first determining module is used for determining the unicast load of the data packet for sending the service according to the multicast QoS stream 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 stream 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 stream information of the service according to the multicast service identifier.

The first determination module is further to: if the first session management network element receives eighth indication information indicating that the service supports service continuity, determining a unicast QoS stream corresponding to the service according to the information of the multicast QoS stream.

In an 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, switching the data packet of the service from the transmission to the terminal equipment through the unicast bearer to the transmission to the terminal equipment through a Protocol Data Unit (PDU) session, adding 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 the transmission to the terminal equipment through the PDU session to the transmission 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 informing the first user plane network element to stop sending the service data 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 the data packet sent to the terminal equipment through the unicast bearer to the data packet sent to the terminal equipment through the multicast session.

Optionally, the method further includes: a second determining module, configured to determine that the service supports sending in a multicast mode through the second network before the first session management network element joins the terminal device in 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, policy or charging, the first rule comprises third indication information, and the third indication information is used for indicating that the service supports multicast mode transmission.

Optionally, the system further includes 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 of establishing packet data network PDN connection by the terminal equipment, 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 includes: 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.

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 Protocol Data Unit (PDU) session, the PDU session is associated with the service, the service sent by 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 add 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 service data is stopped being sent through the unicast bearer. The sending module is further configured to notify the first user plane network element to stop sending the data of the service through a 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 the 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 is handed over 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 the multicast mode to send the service data to the terminal equipment. Correspondingly, the adding module is specifically configured to: and receiving fifth indication information, wherein the fifth indication information is used for indicating that the terminal equipment is added into the multicast session corresponding to the service, and adding the terminal into 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, where the sixth indication information is used to indicate that the first notification message is sent to the AS when data of a service is supported to be sent to the terminal device in a multicast mode.

Optionally, the method further includes a determining module, where 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 that 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 indicate that the terminal device moves 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; a sending module, 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 that a data packet of the service is sent to the terminal device through a unicast bearer.

Optionally, the sending module is further configured to: and sending 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 sending module sends third indication information to the core network device, specifically: and sending a second message to the core network device, wherein the second message comprises the third indication information and a 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 device 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 device and/or the first session management network element, where 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 device, where the sixth indication information is used to indicate that the first notification message is sent to the AS when supporting to send service data to the terminal device in a multicast manner.

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 that data of the service is supported to be sent to the terminal device in a multicast mode, and the sending module is further used to: and responding to the first notification message, and sending a second notification message to the terminal device, wherein the second notification message is used for notifying the terminal device 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 that data of the service is supported to be sent to the terminal device in a multicast mode, and the sending module is further used to: and responding to the first notification message, and sending 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 added to the multicast session corresponding to the service.

In an exemplary manner, the receiving module is further configured to: and when the terminal equipment moves from a non-MBMS area to an 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 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 service data through the unicast bearer is stopped.

An eighth aspect of the present application provides a terminal device, including: a sending module, configured to send, to a first session management network element, multicast capability indication information 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 to the terminal device by a target access network device in a second network, where the configuration information of the radio resource is used for the terminal device to receive data of the service in the second network in a multicast mode; the receiving module is further configured to receive the 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 notification message from an Application Server (AS), wherein the fourth notification message is used for notifying the terminal equipment to use the multicast session in the second network to receive the data of the service.

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 obtaining module, configured to obtain a parameter of a multicast QoS stream of the multicast session; a resource allocation module, configured to allocate radio resources to the multicast QoS stream according to the seventh indication information and the parameter of the multicast QoS stream; a sending module, configured to send configuration information of the wireless resource of the multicast QoS stream to the terminal device through a source access network device, where the source access network device is an access network device to which the terminal device is accessed before accessing the target access network device.

A tenth aspect of the present application provides a first session managing network element, comprising a processor, a memory and a transceiver, wherein the memory is configured to store instructions, and the transceiver is configured to communicate with other devices, and the processor is configured to execute the instructions stored in the memory, so as to cause the first session managing network element to perform the method according to the first aspect or any manner 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 according to the second aspect or any manner of the present application.

A twelfth aspect of the application provides a terminal device comprising a processor, a memory and a transceiver, the memory being configured to store instructions, the transceiver being configured to communicate with other devices, and the processor being configured to execute the instructions stored in the memory to cause the terminal device to perform the method according to the third aspect or any manner of the application.

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

A fourteenth aspect of the present application provides a computer-readable storage medium having stored thereon instructions that, 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 that, 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 managing network element and an AS, the first session managing network element being configured to perform the method according to the first aspect of the present application or any manner of the first aspect of the present application, and the AS being configured to perform the method according to the second aspect of the present application or any manner of the second aspect of the present application.

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

According to the method and the device for switching the multicast service, 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, the first indication information is used for indicating a data packet for sending the service to the terminal device through unicast bearer, 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 that the data packet is sent to the terminal device through the unicast bearer, and when the terminal device accesses through a second network, the first 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 service is 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-capable 4G network;

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

FIG. 5 is a diagram illustrating a network architecture suitable for use in embodiments of the present application;

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

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

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

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

fig. 10 is a signaling flowchart of a method for switching a multicast service according to a fifth embodiment of the present application;

fig. 11 is a signaling flowchart of a method for switching a multicast service according to a sixth embodiment of the present application;

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

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

fig. 14 is a schematic structural diagram of a first session managing network element according to a ninth embodiment of the present application;

fig. 15 is a schematic structural diagram of an AS according to a tenth embodiment 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 managing network element according to a thirteenth embodiment of the present application.

Detailed Description

The embodiment of the application provides a method for switching multicast services, which can realize that the multicast services are not interrupted in the process of switching a terminal device 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 referred to as a New wireless communication system, a New Radio (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: user Equipment (UE), Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), Mobility Management Entity (MME), Serving Gateway (SGW), Packet Data Network Gateway (PGW), Policy and Charging Rule Function (PCRF), Home Network Server (HSS), and IP traffic of an operator, etc.

The core network of the LTE network mainly includes three logic functions, namely, an MME, an SGW, and a PGW, where the MME is a signaling management network element and is responsible for Non-Access Stratum (NAS) signaling encryption, allocating a temporary identity to the UE, selecting core network devices such as the SGW and the PGW, and providing functions such as roaming, tracking, and security; the SGW is a mobility anchor point for switching between local evolved nodes (enbs), and provides functions related to lawful interception, and the eNB is a base station in the LTE system; the PGW is responsible for the functions of user address allocation, scheme control, execution of charging rules, lawful interception 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, AN access network in the 5G network may be a radio access network (R) AN, and AN (R) AN device in the 5G network may be composed of a plurality of 5G- (R) AN nodes, and the 5G- (R) AN nodes may include: non-3 GPP access networks, such as Access Points (APs) of a WiFi network, next generation base stations (which may be collectively referred to as a new generation radio access network node (NG-RAN node), where the next generation base stations include a new air interface base station (NR node b, gNB), a new generation evolved base station (NG-eNB), a Central Unit (CU), a Distributed Unit (DU), a split-form gNB, and the like), a transceiving point (TRP), a Transmission Point (TP), or other nodes.

The 5G core Network (5G core/new generation core, 5GC/NGC) includes a plurality of functional units such as an Access and Mobility Management Function (AMF) Network element, a Session Management Function (SMF) Network element, a User Plane Function (UPF) Network element, an Authentication Server Function (AUSF) Network element, a Policy Control Function (PCF) Network element, an Application Function (AF) Network element, a unified data Management Function (UDM) Network element, and a Network Slice Selection Function (NSSF) Network element.

The AMF network element is mainly responsible for services such as mobility management, access management and the like. 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, and the like. The UPF is mainly responsible for routing and forwarding data packets externally connected to a Data Network (DN) and a user plane, filtering packets, and performing quality of service (QoS) control related functions. The AUSF is mainly responsible for authentication functions of the terminal device, and the like. 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, and the like. It should be noted that these functional units may work independently, or may be combined together 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 establishment, release, and modification of a user plane transmission path, etc.

The functional units in the 5GC can communicate with each other through a next generation Network (NG) interface, such as: the UE can transmit control plane information with the AMF network element through AN NG interface 1 (N1 for short), the RAN equipment can establish a user plane data transmission channel with the UPF through AN NG interface 3 (N3 for short), the AN/RAN equipment can establish control plane signaling connection with the AMF network element through AN NG interface 2 (N2 for short), the UPF can perform information interaction with the SMF network element through AN NG interface 4 (N4 for short), the UPF can perform information interaction with the data network DN through AN NG interface 6 (N6 for short), the AMF network element can perform information interaction with the SMF network element through AN NG interface 11 (N11 for short), the SMF network element can perform information interaction with the PCF network element through AN NG interface 7 (N7 for short), and the AMF network element can perform information interaction with the AUSF through AN NG interface 12 (N12 for short). 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.

The UEs in the 4G network and the 5G network are also referred to as terminal equipment, Mobile Stations (MSs), mobile terminals (mobile terminals), terminals (terminals), 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 having wireless connection capability, 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 (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless communication capability, 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 (AR) terminal device, a wireless terminal in industrial control (industrial control), a wireless terminal in self driving (self driving), a wireless terminal in remote medical (remote medical), a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in smart city (smart city), a wireless terminal in smart home (smart home), and the like. The embodiments of the present application are not particularly limited.

In the 4G network, MBMS and eMBMS are introduced aiming at group communication, the eMBMS is the evolution of the MBMS, the MBMS supports two modes of multimedia broadcast service and multicast service, multimedia video information can be directly broadcast to all users and can also be sent to a group of subscription users for charging to be watched, and operators can be helped to develop various commercial applications such as multimedia advertisement, free and charged television channels, multimedia message group sending and the like. The operators can develop the mobile TV service with lower network deployment cost.

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

The GCS AS may send data to the UE in two ways: unicast bearer mode and MBMS bearer mode. The path corresponding to the unicast bearer (or referred to as a unicast path) is: 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, and E-UTRAN sends the data to UE. The path corresponding to the MBMS bearer is as follows: 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, and E-UTRAN sends the data to UE.

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

In 4G networks, MBMS has a certain service area, i.e. not all base stations support MBMS bearers. If some base stations do not support MBMS bearer, multicast service data cannot be sent through MBMS bearer, and at this time, in order to ensure service continuity, data is switched to be sent through unicast bearer, that is, data is sent through Packet Data Network (PDN) connection, that is, data is sent through S/P-GW.

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

In fig. 3, there is a signaling interface between the UE and the GCS AS, and the signaling between the UE and the GCS AS is also sent through the PDN connection, i.e., through the unicast bearer. The GSC AS and the BM-SC comprise an MB2-U interface and an MB2-C interface, wherein 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, the UE may also receive the service data in a 5G multicast manner. AS shown in fig. 4, when the UE receives the service data in the 5G multicast mode, the multicast service data may be transmitted through a multicast path, for example, the AS (which may be a GCS AS) transmits the multicast service data to the UPF, and transmits the multicast service data to the 5G base station through a shared tunnel between the UPF and the base station (only one copy of the multicast service data is transmitted to the base station through the tunnel UPF, and the base station may transmit the one copy of the multicast service data to a plurality of UEs).

The 5G base station may flexibly determine a playing mode according to the air interface condition, the number of terminals listening to the service, and the like, where the playing mode may be a Point To Multipoint (PTM) mode or a Point To Point (PTP) mode. In the PTM mode, the base station only sends one part of data, and a plurality of terminal devices can receive the data; in the PTP method, a base station transmits a copy of data that can only be received by a terminal device. For the same multicast service, the base station may enable both PTM and PTP modes, e.g., PTM for UE1, UE2, and PTP for UE 3.

The 5G multicast path includes: AS- > UPF- >5G AN- > UE. There is also a unicast path, i.e. a path of PDU sessions, in a 5G network, the unicast path comprising: 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 PGW-C + SMF, or by other SMFs, and the UPF may be the same UPF as 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 of a user plane function, and the PGW-U + UPF may be a combined network element having both a PGW-U function and a UPF function, or may be composed of two physically independent network elements. Similarly, the 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 both the PGW-C function and the SMF function, or may be composed of 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 of the 5G base station, how to make the UE switch to 5G, the multicast service data received by the UE through MBMS maintains service continuity during the switching process.

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 to which the method of the present invention is applied, and as shown in fig. 5, when a 5G network and a 4G network are in interworking, a PGW-C and an SMF on a unicast path are combined and called PGW-C + SMF, and a PGW-U and a UPF are combined and called PGW-U + UPF. The PCRF in the 4G network is replaced by a PCF, and an interface exists between the PCF and the PGW-C + SMF so as to receive the 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 a possible implementation manner, only an interface exists between a specific UPF and an AS, that is, the AS can only send multicast service data to the specific UPF, in this implementation manner, a PGW-U + UPF of a PDU session of a terminal device may not directly receive data of the multicast service from the AS, at this time, if the data of the multicast service is sent through the PDU session, the PGW-U + UPF needs to receive data of the multicast service from the specific UPF, that is, a path from the specific UPF to the PGW-U + UPF needs to be established. In order to support that a multicast service sent through a 5G multicast path may be switched to be sent through a 4G network, in an implementation manner, in an embodiment of the present application, a path corresponding to a unicast bearer of the multicast service in the 4G network is modified, 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, that is, in the architecture shown in fig. 5, the multicast traffic needs to pass through UPF in 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 transmitted through the unicast path of 4G is the multicast address of the multicast service, 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 multicast service data transmitted by the GCS AS over a unicast bearer in the 4G network is a unicast address (i.e. the address of a terminal device), and the destination address of multicast service data transmitted over an MBMS bearer is a multicast address. In the architecture diagram shown in fig. 5, in the 4G network, the destination addresses of the multicast service data sent by the AS through the unicast bearer or the MBMS bearer are the same, that is, the destination addresses are the multicast addresses of the multicast service.

In actual deployment, the UPF and PGW-U + UPF shown in fig. 5 may be combined or may not be combined, which is not limited in the embodiment of the present application, and if the UPF and PGW-U + UPF are combined, there is no path from the UPF to PGW-U + UPF.

In this embodiment of the present application, a 4G multicast mode (or referred to as a 4G multicast path) uses an MBMS bearer to transmit data, a 4G unicast mode (or referred to as a 4G unicast path) uses a 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 (EPS bearer). The 5G multicast mode adopts a 5G multicast session (or referred to as a 5G multicast path) to transmit data, and actually transmits the data by a multicast QoS stream in the 5G multicast session, and the 5G unicast mode adopts a PDU session to transmit data, and actually transmits the data by a unicast QoS stream in the PDU session.

In addition, although the multicast service is described as an example in the embodiment of the present application, the method in 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 the present embodiment, a method for providing multicast service switching is provided, and in the present 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 also be other networks supporting multicast service, for example, as the network evolves, the second network may also be a next generation network. Fig. 6 is a flowchart of a method for switching a multicast service according to a first embodiment of the present application, and as shown in fig. 6, the method according to the present embodiment includes the following steps:

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

The terminal device receives service data in a multicast mode currently, wherein the first session management network element may be PGW-C + SMF, and the first indication information is sent to the PGW-C + SMF by the PCF after receiving the second message from the AS, or sent to the PGW-C + SMF by the AS directly. When the AS learns 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 or is 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 can determine that the terminal equipment is about to move out of or is moved out of the MBMS area of the service through receiving a first report of the terminal equipment, or learn that the signal of the MBMS area of the service where the terminal equipment is currently located is weak, wherein the first report is used for indicating that the terminal equipment is moved out of or about to move out of the MBMS area of the service, or the signal of the MBMS area of the service where the terminal equipment is currently located is weak.

The first indication information is used to instruct the first session management network element to send a data packet of a service to a terminal in the first network by using a unicast bearer, or to instruct to allocate a unicast bearer for the service of the terminal device in the first network, or to instruct to switch or migrate the service of the terminal device from an MBMS bearer to a unicast bearer.

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

in case one, 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 case two, 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.

In view of the foregoing first situation, the first indication information may further include the first rule, or the first indication information and the first rule are sent to the first session management network element together, or the first indication information is the first rule. The first rule may be a Policy Control and Charging (PCC) rule corresponding to the service when the AS sends the data of the service in a case one manner, and correspondingly, the first indication information is used to indicate that the first session management network element creates a unicast bearer according to the first rule. The first rule is determined by the PCF according to the first description information, which is the service information corresponding to the service when the service is sent in a situation mode, including the service identification information and the corresponding QoS parameter. 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 managing network element already obtains 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 the identification information of the service, so that the first session managing 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 S102. The identification information of the service 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 embodiment.

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 the second rule, or the first indication information and the second rule are sent together to the first session management network element, 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 the data of the service in the manner of case two, and different from the first rule, the second rule may include third indication information, the second rule does not include the third indication information, and correspondingly, the first indication information is used to indicate 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 the second description information, which is the service information corresponding to the service when the service is sent in the second mode, including the service identification information and the corresponding QoS parameter.

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

Optionally, in this embodiment of the application, after receiving the first indication information, the first session management network element obtains multicast QoS stream 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 stream information of the service. The first session management network element may obtain multicast QoS stream information of the service from the UDM or the UDR or the second session management network element according to the multicast service identifier, where the multicast service identifier may be an AS or a core network device and the first indication information are sent to the first session management network element together, 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 (e.g., a five-tuple or a service identifier, where a destination address in the five-tuple information is a multicast IP address of the service) mapped to the QoS flow, and QoS parameters of the QoS flow (e.g., a 5QI corresponding to the QoS flow, a maximum bandwidth requirement, etc.).

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 performing cross-system handover, where the service continuity refers to ensuring that data packets of the service are not lost and/or are sent in sequence as far as possible when the terminal device moves. And if the first session management network element receives the eighth indication information, determining a unicast QoS stream corresponding to the service according to the information of the multicast QoS stream.

S102, the first session management network element sends, according to the first indication information, second indication information to the first user plane network element, where the second indication information is used to indicate that the data packet of the service is sent to the terminal device through the unicast bearer.

In view of the second situation, 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 service data in the second situation. Optionally, the service identification information includes an IP address of the terminal device. And when the first user plane network element receives a data packet of a service, determining the information of a first tunnel for sending the data packet according to the service identification information of the data packet and the third mapping relation. Each unicast bearer corresponds to information of a first tunnel, the information of the first tunnel is tunnel information of a downlink node, and the downlink node is an SGW or an access network device (when the SGW is combined with other network elements).

In view of the above first situation, 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 service data in the first situation, or a first mapping relationship between the identifier QFI of the multicast QoS stream of the service and the information of the first tunnel. For the architecture shown in fig. 5, when the unicast path is AS- > PGW-U + UPF- > eNB- > UE, the second indication information includes the second mapping relationship; 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 the first user plane network element to determine, according to the QFI in the data packet received from the UPF, the information of the first tunnel used for sending the data packet, that is, determine the unicast bearer corresponding to the data packet. Each unicast bearer corresponds to information of a first tunnel, the information of the first tunnel is tunnel information of a downlink node, and the downlink node is an SGW or an access network device (when the SGW is combined with other network elements).

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

Or, when the unicast path is AS- > UPF- > PGW-U + UPF- > eNB- > UE, the second indication information further includes 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 relationship.

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

For the above situation, when the unicast path is AS- > PGW-U + UPF- > eNB- > UE, the second tunnel from the AS to PGW-U + UPF needs to be established, and then PGW-C + SMF needs to further send information of the second tunnel to the 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 the service data using the information of the second tunnel. Further, the fifth notification message is further configured to notify that a unicast bearer for sending the service data 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 used to notify the terminal device to receive the service data using the unicast bearer.

For the first situation, 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 that manages the second user plane network element, the first session management network element directly sends the information of the second tunnel to the second user plane network element; and 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.

It should be noted that, in order to support switching of data of the service sent through the MBMS bearer of the first network to be sent 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 being sent to the terminal device through the MBMS bearer to being sent to the terminal device through a unicast bearer (i.e., EPS bearer). Specifically, the steps S101 and S102 complete. In order to enable 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, the terminal device may be configured with an appropriate MBMS signal strength threshold, and when the terminal device detects that the MBMS signal is lower than the threshold, the terminal device sends the first report.

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

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

In the method, a data packet transmitted through MBMS bearer is switched from the MBMS bearer to the unicast path of the 4G network, then the unicast path of the 4G network is switched to the unicast path of the 5G network, and then the unicast path of the 5G network is switched to the multicast path of the 5G network, so that the continuity of the multicast service is ensured 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. For switching from the unicast path of the 4G network to the unicast path of the 5G network, reference may be made to the description of the switching process from the 4G network to the 5G network in the prior art, which is not described again.

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

The second multicast service switching mode: in the process that 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 a data packet of the service is switched from being sent to the terminal equipment through a unicast bearer of the first network to being sent to the terminal equipment through the multicast session.

Compared with the first switching mode, the second switching mode is that 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 without switching from the unicast bearer of the first network to the unicast bearer of the second network first and then switching 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 needs to determine whether the service supports multicast transmission through the second network, and whether the terminal device supports multicast in the second network. And when the service supports the multicast transmission through the second network and the terminal equipment supports the multicast in the second network, the first session management network element adds the terminal equipment into the multicast session of the service in the second network.

The first session management network element may determine whether the service supports multicast transmission through the second network by: and the first session management network element receives third indication information, wherein the third indication information is used for indicating 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 the PCC rule as an example, the PCF sends the first rule to the first session managing network element. The third indication information may indicate that the service supports multicast mode transmission of the second network in an explicit manner or an implicit manner, where the third indication information in the explicit manner is an indication newly added in the PCC rule, for example, the PCF may add an indication whether to support multicast mode transmission in the PCC rule corresponding to each service, or the PCF adds an indication indicating multicast mode 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 a Temporary Mobile Group Identity (TMGI) of the service, a multicast address when the service is played in a multicast mode in the second network, or another identifier for identifying the multicast service, which is not limited.

In the implicit mode, whether the service supports multicast mode transmission may be indicated by the multicast service identifier, and when the PCC rule of the service includes the multicast service identifier of the service, the first session management network element determines that the service supports 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 not be carried in the PCC rule, but is directly sent to the PGW-C + SMF by the AS, the AS may carry the third indication information in the service information and send the service information to the PGW-C + SMF, where the service information may include service description information (e.g., five-tuple information such AS an IP address, a port number, a protocol number, and the like) and QoS requirement information (e.g., a bandwidth requirement, a delay requirement, and the like).

In an implementation manner, the first indication information may be carried in the same message as the first rule and sent to the first session management network element, or the first rule may also be used as the first indication information, that is, the first rule indicates to send a data packet of a service to the 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 managing network element may receive the first rule before receiving the first indication information. In this implementation, the first indication information includes identification information of the service, and the identification information of the service may be a multicast service identification corresponding to the service. The first session management network element may obtain a first rule during PDN connection establishment, or when data of the service is sent to the terminal device in a unicast bearer mode of the first network for the first time, for example, at the above occasion, the AS sends information of the service to the PCF, where the information of the service includes indication information used to indicate whether the service supports multicast sending and description information when the service is sent in a case one (destination address of data packet is multicast address), where the description information includes identification information of at least one data service flow of the service in the case one 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, and may be implemented as follows:

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

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 the 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, indicates that the terminal device supports the multicast service in the second network when the value of the bit is 1, and indicates that the terminal device does not support the multicast service in the second network when the value of the bit is 0.

Or, when the terminal device does not support the multicast service in the second network, the terminal device does not carry the multicast capability indication information in the process of establishing the PDN connection. In the process of establishing the PDN connection by the terminal device, the first session management unit determines that the terminal device does not support the multicast service in the second network if the multicast capability indication information is not received, and determines that the terminal device 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 add 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 managing network element triggers the establishment of the multicast session. For the triggering of the multicast session establishment by the first session management network element, reference may be made to the description of the prior art, which is not described in detail in this embodiment.

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 by a unicast bearer supports multicast service transmission, and a 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.

Illustratively, the request message is 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, and the request message indicates that the switching is completed, and the first session management network element indicates, after receiving the request message, the target access network device in the second network to add the terminal device to the multicast session, that is, after completing the switching, the first session management network element indicates, to add the terminal device to the multicast session, the target access network device in the second network.

In the second multicast service handover mode, the request message may be a session creation request message, and the request message may indicate handover preparation, where the first session management network element indicates that the target access network device in the second network adds the terminal device to the multicast session and includes a message of adding the message to the multicast session in a handover request (HO request) message, and sends the message to the target access network device, that is, the first session management network element indicates, in a handover preparation phase, the target access network device in the second network adds the terminal device to the multicast session. The switching request message includes seventh indication information, where the seventh indication information is used to indicate that the terminal device is added into a multicast session corresponding to the service, after receiving the switching request message, the target access network device allocates a radio resource for receiving data of the service through the multicast session to the terminal device according to the seventh indication information in the switching request message, encapsulates the radio resource in a transparent container, and 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 example that the first session management network element is PGW-C + SMF, the first network is a 4G network, and the second network is a 5G network, the PGW-C + SMF further obtains a parameter of a multicast QoS stream when the service is sent in a multicast manner in 5G, and sends the parameter of the multicast QoS stream to the target access network device in the process of instructing the target access network device in the second network to join the terminal device into the multicast session, or before instructing the target access network device in the second network to join the terminal device into 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, where the third notification message is used to notify the terminal device to switch to the second network, or is used to notify the AS to send the data of the service to the terminal device by using the multicast session. 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 using the multicast session to receive the data of the service.

In the third multicast service switching manner, a process of switching data of a multicast service from an MBMS bearer to a unicast bearer is the same as that in the prior art, or a process of establishing a unicast bearer by a first session management network element is the same as that in the prior art, which is different from that in the prior art: when receiving the indication information indicating the preparation of the handover or the 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 that the terminal device supports or is about to support sending the data of the service to the terminal device in a multicast mode of the second network, or is used to notify that the terminal device is switched or is about to be switched to the second network, or is used to notify the AS of the usage situation.

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 the AS sends the first notification message to the AS when the first session management network element supports or is about to support sending of service data to the terminal device in a multicast mode of the second network, or when the terminal device is switched or is about to be switched to the second network. 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 managing network element together with the first indication information, for example, the first session managing 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 transmits the data of the multicast service (that is, the destination address is the address of the terminal device) in the case two. Therefore, in this manner, 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, and it is understood that the sixth indication information is included in the second rule, where the sixth indication information may be a subscription request.

In a third multicast service switching manner, the adding, by the first session management network element, the terminal device into the multicast session corresponding to the service may be: and the first session management network element receives fifth indication information, wherein the fifth indication information is used for indicating that the terminal equipment is added into the multicast session corresponding to the service, and the first session management network element adds the terminal equipment into the multicast session corresponding to the service according to the fifth indication information.

The fifth indication information may be sent to the first session management network element by the core network device or the terminal device. 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, after receiving 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 service data 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.

Similar to the first or second multicast service switching manner, the first session management network element also needs to determine whether the terminal device supports multicast in the second network, which may specifically refer to the related description of 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 add the terminal device into the multicast session may refer to the first or second multicast service switching manner, which is not described in detail herein.

It should be noted that, in the third multicast service switching manner, before the terminal device is switched to the second network, the service is sent to the terminal device through the unicast bearer of the first network, and after the terminal device is switched to the second network, the service is switched to the unicast bearer of the second network and sent to the terminal device. The first session management network element can delete the unicast resource corresponding to the service after adding the terminal device into the multicast session. In one implementation, the AS sends a request for deleting second description information to the core network device after receiving the first notification message, where the second description information is service information when the AS sends service data in a case two manner, and includes service identification information and QoS parameters, and the core network device sends an instruction for deleting the second rule to the first session management network element when receiving the request for deleting 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 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, 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 a data packet for sending a terminal device through a unicast bearer, and when the terminal device accesses through a second network, the first session management network element adds the terminal device to a multicast session corresponding to the service. The data of the service is switched from the multicast path of the first network to the unicast path of the first network, then switched to the multicast session after being switched to the unicast path of the second network, or the data of the service is directly switched from the unicast path of the first network to the multicast session of the second network, or the AS is notified in the first session management network element during the process of switching the data of the service from the unicast path of the first network to the unicast path of the second network or after the switching is completed, so that the AS directly notifies the core network device, or the AS notifies the first session management network element through the terminal device, and adds the terminal into the multicast session of the second network, thereby ensuring that the 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 being switched to the second network in the process of switching the terminal device from the first network to the second network, and maintains the continuity of the service.

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

s201, the AS receives a first report from the terminal equipment, and the first report is used for indicating that the terminal equipment moves out of the MBMS area.

The terminal device may send the first report in case that the signal of the MBMS area where the terminal device is currently located is weak, or send the first report in case that the terminal device is about to move or has moved from the MBMS area to the 5G network. In order to support smooth handover of data transmitted via an MBMS bearer to a multicast path in the second network, it is assumed in this embodiment that the terminal device is configured with an appropriate predetermined value, for example, when the signal quality of the MBMS detected by the terminal device is worse than the predetermined value, the terminal device transmits the first report to the AS, the first report being used to instruct the terminal device to move out of an MBMS area, which is an area in the first network.

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

S202, the AS determines to send the data packet of the service to the terminal equipment through unicast bearing according to the first report.

And the AS determines to send a data packet of the service to the terminal equipment through unicast bearing of the first network under the condition that the AS learns that the signal of the MBMS area where the terminal equipment is located is weak according to the first report or determines that the terminal equipment is about to move out of the MBMS area or is moved out of the MBMS area according to the first report.

S203, the AS sends first indication information to the core network device and/or the first session management network element, where the first indication information is used to indicate that the data packet of the service is sent to the terminal device through a unicast bearer.

The first session management network element may be PGW-C + SMF, the AS may directly send the first indication information to the PGW-C + SMF, or may send the first indication information to the core network device, and the core network device sends the first indication information to the PGW-C + SMF, where 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.

The data packet of the service sent by the AS to the terminal device in the first network through the unicast bearer in the first network is divided into two cases:

in case one, the data packet of the service sent by the AS includes the data of the service and a destination address, and the destination address is a multicast address.

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

In view of the foregoing first situation, the first indication information may further include the first rule, or the first indication information and the first rule are sent to the first session management network element together, 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 the data of the service in the manner of case one. The first rule is determined by the PCF according to the first description information, which is the service information corresponding to the service when the service is sent in a situation mode, including the service identification information and the corresponding QoS parameter. The first indication information is used to instruct the first session managing 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 transmission, 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 includes, in addition to the third indication information, a multicast service identifier corresponding to the service, that is, 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 the second rule, or the first indication information and the second rule are sent together to the first session management network element, 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 the data of the service in the manner of case two. The first indication information is used to instruct the first session managing network element to create a unicast bearer according to the second rule. The second rule is determined by the PCF according to the second description information, which is the service information corresponding to the service when the service is sent in the second mode, including the service identification information and the corresponding QoS parameter.

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 carries the first indication information in the first message and sends the first indication information to the PGW-C + SMF. The first rule is sent to the PCF, the NEF, or the PGW-C + SMF before sending the first indication information. 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 carries the first indication information and the multicast service identifier in the first message and sends the first message to the PGW-C + SMF.

In another 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 first description information, and the PCF or the NEF carries the first indication information and the first rule in the first message and sends the first message to the PGW-C + SMF. 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 situation, when determining that the terminal device is ready to switch to the second network or the handover is completed, the first session management network element sends a first notification message to the AS, where the first notification message is used to notify that the terminal device supports or is about to support sending the data of the service to the terminal device in a multicast mode of the second network, or is used to notify that the terminal device switches to or is about to switch to the second network, or is used to notify the AS of a usage situation that the data of the service is sent to the terminal device in a first mode.

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 adding the terminal device to 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 device according to the first notification message, where the second notification message is used to notify the terminal device to receive the service data using the multicast session, and the terminal device 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 the AS sends the first notification message when the AS supports or is about to support sending service data to the terminal device in a multicast mode of the second network, or when the terminal device switches to or is about to switch to the second network. 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 the data of the service using the unicast bearer of the first network. And the AS sends a sixth notification message to the terminal device according to the fifth notification message, wherein the sixth notification message is used for notifying the terminal device 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 indicate that the terminal device moves out of the MBMS area, and according to the first report, the AS determines to send a data packet of a service to the terminal device through a unicast bearer of the first network, and the core network device and/or the first session management network element send first indication information indicating 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 device, switches the data packet of the service to the unicast bearer in the first network first, and then switches the unicast bearer to the multicast session in the second network, thereby ensuring that the multicast service data received by the terminal device through the MBMS bearer maintains service continuity in the switching process in the process of switching the terminal device from the first network to the second network.

On the basis of the first embodiment and the second embodiment, fig. 8 is a signaling flow diagram of a method for switching a multicast service provided in the third embodiment of the present application, and this embodiment is described by taking the first multicast service switching manner as an example, that is, data transmitted by an MBMS bearer is first switched from the MBMS bearer to a unicast bearer in a 4G network, in a switching process of a terminal device from the 4G network to a 5G network, a PGW-C + SMF switches the data transmitted by the MBMS bearer from the unicast bearer in the 4G network to a PDU session (i.e., a unicast path in the 5G network), and after the terminal device is switched from the 4G network to the 5G network, the PGW-C + SMF adds the terminal device to the 5G multicast session, i.e., switches 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 first sends the data to the UPF, and then sends the data to the PGW-U + UPF through the UPF.

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

and S301, establishing PDN connection.

The terminal equipment establishes PDN connection in the 4G network, after the PDN connection is established, 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, eNB is the access network equipment in the 4G network. And, if the current location of the terminal device supports the MBMS, the AS may notify the terminal device to receive data (e.g., media data) of the service through the MBMS bearer. The route for transmitting data to the terminal equipment by the AS through the MBMS bearer is AS follows: AS- > BM-SC- > MBMS GW- > eNB- > UE.

The process of establishing the PDN connection may refer to the prior art, and is not described herein. Different from the prior art, if the terminal device supports the 5G multicast capability, the terminal device carries the 5G multicast capability indication information in a Protocol Configuration Option (PCO) of the PDN connection establishment request message.

In order to support interworking between 4G and 5G, the PGW-C selected by the MME for the PDN connection is PGW-C + SMF, and the UPF selected by the PGW-C + SMF for the PDN connection is PGW-U + UPF.

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

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

Optionally, the AS may establish a policy session to a core network device (e.g., PCF/NEF) associated with the PDN connection. The AS can send the description information of the service to the core network equipment through the strategy session so that the mobile network can allocate corresponding unicast bearing resources for the service. The description information of the service sent to the core network includes identification information of the service (e.g., quintuple information such as an IP address, a port number, a protocol number, etc.) and QoS requirement information (e.g., bandwidth requirement, delay requirement, etc.). 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 the service to be transmitted by a multicast mode (5G multicast mode or MBMS multicast mode), the AS includes third indication information in the description information of the service, and the third indication information is used for indicating that the service supports the multicast mode transmission.

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. When the AS sends the description information of the service, the AS indicates that the service is not currently sent through unicast bearing (or is currently sent through an MBMS bearing mode).

The step may also create an interface between the AS and the PGW-U + UPF for the service supporting multicast mode transmission, and of course, the interface may also be created in step S305. Specifically, the AS may send a processing requirement of the multicast service to the core network device, for example, the AS may request the core network to perform Robust Header Compression (ROHC) or Forward Error Correction (FEC) coding on the service data. The AS may include the above-mentioned 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 AS indicates that the service supports the multicast mode transmission, PCF also transmits the indication information to PGW-C + SMF, so that PGW-C + SMF can know that the service supports the multicast mode transmission. For example, the PCF may carry third indication information in the PCC rule, where the third indication information is used to indicate whether multicast mode 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, for example, the PCC rule carries the processing requirement. If the service information sent by the AS includes a 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 the 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.

And if the transmission path between the PGW-U + UPF and the AS or the 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 the PGW-C + SMF requests the PGW-U + UPF to allocate information of the MB2-U interface, and the information of the MB2-U interface includes a User data packet 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, the service is transmitted between the AS and the PGW-U + UPF through the second tunnel, and the UDP port number + IP address may be created for the service or created for the service of the terminal device. When the information of the MB2-U interface is created for a service, the data of the service on the PGW-U + UPF from the AS can be used to send 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 for 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 above tunnel, which is not described in detail 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 in a fifth notification message or send the information of the second tunnel in another message to the AS, 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 service data to the UPF first 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, aiming at the second Tunnel between the PGW-U + UPF and the UPF, the second Tunnel is based on the GTP-U, the PGW-C + SMF can request the PGW-U + SMF to distribute Tunnel information of the second Tunnel, including Tunnel Endpoint Identifiers (TEIDs) and IP addresses, and sends the Tunnel information to the UPF, if the UPF is managed by other SMFs, the PGW-C + SMF sends the information of the second Tunnel to the SMF and sends the SMF to the UPF. In this scenario, the UPF maps the service data to the multicast QoS stream and sends the multicast QoS stream to the PGW-U + UPF through the second tunnel. The SMF managing the UPF may determine, according to the first rule of the service, at least one multicast QoS flow corresponding to the service, including the QFI of the multicast QoS flow, the data flow of the service mapped to the multicast QoS flow, the 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 that the terminal equipment moves out of the MBMS area.

It is assumed that in step S301, 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. 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 switch occurs from the 4G network to the 5G network by configuring an appropriate signal predetermined value, e.g., when the terminal device detects that the signal quality of the MBMS is worse than the signal predetermined value, the terminal device sends the first report to the AS reporting to the AS the event that the MBMS channel quality of the terminal device is worse than 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 to indicate to send a data packet of a service to the terminal device located in the first network through unicast bearer, and optionally, the first indication information includes a multicast service identifier. Or, the second message includes the first indication information and the multicast service identifier.

When it is needed to be clear, the service includes multiple service data streams, in one case, all service data streams in the service are currently sent through an MBMS bearer, and in another case, a part of service data streams in the service are currently sent through an MBMS bearer, and another part of service data streams are currently sent through a unicast bearer. In the embodiment of the application, when the service of the terminal device is switched from the MBMS bearer to the unicast bearer, only the service data stream currently transmitted through the MBMS bearer is switched to the unicast bearer, and the service data stream currently transmitted through the unicast bearer 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 stream that needs 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 stream that needs to be switched to the unicast bearer. If the AS has sent the description information of the service data stream that needs to be switched to the unicast bearer to the PCF/NEF in step S301, the second message may include the description information of the service data stream that needs to be switched to the unicast bearer, or may not include the description information of the service data stream that needs to be switched to the unicast bearer.

The description information of the service data streams needing to be switched to the unicast bearer includes third indication information, and the third indication information indicates that the service data streams support being sent by a multicast mode (5G multicast or MBMS multicast). The third indication information may be indicated in a display manner or an implicit manner, refer to the related description of the first embodiment, and will not be described herein again.

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

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

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

Optionally, in other embodiments, the AS may send the second message directly to the PGW-C + SMF.

It should be noted that, 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 used to indicate a data packet for sending a service to the terminal device located in the first network through a unicast bearer, but names of the first message and the second message may be different.

S305, PGW-C + SMF establishes unicast load for the service which supports multicast mode transmission.

If the second tunnel is not established, the second tunnel is established in this step, which may specifically refer to the related description in step S301 and is not described herein again. The establishment of the unicast bearer for the service supporting multicast mode transmission comprises the following steps:

and 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 that a data packet is sent to the terminal equipment through the unicast bearer. And the PGW-U + UPF receives the second indication information, and if the transmission path between the PGW-U + UPF and the AS is not established yet for the first condition, establishes a second tunnel between the PGW-U + UPF and the AS according to the step in S301. The related information of the second indication information refers to the description of the first embodiment, and is not described herein again.

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, the second mapping relationship is a mapping relationship between the service identification information and the information of the first tunnel when the AS sends the data of the service in a case one manner, the PGW-U + UPF may match the data 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 data packet is sent through the matched first tunnel. The PGW-C + SMF may determine a bearer corresponding to each service data flow according to the PCC rule of the service, 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 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 service data packet. When mapping the data flow of the service to the unicast bearer, the PGW-C + SMF may map the data flow of the service to a new bearer, i.e., create a new bearer for the data flow of the service, or the PGW-C + SMF may also map the data flow of the service to an existing bearer, i.e., modify the existing bearer to add the data flow of the service.

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 stream 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 PGW-U + UPF according to the QFI of the packet received from the second tunnel, so as to send the packet using the first tunnel, that is, the second indication information includes the first mapping relationship.

Establishing the unicast bearer further includes notifying the SGW, a base station in the first network, and the like, to allocate tunnel information for the bearer and allocate corresponding resources. Reference may be made in particular to the prior art, which is not described in detail herein.

In addition, in order to switch the service from the unicast bearer transmission via the first network to the PDU session transmission via 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 via the PDU session of the second network, for example, the 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 the 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 use the unicast bearer to send the data of the service, 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 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, the AS sends a sixth notification message to the terminal equipment.

And responding to the fifth notification message, the AS sends a sixth notification message to the terminal equipment, wherein the sixth notification message is used for notifying the terminal equipment to use the unicast bearer to receive the data of the service, or notifying the terminal equipment 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, that is, 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 the fifth notification message to the AS, and the AS does not send the sixth notification message to the terminal device.

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

In this 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 data is carried in a unicast QoS stream in the PDU session.

It can be understood that data in the 5G network is transmitted by QoS flow, and the QoS flow in this embodiment includes two types: the service data stream transmitted on the MBMS bearer is mapped to the unicast QoS stream or the multicast QoS stream, wherein the unicast QoS stream is a data carrier in a 5G unicast path, and the multicast QoS stream is a data carrier in a 5G multicast path.

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

If the service is supported to be sent in a multicast mode, the terminal device can be added into the 5G multicast session corresponding to the service after the terminal device is successfully switched to the 5G network. It can be understood that, after the terminal device is switched to the 5G network, the 5G multicast session may be already established or may not be established, if the 5G multicast session is not established, the PGW-C + SMF triggers the establishment of the 5G multicast session, and the PGW-C + SMF triggers the establishment of the 5G multicast session may refer to the prior art and is not described again.

After the terminal device is successfully switched to the 5G network, the PGW-C + SMF judges whether the terminal device supports the 5G multicast service, and if the service supports the multicast mode transmission, the PGW-C + SMF determines to add the terminal device 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 add the terminal device to 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 accessed in a 5G network. For example, in the handover procedure, the PGW-C + SMF may obtain the 5G multicast capability of the target base station, e.g., the PGW-C + SMF obtains the capability of the target base station from the AMF (the capability may be sent to the AMF when the target base station supports the 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 successfully created, it indicates that the base station supports the 5G multicast capability).

Optionally, the PGW-C + SMF may also not obtain the 5G multicast capability of the target base station in the handover process, but requests the target base station to add the terminal device to the 5G multicast session when determining that the terminal device supports the 5G multicast service and the service supports the multicast mode transmission, and agrees to add if the target base station supports the 5G multicast service, and fails to add 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 the addition failure event.

It can be understood that joining the terminal device into the 5G multicast session needs to be completed jointly by a plurality of network elements, for example, a base station gNB (i.e., a target base station) and a PGW-C + SMF in the 5G network are needed. The PGW-C + SMF may notify the target base station to add the terminal device to the 5G multicast session after the 5G multicast session is established, or the PGW-C + SMF may also notify the target base station to add the terminal device to the 5G multicast session in the 5G multicast session establishment process, that is, notify the target base station to add the terminal device to the 5G multicast session when the parameter of the multicast QoS stream of the service is sent to the target base station. When receiving a request for joining the terminal device to the 5G multicast session, the target base station configures corresponding wireless resources for the terminal device, so as to receive service data corresponding to the 5G multicast session from the target base station.

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

In this embodiment, after the PGW-C + SMF adds the terminal device to 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 the terminal device to switch 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, the AS sends a fourth notification message to the terminal equipment.

And responding to the third notification message, the AS sends a fourth notification message to the terminal device, wherein the fourth notification message is used for notifying the terminal device to receive the data of the service by using the 5G multicast session.

S312, deleting the unicast QoS stream.

When the PGW-C + SMF switches the service data stream of the service to be sent via the 5G multicast session, the PGW-C + SMF may delete the radio resource of the unicast QoS stream previously allocated to the service data stream.

Optionally, the PGW-C + SMF may reserve the context of the unicast QoS flows, but the PGW-C + SMF requests the gNB to delete the radio resources of these unicast QoS flows, so as to save the resources of the gNB.

Optionally, the PGW-C + SMF further notifies the PGW-U + UPF to stop sending the service data stream, which has been migrated to be sent through the 5G multicast session, to the terminal device.

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

and S401, establishing PDN connection.

The specific implementation manner of this step refers to the description of step S301 in the third embodiment, and is not described herein again. The PDN connection is used to send signaling between the terminal device and the AS.

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

Different from 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 descriptions of steps S301 to S307 in the third embodiment, that is, when the terminal device moves out of the MBMS area, the data of the multicast service is migrated to be sent through the unicast bearer.

And 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 bearer.

When the terminal equipment moves into the MBMS area from the non-MBMS area, the terminal equipment detects the MBMS signal and detects that the data corresponding to the service is being sent through the MBMS bearer (the base station can send the TMGI corresponding to the service), the terminal equipment sends a second report to the AS, and the AS learns that the multicast service data stream of the service can be sent 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 to indicate to stop sending the data of the service through the unicast bearer, or to indicate the terminal device to receive the data of the service through the MBMS bearer, or to indicate the core network element to delete the unicast bearer resource corresponding to the multicast service.

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

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

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

Corresponding to the former implementation manner of S404, the PCF notifies 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, the PCF notifies the PGW-C + SMF to delete the unicast bearer resource of the service data stream supporting the multicast mode only through the fourth indication information, and the PCC rule is reserved.

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

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

The PGW-C + SMF deletes the unicast bearer resource created in the foregoing step, for example, the PGW-C + SMF notifies the SGW, MME, eNB to delete the resource corresponding to the unicast bearer, which may be referred to 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 former implementation in steps S404 and S405, PGW-C + SMF deletes the corresponding PCC rule. For the latter implementation in steps S404 and S405, the PGW-C + SMF still retains the corresponding PCC rule.

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

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

On the basis of the first embodiment and the second embodiment, fig. 10 is a signaling flow chart of a method for switching a multicast service provided in the fifth embodiment of the present application, which is different from the third embodiment in that: the present embodiment takes the 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, that is, the switching from the unicast bearer in the 4G network to the unicast bearer in the 5G network is not needed, so that the establishment of the unicast QoS stream in the 5G network is omitted. As shown in fig. 10, the method provided by this embodiment includes the following steps:

and S501, establishing PDN connection.

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

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

Optionally, the first indication information includes a multicast service identifier, or the second message includes the first indication information and the multicast service identifier.

S504, PCF sends the first message to PGW-C + SMF, the first message includes the first instruction information.

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

And S505, the PGW-C + SMF establishes a unicast bearer for the service which supports the multicast mode transmission.

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

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

The specific implementation of steps 501 and 507 refers to the description of steps S301 to S307 in the third embodiment, and is not described herein again. In addition to the descriptions of S301 to S307, the following is also included in this embodiment:

optionally, in step S501 or step S505, the PGW-C + SMF further obtains multicast QoS stream information of the service, and sends parameters of the multicast QoS stream to the terminal device, where the parameters of the multicast QoS stream include a QFI of each multicast QoS stream, an optional QoS parameter, and the like. And sending the parameters of the multicast QoS stream to the terminal equipment, wherein the parameters are used for receiving the service data according to the parameters of the multicast QoS stream after the terminal is added into 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 handover to a target base station, i.e., a gNB, in a 5G network.

S509, the MME sends the 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 (Create SM Context Request) to the PGW-C + SMF.

The specific implementation of S508-S510 refers to the prior art, and is not described herein.

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

If the multicast session corresponding to the service is not established, a session establishment request message is used for triggering the establishment of the 5G multicast session of the service, and after receiving the session establishment request message, the PGW-C + SMF determines that the PDN connection comprises the service which supports the transmission in the 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 the third indication information, the service supports a 5G multicast mode. It should be understood that the service data streams supported by the PDN connection and sent in a multicast manner may correspond to different 5G multicast sessions, and the PGW-C + SMF determines whether the service data streams belong to the same 5G multicast session according to the PCC rule corresponding to the service data streams.

The establishment of the 5G multicast session refers to the related description in the prior art, and is not described in detail here. The establishment of the 5G multicast session comprises the following steps: and sending the parameters of the multicast QoS flow to the target base station so that the target base station creates a corresponding context, and establishes a first tunnel from a UPF (the UPF can be PGW-U + UPF) to the target base station, wherein the first tunnel is used for the UPF to send data of the multicast service.

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

After the 5G multicast session is established, the PGW-C + SMF sends a session creation request response to the AMF, where the session creation request response includes a message sent to a target base station in the 5G network, and the message sent to the target base station includes seventh indication information, where the seventh indication information is used to indicate that the terminal device is to be added to the multicast session corresponding to the service, that is, the 5G multicast session.

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

Optionally, the parameter of the multicast QoS stream may also be sent in step S511, that is, in the process of establishing the 5G multicast session, the PGW-C + SMF sends the parameter of the multicast QoS stream to the target base station.

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

And the gNB is the target base station, the AMF carries seventh indication information received from the PGW-C + SMF in the second switching request and sends the second switching request to the gNB, and if the session creation request response comprises the parameters of the multicast QoS stream, the second switching request comprises the parameters of the multicast QoS stream. And the gNB allocates wireless resources for the multicast QoS flow according to the seventh indication information and the parameter 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) that includes configuration information of radio resources of the multicast QoS stream allocated by the gNB for the terminal device to join the 5G multicast session.

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

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

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

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

In S514 to S516, the target base station sends the configuration information of the radio resource of the multicast QoS stream to the terminal device through the source base station.

And S517, carrying out subsequent switching process.

The subsequent handover procedure includes that after the terminal device accesses the gbb, the gbb sends a notification to the AMF, and the AMF notifies the PGW-C + SMF to switch the path, and the like.

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

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

The specific implementation manner of S518 and S519 may refer to the description related to steps S310 and S311 in the third embodiment, and details are not described here again.

Compared with the third embodiment, in this embodiment, the data transmitted by the MBMS bearer is directly switched to the 5G multicast session from the unicast bearer in the 4G network, that is, it is not necessary to switch from the unicast bearer in the 4G network to the unicast bearer in the 5G network first, and then switch from the unicast bearer in the 5G network to the 5G multicast session, so that the establishment of the unicast QoS stream in the 5G network is omitted, and the time for switching the multicast service from the MBMS bearer to the 5G multicast session is shortened.

On the basis of the first embodiment and the second embodiment, fig. 11 is a signaling flow chart of a method for switching a multicast service according to a sixth embodiment of the present application, which is different from the third embodiment in that: the present embodiment takes the third multicast service switching method as an example. As shown in fig. 11, the method provided by this embodiment includes the following steps:

and S601, establishing PDN connection.

S602, the terminal equipment sends a first report to the AS, wherein the first report is used for indicating that the terminal equipment moves 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, PCF sends a first message to PGW-C + SMF, wherein the first message comprises first indication information and sixth indication information.

S605, PGW-C + SMF establishes unicast load for the service which supports multicast mode transmission.

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 in the third embodiment, except that: in this embodiment, the description information of the service sent by the AS is the second description information when sent in the manner of the above-mentioned case two, and accordingly, the first indication information includes the second rule, 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 above-mentioned case one, the first indication information includes the first rule, the first rule is determined by the PCF according to the first description information, and the first rule includes the third indication information. In addition, in this embodiment, the first message and the second message include the sixth indication information, and in the third embodiment, the first message and the second message sent by the AS do not include the sixth indication information.

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

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

In this embodiment, according to the sixth indication information, after the terminal device successfully switches from the 4G network to the 5G network (that is, when the PGW-C + SMF completes the first switching indication information), 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 it supports or is about to support using a multicast mode to send data of the service to the terminal device, or is used to notify that the terminal device switches to the 5G network, or is used to notify that the AS uses the mode to send 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 is ready to handover, that is, the PGW-C + SMF sends the first notification message when receiving the handover preparation indication information.

Of course, the PGW-C + SMF may also send the first notification message at other occasions after receiving the handover preparation, which is not limited.

S610, AS sends request message for adding terminal device into multicast session to PCF.

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

S611, PCF sends the 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 manner of step S612 may refer to the description of step S309 in the embodiment, and is not described herein again.

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

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

Steps S613 and S614 are optional steps.

S615, deleting the unicast QoS stream.

The specific implementation manner of steps S613-615 refers to the related description of steps S310-S312 in the third embodiment, and is not described herein again.

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, notify the terminal device to receive data using a 5G multicast session, and send the fifth indication information to the PGW-C + SMF by the terminal device according to the second notification message.

On the basis of the first embodiment and the second embodiment, fig. 12 is a signaling flow diagram of a method for switching a multicast service according to a seventh embodiment of the present application, where this embodiment takes the first multicast service switching manner as an example, that is, data transmitted by an MBMS bearer is first switched from the MBMS bearer to a unicast bearer in a 4G network, in a switching process of a terminal device from the 4G network to a 5G network, a PGW-C + SMF switches the data transmitted by the MBMS bearer from the unicast bearer in the 4G network to a PDU session (i.e., a unicast path in the 5G network), and after the terminal device is switched from the 4G network to the 5G network, the PGW-C + SMF adds the terminal device to the 5G multicast session, i.e., switches the unicast path in the 5G network to the 5G multicast path.

In this embodiment, the AS first 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 five-tuple information, when the service is sent in a multicast manner. Illustratively, the destination IP address in the service description information in the multicast service information of the service is 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, for example, 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 NEF, the NEF receives the multicast service information of the service, stores it in UDR, and sends the multicast service information of the service to PCF by UDR. The PCF determines the multicast PCC rule of the service according to the multicast service information of the service, and sends the multicast PCC rule to the second SMF, the second SMF may determine the multicast QoS stream information of the service according to the multicast service information of the service, the multicast service information includes a multicast service identifier, and the specific determination process may refer to the prior art and is not described again.

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 when performing cross-system handover. If the multicast service information includes the eighth indication information, the PCF sends the eighth indication information to the second SMF, to indicate that the service needs to support service continuity when the service is switched across systems. 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 practical applications, but the roles are both used to indicate that the service needs to support service continuity. Here, the service continuity refers to that when the terminal device moves, the data packets of the service are guaranteed as far as possible not to be lost, and/or sent in sequence, and the like.

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

and S701, establishing PDN connection.

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

The specific implementation of S701-S702 refers to the description of steps S301 and S302 in the third embodiment, and is not described herein again.

S703, AS sends the second message to PCF, the second message includes the first indication information and the multicast service mark.

The multicast service identifier may be a TMGI, or may be other identification information, which is not limited in this embodiment. The first indication information is used for indicating a data packet of service to be sent to the terminal equipment 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, PCF sends the first message to PGW-C + SMF, the first message includes the first instruction information and multicast service mark.

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

S705, the PGW-C + SMF acquires the multicast QoS stream 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 stream information of the service according to the multicast service identifier. The PGW-C + SMF may request the second SMF for the multicast QoS stream information of the service according to the multicast service identifier, the second SMF may acquire the multicast service information according to the multicast service identifier, and determine the multicast QoS stream information of the service according to the multicast service information, and the specific determination process may refer to the prior art and is not 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 a QFI of the QoS flow, service identification information (e.g., a five-tuple or a service identifier, where a destination address in the five-tuple information is a multicast IP address of the service) mapped to the QoS flow, and a QoS parameter of the QoS flow (e.g., a 5QI corresponding to the QoS flow, a maximum bandwidth requirement, etc.).

In an implementation manner, the PGW-C + SMF may obtain the multicast QoS stream 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 stream 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 that the second SMF is stored in the UDM/UDR, for example, the second SMF acquires the information of the service from the PCF, for example, a PCC rule of the service, and determines the multicast QoS flow information of the service according to the PCC rule of the service acquired 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 the multicast QoS flow information for the service from the second SMF. And after receiving the first message, the PGW-C + SMF sends the multicast service identifier to a second SMF, and the second SMF sends the multicast QoS stream information of the service to the PGW-C + SMF according to the multicast service identifier. The PGW-C + SMF can acquire the information of the second SMF corresponding to the service from the UDM/UDR according to the multicast service identifier so as to acquire the multicast QoS stream information of the service from the second SMF.

And if the service needs to support service continuity in the process of moving across the system, the second SMF or the UDM/UDR sends eighth indication information to the PGW-C + SMF to indicate that the service needs to support the service continuity.

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

And the PGW-C + SMF determines a unicast bearer for sending the data packet of the service according to the multicast QoS stream information of the service, wherein the unicast bearer can be an EPS bearer. For example, 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 to the existing EPS bearer, or may map the multicast QoS flow of the service to a new EPS bearer.

PGW-C + SMF can map some multicast QoS flow to existing bearing, some multicast QoS flow maps to the new bearing; or, the PGW-C + SMF maps all multicast QoS flows to the existing bearer; or the PGW-C + SMF maps all multicast QoS flows to the new bearer, which is not limited in this embodiment.

In addition, if the PGW-C + SMF receives the eighth indication information, that is, the service supports service continuity, in order to switch the service from unicast bearer transmission via the first network to PDU session transmission via 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 via 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 a service data flow mapped to the unicast QoS flow. If the unicast QoS stream information does not need to be transmitted to the terminal device, the process of determining the unicast QoS stream may be performed at the time of switching, that is, step S711, which is not limited.

In the embodiment of the present application, establishing a unicast bearer for the service includes modifying a bearer (if the multicast QoS stream of the service is mapped to an existing bearer) and/or creating a bearer (if the multicast QoS stream of the service is mapped to 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 stream of the service is mapped to the existing bearer) and/or to establish the bearer (if the multicast QoS stream of the service is mapped to the new bearer). In the process, the PGW-C + SMF obtains first tunnel information of one or more EPS bearers corresponding to the service.

Optionally, in the process of modifying a bearer and/or creating a bearer, the PGW-C + SMF sends information of the EPS bearer corresponding to the service, including a 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 that a data packet is sent to the terminal device through a unicast bearer, after the unicast bearer is established by the PGW-C + SMF, a first mapping relationship is determined, the first mapping relationship is a mapping relationship between the QFI of the multicast QoS stream of the 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 co-located 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 the PGW-U + UPF to determine, according to the first mapping relationship, first tunnel information corresponding to a unicast bearer corresponding to the QFI of the data received from the second tunnel (the second tunnel is a tunnel between the PGW-U + UPF and the UPF).

And 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.

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

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

And the UPF sends the data packet of the service to the GW-U + UPF by using the second tunnel information.

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

After the unicast bearer establishment is completed, the AS may transmit the traffic data through 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 the data of the service using the unicast bearer, or is used to notify the AS network that the service data stream 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 to receive the data of the service 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.

And S711, the terminal equipment is switched to the 5G network from the 4G 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 is not described herein again.

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, that is, steps S711 to S712 may be replaced with steps S508 to S517.

And S712, adding the terminal device 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 is not described herein again.

S713, deleting the unicast QoS stream.

The specific implementation of step S713 refers to the description of step S312 in the third embodiment, and is not described herein again.

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 to switch 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. And responding to the third notification message, the AS sends a fourth notification message to the terminal device, wherein the fourth notification message is used for notifying the terminal device to receive the data of the service by using the 5G multicast session.

On the basis of the first embodiment and the second embodiment, fig. 13 is a signaling flow chart of a method for switching a multicast service provided in an eighth embodiment of the present application, and the difference between the present embodiment and the seventh embodiment is that: in this embodiment, data transmitted by an MBMS bearer is not switched from the MBMS bearer to a unicast bearer of a 4G network, but directly in a switching process in which a terminal device switches from the 4G network to a 5G network, a PGW-C + SMF creates a corresponding unicast QoS stream for the service in the 5G network, so that the service can be transmitted through the unicast QoS stream after the terminal device switches to the 5G network, and after the terminal device switches from the 4G network to the 5G network, the PGW-C + SMF adds the terminal device to a 5G multicast session, that is, switches from a unicast path in the 5G network to a 5G multicast path. As shown in fig. 13, the method of the present embodiment may include the following steps:

and S801, establishing PDN connection.

The specific implementation manner of S801 refers to the description of step S301 in the third embodiment, and is not described herein again.

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

In one implementation, the terminal device sends a message to the PGW-C + SMF via the PDN connection, where the message includes an identifier of the multicast service, e.g., the terminal device sends an IGMP Join, and the PGW-C + SMF receives an IGMP Join message (the message is sent to the PGW-C + SMF via the PGW-U + UPF), where the IGMP Join includes multicast address information when the service is sent in a multicast manner, and the multicast address information can be used to identify the service (i.e., as an identifier of the multicast service). It should be noted that the multicast service identifier of the service may include a variety of different identifiers, such as multicast address information (e.g., for identifying the service in an IGMP message), TMGI (for identifying the service in 4G MBMS), or 5G multicast service identifier (for identifying the service in 5G network). In this implementation, the terminal device may send the multicast service identifier to the PGW-C + SMF when determining that the service needs to be received, and further, the terminal device may send the multicast service identifier to the PGW-C + SMF when determining that the service needs to support continuity.

The terminal equipment sends the identifier of the multicast service through PDN connection, so that the PGW-C + SMF associates the service with the PDN connection, when the terminal equipment is switched to a second network, the PGW-C + SMF can associate the service with the PDU session corresponding to the PDN connection, and the terminal equipment 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 the process of performing application layer signaling interaction between the terminal device and the AS through 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 signaling description information of an application to a core network device, the AS sends a multicast service identifier of the service to the core network device, and when sending a PCC rule corresponding to a signaling, a core network device (e.g., PCF) sends the multicast service identifier to the PGW-C + SMF. The AS may send the multicast service identifier to the core network device when the service needs to support continuity. The AS can send the multicast service identifier of the service to the PGW-C + SMF after receiving the message which is sent by the terminal equipment and requests to receive the service.

And S803, the PGW-C + SMF acquires the multicast QoS stream information of the service according to the multicast service identifier.

And when the PGW-C + SMF acquires the multicast service identifier, acquiring the multicast QoS stream information of the service according to the multicast service identifier, and storing the multicast QoS stream information. For a specific obtaining manner, refer to the description of step S705, which is not described herein again. Here, 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 (for example, the PGW-C + SMF may perceive that the interface type with the downlink node is an S5 interface or an S8 interface, so as to determine 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 device is switched to the 5G network from the 4G network, and a unicast QoS stream is created in the 5G network according to the multicast QoS stream 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 the seventh embodiment are not executed, in the handover process, the PGW-C + SMF determines, according to the multicast QoS stream information of the service, unicast QoS stream information corresponding to the PDU session transmission through the second network. And sending a request for creating the unicast QoS flow to the target base station (i.e., the gNB), so as to create the unicast QoS flow for the service in the second network during the handover process, so that the service can be sent through 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 the multicast QoS flow information may refer to step S706 in the seventh embodiment.

Optionally, in other embodiments of the present application, in a process that the terminal device is switched from the 4G network to the 5G network, the PGW-C + SMF may also directly join the terminal device into the 5G multicast session corresponding to the service without establishing a unicast QoS stream, that is, directly switch the service from MBMS bearer transmission to the 5G multicast session, without passing through a 4G unicast bearer and a 5G unicast QoS stream in the middle, and ensure that the multicast service of the terminal device maintains service continuity in a cell switching process.

And S805, adding 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, that is, steps S804 to S805 are replaced with steps S508 to S517.

S806, deleting the unicast QoS stream.

The specific implementation manner of step S806 refers to the description of step S312 in the third embodiment, and is not described herein again.

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 to switch 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. And responding to the third notification message, the AS sends a fourth notification message to the terminal device, wherein the fourth notification message is used for notifying the terminal device to receive the data of the service by using the 5G multicast session.

In the method, the PGW-C + SMF establishes unicast QoS stream information in a second network (e.g., a 5G network) according to multicast QoS stream information of a service during a process in which a terminal device switches from the first network to the second network (e.g., the 5G network), and after the unicast QoS stream is established, may send the service to the terminal device through the unicast QoS stream, and subsequently, after the terminal device switches to the second network, join the terminal device into a 5G multicast session corresponding to the service. The method switches the service from MBMS transmission to unicast QoS stream transmission of 5G, and switches the unicast QoS stream transmission of 5G to 5G multicast session transmission, thereby ensuring that the multicast service data received by the terminal equipment through a multicast path of a first network keeps 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 executed before step S508 in the fifth embodiment, or the method of the fourth embodiment may be executed before step S608 in the sixth embodiment, or the method of the fourth embodiment may be executed before step S711 in the seventh embodiment, or the method of the fourth embodiment may be executed before 804 in the eighth embodiment.

Fig. 14 is a schematic structural diagram of a first session managing network element according to a ninth embodiment of the present application, and as shown in fig. 14, the first session managing network element 100 includes:

a receiving module 11, configured to receive first indication information, where the first indication information is used to indicate that a data packet of a service 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 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 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 managing network element 100 further includes: the acquisition module is used for acquiring the multicast service quality QoS stream information of the service; and the first determining module is used for determining the unicast load of the data packet for sending the service according to the multicast QoS stream 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 stream 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 stream information of the service according to the multicast service identifier.

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

In an exemplary manner, the joining module 13 is specifically configured to: and in the process of switching the terminal equipment from the first network to the second network, switching the data packet of the service from the transmission to the terminal equipment through the unicast bearer to the transmission to the terminal equipment through a Protocol Data Unit (PDU) session, adding 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 the transmission to the terminal equipment through the PDU session to the transmission 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 informing the first user plane network element to stop sending the service data 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 the data packet sent to the terminal equipment through the unicast bearer to the data packet 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 Protocol Data Unit (PDU) session, the PDU session is associated with the service, the service sent by 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 add 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 service data is stopped being sent through the unicast bearer. The sending module 12 is further configured to notify the first user plane network element to stop sending the data of the service through a unicast bearer according to the fourth indication information.

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 the application server by the first user plane network element through the second tunnel. The sending 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 is handed over 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 the multicast mode to send the service data to the terminal equipment. Correspondingly, the adding module 13 is specifically configured to: and receiving fifth indication information, wherein the fifth indication information is used for indicating that the terminal equipment is added into the multicast session corresponding to the service, and adding the terminal into 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, where the sixth indication information is used to indicate that the first notification message is sent to the AS when data of a service is supported to be sent to the terminal device in a multicast mode.

The first session managing network element of this embodiment may be configured to execute the method performed by the first session managing network element in the first to sixth embodiments of the foregoing method, and specific implementation manners and technical effects are similar, and are not described herein again.

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

a receiving module 21, configured to receive a first report from a terminal device, where the first report is used to indicate that the terminal device moves 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 that a data packet of the service is sent 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 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 sending module 23 sends third indication information to the core network device, specifically: and sending a second message to the core network device, wherein the second message comprises the third indication information and a 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 device, where the sixth indication information is used to indicate that the first notification message is sent to the AS when supporting to send service data to the terminal device in a multicast manner.

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 a 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 that data of the service is supported to be sent to the terminal device in a multicast manner, and the sending module 23 is further configured to: and responding to the first notification message, and sending a second notification message to the terminal device, wherein the second notification message is used for notifying the terminal device 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 that data of the service is supported to be sent to the terminal device in a multicast manner, 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 device, where the fifth indication information is used to indicate that the terminal device is added to 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 from a non-MBMS area to an 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 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 service data through the unicast bearer is stopped.

The AS of this embodiment may be configured to execute the method executed by the AS in the first to sixth embodiments of the method, and the specific implementation manner and the technical effect are similar and will not be described again here.

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

a sending module 31, configured to send, to a first session management network element, multicast capability indication information 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 32, configured to receive, from a source access network device in a first network, configuration information of a radio resource allocated to the terminal device by a target access network device in a second network, where the configuration information of the radio resource is used for the terminal device to receive data of the service in the second network in a multicast mode; the receiving module is further configured to receive the 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 notification message from an Application Server (AS), wherein the fourth notification message is used for notifying the terminal equipment to use the multicast session in the second network to receive the data of the service.

The terminal device of this embodiment may be configured to execute the method executed by the terminal device in the first to sixth embodiments of the method, and specific implementation manners and technical effects are similar and will not be described herein again.

Fig. 17 is a schematic structural diagram of a target access network device according to a twelfth embodiment of the present application, and as shown in fig. 17, 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, configured to obtain parameters of a multicast QoS flow of the multicast session.

And a resource allocation module 43, configured to allocate radio resources to the multicast QoS stream according to the seventh indication information and the parameter of the multicast QoS stream.

A sending module 44, configured to send, by a source access network device, configuration information of a radio resource of the multicast QoS stream to the terminal 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 this embodiment may be configured to execute the method executed by the target access network device in the first to sixth embodiments of the foregoing method, and specific implementation manners and technical effects are similar, and are not described herein again.

Fig. 18 is a schematic structural diagram of a first session managing network element according to a thirteenth embodiment of the present application, and as shown in fig. 18, the first session managing network element 500 includes: a processor 51, a memory 52 and a transceiver 53, the memory 52 and the transceiver 53 being in communication with the processor 51 via a bus 54, the memory 52 being configured to store instructions, the transceiver 53 being configured to communicate with other devices, and the processor 51 being configured to execute the instructions stored in the memory 52, so as to enable the first session managing network element 500 to perform the method performed by the first session managing network element in the first to sixth embodiments.

It is to be understood that, in the embodiments of the present application, the processor used by the first session management network element 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 illustrative logical blocks, modules, and circuits described in connection with the disclosure. The processor may also be a combination of computing functions, e.g., comprising one or more microprocessors, DSPs, and microprocessors, among others.

The bus described in the embodiments of the present application may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an Extended ISA (enhanced industrial Standard Architecture) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, the buses in the figures of the present application are not limited to only one bus or one type of bus.

In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed 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 can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.

The integrated unit implemented in the form of a software functional unit may be stored in a computer readable storage medium. The software functional unit is stored in a storage medium and includes several instructions to enable a computer device (which may be a personal computer, a server, or a network device) or a processor (processor) to execute some steps of the methods according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

Claims

1. A method for multicast service handoff, comprising:

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

the first session management network element sends second indication information to a first user plane network element, wherein the second indication information is used for indicating that the data packet is sent to the terminal equipment through the unicast bearer;

2. The method of claim 1, further comprising:

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

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

3. The method of claim 2, wherein the receiving, by the first session management network element, the first indication information comprises:

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 acquiring, by the first session management network element, the multicast QoS stream information of the service includes:

and the first session management network element acquires the multicast QoS stream 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 identifier of the service, and wherein the obtaining, by the first session management network element, multicast QoS flow information of the service includes:

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

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

6. The method according to any one of claims 1 to 5, wherein the adding, by the first session management network element, the terminal device into the multicast session corresponding to the service includes:

in the process that the terminal device switches 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 device through the unicast bearer to being sent to the terminal device 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 device via the PDU session to being sent to the terminal device via the multicast session.

7. The method according to any one of claims 1 to 5, wherein the adding, by the first session management network element, the terminal device into the multicast session corresponding to the service includes:

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

8. The method of claim 1, wherein the adding, by the first session management network element, the terminal device into the multicast session corresponding to the service comprises:

9. The method of claim 1, wherein the adding, by the first session management network element, the terminal device into 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 managing network element joins the terminal device in the multicast session, further comprising:

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

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

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

12. The method according to any of claims 6-9, wherein before the first session managing network element joins the end device to the multicast session, further comprising:

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

13. The method of 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 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 determining, by the first session management network element, that the terminal device supports multicast in the second network includes:

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 according to claim 6 or 8, wherein after the end device joins the multicast session, the method further comprises:

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

15. The method according to any one of claims 1-14, further comprising:

when the terminal equipment moves into a Multimedia Broadcast Multicast Service (MBMS) area or moves into the MBMS area, the first session management network element receives fourth indication information, wherein the fourth indication information is used for indicating to stop sending the data of the service 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 unicast bearer according to the fourth indication information.

16. The method of 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 stream of the service, the first tunnel is a tunnel corresponding to the unicast bearer, the QFI is a QFI of a packet of the service received by the first user plane network element, and the first mapping relationship is used for the first user plane network element to determine a first tunnel through which the packet of the service is sent.

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 a 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 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 of the multicast address to the terminal device through the unicast bearer.

19. The method of claim 1, wherein after the terminal device is handed over to the second network, further comprising:

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 to support the multicast mode to send the service data to the terminal equipment;

the adding, by the first session management network element, the terminal device into the multicast session corresponding to the service includes:

the first session management network element receives fifth indication information, where the fifth indication information is used to indicate that the terminal device is added to a 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, the method further comprises:

and 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 to send service data to the terminal device in a multicast mode.

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

22. A first session management network element, comprising:

a receiving module, configured to receive first indication information, where the first indication information is used to indicate a data packet for sending a service to a terminal device in a 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 is sent to the terminal device through the unicast bearer;

and the adding module is used for adding the terminal equipment into the multicast session corresponding to the service when the terminal equipment is accessed through a second network.

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

the acquisition module is used for acquiring the multicast service quality QoS stream information of the service;

and the first determining module is used for determining the unicast load of the data packet for sending the service according to the multicast QoS stream 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 stream 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:

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

27. The network element according to any of claims 22-26, wherein the joining module is specifically configured to:

in the process that the terminal equipment is switched from the first network to the second network, switching the data packet of the service from the data packet sent to the terminal equipment through the unicast bearer to the data packet sent to the terminal equipment through a Protocol Data Unit (PDU) session;

and after the terminal equipment is switched from the first network to the second network, the terminal equipment 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 equipment through the multicast session.

28. The network element according to any of claims 22-26, 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 the data packet sent to the terminal equipment through the unicast bearer to the data packet sent to the terminal equipment through the multicast session.

29. The network element of claim 22, wherein the joining module is specifically configured to:

30. The network element of claim 22, wherein the joining module is specifically configured to:

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

a second determining module, configured to determine that the service supports multicast mode transmission through the second network before the joining module joins the terminal device in 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, policy or charging, the first rule comprises third indication information, and the third indication information is used for indicating that the service supports multicast mode transmission.

33. The network element of any one of claims 27-30, further comprising:

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 device, wherein the multicast capability indication information is used for indicating the multicast capability of the terminal device 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 or 29, wherein the sending module is further configured to:

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

36. The network element of any one of claims 22-35, 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 to stop sending the data of the service through the unicast bearer;

the sending module is further configured to: and informing the first user plane network element to stop sending the service data through unicast load 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 stream of the service, the first tunnel is a tunnel corresponding to the unicast bearer, the QFI is a QFI of a packet of the service received by the first user plane network element, and the first mapping relationship is used for the first user plane network element to determine the first tunnel through which the packet of the service is sent.

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, and receiving a data packet of the service from a 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.

39. The network element of claim 22, wherein 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 of the multicast address to the terminal device through the unicast bearer.

40. The network element of claim 22, wherein after the terminal device is handed over 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 to support the multicast mode to send the service data to the terminal equipment;

the adding module is specifically configured to:

receiving fifth indication information, where the fifth indication information is used to indicate that the terminal device is added to a multicast session corresponding to the service;

and adding the terminal into the multicast session corresponding to the service according to the fifth indication information.

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

and receiving sixth indication information, where the sixth indication information is used to indicate that the first notification message is sent to the AS when data of a service is supported to be sent to the terminal device in a multicast mode.

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

a 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.

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 that the terminal device moves out of a Multimedia Broadcast Multicast Service (MBMS) area; determining a data packet for sending service to the terminal equipment through unicast bearing according to the first report; sending first indication information to the first session management network element, where the first indication information is used to indicate that a data packet of the service is sent to the terminal device through unicast bearer;

the first session management network element is configured to receive the first indication information; sending 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 equipment accesses through a second network, the first session management network element adds the terminal equipment into the multicast session corresponding to the service.

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

45. The system according to claim 43, wherein after said terminal device switches to said second network, said first session managing network element is further configured to send a first notification message to an application server AS, said first notification message being used to notify said AS of supporting the multicast data transmission for said service to said terminal device; and specifically, the fifth indication information is used to indicate that the terminal device is added to the multicast session corresponding to the service, and the terminal is added to the multicast session corresponding to the service according to the fifth indication information.