Communication method, device and system

Abstract

The embodiment of the invention discloses a communication method, a communication device and a communication system, which are used for adding a terminal into a multicast group through an establishment process of a unicast PDU (Protocol Data Unit) session. The method may comprise: a terminal sending a PDU session establishment request message comprising identification information of a multicast group to a mobility management network element, the PDU session establishment request message being used for the terminal to join in the multicast group, the mobility management network element receiving the PDU session establishment request message, sending the identification information of the multicast group to a session management network element, and triggering the session management network element to establish the multicast PDU session, and feeding back the context information of the multicast PDU session to the terminal, so that the terminal is added into the multicast group, and the terminal can receive multicast data through the multicast PDU session.

Description

[0001] This application is a divisional application. The application number of the original application is 202010461724.1, and the original application date is May 27, 2020. The entire contents of the original application are incorporated into this application by reference. Technical Field

[0002] The embodiments of the present application relate to the field of communication technology, and in particular, to a communication method, device, and system. Background Art

[0003] In the 3rd Generation Partnership Project (3GPP) network, there is a multicast communication / groupcast communication demand, such as multiple terminals can join the same multicast group and request a network side device (such as an application server) to send multicast data to the multicast group.

[0004] At present, a terminal can join a multicast group through an Internet Group Management Protocol (IGMP) message. For example, the terminal sends a user plane message: IGMP message to the corresponding user plane function (UPF) of the unicast PDU session through the unicast packet data unit (PDU) session established by the network. After the UPF identifies the received user plane message as a multicast message: IGMP message, it forwards the IGMP message to the application server that provides multicast data. After receiving the IGMP message, the application server adds the terminal to the multicast group and triggers the UPF to send multicast data to the terminals in the multicast group.

[0005] As can be seen from the above, in the above-mentioned method where the terminal uses IGMP messages to join a multicast group, the UPF is required to have the ability to identify multicast messages such as IGMP messages. However, in the existing 3GPP network, not all UPFs may have the ability to identify message types. For UPFs that do not have the ability to identify message types, they will not be able to identify IGMP messages and will not be able to forward the IGMP messages sent by the terminal to the application server, resulting in the failure of the terminal to join the multicast group and the inability of the network side device to send multicast data to the terminal. Summary of the invention

[0006] The embodiments of the present application provide a communication method and apparatus to enable a terminal to join a multicast group through a unicast PDU session establishment process, thereby ensuring normal transmission of multicast data.

[0007] In order to achieve the above-mentioned purpose, the embodiment of the present application adopts the following technical solution.

[0008] According to a first aspect of an embodiment of the present application, a communication method is provided, the method comprising: a terminal sends a PDU session establishment request message including identification information of a multicast group to a mobility management network element, the PDU session establishment request message is used for the terminal to join the multicast group; the terminal receives a PDU session establishment acceptance message including context information of a multicast PDU session corresponding to the multicast group from the mobility management network element, the context information of the multicast PDU session is used for the terminal to receive multicast data through the multicast PDU session.

[0009] Based on the method described in the first aspect, the terminal sends a PDU session establishment request message including the identification information of the multicast group to the mobility management network element through the PDU session establishment process, requesting to join the multicast group, so that after the mobility management network element receives the PDU session establishment request message, it triggers the session management network element that manages the multicast PDU session to obtain the context information of the multicast PDU session when determining that the terminal has joined the multicast group, and triggers the mobility management network element to carry the context information of the multicast PDU session in the PDU session establishment acceptance message to the terminal, so that the terminal receives multicast data according to the context information of the multicast PDU session. In this way, the terminal can be added to the multicast group through the PDU session establishment process, so that the terminal can receive data through the multicast PDU session of the multicast group, and group communication can be realized. At the same time, the PDU session establishment process is the same as the process of establishing a unicast PDU session for the terminal, reducing the design complexity.

[0010] In a possible design, the method further includes: the terminal receives the multicast data through a multicast PDU session. Based on this possible design, the multicast data can be sent to the terminal through the multicast PDU session corresponding to the multicast group, so that the multicast data can be integrated and transmitted on a multicast PDU session, thereby improving resource utilization.

[0011] In one possible design, the PDU session establishment request message carries an N1 session management container, and the N1 session management container includes identification information of the multicast group. Based on this possible design, the terminal can carry the identification information of the multicast group in the N1 session management container and send it to the mobility management network element, so that the mobility management network element does not need to parse the identification information of the multicast group carried by the N1 session management container, and transparently transmits the identification information of the multicast group to the session management network element that manages the multicast PDU session, thereby reducing the design complexity of the mobility management network element.

[0012] In a possible design, the PDU session establishment request message also includes one or more information such as identification information of a data network used to transmit multicast data, identification information of a network slice used to transmit multicast data, identification information of a unicast PDU session of the terminal, and identification information of a multicast PDU session. Based on this possible design, the terminal can carry some other auxiliary information in the PDU session establishment request message and send it to the mobility management network element, so that the mobility management network element determines the session management network element that manages the multicast PDU session in combination with the identification information of the multicast group and the auxiliary information, thereby improving the accuracy of determining the session management network element that manages the multicast PDU session.

[0013] In one possible design, the context information of the multicast PDU session includes the start time of sending the multicast data, the end time of sending the multicast data, the receiving frequency of the multicast data, the quality of service (QoS) information of the multicast data, etc. Based on this possible design, the terminal can receive the multicast data according to various information of the multicast PDU session, thereby improving the reception accuracy of the multicast data.

[0014] In another possible design, the method further includes: the terminal receives context information of a unicast PDU session for the terminal to receive multicast data through a unicast PDU session from a mobility management network element. Based on this possible design, while the terminal joins the multicast group through the PDU session establishment process, transmission resources for the unicast PDU session can be established for the terminal at the same time, so that when the number of terminals joining the multicast group is too low, resulting in the release of the multicast PDU session corresponding to the multicast group, or when the terminal moves out of the multicast / broadcast area and does not support receiving multicast data through a unicast PDU session, the multicast data is sent to the terminal through the unicast PDU session to ensure that the continuity of the terminal receiving multicast data is not affected.

[0015] In another possible design, the method further includes: the terminal sends a first message including identification information of the terminal and identification information of the multicast group to the mobility management network element, the first message being used for the terminal to leave the multicast group; and the terminal receives a response to the first message returned by the mobility management network element. Based on this possible design, the terminal can notify the mobility management network element of the message for the terminal to leave the multicast group, so that the network side device learns that the terminal has left the multicast group and manages the terminals that have joined the multicast group.

[0016] In another possible design, the first message is a PDU session release request message or a PDU session modification request message. Based on this possible design, the terminal can inform the mobility management network element of the message of leaving the multicast group through the PDU session release process or the PDU session modification process, and use the existing signaling message to carry the first message to reduce signaling overhead.

[0017] In a second aspect, the present application provides a communication device, which may be a terminal on a terminal or a chip or system on chip in a terminal; it may also be a server that provides business services to the terminal or a chip or system on chip in the server. The communication device may implement the functions performed by the communication device in the above-mentioned first aspect or a possible design of the first aspect, and the functions may be implemented by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above-mentioned functions. For example: the communication device may include a sending unit and a receiving unit;

[0018] A sending unit, configured to send a PDU session establishment request message including identification information of a multicast group to a mobility management network element, wherein the PDU session establishment request message is used for a terminal to join the multicast group;

[0019] The receiving unit is used to receive a PDU session establishment acceptance message from a mobility management network element, wherein the PDU session establishment acceptance message includes context information of a multicast PDU session corresponding to the multicast group, and the context information of the multicast PDU session is used for the terminal to receive multicast data through the multicast PDU session.

[0020] Among them, the specific implementation method of the communication device can refer to the behavior function of the terminal in the communication method provided in the first aspect or any possible design of the first aspect, and will not be repeated here. Therefore, the provided communication device can achieve the same beneficial effects as the first aspect or any possible design of the first aspect.

[0021] In a third aspect, a communication device is provided, comprising: a processor and a memory; the memory is used to store computer execution instructions, and when the communication device is running, the processor executes the computer execution instructions stored in the memory to enable the communication device to perform the communication method described in the first aspect or any possible design of the first aspect.

[0022] In a fourth aspect, a computer-readable storage medium is provided, in which instructions are stored. When the computer-readable storage medium is run on a computer, the computer can execute the communication method described in the first aspect or any possible design of the above aspects.

[0023] In a fifth aspect, a computer program product comprising instructions is provided, which, when executed on a computer, enables the computer to execute the communication method described in the first aspect or any possible design of the above aspects.

[0024] In a sixth aspect, a chip system is provided, which includes a processor and a communication interface, and is used to support a communication device to implement the functions involved in the above-mentioned first aspect or any possible design of the first aspect, such as the processor sending a PDU session establishment request message including identification information of a multicast group to a mobility management network element through a communication interface, and the PDU session establishment request message is used for the terminal to join the multicast group; and receiving a PDU session establishment acceptance message from the mobility management network element through the communication interface, and the PDU session establishment acceptance message includes context information of a multicast PDU session corresponding to the multicast group, and the context information of the multicast PDU session is used for the terminal to receive multicast data through the multicast PDU session. In one possible design, the chip system also includes a memory, and the memory is used to store program instructions and data necessary for the communication device. The chip system can be composed of a chip, and can also include a chip and other discrete devices.

[0025] Among them, the technical effects brought about by any design method in the third to sixth aspects can refer to the technical effects brought about by the above-mentioned first aspect or any possible design of the first aspect, and will not be repeated here.

[0026] In the seventh aspect, an embodiment of the present application provides another communication method, which may include: a mobility management network element receives a PDU session establishment request message including identification information of a multicast group from a terminal, sends the identification information of the multicast group to a session management network element according to the PDU session establishment request message, receives context information of the multicast PDU session from the session management network element, and sends a PDU session establishment acceptance message including the context information of the multicast PDU session to the terminal.

[0027] Based on the method described in the seventh aspect, the mobility management network element can receive a PDU session establishment request message initiated by the terminal, and send the identification information of the multicast group in the PDU session establishment request message to the session management network element. After the session management network element determines to add the terminal to the multicast group, it sends the context information of the multicast PDU session to the mobility management network element. The mobility management network element receives and sends the context information of the multicast PDU session to the terminal, so that the terminal receives the context information of the multicast PDU session. In this way, the terminal can be added to the multicast group through the PDU session establishment process between the terminal and the core network device, and multicast data can be transmitted through the multicast PDU session to achieve group communication.

[0028] In a possible design, the PDU session establishment request message carries an N1 session management container, and the N1 session management container includes identification information of the multicast group. Based on this possible design, the mobility management network element can receive the N1 session management container carrying the identification information of the multicast group from the terminal, so that the mobility management network element does not need to parse the identification information of the multicast group carried by the N1 session management container, and transparently transmits the identification information of the multicast group to the session management network element that manages the multicast PDU session, thereby reducing the design complexity of the mobility management network element.

[0029] In one possible design, the PDU session establishment request message also includes one or more of the following information: identification information of a data network used to transmit multicast data, identification information of a network slice used to transmit multicast data, identification information of a unicast PDU session of a terminal, and identification information of a multicast PDU session. Based on this possible design, the mobility management network element may receive some other auxiliary information from the terminal, so that the mobility management network element determines the session management network element that manages the multicast PDU session in combination with the identification information of the multicast group and the auxiliary information, thereby improving the accuracy of determining the session management network element that manages the multicast PDU session.

[0030] In one possible design, the context information of the multicast PDU session includes one or more of the following: the start time of sending the multicast data, the end time of sending the multicast data, the receiving frequency of the multicast data, and the QoS information of the multicast data. Based on this possible design, the terminal can receive the multicast data according to the various information of the multicast PDU session, thereby improving the reception accuracy of the multicast data.

[0031] In one possible design, the method further includes: the mobility management network element receives a first message from the terminal for the terminal to leave the multicast group, the first message carries the identification information of the terminal and the identification information of the multicast group; the mobility management network element sends the first message to the session management network element, the mobility management network element receives a response to the first message, and sends a response to the first message to the terminal. Based on this possible design, the mobility management network element can report the event of the terminal leaving the multicast group to the session management network element, so that the session management network element can manage the terminals in the multicast group in real time, and release the multicast PDU session corresponding to the multicast group when the number of terminals joining the multicast group is too low or the terminal moves out of the multicast / broadcast area and does not support receiving multicast data through a unicast PDU session, thereby improving resource utilization.

[0032] In a possible design, the mobility management network element sends the identification information of the multicast group to the session management network element according to the PDU session establishment request message, including: the mobility management network element sends the identification information of the multicast group to the first network element; the mobility management network element receives the identification information of the session management network element from the first network element; wherein the first network element includes a unified data repository (UDR) or a policy control function (PCF) or a unified data management (UDM) or a network repository function (NRF). Based on this possible design, the mobility management network element can obtain the session management network element that manages the multicast PDU session from the UDR or PCF or UDM or NRF, thereby improving the design flexibility.

[0033] In an eighth aspect, a communication device is provided, which may be a mobility management network element or a chip or system on chip in a mobility management network element. The communication device may implement the functions performed by the mobility management network element in the seventh aspect or a possible design of the seventh aspect, and the functions may be implemented by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions. For example, the communication device may include: a receiving unit, a sending unit;

[0034] A receiving unit, configured to receive a packet data unit (PDU) session establishment request message from a terminal, wherein the PDU session establishment request message includes identification information of a multicast group, and the multicast PDU session establishment request message is used by the terminal to join the multicast group;

[0035] A sending unit, configured to send identification information of a multicast group to a session management network element according to a PDU session establishment request message, wherein the session management network element is configured to manage a multicast PDU session corresponding to the multicast group;

[0036] The receiving unit is further used to receive context information of a multicast PDU session from a session management network element, where the context information of the multicast PDU session is used for the terminal to receive multicast data through the multicast PDU session;

[0037] The sending unit is further used to send a PDU session establishment acceptance message to the terminal, where the PDU session establishment acceptance message includes context information of the multicast PDU session.

[0038] Among them, the specific implementation method of the communication device can refer to the behavior function of the mobility management network element in the communication method provided by the seventh aspect or any possible design of the seventh aspect, and the seventh aspect or any possible design method of the seventh aspect can be implemented accordingly by the receiving unit and the sending unit included in the communication device.

[0039] In the ninth aspect, a communication device is provided, comprising: a processor and a memory; the memory is used to store computer execution instructions, and when the communication device is running, the processor executes the computer execution instructions stored in the memory to enable the communication device to perform the communication method described in the seventh aspect or any possible design of the seventh aspect.

[0040] In the tenth aspect, a computer-readable storage medium is provided, which stores instructions, and when the computer-readable storage medium is run on a computer, the computer can execute the communication method described in the seventh aspect or any possible design of the above aspects.

[0041] In the eleventh aspect, a computer program product comprising instructions is provided, which, when executed on a computer, enables the computer to execute the communication method described in the seventh aspect or any possible design of the above aspects.

[0042] In the twelfth aspect, a chip system is provided, which includes a processor and a communication interface, and is used to support a communication device to implement the functions involved in the above aspects, such as the processor receiving a PDU session establishment request message including identification information of a multicast group from a terminal through the communication interface; sending identification information of the multicast group to a session management network element according to the PDU session establishment request message, receiving context information of the multicast PDU session, and sending a PDU session establishment acceptance message including context information of the multicast PDU session to the terminal. In one possible design, the chip system also includes a memory, and the memory is used to store program instructions and data necessary for the communication device. The chip system can be composed of a chip, or include a chip and other discrete devices.

[0043] Among them, the technical effects brought about by any design method in the ninth to twelfth aspects can refer to the technical effects brought about by the above-mentioned seventh aspect or any possible design of the seventh aspect, and will not be repeated here.

[0044] In the thirteenth aspect, a communication method is also provided, the method comprising: a session management network element receives identification information of a multicast group, and sends context information of a multicast PDU session corresponding to the multicast group to the mobility management network element according to the identification information of the multicast group. Based on this possible design, the session management network element can add the terminal to the multicast PDU session according to the received identification information, and return the context information of the multicast PDU session. In this way, the terminal can be added to the multicast group through the PDU session establishment process initiated by the control plane, and multicast data can be sent to the terminal through the multicast PDU session. There is no need to join the multicast group through the multicast message of the user plane, and the existing PDU session establishment process is used to reduce the design complexity and signaling overhead.

[0045] In one possible design, the method further includes: the session management network element sends identification information of the multicast group to the first network element, and the session management network element receives context information of the multicast PDU session from the first network element; wherein the first network element includes a UDR or a PCF or a UDM or an NRF. Based on this possible design, the mobility management network element can obtain the context information of the multicast PDU session from the UDR or the PCF or the UDM or the NRF, thereby improving design flexibility.

[0046] In a possible design, the method further includes: when the number of terminals joining the multicast group is greater than a first threshold, the session management network element obtains context information of the multicast PDU session. Based on this possible design, when the number of terminals joining the multicast group is large, the context information of the multicast PDU session can be obtained again, and multicast data can be transmitted through the multicast PDU session, so that multicast data can be sent to more terminals through one PDU session, thereby improving resource utilization.

[0047] In one possible design, the method further includes: the session management network element receives one or more of the following information from the mobility management network element: identification information of the data network used to transmit multicast data, identification information of the network slice used to transmit multicast data, identification information of the unicast PDU session of the terminal, and identification information of the multicast PDU session. Based on this possible design, the session management network element can obtain some other auxiliary information in addition to the identification information of the multicast group from the mobility management network element, so that the session management network element obtains the context information of the multicast PDU session based on this information, and ensures that the context information of the multicast PDU session is accurately obtained.

[0048] In one possible design, the context information of the multicast PDU session includes one or more of the following: the start time of sending the multicast data, the end time of sending the multicast data, the receiving frequency of the multicast data, and the QoS information of the multicast data. Based on this possible design, the session management network element can send various information of the multicast PDU session to the terminal, so that the terminal receives the multicast data according to the context information of the multicast PDU session, thereby improving the reception accuracy of the multicast data.

[0049] In one possible design, the method further includes: the session management network element sends context information of a unicast PDU session used for the terminal to receive multicast data through a unicast PDU session, and context information of the unicast PDU session. Based on this possible design, the session management network element can establish transmission resources for a unicast PDU session for the terminal while the terminal joins the multicast group through the PDU session establishment process, so that when the number of terminals joining the multicast group is too low, resulting in the release of the multicast PDU session corresponding to the multicast group, or when the terminal moves out of the multicast / broadcast area and does not support receiving multicast data through a unicast PDU session, the multicast data is sent to the terminal through the unicast PDU session to ensure that the continuity of the terminal receiving multicast data is not affected.

[0050] In one possible design, the method further includes: a session management network element receives a first message for a terminal to leave a multicast group, the first message includes identification information of the multicast group, the session management network element updates the context of the multicast group according to the first message, and the session management network element sends a response to the first message. Based on this possible design, the session management network element can update the context of the multicast group in real time when the terminal leaves the multicast group and manage the multicast group.

[0051] In a possible design, the method further includes: if the number of terminals joining the multicast group is less than a second threshold after the terminal leaves the multicast group, the session management network element sends a release notification message to the user plane network element corresponding to the multicast PDU session to notify the user plane network element to release the multicast PDU session. Based on this possible design, when there is no multicast group or the number of terminals in the multicast group is small, the multicast PDU session used to transmit multicast data can be released to improve resource utilization.

[0052] In one possible design, the method further includes: the session management network element sends indication information to the user plane network element corresponding to the unicast PDU session to instruct the user plane network element corresponding to the unicast PDU session to send multicast data through the unicast PDU session. Based on this possible design, the session management network element can notify the user plane network element to switch the PDU session transmitting multicast data to the unicast PDU session, and notify the UPF to transmit the multicast data through the unicast PDU session to ensure the continuity of multicast data transmission.

[0053] In a fourteenth aspect, the present application provides a communication device, which may be a session management network element or a chip or system on chip in a session management network element. The communication device may implement the functions performed by the session management network element in the above-mentioned thirteenth aspect or a possible design of the thirteenth aspect, and the functions may be implemented by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above-mentioned functions. For example, the communication device may include: a receiving unit, a sending unit;

[0054] A receiving unit, configured to receive identification information of a multicast group;

[0055] The sending unit is used to send the context information of the multicast PDU session corresponding to the multicast group to the mobility management network element according to the identification information of the multicast group.

[0056] Among them, the specific implementation method of the communication device can refer to the behavior function of the session management network element in the communication method provided by the thirteenth aspect or any possible design method of the thirteenth aspect, and the thirteenth aspect or any possible design method of the thirteenth aspect can be implemented accordingly by the communication device including an acquisition unit and a sending unit.

[0057] In the fifteenth aspect, a communication device is provided, comprising: a processor and a memory; the memory is used to store computer execution instructions, and when the communication device is running, the processor executes the computer execution instructions stored in the memory, so that the communication device executes the communication method described in the above-mentioned thirteenth aspect or any possible design of the thirteenth aspect.

[0058] In the sixteenth aspect, a computer-readable storage medium is provided, in which instructions are stored, and when the computer-readable storage medium is executed on a computer, the computer can execute the communication method described in the thirteenth aspect or any possible design of the above aspects.

[0059] In the seventeenth aspect, a computer program product comprising instructions is provided, which, when executed on a computer, enables the computer to execute the communication method described in the thirteenth aspect or any possible design of the above aspects.

[0060] In the eighteenth aspect, a chip system is provided, which includes a processor and a communication interface, and is used to support a communication device to implement the functions involved in the above aspects, such as the processor receiving identification information of a multicast group through the communication interface, and sending context information of a multicast PDU session corresponding to the multicast group to a mobility management network element based on the identification information of the multicast group. In one possible design, the chip system also includes a memory, and the memory is used to store program instructions and data necessary for the communication device. The chip system can be composed of a chip, or it can include a chip and other discrete devices.

[0061] Among them, the technical effects brought about by any design method from the fifteenth to the eighteenth aspects can refer to the technical effects brought about by the above-mentioned thirteenth aspect or any possible design of the thirteenth aspect, and will not be repeated here.

[0062] In the nineteenth aspect, a communication system is provided, which may include a terminal as described in any one of the second to sixth aspects, a mobility management network element as described in any one of the eighth to twelfth aspects, and a session management network element as described in any one of the fourteenth to eighteenth aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 A schematic diagram of the architecture of a communication system;

[0064] Figure 2a is a schematic diagram of the architecture of a 5G communication system;

[0065] Figure 2b It is a schematic diagram of the architecture of a 4G communication system;

[0066] Figure 3 A schematic diagram of the composition of a communication device 300 provided in an embodiment of the present application;

[0067] Figure 4 A flow chart of a communication method provided in an embodiment of the present application;

[0068] Figure 5 A flowchart of another communication method provided in an embodiment of the present application;

[0069] Figure 6 A flowchart of another communication method provided in an embodiment of the present application;

[0070] Figure 7 A flowchart of another communication method provided in an embodiment of the present application;

[0071] Figure 8 A schematic diagram of the composition of a communication device 80 provided in an embodiment of the present application;

[0072] Fig. 9 A schematic diagram of the composition of a communication device 90 provided in an embodiment of the present application;

[0073] Fig.10 A schematic diagram of the composition of a communication device 100 provided in an embodiment of the present application;

[0074] Fig.11 A schematic diagram of the composition of a communication system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0075] In a communication system, when a network side device sends the same multicast data to multiple terminals, in order to improve resource utilization, the data is sent to the multiple terminals through the same PDU session, such as a multicast PDU session. In order to receive the multicast data through the multicast PDU session, the multiple terminals receiving the same multicast data need to join the same multicast group in advance.

[0076] Exemplarily, the terminal joins the multicast group through an IGMP message, such as: the terminal sends an IGMP message to the UPF corresponding to the unicast PDU session of the terminal, and the UPF identifies the received message as a multicast message: after the IGMP message, the IGMP message is forwarded to the application server. After receiving the IGMP message, the application server sends the relevant configuration information for the terminal to receive multicast data through the multicast PDU session to the terminal through the application layer, and joins the terminal to the multicast group.

[0077] However, not all UPFs in the communication system have the ability to identify message types. For UPFs that do not have the ability to identify message types, they will not be able to recognize IGMP messages and will not be able to forward the IGMP messages sent by the terminal to the application server, resulting in the terminal failing to join the multicast group and the network side equipment being unable to send multicast data to the terminal.

[0078] To solve this technical problem, an embodiment of the present application provides a communication method, which includes: a terminal sends a PDU session establishment request message for the terminal to join a multicast group to a mobility management network element, and the PDU session establishment request message includes identification information of the multicast group. The mobility management network element receives the PDU session establishment request message from the terminal, and according to the PDU session establishment request message, sends the identification information of the multicast group to the session management network element that manages the multicast PDU session corresponding to the multicast group. The session management network element receives the identification information of the multicast group, sends the context information of the PDU session to the mobility management network element, and the mobility management network element receives the context information of the multicast PDU session, and sends a PDU session establishment acceptance message including the context information of the multicast PDU session to the terminal. The terminal receives the PDU session establishment acceptance message, and receives multicast data according to the context information of the multicast P DU session. That is, the terminal joins the multicast group with the help of the existing PDU session establishment process, receives multicast data according to the context information of the multicast PDU session corresponding to the multicast group, and realizes group communication. At the same time, the PDU session establishment process is the same as the process of establishing a unicast PDU session for the terminal, reducing the design complexity.

[0079] The communication method provided in the embodiment of the present application is described below in conjunction with the drawings in the embodiment of the present application.

[0080] The communication method provided in the embodiment of the present application can be applied to Figure 1 The communication system shown in Figure 1 As shown, the communication system may include a terminal, a mobility management network element, and a session management network element; it may also include an access network device, a user plane network element, a network slice selection network element, a network storage network element, a policy control network element, a network open function network element, and a data network (data network, DN). The DN may include an application server, and the application server may be an application function (application function, AF). The session management network element may include a unicast session management network element and a multicast session management network element; the user plane network element may include a multicast user plane network element and a unicast user plane network element. Figure 1In the system shown, there may be two types of PDU sessions: unicast packet data unit (PDU) sessions and multicast PDU sessions. A unicast PDU session is a PDU session for a specific terminal, and is used to send data to the specific terminal. The transmission path of the unicast PDU session may be: application server <-> unicast user plane network element <-> access network device <-> terminal. A multicast PDU session may be a PDU session for a specific communication group, and is used to send multicast data to all terminals in the communication group. The transmission path of the multicast PDU session may be: application server <-> multicast user plane network element <-> access network device <-> all terminals in a communication group. Among them, the unicast user plane network element and the multicast user plane network element may be the same or different, without limitation. Figure 1 In the system shown, the session management network element that manages the multicast PDU session can be called a multicast session management network element, and the session management network element that manages the unicast PDU session can be called a unicast session management network element. The multicast session management network element and the unicast session management network element can be the same network element or different network elements.

[0081] Below Figure 1 Introduce the network elements or devices involved in the shown architecture.

[0082] A terminal may be a device for realizing wireless communication functions, such as a terminal or a chip that can be used in a terminal, etc. The terminal may be a user equipment (UE), an access terminal, a terminal unit, a terminal station, a mobile station, a mobile station, a remote station, a remote terminal, a mobile device, a wireless communication device, a terminal agent or a terminal device, etc. in a 5G network or a future evolved communication system. The access terminal 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 with wireless communication function, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device or a wearable device, a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless terminal in industrial control, a wireless terminal in self driving, a wireless terminal in remote medical, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in smart city, a wireless terminal in smart home, etc. The terminal may be mobile or fixed.

[0083] Access network equipment is mainly used to implement physical layer functions, resource scheduling and management, terminal access control, mobility management and other functions. The access network equipment can be a device that supports wired access or a device that supports wireless access. Exemplarily, the access network equipment can be an access network (AN) / radio access network (RAN), which is composed of multiple 5G-AN / 5G-RAN nodes. 5G-AN / 5G-RAN nodes can be: access point (AP), base station (nodeB, NB), enhanced base station (enhance nodeB, eNB), next generation base station (NR nodeB, gNB), transmission reception point (TRP), transmission point (TP) or some other access node.

[0084] The mobility management network element is mainly responsible for terminal access authentication, mobility management, signaling interaction between various functional network elements, such as: management of user registration status, user connection status, user registration and network access, tracking area update, cell switching user authentication and key security.

[0085] The session management network element is mainly used to implement user plane transmission logical channels, such as the establishment, release and modification of PDU sessions and other session management functions.

[0086] The user plane network element can be used as an anchor point on the user plane transmission logical channel to complete functions such as routing and forwarding of user plane data, such as: establishing a channel with the terminal (i.e., the user plane transmission logical channel), forwarding data packets between the terminal and DN on the channel, and being responsible for filtering terminal data packets, data forwarding, rate control, and generating billing information.

[0087] The network open function network element can be used to open core network events and capabilities, translate core network external parameters and internal parameters, receive and store identification information provided by core network external network elements, select core network network elements, etc. Among them, core network external network elements may include application servers, etc.

[0088] The policy control network element can be used to provide policies to the mobility management network element and the session management network element, such as quality of service policy, slice selection policy, etc.

[0089] The network storage element can be used to store user data, such as user contract information, authentication or authorization data, etc. Specifically, the network storage element can be a unified data management (UDM) or a network repository function (NRF) or a unified data repository (UDR), etc.

[0090] The network slice selection network element can be used to select a network slice (NS), select a set of mobility management network elements, select a set of (network repository function, NRF), and so on.

[0091] DN can be an operator network that provides data transmission services to users, such as an operator network that provides Internet protocol (IP) multimedia services (IMS) to users. An application server (AS) can be deployed in the DN, and the application server can provide data transmission services to users.

[0092] It should be noted that Figure 1 This is only an exemplary architecture diagram. Figure 1 In addition to the functional units shown in , the system may also include other functional network elements, such as: operation and management (O&M) network elements, etc., which are not limited in the embodiments of the present application. Figure 1 The names of the devices in the Figure 1 In addition to the names shown, each device can also be named with other names, such as replaced with network element names with the same or similar functions, without limitation.

[0093] in, Figure 1 The system shown can be a third generation partnership project (3GPP) communication system, such as a fourth generation (4G) communication system, a long term evolution (LTE) system, or a fifth generation (5G) communication system or a new radio (NR) system, a next generation communication system, etc. It can also be a non-3GPP communication system without restriction.

[0094] by Figure 1 The communication system shown is Figure 2a As an example, the 5G communication system shown in FIG. Figure 2aAs shown, the network element or entity corresponding to the multicast session management network element may be a session management function (SMF) in a 5G communication system, the multicast session management network element may be a multicast session management function (M-SMF) in a 5G communication system, the network element or entity corresponding to the user plane network element may be a user plane function (UPF) in a 5G communication system, and the multicast user plane network element may be a multicast user plane function (M-UPF) in a 5G communication system. The network element or entity corresponding to the access network device may be the radio access network (RAN) in the 5G communication system, the network element or entity corresponding to the mobility management network element may be the access and mobility management function (AMF) in the 5G communication system, the policy control network element may be the policy control function (PCF) in the 5G communication system, the network element or entity corresponding to the network exposure function network element may be the network exposure function (NEF) in the 5G communication system, the network element or entity corresponding to the network slice selection network element may be the network slice selection function (network slice selection function) in the 5G communication system, and the network element or entity corresponding to the network storage network element may be the NRF or UDR or UDM in the 5G communication system.

[0095] by Figure 1 The communication system shown is Figure 2b Take the 4G communication system shown in the figure as an example. Figure 2bAs shown, the network element or entity corresponding to the multicast session management network element may be a multicast / broadcast service controller (MBSC) in a 4G communication system, the session management network element may be a packet data network (PDN) gateway control plane function (PGW-C) in a 4G communication system, and the network element or entity corresponding to the user plane network element may be a PDN gateway user plane function (PGW-U) in a 4G communication system. The network element or entity corresponding to the access network device may be a universal mobile telecommunications system terrestrial access network (UMTS terrestrialradio access network, UTRAN) in a 4G communication system, and the network element or entity corresponding to the mobility management network element may be a mobility management entity (MME) in a 4G communication system. In addition, Figure 2b The 4G communication system shown also includes a multicast / broadcast service-gate way (MBSC-GW) and a service gateway (SGW).

[0096] Optionally, the session management network element and the mobility management network element in the embodiment of the present application may also be referred to as a communication device, which may be a general device or a dedicated device, and the embodiment of the present application does not specifically limit this.

[0097] Optionally, the relevant functions of the session management network element or the mobility management network element in the embodiment of the present application can be implemented by one device, or by multiple devices together, or by one or more functional modules in one device, and the embodiment of the present application does not specifically limit this. It can be understood that the above functions can be network elements in hardware devices, or software functions running on dedicated hardware, or a combination of hardware and software, or virtualized functions instantiated on a platform (e.g., a cloud platform).

[0098] In the specific implementation, Figure 1 Each device shown (such as mobility management network element, session management network element, etc.) can use Figure 3 The structure shown, or including Figure 3 Parts shown. Figure 3A schematic diagram of the composition of a communication device 300 provided in an embodiment of the present application, the communication device 300 may include a processor 301 and a memory 304. Further, the communication device 300 may also include a communication line 302 and a communication interface 303. The processor 301, the memory 304 and the communication interface 303 may be connected through the communication line 302.

[0099] The processor 301 may be a central processing unit (CPU), a general processor, a network processor (NP), a digital signal processor (DSP), a microprocessor, a microcontroller, a programmable logic device (PLD), or any combination thereof. The processor 301 may also be other devices with processing functions, such as circuits, devices, or software modules, without limitation.

[0100] The communication line 302 is used to transmit information between the components included in the communication device 300 .

[0101] The communication interface 303 is used to communicate with other devices or other communication networks. The other communication networks may be Ethernet, radio access network (RAN), wireless local area network (WLAN), etc. The communication interface 303 may be a module, a circuit, a transceiver or any device capable of achieving communication.

[0102] The memory 304 is used to store instructions, where the instructions may be computer programs.

[0103] Among them, the memory 304 can be a read-only memory (ROM) or other types of static storage devices that can store static information and / or instructions, or a random access memory (RAM) or other types of dynamic storage devices that can store information and / or instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical disc, laser disc, optical disc, digital versatile disc, Blu-ray disc), magnetic disk storage medium, other magnetic storage devices, without limitation.

[0104] It should be noted that the memory 304 may exist independently of the processor 301 or may be integrated with the processor 301. The memory 304 may be used to store instructions or program codes or some data, etc. The memory 304 may be located inside the communication device 300 or outside the communication device 300, without limitation.

[0105] The processor 301 is configured to execute the instructions stored in the memory 304 to implement the service switching method provided in the following embodiments of the present application. For example, when the communication device 300 is a session management network element or a chip or system on chip in the session management network element, the processor 301 executes the instructions stored in the memory 304 to implement the steps performed by the session management network element in the following embodiments of the present application. For another example, when the communication device 300 is a mobility management network element or a chip or system on chip in the mobility management network element, the processor 301 may execute the instructions stored in the memory 304 to implement the steps performed by the mobility management network element in the following embodiments of the present application.

[0106] In one example, the processor 301 may include one or more CPUs, such as Figure 3 CPU0 and CPU1 in.

[0107] As an optional implementation, the communication device 300 includes multiple processors, for example, Figure 3 In addition to the processor 301, a processor 307 may also be included.

[0108] As an optional implementation, the communication device 300 further includes an output device 305 and an input device 306. Exemplarily, the input device 306 is a device such as a keyboard, a mouse, a microphone or a joystick, and the output device 305 is a device such as a display screen and a speaker.

[0109] It should be noted that the communication device 300 can be a desktop computer, a portable computer, a network server, a mobile phone, a tablet computer, a wireless terminal, an embedded device, a chip system or a Figure 3 In addition, Figure 3 The structure shown in the figure does not constitute a limitation on the communication device, except Figure 3 In addition to the components shown, the communication device may include more or fewer components than shown, or combine certain components, or arrange the components differently.

[0110] In the embodiment of the present application, the chip system may be composed of a chip, or may include a chip and other discrete devices.

[0111] In addition, the actions, terms, etc. involved in the various embodiments of the present application can refer to each other without limitation. The message name or parameter name in the message exchanged between the various devices in the embodiments of the present application is only an example, and other names can also be used in the specific implementation without limitation.

[0112] Below Figure 1 Taking the architecture shown in the figure as an example, the communication method provided by the embodiment of the present application is described. Each network element in the following embodiment may have Figure 3 The components shown are not described in detail. It should be noted that the message names or parameter names in the messages exchanged between the various devices in the embodiments of the present application are only examples, and other names may also be used in the specific implementation. For example, the multicast described in the embodiments of the present application can be replaced by terms such as broadcast, groupcast, multicast communication, and multicast / broadcast. The determination in the embodiments of the present application can also be understood as creation (create) or generation (generate), and the "include" in the embodiments of the present application can also be understood as "carry", which is uniformly explained here, and the embodiments of the present application do not specifically limit this.

[0113] Figure 4 A communication method provided in an embodiment of the present application, such as Figure 4 As shown, the method may include:

[0114] Step 401: The terminal sends a PDU session establishment request message to a mobility management network element.

[0115] The terminal can be Figure 1 Any terminal that supports multicast data transmission, such as Figure 1 The terminal 1 or the terminal 2 or the terminal 3 in the example. The mobility management network element may be a mobility management network element for managing the terminal.

[0116] Among them, a PDU session establishment request message can be used for a terminal to join a multicast group. In the present application, the terminal joining a multicast group can also be replaced by the description of the terminal joining a multicast PDU session corresponding to the multicast group. The PDU session establishment request message may include identification information of the multicast group, and may also include other information. Among them, the other information may include: identification information of a data network used to transmit multicast data, identification information of a network slice used to transmit multicast data, identification information of a unicast PDU session of the terminal, and identification information of a multicast PDU session, one or more of these. Furthermore, the other information may also include identification information of the terminal, etc., that is, the terminal may send a variety of information including identification information of the multicast group to the mobility management network element, so that the mobility management network element can accurately determine the session management network element that manages the multicast PDU session corresponding to the multicast group based on the various information.

[0117] The multicast group may be a combination of multiple terminals that receive the same data, such as a fleet that receives commands from the same command center or a user group that receives the same TV program. Data directed to a multicast group may be called multicast data, and the recipients of the multicast data may be two or more terminals. When multicast data is directed to multiple terminals in a multicast group, all terminals in the multicast group may be authorized or may not need authorization to receive the multicast data.

[0118] Among them, the identification information of the multicast group can be used to identify the multicast group. The identification information of the multicast group can be a temporary mobile group identifier (TMGI) of the multicast group, or an Internet protocol (IP) address of an application server (such as an AF providing multicast data), or a service identifier (service ID) of the multicast data, or identification information of a multicast PDU session corresponding to the multicast group, or packet filter information of the multicast data, or service data flow (SDF) identification rules of the multicast data, etc. In addition, the identification information of the multicast group can be pre-configured in a multicast group list, and the relevant description of the multicast group list is as follows.

[0119] The identification information of the data network may be a data network name (DNN), and the identification information of the data network may be used to identify / indicate a DN that provides multicast data.

[0120] Among them, the identification information of the network slice can be used to identify / indicate the network slice that transmits multicast data, and the identification information of the network slice can be single network slice selection assistance information (single network slice selection assistance information, S-NSSAI).

[0121] In addition, there may be a correspondence between the identification information of the data network, the identification information of the network slice and the multicast data, and the correspondence may be included in the terminal route selection policy (URSP), and the URSP may be pre-configured for the terminal. When the terminal determines to join the multicast group, the terminal may obtain the URSP locally, obtain the identification information of the data network and / or the identification information of the network slice from the URSP, and carry the identification information of the data network and / or the identification information of the network slice in the PDU session establishment request message.

[0122] The identification information of the unicast PDU session of the terminal can be used to identify the PDU session established for the terminal, and the identification information of the unicast PDU session of the terminal can be configured by the terminal itself. The identification information of the unicast PDU session can be an identifier (ID) of the unicast PDU session.

[0123] Among them, the identification information of the multicast PDU session can be used to indicate the multicast PDU session corresponding to the multicast group. The identification information of the multicast PDU session can be the ID of the multicast PDU session. The ID of the multicast PDU session can be configured by the terminal itself; the identification information of the multicast PDU session can also be the IP address of the application server providing multicast data or the TMGI of the multicast group, etc. At this time, the terminal can obtain the identification information of the multicast PDU session from the application server, or obtain the identification information of the multicast PDU session from the broadcast message of the access network device (such as the system information block (SIB)), or obtain the identification information of the multicast PDU session from the non-access stratum (NAS) message sent by the network side device.

[0124] The multicast PDU session may be established or not established before executing step 401. The multicast PDU session is a logical channel for transmitting multicast data, and the multicast PDU session may be established and maintained by a multicast session management network element.

[0125] The terminal identification information may be used to identify the terminal. The terminal identification information may be an Internet protocol (IP) address of the terminal, a media access control (MAC) address of the terminal, or an international mobile subscriber identity (IMSI) of the terminal. The terminal identification information may be pre-configured to the terminal, such as being configured to the terminal when the terminal is factory set.

[0126] Exemplarily, when a user using a terminal has a need to receive multicast data / join a multicast group, the terminal is triggered to send a PDU session establishment request message to the mobility management network element. For example, the terminal displays the multicast group list to the user through a human-computer interaction interface, and the user selects the multicast group of interest from the multicast group list and sends the selection result to the terminal. The terminal determines to join a multicast group based on the user's selection result, and triggers the terminal to send a PDU session establishment request message to the mobility management network element. For example, assuming that the multicast group list includes television programs such as CCTV1 and CCTV2, and the terminal is a set top box (STB) 1, STB1 can display relevant information of these television programs to the user, and the user can manually select the television program he wants to watch, such as CCTV1, and send the selection result to STB1. STB1 sends a PDU session establishment request message carrying the identification information of CCTV1 to the mobility management network element based on the selection result.

[0127] The multicast group list may include identification information of one or more multicast groups, and the multicast group list may be pre-configured on the terminal or dynamically configured to the terminal by the application server. If the terminal is in an initial state, the multicast group list may be empty. After the application server determines to establish / form a multicast group, it sends a service announcement message carrying the identification information of the multicast group to the application layer of the terminal. The application layer of the terminal receives the service announcement message from the application server, obtains the identification information of the multicast group from the service announcement message, and adds the obtained identification information of the multicast group to the multicast group list. Alternatively, the application server configures the identification information of the multicast group to the access network device through operation and management (OAM), triggering the access network device to send a broadcast message including the identification information of the multicast group, and the terminal listens to the broadcast message sent by the access network device, obtains the identification information of the multicast group from the broadcast message, and adds the identification information of the multicast group to the multicast group list. Alternatively, the application server triggers a short message service center (SMSC) to send a short message carrying identification information of the multicast group to the terminal. The terminal receives the short message, obtains the identification information of the multicast group from the short message, and adds the identification information of the multicast group to the multicast group list.

[0128] In an example, in step 401, the terminal sending a PDU session establishment request message to the mobility management network element may include: the terminal sending a PDU session establishment request message to the access network device through an interface between the terminal and the access network device.

[0129] Correspondingly, after receiving the PDU session establishment request message, the access network device forwards the PDU session establishment request message to the mobility management network element.

[0130] In another example, step 401 may include: the terminal directly sends a NAS message to the mobility management network element through an interface between the terminal and the mobility management network element, where the NAS message carries a PDU session establishment request message.

[0131] In order to reduce the parsing complexity of the mobility management network element, the PDU session establishment request message may carry an N1 session management container, and the N1 session management container may include identification information of the multicast group. The N1 session management container may be regarded as an information element in the PDU session establishment request message, and the type of the information element may implicitly indicate that the mobility management network element does not parse the content in the N1 session management container, but transparently transmits the N1 session management container to the session management network element that manages the multicast PDU session. In this way, after the mobility management network element receives the PDU session establishment request message carrying the N1 session management container, it may not parse the content included in the N1 session management container, thereby reducing the complexity of the mobility management network element parsing the content carried by the PDU session establishment request message. In the embodiment of the present application, the N1 session management container may also be named a transmission container (transparent container) or an N1 session management (session management, SM) container or a transparent container, etc.

[0132] In the case where the N1 session management container carries the identification information of the multicast group, one or more of the identification information of the data network used to transmit multicast data, the identification information of the network slice used to transmit multicast data, the identification information of the unicast PDU session of the terminal, and the identification information of the multicast PDU session can be carried in the N1 session management container or outside the N1 session management container without limitation. For example, the PDU session establishment request message may include the N1 session management container {identification information of the multicast group, identification information of the unicast PDU session of the terminal, identification information of the multicast PDU session}, identification information of the data network, and identification information of the network slice; or, the PDU session establishment request message includes the N1 session management container {identification information of the multicast group, identification information of the unicast PDU session of the terminal, identification information of the multicast PDU session, identification information of the data network, and identification information of the network slice}.

[0133] Step 402: The mobility management network element receives the PDU session establishment request message, and sends identification information of the multicast group to the session management network element according to the PDU session establishment request message.

[0134] The session management network element can manage the multicast PDU session corresponding to the multicast group and is a multicast session management network element. The process in which the mobility management network element sends the identification information of the multicast group to the session management network element according to the PDU session establishment request message may include the following example 1 or example 2:

[0135] Example 1: After receiving a PDU session establishment request message, the mobility management network element parses the PDU session establishment request message to obtain the identification information of the multicast group, and the mobility management network element sends the identification information of the multicast data to the first network element; the first network element receives the identification information of the multicast data, queries the first corresponding relationship using the identification information of the multicast data as an index, finds the identification information of the session management network element corresponding to the identification information of the multicast data, and sends the identification information of the session management network element to the mobility management network element; the mobility management network element sends the identification information of the multicast group to the session management network element based on the identification information of the session management network element. On the contrary, if no session management network element is found according to the identification information of the multicast group, the mobility management network element obtains candidate multicast session management network elements, and selects a session management network element that manages the multicast PDU session corresponding to the multicast group from the candidate multicast session management network elements, such as randomly selecting a multicast session management network element from the candidate multicast session management network elements as the session management network element that manages the multicast PDU session corresponding to the multicast group, or selecting a multicast session management network element with a smaller load or better communication quality as the session management network element that manages the multicast PDU session corresponding to the multicast group, and sending the identification information of the multicast group to the selected session management network element.

[0136] Among them, the first network element can be NRF or UDM or UDR or PCF.

[0137] The first correspondence may include a correspondence between the identification information of the multicast data and the identification information of the session management network element. In this way, the correspondence between the identification information of the multicast data and the identification information of the session management network element may be pre-stored in the first network element, so that the mobility management network element obtains the identification information of the session management network element that manages the multicast PDU session from the first network element according to the identification information of the multicast group, which is simple and easy to implement, simplifies the system design, and reduces the power consumption of the session management network element that manages the multicast PDU session when the mobility management network element determines.

[0138] The identification information of the session management network element may include the IP address of the session management network element, the MAC address of the session management network element, or the fully qualified domain name (FQDN) of the session management network element.

[0139] It should be noted that the first correspondence can be pre-configured to the first network element, such as for certain multicast groups, certain session management network elements are fixedly / pre-configured to manage these multicast groups, and the network management system configures the correspondence between the identification information of the session management network element that manages the multicast group and the identification information of the multicast group to the first network element. Alternatively, before the network receives the PDU session establishment request message of the terminal, the core network network element has previously received a request from the application server, and the request includes relevant information of the multicast data corresponding to the multicast group (such as identification information of the multicast data, QoS requirement information of the multicast data, etc.). At this time, the core network network element (such as NEF or PCF, etc.) selects the corresponding session management network element according to the request of the application server, and stores the first correspondence to the first network element.

[0140] Among them, the candidate multicast session management network elements may include one or more multicast session management network elements. In one possible design, the mobility management network element may obtain the candidate session management network elements from the NRF. For example, the mobility management network element may send a query request to the NRF, and the query request may include the identification information of the multicast group. The query request may be used to request a query for a session management network element that has the function of managing the multicast PDU session corresponding to the multicast group; the NRF receives the query request, determines the identification information of the session management network element that manages the multicast PDU session corresponding to the multicast group according to the identification information of the multicast group, and sends the identification information including the candidate multicast session management network element to the mobility management network element. If the identification information of the multicast group and the identification information of the candidate multicast session management network element are pre-correlated on the NRF, after receiving the query request, the NRF sends the identification information of the candidate multicast session management network element corresponding to the identification information of the multicast group to the mobility management network element. Or,

[0141] In another possible design, when the mobility management network element parses the PDU session establishment request message to obtain identification information of the data network used to transmit multicast data and / or identification information of the network slice used to transmit multicast data, the mobility management network element determines, based on the identification information of the data network used to transmit multicast data, one or more session management network elements that provide session services for the DN identified by the identification information of the data network, and / or, based on the identification information of the network slice used to transmit multicast data, determines one or more session management network elements included in the network slice identified by the identification information of the network slice, and determines the intersection of the one or more session management network elements included in the network slice and the one or more session management network elements that provide network services for the DN as a candidate session management network element.

[0142] It should be noted that in Example 1, if the mobility management network element parses the PDU session establishment request message to obtain the identification information of the multicast PDU session, then before executing Example 1, the mobility management network element may also use the identification information of the multicast PDU session as an index to query whether the corresponding relationship between the identification information of the multicast PDU session and the identification information of the session management network element is stored locally. If the corresponding relationship between the identification information of the multicast PDU session and the identification information of the session management network element is found to be stored locally, the identification information of the multicast group is sent to the mobility management network element according to the identification information of the session management network element in the corresponding relationship, and there is no need to execute the process described in Example 1. Conversely, if the corresponding relationship between the identification information of the multicast PDU session and the identification information of the session management network element stored locally is not found, the process described in Example 1 is executed.

[0143] Among them, the correspondence between the identification information of the multicast PDU session and the identification information of the session management network element can be stored in the mobility management network element before step 401. For example, before step 401, the session management network element is triggered by other terminals or application servers to establish a multicast PDU session. After the session management network element establishes the multicast PDU session, it sends a multicast PDU session establishment completion message carrying the identification information of the multicast PDU session to the mobility management network element. After receiving the multicast PDU session establishment completion message, the mobility management network element saves the correspondence between the identification information of the multicast PDU session and the identification information of the session management network element.

[0144] In Example 2, the session management network element is the default multicast session management network element. Once the mobility management network element receives the PDU session establishment request message, it sends the identification information of the multicast group to the default multicast session management network element. In Example 2, the mobility management network element does not need to parse the PDU session establishment request message, but determines that this is a message for adding a terminal to a multicast group based on the message type of the PDU session establishment request message, and forwards the message carried by the PDU session establishment request message (such as the identification information of the multicast group and other information, etc.) to the default multicast session management network element.

[0145] In the present application, the mobility management network element can carry the identification information of the multicast group in the PDU session modification context request and send it to the session management network element. For example, when the PDU session establishment request message carries the N1 session management container, the mobility management network element does not parse the N1 session management container, but carries the N1 session management container in the PDU session modification context request and sends it to the session management network element. The embodiment of the present application does not limit the naming of the PDU session modification context request, and the PDU session modification context request can also be named Nsmf_PDU session_create SM context request message or session management context request (session manegement context request, SM context request) message.

[0146] In addition to sending the identification information of the multicast group to the session management network element, the mobility management network element can also send the session management network element one or more of the identification information of the data network used to transmit multicast data, the identification information of the network slice used to transmit multicast data, the identification information of the unicast PDU session of the terminal, and the identification information of the multicast PDU session, and can also send the identification information of the terminal to the session management network element.

[0147] Step 403: The session management network element receives the identification information of the multicast group, and sends the context information of the multicast PDU session to the mobility management network element according to the identification information of the multicast group.

[0148] Among them, the context information of the multicast PDU session can be used by the terminal to receive multicast data through the multicast PDU session. The context information of the multicast PDU session may include one or more of the following information: the start time of sending the multicast data, the end time of sending the multicast data, the receiving frequency of the multicast data, and the quality of service (QoS) information of the multicast data, so that the terminal can configure the time and frequency resources and processing resources for receiving the multicast data according to the information included in the context information of the multicast PDU session, thereby improving the accuracy of the terminal receiving the multicast data.

[0149] Among them, the context information of the multicast PDU session can be saved in the context of the multicast PDU session, and the context of the multicast P DU session can be saved in the first network element or the session management network element after the multicast PDU session is established. Specifically, the network element in which the context of the multicast PDU session is saved can be set as needed without restriction. In addition to the context information of the multicast PDU session, the context of the multicast PDU session can also include first information, and the first information can include identification information of the multicast group, and can also include: identification information of the data network used to transmit multicast data, identification information of the network slice used to transmit multicast data, and one or more of the identification information of the multicast PDU session. Among them, what the first message specifically includes can be pre-set as needed without restriction.

[0150] In one example, the session management network element may query whether the context of the multicast PDU session including the first information is stored locally. If so, it indicates that the multicast PDU session has been established. The context information of the multicast PDU session is obtained from the queried context of the multicast PDU session, and the context information of the multicast PDU session is sent to the mobility management network element. Alternatively, the session management network element sends the first information to the first network element that stores the context of the multicast PDU session, triggering the first network element to query whether the context of the multicast PDU session including the first information is stored locally. If so, it indicates that the multicast PDU session has been established. The first network element obtains the context information of the multicast PDU session from the queried context of the multicast PDU session, sends the context information of the multicast PDU session to the session management network element, and the session management network element receives the context information of the PDU session and sends the context information of the multicast PDU session to the mobility management network element.

[0151] Furthermore, the session management network element updates the context of the multicast group. For example, if the context of the multicast group includes a terminal list, and the terminal list includes identification information of the terminals joining the multicast group, then the session management network element receives the identification information of the terminal and adds the identification information of the terminal to the terminal list, and / or the context of the multicast group includes the number of terminals, which may refer to the number of terminals joining the multicast group. At this time, the session management network element adds 1 to the number of terminals.

[0152] Among them, the multicast PDU session can be established by referring to the following method 1 or method 2.

[0153] Method 1: Other terminals send a PDU session establishment request message to join the multicast group to the mobility management network element, triggering the session management network element to join the terminal to the multicast PDU session corresponding to the multicast group. The session management network element obtains the multicast policy and charging control rule (PCC) rule from the policy control network element, and obtains the QoS information of the multicast data according to the multicast PCC rule; the session management network element sends the QoS information of the multicast data to the access network device, and requests the access network device to configure the wireless transmission resources of the multicast PDU session for the terminal. At the same time, the session management network element sends the corresponding relationship between the identification information of the multicast data and the service quality flow identifier (QoS flow identifier, QFI) to the user plane network element. The user plane network element receives and saves the corresponding relationship between the identification information of the multicast data and the QFI information, and completes the establishment of the multicast PDU session. It should be noted that the identification information of the multicast data described in the embodiment of the present application may refer to the identifier of the service data flow (SDF). Specifically, the process shown in the first method can refer to the prior art and will not be described in detail.

[0154] Method 2: The application server triggers the establishment of a multicast PDU session. If the application server determines to form a multicast group and configures the identification information of the multicast group for the multicast group, the identification information of the multicast group and the multicast description information corresponding to the multicast group are sent to the PCF. The PCF formulates a multicast PCC rule according to the multicast description information and sends the multicast PCC rule to the multicast session management network element. The multicast session management network element can generate QoS information of the multicast data according to the multicast PCC rule. The session management network element sends the QoS information of the multicast data to the access network device and requests the access network device to configure the wireless transmission resources of the multicast PDU session for the terminal. At the same time, the session management network element sends the corresponding relationship between the identification information of the multicast data and the QFI to the user plane network element. The user plane network element receives and saves the corresponding relationship between the identification information of the multicast data and the QFI information, and completes the establishment of the multicast PDU session. Specifically, the process shown in method 2 can refer to the existing technology and will not be described in detail. The message sent by the application server to the PCF may be sent directly from the application server to the PCF, or may be sent to the PCF via the NEF network element or other network elements, which is not limited here.

[0155] In this example, if the established multicast PDU session cannot cover the area where the terminal is located, that is, the multicast data cannot be sent to the access network device accessed by the terminal through the multicast PDU session or the tunnel between them is not opened, the method also includes: the session management network element obtains the tunnel information of the access network device through the mobility management network element, and configures the tunnel information of the access network device to the user plane network element corresponding to the multicast PDU session, so that the user plane network element corresponding to the multicast PDU session uses the tunnel to send multicast data to the access network device. At the same time, the QoS information of the multicast data is sent to the access network device, requesting the access network device to configure wireless resources for the terminal so that the multicast data can be sent from the access network device to the terminal through the wireless resources.

[0156] Among them, the QoS information of the above-mentioned multicast data includes one or more of the QFI of the multicast PDU session, the ARP information of the multicast PDU session, the rate guarantee information of the multicast PDU session, the delay budget information of the multicast PDU session, and the error rate information of the multicast PDU session.

[0157] In another example, if the context of the multicast PDU session corresponding to the identification information carrying the multicast data is not found according to the first information, it indicates that the multicast PDU session has not been established, and the session management network element is immediately triggered to establish the multicast PDU session in the above-mentioned method 1, and further, the context of the multicast group can be updated in the above-mentioned method. If the context of the multicast PDU session corresponding to the identification information carrying the multicast data is not found according to the first information, the context of the multicast group is updated in the above-mentioned method, and when it is determined that the number of terminals joining the multicast group is greater than the first threshold, the session management network element is triggered to establish the multicast PDU session in the above-mentioned method 1.

[0158] The first threshold can be set as needed without limitation.

[0159] Exemplarily, the session management network element sending the context information of the multicast PDU session to the mobility management network element may include: the session management network element sending an Nsmf_N1N2 message transfer message to the mobility management network element, the Nsmf_N1N2message transfer message carries the context information of the multicast PDU session, or the session management network element sending an Nsmf_PDU session_create SM context response message to the mobility management network element, the Nsmf_PDU session_create SM context response message carries the context information of the multicast PDU session.

[0160] Furthermore, in addition to sending the context information of the multicast PDU session to the mobility management network element, the session management network element may also send transmission information used for the access network device to configure radio bearer resources to the mobility management network element.

[0161] Furthermore, the session management network element can also send the correspondence between the identification information of the multicast PDU session and the identification information of the session management network element to the mobility management network element, so that the mobility management network element saves the correspondence between the identification information of the multicast PDU session and the identification information of the session management network element. Subsequently, when other terminals apply to join the multicast group, the mobility management network element can find the session management network element that manages the multicast PDU session based on the correspondence between the identification information of the multicast PDU session and the identification information of the session management network element.

[0162] Step 404: The mobility management network element receives the context information of the multicast PDU session, and sends a PDU session establishment accept message to the terminal, where the PDU session establishment accept message includes the context information of the multicast PDU session.

[0163] Among them, the PDU session establishment accept message can be a downlink NAS message, the PDU session establishment accept message can be named PDU session establishment accept message, and the PDU session establishment accept message can be used to indicate that the terminal joins the multicast group or replace the description as the multicast PDU session corresponding to the terminal joining the multicast group.

[0164] Step 405: The terminal receives a PDU session establishment acceptance message.

[0165] Furthermore, the terminal can receive multicast data through a multicast PDU session based on the context information of the multicast PDU session. In this way, a copy of multicast data can be sent to one or more terminals through a multicast PDU session, thereby improving resource utilization and transmission efficiency. For example, an application server sends a copy of multicast data to a user-plane network element, and the user-plane network element sends the copy of multicast data to an access network device through a multicast PDU session; the access network device broadcasts the scheduling information corresponding to the multicast group in the control channel, and the terminal receives the multicast data at the receiving frequency of the multicast data based on the scheduling information broadcast by the access network device and the context information of the multicast PDU session.

[0166] based on Figure 4In the method shown, the terminal uses the existing PDU session establishment process to send a PDU session establishment request message including the identification information of the multicast group to the mobility management network element. After receiving the PDU session establishment request message, the mobility management network element sends the identification information of the multicast group in the PDU session establishment request message to the session management network element that manages the multicast PDU session. The session management network element obtains the context information of the multicast PDU session according to the identification information of the multicast group, and sends the context information of the multicast PDU session to the terminal through the mobility management network element, so that the terminal receives multicast data according to the context information of the multicast PDU session. In this way, the existing PDU session establishment process between the terminal and the core network can be reused to add the terminal to the multicast group, which not only realizes group communication through the multicast PDU session, but also reduces signaling overhead and simplifies system design.

[0167] It should be noted that Figure 4 The PDU session establishment request message in the method shown can also be replaced by a PDU session modification request message, and correspondingly, the PDU session establishment acceptance message can also be replaced by a PDU session modification acceptance message, that is, the terminal is added to the multicast group through the PDU session modification process.

[0168] Further, in Figure 4 In a possible design shown, in order to ensure the continuity of multicast data transmission, a unicast PDU session can also be established for the terminal. Specifically, the process of establishing a unicast PDU session may include: after the mobility management network element receives the PDU session establishment request message, it selects the session management network element that manages the unicast PDU session and sends a PDU session context modification request to the session management network element; after receiving the PDU session context modification request, the session management network element determines the QF and selects a user plane network element as the anchor point of the unicast PDU session, establishes the unicast PDU session, and sends the context information of the unicast PDU session to the terminal through the mobility management network element.

[0169] The context information of the unicast PDU session can be used by the terminal to transmit multicast data through the unicast PDU session. The context information of the unicast PDU session may include one or more of the following: the start sending time of the multicast data / the end sending time of the multicast data when the multicast data is transmitted through the unicast PDU session, the receiving frequency of the multicast data when the multicast data is transmitted through the unicast PDU session, and the QoS information of the multicast data when the multicast data is transmitted through the unicast PDU session.

[0170] Specifically, the detailed process of establishing a unicast PDU session can refer to the prior art and will not be described in detail.

[0171] Further, after the terminal successfully establishes a unicast PDU session, the mobility management network element may save the correspondence between the identification information of the unicast PDU session and the identification information of the session management network element. The session management network element may save the correspondence between the identification information of the unicast PDU session and the identification information of the user plane network element, such as: saving the correspondence between the identification information of the unicast PDU session and the identification information of the user plane network element in the context of the unicast PDU session.

[0172] It should be noted that the session management network element that manages the unicast PDU session and the session management network element that manages the multicast PDU session can be the same or different, and the UPF corresponding to the unicast PDU session and the UPF corresponding to the multicast PDU session can be the same or different, without restriction.

[0173] Based on this possible design, when the number of terminals joining the multicast group is low, the multicast PDU session is released / unavailable, or the terminal moves out of the coverage area corresponding to the multicast PDU session, multicast data can be sent to the terminal through a unicast PDU session to ensure that the continuity of the terminal's reception of multicast data is not affected and to avoid data transmission interruption.

[0174] Further, in Figure 4 In another possible design of the method shown, as a reverse process of the terminal joining the multicast group, the terminal can also leave the multicast group through the existing PDU release process / PDU session modification process. Specifically, the process may include: the terminal sends a first message to the mobility management network element; the first message is used for the terminal to leave the multicast group, the first message includes identification information of the multicast group, and the first message may also include identification information of the terminal;

[0175] The mobility management network element receives the first message, and sends the first message to the session management network element;

[0176] The session management network element receives the first message, finds the context of the multicast group according to the first message, and updates the context of the multicast group. For example, the context of the multicast group includes a terminal list, and the terminal list includes identification information of terminals joining the multicast group. At this time, the session management network element receives the identification information of the terminal and deletes the identification information of the terminal from the terminal list. And / or, the context of the multicast group includes the number of terminals, and the number of terminals may refer to the number of terminals joining the multicast group. At this time, the session management network element reduces the number of terminals by 1.

[0177] The session management network element sends a response to the first message to the mobility management network element. Correspondingly, the mobility management network element receives the response to the first message and sends the response to the first message to the terminal.

[0178] The first message may be a PDU session release request message, and the response to the first message may be a PDU session release response. Alternatively, the first message may be a PDU session modification request message, and the response to the first message may be a PDU session modification response.

[0179] Based on this possible design, the terminal can leave the multicast group through the PDU session release process / PDU session modification process, simplifying the system design and reducing signaling overhead.

[0180] Furthermore, in order to reduce resource utilization, if the number of terminals joining the multicast group is less than the second threshold after the terminal leaves the multicast group, such as the number of terminals joining the multicast group is zero, the session management network element can send a release notification message to the user plane network element corresponding to the multicast PDU session, notifying the user plane network element corresponding to the multicast PDU session to release the multicast PDU session. In this way, the multicast PDU session can be released when the number of terminals joining the multicast group is small, especially when no terminal joins the multicast group, thereby improving resource utilization.

[0181] The second threshold can be set as needed without limitation.

[0182] Furthermore, after releasing the multicast PDU session, in order to ensure the continuity of multicast data transmission, the session management network element can also send indication information to the user plane network element corresponding to the unicast PDU session of the terminal that needs multicast data, instructing the user plane network element corresponding to the unicast PDU session to transmit multicast data through the unicast PDU session. In this way, the user plane network element corresponding to the unicast PDU session can be notified to send multicast data to the terminal, ensuring that the continuity of the terminal receiving multicast data is not affected, avoiding data transmission interruption.

[0183] Among them, the user plane network element corresponding to the multicast PDU session and the user plane network element corresponding to the unicast PDU session can be the same or different. If they are different, the session management network element can send indication information to the session management network element that manages the unicast PDU session, and the session management network element that manages the unicast PDU session forwards the indication to the user plane network element corresponding to the unicast PDU session.

[0184] Combine the following Figure 2aIn the system shown in the figure, a terminal requests to join multicast group 1. Before the terminal requests to join multicast group 1, a multicast PDU session corresponding to multicast group 1 has been established, the session management network element for managing the multicast PDU session corresponding to multicast group 1 is SMF1, the mobility management network element is AMF, and the access network device is RAN. Figure 4 The method shown is described.

[0185] Figure 5 Another communication method provided in the embodiment of the present application is as follows: Figure 5 As shown, the method may include:

[0186] Step 501: Establish a multicast PDU session corresponding to multicast group 1.

[0187] For example, it can be used Figure 4 Method 1 or method 2 in the method shown establishes a multicast PDU session corresponding to multicast group 1, which will not be described in detail.

[0188] Further, after the multicast PDU session is established, SMF1 stores the context information of the multicast PDU session and the identification information of the multicast group 1 in the context of the multicast PDU session in correspondence.

[0189] Furthermore, SMF1 may also send identification information of SMF1 and identification information of multicast group 1 to NRF, and NRF stores the identification information of SMF1 and identification information of multicast group 1 locally accordingly.

[0190] In another possible implementation, SMF1 may also send identification information of SMF1 and identification information of multicast group 1 to UDR or PCF, and UDR or PCF stores the identification information of SMF1 and identification information of multicast group 1 locally accordingly.

[0191] Step 502: The terminal determines to join multicast group 1 and sends a PDU session establishment request message to the AMF.

[0192] The PDU session establishment request message carries the identification information of the multicast group 1.

[0193] In another possible implementation, the terminal sends a PDU session modification request message to the AMF, where the PDU session modification request message carries identification information of multicast group 1.

[0194] Specifically, the execution process of step 502 may refer to the description of step 401 and will not be described in detail.

[0195] Step 503: AMF receives the PDU session establishment request message, and determines the SMF: SMF1 that manages the multicast PDU session corresponding to multicast group 1 according to the identification information of multicast group 1.

[0196] In another possible implementation, the AMF receives a PDU session modification request message, and the AMF determines the SMF: SMF1 that manages the multicast PDU session corresponding to the multicast group 1 according to the identification information of the multicast group 1.

[0197] Among them, AMF can send the identification information of multicast group 1 to NRF, NRF receives the identification information of multicast group 1, and uses the identification information of multicast group 1 as an index to query the identification information of SMF1 and the correspondence between the identification information of multicast group 1, and determines SMF1 identified by the identification information of SMF1 as the SMF that manages the multicast PDU session.

[0198] In another possible implementation, the AMF may send identification information of the multicast group 1 to the UDR, UDM or PCF, and the UDR, UDM or PCF is determined as the SMF that manages the multicast PDU session. The determination method is similar to that of the NRF, which will not be described here.

[0199] Step 504: AMF sends a PDU session modification context request to SMF1.

[0200] The PDU session modification context request may include identification information of the multicast group 1.

[0201] Step 505: SMF1 receives the PDU session modification context request, and acquires the context information of the multicast PDU session according to the identification information of the multicast group 1 carried in the PDU session modification context request.

[0202] For a description of the context information of a multicast PDU session, see Figure 4 It has been described in the previous section and will not be elaborated here.

[0203] Exemplarily, SMF1 may use the identification information of multicast group 1 as an index to query and obtain the context of the multicast PDU session including the identification information of multicast group 1, and obtain the context information of the multicast PDU session from the queried context of the multicast PDU session.

[0204] Furthermore, SMF1 increases the number of terminals in the context of multicast group 1 by 1.

[0205] Step 506: SMF1 sends the context information of the multicast PDU session to AMF.

[0206] Among them, SMF1 can send a PDU session modification context response to AMF, and the PDU session modification context response includes context information of the multicast PDU session.

[0207] Step 507: AMF receives the context information of the multicast PDU session and sends a PDU session establishment accept message to the terminal. The PDU session establishment accept message carries the context information of the multicast PDU session.

[0208] In another possible implementation, the AMF receives the context information of the multicast PDU session and sends a PDU session modification accept message to the terminal, where the PDU session modification accept message carries the context information of the multicast PDU session.

[0209] Step 508: The terminal receives a PDU session establishment accept message.

[0210] In another possible implementation manner, the terminal receives a PDU session modification accept message.

[0211] Furthermore, the terminal may receive multicast data according to the context information of the multicast PDU session.

[0212] Optionally, in order to ensure the continuity of multicast data transmission when the terminal moves out of the multicast area and does not support receiving multicast data through a multicast PDU session, SMF1 also triggers the establishment of a unicast PDU session of the terminal and switches to transmitting multicast data through a unicast PDU session. Specifically, the process of SMF1 establishing a unicast PDU session may include steps 509 to 510:

[0213] Step 509: SMF1 establishes a unicast PDU session for the terminal.

[0214] For details, please refer to the process of establishing a unicast PDU session in SMF1. Figure 3 It is shown in , which will not be described in detail.

[0215] Step 510: SMF1 sends the context information of the unicast PDU session to the terminal through AMF, and correspondingly, the terminal receives the context information of the unicast PDU session.

[0216] Furthermore, the terminal can receive multicast data through a unicast PDU session based on the context information of the unicast PDU session. It should be noted that when establishing a unicast PDU session and a multicast PDU session, the context information of the unicast PDU session and the context information of the multicast PDU session can be carried together in a PDU session establishment acceptance message and sent to the terminal, or carried in different messages and sent to the terminal without restriction.

[0217] based on Figure 5In the method shown, the terminal uses the existing session establishment process to send a PDU session establishment request message including the identification information of multicast group 1 to AMF. After receiving the PDU session establishment request message, AMF sends the identification information of multicast group 1 in the PDU session establishment request message to SMF1. SMF1 obtains the context information of the multicast PDU session based on the identification information of multicast group 1, and sends the context information of the multicast PDU session to AMF at the same time. AMF carries the context information of the multicast PDU session in the PDU session establishment acceptance message and sends it to the terminal, so that the terminal receives multicast data based on the context information of the multicast PDU session. In this way, the existing PDU session establishment process between the terminal and the core network can be reused to add the terminal to multicast group 1, which not only realizes group communication through multicast PDU sessions, but also reduces signaling overhead and simplifies system design.

[0218] Figure 5 The method shown is described as an example in which a multicast PDU session has been established before the terminal requests to join multicast group 1. Figure 2a In the system shown in FIG. 1 , a terminal requests to join multicast group 1, a multicast PDU session is not established before the terminal requests to join multicast group 1, the session management network element for managing the multicast PDU session corresponding to multicast group 1 is SMF1, and the mobility management network element is AMF. Figure 4 The method shown is described as follows:

[0219] Figure 6 Another communication method provided in the embodiment of the present application is as follows: Figure 6 As shown, the method may include:

[0220] Step 601: The terminal determines to join multicast group 1 and sends a PDU session establishment request message to the AMF.

[0221] The terminal may be the first terminal to join the multicast group 1 or may not be the first terminal to join the multicast group 1, without limitation. The PDU session establishment request message carries the identification information of the multicast group 1.

[0222] Specifically, the execution process of step 602 may refer to the description of step 401 and will not be described in detail.

[0223] Step 602: AMF receives a PDU session establishment request message, and determines the SMF: SMF1 that manages the multicast PDU session corresponding to multicast group 1 according to the identification information of multicast group 1.

[0224] Among them, AMF does not obtain the identification information of SMF that manages the multicast PDU session from NRF based on the identification information of multicast group 1, so AMF selects SMF1 from the candidate multicast session management network elements.

[0225] Among them, the way in which AMF obtains the candidate multicast session management network element can refer to the description in step 402 and will not be repeated here.

[0226] Step 603: AMF sends a PDU session modification context request to SMF1.

[0227] The PDU session modification context request may include identification information of the multicast group 1.

[0228] Step 604: SMF1 receives a request to establish a context modification for a PDU session. If the context of the multicast PDU session including the identification information of the multicast group 1 is not found according to the identification information of the multicast group 1 carried in the request to modify the context for the PDU session, then steps 605 to 607 are executed to establish a multicast PDU session and the process ends; or, steps 608 to 609 are executed to establish a unicast PDU session and the process ends; or, steps 605 to 609 are executed to establish a unicast PDU session and a multicast PDU session.

[0229] For a description of the context information of a multicast PDU session, see Figure 4 It has been described in the previous section and will not be elaborated here.

[0230] Step 605: SMF1 adds 1 to the number of terminals in the context of multicast group 1. If the number of terminals after adding 1 is greater than the first threshold, SMF1 establishes a multicast PDU session.

[0231] Among them, the relevant description of the first threshold and the process of SMF1 establishing a multicast PDU session are as shown above and will not be repeated here.

[0232] On the contrary, if the number of terminals after adding 1 is less than or equal to the first threshold, SMF1 establishes a unicast PDU session for the terminal.

[0233] Furthermore, after the multicast PDU session is established, the SMF stores the context information of the multicast PDU session and the identification information of the multicast group 1 in the context of the multicast PDU session. Furthermore, SMF1 can also send the identification information of SMF1 and the identification information of the multicast group 1 to the NRF, and the NRF stores the identification information of SMF1 and the identification information of the multicast group 1 locally.

[0234] Step 606: SMF1 sends the context information of the multicast PDU session to AMF.

[0235] Among them, SMF1 can send a PDU session modification context response to AMF, and the PDU session modification context response includes context information of the multicast PDU session.

[0236] Step 607: AMF receives the context information of the multicast PDU session and sends a PDU session establishment acceptance message to the terminal, the PDU session establishment acceptance message carries the context information of the multicast PDU session. Correspondingly, the terminal receives the PDU session establishment acceptance message.

[0237] Furthermore, the terminal may receive multicast data according to the context information of the multicast PDU session.

[0238] Step 608: SMF1 establishes a unicast PDU session for the terminal.

[0239] Specifically, the process of SMF1 establishing a unicast PDU session for a terminal can be referred to Figure 3 It is shown in , which will not be described in detail.

[0240] Step 609: SMF1 sends the context information of the unicast PDU session to the terminal through AMF, and correspondingly, the terminal receives the context information of the unicast PDU session.

[0241] Furthermore, the terminal may receive multicast data according to the context information of the unicast PDU session.

[0242] It should be noted that when executing steps 605 to 609 to establish a unicast PDU session and a multicast PDU session, the context information of the unicast PDU session and the context information of the multicast PDU session can be carried together in the PDU session establishment acceptance message and sent to the terminal, or can be carried in different messages and sent to the terminal without restriction.

[0243] based on Figure 6 In the method shown, the terminal uses the existing session establishment process to send a PDU session establishment request message including the identification information of multicast group 1 to AMF. After receiving the PDU session establishment request message, AMF sends the identification information of multicast group 1 in the PDU session establishment request message to SMF1. SMF1 establishes a multicast PDU session and sends the context information of the multicast PDU session to AMF. AMF carries the context information of the multicast PDU session in a PDU session establishment acceptance message and sends it to the terminal, so that the terminal receives multicast data according to the context information of the multicast PDU session. In this way, the existing PDU session establishment process between the terminal and the core network can be reused to add the terminal to multicast group 1, which not only realizes group communication through multicast PDU sessions, but also reduces signaling overhead and simplifies system design.

[0244] Above Figure 5 , Figure 6The method shown is described by taking the terminal joining multicast group 1 as an example. As the reverse process of the terminal joining the multicast group, the terminal can also leave the multicast group 1 through / with the help of existing processes, such as the PDU session release process / PDU session modification process. Figure 2a In the system shown in the figure, the terminal leaves multicast group 1, the session management network element for managing the multicast PDU session corresponding to multicast group 1 is SMF1, the mobility management network element is AMF, the user plane network element corresponding to the multicast PDU session is UPF1, and the user plane network element corresponding to the unicast PDU session is UPF2 as an example. Figure 4 The method shown describes a process in which a terminal leaves a multicast group through a PDU session release process.

[0245] Figure 7 Another communication method provided in the embodiment of the present application is as follows: Figure 7 As shown, it may include:

[0246] Step 701: The terminal determines to leave multicast group 1.

[0247] Exemplarily, the terminal may determine to leave multicast group 1 according to user requirements. For example, the user may view various multicast groups in the multicast group list through a user interaction interface or other means, select multicast group 1 that the user wishes to leave from the multicast group list, and send the selection result to the terminal. The terminal receives the selection result of the user and determines to leave multicast group 1 according to the selection result.

[0248] For example, assuming that multicast group 1 is the multicast group corresponding to a TV program, the multicast group list includes relevant information of multiple TV programs, such as: CCTV1, CCTV2... and so on, and the terminal is STB. When a user who is watching CCTV1 leaves CCTV1, such as: when the user switches from CCTV1 to CCTV2, the user can manually select CCTV2 he wants to watch and send the selection result to STB. STB can determine to leave multicast group 1 corresponding to CCTV1 based on the selection result.

[0249] Step 702: The terminal sends a PDU session release request message to the AMF.

[0250] Among them, the PDU session release request message can be used for the terminal to leave the multicast group 1.

[0251] Exemplarily, the PDU session release request message may include identification information of multicast group 1. The PDU session release request message may also include identification information of the terminal, identification information of the data network used to transmit multicast data, identification information of the network slice used to transmit multicast data, identification information of the multicast PDU session, and one or more types of information.

[0252] In order to reduce the parsing complexity of AMF, the PDU session release request message can carry an N1 session management container, which can include identification information of the multicast group. The N1 session management container can be regarded as an information element in the PDU session release request message. The type of the information element can implicitly indicate that the AMF does not parse the content in the N1 session management container, but instead transparently passes the N1 session management container to the SMF that manages the multicast PDU session. In this way, after receiving the PDU session release request message carrying the N1 session management container, the AMF does not need to parse the content included in the N1 session management container, thereby reducing the complexity of the AMF parsing the content carried by the PDU session release request message.

[0253] Step 703: AMF receives the PDU session release request message, and determines the SMF that manages the multicast PDU session: SMF1 according to the PDU session release request message.

[0254] Among them, the process of AMF determining SMF1 according to the PDU session release request message can refer to the above-mentioned process of AMF determining SMF1 according to the PDU session establishment request message, and will not be repeated here.

[0255] Step 704: AMF sends identification information of multicast group 1 to SMF1.

[0256] Among them, the identification information of multicast group 1 sent by AMF to SMF1 can be carried in the PDU session update context request (PDU session manegement context request) or the Nsmf_PDUSession_update SMContext Request.

[0257] Step 705: SMF1 receives the identification information of multicast group 1, finds the context of multicast group 1 according to the identification information of multicast group 1, and reduces the number of terminals in the context of multicast group 1 by 1. If the number of terminals after reduction by 1 is less than the second threshold, SMF1 sends a release notification message to UPF1 corresponding to the multicast PDU session, notifying UPF1 to release the multicast PDU session.

[0258] The description of the second threshold can be found in Figure 3 The corresponding embodiments are described in detail and will not be repeated here.

[0259] On the contrary, if the number of terminals after subtracting 1 is greater than or equal to the second threshold, other terminals will still receive multicast data through the multicast PDU session without affecting it. In order to improve resource utilization, the wireless transmission resources between the terminal and the RAN can be released and the multicast PDU session can be retained. For example, SMF1 can send a message to the RAN through the AMF to notify the RAN to release the wireless transmission resources between it and the terminal.

[0260] Step 706: SMF1 sends a PDU session release response to AMF.

[0261] The PDU session release response may carry identification information of multicast group 1, and the PDU session release response may be used to indicate that the terminal has successfully left the multicast PDU session corresponding to multicast group 1. The PDU session release response may be carried in a PDU session update context response or Nsmf_PDUSession_update SM Context Response.

[0262] Step 707: The AMF receives the PDU session release response and sends the PDU session release response to the terminal. Correspondingly, the terminal receives the PDU session release response.

[0263] At this point, the terminal leaves the multicast group 1. Further, the terminal may turn off the receiving frequency of the communication group 1 to reduce the power consumption of the terminal.

[0264] Furthermore, if a unicast PDU session is established for the terminal, in order to ensure the continuity of multicast data transmission, Figure 7 The method may further include:

[0265] Step 708: SMF1 sends indication information to UPF2 corresponding to the unicast PDU session.

[0266] Exemplarily, step 708 sends indication information to the UPFs corresponding to the unicast PDU sessions of the terminals that are currently still in multicast group 1 and have established unicast PDU sessions.

[0267] The indication information is used to instruct the UPF2 corresponding to the unicast PDU session to use the unicast PDU session to send multicast data. It should be noted that if SMF1 is not the SMF that manages the unicast PDU session, then SMF1 sending the indication information to the UPF2 corresponding to the unicast PDU session may include: SMF1 sends the indication information to the SMF that manages the unicast PDU session, and the SMF that manages the unicast PDU session sends the indication information to the UPF2 corresponding to the unicast PDU session.

[0268] based on Figure 7In the method shown, the terminal uses the existing session release process to send a PDU session release request message including the identification information of multicast group 1 to AMF. After receiving the PDU session release request message, AMF sends the identification information of multicast group 1 in the PDU session release request message to SMF1. SMF1 reduces the number of terminals in multicast group 1 by 1 according to multicast group 1, and the terminal leaves the multicast group, and no longer sends multicast data to the terminal through the multicast PDU session. In this way, the existing PDU session release process can be reused to make the terminal leave multicast group 1, reducing signaling overhead and simplifying system design.

[0269] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of the interaction between each node. It can be understood that each node, such as a terminal, a mobility management network element, a session management network element, etc., includes a hardware structure and / or software module corresponding to each function in order to realize the above functions. It should be easy for those skilled in the art to realize that, in combination with the algorithm steps of each example described in the embodiments disclosed in this document, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0270] The embodiment of the present application can divide the functional modules of the terminal, mobility management network element, session management network element, etc. according to the above method example. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present application is schematic and is only a logical functional division. There may be other division methods in actual implementation.

[0271] Figure 8 The present invention provides a schematic diagram of a communication device 80, which may be a terminal or a chip or system on chip in the terminal. Figure 8 As shown, the communication device 80 may include: a sending unit 801, a receiving unit 802;

[0272] The sending unit 801 is configured to send a PDU session establishment request message including identification information of a multicast group to a mobility management network element. For example, the sending unit 801 supports the communication device 80 to execute step 401, step 502 and step 601.

[0273] The receiving unit 802 is configured to receive a PDU session establishment accept message including the context information of the multicast PDU session sent by the mobility management network element. For example, the receiving unit 802 can be configured to support the communication device 80 to execute step 410, step 508, step 607, and the like.

[0274] Specifically, in this possible design, the above Figure 4 to Figure 7 All relevant contents of each step involving the terminal in the method embodiment shown can be referred to the functional description of the corresponding functional module, and will not be repeated here. The communication device 80 described in this possible design is used to perform Figure 4 to Figure 7 The function of the terminal in the communication method shown can therefore achieve the same effect as the above-mentioned communication method.

[0275] It should be noted that, as another possible implementation method, Figure 8 The communication device 80 shown may include: a processing module and a communication module. The communication module may integrate the functions of the sending unit 801 and the receiving unit 802. The processing module is used to control and manage the actions of the communication device 80. For example, the processing module is used to support the communication device 80 to perform other processes of the technology described herein. The communication module is used to support the communication device 80 to perform steps 401, 502, 601, 410, 508, 607, etc. and communicate with other network entities. Further, Figure 8 The communication device 80 shown may also include a storage module for storing program codes and data of the communication device 80 .

[0276] The processing module may be a processor or a controller. It may implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc. The communication module may be a transceiver circuit or a communication interface, etc. The storage module may be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, Figure 8 The communication device 80 shown may be Figure 3 The communication device shown.

[0277] Fig. 9 The present invention provides a schematic diagram of the composition of a communication device 90, which may be a mobility management network element or a chip or system on chip in a mobility management network element. Fig. 9 As shown, the communication device 90 may include: a receiving unit 901 and a sending unit 902;

[0278] The receiving unit 901 is configured to receive a PDU session establishment request message including identification information of a multicast group from a terminal. For example, the receiving unit 901 may be configured to support the communication device 90 to execute step 402, step 503, step 602, and the like.

[0279] The sending unit 902 is used to send the identification information of the multicast group to the session management network element according to the PDU session establishment request message. For example, the sending unit 902 is used to support the communication device 90 to execute step 402, step 504, step 603, etc.

[0280] The receiving unit 901 is further configured to receive the context information of the multicast PDU session from the session management network element. For example, the receiving unit 901 can also be configured to support the communication device 90 to execute step 409, step 507, and step 607, etc.

[0281] The sending unit 902 is further configured to send a PDU session establishment accept message including the context information of the multicast PDU session to the terminal. For example, the sending unit 902 is configured to support the communication device 90 to execute step 409, step 507 and step 607.

[0282] Specifically, in this possible design, the above Figure 4 to Figure 7 All relevant contents of each step involving the mobility management network element in the illustrated method embodiment can be referred to the functional description of the corresponding functional module, and will not be repeated here. The communication device 90 described in the possible design is used to perform Figure 4 to Figure 7 The function of the mobility management network element in the communication method shown can therefore achieve the same effect as the above communication method.

[0283] It should be noted that, as another possible implementation method, Fig. 9 The communication device 90 shown may include: a processing module and a communication module. The communication module may integrate the functions of the sending unit 902 and the receiving unit 901. The processing module is used to control and manage the actions of the communication device 90. For example, the processing module is used to support the communication device 90 to perform other processes of the technology described herein. The communication module is used to support the communication device 90 to perform steps 402, 503, 703, etc. and communicate with other network entities. Further, Fig. 9 The communication device 90 shown may also include a storage module for storing program codes and data of the communication device 90 .

[0284] The processing module may be a processor or a controller. It may implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc. The communication module may be a transceiver circuit or a communication interface, etc. The storage module may be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, Fig. 9 The communication device 90 shown may be Figure 3 The communication device shown.

[0285] Fig.10 The present invention provides a schematic diagram of the composition of a communication device 100, which may be a session management network element or a chip or system on chip in a session management network element. Fig.10 As shown, the communication device 100 may include: a receiving unit 1001, a sending unit 1002;

[0286] The receiving unit 1001 is configured to receive identification information of a multicast group from a mobility management network element. For example, the receiving unit 1001 may be configured to support the communication device 100 in executing step 403 , step 505 , and step 604 .

[0287] The sending unit 1002 is configured to send the context information of the multicast PDU session to the mobility management network element according to the identification information of the multicast group. For example, the sending unit 1002 can be configured to support the communication device 100 to execute step 403, step 506 and step 606.

[0288] Specifically, in this possible design, the above Figure 4 to Figure 7 All relevant contents of each step of the session management network element for managing the multicast PDU session in the method embodiment shown can be referred to the functional description of the corresponding functional module, and will not be repeated here. The communication device 100 described in the possible design is used to perform Figure 4 to Figure 7 The function of the session management network element for managing the multicast PDU session in the communication method shown can therefore achieve the same effect as the above communication method.

[0289] It should be noted that, as another possible implementation method, Fig.10 The communication device 100 shown may include: a processing module and a communication module. The communication module may integrate the functions of the receiving unit 1001 and the sending unit 1002. The processing module is used to support the communication device 100 to control and manage the actions of the communication device 100, and the communication module is used to support the communication device 100 to execute steps 403, 505, 604, 403, 506, 606, etc. and communicate with other network entities. Further, Fig.10The communication device 100 shown may further include a storage module for storing program codes and data of the communication device 100 .

[0290] The processing module may be a processor or a controller. It may implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc. The communication module may be a transceiver circuit or a communication interface, etc. The storage module may be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, Fig.10 The communication device 100 shown may be Figure 3 The communication device shown.

[0291] Fig.11 A schematic diagram of the composition of a communication system provided in an embodiment of the present application is shown in FIG. Fig.11 As shown, the communication system may include a terminal 110, an AMF 111, and an SMF 112. Further, Fig.11 The system shown may also include access network equipment and other network elements such as UPF. Among them, the terminal 110 has the same function as the communication device 80, the AMF 110 has the same function as the communication device 90, and the SMF 112 has the same function as the communication device 100.

[0292] For example, the terminal 110 is used to send a PDU session establishment request message including the identification information of the multicast group to the AMF 111. The AMF 111 is used to send the received identification information of the multicast group to the SMF 112. The SMF 112 is used to send the context information of the multicast PDU session to the AMF 111 according to the identification information of the multicast group. The AMF 111 is also used to receive the context information of the multicast PDU session and send the received context information of the multicast PDU session to the terminal 110.

[0293] Specifically, Fig.11 The execution process of each network element in the method can refer to the execution steps of the network element in the above method, which will not be described in detail. Fig.11In the system shown, the terminal 110 uses the existing session establishment process to send a PDU session establishment request message including the identification information of the multicast group to AMF111. After receiving the PDU session establishment request message, AMF111 sends the identification information of the multicast group in the PDU session establishment request message to SMF112 that manages the multicast PDU session, so that SMF112 sends the context information of the multicast PDU session to AMF111 according to the identification information of the multicast group, and AMF111 sends the context information of the multicast PDU session to the terminal 110, so that the terminal 110 receives the multicast data according to the context information of the multicast PDU session. In this way, the existing PDU session establishment process between the terminal 110 and the core network can be reused to add the terminal 110 to the multicast group, realize group communication, and simplify the system design.

[0294] Through the description of the above implementation methods, technical personnel in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0295] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0296] The units described as separate components may or may not be physically separated, and the components shown as units may be one physical unit or multiple physical units, that is, they may be located in one place or distributed in multiple different places. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0297] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0298] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium, including several instructions to enable a device (which can be a single-chip microcomputer, chip, etc.) or a processor (processor) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard drives, ROM, RAM, magnetic disks or optical disks.

[0299] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A communication method, characterized in that: The method comprises: The terminal device establishes a multicast packet data unit PDU session corresponding to the first multicast group; The first terminal device determines to join the first multicast group; The first terminal device sends a PDU session establishment request message to the mobility management function AMF network element; The first terminal device receives a PDU session establishment acceptance message and context information of a unicast PDU session.

2. A communication method, characterized in that: The method comprises: The mobility management function AMF network element receives a packet data unit PDU session establishment request message; The AMF network element determines, according to the identification information of the first multicast group, a session management function SMF network element for managing the multicast PDU session corresponding to the first multicast group: a first SMF network element; The AMF network element sends a PDU session modification context request to the first SMF; The AMF network element receives the context information of the multicast PDU session and sends a PDU session establishment acceptance message to the terminal, where the PDU session establishment acceptance message carries the context information of the multicast PDU session.

3. A communication device, characterized in that: The communication device comprises one or more processors and a communication interface, wherein the one or more processors and the communication interface are used to support the communication device to execute the communication method according to claim 1.

4. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes computer instructions, which, when executed on a computer, cause the computer to perform the communication method according to claim 1 .

5. A computer program product, characterized in that The computer program product comprises computer instructions, which, when executed on a computer, cause the computer to perform the communication method according to claim 1 .

6. A communication device, characterized in that: The communication device comprises one or more processors and a communication interface, wherein the one or more processors and the communication interface are used to support the communication device to execute the communication method according to claim 2.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes computer instructions, which, when executed on a computer, cause the computer to perform the communication method according to claim 2 .

8. A computer program product, characterized in that The computer program product comprises computer instructions, which, when executed on a computer, cause the computer to perform the communication method according to claim 2 .

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