Communication method and apparatus

Abstract

The present application relates to the technical field of communications, and provides a communication method and apparatus. The method comprises: a first network element sends a first request message to a second network element, the first request message being used for establishing a call between a first terminal and a second terminal, and when the access type of the first terminal is satellite access type, the first request message comprising access information of the first terminal; the first network element receives a first response message from the second network element, the first response message being used for determining whether communication data between the first terminal and the second terminal is directly exchanged by means of a satellite; and the first network element selects, on the basis of the first response message, a first gateway for serving the first terminal and sends a second request message to the second network element, the second request message comprising information of the first gateway. By using the described method, the first network element can learn whether communication data between the first terminal and the second terminal is directly exchanged by means of a satellite, and accurately selects the first gateway for the first terminal, thereby avoiding media re-negotiation, and reducing delay during session establishment.

Description

A communication method and apparatus

[0001] Cross-reference to Related Applications

[0002] This application claims priority to the Chinese Patent Application No. 202411295957.3, filed on September 14, 2024, and entitled "A communication method and apparatus", the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of communication, in particular to a communication method and apparatus. BACKGROUND

[0004] Communication between terminals accessing via satellites (UE-satellite-UE, UE-Sat-UE) is a concept proposed in Release 19 of the 3rd generation partnership project (3GPP), which refers to the exchange of user plane data (including media streams of a call) directly on a satellite when all parties participating in the call are satellite access, without returning to the ground. The above-mentioned parties participating in the call can access the same satellite or different satellites, and if they access different satellites, the two satellites are connected through one or more inter-satellite links (ISL). UE-Sat-UE communication can avoid the transmission delay caused by the exchange of user plane data returning to the ground, and can save the cost of backhaul resources.

[0005] In the process of establishing an IP multimedia subsystem (IMS) session, if the calling UE is satellite access, the proxy-call session control function (P-CSCF) corresponding to the calling UE (hereinafter referred to as the calling P-CSCF) may select an on-satellite IMS access gateway (IMS-AGW) or a ground IMS-AGW after receiving the session establishment request from the calling UE, because it cannot determine whether the current session can use UE-Sat-UE communication. This may result in media re-negotiation after the calling P-CSCF and the called P-CSCF perform initial media negotiation, increasing the session establishment delay and affecting user experience. SUMMARY

[0006] Embodiments of the present application provide a communication method and device to solve the problem of media renegotiation and increased session establishment delay caused by the inability of the calling P-CSCF to determine whether the current session can use UE-Sat-UE communication.

[0007] In a first aspect, the present application provides a communication method applied to a first network element in a first communication network or a chip or module in the first network element, the first network element being an entry control node for a first terminal to access the first communication network. In the case of the method being applied to the first network element, the first network element sends a first request message to a second network element, the first request message being used to establish a call for the first terminal and a second terminal, the first request message including access information of the first terminal in the case of the access type of the first terminal being satellite access, the second network element being an entry control node for the second terminal to access a second communication network; the first network element receives a first response message from the second network element, the first response message being used to determine whether communication data between the first terminal and the second terminal is exchanged directly through a satellite, and the first network element selects a first gateway serving the first terminal according to the first response message and sends a second request message to the second network element, the second request message including information of the first gateway.

[0008] With the above method, after receiving the first response message, the first network element can know whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite, that is, the first network element can determine whether the current session can use UE-Sat-UE communication. Therefore, the first network element can accurately select the first gateway for the first terminal according to the first response message, avoid media renegotiation, reduce session establishment delay, and improve user experience.

[0009] The first network element does not select a gateway serving the first terminal, and therefore, the first request message does not include information of the gateway, or it can also be understood that, if the first communication network and the second communication network are both IMS networks, the first request message is a session initiation protocol (SIP) session invitation (INVITE) request message or a SIP request message, and the first request message does not include a session description protocol (SDP) offer. The first network element belongs to the first communication network, and the first network element is an entry control node for the first terminal to access the first communication network. The second network element belongs to the second communication network, and the second network element is an entry control node for the second terminal to access the second communication network. The first communication network and the second communication network can be the same or different, and the first network element and the second network element can be the same or different.

[0010] The communication data between the first terminal and the second terminal is exchanged directly through the satellite, which means that the communication data between the first terminal and the second terminal is exchanged through the satellite and is not exchanged through the ground. Alternatively, it can be understood that the communication data between the first terminal and the second terminal is exchanged only through the satellite. The communication data between the first terminal and the second terminal is not exchanged directly through the satellite, which means that the communication data between the first terminal and the second terminal needs to be exchanged through the ground.

[0011] In a possible implementation, before the first network element sends the first request message to the second network element, the first network element can obtain the access information of the first terminal. In an example, the first network element can obtain the access information of the first terminal from the received call request message. Exemplarily, the call request message carries the access information of the first terminal. In another example, the first network element can obtain the access information of the first terminal from a core network accessed by the first terminal.

[0012] In a possible design, when the first gateway serving the first terminal is selected according to the first response message, the first network element determines, according to the first response message, that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, and selects the first gateway deployed on the satellite to serve the first terminal.

[0013] With the above design, the first network element determines, according to the first response message, that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, and can select the first gateway deployed on the satellite to serve the first terminal.

[0014] In a possible design, when the first gateway serving the first terminal is selected according to the first response message, the first network element determines, according to the first response message, that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, and selects the first gateway deployed on the ground to serve the first terminal.

[0015] With the above design, the first network element determines, according to the first response message, that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, and can select the first gateway deployed on the ground to serve the first terminal.

[0016] In a possible design, the first network element sends the information of the first gateway to the first terminal, and the information of the first gateway is used for transmitting the communication data between the first terminal and the first gateway.

[0017] In a possible design, the first response message includes information of a second gateway, the second gateway being a gateway selected by the second network element to serve the second terminal; and the first network element sends the information of the second gateway to the first gateway, and the information of the second gateway is used for transmitting the communication data between the first gateway and the second gateway.

[0018] In a possible design, the first communication network and the second communication network are both IMS networks, the first response message is a SIP response message, and the second request message is a SIP request message; the first response message includes a session description protocol (SDP) offer, and information of the second gateway is carried in the SDP offer; and the second request message includes an SDP answer, and information of the first gateway is carried in the SDP answer. For example, the first response message can be a SIP response message, for example, a 183 response, or a 180 response, or a 200 OK response. The second request message is a SIP request message, and is used to acknowledge receipt of the SIP response message. For example, if the first response message is a 183 response, the second request message is a provisional response acknowledgement (PRACK) request message; and if the first response message is a 200 OK response, the second request message is an acknowledgement (ACK) request message.

[0019] In a possible design, the first response message includes indication information, and the indication information indicates that communication data between the first terminal and the second terminal is directly exchanged through the satellite; or the first response message includes indication information, and the indication information indicates that communication data between the first terminal and the second terminal is not directly exchanged through the satellite; or the first response message does not include indication information, and the first response message is used to indicate that communication data between the first terminal and the second terminal is not directly exchanged through the satellite.

[0020] In a possible design, before sending the first request message, the first network element obtains subscription information of the first terminal, and determines, according to the subscription information, that the first terminal supports directly exchanging communication data through the satellite. For example, if the first terminal supports directly exchanging communication data through the satellite and an access type of the first terminal is satellite access, the first request message carries access information of the first terminal.

[0021] In a possible design, the access information of the first terminal includes that an access type of the first terminal is satellite access, and an identifier of a satellite accessed by the first terminal, or the access information of the first terminal includes an identifier of a satellite accessed by the first terminal.

[0022] In a second aspect, the present application provides a communication method applied to a second network element in a second communication network or a chip or module in the second network element, the second network element being an ingress control node for a second terminal to access the second communication network. In the case that the method is applied to the second network element, the second network element receives a first request message from a first network element, the first request message being used to request to establish a call between the first terminal and the second terminal, the first request message including access information of the first terminal, the first network element being an ingress control node for the first terminal to access a first communication network; the second network element acquires access information of the second terminal, determines whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal, and sends a first response message to the first network element according to a determination result; and the second network element receives a second request message from the first network element, the second request message including information of a first gateway, the first gateway being a gateway selected by the first network element to serve the first terminal.

[0023] By using the above method, the second network element determines whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal, and sends a first response message to the first network element according to a determination result, so that the first network element can know whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the first response message, and then accurately selects a first gateway for the first terminal, thereby avoiding media renegotiation, reducing session establishment delay, and improving user experience.

[0024] In the case that the second network element determines whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal, it can also be understood that the second network element determines whether the first terminal and the second terminal use UE-Sat-UE communication according to the access information of the first terminal and the access information of the second terminal.

[0025] In a possible design, the access information of the first terminal includes that an access type of the first terminal is satellite access and an identifier of a satellite accessed by the first terminal, and the access information of the second terminal includes that an access type of the second terminal is satellite access and an identifier of a satellite accessed by the second terminal; when determining whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal, the second network element determines that the first terminal and the second terminal are both satellite access according to the access type of the first terminal and the access type of the second terminal, and determines that the communication data between the first terminal and the second terminal is exchanged directly through a satellite when the first terminal accesses the same satellite as the second terminal or there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal.

[0026] In a possible design, the access information of the first terminal includes that the access type of the first terminal is satellite access, and an identity of a satellite accessed by the first terminal; the access information of the second terminal includes that the access type of the second terminal is satellite access, and an identity of a satellite accessed by the second terminal; when determining whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal, the second network element determines, according to the access type of the first terminal and the access type of the second terminal, that the first terminal and the second terminal are both satellite access, but determines, according to the identity of the satellite accessed by the first terminal and the identity of the satellite accessed by the second terminal, that there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, and determines that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0027] In a possible design, the access information of the second terminal includes that the access type of the second terminal is not satellite access; when determining whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal, the second network element determines, according to the access type of the second terminal, that the second terminal is not satellite access, and determines that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0028] With the above design, the second network element determines whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal.

[0029] In a possible design, when sending the first response message to the first network element according to the determination result, the second network element includes indication information in the first response message to indicate that the first terminal and the second terminal exchange directly through the satellite when the communication data between the first terminal and the second terminal is exchanged directly through the satellite; includes indication information in the first response message to indicate that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, or does not include indication information in the first response message, when the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0030] In a possible design, the second network element selects the second gateway serving the second terminal according to the determination result.

[0031] In a possible design, when selecting the second gateway serving the second terminal according to the determination result, the second network element selects the second gateway deployed on the satellite to serve the second terminal when the communication data between the first terminal and the second terminal is exchanged directly through the satellite.

[0032] In a possible design, when the second network element determines that the communication data between the first terminal and the second terminal is not directly exchanged through the satellite, the second gateway deployed on the ground is selected to serve the second terminal according to the determination result.

[0033] With the above design, the second network element can select the gateway serving the second terminal according to whether the communication data between the first terminal and the second terminal is directly exchanged through the satellite.

[0034] In a possible design, the first response message includes the information of the second gateway.

[0035] In a possible design, the second network element sends the information of the second gateway to the second terminal, and the information of the second gateway is used to transmit the communication data between the second terminal and the second gateway.

[0036] In a possible design, the second network element sends the information of the first gateway to the second gateway, and the information of the first gateway is used to transmit the communication data between the first gateway and the second gateway.

[0037] In a possible design, the first communication network and the second communication network are both IMS networks, the first response message is an SIP response message, and the second request message is an SIP request message; the first response message includes an SDP offer, and the information of the second gateway is carried in the SDP offer; the second request message includes an SDP answer, and the information of the first gateway is carried in the SDP answer.

[0038] In a third aspect, a communication method is provided. The method is applied to a first network element in a first communication network or a chip or module in the first network element. The first network element is an ingress control node for a first terminal to access the first communication network. In the case that the method is applied to the first network element, the first network element sends a first request message to a second network element. The first request message is used to establish a call between the first terminal and a second terminal. In the case that an access type of the first terminal is satellite access, the first request message includes access information of the first terminal, information of a first gateway, and information of a second gateway. The first gateway and the second gateway are both determined by the first network element to serve the first terminal. The first gateway is a gateway deployed on a satellite, and the second gateway is a gateway deployed on the ground. The second network element is an ingress control node for the second terminal to access a second communication network. The first network element receives a first response message from the second network element. The first response message is used to determine whether communication data between the first terminal and the second terminal is directly exchanged through the satellite. The first network element releases communication resources reserved by the first gateway for the first terminal or communication resources reserved by the second gateway for the first terminal according to the first response message.

[0039] By using the method, the first network element can provide information of two gateways first, information of a gateway deployed on the ground and information of a gateway deployed on a satellite. After receiving the first response message, the first network element can release communication resources reserved by one of the two gateways for the first terminal according to the first response message, avoid media renegotiation, reduce session establishment delay, and improve user experience.

[0040] The first response message is used to determine whether communication data between the first terminal and the second terminal is exchanged directly through the satellite. Alternatively, it can also be understood that the first response message is used by the first network element to determine whether to release communication resources reserved by the first gateway for the first terminal or communication resources reserved by the second gateway for the first terminal, or the first response message is used by the first network element to determine whether the gateway in communication with the gateway serving the second terminal is the first gateway or the second gateway.

[0041] In a possible design, when the first network element releases the communication resources reserved by the first gateway for the first terminal or the communication resources reserved by the second gateway for the first terminal according to the first response message, the first network element determines, according to the first response message, that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, and releases the communication resources reserved by the first gateway for the first terminal.

[0042] By using the above design, the first network element can release the communication resources reserved by one of the two gateways for the first terminal according to whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite.

[0043] In a possible design, when the first network element releases the communication resources reserved by the first gateway for the first terminal or the communication resources reserved by the second gateway for the first terminal according to the first response message, the first network element determines, according to the first response message, that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, and releases the communication resources reserved by the first gateway for the first terminal.

[0044] By using the above design, the first network element can release the communication resources reserved by one of the two gateways for the first terminal according to whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite.

[0045] In a possible design, the first response message includes indication information, the indication information indicates that the communication data between the first terminal and the second terminal is exchanged directly through the satellite; or the first response message includes indication information, the indication information indicates that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite; or the first response message does not include indication information, and the first response message is used to indicate that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0046] In a possible design, the first network element sends information about the gateway that has not released the communication resource to the first terminal, and the information about the gateway that has not released the communication resource is used to transmit communication data between the first terminal and the gateway that has not released the communication resource.

[0047] In a possible design, the first response message includes information about a third gateway, and the third gateway is a gateway selected by the second network element to serve the second terminal; the first network element sends the information about the third gateway to the gateway that has not released the communication resource, and the information about the third gateway is used to transmit communication data between the third gateway and the gateway that has not released the communication resource.

[0048] In a possible design, the first communication network and the second communication network are both IMS networks, the first request message is an SIP request message, and the first response message is an SIP response message; the first request message includes an SDP offer, and the information about the first gateway and the information about the second gateway are carried in the SDP offer; the first response message includes an SDP answer, and the information about the third gateway is carried in the SDP answer.

[0049] In a possible design, the SDP offer includes first information and second information, the first information includes the information about the first gateway, and the second information includes the information about the second gateway; the information about the first gateway includes an IP address and a port number of the first gateway, and deployment location description information of the first gateway, the deployment location description information of the first gateway indicating that the first gateway is a gateway deployed on a satellite; the information about the second gateway includes an IP address and a port number of the second gateway, and deployment location description information of the second gateway, the deployment location description information of the second gateway indicating that the second gateway is a gateway deployed on the ground; the SDP answer includes third information and fourth information, the third information corresponding to the first information, and the fourth information corresponding to the second information; the third information includes information about a third gateway, and the information about the third gateway includes an IP address and a port number of the third gateway, and deployment location description information of the third gateway, the deployment location description information of the third gateway indicating that the third gateway is a gateway deployed on a satellite, and the fourth information includes a preset port number; or the third information includes a preset port number, the fourth information includes information about a third gateway, and the information about the third gateway includes an IP address and a port number of the third gateway, and deployment location description information of the third gateway, the deployment location description information of the third gateway indicating that the third gateway is a gateway deployed on the ground.

[0050] With the above design, the first network element can learn, through the location description information of the third gateway, whether the third gateway is deployed on the ground or on a satellite, and then can release the communication resource reserved for the first terminal by one of the two gateways according to the deployment location of the third gateway.

[0051] In a possible design, before sending the first request message, the first network element acquires subscription information of the first terminal, and determines, according to the subscription information, that the first terminal supports exchanging communication data directly through the satellite. If the first terminal supports exchanging communication data directly through the satellite and the access type of the first terminal is satellite access, the first request message carries access information of the first terminal, information of the first gateway, and information of the second gateway.

[0052] In a possible design, the access information of the first terminal includes that the access type of the first terminal is satellite access, and an identifier of a satellite accessed by the first terminal, or the access information of the first terminal includes an identifier of a satellite accessed by the first terminal.

[0053] In a fourth aspect, this application provides a communication method, which is applied to a second network element in a second communication network or a chip or module in the second network element, the second network element being an ingress control node for a second terminal to access the second communication network. For example, the second network element receives a first request message from a first network element, the first request message being used to establish a call between the first terminal and the second terminal, the first request message including access information of the first terminal, information of a first gateway, and information of a second gateway, the first gateway and the second gateway both being determined by the first network element to serve the first terminal, the first gateway being a gateway deployed on a satellite, the second gateway being a gateway deployed on the ground, and the first network element being an ingress control node for the first terminal to access a first communication network. The second network element acquires access information of the second terminal, determines whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal, and sends a first response message to the first network element according to a determination result.

[0054] By using the method, the second network element receives the first request message, and then obtains information of two gateways according to the first request message, i.e., information of a gateway deployed on the ground and information of a gateway deployed on a satellite. The second network element can determine whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal, and send a first response message to the first network element according to a determination result, so that the first network element releases communication resources reserved by one of the two gateways for the first terminal after receiving the first response message, thereby avoiding media renegotiation, reducing session establishment delay, and improving user experience.

[0055] The communication data between the first terminal and the second terminal is directly exchanged through the satellite, which can be understood as that the communication data between the first terminal and the second terminal is exchanged through the satellite and is not exchanged through the ground. Alternatively, it can be understood that the communication data between the first terminal and the second terminal is exchanged only through the satellite. The communication data between the first terminal and the second terminal is not directly exchanged through the satellite, which can be understood as that the communication data between the first terminal and the second terminal needs to be exchanged through the ground.

[0056] The second network element determines, according to the access information of the first terminal and the access information of the second terminal, whether the communication data between the first terminal and the second terminal is directly exchanged through the satellite, which can also be understood as that the second network element determines, according to the access information of the first terminal and the access information of the second terminal, whether the first terminal and the second terminal adopt UE-Sat-UE communication, or the second network element determines, according to the access information of the first terminal and the access information of the second terminal, which of the first gateway and the second gateway needs to be released by the first network element for the communication resource reserved for the first terminal.

[0057] In a possible design, the access information of the first terminal includes that the access type of the first terminal is satellite access and the identifier of the satellite accessed by the first terminal; the access information of the second terminal includes that the access type of the second terminal is satellite access and the identifier of the satellite accessed by the second terminal; when determining, according to the access information of the first terminal and the access information of the second terminal, whether the communication data between the first terminal and the second terminal is directly exchanged through the satellite, the second network element determines, according to the access type of the first terminal and the access type of the second terminal, that the first terminal and the second terminal are both satellite access, and determines, according to the identifier of the satellite accessed by the first terminal and the identifier of the satellite accessed by the second terminal, that the communication data between the first terminal and the second terminal is directly exchanged through the satellite when the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal or there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal.

[0058] With the above design, the second network element determines, according to the access information of the first terminal and the access information of the second terminal, whether the communication data between the first terminal and the second terminal is directly exchanged through the satellite.

[0059] In a possible design, the access information of the first terminal includes that the access type of the first terminal is satellite access, and the identity of the satellite accessed by the first terminal; the access information of the second terminal includes that the access type of the second terminal is satellite access, and the identity of the satellite accessed by the second terminal; when determining whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal, the second network element determines, according to the access type of the first terminal and the access type of the second terminal, that the first terminal and the second terminal are both satellite access, but determines, according to the identity of the satellite accessed by the first terminal and the identity of the satellite accessed by the second terminal, that there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, and determines that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0060] By using the above design, the second network element determines whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal.

[0061] In a possible design, the access information of the second terminal includes that the access type of the second terminal is not satellite access; when determining whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal, the second network element determines, according to the access type of the second terminal, that the second terminal is not satellite access, and determines that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0062] By using the above design, the second network element determines whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal.

[0063] In a possible design, when the second network element determines that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, the first response message includes indication information indicating that the first terminal and the second terminal are exchanged directly through the satellite; when the second network element determines that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, the first response message includes indication information indicating that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, or the first response message does not include the indication information, and the response message is used to indicate that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0064] In a possible design, the second network element selects a third gateway serving the second terminal according to the determination result, and determines, according to the determination result, a gateway in the first gateway and the second gateway that communicates with the third gateway.

[0065] In a possible design, the second network element determines the third gateway serving the second terminal according to the determination result, and determines the gateway communicating with the third gateway from the first gateway and the second gateway according to the determination result, when the communication data between the first terminal and the second terminal is directly exchanged through the satellite, the third gateway deployed on the satellite is selected to serve the second terminal, and the gateway communicating with the third gateway is determined as the first gateway; or when the communication data between the first terminal and the second terminal is not directly exchanged through the satellite, the third gateway deployed on the ground is selected to serve the second terminal, and the gateway communicating with the third gateway is determined as the second gateway.

[0066] With the above design, the second network element can determine the third gateway serving the second terminal according to whether the communication data between the first terminal and the second terminal is directly exchanged through the satellite, and determine the gateway communicating with the third gateway from the first gateway and the second gateway.

[0067] In a possible design, the first response message includes information of the third gateway.

[0068] In a possible design, the first communication network and the second communication network are both IMS networks, the first request message is an SIP request message, and the first response message is an SIP response message; the first request message includes an SDP offer, and the information of the first gateway and the information of the second gateway are carried in the SDP offer; the first response message includes an SDP answer, and the information of the third gateway is carried in the SDP answer.

[0069] In a possible design, the SDP offer includes first information and second information, the first information includes the information of the first gateway, and the second information includes the information of the second gateway, the information of the first gateway includes an IP address and a port number of the first gateway, and deployment location description information of the first gateway, the deployment location description information of the first gateway indicates that the first gateway is a gateway deployed on a satellite; the information of the second gateway includes an IP address and a port number of the second gateway, and deployment location description information of the second gateway, the deployment location description information of the second gateway indicates that the second gateway is a gateway deployed on the ground; the SDP answer includes third information and fourth information, the third information corresponds to the first information, and the fourth information corresponds to the second information; the third information includes the information of the third gateway, the information of the third gateway includes an IP address and a port number of the third gateway, and deployment location description information of the third gateway, the deployment location description information of the third gateway indicates that the third gateway is a gateway deployed on a satellite, and the fourth information includes a preset port number; or the third information includes a preset port number, the fourth information includes the information of the third gateway, the information of the third gateway includes an IP address and a port number of the third gateway, and deployment location description information of the third gateway, the deployment location description information of the third gateway indicates that the third gateway is a gateway deployed on the ground.

[0070] In a possible design, the second network element sends information of the third gateway to the second terminal, and the information of the third gateway is used to transmit communication data between the second terminal and the third gateway.

[0071] In a possible design, the second network element sends information of a gateway in communication with the third gateway to the third gateway, and the information of the gateway in communication with the third gateway is used to transmit communication data between the gateway in communication with the third gateway and the third gateway.

[0072] In a fifth aspect, a communication apparatus is provided. The communication apparatus can be the first apparatus, or can be a module or unit (e.g., a chip, or a chip system, or a circuit) corresponding to the method / operation / step / action described in any one of the first aspect or the third aspect, or can be used in matching with the first apparatus.

[0073] In a sixth aspect, a communication apparatus is provided. The communication apparatus can be the second apparatus, or can be a module or unit (e.g., a chip, or a chip system, or a circuit) corresponding to the method / operation / step / action described in any one of the second aspect or the fourth aspect, or can be used in matching with the second apparatus.

[0074] In a seventh aspect, a communication device is provided. The communication device includes at least one processing element, and at least one storage element for storing programs and data. The at least one processing element is configured to read and execute the programs and data stored in the storage element, so that the method described in any one of the aspects of the present application is implemented.

[0075] In a possible design, the communication device further includes the at least one storage element.

[0076] In an eighth aspect, a computer program is provided. When the computer program is run on a computer, the computer is caused to perform the method described in any one of the aspects.

[0077] In a ninth aspect, a communication apparatus is provided. The communication apparatus includes an interface circuit and at least one processor. The interface circuit is configured to provide input and / or output of programs or instructions for the at least one processor. The at least one processor is configured to execute the programs or instructions, so that the communication apparatus can implement the method described in any one of the aspects.

[0078] In a possible design, the communication apparatus includes the at least one storage element, and the at least one storage element is configured to store the programs or instructions.

[0079] In a tenth aspect, the present application provides a computer storage medium, which stores a software program, and the software program, when read and executed by one or more processors, can implement the method in any one of the aspects above.

[0080] In an eleventh aspect, the present application provides a computer program product comprising instructions which, when executed on a computer, cause the computer to carry out the method in any one of the aspects above.

[0081] In a twelfth aspect, the present application provides a chip system, which comprises at least one chip and a memory, and the at least one chip is configured to read and execute a program stored in the memory to implement the method in any one of the aspects above.

[0082] On the basis of the implementation provided in the aspects above, the present application can be further combined to provide more implementations. BRIEF DESCRIPTION OF DRAWINGS

[0083] FIG. 1 shows a possible system architecture diagram of an IMS network;

[0084] FIG. 2 shows a possible system architecture diagram of a future real-time communication network;

[0085] FIG. 3 shows a schematic diagram of UE-Sat-UE communication;

[0086] FIG. 4 shows a schematic diagram of SIP message interaction;

[0087] FIG. 5 shows an overview flowchart of a communication method in the present application;

[0088] FIG. 6 shows a flowchart of UE initiating registration to an IMS network in the present application;

[0089] FIG. 7 shows one of the specific flowcharts of UE A and UE B establishing a call;

[0090] FIG. 8 shows another of the specific flowcharts of UE A and UE B establishing a call;

[0091] FIG. 9 shows an overview flowchart of another communication method in the present application;

[0092] FIG. 10 shows a specific flowchart of UE A and UE B establishing a call;

[0093] FIG. 11 shows another specific flowchart of UE A and UE B establishing a call;

[0094] FIG. 12 shows a structural schematic diagram of a communication apparatus in the present application;

[0095] FIG. 13 shows a structural schematic diagram of another communication apparatus in the present application. DETAILED DESCRIPTION

[0096] The specific implementation manners of the present application are described below by combining the drawings in the embodiments of the present application. However, the implementation manners of the present application can also include combining the embodiments without departing from the scope of the present application, such as using other embodiments and making structural changes. Therefore, the detailed description of the following embodiments should not be understood in a limiting sense. The terms used in the embodiment part of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application.

[0097] The embodiments of the present application can be applied to an IMS network or a future real-time communication network. The system architectures of the above two networks are described below:

[0098] 1. IMS network

[0099] A possible system architecture diagram of the IMS network is shown in FIG. 1. The terminal can access the IMS network, and the IMS network can communicate with the 5G core network (5G core, 5GC) or the 4G core network (evolved packet core, EPC). Among them, FIG. 1 mainly involves but is not limited to the following network elements: home subscriber server (HSS), unified data management (UDM) network element, interrogating-call session control function (I-CSCF), serving-call session control function (S-CSCF), P-CSCF, policy control function (PCF) network element, policy and charging rules function (PCRF) network element, IMS application server (AS). Table 1 briefly introduces the functions of each network element involved in FIG. 1.

[0100] Table 1

[0101] In Table 1, the IMS user can be understood as a terminal. The terminal can be a user equipment (UE), a mobile station, a mobile terminal, etc. The terminal can be widely applied to various scenarios, such as device-to-device (D2D), vehicle to everything (V2X) communication, machine-type communication (MTC), internet of things (IOT), virtual reality, augmented reality, industrial control, automatic driving, remote medical treatment, smart power grid, smart furniture, smart office, smart wear, smart transportation, smart city, etc. The terminal can be a mobile phone, a tablet computer, a computer with wireless transceiver function, a wearable device, a vehicle, an urban air vehicle (such as a pilotless plane, a helicopter, etc.), a ship, a robot, a mechanical arm, a smart home device, etc.

[0102] 2. Future real-time communication network

[0103] A possible system architecture diagram of the future real-time communication (RTC) network is shown in FIG. 2. The terminal can access the future RTC network. For example, in FIG. 2, the call media stream between UE A and UE B can be transmitted through media function (MF) A and MF B. The control signaling between UE A and UE B can be transmitted through unified session control function (USF) A and USF B. The MF can be used to implement media processing capabilities such as media negotiation and media forwarding. The USF can be used to implement session access and connection control.

[0104] In the following, only the above IMS network is taken as an example for description. It can be understood that the embodiments of the present application can also be applied to other networks, and the present application does not limit this.

[0105] The following first explains the related terms or technologies involved in the embodiments of the present application. It should be noted that these explanations are to make the embodiments of the present application easier to understand, and should not be regarded as limiting the scope of protection required by the present application.

[0106] 1. UE-Sat-UE communication

[0107] UE-Sat-UE (also referred to as UE-Satellite-UE) communication refers to a communication mode in which user plane data (including media stream of a call) can be exchanged directly on a satellite without going back to the ground when all parties involved in the call are accessing the satellite. The parties involved in the call can access the same satellite or different satellites, and if the parties access different satellites, there is one or more ISLs between the satellites to connect them.

[0108] UE-Sat-UE communication can be understood as a call mode or call manner adopted by the parties involved in the call. UE-Sat-UE communication can also be referred to as UE-Sat-UE mode.

[0109] FIG. 3 shows a schematic diagram of UE-Sat-UE communication.

[0110] Example 1: UE A and UE B access through different satellites, and UE A and UE B can transmit call media stream through the inter-satellite link (ISL) between the two satellites. It can be understood that UE-Sat-UE communication can also use multiple ISLs, that is, there can be one or more satellites between the satellites accessed by the two parties for relaying. For example, the transmission of call media stream between UE A and UE C uses two ISLs (including ISL1 and ISL2).

[0111] Example 2: UE C and UE D access through the same satellite, and UE-Sat-UE communication between UE C and UE D can directly complete the exchange of call media stream on the accessed satellite without involving ISL.

[0112] 2. SIP

[0113] There are two types of responses for SIP:

[0114] (1) Provisional response

[0115] Exemplarily, the provisional response can be represented by 1XX response, where XX represents 00-99, and the response code of the SIP response is 100-199. The provisional response can provide processing progress information of the request message, but cannot be reliably sent.

[0116] (2) Final response

[0117] Exemplarily, responses other than 1XX response are final responses, such as 2XX response, 3XX response, 4XX response, 5XX response, and 6XX response, etc., where XX represents 00-99. The final response can provide the processing result of the request message and can be reliably sent.

[0118] To meet the needs of certain service scenarios, the SIP 100rel extension is currently defined to provide a reliability mechanism for 1XX responses (except 100 response). Illustratively, after a user agent client (UAC) receives a 1XX response other than 100 response, the UAC sends a PRACK request to a user agent server (UAS), the PRACK request is used to confirm that the 1XX response has been received, otherwise the UAS will periodically resend the 1XX response.

[0119] The above process is described below in combination with FIG. 4:

[0120] S401: The UAC sends an INVITE request to the UAS.

[0121] Illustratively, if the UAC supports the 100rel extension, the UAC can carry the 100rel tag in the Supported header field in the INVITE request. If the UAC requires the UAS to reliably transmit a 1XX response (except 100 response), the UAC can carry the 100rel tag in the Require header field in the INVITE request.

[0122] S402: The UAS sends an 18X response to the UAC. The Require header field in the 18X response can carry the 100rel tag, indicating that the UAS requires the UAC to confirm the 18X response.

[0123] S403: The UAC sends a PRACK request to the UAS. The PRACK request is used to confirm that the 18X response has been received. Since the Require header field in the 18X response carries the 100rel tag, the UAC sends the PRACK request to the UAS.

[0124] S404: The UAS sends a 200 OK response to the UAC. The 200 OK response is used to confirm the PRACK request.

[0125] 3. SDP

[0126] SDP offer: The SDP sent by the initiator of media negotiation (SDP offerer) is referred to as an SDP offer, which carries the media types and corresponding media attributes supported by the initiator of media negotiation, for example, the SDP offer can include but is not limited to the IP address and port number of the initiator of media negotiation, codec type, packet length, etc.

[0127] SDP answer: the party receiving the SDP offer (SDP answerer) needs to send an SDP answer to the initiator of the media negotiation, and the party receiving the SDP offer can confirm the media types and corresponding media attributes used in this call from the media types and corresponding media attributes contained in the SDP offer, for example, the SDP answer can include but is not limited to IP address and port number, codec type, packaging duration, etc.

[0128] In the present application, "sending information" can be understood as one device sending information to another device, or also can be understood as one logical module sending information to another logical module in the device. In the present application, "receiving information" can be understood as one device receiving information from another device, or also can be understood as one logical module receiving information from another logical module in the device.

[0129] In the present application, "sending information to (for example, terminal)" or related illustrations in the drawings can be understood as that the destination of the information is the terminal. It can include directly or indirectly sending information to the terminal. "Receiving information from (for example, terminal)" or "receiving information from (for example, terminal)" or "receiving information sent by (for example, terminal)", or related illustrations in the drawings can be understood as that the source of the information is the terminal, which can include directly or indirectly receiving information from the terminal. The information between the source and the destination of the information transmission may be processed as necessary, such as format change, etc., but the destination can understand the valid information from the source. Similar expressions in the present application can be understood similarly, and will not be repeated here.

[0130] When the calling UE accessing the satellite initiates a call to the called UE, since the calling P-CSCF cannot determine whether the current session can use UE-Sat-UE communication, the calling P-CSCF may select the on-board IMS-AGW or the ground IMS-AGW, which may further cause the media re-negotiation after the initial media negotiation is performed by the calling P-CSCF and the called P-CSCF, and further cause the session establishment delay to increase, affecting the user experience. The following are two possible situations that need to perform media re-negotiation:

[0131] Case 1: If the calling P-CSCF selects an on-board IMS-AGW for the calling UE, and the called UE is a non-satellite access, the called P-CSCF selects a ground IMS-AGW for the called UE. Therefore, the path of the end-to-end media stream (i.e., the media stream between the calling UE and the called UE) after the initial media negotiation is completed is: calling UE - on-board IMS-AGW (serving the calling UE) - ground IMS-AGW (serving the called UE) - called UE. Since the current session does not meet the condition of UE-Sat-UE communication (where the called UE is a non-satellite access), the calling P-CSCF needs to reselect a ground IMS-AGW for the calling UE and trigger media re-negotiation to notify the called P-CSCF, so that the path of the end-to-end media stream is changed to: calling UE - ground IMS-AGW (serving the calling UE) - ground IMS-AGW (serving the called UE) - called UE.

[0132] Case 2: If the calling P-CSCF selects a ground IMS-AGW for the calling UE, and the called UE is a satellite access, since the current session meets the condition of UE-Sat-UE communication (where the calling UE and the called UE are both satellite accesses and the satellites accessed by the two are connected), the called P-CSCF selects an on-board IMS-AGW for the called UE. Therefore, the path of the end-to-end media stream after the initial media negotiation is completed is: calling UE - ground IMS-AGW (serving the calling UE) - on-board IMS-AGW (serving the called UE) - called UE. At this time, the calling P-CSCF needs to reselect an on-board IMS-AGW for the calling UE and trigger media re-negotiation to notify the called P-CSCF, so that the path of the end-to-end media stream is changed to: calling UE - on-board IMS-AGW (serving the calling UE) - on-board IMS-AGW (serving the called UE) - called UE.

[0133] Based on this, the embodiments of the present application provide a communication method as shown in FIGS. 5 to 11, which is used to avoid media re-negotiation, reduce session establishment delay, and improve user experience. In the present application, the on-board gateway refers to a gateway deployed on a satellite, for example, an on-board IMS-AGW. The ground gateway refers to a gateway deployed on the ground, for example, a ground IMS-AGW.

[0134] For the convenience of description, in each of the following embodiments, the interaction between the first terminal, the first network element, the second network element, the second terminal and the like is taken as an example for illustration. It can be understood that the application does not limit the execution subject participating in the interaction. The above-mentioned devices can also be replaced by a communication apparatus having a corresponding device function, or a chip, unit or module inside the communication apparatus having a corresponding function. It should be noted that the first network element belongs to the first communication network, and the first network element is an entry control node for the first terminal to access the first communication network. The second network element belongs to the second communication network, and the second network element is an entry control node for the second terminal to access the second communication network. The first communication network and the second communication network can be the same or different, and the first network element and the second network element can be the same or different. For example, the first communication network is a first IMS network, the second communication network is a second IMS network, the first network element is a P-CSCF in the first IMS network, which can also be referred to as a calling P-CSCF, and the second network element is a P-CSCF in the second IMS network, which can also be referred to as a called P-CSCF.

[0135] The application provides a communication method, as shown in FIG. 5, the method comprises the following steps:

[0136] Step 500: The first network element sends a first request message to the second network element. Correspondingly, the second network element receives the first request message from the first network element.

[0137] The first request message is used to establish a call for the first terminal and the second terminal. When the access type of the first terminal is satellite access, the first request message comprises access information of the first terminal. In addition, the first network element does not select a gateway serving the first terminal, and therefore, the information of the gateway is not included in the first request message, or it can also be understood that if the first communication network and the second communication network are both IMS networks, the first request message is a SIP request message, and the first request message does not include an SDP offer.

[0138] Exemplarily, before the first network element sends the first request message to the second network element, the first network element receives a call request message from the first terminal, and the call request message is used by the first terminal to request to establish a call with the second terminal. The first network element sends the first request message to the second network element according to the call request message. The call request message can carry a user identifier of the first terminal and a user identifier of the second terminal. The user identifier of the first terminal can be an IP multimedia public identity (IMPU) of the first terminal, and the user identifier of the second terminal can be an IMPU of the second terminal.

[0139] In addition, the call request message can also include other contents, which can be referred to in the following S701.

[0140] In a possible implementation, before the first network element sends the first request message to the second network element, the first network element can obtain the access information of the first terminal. In an example, the first network element can obtain the access information of the first terminal from the received call request message. Illustratively, the call request message carries the access information of the first terminal. In another example, the first network element can obtain the access information of the first terminal from a core network accessed by the first terminal.

[0141] Further, the first network element can determine whether the access type of the first terminal is satellite access according to the obtained access information of the first terminal. If the access type of the first terminal is satellite access, the first request message carries the access information of the first terminal, otherwise the first request message can not carry the access information of the first terminal.

[0142] In a possible implementation, the first network element can further obtain the subscription information of the first terminal, and determine whether the first terminal supports exchanging communication data directly through a satellite according to the subscription information of the first terminal. If the first terminal supports exchanging communication data directly through a satellite and the access type of the first terminal is satellite access, the first request message carries the access information of the first terminal. If the first terminal does not support exchanging communication data directly through a satellite, or the access type of the first terminal is not satellite access, the first request message can not carry the access information of the first terminal. The first network element can obtain the subscription information of the first terminal in a registration process of the first terminal, and the specific process of obtaining the subscription information of the first terminal by the first network element can refer to the embodiment shown in FIG. 6.

[0143] Step 510: The second network element obtains the access information of the second terminal.

[0144] Illustratively, after the second network element receives the first request message from the first network element, the second network element can obtain the access information of the second terminal from a core network accessed by the second terminal.

[0145] Step 520: The second network element determines whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal.

[0146] The communication data between the first terminal and the second terminal exchanged directly through a satellite can be understood as that the communication data between the first terminal and the second terminal is exchanged through a satellite and is not exchanged through the ground. Or it can be understood as that the communication data between the first terminal and the second terminal is exchanged only through a satellite. The communication data between the first terminal and the second terminal not exchanged directly through a satellite can be understood as that the communication data between the first terminal and the second terminal needs to be exchanged through the ground.

[0147] The second network element determines, according to the access information of the first terminal and the access information of the second terminal, whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite, which can also be understood as that the second network element determines, according to the access information of the first terminal and the access information of the second terminal, whether the first terminal and the second terminal adopt UE-Sat-UE communication.

[0148] The following describes the specific process of the second network element determining whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite in combination with different scenarios:

[0149] Scenario 1: The first terminal accesses through the satellite, and the second terminal accesses through the satellite.

[0150] In a possible implementation, the access information of the first terminal includes that the access type of the first terminal is satellite access, and the identifier of the satellite accessed by the first terminal, and the access information of the second terminal includes that the access type of the second terminal is satellite access, and the identifier of the satellite accessed by the second terminal. For example, the access type of the first terminal is that the first terminal accesses a low-earth orbiting (LEO) satellite based on a new radio (NR) technology or a medium-earth orbiting (MEO) satellite based on the NR technology. The access type of the second terminal is that the second terminal accesses a LEO satellite based on the NR technology or a MEO satellite based on the NR technology.

[0151] Under scenario 1, the second network element can determine, according to the access type of the first terminal and the access type of the second terminal, that the first terminal and the second terminal are both satellite access, and determine, according to the identifier of the satellite accessed by the first terminal and the identifier of the satellite accessed by the second terminal, whether the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal or whether there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal. If the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal, or if there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element determines that the communication data between the first terminal and the second terminal is exchanged directly through the satellite. If the satellite accessed by the first terminal is different from the satellite accessed by the second terminal, and there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element determines that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite. The second network element can determine, according to local configuration data or by querying an external database, whether there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal.

[0152] In another possible implementation, the access information of the first terminal includes the identifier of the satellite accessed by the first terminal, and the access information of the second terminal includes the identifier of the satellite accessed by the second terminal.

[0153] In the scenario 1, the second network element can determine, according to the identity of the satellite accessed by the first terminal and the identity of the satellite accessed by the second terminal, that the first terminal and the second terminal are both satellite access, and judge whether the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal, or whether there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal. If the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal, or it is determined that there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element determines that the communication data between the first terminal and the second terminal is directly exchanged through the satellite. If the satellite accessed by the first terminal is different from the satellite accessed by the second terminal, and there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element determines that the communication data between the first terminal and the second terminal is not directly exchanged through the satellite. Wherein, the second network element can determine whether there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal according to the local configuration data or querying an external database.

[0154] In addition, if the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal, or there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element can select the second gateway deployed on the satellite to serve the second terminal. If the satellite accessed by the first terminal is different from the satellite accessed by the second terminal, and there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element can select the second gateway deployed on the ground to serve the second terminal.

[0155] Scenario 2: The first terminal accesses through a satellite, and the second terminal does not access through a satellite.

[0156] The access information of the first terminal includes that the access type of the first terminal is satellite access, and the identity of the satellite accessed by the first terminal; or the access information of the first terminal includes and the identity of the satellite accessed by the first terminal.

[0157] The access information of the second terminal includes an access type of the second terminal, which is a non-satellite access type such as a ground cellular network access type or a ground wireless local area network (WLAN) access type, and an identifier of a device accessed by the second terminal. The ground cellular network can be a universal terrestrial radio access network (UTRAN) access, an evolved universal terrestrial radio access network (EUTRAN) access, NR, or long term evolution (LTE), and the like. The identifier of the device accessed by the second terminal can be an identifier of a base station or a cell accessed by the second terminal.

[0158] In the scenario 2, when the second network element determines, according to the access type of the second terminal, that the second terminal is not a satellite access, the second network element determines that the communication data between the first terminal and the second terminal is not directly exchanged through the satellite.

[0159] In addition, when the second network element determines, according to the access type of the second terminal, that the second terminal is not a satellite access, the second network element can select a second gateway deployed on the ground to serve the second terminal.

[0160] In a possible implementation, the second network element can also select the second gateway serving the second terminal according to the determination result. The determination result refers to a determination result of whether the communication data between the first terminal and the second terminal is directly exchanged through the satellite.

[0161] For example, when the second network element determines that the communication data between the first terminal and the second terminal is directly exchanged through the satellite, the second network element selects a second gateway deployed on the satellite to serve the second terminal. Or when the second network element determines that the communication data between the first terminal and the second terminal is not directly exchanged through the satellite, the second network element selects a second gateway deployed on the ground to serve the second terminal.

[0162] Step 530: The second network element sends a first response message to the first network element according to the determination result. Correspondingly, the first network element receives the first response message from the second network element. The first response message is used to determine whether the communication data between the first terminal and the second terminal is directly exchanged through the satellite.

[0163] For example, when the second network element determines that the communication data between the first terminal and the second terminal is directly exchanged through the satellite, the first response message includes indication information indicating that the first terminal and the second terminal are directly exchanged through the satellite.

[0164] Exemplarily, the first response message includes the indication information indicating that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, or the first response message does not include the indication information, and the first response message is used to indicate that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0165] If the first communication network and the second communication network are both IMS networks, the specific implementation manner of the first response message is exemplified below in combination with the following examples 1 to 4. It can be understood that the following examples are not a limitation of the present application.

[0166] Example 1: The first response message can include a first header field, and the first header field can be a newly added header field. The newly added header field includes a declarative parameter. The first response message includes the first header field, indicating that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, and the first response message does not include the first header field, indicating that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0167] For example, the first header field can be represented as NTN-attribute: ue-sat-ue or NTN-attribute: ue-satellite-ue.

[0168] Example 2: The first response message can include a first header field, and the first header field can be a newly added header field. The newly added header field includes an assignment parameter. For example, if the parameter value of the parameter is Yes or True, it indicates that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, and if the parameter is not carried or is carried but the parameter value of the parameter is No or False or the newly added header field does not carry the parameter, it indicates that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite. For details, refer to Table 2 below.

[0169] Table 2

[0170] Example 3: The first response message can include a first header field, and the first header field can be an existing header field. A declarative parameter is added to the existing header field. The existing header field carries the parameter to indicate that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, and does not carry the parameter to indicate that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0171] For example, the existing header field is the Contact header field in the SIP message, and the newly added declarative parameter can be ue-sat-ue or ue-satellite-ue. The following two examples indicate that the communication data between the first terminal and the second terminal is exchanged directly through the satellite.

[0172] Example 1, Contact: <sip:+8675520000001@172.16.128.107:10993; transport=udp> ; expires=3600; ue-sat-ue

[0173] Example 2, Contact: <sip:+8675520000001@172.16.128.107:10993; transport=udp> ; expires=3600; ue-satellite-ue

[0174] Example 4: The first response message can comprise a first header field, the first header field can be an existing header field, and a new assignment parameter is added in the existing header field, for example, ue-sat-ue = "yes" / "no" / "true" / "false" or ue-satellite-ue = "yes" / "no" / "true" / "false". For example, if the parameter value of the parameter is Yes or True, it indicates that the communication data between the first terminal and the second terminal is directly exchanged through the satellite, and if the parameter is not carried or is carried but the parameter value of the parameter is No or False, it indicates that the communication data between the first terminal and the second terminal is not directly exchanged through the satellite.

[0175] For example, the existing header field is Contact in the SIP message, and the specific reference can be shown in Table 3.

[0176] Table 3

[0177] In addition, in a possible design, the first response message comprises information of the second gateway.

[0178] Exemplarily, the information of the second gateway can comprise an IP address and a port number of the second gateway. The IP address and the port number can be used for transmitting communication data between the second gateway and the second terminal, and can also be used for transmitting communication data between the second gateway and the gateway serving the first terminal.

[0179] Alternatively, the information of the second gateway can comprise a network-side IP address and a port number of the second gateway, which can be understood as an IP address and a port number used for transmitting communication data between the second gateway and the gateway serving the first terminal. At this time, the information of the second gateway can also be referred to as network-side information of the second gateway.

[0180] Further, the second network element can also send the information of the second gateway to the second terminal, and the information of the second gateway is used for transmitting the communication data between the second terminal and the second gateway.

[0181] Exemplarily, the information of the second gateway can include the IP address and the port number of the second gateway. The IP address and the port number are used for transmitting the communication data between the second gateway and the second terminal, and are also used for transmitting the communication data between the second gateway and the gateway serving the first terminal.

[0182] Alternatively, the information of the second gateway can include the terminal-side IP address and the port number of the second gateway, which can be understood as the IP address and the port number used by the second gateway for transmitting the communication data with the second terminal. In this case, the information of the second gateway can also be referred to as the terminal-side information of the second gateway.

[0183] In addition, the second network element can also send the information of the second terminal to the second gateway, and the information of the second terminal is used for transmitting the communication data between the second terminal and the second gateway. The information of the second terminal includes the IP address and the port number of the second terminal. In this way, the communication data can be transmitted between the second terminal and the second gateway. The specific process can also refer to the embodiments shown in FIG. 7 and FIG. 8.

[0184] Step 540: The first network element selects the first gateway serving the first terminal according to the first response message.

[0185] Exemplarily, the first network element can determine whether the communication data between the first terminal and the second terminal is directly exchanged through the satellite according to the first response message. If the communication data between the first terminal and the second terminal is directly exchanged through the satellite according to the first response message, the first network element selects the first gateway deployed on the satellite to serve the first terminal. If the communication data between the first terminal and the second terminal is not directly exchanged through the satellite according to the first response message, the first network element selects the first gateway deployed on the ground to serve the first terminal.

[0186] Step 550: The first network element sends a second request message to the second network element. Correspondingly, the second network element receives the second request message from the first network element.

[0187] The second request message includes the information of the first gateway. Exemplarily, the information of the first gateway can include the IP address and the port number of the first gateway. The IP address and the port number are used for transmitting the communication data between the first gateway and the first terminal, and are also used for transmitting the communication data between the first gateway and the second gateway.

[0188] Alternatively, the information of the first gateway can comprise a network-side IP address and a port number of the first gateway. The network-side IP address and the port number of the first gateway can be understood as the IP address and the port number used by the first gateway to transmit the communication data with the second gateway. In this case, the information of the first gateway can also be referred to as network-side information of the first gateway.

[0189] In addition, after the first network element receives the first response message (comprising the information of the second gateway) from the second network element, the first network element sends the information of the second gateway to the first gateway. After the second network element receives the second request message (comprising the information of the first gateway) from the first network element, the second network element sends the information of the first gateway to the second gateway. Thus, the communication data can be transmitted between the second gateway and the first gateway.

[0190] The first network element can also send the information of the first gateway to the first terminal, and the information of the first gateway is used to transmit the communication data between the first terminal and the first gateway.

[0191] In this case, the information of the first gateway can comprise an IP address and a port number of the first gateway. The IP address and the port number are used to transmit the communication data between the first gateway and the first terminal, and are also used to transmit the communication data between the first gateway and the second gateway.

[0192] Alternatively, the information of the first gateway can comprise a terminal-side IP address and a port number of the first gateway. The terminal-side IP address and the port number of the first gateway can be understood as the IP address and the port number used by the first gateway to transmit the communication data with the first terminal. In this case, the information of the first gateway can also be referred to as terminal-side information of the first gateway.

[0193] In addition, the first network element can also send the information of the first terminal to the first gateway, and the information of the first terminal is used to transmit the communication data between the first terminal and the first gateway. The information of the first terminal comprises an IP address and a port number of the first terminal. Thus, the communication data can be transmitted between the first terminal and the first gateway. The above specific process can also refer to the embodiments shown in FIG. 7 and FIG. 8.

[0194] As can be seen from the above, the path of the end-to-end media stream, i.e., the first terminal— the first gateway (serving the first terminal)— the second gateway (serving the second terminal)— the second terminal, can be established through one media negotiation. Since the first network element can determine whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite after receiving the first response message, i.e., the first network element can determine whether the current session can use UE-Sat-UE communication, the first network element can accurately select the first gateway for the first terminal, thereby avoiding media re-negotiation, reducing the session establishment delay, and improving the user experience.

[0195] Exemplarily, if the first communication network and the second communication network are both IMS networks, the first response message can be a SIP response message, for example, a 183 response, or a 180 response, or a 200 OK response. The second request message is a SIP request message, used to confirm the reception of the SIP response message. For example, if the first response message is a 183 response, the second request message is a PRACK request message; if the first response message is a 200 OK response, the second request message is an ACK request message. The first response message can include an SDP offer, and the information of the second gateway is carried in the SDP offer. The second request message can include an SDP answer, and the information of the first gateway is carried in the SDP answer. For details, refer to the embodiments shown in FIG. 7 and FIG. 8.

[0196] The embodiment shown in FIG. 6 is a process in which the UE initiates registration to the IMS network. Through the following process, the P-CSCF can obtain the subscription information of the UE, and then determine whether the UE supports direct communication data exchange through the satellite according to the subscription information of the UE. The following UE can correspond to the first terminal (or the second terminal) in the embodiment shown in FIG. 5, and the following P-CSCF can correspond to the first network element (or the second network element) in the embodiment shown in FIG. 5.

[0197] S601: The UE sends a first registration request to the P-CSCF.

[0198] S602: The P-CSCF forwards the first registration request to the I-CSCF.

[0199] S603: The I-CSCF interacts with the HSS / UDM, and the I-CSCF selects a suitable S-CSCF.

[0200] S604: The I-CSCF forwards the first registration request to the S-CSCF.

[0201] S605: The S-CSCF interacts with the HSS / UDM to obtain an authentication element.

[0202] S606: The S-CSCF sends a 401 response to the UE.

[0203] The 401 response carries the authentication element, which is used for the UE to authenticate the network.

[0204] S607: The UE completes the authentication of the network according to the authentication element carried in the 401 response.

[0205] S608: The UE sends a second registration request to the P-CSCF, wherein the second registration request carries an authentication parameter.

[0206] S609: The P-CSCF forwards the second registration request to the I-CSCF.

[0207] S610: The I-CSCF interacts with the HSS / UDM, and the I-CSCF selects a proper S-CSCF.

[0208] S611: The I-CSCF forwards the second registration request to the S-CSCF.

[0209] S612: The S-CSCF interacts with the HSS / UDM, and the S-CSCF completes the authentication of the UE according to the authentication parameter carried in the second registration request.

[0210] S613: The S-CSCF sends a request message to the HSS / UDM, where the request message is used to acquire the subscription information of the UE.

[0211] The request message can be a Cx interface server assignment request (SAR), or an IMS user data management (Nhss_ImsSubscriberDataManagement, Nhss_ImsSDM) request message of the N70 interface.

[0212] S614: The HSS / UDM returns a response message to the S-CSCF, where the response message includes the subscription information of the UE.

[0213] S615: The S-CSCF returns a 200OK response to the I-CSCF, and the 200OK response includes the subscription information of the UE.

[0214] S616: The I-CSCF forwards the 200OK response to the P-CSCF.

[0215] S617: The P-CSCF saves the subscription information of the UE.

[0216] The subscription information of the UE can indicate whether the UE supports exchanging communication data directly through a satellite, or whether the UE supports UE-Sat-UE communication, or whether the UE has subscribed to a UE-Sat-UE service.

[0217] For example, when the P-CSCF determines that the subscription information of the UE includes UE-Sat-UE subscription information, it is determined that the UE supports exchanging communication data directly through a satellite; when the P-CSCF determines that the subscription information of the UE does not include UE-Sat-UE subscription information, it is determined that the UE does not support exchanging communication data directly through a satellite.

[0218] S618: The P-CSCF forwards the 200OK response to the UE.

[0219] Further, in a possible implementation, after obtaining the subscription information of the UE, the S-CSCF can determine whether the UE supports exchanging communication data directly through the satellite according to the subscription information of the UE, and can send a notification message to the P-CSCF according to the determination result, the notification message can be carried by the 200 OK response or be sent separately, which is not limited in the application.

[0220] For example, when the S-CSCF determines that the subscription information of the UE includes the UE-Sat-UE subscription information, it is determined that the UE supports exchanging communication data directly through the satellite, and further, the S-CSCF can send a notification message to the P-CSCF, the notification message indicating that the UE supports exchanging communication data directly through the satellite. For example, the notification message includes the UE-Sat-UE subscription information.

[0221] Alternatively, when the S-CSCF determines that the subscription information of the UE does not include the UE-Sat-UE subscription information, it is determined that the UE does not support exchanging communication data directly through the satellite. Further, the S-CSCF can send a notification message to the P-CSCF, the notification message indicating that the UE does not support exchanging communication data directly through the satellite. In addition, when the UE does not support exchanging communication data directly through the satellite, the S-CSCF can also not send a notification message to the P-CSCF, and the P-CSCF determines that no notification message is received, and then determines that the UE does not support exchanging communication data directly through the satellite.

[0222] FIG. 7 shows one of the specific flowcharts of establishing a call between UE A and UE B, wherein UE A corresponds to the first terminal in FIG. 5, UE B corresponds to the second terminal in FIG. 5, P-CSCF A corresponds to the first network element in FIG. 5, and P-CSCF B corresponds to the second network element in FIG. 5. P-CSCF A is an entry control node for UE A to access IMS network A. P-CSCF B is an entry control node for UE B to access IMS network B. The IMS network A and the IMS network B can be the same or different IMS networks.

[0223] S701: UE A sends a first call request message to P-CSCF A.

[0224] The first call request message is used by UE A to request to establish a call with UE B. For example, the first call request message includes the user identifier of UE A (for example, the IMPU of UE A) and the user identifier of UE B (for example, the IMPU of UE B). The first call request message also includes an SDP offer, and the media address in the SDP offer is the IP address and port number of UE A.

[0225] Exemplarily, UE A initiates a call to UE B, UE A sends a first call request message to P-CSCF A.

[0226] Exemplarily, the first call request message further comprises a first tag, the first tag is used to indicate that the local side supports reliably transmitting 1XX response to the request response side, or to indicate that the local side supports reliably transmitting 1XX response to the request response side and requires the request response side to reliably transmit 1XX response. For example, the first tag is 100rel tag. For example, the support header field in the first call request message can carry the 100rel tag, or the support header field and the requirement header field in the first call request message can carry the 100rel tag.

[0227] S702: P-CSCF A obtains the access information of UE A.

[0228] Exemplarily, after receiving the first call request message, P-CSCF A can obtain the access information of UE A. In an example, P-CSCF A can extract the access information of UE A from a specific header field in the received first call request message. For example, the specific header field is the access network information (P-Access-Network-Info) header field. In another example, P-CSCF A can obtain the access information of UE A from 5GC A or EPC A according to the identifier of UE A. 5GC A or EPC A is the core network accessed by UE A.

[0229] Exemplarily, the access information of UE A can comprise the access type of UE A and the information of the device accessed by UE A. For example, the access type of UE A indicates that UE A accesses LEO satellite based on NR technology or MEO satellite based on NR technology, and the information of the device accessed by UE A is the satellite identifier (Satellite ID) of the satellite accessed by UE A. Or, the access type of UE A indicates that UE A accesses ground NR base station or ground LTE base station, and the information of the device accessed by UE A indicates the identifier of the ground access network device accessed by UE A, such as station ID (Station ID) and cell ID.

[0230] Further, P-CSCF A can determine whether UE A accesses through satellite according to the access information of UE A, or whether the access type of UE A is satellite access.

[0231] S703: P-CSCF A sends a second call request message to P-CSCF B.

[0232] The second call request message is used to establish a call between the UE A and the UE B. The second call request message corresponds to the first request message in FIG. 5. The P-CSCF A stores the SDP offer in the first call request message and generates the second call request message according to the first call request message. In combination with the S702, the P-CSCF A can determine whether the UE A accesses through the satellite according to the access information of the UE A. When the P-CSCF A determines that the access type of the UE A is the satellite access according to the access information of the UE A, the second call request message further includes the access information of the UE A. When the access type of the UE A is the satellite access, the P-CSCF A does not select the gateway serving the UE A, and the second call request message does not include the SDP offer.

[0233] In addition, the P-CSCF A can further obtain the subscription information of the UE A, and determine whether the UE A supports exchanging communication data through the satellite directly based on the subscription information of the UE A. When the UE A supports exchanging communication data through the satellite directly and the access type of the UE A is the satellite access, the second call request message further includes the access information of the UE A. When the UE A does not support exchanging communication data through the satellite directly or the access type of the UE A is the non-satellite access, the second call request message can not include the access information of the UE A. The content included in the second call request message can refer to the existing process. The P-CSCF A can select the gateway deployed on the ground to serve the UE A, and the second call request message can include the SDP offer. The media address in the SDP offer is the network side IP address and the port number of the ground gateway serving the UE A.

[0234] Optionally, the second call request message further includes the first label.

[0235] The P-CSCF A can send the second call request message to the P-CSCF B through the IMS Core A network and the IMS Core B network according to the IMPU of the UE B.

[0236] The P-CSCF B obtains the access information of the UE B in S704.

[0237] The P-CSCF B can obtain the access information of the UE B from the 5GC B or the EPC B after receiving the second call request message. The 5GC B or the EPC B is the core network accessed by the UE B.

[0238] It can be understood that the P-CSCF B can obtain the access information of the UE B after receiving the second call request message. Alternatively, the P-CSCF B can obtain the access information of the UE B before determining whether the communication data between the UE A and the UE B is exchanged directly through the satellite. The present application does not limit the specific timing of the P-CSCF B obtaining the access information of the UE B.

[0239] S705: The P-CSCF B sends a third call request message to the UE B.

[0240] Exemplarily, the P-CSCF B determines the third call request message according to the second call request message, where the third call request message is used to establish a call between the UE A and the UE B. The third call request message further includes the first label.

[0241] S706: The UE B sends a third call response message to the P-CSCF B.

[0242] The third call response message is a response message for the third call request message. The third call response message includes an SDP offer, and the media address in the SDP offer is the IP address and the port number of the UE B. The third call response message further includes the first label. For example, the third call response message is a 183 response message, and the Require header field in the 183 response message carries a 100rel tag, indicating that the UE A needs to confirm the third call response message.

[0243] The P-CSCF B saves the IP address and the port number of the UE B.

[0244] S707: The P-CSCF B determines whether the communication data between the UE A and the UE B is exchanged directly through the satellite according to the access information of the UE A and the access information of the UE B.

[0245] Exemplarily, if the access type of the UE A is satellite access and the access type of the UE B is satellite access, and the satellite accessed by the UE A is the same as the satellite accessed by the UE B, the P-CSCF B determines that the communication data between the UE A and the UE B is exchanged directly through the satellite, that is, the P-CSCF B determines that the UE A and the UE B use UE-Sat-UE communication. If the access type of the UE A is satellite access and the access type of the UE B is satellite access, and there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the P-CSCF B determines that the communication data between the UE A and the UE B is exchanged directly through the satellite.

[0246] If the access type of UE B is non-satellite access, P-CSCF B determines that the communication data between UE A and UE B is not exchanged directly through a satellite, i.e., P-CSCF B determines that UE A and UE B do not use UE-Sat-UE communication.

[0247] S708: P-CSCF B selects a gateway serving UE B and applies for media resources.

[0248] For example, P-CSCF B selects a gateway serving UE B and applies for media resources based on the determination result of S707.

[0249] For example, if P-CSCF B determines that the communication data between UE A and UE B is exchanged directly through a satellite, P-CSCF B can select a gateway deployed on the satellite indicated by the satellite identifier of UE B as the gateway serving UE B according to the satellite identifier of UE B. For the convenience of description, the gateway serving UE B is recorded as IMS-AGW B. Further, P-CSCF B can send a media resource application to IMS-AGW B. After receiving the media resource application, IMS-AGW B can allocate media resources for the call between UE A and UE B. Specifically, IMS-AGW B can determine the network-side IP address and port number of IMS-AGW B and the terminal-side IP address and port number of IMS-AGW B. The network-side IP address and port number of IMS-AGW B are used for transmitting communication data between IMS-AGW B and the gateway serving UE A, and the terminal-side IP address and port number of IMS-AGW B are used for transmitting communication data between IMS-AGW B and UE B. At this time, the second call response message in S709 includes an SDP offer, and the media address in the SDP offer is the network-side IP address and port number of IMS-AGW B. The third PRACK request message in S716 includes an SDP answer, and the media address in the SDP answer is the terminal-side IP address and port number of IMS-AGW B.

[0250] For example, if P-CSCF B determines that the communication data between UE A and UE B is not exchanged directly through the satellite, P-CSCF B can select a gateway deployed on the ground as the gateway serving UE B, and for the convenience of description, the gateway serving UE B is recorded as IMS-AGW B'. Further, P-CSCF B can send a media resource application to IMS-AGW B', and after receiving the media resource application, IMS-AGW B' can allocate media resources for the call between UE A and UE B. Specifically, IMS-AGW B' can determine the network side IP address and port number of IMS-AGW B' and the terminal side IP address and port number of IMS-AGW B'. Wherein, the network side IP address and port number of IMS-AGW B' are used for transmitting communication data between IMS-AGW B' and the gateway serving UE A, and the terminal side IP address and port number of IMS-AGW B' are used for transmitting communication data between IMS-AGW B' and UE B. At this time, the second call response message in S709 includes an SDP offer, and the media address in the SDP offer is the network side IP address and port number of IMS-AGW B'. The third PRACK request message in S716 includes an SDP answer, and the media address in the SDP answer is the terminal side IP address and port number of IMS-AGW B'.

[0251] S709: P-CSCF B sends a second call response message to P-CSCF A.

[0252] Exemplarily, the second call response message is a response message to the second call request message. The second call response message corresponds to the first response message in the above-mentioned FIG. 5. The second call response message further includes a first label. For example, the second call response message is a 183 response message, and the 100rel tag is carried in the requirement header field of the 183 response message.

[0253] Exemplarily, P-CSCF B sends the second call response message based on the determination result of S707. The specific implementation of the second call response message can refer to examples 1 to 4 in the above-mentioned embodiment shown in FIG. 5, and will not be described here.

[0254] Exemplarily, P-CSCF B sends the second call response message to P-CSCF A through the IMS Core B network and the IMS Core A network.

[0255] S710: P-CSCF A selects a gateway for UE A and applies for media resources according to the second call response message.

[0256] For example, if P-CSCF A determines that the communication data between UE A and UE B is exchanged directly through the satellite according to the second call response message, P-CSCF A can select a gateway deployed on the satellite indicated by the satellite identifier of UE A as the gateway serving UE A according to the satellite identifier of UE A, and for the convenience of description, the gateway serving UE A is recorded as IMS-AGW A. Further, P-CSCF A can send a media resource application to IMS-AGW A, and IMS-AGW A can allocate media resources for the call between UE A and UE B after receiving the media resource application, specifically, IMS-AGW A can determine the network side IP address and port number of IMS-AGW A and the terminal side IP address and port number of IMS-AGW A. Wherein, the network side IP address and port number of IMS-AGW A are used for transmitting communication data between IMS-AGW B and IMS-AGW A, and the terminal side IP address and port number of IMS-AGW A are used for transmitting communication data between IMS-AGW A and UE A. At this time, the first call response message in S712 includes an SDP answer, and the media address in the SDP answer is the terminal side IP address and port number of IMS-AGW A. The second PRACK request message in S714 includes an SDP answer, and the media address in the SDP answer is the network side IP address and port number of IMS-AGW A

[0257] For example, if P-CSCF A determines that the communication data between UE A and UE B is exchanged directly through the satellite according to the second call response message, P-CSCF A can select a gateway deployed on the satellite indicated by the satellite identifier of UE A as the gateway serving UE A according to the satellite identifier of UE A, and for the convenience of description, the gateway serving UE A is recorded as IMS-AGW A. Further, P-CSCF A can send a media resource application to IMS-AGW A, and IMS-AGW A can allocate media resources for the call between UE A and UE B after receiving the media resource application, specifically, IMS-AGW A can determine the network side IP address and port number of IMS-AGW A and the terminal side IP address and port number of IMS-AGW A. Wherein, the network side IP address and port number of IMS-AGW A are used for transmitting communication data between IMS-AGW B and IMS-AGW A, and the terminal side IP address and port number of IMS-AGW A are used for transmitting communication data between IMS-AGW A and UE A. At this time, the first call response message in S712 includes an SDP answer, and the media address in the SDP answer is the terminal side IP address and port number of IMS-AGW A. The second PRACK request message in S714 includes an SDP answer, and the media address in the SDP answer is the network side IP address and port number of IMS-AGW A

[0258] S711: P-CSCF A interacts with the core network accessed by UE A to establish a dedicated bearer for the current call.

[0259] Exemplarily, when the communication data between UE A and UE B is exchanged directly through the satellite, the core network accessed by UE A will also first insert an uplink classifier (UL CL) UPF and a local protocol data unit session anchor (PSA) UPF for UE A on the satellite indicated by the satellite identifier of the UE A.

[0260] S712: P-CSCF A sends a first call response message to UE A.

[0261] Exemplarily, P-CSCF A generates the first call response message according to S710, the first call response message includes an SDP answer, and the media address in the SDP answer is the terminal side IP address and port number of the gateway selected in S710. The first call response message also includes a first tag, for example, the first call response message is a 183 response message, and the requirement header field in the 183 response message carries a 100 rel tag.

[0262] S713: UE A sends a first PRACK request message, wherein the first PRACK request message is used to confirm that the first call response message has been received.

[0263] S714: P-CSCF A sends a second PRACK request message to P-CSCF B.

[0264] Exemplarily, P-CSCF A generates the second PRACK request message according to S710, the second PRACK request message includes an SDP answer, and the media address in the SDP answer is the network side IP address and port number of the gateway selected in S710.

[0265] S715: P-CSCF B interacts with the core network accessed by UE B to establish a dedicated bearer for the current call.

[0266] Exemplarily, when the communication data between UE A and UE B is exchanged directly through the satellite, the core network accessed by UE B will also first insert an UL CL UPF and a local PSA UPF for UE B on the satellite indicated by the satellite identifier of the UE B.

[0267] It can be understood that S715 can be executed after S708, and the execution order of S715 is not limited in the present application.

[0268] S716: P-CSCF B sends a third PRACK request message to UE B.

[0269] Exemplarily, P-CSCF A generates the third PRACK request message according to S708 after receiving the second PRACK request message, and the third PRACK request message includes an SDP answer, and the media address in the SDP answer is the terminal side IP address and the port number of the gateway selected in S708.

[0270] S717: UE B sends a 200 OK response message to UE A, and the 200 OK response message is used to acknowledge the third PRACK request message. The 200 OK response message is sent to UE A through each network and network element shown in S717 in FIG. 7.

[0271] Up to now, UE A and UE B complete the call establishment.

[0272] With the embodiment shown in FIG. 7, the establishment of the call media stream path between UE A and UE B can be completed through one-time media negotiation. Since P-CSCF A can learn from P-CSCF B whether the communication data between UE A and UE B is directly exchanged through a satellite, that is, whether UE A and UE B can use UE-Sat-UE communication, P-CSCF A can accurately select a gateway for UE A, and only needs to select a gateway once, thereby avoiding media renegotiation, reducing session establishment delay, and improving user experience.

[0273] FIG. 8 shows a second specific flowchart of establishing a call between UE A and UE B. UE A corresponds to the first terminal in FIG. 5, UE B corresponds to the second terminal in FIG. 5, P-CSCF A corresponds to the first network element in FIG. 5, and P-CSCF B corresponds to the second network element in FIG. 5. P-CSCF A is an entry control node of UE A accessing IMS network A. P-CSCF B is an entry control node of UE B accessing IMS network B. IMS network A and IMS network B can be the same or different IMS networks.

[0274] S801: UE A sends a first call request message to P-CSCF A.

[0275] The first call request message is used by UE A to request to establish a call with UE B. For example, the first call request message includes a user identifier (for example, IMPU of UE A) of UE A and a user identifier (for example, IMPU of UE B) of UE B. The first call request message further includes an SDP offer, and the media address in the SDP offer is the IP address and the port number of UE A.

[0276] Exemplarily, the first call request message does not include the first label.

[0277] S802: The P-CSCF A acquires the access information of the UE A.

[0278] For details, reference can be made to the above S702.

[0279] S803: The P-CSCF A sends a second call request message to the P-CSCF B.

[0280] Since the first call request message does not include the first label, the second call request message also does not include the first label, and other contents can be referred to the above S703.

[0281] S804: The P-CSCF B acquires the access information of the UE B.

[0282] For details, reference can be made to the above S704.

[0283] S805: The P-CSCF B sends a third call request message to the UE B.

[0284] Since the second call request message does not include the first label, the third call request message also does not include the first label, and other contents can be referred to the above S705.

[0285] S806: The UE B sends a temporary response message to the UE A.

[0286] Since the first label is not carried in the third call request message, that is, the reliable transmission of the 1XX response is not required, the UE B generates a temporary response message, for example, a 183 response message, without carrying the SDP. The temporary response message is sent to the UE A through each network and network element shown in S806 in FIG. 8.

[0287] S807: After the UE B is off-hook, the UE B sends a third call response message to the P-CSCF B.

[0288] The off-hook of the UE B can be understood as that the user of the UE B answers the call from the UE A. The third call response message is a response message to the third call request message. The third call response message includes an SDP offer, and the media address in the SDP offer is the IP address and the port number of the UE B. For example, the third call response message is a 200 OK response message.

[0289] The P-CSCF B saves the IP address and the port number of the UE B.

[0290] S808: P-CSCF B determines whether the communication data between UE A and UE B is exchanged directly through the satellite according to the access information of UE A and the access information of UE B.

[0291] For details, refer to S707 above.

[0292] S809: P-CSCF B selects a gateway serving UE B and applies for media resources.

[0293] For details, refer to S708 above.

[0294] S810: P-CSCF B sends a second call response message to P-CSCF A.

[0295] For example, the second call response message is a response message to the second call request message. The second call response message corresponds to the first response message in FIG. 5. For example, the second call response message is a 200 OK response message, and other contents can refer to S709 above.

[0296] S811: P-CSCF A selects a gateway serving UE A and applies for media resources according to the second call response message.

[0297] For details, refer to S710 above.

[0298] S812: P-CSCF A interacts with the core network accessed by UE A to establish a dedicated bearer for the current call.

[0299] For details, refer to S711 above.

[0300] S813: P-CSCF A sends a first call response message to UE A.

[0301] For example, P-CSCF A generates the first call response message according to S809, and the first call response message includes an SDP answer, and the media address in the SDP answer is the terminal side IP address and port number of the gateway selected in S811. For example, the first call response message is a 200 OK response message.

[0302] S814: UE A sends a first ACK request message, wherein the first ACK request message is used to confirm that the call response message has been received.

[0303] S815: P-CSCF A sends a second ACK request message to P-CSCF B.

[0304] Exemplarily, the P-CSCF A generates a second ACK request message according to S811, the second ACK request message includes an SDP answer, and a media address in the SDP answer is a network side IP address and a port number of the gateway selected by S811.

[0305] S816: The P-CSCF B interacts with a core network accessed by the UE B to establish a dedicated bearer for the current call.

[0306] For details, refer to S715 described above.

[0307] S817: The P-CSCF B sends a third ACK request message to the UE B.

[0308] Exemplarily, after receiving the second ACK request message, the P-CSCF A generates a third ACK request message according to S809, the third ACK request message includes an SDP answer, and a media address in the SDP answer is a terminal side IP address and a port number of the gateway selected by S809.

[0309] Up to now, the UE A and the UE B complete call establishment.

[0310] With the embodiment shown in FIG. 8, the establishment of the path of the call media stream between the UE A and the UE B can be completed through one media negotiation. Since the P-CSCF A can learn from the P-CSCF B whether the communication data between the UE A and the UE B is directly exchanged through a satellite, that is, whether the UE A and the UE B can use UE-Sat-UE communication, the P-CSCF A can accurately select a gateway for the UE A, and only needs to select the gateway once, thereby avoiding media renegotiation, reducing session establishment delay, and improving user experience.

[0311] The present application provides a communication method, as shown in FIG. 9, which includes the following steps:

[0312] Step 900: A first network element sends a first request message to a second network element. Correspondingly, the second network element receives the first request message from the first network element.

[0313] The first request message is used to establish a call for a first terminal and a second terminal. In the case that the access type of the first terminal is satellite access, the first request message includes access information of the first terminal, information of a first gateway, and information of a second gateway. The first gateway and the second gateway are both determined by the first network element to serve the first terminal. The first gateway is a gateway deployed on a satellite, and the second gateway is a gateway deployed on the ground.

[0314] The information of the first gateway is used for transmitting communication data between the first gateway and the gateway serving the second terminal. The information of the first gateway can include an IP address and a port number of the first gateway, wherein the IP address and the port number are used for transmitting communication data between the first gateway and the first terminal, and are also used for transmitting communication data between the first gateway and the gateway serving the second terminal.

[0315] Alternatively, the information of the first gateway can include a network-side IP address and a port number of the first gateway, which can be understood as the IP address and the port number used for transmitting communication data between the first gateway and the gateway serving the second terminal. At this time, the information of the first gateway can also be referred to as network-side information of the first gateway.

[0316] The information of the second gateway is used for transmitting communication data between the second gateway and the gateway serving the second terminal. The information of the second gateway can include an IP address and a port number of the second gateway, wherein the IP address and the port number are used for transmitting communication data between the second gateway and the first terminal, and are also used for transmitting communication data between the second gateway and the gateway serving the second terminal.

[0317] Alternatively, the information of the second gateway can include a network-side IP address and a port number of the second gateway, which can be understood as the IP address and the port number used for transmitting communication data between the second gateway and the gateway serving the second terminal. At this time, the information of the second gateway can also be referred to as network-side information of the second gateway.

[0318] Exemplarily, before the first network element sends the first request message to the second network element, the first network element receives a call request message from the first terminal, which is used by the first terminal to request to establish a call with the second terminal. The first network element sends the first request message to the second network element according to the call request message. The specific content of the call request message can refer to the above step 500 or S701.

[0319] In a possible implementation, before the first network element sends the first request message to the second network element, the first network element can obtain the access information of the first terminal. The specific implementation of the first network element obtaining the access information of the first terminal can refer to the above step 500. Further, the first network element can determine whether the access type of the first terminal is satellite access according to the obtained access information of the first terminal. If the access type of the first terminal is satellite access, the first request message carries the access information of the first terminal, the information of the first gateway and the information of the second gateway, otherwise, the content included in the first request message can refer to the existing process, for example, the first network element selects a gateway deployed on the ground for the first terminal, and includes the information of the gateway in the first request message.

[0320] In a possible implementation, the first network element can further acquire subscription information of the first terminal, and determine whether the first terminal supports exchanging communication data directly through the satellite according to the subscription information of the first terminal. If the first terminal supports exchanging communication data directly through the satellite and the access type of the first terminal is satellite access, the first request message carries the access information of the first terminal, the information of the first gateway, and the information of the second gateway. If the first terminal does not support exchanging communication data directly through the satellite, or the access type of the first terminal is not satellite access, the content included in the first request message can refer to the existing process. The specific process in which the first network element acquires the subscription information of the first terminal can refer to the embodiment shown in FIG. 6.

[0321] The difference between the embodiment shown in FIG. 5 and the embodiment shown in FIG. 6 is that, in the embodiment shown in FIG. 5, the first network element does not select the gateway serving the first terminal, while in the embodiment shown in FIG. 6, the first network element selects two gateways for the first terminal, or in other words, the first network element selects the two gateways to serve the first terminal, and the two gateways are the first gateway and the second gateway. For example, if the first communication network and the second communication network are both IMS networks, the first request message includes an SDP offer, and the SDP offer includes the information of the first gateway and the information of the second gateway. The SDP offer including the information of the first gateway and the information of the second gateway can adopt, but is not limited to, the following possible implementation A and possible implementation B:

[0322] Possible implementation A: the SDP offer includes first information and second information, which can also be referred to as first SDP media description and second SDP media description, the first information includes the information of the first gateway, and the second information includes the information of the second gateway, the information of the first gateway includes the IP address and the port number of the first gateway, and optionally, the information of the first gateway further includes the deployment location description information of the first gateway, the deployment location description information of the first gateway indicating that the first gateway is a gateway deployed on a satellite; the information of the second gateway includes the IP address and the port number of the second gateway, and optionally, the information of the second gateway further includes the deployment location description information of the second gateway, the deployment location description information of the second gateway indicating that the second gateway is a gateway deployed on the ground.

[0323] In the following examples, the first information is represented by the first SDP media description, the second information is represented by the second SDP media description, the information of the first gateway is represented by the network side information of the first gateway, and the information of the second gateway is represented by the network side information of the second gateway.

[0324] The following describes the possible implementation A in combination with examples a to c:

[0325] Example a, the SDP offer includes a first SDP media description and a second SDP media description, which contain the network side information of the first gateway and the network side information of the second gateway respectively, the network side information of the first gateway includes the network side IP address and port number of the first gateway, and the deployment location description information of the first gateway; the network side information of the second gateway includes the network side IP address and port number of the second gateway, and the deployment location description information of the second gateway. For example, a possible example of the SDP offer is shown in Table 4-1.

[0326] Table 4-1

[0327] In combination with Table 4-1, the "m=" line contains the port number of the gateway, the "c=" line represents the IP address of the gateway, and the "a=content" line represents the deployment location description information of the gateway, indicating whether the deployment location of the gateway is on the satellite or on the ground. In Table 4-1, there are two groups of "m=" lines and "c=" lines, and there are also two "a=content" lines.

[0328] It can be understood that the application does not limit the specific implementation of the deployment location description information of the gateway, and the following introduces several possible implementation examples:

[0329] Example 1: Use the existing "a=" line, such as the "a=content" line defined in the existing protocol IETF RFC 4796 [6], which can be extended by the token to distinguish the gateway deployed on the satellite and the gateway deployed on the ground, for example, Table 4-1.

[0330] a=content:on-satellite, the token value is on-satellite, indicating the gateway deployed on the satellite;

[0331] a=content:on-ground, the token value is on-ground, indicating the gateway deployed on the ground.

[0332] Example 2: Define a new "a=" line, such as "a=resource-addr", and distinguish the gateway deployed on the satellite and the gateway deployed on the ground through the token.

[0333] a=resource-addr:on-satellite, the token value is on-satellite, indicating the gateway deployed on the satellite;

[0334] a=resource-addr:on-ground, the token value is on-ground, indicating the gateway deployed on the ground.

[0335] Example b, the SDP offer includes a first SDP media description and a second SDP media description, respectively containing the network-side information of the first gateway and the network-side information of the second gateway, the SDP media description in the front of the two SDP media descriptions indicates the gateway deployed on the satellite, the SDP media description in the back indicates the gateway deployed on the ground, or, the SDP media description in the back of the two SDP media descriptions indicates the gateway deployed on the satellite, the SDP media description in the front indicates the gateway deployed on the ground. The network-side information of the first gateway includes the network-side IP address and port number of the first gateway, and does not include the deployment location description information of the first gateway; the network-side information of the second gateway includes the network-side IP address and port number of the second gateway, and does not include the deployment location description information of the second gateway.

[0336] For example, a possible example of the SDP offer is shown in Table 4-2, in which the order of the two SDP media descriptions in the SDP offer is agreed in advance, wherein the first SDP media description (e.g., all content before the second "m=" line from the first "m=" line) indicates the gateway deployed on the satellite, and the second SDP media description (e.g., all content between the second "m=" line and the last "a=" line) indicates the gateway deployed on the ground. At this time, there is no need for a specific "a=" line to indicate whether the deployment location of the gateway is on the satellite or on the ground.

[0337] Table 4-2

[0338] Example c, the SDP offer includes a first SDP media description and a second SDP media description, respectively including the network-side information of the first gateway and the network-side information of the second gateway, the network-side information of the first gateway includes the network-side IP address and port number of the first gateway, and the deployment location description information of the first gateway; the network-side information of the second gateway includes the network-side IP address and port number of the second gateway, and does not include the deployment location description information of the second gateway. Alternatively, the network-side information of the first gateway includes the network-side IP address and port number of the first gateway, and does not include the deployment location description information of the first gateway; the network-side information of the second gateway includes the network-side IP address and port number of the second gateway, and the deployment location description information of the second gateway.

[0339] For example, a possible example of the SDP offer is shown in Table 4-3, in which only for the gateway deployed on the satellite, the corresponding "a=resource-on-satellite" line is added. The "m=" line and "c=" line in the SDP media description containing this "a=" line indicate the network-side IP address and port number of the gateway deployed on the satellite. The "m=" line and "c=" line in another SDP media description not containing this "a=" line indicate the network-side IP address and port number of the gateway deployed on the ground.

[0340] Table 4-3

[0341] For example, a possible example of the SDP offer is shown in Table 4-4, where the corresponding "a=resource-on-ground" line is added only for the gateway deployed on the ground. The "m=" line and the "c=" line in the SDP media description containing this "a=" line indicate the network side IP address and port number of the gateway deployed on the ground. The "m=" line and the "c=" line in the other SDP media description not containing this "a=" line indicate the network side IP address and port number of the gateway deployed on the satellite.

[0342] Table 4-4

[0343] Possible implementation B: the SDP offer includes the network side information of the second gateway in one SDP media description, the network side information of the second gateway including the network side IP address and port number of the second gateway; and a newly defined "a=" line is added in this SDP media description to carry the network side information of the gateway deployed on the satellite, i.e. the network side information of the first gateway is carried by the newly defined "a=" line. The network side information of the first gateway includes the network side IP address and port number of the first gateway.

[0344] A possible example of the SDP offer is shown in Table 5.

[0345] Table 5

[0346] In combination with Table 5, the "m=" line contains the port number of the gateway deployed on the ground, and the "c=" line indicates the IP address of the gateway deployed on the ground. Table 5 includes a group of "m=" lines and "c=" lines. A newly defined "a=" line is shown in Table 5 as the "a=satcon" line, which indicates the IP address and port number of the gateway deployed on the satellite.

[0347] The specific format of the above "a=" line can be: a=[attribute name]:[IP type][IP address][port number]. Wherein, the IP type takes the value of "IP4" or "IP6", representing IPv4 and IPv6 respectively.

[0348] For "a=satcon:IP4 192.0.2.1 12340" in Table 5, "192.0.2.1" is the IP address of the first gateway, "12340" is the port number of the first gateway, and "IP4" indicates that the IP address type of the first gateway is IPv4.

[0349] Step 910: The second network element acquires the access information of the second terminal.

[0350] The step 510 can be specifically referred to.

[0351] Step 920: The second network element determines whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal.

[0352] The communication data between the first terminal and the second terminal exchanged directly through the satellite can be understood as that the communication data between the first terminal and the second terminal is exchanged through the satellite and is not exchanged through the ground. Or it can be understood as that the communication data between the first terminal and the second terminal is exchanged only through the satellite. The communication data between the first terminal and the second terminal is not exchanged directly through the satellite can be understood as that the communication data between the first terminal and the second terminal needs to be exchanged through the ground.

[0353] The second network element determines whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal can also be understood as that the second network element determines whether the first terminal and the second terminal adopt UE-Sat-UE communication according to the access information of the first terminal and the access information of the second terminal, or the second network element determines the gateway in the first gateway and the second gateway which communicates with the gateway serving the second terminal according to the access information of the first terminal and the access information of the second terminal, or the second network element determines the gateway in the first gateway and the second gateway which needs the first network element to release the communication resource reserved for the first terminal according to the access information of the first terminal and the access information of the second terminal.

[0354] The following is described in combination with different scenarios:

[0355] Scenario 1: The first terminal accesses through the satellite, and the second terminal accesses through the satellite.

[0356] Under scenario 1, the specific process in which the second network element determines whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite can be referred to the related description of scenario 1 in the embodiment shown in FIG. 5.

[0357] In addition, if the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal, or there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element can select a third gateway deployed on the satellite to serve the second terminal; or, if the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal, or there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element can select a third gateway deployed on the satellite to serve the second terminal, and determine the gateway in communication with the third gateway as the first gateway; or, if the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal, or there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element can select a third gateway deployed on the satellite to serve the second terminal, and determine the gateway that needs to be released by the first network element to reserve the communication resource for the first terminal as the second gateway.

[0358] If the satellite accessed by the first terminal is different from the satellite accessed by the second terminal, and there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element can select a third gateway deployed on the ground to serve the second terminal; or, if the satellite accessed by the first terminal is different from the satellite accessed by the second terminal, and there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element can select a third gateway deployed on the ground to serve the second terminal, and determine the gateway in communication with the third gateway as the second gateway; or, if the satellite accessed by the first terminal is different from the satellite accessed by the second terminal, and there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, the second network element can select a third gateway deployed on the ground to serve the second terminal, and determine the gateway that needs to be released by the first network element to reserve the communication resource for the first terminal as the first gateway.

[0359] Scenario 2: The first terminal accesses through a satellite, and the second terminal does not access through a satellite.

[0360] Under scenario 2, the second network element determines that the communication data between the first terminal and the second terminal is not directly exchanged through a satellite, and the specific process can refer to the related description of scenario 2 in the embodiment shown in FIG. 5.

[0361] In addition, when the second network element determines, according to the access type of the second terminal, that the second terminal is not satellite access, the second network element can select a third gateway deployed on the ground to serve the second terminal; or when the second network element determines, according to the access type of the second terminal, that the second terminal is not satellite access, the second network element can select a third gateway deployed on the ground to serve the second terminal and determine a gateway in communication with the third gateway as the second gateway; or when the second network element determines, according to the access type of the second terminal, that the second terminal is not satellite access, the second network element can select a third gateway deployed on the ground to serve the second terminal and determine a gateway that needs the first network element to release the communication resource reserved for the first terminal as the first gateway.

[0362] In a possible implementation, the second network element can further select, according to the determination result, a third gateway to serve the second terminal; or the second network element can further select, according to the determination result, a third gateway to serve the second terminal and determine a gateway in communication with the third gateway from the first gateway and the second gateway as the second gateway; or the second network element can further select, according to the determination result, a third gateway to serve the second terminal and determine a gateway that needs the first network element to release the communication resource reserved for the first terminal from the first gateway and the second gateway.

[0363] The determination result refers to a determination result of whether the second network element determines that the communication data between the first terminal and the second terminal is directly exchanged through the satellite.

[0364] For example, when the second network element determines that the communication data between the first terminal and the second terminal is directly exchanged through the satellite, the second network element can select a third gateway deployed on the satellite to serve the second terminal; or when the second network element determines that the communication data between the first terminal and the second terminal is directly exchanged through the satellite, the second network element can select a third gateway deployed on the satellite to serve the second terminal and determine a gateway in communication with the third gateway as the first gateway; or when the second network element determines that the communication data between the first terminal and the second terminal is directly exchanged through the satellite, the second network element can select a third gateway deployed on the satellite to serve the second terminal and determine a gateway that needs the first network element to release the communication resource reserved for the first terminal as the second gateway.

[0365] Exemplarily, when the second network element determines that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, the second network element can select the third gateway deployed on the ground to serve the second terminal; or, when the second network element determines that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, the second network element can select the third gateway deployed on the ground to serve the second terminal, and determine the gateway in communication with the third gateway as the second gateway; or, when the second network element determines that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, the second network element can select the third gateway deployed on the ground to serve the second terminal, and determine the gateway that needs to be released by the first network element to reserve the communication resource for the first terminal as the first gateway.

[0366] Further, the second network element can also send the information of the third gateway to the second terminal, and the information of the third gateway is used to transmit the communication data between the second terminal and the third gateway.

[0367] Exemplarily, the information of the third gateway can include the IP address and the port number of the third gateway, wherein the IP address and the port number are used to transmit the communication data between the third gateway and the second terminal, and are also used to transmit the communication data between the third gateway and the gateway serving the first terminal.

[0368] Or the information of the third gateway can include the terminal-side IP address and the port number of the second gateway, and the terminal-side IP address and the port number of the third gateway can be understood as the IP address and the port number used by the third gateway to transmit the communication data with the second terminal. At this time, the information of the third gateway can also be referred to as the terminal-side information of the third gateway.

[0369] The second network element can also send the information of the second terminal to the third gateway, and the information of the second terminal is used to transmit the communication data between the second terminal and the third gateway, wherein the information of the second terminal includes the IP address and the port number of the second terminal. At this time, the communication data can be transmitted between the second terminal and the third gateway.

[0370] In addition, the second network element can also send the information of the gateway in communication with the third gateway to the third gateway, for example, if the gateway in communication with the third gateway is the first gateway, the second network element sends the information of the first gateway to the third gateway, or if the gateway in communication with the third gateway is the second gateway, the second network element sends the information of the second gateway to the third gateway. At this time, the communication data can be transmitted between the gateway in communication with the third gateway and the third gateway. The above specific process can also refer to the embodiment shown in FIG. 10.

[0371] Step 930: The second network element sends a first response message to the first network element according to the determination result. Correspondingly, the first network element receives the first response message from the second network element. The first response message is used to determine whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite.

[0372] Alternatively, the first response message can be used by the first network element to determine whether to release the communication resource reserved by the first gateway for the first terminal or the communication resource reserved by the second gateway for the first terminal, or the first response message can be used by the first network element to determine whether the gateway communicating with the gateway serving the second terminal is the first gateway or the second gateway.

[0373] The first response message further includes information of a third gateway.

[0374] Exemplarily, the information of the third gateway can include an IP address and a port number of the third gateway. The IP address and the port number can be used for transmission of communication data between the third gateway and the second terminal, or can be used for transmission of communication data between the third gateway and the gateway serving the first terminal.

[0375] Alternatively, the information of the third gateway can include a network-side IP address and a port number of the third gateway, which can be understood as the IP address and the port number used by the third gateway for transmission of communication data with the gateway serving the first terminal. At this time, the information of the third gateway can also be referred to as network-side information of the third gateway.

[0376] Exemplarily, if the first communication network and the second communication network are both IMS networks, the first response message includes an SDP answer, and the SDP answer includes the information of the third gateway.

[0377] Step 940: The first network element releases the communication resource reserved by the first gateway for the first terminal or the communication resource reserved by the second gateway for the first terminal according to the first response message.

[0378] The following describes several possible implementation manners of the first response message and how to release the communication resource reserved by the first gateway for the first terminal or the communication resource reserved by the second gateway for the first terminal according to the first response message:

[0379] Possible implementation manner 1:

[0380] When the second network element determines that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, the first response message includes indication information indicating that the first terminal and the second terminal exchange directly through the satellite. Further, the first network element determines, according to the first response message, that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, and releases the communication resource reserved by the second gateway for the first terminal.

[0381] The first response message includes indication information indicating that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, or the first response message does not include the indication information, and the first response message is used to indicate that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite. Further, the first network element determines, according to the first response message, that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, and releases the communication resource reserved by the first gateway for the first terminal.

[0382] In addition, the possible implementation manner 1 is similar to the possible implementation manner of the first response message in the embodiment shown in FIG. 5, and specific reference can be made to examples 1 to 4 in the embodiment shown in FIG. 5, which will not be described herein again.

[0383] Possible implementation manner 2:

[0384] If the first communication network and the second communication network are both IMS networks, the first response message includes an SDP answer, and in combination with the possible implementation manner A, the SDP answer includes third information and fourth information, which can also be referred to as third SDP media description and fourth SDP media description, the third information corresponds to the first information, and the fourth information corresponds to the second information; wherein the third information includes information of the third gateway, the information of the third gateway includes an IP address and a port number of the third gateway, optionally, the third information further includes deployment location description information of the third gateway, the deployment location description information of the third gateway indicates that the third gateway is a gateway deployed on a satellite, and the fourth information includes a preset value of the port number; or the third information includes a preset value of the port number, and the fourth information includes information of the third gateway, the information of the third gateway includes an IP address and a port number of the third gateway, optionally, the fourth information further includes deployment location description information of the third gateway, and the deployment location description information of the third gateway indicates that the third gateway is a gateway deployed on the ground. For example, the preset value of the port number can be 0.

[0385] In the following examples, the third information is represented by the third SDP media description, the fourth information is represented by the fourth SDP media description, and the information of the third gateway is represented by network side information of the third gateway.

[0386] Corresponding to the above example a, the SDP answer includes a third SDP media description and a fourth SDP media description, wherein one SDP media description includes the network side information of the third gateway, and the network side information of the third gateway includes the network side IP address and port number of the third gateway, and the deployment location description information of the third gateway. The other SDP media description includes the preset value of the port number and the deployment location description information of the non-third gateway. Taking the third gateway as the gateway deployed on the satellite as an example, and in combination with the above table 4-1, a possible example of the SDP answer is shown in table 6-1.

[0387] Table 6-1

[0388] Corresponding to the above example b, the SDP answer includes a third SDP media description and a fourth SDP media description, wherein one SDP media description includes the network side information of the third gateway, and the other SDP media description includes the preset value of the port number, and the network side information of the third gateway includes the network side IP address and port number of the third gateway, and does not include the deployment location description information of the third gateway. If the third gateway is the gateway deployed on the satellite, the SDP media description including the network side information of the third gateway is arranged in front of the SDP media description including the preset value of the port number in the SDP answer, or the SDP media description including the network side information of the third gateway is arranged behind the SDP media description including the preset value of the port number in the SDP answer. The order of the two SDP media descriptions in the SDP answer is consistent with the order of the two SDP media descriptions in the SDP offer. For example, in the SDP offer, the first SDP media description is arranged in front of the second SDP media description, then in the SDP answer, the third SDP media description is arranged in front of the fourth SDP media description. If the first SDP media description indicates the gateway deployed on the satellite, when the third SDP media description includes the network side information of the third gateway, the third gateway is the gateway deployed on the satellite.

[0389] Taking the third gateway as the gateway deployed on the satellite as an example, assuming that the network side information contained in the SDP media description in front of the order in the SDP offer indicates the gateway deployed on the satellite, and the network side information contained in the SDP media description behind the order in the SDP offer indicates the gateway deployed on the ground, in combination with the above table 4-2, a possible example of the SDP answer is shown in table 6-2. The third gateway is the gateway deployed on the satellite.

[0390] Table 6-2

[0391] Corresponding to the example c, the SDP answer includes a third SDP media description and a fourth SDP media description, wherein one SDP media description includes the network side information of the third gateway, and the other SDP media description includes the preset value of the port number, the network side information of the third gateway includes the network side IP address and the port number of the third gateway, and the deployment location description information of the third gateway. Alternatively, one SDP media description includes the network side information of the third gateway, the information of the third gateway includes the IP address and the port number of the third gateway, and does not include the deployment location description information of the third gateway, and the other SDP media description includes the preset value of the port number and the deployment location description information of the non-third gateway.

[0392] The following takes the third gateway as the gateway deployed on the satellite, and the information of the third gateway includes the deployment location description information of the third gateway as an example for description. In combination with the above Table 4-3, one possible example of the SDP answer is shown in Table 6-3.

[0393] Table 6-3

[0394] The following takes the third gateway as the gateway deployed on the satellite, and the information of the third gateway does not include the deployment location description information of the third gateway as an example for description. In combination with the above Table 4-4, one possible example of the SDP answer is shown in Table 6-4.

[0395] Table 6-4

[0396] Through the above possible implementation manner 2, the first response message can not directly indicate whether the communication data between the first terminal and the second terminal is directly exchanged through the satellite, or in other words, the first response message can not add a new header field or add a new parameter in an existing header field. The first response message can directly or indirectly indicate that the third gateway is a gateway deployed on a satellite or a gateway deployed on the ground, so that the first network element can determine, according to the first response message, that the third gateway is a gateway deployed on a satellite or a gateway deployed on the ground, thereby releasing the resources reserved by the second gateway for the first terminal when the third gateway is a gateway deployed on a satellite, and releasing the resources reserved by the first gateway for the first terminal when the third gateway is a gateway deployed on the ground. Alternatively, it can also be understood that the first response message can directly or indirectly indicate that the rejected gateway is a gateway deployed on a satellite or a gateway deployed on the ground, so that the first network element can determine, according to the first response message, that the rejected gateway is a gateway deployed on a satellite or a gateway deployed on the ground, thereby releasing the resources reserved by the first gateway for the first terminal when the rejected gateway is a gateway deployed on a satellite (i.e., the first gateway), and releasing the resources reserved by the second gateway for the first terminal when the rejected gateway is a gateway deployed on the ground (i.e., the second gateway).

[0397] Possible implementation manner 3:

[0398] If the first communication network and the second communication network are both IMS networks, the first response message includes an SDP answer, and the SDP answer includes network-side information of the third gateway. In combination with the above possible implementation manner B, the following takes the third gateway as an example of a gateway deployed on a satellite, and in combination with the above Table 5, one possible example of the SDP answer is shown in Table 7-1.

[0399] Table 7-1

[0400] In combination with Table 7-1, the port number in the “m=” line is zero, indicating that the third gateway is a gateway deployed on a satellite, and also indicating that the first network element needs to release the resources reserved by the second gateway for the first terminal.

[0401] In combination with the above possible implementation manner B, the following takes the third gateway as an example of a gateway deployed on the ground, and in combination with the above Table 5, one possible example of the SDP answer is shown in Table 7-2.

[0402] Table 7-2

[0403] In combination with Table 7-2, the port number in the “m=” line is a valid value, indicating that the third gateway is a gateway deployed on the ground, and also indicating that the first network element needs to release the resources reserved by the first gateway for the first terminal.

[0404] In addition, the first network element sends the information of the gateway that has not released the communication resources to the first terminal, and the information of the gateway that has not released the communication resources is used for transmitting communication data between the first terminal and the gateway that has not released the communication resources.

[0405] At this time, the information of the gateway that has not released the communication resources can include the IP address and the port number of the gateway that has not released the communication resources, wherein the IP address and the port number are used for transmitting communication data between the gateway that has not released the communication resources and the first terminal, and are also used for transmitting communication data between the gateway that has not released the communication resources and the third gateway.

[0406] Alternatively, the information of the gateway that has not released the communication resources can include the terminal-side IP address and the port number of the gateway that has not released the communication resources, and the terminal-side IP address and the port number of the gateway that has not released the communication resources can be understood as the IP address and the port number used for transmitting communication data between the gateway that has not released the communication resources and the first terminal. At this time, the information of the gateway that has not released the communication resources can also be referred to as the terminal-side information of the gateway that has not released the communication resources.

[0407] Further, the first network element can also send the information of the first terminal to the gateway which has not released the communication resource, and the information of the first terminal is used for transmitting the communication data between the first terminal and the gateway which has not released the communication resource. The information of the first terminal includes the IP address and the port number of the first terminal. In this way, the communication data can be transmitted between the first terminal and the gateway which has not released the communication resource. The specific process can also refer to the embodiment shown in FIG. 10.

[0408] From the above, it can be known that the path of the end-to-end media stream can be established through one media negotiation. The first network element can provide the information of the two gateways first, and after receiving the first response message, release the communication resource reserved for the first terminal by one of the gateways, thereby avoiding media renegotiation, reducing the session establishment delay, and improving the user experience.

[0409] FIG. 10 shows a third specific flowchart of establishing a call between UE A and UE B. UE A corresponds to the first terminal in FIG. 9, UE B corresponds to the second terminal in FIG. 9, P-CSCF A corresponds to the first network element in FIG. 9, and P-CSCF B corresponds to the second network element in FIG. 9. P-CSCF A is an entry control node for UE A to access IMS network A. P-CSCF B is an entry control node for UE B to access IMS network B. IMS network A and IMS network B can be the same or different IMS networks.

[0410] S1001: UE A sends a first call request message to P-CSCF A.

[0411] For details, refer to S701.

[0412] S1002: P-CSCF A obtains the access information of UE A.

[0413] For details, refer to S702.

[0414] S1003: P-CSCF A selects the gateway serving UE A.

[0415] In combination with S1002, P-CSCF A can determine whether UE A accesses through a satellite according to the access information of UE A. When P-CSCF A determines that the access type of UE A is satellite access according to the access information of UE A, P-CSCF A selects the gateway serving UE A, including IMS-AGW A and IMS-AGW A', wherein IMS-AGW A is a gateway deployed on a satellite indicated by the satellite identifier of UE A, and IMS-AGW A' is a gateway deployed on the ground.

[0416] Further, the P-CSCF A can also acquire the subscription information of the UE A, and determine whether the UE A supports exchanging communication data directly through the satellite based on the subscription information of the UE A. If the UE A supports exchanging communication data directly through the satellite and the access type of the UE A is satellite access, the P-CSCF A selects the IMS-AGW A and the IMS-AGW A'. If the UE A does not support exchanging communication data directly through the satellite, or the access type of the UE A is non-satellite access, the P-CSCF A can select a gateway deployed on the ground to serve the UE A.

[0417] The P-CSCF A can send a media resource application to the IMS-AGW A, and the IMS-AGW A can allocate media resources for the call between the UE A and the UE B after receiving the media resource application. Specifically, the IMS-AGW A can determine the network side IP address and port number of the IMS-AGW A and the terminal side IP address and port number of the IMS-AGW A. The P-CSCF A can also send a media resource application to the IMS-AGW A', and the IMS-AGW A' can allocate media resources for the call between the UE A and the UE B after receiving the media resource application. Specifically, the IMS-AGW A' can determine the network side IP address and port number of the IMS-AGW A' and the terminal side IP address and port number of the IMS-AGW A'.

[0418] S1004: The P-CSCF A sends a second call request message to the P-CSCF B.

[0419] The second call request message is used to establish a call between the UE A and the UE B. The second call request message corresponds to the first request message in FIG. 9. Illustratively, the P-CSCF A saves the SDP offer in the call request message, and generates the second call request message according to the first call request message. The second call request message includes the access information of the UE A, the network side information of the IMS-AGW A, and the network side information of the IMS-AGW A'. The network side information of the IMS-AGW A includes the network side IP address and port number of the IMS-AGW A. The network side information of the IMS-AGW A' includes the network side IP address and port number of the IMS-AGW A'.

[0420] Optionally, the second call request message further includes the first label.

[0421] Illustratively, the P-CSCF A can send the second call request message to the P-CSCF B through the IMS Core A network and the IMS Core B network according to the IMPU of the UE B.

[0422] S1005: The P-CSCF B acquires the access information of the UE B.

[0423] For details, refer to S704 above.

[0424] S1006: The P-CSCF B determines whether the communication data between the UE A and the UE B is exchanged directly through the satellite based on the access information of the UE A and the access information of the UE B.

[0425] For details, refer to S707 above.

[0426] S1007: The P-CSCF B selects a gateway serving the UE B and applies for media resources and determines a gateway communicating with the gateway serving the UE B.

[0427] For example, the P-CSCF B selects the gateway serving the UE B and applies for media resources based on the determination result of S1005.

[0428] For example, if the P-CSCF B determines that the communication data between the UE A and the UE B is exchanged directly through the satellite, the P-CSCF B can select a gateway deployed on the satellite indicated by the satellite identifier of the UE B to serve the UE B according to the satellite identifier of the UE B. For the convenience of description, the gateway serving the UE B is denoted as IMS-AGW B. Further, the P-CSCF B determines that the gateway communicating with the IMS-AGW B is the IMS-AGW A.

[0429] In addition, the P-CSCF B can send a media resource application to the IMS-AGW B, and the IMS-AGW B can allocate media resources for the call between the UE A and the UE B after receiving the media resource application. Specifically, the IMS-AGW B can determine the network side IP address and port number of the IMS-AGW B and the terminal side IP address and port number of the IMS-AGW B. The network side IP address and port number of the IMS-AGW B are used for transmitting communication data between the IMS-AGW B and the IMS-AGW A, and the terminal side IP address and port number of the IMS-AGW B are used for transmitting communication data between the IMS-AGW B and the UE B. At this time, the second call response message in S1010 includes an SDP answer, and the media address in the SDP answer is the network side IP address and port number of the IMS-AGW B. The third call request message in S1008 includes an SDP request, and the media address in the SDP request is the terminal side IP address and port number of the IMS-AGW B.

[0430] For example, if P-CSCF B determines that the communication data between UE A and UE B is not exchanged directly through the satellite, P-CSCF B can select a gateway deployed on the ground to serve UE B, and for the convenience of description, the gateway serving UE B is recorded as IMS-AGW B'. Further, P-CSCF B determines that the gateway communicating with IMS-AGW B' is IMS-AGW A'.

[0431] In addition, P-CSCF B can send a media resource application to IMS-AGW B', and IMS-AGW B' can allocate media resources for the call between UE A and UE B after receiving the media resource application. Specifically, IMS-AGW B' can determine the network-side IP address and port number of IMS-AGW B' and the terminal-side IP address and port number of IMS-AGW B'. Wherein, the network-side IP address and port number of IMS-AGW B' are used for transmitting communication data between IMS-AGW B' and IMS-AGW A', and the terminal-side IP address and port number of IMS-AGW B' are used for transmitting communication data between IMS-AGW B' and UE B. At this time, the second call response message in S1010 includes an SDP answer, and the media address in the SDP answer is the network-side IP address and port number of IMS-AGW B'. The third call request message in S1008 includes an SDP request, and the media address in the SDP request is the terminal-side IP address and port number of IMS-AGW B'.

[0432] S1008: P-CSCF B sends a third call request message to UE B.

[0433] Wherein, the third call request message includes an SDP request, and the media address in the SDP request is the terminal-side IP address and port number of the gateway serving UE B determined by P-CSCF B.

[0434] S1009: UE B sends a third call response message to P-CSCF B.

[0435] Wherein, the third call response message is a response message to the third call request message. The third call response message includes an SDP answer, and the media address in the SDP answer is the IP address and port number of UE B.

[0436] S1010: P-CSCF B sends a second call response message to P-CSCF A.

[0437] Exemplarily, the second call response message is a response message for the second call request message. The second call response message corresponds to the first response message in the above-mentioned FIG. 9. For example, the second call response message is a 183 response message, and the second call response message can further include the first label.

[0438] Exemplarily, the P-CSCF B sends the second call response message based on the determination result of S1006. The specific implementation of the second call response message can refer to the possible implementation manner A to the possible implementation manner C in the above-mentioned embodiment shown in FIG. 9, and details are not described herein again.

[0439] Exemplarily, the P-CSCF B sends the second call response message to the P-CSCF A through the IMS Core B network and the IMS Core A network.

[0440] The second call response message includes an SDP answer, and the media address in the SDP answer is the network side IP address and the port number of the gateway serving the UE B determined by the P-CSCF B.

[0441] S1011: The P-CSCF A releases the communication resource reserved by the IMS-AGW A or the IMS-AGW A' for the UE A according to the second call response message.

[0442] For example, if the P-CSCF A determines that the communication data between the UE A and the UE B is directly exchanged through the satellite according to the second call response message, or the gateway serving the UE B is the gateway deployed on the satellite, or the IMS-AGW A' is rejected, the P-CSCF A can release the communication resource reserved by the IMS-AGW A' for the UE A, and determine that the gateway serving the UE A is the IMS-AGW A. At this time, the first call response message in S1013 includes an SDP answer, and the media address in the SDP answer is the terminal side IP address and the port number of the IMS-AGW A.

[0443] For example, if the P-CSCF A determines that the communication data between the UE A and the UE B is not directly exchanged through the satellite according to the second call response message, or the gateway serving the UE B is the gateway deployed on the ground, or the IMS-AGW A is rejected, the P-CSCF A can release the communication resource reserved by the IMS-AGW A for the UE A, and determine that the gateway serving the UE A is the IMS-AGW A'. At this time, the first call response message in S1013 includes an SDP answer, and the media address in the SDP answer is the terminal side IP address and the port number of the IMS-AGW A'.

[0444] S1012: The P-CSCF A interacts with the core network accessed by the UE A to establish a dedicated bearer of the current call.

[0445] Exemplarily, when the communication data between UE A and UE B is exchanged directly through the satellite, the core network accessed by UE A also inserts the UL CLUPF and the local PSA UPF on the satellite for UE A at first.

[0446] S1013: P-CSCF A sends a first call response message to UE A.

[0447] Exemplarily, P-CSCF A generates the first call response message according to S1011, and the first call response message includes an SDP answer, and the media address in the SDP answer is the terminal side IP address and the port number of the gateway of the unreleased communication resource determined in S1011. For example, the first call response message is a 183 response message, and the first call response message can also include the first label.

[0448] S1014: UE A sends a first PRACK request message to UE B.

[0449] S1015: P-CSCF B interacts with the core network accessed by UE B to establish a dedicated bearer for this call.

[0450] For details, refer to S715.

[0451] S1016: UE B sends a 200 OK response message to UE A. The 200 OK response message is sent to UE A through each network and network element in FIG. 10.

[0452] At this point, UE A and UE B complete the call establishment.

[0453] With the embodiment shown in FIG. 10, the path of the call media stream between UE A and UE B can be established through one media negotiation. P-CSCF A can provide the information of the two gateways first, and release the communication resource reserved by one of the gateways for UE A according to the second call response message after receiving the second call response message, which avoids media renegotiation, reduces the session establishment delay, and improves user experience.

[0454] FIG. 11 shows a fourth specific flowchart of establishing a call between UE A and UE B. UE A corresponds to the first terminal in FIG. 9, UE B corresponds to the second terminal in FIG. 9, USF A corresponds to the first network element in FIG. 9, and USF B corresponds to the second network element in FIG. 9. USF A is an entry control node of future real-time communication network A accessed by UE A. USF B is an entry control node of future real-time communication network B accessed by UE B. Future real-time communication network A and future real-time communication network B can be the same or different.

[0455] S1101: UE A sends a first session connection request message to USF A.

[0456] The first session connection request message includes a media negotiation address of UE A.

[0457] S1102: USF A obtains access information of UE A.

[0458] For example, USF A can extract from the received first session connection request message, or can be obtained from the packet network.

[0459] Further, USF A can determine whether UE A accesses through a satellite according to the access information of UE A, or whether the access type of UE A is satellite access.

[0460] S1103: USF A selects a gateway serving UE A.

[0461] In combination with the above S1102, USF A can determine whether UE A accesses through a satellite according to the access information of UE A, and USF A selects a gateway serving UE A, including MFA and MFA', when USF A determines that the access type of UE A is satellite access according to the access information of UE A. MFA is a gateway deployed on the satellite indicated by the satellite identifier of the UE A, and MFA' is a gateway deployed on the ground.

[0462] In addition, USF A can also obtain the subscription information of UE A, and if USF A determines that the access type of UE A is satellite access according to the access information of UE A, and determines that UE A supports direct exchange of communication data through a satellite according to the subscription information of UE A, USF A selects MFA and MFA'.

[0463] S1104: USF A sends a second session connection request message to USF B.

[0464] The second session connection request message is used to establish a call between UE A and UE B. The second session connection request message corresponds to the first call request message in the above-mentioned FIG. 9. Illustratively, USF A saves the media negotiation address of UE A, and generates the second session connection request message according to the first session connection request message. The second session connection request message includes the access information of UE A, the information of MFA and the information of MFA'. The information of MFA includes the media negotiation address of MFA, and the information of MFA' includes the media negotiation address of MFA'.

[0465] Wherein each Media-Conn-Info is represented by a set of [Parameter Name] and [Parameter Value], wherein [Parameter Value] includes not only IP address and port number, but also a label indicating that the MF corresponding to the Media-Conn-Info is either a MF deployed on ground or a MF deployed on satellite. Below is an example:

[0466] "Media-Conn-Info":"192.168.176.2:6060on-satellite"

[0467] "Media-Conn-Info":"192.168.232.1:6060on-ground"

[0468] Wherein "Media-Conn-Info" is the parameter name. The parameter value is divided into two parts, the front part is IP address and port number, and the label in the back part indicates that the MF corresponding to the Media-Conn-Info is either a MF deployed on ground or a MF deployed on satellite.

[0469] S1105: USF B acquires the access information of UE B.

[0470] For example, USF B can acquire the access information of UE B from the packet network.

[0471] S1106: USF B determines whether the communication data between UE A and UE B is exchanged directly through satellite according to the access information of UE A and the access information of UE B.

[0472] For details, please refer to S707 above.

[0473] S1107: USF B selects the gateway serving UE B and applies for media resources and determines the gateway communicating with the gateway serving UE B.

[0474] For example, USF B determines that the communication data between UE A and UE B is exchanged directly through satellite according to S1106, then selects MF B deployed on the satellite indicated by the satellite identifier of UE B and applies for media resources for UE B, and determines that MFA is the gateway communicating with MF B, further, USF B also sends the information of MFA to MF B, wherein the information of MFA includes the media negotiation address of MFA.

[0475] Alternatively, the USF B determines that the communication data between the UE A and the UE B is not exchanged directly through the satellite according to the S1106, selects the MFB' deployed on the ground for the UE B and applies for media resources, and determines the MFA' as a gateway for communicating with the MFB', and further, the USF B sends the information of the MFA' to the MFB', wherein the information of the MFA' includes the media negotiation address of the MFA'.

[0476] The S1108: The USF B sends a third session connection request message to the UE B.

[0477] The third session connection request message includes the information of the gateway determined in the S1107, and the information includes the media negotiation address of the gateway determined in the S1107.

[0478] For example, if the gateway serving the UE B is determined as the MFB in the S1107, the third session connection request message includes the media negotiation address of the MFB.

[0479] For example, if the gateway serving the UE B is determined as the MFB' in the S1107, the third session connection request message includes the media negotiation address of the MFB'.

[0480] The S1109: The UE B sends a third session connection response message to the USF B.

[0481] The third session connection response message includes the media negotiation address of the UE B.

[0482] The S1110: The USF B sends a second session connection response message to the USF A.

[0483] The second session connection response message includes the information of the gateway determined in the S1107, and the information includes the media negotiation address of the gateway determined in the S1107. The second session connection response message corresponds to the first response message in the above-mentioned FIG. 9.

[0484] For example, if the gateway serving the UE B is determined as the MFB in the S1107, the second session connection response message includes the media negotiation address of the MFB. The media negotiation address of the MFB is similar to the above-mentioned representation, which is not described herein again.

[0485] For example, if the gateway serving the UE B is determined as the MFB' in the S1107, the second session connection response message includes the media negotiation address of the MFB'. The media negotiation address of the MFB' is similar to the above-mentioned representation, which is not described herein again.

[0486] The S1111: The USF A releases the media resources reserved for the UE A by the MFA or the MFA' according to the second session connection response message.

[0487] If the USF A determines from the second session connection response message that the gateway serving the UE B is the gateway deployed on the satellite (i.e., the MFB), the MFA releases the media resources reserved for the UE A, and further, the USF A sends the information of the MFB to the MFA, the information of the MFB including the media negotiation address of the MFB.

[0488] Or, if the USF A determines from the second session connection response message that the gateway serving the UE B is the gateway deployed on the ground (i.e., the MFB'), the MFA releases the media resources reserved for the UE A, and further, the USF A sends the information of the MFB' to the MFA, the information of the MFB' including the media negotiation address of the MFB'.

[0489] S1112: The P-CSCFA sends the first session connection response message to the UE A.

[0490] The first session connection response message includes the information of the gateway that does not release the media resources.

[0491] For example, if the MFA releases the media resources reserved for the UE A in S1111, the first session connection response message includes the information of the MFA', the information of the MFA' including the media negotiation address of the MFA'. If the MFA' releases the media resources reserved for the UE A in S1111, the first session connection response message includes the information of the MFA, the information of the MFA including the media negotiation address of the MFA.

[0492] At this point, the UE A and the UE B complete the call establishment.

[0493] With the embodiment shown in FIG. 11, the establishment of the path of the call media stream between the UE A and the UE B can be completed through one media negotiation. The USF A can provide the information of the two gateways first, and after receiving the second session connection response message, release the communication resources reserved for the UE A by one of the two gateways according to the second session connection response message, avoiding media renegotiation, reducing the session establishment delay, and improving the user experience.

[0494] It can be understood that, in order to implement the functions in the above embodiments, each communication device (such as a terminal or an access network device, etc.) includes a hardware structure and / or a software module that performs each function. Those skilled in the art should easily realize that, in combination with the units and method steps of the examples described in the embodiments disclosed in the present application, the present application can be realized in the form of hardware or a combination of hardware and computer software. Whether a certain function is executed in hardware or computer software driven hardware depends on the specific application scenario and design constraints of the technical solution.

[0495] FIG. 12 and FIG. 13 are structural diagrams of possible communication apparatuses provided by embodiments of the present application. The communication apparatuses can be used to implement the functions of the communication apparatuses in the above-mentioned method embodiments, and thus can also achieve the beneficial effects possessed by the above-mentioned method embodiments.

[0496] As shown in FIG. 12, the communication apparatus 1200 includes a processing unit 1210 and a transceiver unit 1220.

[0497] When the communication apparatus 1200 is used to implement the functions of the first network element (for example, P-CSCF A) in the above-mentioned embodiments shown in FIG. 5, FIG. 7, and FIG. 8, the processing unit 1210 is configured to:

[0498] The transceiver unit 1220 is configured to send a first request message to a second network element, the first request message being used to establish a call for a first terminal and a second terminal, and the first request message including access information of the first terminal in a case where an access type of the first terminal is satellite access, the second network element being an entry control node for the second terminal to access a second communication network; and receive a first response message from the second network element, the first response message being used to determine whether communication data between the first terminal and the second terminal is exchanged directly through a satellite.

[0499] The processing unit 1210 is configured to select a first gateway serving the first terminal according to the first response message.

[0500] The transceiver unit 1220 is configured to send a second request message to the second network element, the second request message including information of the first gateway.

[0501] In a possible design, when the processing unit 1210 selects the first gateway serving the first terminal according to the first response message, the processing unit 1210 is configured to determine, according to the first response message, that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, and select the first gateway deployed on the satellite to serve the first terminal.

[0502] In a possible design, when the processing unit 1210 selects the first gateway serving the first terminal according to the first response message, the processing unit 1210 is configured to determine, according to the first response message, that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, and select the first gateway deployed on the ground to serve the first terminal.

[0503] In a possible design, the transceiver unit 1220 is configured to send the information of the first gateway to the first terminal, the information of the first gateway being used to transmit the communication data between the first terminal and the first gateway.

[0504] In a possible design, the first response message includes information of the second gateway, the second gateway being a gateway selected by the second network element to serve the second terminal; and the transceiver 1220 is configured to send the information of the second gateway to the first gateway, the information of the second gateway being used to transmit communication data between the first gateway and the second gateway.

[0505] In a possible design, the first communication network and the second communication network are both IMS networks, the first response message is an SIP response message, and the second request message is an SIP request message; the first response message includes an SDP offer, and the information of the second gateway is carried in the SDP offer; and the second request message includes an SDP answer, and the information of the first gateway is carried in the SDP answer.

[0506] In a possible design, the first response message includes indication information, the indication information indicating that communication data between the first terminal and the second terminal is directly exchanged via the satellite; or the first response message includes indication information, the indication information indicating that communication data between the first terminal and the second terminal is not directly exchanged via the satellite; or the first response message does not include indication information, and the first response message is used to indicate that communication data between the first terminal and the second terminal is not directly exchanged via the satellite.

[0507] In a possible design, the processing unit 1210 is configured to, before sending the first request message, acquire subscription information of the first terminal, and determine, according to the subscription information, that the first terminal supports directly exchanging communication data via the satellite.

[0508] In a possible design, the access information of the first terminal includes an access type of the first terminal being satellite access and an identity of a satellite accessed by the first terminal, or the access information of the first terminal includes the identity of the satellite accessed by the first terminal.

[0509] When the communication apparatus 1200 is configured to implement the second network element (for example, P-CSCF B) in the embodiments shown in FIG. 5, FIG. 7 and FIG. 8 described above, the processing unit 1210 is configured to:

[0510] The transceiver 1220 is configured to receive a first request message from a first network element, the first request message being used to request establishment of a call for a first terminal and a second terminal, the first request message including access information of the first terminal, and the first network element being an entry control node for the first terminal to access a first communication network;

[0511] The processing unit 1210 is configured to acquire access information of the second terminal, determine, according to the access information of the first terminal and the access information of the second terminal, whether communication data between the first terminal and the second terminal is directly exchanged via a satellite, and send, according to a determination result, a first response message to the first network element via the transceiver 1220;

[0512] The transceiver 1220 is configured to receive a second request message from the first network element, and the second request message comprises information of the first gateway, and the first gateway is a gateway selected by the first network element to serve the first terminal.

[0513] In a possible design, the access information of the first terminal comprises that the access type of the first terminal is satellite access, and the satellite accessed by the first terminal is identified; the access information of the second terminal comprises that the access type of the second terminal is satellite access, and the satellite accessed by the second terminal is identified; and when it is determined according to the access information of the first terminal and the access information of the second terminal whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite, the processing unit 1210 is configured to determine, according to the access type of the first terminal and the access type of the second terminal, that both the first terminal and the second terminal are satellite access, and according to the satellite accessed by the first terminal and the satellite accessed by the second terminal, determine that the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal or that there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, and determine that the communication data between the first terminal and the second terminal is exchanged directly through the satellite.

[0514] In a possible design, the access information of the first terminal comprises that the access type of the first terminal is satellite access, and the satellite accessed by the first terminal is identified; the access information of the second terminal comprises that the access type of the second terminal is satellite access, and the satellite accessed by the second terminal is identified; and when it is determined according to the access information of the first terminal and the access information of the second terminal whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite, the processing unit 1210 is configured to determine, according to the access type of the first terminal and the access type of the second terminal, that both the first terminal and the second terminal are satellite access, and according to the satellite accessed by the first terminal and the satellite accessed by the second terminal, determine that there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, and determine that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0515] In a possible design, the access information of the second terminal comprises that the access type of the second terminal is not satellite access; and when it is determined according to the access information of the first terminal and the access information of the second terminal whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite, the processing unit 1210 is configured to determine, according to the access type of the second terminal, that the second terminal is not satellite access, and determine that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0516] In a possible design, when the processing unit 1210 sends the first response message to the first network element according to the determination result, when it is determined that the communication data between the first terminal and the second terminal is directly exchanged through the satellite, the first response message includes indication information, and the indication information indicates that the first terminal and the second terminal directly exchange through the satellite; when it is determined that the communication data between the first terminal and the second terminal is not directly exchanged through the satellite, the first response message includes indication information, and the indication information indicates that the communication data between the first terminal and the second terminal is not directly exchanged through the satellite, or the first response message does not include the indication information, and the first response message is used to indicate that the communication data between the first terminal and the second terminal is not directly exchanged through the satellite.

[0517] In a possible design, the second network element selects the second gateway serving the second terminal according to the determination result.

[0518] In a possible design, when the processing unit 1210 selects the second gateway serving the second terminal according to the determination result, when it is determined that the communication data between the first terminal and the second terminal is directly exchanged through the satellite, the processing unit 1210 selects the second gateway deployed on the satellite to serve the second terminal.

[0519] In a possible design, when the processing unit 1210 selects the second gateway serving the second terminal according to the determination result, when it is determined that the communication data between the first terminal and the second terminal is not directly exchanged through the satellite, the processing unit 1210 selects the second gateway deployed on the ground to serve the second terminal.

[0520] In a possible design, the first response message includes information of the second gateway.

[0521] In a possible design, the transceiver 1220 sends the information of the second gateway to the second terminal, and the information of the second gateway is used to transmit the communication data between the second terminal and the second gateway.

[0522] In a possible design, the transceiver 1220 sends the information of the first gateway to the second gateway, and the information of the first gateway is used to transmit the communication data between the first gateway and the second gateway.

[0523] In a possible design, the first communication network and the second communication network are both IMS networks, the first response message is an SIP response message, and the second request message is an SIP request message; the first response message includes an SDP offer, and the information of the second gateway is carried in the SDP offer; the second request message includes an SDP answer, and the information of the first gateway is carried in the SDP answer.

[0524] Some possible designs and advantages of the communication apparatus 1200 can refer to the related content in the above-described embodiments of FIG. 5, FIG. 7, and FIG. 8, and details are not described herein again.

[0525] When the communication apparatus 1200 is used to implement the first network element (e.g., P-CSCF A or USF A) in the embodiments shown in FIG. 9, FIG. 10, and FIG. 11:

[0526] The transceiver 1220 is configured to send a first request message to a second network element, the first request message being used to establish a call for a first terminal and a second terminal, the first terminal having a satellite access type, the first request message including access information of the first terminal, information of a first gateway, and information of a second gateway, the first gateway and the second gateway both being determined by the first network element to serve the first terminal, the first gateway being a gateway deployed on a satellite, the second gateway being a gateway deployed on the ground, and the second network element being an ingress control node for the second terminal to access a second communication network; and receive a first response message from the second network element, the first response message being used to determine whether communication data between the first terminal and the second terminal is exchanged directly through a satellite.

[0527] The processing unit 1210 is configured to release, according to the first response message, a communication resource reserved by the first gateway for the first terminal or a communication resource reserved by the second gateway for the first terminal.

[0528] In a possible design, when the communication resource reserved by the first gateway for the first terminal or the communication resource reserved by the second gateway for the first terminal is released according to the first response message, the processing unit 1210 is configured to determine, according to the first response message, that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, and release the communication resource reserved by the second gateway for the first terminal.

[0529] In a possible design, when the communication resource reserved by the first gateway for the first terminal or the communication resource reserved by the second gateway for the first terminal is released according to the first response message, the processing unit 1210 is configured to determine, according to the first response message, that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, and release the communication resource reserved by the first gateway for the first terminal.

[0530] In a possible design, the first response message includes indication information, the indication information indicating that the communication data between the first terminal and the second terminal is exchanged directly through the satellite; or the first response message includes indication information, the indication information indicating that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite; or the first response message does not include the indication information, and the first response message is used to indicate that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0531] In a possible design, the transceiver 1220 is configured to send, to the first terminal, information of the gateway that has not released the communication resource, where the information of the gateway that has not released the communication resource is used for transmitting communication data between the first terminal and the gateway that has not released the communication resource.

[0532] In a possible design, the first response message includes information of a third gateway, where the third gateway is a gateway selected by the second network element to serve the second terminal; and the transceiver 1220 is configured to send, to the gateway that has not released the communication resource, the information of the third gateway, where the information of the third gateway is used for transmitting communication data between the third gateway and the gateway that has not released the communication resource.

[0533] In a possible design, the first communication network and the second communication network are both IMS networks, the first request message is an SIP request message, and the first response message is an SIP response message; the first request message includes an SDP offer, and the information of the first gateway and the information of the second gateway are carried in the SDP offer; and the first response message includes an SDP answer, and the information of the third gateway is carried in the SDP answer.

[0534] In a possible design, the SDP offer includes first information and second information, the first information includes the information of the first gateway, and the second information includes the information of the second gateway; the information of the first gateway includes an IP address and a port number of the first gateway, and deployment location description information of the first gateway, where the deployment location description information of the first gateway indicates that the first gateway is a gateway deployed on a satellite; and the information of the second gateway includes an IP address and a port number of the second gateway, and deployment location description information of the second gateway, where the deployment location description information of the second gateway indicates that the second gateway is a gateway deployed on the ground.

[0535] The SDP answer includes third information and fourth information, the third information corresponds to the first information, and the fourth information corresponds to the second information; the third information includes the information of the third gateway, and the information of the third gateway includes an IP address and a port number of the third gateway, and deployment location description information of the third gateway, where the deployment location description information of the third gateway indicates that the third gateway is a gateway deployed on a satellite; and the fourth information includes a preset port number; or the third information includes a preset port number, the fourth information includes the information of the third gateway, and the information of the third gateway includes an IP address and a port number of the third gateway, and deployment location description information of the third gateway, where the deployment location description information of the third gateway indicates that the third gateway is a gateway deployed on the ground.

[0536] In a possible design, the processing unit 1210 is configured to, before sending the first request message, acquire subscription information of the first terminal, and determine, according to the subscription information, that the first terminal supports exchanging communication data directly through a satellite.

[0537] In a possible design, the access information of the first terminal includes an access type of the first terminal being satellite access and an identifier of a satellite accessed by the first terminal, or the access information of the first terminal includes the identifier of the satellite accessed by the first terminal.

[0538] When the communication apparatus 1200 is used to implement the second network element (for example, the P-CSCF B or the USF B) in the embodiments shown in FIG. 9, FIG. 10, and FIG. 11, the processing unit 1210 is configured to:

[0539] The transceiver 1220 is configured to receive a first request message from the first network element, the first request message being used to establish a call for the first terminal and the second terminal, the first request message including access information of the first terminal, information of a first gateway, and information of a second gateway, the first gateway and the second gateway both being determined by the first network element to serve the first terminal, the first gateway being a gateway deployed on a satellite, the second gateway being a gateway deployed on the ground, and the first network element being an ingress control node of the first terminal accessing a first communication network;

[0540] The processing unit 1210 is configured to obtain access information of the second terminal, determine whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal, and send a first response message to the first network element through the transceiver 1220 according to a determination result.

[0541] In a possible design, the access information of the first terminal includes an access type of the first terminal being satellite access and an identifier of a satellite accessed by the first terminal; the access information of the second terminal includes an access type of the second terminal being satellite access and an identifier of a satellite accessed by the second terminal; and when the processing unit 1210 determines whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal, the processing unit 1210 is configured to determine, according to the access type of the first terminal and the access type of the second terminal, that the first terminal and the second terminal are both satellite access, and determine, according to the identifier of the satellite accessed by the first terminal and the identifier of the satellite accessed by the second terminal, that the communication data between the first terminal and the second terminal is exchanged directly through the satellite when the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal or there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal.

[0542] In a possible design, the access information of the first terminal includes that the access type of the first terminal is satellite access, and an identifier of a satellite accessed by the first terminal; the access information of the second terminal includes that the access type of the second terminal is satellite access, and an identifier of a satellite accessed by the second terminal; when determining whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal, the processing unit 1210 is configured to: determine, according to the access type of the first terminal and the access type of the second terminal, that the first terminal and the second terminal are both satellite access, and determine, according to the identifier of the satellite accessed by the first terminal and the identifier of the satellite accessed by the second terminal, that there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal, and determine that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0543] In a possible design, the access information of the second terminal includes that the access type of the second terminal is not satellite access; when determining whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal, the processing unit 1210 is configured to: determine, according to the access type of the second terminal, that the second terminal is not satellite access, and determine that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0544] In a possible design, when sending the first response message to the first network element according to the determination result, the processing unit 1210 is configured to: when the communication data between the first terminal and the second terminal is exchanged directly through the satellite, the first response message includes indication information, and the indication information indicates that the first terminal and the second terminal are directly exchanged through the satellite; when the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, the first response message includes indication information, and the indication information indicates that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, or the first response message does not include the indication information, and the response message is used to indicate that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0545] In a possible design, the processing unit 1210 is configured to: select, according to the determination result, a third gateway serving the second terminal, and determine, according to the determination result, a gateway of the first gateway and the second gateway that communicates with the third gateway.

[0546] In a possible design, the processing unit 1210 is configured to: select the third gateway deployed on the satellite to serve the second terminal according to the determination result, and determine the gateway in the first gateway and the second gateway that communicates with the third gateway according to the determination result when the communication data between the first terminal and the second terminal is exchanged directly through the satellite; or select the third gateway deployed on the ground to serve the second terminal according to the determination result, and determine the gateway in the first gateway and the second gateway that communicates with the third gateway according to the determination result when the communication data between the first terminal and the second terminal is not exchanged directly through the satellite.

[0547] In a possible design, the first response message includes information of the third gateway.

[0548] In a possible design, the first communication network and the second communication network are both IMS networks, the first request message is an SIP request message, and the first response message is an SIP response message; the first request message includes an SDP offer, and the information of the first gateway and the information of the second gateway are carried in the SDP offer; the first response message includes an SDP answer, and the information of the third gateway is carried in the SDP answer.

[0549] In a possible design, the SDP offer includes first information and second information, the first information includes the information of the first gateway, and the second information includes the information of the second gateway; the information of the first gateway includes an IP address and a port number of the first gateway, and deployment location description information of the first gateway, the deployment location description information of the first gateway indicating that the first gateway is a gateway deployed on a satellite; and the information of the second gateway includes an IP address and a port number of the second gateway, and deployment location description information of the second gateway, the deployment location description information of the second gateway indicating that the second gateway is a gateway deployed on the ground.

[0550] The SDP answer includes third information and fourth information, the third information corresponding to the first information, and the fourth information corresponding to the second information; the third information includes the information of the third gateway, and the information of the third gateway includes an IP address and a port number of the third gateway, and deployment location description information of the third gateway, the deployment location description information of the third gateway indicating that the third gateway is a gateway deployed on a satellite, and the fourth information includes a preset port number; or the third information includes a preset port number, the fourth information includes the information of the third gateway, and the information of the third gateway includes an IP address and a port number of the third gateway, and deployment location description information of the third gateway, the deployment location description information of the third gateway indicating that the third gateway is a gateway deployed on the ground.

[0551] In a possible design, the transceiver 1220 is configured to send, to the second terminal, information of the third gateway, the information of the third gateway being used to transmit communication data between the second terminal and the third gateway.

[0552] In a possible design, the transceiver 1220 is configured to send, to the third gateway, information of a gateway in communication with the third gateway, the information of the gateway in communication with the third gateway being used to transmit communication data between the gateway in communication with the third gateway and the third gateway.

[0553] Some possible designs and advantages of the communication apparatus 1200 can refer to the related content in the above-described embodiments of FIG. 9, FIG. 10 and FIG. 11, and will not be repeated here.

[0554] For more detailed description of the processing unit 1210 and the transceiver 1220, refer to the related description in the above-described method embodiments, which will not be repeated here.

[0555] As shown in FIG. 13, the communication apparatus 1300 includes a processor 1310 and an interface circuit 1320. The processor 1310 and the interface circuit 1320 are coupled to each other. It can be understood that the interface circuit 1320 can be a transceiver or an input / output interface. Optionally, the communication apparatus 1300 can further include a memory 1330, configured to store instructions executed by the processor 1310 or store input data required by the processor 1310 to execute instructions or store data generated after the processor 1310 executes instructions.

[0556] When the communication apparatus 1300 is used to implement the above-described method embodiments, the processor 1310 is configured to implement the functions of the above-described processing unit 1210, and the interface circuit 1320 is configured to implement the functions of the above-described transceiver 1220.

[0557] It can be understood that the processor in the embodiments of the present application can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The general-purpose processor can be a microprocessor or any conventional processor.

[0558] In the present application, another example of the apparatus is provided, the notification apparatus comprising at least one processor and at least one memory, the at least one processor and the at least one memory being coupled, the at least one memory for storing instructions which, when executed by the at least one processor, cause the communication apparatus to perform the method in the above embodiments. Taking the communication apparatus comprising one processor and one memory as an example, as shown in FIG. 13, the communication apparatus 1300 comprises one processor 1310 and one memory 1330. The processor 1310 and the memory 1330 are coupled, and the memory 1330 stores instructions, when the instructions stored in the memory 1330 are executed by the processor 1310, the communication apparatus 1300 performs the method performed by each communication apparatus in the above embodiments.

[0559] The method steps in the embodiments of the present application can be implemented in hardware, or in software instructions executable by a processor. The software instructions can be composed of corresponding software modules, which can be stored in a random access memory, a flash memory, a read-only memory, a programmable read-only memory, an erasable programmable read-only memory, an electrically erasable programmable read-only memory, a register, a hard disk, a mobile hard disk, a CD-ROM, or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor, so that the processor can read information from, and write information to, the storage medium. The storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC. In addition, the ASIC can be located in the terminal or the access network device described above. The processor and the storage medium can also exist as discrete components in the terminal or the access network device.

[0560] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware or any combination thereof. When implemented by software, all or part of the embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer programs or instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments are performed. The computer can be a general purpose computer, a special purpose computer, a computer network, a network device, a user equipment or other programmable apparatus. The computer programs or instructions can be stored in a computer readable storage medium or transferred from one computer readable storage medium to another computer readable storage medium, for example, the computer programs or instructions can be transferred from one website site, computer, server or data center to another website site, computer, server or data center through wired or wireless manner. The computer readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server, data center and the like integrated with one or more available media. The available media can be a magnetic medium, such as a floppy disk, a hard disk, a magnetic tape; or an optical medium, such as a digital video disc; or a semiconductor medium, such as a solid state disk. The computer readable storage medium can be a volatile or non-volatile storage medium, or can include both volatile and non-volatile storage media.

[0561] In various embodiments of the present application, the terms and / or descriptions of different embodiments are consistent and can be referred to each other if there is no special description and logical conflict. The technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationship.

[0562] In the present application, "at least one" means one or more, and "multiple" means two or more. The association relationship between the associated objects is described, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the following cases: A exists alone, A and B exist together, and B exists alone, where A and B can be singular or plural. In the literal description of the present application, the character " / ", generally represents that the associated objects before and after are in an "or" relationship; in the formula of the present application, the character " / ", represents that the associated objects before and after are in a "division" relationship. "Including at least one of A, B and C" can mean: including A; including B; including C; including A and B; including A and C; including B and C; including A, B and C.

[0563] It can be understood that various numbers involved in the embodiments of the present application are only distinguished for convenience of description, and are not used to limit the scope of the embodiments of the present application. The size of the serial number of the above processes does not mean the execution order, and the execution order of the processes should be determined according to their functions and inherent logic.

Claims

A communication method characterized by comprising: The method is applied to a first network element in a first communication network, the first network element being an entry control node for a first terminal to access the first communication network, and the method comprises: sending a first request message to a second network element, the first request message being used for establishing a session between the first terminal and a second terminal, the first terminal being of a satellite access type, the first request message comprising access information of the first terminal, the second network element being an entry control node for the second terminal to access a second communication network; receiving a first response message from the second network element, the first response message being used for determining whether communication data between the first terminal and the second terminal is exchanged directly through a satellite; selecting a first gateway serving the first terminal according to the first response message; sending a second request message to the second network element, the second request message comprising information of the first gateway. The method of claim 1, wherein The selecting a first gateway serving the first terminal according to the first response message comprises: determining, according to the first response message, that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, and selecting the first gateway deployed on the satellite to serve the first terminal. The method of claim 1, wherein The selecting a first gateway serving the first terminal according to the first response message comprises: determining, according to the first response message, that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, and selecting the first gateway deployed on the ground to serve the first terminal. The method according to any one of claims 1 to 3, characterized in that The method further comprises: sending the information of the first gateway to the first terminal, the information of the first gateway being used for transmitting the communication data between the first terminal and the first gateway. The method according to any one of claims 1 to 4, characterized in that The first response message comprises information of a second gateway, the second gateway being a gateway selected by the second network element to serve the second terminal; The method further comprises: sending the information of the second gateway to the first gateway, the information of the second gateway being used for transmitting the communication data between the first gateway and the second gateway. The method of claim 5, wherein The first communication network and the second communication network are both IP multimedia subsystem (IMS) networks, the first response message is a session initiation protocol (SIP) response message, and the second request message is a SIP request message; The first response message comprises a session description protocol (SDP) offer, and the information of the second gateway is carried through the SDP offer; The second request message comprises an SDP answer, and the information of the first gateway is carried through the SDP answer. The method according to any one of claims 1 to 6, characterized in that The first response message comprises indication information, the indication information indicating that the communication data between the first terminal and the second terminal is exchanged directly through the satellite; or The first response message comprises indication information, the indication information indicating that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite; or The first response message does not comprise indication information, and the first response message is used for indicating that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite. The method according to any one of claims 1 to 7, characterized in that Before sending the first request message, the method further comprises: obtaining subscription information of the first terminal, and determining that the first terminal supports exchanging communication data directly through a satellite according to the subscription information. The method according to any one of claims 1 to 8, characterized in that The access information of the first terminal comprises that an access type of the first terminal is satellite access, and an identity of a satellite accessed by the first terminal. A communication method characterized by comprising: The method is applied to a second network element in a second communication network, the second network element being an entry control node for a second terminal to access the second communication network, and the method comprises: receiving a first request message from a first network element, the first request message being used for requesting to establish a call between the first terminal and the second terminal, the first request message comprising access information of the first terminal, the first network element being an entry control node for the first terminal to access a first communication network; obtaining access information of the second terminal; determining whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal; sending a first response message to the first network element according to the determination result; receiving a second request message from the first network element, the second request message comprising information of a first gateway, the first gateway being a gateway selected by the first network element to serve the first terminal. The method of claim 10, wherein The access information of the first terminal comprises that an access type of the first terminal is satellite access, and an identity of a satellite accessed by the first terminal; and the access information of the second terminal comprises that an access type of the second terminal is satellite access, and an identity of a satellite accessed by the second terminal. The determining whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal comprises: determining that the first terminal and the second terminal are both satellite access according to the access type of the first terminal and the access type of the second terminal, and determining that the communication data between the first terminal and the second terminal is exchanged directly through the satellite when the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal or there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal according to the identity of the satellite accessed by the first terminal and the identity of the satellite accessed by the second terminal. The method of claim 10, wherein The access information of the first terminal comprises that an access type of the first terminal is satellite access, and an identity of a satellite accessed by the first terminal; and the access information of the second terminal comprises that an access type of the second terminal is satellite access, and an identity of a satellite accessed by the second terminal. The determining whether the communication data between the first terminal and the second terminal is exchanged directly through the satellite according to the access information of the first terminal and the access information of the second terminal comprises: determining, according to the access type of the first terminal and the access type of the second terminal, that the first terminal and the second terminal are both satellite access, but determining that communication data between the first terminal and the second terminal is not directly exchanged through a satellite when it is determined, according to an identity of a satellite accessed by the first terminal and an identity of a satellite accessed by the second terminal, that there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal. The method of claim 10, wherein The access information of the second terminal includes that the access type of the second terminal is not satellite access. determining, according to the access information of the first terminal and the access information of the second terminal, whether communication data between the first terminal and the second terminal is directly exchanged through a satellite, including: when it is determined, according to the access type of the second terminal, that the second terminal is not satellite access, determining that communication data between the first terminal and the second terminal is not directly exchanged through a satellite. The method according to any one of claims 10 to 13, characterized in that The sending, according to the determination result, of a first response message to the first network element includes: when it is determined that communication data between the first terminal and the second terminal is directly exchanged through a satellite, the first response message includes indication information indicating that the first terminal and the second terminal are directly exchanged through a satellite; when it is determined that communication data between the first terminal and the second terminal is not directly exchanged through a satellite, the first response message includes indication information indicating that communication data between the first terminal and the second terminal is not directly exchanged through a satellite, or the first response message does not include indication information, and the first response message is used to indicate that communication data between the first terminal and the second terminal is not directly exchanged through a satellite. The method according to any one of claims 10 to 14, characterized in that The method further includes: selecting, according to the determination result, a second gateway serving the second terminal. The method of claim 15, wherein The selecting, according to the determination result, of a second gateway serving the second terminal includes: when it is determined that communication data between the first terminal and the second terminal is directly exchanged through a satellite, selecting the second gateway deployed on a satellite to serve the second terminal. The method of claim 15, wherein The selecting, according to the determination result, of a second gateway serving the second terminal includes: when it is determined that communication data between the first terminal and the second terminal is not directly exchanged through a satellite, selecting the second gateway deployed on the ground to serve the second terminal. The method according to any one of claims 15 to 17, characterized in that The first response message includes information of the second gateway. The method according to any one of claims 15 to 18, characterized in that The method further includes: sending the information of the second gateway to the second terminal, the information of the second gateway being used to transmit communication data between the second terminal and the second gateway. The method according to any one of claims 15 to 19, characterized in that The method further includes: sending information of the first gateway to the second gateway, the information of the first gateway being used to transmit communication data between the first gateway and the second gateway. A communication method characterized by comprising: The method is applied to a first network element in a first communication network, the first network element being an entry control node for a first terminal accessing the first communication network, and the method includes: sending a first request message to a second network element, the first request message being used for establishing a call between the first terminal and a second terminal, the first terminal being of a satellite access type, the first request message comprising access information of the first terminal, information of a first gateway and information of a second gateway, the first gateway and the second gateway both being determined by the first network element to serve the first terminal, the first gateway being a gateway deployed on a satellite, the second gateway being a gateway deployed on the ground, the second network element being an ingress control node for the second terminal to access a second communication network; receiving a first response message from the second network element, the first response message being used for determining whether communication data between the first terminal and the second terminal is exchanged directly through a satellite; releasing, according to the first response message, a communication resource reserved by the first gateway for the first terminal or a communication resource reserved by the second gateway for the first terminal. The method of claim 21, wherein releasing, according to the first response message, a communication resource reserved by the first gateway for the first terminal or a communication resource reserved by the second gateway for the first terminal, comprises: determining, according to the first response message, that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, releasing the communication resource reserved by the second gateway for the first terminal. The method of claim 21, wherein releasing, according to the first response message, a communication resource reserved by the first gateway for the first terminal or a communication resource reserved by the second gateway for the first terminal, comprises: determining, according to the first response message, that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, releasing the communication resource reserved by the first gateway for the first terminal. The method of any one of claims 21-23, wherein The method further comprises: sending information of a gateway with unreleased communication resource to the first terminal, the information of the gateway with unreleased communication resource being used for transmitting communication data between the first terminal and the gateway with unreleased communication resource. The method of any one of claims 21-24, wherein The first response message comprises information of a third gateway, the third gateway being a gateway selected by the second network element to serve the second terminal; The method further comprises: sending the information of the third gateway to a gateway with unreleased communication resource, the information of the third gateway being used for transmitting communication data between the third gateway and the gateway with unreleased communication resource. A communication method characterized by comprising: The method is applied to a second network element in a second communication network, the second network element being an ingress control node for a second terminal to access the second communication network, the method comprising: receiving a first request message from a first network element, the first request message being used for establishing a call between the first terminal and a second terminal, the first request message comprising access information of the first terminal, information of a first gateway and information of a second gateway, the first gateway and the second gateway both being determined by the first network element to serve the first terminal, the first gateway being a gateway deployed on a satellite, the second gateway being a gateway deployed on the ground, the first network element being an ingress control node for the first terminal to access a first communication network; receiving a first request message from a first network element, the first request message being used for establishing a call between the first terminal and a second terminal, the first request message comprising access information of the first terminal, information of a first gateway and information of a second gateway, the first gateway and the second gateway both being determined by the first network element to serve the first terminal, the first gateway being a gateway deployed on a satellite, the second gateway being a gateway deployed on the ground, the first network element being an ingress control node for the first terminal to access a first communication network; obtaining access information of the second terminal; determining whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal; sending a first response message to the first network element according to the determination result. The method of claim 26, wherein the access information of the first terminal comprises that the access type of the first terminal is satellite access and an identifier of a satellite accessed by the first terminal, and the access information of the second terminal comprises that the access type of the second terminal is satellite access and an identifier of a satellite accessed by the second terminal; the determining whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal comprises: when it is determined that the first terminal and the second terminal are both satellite access according to the access type of the first terminal and the access type of the second terminal, and that the satellite accessed by the first terminal is the same as the satellite accessed by the second terminal or there is an inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal according to the identifier of the satellite accessed by the first terminal and the identifier of the satellite accessed by the second terminal, it is determined that the communication data between the first terminal and the second terminal is exchanged directly through a satellite. The method of claim 26 wherein the access information of the first terminal comprises that the access type of the first terminal is satellite access and an identifier of a satellite accessed by the first terminal, and the access information of the second terminal comprises that the access type of the second terminal is satellite access and an identifier of a satellite accessed by the second terminal; the determining whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal comprises: when it is determined that the first terminal and the second terminal are both satellite access according to the access type of the first terminal and the access type of the second terminal, and that there is no inter-satellite link between the satellite accessed by the first terminal and the satellite accessed by the second terminal according to the identifier of the satellite accessed by the first terminal and the identifier of the satellite accessed by the second terminal, it is determined that the communication data between the first terminal and the second terminal is not exchanged directly through a satellite. The method of claim 26, wherein the access information of the second terminal comprises that the access type of the second terminal is not satellite access; the determining whether communication data between the first terminal and the second terminal is exchanged directly through a satellite according to the access information of the first terminal and the access information of the second terminal comprises: when it is determined that the second terminal is not satellite access according to the access type of the second terminal, it is determined that the communication data between the first terminal and the second terminal is not exchanged directly through a satellite. The method of any one of claims 26-29, wherein the sending a first response message to the first network element according to the determination result comprises: when it is determined that the communication data between the first terminal and the second terminal is exchanged directly through a satellite, the first response message comprises indication information, and the indication information indicates that the first terminal and the second terminal are exchanged directly through a satellite; When it is determined that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, the first response message comprises indication information indicating that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, or the first response message does not comprise indication information, and the response message is used to indicate that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite. The method of any one of claims 26-30, wherein The method further comprises: selecting a third gateway serving the second terminal according to the determination result, and determining a gateway of the first gateway and the second gateway in communication with the third gateway according to the determination result. The method of claim 31, wherein The selecting a third gateway serving the second terminal according to the determination result, and determining a gateway of the first gateway and the second gateway in communication with the third gateway according to the determination result comprises: When it is determined that the communication data between the first terminal and the second terminal is exchanged directly through the satellite, selecting the third gateway deployed on the satellite to serve the second terminal, and determining that the gateway in communication with the third gateway is the first gateway; or When it is determined that the communication data between the first terminal and the second terminal is not exchanged directly through the satellite, selecting the third gateway deployed on the ground to serve the second terminal, and determining that the gateway in communication with the third gateway is the second gateway. The method of claim 31 or 32, wherein The first response message comprises information of the third gateway. A communication device, characterized by The communication device comprises at least one processor; the at least one processor is used to execute the method as claimed in any one of claims 1 to 33.

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