CN111988821A

CN111988821A - Voice communication method and device

Info

Publication number: CN111988821A
Application number: CN201910430874.3A
Authority: CN
Inventors: 姜传奎; 杜如川; 陶振宇
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2019-05-22
Filing date: 2019-05-22
Publication date: 2020-11-24
Anticipated expiration: 2039-05-22
Also published as: WO2020233688A1; CN111988821B

Abstract

The embodiment of the application provides a voice communication method and a device thereof, wherein the method comprises the following steps: in the process of registering the terminal to the first network, the access management network element in the first network also registers the terminal to a circuit switched domain in the second network; when the terminal needs to perform voice communication, the access management network element firstly drops the terminal from the first network to the third network, and then drops the terminal from the third network to the circuit switching domain in the second network, so that the terminal performs voice communication in the circuit switching domain. By adopting the embodiment of the application, the normal operation of the voice service under the 5G network can be ensured, the utilization rate of the 5G network is further improved, and the user experience is improved.

Description

Voice communication method and device

Technical Field

The embodiment of the application relates to the technical field of communication, in particular to a voice communication method and a voice communication device.

Background

With the development of mobile communication technology, the fifth generation (5)^thGeneration, 5G) network, and 5G terminals.The 5G terminal under the 5G network can provide a faster transmission rate for the user and provide better user experience. 5G networks have improved not only in data services but also in voice services. In the third generation partnership project (3) ^rdGeneration park requirement, 3GPP) defines two 5G voice communication methods, Evolved Packet System (EPS) fallback (fallback) and new air interface based voice communication (VoNR), which are essentially network protocol multimedia subsystem (IMS) based voice communication, i.e. voice over IMS. In the EPS fallback method, a 5G terminal performs data service and voice service through an access network device, an Evolved Packet Core (EPC) and a 5G core network in a Long Term Evolution (LTE) network. In the VoNR method, both data service and voice service are carried over a 5G network, and a 5G terminal directly performs the data service and the voice service over an access network device and a 5G core network in the 5G network.

In the two voice communication methods, voice services are both provided by the IMS, and the voice services can be implemented only by deploying the IMS. Under the condition that the IMS is not deployed or the condition that the IMS is deployed but can not be used, the two voice communication methods can not be realized, so that the terminal can not carry out voice service. Therefore, how to ensure normal operation of voice service in a 5G network is an urgent technical problem to be solved.

Disclosure of Invention

The embodiment of the application provides a voice communication method and a voice communication device, which can ensure normal operation of voice services in a 5G network, further improve the utilization rate of the 5G network, and improve user experience.

A first aspect of an embodiment of the present application provides a voice communication method, where the method includes:

in the process of registering the terminal to the first network, the access management network element in the first network also registers the terminal to a circuit switched domain in the second network;

under the condition that the terminal needs to carry out voice communication, the access management network element drops the terminal from the first network back to the third network; and then dropping the terminal from the third network back to the circuit switched domain in the second network.

Wherein, the first network, the second network and the third network have different communication systems, for example, the first network is a 5G network, the third network is a 4G network, the second network is a second generation (2)^nd-generation, 2G) networks or third generation (3rd-generation, 3G) networks.

In the first aspect of the embodiment of the present application, in the process of registering the terminal in the first network, the terminal is also registered in the circuit switched domain in the second network, so that the terminal can perform voice communication in the circuit switched domain, and when the terminal needs to perform voice communication, the terminal falls back to the third network and then falls back to the circuit switched domain, so that the terminal performs voice communication in the circuit switched domain. Even if the IMS is not deployed in the current environment or the deployed IMS cannot be used, voice communication can be carried out through the circuit switching domain, so that normal operation of voice services in the 5G network is ensured, the utilization rate of the 5G network is further improved, and user experience is improved.

In a possible implementation manner, the embodiments of the present application may be applied to a roaming scenario, and then the first network, the second network, and the third network are visited networks of the terminal.

In a possible implementation manner, the embodiments of the present application may be used in a non-roaming scenario, and then the first network, the second network, and the third network are home networks of the terminal. For example: the first network, the second network and the third network are three communication systems under an operator to which the terminal belongs.

In one possible implementation, the access management network element requests the second network to register the terminal to a circuit switched domain in the second network. Specifically, the access management network element sends a first request to the second network, where the first request is used to request the second network to register the terminal in the circuit switched domain of the second network; a first response is received from the second network indicating that the terminal is registered to the circuit switched domain in the second network. The terminal is registered to a circuit switched domain in the second network so that the terminal can perform voice communication in the circuit switched domain.

In a possible implementation manner, the first response further includes identification information allocated by the second network to the terminal, where the identification information is used by the terminal to determine a circuit switched domain location for performing voice communication. And under the condition that the access management network element acquires the identification information, the access management network element informs the third network in the process of falling back from the first network to the third network, and then the third network informs the terminal.

In a possible implementation manner, after the access management network element registers the terminal to the circuit switched domain in the second network, the access management network element sends first indication information to the terminal, where the first indication information is used to indicate that the first network supports voice communication based on the packet switched domain, so that a subsequent procedure, such as a data connection establishment procedure, can be performed.

In a possible implementation manner, for a roaming scenario, the access management network element further obtains subscription data of the terminal from a home network of the terminal in a process of registering the terminal in the first network, where a communication system corresponding to the subscription data of the terminal is the same as a communication system of the first network, for example, when the first network is a 5G network, the subscription data of the terminal is the 5G subscription data of the terminal.

And if the communication system of the home network is the same as that of the first network, the access management network element acquires the subscription data of the terminal from the unified data management network element in the home network.

If the communication system of the home network is the same as the communication system of the third network, the access management network element acquires the subscription data of the terminal corresponding to the communication system of the third network from the home subscriber server in the home network, and converts the subscription data of the terminal corresponding to the communication system of the third network into the subscription data of the terminal corresponding to the communication system of the first network. For example, if the communication system of the home network is a 4G network, the access management network element converts the 4G subscription data of the terminal into 5G subscription data.

In a possible implementation manner, after registering the terminal in the circuit switched domain in the second network, the access management network element executes a process of establishing a data connection, and in the process of establishing the data connection, sends a connection establishment request to the session management network element in the first network, where the connection establishment request includes second indication information and subscription data of the terminal, and the second indication information is used to indicate the session management network element to directly establish the data connection according to the received subscription data, which can save time consumed for establishing the data connection.

In a possible implementation manner, in a case that the terminal needs to initiate voice communication, the access management network element sends a second request to the third network, where the second request includes third indication information, where the third indication information is used to trigger the third network to send fourth indication information to the terminal, and the fourth indication information is used to indicate that the third network supports packet switched domain-based voice communication, so that the terminal can fall back from the first network to the third network, and avoid interruption of voice service.

The second request may also trigger the third network to send a notification message of a failure of establishing the voice service bearer to the terminal, where the notification message is used to trigger the terminal to initiate voice communication in a circuit switched domain in the second network. Or, the access management network element triggers the third network to send a notification message of the failure of establishing the voice service bearer to the terminal, where the notification message is used to trigger the terminal to initiate voice communication in the circuit switched domain in the second network. This allows the terminal to initiate voice communications in the circuit switched domain, thereby ensuring that voice traffic is proceeding properly.

In one possible implementation, in a case that an access management network element receives a paging request for a terminal, the access management network element requests an access network device in a first network to establish a data stream, where the data stream is used for carrying a voice service; upon receiving the rejection message from the access network device, the terminal is dropped from the first network back to the third network.

In the process of dropping the terminal from the first network back to the third network, the access management network element sends a second request to the third network, the second request comprises third indication information, the third indication information is used for triggering the third network to send fourth indication information to the terminal, and the fourth indication information is used for indicating that the third network supports voice communication based on a packet switched domain, so as to avoid voice service interruption.

The third indication information is also used for triggering the third network to send a notification message of the circuit switched domain service to the terminal, and the notification message is used for triggering the terminal to perform voice response in the circuit switched domain in the second network.

The data stream is an analog data stream, and when the access management network element requests the access network device in the first network to establish the data stream, the session management network element in the first network may also participate, that is, before requesting the access network device to establish the data stream, the session management network element is requested to establish the data stream, and then the access network device is requested to establish the data stream.

In one possible implementation, in case the first response includes identification information, the second request further includes the identification information, the identification information being used for the terminal to determine a circuit switched domain location for voice communication.

A second aspect of embodiments of the present application provides a voice communication apparatus having a function of implementing the method provided in the first aspect. The voice communication device may be an access management network element, specifically, an access management network element in the first network. The functions can be realized by hardware, and the functions can also be realized by executing corresponding software by hardware. The hardware or software includes one or more modules corresponding to the above-described functions.

In one possible implementation, the voice communication apparatus includes a processing module, configured to, in registering the terminal with the first network, further register the terminal with a circuit switched domain in a second network; the method comprises the steps that under the condition that a terminal needs to carry out voice communication, the terminal falls back from a first network to a third network; the terminal is dropped from the third network back to the circuit switched domain in the second network.

In one possible implementation, the voice communication apparatus includes a processor and a memory, where the memory stores a computer program, the computer program includes program instructions, and the processor is configured to call program code to perform the following operations: in the process of registering the terminal to the first network, the terminal is also registered to a circuit switched domain in a second network; the method comprises the steps that under the condition that a terminal needs to carry out voice communication, the terminal falls back from a first network to a third network; the terminal is dropped from the third network back to the circuit switched domain in the second network.

Based on the same inventive concept, as the principle and the beneficial effects of the voice communication apparatus for solving the problems can refer to the method and the beneficial effects brought by the method in the first aspect, the implementation of the apparatus can refer to the implementation of the method, and repeated details are not repeated.

A third aspect of the embodiments of the present application provides a computer-readable storage medium, in which a computer program is stored, and the computer program, when executed by a processor, implements the method according to the first aspect.

A fourth aspect of the embodiments of the present application provides a computer program product containing instructions, which when run on a computer, causes the computer to perform the method according to the first aspect.

A fifth aspect of the present invention provides a voice communication method, including:

in the process of registering the terminal to the first network, the first access management network element in the first network also registers the terminal to a circuit switched domain in the second network;

under the condition that the terminal needs to carry out voice communication, the first access management network element drops the terminal from the first network back to the third network;

a second access management network element in the third network drops the terminal from the third network back to the circuit switched domain in the second network.

In one possible implementation, the first access management network element requests the second network to register the terminal to a circuit switched domain in the second network. Specifically, a first access management network element sends a first request to a second network, where the first request is used to request the second network to register a terminal in a circuit switched domain in the second network; a first response is received from the second network indicating that the terminal is registered to the circuit switched domain in the second network.

In a possible implementation manner, the first response further includes identification information allocated by the second network to the terminal, where the identification information is used by the terminal to determine a circuit switched domain location for performing voice communication. And under the condition that the first access management network element acquires the identification information, the first access management network element informs the second access management network element in the process of falling back from the first network to the third network, and then the second access management network element informs the terminal.

In a possible implementation manner, after registering the terminal to the circuit switched domain in the second network, the first access management network element sends first indication information to the terminal, where the first indication information is used to indicate that the first network supports voice communication based on the packet switched domain.

In a possible implementation manner, for a roaming scenario, in the process of registering the terminal to the first network, the first access management network element further obtains subscription data of the terminal from a home network of the terminal, and a communication system corresponding to the subscription data of the terminal is the same as a communication system of the first network.

And if the communication system of the home network is the same as that of the first network, the first access management network element acquires the subscription data of the terminal from a unified data management network element in the home network of the terminal.

If the communication system of the home network is the same as the communication system of the third network, the first access management network element acquires the subscription data of the terminal corresponding to the communication system of the third network from the home subscriber server in the home network, and converts the subscription data of the terminal corresponding to the communication system of the third network into the subscription data of the terminal corresponding to the communication system of the first network.

In a possible implementation manner, after registering the terminal to the circuit switched domain in the second network, the first access management network element sends a connection establishment request to the session management network element in the first network in the process of establishing the data connection, where the connection establishment request includes second indication information and subscription data of the terminal, and the second indication information is used to indicate the session management network element to establish the data connection according to the received subscription data.

In a possible implementation manner, when a terminal needs to initiate voice communication, a first access management network element sends a second request to a second access management network element, where the second request includes third indication information, the third indication information is used to trigger the second access management network element to send fourth indication information to the terminal, and the fourth indication information is used to indicate that a third network supports packet switched domain-based voice communication.

In a possible implementation manner, in a calling situation, the second access management network element triggers the third network to send a notification message indicating that the establishment of the voice service bearer has failed to the terminal, where the notification message is used to trigger the terminal to initiate voice communication in a circuit switched domain in the second network. Specifically, the second access management network element sends a bearer modification request to the session management network element, where the session management network element may include a session management network element in the first network and/or a control plane packet data network element in the third network; the session management network element receives the bearer modification request from the session management network element, and sends a failure notification message to the IMS in the third network according to the second indication information, wherein the failure notification message is used for indicating that the establishment of the voice service bearer fails; and the IMS in the third network sends a notification message of the failure of establishing the voice service bearer to the terminal under the condition of receiving the failure notification message, wherein the notification message is used for triggering the terminal to initiate voice communication in a circuit switching domain in the second network.

In a possible implementation manner, in the case of a calling party, after sending the fourth indication information to the terminal, the access management network element sends a fallback success message to the session management network element; and when receiving the fallback success message, the session management network element sends a failure notification message to the IMS in the third network according to the second indication information.

In a possible implementation manner, in a called situation, that is, in a situation where a first access management network element receives a paging request for a terminal, the first access management network element requests an access network device in a first network to establish a data stream, where the data stream is used to carry a voice service; and when the first access management network element receives the rejection message from the access network equipment, the terminal falls back to the third network from the first network.

In a possible implementation manner, in a called case, before the first access management network element requests the access network device in the first network to establish the data stream, the session management network element in the first network is requested to establish the data stream.

In a possible implementation manner, in a called situation, the first access management network element sends a second request to the second access management network element, where the second request includes third indication information, the third indication information is used to trigger the second access management network element to send fourth indication information to the terminal, and the fourth indication information is used to indicate that the third network supports voice communication based on a packet switched domain.

In a possible implementation manner, in the case of a called party, the third indication information is further used to trigger the second access management network element to send a notification message of a circuit switched domain service to the terminal, where the notification message is used to trigger the terminal to perform a voice response in the circuit switched domain in the second network.

In one possible implementation, in case the first response includes identification information, the second request further includes the identification information, the identification information being used for the terminal to determine the circuit switched domain location for voice communication.

A sixth aspect of embodiments of the present application provides a communication system, which includes a first access management network element in a first network and a second access management network element in a third network,

the first access management network element is used for registering the terminal to a circuit switching domain in a second network in the process of registering the terminal to the first network; the method comprises the steps that under the condition that a terminal needs to carry out voice communication, the terminal falls back from a first network to a third network;

and the second access management network element is used for dropping the terminal from the third network back to the circuit switching domain in the second network.

In a possible implementation, the first access management network element is specifically configured to request the second network to register the terminal to a circuit switched domain in the second network. Specifically, a first access management network element sends a first request to a second network, where the first request is used to request the second network to register a terminal in a circuit switched domain in the second network; a first response is received from the second network indicating that the terminal is registered to the circuit switched domain in the second network.

In a possible implementation manner, the first access management network element is further configured to send, after registering the terminal to a circuit switched domain in the second network, first indication information to the terminal, where the first indication information is used to indicate that the first network supports voice communication based on the packet switched domain.

In a possible implementation manner, for a roaming scenario, the first access management network element is further configured to acquire subscription data of the terminal from a home network of the terminal in a process of registering the terminal in the first network, where a communication system corresponding to the subscription data of the terminal is the same as a communication system of the first network.

And if the communication system of the home network is the same as that of the first network, the first access management network element is specifically used for acquiring the subscription data of the terminal from a unified data management network element in the home network of the terminal.

If the communication system of the home network is the same as the communication system of the third network, the first access management network element is specifically configured to acquire, from the home subscriber server in the home network, subscription data of the terminal corresponding to the communication system of the third network, and convert the subscription data of the terminal corresponding to the communication system of the third network into subscription data of the terminal corresponding to the communication system of the first network.

In a possible implementation manner, the first access management network element is further configured to send a connection establishment request to a session management network element in the first network in a process of establishing a data connection after registering the terminal to a circuit switched domain in the second network, where the connection establishment request includes second indication information and subscription data of the terminal, and the second indication information is used to indicate the session management network element to establish the data connection according to the received subscription data.

In a possible implementation manner, the first access management network element is specifically configured to send a second request to the second access management network element when the terminal needs to initiate voice communication, where the second request includes the third indication information;

and the second access management network element is used for receiving the second request from the first access management network element and sending fourth indication information to the terminal according to third indication information carried by the second request, wherein the fourth indication information is used for indicating that the third network supports voice communication based on the packet switched domain.

In a possible implementation manner, in the case of a called party, the fourth indication information is further used to instruct the access management network element of the third network to send a notification message of a circuit switched domain service to the terminal, where the notification message is used to trigger the terminal to perform a voice response in the circuit switched domain in the second network.

In a possible implementation manner, in the calling case, the communication system further includes a session management network element and an IMS in the third network, and the session management network element may include the session management network element in the first network and/or a control plane packet data gateway in the third network.

The second access management network element is specifically configured to send a bearer modification request to the session management network element when receiving the second request from the first access management network element;

the session management network element is configured to receive the bearer modification request from the session management network element, and send a failure notification message to the IMS in the third network according to the second indication information, where the failure notification message is used to indicate that the establishment of the voice service bearer fails;

and the IMS in the third network is used for sending a notification message of the failure of establishing the voice service bearer to the terminal under the condition of receiving the failure notification message, wherein the notification message is used for triggering the terminal to initiate voice communication in a circuit switching domain in the second network.

In a possible implementation manner, in the case of a calling party, the second access management network element is further configured to send a fallback success message to the session management network element after sending the fourth indication information to the terminal;

and the session management network element is specifically configured to send a failure notification message to the IMS in the third network according to the second indication information when the fallback success message is received.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be described below.

FIG. 1a is a schematic diagram of a network architecture to which the embodiments of the present application are applied;

FIG. 1b is a schematic diagram of another network architecture to which the embodiments of the present application are applied;

fig. 2 is a flowchart illustrating a voice communication method according to an embodiment of the present application;

fig. 3a is a schematic diagram illustrating a process of registering a UE to a 5G network in a roaming scenario according to an embodiment of the present application;

fig. 3b is a schematic diagram illustrating a process of registering a UE to a 5G network in a non-roaming scenario according to an embodiment of the present application;

fig. 4a is a schematic diagram of a data connection establishment process in a roaming scenario according to an embodiment of the present application;

fig. 4b is a schematic diagram of a data connection establishment process in a non-roaming scenario according to an embodiment of the present application;

fig. 5a is a schematic diagram of an SIP registration process in a roaming scenario according to an embodiment of the present application;

fig. 5b is a schematic diagram of an SIP registration process in a non-roaming scenario according to an embodiment of the present application;

fig. 6a is a schematic diagram of a fallback procedure in a UE calling situation in a roaming scenario according to an embodiment of the present application;

fig. 6b is a schematic diagram of a fallback procedure in a UE calling situation in a non-roaming scenario according to an embodiment of the present application;

Fig. 7 is a schematic diagram of a fallback procedure in a case that a UE is called according to an embodiment of the present application;

fig. 8 is a schematic logical structure diagram of a voice communication apparatus according to an embodiment of the present application;

fig. 9 is a simplified schematic diagram of an entity structure of a voice communication apparatus according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Where in the description of the present application, "/" indicates a relationship where the objects associated before and after are an "or", unless otherwise stated, for example, a/B may indicate a or B; in the present application, "and/or" is only an association relationship describing an associated object, and means that there may be three relationships, for example, a and/or B, and may mean: a exists alone, A and B exist simultaneously, and B exists alone, wherein A and B can be singular or plural. Also, in the description of the present application, "a plurality" means two or more than two unless otherwise specified. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple. In addition, in order to facilitate clear description of technical solutions of the embodiments of the present application, in the embodiments of the present application, terms such as "first" and "second" are used to distinguish the same items or similar items having substantially the same functions and actions. Those skilled in the art will appreciate that the terms "first," "second," etc. do not denote any order or quantity, nor do the terms "first," "second," etc. denote any order or importance.

At present, a 5G network relates to two voice communication methods, which are voice over IMS essentially, voice services are provided by the IMS and can be realized only by deploying the IMS. For non-roaming scenarios, IMS may or may not be deployed under the 5G network, or the deployed IMS may not be available. For a roaming scenario, the IMS may not be deployed at the visited and/or home locations of the 5G terminal, or the deployed IMS may not be used, so that the two voice communication methods cannot be used, and the terminal cannot perform a voice service.

Fourth generation (4)^thGeneration, 4G) network, which refers to a terminal for voice over LTE (VoLTE) based voice services, which can continue to use VoLTE services after moving to a country or place other than the country or place to which the home operator belongs. The IMS roaming includes two methods, one is roaming architecture for voice over IMS with local breakout, RAVEL, and the other is a roaming method (S8home routed, S8HR) for selecting a home gateway to access a Packet Data Network (PDN) through an S8 interface. Among them, the RAVEL deployment is complex (for example, the visited network and the home network are required to deploy IMS at the same time), and there are many usage restrictions (for example, Policy and Charging Control (PCC) that the roaming terminal does not support to use the home network). The S8HR is relatively simple to deploy, and the interworking between the visited place and the home place is realized through the S8 interface between the Serving Gateway (SGW) in the visited place network and the PDN Gateway (PGW) in the home place network, so that the VoLTE terminal can still continue to use the VoLTE service of the home place after moving to the outside of the home place. However, S8HR has some problems, such as network protocol message exchange (Internet pr) otocol packet exchange, IPX), visited operators charge according to the flow, and home operators charge according to the duration, and the charging modes are not uniform.

In view of the defects of IMS roaming in 4G networks, these two methods cannot be applied to the IMS roaming scenario of 5G networks. In a 5G network IMS roaming scene, IMS is required to be deployed in both a home location and a visited location, and if IMS is not deployed in the home location or the visited location, voice communication cannot be achieved. For example, when the home location of the international roaming user is country a, country a does not deploy a 5G network, the international roaming user roams to country B, country B deploys a 5G network, and the international roaming user accesses the 5G network deployed by the operator of country B through the 5G terminal, since the operator does not activate IMS roaming for the international roaming user, and cannot provide CS domain roaming for the international roaming user, the 5G terminal cannot reside in the 5G network of country B, cannot use the 5G network of country B, and cannot perform voice communication. For another example, when the home location of the domestic roaming user is city a, city a does not deploy a 5G network, the user roams to city B, and city B deploys a 5G network, and the user accesses the 5G network of city B through the 5G terminal, since the operator of city B does not activate IMS roaming for the user, CS domain roaming cannot be provided for the user, the 5G user terminal cannot reside in the 5G network of city B, and cannot use the 5G network of city B, and voice communication cannot be performed.

Therefore, the embodiment of the application provides a voice communication method and a device thereof, which can be used for both roaming scenes and non-roaming scenes, so that the normal operation of voice services in a 5G network is ensured, the utilization rate of the 5G network is further improved, and the user experience is improved. The embodiment of the application can be applied to a non-roaming scene, namely a scene that a user performs voice communication in a 5G network through a 5G terminal, for example, an IMS is not deployed in the 5G network to which the 5G terminal belongs. The embodiment of the application can be applied to a roaming scene, and under the scene that an international roaming user or a domestic roaming user is not provided with a 5G network at the home location and an IMS roaming is not provided for the roaming user by an operator of a 5G network at a visit location, when the 5G terminal roams to the visit location and visits the 5G network at the visit location, a voice service can be provided for the 5G terminal, a 5G data service can also be provided for the 5G terminal, and further user experience is improved. The embodiment of the application can be applied to a scene that an international roaming user accesses the 5G network of the visited place through the 5G terminal, and can also be applied to a scene that a domestic roaming user accesses the 5G network of the visited place by using the 5G terminal.

The terminals according to the embodiments of the present application are, without specific reference, 5G terminals or terminals in future communication networks, for example, sixth generation (6) ^th-generation, 6G) terminal. Terminals, which may include various handheld devices with wireless communication capabilities, in-vehicle devices, wearable devices, computing devices, or other processing devices connected to a wireless modem; user Equipment (UE), subscriber unit (subscriber unit), cellular phone (cellular phone), smart phone (smart phone), wireless data card, Personal Digital Assistant (PDA) computer, tablet computer, wireless modem (modem), hand-held device (hand), laptop computer (laptop computer), cordless phone (cordless phone) or Wireless Local Loop (WLL) station, Machine Type Communication (MTC) terminal, internet of things device, mobile station (mobile station, MS), terminal device (terminal device) or relay user equipment, etc. may also be included. The relay user equipment may be, for example, a 5G home gateway (RG).

The user related to the embodiment of the present application may refer to a user who actually operates the terminal, or may refer to a communication card installed on the terminal, such as a Subscriber Identity Module (SIM) card, an embedded SIM (embedded-SIM) card, and the like.

The embodiment of the application can be applied to a scene that the terminal is provided with the 5G communication card and can also be applied to a scene that the terminal is provided with the 4G communication card. The voice service related to the embodiment of the application can be a voice service for dialing a telephone number and can also be a video voice service. If the international roaming user initiates an IMS video voice service request in the 5G network of the visited place, the 5G network of the visited place converts the IMS video voice service request into a dial-up voice service request.

Please refer to fig. 1a, which is a schematic diagram of a network architecture according to an embodiment of the present application, the schematic diagram of the network architecture includes a first network, a second network, and a third network.

For a non-roaming scenario, the first network, the second network, and the third network are home networks of the terminal, for example, networks of three communication systems deployed under an operator to which the terminal belongs. For a roaming scenario, the first network, the second network, and the third network are visited networks of the terminal, referring to another network architecture diagram shown in fig. 1b, the network architecture diagram is a network architecture diagram in the roaming scenario, and includes a visited network and a home network, and the visited network includes the first network, the second network, and the third network.

The communication system of the first network is a 5G network, and the communication system of the third network is a 4G network. In one possible implementation, the first network may deploy IMS. In another possible implementation, the third network may include an IMS. The communication system of the second network is a 2G network or a 3G network and comprises a Circuit Switching (CS) domain.

The first network includes an access management network element, which is an access and mobility management function (AMF) in the 5G core network and is responsible for mobility and access management of the terminal. The access management network element may also be a network element responsible for mobility and access management in future communication systems. In this embodiment, the AMF provides an SGs interface with the second network, where the SGs interface is specifically an interface between the AMF and a Mobile Switching Center (MSC) in the second network, so that the AMF registers the terminal with the MSC, and the terminal can perform voice communication in the CS domain. In a roaming scenario, the AMF further provides an interface with a home network, and specifically includes a Gr interface between the AMF and a Home Location Register (HLR) in the home network, and an S6a interface between the AMF and a Home Subscriber Server (HSS) in the home network. The Gr interface is used for AMF to obtain 2G/3G subscription data and dynamic position information from HLR, and the S6a interface is used for AMF to obtain 4G subscription data and dynamic position information from HSS. The subscription data includes package information, user validity and other data.

In this embodiment, the first network further includes an access network device, and the access network device may be a next generation base station Node (gNB) in a 5G network, or an access network device in a future communication system.

In this embodiment, the first network further includes a policy control network element, where the policy control network element may be a Policy Control Function (PCF) in the 5G network, and is configured to support a unified policy framework to manage network behaviors, provide policy rules for the control plane function, and the like.

The IMS in the third network may comprise an IMS-home subscriber server (IMS-HSS) for user IMS data storage, authentication and addressing. In the embodiment of the present application, in a roaming scenario, the IMS-HSS provides an interface with a home network, specifically, a C/D interface between the IMS-HSS and an HLR in the home network, and is used for the IMS-HSS to acquire authentication data (authentication information) from the HLR in the home network.

The second network comprises an MSC responsible for access and mobility management of the user in the CS domain. In the embodiment of the present application, the MSC may register the terminal in the CS domain during the registration of the terminal in the first network, so as to ensure the voice service of the terminal.

The communication system of the home network may be a 4G network or a 5G network.

In this embodiment, when the access management network element in the first network registers the terminal to the first network, the terminal is also registered to the CS domain of the second network, and when the terminal needs to perform voice communication, the access management network element drops the terminal from the first network to the third network, and then drops the terminal from the third network to the second network, so that the terminal performs voice communication in the circuit switched domain. Even if the IMS is not deployed in the 5G network, the normal operation of voice service in the 5G network can be ensured.

Further, with communication technologyDevelopment of (4), the sixth generation (6) may appear in the future^thGeneration, 6G) network, or the idea of the present application may be applied in future communication systems, for example, in the process of registering the terminal in the 6G network, the terminal is also registered in the CS domain, and when the terminal needs to perform voice communication, the terminal falls back from the 6G network to the 5G network, then falls back from the 5G network to the 4G network, and then falls back from the 4G network to the CS domain.

According to the embodiment of the application, the local network user or the roaming user successfully registers VoLTE, the terminal can stay in the 5G network, the AMF completes joint attachment through simulation of the SGs interface and the S6a interface in a roaming scene, then the terminal falls back to the EPS and then to the CS domain when initiating voice communication or called voice communication, and voice communication is carried out in the CS domain. Therefore, the terminal is registered with VoLTE so that the terminal can perform data service, and the voice service of the terminal can be ensured by falling back to the EPS and then falling back to the CS domain, so that the user experience is improved, and the terminal is prevented from being incapable of enjoying the advantages of the 5G network under the 5G network.

Based on the network architecture shown in fig. 1a or fig. 1b, the communication method provided by the embodiment of the present application will be described in detail below. The method is applied to a scene that the terminal roams from a home network to a first network and accesses the first network, the communication mode of the first network is 5G network as an example, and the terminal carries out voice communication through a CS domain at the home. The method can also be applied to the scene that the terminal accesses the local 5G network. In the introduction, the first network is exemplified by 5G, the second network is exemplified by 2G/3G, and the third network is exemplified by 4G. In the following embodiments, the names of the messages do not limit the embodiments of the present application.

Referring to fig. 2, a flow chart of a voice communication method provided in the embodiment of the present application is schematically illustrated, where the method may include, but is not limited to, the following steps:

step 201, in the process of registering the terminal to the first network, an access management network element in the first network registers the UE to a CS domain in the second network.

Wherein, a terminal refers to a 5G terminal, for example: the roaming user's 5G terminal may be an international roaming user's 5G terminal or a domestic roaming user's 5G terminal. When the 5G terminal of the roaming user roams to the 5G network of the visit place and visits the 5G network of the visit place, the UE is firstly registered in the 5G network to obtain corresponding service.

And registering the UE to the 5G network, namely verifying the legality of the UE by the 5G network, wherein if the verification is passed, the UE is allowed to be registered to the 5G network, and if the verification is not passed, the UE is not allowed to be registered to the 5G network. See in particular the description of the prior art.

The UE in the 4G network may actively initiate a joint attachment procedure, and send a joint attachment request to a Mobility Management Entity (MME) in the 4G network through an access network device in the 4G network, and when receiving the joint attachment request, the MME may initiate a location update (location update) procedure to an MSC in the 2G/3G network for the UE in the 4G network, so as to register the UE in the 4G network to a CS domain, so as to ensure a voice service and a short message service of the UE in the 4G network. However, voice services in the 5G network are provided by IMS, and the protocol specifies that the 5G network has no function of joint attachment, so the access management network element needs to register the terminal to the CS domain.

The access management network element requests the 2G/3G network to register the terminal to the CS domain, and the access management network element can initiate a location updating process to the MSC in the 2G/3G network so as to register the terminal to the CS domain and ensure the voice service of the terminal. Specifically, the access management network element sends a first request to the MSC, where the first request is used to request the MSC to register the terminal in the CS domain, and the first request may be a location update request; the MSC registers the terminal to the CS domain upon receiving the first request, and sends a first response to the access management network element after the registration, the first response being used for responding to the first request for indicating that the terminal is registered to the CS domain, and the first response may be location update response or location update accept.

In a possible implementation manner, the first response includes identification information allocated by the MSC to the terminal, and the identification information may include CS-related information such as a Temporary Mobile Subscriber Identity (TMSI) and a Location Area Identity (LAI). The MSC informs the access management network element of the identification information allocated to the terminal, so that the access management network element informs the MME of the identification information, so that the MME informs the terminal, and the terminal determines the CS domain position for voice communication according to the identification information, namely determines the CS domain in which the voice communication is carried out.

In the embodiment of the application, the access management network element registers the terminal in the CS domain in the process of registering the terminal in the first network, so that the terminal can enjoy the data service provided by the 5G network and can ensure normal operation of the voice service.

For a roaming scenario, in a possible implementation manner, in the process of registering a terminal in a first network, an access management network element further obtains subscription data of the terminal from a home network, where a communication system corresponding to the subscription data is the same as that of the first network, that is, the subscription data corresponds to a 5G network. The subscription data may include package information, user legitimacy, and the like. If the terminal is a 5G terminal 5G card, the access management network element obtains the subscription data of the terminal from a Unified Data Management (UDM) network element in the home network. If the terminal is a 5G terminal 4G card, the access management network element acquires the subscription data of the communication system of the terminal corresponding to the third network, namely the subscription data under the 4G network, from the HSS in the home network, and converts the subscription data corresponding to the 4G network into the subscription data corresponding to the 5G network.

The process of registering the terminal to the first network will be described in detail in the embodiments shown in fig. 3a and 3 b.

After the terminal is registered to the first network, a data connection establishment procedure and a Session Initiation Protocol (SIP) registration procedure are further included, which are respectively described in detail in the embodiments shown in fig. 4a and 5a for the roaming scenario, and in the embodiments shown in fig. 4b and 5b for the non-roaming scenario. After the process of registering the UE to the 5G network is performed, a data connection establishment process is performed, and then a SIP registration process is performed. The data connection establishment procedure may be a Protocol Data Unit (PDU) session establishment procedure.

Step 202, the access management network element drops the terminal from the first network back to the third network under the condition that the terminal needs to perform voice communication.

The condition that the terminal needs to perform voice communication may include a condition that the terminal actively initiates voice communication, that is, a calling condition, and a condition that the terminal is called, that is, a called condition. For the international roaming user, the calling condition is that the terminal initiates a voice call to other users of the home location, and the called condition is that other users of the home location initiate a voice call to the international roaming user.

The access management network element drops the terminal from the first network back to the third network, i.e. from the 5G network back to the 4G network or from the 5G network back to the EPS.

In case of a calling party, the access management network element drops the terminal from the first network back to the third network when receiving the indication information rejecting the modification of the data connection.

In the called case, the access management network element, upon receiving a paging request for the terminal, requests the access network device in the first network to establish a data flow, which may be a proprietary quality of service (QoS) flow (flow) that is used to carry voice traffic. And the access management network element drops the terminal from the first network back to the third network when receiving the rejection message from the access network equipment.

Step 203, the access management network element drops the terminal from the third network back to the CS domain in the second network.

The access management network element drops the terminal from the third network back to the CS domain in the second network, so that the terminal performs voice communication in the CS domain, thereby ensuring that the voice service of the terminal can be performed normally.

For the calling situation in the roaming scenario, the access management network element drops the terminal from the 5G network back to the EPS and drops the terminal from the EPS to the CS domain, which will be specifically described in the embodiment shown in fig. 6 a.

For the calling situation in the non-roaming scenario, the access management network element drops the terminal from the 5G network back to the EPS and drops the terminal from the EPS to the CS domain, which will be specifically described in the embodiment shown in fig. 6 b.

For the called situation in the roaming scenario or the non-roaming scenario, the access management network element drops the terminal from the 5G network back to the EPS and drops the terminal from the EPS to the CS domain, which will be described in the embodiment shown in fig. 7.

In the embodiment shown in fig. 2, for a scenario in which a user accesses a 5G network through a 5G terminal, an access management network element registers the terminal in the 5G network, and registers the terminal in a CS domain in a process of registering the terminal in the 5G network, when the terminal needs to perform voice communication, the terminal falls back from the 5G network to an EPS, and then falls back from the EPS to the CS domain, so that the terminal performs voice communication in the CS domain, thereby ensuring that a voice service of the terminal can be performed normally.

In a roaming scene, the terminal uses the CS domain to carry out voice communication, so that the charging mode of the terminal in the visited network is consistent with the charging mode of the home network, and the influence caused by the inconsistent charging modes of the home network and the visited network is avoided.

For example, in a roaming scenario, the home location of the international roaming user X is country a, country a does not deploy a 5G network, when the international roaming user X roams from country a to country B, country B deploys a 5G network, and when the 5G UE accesses the country B5G network, an access management network element of the 5G network registers the 5G UE to a CS domain in the process of registering the 5G UE to the 5G network, and then when the UE needs to perform voice communication, triggers the 5G UE to fall back from the 5G network to an EPS, and then triggers the UE to fall back from the EPS to the CS domain, thereby performing voice communication in the CS domain. Therefore, when the national roaming user X uses the 5G UE in the country B, the national roaming user X can carry out voice communication through the CS domain and can enjoy data services provided by the 5G network by using the 5G UE.

In a possible implementation manner, the access management network element in the first network and the access management network element in the third network may be combined, that is, the AMF in the 5G network and the MME in the 4G network may be combined, for example, the function of the MME is integrated in the AMF. In this way, the above steps 201 to 203 are performed by the access management network element after the provisioning, for example, by the AMF after the provisioning.

In a possible implementation manner, the access management network element in the first network and the access management network element in the third network are deployed separately, that is, the AMF in the 5G network is deployed in the 5G network, and the MME in the 4G network is deployed in the 4G network. In this way, the above steps 201 to 202 are performed by the AMF, and step 203 is performed by the MME.

Wherein the access management network element in the first network corresponds to the first access management network element in the claims and the summary, for example, AMF; the access management network element in the third network corresponds to the second access management network element in the claims and summary, e.g. being an MME.

In the introduction process of the subsequent embodiment, the AMF and the MME are introduced by taking the respective deployments as examples, and if the AMF and the MME are combined, the interactive message between the AMF and the MME can be omitted. In the introduction process of the subsequent embodiment, the access management network element in the first network takes the AMF as an example, the access management network element in the third network takes the MME as an example, and the terminal takes the UE as an example.

Referring to fig. 3a, a schematic diagram of a process for registering a UE to a 5G network in a roaming scenario provided in the embodiment of the present application may include, but is not limited to, the following steps:

in step 301-1, the UE transmits a registration request (registration request) to the AMF. Accordingly, the AMF receives a registration request from the UE.

Specifically, the UE sends a registration request to the AMF through the access network device in the 5G network, that is, the UE first sends a registration request to the access network device, and the access network device selects the AMF for the UE and then sends the registration request to the AMF. The registration request is for requesting registration to the 5G network.

The registration request may include information such as a registration type, UE capability, security parameters, and the like, so that the 5G network performs authentication, access control, and the like on the UE.

Step 302-1, the AMF obtains authentication data to the UDM/HSS of the home network.

If the UE is a 5G terminal 4G card, the registration request further includes a non-encrypted user hidden identifier (sui), the routing indicator (routing indicator) included in the non-encrypted sui is 000 or 0fff according to the protocol, and the AMF determines whether the UE is an International roaming user by using a user permanent identifier (SUPI) (i.e., International Mobile Subscriber Identity (IMSI)), and if the UE is the 5G terminal 4G card and the roaming protocol is signed, the AMF acquires authentication data from the HSS in the home location through an S6a interface, where the authentication data is authentication data in the 4G network. In this case, the AMF serves as an authentication server function (AUSF) of the international roaming user, converts authentication data in the 4G network into authentication data in the 5G network, and initiates an authentication procedure to the UE.

Among them, SUCI and SUPI are concepts introduced for 5G protocols, and although the UE is a 5G terminal 4G card, the UE is a 5G terminal, and may include these two identifiers.

If the UE is a 5G terminal 5G card, the AMF directly acquires authentication data under the 5G network from the UDM according to the routing indicator.

Step 303-1, the AMF obtains subscription data of the UE to the UDM/HSS of the home network. The subscription data is subscription data corresponding to a 5G network.

If the UE is a 5G terminal 4G card, the AMF acquires the subscription data of the UE corresponding to the 4G network from the HSS of the home network, and converts the subscription data of the UE corresponding to the 4G network into the subscription data of the UE corresponding to the 5G network. For example, the AMF converts an Access Point Name (APN) in subscription data of the UE corresponding to the 4G network into a Data Network Name (DNN) in subscription data of the UE corresponding to the 5G network, converts the 4G QoS into the 5G QoS, and the like.

And if the UE is a 5G terminal 5G card, the AMF acquires the subscription data of the UE from the UDM of the home network.

In step 304-1, the AMF requests the MSC to register the UE with the CS domain.

Specifically, the AMF sends a first request to the MSC, where the first request is used to request the MSC to register the UE to the CS domain, and the first request may be a location update request; the MSC registers the UE with the CS domain upon receiving the first request, and sends a first response to the AMF after the registration, the first response being for responding to the first request for indicating that the UE has registered with the CS domain, the first response may be location update response or location update accept.

In a possible implementation manner, the first response includes identification information allocated by the MSC to the UE, and the identification information may include CS-related information such as a Temporary Mobile Subscriber Identity (TMSI) and a Location Area Identity (LAI). The MSC informs the AMF of the identification information distributed by the MSC for the UE, so that the AMF informs the MME of the identification information, so that the MME informs the UE, and the UE determines the CS domain position for voice communication according to the identification information, namely determines the CS domain in which the voice communication is carried out. And the AMF stores the identification information so as to inform the MME of the identification information when receiving the identification information.

In step 305-1, the AMF sends a registration accept (registration accept) to the UE. Accordingly, the UE receives a registration acceptance from the AMF.

Specifically, the AMF sends a registration acceptance to the UE through the access network device in the 5G network, that is, the AMF first sends the registration acceptance to the access network device, and then the access network device sends the registration acceptance to the UE.

Wherein the registration acceptance includes a registration area, a mobility restriction condition, a registration update timer period, and indication information of whether the 5G network supports voice communication over a Packet Switching (PS) domain, and indication information of whether the 5G network supports interoperation of the N26 interface.

In the embodiment of the present application, the registration acceptance includes first indication information, where the first indication information is used to indicate that the 5G network supports voice over PS (VoPS) based on a PS domain, that is, VoPS support. Since the international roaming user of the UE may not support the IMS subscription data, the AMF carries the first indication information in the registration acceptance to indicate that the 5G network supports VoPS regardless of whether the UE supports the IMS subscription data. And under the condition that the first indication information carries the VoPS support, triggering the execution of the PDU session establishment process and the SIP registration process. And if the first indication information does not carry the VoPS support, not executing the PDU session establishment process and the SIP registration process.

In the embodiment shown in fig. 3a, for a scenario that a roaming user roams to a visited place through a 5G UE and accesses a 5G network of the visited place, the AMF registers the UE to the 5G network, and registers the UE to a CS domain during the process of registering the UE to the 5G network, so as to ensure that the UE can perform a voice service in the CS domain.

Referring to fig. 3b, a schematic diagram of a process for registering a UE to a 5G network in a non-roaming scenario provided in the embodiment of the present application may include, but is not limited to, the following steps:

in step 301-2, the UE sends a registration request to the AMF. Accordingly, the AMF receives a registration request from the UE.

In step 302-2, the AMF requests the MSC to register the UE with the CS domain.

In step 303-2, the AMF sends a registration acceptance to the UE. Accordingly, the UE accepts the registration acceptance from the AMF.

Step 301-2 can refer to the detailed description of step 301-1 in the embodiment shown in fig. 3a, step 302-2 can refer to the detailed description of step 304-1 in the embodiment shown in fig. 3a, and step 303-2 can refer to the detailed description of step 305-1 in the embodiment shown in fig. 3a, which is not repeated herein.

Since FIG. 3b is a non-roaming scenario, steps 302-1 and 303-1 in FIG. 3a are not present.

In the embodiment shown in fig. 3b, for a scenario that a user of the home network accesses the 5G network through the 5G UE, the AMF registers the UE to the 5G network, and registers the UE to the CS domain during the process of registering the UE to the 5G network, so as to ensure that the UE can perform a voice service in the CS domain.

After step 305-1, a data connection establishment procedure may be executed, please refer to fig. 4a, which is a schematic diagram of a data connection establishment procedure in a roaming scenario provided in the embodiment of the present application, where the data connection establishment procedure takes a PDU session establishment procedure as an example, and the procedure may include, but is not limited to, the following steps:

in step 401-1, the UE sends a PDU session establishment request to the AMF. Accordingly, the AMF receives a PDU session setup request from the UE.

Specifically, the UE first sends a PDU session establishment request to the AMF to the access network device in the 5G network, that is, the UE first sends a PDU session establishment request to the access network device, and the access network device sends a PDU session establishment request to the AMF. The registration request is for requesting establishment of a PDU session. The PDU session may be used to carry data traffic and may also be used to carry voice traffic, but in this application embodiment, the voice traffic is ultimately carried by the CS domain.

The PDU session establishment request sent by the UE to the AMF may be, for example, a PDU session establishment request.

Step 402-1, the AMF sends a PDU session establishment request to a Session Management Function (SMF). Accordingly, the SMF receives a PDU session setup request from the AMF.

And the PDU session establishment request sent by the AMF to the SMF comprises second indication information and subscription data. The subscription data is subscription data of the UE corresponding to the 5G network. And the second indication information is used for indicating the SMF to establish the PDU session according to the received subscription data. The second indication may be a feature 5G subscriber identity identifying that the 5G subscriber is a simulated 5G voice subscriber and not a real voice 5G subscriber, but that the SMF is still establishing a PDU session for the UE and allowing the UE to establish an IMS PDU session. The PDU session setup Request sent by the AMF to the SMF may be, for example, Nsmf _ pdusesion _ CreateSMContext Request.

In step 403-1, the SMF sends a PDU session setup response to the AMF. Accordingly, the AMF receives the PDU session setup response from the SMF.

When receiving a PDU session establishment request from the AMF, the SMF determines that the PDU session is established directly according to the received signing data and allows the establishment of the IMS PDU session according to the second indication information without acquiring the signing data from the UDM/HSS of the home location. The strategy information of SMF for establishing PDU session is sent by PCF by default.

The PDU session setup response sent by the SMF to the AMF may be, for example, Nsmf _ pdusesion _ CreateSMContext.

In step 404-1, the AMF sends a PDU session setup response to the UE. Accordingly, the UE receives the PDU session setup response from the AMF.

The PDU session setup response sent by the AMF to the UE may be, for example, a PDU session initialization accept.

In the embodiment shown in fig. 4a, a PDU session is established for a 5G voice subscriber, and the SMF establishes the PDU session directly according to the received subscription data, so that the establishment duration of the PDU session can be shortened.

After step 303-2, a data connection establishment procedure may be executed, please refer to fig. 4b, which is a schematic diagram of a data connection establishment procedure in a non-roaming scenario provided in the embodiment of the present application, where the data connection establishment procedure takes a PDU session establishment procedure as an example, and the procedure may include, but is not limited to, the following steps:

In step 401-2, the UE sends a PDU session establishment request to the AMF. Accordingly, the AMF receives a PDU session setup request from the UE.

At step 402-2, the AMF sends a PDU session establishment request to the SMF. Accordingly, the SMF receives a PDU session setup request from the AMF.

Wherein, the PDU session establishment request sent by the AMF to the SMF comprises second indication information. The SMF identifies that the G user is a simulated 5G voice user and is not a real 5G voice user according to the second indication information, and sends the address of the SMF to the UE as the address of a proxy-call session control function (P-CSCF).

In step 403-2, the SMF sends a PDU session establishment response to the AMF. Accordingly, the AMF receives the PDU session setup response from the SMF.

Wherein, the PDU session setup response sent by the SMF to the AMF includes the address of the P-CSCF, so that the AMF informs the UE of the PDU session setup response, and the UE can perform SIP registration according to the address of the P-CSCF.

In step 404-2, the AMF sends a PDU session establishment response to the UE. Accordingly, the UE receives the PDU session setup response from the AMF.

And the PDU session establishment response sent by the AMF to the UE comprises the address of the P-CSCF, so that the UE can perform SIP registration according to the address of the P-CSCF.

The same parts in fig. 4b as fig. 4a can be referred to the detailed description of fig. 4a, and are not repeated herein.

In the embodiments shown in fig. 4a and fig. 4b, the detailed procedure of PDU session establishment may refer to the description of the prior art, and is not described herein again.

After step 404-1, a SIP registration procedure may be executed, please refer to fig. 5a, which is a schematic diagram of a SIP registration procedure in a roaming scenario provided by the embodiment of the present application, and the procedure may include, but is not limited to, the following steps:

in step 501-1, the UE sends a SIP registration to the IMS.

The IMS includes an IMS-HSS, a P-CSCF, a serving-call session control function (S-CSCF), and an interrogating-call session control function (I-CSCF).

Step 502-1, the IMS acquires authentication data from the HLR of the home network and completes SIP authentication.

The IMS-HSS acquires authentication data from the home HLR through the C/D interface.

In the SIP registration process, the UE initiates the registration process of the IMS by issuing a SIP registration request (SIP registration). The SIP registration request can comprise user information, session description information and the like, and the registration request firstly reaches the P-CSCF; then, the P-CSCF obtains an I-CSCF of the home location and forwards the SIP registration request to the I-CSCF; IMS-HSS obtains the authentication data from home HLR through C/D interface, by inquiring IMS-HSS, I-CSCF will select a S-CSCF for UE and forward SIP register request to S-CSCF, then S-CSCF will calculate and feed back the authentication data for UE with the help of the authentication data obtained from HLR, and after confirming that UE is legal, it sends down message to inform UE that register is successful, and completes SIP authentication.

The SIP registration procedure shown in fig. 5a, so that the UE can fall back from the 5G network to the EPS when voice communication is required.

In the embodiment shown in fig. 5a, the detailed procedure for sending the SIP registration from the UE to the IMS may refer to the description of the prior art, and is not described herein again.

After step 404-2, a SIP registration procedure may be executed, please refer to fig. 5b, which is a schematic diagram of a SIP registration procedure in a non-roaming scenario provided by the embodiment of the present application, and the procedure may include, but is not limited to, the following steps:

in step 501-2, the UE sends a SIP registration request to the SMF.

In step 502-2, the SMF sends a SIP REGISTER response to the UE.

Other network elements between the UE and the SMF, e.g. access network equipment, AMF, are omitted in fig. 5 b. When receiving the SIP registration request, the SMF parses the SIP packet, and determines that the 5G user is an analog 5G voice user according to the second indication information carried in step 402-2 in the embodiment shown in fig. 4b, and the SMF simulates an IMS function, thereby completing the SIP registration of the UE.

After the SIP procedure, the embodiments shown in fig. 6a or fig. 6b or fig. 7 may be performed.

Referring to fig. 6a, a schematic diagram of a fallback procedure in a UE calling situation in a roaming scenario provided in the embodiment of the present application is shown, where the procedure may include, but is not limited to, the following steps:

Step 601-1, the UE initiates a calling to the IMS.

In step 602-1, the IMS initiates a PDU session modification to the access network device in the 5G network. The access network device may be a gbb.

Specifically, the IMS sends a PDU session modification request to the PCF, and then the PCF sends the PDU session modification request to the access network device in the 5G network through the network elements of the 5G core network, such as the SMF and the AMF.

Step 603-1, the access network equipment in the 5G network sends indication information for refusing to modify PDU session to SMF. Accordingly, the SMF receives an indication from the access network device to reject modification of the PDU session. Step 603-1 is followed by a procedure of dropping the UE from the 5G network back to the EPS, i.e. an EPS fallback procedure. In the course of executing the EPS fallback flow, step 604-1 to step 609-1 are executed.

Step 604-1, the AMF sends a second request to the MME. Accordingly, the MME receives a second request from the MME.

The second request may be a forward migration request, i.e., a forward location request. The second request comprises third indication information, the third indication information is used for triggering the MME to send fourth indication information to the UE, and the fourth indication information is used for indicating that the 4G network supports VoPS so as to avoid that the UE deletes the IMS bearer and avoid communication interruption. The third indication information may be, for example, MO _ CSFB _ Indicator.

In step 605-1, the MME sends a modify bearer request to the SMF. Accordingly, the SMF receives a modify bearer request from the MME. Here, the MME may send the modify bearer request to the SMF, or the MME may send a modify bearer request to the SMF + control plane PDN gateway (PGW-C) (that is, the SMF and the PGW-C are co-located).

At step 606-1, the SMF sends a failure notification message to the IMS. Accordingly, the IMS receives the failure notification message from the SMF.

Specifically, the SMF first sends a failure notification message to the PCF, and then the PCF sends the failure notification message to the IMS. The failure notification message is used for informing PCF/IMS voice service bearing establishment failure. The failure notification message may be, for example, a voice truncated bearer interest fall.

After receiving the request for modifying the bearer, the SMF recognizes that the UE needs to fall back to the CS domain to execute the voice call according to the second indication information carried in step 402-1 in the PDU session establishment procedure, so that the SMF sends a failure notification message to the IMS through the PCF.

After receiving the failure notification message, the IMS may send a notification message indicating that the establishment of the voice service bearer failed to the UE, where the notification message is used to trigger the UE to actively initiate fallback to the CS domain, so as to initiate voice communication in the CS domain. The notification message may be, for example, a 500/503/380 message.

Step 607-1, the UE sends a Tracking Area Update (TAU) request to the MME. Accordingly, the MME receives a tracking area update request from the UE.

In step 608-1, the MME performs location update with the MSC. Specifically, the MME sends a location update request to the MSC, and the MSC sends a location update response to the MME after the update.

Step 609-1, the MME sends a tracking area update response to the UE. Accordingly, the UE receives a tracking area response from the MME. It should be noted that 4G access network equipment is omitted between the MME and the UE.

And the tracking area update response comprises fourth indication information, wherein the fourth indication information is used for indicating that the 4G network supports VoPS so as to avoid that the UE deletes the IMS bearer and avoid communication interruption.

If the SMF sends a failure notification message to the IMS in step 606-1, the UE may receive the notification message of the voice service bearer setup failure in step 610-1 before initiating step 607-1 to send the TAU request, resulting in step 607-1 and step 611-1 being out of order. Therefore, step 609-1a is added after step 609-1, the MME identifies that the UE needs to actively fall back to the CS domain through the third indication information, and then after the TAU procedure, the SMF EPS Fallback procedure is notified through a separate message to be successful, and then the SMF performs step 606-1, and the SMF sends a failure notification message to the IMS. The separate message may be a Fallback success message indicating that the EPS Fallback procedure is successful. This ensures that process step 611-1 occurs after the TAU process. In other words, the SMF performs step 606-1 after receiving the modify bearer request and the separate message.

Step 610-1, the IMS sends a notification message that the establishment of the voice service bearer has failed to the UE. Correspondingly, the UE receives a notification message of the failure of the establishment of the voice service bearer from the IMS.

The notification message is used to trigger the UE to actively initiate a fallback to the CS domain in order to initiate voice communication in the CS domain. The notification message may be, for example, an 500/503/380 message.

In step 611-1, the UE initiates a voice call in the CS domain.

When receiving the notification message of the failure of establishing the voice service bearer, the UE actively initiates a voice call in the CS domain.

In the embodiment shown in fig. 6a, based on that the UE is registered in the CS domain, when the UE needs to initiate a voice call, the AMF drops the UE from the 5G network back to the EPS, and then the MME drops the UE from the EPS to the CS domain, so that the UE initiates the voice call in the CS domain, thereby ensuring normal operation of the UE voice service.

As a possible implementation manner, in case that the first response of step 304 includes identification information, the second request of step 604-1 further includes the identification information, and the MME carries the identification information through the tracking area update response of step 609-1 to inform the UE of the identification information, so that the UE determines in which CS domain to initiate the voice call.

Referring to fig. 6b, a schematic diagram of a fallback procedure in a non-roaming scenario for a UE calling scenario is provided in this embodiment, where the procedure may include, but is not limited to, the following steps:

In step 601-2, the UE initiates a caller to the SMF.

At step 602-2, the SMF initiates a PDU session modification to an access network device in the 5G network. The access network device may be a gbb.

Step 603-2, the access network equipment in the 5G network sends indication information for refusing to modify PDU session to SMF. Accordingly, the SMF receives an indication from the access network device to reject modification of the PDU session. Step 603-2 is followed by a procedure of dropping the UE from the 5G network back to the EPS, i.e. an EPS fallback procedure. In the course of executing the EPS fallback flow, step 604-2 to step 608-2 are executed.

At step 604-2, the AMF sends a second request to the MME. Accordingly, the MME receives a second request from the MME.

In step 605-2, the MME sends a modify bearer request to the SMF. Accordingly, the SMF receives a modify bearer request from the MME.

The implementation process of step 601-2 to step 605-2 can refer to the detailed description of step 601-1 to step 605-1 in the embodiment shown in fig. 6a, and is not described herein again.

Step 606-2, the UE sends a tracking area update request to the MME. Accordingly, the MME receives a tracking area update request from the UE.

In step 607-2, the MME performs location update with the MSC. Specifically, the MME sends a location update request to the MSC, and the MSC sends a location update response to the MME after the update.

Step 608-2, the MME sends a tracking area update response to the UE. Accordingly, the UE receives a tracking area response from the MME.

The implementation process of the above step 606-2 to step 608-2 can refer to the detailed description of the step 607-1 to the step 609-1 in the embodiment shown in fig. 6a, and is not repeated herein.

In step 609-2, the SMF sends a notification message of the failure of the establishment of the voice service bearer to the UE. Correspondingly, the UE receives a notification message of the failure of the establishment of the voice service bearer from the SMF.

Similar to fig. 6a, to avoid the out-of-order, after sending the tracking area update response to the UE, the MME sends a fall back success message to the SMF to notify that the SMF EPS Fallback procedure is successful, and then the SMF performs step 609-2.

In step 610-2, the UE initiates a voice call in the CS domain.

In the embodiment shown in fig. 6b, based on that the UE is registered in the CS domain, when the UE needs to initiate a voice call, the AMF drops the UE from the 5G network back to the EPS, and then drops the UE from the EPS to the CS domain through the SMF, so that the UE initiates the voice call in the CS domain, thereby ensuring normal operation of the UE voice service.

Referring to fig. 7, a schematic diagram of a fallback procedure under a UE called condition provided in the embodiment of the present application is applicable to a roaming scenario and a non-roaming scenario, where the procedure may include, but is not limited to, the following steps:

in step 701, the MSC at the visited site receives a paging request. The paging request is a paging request initiated by other users at the home to the international roaming user through the CS domain.

In step 702a, the MSC sends a paging request to the AMF. Accordingly, the AMF receives a paging request from the MSC.

In step 702b, the AMF sends a paging response to the MSC. Accordingly, the MSC receives a paging response from the AMF, the paging response being used to respond to the paging request.

In step 703, the AMF sends a PDU session modification request to the access network device in the 5G network. Accordingly, the access network equipment receives the PDU session modification request from the AMF.

In step 704, the access network device sends a reject message to the AMF. Accordingly, the AMF receives a rejection message from the access network device.

Wherein, the PDU session modification request includes an identification of the proprietary QoS flow (5G QoS identity, 5QI) for requesting the access network device to establish the proprietary QoS flow. The dedicated QoS flow is used to carry voice traffic, and a QoS flow with 5QI ═ 1, in other words, 5QI of 1, is dedicated to carry voice traffic.

In one possible implementation, the AMF directly emulates a 5QI ═ 1 QoS flow, requesting the access network device to establish the proprietary QoS flow.

In one possible implementation, the AMF requests the SMF to participate in a QoS flow emulating 5QI ═ 1. Specifically, before performing step 703, the AMF sends an update request to the SMF, where the update request is used to request the SMF to establish a QoS flow with 5QI ═ 1. The SMF sends an update response to the AMF indicating that the SMF received the update request. After establishing the proprietary QoS flow, the SMF sends a notification message to the AMF, the notification message indicating that the SMF has established the proprietary QoS flow.

It will be appreciated that the proprietary QoS flow is a QoS flow that emulates voice-bearing traffic and does not actually exist.

After step 704, a procedure of dropping the UE from the 5G network to the EPS, i.e. an EPS fallback procedure, is performed. In the process of executing the EPS fallback flow, steps 705 to 707 are executed.

Step 705, the AMF sends a second request to the MME. Accordingly, the MME receives a second request from the MME.

The second request may be a forward migration request, i.e., a forward location request. The second request comprises third indication information, the third indication information is used for triggering the MME to send fourth indication information to the UE, and the fourth indication information is used for indicating that the 4G network supports VoPS so as to avoid that the UE deletes the IMS bearer and avoid communication interruption. The third indication information may be, for example, an MT _ CSFB _ Indicator.

The second request further includes identification information included in the first response in step 304-1 or step 302-2 so that the AMF informs the UE of the identification information so that the UE determines in which CS domain to answer the voice.

In step 706, the UE sends a tracking area update request to the MME. Accordingly, the MME receives a tracking area update request from the UE.

In step 707, the MME sends a tracking area update response to the UE. Accordingly, the UE receives a tracking area response from the MME. It should be noted that 4G access network equipment is omitted between the MME and the UE.

The tracking area update response also includes identification information for the UE to determine in which CS domain to voice reply.

In step 708, the MME sends a notification message for CS domain services to the UE. Accordingly, the UE receives a notification message of the CS domain service from the MME.

The notification message of the CS domain service is used for triggering the UE to perform voice response in the CS domain. The notification message of the CS domain Service may be, for example, CS Service Notificatoin.

And the MME identifies that the UE needs to be triggered to carry out voice response in the CS domain according to the third indication information, so that a notification message of the CS domain service is sent to the UE. Meanwhile, the MME suspends the EPS bearer.

In step 709, the UE sends an extended service request to the MME. Accordingly, the MME receives an extended service request from the UE.

The extended Service Request may be, for example, an extended Service Request, which is used to respond to a notification message of the CS domain Service.

Step 710, the UE performs voice response in the CS domain.

In the embodiment shown in fig. 7, based on that the UE is registered in the CS domain, in the case of calling the UE, the AMF drops the UE from the 5G network back to the EPS, and then drops the UE from the EPS to the CS domain through the MME, so that the UE performs a voice response in the CS domain, thereby ensuring normal operation of the UE voice service.

The method of the embodiments of the present application is set forth above in detail and the apparatus of the embodiments of the present application is provided below.

Referring to fig. 8, which is a schematic diagram of a logical structure of a voice communication apparatus according to an embodiment of the present application, the voice communication apparatus 80 includes an interface module 801 and a processing module 802. The voice communication device 80 may be (or may be a component of) an access management network element in the first network, and the access management network element may integrate the functions of the AMF and may also integrate the functions of the AMF + MME.

A processing module 802, configured to register the terminal to a circuit switched domain in a second network in a process of registering the terminal to a first network; the method comprises the steps that under the condition that a terminal needs to carry out voice communication, the terminal falls back from a first network to a third network; the terminal is dropped from the third network back to the circuit switched domain in the second network.

The first network, the second network and the third network are visited network of the terminal.

In a possible implementation manner, the processing module 802 is configured to control the interface module 801 to send a first request to the second network, where the first request is used to request the second network to register the terminal to a circuit switched domain in the second network; a first response is received from the second network indicating that the terminal is registered to the circuit switched domain in the second network.

In a possible implementation manner, the interface module 801 is configured to send, to the terminal, first indication information, where the first indication information is used to indicate that the first network supports voice communication based on a packet switched domain.

In a possible implementation manner, the processing module 802 is configured to control the interface module 801 to further obtain subscription data of the terminal from a home network of the terminal in a process of registering the terminal in the first network, where a communication system corresponding to the subscription data of the terminal is the same as a communication system of the first network.

In a possible implementation manner, the communication system of the home network is the same as the communication system of the first network;

the processing module 802 is configured to control the interface module 801 to obtain subscription data of the terminal from a unified data management network element in a home network of the terminal.

In a possible implementation manner, the communication system of the home network is the same as the communication system of the third network;

the processing module 802 is configured to control the interface module 801 to obtain, from a home subscriber server in a home network of the terminal, subscription data of the terminal corresponding to a communication system of the third network, and convert the subscription data of the terminal corresponding to the communication system of the third network into subscription data of the terminal corresponding to the communication system of the first network.

In a possible implementation manner, the processing module 802 is configured to control the interface module 801 to send a connection establishment request to a session management network element in a first network in a process of establishing a data connection, where the connection establishment request includes second indication information and subscription data of a terminal, and the second indication information is used to indicate the session management network element to establish a data connection according to the received subscription data.

In a possible implementation manner, the processing module 802 is configured to control the interface module 801 to send, to the third network, a second request in a case that the terminal needs to initiate voice communication, where the second request includes third indication information, the third indication information is used to trigger the third network to send fourth indication information to the terminal, and the fourth indication information is used to indicate that the third network supports packet-switched domain-based voice communication.

In a possible implementation manner, the processing module 802 is configured to trigger the third network to send a notification message indicating that the establishment of the voice service bearer fails to the terminal, where the notification message is used to trigger the terminal to initiate voice communication in a circuit switched domain in the second network.

In a possible implementation manner, the processing module 802 is configured to control the interface module 801 to request, when receiving a paging request for a terminal, an access network device in a first network to establish a data stream, where the data stream is used to carry a voice service; and when the rejection message from the access network equipment is received, the terminal falls back from the first network to the third network.

In one possible implementation, the processing module 802 is configured to control the interface module 801 to request a session management network element in the first network to establish a data flow.

In a possible implementation manner, the processing module 802 is configured to control the interface module 801 to send a second request to the third network, where the second request includes third indication information, the third indication information is used to trigger the third network to send fourth indication information to the terminal, and the fourth indication information is used to indicate that the third network supports voice communication based on the packet switched domain.

In a possible implementation manner, the third indication information is further used to trigger the third network to send a notification message of the circuit switched domain service to the terminal, where the notification message is used to trigger the terminal to perform a voice response in the circuit switched domain in the second network.

In a possible implementation manner, the first response includes identification information allocated by the second network to the user terminal, and the second request further includes identification information, and the identification information is used for the terminal to determine a circuit switched domain position for performing voice communication.

It should be noted that, the functions and operations of the respective modules in the voice communication apparatus 80 may further refer to the related descriptions in the method embodiments.

Please refer to fig. 9, which is a simplified schematic diagram of an entity structure of a voice communication apparatus according to an embodiment of the present application, where the voice communication apparatus 90 may be an access management network element (or a component used for the access management network element) in a first network, and the access management network element may integrate functions of an AMF and may also integrate functions of an AMF + MME. The voice communication device 90 includes one or more communication interfaces 901, a processor 902, and optionally a memory 903. The communication interface 901, the processor 902, and the memory 903 may be connected to each other by a bus 904, or may be connected by other means. The related functions implemented by the processing module 802 shown in fig. 8 may be implemented by one or more processors 902. The related functions implemented by the interface unit 801 shown in fig. 8 can be implemented by the communication interface 901. The communication interface 901 may also be an input/output interface.

The memory 903 includes, but is not limited to, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or a portable read-only memory (CD-ROM), and the memory 903 is used for related instructions and/or data. The processor 902 may invoke instructions in the memory 903 to cause the voice communication device to implement the corresponding methods in the various embodiments described above.

Communication interface 901 is used for transmitting data and/or signaling and for receiving data and/or signaling.

In the embodiment of the present application, for the case that the voice communication apparatus 90 is an AMF, the communication interface 901 is used for communicating with devices such as an SMF, a UDM/HSS, an MSC, an HLR, and a gNB, for example, to perform steps 301-1 to 305-1 in the embodiment shown in fig. 3 a; step 301-2 to step 303-2 in the embodiment shown in FIG. 3 b; steps 401-1 to 404-1 in the embodiment shown in FIG. 4 a; steps 401-2 to 404-2 in the embodiment shown in FIG. 4 b; step 501-1 to step 502-1 in the embodiment shown in FIG. 5 a; steps 501-2 to 502 in the embodiment shown in fig. 5 b; step 604-1 in the embodiment shown in FIG. 6 a; step 604-2 in the embodiment shown in FIG. 6 b; step 705 in the embodiment shown in fig. 7.

The processor 902 may include one or more processors, such as one or more Central Processing Units (CPUs), and in the case that the processor 902 is one CPU, the CPU may be a single-core CPU or a multi-core CPU. In the embodiment of the present application, the processor 902 controls the communication interface 901 to perform transceiving actions.

The memory 903 is used to store program codes and data of the voice communication apparatus 90.

For the steps executed by the processor 902 and the communication interface 901, reference may be specifically made to the description of the embodiment shown in the method, and details are not described here again.

It will be appreciated that fig. 9 only shows a simplified design of the voice communication apparatus. In practical applications, the voice communication apparatus may also respectively include other necessary elements, including but not limited to any number of transceivers, processors, controllers, memories, communication units, etc., and all devices that can implement the present application are within the protection scope of the present application.

One of ordinary skill in the art will appreciate that all or part of the processes in the methods of the above embodiments may be implemented by hardware related to instructions of a computer program, which may be stored in a computer-readable storage medium, and when executed, may include the processes of the above method embodiments. And the aforementioned storage medium includes: various media capable of storing program codes, such as ROM or RAM, magnetic or optical disks, etc. Accordingly, a further embodiment of the present application provides a computer-readable storage medium having stored therein instructions, which, when executed on a computer, cause the computer to perform the method of the above aspects.

Yet another embodiment of the present application provides a computer program product containing instructions which, when run on a computer, cause the computer to perform the method of the above aspects.

Those of ordinary skill in the art would appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

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

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

In addition, functional units in the embodiments of the present application may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one unit.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in or transmitted over a computer-readable storage medium. The computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)), or wirelessly (e.g., infrared, wireless, microwave, etc.). 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, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

Claims

1. A method of voice communication, comprising:

in the process of registering a terminal to a first network, an access management network element in the first network also registers the terminal to a circuit switched domain in a second network;

the access management network element drops the terminal from the first network back to a third network under the condition that the terminal needs to perform voice communication;

and the access management network element drops the terminal from the third network back to a circuit switched domain in the second network.

2. The method of claim 1, wherein the first network, the second network, and the third network are visited networks of the terminal.

3. The method of claim 1, wherein the registering, by the access management network element, the terminal to the circuit-switched domain in the second network comprises:

the access management network element sends a first request to the second network, wherein the first request is used for requesting the second network to register the terminal to a circuit switched domain in the second network;

the access management network element receives a first response from the second network, the first response indicating that the terminal is registered to a circuit switched domain in the second network.

4. The method of claim 3, wherein after the access management network element registers the terminal with a circuit-switched domain in the second network, the method further comprises:

and the access management network element sends first indication information to the terminal, wherein the first indication information is used for indicating that the first network supports voice communication based on a packet switched domain.

5. The method of claim 2, further comprising:

in the process of registering the terminal to the first network, the access management network element also acquires the subscription data of the terminal from the home network of the terminal, and the communication system corresponding to the subscription data of the terminal is the same as the communication system of the first network.

6. The method according to claim 5, wherein the communication standard of the home network is the same as the communication standard of the first network;

the acquiring, by the access management network element, subscription data of the terminal from a home network of the terminal includes:

and the access management network element acquires the subscription data of the terminal from a unified data management network element in a home network of the terminal.

7. The method according to claim 5, wherein the communication standard of the home network is the same as the communication standard of the third network;

and the access management network element acquires the subscription data of the terminal corresponding to the communication system of the third network from a home subscriber server in a home network of the terminal, and converts the subscription data of the terminal corresponding to the communication system of the third network into the subscription data of the terminal corresponding to the communication system of the first network.

8. The method of claim 3, wherein after the access management network element registers the terminal with a circuit-switched domain in the second network, the method further comprises:

the access management network element sends a connection establishment request to a session management network element in the first network in a process of establishing data connection, wherein the connection establishment request comprises second indication information and subscription data of the terminal, and the second indication information is used for indicating the session management network element to establish data connection according to the received subscription data.

9. The method of claim 3, wherein, in a case that the terminal needs to perform voice communication, the dropping the terminal from the first network to a third network by the access management network element comprises:

And under the condition that the terminal needs to initiate voice communication, the access management network element sends a second request to a third network, wherein the second request comprises third indication information, the third indication information is used for triggering the third network to send fourth indication information to the terminal, and the fourth indication information is used for indicating that the third network supports the voice communication based on a packet switched domain.

10. The method of claim 9, wherein the dropping, by the access management network element, the terminal from the third network back to the circuit-switched domain in the second network comprises:

and the access management network element triggers the third network to send a notification message of voice service bearer establishment failure to the terminal, wherein the notification message is used for triggering the terminal to initiate voice communication in a circuit switched domain in the second network.

11. The method of claim 3, wherein, in a case that the terminal needs to perform voice communication, the dropping the terminal from the first network to a third network by the access management network element comprises:

under the condition that the access management network element receives a paging request aiming at the terminal, the access management network element requests the access network equipment in the first network to establish a data stream, wherein the data stream is used for bearing voice service;

And when receiving the rejection message from the access network equipment, the access management network element drops the terminal from the first network back to a third network.

12. The method of claim 11, wherein before the access management network element requests the access network device in the first network to establish the data flow, the method further comprises:

the access management network element requests a session management network element in the first network to establish the data stream.

13. The method of claim 11, wherein the dropping, by the access management network element, the terminal from the first network to a third network comprises:

the access management network element sends a second request to a third network, the second request includes third indication information, the third indication information is used for triggering the third network to send fourth indication information to the terminal, and the fourth indication information is used for indicating that the third network supports voice communication based on a packet switched domain.

14. The method of claim 13, wherein the third indication information is further used for triggering the third network to send a notification message of a circuit switched domain service to the terminal, and wherein the notification message is used for triggering the terminal to perform voice response in a circuit switched domain in the second network.

15. The method according to claim 9 or 13, wherein the first response comprises identification information allocated by the second network to the user terminal, and wherein the second request further comprises the identification information, and wherein the identification information is used for determining a circuit switched domain location for voice communication by the terminal.

16. A voice communication apparatus comprising a memory and a processor,

the memory is used for storing a computer program;

the processor invokes the computer program to cause the voice communication apparatus to perform the steps of:

in the process of registering a terminal to a first network, the terminal is also registered to a circuit switched domain in a second network;

under the condition that the terminal needs to carry out voice communication, the terminal falls back from the first network to a third network;

dropping the terminal from the third network back to a circuit switched domain in the second network.

17. The apparatus of claim 16, wherein the first network, the second network, and the third network are visited networks of the terminal.

18. The apparatus of claim 16, wherein the processor invokes the computer program to cause the voice communication apparatus to perform the following steps when registering the terminal with a circuit switched domain in a second network:

Sending a first request to the second network, the first request requesting the second network to register the terminal to a circuit switched domain in the second network; receiving a first response from the second network, the first response indicating that the terminal is registered to a circuit switched domain in the second network.

19. The apparatus of claim 18, wherein the processor invokes the computer program to cause the voice communication apparatus to further perform the steps of:

and sending first indication information to the terminal, wherein the first indication information is used for indicating that the first network supports voice communication based on a packet switched domain.

20. The apparatus of claim 17, wherein the processor invokes the computer program to cause the voice communication apparatus to further perform the steps of:

in the process of registering the terminal to the first network, acquiring the subscription data of the terminal from a home network of the terminal, wherein the communication system corresponding to the subscription data of the terminal is the same as the communication system of the first network.

21. The apparatus according to claim 20, wherein the communication standard of the home network is the same as the communication standard of the first network;

The processor calls the computer program to enable the voice communication device to execute the following steps when acquiring the subscription data of the terminal from the home network of the terminal:

and acquiring the subscription data of the terminal from a unified data management network element in a home network of the terminal.

22. The apparatus according to claim 20, wherein the communication standard of the home network is the same as the communication standard of the third network;

and acquiring the subscription data of the terminal corresponding to the communication system of the third network from a home subscriber server in a home network of the terminal, and converting the subscription data of the terminal corresponding to the communication system of the third network into the subscription data of the terminal corresponding to the communication system of the first network.

23. The apparatus of claim 18, wherein the processor invokes the computer program to cause the voice communication apparatus to further perform the steps of:

In the process of establishing data connection, sending a connection establishment request to a session management network element in the first network, where the connection establishment request includes second indication information and subscription data of the terminal, and the second indication information is used to indicate the session management network element to establish data connection according to the received subscription data.

24. The apparatus according to claim 18, wherein the processor invokes the computer program to cause the voice communication apparatus to perform the following steps when the terminal falls back from the first network to a third network if the terminal needs to perform voice communication:

and sending a second request to a third network under the condition that the terminal needs to initiate voice communication, wherein the second request comprises third indication information, the third indication information is used for triggering the third network to send fourth indication information to the terminal, and the fourth indication information is used for indicating that the third network supports the voice communication based on a packet switching domain.

25. The apparatus of claim 24, wherein the processor invokes the computer program to cause the voice communication apparatus to perform the following steps when the terminal falls back from the first network to a third network:

And triggering the third network to send a notification message of voice service bearer establishment failure to the terminal, wherein the notification message is used for triggering the terminal to initiate voice communication in a circuit switched domain in the second network.

26. The apparatus according to claim 18, wherein the processor invokes the computer program to cause the voice communication apparatus to perform the following steps when the terminal falls back from the first network to a third network if the terminal needs to perform voice communication:

under the condition that a paging request aiming at the terminal is received, requesting access network equipment in the first network to establish a data stream, wherein the data stream is used for bearing voice service; and when the transceiver receives the rejection message from the access network equipment, the transceiver drops the terminal from the first network back to a third network.

27. The apparatus of claim 26, wherein the processor invokes the computer program to cause the voice communication apparatus to further perform the steps of:

requesting a session management network element in the first network to establish the data flow.

28. The apparatus of claim 26, wherein the processor invokes the computer program to cause the voice communication apparatus to perform the following steps when the terminal falls back from the first network to a third network:

Sending a second request to a third network, wherein the second request comprises third indication information, the third indication information is used for triggering the third network to send fourth indication information to the terminal, and the fourth indication information is used for indicating that the third network supports voice communication based on a packet switched domain.

29. The apparatus of claim 28, wherein the third indication information is further configured to trigger the third network to send a notification message of a circuit switched domain service to the terminal, and wherein the notification message is configured to trigger the terminal to perform a voice response in a circuit switched domain in the second network.

30. The apparatus according to claim 24 or 28, wherein the first response comprises identification information allocated by the second network to the user terminal, and wherein the second request further comprises the identification information, and wherein the identification information is used by the terminal to determine a circuit switched domain location for voice communication.

31. A voice communication system, characterized in that the voice communication system comprises a first access management network element in a first network and a second access management network element in a third network;

the first access management network element is configured to register a terminal to a circuit switched domain in a second network in a process of registering the terminal to a first network, and drop the terminal from the first network back to a third network when the terminal needs to perform voice communication;

The second access management network element is configured to drop the terminal from the third network back to a circuit switched domain in the second network.